1957-1997: NEA's fortieth

anniversary

Safety research needs for

Russian-designed reactors

Nuclear energy in relation to

sustainable development

The OECD/NEA RASPLAV project

Reactor fuel performance and

safety margins

The NEA's programme on

decommissioning

A new NEA report discusses

radiation

Nuclear power in NEA countries

•

su rn mary Newsletter

spring 1997 volume 15 no.1

Th e NEA Ne wslelfer is publish ed

twice yea rly in English and french by

the OECD Nuclear Energy Age ncy. The opinions expressed in the Newsleffer ore those of the contri butors clone and

do not necessarily refl ect the vi ews of the Organisation or of ils Member countri es. Materiel in the Newslelfer

moy be freely used provided the sou rce

is ocknowledged.

Ali correspondence shoul d be

addressed to:

The Editor NEA Newsletter OECD Nucleor Enersy Agency 12, boulevard des lies 92130 Issy-les-Moulineaux France

Tel. 01 45 24 10 10 Fax 0 1 45 24 11 1 0

The OECD Nudear Energy Agency IN EAJ was established in 1958 as the

OEEC European Nudear Energy Agency

and took ils present designation in 1972,

when ils membersh ip wos extended to non-E uropean countries. lts purpose is to further the development of nudear energy

by sponsoring economie, technical and scienti fic studies and projects, and by contr ibuting to the optimisation of sofety

and regulatory policies and practices. lt currently consists of 27 Member countries :

Australia, Austria, Belgium, Canada, the Czech Re pu blic , Denmork, f inland ,

fronce , Germony, Greece, Hungory,

lceland , lrelond , ltoly, Japon , Korea,

luxembourg, Mexico, the Netherlonds,

Norway, Portugal , Spain, Sweden,

Switze rlond, Turkey, the United Kingdom, and the United States. The European Commission tokes port in the NEA's work

and a cO<>peration agreement is in lorce with the International Atomic Energy Age ney.

For more information about the NEA,

see:

http:/ /www.nea.fr/

Facts and . . op1 n1ons

The NEA' s 40th anniversary 1957-1997

Safety research needs for Russian­designed reactors

Nuclear energy in relation to sustain­able development

Nuclear liability and insurance in Russia

NEA update Technical achievements and significance of the OECD/NEA RASPLAV project

Nuclear criticality safety

Reactor fuel performance and safety margins

The NEA's co-operative programme on decommissioning

A new NEA report discusses radiation

Nuclear power in NEA countries

NEA in brief

News briefs

New publications

Editorial Board:

Jacques de la Ferté Cynthia Picot Diane Jenkins

Co·ordinotion: Solange Quarmeau

Annick Bruche!

Loyout/ Grophics: Annette Meunier

Jennifer Chapman

Photo Reseorch: Marie-France Phalip

Design: Paragramme

Caver photo: MOX fuel ossembly being loaded into the Assembly Store in MOX Demonstration Focility al Sellafield, UK. Photo courtes y of British Nuclear Fuels pic, United Kingdom .

editorial

Inauguration of the Eurochemic plant, the first NEA joint undertaking, on 7 July 1966. From right to left: King Baudouin; Dr. R. Rometsch *, Managing Director of Eurochemic; Dr. E. Saeland, Director-General of the ENEA; and Dr. W. Schulte-Meermann, Chairman of the Eurochemic Board of Directors.

* We were sad to learn just before going to pre ss that Dr. Rom etsch passed away on 7 Ju ly 1997.

1

View of the Eurochemic plant in the 1960s.

This year is of partiwlar historical significance for the Nuclear Energy Agency (NEA) because it marks the 40th anniversary of the adoption of its Statute. In recognition of this important anniversary, this iss ue of the N EA Newsletter includes a brief exami.nation of the Agency's creation, its early role in internationalnuclear co-operation, and its evolLtti.on over Jo ur decades .

Th e world has changed considerably since the NEA was created. In the late 1950s there was great optimism about the potential near and long-term benefits of nuclear power By contrast, in 1997, although nuclear power wi ll most lihely be relied upon increasingly in the long term, it has no prospects for near-term growth in most NEA Member wuntries, with the exception of those in the Asian region. At the same time, bw:lge ts of international organisations are fac ing increasing constraints as member cou nt ries look for ways to save mo ney. This situation, coup led with the Jact that the NEA has inherently less visibility than sorne large r intemationalnuclear organisations, means that the Agency must not only maintain its comparative strengths, but must also be particularly responsive toits Members needs if it is to retain their support.

As the NEA contimtes to adapt to the changing needs of its Members, we should remember the expelience of its past. An awareness of how the A geney evolved mahes it rnuch easier to understand and appreciate the role it pla ys toda y and greatly facilitates consideration of where it should be going in the next Jive or ten years, and even beyo ncl .

Sam Thompson DepLtty Director-General

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The NEA's 40th anniversary 1957-1997

While the NEA has evolved in important ways

over the past 40 years, it has nevertheless maintained the key

features from which it derives its comparative

advantage. These include the homogeneity of its

membership, its flexible working methods, the

depth and quality of its technical work, and its

small size and cost­effectiveness. These

features will continue to be the key to the role

that the Agency plays in the future, as the role of

nuclear power itself evolves.

This yea r marks the 40th anniversary of the adoption of the Stature of the European Nuclea r

Energy Agency (ENEA) - later to become the N uclea r Energy Agency (N EA) - by the Council of the Organisation fo r European Economie Co-operation (OEEC) in Dece mber 1957.

The impetus fo r the creation of the ENEA arose in the 1950s, with rapid ly growi ng energy needs in Europe resulting from its reconstruc­tion after World War Il coinciding with increasing European fears of an energy fu el shortage These fe ars stemmed particularly fro m dwindling suppli es of European domestic oil and coal and instabi lity in the Middle East res ulting from the three -year suspens ion of l ranian oil production and the cl osing of the Suez Canal (1956-57) On 14 December 1953 , the Secretary-G eneral of the OEEC subm itted to the Organ isat ion's Co uncil a report on energy suppl y diffi culties and the mounting cost of energy ln his report , Louis Armand, one of the "Wise Men" who assisted in the creation of Euratom (see below), reviewed the energy situation and strongly affirmed the importance of develop ing nuclear energy

A fa vorable cl imate for inter­national co -operation in nuclear energy was also deve loping else ­where. ln response to President Eisenh ower's December 1953

* Mr. Sa m Th ompson is Deputy Di r.ector-Ceneral of the NEA.

proposa! for an internat ional age ncy devoted to the peaceful uses of atomic energy, the United Nations organisee! a wo rldwide conference and later app ointee! a preparatory commission , which helped es tab lish the Interna tional Atom ic En ergy Agency (29 July 1957) ln addit ion, a European Atomic Energy Com­munity (Euratom) was conce ived at the 1955 Mess ina Co nfe rence as a nuclea r coun te rpart of the Common Market , and cam e into being as a result of the Treaty of Rome, whi ch ente red into force on 1 january 1958. lnterestingly, the actual establishment of the EN EA was delayed until l February 1958 , after the establish­ment of Eu rato m, as a res ul t of conce rn on the part of Eu ropean integrationists

The rationale and enviro n ment for the crea tion of th e ENEA must be see n in the context of th e ge neral economie and technological co ndi­tio ns prevailing in Europe at that rime . ln th e afterm ath of Worl d Wa r Il the bulk of the technological and economie resources of the West we re co ncentrated in the Uni ted States . This disparity was even greater in the field of nuclea r energy because of the secrecy of nuclear inform ation and the emigratio n to th e United States of many of the elite Eu ropea n scientists. ln these circum stances, many in Europe saw th e best chance for narrowing the gap in the co­ordination of developmenl efforts and the poo ling of resources through JOint projects

lnitiall y, th e OEEC gave effect to its interest in nuclear energy by creat ing a "Steering Group on Nuclea r Energy", which was to keep the Council of the OEEC advised on

• The NEA's 40th annive rs ary - 1957-1997

ali nu clear energy matters. lt was evident , however, that a hi gh-level Steering Committee alone, consist ing genera ll y of the heads or se nior officiais of the eme rging nati onal

nu clea r programmes, wou ld not suffi ce to mount and ma nage a co-operati ve effort . To play thi s ro le, Pi erre Huet, a French official of th e

1

A late 1950s view of the Dragon High -Temperature Reactor, one of the earliest NEA joint undertakings .

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OEEC , proposecl the creation of a European Nuclear Ene rgy Agency as a semi-autonomous body und er the aegis of the OEEC

As envisaged by Huet, the Agency wo uld have three maJor responsi­bilities the es tablishm ent of jo int proJects; the so lu tion of legal problems rela ted to nuclea r energy through the harm on iza ti on of national laws and the adopt ion of regional conve nti ons; and th e

provision of a forum in which the national nuclea r energy programmes of the Members coulcl be discussed and co-o rdin atecl. The creat ion of JOint proj ects was clearly the priOJ·ity object ive and th e key to th e establi shment of the ENEA. ln fact, the formu lat ion of se lectecl proj ects was und ertaken concu rrently with the discussions on the creation of the organisa ti on itself; and two signifi­cant projects - the Eurochemi c

reprocessing plant in Mol , Bel gium , and the Dragon High-TemperaLUre Reactor project - had reac hed th e po int where they seemed achi evable by late- 1957 , when the Agency itse lf was ready for launching.

The establishment of the ENEA as a se mi-autonomous bod y in th e OEEC framework provid ed iL a ready- made institutional base, wh ich eliminated the time-consuming step of nego tiating a new international

convention and made it possible to estab lish th e Age ncy by dec ision of the OEEC Cou ncil in a fraction of the ti me thaL would have been need­ed to create an ent irely new bod y ln addition , the ENEA was faced wi th fewer diffi cult po liti cal issues th an a supranationa l organisa­tion like Euratom .

Despite its lack of supranational authority and of budgetary re­sources beyond the cost of a small staff , th e ENEA had considerable ea rly success in esta b­lishing joint projec ts through the voluntary co-operation of interestecl Members. The Agency was also sucees fui in the legal area. The Pari s Convention on Thircl Party Liability for Nuclear Dam age was the fir st internatio nal convention in this area , sett ing the stage for the Supplementary Brussels Convention and also for the Vienna Convention which , together, are the backbone of the wor lcl ­wide third party li abi lity system.

Controls at the Dragon High-Temperature Reactor, as they looked in the late 1950s.

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As time passed , smaller joint projects were established, including the Halden Project fo r the operation of the Norwegian Boiling Heavy Water Reactor, the international food irradiation project, and the European­American Nuclear Data Commit tee. ln the process, a numbe r of tech­niques fo r internationa l colla bora­tion in major R&D activities were tri ed and demonstrated, investing the Agency with a considerable body of experience and expertise in the development of such undertakings

ln 1960 , the OEEC became the Organisa tion fo r Eco nomie Co­operation and Development (O ECD) The change was fu ndamental, sig­naling a change in th e role of the Organisation from allocating outside assistance and co-ordinat ing its own development to concerting economie policy among its Members in pro­motion of their welfare and that of the rest of the wo rld . During th e decade tha t fol lowed, the ENEA also began to change. By the mid-1960s, as a res ul t of declining expectations fo r an earl y burgeoning of nuclear power in Europe , a shi ft in emphasis from R&D to industrial deployment, and a revived emphas is on na tional programmes , there appeared to be few prospects fo r further major joint projects , and the individual who had

• The NEA's 40th anniversary- 1957-1997

played the key ro le in guid ing the Agency in its ea rl y days as its fi rst Director-General, Pierre Huet, departed.

During th is period, em phasis in the Agency shifted from joint proJects and development of techno logy to programme co-ordinati on, consensus building and the pursuit of studies by specialised committees established within the Agency. There was also increasing focus on regulatory aspects as the protection of wo rk ers, th e pop ulatio n, and the environment against harmful effects of radi ation ga ined importance, as we ll as on nuclear reactor sa fety and the management of radioactive waste. ln addition , both the Neutron Data Co mp ilation Ce ntre, at Saclay, France, and the Computer Program Library, at Ispra , Italy, were crea ted in 1964 These bodies were later to be merged into the NEA Data Bank , established in 1978.

In the 1970s the membership of th e Agency also change d. The original Members had been Western European countries, but Japan and Australia joined in 1972, Canada in 1975, and the United States in 1976 . Meanwhile, the name of th e Agency was·changed in 1972 to refl ec t the ex pans ion of membership beyo nd Eu rope The membership of the

View of the Norwegian Boiling Water Reactor (Halden project) in the early years of its operation.

Agency was to remain stable until the mid-1 99 0s, when Korea joined in 1994, Mexico in 1995, and the Czech Republic and Hungary in 1996 . ln the ea rly 1990s, in the wake of the dissolution of the Soviet Bloc, the Agency followed the lead of the OECD and init iated a limited pro­gramme of outreach , focusing pri­marily on the co untries of Ce ntral and Eastern Europe and the former Soviet Union Some of the activities in th e outreach programme have increasingly become an integra l part of the co re programme of the Agency as additional countries with reactors of Soviet design have becom e Members. While the Agency has evo lved in important ways, it has maintained the key fea tures from which it derives its comparative advantage , including the homo­geneity of its membership , its flexible working methods, the depth and quality of its technical work , and its small size and cost- effec tiveness . These features will continue to be the key to th e role that the Agency pla ys in the future, as the role of nuclear power itself evolves . •

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E. S. Beckjord*

Safety research needs for Russian-designed reactors

The NEA programme of co-operation and assistance with the Central and Eastern European Countries (CEEC) and the New Independent States {NIS} of the former

Soviet Union is concerned inter alia

with the planning and execution of safety

research programmes. The purpose is to build

up know-how and capabilities in safety

technology pertaining to their nuclear power plants. As part of this

programme, a new study was recently completed

on safety research needs for Russian­designed reactors. 1

T he purpose of this study is to make recommendations for safe ty research that should be car ried out to

assist in the safety improvement of Russian-designed reactors. The study takes into co nsideration safe ty resea rch clone by NEA Member countries for nuclear power reactors, and th e relevance of this work to Russian-designed reacto rs, i. e. reac­tors of th e VVE R and RBMK types

The transfer of knowledge from EA Member co untri es, in co­

operation with Russian and Eastern European organisations , has already helped to improve the operational safety of Russian-designed reactors by introduci ng changes in operating procedures and systems. These improvements we re the result of applying known technology in th e nea r term. Further safety improve ­ment for Russian-designed reactors can be expec ted from safety research to be carried out in the coming years. Iwo facts support th is expectation

• Nuclear sa fety research in NEA Member countri es has helped to improve the sa fety of NEA nuclear power plants over many years.

• I wo of Finland's reactors are in fact Ru ssian-designed, and have benefited from the application of Western nu clea r reactor safe ty

* Dr. Eric Bcàjord is Clwirman of the OECD Support Cn1up on Sa{cty Rcscarch Nccds of Russian-Dcsigned Reac tors, former Chai•·man of the NEA Committee on the Safcty of Nuclear In stallations (CS NI ) , and former Director of Rcscarch al the US 1\'uclear Rcgulatorv Commission.

resea rch since th eir in ce ption . The potential benefits of sa fety re­search applying to Russian-des i­gned reactors are therefore an im­portant subj ect for the auemi on of EA Member coumries, and all countries with nucl ear powe r programmes.

ln addition to technical ex perts from Ru ssia, the NEA Member co untri es participating in this study were Canada , Finland, France, Germany, ltaly, j apan, the United Kingdom and the United States

Obje · · ~ o~ e st r1'

The basic objectives of this study were:

• to carry out a detailed study of the safety research needs for Russian­designed nuclear power plants of the VV ER and RBMK types;

• to identify the safety issues where add itional experimental and ana­lytical research efforts are needed, adequ ate conside rat ion ha\' in g been given to the applicability of safety research data already a\'a il ­able in NEA Member count ri es to limit additional research needs;

• to make the information a\'ailab le, as a reference documem for futu re acti vities, to governments, appro­priate funding agencies and research institutions in Easte rn Europe, Ru ssia, and Wes tern co untries.

Major sources used to identify these issues included th e large base of operating experience and app li ed safety research in NEA

'0

Member countries, and a smaller, but nevertheless significa nt base of operating ex perien ce in the NJS and CEEC.

lt was estab lished thar fulfilment of these objectives would hel p to develop responsive research pro­posais and programmes, and provide justification for their fu nding by appropriate national and inter­national funding authorities. These objectives we re a)so found l O be important not only for their app lica­ti on Lo th e resolu tion of the sa fety issues thaL have already been iden­tifi ee! , but also, in a more extensive se nse, fo r continuing sa fety research as pan of the regula tory respon­sibility for the sa fe operation of reactors in NIS and CEEC countries. A conti nuing progra mme of safety research for these reactors wi ll help to ensure sa fe operation , as it has in NEA Member countri es.

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• Safety research needs for Russian-designed reactors

Research objectives in NEA Member countries

With the above -mentioned objectives in mind , it is appropriate to ask what the objectives of nuclear safety researc h in NEA Member countries have been. There are three major motiva ti ons for ca rrying out safety resea rch:

• to enhance public sa fety, of which regulatory auth orities are major sponsors;

• to improve reactor operations, of which reactor owner-operators are major sponso rs;

• to develop improved plants, sys­tems, and components, of wh ich reactor designers-manu fac turers are major sponsors.

Research to ensure the protecti on of public sa fety has been underway fo r a long rim e. Sa fety resea rch fin din gs typi ca lly affec t plant safety

assess ment , making it poss ible to id entify safety wea kn esses and to eva luate the effec tive ness of propose e! remedi es, whether these are changes in plant sys tems or components, or changes in operating procedures Specifie research appli­ca ti ons includ e better reactor pressure vesse! safety, adequacy and reli abil ity of emergency sa fety systems, ge neri c sa fety iss ues appl yin g to a number of plants, ensurin g thar reactors can survive ea rth quakes safely, und erstand ing seve re acc idents, and acc ident management to prevent or limit th e release of radioactivity Research find ings have also been incorporated into regulatory requirements within NEA Member countri es and have co ntributed to improved safety in many ways.

View of the Paks Nuclear Power Plant, H un gary.

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Safety research needs for Russian-designed reactors •

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Research and development to improve plant des ign is leading to advances in perform ance without redu cing sa fety margins in NEA Member countries. Deve lopment of new fue l design and bigher burnup fu el makes longer plant operating cycles and improved economi es possible.

Research to improve reactor oper­ations has been very produ ctive . Examples include thermal annealing of reactor pressure vessels in Russia, steam generator cleani ng and co rro­sion inhibitors, non-destructive examination of pressure vessels and piping for growth of fl aws, and reduction of fire haza rd s.

NEA Member countries bave clone research on human pe rformance at nuclear plants leading to important applications such as operator qualification and training, im prove­ment of co ntrol roo m instrumen­tation displays and th e persan­machine interface in co nt ro l rooms to reduce or eliminate operator error, development of maintenance proce­dures and emergency operat ing procedures.

VVER and RBMK reactors NEA Memb er co unt ries have a

large base of operating experience and sa fety knowledge fo r light water reac tors (LW R) Operating ex per­ience is important beca use it un cove rs des ign weaknesses in th e form of operating events. Feedbac k of this experience, after analysis and determination of root causes, leads to plant imp ro vements that eliminate, or reduce the frequency of accidents in the future. LWRs and VVERs are similar in co nce pt and sys te ms design, and consequently much of the light water reac tor operating experience in NEA Member coun­tries is applicable to VVERs. For essentiall y the sa me reason, extensive sa fety research carried out in EA Member co unt ries is also , for th e most part , applicable to VVERs. The appli cat ion of OECD research findin gs to VV ERs is under way, but lags bebind the application of operating experience. As a result , there are stiJl benefits to be achieved througb the application of research findings.

VVER-440 Reactor Design (Mode! V230).

Because of majo r differences in conce pt and des ign betwee n RBM K and VV ER reactors , operating ex pe­rience wi th LWRs is not as di rec tly ap plicable to RB MKs as to VVE Rs. Also, because of the smaller number of RBMK reactors, the base of RBM K operating ex perience is considerably Jess tban the LWR/VVER base. Feedback of RBMK operating ex pe­rience to RBMK plants is th erefore at an earlier stage than thal of VVERs.

There is pressure tube reactor technology in NEA Member coun­tries, but it is less extensive than light wa ter reacto r sa fety rechnology. Accordingly, the report refl ec ts signifi cant differences in the sco pe an d depth of resea rch recommen­dations for the two reactor types; tbese are more complex in the case of VVERs.

With regard to RBMK safety research, the report focuses on wo rk thar can reduce risk in the nea r term. Specifica lly, it recommends resea rch to provide an adeq uate tec bnica l basis for improved operating proce­dures in emergency conditi ons.

Organisation of the study Specifie technical areas whi ch

we re investigated as part of the study were:

• thetmal-hydraulics/plant transients;

• integ ri ty of plant equipment and structures;

• seve re accidents ;

• operating safety issues.

This organisation of disc iplines provided a comprehensive scheme of safety research review. Thermal­hydrau lics/plant transients includes the ph ysical mod els and computer codes thar describe plant and sa fety systems behaviour under accident conditions and indicate whet her respon se is norm al, or whet her conditions are unsafe and coulclleacl to an accident , fuel damage and release of racl ioactivit y. It also includ es reactor physics and th e short- te rm analys is of containment sys tem performance cluring accid ents. lntegrity of plant equip­ment and structures relates to assess­ment of reactor pressure bounclary integrity, and prevention of pressure vessel and piping ruptures thar cause loss-of-cool ant accidents. Severe acc idents inclucles the knowleclge of eve nts and ph enom ena occurring when core cooling fails ancl leacls to fue l da mage, co re meltcl own and release of radioac ti vit y. Finall y, operating safety issues brings in the knowledge of contributing factors to operating events thar have causecl or coulcl cause accidents .

ln order to focus sharply and consistently on key safety research top ics, the stucl y aclclressecl th ree basic questi ons:

• What is the safety concern7

• What are the open safety issues?

• What are the safety research needs7

Conclusions of the study

Operational safety

The stucl y strongly urges research for the purpose of improving human perfo rmance, human error being a

• Safety resea rch need s fo r Rus sian-designed reactors

maJor contributor to acc idents, and because procedures for operator action can be moclified with minimal delay and therefore lead to rapid safety improve ments. In add ition , there are usually fewer barriers to improvements in this area than there are to moclifying the design of the plan t. Other important research in cludes the app lica tion of Proba­bilist ic Safety Assessment (PSA) methods to help iclentify plant sa fety weaknesses, bett er monitoring of operational readiness of safety­relatecl equipment , and the assess­ment of the technical basis for emergency opera ting procedures, i. e. the basis for reactor operator actions to terminate progression of an acci­dent , or mitiga te its consequences.

VVERs Thermal-hycl raulics and reactor

kinetics govern almost ail accidents relating to reactor safety. The cocles that describe these phenomena are the refore essential to ols fo r safety assessment , and must be ve rified in orcler tha t they may be usecl with confidence. Both Russian-developecl cocl es and OECD codes modifi ecl to ana lyse Russia n-clesigned reacto rs require additional verifi ca tion for this purpose. For the verification of Ru ss ian -cl eveloped cod es, VVER exp erimental data is nee clecl Similarly, OECD cocles mod ified fo r Russ ian-clesigned reactors must incorporate WER-specific features, and be validated with VVE R experimental data. With respect to thermal -hydrauli c perfo rm an ce of containment sys tems, additional ve rification and validation of Russian and modified OECD codes are needed. The W ER-440/21 3 Bubble Condenser Containment requires aclcl itional experimental data for this purpose.

The integrity of VVER equipment and structures is another important research area. lntegrity of the reactor coolant boundary and leak-tightness of containment or confinement are both necessary for safety. Methocl s to assess th ese requirements must

therefo re be ve rifiecl. For reacto r pressure vesse ls, research is neecl ed to extencl th e materia ls propert y clatabases , inclucling welcling mate­rial subject to irradiation. lmproved models are needed for other pressure bound ary components, and experi­mental data are needed for ve ri fi­ca tion . Also, clevelopment of im provecl Non-Destructive-Tes ting (NDT) methods to moni tor actual materi al properti es is needed to assess the remainin g sa fe li fe of components

Severe accidents is another maJor resea rch area. The seve re accident resea rch performecl in NEA Member countries is in large part app licab le to VVERs. The most important task concerning VVERs is to improve the codes thar describe severe accidents in order to validate VVER accident management procedures . The neecl for aclcliti onal experim ents and analyses related to VVER-uni que design fea tu res shou ld also be assessed in view of their contri­butions to risk.

RBMKs As in the case of VVERs, safety

improvement in RBMK reactors depends on the qua lity of analysis and validated thermal-hyclraulic and reactor kinetics cocles. Resea rch is needecl to improve the neutronic data base, the co upling between neut ronic and thermal-hydraulic cocl es, and to valid ate the codes . Research is needed to improve the technical basis for safety criteria for initi ati on of fu el fail ure and fu el channel failure, and to determine hyclrogen dis tribution after initiation of accidents For containment safety assess ment, resea rch is nee cl ecl to improve and valid ate cod es that clesc ribe contai n ment performance.

The integrity of the primary coo lant circui t, and es pec ially the fuel chann el, is a maJor safety issue for the RBMK, and methocls of safety assessment require ve rifi cation . Research is urgently requirecl to clevelo p improved ln-Service ­Inspection systems, and mo nitoring

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Safety research needs for Russian-designed reactors •

of fu el channel integrity for effects of age ing. Analyses are requi red to develop fu el chann el rupture models, and respo nses to load ings thar are the result of rupture or ea rthquakes ln arder to comp lete in tegrity assessment , experi ments are needed to provide add itional materials pro perty da ta.

There is every expecta ti on th ar the research identified in this report will make a difference to the safety of the Ru ssian-d esigned plants, based on similar experience with the appli ca tion of safety research to OECD plants Experts have more experience with western LW R and similar VVER technology than with RBMK technology. Accord ingly, the report reflects signifi cant differences in the scope and depth of the research recommendations for the two reactor types; these are more comp lex in the case of VVERs.

Recommendations The report recommends prepara­

tio n of a Na tio nal Sa fety Research Strategie Plan that establishes goals, defines products requ ired of safety research , and desc ribes ho w and when work will be ca rried out.

The RBMK does not have a co ntain ment structure that sur­rounds the reactor system, and it is therefore necessary to rely more on acc ident management for ri sk reduction. ln th e case of slow accident initiators , such as loss-of­coo lant acci dents, there is enough time for accident management to be effective in red ucing severi ty Research is needed to develop simple phys ical mod els and pa rametric codes, based on existing Russian and OECD codes, that describe th e situat ion and thar are use fu l at ind ividual plants for deve lop ing effective accident management pro­cedures . Integral experiments and separate effec ts tes ts are needed to ve rify these codes . Accident ma n­agement is im portant, bu t cann at solve al! problems. lt is not useful in the case of fas t reactivity transients in the RBMK as there is insufficient ti me to take effec tive acti on . ln thi s case, development should focus on preventing or limi ti ng fast reactivity increases .

lt would also es tab li sh research ::3

priorit ies base d on the needs of ~ research users, that is, the regulators, ~ the reactor owner-operato rs, and the .f reactor designer-manu facturers. Such ~ a plan would become the ocgamsing ~ F : ~ -;.:- À-- = ,ç~ pnn c1pl e fo r the sa fety resea rch ~ · · ; _ /,. ~-programm e, and would help to ~ Jf ±

General conclusions Reacto r safety research is a maj or

contributo r to im proving safety. The most important near-term appli ­ca tion of safety research for both the VV ER and RBMK reactors is to establish a sound technical basis for symptom-based accident ma nage­ment procedures to be used by plant staff to prevent or hait the pro­gression of accidents, and to plan for future safety improve ments.

Eastern experts should have the opportunity to wo rk at the cutt ing edge of sa fety resea rch so th ar the re will be no significa nt ga ps in th e transfer of this important technology.

answer the ques ti ons thar fund ing ~ authori ties will ask when they are 3 considering proposais.

The key playe rs in the national nuclear communi ty should be involved in planning and carryin g out the research, and in applying the results to improving sa fety These key playe rs are the government officiais res ponsible fo r energy and safety regula tion , researchers, nuclear plant owner-o perators, and reactor design and constructi on organ isa tions. Th e in volvement of th ese key players is essential to a success ful and useful research programme.

Nuclea r safety is an area of intern ati onal interes t , and one in which international co-operation is ve ry important . Give n the adva n­tages of sha ring knowledge , tec h­nical contri butions, and fu nding, the

report recommends co-operation in reactor sa fety research so as to offer the possibil ity of bringin g together the bes t peo ple and fac ili ti es on a worldwide rather than on a na tional bas is to improve resea rch qu ality Wh ile co-o peration with Eas tern Europea n cou ntries has in creased substanti ally in the last severa! yea rs, and must co nti nue to increase to prevent tech nical isolation in sa fety tec hnology in the future, it is important to po int out thaL total rel iance on internat ional resea rch ca nn at be a subst itULe fo r heal th y, national programmes , whi ch are the prerequisite for strong interna tional co-ope ration.

Finally, there is a large amount of research information available within

NEA Member countri es that is potentia lly applicable to Ru ssian­designed reactors. The report recom­mends fin ding new approaches to info rmation and technology transfer, such as es tabli shing a forum for spec ifie technical tapies with the aim of transferring technology and safety in formation .

Will the study make a difference?

The study identifi es sa fety issues fo r nuclea r power reactors of the W ER and RBMK types. lt points out research findings on reacto rs from NEA national programmes that apply to Russian-designed reactors, and it ident ifi es add iti onal VVER and RBMK-s pecific research thar is

Safety research nee ds for Russian-designed reactors

needed to resolve these safety issues. These are important , bUL they are only the first step in the process, and the question now is what use will be made of them. Fo llow- thro ugh to develop ment of research pro posais, funding of research proj ects, getting work clone, and app lying results to resolving the safety issues are the vital nex t steps The ex perts who contri buted to the study believe thar although the study makes a stan , it is the follow-thro ugh to completion that all of them hope for thar will help to resolve the issues and thereby ensure safe operation of the plants.

A second implica tion emerges from this stud y Identifi cat ion of safety issues is a continuing process, and events thar occur during plant operati on are a major part of

identifi cation lt is prematu re at this rime to conc lude th ar ali the impo rtant safety issues for VVERs and RBMKs have been identified This is wh y it is essential to establish a continuing program me of sa fety review and resea rch as pa rt of the regulatory responsibility fo r safe operation of NlS and CEEC reactors. This type of programme has been, and continues to be, a vital part of sa fety regulation of nuclear power plants in NEA Member countries. •

Note 1. Safe Ly Researc h Needs for Ru ss ian­

Designed ReacLO rs (to be published in Fall/99 7)

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Nuclear energy in relation to sustainable development

One important outcome of the Rio Earth Summit

in 1992 was the United Nations

Framework Convention on Climate Change.

The third Conference of Parties to the Convention

will be held in Kyoto, Japan in December of this

year. The discussion in such international fora of the relationship between

energy and sustainable development has

motivated the N EA to synthesise the results of

recent, relevant work and to make them available

to policy makers.

T he concept of "sustainable development" has many possibl e in te rpretations A Symp osiu m in Oslo in

1994 produced a widely accepted working definition

Th e use of services and related pmducts which respond ta basic needs and bring a better quali ty of life while minimising the use of natural resmtrces and taxie materials as weil as emissions of waste and pol lutants ove r the life cycle of the service or pmducts sa as not ta jeopardize the needs of fu tu re generations

While there can be deba te about what co nstitute "basic needs", the re can be no doubt that energy is one of th em and little doubt that elec tricity is an esse ntial form of energy for many aspects of life in deve loped countries. ln terms of the above defini tion , the challenge is to show that the cu rrent and foreseeab le use of nuclear power generation does not jeopardize future possibilities for the sati sfaction of society's economie and other needs.

The starting poi nt fo r consider­ation is that nuclear reac tors are a we ll- es tab lished source of energy, providing some 17 pe r cent of the wo rld's elec trici ty in 1996. This equates to about 7 per cent of tota l primary energy used in the commer­ciall y traded energy sector. Nuclear powe r reactors are operated in 32 co untri es, in cluding 16 OECD Member countries where some 85 per cent of the world 's reactor capacity of 35 1 GWe is found

* Mr. Geoffrey Steve ns is Head of the NEA Nuclea r Developm ent Divisio n.

Re sources Nuclear energy does use a natural

resource , uranium , for whi ch there is no other significant use. There are large known world resources of exp loitable uranium, amounting to 3.85 million tonnes, with geological modell ing and other indications suggesting that a further ll million tonnes cou ld be available. At current rates of use , and using current ly exploited reactor technology, this would suffice for 220 yea rs. On the assumption that nuclear energy is accepted as playing a role in energy policy responses in harmon y wit h sustainable development , its use would grow, and so would the demand for uranium. Using th e central scenario for nuclear ca pacity growth adopted by the World Energy Council (which envisages a capacity of 1 150 GWe in the year 205 0) , known uranium resources would lasL for 50 years. Using th e already known , but not ye t comm erciall y exploited breeder reactor techn ology would multiply the energy ca ment of the uranium resource base by a factor of 50 to 60. The total ultimate resources of uranium, including th at widely distributed in the ea rth 's crusL and in seawater, is estimated at ove r 4 billion tonnes (see Graphie 1)

Another potential source th at cou ld be used as nuclear fuel in the longer term is thorium ; it is also widely distributed on the planet. lt tao has no major uses other thanas a potential fuel Thorium is estimated to be more abundant than uranium , although not as much exp loration has been clone to identify its

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• Nuclear energy in relation to sustainable development

Graphie 1: Uranium resources and cumulative requirements to 2050

1

Overall resources (million to nnes U)

!. Conventional (15 4 6)

Il. Sea water ( 4 000)

and phos phates (22)

geo logical occ urrence in readi ly exp loitable deposits. The fuel cycle and reacto r technology fo r using thorium has been demonstrated in experim ental programmes.

As with other minin g ind ustries , the extraction of uranium ore has to be perfo rm ed carefull y in ord er to avo id long-term damage to the local and regional environmem. This care was not particularly evident in the earl y stages of uranium min ing, carried out und er the exigencies of milita ry programmes , but the oper­ation and decommissioning of uraniu m mines in recent years has demonstrated that environm enta l pro tection can be achieved.

Only a small proportion of these uranium and thorium resources cou ld be accessed economicall y, but iL would be difficult to argu e that using them for energy purmposes in a safe and well-controlled fuel cycle would "jeopardize the needs of future generations".

3

1

Conventional resources (million tonnes U)

l. Rese rves (2. 2)

2. Other known resou rces (2.39)

3. Other conve nti onal resources (l ü 95)

Necessary conditions for sustainability

2

There is, therefore, a basic case fo r treating nuclear energy as a contrib­utor to sustainable development. ln terms of the Os lo Symp osium defini tion qu oted above , there is concern about the use of toxic mate­rials. These do arise in the course of the operation of nuclear facilities but the response of nuclea r industry and governments is to ensure that the toxicity is isolated from the biosphere or is released in quantities that do not have an impact on human health.

ln addi tion to co nce rns about radioactive emissions during the operation of nuclear facilities and the management of rad ioac tive wastes, the sa fety of plant operation, the eco­nomie competit ivity of nuclear energy and avoiding the spread of nuclear weapons must all be addressed sa tisfacto rily if nuclea r energy is to be an acceptab le contribu to r. The creat ion and

c

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Expected requirements in relation to conventional

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B

A. Cumulative requi rements to 2010 (0 9)

B. Cumulative requirements to 2050 ( 4 l )

C. Uncomm itted resources (10 .46)

prese rva tion of adequate conditions is largely in fl uenced by gove rnments, with the NEA being direct! y involved in the first four of the above areas, and the lAEA dealing with the weapons area .

The gove rn ment ro le extends to prov idi ng a wide infras tructu re of education, regulatory and resea rch in stitu tions and to ensuring publi c supervision of the nuclear industry This necess itates a considerable investment in people with high-level technical qualifications. Manu factur­ing and service industries , capable of prov iding an d maintaining high quali ty equip ment, are also needed to ensure co ntinued good perfo r­mance by the nuclear power industry. ln OECD countries these elements of infras tru cture all developed ou t of governm ent activities . The NEA studies the government role in pre­serving adequate infrastructure. The work of the NEA also covers the first fo ur points above by aiming to assist

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Nuclear energy in relation to sustainable development

governments in crea ting the co n­ditions under whi ch they and the public can have co nfidence in the co ntinuee! use of nuclear energy

Radiation protection Ali operations in th e nuclear fue l

cyc le are carri ed out with in the fram ework of regulations that ensure th at d isc harges of rad ioact ivity or

Uranium mining at the Rabbit Lake Operation , Canada.

other pollutants to the environment are kept below levels where health risks mi ght ari se. The work of the

EA on rad iation protection has helped governments to implement , in a practicable mann er, the scienti fic recommendations for the avo idance of emission levels thar cou le! lead to unacceptable risks to health. The Agency's wo rk also enhances the dissemination of good practice in

radiat ion protec tion , bot h among regulators and within th e nu clea r industry

Radioactive waste a t

ln thi s fi eld the NEA has co n­centrated its efforts on the develop­ment of methods of ana lys ing the expected performance of repositories and assoc iated technology for th e

conditioning and dis­posa! of highl y radio­active and long- li ved waste. The exchange of information and the ca rryin g ou t of joint studies between Mem­ber co untri es, in clud ­ing , for exa mpl e, studies on natural analogues for deep geologica l reposito ­ri es, has led to the publication of interna­tional consensus opin ­ions such as that on the methods of eva l­uating the safety of such repositories. lt is a feature of these con­sensus op ini ons thar they are subsc ribed to by countri es tha r have no nucl ea r powe r plants as well as by co untri es where nuclear power plants are opera red.

The stud y of the tec hn ica l safe ty of nuclear insta llations is the subj ec t of a ve ry valuabl e exchange within committees and working groups of the NEA. Technical infor­mation nows freely to enable ali countries to benefit from the research and oper­at ional expe ri ence of oth er Member

• Nuclea r ene rgy in relation to sustainable development

Graphie 2: C0 2 emissions from electricity generation by different sources

14 00 1400

(g rammes of C0 2 equi valent/kWh)

1200 --- 1200

1000 1000

800 D ---- 800

GOO D 600

400 400

; ": = D ... .... ,, " 0 Nuclear power Renewable sources Natura l gas Oil Co al g ~

:5 ::; Note: The ra nges correspond to di ffere nces in genera tion technology for the sa me primary source.

count ries . Senio r nuclear regulators from Member countries have their own committee and regularly discuss options for improving the effect ive­ness of nuclear regulation, as well as issuing consensus opinions con­cerning their approaches.

Economies of nuclear energy

The futu re co mpetitivity of n ucl ea r energy in bath developed and developing countri es will depend in the medium tenn on the course of fossil fue l priees and the means adopted to reflect the external costs associated with their use. Studies over the last decade or so indicate that for man y co untries a ve ry moderate increase in fossi l fue l pri ees woul d render nuclear energy competitive , if it is not already so. A major conclusion reached in the course of the N EA's wo rk is tha t there are no significant externa l costs associated with the use of nuclea r energy, with back-end costs and decommissioning being funded from current revenues. This is a conclusion th at has been supported in man y other studies outside the OECD.

Low environmental impacts

Nuclear generation is one of two techno logies (the other is hydra­power) that provides bulk supplies of electric ity without causing the release of gases or particles th at produce environmental degrada tion such as ac id ra in , urban smog, or depletion of the ozone laye r. Green­house gas emissions from the nuclear fue l cyc le are of the arder of 25 g/kWh compared with some 450 to l 250 g/kWh from foss il fue ls. Therefore, replacing nuclear gener­at ion capacity by generation based on foss il fuels would entai! an increase in these emi ssions. Doing this across the world would result in increasing the carbo n diox ide emiss ions of the wo rld 's energy secto r by about 8 percent. Even in comparison with the complete fuel cycles for renewables, as has been shawn in studies by a numb er of independent institutions, the nuclear fuel cycle, from mining through to final decommissioning of nuclear plants and disposai of was tes , is relatively benign in its effec t on the environment (see Graphie 2)

Broader considerations

Produ cti on of elec tri city from nu clear plants is appropriate for relative ly large distribution grids. This is not a constraint on its use in OECD countries but could be else­where. Furthermore, its exploitation calls for a high degree of technical co mpetence in the associated industries and regulatory bodies. The acquisition of this competence, and the rigo ur that co rn es with nuclear technology in matters of qu ality assurance and safety regul ation can in themselves be very valuable to the development of an industrial econo­my, as has been seen in the evolution of nuclear energy in severa! OECD countries. These spin-off benefits can be significant. However, to acquire these and the direc t be nefits of nuclear energy does require a long­term commitment to this form of generati on . For that there needs to be acceptance by public and political opinion that the advantages, includ­ing effects on the long-term security of supply, outwe igh the risks. The aim of the NEA' s wo rk is to ens ure that governments are full y informed of this balance. •

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Nuclear liability and insurance in Russia

One of the consequences of the Chernobyl

accident, and the break­up of the Soviet Union a few years Later, was the

establishment of a programme of

co-operation and assistance between the

East and the West on matters of nuclear safety.

lt was understood, however, that unless and

until the countries of the East established a proper

Legal framework within which those co-operative

activities could be carried out, progress on

improving the safety of many of their existing

nuclear power plants would be difficult.

A co rnerstone of this legal framework is the adop­tion of national legis­lat ion pro viding for

liability and compensa tion for damage in the even t of a nuclea r incident , and adherence to the international nuclear liability regime which provides for co mpensa tion in case of damage in more than one country The Declaration emanating from the 1996 Moscow Summit on Nuclear Safety and Security addresses the issue of nuclear liabili ty with the following statements

An effective nuclear liability regime must assure adequate compensation ta victims of, and for damage caused by, mtclear accidents. In addition, ta secure the degree of private sector involvement needed ta undertake vita l safety improvements, the regime shmdd at the same time protect industrial Sttpplie rs from unwarranted legal action.

The essential princip/es in this arca are the exclttsive and strict liability of the operator of the nuclear installation and ensuring needed financial security for adequate compensation

1t is esse ntial that countries with nuclear installations that have not yet donc sa es tab!ish an effective regime for liability for nuclear damage corre ­sponding ta these princip/es

It is important ta work together on enhancing the international regime of liability fo r nuclear damage with a view ta ensuring that it will attract wide adherence and accommodate any state which may wish ta become a party. We encourage the experts ta make fttrther progress ta this end. ln this connection, the rei nforcement of regional co-operation is welcomed

For se vera! years now, western governments and industr y ha ve expressed strong interest in enco ur­aging the Russian authorities to adopt legislation renectin g th e principl es set forth in the Declaration, to adhere to the international nuclear liability regime by joining the 1963 Vienna Convention on Civil Liab il ity for Nuclear Damage and the j oint Protocol of 1988 relating to the Application of the Vienna Convention and the Paris Convention , the two basic conventions govern ing nuclear liability. They have also encourage e! the Russian authorities to establi sh effective mechan isms by whi ch liability for nuclear damage ca n be covered by insurance or oth er forms of financial security. They have cl one so , not only because they believe it is essential to the future existence and further development of nuclear energy utilisation , but beca use iL is a necessary prerequisite to progress in the East-West programme of nuclea r safety co-operation and assistance .

Partly in response to this enco ur­agement , Russ ia adopt ed general legislation on the uti lisation of nuclea r ene rgy in 19951 Howeve r, it has yet to implement legislation dealing specifically with liability and compensation for damage caused by a nuclear incident , or legislation dealing with the es tablishment of insurance or other forms of finan cial security to guarantee payment of that compensation. While it is true that va rious drafts of such legislation have been proposee! by the Gove rnmem of the Ru ss ian Federat ion ove r th e

* Ms. juli a Sc hwa rtz is a mcmber of the NEA Legal Affa irs Sectio n.

lasL two years, none has refl ected all of the basic prin ciples requirecl to bring th e Russian legislative regime in Lo alignment with the existing internati onal regime.

ln add ition , although Ru ss ia signee! the 1963 Vienna Co nve nti on on Civil Liability for Nuclear Damage on 8 May 1996, it has not yet ratifi ed th at conventi on. Nor has it expresse cl any intention ofbecoming a member of the 1988 joint Protocollinking the Vienna and Paris Conventions.

Given th is state of affairs, western cont ractors have ex pressed relue­Lance , if no t outright refu sa!, to unclenake nuclear safety co-operation and assistance activities that involved on-si te wo rk at Ru ssia n nuclea r power plants. While act iviti es such as engi neering studies, staff traini ng, the Lransfe r of limitee! amounts of Lechnology and the supply of certain types of equipment mi ght be uncler­taken without incurring un ma n­ageab le liab il ity ri sks on the pa rt of western contracto rs, in the absence of a co mprehensive li ab ili ty and

• Nuclear Liability and insurance in Russia

compensat ion regime in place, either nationally or internationally, western contrac tors cou le! not ass ume the potentially enormous ri sks attachee! to carrying out "hands-on" work on Russian reactors, such as the actual installation of equip ment.

ln an attempt to allev iate the impasse, a num ber of agree ments were enterecl into pursuant to which the Government of the Russian Fede ration und ertook to indem­ni fy wes tern contractors (and sub- contracto rs) agai nst loss or damage to their on -site property and aga inst liabili ty arising from third party d aims for damage in the event of a nuclear incid ent arising in connection with work cl one at a Russian nuclear install at ion. These includecl an agree ment between the Russian Federati on and the Gove rn­ment of the United States in 1994, then anoth er between the Russian Federation and th e Euro pea n Co mmi ssion in 1995, and fin ally an agreement belwee n th e Ru ssian Federation and the Europea n Bank

for Reconstruction and Development (EBRD) that same year covering work to be cl one at speci fi c nuclear power plants and to be fun ded by the EBRD­manage d Nuclear Safety Accoun t. These agree ments were viewecl at the tim e as th e best protec tion contrac tors could hope for, but the fac t of the matter was th ar the best simply was no t good enough for many contracto rs who continuee! to fea r the potenti all y ove rwhelming risk of thire! party nuclear damage claims being macle against them from outside th e Russian terri tory, and in so me cases even fro m within .

lt was aga inst this background thar a three- cl ay international se minar on Nuclea r Li ab ili ty and lnsurance Iss ues in Ru ssia too k place in Moscow in mid -A pril 1997.

From left to right: Dr. Y. Vishnevsky, Chairman , Gosatomnadzor; Dr. V. Nersesyan, Armenian Nuclear Regulatory Authority; Dr. A. Zhokin, Deputy Chairman , Gosatomnadzor; and Mr. P. Reyners, Head of Legal Affairs, NEA.

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Nuclear liabi lity and 1nsurance 1n Russia •

The mee ting was co -sponsored by the NEA, by Gosa tomnadzor (the Russian nuclear regulatory age ncy) and by the lnsurance Department of the Russian Ministry of Finance . The date fel! just bef ore the fi rst anniver­sary of the 1996 Moscow Summit , an event which itself co incided with the ten-year commemoration of the 1986 accident at the Chernobyl Nuclea r Powe r Plant. The NEA has been involved for severa! years in pro­vi ding nuclear sa fety co -operati on and assista nce to Russia, and it has also prov ided assistance in the devel­opment of their domestic legislation in the nuclea r fi eld . The Age ncy thus welcomed this offe r to parti ci­pate in what was seen by many of its Member countri es as a fu rther opportunity to ass ist both the Government of the Russian Federation and the evolving Russian insurance industry to meer the obj ec ti ves set forth in the Summit Decla rat ion.

Fo r th is reason , other inter­nat ional orga nisa tions who have ac tively su pported the NEA's efforts to promote and to strengthen nuclear liability regimes in the countries of Central and Eastern Europe - the International Atomic Energy Agency (IAEA), the European Community (EC) and the EBRD - were invited to participate in the seminar. Other representatives from the West who attended the seminar include d nuclear law ex perts from severa! NEA Member co untries toge ther wi th representati ves from both American and Eu ropean nuclea r insurance pools. From the Russian side, the seminar attrac ted senior­leve! representati on not only from Gosatomnadzor and the Ministry of Finance, bu t also fro m the State Duma (the Russian Parliament), the Federal Asse mbly of the Ru ssian Federati on and the Ministries of Atomic Energy (Mi natom); Foreign Affairs; Eco nomies; and Civil Deferr ee, Emergencies and Mitigation of National Disasters. Representatives of other agencies and of the major in surance co mpanies ope rating in

Russia today also too k part . Finally, there were a small number of repre­sentatives from neighbouring states, such as Ukraine, Kazakstan, Armenia and Belarus.

The obJeCti ves of the seminar were to assess the potential benefits which the Russian Federation would derive fro m joining the in ternational nucl ear li abili ty regime, from adapting its domeslic legis lation to correspond to the principles embod­ied in thar regime and to es tab lish ap propriate nuclear insurance struc­tures, such as a nat iona l nuclear insurance poo l, to provide financ ial securi ty for the liability to be assumed under thar regime.

The seminar was divided into three sess ions, the first of which addressed in te rnational principles of nuclear liability and the current state of rela ted legislat ion in the Ru ss ian Federat ion. This session includ ed presentations and com­mentary on the Russian draft law on Com pensation for Nuclear Damage and Nuclear Risk lnsurance , and on the re lat ionship between the ob li­gati ons called for under the Vienna Conventi on and the provisions contained in Ru ssia 's proposed legislation on nuclear liab ility The representati ves from the weste rn nuclea r insurance poo ls also commented on the need for Russia to implement appropriate legislation before any meaningful collaboration co uld take place betwee n nuclear risk insurers from the East and the West. Fo r th ei r part , th e Russian offi ciais info rmed se minar partic­ipants thar the Government intended to submit the draft law on Com­pensation for Nuclear Damage to the Duma shortly and thar a draft law allowing for th e ratifica tion of the Vienna Co nve ntion wo uld also be submitted in the near future. Furtherm ore, to the extent that the current version of the draft law does not co rres pond fully with Russia's obli ga tions und er the Vienna Convention, the Government of the Ru ssian Federation exp ressed it s

intention to amend that legislat ion, but only after ratifi cat ion of the convention.

Also co vered during the first session were recent developments in the international nucl ear li abili ty regi me, such as th e proposee! revi­sion of the Vienna Co nve ntion and the adoption of a Supplementa ry Funcling Convention to provicle an additionalleve l of fundin g for the compensa tion of nu clea r damage, togeth er with Russia's views on the propose e! modernisa ti on of th aL regime lastly, the issue of indemnity agreements was aclclressed , with particular emphasis being placed on the need for the Government of th e Russian Federati on to es tabl ish inclemnity arrange ments acce ptable to western contrac tors cluring the in terim period when there is insufficient capacity in the Russ ian insurance market to cove r the nuclear ri sks to be assumed by th ose contractors.

The second session focusecl on the ways and means by which nuclea r risk could be insu red by the Russian insurance market, recognising tha L a finan cially stable and cohes ive insurance market is an essential pre­condition to establishing reinsurance arrangements with the wes tern nuclear insurance pools. lt must be remembered thar the Ru ssians cons icler the organisation of their nuclear insurance sector as an essen­rial element in the preparation and implementation of their clraft Law on Compensation for Nuclea r Damage and Nuclear Risk lnsurance. lt must also be borne in minci that under this clraft law, insurance companies wishing to prov icle financial security for nuclear ri sks must seek approva l from the Gosatomnadzor

During this session, presentations were given by Russian represe n­tatives from both the gove rnm ent sector and the (private) insurance incl ustry Topics covered includecl the basic ap proach to be adoptee! by the insuran ce industry in provicl ing nuclear risk insurance, the methods

• Nuclea r liability and insu rance in Russia

The Electrogorsk Research and Engineering Centre, near Moscow, is the host of a la rge-scale nuclear safety test facil ity for VVER-1000 reactors, which receives assistance through an International Support Group sponsored by the NEA.

of evaluating and limiting nuclear ri sks at particular types of nu clear installations and the maJor principles pursuant to which a Russian nuclear in suran ce pool could be organised. On this last point , a presentation give n by representatives from the Czec h insurers on their recent experience in estab lishing a nuclear insurance pool was considered parti­cularly helpfuL ln addition, the issue of developing appropria te insurance cove rage for facilities and personnel under the Jurisdiction of the Ministry of Atomi c En ergy, th e particular conce rns of Rosenugoatom (th e operator of most nu clea r power pl ants in Russia) with regard to

nuclear ri sk insurance, and fina lly, the rol e that might be played by an insurance broker in insuring nuclear insta ll ations in Ru ssia were also addressed.

The third session emphasised the fin ancial aspects of putting nuclear ri sk insurance into place for Russian nuclea r installations. An interesting example was given by a represen­tative of the Uk rai nian Nuclea r lnsurance Pool who spoke about the nuclear ri sk insurance experience in thar country and the recent creat ion of their pooL Presentations were also made on th e development of

methods for evaluating radiation and nuclear risks, and the damage resulting from a nu clear incident either at a nuclear install ation or in the course of transportation of nuclear substances.

Oth er issues add ressed in th is session were the growth and capacity of the nuclear risk insurance market in Ru ssia, including prospects for coll aboration with western nuclear insurance pools. On this point , it was noted th ar there are something like 2 500 insurance companies registered to do business in Russia, although it is acknowledged that only about lOO of such companies carry out between 50 and 60 per cent of ail in surance transact ions in the countr y. Tradi­tionally the largest of th ese ca mpa­nies is lngosstrakh lnsurance Co Ltd., an insurance company thar predates the break-up of the Soviet Union and that appears interested to establish a Russian nuclear insurance pool and to collaborate with foreign partners. However, in recent years other insur­ance co mpanies such as Vesta and Maks have equally demonstrated an interest in tackling the nuclear risk arena . Nevertheless, it was openly ack nowledged that no matter how ambitious or anxious these ca mpa­nies might be to get into the nuclear

ri sk fi eld , they have limited capacity and are co nsequently still sorne distance from establishing a national poo l which co uld attract inter­nati onal re- insurance support .

The representatives of the western pools made it clear during the seminar that they were well aware of the importance for Ru ssian nuclear insurers of obtaining western support for the development of the domestic nuclear insuran ce market. However, they also made it quite clea r that , given the absence of comprehensive nuclear liabi lity, compensation and insurance legislation in Russia, the limitee! ca pacity of the existing insu rance companies in that country, the Jack of an es tablishecl Ru ss ian nu clear insurance pool , and the technical uncen ainti es associated with the sa fety of particular Russian nuclear power plants, it might take sorne time before th ey coule! partici­pate in the cove rage of nuclear risks in that country.

ln the view of both the organisers and the participants the goals of the seminar were accomplishecl , in large measure due to the high quality of presentations which were made, the opportunity to learn from the expe­riences of others and the frank exchange of views which took place on ali of the issues aclclressed during the co urse of the three sessions. lt remains to be seen , though , to what extent the information provided and op inions expressed will be refl ected in substanti ve actions by the Russian Duma in ratifying the Vienna Conventi on and in adopting appropriate implementing legislation, as weil as by the country's insurance industry in es tablishing a Russian nuclea r insurance pool and in being abl e to attract th e support of the international re-insurance community. •

Note 1 The Fedual La w on th e Utili sat io n of

N uclear Energy was sig nee/ by Pres ident Yeltsi n on 21 Novembe r 1995 and ente re d into fo rce on 28 Nove mber 1995 .

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Technical achievements and significance of the RASPLAV project

T he NEA has established a number of "autonomous" or joint proj ects in the fi eld of nuclea r safety

direc tly benefiting parti cipating Member countries . The Sta tute of the NEA specifically provides for such international collaboration projects , co-ordinated by the Agency, which enable intere sted Member countries to pool their resources in pursuit of specifi e research obj ec ­tives . I wo previous proj ec ts con­cerning Three Mile Island involved analyses of samples of the fuel debris and the reactor vesse! itself. Another, the OECD LOFT Project, involved studying transient behaviour in simulated loss-of-coolant accidents in pressurised water reactors. The ongoing OECD Halden Reac tor Proj ect involves the investigation of reactor fuel , material beha viour, incore instrum entati on, and man­machine systems. The lates t such project, the RASPLAV Proj ect, is a major innova tion because it is th e first 0 ECD-sponsored JOint nuclear safety research proj ect to be ca rried out in a non-OECD Member coun­try Ru ss ia. This projec t, which exa mines the potential for externat cooling to maintain the integrity of the lowe r head of a reactor pressure vesse! during a core melt accident , opens up the possibility for carrying ou t other such projects in non­Member countries.

The OECD RASPLAV Project officiall y began in july 1994. The Project agree ment was ratified by 14 OECD Member countri es (Belgium , Canada, Finland , France , Ge rmany, ltaly, j apan , Korea , the Ne therlands , Spain , Sweden , Switzerland , the Uni ted Kingdom and the United States), and by Russia Since then , the Czec h Republic and Hungary have become Members of the NEA, and have subsequently joined the RAS PLAV Proj ect. The operating agent is the Kurchatov lnstitute in Moscow.

The agreement called for a series of integral tests with prototypic core materials and with molten salt as well as small er-scale separate effect tests to measure material properti es and expl ore other phenomena of interest. The du ration of the project is three years. The obj ec tives of the proj ect are to perform confirmatory experiments with prototypic mate­rials (i.e. reactor materials under very high temperatures) and with molten sa lt to measure the heat loads to the reactor pressure vesse! (RP V) under severe accident condi tions , and to assess the effects of materials interactions under these conditions. This information is important to the develop ment of accident manage­ment strategies dea ling with the retention of a molten core inside the RP V The results of the project are also usefu l for other aspects of severe accident man agement , such as increasing knowledge abo ut the relocation mechanisms of the molten

corium into the lower head , and the behaviour of corium aft er it has penet rated the RPV wall .

Iwo large-scale (200 kg) integral corium tests have been performed along with two smaller- scale (12 kg and 40 kg) corium tests. Ten integral tests using molten salt and nu merous small-scale ex perime nts to measure material properties and materia l in terac tions have also been con­ducted. As a result of the success of the first large-scale integral corium test , interest has been expressed in extending the project beyond its current expiration date to further enhan ce our und ers tanding and co nfidence in working with real reac tor materials, including the exploration of additional phenom­ena (e.g. strati fica tion) and pa ra­meters (e .g. corium compositions) not included in the fi rst test se ries .

How weil have the genera l pro­gramme obj ectives be en met 1 First, in terms of the exa ct number of large-scal e (200 kg) tests of corium initially planned , the programme fell short of its objectives , even though it can be argued that of the total number of five tests envisioned , four will have been completed by 30 june 1997, although two of them of smaller scale. The original goal of a Rayleigh number of 1016 for the salt tests was also not met. To a large degree the reduced number of large­scale corium tests was the result of more ex tensive preparations th an

* Dr. Alex Miller is a member of the NEA Nuclea r Sajety Divisi on.

origi nally envisioned , includ ing exploring differ­ent heating methods and structural materials, as weil as the development of high­temperature instrumen­tation. Howeve r, these more ex tensive prepara­ti ons res ulted in the success of the fi rst large­sca le tes t and will help ensure th e success of the rema in ing tests. ln addi­tion, an extensive data base of material properties and information related to mol ten corium technology has bee n produced. Acco rdin gly, the pro­gramm e has met exceed­ingly weil a numbe r of impo rtant objectives asso­ciated with the issues of in­vesse! retent ion of a molten co re. Among these are:

• experience in handling and working with rea l material under relevant co nditions, this being th e only way to und er­stand these materials, and this has no t hap­pened before;

• a substantial increase in ou r understanding of reactor-type material interactions and our a bi 1 i ty to control the se interactions under the relevant conditions;

• th e measurement of materia ls properties up to the relevant co nd i tians;

• the determining of heat transfer behaviour in regim es ranging from conduction , to melting and mixing, to as high a natura l convection regime as possibl e;

• the providing of additiona l confide nce and perspective regard­ing the ability for in ­vesse! retention of a degraded/molten co re.

• Technical achievements and significance of the RASPLAV project

Experimental section of RASPLAV-AW-200.2. Arrangement of C-22 briquettes before the test.

Experimental section of RASPLAV-AW-200.2. View of the ingot after the test.

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Technical achievements and significance of the RASPLAV project •

Specifie technical achievements of the RASPLAV project

The RASPLAV proj ect's technical achieve ments fall into two broad categori es: those assoc iated with the development of unique tes t capabi liti es, and those assoc iated with condu ctin g experiments and measuring physical properties

Unique tes t capabilities

• the development of a heating tech­nique and of structural materials to contain molten co rium at temperatures up to 2 sooc and to es tablish and maintain natura l convection in the molten corium;

• the development of instrum en­tation capable of wo rking for extend ed periods of time at the test temperatures;

• the develop ment of tes t equip ­ment capable of measuri ng the phys ica l properties (e.g. thermal co ndu ctivit y, viscosity, etc.) of molten corium ;

• th e deve lopment of ana lytica l tools to help in th e design of the tes ts, as we il as to predict tes t results;

• the training of a team of people capable of designing, anal ys ing and condu cting such a tes t programme.

Experimental measurements:

• physica l property measurements of various molten corium compo­sitions with va rying degrees of zirconium oxidation;

• material interaction tests between molten corium and various struc­tural materials;

• heat transfer rate to the RPV test wall (as a function of angle) under natura l convection conditions using molten corium of uniform composition;

• heat transfer rate to the RPV test wall (as a function of angle) un der natural convec tion , with cru st formation on the boundary, using molten salt that can be compared with and used to extend the range

of th e test data from the corium experiments;

• post-tes t examination of the 200 kg corium test;

• post-test anal yses to determine chemical reactions between melt constituents and between the melt and the vesse ! wall. (T his is to establish thar chemical reactions in no way limit the potential of long-term retention of melt inside the vesse! with externat cooling. )

These technical achievements are of maJor significance in redu cing uncertainties and confirming the validity of using ex-vessel flooding as a means of retainin g a molten reactor core in the RPV They have also advanced the state-of-the-art in experimental capability to conduct and control experiments wi th rea l materials under prototypica l condi­tions (e .g. hi gh temperatures). As such , the RASPLAV facilitie s and experiments are first-of-a-kind , unique facilities that have provided , an d co ntinue to prov ide, data tha r cave r th e range of conditi ons of interes t (corium composition, tem­pe rature, etc) This will all ow safety decisions on the viabili ty of retaining molten core material in the RPV to be taken with a high degree of confidence The significance of the technical achievements includes :

• obtaining heat transfer data based on measurements with real mate­rials at high temperatures;

• experience in working with real · materia ls so as to uncover any new phenomena thar may not have been uncovered in previous experiments with simulant materials;

• experience in working with real materials so as to determine the extent , if an y, of chemical interac tions between corium and the RPV; such chemical inter­actions can only be obtain ed with real materials at prototypi c temperatures;

• direc t comparison of the hea t transfer rate obtained from corium ex peri ments wi th thar obtained

fro m salt expe riments, so asto extrapolate data to full-size reacto r conditions.

In addition, the act ual materia l properties data thar have been measured will improve the capabil ity to analyse a fu ll -scale reactor. The fa cili ties and a team of dedi cated experi mentalists and analysts with the capability to explore the range of co nditions of interest have bee n assembled, so that all remaining open questions can be addressed.

The limited amount of results so fa r are in broad agreement with simulant experiments and have not revealed any new phenomena. However, they do not caver impor­tant aspects such as strat ifi cation, which cannat be represented in simulant experiments. The success of the initial simpl e experiments, together with the development of successful melt technology, provide a good basis for moving on to more complex experiments involving, for instan ce, melt stratifica tion.

Discussions have started on a possible fo llow-up RA SPLAV pro­gramme to further our expe rience and understanding in working with real materials. The follow-up wou ld focus on:

• the effects of the diffe rent coriu m compositions;

• the potentia l for , and effec ts of, ma te rial stratification;

• the effects of variations in bound­ary conditions (e.g. top surface heat removal).

The effects of material inhomo­geneities (e.g. crust formation , and the possible consideration of a metal layer) should be studied using molten salt simulant at reactor scale Rayleigh numbers 10 16 to avoid the need to extrapolate data. Therefore, a follow­on RASPLAV programme could build up on and take full advantage of capabilities developed in the initial phase to fu ll y explore the phenomena of interest and provide relevant information to address the remaining un certa in ties associated with in­vesse) retention of a degraded core. •

M.C. Brady, J.B. Briggs, E. Sartori *

Nuclear criticality safety A subject of growi ng international importa nee

N uclear Criticality Sa fety was established as a discipline more than 50 years ago, in response

to severa! acc idents that had occurred in nuclear weapons programmes. The number of documented critica lity accidents in "Western" facilities over this period is slightly under 50 . Informat ion has recently been published concerning accidents that occurred in the ex-Soviet Union and more data is in the process of being released About 20 per cent of these acc idents occurred in production plants, 10 per cent in wo rking reactors (Chernobyl being the best­known and the most d ramatic accident ) and the remainde r in crit ical facili ties where the properties of th e assemblies themselves were being investigated. The rate at which these accidents occur has strongly decreased over the years. Such events have now become very ra re.

The importance of the safe han­dli ng of all fissile materia ls was recognised at an early stage both by the scientific com mun ity and the responsible authorities. At the begin­ning, intensive experimentation with a large variety of con figurations and materia ls took place in order to establish a basis of knowledge of su ch sys tems. At the time , computa tional methods and basic nuclear data were either not yet properly developed or had not reached su fficient sophisti­cation to reliably pred ict the critical status of fi ss ile materials.

Over the years, substantial expe­ri ence has been gained in both experimentation and in data and code development. This state-of-the­art knowledge in criticality safety also hasan economie impact. The reduc­tion of uncertainties in safety margins allows improved and more economi­cal designs for manipulation, storage and transportation of fi ssile materials.

New fu el cyc les, handli ng of excess fi ss ile materi als from the weapons programm es and its poss i­ble use for civil energy applica tions make new demands on method deve lopment , experimentation and regulations.

This art icle briefly describes the work carried out by the NEA in thi s field and outlines perspectives for the future.

Overview of activities The following activities have been

carri ed out by the NEA on reactor fuel cycle safety

• A publica tion entitl ed The Safety of the Nuclear Fu el Cycle 1 gave a general overview of the safety is­sues and procedures in Member countri es . lt also included a chapter on regulatory issues .

• An incident reporting system specifie to significant events from the fuel cycle has recently been set up FINAS (Fuel Incident Notifi­cation and Analysis System).

• An international working group carries out a work programme on cri ti cali ty safety

Criticality safety Work has concentrated on th e

follo wing studies of interes t to Member countries :

• criticality of nuclear fuel packages for transportation and storage;

• criticality of fu el und ergoing dissolution for reprocessing and partitioning;

• burn-up credit criti cality;

• ex perim ental data relevant to criticality sa fety

Criticality of nuclear fuel packages

A first study examined the ability of various computational methods to acc ura tely compute criticality for sys tems which have been measured as experimentally critical. A proce ­dure which evolved from this work allows to assess wh ether a given co mputational meth od produces "valid" results. Thi s procedure prov ides a basis for acceptance of computationa l results by regulatory authorities on an international basis.

Critica lity of fuel undergoing disso lu tion

Eighteen experimental configura­tions were studied. ln addition three calcul ational benchmarks on criticality codes for dissol ving fi ssile oxides in acids have been completed.

* Dr. Mi cha ele Brady worh s for Sandia Nati onal Laborator ies (Albuquerqu e, New Mexico, USA ) and Mr Bla ir Briggs fo r th e Idaho Nati onal En gi neer ing & En vironm ental Laboratory (Idah o Fall s, Idah o, USA) Dr. Enri co Sartori is a member of th e NEA Nuclear Sc 1en ce Di vision/ Da ta Banh.

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Nuclea r criticality safety •

A part ic ularly difficu lt prob lem proved to be th e trea tment of fuel double heterogeneiti es (so lid fiss ile material surroundecl by fissile materia l in so lution). A refe rence calculationa l method for this type of problem was identifi ee! and adopted.

Burn-up credit Burn-up cred it is a term that

applies to the reduction in reactivity of burnecl nuclear fu el clue to the change in composition cluring irradi­ation. Co nve nti ona l reactor codes and data used for in- co re ph ys ics ca lculations can be usee! to evaluate the criticality state of bu rned , light water reactor (LWR) fu el. However, these codes in volve comp li cated moclels and have large computat ional and data requireme nts. ln reactor applications, these detai lecl ana lyses are requirecl for the efficient opera­tion of specifi e reacto rs. ln away­from-reactor ap plicati ons such as the design of casks (fl asks) for the transportation of spent nuclear fuel, the candidate fuel for use in the cask may come from any reactor and it is desirable that the des ign all ow for the inclusion of as much of the existing and expected fuel inventories as safely possible. ln other worcls, for reactor operations the obj ective is to

use most effectively very specifie fuel in a speci fie app licat ion. For away­from-reactor applications the obJeC­tive is a genera l design for a wid e variety of fuels 2

Traditi onall y, es tablished away­from-reactor codes have been used for applica tions such as the design of storage and transportation (S/T) casks. ln this type of analysis, the fuel is usually assumed to be at it s full initial enrichment to provide a large safe ty margin for criti ca lity safety analyses. The incentives for pursuing burn-up credit over the current , fresh fuel approach are widely recognised the approach can extend enrich ment limitations for exist ing S/T ccntain­ers, and may contribute to the development of higher capacity S/T systems that wo uld result in fewer fuel shipments and therefore decreased risk to the public There is also potentia l applica tion to criticality safety in dissolvers for fuel reprocessing as we il as fo r timely and efficient tra nspo rt to and from reprocessing fa cilities .

However, before such an approach ca n be approvecl by licensing agencies , it wou ld be necessa ry to demonstrate that the available criti cali ty sa fety ca lculat ional tools are ap prop ri ate for app licat ion to

burned fu el sys tems and that a reasonable safety margin can be established. To this end , a suite of burn-up credit criticality benchmarks have bee n established by the NEA . The benchmarks have been selec ted to all ow a comparison of results among participant s using a wide variety of calculational too ls and nuclear data se ts. The nature of the burn-up credit problem requires that the capability to calculate both spent fuel composition and reactivity be demonstrated. The benchmark prob­lems were selected to investigate code performance over a variety of physics issues associated with burn-up credit as described in Table l .

The focus here is the co mpari son of the results submitted by each participant to assess the capability of comm only used code systems, notto quantify the physical ph enomena inves tigated in the compari sons or to make recommendati on s fo r licensing ac tion. Participants use a wide va ri ety of codes and meth ods using both deterministic and stochas­tic (Monte Carlo) techniques. Nuclear data were taken from seve ra! sources - the Evaluated Nuclear Data Files (ENDF/B), the japan Evalua ted Nuclear Data Libraries UE NDL) and the j oint Evaluated Files UEF).

Table 1: Summary of recent burn-up credit, benchmark problems addressed

Benchmark

Phase I

Phase Il

Phase III

Phase IV

Phase V

Primary obj ective

• Examine effec ts of 7 maj or actinides and 15 major fi ssion products for an infinite array of pressurisee! water reacto r (PWR) rods at different burn-ups and cooling times .

• Compare computed nuclide concentrations for depletion in a simple PWR pin-cel! mode! to actual measurements at different burn-ups.

• Examine the effect of axially distributed burn-up in an array of PWR pins as a fun ction of initi al enrichment , burn-up and cooling time.

• Repeat study in a 3-D geometry representative of a conceptual burn-up credit transportation container.

• lnvestigate the effects of moderator vo id distribution in addition to burn-up profile, initial enrichment , burn-up and coo ling time sensitivities for an array of boiling water reactor (BWR) pins.

• Compare computed nucl ide concentrations fo r depletion in a BWR pin -cel! mode!.

• ln vestiga te burn-up credit for mixed oxid e (MOX) spent fuel.

• ln vestigate burn-up credit in subcritical systems.

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Experimental data relevant to criticality safety

ln support of evalua tion and validation of methods for cri tica li ty sa fety, seve ra! databases have been established

Spent fuel isotopie compos ition database

A da tabase of light water reactor (LWR) spent fu el assay data that has been compiled and contains isotopi e inve nto ry data coll ec ted from 13 LWRs, incl uding 7 pressuri sed water reactors (PWRs) and 6 boiling water reactors (BWRs) in Europe, the United States and j apan as well as axial burn~up profiles.

International handbook of evaluated criticality safety benchmark experiments

This handbook (lCSBEP) contains criticality safety benchmark spec ifica~

tions that have been derived from experiments tha t were perfo rmed at va ri ous nuclear critical faci liti es

• Nuclear criticality safety

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around the world . The benchmark specifications are intended for use by criticality safety engineers to va li date calcu lational techniques used to establish minimum subcritica l mar~ gins for ope rations wi th fi ss il e material At prese nt the handbook compri ses l 000 critical co nfigura~

tions and is ava ilable both in hard copy and on CD-ROM 3

Criticality benchmark experiments

There have been seve ra! activities that involve experiments applicable to burn~up credit

• exponential Experiments in the Tank Typed Critical Assembly (ICA) of JAE Rl ;

• intern ational CERES Exper i~

mental Program designed for the va lidation of cross-section data and inventory predictions for ac tinides and fi ss ion products (France, UK and USA);

• fi ssion Product Experiments by the Institut de protection et de sûreté nucléaire (IPSN) , France;

• a set of experiments proposed by th e United States called Spent Fuel Safety Experiment (SFSX) to provide integral benchmarks for validating spent fuel reactivity;

• experiments on waste matrix materials planned at the Los Alamos National Laboratory, USA and at the lnstitute of Physics and Power Engineering, Obninsk, Russian Federation.

Working party on nuclear criticality safety

During a recent experts meeting on Needs for Critica l Experiments, it was concluded that , in view of the limited number of operational critical fac ilities and the international scope of th e needs for critica lity sa fety technology, the NEA should encour~ age the performance of new critical meas urements on a multi lateral , international basis with regard to the sharing of fac ilities, staff expertise and funding resources. Also , given the absence of sorn e experimental capabilities in many countries and

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the near-unique ca pabili ties in others, the NEA should , through its Member countries' representatives, recommend to their sponso rin g agencies that certain facilities with unique capabilities be made available for international measurements pro­grammes. This policy would reduce the need for redund ancy in ca pa­bilities and promote stable fundin g fo r maintaining staff and equipment . With the expandin g number and scope of NEA activities on criticality and sa fety, a Working Party for Nuclear Criticality Safety was estab­lished to provide guidance and over­all co-ordination of these activities . This working party will deal with technical, away-from-reactor, cri tical­ity safety issues relevant to fabrica­tion , transportation , storage and other operations in the fu el cycle of nuclear materials. Its areas and items of ac tivity are illustrated in th e diagram.

Perspectives lf nu clea r energy is to play an

important role in our economies in the future (it currently represents 25 per cent of electricity producti on in the OECD area), fi ss ile mate rials must be handled sa fely ove r the whole fu el cycle. Seve ra] fu el cycle options exist, and their advantages

and disadvantages are being hotly debated at the technical, economical , political and public level. One of the qu es tions being asked is should plutonium be considered as a liability or an energy source?

In the coming years there will likely be furth er clarifi ca ti on of potential nuclear fuel cycle strategies , each one with its specifie needs in criti cality safety. Although a wealth of information is available from more than 50 years of cumulative knowl­edge acquired, case-specifie analyses will be needed and will dominate criticality safety.

The release of fi ssile mate rials from sorne countries' weapons pro­grammes to the civil nu clear fu el cycle will influence future work according to available options Open or closed fu el cycles, once-through or recycle will dominate the debate and research .

Di versity in national po li cies is expected to persist in this area in the short term. ln the long term , and in arder to leave the options open fo r future generati ons, it is worth shar­ing criticality information beyond national poli cies. lt is for that reason th ar the Working Party on Nuclear Criticality Safety was set up, address­ing issues that are of common inte rest to all countri es with fue l cycle

facilities. An international conference is sc heduled for 1999 in France to address these themes as they relate to cri ticality sa fety, and to caver in pa rt ic ular the different fuel cycle options such as once-through, recycle and act inide partit ioning, burning and transmutation .

ln conclusion , criticality safety calls for constant support and att ention. A sou nd understa nding and correct application of the princi­ples of nuclear criticality safety are vital to the nu clea r industry The obj ec tive is to pursue an accident­free goal , wh ile keeping in mind the repercuss ions that an avoidable cri tica lity excurs ion could ha ve Cu rrent activities and future initiatives will obviously build upon past accomplishments. Events have shawn that cri ticality sa fety is an international issue. lt is therefore in the interest of all that information be widely shared and disseminated , notably through the NEA. •

Notes 1 . The Sa fety o f th e Nuclea r Fue l Cyc le,

OE CD, 1993 (IS BN 92-64-1382-1-2 )

2 . M .C Brady e l al.· " Fi nd ings of an Int ernati onal Si udy on BL< r n-up Credit", Physo r'96 Co nfue nce, Milo, japan.

3. jB. Briggs ed .. "Inte rn ational 1-I andbooh of EvalLt ated Crili cal ity Safe ty Be nch marh Experiments", NEA/NSC! DOC(95)03 Rcv. 1, 1996.

C OMMIHEE ON TH E SAFETY N UC LEAR SCIENCE C OMMIHEE ~- - - - - --- - -.

O F N UCLEAR INSTALLATIONS

WORKING PARTY ON

N UCLEAR CRITICALITY SAFETY

1 1 1 1 1 1 1 1

CRJTICAL SuB- AXIAL CONIPOSITION MINIMAL CRJTICALITY

NEED toR BURl'I-UP OF FuEL

SYSTEMS CRJTICAL BuRN -ur OF SPENT CREDIT

CRJTICAL CYCLE

CRJTICA LITY

(ICSBEP) SYSTEMS PRo m ES FuEL MASSES Ex PERl EMEI\'TS f ACILITlES

1 1 1 1

DATA BASESIHANDBOOKS

NEA activities under the Working Party on Nuclear Criticality Safety.

NEA/CSNI-CNRA Collective opinion

Reactor fuel performance and safety margins

n a joint statement released earlier in 1997, the Committee on Nuclear Regulatory Activities (CNRA) and the Committee on the Safety of Nuclear

Installations (CS NI) of the N uclear Energy Agency (NEA)- the two major committees of the NEA in nuclear safety and regu­lation - support enhanced co-operation

"Over the past severa! yea rs, there has been much interest in improving the performance of nuclea r fuel. Work has been performed to develop new cladding material s, new fuel designs and manufacturing processes intended to improve reliability and safety, allow higher burnup and longer fu el cycles , and support the use of MOX fu els

"Some of these new designs are currently being used in reactors and others are planned for use in the short term. However, in some cases, these new designs raise safety and regu lato ry issues that need to be addressed. These issues involve the fuel safety margins under accident conditions as well as the possible impact of fuel behaviour on the performance of safety systems (e.g. hindering control rod insertion) ln particular, one issue relates to the cumulative effect of many "minor" changes , each of which bas been deemed too small to warrant suitab le resea rch and · qua li fi cati on programmes. These issues we re discussed by the CNRA and the CSNl at thei r 1996 annual meetings.

"As part of their responsibiliti es to ensure that criteria are developed and limits are specified to ass ure the safety of reactor operation s, some regulatory bodies an d/or their technical support organisations in OECD countries are sponsoring or

with the nuclear industry, and encourage the nuclear industry to take a more active role in developing the experimental and analytical basis to support its proposais for new reactor fuel designs and extended operational characteristics.

The full statement of the CSNI and the CNRA is given below.

deve loping a number of fuel research programmes addressing fu el behaviour tmder normal, transient and accident conditions, such that sufficient inde­pendent data is available to support regulati on. How­ever, ultimately the responsibility for developing an adequate safety case for introducing optimised or new fuel designs rests with the industry Accordingly, the CNRA and th e CSN I support co-operation with th e nuclea r industr y and encourage th e nuclear inclustry to take a more active role in cl eveloping the experimental and analytical bases to support its proposa is for new fu el des igns and extend ed operationa l characteristics. Iss ues related to cases with a mix of fue l designs should also be addressed. A more active role implies the sponsoring of adequate qualifica tion programm es to demonstrate the per­formance of the fu el under normal , transient and acc id ent co ndi tions, the sharing of relevant informa ti on with , and the submission of well supported safety cases to regulatory bodies and their techni ca l support organisa tions

"Regulatory bodies will review the adequacy of sa fety crite ria for these new designs based upon available information , thus it is in the imerest of the nuclear industry to ensure sufficient information is available to support achieving the fuel performance goals desired. "

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T he operating li fe time of nuclea r fac iliti es is large ly determined by economie and sa fety co nsiderat ions.

Nuclear power plants are normally designed for an operating lifetime of severa! decades. By appropriate refur­bishment, replacement or upgrading of sorne equipment , operatio ns at many of th ese plants can reach an operating lifetime of about 40 yea rs. Ultimately, however, it beco mes either techni ca lly or economi ca ll y advantageous to retire a facility from operation and , if necessa ry, replace it with a new insta llation .

Today, more than 60 nuclea r reactors have been permanently shut down in the OECD area; at the end of 1996, sorne 360 nuclear power plants were in operation.

Table 1 illustrates the important increase in decommiss ioning wo rk that lies ahead, and gives an indi ca­tion that deco mmissioning will representa sizeable industry as soon as the tu rn of the century, depénding though on the rate of pl ant retire­ments from exist ing nuclear powe r programmes, and on the rate of future deployment of sorne of these programmes.

In response to the growing interest in th e deco mmissioning of nucl ea r fac ilities, in 1978 the OECD Nuclea r En ergy Agency laun ched a pro­gramme of activities in this field . The work of the NEA was initial! y limited to the organisati on of international meetings of experts and the prepa­rati on of surveys and state-o f-the-a rt

reports. Subsequently, however, in 1985 the Agency se t up the Inter­national Co-operative Programme for th e Exchange of Scienti fic and Technical Information Co ncerning Nuclear Install ati on Decom mis ­sionin g Projects. This concep t of bringing together a number of decommissioning projects , exchang­ing informat ion , experience and possibly personnel , and co-operating in other ways, as app ropriate , was strongly sup ported by all those OECD coun tries having one or more deco mmi ssioning projects ei the r under way or in the planning stage

The programme was forma lly initi ated in September 1985 for a fi ve-year term, and was subsequent! y extended fo r a furth er five-year term in view of its successful performance. As thi s success has continued with an even broader range of pa rticipat­ing co untries and projec ts than previously, th e agreement has again been extended fo r a five-year period.

The first fi ve yea rs of the pro ­gramme represented a wa tershed in the evolution of decommi ssioning as a mature technical discipline. In its own right , each of the participating projects made a significant contri­buti on, not only towards developing various decommissioning technolo­gies, but also in demonstrating them in the fi eld For the second fi ve-year period the primary objective has been to contribute to the industrialisation of decommissionin g by facili tating the exchange of informatio n and re lated experience between partici-

pating projects This objec ti ve can be said to have been met, as evidenced by the continuing increase in participating organisations.

One of the obj ectives of th e Programme has always been the dissemination of information , includ­ing the publication of authoritati ve reports on various decommissioning subjects.

The programme Currentl y, 31 proJeCLs from

ll countries participate in the Programme, including proj ects from two NEA non-member countries (the Slovak Republic and Estoni a) Th ese include the decommi ssionin g of 2l reactors, seven reprocessing plants, two fuel ma terial plants, and one isotope handling facility. As a result of the wide variation in th e type of facility being decommissioned, and in the environment in whi ch the activity is to be undenaken , and to ass ist in the comparison of in fo r­mation and experience, the focus of the Programme has been on seve n broad areas:

• the assessment of ac ti vity inventories;

• cutting techniques;

• remote operation;

• decontamina tion ;

• melt ing;

• radioactive waste manage ment , and ;

• health and safet y. * Dr. Edward La zo is a member of the NEA Radiation P1·otee1ion and Radioa clivr Wastr Mana gement Division.

• The NEA's co-operative programme on decommissioni ng

Table 1: Nuclear power plants to be taken out of service in the OECD area

Year 2000

Number of plants 8

Capacity (GWe) 1.7

Average li fetime 34 (yea rs)

The study of these a reas has led to a greater depth of knowledge , and in so rn e areas the ability to compare results found in various projects For example, the assessment of radio­ac tive inve ntori es is seen as the esse ntia l first step in defining the requirements of a decommissioning projec t. lndeed, radioac tive inven­to ries are needed for decommis­sioni ng planning, was te categori­sa ti on , waste transportation and sa fety assessments. ln addition , li censing auth oriti es frequ ently requi re in formation on the radio­ac tive was te inventor y. Where measurements have been made, it has been possible to ve ri fy calculations against measured inventori es with reaso nable ag reement.

ln th e va ri ous participating projects, a wide range of cutting tech­niques have been demonstrated and employed on both metals and con­crete. For meta l cutting, a compar­ison has been made between the various methods available, and it has bee n demonstrated that in sorne situations the use of mechanical cutting techniques offers significant advantages in terms of volume of secondary waste produced. The use of diamond saw cutting for pre ­stressed cono·ete has been shown to be a practical method that can be employed to advantage. Other tech­niq ues under consideration include the cutting of both metal and con­crete without either a lubricant or coolant , using methods such as steel and tungs ten carbide dises , milling and dry milling saws. From the

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studies to date, the use of metal dises has proved successful. But , as it was concluded in the fir st fi ve-year report , there is no ideal cu tting method and it is necessary to select th e appropria te technique for the material to be eut , together with the environment in which il is to be used.

Whilst the use of robot ics or autonomous machines only had limited use in th e parti cipa ting projects during the last five-yea r period, confidence gained will enable wider use in the future. These sys­tems are compa rative ly expensive, but sometimes offer the only practi cal solution to the dismantling of highly active plant components, or to work­ing in extremely high dose-rate areas. Howeve r, even in lowe r dose -rate areas there may also be adva ntages to the use of robot ics in reducing the wo rk force exposure in situations where traditional hands-on working would normally be considered.

The area of decontamination tech­niques is co nsidered to be fund a­menta l to decommissioning activities , and a special working gro up on this subject has been fo rmed to develop a de tailed report of current, state-o f­the-art techniques. A wide range of decontamination techniques has been employed in the va rious projects .

There are fi ve plants currently metting contaminated metals on an industrial scale. The obj ec tive of melting is to allow the recycling of slightly contamina ted metals from the decommissioning process. The melting process provides for sorne

decontamin ati on of the rn etals, with sorne contaminants, generally in the form of oxides, separating from the metal du ring the melting process. For example, no n-fe rrous metals fro m this mel ting process ca n be freely released in many cases. However, in sorne cases , meta ls st il l attain con­tamination levels higher than regula­tory clearance cri te ria , and must remain unde r regulatory control. These can be used for construction within the nuclear industr y, for exampl e. Sorne steel products con­ta mina ted with co balt-60 fall into this category. On! y a brief overview of new developments in this area has been und ertaken, but it is clear that a new industry for minimising the quantity of ac tive metalli c waste is being established. This also convinc­ingly demonstrates that significa nt quanti ties of metal can either be released for u nres tricted use or re leased for reuse in the nu clear industry Another working group was established to study the question of clearance levels for metals from the decommiss ion in g process, and a report has been published to add the views of decommissioning impie­mentors to the ongoing international debate on this subj ec t.

As can be expected from the range of proJects participating in the Programme, a diverse range of wastes must be managed, and thi s has led to a wide variety of methods for deal­ing with them. Often, however, the most important factors to be consid­ered and sa tisfied are nationa l regu­latory requirements.

ln terms of occupational exposure, the actual radiation doses received by the work force are in generallower than those calculated when assessing the work . Of particular interest is the work carried out to improve physical comfo rt when working in a ventilated suit. A system has been developed that includes breath-activated deviees to increase air supply, provide special air to refresh the operator's face and remove condensation.

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Decommissioning costs One of the in-depth studies per­

formed concerns the cast of deco m­missioning lnitially, cast data from 12 proj ec ts were used to establi sh a basis for the comparison of costs, and fro m this comparison it has been pos­sible to gain a better understanding of the costs of deco mmissionin g pro­Jects, although the analysis technique employee! cannat be used to predict deco mmissioning costs for a part ic­ular proJ eCt

An important observation mad e during this study was that a standard­ised listing of cost items or an es ti ­mating methodo logy does not exist for deco mmissioning projects. Such standardisa tion wo uld not on ly make cast compari sons possible, but wou ld , in additi on, provid e a sound tool for proj ect cos t management Basee! on th is observation, the NEA has set up a joint project with the EC and the lAEA to establish a standard list of cast groups , and with in these groups cost items wi th re latively precise definitions. Using this struc­ture, the costs of any decommissioning

Removal of a 15 MW generator at the AVR power plant in Jülich, Germany .

proj ec t, in any co untry, can be meaningfully co mpare e! with those of other proJects lt is hoped that this wo rk will be completed ea rl y in 1998 and published as a joint NEA , EC , IAEA repo rt Basee! on this wo rk , a number of projects participating in the Programme have remodelled thei r cast-management structure.

Decontamination As prev iously mentioned, a stud y

of the state -ot-th e-a n decontam­ination tec hniqu es to be used in co nnection wi th deco mmissioning has been undertaken. Deco ntami ­nat ion is frequently requ ired in a decommissioning proj ect in order to:

• reduce radiation exposure of the ope rating staff;

• salvage equipment and materials for poss ible reuse;

• reduce the vo lume of equipment and materia ls requiring disposa! in li censed burial fac ili ties ;

• restore the site and facility, or parts thereo f, to an unrest ricted use condition;

• remove loose radioactive contam­inants and fi x the remai ni ng contamination in place in prep­aration for protec tive storage or permanent disposa! wo rk ac ti viti es;

• redu ce the magnitud e of th e residual radioac ti ve so urce in a protecti ve stara ge mode for pub! ic health and sa fety reaso ns, or reduce the protec ti ve sLOrage period.

A number of ph ys ica l, elec tro­chemical and chemical processes that are relevant to decommissioning have been identifi ed, and the charac ter­istics of each method ha ve bee n considered. The studies are contin ­uing to enab le guid elines to be produced for th e selec ti on for an y particular application , and a final report is expected in 1997.

Recyc•ing nd re se As mentioned above, the recycling

of materials from decommissioning activities is an effe cti ve way to optimise the use of valu ab le resources , and can also be ve ry cast

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effective A working group was established to examine the means for maximising the recove ry of val ua ble materials ari sing from decommis­sioning operations, while at the same ti me minimi sing wastes for di sposal. Th e stud y has been completed with rega rd to metallic wastes and is to be continued for non-meta llic wastes.

The key to this study has been the cos t-benefit analysis used to deter­mine regulatory clearance levels , that is, those regulatory levels of contami­nation below which materials can be released fo r uncon trolled use. The working group focused on this cost­benefit analysis, using an integrated risk management approach to take in to account not only the costs relati ng to the radiological risks associated with material containing contamination levels above natural background , bu t also th e ri sks associated with replacing, as opposed to recycling, such materials (mining, mi ll ing , transportation , etc) In addit ion , the wo rking group suggested the concept of the tiered release of metal s. Sorne hi ghly contami nated meta ls wi ll al ways requ ire regulatory control, sorne slightly contaminated metals could

be released to a regulated smelting facility where these could be mixed and diluted, resulting in metals below the release criteria , and some metals below regula to ry clea rance levels could be released outright for immediate reuse .

Current ly, there are no inter­nationally accepted standards for the clearance of contaminated materials, although documents from the IAEA and the EC have proposed clearance levels based on radiation-risk consid­erations alone. A report summarising the findin gs of the working group was recently published by the NEA, entitled Nuclear Decommissioning: Recycling and Reuse of Scrap Metals, and it is hoped that this document will contribute new and interesting ideas to th e ongoing internati onal debate in thi s area .

Conclusion As the world's nuclear reactors age ,

increasing numbers of plants will begin decommissioning operations. In orcier to perform this work in the most effi cient manner, in terms of wo rker sa fety, was te generation, desired end results, and cost

The decommissioning process.

effectiveness, the experience gained today must be effectively shared. For the past ten years the NEA's Co-operati ve Programme on Decom­missioning has served as a very useful forum for the exchange of infor­mation in this highly important area. For th e next fi ve -year period the exchange of information and expe­rience will continue, and additional emphasis will be put on ensurin g promulga tion of this valuable infor­mation and experience to a wider audience than the participating proj ects alone. lt is also hoped that the continuing work of the Pro­gramme, with its vas t practical experience, will be useful in the development of national and inter­national standards and regulations in the area of decommissioning. •

References • The N EA Co-o pe ra ti ve Programm e o n

Deco mm iss io ning- The First Ten Years 1985-95 , OECDINEA, 1996.

Recyc lin g and Re use o f Sc ra p Me ta ls, A Re po rt by a Task G ro up o f the Co-o pe ra ti ve Program me o n Deco m ­missioning, OECDINEA , 1996.

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P. Saunders, J-C. Nénot*

A new NEA report discusses radiation As part of its series of pctbli cations intended for an interested, non-specialist readership, the Nuclear Energy Agency has just published a new report "Radiation in Perspec tive Applications, Rishs and Protection" with the aim of provoking an enlightenecl debate on this subjec t. The report discusses th e development of radiation protection measures and international/y agreed princip/ es, and addresses social and economie imtes such as ethical qu es tions, risk perception, risk comparison, public pa rticipation in decision-making and the cast of protec tion Below are some exce rpts f rom the in troductory pages of this new publication

D espite its many beneficia! applica tions throughout medicine, inclustry and research , ion ising radiation

has led to much public co ntroversy The issue sprang to prominence in the immediate aftermath of the Hi roshima and Nagasa ki bombings , and it has playecl a large part in the clebate about the generation of electri city by nuclear powe r.

Although unknown JUSt a hunclrecl years ago , ionising radiation is harcl ly a new phenomenon. Mankincl has always been exposecl to radiation fro m outer space and from radioactive materials in the earth itself. But it is man-macle radiation thar gives rise to the greatest concern .

A funcl amental requirement , both in cl evelopecl and in cleve loping countries, is to enable the benefits of technology to be enj oye cl wit hout unacce ptable consequences . Th e clebate about radiation is just one of many similar clebates thar have ari sen in coun tries, such as the Member countries of the OECD, in which high standards of living depend on a wicle range of technologies, applieclthro ugh a complex infras tructure of manu ­facturing and energy industries and transport systems The chall enge is to main tain or im prove these stan­dards without unclue damage to the environment , and without compro­mising the ability of fu ture generations to meet their own neecls- to achieve sustainable clevelopment , as clefinecl

in the 1987 report of the Wo rlcl Com mission on Environment and Development, entitlecl Our Co mmon Future, the Brundtland Report.

The contl~oversy about radiation is base cl on a se ries of apparent para­doxes: it is uni versai, ye t unseen and unfelt; it has many beneficia\ applica­tions, ye t can be harmfu l; it is we il unclerstoocl , yet often fearecl . Mea­sures to safeguarcl heal th and the environment fro m the harmful effects of rad iation are weil clevelopecl and appl iecl through strin gent national legislation in most countries . There is a broacl scientifi c and technica l consensus thar the degree of scientific knowleclge of radiation and its effects constitutes an acce ptable basis for a conse rvative system of protection. Yet the clebate continues.

Early discoveries The founclations of tocla y's

extensive uncle rstancling of ionising radiation were laid cluring a short periocl of brill iant research, starting with Rontgen's cliscovery of X-rays in November 1895. Rontgen was work­ing in a darkenecl laborato ry, stuclying what happenecl when an elec tric current passed through a glass tube out of which most of the air had been pumped. The current macle the remaining air in the tube glow He covered the tube with black carel­board , so thar the glow coulcl not be seen. A sheet of paper thar hacl been made sensitive to light happenecl to

be lyin g on the table and Rontge n founcl thar this paper glowecl eve ry time the current fl owecl , although no light was esca ping throu gh the carclboard. He then founcl thar what­eve r was coming from the tube also clarkenecl a photographi e pl ate. He realisecl thar some sort of radiati on in visibl e to the human eye was being emitted and he callecl this X-rays . He soon fou ncl thar X-rays co uld be stoppecl by some substances more easily than by others. One of his most dramatic earl y demonstrations was to

put his hancl between the tube and a fluorescent screen; the image on the screen clearly showed up the bones With in a very short rime, X-rays were being putto medical use, first to locaLe shotgun pellets in a man's hancl and soon for a very wicl e ran ge of diagnoses in hospitals and surge ries throughout the world.

ln 1896 Becquerel found thaL pitchblende, an ore of uranium , ca usecl the cl arkenin g of a photo­graphie plate; he had d iscove recl raclioactivity Rutherford ident ifi ed two types of radiation being emitted from pitchbl ende, neither of which we re visible to the human eye; he called these alpha an d beta rays . He showed thar the alpha rays (or alpha particles) consisted of nuclei of the

* Mr. P Saunders is a technical writer and a consultant on energy and environmental issues. Dr j-C. Nénot is Director for Research at the lnslitute for Protection and Nuclear· Safety of the French Atomic Energy Commission.

ele ment helium. Becquerel showed that beta rays (or beta particles) were electrons. Villard found a third type of radiation emitted from pitchblende

which he ca lled ga mma rays. These were later shown to be elec tro mag­netic radiation similar to , but more penetrating than X-rays. ln 1896 Pi erre and Mari e Curi e extrac ted a minute a mount of radium -less than one gramme - from many tonnes of pitchblende, and radium was soon being used in cance r t reatment because of th e intense radi ation it emitted.

Thus, by the beginning of the twe nti eth century many of the ke y discove ries needed to understand man's radiation environment had been made, and the stage was se t for the development of applica tions of radi­ati on in medicine, industry and resea rch.

• A new NEA re po rt di scusses radia t ion

Modern alchemists A second dramatic se ri es of

discoveries was initiated in 1919 when Rutherford fired alpha particles from a radium source down a tube contain­ing nitrogen gas At the end of the tube he detected protons as weil as al ph a particles . Proto ns are the nu clei of hydrogen, but there was no hydrogen in the tube. What was happening in Rutherford 's experiment was that some of th e alpha particl es were being captured by the ninogen nuclei, and the subsequent nuclear rea rrange ­ments resulted in the fo rmation of oxygen and the emission of protons. One element had bee n transmuted into another, the alchemist's drea m, only in this case nitrogen was changed into oxygen rather than lead into gold.

ln 1932, Coc kcro ft and Walton showed that nuclear transmutations could be caused by protons acceler­ated by electr ica l mea ns in the

laboratory as weil as by alpha particles from natu rally rad ioactive materials. In 1934, lrene Curie and frederic j oliot round th at in sorne circumstances transmutation resultee! in the forma­tion of new elements that were radioactive (a radioactive element is ca ll ecl a ra di onucl ide) They hacl cli scove recl art ificia l, or ma n-made racl ioactivit y. The next yea r, f ermi found that a much greater variety of artificial radi onucl ides coule! be crea tecl when neutrons were used insteacl of al ph a parti cles or protons Neutrons - particles of approximately the same mass as protons but elect rica lly neutra!, present in the nu clei of ali elements exce pt hycl rogen - hacl been identifiee! by Chadwick in 1932.

Although the quantities of artificial radionucl ides produ ced in these vari ous ways were minute, the radi­ation th ey emittecl coule! easily be detected, and this enablecl them to be

used as tracers (small amounts of easily detectable material fi xed to some substance whose movement one wishes to follow) The use of radioactive tracers, a techni que inve ntee! by Hevesy, has since revolu­tionised our understanding of the working of the hu man body, in health and in sickn ess. A radionuclide behaves chemically in exactly the same way as the non-radioactive fonn of the same element. So adding a minute amount of a radio­active tracer to a chemical and measuring the radiation it emits allows the movement and metabolism of the chemical to be studied with enormous sensitivity, typi­cally ove r a million times greater than that attainable by other means. Radioactive

Radionuclides are used to track the movement of pollution in ri vers.

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tracers are also widely used in industry and research as weil as in medicine (most are now produced in nuclear reactors).

From 1934 onwards, Fe rmi and other researchers irradiated a wide range of elements with neutrons, including the heaviest known element , uranium . Fo r most elements, the absorpti on of a neutron results in the formation of a heavier element. In the case of uranium , however, a wi de range of elements results, sorne of which are heavier but others much lighter than the original uranium. The absorption of the neutron canin fact cause the nucleus to split into two (or sometimes more) fragments, most of which are radioactive. The process is called fission. Fission had been occur­ring in the experiments of Fermi and others but this was not realised until Hahn , Strassmann and Meitner in 1939 showed that one of the new elements formed was barium, an element about half the weight of uranium.

Nuclear power The charac teristics of nuclear

fi ssion were soon establi shed as a result of a series of further experiments and theoretical studies . A key feature is that the fi ssion products contain fewer neutrons than the uranium from which they originate , the surplus neutrons being emitted during the fission process . There was clearly the possibility of achieving a chain reac­tion in which sorne of the emitted

. neutrons induce fi ssions in other uranium nuclei, resulting in more neutrons, more fi ssions, and so on . Furthermore, the mass of the fi ssion products plus the neutrons was less than the mass of the original uranium, with the difference in mass (rn) appearing in the form of the kinetic energy (E) of the fission fragments and neutrons, in accordance with the Einstein relationship E=mc2 (c being the velocity of light), leading to the possibility of releasing enormous amounts of energy. This is the only formula that will be found in this report.

On 2 December 1942, the possi­bility of a self-sustaining nuclear chain reaction was first confirmed by Fermi using an assembly (or pile) consisting of uranium, graphite which slowed the neutrons emitted from the fission reactions down to the optimum speed for initiating further fission reactions, and cadmium wh ich controlled the chain reaction by absorbing neutrons. This, the fir st nuclear reac tor, was constructed in a squash court under the stand of a baseball stadium in Chicago The possibility of an enar­mous energy release was confirmed at the Alamogordo Bombing Range in New Mexico on 16 July 1945 when the first nuclear weapon was tested. Both these events were shrouded in the strictest secrecy. The world fi rst learned about the power of th e nucleus at Hiroshima and Nagasaki .

The Chicago reactor showed that the power of nuclear fission cou Id be produced under controlled condi­tions. Many reactor types were devel­oped during the subsequent decades. Ali are based on assemblies of fi ssile materials, uranium and plutonium in various forms, together with means of controlling the numbers of neutrons and , if necessary, their speed, and of removing the energy released and using it to generate electricity. Plu to­nium is one of the new elements that result from the absorption of a neutron by uranium; it is another element in which a neut ron chain reaction can be sustained and was the material used in the Nagasaki bomb.

Nuclear weapons and nuclear electricity generation have been important and contentious topics for half a century. For better or worse, nuclear weapons have dominated much military thinking and national and international defence strategies throughout the period. Nuclear elec­tricity generation has grown steadily since the early 1960s and now provides one quarter of the electricity generated in OECD countries , the second largest source after coal. The importance of these two radically different activities in the context of

this report is in their inescapable association with radiation. Although they contribute only a small fract ion of mankind's total radiation exposure , they are strongly connected in most people's minds with the "problem" of radiation and its safe control. Atten­tion foc used initially on radiat ion exposures fro m the fallout from atmospheric testing of nuclea r wea p­ons, and later, following international ag ree ments banni ng atm ospheric testing, on radiation associated with nuclear electri city generation

Risks and benefits The possible dangers of radiation

were recognised within a very short time of its ini tial discove ry. Speaking of X-rays in 1896, Lord Lister sa id "If the skin is long exposed to their action it becomes ve ry mu ch irri tated, affected with a sort of aggravated sun ­burning. This suggests that transmis­sion through the human body may not be altoge ther a matter of ind if­ference to the interna i organs." Rutherford visited the Curies in 1903 and no ted "We could not help but observe that the hands of Professo r Curie we re in a very inflamed an d painfu l state du e to exposure to radium rays. "

Several hundred cases of radiation injury were reported during the ea rl y years of the medical use of radiation, mainly among resea rchers, docto rs and technicians - there is a monument in Hamburg to 169 radiologists who died from such inj uries. It was this earl y experience that led to the devel­opment of measures for the protection of people from the harmful effects of radiation.

Within a few years, it was realised that, as weil as causing gross damage such as skin burns, large or repeated exposures to radiation could so rne­times cause cancer. Later, experiments on animais and other living matter showed that radiation exposures could produce effects which only show up in the offspring of the exposed organisms - genetic or hereditary effects

A ne w NEA report di scusses radiation

Determini sti c ( ear 1 y) effects

No earl y effects below th resho ld

Effects of radiation

Stochas ti c (l a te) effects

0.00 1 mSv Av. 1 yeardose from nuc lear industry

0 .05 mS v 2 hr. fli ght

0.0 1 mS v

No evidence

0. 1 mSv 1 chest X-ray of human health effec ts below 50 mS v l l mS'

2.4 mSv Av. 1 year dose from natural background

10 mSv Typical 1 year radon dose in hi gh radon area

50 mSv Probabi li ty

the benefits to patients from the use of radiation and radio­acti ve materials for di agnosis and treatment general! y fa r ex­ceeds any associated risks The balance becomes more difficult if the benefits are general but the ri sk is concentrated on a few people

Th e benefits of nuclear powe r, for example, are general - it helps to reduce the problems of acid rai n and greenhouse gas emissions from

LOO mS v 1 year radon of occurrence

fossil f uelled electrici ty gener­ari on and contributes to th e diversity of energy supply. But set aga inst such benefits there are risks to tho se worki ng in the industry and to the public around nuclea r installations. Such co mplex problems are not unique to th e nuclear industry, they also arise when consid ering the siting of motorways, airports, chemical plants and waste disposai sites. ln all these cases, the benefits are ge neral bu t the risks and disadvantages are mainly loca l.

dose in a few of effects are as 1 increases

with dose 1

Thresho ld --1 Gy 1000 mS v (= 1 Sv) (no evidence

Fu rther qu es tions ari se whe n co nsidering tss ues thar are essentia ll y socio­economic rather than techni­ca l. To what extent shou ld decision-makers take public pe rce pti ons of risk into account when there is a discrepancy between such perce ptions and quantitative ri sk es timates derived from

Se verity of effects increases with dose 10 Gy Lü Sv

There is a threshold leve! of rad i­ation exposure (or dose) below which no acute damage is observed. How­eve r, there is nowa substantial body of evidence which shows that cancers can be caused by rad iation even at dose levels thar are below th is thresho ld . There is no evidence of inherited damage in humans at any dose leve!, but the fact thar such damage is found to occur in other li fe fonns suggests thar it could also occur

of hereditary effects in humans at

/ any dose levels)

in humans. White th e qu es ti on of whether or not ve ry low doses of radiation, we ll below the threshold for acute effects, result in cancers or genetic effects remains an open ques- · tian , the assumption thar a dose, however small , ca rries with it an ele­ment of risk has nevertheless become a key concept in rad iation protection.

A central problem of radiation protection is thar of balancing risks and benefits There is little doubt thar

technical analysis of engineer­ing systems? How much should be spent on the further reduction of risks that are already low7 How should benefits to current generations be balanced aga inst possible risks to

future generat ions?

There are no simple answers to such questions, but they can only be addressed on the bas is of a clear understandi ng of the scientific, tech ­nica l, econo mi e, soc ial and other factors involved. •

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Nuclear power in NEA countries Situation as of 31 December 1996

At the end of 1996 , the to tal capacity providecl by th e 357 reactors now install ecl was 297.5 gigawatts (GWe) Another 14 reac to rs totall i ng 14.6 GWe were un cler construction and four reac tors to ta l ling 3. 9 GWe were fi rmly

committecl . The to tal capacity of nuclear power plants in NEA coun tries in the year 2000 and 2010 is projected to be about306 5 and 331.9 GWe, respec tively. The 1.7 GWe of capacity tha t is expected to be retirecl by the year 2000 is alreacl y deducted from th ese projec ti ons.

Nuclear electricity capacity in NEA countries

1996 (Actual) 2000 2005 2010 NEA Country

Net GWe % Net GWe % Net GWe % Net GWe %

Belgi um 5.7 37.5 5.7 37.0 5.7 36.3 5.7 32.0 Canada 16.0 138 16.0 137 16.0 13.6 15.0 12 .6 Czech Repub lic u 12 .0 3.5 231 3.5 20.5 3.5 18.4 Fin land 23 17.1 2.6 15.8 2.6 15 .6 2.6 15.6 France 60.0 54.5 64.3 56.4 64.3 55.9 64.3 55.9 German y 22.4 21.8 22.4 21.2 22.0 20.2 23.1 * * 18.7 Hungary 1.8 24.4 1.8 22.6 1.8 213 2.5 270 japan*** 423* 20.0 42 .9 18.3 54.0 ** 21.6 66.5 237 Korea 9.6 270 137 26.0 18.7 275 26.3 33.1 Mexico lJ J6 14 3.7 14 3.0 14 2.4 Netherlands 0.5 2.6 0.4 1.9 00 00 0.0** 00 Spain 7.1 15.0 7.1 14.9 7.1 14.7 7.1 14.6 Sweden 10.0 29.7 9.4** 270 8.8** 25.3 8.8** 28.9 Switze rland 3.1 19.4 3.2 20.0 3.2 18.8 3.2 18.1 Turkey 0.0 00 0.0 00 1.0 2.4 2.0 3.3 Uni ted Kingdom 12.8 18.2 12.1 14.9 9.3* * 10.9 7.0 ** 8.2 United States lOLO 12.9 100.0 12.0 100.0 11.4 93.0 10.0

NEA Total 297.5 18.0 306.5 17.1 319.4 16.8 33 L9 16.2

Status of nuclear power plants

Co nnected LO the gri d Under co nstruct ion Firmly co mmitted Planned NEA Country

Units et GWe Units Net GWe Units etGWe Units etGWe

Belgium 7 5.7 - - - - - -

Canada 22 16.0 - - - - - -

Czech Republic 4 u 2 2.0 - - - -

Fin land 4 23 - - - - - -

France 57 60.0 3 4.3 - - - -

German y 20 22.4 - - - - - -

Hunga ry 4 L8 - - - - l 0.6 japan*** 53 423 2 2.2 2 1.9 20 21.8 Korea ll 9.6 7 6.1 2 2.0 8 9.2 Mexico 2 lJ - - - - - -

etherlands 2 0.5 - - - - - -

Spain 9 7.1 - - - - - -

Sweden 12 10.0 - - - - - -

Switzerland 5 3.1 - - - - - -

Turkey - - - - - - 2 2.0 Un ited Kingdom 35 12.8 - - - - - -United States llO lOLO - - - . - - -

NEA Total 357 297.5 14 14.6 4 3.9 31 33.6

Pro visional d ata. * * * Gross capac ity data conve rt ed to ne t by the EA Secreta ri at. Estima te es tab lished by the NEA Sec retariat.

News briefs NEA/IAEA international review of the 1996 performance assessment of the Waste Isolation Pilot Plant (WIPP)

At the request of the United States Depart ment of Energy Carlsbad Area Office (DOE/CAO), the NEA

and the International Atomic Energy Agency (IAEA) ca rried out a peer review of the 1996 Performan ce Assessment of the Waste Isolation Pilot Plant. For this pu rpose, the NEA and the IAEA assembled an international team of experts specialised in the assessment of the long­Lerm safety of nuclear waste disposa!.

ln the United States, the DOE is responsible fo r the management of transuranic (TRU) wastes 1 generated by defe nce- related activ ities. At present , approxima tely 62 000 cu bic met res of TRU wastes have been gene rated and are retrievab ly stored at government installations across the country It is projected that an ad ditional 88 000 cubic metres of such wastes will be generated up to 2022.

As in most count ries wi th nuclear programmes , the preferred method fo r the disposai of long-lived radioactive waste, such as transuranic waste , is long-term isolation in a system of multiple barriers located in deep and stable geo logical formations The Waste Isolation Pilot Plant (WIPP), located nea r Carlsbad in south- eas tern New Mexico, has been sited and constructed to meet the cri teria es tabli shed by the US Environmental Protection Agency (EPA) fo r the safe , long- tenn disposa! of such wa stes. The fac ili ty, co n­sisting of above -ground and underground parts, is designed to receive, isolate and contain the TRU waste. The underground fa cili ty (repository) is located at a depth of 650 metres below the sur face in a 600-metre thi ck, bedded rock sa lt formation da ting back from the Permi an geo logical age (approximately 225 million years old)

A forma! licence appli­ca tion for the disposa! of TRU waste at the WIPP site

was submitted by the DOE to the EPA in October 1996. Thi s app li cation , ca lled the Comp liance Certifica tion Application (CCA), includes an assessment of the isolation capacity of the system for a 10 000- year period , as specified in the EPA regulations. The DOE has developed an approach to demonstrating the long-term performance of the WIPP repository basee! on probabilistic performance assessment. This is designee! to es timate how the W!PP disposa i sys tem will perform cluring the 10 000- year period , taking account of unce rtainties clu e both to uncertain future events and conditions, and to imprecise or incomplete descriptions of the relevant fea tures and processes as they exist today. Probabilistic performance (or sa fety) assessment is a qu antitative methocl of eva lu ating the potentia l long-term sa fety of geological disposai sys tems and the associatecl uncertainties. The method is not expectecl to provicle a precise prediction of the evolution and performance of a disposai sys tem, but to provicle a suitable basis for clec icling on whether specifi e di sposai systems wo uld offer a sa tisfactory

leve! of sa fety to both View of the Waste Isolation cu rrent and future Pilot Plant (WIPP} ne ar generati ons. Carlsbad, New Mexico, United

States.

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For th e pur pose of the rev iew, the NEA and lAEA constituted a JO int sc ientific sec retariat and appointee! a team of independ ent internat iona l experts from was te manage ment orga ni sat ions, nat ional regulatory bodies , resea rch establishm ents and scient ifi c co nsultancies who are active ly in vo lved in nationa l radio ac ti ve waste manage ment programmes .

The primary focus of th e review was on the technica l sound ness of the analyses and on the DOE app roach to

post-closure performance assessment , exa minee! from an international perspec ti ve . The rev iew did no t fo rmally consider compliance with the US regula tions.

The review was co nducted ove r a six-month periocl starting in October 1996, on th e bas is of deta iled documentation provided by the DOE (the CCA, with its appe ndices , rep rese nts app rox imately 21 vo lu mes of documentati on) , a visit to th e WIPP site, and focuse d discussion meetings between the team of experts and DOE staff and contracto rs.

The final repo rt representing the co mb inee! views and conclusions of the team of ex perts was submitted to the DOE on 9 April 1997 The report conclud es th at th e performance assessment methodology is we ll -fou nd ed and that the analyses reportee! in the CCA are, in the main ,

technica lly sound. The team of expe rts identifiee! technical areas deserving fu rth er attention by the DOE in futu re iterations of their assessment of the WlPP. These areas relate to the physico-chemical conditions in th e disposai room s after closure. The review also recognised that the DOE is already co nducting work in these area

This peer review was organisee! as part of the services offered by the NEA and the lAEA in the field of radioactive waste management to their Member countries Through such peer revi ews, il is possible to benefit from the ex perience of the wo rld 's leading experts in nuclear waste d isposal and rad iological sa fety assessments and to take into account the approaches fo ll owed by other advanced co untries towards th e safe di sposa! of long-livecl rad ioactive waste. Th ese reviews are in tine with th e NEA and the lAEA objectives of promoting the adoption of sa fe policies and practices for the cl isposal of radioactive waste in their respecti ve Member countries.

Note 1 Wa ste tlwt contains more than 3 700 becquerels of a/pha-cmilling

u·ansuranic isoto1Jes, with half-livcs greater than 20 ycars, pu gra mme of waste. So me of thcse radioactive wastcs are mixcJ with ha~ardou s chemicals (mixee/ TRU wastes).

Excavation work through salt rock at the WIPP underground facilities.

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Work management

As we near the beginning of the 2l sl cent ury, the industrialisee! world cont inues to change .

~ o re and more , in ali areas of modern in dustry, eco nomie pressures have made th e concepts of proclucti vity and cost competit ive ness essential lo th e very survival of companies. ln response to th ese pressures, many companies have adoptee! a global ap proach to their wo rk, stressing the importance of approaching jobs from th e multi­di sc iplinary team perspective, an d of following them through the conception , design, planning, preparation, implementati on, an d fo llow-up stages By fo cusing su ch attenti on on jobs, their successful completion- on schedule, within bud­ge t, with a suffi cient leve! of qu alit y, wit h min imum cosl, and with a maximum chance of ful filling the originall y desiree! goal - can be assu reel .

This multi-disciplinary, start-to-finish approach is broadl y termed "work manage ment".

The nu clea r power inclust ry is experiencing the sam e economie pressu res as most other mod ern industries, and is wo rking to increase revenues and recluce costs, while maintaining a suffi ciem ma rgin of sa fety for the public, and reclu cin g the risks to which its wo rkers are exposee! . ln the case of nuclear power, increasing revenues means maximising the operati on ti me (or minimising the omage Lime) of nuclear reactors. Reclucing costs mean s lowerin g expend itures for ma intenance during norm al operati on and during refuelling outages While these two goals may at first seem to be in confl ict wit h those of maintain ing a sufri cient ma rgin of publi c safety and reducin g risks to nuclear wo rkers, 30 years of nuclear power plant opera tion have demonstrated that th e app lica tion of the above-mentioned wo rk management pri nciples in the nuclear power in cl ustry can ensure that they are all attained simul taneously.

To funher stuc! y the process of the applica tion of wo rk manage ment techniques in the nuclear power inclustry, in February 1992 the NEA sponsored a workshop on Worh Man agement to Reduce Occupational Doses. As a fo llow-up , in ] 994 an expert group on th e NEA' s Inte rnational System on Occupa tiona l Exposure (lSO E) Programm e laun ched a stucly to attempt to show, using concrete exa mpl es from inclus tr ia l case studi es , how work manage ment should be applied in the nuclea r inclustry lo save lime and money and at th e same tim e recluce worke r exposure. The work of th e expert group enclecl in

Simulation , on a full-size model, of an intervention in a steam generator.

1996, and a second workshop on the subj ect, produced a "how-to" publication ent itled Wo rh Management in the

uclea r Power lndt1 stryl, ex pl ai ning all the elements a

co mp lete work manage ment progra mme must have to succeed Examples given in thi s doc um ent show how

some of th e best power plants in th e world (in terms of capacity factor, outage length, worker ex posure, etc) apply wo rk management to their adva ntage Seven areas are discussed, including regulatory issues; wo rk management

po licy; wo rker involvement ; work selection , planning and

scheclu ling; work preparat ion; work implementation; and assessment and feedback.

Although this work was motivated by a desire to recluce worker exposure, the docum ent is cl irec ted not only at the radiation protec ti on co mmuni ty, but also at other groups such as pl ant manage rs, maintenance manage rs, outage scheclulers, etc., who co ule! appl y wo rk management techniques in thei r own fields to en han ce

the ir effi ciency. •

Note 1. See "New pub li cati o ns"

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NEA signs a co-operation agreement with the American Nuclear Society

The NEA and th e America n uclear Society (ANS) signee! a co-operati on agreement on 5 June 1997 aimee! at promoting scienti fic and technical exchanges between the two parties.

This agreement is the first of its kind that the NEA has concluded with a national nuclear society, and one of the first to be signee! by the ANS with an intergovernmental organisation It reflects the NEA's desire to improve the

Come and visit us:

visibility of its programmes and products in the gov­ernmental , industri al and sc ientific circles in th e United States and other Mem ber countries, and off ers the prospects of a broader exposure of ANS activities with in those other countries.

The agreement will initia ll y focus on joint sponsorship of scientific andtechnical meetings and on joint marketing of publications. •

New N EA site on the WEB • • •

other Resources

llllllF.2 ai'ia Th e objective of the Age ney is to con tribute to the devel opment of nuclear energy as a safe , environmentall·y-acceptab le and economical energy source through co-operation am ong its participating co untries.

1 La mission de l'Agence est de favoriser, à t rave rs la coopération entre ses pays Membres, le développeme nt de l'énergie nuclé aire en tant que source d'énergie sû re, économique et acceptable

po ur l'envi ronnement.

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Radi ation in Perspective: App lications, Risks and Protection

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Everyone on earth is exposed to natural radiation. Radiation produced artificially is no different, either

in kind or in effect , from that originating naturally. Although radiation has many beneficial applications, in medicine, industry and research , it can be harmful to human beings who must be adequately protected from unnecessary or excessive exposures. For this purpose, a thorough system of international principles and standards and stringent national regulations have been put in place. Yet radiation continues to be the subject of much public fear and controversy. This report, intended for the non­specialist reader, aims to contribute to an enlightened debate on this subject by presenting the most up-to­date and authoritative material on the sources, uses and effects of radiation, and the ways in which people are protected from its risks. It discusses the development of radiation protection measures, its internationally agreed principles, and also addresses social and economie issues such as ethical questions, risk perceptions, risk comparisons, public participation in decision-making and the cost of protection.

Management of Separated Plutonium - The Technical Options

ISBN 92-64- 15410-8

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Stocks of separated plu­tonium in the civil nuclear

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Nuclear Safety Research in OECD Countries Areas of Agreement, Areas for Further Action , Increasing Need for Collaboration

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The international nuclear safety community shares

a range of specifie concerns. Continuing research is neces­sary to address many of them. In this report, senior experts discuss research areas of special importance for safety and regulation, safety

research areas for which a common technical position exists, a reas for which further discussion is needed in arder to achieve a common technical position , and areas to which priority should be assigned.

4

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Work Management in the Nuclear Power Industry A manual prepared for the NEA Committee on Radiation Protection and Publi c Health by the Information System on Occupational Exposure (ISOE) Expert Group on th e Impact of Work Management on Occupational Exposure.

ISBN 92-64-15459-0

Pri ee. ff 150 US$ 30 DM 44 L 19 7" 3150

As we ne ar the begin ni ng of the 21st century, the industrialised world continues to change. Economie

pressures in all facets of modern industry have made productivity and cast competiti veness increasingly esse ntial to th e ve ry survival of campa nies. Many of them have therefore adopted a global approach to their work, stressing the importance of considering jobs from a multidi sciplinary team perspective, and of follo wing them through all stages of co nception, design , planning, preparation , implementation and follo w-up. Thi s

C-\ 1• ' 1 1 1

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OECD DOCUMENTS

Work Management in the

Nuclear Power Industry

~AEN Qd' N EA

focus assures sucessful job completion - on schedule, within budget, with a sufficient level of quality, with minimum cast, and with a ma ximum chance of fulfilling the originally desired goal. This multidi sciplinary, start-to-fini sh approa ch to jobs can be broadly termed "work management".

This publication presents the concept of work management in very concrete terms: it presents details of ho w to implement work management in such areas as regulation, work-management policy, worker in volvement, work selection, planning and scheduling , work preparation , work implementation , and work assessment and feedback. Numerous case studies are presented of actual experience from the commercial nuclear power industry. This is a useful tool to help plant managers , maintenance engineers, outage planners, and radiation protection personnel to improve their implementation of work management, which can lead to reduced numbers of workers needed to perform a job, of persan -hours spent in the radiologically controlled zone, and thus the overall cast of doing work. Moreover, this also leads to reduced occupational exposures in an "ALARA" (a s la w as reasonable achievable) fashion.

Nuclear Law Bulletin

ISSN 0304-3 41-X

Ann ual SubscripUon

FF 290 US$ 58 DM 88

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No. 59+ Suppl ement

June 1997

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NUCLEAR LAW

Law Bulletin is a unique international pub li cation providing its subsc ribers with up-to-date in fo rm ation on all majo r developments falling within the domain of nuclear law. Pub lished twice a yea r in bath Engli sh an d French, it covers legis lative developments in almost 60 countries aro und the world as well as reporting on relevant juri sprudence and ad mini stra t ive decisions, bilateral and international ag reements and regu latory acti vities of internationa l organ isatio ns.

Implementing Severe Accident Management in Nuclear Power Plants

ISBN 92-64-15286-5

Priee: FF 220 US$ 43 DM 64 L 28 7" 4600

Many countries ha ve pro gressed in their work on implementing severe accide nt mana gement prog rammes.

In this report, sen ior experts analyse and inte­grate the res ults of severe accident manage­ment research and imple­mentation to date by describing the major decisions associated with severe accident manage­ment, the remaining open items and areas of u ncertai nt y, a nd the status of implementation in OECD countries.

SMORN VII A Symposium on Nuclear Reactor Surveillance and Diagnostics Avignon, France, 19-23 June 1995

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Un symposium sur la surveillance et le diagnostic des réacteurs nucléaires

Free on request.

Nuclear Energy Data- 1997

ISB N 92-6-f-05520-7

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Nuclear Energy Datais the OECD Nuclear Energy Agency's annual co mpila ti on of basic statistics on electricity

genera ti on and nuclear power in OECD cou ntries. The reade r will have quick and easy reference to the status of and projected trends in total electrici ty generating capacity, nuclear generating capacity, and actual electricity production, as well asto supply and demand for nuclear fuel cycles se rvices. This publication contains, for the first ti me, data for the Czech Republic and Hungary.

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Nuclear Safety Research in OECD Countries Capabilities and Facilities

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I n this publi cation , senior experts discuss existing

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needs identified in two previo us publications: Nuclear Safety Research in OECD Countries and Nuclear Safety Research in OECD Countries: Areas of Agreement, Areas for Further Action, Need for Collaboration. Practical means are proposed to address the concerns.

Computing Radiation Dose to Reactor Pre-ssure Vessel and lnternals

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COMPUTING RADIATION DosE TO

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Employment Opportunities

OECD Nuclear Energy Agency, Paris area

Vacancies occur in the OECD Nuclear Energy Agency Secretariat in the following a reas:

Energy Economies Nuclear Safety Radioactive Waste Management Radiation Protection Nuclear Energy Economies Nuclear Science Nuclear Law Nuclear Engineering Computing

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Basic annual salary: From FF 300 000 (Administrator) and from FF 430 000 (Principal Administrator), supplemented by allowances depending on residence and family situation. Vacancies are open to candidates from OECD Member countries. OECD is an equal opportunity employer. Applica tions, in English or French (specifying area of specialisation and enclosing detailed curriculum vitae) should be marked "NENNL" and sent to:

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