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TITLE: REYIWOF NEW DEVELOPMENTSIN F’USIO:: RE4CTOR IWCLEONICS

AUTHOR(S) I Donald J. DudziakPhillip G. Yaung

MM’ERSUBMITTED TO: Submitted to Fourth Topical Meeting on The

Technology of Controlled Nuclear Fusion,14-li October 1980, King of Prussia, PA

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Fom No,M R3St.No, ?S?912/70

RIVIIWOF NEw DIVILOPMINTS IN FuSION REACTOR NUCLIONICS

Donald J. Dudzfak and Phillip C. youngTheoretical Division, Los Alamos Scientific laboratory,

University of California, Los Alamos, New Nexico

A9STRACT

A re<iew is presented of recent develop-ments in nuclear data, computational m~thods,and computer codes, especially as pertainsto fusion reactor nucleonics, Importantnuclear data measurements, evaluations,nuclear model c~des and processing codesare discussed. Progress in solution accel-eration and deterministic streaming methodsfor discrete-ordinates codes is covered,along &ith comments on recent Monte Carlodevelopments. Finally, sensitivity anduncertainty analysis methcds are reviewed,

INTRODUCTION

Two main paths of development haveoccurred for fusion reactor nucleonics -nuclear data and neutron/gammd-ray transportmethods, Each path has included basicfoundations which were laid down {n thepast for other nuclear programs, Witha few notable exceptions, the data, methodsand codes in use toda] for fusion reactornuclrar analysis are adapted from thosrprograms, The present review is confinedorimarily to recent dev~lopments in directsupport of the U.S, fusion reactor technologyprogram, previous work in other programsalready havi,~gbeen cxtensivaly r~viewed ‘-6for \ts applicability to fusion raaCtOrS,

Over the past sev~ral years, consider-able effort has

!or,e into identifying

deficiencies in nuc ear data that impactfusion reactor designs, Problems that hawbeen en?phesized fnclude evaluation formatdeficiencies,e lack of energy balance inENi)F/B-k evaluations,? gaps in the avail-ability of particular types of data,”’t andinadequate accurac in certain evaluated dataas identified !. Sptcific sensitivity/covariance analyses,lo A fusion energy datar,,que$tIistll has evolved and has ~~rved tofocu$ certain differential dnta measurementprograms on fu$lon data nepds, Progress hasbeen made in \everal important arms,including n~w data on tritium production andother IWkJtrOII reactions with ‘Li and 7Li,neutron reactions with W isotopes, charged-

pssrticledata, emission spectra for secondaryradiation, nuclear mode1 codes, afid newevaluated cross sections and covariance datai’iles,

Processing codes have been expanded toaccommodatenew fNDF/B formats and to general-ly provide fncreased {nformatfon. Generalpurpose data libraries such as ENDf.iB-V,GAMDAT78 12 and series 1-7 of the MAT)(SIibrary]i are now available at the NationalMagnetic F!lsion [nergy cOKIl)Llting cf?f’ItCr

(NMF[CC), In addition, the TRANSXIS andNJOY]4 processing code systems as well as theGAMMON activation librarylb are operationalat the NMf[CC. The GAMMON library, which{S specifically desiqned for fusion reactorapplications, contains multigroup crosssections (100 energy groups) for 420 neutron-induced reactions, multigroup

7aroma-ray

spectra (25 em=rgy groups) for 10 uniquedaughter products, maximum permissible con-centrations (MPC’S) for 200 reaction pro-ducts, and absorbable decay energy (stnsibleheat) for 85 products,

Because of the breadth of data needs,we will restrict our discussion to a f~wof the more visible problems and willtmpha$ize the measurement, calculation, andevaluation efforts for these cases, A morecomPlete r@vi@w of fusion data activitieswas recently given by haight.’6

Specific are~s of development fn trans-port methods and cod~s during recent yaarshave fncluded new one-dimensional (l-O) and2-0 discrete-ordinates codes, with faaturesSpecifically de$igned for :,Id/o! applicableto fusion reactor design, The principalnew features in 1-D have included greatlyimproved @ffici@ncy (i.e., reduced computationtiMeS) by di?fu:ion synthetic acceleration, acompletely new and mnrmonic-orlcntpd fre~-field input format, and evolutionary improve-ments in hiercrchlcal ttorage ctrate ies,output and @alit features, *tc, 1!The ON OAN1codel!, incorporating these features, is nowgenerdlly available on the NMIECC along withmultigroup data libraries, Simila!ly, the

2-D triangular-mesh code, TRIDENT-CTR,la isavailable on the NMFECC for fusion reactorblanket/shield analysis. Reseirch is pre-s,>ntly underway to incorporate deterministicstreaming methods into TRIDENT-CTR, with theultimate goal of achieving accurate discrete-ordinates solutions in the vicinity of largevoid regions such as vacuum ducts, plasmachambers, etc.

The principal recent developments forMonte Carlo codes have consisted ofevolutionary improvemc.nts in geometryroutines, output of physically significantparticie history data, variance reductionguidance for the user, and general codearchitecture. Adaptations for fusiontechnology applications have been made to theMCNP code,lg which is being used on theNMFECC for nucleonic analyses of the FusionMaterials Irradiation Test (fMIT) facilityand se~lr#S fusion reactor concepts (e.g.,EBTR, Fast liner Reactor, ReverseField Pinch ~eactor). Of particular interestis the increased use of both deterministicand stochastic transport codes for analyzingneutral atom distributions in plasma, limiterand divertor regions.20’zi

NUCLEAR DATA

Neutron Reactions on 6Li and ?Li

Extremely important processes for a D-Tfusion reactor economy are the tritium pro-duction reactions for 6Li and 7Li. While theaLi(n,t) cross section is thought to bereasonably well known in the r~gion ofimportance, serious questi2ns have beenraised about the accuracy of the ‘li(n,n’t)reaction cross section that is currently inthe ENDF/B-V evaluated data file, The over-prediction of tritium production in integralexperiments suggests that the ENDF/B tritiumproduction cross section for 7Li mi ht befrom 10 to 35% too high near 14 MeV.a2’14 T~c

new differential data from Swin$oe anduttley~b and Smith et al,,26 which areillustrated

r&t this

meet{ng,27 inj~cat~nO~t$rENDYBerdata shouldbe lowered from 15 to 25%, Ot,hernew tritiumpro{ lction data ●t 6 and 10 MeV (fnferredfrom the n~utron emission results of Lisowskiat al,aa) te+ndto support the @xisting ENDf/8valu@6, but with relati~ely large uncert-ainties, 10 summarize, th~se new resultsare all consistent with a lowering of theENDF/B-V tritium production cross tection,but there is disagreeme~~ton th~ magnitudeof the corrections, An additional diftm-ential measurem~nt is in progress at Geel,wh{ch should help clarify the situation.

Other new differentitildata hav~ becomeavailable rec@ntly that should indirectly aidin determining tha ?Li(n,n’~) cross section,

as well as in generally improving 6Li and?Li neutroniC5 data. These results includenew total cross section measurementsz9’30between 0.1 and 50 MeV, differential elasticangular distributions3]’32 between 4 and 14MeV, measurements of neutron emission

, and several new“~~~~~~~~~nt~\~fssandoflOt~~vTLi(n,n’y) CrOSS

“section that cover the energy range fromthreshold to 20 MeV. Of particular importancefor fusion applications are the differentialelastic and n~utron emission spectrum measure-ments between 9 and 14 MeV. The elasticangular distrib~ltions measured by Hogueat al,32 between lC and 14 MeV are compared tothe ENDF/B-V evaluation in Fig. 1. Signifi-cant differences between experiment andevaluation are seen at some angles. Newevaluations for 6Li and ?Li that consider bothold and new experimental data are currentlyin progress at Los Alamos Scientific Labora-tory (LASL) by one of the authors (Young),

Neutron Reactions on Tungsten

One of the conclusions of a recent un-certainty analysis by Gerstl et al,]o is thatboth the cross sections and neutron emissionspectra for tungsten are probably inadequatefor fusion reactor designs that employ signi-ficant amounts of tungsten for shielding.

~~z;~~~:{~ as shownin another paper at this

measurements from the L~ ‘ermorePulsed Sphere program also indicate that the[NDF/B-V tungsten isotope evaluations leadto seriously deficient neutron emissionspectra for la-MeV incident neutrons,

As a result of these problems, a newevaluation of the ns+utron-induced data fortungsten isotopes is in progress,a6 Thenew evaluation couples recent tot’1, elasticscattering, and (n,2n) cross-sectionmeasurements with a modern nuclear theoryanalysis that should significantly improvetungsten data in the 0,1-20 MeV re ion, The

!UC? of nucldar-inodelcalculations w 11 removethe discrepancies between neutron and gamma-ray emission spectra that have led to theserious energy balance problems ~vident inthe END(/9-V evaluations.? The calculatedneutron 9m{ssion spectrum for 14,6-MeVincident neutrons is compared in Fig, 2 toboth ENDF/B-V and to a measurement byHerm$dorf et al,a? Note that the discre-pancy between lNDF/B and the measurementsbetwem 5 and 11 MeV is greatly reduced bythe new calculations, although not entirelyrea!ovtd.

~harg~d-Particle Reactions

Whil@ v~ry thorough R-mutrirnsnalysetsahave been performed for th~ most im ortantfusion reactions, 1’the results are st 11 dP-pendent on the ●ccuracy of ttw experimental

2

data base used in the analyses. The experi-mental data for certain key ,eactions, suchas D(t,n)4He, D(d,n)3He, D(d,p)l, and T(t,2n)~He, mainly consist of measurements perform-ed 25 years ago, and the accurac::::l:s subject to some question.i9*:i ‘:;s:

a program to measure these crosssectio;s down to as low an energy as possibleis in progress at LASL.do The energy rangefor the new measurements is lC-120 keV, whichcorresponds to plasma ion temPeratur@$ of2-20 keV. The desired accuracy is i5% orless, which is as much as an order of magni-tude better than existing knowledge at thelower end of the energy ~ange The experi-mental approach consists of using a sourceof negative hydrogen ions to bombard awindowless, cryogenically pumped ga$ target.The beam intensity is determined by c~lori-metric means, and the crucial beam-energymeasurement is to be facilitated by a plannedlaser-photodetachment, time-of-flight techni-que. The target density is calibrated duringthe experiment by using scattering or re-actions of known cross sections induced by10-15 MeV particles from a tandem Van deGraaff accelerator.

To avoid tritium contamination problemsuntil the equipment is thoroughly developed,the initial experiments involve only theD + D reactions, Preliminary data have beenobtained for the D(d,p)T reactions between40 and 118 keV, It is expected that during1981 final data on the D + D reactions willbe obtained and work on the D(t,n)+He reac-tion will begin, The T(t,2n)4He measurementswill be performed last because of theirrelatively greater difficulty,

Neutron, Charq@d-Particle, and Gamma-Rav—.~mIssIon Data

The need for more accurate ●mission datafor secondary neutrons, gamma-rays, andcharged-particles has become tncreosinglyevident with improvements in methods and codesfor neutron transport, heating, and radiationdamage calculations, Experimental facilitieshave been develop~d at LA>L and at theTriangle Universities Nuclear L@oratory(TuNL) for measuring neutron emission spectrainduced by neutrons in the PieV●rrrgy r6Jion.Thus far, measurements have been made for &10”, and 14-MeV incident neutrons at LASl*~’41for 61i, ?;1, ‘Be, 10B, and “D, &nd atseveral energies between 8 and 14 McV atTUNL42 for Fe, Cu, Ni, and Pb, Similarly,neutron spectrum measurements have been snateat the Oak Ridge Electron Lfnac Accel@rs*,or(OR[LA)43 for ‘Li, Al, 1(, Cu, and Nb Anexample of Pmeasurement forThese data haveQvaluat{ona thatENOf/B-V,

neutron em{stion spectrum‘Be is shown In Ffg, 5,b~en incorporated Into andiffers significantly from

hn extensive set of measurements ofgamma-ray emission spectra using the ORELAwhite neutron source has been carried out atOak Ridge.4s These results gefi~rally spanthe incident neutron energy range from 1 to20 MeV and have been performed for most ofthe common materials. In addition, a seriesof gamma--3y spertrum measurements for mono-energetic 14-MeV neutrons has been carriedout at LASL44 for a variety of materials.These measurements have been very usefu’1forgamma-ray production evalua+.ions, althoughsome discrepancies are known to exist betweenthe two sets of data.

The information on charged-partizl~emission cross sections and spectra isdecidedly less abundant than for gamma rays.Two experimental programs that deservespecial mention are recent helium productionc,’oss-sectionmeasurements that utilize highsensitivity mass spectrometry45 and charged-pdrticle emission spectrum meas~rements madewith magnetic quadruple spectrometers.46These programs hav~ provided data for severalmater{als of tnterest at E = 15 MeV andshwld be very useful In the future as moreenergies and eleme,]tsare covered.

Nuclear Model Codes and Higher-Enerw Oata

Considerable progress has been made overthe past decade in development of nuclear-model codes for use in Complementing;experi-me,,taldata in evaluations and even for pre-dicting unmeasured data (see Refs. 47 and 48for recent reviews). Of most interest forfusion reactor applications are several newmultistep Hauser-Feshbach/preequil~briummodel codes tnat are capable of handling thenumerous reaction channels that open in theneutron energy ~ange from 7 to 50 MeV, Thecodes in most comnon use in the UnitedStates are GNASti,40HAUSER-5,s0 STAPREbl andTNG,S2 When care is taken to obtain physicallymeaningful model parameters, these codeshave been quite successf~l in tying togwtherand extrapolating ●xperimental information.Such calculation have the additionaladvantage that ●nergy conservation is builtInto the models. It is expected that thesemodels will be a Aey element in augmentingexperimental data in the 1O-5G MeV regionfor the FMIT facility.

Analys~s covering the incident neutronenergy range from %3 to 40-50 MeV haver~cently been carried out for “’s6Fe, **CO,and aa’60Ni at LASL using tht GNASH code,Neutron, gamma-rly, and proton emis$ionsp?ctrs for 14-MeV neutrons incident on ironfrom a sin le colculat~ongs are compared toexperlmenta! data44’46’B4 In Fig. 4. Thea reement is reasonable, especially con-!t dering +jh#t these m~asurelfi~nt~were no:used fn dctetvnining the mod~l paramet~rs.

Results from the 5gCo analysisss are comparedto measurements of (n,xn) cross sections inFig, 5, and the full bsCo cross-section pre-dictions to 50hieV are shown in Fig. 6.

Covariances

A significant expansion of covariancedata occurred between ENDF/B Versions IV ?.ndv. The number of ENDF/B-V general purposeevaluations containing covariance data is nowabout 24 and includes many important fusionmaterials. For the first time: covariancesfor resonance parameters are given for somematerials, although the information is notcomplete. Materials having covariancesinclude W, 6Li, ‘%, C, “N, 160, 27AQ, Si,Cr, Fe, Ni, and Pb. The covariances aremail?y for smooth cross sections and theentire energy range Is not covered in allcases. Important omissions in the list ofmaterials are ?Li, Cu, ant the W isotopes.Additionally, there are no covariances forangular distributions or secondary energydistributions. Simplified, ad hoc analysesof secondary energy distribufion~have beenperformed for use in sensitivity analyses,ioand the need for such data in evaluations isevident.

Summary Comments on Nuclear Data

In the abov~ sections, we t,ave high-lighted some of the nuclear-data developmentsof the past few years, Progress is evidentin several important areas, and significantadvances have clearly been made. However,we should point out that a number of problemareas remain in the data. For example, thereis still significant disagreement among eventhe new ?Li(n,n’t) measu~ements; betwem 7and 14 MeV, there are still large gaps Inmost of the required data, especially neutronand charged-particle ●mission spectra;experimental data of any type are very sparsebet~een 15 and 50 tleV; reaction data forneutrons incident on radioactive nucle{ arevirtually nonexistent; energy imbalanceproblems are present in many ENDF/B-V evalu-ations; significant deficiencies still Qxistin theoretical model codes and improvementsare needed; and the covariancc data presentlyavailable in ENDF/B-V is l{m{ted both Inqual{ty and In the extent of reactfons andmaterials for which data are provid~d.

sINS:TIVITY AND UNCERTAIN?YMETHOOS

]nextr{cably tntwined with the assess-ment of nucl~ar data needs snd adequacy ftthe quantttatfve methodology known genericallyas sen$itlvity analysis, but includ{ng bothsensitivity and uncertainty calculations.The theory is founded on ${m lC pstrturbation

rmethods, with wid~ applicat ons to fios{onand fusion reactors. A racent cxpocition!a

gives an excellent summary of numerous appli-cations of ordinary and generalized perturba-tion theary. Specific fusion reactor appli-cations usually require only the inhomo-geneous source case, and have been reviewedextensively.??’58 An exception to the inhomo-geneous source restriction occurs for fusion/fission hybrid reactor analysis.!*’60 Beca~seof the extensive review literature available,the present discussion is confined to (1) therecently released SENSIT code; (2) secondaryenergy and angle distribution sensitivity;and (3) 2-D sensitivity analysis.

A latest generation sensitivity code,SENSIT,8i is cttrrently operational on theNM~ECC network. The code is specificallytailored for fusion reactor sensitivity anduncertainty analyses, both for cross-sectior,errors and design perturbations. Included inthe cross-section category is the capabilityto compute sensitivities and uncertaintiescaused by secol~dary-neutronenergy and cngledistribution errors.c2 As has been shown ina comprehensive analysis for a fusionreactor,io the secondary-en~rgy-distribution(SED) contribution to response uncertaintiesis generally lower than that from cross-section uncertainties, but not negligible.For the TNS design analyzed “in Ref. 10, theoverall uncertainties in TF-coil dpa were 72%and 33% (at the 68% confidence level) fromcross-section find SED uncertainties,respectively.

Capabilities for design sensitivityanalysis have yei to be ●xploited exten-sively. Effects on various mscleonic designparameters (e.g., dpa and kerma) can Deeasily determined for small perturbations inblariket/shield region dimensions, densities,material compositions, ●tc. Such analyseswith a dtsign sensitivity code could readilybe adapted to shield optimization studies.

Two-dimensional sensitivity analyses havenot yet been warranted for fusion reactorstudi~s, mostly because of the conceptualnature (and therefore lack of detail) of suchd@SfQni, However, the ETF project or itssequel (FED) w{ll providt a requirement forsuch malyses in the next few years, as thesh{cld designs firm. Some capability alreadexfsts for 2-D rross-section sensftivity,?e’e{

and has been applied to a p“eanalysic of theORN1 fu$lon reactor shielding experiments.a’For this particular applicatfcn, the adequ~c,vof a 1-D sens{t!vfty study was demonstratedby comparison with the 2-II analysts, As iSthe case for 1-E), the 2-D methods and coc%sare read{ly expendable to design $@n${tivity#nd shield optlm{zatfon when requ{red,

TRANSPORT METHODS AND COOES

[~tensive work to improve neutron/gamme.ray transport numerical methods has been per-

4

formed in the last few years. An adequatereview, however, is beyond the scope of thispaper. Thus, we will confine ourselves tobrief dis~:lssions of some major new methods,codes or cod(? versions of particular interestto the fusion community.

One-dime,,>ional discrete-ordinates codesare the workhorses of the routine, but veryimportant, blankeL/shield design tradeoffstudies. Such codes are long established,but still have been greatly improved inrecent years. Some of these improvementshave consisted of correcting ●sotericanomolies of the solution algorithms, butothers have provided more stablt ●rid/oraccelerated solut,ons to the majority oftypical fusion reactor transport applications.In the latter category is the diffu$ion syn-thetic acceleration technique employed in ‘heONIDANT code.l? Th{s acceleration techniqueis increasingly ●ffective as a transportproblem approaches one amenable to diffus{ontheory, so Its value may be grentest infusion/fission hybrid reactor ana?ysis.Typical reductions of the solution times,●xclusive of input and edit data processing,are a factor of 2 to 5, depending on theproblem spectra, source distribution, scat-tering-to-absorption ratios, ●tc. Anotherrecent enhancement of ONECANT, specificallyincluded for neutral-atom transport analysis,is a general albedo boundary condition allow-ing returiling particles in all energy groups.

Reduction in computation time have theirgreatest payoff in 2-D transport codes, whichtypically run about two orders of magnitudelonger tfmes than 1-0 codes. One such 2-Dcode , TUOOAtiT, {s s.chedul~d for r~lea$e inab~ut a year. Realistic test probltmsa! witha preliminary version of the code {n use atLASL , THGTRAN-DA, also have shown reducsdcomputation times bv factors of 2 to 5,

Another 2-D discrtte-ordlnatcc cwh ofdirect fnterrst to the fusion raactor corrrnu-nity Is TRIDENT-CTR Although this tri-angular-mesh code ha~ been avallcbl~ for sometime on the NMFECC, it has b~en continuallyundergoing ‘mprovcm*nt as new and chall~nglngfusion r*i~~tornucl~onlc probloms arfcs (o,g,,cf. other I)ap?rsin this S@ssion dealing w~thapplicat(on$ of TRIDENT-CTR to ETF and EBTR).For ●xample, the code now allows fnternalboul,rjarysourczs (tuch at tht w~llt of NB1or vacuum d~rts) and is llnkcd to r surfacesource produced by a Monte Carlo cod., Thcrsquircd linking to MontQ Carlo output!llu6tratts m current shortcoming of alldiscr~te-ordinates cod~s; viz, tho str~aming@ffectt problem {n larg~ votd

!r~ tons.

DcvrlopmPnt cffortl for ditcra:t-ord natotcod~ applicat~on~ to fution problomt art nwdlrrnc:cd mainly to thli shortcoming

!’Effortt

to onwli,lrat~ the num?r{cal .trtam ng offccts

are being undertaken in what 1s called d~te~ministic streaming methods. One such ●ethodthat shows considerable promise of short-termpayoff {s being actively pursueduu for x-y andr-z geometries. Plans are to ●xtend themethod from the presently developed orthogonal●eshes to triangular meshes, for ultimateincorporation into TRIDENT-CTR. implementa-tion of deterministic streaming methodolowshould allow the direct use of discreteordinates in regular geometries, where MonteCarlo calculations are now required solelyfor the streaming aspects of problems ratherthan because of geometric complexity.

Development of 3-D discrete-ordinatescodes hcs lain dormant for the last two years,since the completion of the THREETRAN ●ndTHREETRAN(hex,Z)e? codes.* However, interestin ●xtending these codes has been shown inthe statement uf ETF supporting R&D needs,*?where analysis of divertor coil shieldsr~quires such capability. Adaptation ofthe 3-D codes to the selected specializedfusion application~ (which could includeneutral-atom transport in diverters orlimiters) could probably best be done on an~d hoc basi However, additional code=ve@iment wu~ld be required beforehand to●xtend the capability:’ to P3 scattering ●ndincreased convergence ●cceleration.

Rec@n: developments In Monte Carlomethods and cod~s were discussed ●xtensively‘t the April 1980 RSIC Monte Carlo Theory~nd Application Seminar-Workshop, the pro-ceedings of which were published as ORNL/R’iIc-44. Host fusion applications haveil,volved MCNP, MORSE or TARTNP. Evolution-ary improve~nts in the first two codes werecovered in paperc at the abovsmentionedseminar. and cannot be r~vl~wed in detailwithin th~ scope of thit paper. Hwavtr, ●sa generalization It appears that progr~ss hssoccurred on two fronts whfch w?r~ r~comm+ndedby variousF;:;Jon r~actor nuclconics WorkingGroups, user-orltnted Inputm{~ulcs (e.g., ‘geo~eyry specifications) ●ndcode mnuals •r~ ~ppeavtng; and, second,u~eful “event” information it being computodand cditod to improvt the us~r’r understandingof the phytfcs of tht problem solution m5 Itprogrcssct, Ret@arch has contfnucd onimproved b{aslng tcrhnlqu~s and protocolsfor employing the techniqutsl” ’so’ce, butlittlt progrets has occurred in automatings?l~ctlon of, for cxampl~, exponential-biasor splitting parameters in production codes.

~est codrs (IOWprovidr only tfw rudlm~ntarycapabil~ty to gentratc virtually unacctlt-ratcd solutlons for PI scattering.

In summary, we have attempted to reviewrecent developments in transport codes, with-out necessarily commenting on the adequacyof the effort as compared to the needs.Another paper2? at this meeting addressesthe status and needs questions. It is ourobservation that the present pace of devplcp-ment is inadequate for even the well-definedneeds, without accountf~g fur the unpredictedrequirements which inevitably ●volve asprojects such as ETF approach a detaileddesign st~ge.

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m-

Zyg~

E U MEV

w

B““o5,

~

T

t

c’ 1 , , \Ino m 030 0ss OCCI-02s -m -m -sm

C08 THETA (CM)

Fig. 1, Elastic scattering angular dis-tribution for n + ‘Li. Iiisolid curve- sre from ENDF/B-Vand the ●xperimental point- ●rmfrom Baf. 32.

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W(N,XN) EMISS. SPECX. - 14.6 MEV

-r 1

‘.L--++-tQ-b : I0.0

I

rig. 2.

20 io 60 tio 10.0 12.O 140 160NEUTRON ENERGY (MEV)

Neutron ●mission epectra from 1,4.6WVneutron Interaction with W. The filialcurve is from recent calculations,the dashed curve is from ENDF/B-V. andthe points are ●xperimental data from8af. 37.

9

.— —

- /\ -1

-d●

9

9Hi!

“ ‘o

i

-.0 hhl

. Ww B-IV[—)— - -.70 ,1- OD 20

~40 60 so 10 0

Ntu~rol\tnrr~v (McV)

Fig. 3. 9Be neutron ●m-lesion npec[ra .C35° induced by 10.1-WV neutrcns.The .9nlid curve is ● new ●vslua.tion,’ [he dashed curve la ENDF!B-V, ●nd che poiocn are from

Ref. 41.

MEWRON ENERGY (MEv)

E= N+FE GAMMA-RAY EMISSION AT 14 w

N+FT PROTON EMISION AT 14 UTV

u

PROTOS ENERGY (MEv)

?i~. 4. Neutron, gmma-ray, and proton ●missionspectra from 14-WV neutron Interactionswith Fe. The curveE repreRent a recent

calculation,” and the ●rperiunt~l

Win[- ● re from Refb. 44, 46, md 54.

L41 i I I i I 1 1 I I I I I I

1.2~\

5gCo(n, xn)-i

Ot-l.- \ I I

,:, y.”]

(n,n’)

[/

‘!

0.4

0.2I

J21-14Jllld”(n,3n)10 12 !4 16= 18 20 22 24 25

En(MeV)

Fig. 5. S9co(n, n) ~ro6S sections from 1o-25 ~VOThe solid curves ● re

c.llculstions by Arthur et al. ,$s end the points are ●xperi~ntaldsta from several sources (see Ref. 55 for details).

L I I I I I I I I I i 1 I I ,1

JJLLIAd‘V.zm...-”.

040 12 16 20 24 28 32 36 40 44 48En(MeV)

Fig. 6. Cross section. in n + ‘s~ remction~ calculated (Ref. 55) between3 end 50 USV.

$

11