THE FUKUSHIMA ACCIDENT: CAUSES, RESULTS AND …New calculation of accident progression in Unit 4...

07-Nov-11 Lecture 3: Fukushima andSimilar Units in Europe

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THE FUKUSHIMA ACCIDENT: CAUSES, RESULTS AND

IMPLICATIONS FOR EUROPE

Steven C. Sholly, Senior ScientistInstitute of Safety and Risk Sciences

Department of Water, Atmosphere & EnvironmentUniversity of Natural Resources & Life Sciences

Course 818022 (Winter 2011)


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Fukushima Accident Update

Fukushima Update 1

• New calculation of accident progression in Unit 4 spent fuel pool by Dr. John Luxat (Research Chair in Nuclear Safety Analysis, Department of Engineering Physics, McMaster University, Canada

• Presented at the NURETH-14 conference in Toronto, 27 September 2011


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Presenter

Presentation Notes

SOURCE: http://nureth14.org/media/NURETH-14_Panel_LessonsLearnedfromFukushimaAccident/LuxatJohn%20FUKUSHIMA%20DAIICHI%20ACCIDENT%20PROGRESSION%20-%20NURETH%2014.pdf

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Fukushima Update 2• Recall from Block Lecture Number 2, Japanese

government reports suggest that hydrogen was transported from Unit 3 through the stack release ductwork, and flowed backwards into Unit 4

• But why didn't Unit 4 explode when Unit 3 detonated?

• And note – the ductwork at Unit 3 was blown apart in the Unit 3 hydrogen detonation, so no further hydrogen could have moved from Unit 3 to Unit 4 after the Unit 3 detonation

• You will recall the NGOs and independent scientists suggested that the Unit 4 spent fuel pool was the source of the hydrogen in Unit 4

Lecture 3: Fukushima andSimilar Units in Europe

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Fukushima Update 3

• On 17 March 2011, US NRC Chairman Gregory Jaczko announced that the US had indications that the Unit 4 spent fuel pool was dry

• Spraying of fresh water onto the Unit 4 spent fuel pool did not take place until 20 & 21 March 2011

• Concrete pumping truck started pumping sea water to the spent fuel pool on 22 March; pumping of fresh water began on 30 March


Presenter

Presentation Notes

Bullet #2: First Japanese Government Report to IAEA, page 13. Bullet #3: First Japanese Government Report to IAEA, page IV-35

Fukushima Update 4• When cameras were finally able to film the Unit 4

spent fuel pool, the pool was found to have the fuel covered by water that was steaming

• There is no visible evidence of fuel damage (i.e., no warping of fuel channels, no warping of fuel assemblies, no charring of pool walls due to hydrogen combustion, no settling of fuel assemblies due to slumping from melting

• Pool water water samples provide no evidence of fuel damage, etc.).


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Fukushima Update 5• Water volume = 1,425 m3, 2.3 MWt of heat

generation in Unit 4 spent fuel pool• # of spent fuel assemblies in pool = 1,331 (large

number due to full core offload to spent fuel pool to allow replacement of core shroud)

• Newly calculated timeline for Unit 4:– 11 March, 1447 hrs – Earthquake offshore– 11 March, 1538 hrs – Tsunami strikes plant resulting in station

blackout, loss of spent fuel pool cooling, loss of capability to pump additional water to spent fuel pool to make up for losses due to boiling of pool

– 12 March, 2100 hrs – Uncovery of fuel in Unit 4 spent fuel pool starts (calculated)


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Presentation Notes


Fukushima Update 6

• Newly calculated timeline for Unit 4 (continued from previous page):– 14 March, 1101 hrs – Hydrogen detonation in Unit 3 causes

damage to reactor building wall of Unit 4– 14 March, 2100 hrs – Hydrogen generation begins from

oxidation pf spent fuel in Unit 4 spent fuel pool (metal water reaction of spent fuel cladding with steam) (calculated)

– 15 March 0600 hrs – Hydrogen deflagration/detonation at Unit 4

– No significant release of radioactivity from fuel in spent fuel pool (calculated)


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Presentation Notes


Fukushima Update 7• If Unit 3 was so closely connected to Unit 4 via

the exhaust piping, when Unit 3 exploded so would Unit 4 likely have exploded simultaneously

• Instead, the Unit 4 hydrogen detonation/deflagration occurred 19 hours after the Unit 3 detonation

• It appears that even if some hydrogen migrated from Unit 3 to Unit 4, the quantity was not enough to cause a hydrogen deflagration at Unit 4 when Unit 3 exploded (and note that the Unit 3 explosion was violent enough to damage walls at Unit 4)


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Presentation Notes


Fukushima Update 8• The calculations by Dr. Luxat indicate that

hydrogen production from the Unit 4 spent fuel pool started 10 hours after the Unit 3 explosion

• The Unit 4 explosion occurred 9 hours after hydrogen generation is calculated to have begun in the Unit 4 spent fuel pool

• My tentative conclusion is that the Japanese Government report is incorrect about the source of the Unit 4 hydrogen – it came primarily from metal/water reaction in the Unit 4 spent fuel pool, not from Unit 3 via the exhaust piping


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Presentation Notes



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Introduction


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Lecture Scope

• This lecture covers similarities between the Fukushima reactors and reactors in Europe.

• The similar reactors include General Electric BWRs, Asea Atom BWRs, Siemens BWR/69 & BWR/72 reactors, and VVER-440/213 PWRs.

European "Cousins"

• There are no exact duplicates of the Fukushima reactors in Europe.

• However, there are what one might refer to as European "cousins" to the Fukushima reactors.

• These reactors fall into three groups:– BWRs supplied by General Electric.– BWRs supplied by Asea Atom and Siemens.– PWRs of the type VVER-440/213 supplied by

Atomstroyexport and which have pressure suppression confinements and reactor compartment end caps.


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GE BWRs in Europe

GE BWRs in Europe

• There are four General Electric BWRs in Europe:– Santa María de Garoña (BWR/3 Mark I) and Cofrentes

(BWR/6 Mark III) in Spain.– Mühleberg (BWR/4 Mark I) and Leibstadt (BWR/6 Mark III)

in Switzerland.


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Presentation Notes

Santa María de Garoña (Spain) (1)

• Santa María de Garoña is a 1,381 MWt/446 MWe (net) BWR/3 Mark I unit operating since 1970, and is similar to Fukushima Unit 1

• The plant is located in the Tobalina Valley on the bank of the Ebro River

• The plant is operated by Nuclenor• This plant is scheduled to be finally shut down on

6 July 2013 according to its operating permit from the Ministry of Industry, Tourism and Trade (MITYC)


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Presenter

Presentation Notes

Bullet #4Consejo de Seguridad Nuclear (CSN), Spain: Convention on Nuclear Safety, Fifth National Report, August 2010, http://www.csn.es/images/stories/publicaciones/otras_publicaciones/quinto_informe_2010_ingles.pdf.

Santa María de Garoña (Spain) (2)

• The most recent reported PSA results for Santa Maria de Garoña are a CDF of 1.89×10-6/a, and a large early release frequency (LERF) of 5.17×10-8/a (these are internal events results only)


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Presenter

Presentation Notes

SOURCE:Consejo de Seguridad Nuclear (CSN), Spain: Convention on Nuclear Safety, Fourth National Report, September 2007, http://www.csn.es/images/stories/english/publications/cuartoinformein.pdf.

Santa Maria de Garoña NPP, Spain

07-Nov-11 18Lecture 3: Fukushima andSimilar Units in Europe

Presenter

Presentation Notes

SOURCE: http://2.bp.blogspot.com/_IheePluCzY4/Sk_xzy8BYLI/AAAAAAAAAHU/_fhQRRdYnYY/s320/Santa+Maria+de+Garo%C3%B1a.jpg

Cofrentes (Spain) (1)

• Cofrentes is a BWR//6 Mark III BWR with power levels of 3237 MWt/1092 MWe (gross)

• The plant is located in Valencia province on the bank of the Júcar River on the Embarcaderos reservoir

• The plant is operated by Iberdrola• The Mark III containment, unlike the Mark I and

Mark II containments, is not inerted• Hydrogen igniters are provided in the wetwell

only at Cofrentes


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Cofrentes (Spain) (2)

• The most recent reported PSA results for Cofrentes are a CDF of 1.27×10-6/a, and a large early release frequency (LERF) of 1.15×10-7/a (these are internal events results only)


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Presenter

Presentation Notes

SOURCE: Consejo de Seguridad Nuclear (CSN), Spain: Convention on Nuclear Safety, Fourth National Report, September 2007, http://www.csn.es/images/stories/english/publications/cuartoinformein.pdf.

Cofrentes NPP, Spain


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Presentation Notes

SOURCE: http://upload.wikimedia.org/wikipedia/commons/b/b2/Cofrentes_nuclear_power_plant_-_General_view.JPG

Cofrentes NPP Cross Section


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Presentation Notes

SOURCE: http://www.cncofrentes.es/wcofrnts/gc/prod/en_US/conteni/imgs/Caracteristicas_tecnicas_Recargas_de_combustible_recargas_ing.jpg

Mühleberg (Switzerland)

• Mühleberg is a BWR/4 Mark I General Electric BWR producing 1097 MWt/373 MWe (net)

• The plant is located on the Aare River, 1.2 km downstream from a dam that impounds the Wohlensee Reservoir

• The plant is operated by BKW FMB Energie AG

• Mühleberg is expected to cease operation in 2022


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Mühleberg Design 1

• Although Mühleberg is a BWR/4 Mark I plant like Fukushima Units 2-5, it has major design differences compared to these units making it unique among BWR/4 Mark I units in the world

• Mühleberg has a full, flood-proof, double containment; the secondary containment is a steel-lined, reinforced concrete structure with walls 0.9 meters thick at the base, and 0.6 meters thick above +29 meters elevation


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Mühleberg Design 2

• Mühleberg also has a redundant "outer" suppression pool in the secondary containment

• The pool contains a multi-venturi scrubber system (MVSS) that filters air vented from the drywell and from the wetwell airspace

• The vent lines can be opened manually, but open automatically via rupture disc at a pressure of 0.7 MPa


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Mühleberg Design 3

• Mühleberg also has a bunkered, flood- proofed, reinforced concrete safety complex known as SUSAN

• SUSAN houses 2 of the 3 diesel generators; a separate control room; a redundant RCIC system; a redundant 2- train low pressure injection system; and a redundant 2-train suppression pool cooling system


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Mühleberg Design 4

• The condensate storage tank at Mühleberg is twice as large as the much higher power level Peach Bottom BWR/4 Mark I

• The overall primary containment at Mühleberg is approximately double in volume compared with Peach Bottom on a per MWt basis, as is the suppression pool water volume


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Mühleberg External View


Presenter

Presentation Notes

SOURCE: ENSI, http://static.ensi.ch/1313999257/kkw_muhleberg.jpg

Mühleberg NPP Cross Section


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Presentation Notes

SOURCE: BKW EMG Energie AG, from Hauptabteilung für die Sicherhet der Kernanlagen (HSK). Sicherheitstechnische Stellunghahme zur Periodischen Sicherheitsüberprüfung des Kernkraftwerks Mühleberg: Zusammenfassung, Ergebnisse und Bewertung, HSK 11/1100, Würenlingen, Switzerland, 12 November 2007, http://static.ensi.ch/1314202963/psu_muehleberg_2007.pdf, and at http://www.umweltbundesamt.at/fileadmin/site/umweltthemen/kernenergie/Muehleberg/psu_muehleberg_2007.pdf (in German). �

Mühleberg Design 5

• The result of these design changes is that a full scope probabilistic safety assessment (PSA) of Mühleberg estimates the core damage frequency (CDF) at 1.19×10-5/a.

• 64.4% of all core damage accidents are estimated in the PSA to end with the reactor vessel intact, the containment intact, and only normal leakage


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Mühleberg Design 6

• Another 32% of the CDF is estimated to end with the RPV failed, but the containment intact due to manually-initiated filtered venting

• In another 0.5% of the CDF, the RPV is failed, but the containment is intact the the filtered venting system is actuated by the rupture disc bursting

• The remaining 0.5% of the CDF are moderate to large release accidents involving containment isolation failure, early containment failure, drywell melt-through, and containment bypass

• The large release frequency is this estimated at about 6×10-8/a


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Leibstadt (Switzerland) (1)

• Leibstadt is a BWR/6 Mark II General Electric BWR producing 3600 MWt/1165 MWe (net)

• The plant is located on the Rhine River

• The plant is operated by AXPO AG• Final shutdown is scheduled for 2034


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Leibstadt (Switzerland) (2)

• Leibstadt is unique among BWR/6 Mark III units in having a full double pressure suppression containment, as well as a bunkered safety complex and a filtered venting system

• A 2009 PSA estimated the internal events CDF at 4.30×10-7/a, and external events at 3.91×10-6/a (dominated by earthquakes)

• Most likely large release is from early failure of the containment airlock, with an estimated frequency of 2.13×10-7/a


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Presenter

Presentation Notes

Bullet #2: Swiss Federal Nuclear Safety Inspectorate (ENSI), Sicherheitstechnische Stellungnahme zur Periodischen Sicherheitsüberprüfung des Kernkraftwerks Leibstadt, ENSI 12/1300, 10 August 2009, http://www.ensi.ch/fileadmin/deutsch/files/psue_KKL-2009.pdf

Leibstadt External View


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Presentation Notes

SOURCE:http://www.kkl.ch/upload/cms/user/test1123.jpg


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Other BWRs in Europe

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Other BWRs in Europe

• ASEA-ATOM produced BWRs that are operating in Finland (Olkiluoto 1 & 2) and Sweden (Forsmark 1, 2 & 3; Oskarshamn 1, 2 & 3; Ringhals 1). See next viewgraph.

• Siemens produced two lines of BWRs (BWR/69 and BWR/72) in Germany. All of the BWR/69 units are now closed. Only the BWR/72 units at Gundremmingen B & C remain in operation.



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Asea Atom BWRs

07-Nov-11 38

Asea-Atom BWRs (1)

• Asea-Atom produced BWRs that are operating in Finland (Olkiluoto 1 & 2) and Sweden (Forsmark 1, 2 & 3; Oskarshamn 1, 2 & 3; Ringhals 1).

• Asea-Atom merged with another company to form ABB. ABB purchased Combustion Engineering, and was later merged with BNFL. BNFL subsequently sold its nuclear operations to Westinghouse, and then Westinghouse was acquired by Toshiba.


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Asea-Atom BWRs (2)• The Asea-Atom BWRs were equipped with MVSS

filtered venting systems after the Three Mile Island accident.

• Note that the end cap in the Asea-Atom BWR design is under water during normal operation. This feature, combined with the filtered venting system, could significantly reduce radiological releases to the environment ("source terms").

• 2009 PSA results for Olkiluto 1 & 2: CDF estimated at 1.3E-5/a; large early release frequency (LERF) estimated at 6E-6/a (corresponding to 0.1% or greater release of Cesium-137 or the equivalent)


Presenter

Presentation Notes

Bullet #3: Radiation and Nuclear Safety Authority (STUK), Finnish Report on Nuclear Safety: Finnish 5th National Report as Referred to in Article 5 of the Convention on Nuclear Safety, STUK-B 120, August 2010, page 40, www.stuk.fi/julkaisut/stuk-b/stuk-b120.pdf

ASEA-ATOM BWR Containment


Presenter

Presentation Notes

SOURCE:TVO, Nuclear Power Plant Units Olkiluoto 1 and Olkiluoto 2, January 2008.


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Siemens BWR/69 & BWR/72

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Siemens BWRs• Siemens built four BWR/69 units that operated in

Germany (Brunsbüttel, Isar Unit 1, Krümmel, and Philippsburg Unit 1)l the never operated Zwentendorf plant in Austria was also a BWR/69 design

• All BWR/69 units in Germany were permanently closed following the Fukushima accidents

• Only the BWR/72 units at Gundremmingen B&C remain in operation

• No recent publicly-available PSA results for Gundremmingen have been located so far


Gundremmingen External View


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Presentation Notes

SOURCE: Wikipedia, http://upload.wikimedia.org/wikipedia/commons/thumb/b/bb/Gundremmingen_Nuclear_Power_Plant.jpg/774px-Gundremmingen_Nuclear_Power_Plant.jpg

Zwentendorf External View


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Presentation Notes

SOURCE:Wikipedia, http://upload.wikimedia.org/wikipedia/commons/thumb/3/32/AKW_Zwentendorf.jpg/796px-AKW_Zwentendorf.jpg


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VVER-440/213 PWRs

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VVER-440/213 (1)• VVER-440/213 units are operating in the

Czech Republic (Dukovany 1-4), the Russian Federation (Kola 3 & 4), Slovakia (Bohunice V2 3 & 4, Mochovce 1 & 2), and Ukraine (Rovno 1 & 2). Two more units are under construction at Mochovce.

• These reactors are six-loop PWRs with horizontal steam generators housed in a pressure suppression confinement.


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VVER-440/213 (2)• There are three main similarities between

GE Mark I BWRs and VVER-440/213s (despite the fact that the latter are PWRs and not BWRs):– First, VVER-440/213 plants rely on a pressure suppression

system to reduce steam pressure in case of an accident (via a so-called "bubbler-condenser" tower).

– Second, the reactor shaft is closed by an end cap similar in concept to the BWR Mark I drywell closure cap.

– Third, the structure above the refueling deck is simple industrial construction, and is not designed either to retain pressure or radioactivity released in an accident.


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VVER-440/213 (3)• Most (if not all) VVER-440/213 units have

been retrofitted with passive autocatalytic recombiners (PARs) to reduce the threat of hydrogen combustion

• Other retrofits include reactor cavity flooding provisions to attempt to retain core debris in the reactor vessel, additional water sources for confinement spray and vessel injection, and extra protection for the reactor cavity door


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VVER-440/213 (4)• VVER-440/213 units are vulnerable to severe

accidents occurring when the reactor shaft end cap and reactor vessel heads are removed (for refueling). Such accidents result in rapid failure of the industrial structure above, and a large direct release path to the environment (as well as contamination of the adjacent unit)

• Other VVER-440/213 vulnerabilities are steam generator tube ruptures and collector failures, unmitigated core debris interaction with the reactor cavity door, and unmitigated high pressure melt ejection & direct confinement heating


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VVER-440/213 (5)• Recent probabilistic safety assessment

(PSA) studies for VVER-440/213 units indicate core damage frequencies in the range of about 4 ×10-6/a to 2 ×10-4/a


VVER-440/213 Design


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SOURCE:International Nuclear Safety Center, Pacific Northwest National Laboratory (PNNL), http://insp.pnnl.gov/-profiles-reactors-vver213.htm

Dukovany Design Cutaway


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Presentation Notes

SOURCE:CEZ

Passive Autocatalytic Recombiner (PAR)


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Presentation Notes

SOURCE:Framatome ANP GmbH, http://www.jso.kiev.ua/index.files/main.files/pictures/Pic15_97B.jpg


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Next Lecture


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Next Lecture

• Block Lecture 4 can take place on either 14 November or 28 November from 18:30 – 20:00. We will discuss the Japanese Government's two official reports on the Fukushima accidents, as well as the IAEA's "Fact-Finding" Mission report.– http://fukushima.grs.de/sites/default/files/NISA-IAEA-

Fukushima_2011-06-08.pdf – http://www.iaea.org/newscenter/focus/fukushima/japan-

report2/japanreport120911.pdf– http://www-

pub.iaea.org/MTCD/Meetings/PDFplus/2011/cn200/documentation/ cn200_Final-Fukushima-Mission_Report.pdf


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Contact Information

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Contact Information

• Email: [email protected]• Direct line: +43-1-47654-7711; Secretariat: -7700• Institute URL (Deutsch): http://www.risk.boku.ac.at

• Course URL (English): https://online.boku.ac.at/BOKUonline/lv.detail?clvnr=259955&cperson_nr=&sprache=2

• Course URL (Deutsch): https://online.boku.ac.at/BOKUonline/lv.detail?clvnr=259955

• Lecture Details (date, room, time):https://online.boku.ac.at/BOKUonline/te_ortzeit.liste?corg=16590&clvnr=259955

• Viewgraphs:http://www.risk.boku.ac.at/materials


THE FUKUSHIMA ACCIDENT: CAUSES, RESULTS AND …New calculation of accident progression in Unit 4...

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