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Fukushima's Lessons
Fukushima's Lessons
Fukushima's Lessons
Fukushima's Lessons
Fukushima's Lessons
Fukushima's Lessons
Fukushima's Lessons
Fukushima's Lessons
Fukushima's Lessons
Fukushima's Lessons
Fukushima's Lessons
Fukushima's Lessons
Fukushima's Lessons
Fukushima's Lessons
Fukushima's Lessons
Fukushima's Lessons
Fukushima's Lessons
Fukushima's Lessons
Fukushima's Lessons
Fukushima's Lessons
Fukushima's Lessons
Fukushima's Lessons
Fukushima's Lessons
Fukushima's Lessons
Fukushima's Lessons
Fukushima's Lessons
Fukushima's Lessons
Fukushima's Lessons
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Fukushima's Lessons

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A July 19, 2012 presentation by David Lochbaum and Edwin Lyman of the Union of Concerned Scientists on the lessons the 2011 Fukushima disaster offers for nuclear power safety in the U.S.

A July 19, 2012 presentation by David Lochbaum and Edwin Lyman of the Union of Concerned Scientists on the lessons the 2011 Fukushima disaster offers for nuclear power safety in the U.S.

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  • 1. Fukushima’s Lessons July 19, 2012David Lochbaum Edwin LymanDirector, Nuclear Safety Project Senior Scientist www.ucsusa.org
  • 2. BackgroundUnion of Concerned Scientists (UCS) • Formed in 1969 with nuclear power safety as major focus • Neither proponent nor opponent of nuclear power • Safety advocateDave Lochbaum • Bachelor’s degree in nuclear engineering • Worked more than 17 years in the nuclear industry before joining UCS in 1996 • Worked at NRC as a boiling water reactor technology instructor for a year in 2009-2010Edwin Lyman • Doctorate degree in physics • President of Nuclear Control Institute before joining UCS in 2003Lochbaum and Lyman have: • Testified before Senate and House on Fukushima’s lessons • Submitted formal comments to NRC on its post-Fukushima plans 2
  • 3. Fukushima: Could it happen here? YES:• U.S. nuclear plants were not designed or hardened to survive major natural disasters, multiple system failures or terrorist attacks (example: fire protection)• U.S. nuclear plants are not much better equipped than Japanese plants to control a severe accident before a meltdown occurs• U.S emergency plans are not designed to protect the public after Fukushima-scale accidents
  • 4. Fukushima: Could it happen here?Fire ProtectionJack Grobe, recently retired NRC senior manager,during a Commission briefing on 17 July 2008: “Approximately one-half of the core damage risk at operating reactors results from accident sequences that initiate with fire events.” NRC’s fire protection regulations assume: • no other event • no equipment failures other than those due to the fire • no worker mistakes
  • 5. Station Blackout (SBO)• Nuclear reactors generally use AC power from the offsite grid, backed up by onsite emergency diesel generators, to operate motor-driven equipment• Failure of all AC power: ―station blackout‖• Only source of electricity is DC battery power – Can maintain instrumentation, controls and lighting – Enables use of steam-driven pumps • e.g., Reactor Core Isolation Cooling (RCIC) – Only lasts from 2-8 hours, depending on the charge – At Fukushima, DC power and electrical circuits were partially lost because of flooding
  • 6. Severe Accident Management• Once DC power is lost, core meltdown will occur unless power or cooling are restored – Portable power supplies, diesel-driven fire pumps, fire engines – Manual manipulation of valves – ―Black run‖ of steam-driven systems• Fukushima demonstrated the practical difficulties of carrying out such actions
  • 7. Focus on Two Issues:1) Minimizing onsite consequences2) Minimizing offsite consequences 7
  • 8. Minimizing Onsite Consequences1) Power reliability (i.e., protection against station blackout)2) Hydrogen control3) Spent fuel risk management4) Industry FLEX plan5) Design-basis / beyond-design-basis disconnect 8
  • 9. Power Reliability• NRC’s proposed three-phase approach for coping with an extended SBO seems sound (with a large caveat about reliability of portable equipment). • First phase: only permanently installed equipment • Interim phase: portable emergency equipment staged at the site, if it can be shown to survive the challenge (e.g. flood) • Final phase: equipment from offsite areas, if it can be shown to arrive in time• Near Term Task Force recommended 8-hour and 3-day durations for the first two phases; UCS proposed 24 hours and 7 days 9
  • 10. Hydrogen Control• The secondary containments—final barriers in BWRs to the release of radioactivity from damaged reactor cores and spent fuel pools to the environment—were damaged by explosions on Units 1, 2, 3, and 4.• The Unit 2 primary containment may have been damaged by an explosion.• Explosions most likely caused by detonation of hydrogen created by overheated fuel rod cladding. 10
  • 11. Hydrogen ControlRecommendations Short term: • All structures in which hydrogen can accumulate (e.g., secondary containments of BWR Mark I and II and fuel handling buildings for BWR Mark IIIs and PWRs) should have hydrogen monitoring equipment • Ice-condenser PWRs and BWR Mark IIIs must have reliable back-up power for hydrogen igniter systems in the event of an SBO Long term: • Research and development on fuel cladding that cannot generate large amounts of hydrogen (e.g., DOE project) 11
  • 12. Spent Fuel Risk ManagementQuestions to answer:1. What would have happened to the irradiated fuel in the Unit 1, 3 and 4 spent fuel pools had their reactor buildings not exploded, providing access paths for water makeup via helicopter drops, concrete pumper trucks, and fire truck hoses?2. Have the NRC’s spent fuel studies in the last decade fully resolved concerns regarding the risk of pool fires and criticality accidents in densely packed configurations, or do they remain uncertain and incomplete?3. How did irradiated fuel in dry storage fare? 12
  • 13. Spent Fuel Risk ManagementRecommendations:• All spent fuel removed from the reactor core within the past 5-6 years should be in dry storage instead of spent fuel pools. • This will promote the ―passive‖ safety of spent fuel storage in view of uncertainties in accident progression.• NRC’s proposal for a rulemaking to require carwash- style sprays for spent fuel pools at BWRs with Mark I and II containments must NOT proceed without full evaluation of potential flooding and wetting effects inside secondary containment. • A lesson from Fukushima must NOT replace its natural tsunami with a man-made one. 13
  • 14. Spent Fuel Risk ManagementThe spent fuel pool atmost BWRS is inside thereactor building severalfloors above the ground.ALL the emergency corecooling pumps are insidethe reactor building in thebasement or 1st floor.
  • 15. Industry FLEX PlanQuestions to answer:1. FLEX guidance states that ―FLEX strategies are not tied to any specific damage state or mechanistic assessment of external events.‖ Is this guidance too general to be useful?2. If reactor core and/or spent fuel damage occurs, will FLEX still work, or will radiation levels prevent or impede workers from implementing FLEX in a timely manner?3. In other words, is FLEX really a fix or merely an alternate pathway to the same disastrous outcome? 15
  • 16. Industry FLEX PlanRecommendations:• No credit for FLEX measures unless they can be implemented in the presence of the radiation levels associated with core or spent fuel damage.• FLEX success paths should be demonstrated for a number of well-defined severe accident scenarios.• To really be FLEXible, the measures must be able to both prevent fuel damage and mitigate it should it occur. 16
  • 17. Design-Basis / Beyond-Design-Basis DisconnectQuestions to answer:• Will beyond-design-basis, commercial-grade equipment, like FLEX, be subject to sufficient protective measures, training and procedural controls to provide proper assurance that it will work when needed?• Or should the U.S. adopt an approach more like the ―hardened core‖ concept in France, which would require more robust protection of emergency equipment against beyond-design-basis events? 17
  • 18. Design-Basis / Beyond-Design-Basis DisconnectExample 1:• Last year, significant events at Millstone and Pilgrim occurred during routine evolutions because operators made multiple mistakes. • Millstone – numerous mistakes during testing resulted in uncontrolled 8% increase in reactor power level • Pilgrim – numerous mistakes during startup resulted in uncontrolled and rapid increase in reactor power level• Without training, operators will make mistakes during severe accidents. 18
  • 19. Design-Basis / Beyond-Design-Basis DisconnectExample 2:• To resolve Generic Safety Issue 191 (within design- basis) some owners installed curbs and dams on floors to prevent water released from a broken pipe from carrying debris that could clog screens and block the flow of water to emergency core and containment cooling pumps.• To resolve beyond-design-basis 9/11 security issues, owners procured portable pumps and generators, some on wheeled carts for mobility.• Wheeled carts and floor curbs are at odds. 19
  • 20. Minimizing Offsite Consequences1) Filtered vents2) Potassium iodide (KI)3) One voice4) Public notification 20
  • 21. Filtered Vents• Normal gaseous effluents from U.S. BWRs are filtered using the offgas system to reduce radiation levels.• Gaseous effluents during design-basis accidents at U.S. BWRs are filtered using the standby gas treatment system to reduce radiation levels.• The industry proposes NOT to filter gaseous effluents during beyond-design-basis accidents. 21
  • 22. Filtered VentsRecommendation: All venting during beyond-design-basis accidents, just like venting during normal plant operation and during design-basis accidents, must be filtered. 22
  • 23. Filtered Vents Design-basis accident vent: filteredBeyond-design-basis Normal vent: filtered 23accident vent: unfiltered
  • 24. Potassium Iodide (KI)Questions to answer:• If the NRC team in Japan working more than 10 miles from Fukushima felt it prudent to have KI, why isn’t it equally prudent for American public living more than 10 miles from U.S. nuclear reactors to have KI?• How far away from Fukushima was the FDA threshold dose for KI (5 rem thyroid) exceeded? • French Institute for Radiological Protection and Nuclear Safety (IRSN): ―as far as 60 km (36 mi) to the south‖ • NRC: ―it is unlikely that the FDA thyroid dose PAGs were exceeded beyond 10 miles as a result of the accident at Fukushima.‖ 24
  • 25. Potassium IodideRecommendation:• KI should be pre-staged and readily available more than 10 miles from U.S. reactors. • American public deserves the same protection following accidents as NRC staff members received. 25
  • 26. One VoiceQuestion to answer:• If the governor of a state issued a recommendation for evacuation or sheltering of people following an accident that the NRC disagreed with, would the NRC remain silent or would it release its own recommendation? • U.S. government recommended different protective measures for U.S. citizens than the Japanese government, prompting several U.S. states to question whether the NRC would publicly second-guess their decisions. 26
  • 27. Public NotificationQuestion to answer:• Will the public needing to evacuate or shelter get this notification in time, even if the infrastructure is impaired? • Majority of nearby Japanese citizens did not know about Fukushima accident when the initial evacuation orders were issued.Recommendation:• The biennial emergency exercises should periodically simulate significant loss of public notification methods to test the effectiveness of alternate methods. 27
  • 28. ACRONYMSAC Alternating CurrentBWR Boiling Water ReactorDC Direct CurrentDOE Department of EnergyFDA Food and Drug AdministrationKI Potassium IodideNRC Nuclear Regulatory CommissionPAG Protective Action GuidelinePWR Pressurized Water ReactorRCIC Reactor Core Isolation CoolingSBO Station BlackoutUCS Union of Concerned Scientists 28

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