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Response of t heFuk ushim a Dai -ich iNuc lear Plant t o theMarc h 11, 2011Ear t hquake in Japan
Dr. George Flanagan
Oak Ridge National Laboratory
Presented to the EERI/NECMeeting
Apri l 12, 2012
2 Managed by UT-Battellefor the U.S. Department of Energy EERI/NEC April 12,2012
Present at ion Out l ine
Basic Reactor Physics and Boiling Water Design
Sequence of Events
Consequences and Mitigation
Conclusions and Lessons Learned
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Basic React or Phys icsand
Boi l ing -Wat er Reac t or (BWR) Design
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Af ter a React or is Shutdow n Heat is St i l lGenerated Bec ause o f t he Decay o f theRadioact ive Fiss ion product s(Fragm ents)
6 Managed by UT-Battellefor the U.S. Department of Energy EERI/NEC April 12,2012
Boi l ing-Wat er Reac t or (BWR) Uses
Nuclear Heat t o Boi l Water t o Creat eSteam t o Produce Elec t r i c i t y
CourtesyofNEXTERAEnergy
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Nuclear Plants are Designed With ManyBarr iers t o Prevent Release of Radioact iveMater ia l Resul t ing f rom Fiss ion
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Mark 1 Boi l ing-Water React or
Cont a inment Des ign Major Structures Biological Shield
Secondary Containment Build ing
Reactor Pressure Vessel
Reactor Containment (Dry Well, Duct, Suppression Chamberor Pool-torus)
Spent Fuel Pool
CourtesyofTVA
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GE BWR Mar k I Containm ent
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Sequence of Events
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9.0 Ear t hquake Occ urs o f the Coast o fJapan at 2 :46 PM, March 11, 2011
12 Managed by UT-Battellefor the U.S. Department of Energy EERI/NEC April 12,2012
Eart hquake/Tsunami Af fec t ed
Fourt een Plant s on the Easter n Coasto f Japan
CourtesyofTEPCO
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Some Uni t s o f Fuk ushima 1 (Dai -ich i )w ere in Opera t ion a t t he T ime o fEar thquake
Units 13 were operating at full power
Unit 4 was defueled (entire core stored in spent fuelpool)
Unit 56 in a refueling outage
14 Managed by UT-Battellefor the U.S. Department of Energy EERI/NEC April 12,2012
Nuclear Plant Safety Featur es Per form
as Designed Unt i l t he Tsunami Hi t s
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15 Managed by UT-Battellefor the U.S. Department of Energy EERI/NEC April 12,2012
Hor izonta l E-W Acc elerat ion Exc eededthe Seismic Design on Uni t s 2,3, and 5
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CourtesyofTEPCO
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Tsunami Waves (47 feet ) Hi t Fukushim a 1
Plant About 1 Hour Af te r t he Ear t hquake
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Near ly a l l t he Dai ich i S i te Was
Flooded
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Only One Diesel Generat or Surv ived atDai- ichi
22 Managed by UT-Battellefor the U.S. Department of Energy EERI/NEC April 12,2012
Eart hquake Resul ted in Loss of Of fs i te
Pow er/Tsunam i Resul t ed in Loss of Al lOns i t e AC Pow er (exc ept un i t 6)- Emergency P lan t sys tems w ork as des igned a f te r
ear thquake- D iese l generato rs w ere submerged by t sunami
(un i t 1 Bat ter ies w ere submerged)- Back up bat t er ies were deple ted af ter 810 hours
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Loss o f Bat t e ry Pow er Resu l ts in Lossof Abi l i ty t o Rem ove Decay Heat Fromt he Core
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Loss of Al l AC/DC Pow er PreventedUse of Cool ing and Vent ing System s
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Possib le Sequence Leading t o CoreDama ge and Release of Hydrogen
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Hydrogen Produced by Zr Clad
In te rac t i ng w i th the Steam
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Overpressure of t he Conta inm ent Resul tedin Opening Leakage Pathw ays for SomeSt eam and Hydrogen to Ent er the React or
Bui ld ingBypassing t he Vent L ines
Resulted in explosive mixture of hydrogen gas toaccumulate in the reactor buildings of Units 1 and 3
A panel was removed from Unit 2 to vent the building
A fire and explosion occurred in Unit 4 (reactor wasdefueled)
Thought to be a result of uncovering of the spent fuel
Appears this was not the case
Cause of Unit 4 explosion is now thought to be from Hydrogengenerated in unit three being carried into unit 4 through a shared ventline.
28 Managed by UT-Battellefor the U.S. Department of Energy EERI/NEC April 12,2012
Resul t Was An Explos ion in Uni ts 1 and 3Destr oy ing Par t s of t he React or Bui ld ings
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Afterm ath Destroyed the Secondary Conta inment , SomeVent L ines - A l low ed Uncon t ro l l ed Re lease o fRadioact iv i t y to the At mosphere, to the Site , and toAreas Surrounding t he Si teResult ing in An Evacuat ion
(20 km )
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Consequences and Mi t igat ion
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Most o f t he T ime Fo l low ing theAcc iden t the Wind w as B low ing
Tow ards t he Sea, How ever, ThereWere Tim es When the Winds Blew
Towards t he Nor t hw es t
Resulted in a Plume Carrying Radiation to Drift Inland
Mandatory Evacuation Ordered for 20 km around the plant
Area between 20-30km asked to shelter in place and lateradvised to evacuate
Some areas in path of plume affected beyond 30km
Over 70,000 inhabitants affected by evacuation
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Est im ated Dose Is About 10 T im es
Average Back ground (240mrem)
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With t he Succ ess ful Evacuat ion T hereWas No Sign i f icant Radiat ion Dose t ot he Genera l Publ ic Currently there are no acute radiation effects (even to workers onsite)
Estimated cancer increase is expected to be below statistical measurement threshold
Economic impacts enormous
Evacuees only allowed limited access within 30 km radius in March 2012
some limited access allowed to some areas within 20 km radius in early April2012
Loss of Productivity (manufacturing, agricultural, fishing)
Decontamination Activiti es have begun (estimates in 10 -250 billion of dollars)
Radioactive waste volumes are very large and pose a problem finding appropriate
disposal sites in a country with limited land mass
36 Managed by UT-Battellefor the U.S. Department of Energy EERI/NEC April 12,2012
React or Cores Are Being Cooled and
Are St abi l ized
All reactors declared to be in cold shutdown inDecember 2011
Temperatures inside the reactors are below 100 C
Cooling water leaking out of reactors is collected
Treated to remove radioactive materials
Recirculated back into the reactor
Radioactive water accumulated on site immediately fol lowingaccident is being collected and treated as well
Water has been prevented from entering the ocean by use ofdikes and dams
Decontamination of areas surrounding the reactors (on site)is ongoing- surfaces have been treated to prevent dust
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Cover Has Been Inst a l led Around Uni t 1Debris Is Being Removed BeforeCovering Uni t s 3 and 4
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Socia l /Pol i t ic a l Impac t s in Japan andWorl d Wide
Resignation of Japans Prime Minister
Reorganization of Japanese Nuclear Regulatory Structure
Lack of Confidence in TEPCO and the government
Shutdown of 50+ reactors in Japan (electricity shortage predicted thissummer)
Germany, Switzerland will shutdown their existing plant and Italy has chosennot to restart their nuclear program
US NRC just issued orders to nuclear plant owners to reexamine all existingnuclear reactors regarding seismic design, AC power sources, and venting
Some delay of new reactor builds worldwide
40 Managed by UT-Battellefor the U.S. Department of Energy EERI/NEC April 12,2012
Conclus ions and Lessons Lear ned External events may pose the greatest threat to nuclear plants
Multiple system failures can lead to significant plant damage
Loss of infrastructure (roads, bridges, water, power) prevented assistance
Planning/training i s essential to prevent injury and death (emergency planning, severeaccident plans)
Communication dur ing and following an event is crucial
Significant delays in transmission of information between onsite and centralizedlocations probably contr ibuted to the event
Instrumentation used to transmit plant status was lost
Public relations during an event is very important
Information was difficult to obtain both within Japan and clearly in other countries
Contradictions led to lack of trust by the public and media Lack of information prevented early assistance from outside sources