Fukushima Daiichi Disaster. Facts and lessons learned. July Takashi Shoji Programme Director of WANO

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1 Fukushima Daiichi Disaster Facts and lessons learned July Takashi Shoji Programme Director of WANO 7/12/2011 1

2 Earthquake occurrence and automatic shut-down of nuclear reactors The Tohoku Pacific Earthquake of magnitude 9.0 struck the northeastern part of Japan at 2:46 pm on March 11th, While 3 reactors (Fukushima Dai-ichi (I) Unit 4,5,6) were under periodic inspection, 11 reactors (Onagawa Unit 1,2,3; Fukushima Dai-ichi (I) 1,2,3; Fukushima-Dai-ni (II) Unit 1,2,3,4; and Tokai Dai-ni (II)) were automatically shut-down. After the automatic shut-down, the Unit 1-3 at Onagawa Nuclear Power Station, the Unit 1-4 at Fukushima II Nuclear Power Station, and the Unit at Tokai II Nuclear Power Station have been cold shut down safely. 7/12/2011 2

3 Overview of Fukushima Daiichi Nuclear Power Station 7/12/2011 3

4 Before the quake 7/12/2011 4

5 After Tsunami attack 7/12/2011 5

6 Image of ultimate heat sink Spent Fuel pool Heat Exchanger Reactor Pressure Vessel (RPV) Primary Containment Vessel (PCV) Sea Suppression Chamber (S/C) Reactor Building Power supply 7/12/2011 6

7 Chronology of Daiichi Fukushima Unit 1 in early stage March 11(0) March 12(1) March 13(2) March 14(3) March 15(4) 14;46 Quake occurred DG 1 train started 15;41 SBO Started core cooling by IC system 4;00 Core cooling by IC suspended 4;30 PCV pressure increased to 840 KPa (design pressure is 400 KPa) 11;00 PCV pressure is still increasing Injection to the reactor is being performed 15;36 Explosion occurred 21;00 Borated seawater 7/12/ injected into RPV in progress 9;00 Seawater injection into drywell using fire protection piping

8 Chronology of Daiichi Fukushima Unit 2 in the early stage March 11(0) March 12(1) March 13(2) March 14(3) March 15(4) 14;46 Quake occurred DG 1 train started SBO(15;41 ) Started RCIC 0;00 Install temporary battery 4;00 RCIC is in service Reactor water revel is found stable by installation of temporary battery 15;56 RCIC has shut down Depressureris ation of the drywell is being considered 23;00 RCIC in service 12;00 Starting depressurisa tion of the drywell was decided. 14;00 RCIC in service Maintain DC power and keep injection function 3;00 RCIC has shut down Sea water injection into the reactor is being prepared 5;00 RCIC in service 24;00 Reactor water revel decreasing 6;00 Abnormal sound was observed near suppressio n chamber and its pressure has decreased Seawater cooling is ongoing 7/12/2011 8

9 Chronology of Daiichi Fukushima Unit 3 in early stage March 11(0) March 12(1) March 13(2) March 14(3) March 15(4) 14;46 Quake occurred DG 1 train started SBO(15;4 1) Started RCIC 4;00 RCIC is in service 13;00 Core cooling is performed by HPCI Depressuriz ation of drywell is being prepared 5;00 HPCI has stopped An attempt to inject coolant using other system failed Starting depressurisa tion of drywell is decided (tried to maintain reactor 7/12/ water level) 1;00 sea water injection stopped because of lack of sea water in the sea water pit 11;00 Hydrogen explosion occurred in the reactor building.

10 What is the cause of this disaster Emergency Diesel Engine started immediately,however sea water pump to provide coolant to the DG tripped because of wet condition of motor caused by tsunami The design tsunami height is 5.7m (Daini 5.2m) Tentatively actual tsunami was assumed as 14 m This disaster was caused by common failure by Tsunami Loss of ultimate heat sink resulted to prevent decay heat removal from fuel assembly Finally this loss of final heat sink lead to damage of fuel assembly in the core and spent fuel pool 7/12/

11 Radiation Dose at Fukushima Daiichi NPP (μsv/h) 7/12/

12 Evacuation Advice of Government 11th 20:50: Evacuate from 2km sphere 21:23: Evacuate from 3km sphere ~ 6,000 persons 12th 05:44: Evacuate from 10 km sphere > 50,000 persons 18:25: Evacuate from 20 km >170,000 persons [Report of Prime Minister of Japan and his Cabinet 2011/3/20 22:00 P10/32] 7/12/

13 Radiation Contamination Food Contamination(20 th March) Element Food Prefecture Radiation (Bq) Iodine Milk Fukushima 932~1,510 Spinach Ibaragi 61,00~15,02 0 Cesium Spinach Ibaragi 524 The Government requested that the contaminated food (Spinach,Milk) do not to be distributed in the market on 20 th March The Radioactive material (Co,CS) was detected in the sea water near NPP on 22th March 7/12/

14 Overview of Unit 1~4 (Before Accident) 7/12/

15 Overview of Unit 1~4 (after Accident) 7/12/

16 Japanese utilities s response to Fukushima Disaster Chubu EPCO announced to build a High Wall(14m) as a countermeasure in two years and other countermeasures as well J-Power Co halted its Oma NPP construction Chubu also announced to halt its Hamaoka Unit 6 construction project Kansai announced they will invest about 0.74 Billion for upgrading seismic design Chubu & Chugoku EPCO announced to install additional DGs on a high elevation area. Details including numbers of DG will be determined Kyushu EPCO announced to wait restart of Genkai Unit 2&3,which is now on outage,till regulator will make an order regarding this disaster. Kyushu also announced they will face shortage of electricity in summer, if they can not restart Genkai 2&3 JAPC announced to invest 0.15 Billion for upgrading seismic design of 2 units in Tsuruga area. Design tsunami height of Tsuruga site is 2.8m Kansai EPCO announced to wait restart of three stations,which is now on outage,till regulator will make an order regarding this disaster. 7/12/

17 Japanese regulator asked utilities to take additional safety actions and revise technical specifications on 30 th March Immediate inspections of equipment in place for the event of a tsunami Review of emergency preparedness and training Provision of alternative power source Preparation for prompt restoration of ultimate heat sink, where it is lost Preparation for prompt restoration of SFP cooling, when it is lost Other necessary actions specific to plant structure and configurations 7/12/

18 What is WANO s response to this disaster London office established a 24 hours response shift just after this accident and publishes CEO update and communicating with the members. WANO Chairman made a statement and communicate with the media through interviews Managing Director requests support to Regional Centres and established a support organization in Tokyo Centre WANO published SOER regarding this accident and request members to check the preparedness against disaster WANO established the High Commission of the members and discuss WANO s role regarding this accident 7/12/

19 How Tokai-2 survived (fact) Tsunami counter measures modification was under taken on the south and north sea pump area.the work was finished on the south of sea water pump area. Tokai-2 lost off site power and also tsunami affected one of sea water pump which provides coolant to DG(C), that is located in the north side area. However other ECCS system including sea water pump, located in the south side area, was not damaged and established a safe shut down 7/12/

20 How Onagawa was survived (fact) Town of Onagawa was totally destroyed by 14m of height Tsunami this time Some damage,loss of off site power,water spill in the reactor building was observed, however all three units safely achieved a safe shut down after the quake Some advantage is observed in its design,design tsunami height is 9.1m,reactor building is installed on 14.8m height from sea level, sea water pond is located away from sea shore (details should be analyzed) 7/12/

21 Leaned from current research (fact) Active Fault Research Centre of the National Institute of Advanced Industrial Science and Technology (AIST) of Japan reported with their research that Jogan tsunami(ad 869),analyzing this tsunami deposite, inundated 2.5~3 km inland from paleo-shoreline,which was about 0.8~1.3 km inland of present shoreline of Ishinomaki plain. Jogan earthquake occurred in quite similar area as this time. This was discussed at the Council of METI(the Ministry of International Trade and Industry) in 2009,however this was handled as pending issue. AIST also reported they have detected at least five layers of sand,possibly caused by a huge tsunami. They assumed it occurred in 3100~2800 cal ybp, in 2300~2100 cal ybp, in AD 869(Jogan tsunami), in 1300~1400 and after in AD 1400(possibly AD 1611 Keicho Tsunami) 7/12/

22 Could this accident prevented? Seeing the facts that Onagawa &Tokai-Daini NPP was survived, I strongly believe that we can avoid this accident. We should improve our performance through exchange of information and emulation of best practices. I think this is WANO s role. 7/12/

23 Lessons learned from this event (As of July 13 th 2011) Strengthen measures against earthquake and tsunamis Ensure power supplies Ensure robust cooling functions of reactor and PCVs Ensure robust cooling functions of spent fuel pools Through accident management (AM) measures

24 Response to issue concerning the siting with more than one reactor Consideration of NPS arrangement in basic design Ensure the water tightness of essential equipment facilities

25 Enhancement of measures to prevent hydrogen explosions Enhancement of containment venting system Improvement to the accident response environment

26 Enhancement of training responding to severe accidents Enhancement of instrumentation to identify the status of the reactors and PCVs Central control of emergey supplies and setting up rescue team

27 Response to combined emergency of both large-scale natural disasters and prolonged nuclear accident Reinforcement of environment monitoring Establishment of a clear division of labor between relevant central and local organization

28 Enhancement of communication relavant to the accident Adequate identification and forecasting of the effort of released radioactive materials Clear definitions of widespread evacuation areas and radiological protection guidelines in nuclear emergency.

29 7/12/