Attachment - 1 Progression of Accident at Fukushima Daiichi Nuclear Power Station and the Lessons Learned ＆ Measures based on the Fukushima Daiichi accident Confidential Information. No unintended use, reproduction, or disclosure. TEPCO Att1 - 1 Use other than purposes/copy/disclosure are prohibited Tokyo Electric Power Co.,Inc. Attachment - 1 I. Progression of Accident at Fukushima Daiichi Nuclear Power Station and the Lessons Learned Confidential Information. No unintended use, reproduction, or disclosure. TEPCO Att1 - 2 Use other than purposes/copy/disclosure are prohibited Tokyo Electric Power Co.,Inc. Accident at Fukushima Units 1~3 Course of Accident Progression Flow at 1F-1 Attachment - 1 Date Time RPV control PCV control March 11,2011 14:46 Reactor scram signal transmitted due to earthquake •Reactor automatically shutdown 14:47 EDG automatically started up (automatic scram) •Turbine & generator shut down 14:52 IC automatically started up Determined that the reactor •MSIV closed coolant cooling rate of •Off-site power source lost 15:03 IC was manually shutdown → 5p5ro℃ce/dhu, raess s, tcipanunlaotte db ei n the 15:10 Standby maintained S/C cooling commenced Controlled reader pressure at around 6-7MPa, as ※ stipulated in procedure, with IC system A 1st wave15:27 2nd wave15:35 Reactor could not be cooled because Tsunami arrival the isolation valve 3A of return line of IC system A was closed. 15:37 EDGA and B were tripped → Station black out (SBO) 15:42 Determined to be an event corresponding to Article 10 of the Nuclear Disaster Act (SBO) •DC power sources were lost •SBO causes loss of function for •Isolated due to loss of DC power source removing residual heat from PCV (control power source) IC function was lost due to a false signal (inferred) Determined to be an event corresponding to Article 15 of the Nuclear Disaster Act (the loss of ECCS injection source) 16:36 Reactor water level dropped •March 12, Around 0:00 It is prepared for D/W pressure may have reshuffling parallel to fresh March 4:00頃 Fresh water injection was water injectionto seawater exceeded 600KPa PCV venting •March 12, 9:04 12,2011 commenced using ithneje fcrteioshn wtoa bteer loimf tihteed f iinre (D/Wpressure Work commenced for PCV 14:30 fire brigade vehicle prevention water tank decline was venting •March 12, 9:15 confirmed） ・Venting line MO valve 25% 15:36 Hydrogen explosion n・ot AbeO o vpaelrvaete idn mthaen fuiaellldy cionu hldig h radiation dose environment ・Temporary air compressor set 19:04 Seawater injection was commenced using fire engine up to operate AO valve and venting operation performed ※Weshow the arrival time to tide gaugeat the arrival time of the tsunami(Following page too) Att1 - 3 Use other than purposes/copy/disclosure are prohibited Tokyo Electric Power Co.,Inc. Accident at Fukushima Units 1~3 Plant Status Immediately After Earthquake Struck (Unit 1) Attachment - 1 IImmmmeeddiiaatteellyy aafftteerr The earthquake interrupted off-site power and the condensate & feed water pumps were shut down. eeaarrtthhqquuaakkee The emergency diesel generators started up and all emergency functions worked properly. Main-steam safety S t relief valve a c Isolation Generator Regular power source k Batteries Condenser system Turbine Off-site power p C/B B1F r e Main steam isolation valve s Motor-operated suR Condenser Circulating water pump vent valve Dry well re vent valve Standby liquid e veacto Feepdiwpeater control system sr s pump e l Sea Feedwater pump Suppression chamber vent Primary Condensate pump Operational valve containment vessel Main equipment unit inundated Seawater cooling lost Control rod Emergency AC power lost H PCV cooling drive hydraulic Core sppuramyp system eat ex system pump sCtoornadgeen psaotoel DC power lost c h a Normal AC power lost n High-pressure coolant g Make-up water e injection system pump r condensate system pump Power C/B B1F panels Filtered water R/B：Reactor building tank Seawater pump T/B：Turbine building Diesel generator Sea Diesel-driven fire C/B：Control building T/B B1F protection system pump Att1 - 4 Use other than purposes/copy/disclosure are prohibited Tokyo Electric Power Co.,Inc. Accident at Fukushima Units 1~3 Plant Status After Tsunami Arrival (Unit 1) Attachment - 1 The seawater pump shut down and the emergency diesel generators shut down. AAfftteerr ttssuunnaammii The tsunami inundated the building interiors, and battery and power panel function was also lost. iinnuunnddaattiioonn All instrument displays, operational function and lightening were lost. S t Main-steam safety relief valve] a ck Isolatiosyns cteomndenser Batteries Generator Regular power source Turbine Off-site power R C/B B1F ve Main steam isolation valve ea Mveontto vra-olvpeerated Dry well vent ssecto Condenser Circulating water pump valve Standby l (Rr pr Feepdiwpeater liquid Pe control Vs system )su pump r e Sea Feedwate rpump Suppression Primary chamber containment Condensate pump Operational vent valve vessel Main equipment unit inundated Seawater cooling lost Control rod Emergency AC power lost H PCV cooling drive hydraulic Core spray system ea system pump Condensate DC power lost pump t e storage pool x c h Normal AC power lost a High-pressure coolant n Make-up water ge injection system pump condensate system r Power pump panels C/B B1F Filtered water R/B：Reactor building Seawater pump Diesel generator tank T/B：Turbine building Diesel-driven fire Sea protection system C/B：Control building T/B B1F pump Att1 - 5 Use other than purposes/copy/disclosure are prohibited Tokyo Electric Power Co.,Inc. Accident at Fukushima Units 1~3 Progression of Accident at Unit 1 and Necessary Measures Attachment - 1 【3/11 14:46 Earthquake occurs】 【3/11 15:35 Tsunami arrives 】 Isolation condenser system (IC) There are no facilities capable of injecting cooling Tsunami caused loss of power for automatically started up and water water when the reactor is in a high pressure state. operating valves, and closed valves no level was maintained ↓ longer opened. In 2~3 hours, the water level drops to reactor core Reactor pressure vessel (RPV) S h utd o w n Tsunami arrival Water level falls ※ IC Confusion when first tsunami wave, Not able to ascertain surpassing assumptions, condition of reactor arrives 【Tangible measure】 【Intangible measure】 【Tangible measure 】 【Intangible measure 】 【Tangible measure 】 Enhance seismic performance Accident assumptions, Tsunami countermeasures, Information sharing Strengthen high-pressure cooling of off-site power source response to multiple unit accident reinforcing power sources water injection function 【3/11 ~18:18 】 【3/11 20:00 〜3/12 in the morning】 【3/12 15:36】 vTahlvee o spteartuatso irn dopiceant otrh ela vmaplv eli tb uecpa, ubsuet tthhee Reactor core Wcaoterre ldeavmel afgaell sp fruorgtrheesrs easn d PCV damaged, and Hydrogbeuni ledxinpglosion at damage begins After short operator closed the valve again because Primary containment vessel hydrogen leaks into time, steam steam generation from IC stopped. (hydrogen generated) pressure rises reactor building stopped Difficult to perform venting (R/B) Fuel exposed and damaged, and hydrogen generated Damage progresses ※ IC Water level falls Shortage of machinery, materials(personal 【Tangible measure 】 dosimeters, etc.) Strengthen low-pressure cooling Contamination spreads Not able to ascertain water injection function 【Intangible measure 】 condition of reactor 【Tangible measure 】 Transport of materials Hydrogen countermeasures 【Intangible measure 】 【Tangible measure 】 and equipment PCV damage countermeasures Information sharing Strengthen venting function Strengthen radiation control framework Att1 - 6 Use other than purposes/copy/disclosure are prohibited Tokyo Electric Power Co.,Inc. Accident at Fukushima Units 1~3 State of SSCs after the earthquake struck (1F-1) Attachment - 1 Reactor pressure analysis and visual confirmation were conducted to confirm effects of the earthquake for Unit 1 Reactor pressure analysis Technical findings for hearing opinion of NISA Technical findings about Fukushima Daiichi for hearing opinion of NISA reported that if less than 0.3 cm2 crack occurred, it is not clear RPV pressure difference to check the leakage of coolant. On the other hand, if there is ca, 0.3 cm2 crack, it effects the accident progression so that amount of 10 ton water leaks from RPV The RPV pressure analysis was conducted under the PCV pressure conditions of occurring 0.3 cm2 crack as to these findings The safety regulations requires that the coolant leak rate to PCV is within 0.23 m3/h.Following figure shows that the result of 0.23m3/h crack occurs Earthquake Result of RPV pressure (correspond to 8mm2@vapor condition, 2mm2@liquid condition ) / SCRAM IC automatically start up This analysis show that analytical value and s] b measured value did not a,a 8mm2(vopor condition) make significant deference. P g] M MPa, IsCta rmt uanpu/ astlo p Pressure gauge ure [ 2mm2(liquid condition) ure [ IC manual stop press ss V V pre PC Observed value Analytical value (vapor dome) P No leakage condition R measured value (transient record device) measured value (record chart) Reference：JNES Time The observed value (red line) is under analytical values (green, blue line) Time Reference：JNES Judging from PCV pressure trend, it is less likely to effect the accident progression even if some cracks occur. Att1 - 7 Use other than purposes/copy/disclosure are prohibited Tokyo Electric Power Co.,Inc. Accident at Fukushima Units 1~3 State of SSCs after the earthquake struck (1F-1) Attachment - 1 Ex. visual confirmation (IC, Unit 1) There was no definite evidence leading LOCA at outside of PCV result of visual confirmations Othet visual confirmation check points Unit 5,6 : R/B, T/B Unit 1,2,3 : T/B Unit 2 : R/B Level Unit 1,2,3,4 gauge IC : outside installations IC (B) condensate water return pipe line IC entrance vapor pipe line MO- 1301-2 MO- 1301-10 Note: These valves drown by this figure are in MO- 1301-1 stand-by state. 原原原 MO- 子子子 1301-4 炉炉炉 V圧圧圧 RP力容力容力容 器器器 MO- 1301-3 2FL PPLLRR--AA PPLLRR--BB IC (A) condensate water return pipe line The result of visual confirmations and seismic response analysis for unit 1,2 and 3 using observed records shows that SSCs would sustain these requisite functions after the earthquake. Att1 - 8 Use other than purposes/copy/disclosure are prohibited Tokyo Electric Power Co.,Inc. Accident at Fukushima Units 1~3 IC operating condition and indication of water level gauge (1F-1) Attachment - 1 The presumed RPVwater level by a MAAP analysis result. ①【3/11 14:46 Earthquake occurs】②【3/11 15:35 Tsunami arrives 】 ③ 【3/11 ~18:18 】 ④ 【3/11 20:00 〜3/12 【3/12 15:36】 in the morning】 Isolation condenser system (IC) Tsunami caused loss of power The operator open the valve because Water level falls further and core Hydrogen automatically started up and water for operating valves, and closed the valve status indicator lamp lit up, damage progresses explosion at level was maintained valves no longer opened. agbaiunt btheec aoupseer astteoarm cl goesende rtahtei ovna lfvreo m Primarpyr ceosnsutarien rmiseenst vessel building Primary containment vessel IC stopped. Difficult to perform venting Reactor pressure vessel (RPV) S h utd o w n Isolation Tsunami arrival Water Water Damage condenser level falls level falls progresses Recognition of those days ② ③ ④ ① Tsunami caused became Since the vapor efflux of IC Since preparation of a ICwas completed, the The cold shutdown impossible to check stopped, failure of IC is operation which opens IC valve was carried out procedure of training is parameters, such as RPV considered and it stops. and started at 21:30. carried out. water level. ① ② MCR indicated value Earthquake Tsunami It was recognized as the ability of the reactor Core damage 5000 L-8（4643mm） presumed core to be cooled by that the water gauge of m] 4000 NWL（4370mm） 21:19 showed more than TAF, and operation of m D/D FPand IC. [ 3000 el v 2000 L-L（1950mm） e However, ... l 1000 ater 0 TAF ③ w It is presumed around 21:00 that reactor or -1000 L-0（-1405mm） ④ water levels were few, cooling by IC is not t -2000 c a carried out, and core damage had already e -3000 R 3/11 3/11 3/11 3/11 3/11 3/11 3/11 3/11 3/11 3/11 3/11 3/11 3/12 3/12 3/12 advanced. 12:00 13:00 14:00 15:00 16:00 17:00 18:00 19:00 20:00 21:00 22:00 23:00 0:00 1:00 2:00  As for the reactor water gauge of 21:19, the surface of the water established outside of RPV evaporated by a temperature rise by the core damage and was not able to measure exact differential pressure.It was thought that this showed the high water level on appearance, and it was convinced that a reactor core is normal till time (3/11 23:50) for a D/W pressure gauge to restore the persons concerned those days. Att1 - 9 Use other than purposes/copy/disclosure are prohibited Tokyo Electric Power Co.,Inc. Accident at F福u島ku第sh一im１a 〜U３ni号ts 機1~の3事故 About a Water level gauge Attachment - 1 The water level in the RPV measures it by the at the water head in the RPV and the difference in pressure of the adjacent datum level device. Normal case The state after the point in time when a water level gauge showed a constant value in the unit 1.(Estimate) Base level vessel PCV All the water in D/W D/W lost it in evaporation by the core damage. Accident Base water level Base water level decreased by Water level evaporation by the (Calculated value) Reference core damage. water head TAF TAF Difference pressure −1853mm (ΔP) becomes small BAF and overestimates ΔP water level. Fluctuate water head ΔP A water level higher Differential A water level is measured from pressure than an original pressure difference (ΔP). Differential gauge water level is shown. A high water level is shown, so that pressure pressure difference is small. gauge ] m ・When the water of instrumentation piping in m [ PCV is lost, if a water level calculates, it will be el v e about TAF-1853 mm. l r e t wa ・This value is almost the same as the steady or value which is directing the water gauge of Unit 1 t c a on and after 3/12. e R Att1 - 10 Use other than purposes/copy/disclosure are prohibited Tokyo Electric Power Co.,Inc.