Overview of Incident at Fukushima Daiich Nuclear Power Station (1F) (Informal personal observations) April 2011

Operating condition before the Earthquake Unit 6 Type : BWR-5 (GE/Toshiba) Out Put : 1100MWe Commercial operation :1979 Plant Condition : Outage Unit 5 Type : BWR-4 (Toshiba) Out Put : 784MWe Commercial operation :1978 Plant Condition : Outage Unit 2 Type : BWR-4 (GE/Toshiba) Out Put : 784MWe Commercial operation :1974 Plant Condition : Operating Unit 3 Type : BWR-4 (Toshiba) Out Put : 784MWe Commercial operation :1976 Plant Condition : Operating Unit 4 Type : BWR-4 (Hitachi) Out Put : 784MWe Commercial operation :1978 Plant Condition : Outage Unit 1 Type : BWR-3 (GE) Out Put : 460MWe Commercial operation :1971 Plant Condition : Operating

Summary of Tohoku-Kantou Earthquake ② Pacific Ocean plate ④ Philippine Sea Plate ① ③ ④ ② 11 th March 15:08 After shock (M 7.5) ③ Eurasian plate ① North American plate 11 th March 15:25 After shock (M 7.4) 11 th March 14:46 Main shock (M 9.0) Estimated Epicentral Erea 11 th March 15:15 After shock (M 7.3) Fukushima 1st NPP Tokai 2nd NPP

Overview of Incident Sequence (Initial phase) 11 th March Turbine was tripped and Reactor(Unit 1, 2 and 3) was Scram due to Earthquake Transmission Lines were failed due to Earthquake LONP(Loss of Normal Power ) was happened (Emergency Diesel Generators Automatically Started ) 14:46 All of Emergency Diesel Generators were tripped (due to Tunami??) SBO(Station Black Out -Loss of All Alternative Power) was happened 15:41 Declared Site Alert due to SBO15:42

Significant Damage of Intake Structures due to Tumami Before Tunami Attack Unit 1 Unit 2 Unit 3 Unit 4 Unit 1 Unit 2 Unit 3 Unit 4

Schematic Diagram of BWR4’s Core Cooling Systems Feed Water Line Main Steam Line Containment Cooling Pump Core Spray Pump Sea Water Pump High Pressure Core Injection Pump Condensate Storage Tank SRV Emergency Bus Emergency Diesel Generator Hx Fire Protection Sys From Normal Supply Vent Line Stack

Immediately after the earthquake (Under Loss of Normal Power) Feed Water Line Main Steam Line Containment Cooling Pump Core Spray Pump Sea Water Pump High Pressure Core Injection Pump Condensate Storage Tank SRV Emergency Bus Emergency Diesel Generator Hx Fire Protection Sys From Normal Supply Vent Line Stack

After The Tumami Attack (Under the Station Black Out) Feed Water Line Main Steam Line Containment Cooling Pump Core Spray Pump Sea Water Pump High Pressure Core Injection Pump Condensate Storage Tank SRV Emergency Bus Emergency Diesel Generator Hx Fire Protection Sys From Normal Supply Vent Line Stack

Under the Station Black Out (Primary Containment Vessel Venting) Feed Water Line Main Steam Line Containment Cooling Pump Core Spray Pump Sea Water Pump High Pressure Core Injection Pump Condensate Storage Tank SRV Emergency Bus Emergency Diesel Generator Hx Fire Protection Sys From Normal Supply Vent Line Stack

Completely Loss of Coolant Injection Feed Water Line Main Steam Line Containment Cooling Pump Core Spray Pump Sea Water Pump High Pressure Core Injection Pump Condensate Storage Tank SRV Emergency Bus Emergency Diesel Generator Hx Fire Protection Sys From Normal Supply Vent Line Stack

Sea Water Injection from Fire Protection System Feed Water Line Main Steam Line Containment Cooling Pump Core Spray Pump Sea Water Pump High Pressure Core Injection Pump Condensate Storage Tank SRV Emergency Bus Emergency Diesel Generator Hx Fire Protection Sys From Normal Supply Vent Line Stack

Overview of Incident Sequence (Progress phase) 1/2 11 th March Unit 1 Unit 2 Unit 3 Unit 4 16:36 Declared Loss of ECCS 01:20 PCV *1 Pressure Abnormal Rising 12 th March 14:30 PCV Venting 15:36 Reactor Building was destructed due to hydrogen explosion 20:20 Started Sea Water Injection to Reactor Core Reactor water level was maintained by HPCI * 2 system powered DC battery *1 PCV : Primary Containment Vessel *2 HPCI : Hi Pressure Core Injection System During Maintenance Outage Fuel Assemblies were in Fuel Pool

Overview of Accident Sequence (Progress phase) 2/2 Unit 1 Unit 2 Unit 3 Unit 4 13 th March 05:10 Declared Loss of ECCS 09:20 PCV Venting 13:12 Started Sea Water Injection to Reactor Core 11:01 Reactor Building was destructed due to hydrogen explosion 14 th March ~11 Reactor Building Blowout Panel was 0pened due to hydrogen explosion 13:25 Completely loss of coolant injection (Failed HPCI sys) 17:17 Started Sea Water Injection to Reactor Core 06:10 hydrogen explosion at near by S/C under PCV Venting?? 06:14 Reactor Building was destructed due to hydrogen explosion 15 th March

Significant Damage of Reactor Buildings due to hydrogen explosion Unit 1 Unit 2 Unit 3 Unit 4

Bird‘s Eye View of Typical BWR-4 Rector Building Fuel Pool Spent Fuel Primary Containment Vessel (PCV) Reactor Pressure Vessel (RPV) Suppression chamber Spent Fuel Main Steam Tunnel

Trend of Radiation Dose ① Fukushima City ② Koriyama City ③ Shirakawa City ④ Aizuwakamatsu City ⑤ Minami Souma City ⑥ Iwaki City ⑦ Tamura City ① ② ⑥ ④ ⑤ ③ ⑦ 30km 50km 100km /143/153/163/173/183/193/20 3/213/223/23 3/24 3/25 3/263/273/293/283/303/314/01 Radiation Dose Rate (μSV/h) Date Fukushima 1 st NPP Tokyo ~200km

The current situation and near future measures in Fukushima 1 st NPP -Reactors and spent fuel pools are continuously cooled by cooling water injection from the outside. -Radiation dose levels in outside of the NPP tends to decrease. -However, the contaminated water overflowing from the reactors and spent fuel pools have been leaking through Turbine Buildings and piping trench to the sea. -Continuous cooling of Reactors and Spent fuel pools -Reduce the additional release of radioactivity -Transfer to the contaminated water from Building and Structure to the existing or temporary storage tanks -Establishment of a closed loop Reactors and Spend fuel pools cooling system by the existing or temporary systems