The Fukushima Daiichi Nuclear Power Station Accident

Transcription

1 The Fukushima Daiichi Nuclear Power Station Accident Tomomi Matsunaga Kansai Electric Power Company Cooperation with JEPIC (Japan an Electric Power Information Center)

2 Nuclear Power Plants in Japan 2 1 Cessation of Operation : The Japan Atomic Power Co. Tokai (1998) Chubu EP Co. Hamaoka-1,2 (2009) Number of units Total power (MW) In operation Under construction Total

3 Status of Nuclear Power Plants after the Earthquake 3 The accident caused environmental damage at several units in the Fukushima Daiichi nuclear power Station after the earthquake occurred on March 11. Other nuclear power plants in Japan were in normal operation or safely shutdown. All units (Unit 1-3) were immediately shut down automatically Then safely went into cold shut down The unit was immediately shut down automatically Then safely went into cold shut down Source: Japan Atomic Industrial Forum, INC. (JAIF)

4 4 The Fukushima Daiichi Nuclear Power Station Unit5 Unit6 Unit4 Unit3 Unit2 Unit1 Before the earthquake

5 Overview of Boiling Water Reactor (BWR) (Mark-I Type ;Fukushima Daiichi Unit 1,2,3,4 and 5) 5 Source: NISA (

6 6 Mechanism of Boiling Water Reactor (BWR) Reactor Pressure Vessel Containment Vessel Supply Electricity Steam is generated and sent to the turbine. water steam Electricity is generated by rotating the turbine and the generator with steam. Turbine Generator Pump Dry Well fuel Water is boiled within the reactor. Condenser Control rod Sea water Suppression Chamber Pump Pump

7 Accident Description: Fukushima Daiichi NPS 7 Before the earthquake,unit 1,2 and 3 of the Fukushima Daiichi Power plant were operating. Unit 4,5 and 6 were under periodic inspection. After the earthquake, all control rods were inserted into the reactor as designed and Unit 1,2 and 3 automatically shutdown. Offsite power supply was lost because of the earthquake. The emergency diesel generators installed in each Unit started normally. Direct damage to the safety-related equipment due to the earthquake was not found. Seawater pumps, DGs, and power panels at all Units were flooded by the tsunami, then all AC power sources for Units 1 to 6,except for one air-cooled DG for Unit 6 lost their functionality. All motor operated safety systems, water injection and cooling facilities at Units 1 to 5 became inoperable. This is the major cause of the Fukushima daiichi Source: The Tokyo Electric Power Company, Inc. accident.

8 Inundated and Inflow Area at Fukushima Daiichi and Daini Site 8 Fukushima Daiichi Fukushima Daini inundated inflow Intensive Inflow

9 Core Cooling by Isolation Condenser (3/11 14:52) Accident progression at Unit1(1/3) Effort to sustain reactor water level Isolation Condenser Reactor Bldg. PCV RPV HPCI Inoperable since the battery was soaked in water Main Steam Line Feedwater Line Pump External electricity was inoperable due to the earthquake (3/11 14:46) Turbine Electrical Generator Condenser 9 Inoperable due to the emergency DGs soaked in water (3/11 15:37) PCV Spray Cooling System : Operable : Inoperable Core Spray System Source: Nuclear and Industrial Safety Agency (NISA) Standby Liquid Control System Poison Tank Condensate Storage Tank

10 Accident progression at Unit1(2/3 Decrease in reactor water level due to loss of cooling capability of emergency condenser, followed by uncovering the core 10 Function has not been correct Reactor Bldg. HPCI PCV Main Steam Line Decrease in reactor water level Isolation Condenser RPV Feedwater Line Turbine Condenser Electrical Generator Uncovering the Core (3/11 around 17:00 estimated) Pump -Hydrogen Generation due to a Zirconium- Water reaction - Fuel Rod damage PCV Spray Cooling System Core Spray System : Inoperable Source: Nuclear and Industrial Safety Agency (NISA) Poison Tank Condensate Storage Tank

11 Accident progression at Unit1(3/3) Hydrogen explosion in the operation floor 11 Plaster board Accumulation of Hydrogen Explosion Reinforced Concrete Source: Nuclear and Industrial Safety Agency (NISA) Reactor building Reactor building

12 Accident Progression at Unit 2 through 4 12 Unit 3 Unit 4 Vapors rising from Unit 3 are assumed to be produced from Spent Fuel Pool. Unit 2 Source: Nuclear and Industrial Safety Agency (NISA)

13 Rx Water Level [mm] Rx Pressure [MPa] D/W & S/C Pressure [MPa] RCIC HPCI SRV 0(TAF) FP/Fire Engine PCV Vent Fukushima Daiichi Unit 2 Plant Parameter and Operation Earthquake 14:46 Tusnami 15:27 No Operation Unit1 R/B Explosion 15:36 S/C Pressure (MPa) D/W Pressure (MPa) (2:55) Operation confirmed Fuel Range (A) (mm) Fuel Range (B) (mm) CAMS D/W(A)(Sv/ CAMS S/C(A)(Sv/ Order for Sea Water Injection Preparation 12:05 (11:00 Vent Line Order for Vent Preparation 17:30 Configuration Completed Source: The Tokyo Electric Power Company, Inc. Unit3 R/B Explosion 11:01 Increase in D/W pressure Core Damage Started due to MAAP Analysis Impact sound 6:00-6:10 S/C pressure:0mpa Decrease in D/W pressure 19:Sea Water Hydrogen generation Rx Pressure (A) (MPa) Rx Pressure (B) (MPa) Radioactive (13:25)Out of Service Judged gas released Depressurization Valve Condition into the Unclear air ~18:00 2Valves Open Small Vent Valves Opened 13

14 Plant Parameter: Fukushima Daiichi Unit 2 March 11 March 30, Decrease in D/W pressure around 11:30 around 15:00 Increase in D/W pressure Radioactive gas released into the air Source: NISA and JNES