East Japan Earthquake on March 11, 2011 and Fukushima Dai-ichi Nuclear Power Station

East Japan Earthquake on March 11, 2011 and Fukushima Dai-ichi Nuclear Power Station August 13, 2012 Takeyuki INAGAKI Nuclear Seismic Engineering Centre Tokyo Electric Power Company All Rights Reserved 2011The Tokyo Electric Power Company, Inc.

The Great East Japan Earthquake [Date/Time] 2:46 pm on Fri, March 11, 2011 [Epicenter] Offshore Sanriku Coast (approx. 180 km from Fukushima NPSs) [Seismic Energy] Moment Magnitude (Mw) 9.0 Largest earthquake/tsunami in recorded history of Japan. [Dead/Missing] Approx. 20,000 All Rights Reserved 2011The Tokyo Electric Power Company, Inc. 1

Observed Seismic Data Comparison between Basic Earthquake Ground Motion and the record of intensity Observation Point (The lowest basement of reactor buildings) Horizontal (N-S) Observed data (*interim) Maximum Response Acceleration (gal) Horizontal (E-W) Vertical Maximum Response Acceleration against Basic Earthquake Ground Motion (Gal) Horizontal (N-S) Horizontal (E-W) Vertical Unit 1 460 *2 447 *2 258 2 487 489 412 Unit 2 348 *2 550 *2 302 *2 441 438 420 Fukushima Daiichi Unit 3 322 *2 507 *2 231 *2 449 441 429 Unit 4 281 *2 319 *2 200 *2 447 445 422 Unit 5 311 *2 548 *2 256 *2 452 452 427 Unit 6 298 *2 444 *2 244 445 448 415 Unit 1 254 230 *2 305 434 434 512 Fukushima Daini Unit 2 243 196 *2 232 *2 428 429 504 Unit 3 277 *2 216 *2 208 *2 428 430 504 Unit 4 210 *2 205 *2 288 *2 415 415 504 *1: The above data are preliminary and may be subject to change. *2: The recording finished after about 130-150 seconds All Rights Reserved 2011The Tokyo Electric Power Company, Inc. 2

Status and Actions after the Earthquake (1) The inside of the administration building was seriously damaged. People in the building were assembled at the parking lot to confirm if there were any casualties or injured persons. All Rights Reserved 2011The Tokyo Electric Power Company, Inc. 4

Status and Actions after the Earthquake (2) Emergency Response Team members moved to the seismic isolation building (Emergency Response Room) and confirmed: All the control rods of Unit 1-3 were automatically inserted into the core. The off-site power was lost and all the available EDGs were in operation. The RPV water level of Unit 1-3 was controlled by the isolation condenser (Unit 1) or the RCIC system (Unit 2 & 3). All Rights Reserved 2011The Tokyo Electric Power Company, Inc. 5

Tsunami Observed at 1F 重油タンク Tank (height:5.5m) 撮影日 :2011/3/11 15:42 撮影日 :2011/3/11 15:42 撮影日 :2011/3/11 15:43 Date/time: 2011/3/11 15:42 Date/time: 2011/3/11 15:42 Date/time: 2011/3/11 15:43 Date/time: 撮影日 :2011/3/11 15:43 15:43 Date/time: 撮影日 :2011/3/11 15:43 15:43 Date/time: 撮影日 :2011/3/11 15:44 15:44 All Rights Reserved 2011The Tokyo Electric Power Company, Inc. 7

Impact of Earthquake/Tsunami at Fukushima Daiichi NPS (1F) Observed seismic acceleration exceeded the design-basis in only limited locations. No damage to safety-related equipment due to the earthquake confirmed to date. Tsunami severely flooded most of the major buildings. Estimated tsunami height of approx. 13 m (43 ft) was much greater than the design-basis of 6.1 m (20 ft). Almost the entire area was flooded 1F Unit 6 Unit 5 Unit 1 Unit 2 Unit 3 Unit 4 Radwaste Processing building All Rights Reserved 2011The Tokyo Electric Power Company, Inc. (C)GeoEye 8

Impact of Earthquake/Tsunami at Fukushima Daini NPS (2F) Observed seismic acceleration was smaller than design-basis. Damage due to tsunami was less extreme compared to 1F. Estimated tsunami height of approx. 9 m was much greater than the design-basis of 5.2 m. Limited area was flooded 2F Unit 4 Unit 3 Unit 2 Unit 1 Ran up intensively Radwaste Processing building (C)GeoEye All Rights Reserved 2011The Tokyo Electric Power Company, Inc. 9

Damages caused by the Tsunami (4) 1 2 1Large amount of sea water came even to the place behind the reactor buildings 2Sand and silt carried by the tsunami All Rights Reserved 2011The Tokyo Electric Power Company, Inc. 14

Status of Unit 1-3 immediately after the tsunami (1) Fallen into the Station Black Out (SBO): All safety and non-safety systems driven by electricity were not available. No lights in the control rooms, R/Bs, T/Bs, etc. No important instrumentations for Unit 1 &2 due to loss of AC power sources and DC 125V batteries; the reactor water level/ pressure, drywell pressure, wet-well (S/C) pressure, etc. ; Totally blind! The instrumentation of Unit 3 was available immediately after the tsunami but only lasted for about 30hours because the DC 125V battery charger was flooded. No communication media between the Emergency Response Room (ERR) and workers at the field: only two wired telephones available between the ERR and each control room. All Rights Reserved 2011The Tokyo Electric Power Company, Inc. 18

Status of Unit 1-3 immediately after the tsunami (2) The sea water systems were totally destroyed: no ultimate heat sink. Status of cooling and flooding of the reactors were as follows: Operation of the isolation condenser of Unit 1 was unclear. The RCIC system of Unit 3 tripped after about 21hours since the tsunami. Then the HPCI system was activated but worked only for about 14 hours. The RCIC system of Unit 2 worked for about three days after the tsunami but the actual status could not be confirmed at the control room. All Rights Reserved 2011The Tokyo Electric Power Company, Inc. 19

Integrity of Power Supply System After the Tsunami at 1F and 2F Power panel Unit 1 Unit 2 Can/ can not be used Power panel Can/c an not be used Power panel Fukushima Daiichi Unit 3 Unit 4 Unit 5 Unit 6 Can/can not be used Power panel Can/c an not be used Power panel Can/c an not be used Power panel Can/can not be used Fukushima Daini Unit 1 Unit 2 Unit 3 Unit 4 Power panel Can/c an not b e used Power panel Can/c an not b e used Power panel Can/ca n not be use d Power panel Can/ca n not be use d M/C P/C Emergency DG DC power supply Emergency use Regular use Emergency use Regular use 125V DC DG 1A DG 2A DG 3A DG 4A DG 5A(*2) DG 6A (*2) DG 1A DG 2A (*2) DG 3A (*2) DG 4A (*2) DG 1B DG 2B (air-cooled) (*1) DG 3B DG 4B (air-cooled) (*1) DG 5B(*2) DG 6B (air-cooled) DG 1B DG 2B (*2) DG 3B DG 4B (*2) - - - - - - - - - - HPCS DG (*2) DG 1H DG 2H (*2) DG 3H DG 4H M/C 1C M/C 2C M/C 3C M/C 4C M/C 5C M/C 6C M/C 1C M/C 2C M/C 3C M/C 4C M/C 1D M/C 2D M/C 3D M/C 4D M/C 5D M/C 6D M/C 1D M/C 2D M/C 3D M/C 4D - - M/C 2E - - M/C 4E - - HPCS DG M/C M/C 1H M/C 2H M/C 3H M/C 4H M/C 1A M/C 1B M/C 2A M/C 2B M/C 3A M/C 3B M/C 4A M/C 4B M/C 5A M/C 5B M/C 6A-1 M/C 6B-1 M/C 1A-1 M/C 1B-1 M/C 2A-1 M/C 2B-1 M/C 3A-1 M/C 3B-1 M/C 4A-1 M/C 4B-1 M/C 6A-2 M/C 6B-2 M/C 1A-2 M/C 1B-2 M/C 2A-2 M/C 2B-2 M/C 3A-2 M/C 3B-2 M/C 4A-2 M/C 4B-2 M/C 1S M/C 5SA-1 M/C 1SA-1 M/C 3SA-1 M/C 2SA M/C 3SA M/C 5SA-2 M/C 1SA-2 M/C 3SA-2 - - - M/C 5SB-1 M/C 1SB-1 M/C 3SB-1 M/C 2SB M/C 3SB M/C 5SB-2 M/C 1SB-2 M/C 3SB-2 - P/C 1C P/C 2C P/C 3C P/C 4C P/C 5C P/C 6C P/C 1C-1 P/C 2C-1 P/C 3C-1 P/C 4C-1 P/C 1D P/C 2D P/C 3D P/C 4D P/C 5D P/C 6D P/C 1C-2 P/C 2C-2 P/C 3C-2 P/C 4C-2 - - P/C 2E - - P/C 4E - - P/C 6E P/C 1D-1 P/C 2D-1 P/C 3D-1 P/C 4D-1 P/C 1A P/C 2A P/C 3A P/C 4A P/C 5A P/C 6A-1 P/C 1D-2 P/C 2D-2 P/C 3D-2 P/C 4D-2 P/C 2A-1 - - - - P/C 5A-1 P/C 6A-2 P/C 1A-1 P/C 2A-1 P/C 3A-1 P/C 4A-1 P/C 1B P/C 2B P/C 3B P/C 4B P/C 5B P/C 6B-1 P/C 1A-2 P/C 2A-2 P/C 3A-2 P/C 4A-2 - - - - - - - - P/C 5B-1 P/C 6B-2 P/C 1B-1 P/C 2B-1 P/C 3B-1 P/C 4B-1 P/C 1S - - P/C 3SA - - P/C 5SA - - P/C 1B-2 P/C 2B-2 P/C 3B-2 P/C 4B-2 - - - - - - - - P/C 5SA-1 - - P/C 1SA P/C 3SA - - - P/C 2SB P/C 3SB - - P/C 5SB - - P/C 1SB P/C 3SB - DC125V main DC125V P/C DC125V main DC125V main DC125V P/C DC125V DIST DC125V main DC125V main DC125V main DC125V main bus panel A 2A bus panel 3A bus panel 4A 5A CENTER 6A bus panel A bus panel A bus panel A bus panel A DC125V main DC125V P/C DC125V main DC125V main DC125V P/C DC125V DIST DC125V main DC125V main DC125V main DC125V main bus panel B 2B bus panel 3B bus panel 4B 5B CENTER 6B bus panel B bus panel B bus panel B bus panel B Sea water system A RHRS A RHRS A RHRS A RHRS A RHRS A RHRS A RHRS A RHRS A RHRS A SW B RHRS B RHRS B RHRS B RHRS B RHRS B RHRS B RHRS B RHRS B RHRS B O: operable X: damaged *1 functionality lost due to inundation of power panels *2 functionality lost due to the damage of sea water system All Rights Reserved 2011The Tokyo Electric Power Company, Inc. 20

1F Unit 1 Schematic System Diagram (Status After Tsunami ) Stack D/W vent valve IC SRV Tb Gen RPV Condenser CWP S/C vent valve SLC CRD RFP H/W CP Sea :Operable :Inoperative due to power loss : Briefly Operative CS CCS from CST & H/W HPCI MUWC CST CCSW Sea D/G DD FP Filtrated Water Tank All Rights Reserved 2011The Tokyo Electric Power Company, Inc. 21 Sea

1F Unit 2 Schematic System Diagram (Status After Tsunami ) Stack D/W vent valve SRV Tb Gen RPV Condenser CWP S/C vent valve SL C CRD MD- RFP TD- RFP H/W HPCP LPCP Sea :Operable :Inoperative due to power loss :Inoperative CS RHR from CST & H/W RCIC HPCI CST RHRS Sea D/G MUWC DD FP Filtrated Water Tank All Rights Reserved 2011The Tokyo Electric Power Company, Inc. 22 Sea

1F Unit 3 Schematic System Diagram (Status After Tsunami ) Stack D/W vent valve SRV Tb Gen RPV Condenser CWP S/C vent valve SL C CRD MD- RFP TD- RFP H/W HPCP LPCP Sea :Operable :Inoperative due to power loss :Inoperative CS RHRS Sea RH R from CST & H/W D/G RCIC HPCI MUWC DD FP CST Filtrated Water Tank All Rights Reserved 2011The Tokyo Electric Power Company, Inc. 23 Sea

Actions taken for Unit 1-3 trying to avoid catastrophic conditions during the period since 11 th to 15 th March 2011 Establishing an alternative method to inject water into the reactor pressure vessel (RPV). Reduction of the RPV pressure using the SRVs. (Unit 2&3) Ventilation of the primary containment vessel (PCV). Recovery of the most important instrumentations: reactor water level rector pressure drywell pressure wet-well (suppression chamber: S/C) pressure. Recovery of the lights in the control rooms and other power supply sources. All Rights Reserved 2011The Tokyo Electric Power Company, Inc. 24

What were available for the recovery work after the tsunami? Only very limited devices and tools such as follows were available! Fire Engines: only a few people knew how to operate them. Flashlights Cable Tools (screwdrivers, etc.) Batteries taken from cars Engine driven Generators* Engine driven Air Compressors* *They were in the warehouses of the affiliated companies and difficult to find. All Rights Reserved 2011The Tokyo Electric Power Company, Inc. 25

Chronology of Unit 1 Scram response Deteriorating operability due to the tsunami Preparations for water injection Preparations for venting Water injection started Venting Prior to earthquake March 11, 2011 14:46 March 11 17:12 Site superintendent directed consideration for injection of water into reactors using fire protection lines and vehicles March 12 5:46 Fire-fighting vehicle started injection of fresh water (water source: fire cistern) In rated power operation Great East Japan Earthquake occurred, reactor automatically scrammed [SHUTDOWN] 15:37 Station black out due to tsunami strike (Sea water systems also lost) Water injection Venting [COOLING] [CONTAINMENT] March 12 19:04 Injection of sea water started March 12 0:06 As D/W pressure might have exceeded 600kPa abs, site superintendent directed preparations for PCV venting 10:17 Containment vessel venting commenced 14:30 D/W pressure decreased. Containment vessel venting successful March 12 15:36 Explosion Occurred All Rights Reserved 2011The Tokyo Electric Power Company, Inc. 26

Major Activities at 1F Unit 1 <factors disturbing recovery work (inside the building) > Scram response Due to lack of power sources, initial recovery activities had to be conducted in complete darkness, without any instrumentation, and without most communications means. Deteriorating operability due to the tsunami Many scattered objects were on the floor of the service building. Preparations for water injection Preparations for venting Water injection started Venting Connected temporary batteries to recover instrumentations. All Rights Reserved 2011The Tokyo Electric Power Company, Inc. 27

Major Activities at 1F Unit 1 <factors disturbing recovery work (inside the building) > Scram response Deteriorating operability due to the tsunami Instruments were monitored wearing a full face mask with a flashlight in complete darkness Check indicated values only with a flashlight in complete darkness. Preparations for water injection Preparations for venting Water injection started Venting Supervising at a deputy supervisor s desk wearing a full face mask in complete darkness. All Rights Reserved 2011The Tokyo Electric Power Company, Inc. 28

Major Activities at 1F Unit 1 <factors disturbing recovery work (outside the building) > Scram response Deteriorating operability due to the tsunami Many obstacles on access routes disturbed access to the field. Vehicles had to avoid passing over fire protection hoses laid in the field. Most of the prepared communication tools between the ERC and the control room were unavailable. Preparations for water injection Preparations for venting Water injection started Venting All Rights Reserved 2011The Tokyo Electric Power Company, Inc. 29

Major Activities at 1F Unit 1 <Containment Vessel Venting Operation (1) > Scram response Deteriorating operability due to the tsunami Preparations for water injection Preparations for venting Water injection started Venting Two valves, a PCV vent valve (MO valve) and a S/C vent valve (AO valve: small) were selected as the target for manual PCV venting operation. Manual valve operation were planned to be conducted by 3 teams with 2 shift workers per team (one worker per team would be difficult due to the total darkness) and shift supervisors and vicesupervisors were selected to the team members. Equipment for the teams included fire-resistant clothing, self-contained breathing apparatus, APD, survey meter and flash light. At 9:03, it was confirmed that evacuation from the vicinity of south side of the NPS completed. At 9:04, the team members headed to the site for the venting operation. Cylinder MO MO 210 manually open valve Solenoid valve IA 電磁弁 AO AO 90 IA AO AO ボMO 72 213 ンベラプチャーディスク Shift workers operation to AO AO 83 閉 Closed AO 1 AO 閉 Closed Closed Rupture disc Broke at 0.549MPa-abs 0.549MPabs で破壊閉 Closed ボンベ閉 Cylinder Exhaust 排気筒 stack D/W maximum operating pressure: 0.528MPa-abs D/W 最高使用圧力 0.528MPabs Self-contained breathing apparatus 電磁弁 All Rights Reserved 2011The Tokyo Electric Power Company, Inc. Solenoid valve 30 RPV D/W Venting ベント実施圧力 pressure: 0.954MPabs 0.954MPa-abs

Major Activities at 1F Unit 1 <Containment Vessel Venting Operation (2) > Scram response Supply AC power to the solenoid valve of the AOVs using an engine generator Supply air to the AOVs using an engine compressor Deteriorating operability due to the tsunami Preparations for water injection Preparations for venting Water injection started Venting The AC power was lost: alternative supply from an engine-generator Engine driven Air Compressor for construction work Cylinder MO MO 210 Solenoid valve IA 電磁弁 AO AO 90 IA AO AO ボMO 72 213 ンベ電磁弁 Solenoid valve ラプチャーディスク AO 83 AO AO 1 AO 閉 Closed Closed Rupture disc Broke at 0.549MPa-abs 0.549MPabs で破壊閉 Closed 閉 Closed ボンベ閉 Cylinder Exhaust 排気筒 stack D/W maximum operating pressure: 0.528MPa-abs D/W 最高使用圧力 0.528MPabs RPV D/W Venting ベント実施圧力 pressure: 0.954MPabs 0.954MPa-abs All Rights Reserved 2011The Tokyo Electric Power Company, Inc. 31

Testimonies from the Field (Operators) In an attempt to check the status of Unit 4 D/G, I was trapped inside the security gate compartment. Soon the tsunami came and I was a few minutes before drowning, when my colleague smash opened the window and saved my life. In total darkness, I could hear the unearthly sound of SRV dumping steam into the torus. I stepped on the torus to open the S/C spray valve, and my rubber boot melted. The radiation level in the main control room was increasing 0.01 msv (1 mrem) every 3 seconds but I couldn t leave I felt this was the end of my life. I asked for volunteers to manually open the vent valves. Young operators raised their hands as well; I was overwhelmed. Unit 3 could explode anytime soon, but it was my turn to go to the main control room. I called my dad and asked him to take good care of my wife and kids should I die. All Rights Reserved 2011The Tokyo Electric Power Company, Inc. 32

Testimonies from the Field (Maintenance Persons) We saw our car crashed by the explosion of the Unit 3. If we had gotten on the car a few minutes earlier, all of us would have been dead. We were replacing fire hoses when the explosion of Unit 3 occurred. We felt almost dying since many large rubbles were falling down to us. I urgently ran underneath a nearby fire engine. One of my colleagues got injuries in his leg and stomach. There were so many manholes opened by the tsunami. In order to lay cables, we had to proceed step by step carefully checking safety in the complete darkness. We were working in the Unit 3/4 control room when the explosion occurred. I was resigned to my fate. Dose rate was going up in the room after the explosion and we desperately tried to find places with lower dose rate. After replacing an air cylinder for the PCV ventilation of Unit 3, I heard sound of steam and saw white mist around us. I got into a panic for a while. All Rights Reserved 2011The Tokyo Electric Power Company, Inc. 33

Current Status and Roadmap Towards Restoration On Dec. 16, 2011, goals of Step 2 of Roadmap Towards Restoration was achieved. Reactors were determined to have achieved cold shutdown condition and that sufficiently low radiation dose at the site boundary can be maintained even if unexpected events were to occur. On Dec. 2nd, 2011, Interim Report on Fukushima Nuclear Accidents compiled by the TEPCO-Internal Investigation Committee was released. Consolidated facts regarding the accident, conducted root-cause analyses and identified action items to be implemented. Investigation of facts and identification of lessons learned will continue. Installation of Unit 1 R/B Cover All Rights Reserved 2011The Tokyo Electric Power Company, Inc. 34

Mid- to Long-Term Road Map Towards Decommissioning of 1F Units 1-4 Completion of Step 2 Within 2 years Within 10 years 30 to 40 years Phase-1 Phase-2 Phase-3 Period until commencement of fuel removal from the spent fuel pools Period until commencement of removal of fuel debris Period until completion of decommissioning Illustration of Fuel Debris Removal Process Global collaboration needed to work on unprecedented R&D undertaking. All Rights Reserved 2011The Tokyo Electric Power Company, Inc. 37

Analysis of Core Damage Condition of Fukushima Daiichi Units 1-3 Unit 1 PCV Units 2/3 PCV RPV RPV CS FDW CS FDW 2.6 m 2.6 m 7.6 m 7.6 m Fuels completely melted and relocated to the bottom of RPV. RPV breach likely occurred, leading to molten core-concrete interaction at the PCV pedestal floor. Max. penetration depth of 0.65 m. Fuels damaged but significant damage to the RPV leading to large amount of fuel dropping into the PCV floor unlikely. If damaged fuel had to dropped into the PCV floor, molten core-concrete interaction would have occurred. Max. penetration depth of 0.12 m (Unit 2) / 0.20 m (Unit 3). Core-Concrete Interaction stopped within the PCV steel plate and fuel is currently cooled. All Rights Reserved 2011The Tokyo Electric Power Company, Inc. 38

Summary (1) A large scale earthquake attacked the plant. According to the operation data, however, it can be concluded that plant behaviors before the tsunami was as designed, and up to now no damage due to the earthquake was found on safety-significant Systems, Structures and Components (SSCs). The height of the tsunami at Fukushima Dai-ichi was much higher than the plant design assumption and that observed at Fukushima Dai-ni. All electric power supply including DC 125V was lost for Unit 1-4 after the tsunami. For Unit 5&6, only one diesel generator, DG6B, was survived. After the tsunami, very limited tools and devices such as fire protection cars, batteries taken from cars and handy lights were available. In such circumstance, the Emergency Response Team members made their greatest efforts to avoid catastrophic conditions of Unit 1-3. Also for Unit 5&6, great efforts were made by the operators and maintenance people to make the units into a stable condition. All Rights Reserved 2011The Tokyo Electric Power Company, Inc. 39

Summary (2) Measures taken after the Niigata Chuetsu Oki Earthquake were certainly effective to ease the consequence of the accident: Seismic Isolation Building Self Fire Protection Team and Fire Engines Emergency Response Drills Up to now cooling systems for the reactors and spent fuel pools, and covering for the reactor building of Unit 1 have been established. Many projects are still being implemented. The plant staff members are dully cooperating with engineers of the stabilization centre and headquarters. From the plant point of view, it is very important to treat and manage contaminated water accumulated in the turbine buildings. Industrial safety of the recovery work is also very important. The plant staff members make a lot of efforts to improve work management and environment. All Rights Reserved 2011The Tokyo Electric Power Company, Inc. 40