Fukushima Daini Independent Review and Walkdown

Transcription

1 Fukushima Daini Independent Review and Walkdown IAEA Experts Meeting on Protection Against Extreme Earthquakes and Tsunamis September 2012 Authors: John Richards, EPRI Jim Johnson, JJJ & Assoc. Ken Huffman, EPRI Greg Hardy, SGH Antonio Godoy, JJJ & Assoc.

2 Scope of Independent Review and Walkdown Fukushima Daini Area Seismic Tsunami Safe Shutdown Description Assessment of the earthquake event and effects upon the plants. Assessment of the tsunami effects upon the plants. Technical considerations related to sustaining safe shutdown. Reporting Reporting of walkdown and review of technical results (EPRI report ). Reactor Buildings Turbine Buildings Heat Exchanger Buildings 2

3 Response of Fukushima Daini Units to the Earthquake Event Main Item Main Operation Unit No. 1 Time Status Prior to Earthquake Status of Plants Earthquake Occurrence Reactor Shutdown Reactor Shutdown Power Supply Reactor Pressure, Reactor Cooling Reactor Offsite Power Supply Emergency Diesel Generator Emergency Core Cooling System Rated Power Operation 3 of 4 Circuits Available Standby State Standby State Mar :46 Reactor Auto Scram Yes 14:48 Confirm Subcritical Yes 15:00 External Power Supply Emergency Diesel Generator Emergency Core Cooling System Close Main Steam Isolation Valve (Auxiliary Boiler Trip) Suppression Chamber Cooling (Start-up of Residual Heat Removal) 2 Circuits Available Standby State Standby State Yes 15:36 Yes 15:30 Seismic trip Normal shutdown JMA tsunami warning Tsunami countermeasures initiated All units responded the same, Unit 1 response shown here.

4 Tsunami Inundation Reenactment Calculation Video Record of Tsunami TEPCO calculation results reproducing inundation observations. Direction of View 4

5 Unit 1 Emergency Diesel Generator Exterior Louvered Intake Opening Interior Air Filter Frames Diesel Undergoing Maintenance 5

6 Heat Exchanger Buildings Components in Heat Exchanger Building Unit 4 South Building South Equipment Hatch Power Cubicles in Heat Exchanger Building Unit 3 North Building North Equipment Hatch 6

7 Post-Tsunami Station Capabilities Availability of Several Key Functions After the Tsunami, Before Recovery Actions General Conditions Functions Unit 1 Unit 2 Unit 3 Unit 4 Offsite Power Yes Yes Yes Yes Emergency Diesel Generators Division A Division B High Pressure Cooling System H Power to Heat Exchanger Building Equipment Operable Equipment in Heat Exchanger Building No No No No No No No Yes Yes No No Yes No No Partial No No No Partial No Core Cooling (RHR) No No Yes No Roadway to Site Protected Area Entry Into Unlighted Heat Exchanger Building 7

8 Recovery Efforts RHR Pump Motors First Day Located replacement motors Evaluated flooded motors Second Day Motors delivered by helicopter / overland truck RHR Closed Cooling Pump / Motor Third Day Installed motors Flooded Motor in Heat Exchanger Building 8

9 Recovery Efforts Temporary Power for Heat Exchanger Buildings First Day Located replacement motors Evaluated flooded motors Located temporary cable Obtained emergency power vehicles Second Day Motors delivered by helicopter / overland truck Cable delivered by helicopter Third Day Installed motors Ran cables 9

10 Recovery Efforts Temporary Cable Installation Temporary Cables from RadWaste Building to HX Buildings Temporary Cables Inside Heat Exchanger Building Temporary Cable Connection to Motor 10

11 Seismic Observations Earthquake Motion Evaluation Recorded Motions Compared to Back-Check (Ss) Base Mat PGA (Peak Ground Acceleration) Comparisons East/West (g) North/South (g) Up/Down (g) Recorded S s Recorded S s Recorded S s Unit Unit Unit Unit

12 Seismic Observations Walkdown Conclusions Hair Line Crack In Concrete Four person seismic team inspected a cross-section of 27 types of SSCs Safety-related SSCs did not appear to have evidence of seismic damage Safety-related buildings, foundations and equipment generally in excellent condition, virtually no signs of significant damage 12

13 Seismic Observations Walkdown Conclusions Non-Safety Water Tank Elephant foot Buckling One of a Few Damaged Tank Anchorages Gantry Crane with One Wheel Displaced from Rail Displaced Wheel 13 Non-safety related SSCs performed well, very few instances of seismic damage Cause of non-safety related gantry crane displacement was not determined Inspection results corresponded to the lowest seismic damage intensity level using either the EPRI or IAEA postearthquake guidelines

14 Seismic Observations Recommendations Complete the evaluation of all (in-structure in addition to base mat) motion records from the earthquake Validate truncated motion records by comparison to nontruncated records Assign either No Action Required or Action Level 1* to the event using the IAEA post-earthquake guide action levels Provide additional focus on any components that had not completed the back check process prior to the earthquake and consider Action Level 5* for these * Actions associated with Action Level 1 include focused inspections and tests (to verify function, operability) and if successful restart the plant * Action Level 5 actions are the same as Action Level 1 plus reevaluation of the seismic hazard, if deemed necessary 14

15 Tsunami Observations Direct and Indirect Flooding Direct Flooding Indirect Flooding Unit #1 Heat Exchanger Building Unit #3 Turbine Building B2 Floor Ventilation Louver on the Ground Floor of Unit #1 Reactor Building Pipe Penetration in Unit #1 Reactor Building 15

16 Tsunami Observations Tsunami Recommendations Protection of buildings from major water entry points Significant flooding would not be expected Extent of in-leakage would be manageable Component repair / refurbishment / replacement recommendations >20 component types Test methods and acceptance criteria Actions for reuse Need for on-going periodic testing 16

17 Safe Shut Down Observations Adequate Cooling, Additional Protection Current cooling capabilities were adequate to meet decay heat load needs Temperature margins sufficient to address contingencies like replacement of RHRC / RHRS motors Recommended additional protection of critical, nonredundant RHR capabilities Unintentional damage or disruption of power sources Blockage of damaged seawater intakes Aggressive equipment condition monitoring 17

18 EPRI Review and Walkdown Participants Shiego Hattori Ken Huffman Sam Bass Antonio Godoy Jim Johnson Greg Hardy John Richards Gary Toman Jim Heishman Steve Hess Drew Mantey 18

19 Key TEPCO Review and Walkdown Participants Shinichi Kawamura Unit Superintendent Naohiro Masuda Superintendent Yukiko Ogawa Team Leader Kazuyuki Nagasawa Group Manager Atsushi Taniguchi Team Leader 19

20 Together Shaping the Future of Electricity 20