Development of SAMG Verification and Validation for Kashiwazaki-Kariwa(KK) Nuclear Power Station

Transcription

1 Development of SAMG Verification and Validation for Kashiwazaki-Kariwa(KK) Nuclear Power Station December 12-14, 2016 Toshinobu KITA TEPCO Holdings, Inc.

2 Japan BWRs SAMG Development History 1 Original JP BWRs generic SAMGs were developed in 1990 s Considered EPRI SAMG Technical Basis Report and BWROG EPG/SAG Considered Individual Plant Examinations (IPEs) results for each BWR plant (Level 1, Level 1.5) Plant specific SAMGs were developed and implemented for each Kashiwazaki-Kariwa(KK) unit

3 Generic SAMG and plant specific SAMG 2 basis Plant specific (S)AMG (U.S) EPG SAG research Japanese BWR Utilities & BWR Japanese Plant Vendors result Japanese generic (Severe) Accident Management Guideline (BWR) generic AMG (SOP) BWR Plant A AMG SOP BWR Plant B AMG SOP BWR Plant C AMG SOP

4 After Fukushima Daiichi Accident (TEPCO) 3 Enhanced defense in depth (DID) against external events and adopted concept of Phased Approach Added permanently installed safety measures, portable equipment according to the above basic policy Improved overall design of procedures and guidelines Japan s BWR utilities also had working group and held joint study to improve Japan BWRs generic EPG/SAG considering BWROG EPG/SAG Rev.3 and ABWR EPG/SAG

5 Phased Approach Select safety measures based on time margin Accident Occurence initial response phase Installed equipment Shift team Action by installed equipment Complexity of accident progression (1) (2) (3) second response phase Portable equipment On-sites team Support from off-site Action by Portable Equipment and Management final response phase Support from off-site Augmented by off-site team [time] 4 High pressure injection pump (installed equipment) Fire engines Power supply cars Tank trucks from off-site

6 Safety Measures to Enhance 4 th Layer of DID Protection of the PCV and prevention of uncontrolled fission products release Protection of PCV by preventing over-pressure/temperature: PCV Top Head Flange Cooling, reinforcement of PCV Flange Sealing Mitigation of Radioactive material release: Filtered Vent Prevention of hydrogen explosion: Passive Autocatalytic Recombiners 5

7 Structure of SAM related documents (before 3.11) 6

8 Structure of SAM related documents 7

9 Examples of EOP/SOP improvement for KK 8 Guidance for the control of secondary containment parameters Guidance for the control of SFP level and temperature Guidance not only for power operation but for shutdown conditions, etc.

10 EOP/SOP Verification & Validation for KK 9 Verification: Evaluate table top effectiveness from the viewpoint whether: - Flowcharts meet revision request - Flowcharts are written appropriately Validation: Evaluate operability effectiveness from the viewpoint whether: - Flowcharts are usable for operators - Evaluators could judge that operators were able to use them

11 10 Backup Slides

12 Lessons Learned from the Fukushima Daiichi Accident 11 Protection against a tsunami exceeding assumption was weak Sufficient preparations werenot made for - preventing station blackout (SBO) -mitigating the influence of SBO by ensuring high-pressure core injection, depressurization, low pressure core injection, heat removal in case of SBO Means were not well prepared to mitigate the impact after reactor core damage : prevention of containment failure hydrogen control countermeasures for core melt-through prevention of a large release of radioactive material into the environment, etc.

13 Basic Policies for Reactor Safety Enhancement 12 (1) Enhance defense in depth against external events (2) Adopt the concept of Phased Approach for: Power supply function high pressure water injection, depressurization, low pressure water injection, and heat removal functions in case of SBO (3) Ensure primary containment integrity against severe accident

14 Basic Policies for Reactor Safety Enhancement (Continued) Reinforcement of defense in depth against external events Reinforce defense in depth based on the assumption that multiple function failures could happen by external events Establish safety measures along with defense in depth concept focusing on diversity and physical separation Consider not only earthquake and tsunami but also 40 natural events and 20 human induced external events shown in US NUREG*and the IAEA Safety Guide** Select the external events based on their cliff edge effect and their probability and then establish safety measures against them Strengthen measures also against internal flooding and internal fire Use of probabilistic risk assessment (PRA) to: select accident sequences to be evaluated evaluate effectiveness of the established safety measures * NUREG/CR-2300 Vol.2, PRA Procedures Guide ** IAEA Specific Safety Guide SSG-3, Development and Application of Level 1 Probabilistic Safety Assessment for Nuclear Power Plants 13

15 14 Measures to Enhance 3 rd Layer of DiD and Supporting Systems Water Injection: HP injection, depressurization, LP injection, Heat removal Power supply: Back-up Battery, GTGs, Power Supply Vehicles, Switchgears Additional Water Source: Reservoir

16 Safety Measures to Enhance 4 th Layer of Defense in Depth Protection of the PCV and prevention of uncontrolled fission products release Protection of PCV by preventing over-pressure/temperature: PCV Top Head Flange Cooling, reinforcement of PCV Flange Sealing Mitigation of Radioactive material release: Filtered Vent Prevention of hydrogen explosion: Passive Autocatalytic Recombiners 15

17 Safety Measures to Enhance 4 th Layer of DiD (Continued) Alternative Coolant Circulation System (ACCS) This system makes it possible to cool down the RPV/PCV without increasing the interior water volume of S/P Avoid or delay containment venting 16 Improve the reliability of wet well venting PCV RHR PCV Spry From [i] Injection line Colored line in this picture is in the case of LOCA. In other cases, the flow path from RPV to S/P is through SRVs and these exhaust steam pipes instead of pipe rupture pint in LOCA. Alternate Hx Outside connecting port RHR flushing line CSP MUWC (A) MUWC (B) MUWC (C) SPCU RHR (B) HPCF (B) Hx (B) S/C cooling line HPCF(B) test line To [i] To SPH To S/C To RPV RW/B Existing line Newly installed line

18 Safety Measures to Enhance 4 th Layer of DiD (Continued) Filtered Containment Venting System 17

19 Safety Measures to Enhance 4 th Layer of DiD(Continued) ph Control (alkali control) 18 Inhibit production of iodine gas, and reduce amount of iodine emitted from PCV by making water in PCV alkaline PCV CSP Alkali control Liq u id ch em ica l ta n k A lk a li ch em ica ls MUWC pump (Make Up Water Condensate)

20 Supporting Analysis (Probabilistic Risk Analysis) E E E-04 Before AM 1.0E E E E E E-06 Latest CDF or CFF 1.0E E E E E E E E E E E-11 L1 Internal Operation (CDF) [/RY] L1 Tsunami(CDF) [/RY] L1 Seismic(CDF) [/RY] L1.5 Internal Operation (CFF) [/RY] L1 Internal Shutdown (CDF) [/R Shutdown]