Status on Spanish Regulations and Industry. actions related to Filtered Containment. Venting Systems (FCVS)

Transcription

1 Status on Spanish Regulations and Industry actions related to Filtered Containment Venting Systems (FCVS) Sara González Systems Engineering Department Consejo de Seguridad Nuclear, Spain Technical Meeting on Severe Accident Mitigation through Improvements in Filtered Containment Venting for Water Cooled Reactors IAEA Headquarters; September 2015

2 CONTENT 1. FCVS. Background and Regulatory Requirements 2. Current situation 3. Post stress test ITC and FCVS Technical Criteria 4. Plans of Implementation 5. Conclusions

3 1 FCVS. Background and Regulatory Requirements Fukushima Accident (March 11, 2011) Focus on extreme external events; also Prolonged Station Blackout (PSBO) and Loss of Ultimate Heat Sink (UHS) Stress test: Spanish NPPs decided to implement FCVS CSN required the implementation of FCVS FCVS will be installed in all Spanish NPP by the end of 2017

4 2 Current situation (1/3) 7 operating nuclear reactors (6 PWR and 1BWR): BWR: Cofrentes NPP (GE BWR-6, Mark III) PWR: Almaraz I/II NPP (Westinghouse PWR, 3 loops, 2 units) Ascó I/II NPP (Westinghouse PWR, 3 loops, 2 units) Vandellós II (Westinghouse PWR, 3 loops, 1 unit) Trillo NPP (KWU PWR, 3 loops, 1 unit) 1 BWR nuclear reactor currently shut-down: Santa María de Garoña (GE BWR-3, Mark I). The licensee has applied for the renewal of the plant operating permit

5 2 Current situation (2/3) BWR Cofrentes NPP: Hardened Containment Venting System (HCVS) installed in 1993 Design Modifications to increase the reliability of the HCVS operation in case of SBO and/or earthquake HCVS dual function: prevention and mitigation of severe accidents Santa María de Garoña NPP: HCVS installed in venting paths: from the drywell and form the wetwell HCVS dual function: prevention and mitigation of severe accidents

6 2 Current situation (3/3) PWR Westinghouse PWR (Almaraz I/II, Ascó I/II and Vandellós II): Controlled Hydrogen purge subsystem o Vent flow prefiltered by HEPA and active charcoal filters o The system designed for DBA (LOCA) and is foreseen to act only at low containment pressures SAMG include provisions for containment venting but not designed for severe accident conditions Trillo NPP: Currently Trillo NPP is not provided with any venting path

7 3 Post stress test ITC and FCVS Technical Criteria (1/3) POST STRESS TEST ITC In march 2012, the CSN issued an ITC requiring the installation of FCVS in every Spanish NPP except Cofrentes NPP. Cofrentes NPP was required to analyze the convenience for installing a FCVS taking into account the suppression pool retention capability. Finally, the CSN required the facility to install a FCVS before December 31, 2017.

8 3 Post stress test ITC and FCVS Technical Criteria (2/3) FCVS TECHNICAL CRITERIA On December 2013, CSN issued technical criteria for the implementation of FCVS: Designed to minimize hydrogen risks (in the system) Sufficient instrumentation available to monitor the FCVS performance and the release When applicable, supporting systems should be provided (power supply, pneumatic drive, etc.) to ensure for at least 24 hours (and the next 72 hours only with light equipment)

9 3 Post stress test ITC and FCVS Technical Criteria (3/3) Designed and manufactured to allow: Design pressure according containment design pressure Filter autonomy as long as necessary Decontamination factors (latest technologies available) Manual operation (radiological accessible) Periodic tests Valves considerations: Undesired openings; failure to close Seismic design (seismic margin > DBE) Maintain functionality under internal and external events If, additionally to the mitigating function, FCVS is used to prevent Severe Accident (i.e. BWR for heat removal function and/or hydrogen control), the system should be able to achieve the objective at the foreseen pressures

10 4 Plans of Implementation (1/5) All Spanish NPP have already informed CSN about FCVS selected technology (except Cofrentes NPP): Trillo and Almaraz I/II NPP wet FCVS technology Aerosols DF 10,000 Inorganic iodine DF 300 Organic iodine DF 10 Ascó I/II, Vandellós and Santa María de Garoña NPP Combined Venturi Scrubber Aerosols DF 10,000 (0.5 µm) and 100,000 (1-2 µm) Inorganic iodine DF 1,000 Organic iodine DF 10

11 4 Plans of Implementation (2/5) Wet FCVS technology (Trillo and Almaraz I/II NPPs) Stack Aditive tank Wet Filter CONTAINMENT ADJACENT ROOM Stem Extension Device

12 4 Plans of Implementation (3/5) Combined Venturi Scrubber (Ascó I/II and Vandellós II NPPs) ADJACENT ROOM Stem Extension Device Stack Venturi Scrubber Stage Zeolite filter stage

13 4 Plans of Implementation (4/5) Combined Venturi Scrubber (Santa María de Garoña NPP) Stack MOV Venturi Scrubber Stage Zeolite filter stage AOV AOV CONTAINMENT

14 4 Plans of Implementation (5/5) Cofrentes NPP Cofrentes has developed the system specifications and has already made a pre-selection but hasn t decided the final supplier yet. Cofrentes specifications development: Particles retention in the suppression pool MAAP code aerosols released through the vent would be very small (<0.5 µm) RASCAL code radioactive emissions to the environment Combining mitigation strategies with FCVS specified DF are: Aerosols (<0.5 µm) 100 Inorganic iodine 200 This specification proposal is under evaluation at the CSN

15 5 Conclusions The FCVS installation process will be finished in all the Spanish NPPs by the end of Before installation of the new systems, licensees are requested to send to CSN the detailed proposal of the design modifications (design of the systems, procedures, etc) for the regulatory approval. CSN is currently evaluating the licensees proposals.

16 Thank you for your atention!