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Fire PSA and insights Using for Periodic and Anticipated Safety Review

Fire PSA and insights Using for Periodic and Anticipated Safety Review. June 16 th 2014 / Fontenay -aux-Roses Fabienne NICOLEAU Nuclear Safety Division (PSN) Systems and Risk Assessment Department. Content. Specifics of the French Context PSAs for Safety Review

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Fire PSA and insights Using for Periodic and Anticipated Safety Review

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  1. Fire PSA and insightsUsing for Periodic and Anticipated Safety Review June 16th 2014 / Fontenay-aux-Roses Fabienne NICOLEAU Nuclear Safety Division (PSN) Systems and Risk Assessment Department

  2. Content • Specifics of the French Context • PSAs for Safety Review • Fire PSAs for the Periodic andAnticipated Safety Review • Safety Reviews of Fire PSA • Periodic Safety Review for 1,300MWe NPP • Anticipated Safety Review for EPR • Insights of Safety Reviews

  3. Specifics of the French context • A rather large fleet of NPPs (58 in operation): • Built by the same manufacturer • Operated by the same Licensee standardized in 3 PWR series - soon 4 with EPR (900MWe: 34 plants, 1300MWe (including two types P4 and PP4) : 20 plants and 1450MWe: 4 plants) • This situation has real advantages: • Experience feedback • Data collection • A single PSA and a Fire PSA for each NPP series and type EPR

  4. Periodic Safety Review (PSR) • Periodic process implemented by reactor series (every ten years) • Incorporate operating experience feedback and updated knowledge • Divided into two steps: • To demonstrate the conformity of the reference plant situation with the safety reference system • Rules, criteria and specification applicable resulting from the safety analysis report • The reference plant situation could be updated • The assessment of the safety reference system • Based on analysis of national or international experience feedback or specific studies like PSA

  5. PSAs for Periodic Safety Review • According to the French “PSA Basic Safety Rule », PSAs are used during periodic safety reviews in order to: • Evaluate its change compared with the assessment made on the completion of the previous review (systems characteristics or operating practices) • Assess the global risk (Core damage frequency) and highlight the dominant contributors • Highlight the potential “weak points” for which modifications have to be studied • Identify potential modifications to improve the safety level • When modifications are envisaged, PSAs can be used to assess the advantages and the drawbacks of the various solutions

  6. PSAs for Periodic Safety Review • “Workshop PSA teams”: Technical exchanges between TSO and Licensee • Specificities of the French regulatory framework • The Licenseedevelops “Reference PSAs” for each type of NPP • The TSO(IRSN) supports analysis of “Reference PSAs” study • Since the 90s, IRSN has been: • ReviewingPSAs performed by the Licensee • UsingPSA results and insights in the frame of safety analyses • Also developing its own PSA studies • A way to increase IRSN capability in the verification of Licensee studies • A tool to allow in-depth analyses (sensitivity studies …) and to obtain independent insights

  7. Fire PSAs for Periodic Safety Review • ASN (Nuclear Safety Authority) requested IRSN assessment of theLicensee’s Fire PSA, in particular on: • Method as regards the national and international practices • Screened-out • Fire sources • Targets • Fire compartments • Results: • Quantification on CDF • Main contribution on CDF • Dominating scenarios

  8. Safety Review of Fire PSA • Periodic Safety Review for 1,300MWe NPP • Specific context • Third decennial PSR for the 1,300MWe NPP • First Fire PSA developed by the Licensee • Third Periodic Safety Review is divided into 2 phases: • The first phase started in 2010 and finished in May 2012 • The Licensee developed a Fire PSA • IRSN analysed it compared with his own study: IRSN Fire PSA was used to propose recommendations and modifications accepted by the Licensee at the end of the first phase • The second phase (the Licensee solutions proposal) will take place in 2014 • The Licensee study is updated

  9. Safety Review of Fire PSA • Periodic Safety Review for 1,300MWe NPP • IRSN Fire PSA will be used to approve modifications Which will be taken into account: • In the Licensee Fire PSA • For the NPP series • Because of the first Fire PSA developed by the Licensee • The analysis of the IRSN concerned: • Mainly the method relative to Fire PSA developed by the Licensee • To a lesser extent, on the results • Indeed, the examination of the method has highlighted numerous needs for improvement: • More than 20 actions and modifications accepted by the Licensee • 2 recommendations supported by the Nuclear Safety Authority

  10. Safety Review of Fire PSA • Periodic Safety Review for 1,300MWe NPP • The Licensee Fire PSA has been to provide complements, in particular with regard to: • Improvement of the analysis of the fire scenario in the Control Room • Taking into account firespreading from desks’ component to desks’ component • Consideration of the fire spreading between fire compartments • Assessment of the reliability of the fire barriers • Take into account fireswhich can occur on thecurrent part of cables: • Based on the French experience feedback about those fire

  11. Safety Review of Fire PSA • Periodic Safety Review for 1,300MWe NPP Firedoor Fire zones corridor corridor • Recommendation: Develop a Fire PSA per 1,300MWe NPP’s type • Besides, during the instruction, IRSN showed that the fire risks are different for the two types of 1,300MWe NPP (i.e. P4 and P’4 plants), mainly because of: • Their geometry • Their fire compartment • The present equipment in compartment • Functional consequences of a fire can be different ≠

  12. Safety Review of Fire PSA • Periodic Safety Review for 1,300MWe NPP • Recommendation: The Licensee must change the damage temperature or perform a sensitivity study on the damage temperature in his Fire PSA • Value of damage temperature taken by the Licensee • Licensee: 137°C for electric component and 95 °C for electronic component (only I&C cabinet) • Recommended value of 65°C: international practice and IRSN experimental programs • Conclusions of sensitivity studies • If the damage temperature increases by 30°C, less component are lost in the fire compartment and in the adjacent compartment • The decrease of damage temperature has an important impact on core damage frequency as more initiating events are induced and more equipment important for safety are lost

  13. Safety Review of Fire PSA • Anticipated Safety Review for EPR • Specific context • First time which PSAs developed during the construction phase of a NPP • Regarding Fire PSA • All data are not localized in fire areas and in buildings • Safety measurement of the risk of fire are not yet validated • Anticipated Safety Review is divided into 2 phases: • First phase: started in 2011 and finished in 2014 • Within the framework of the reactor EPR-FA3 commissioning, IRSN assesses the Licensee FPSA • IRSN proposed modifications and recommendations accepted by the Licensee at the end of this first phase • Second phase: (Licensee solutions proposal) will take place in 2016 • IRSN FPSA will be used to approve the updated Licensee FPSA

  14. Safety Review for Fire PSA • Anticipated Safety Review for EPR • The examination of the method and the results has highlighted numerous needs of improvement: • 3 modifications accepted by the Licensee • 2 recommendations • First conclusions • The Fire PSA results are consistent with the general safety objectives: • The global frequency of core damage is lower than 10-5/r.y. • This result supports the EPR design regarding fire risks, in particular the separation of electrical train in four different buildings (one by electrical train and fire areas within every building) • Because of the EPR construction is going on: • Study does not take into account electrical cables and piping of hydrogen, neither as ignition equipment nor as potential targets. • Incomplete evaluation of frequencies for fire ignition (data unknown)

  15. Safety Review for Fire PSA • Anticipated Safety Review for EPR • The Licensee must take into account, in his Fire PSA, the probability of the failure of the fire barrier • Recommendation: The Licensee must update his Fire PSA depending on the results of the deterministic studies assessments • The Licensee first based his EPR Fire PSA on deterministic principle: • Fire barriers are always fire-resistant: the spreading of the fire is not possible from a fire zone to another fire zone • These assumptions will be checked by IRSN during the deterministic studies assessment

  16. Conclusion • Insights of Safety Reviews of Fire PSA • Importance of the analysis of the effects of those choices on the FPSA results and to identify the possible cliff-edge effects and the needs for R&D • Importance of to revalue the risk of core damage in case of fire by taking into account the impact accumulated by all these evolutions • A first conclusion of IRSN assessment was that during the Fire PSA development, hypothesis more or less conservative, as well as parameters values with various uncertainties, are used: • The evolutions asked in the first step of Safety Reviews can have, individually and all the more when they are accumulated, an impact mattering on the results of the Fire PSA

  17. Conclusion • Insights of Safety Reviews of Fire PSA • These two independent works, which could be considered as a particularly deep external review, highly contribute to the quality of the studies It is important to note that a Fire PSA development program is still in progress at IRSN and at the Licensee and both organizations are working in parallel on FPSA developments

  18. Thank you for your attentioninformation: fabienne.nicoleau@irsn.fr

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