1 Interaction between Industry and Regulator to Improve Quality of the PSA Mikhail Lankin (SEC NRS) and Gennady Tokmachev (Atomenergoproekt), Russia E-mail: - презентация

1 1 Interaction between Industry and Regulator to Improve Quality of the PSA Mikhail Lankin (SEC NRS) and Gennady Tokmachev (Atomenergoproekt), Russia Web:

2 2 Presentation Outlines Background Development of PSA regulatory guides Interaction between industry and regulator to resolve particular industry issues Post-Fukushima reality Conclusions

3 3 Background (1) In total 33 power units of different design and completely different age are operated at 10 Russian nuclear plants Five additional units are under construction and several different advanced plants are in design for some new sites in Russia Variety among plants in terms of design, age and site conditions raises an issue of plant specific safety evaluation including PSA for any unit

4 4 Background (2) Rostechnadzor is the Russian regulatory authority Its company SEC NRS carries out practical activity in the area of the nuclear regulatory review and development of nuclear regulatory documents The only utility, Rosenergoatom Concern, is responsible for safety at all stages of NPP life cycle Design companies as subcontractors usually perform PSA and interact with SEC NRS

5 5 Regulatory review practice (1) PSA results can be used only with confirmation of quality and reliability of PSA results by independent review of high quality It is usual practice to invite well-known independent experts from the industry to improve quality of regulatory review PSA teams are intensively involved in oral and written discussions to find the best way of resolving emerging issues Systematic discussions are intended to improve safety of plants in spite of a natural conflict of interest

6 6 Regulatory review practice (2) PSA of high quality should have the following attributes: Methodology and software used for PSA is state-of-the-art For operating NPP - appropriate plant personnel is involved PSA is based on plant-specific and site-specific data PSA reflects the actual design and operational features of NPP Models are supported by deterministic calculations using applicable and proven computer codes Dedicated PSA quality assurance programme is established

7 7 Regulatory review practice (3) Key issues raised during reviews and their impact on the PSA: Scope of many PSAs - still limited Some plant transition modes - out of scope of shutdown PSA Simplified mapping of full power PSA to shutdown one Potentially important accident sequences sometimes missing Incorrect modelling of dependencies National CCF data collection - not established Frequency estimation of the catastrophic SG header rupture Fracture mechanics models for plant life time extension

8 8 Development of reg. PSA guides (1) The licensing process involves PSA Level 1 to get a licence for plant construction and PSA Level 1 and Level 2 to obtain an operational licence The main Russian regulatory document was issued in 1997 and now updated in close cooperation between regulator and industry. Some requirements are quite severe, e.g. probability value of the large release should not exceed 1E-7 per reactor year or software reliability should be quantified Regulatory PSA guidances provide for specific requirements to PSA contents and quality

9 9 Development of reg. PSA guides (2) The regulator and industry intensively communicate while developing regulatory documents. The main activity is performed within a working group where experienced PSA experts delegated by design, research and operating companies discuss key issues related to the document of interest with regulatory experts. A draft document is periodically distributed among regulator and utility organisations and the working group considers official responses. Decision is usually made by consensus. However the Regulatory Authority has a deciding vote.

10 10 Interaction between industry and regulator to resolve industry issues Some regulatory documents revised as a result of nuclear industry pressure. The utility started a program of overhaul period extensions. Justification is supported by PSA and fracture mechanics studies reviewed. However the regulatory document prescribes to perform tests of PSV and inspections of RPV, etc. more frequently. PSA–induced proposals for changing regulatory document result in revising it.

11 11 Post-Fukushima reality (1) Nuclear community has come under public pressure to review the nuclear programme and enhance safety Russian authorities ordered so-called 'stress tests' Follow-up actions from a stress test assessment are implementation of plant modification like autonomous mobile DGs and pumps, extension of battery capacity, tracing of new cable lines, involvement of fire facilities in safe shutdown process, etc. The PSA is used to support the cost benefit evaluation of SAM options and support the ranking, justification, and licensing of plant upgrades based on the level of risk reduction associated with each alternative

12 12 Post-Fukushima reality (2) Following the Fukushima accident special attention has been paid to the development of seismic PSA. A full scope seismic PSA for Balakovo Unit 1 had been finished by the end of Many important findings, especially found during plant walkdowns, are now under regulatory review. Other lessons lеаrnt from the Fukushima accidents are to direct additional efforts to the following points within the PSA development: –investigation of multi-unit accidents –spent fuel pool study –analysis of correlated internal and external events

13 13 Conclusion Regulator and industry have different goals, interests and responsibilities. This conclusion is simultaneously valid and deceptive. The unity and struggle of opposites is one of the dialectical laws through which this situation can be understood. The progressive transition to a higher form is possible only through the complete resolution of the contradictions. The Fukushima accident shows that both are in the same boat called safety. Past experience confirms that regulator-industry cooperation is mutually beneficial.

14 14 Thank you very much for your attention! Questions?!