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Experience with Periodic Safety Review (PSR) at Kozloduy NPP after 20 years of operation

Experience with Periodic Safety Review (PSR) at Kozloduy NPP after 20 years of operation. Vladimir Popov Life time management section Engineering Dept., KNPP Unit 5&6. June 2011,Varna. Content of the presentation.

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Experience with Periodic Safety Review (PSR) at Kozloduy NPP after 20 years of operation

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  1. Experience with Periodic Safety Review (PSR) at Kozloduy NPP after 20 years of operation Vladimir Popov Life time management section Engineering Dept., KNPP Unit 5&6 June 2011,Varna

  2. Content of the presentation • Preparation of NPP Kozloduy PSR process after 20 years of operation • Determination of NPP Kozloduy PSR technical content • Extent of coactions with RB at the implementation of NPP Kozloduy PSR • Lessons learned • Conclusion

  3. Kozloduy NPP Were are we?

  4. Kozloduy NPP

  5. Kozloduy NPPHistory of operation Units 1 & 2 shutdown – 31.12.2002 Units 3 & 4 shutdown – 31.12.2006

  6. General information about Units 5&6 Start of commercial operation Unit 6 05.09.1991 Unit 5 29.11.1987 Main features of Kozloduy NPP Units 5 & 6: - Reactor type WWER-В320, 3000MW thermal; - 4 Main circulation pumps; - 4 SG of horizontal type – pressure – 6.4 MPa; • Coolant – 15.7 MPa pressurized water with boric acid; - Reinforced concrete containment; - Mono-units 1000MW - Turbine K-1000/60-1500-2. 5

  7. Operational data 1987-2009– generated 477 297 433 МWh 2010 – generated 15 248668 MWh, usage factor- 87% (among the best for VVER-1000/В-320 in Europe) Electricity generation units 5&6 in 1987-2010

  8. Lifetime management Within the period 1999-2008 the Modernization program was performed including 212 technical measures in two phases: • “BEP” (1999-2001) – preparation of input data, terms of reference, specifications; • “Main contract" (2001-2007) – detailed design and analysis, production and commissioning, licensing

  9. Kozloduy NPP Мodernization Program Goals: Safety • Improvement of in-depth defence. • Reduction of the risk of nuclear incidents /accidents • Seismic re-qualification and reinforcement of SSC; Reliability • Implementation of modern technological equipment • Replacement of obsolete equipment; Lifetime extension • Confirmation of the possibilities for a longer operational life of the existing equipment.

  10. Benefits from the Programme implementation Change of CDF as a result of the safety enhancement measures (by PIE's)

  11. Operational data Number of unplanned scram at Kozloduy NPP Units 5 and 6 in the period 1992-2010

  12. Approach to NPP Kozloduy PSR after 20 years of operation • Completion of the NPP Kozloduy USAR revision (based on requirements of ПНАЭ Г-01-036-95), was finished in 2006 in frame of Modernization Program - measure 26122. • With regard to preferred trends in EU and IAEA despite of discussions on common aspects and differences between the USAR revision andPeriodic Safety Reviews (PSR), requirement for PSR was included by RB in Operational Licences for Unit 5 and 6 issued in year 2003, already expired in year 2009. • Operational nuclear power plants in many states are subject to both routine and special safety reviews. These safety reviews do not always take account of improvements in safety standards and operating practices, the cumulative effects of plant ageing, modifications, the feedback of operating experience, and developments in science and technology.

  13. Approach to NPP Kozloduy PSR after 20 years of operation • Consequently, the concept of PSR has been developed as a method that is complementary to the existing types of reviews,more general and comprehensive. • In many member states in the EU,PSR have been introduced as part of the regulatory system. • Regular revisions of SAR corresponds to a current applicable licensing practice in Republic of Bulgaria.

  14. Approach to NPP Kozloduy PSR after 20 years of operation In Accordance with Regulation for Providing the Safety of Nuclear Power Plants, 2004,and by agreement of NPP and RB, the NPP Kozloduy PSR approach has been defined as follows: • Implementation was realized by NPP employees (working team), according to IAEA NS-G-2.10 Guidelinewith main goal- comprehensive assessment of the current safety status of the plant. • The NPP Kozloduy PSR implementation according to the IAEA Guideline was motivated by the intention to harmonize the form of PSR implementation with a practice which is standard in EU countries, and to start a process of the future licence renewal. It was a necessary precondition for the reactor units’ operation licence renewal in year 2009.

  15. Approach to NPP Kozloduy PSR after 20 years of operation • A Working team has been nominated at the NPP level to prepare and carry out the PSR (may 2007). • The working team consisted of more than 80 NPP experts: operational, maintenance and engineering staff with high experience and proficiency in PSR areas. • The real process of NPP Kozloduy PSR was launched at the beginning of year 2008, when NPP Kozloduy and RB expert groups prepared a “Plan for NPP Kozloduy PSR implementation”-08.30.ОУ.00.ПЛ.11.

  16. Preparation of NPP Kozloduy PSR process after 20 years of operation • Within that Plan, basic principles of PSR were defined as well as its extent. As a part of preparatory phase –detailed review methodology and set of review criteria was prepared – in cooperation with BNRA experts. (Jan. 2008). • Cooperation of the nuclear regulator with the operator’s activities is one of the principles which is emphasized also in IAEA and EU documents. The Review methodology № 30.ОБ.00.МТ.13was then developed in NPP Kozloduy as operator’s controlling document.

  17. Preparation of NPP Kozloduy PSR process after 20 years of operation Within the Plan, the NPP Kozloduy PSR purpose was defined as follows: • fulfilment of requirements on PSR implementation extent and form defined in IAEA NS-G-2.10 Guideline, • fulfilment of WENRA (West European Nuclear Regulators‘ Association) requirements on PSR defined in the Pilot Study for WENRA Countries Reactor Safety Harmonization, • acquirement of fundamentals for a preparation for the NPP Kozloduy reactor units’ operation licence renewal after year 2009

  18. Extentof NPP Kozloduy PSR • The review was performed for all areas and for all safety factors defined in the IAEA NS-G-2.10 Guideline. A training workshop for working team were held in Kozloduy by WANO and AMEC lecturers. • For the review, Unit 5 of NPP Kozloduy was considered referential, including the outside and common objects in a state as per December 31, 2007.Essential dissimilarities of individual plant units were specified and evaluated at the review in light of their relevance to PSR. • Scope of reviewed SSCs corresponded to the List of SSC important to safety from Technical specification – Class 1 (reactor and primary circuit), 2 (safety systems), 3 (safety related system).

  19. Extentof NPP Kozloduy PSR The PSR technical content has been taken from the IAEA NS-G-2.10 Guideline, but in accordance with Bulgarian nuclear legislation, especially Regulation for Providing the Safety of Nuclear Power Plants, 2004, safety factors was distributed (regrouped) in nine areas. This nine areas were defined as a subject to review as follows: • 1. Site description • 2.1 Power plant design. • 2.2 Actual condition of systems, structures and components. • 2.3. Ageing. • 2.4 Equipment qualification. • 3.1 Deterministic safety analyses. • 3.2 Probabilistic safety analyses. • 3.3. Hazard analysis • 4. Operational safety. • 5. Utilization of other power plants’ operational experience and research results. • 6. Procedures. • 7. Human factor. • 8. Emergency planning. • 9. Radiological effects to environment.

  20. Review Criteria • Specification of adequately detailed review criteria was one of the most important as well as most difficult steps of the whole process. • Without the adequately clearly defined criteria there is a threat of a spontaneous slipping to formalism at the review implementation. • In the last years IAEA and JRC got from utilities in Europe some proposals to organise exchange of utilities' experience about the application of the IAEA Safety Guide NS G.2.10

  21. Review Criteria (cont.): • To organise the discussions andconcentrate on difficult issues a questionnaire has been developped together with the utility Electrabel, Belgium and JRC an workshop was held in Petten in December 2010. • Despite EU activities in this area, there was no comprehensive set of adequately detailed and actual criteria for operated NPPs available on the date of the NPP Kozloduy PSR start. For that reason it has been agreed to compile such a set for the NPP Kozloduy PSR process in conjunction with BNRA.

  22. Review Criteria (cont.): Following principles have been agreed on the criteria compilation: • The review criteria were compiled in an working document called “List of review criteria”. Before its use, the document were submitted to the RB for their opinion. • For each PSR safety factor, two groups of requirements were defined (national, international). • The national requirements were derived from the valid legislation. If in case normative engineering documents were used for the criteria definition, their actual condition were considered.

  23. Review Criteria (cont.) • The international requirements were derived from IAEA requirements and guidelines to the level of the Safety Guide series for operated NPPs; besides, INSAG series documents were applied. • In case it was impossible to derive an applicable or sufficiently concrete criteria, if it were possible to apply, in really respectable cases, even lower series documents, e.g. TECDOC were applied. • As a separate part of the international requirements for individual corresponding areas and safety factors, West European Nuclear Regulators Association (WENRA) requirements were applied.

  24. Review Criteria (cont.) • From the set of the national and international requirements for each corresponding review area and safety factor, a set of technically most explicit requirements called “Review criteria” were worked out. • Safety factors, and Review criteria was the basic element of the PSR. • Each review criterion has its ID code (e.g. O1_F4_K20). • For each review criterion a review paper was prepared.

  25. Review Paper • On the base of review papers documentary outputs were prepared – all findings and corrective actions are traceable back to the review paper for the particular criterion • Total amount of Safety factorsin the 9 areas of RSR was 109, review criterions was 449, total amount of review paper was more than 1500 (for many safety factors from Area No.2 – Design, actual condition of SSC, AM– one criterion was used for about 69 different SSCsfrom the List of SSC important to safety ).

  26. Review Paper (cont.): Each review paper consists of following parts: wording of criterion, ID code of criterion, list of documents used for review, description part – compliance with criterion, additional notices, recommendation to adequacy of available documents for review, list of deviations – brief reasoning, preliminary safety evaluation (based on advises from methodology), strong points, global evaluation of criterion fulfilment, suggested corrective action – term of realization, name of evaluator, date of ending review, final evaluation of safety importance, final specification of corrective action and term of realization • Review Paper Example:

  27. Control of shortcomings • Evaluators designated for each respective area participated, at a consultant level, as early as in the elaboration of the Set of review criteria and the Review methodology for the respective area. • Review methodology gives advise how to perform the review process for a each area and safety factor, specifies which of related aspect should be considered, gives classification of shortcomings (safety unimportant deviations), based on related INSAG and IAEA guides. • Final classification of shortcomings was carried out by group of expert from NS department • Findings (shortcoming or strong-points) and corrective action were found and preliminary classified by evaluators, verified by group of NSD expert (importance of deviation), verified by heads of responsible department (correctness of findings, applicability of corrective action and implementation term).

  28. Control of shortcomings (cont.) Shortcomings were classified into 4 group : • Category NSS1 to 4 -NSS1 to 4 (important, medium importance, low importance, very low importance). • For all shortcomings from NSS1 to 3were suggested corrective actions. • Corrective actions for shortcomings classified as important and medium importance are considered as obligatory and were submitted to RB in Safety review report № 08.30.ОУ.00.ОТЧ.01/0on PSR. • Corrective actions for shortcomings of low and very low importance are considered as optional and were assessed once more on base of the cost-benefit approach.

  29. NPP Kozloduy PSR implementation schedule and Documentary outputs In March 2008 - June 2008 – deviations’ importance assessment and verification of preliminary PSR results by heads of responsible department were elaborated. Outputs of this stage were: • Final set of Review papers. • Topic reports for safety relevant strong points and deviations for each evaluated area, where the listed deviations have already been categorized into four groups according to their safety importance . • June 30, 2008 – PSR report № 08.30.ОУ.00.ОТЧ.01/0were submitted to the RB-BNRA.

  30. NPP Kozloduy PSR implementation schedule and Documentary outputs • July 2008 -December 2008 – Preparation of Programs with corrective measures for enhancement of safety for both units were made. • December 2008 - Programs № 35.ОБ.00.ПР.14/0& 36.ОБ.00.ПР.15/0were issued. • Above mentioned programs, based on review report on PSR for the deviations’ remedy, were complemented and expanded with recommendations from: - IAEA FOLLOW UP MISSION’2008. - Action Plan of Bulgaria as a result of the WENRA study: ”Harmonisation of Reactor Safety in WENRA Countries”. - ІV Bulgarian national reportfor Nuclear safety convention.

  31. Extent of relations with RB at the implementation of NPP Kozloduy PSR • Jointly, the Procedures for NPP Kozloduy PSR implementation was composed. • A consultation support team for the preparation and implementation supervision of the NPP Kozloduy PSR was constituted atRB. • Discussions and adjustment of prospective criteria and methodology modifications . • Continuous consultations (where necessary) with the RB team members at the factual PSR implementation, on the findings and identified deviations assessment, their importance in terms of the in-depth protectionand corrective actions proposal. • Supervision of the NPP Kozloduy Programs № 35.ОБ.00.ПР.14& 36.ОБ.00.ПР.15 implementation – topical review was held in April 2011.

  32. Main results of Kozloduy • Most of the review criterions have been fulfilled with none or minor shortcomings. • As important shortcomings were classified mainly longer known deviations for which corrective actions have already been under realization but delayed (e.g. UKTS replacement). • Most of deviations classified as medium importance are connected with lack of available technical devices for management and mitigation of severe accident effects, missing deterministic analyses for some BDBAand shutdown states, missing PSA level 2 for shutdowns, shortcomings in technical specification, design specific weaknesses, specific design potential hazards that weren't analysed in adequate detail, shortcomings in EQP, mistakes in support technical documentation.

  33. Relations between NPP Kozloduy PSR and LTO • Priority objective of the NPP Kozloduy PSR after 20 years of operation was to perform a safety review with a prospect till the year 2017; perspective overlapping beyond the year 2017 was not a priority goal of this action. • Acquirement of fundamentals for a preparation for the NPP Kozloduy reactor units’ operation license renewal after year 2009. • PSR results make one of the most important inputs for preparation LTO concept (LTO concept give answer to basic question – what should we do if we want to operate after 2017 and stay safe and effective?).

  34. Relations between NPP Kozloduy PSR and LTO • Assessment of NPP Kozloduy real safety preparedness for its operation after the year 2019 will be subject of a following NPP Kozloduy extended PSR (2016-2017). • Preliminary in year 2011-2013 a complex assessment of actual phiscal status and rest lifetime assessment of equipment and facilities of units 5 & 6 will be held on the basis and in compliance with the requirements of their actual Operating licenses.

  35. Relations between NPP Kozloduy PSR and LTO • PSR doesn’t cover safety irrelevant systems and equipment which are, nevertheless, necessary for the operation and may be extremely important from the economic point of view. • PSR doesn’t address economic aspects of the NPP service life optimization. • SAR remains and will remain the licensing document which will be used as a certificate for a further operation licence even after the end of the original design expected service life but will be accompanied by PSR.

  36. Relations between NPP Kozloduy PSR and LTO • Within EU generally, PSR and related SAR revisions are accepted as a sufficient procedure for the NPP operation safety capability assessment in the initially expected period, or the period of the operational licence. • PSR after 20 years of operation was based on agreement between utility and the RB. Future PSR for Unit 5&6 (2016-2017) is required as a licence condition in valid operation Licence, issued by the RB

  37. Lesson learned • PSR is time consuming – time = quality • Team of experts or team of managers – team of managers for future PSR (in case of team of expert – experts have to be real experts and have to share positive approach to PSR and its goals) • Scope of SR SSCs class 3 is too extensive – In area 2 (Actual condition of systems, structures and components) – number of Review papers was too extensive. Time spent on SSCs class 3 could be used on deeper review of SSCs 1 and 2.

  38. Lesson learned • Discussion with RB about easier review procedure for SSC class 3 for prospective PSR is necessary. • Participation of external support or reviewers is useful and enhance quality of PSR – our intention is to use external support for a complex assessment of actual phiscal status and rest lifetime assessment in 2011-2013 and future Kozloduy PSR in 2016 -2017. • Review Team competence should be strong enough to be independent on changes of top management „wishes“ during review

  39. Conclusion • Measures in the long-term Programs for improving safety and radiation protection of unit 5&6, based on PSR outcome and addressed on the units’ operation licence renewalare underway. • NPP Kozloduy intends to fulfils requirements on modern nuclear power plants which occasionally exceeds limits of the effective national nuclear legislation.

  40. Experience with PSR at NPP Kozloduy after 20 years of operation Thank you for your attention! Vladimir Popov Life time management section Engineering Dept., Unit 5&6 June 2011,Varna

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