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TSO support in assessment of level 2 PSA for VVER 440/213

TSO support in assessment of level 2 PSA for VVER 440/213


Beneficiary Organisation Details:

Hungarian Atomic Energy Comission:

Project Aims

The objective of this project was to continue strengthening and enhancing the effectiveness of the nuclear safety regulation in Hungary and to improve the organisation and the performance of the Nuclear Safety Directorate of the Hungarian Atomic Energy Authority.

The specific area addressed by the project was the application of probabilistic safety assessment methodology in the field of severe reactor accidents (Level 2 PSA). The HAEA has benefited from the assistance of the Consortium of Western Regulators (CWR) with the following specific objectives being met:

  • Review of selected parts of the Level 2 PSA for the Paks NPP;
  • Strengthening of the HAEA capabilities in the field of Level 2 PSA and severe reactor accident analysis.

Project Results

The project activities have been divided in the following tasks: collection of information; preparation of review plan; overall review; detailed review; review of safety improvement actions based on Level 2 PSA.

The review procedures were based on IAEA-TECDOC-1229 "Regulatory review of probabilistic safety assessment (PSA) Level 2" and on the experience of the contractor organisations. The review covered topics ranging from the general approach to the detailed technical reports. Issue lists with several hundred questions were submitted to the PSA Production Team for answering. The most important questions were discussed with the PSA Production Team in the project workshops and written answers to the issue list were also received.

The findings based on the review of the Level 2 PSA reports and on the answers provided by the PSA Production Team were presented in technical reports and submitted to the HAEA.

The Review Team made the following general observations regarding the Level 2 PSA:

  • The methods and computer codes used in Paks Level 2 PSA are in general appropriate, but documentation is not always detailed enough for the Review Team to make conclusions on the treatment of specific issues.
  • In addition to full power operation Paks Level 2 covers shutdown states and spent fuel pool accidents. This exceeds the scope of many other Level 2 PSAs. However, the accident sequences in the shutdown modes and in spent fuel pool are not analysed with the same degree of efforts as accident at power operation.
  • Uncertainty analysis of Level 2 PSA has been deferred to later studies. Results of the uncertainty study would be essential, if the Level 2 PSA is used to justify decision making on severe accident management issues.
  • No significant error or omission has been found in the PSA regarding the basic approach, taking into account the limited approach without uncertainty analysis.
  • Regarding the self-assessment report by HAEA, the Review Team's main observation was that HAEA has not issued guidelines or specific requirements how to perform Level 2 PSA. The lack of specific guidelines seems to have contributed to some organisational deficiencies of the Level 2 PSA study.

The budget for this project was 750 000 euro.

Further Project Results:

Further information on the project results could be sought from the beneficiary organisation. See also attached file.

General Information

TSO support in assessment of level 2 PSA for VVER 440/213
Budget year: 
Types of activities: 
Technical Support Organisations
Installation types: 
VVER 440-213
Duration (months): 
STUK (Sateilyturvakeskus)
VTT (Technical Research Centre of Finland)
GRS (Gesellschaft fur Anlagen und Reaktorsicherheit)
VEIKI Safety Engineering Co,Budapest
Old reference: 
Effective contract date: 
Closure date: