VVER/02 : Assessment Severe Accident Mgt

The main objective of this project was to co-operate with and assist the Safety Authorities of Russia (GAN) and related Technical Safety Organisations (TSO) to review:

The Russian severe accident issues;
Regulatory approach in Russia to severe accidents;
Relevant events and associated important severe accident phenomena;
Existing analysis and plant specific studies on severe accidents;
Accident management (AM) measures proposed by the utilities.
On the basis of already elaborated results and relevant information from TACIS-91 industrial project 3.8/91 the material was to be reviewed and assessed, taking into account the experience in other countries.

The tasks in particular were:

Task 1: Russian severe accident issues:
Familiarization with the actual status of the issues in general and the actual situation in industrial projects in specific. Based on the experiences in Western countries assistance was to be given in evaluating the existing plant capabilities and identifying possible mitigation features to cope with severe accidents, mainly to keep the integrity and leak tightness of the containment.

Task 2: Regulatory approach in Russia:
Familiarization with the actual status of the regulatory approach in Russia and introduction (in details) of Western definition of safety goals, of criteria and concepts, use of analytical results (deterministic and probabilistic) and development of severe accident management strategies.

Task 3: Relevant events and associated important severe accident phenomena:
Assistance was to be provided in reviewing design criteria and design basis accidents (DBAs) for selected industrial projects in order to identify events leading to beyond DBAs scenarios and to identify associated important severe accident phenomena.

Task 4: Existing analysis and plant specific studies (probabilistic and deterministic) on severe accidents:
Based on existing data, a review was to be performed with the aim to clarify the in-plant safety margins to improve plant specific severe accident management strategies and to develop upgrading measures for enhancing prevention and/or mitigation features to be implemented at the plants. In case of lacking of analytical information, selected check calculations were to be recommended and performed by using adequate codes as ATLET-CD, CATHARE, etc.

Task 5: Accident management measures proposed by the utilities:
On the basis of analysis results, the effectiveness of the measures proposed by the utilities and the industrial projects coping with dominant beyond DBA sequences identified by the Probabilistic Safety Assessment (PSA) method were to be jointly reviewed and assessed. Focusing on the mitigate measures and the utility strategy to manage severe accident sequences, recommendations will be given for the implementation of appropriate procedures.

Originally, the project results were planned to be used by the Beneficiary as the normative basis for the development of regulatory approach in Russia to severe accidents for VVER 440/213 and VVER 1000 type reactors.
However, due to the limited availability of the results and other relevant information from the industrial project, the project partners have transfered the focus more in the methodology of the analysis and assessment of upgrading measures for enhancing prevention and/or mitigation features to be implemented at the plants.
This was done in accordance with the relevant TOR.

The recommendations elaborated within the project were based on the West European methodology, taking into account the Russian experience and current circumstances. Therefore the project achievements/recommendations will be used for the development of the appropriate licensing methodology and qualification practice in Russia.

Despite the impossibility to achieve all the results, planned for Task 4 in its full scope, the project objectives can be considered as mainly achieved.

In addition, through the review and discussion of the technical documents in a joint exercise between Russian and EU experts, the Russian experts were provided with Western methodologies and know-how in the field of evaluating the existing plant capabilities and identifying possible mitigation features to cope with severe accidents.