R/TSO/VVER/01-A Licensing related

The objective of this project was to assist the GAN-RF and Russian TSOs in reviewing and assessing the accident analysis performed for units 1 and 2 of Kola NPP within project TACIS-91-1.3, further referred to as Industrial Project.

The transfer of know-how from the Western TSOs to the Russian TSOs was another important goal to be achieved.

A detailed review and assessment of all the accident analyses performed in the Industrial Project for the Kola NPP, units 1 and 2 have been performed.
As the main outcome of the assessment it should be stated that the primary goal of the Industrial Project to provide a systematic and consistent state of the art safety analysis in accordance with Western practice was not achieved.

The evaluation of the Industrial Project analyses revealed several shortcomings like incomplete descriptions of initial and boundary conditions, lack of model descriptions, the use of too simple models, insufficient explanation of results and poor graphical presentations. The depth of the assessment was already limited by the quality of the Industrial Project reports.

A major problem of the Industrial Project has originally been the too extensive nature of the project. Obviously the resources have not been sufficient for satisfactory evaluation of calculations and reporting. A smaller number of calculations and more effort to each analysis could have produced more useful results.

The analyses should be interpreted as an exercise and familiarisation with the Western practice of performing safety analyses, but not an example of a complete state-of-the-art accident analysis for licensing a Nuclear Power Plant, in this case the Kola NPP units 1 and 2.

The proposed improvements to the reactor and plant protection system would obviously improve safety of the plant, but implementation of such measures would need more prioritisation and detailed analysis, as well as improved models and methods.

The TSO project has been a successful project in assessing the results of the Industrial Project and supporting the work of the Russian Regulatory Body and its Technical Safety Organisations in dealing with the accident analysis reports submitted for their review and in preparation of the corresponding safety evaluation reports.

The results can be subdivided into the following tasks:

Task 1: Familiarisation of EU-TSOs with the relevant Russian licensing practices.

The relevant documents regarding the actual status and application of Russian licensing practices (laws, rules, standards, special conditions) were collected and translated. These practices were compared to Western practices and the findings were commented and reported. The primary goal of task 1 was to familiarise the EU experts with the Russian licensing practices in order to achieve mutual understanding of the criteria to be applied to accident analyses and their results.

Task 2: Collection of information on already performed analyses in the consortium countries and Russia.

Basic information about already performed relevant analyses in Finland, France, Germany and Russia were collected in tabular form. The provided information included the transient type (initiating event), the main assumptions, the name of the code used and a brief qualitative description of the results. This information was used as a reference when assessing the selection of the accidents in the industrial project and when acquiring detailed information of relevant already performed analyses.

Task 3: Assessment of code validation.

This task focused on assessment of the information of the code validation presented by the industrial project. Special attention was paid to VVER specific validation. A Russian report on the requirements for certification of codes was reviewed and commented (after its translation).

Task 4: Assessment of the accident analyses performed in the industrial project.

First, the reasons for the selection of cases in the industrial project were assessed. This assessment focused on the initial and boundary conditions and other relevant information and assumptions used for the analysis. Second, the results of the accident analyses were assessed, based on experts judgement and existing relevant information and documents.

Task 5: Selection and execution of possible supplementary calculations.

Based on the assessments in task 4 it was concluded whether supplementary calculations were necessary. Observed lacks in the analyses or needs to check important results produced by the industrial project were examples of reasons for performing additional calculations. Due to the limited budget, supplementary calculations could be performed only if code inputs for the Kola NPPs were available for use without a need to prepare inputs from scratch or otherwise spend substantial resources for preparation of the additional analyses. Any suitable European code could be used to perform the calculations, including -but not limited to -the ones listed in the TOR.

Task 6: Final assessment of the results of the industrial project.

Final assessment of the results of the industrial project included additional assessment of the analyses based on the calculations performed in task 5, and, in addition, an assessment of actions, accident management measures and other improvements proposed by the industrial project. A particular objective of this final task was to assist the GAN-RF in preparation of a corresponding safety evaluation report.

The main accident categories considered were:

• Loss of coolant accidents (LOCA), including small break LOCAs;
• Transients without LOCA, including overcooling transient and ATWS;
• Beyond Design Basis accidents (BDBA).

The assessment also included the analysis of confinement behaviour during LOCAs.

The project did not cover the full content of work foreseen in the TOR.
Partially caused by the at that time non availability of the results from the Industrial Project for a longer time due to not settled liability issues.