The PSB-VVER is a large-scale thermal-hydraulics testing facility operated by the Electrogorsk Research and Engineering Centre (EREC) in Russia. The PSB-VVER Project was intended to provide the experimental data needed to allow full validation of the computer codes used in the thermal-hydraulic analysis of VVER-1000 reactors*. 

Currently, there are many VVER-1000 reactors in operation and several more under construction, mostly in central and eastern Europe. These Russian-designed reactors have design characteristics that are similar to western-designed pressurised water reactors (PWRs). There are however important design differences which necessitate specific experimental facilities and data to ensure that the computer codes are validated and that the results of the thermal-hydraulic analyses are of acceptable quality for this type of reactor. To this end, experiments were carried at the PSB-VVER testing facility.

Earlier NEA work established a code validation matrix for both LWRs and VVERs. This matrix is essentially a set of phenomena and experimental data that is used to validate thermal-hydraulic computer codes. This led to the general conclusion that the VVER-1000 matrix was not complete. Consequently, it was decided to develop an NEA project to obtain the required experimental data not covered by the matrix.

The project's objective was to provide unique experimental data needed for the validation of thermal-hydraulic codes and to support refinements to the safety assessment tools for VVER-1000 reactors. The intended PSB-VVER experiments constituted a relevant extension of the existing code validation database. The data would primarily be of relevance to the VVER-1000 system, but potentially could also of interest to other types of pressurised water reactors.

The intended scope of the project work consisted of five PSB-VVER experiments in the following areas:

• scaling effects
• natural circulation
• small cold leg break loss-of-coolant accidents
• primary to secondary leak
• 100% double-ended cold leg break.

Extensive pre- and post-test analyses accompanied the programme throughout the entire experimental series. The possibility of setting up one or more standard problems, either limited to project participants or with broader involvement, were considered. Three project tests were successfully carried out and reported upon. The test matrix for the remaining part of the programme was discussed and revised by members. The fourth test investigated accidental conditions involving a primary to secondary leak (steam generator header rupture) and was carried out in the first half of 2005. A blind test exercise was also organised, where the outcome of the fourth test was predicted by calculations before its execution. The final test simulated thermal-hydraulic conditions arising after a large-break loss-of-coolant accident (LOCA) in a VVER-1000 reactor, and was the first one run under very demanding conditions. A preliminary final test (at 10% power) was run in January 2008; several attempts to run the final test (at full power) were unsuccessful and it was decided to close the project at the end of 2008 with the agreement that the data of the final test would be provided to the project participants whenever it could be completed.

Project data

The data abstract is public.

* Note: In Russian, vodo-vodyanoi energetichesky reaktor meaning water-water power reactor is transliterated as VVER.