R1.4 BIS Probabilistic Safety Analysis

The project objective was to issue PSA reports for Novovoronezh NPP, in particular:
Incorporation of model modifications into the technical reports on systems analysis and human reliability analysis;
Preparation of new updated reports for the Internal Events Analysis incorporating the proposals for model modifications which had already been discussed with the Russian counterpart;
Preparation of an updated PSA Quantification Report for discussion of main technical conclusions with Russian counterpart;
Preparation of new updated reports covering the detailed analysis of the following hazards: fires, flooding, internal missiles, pipe whip and jet impingement, as well as natural and manmade events;
Issue of final edition of the following report: 92C-F-EA-EA-0103, Internal Events Analysis Final Report.

The work on the project has been the preparation and issue of reports on the Novovoronezh NPP PSA, incorporating the modifications to the PSA models and the reports that had been identified and discussed with the Russian Counterpart.
In general, the changes concerned the following aspects:
Most appropriate method of breaking up logic loops: this method of breaking up logic loops without loss of information basically affects the electrical and service water systems;
Coding modifications of transfers to these systems proceeding from other systems, as necessary;
Various adjustments in the fault tree models, in order to improve the quality and representativeness of the models developed;
A number of modifications and additions in the reports, to improve descriptions and facilitate understanding of the hypotheses adopted;
Modifications to the event tree developed for the Loss of Off-Site Power (LOOP), with the corresponding changes in reports;
Inclusion in the fault tree and event tree of the models of the common cause failures (Document No. 92C-F-AP-EA-0026) and of the final values of basic events, which are gathered in the project database (Document No. 92C-F-AP-EA-0025), as well as the values calculated for basic events of man-induced errors, in the framework of the human reliability task;
Once these modifications were incorporated the PSA models were quantified and the reports generated by the PSA were updated and issued.
A quantification report was prepared, containing the main conclusions and recommendations derived from the Analysis of Internal Events, which had been discussed and agreed with the Russian Counterpart.
Updates were also prepared of the analysis of the following external events:
Fire;
Flood;
Internal missiles;
Pipe whip and jet impingement;
Natural and man-made events.
The fire analysis was especially significant; its probabilistic aspects require quantification based on modified models of event and fault trees. The conclusions of this analysis were also discussed and agreed with the Russian counterpart.
The project was carried out as planned, complying with all the objectives. There were no significant obstacles or deviations to prevent completion of the programme on schedule and so there are no important lessons to be learned or recommendations.