For Unit 5 of the plant, Probabilistic Safety Analysis (PSA), Level 1 for shutdown state, and PSA Level 2 for unit operation at full power and for shutdown state were performed.
The Safety Analysis Report for Zaporozhye NPP Unit 5 was performed in order to verify the compliance of the project with the basic safety objectives.
Within the scope of PSA Level 2, the chronological progression of sequences with core damage (CDF - core damage frequency) was assessed together with quantitative evaluation of the phenomena with fuel damage, and the paths were determined whereby the respective radioactive products releases could reach the environment.
The services provided in the framework of PSA, Level 2 are, as follows:
- Development of the analysis methods;
- Analysis of the transition from PSA 1 to PSA 2 for full power operation and for shutdown state;
- Grouping of Plant Damage States (PDS);
- Developing models (for full power and shutdown state) for MELCOR 1.8.5;
- Validation and verification of the model (Engineering Handbook and Data Base Handbook);
- Thermal-hydraulic analysis (using PDS grouping);
- Sensitivity analysis (sensitivity of the parameters to the end state results);
- Detailed model development for containment protection (Structural analysis of containment performance using the Finite Element Method);
- Evaluation of the containment damage state, evaluation of the ultimate bearing capacity and building “fragility curve” (simultaneously accounting for the impact of temperature and pressure);
- Analysis of the Event Trees and Failure Trees for emergency scenarios with core damage;
- Analysis of the physical processes in primary side and containment;
- Quantitative analysis of radiological releases;
- Drafting a report with technical proposals for safety enhancement.