Execution period 2005 - 2007
Contractor Kozloduy NPP Plc.

TUDY OF THE POSSIBLE CAUSES OF LEAKS FROM PRIMARY TO SECONDARY CIRCUIT, AND SOLUTIONS FOR ACCIDENT LOCALIZATION

The task has been accomplished in the framework of Measure 26281 of the Modernization Program of Kozloduy NPP Units 5 and 6.

The services provided under that project are, as follows:

  • Development of the methodology;
  • Analyses of the boundary conditions for all the Initiating Events (IE) groups listed in the "Design accidents IE list";
  • Development (actualization) of Relap5 Mod 3.3 model;
  • Validation and Verification of the model (Engineering hand book & data base book);
  • Thermo-hydraulic analysis (using groups Symptom-Based Emergency Operating Procedures (SBEOP) operator actions);
  • Sensitivity analysis (for operator action sensitivity – to the end-state condition);
  • Development of a detailed model for SG (Steam Generator) critical component dynamic analysis (all boundary elements between primary and secondary circuit). Structural Analysis of the SG performance by using the Finite Element Method;
  • Estimation of the SG components damage state, ultimate stress assessment and stress capacity (the pressure and temperature influence);
  • Estimation of the conditional probability of failure of the SG critical components;
  • Reliability assessment of critical components and estimation of probability of “Primary to secondary LOCA accidents” occurrence;
  • Quantitative Analysis of Radioactive Releases in case of Initiating Event "Primary to secondary Loss of Coolant Accident (LOCA) – SG collector lifting - Dn 43";
  • Technical proposals for safety enhancement.
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