Execution period 2011 - 2012
Contractor Kozloduy NPP Plc.

BORON DILUTION ACCIDENT ASSESSMENT IN CASE OF PRIMARY TO SECONDARY STEAM GENERATOR PIPELINE BREAKS WITH EQUIVALENT DIAMETER OF 100 MM

The project scope includes studies for different accident phenomena during the emergency cool down process using Symptom Based Emergency Operating Procedures (SB EOPs) for Kozloduy NPP Units 5 & 6.

The project has been implemented in accordance with the ToR (Terms of Reference) requirements and the progression of boron dilution accidents has been analyzed consecutively using Thermal-hydraulic (TH) codes, Computational Fluid Dynamics (CFD) code, Neutron kinetic code and Thermal-mechanical code. For the basic TH calculation, the Relap\SCADAPSIM\ R3.4 code has been used. For the neutron kinetics behavior, the coupled TRACE+PARCS codes have been used. For the thermal-mechanical behavior of nuclear fuel assemblies, the “Transuranus” code has been used.

In the scope of the working program, the following activities are included:

  • Preparation of detailed technical methodology for the project regarding the IAEA Guidelines;
  • Data collection for reactor operation at full power regarding the project scope modeling activities;
  • Development of engineering handbooks for the computer codes: ANSYS 14 (FLUENT), TRACE V 5.0, PARCS 2.7, TRANSURANUS;
  • Detailed calculations of the accident progression trough all emergency cool down procedure using SB EOP till safety cool shutdown condition has been reached;
  • Preparation of a report with all safety related issues and proposals for safety upgrading.

The results of the analyses are provided in the scope and with the format required by SAR, Chapter 15: "Design basis accidents safety assessment".

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