engleski

Influence of Detailed PCFV Model on Containment Behaviour During SBO

An explicit model of the passive containment filtered venting system (PCFVS) using the MELCOR code will be developed and connected to an existing model of the NPP Krško. The background for this activity is to enable tracking the radioactive releases, as well as composition of non-condensable gases, through the PCFV piping, aerosol and iodine filters, as well as radionuclide deposition on these structures. The new model will also be used to check the results of the design transient containment calculation. That calculation was performed with the PCFV system modelled as a simple opening with additional valves simulating pressure cycling as prescribed by the system design performance. The focus in the paper will be on the thermal hydraulic containment and PCFVS calculation during a severe accident following a station blackout event. The results will be compared with the calculation carried out with a simple PCFV model and the effect of that model improvement on parameters such as number of pressure cycles and cycle lengths will be discussed. Another important issue, distribution of combustible gases, hydrogen and carbon monoxide, throughout the PFVS, and potential for their ignition will also be covered. Prior to transient calculation, the steady state run will be performed to satisfy design conditions regarding the velocities, mass flows, temperatures and pressure drops in piping, aerosol and iodine filters.

PCFV, containment, MELCOR, severe accident

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