The Research And Application Of The MELCOR Code Containment Modules

The function of the traditional PWR nuclear power plant large dry containment is to contain all the radionuclide products, making them sealed inside the containment. In all kinds of accident conditions especially severe accident condition, the containment, as the last barrier between nuclear reactor and the environment, can prevent the migration of radioactive products into the environment and, suffer thermal load and mechanical load. Once the integrity of the containment failed, it will cause severe environmental disaster. Especially under the severe accident, the magnitude of this disaster will be close to the Chernobyl accident. Thus, the reactor safety study focused more attention on the research and design of the containment.MELCOR code is developed by the Sandia National Laboratories as the second generation nuclear plant risk assessment tool, in succession it can treat the reactor thermal-hydraulic response, phenomenon inside and outside the reactor pressure vessel, and the behavior of the radioactive fission products.At first, this paper developed the MELCOR model for the containment short-term thermal-hydraulic response under the design basis accident. Analyzing and discussing the model calculation results, we evaluate the MELCOR containment model by comparing with the GOTHIC code model results.Secondly, this paper developed the MELCOR model for the containment molten-fuel ejection under the severe accident. Discussing High Pressure Molten-fuel Ejection and Low Pressure Molten-fuel Ejection module of the MELCOR code, revealed the reason for the higher containment load produced by the High Pressure Molten-fuel Ejection module, and inquired the influences of reactor coolant system depressurization on the containment response under the typical High Pressure Molten-fuel Ejection accident.Lastly, this paper developed the MELCOR model for the containment hydrogen transportation under the severe accident. Combining the model calculation results with the research of the MELCOR code referred governing equations, pointed out the flaw of MELCOR code’s simulating the hydrogen transportation process due to its own density buoyancy lift.