Model verification of the debris coolability analysis module in the severeaccident analysis code 'SAMPSON'

The debris coolability analysis module in the severe accident analysis code 'SAMPSON' has been enhanced to predict more mechanistically the safety mar gin of present reactor pressure vessels in a severe accident. The module ca lculates debris spreading and cooling through melting and solidification in combination with the temperature distribution of the vessel wall and it ev aluates the wall failure. Debris cooling after spreading is solved on the b asis of natural convection analysis with melting and solidification on thre e-dimensional Cartesian co-ordinates. The calculated results for the coolin g model are compared with the results from a is solved on the basis of natu ral convection analysis with melting and solidification on three-dimensiona l natural convection experiment. The comparisons show the module capability for predictions of the debris temperature in the cooling process. Furtherm ore, it is seen that the prediction capability in the thermal load of the v essel wall is improved, since the penetration nozzles melting is modeled an d combined with the cooling model. The module provides a good tool for the prediction of the reactor safety margin in a severe accident through the th ree-dimensional analysis of debris cooling.