Assessment of a lower head molten pool analysis module using LIVE experiment

The main objective of this work is assessment and improvement of the COUPLE module, the lower head molten pool analysis model included in a reactor analysis code RELAP/SCDAPSIM, by using LIVE test series. This module is used to calculate the heat-up of reactor core material that slumped into the lower head of the reactor vessel. Heat transfer in the radial and axial directions to the wall structures and water surround the debris is considered in the module. In the LIVE test facility, the behavior of reactor pressure vessel in the late in-vessel phase of a postulated severe accident in a nuclear power plant is investigated. Due to the recent interest in in-vessel melt retention through external reactor vessel cooling as a key strategy of the severe accident management, the ability and applicability of the module need to be assessed and improved. The heat flux, wall temperature, crust thickness and molten pool temperature are compared with the experimental data. The code was modified to allow modelling external cooling vessel and an input deck for the LIVE facility was created. The results using other empirical correlations are also compared and, as a result, better agreement of heat flux and wall temperature is obtained.