ABSTRACT
In the unlikely event of a severe accident in a nuclear power plant, the core may melt through the vessel and slump into the concrete reactor cavity. The hot mixture of the core material called “corium” interacts thermally with the concrete basemat. The WECHSL code, developped at K.f.K. Karlsruhe in Germany is used at the Protection and Nuclear Safety Institute (I.P.S.N.) of CEA to compute this molten corium concrete interaction (MCCI). Some uncertainties remain in the partition of heat from the corium between the basemat and the upper surrounding structures in the cavity where the thermal conditions are not computed.
The CALTHER code, under development to perform a more mechanistic evaluation of the upward heat flux has been linked to WECHSL-M0D2 code. This new version enables the modelling of the feedback effects from the conditions in the cavity to the MCCI and the computation of the fraction of upward flux directly added to the cavity atmosphere.
The present status is given in this paper. Preliminary calculations of the reactor case for silicate and limestone common sand (L.C.S) concretes are presented. Significant effects are found on concrete erosion, gases release and temperature of the upper part of corium, particularly for L.C.S concrete.
