MCCI Simulation for the APR-1400 TLOFW sequence

If retention of molten core debris inside a reactor vessel is not assured during a postulated severe accident, the molten core debris will attack the concrete wall and basemat of the reactor cavity. Thus, this accident might lead to inevitable concrete decompositions and possible radiological releases. In the OECD/NEA MCCI project, a series of tests such as water ingression, melt eruption, and 2-D core concrete interaction tests was performed to secure the data for cooling a molten core spread out at the reactor cavity and for the long-term MCCI (Molten Core Concrete Interaction). This paper deals with the MCCI (Molten Core Concrete Interaction) phenomena for the APR1400 investigated by using the CORQUENCH Version 3.03 and a comparison with the MELCOR 1.8.6 calculations. For the ease of a direct comparison, the same major inputs and basic heat transfer models were used. The CORQUENCH Version 3.03 includes a melt eruption model based on a turbulent jet entrainment correlation and an up-to-date water ingression model which was developed at the Argonne National Laboratory during the OECD/MCCI project. On the other hand, since these models are not incorporated in MELCOR 1.8.6., a phenomenological difference of heat transfer to the upper coolant exists between the codes. Important parameters of the MCCI such as concrete ablations, heat fluxes, and melt temperature etc. are analyzed and compared with the MELCOR 1.8.6 calculation results. Some sensitivity studies with a change of system pressure, heat transfer model at the melt/concrete interface, and coefficient of water ingression and melt eruption models are performed