MELCOR 1.8.2 assessment: The DF-4 BWR Damaged Fuel experiment

Abstract

MELCOR is a fully integrated, engineering-level computer code being developed at Sandia National Laboratories for the USNRC, that models the entire spectrum of severe accident phenomena in a unified framework for both BWRs and PWRs. As a part of an ongoing assessment program, MELCOR has been used to model the ACRR in-pile DF-4 Damaged Fuel experiment. I)F-4 provided data. for early phase melt progression in BWR fuel as,_emblies, parti(:ularly for phenomena associated with eutectic interactions in the BWR control blade and zircaloy oxidation in the canister and cladding. MELCOR provided good agreement with experimental data in the key areas of eutectic material behavior and canister and cladding oxidation. Several shortcomings associated with the MELCOR modeling of BWR geometries were found and corrected. Twenty-five sensitivity studies were pertbrmed on COR, HS and CVH paraLieters. These studies showed that the new MEI_COR eutectics model played an important role in predicting control blade behavior. These studies revealed slight time step dependence and no machine dependen('ies. Comparisons made with the results from four best-estimate codes showed that MELCOR did as well as these codes in matching DF-4 experimental data.

MELCOR 1.8.2 assessment: The MP-1 and MP-2 late phase melt progression experiments

“…Table 5.4.1 shows the COR and CVH subcycle ratios on each platform and the execution time ratios. Note that the HP run time results were closer to ttle IBM results than in previous reports [10], due to a reduction in optimization chosen for the MELCOR code. .…”

“…In particular, the melting temperature of zircaloy was changed from 2098K to 2200K. Other MELCOR assessments have shown the MATPRO value to be superior [10,11,12].…”