MELCOR analysis of the NRU Full-Length High-Temperature-2 test

MELCOR is a fully integrated computer code that models all phases of the progression of severe accidents in nuclear power plants. It is being developed for the US Nuclear Regulatory Commission by Sandia National Laboratories and is designed to provide an improved severe-accident/source term analysis capability relative to the older Source Term Code Package. Early assessment efforts for MELCOR emphasized validation of containment modeling. Current assessment efforts have realized the need to focus more on in-vessel phenomenology, which is an area of major uncertainty in the assessment of severe-accident radiological consequences. In-vessel analyses reported to date using MELCOR have been the Power Burst Facility (PBF) SFD 1-1 test, the Three Mile Island Unit 2 standard problem, both using MELCOR Version 1.7.1, and the PBF SFD 1-4 test, which used MELCOR Version 1.8BC. The purpose of this paper is to describe a MELCOR (Version 1.8DN, the most recent) simulation of the National Research Universal (NRU) Full-Length High-Temperature 2 (FLHT-2) test and to compare results with test data and predictions from the US Nuclear Regulatory Commission's mechanistic code SCDAP.