SIMULATIONS OF SMALL BREAK LOCA TESTS AT THE MULTILOOP INTEGRAL SYSTEM TEST (MIST) FACILITY: APPLICABILITY OF TRACE FOR BABCOCK WILCOX PWR FACILITIES

摘要

The pressurized water reactors (PWRs) designed by Babcock & Wilcox (B&W) possess several unique features that are not found in other currently operating U.S. reactors, most notably the reactor vessel vent valves and once through steam generators. In order for the U. S. Nuclear Regulatory Commmission (NRC) to perform independent reviews of licensee submittals, there is a need to assess and validate the NRC's TRAC-RELAP Advanced Computational Engine (TRACE) code for thermal hydraulic phenomena involving system responses due to the aforementioned characteristics of B&W PWRs. Two tests at the Multiloop Integral System Test facility were used to benchmark the TRACE code for Small Break Loss Of Coolant Accident scenarios based on the importance of the phenomena being studied and the relevance of the phenomena to processes not already covered by the Phenomenon Identification and Ranking Table for other plant types against which TRACE has already been comprehensively benchmarked. All of the important trends and thermal hydraulic phenomena were captured, and the deviations in the results were traced to modeling limitations or lack of sufficient information to accurately capture the test facility system response. Overall, TRACE has shown itself to be very capable of analyzing the thermal hydraulic phenomena of interest in a B&W type PWR plant for design basis accident scenarios.