QUANTIFYING REACTOR SAFETY MARGINS .5. EVALUATION OF SCALE-UP CAPABILITIES OF BEST ESTIMATE CODES

This paper presents the CSAU procedure and rational for: 1. (1) Evaluating the capability of a best estimate code to scale-up processes from reduced scale test facilities to full scale nuclear power plants, and 2. (2) Quantifying the effects of scale distortions and/or a limited data base, on code uncertainty to calculate a safety parameter of interest (for example peak clad temperature). To this end, the procedure uses and integrates information from test facility design and operation, from scenario processes and phenomena and from code documentation. A flow diagram of the procedure is presented together with the prescribed steps. To present the rationale and need for the procedure, the paper also summarizes the scaling techniques developed and used to design and operate loss of coolant accident related test facilities. The procedure is illustrated by applying it to TRAC-PF1/MOD1 calculations of a large break loss of coolant accident in a four loop Westinghouse pressurized water reactor. The application demonstrates that the procedure is sytematic, traceable and practical. © 1990.