COMPARISON OF CALCULATIONS USING THE BEST ESTIMATE REFLOOD HEAT TRANSFER CODE BART-A1 WITH DATA FROM THE FLECHT-SEASET FACILITY

BART-A1 is a Westinghouse computer code which provides a mechanistic evaluation of heat transfer during the reflood phase of a large Loss of Coolant Accident (LOCA) in a Pressurised Water Reactor. The code has been used by NNC in support of the Sizewell ‘B’ safety case with respect to the consequences of fuel clad swelling or ballooning during a LOCA. In support of this application of the code to the safety case, an extensive programme to validate all aspects of the modelling is in progress. In this paper, the results of a comparison with experimental data from the FLECHT-SEASET multi-rod bundle test facility are presented. FLECHT-SEASET provides reflood heat transfer data for a simulation of a complete PWR fuel assembly for forced flooding, low pressure conditions. The comparisons thus provide validation evidence for unblocked heat transfer models in the BART-Al code. Results for one test are provided. Good agreement with the data is obtained and the results thus help to confirm that the code provides an adequate description of the important two phase flow phenomena relevant to reflood in unblocked configurations.