BWR loss of coolant technology review

Over the past few years an integrated technology program has been pursued with the objective of defining the detailed response of the Boiling Water Reactor (BWR) for the entire spectrum of postulated loss of coolant inventory conditions. This program includes large scale experiments and best estimates model development in the United States, as well as large scale experiments overseas (primarily in Japan). While final confirmatory experiments and model comparisons are continuing, the key studies and model developments have now been successfully completed. This paper summarizes the controlling phenomena for these BWR transient events and identifies the similarities among results from the experimental facilities of various scales. The model features necessary for best-estimate predictions are reviewed and compared with the data. Finally, the safety margin implications of the best-estimate models are demonstrated by application to the reactory system. The consistencies among the diverse range of experiments, combined with the demonstrated accuracy of the detailed fundamental prediction model, provide high confidence for extrapolations of the technology to full scale reactors. The results of these reactor applications indicate very large safety margins exist over the entire spectrum of postulated pressure boundary break sizes for the BWR