Considerations for realistic emergency core cooling system evaluation methodology for light water reactors

Various phenomena governing the course of large- and small-break loss-of-coolant accidents in light water reactors and affecting the key parameters such as peak cladding temperature, and timing of the end of blowdown, beginning of reflood, and complete quench have been identified. The models and the correlations for these phenomena in the current literature, in advance codes, and as prescribed in the current emergency core cooling system methodology as outlined in Appendix K of CFR50 have been reviewed. It was found that the models and correlations in the present best-estimate codes such as TRAC or RELAP5 could be made more realistic by incorporating some of these models from the literature. However, an assessment program will be needed for the final selection of the models for the codes