Validation of MAAP code for the analysis of liquid waste boiling accident in the reprocessing plant

Validation of severe accident (SA) analysis code MAAP is carried out for the analysis of aerosol behavior accompanied with liquid waste boiling accident in the reprocessing plant. The applicability of MAAP is confirmed based on the "Standard Method for Safety Evaluation using Best Estimate Code Based on Uncertainty and Scaling Analyses with Statistical Approach" issued by Atomic Energy Society of Japan. Figure of merit for this purpose is leak path factor (LPF) of radioactive aerosol, and the each physical and chemical phenomena included in this accident progression are listed up to develop "Phenomena Identification and Ranking Table (PIRT)". The development of PIRT reveals that most of the important phenomena are common with SA in nuclear power plant, for which the knowledge of the code validation has already been accumulated. The remained items to be validated are separate effect tests of aerosol behavior model and integrated effect tests with full-scale reprocessing plant SA analyses. The former validation is accomplished by comparison with experimental data and code-to-code comparison with ART code that models aerosol particle diameter distribution change and transport mechanistically. The latter validation is covered by code-to-code comparison with MELCOR code that is developed for the analysis of severe accident progression in light water reactor nuclear power plants similar to MAAP. These activities enhance credibility of LPF values estimated by MAAP, and enable to develop effective accident management strategies. (author)