Thermal-hydraulic analysis of boiling event of reprocessed liquid wastes with MELCOR code

Yoshida, Kazuo ; Ishikawa, Jun 

Boiling events of reprocessed liquid wastes are postulated to be occurred caused by the loss of cooling function persisting over a long period of time at a fuel reprocessing plant. Some amounts of radioactive materials could be released from facilities caused by vapor flow from a boiling liquid waste storage tank. Thermal-hydraulic behaviors in compartments of facility building are essential to be analyzed for assessing amount of released radioactive materials. MELCOR, which has been developed for severe accident analysis of nuclear reactors, has been applied in this study. Functional features of Control Functions and Time-Specified Volumes in MELCOR have been used to model key phenomena such as, boiling at higher temperature than water boiling point, vaporization of nitric acid and generation of non-condensable gases due to denitrating reaction. Results of analysis demonstrate applicability of MELCOR to those events.