Fission product behavior during a loss-of-flow/loss-of-power transient in the ATR

The fission product behavior during a postulated loss-of-power induced loss-of-flow accident in the Advanced Test Reactor has been analyzed. This included analysis of the fission product inventory in the fuel prior to accident initiation, release of the fission products from the fuel into the reactor vessel during core melt, the probable chemical forms, and transport of the fission products from the core through the reactor vessel and existing piping to the open confinement. In addition to a best-estimate'' analysis of fission product behavior, a series of analyses was performed to determine the sensitivity of fission product release to a number of parameters including steam flow rate, (structural) aluminum oxidation, and initial aerosol size. The analysis indicates that the volatile fission products (excluding the noble gases) will be transported on aerosols. Approximately 40% of the initial inventories of volatile fission products will be deposited within either the reactor vessel or the intact piping in the confinement and 60% of the inventory will be released into the open confinement. 15 refs., 2 figs., 3 tabs.