Radiological source term into containment under severe accident conditions

The radiological source term into containment used by the U.S. Nuclear Regulatory Commission as the basis for regulatory decisions related to reactor siting and evaluation of important plant performance requirements is derived from the 1962 Atomic Energy Commission report TID-14844. The TID source term, as it is known, postulates the release into containment of 100% of the core inventory of noble gases, 50% of iodines, and 10% of the remaining open-quotes solidclose quotes fission products. These values were based largely on experiments performed in the late 1950s involving heated irradiated UO2, pellets. There has been significant research activity regarding severe accidents following the accident at Three Mile Island unit 2. The objective of the work described in this paper is to utilize the current technical knowledge and understanding of LWR severe accident phenomenology to provide more realistic estimates of source term release into containments in terms of timing, nuclide types, and quantities during a severe core-melt accident