A study on new source term release characteristics

TID-14844, which was established in 1962, has been used for regulatory applications of source terms under design basis accidents. But recently, the USNRC issued NUREG-1465 for regulatory purposes, which represents more realistic source terms than TID-14844 does. NUREG-1465 is based upon research results and insights for accident source terms obtained over 40 years in PWRs. In order to keep up with these trends, in-containment source term calculations for TLOFW and LLOCA at 1400MWe PWRs are calculated and compared with NUREG-1465 source terms. In-containment accident source terms denote the composition and magnitude of the radioactive material within the containment, which is available for leakage from the reactor to the environment. In the case of TLOFW, the maximum atmospheric concentration of Xe/I/Cs/Te radionuclide groups appeared to be smaller than the NUREG-1465 source terms by one order of magnitude. In the case of LLOCA with emergency safety injection recovery at 30 minutes into the accident, the maximum atmospheric concentration of I/Cs/Te radionuclide groups appeared to be a little larger than the NUREG-1465 source terms while Xe was smaller. This study provides not only new source term data using MELCOR1.8.4 and its state-of-the-art models but also an evaluating basis for mitigation capability under severe accidents at 1400MWe PWR