抄録
Research on radionuclide accumulation is significant for analyzing the source term in a severe accident. The previous method utilizing the point depletion computer code to analyze radionuclide accumulation assumes that thermal power density and burnup distribution are uniform. And the different fuel enrichment in different region is also ignored. However, the thermal power density and the burnup distribution are actually not uniform during AP1000 reactor operation. Therefore, the results obtained by the previous method needs further verification. In this paper, a fine structure model was established utilizing CASMO-SIMULATE for AP1000 reactor to calculate the radial and axial thermal power density distribution. Based on this distribution and the different fuel enrichment in different region, the reactor core was divided into ten levels in axial orientation and four rings in radial orientation. A particular level and a particular ring define a core cell. BURNUP code was used to analyze the radionuclide accumulation in each cell. The radionuclides are grouped into three segments as follows: activation products, actinides and fission products. And, each group in each cell was analyzed. Then, radionuclide accumulation characters in entire core were obtained. The result was compared with the result obtained by the previous method. And the influence to the results of each effect factor, fuel concentration, power distribution and burnup, was analyzed. The radionuclide decay characters after reactor emergency shutdown were also obtained.
