Assessment of Radionuclide Inventory Distribution Characteristics in the Bioshield Concrete of a PWR Reactor

In preparation for nuclear power plant decommissioning, an accurate assessment of radionuclide inventories in reactor components is essential. This study investigates the spatial distribution of activated radionuclides in the bioshield concrete of a pressurized water reactor (PWR). Using MCNP6.3 and ORIGEN in SCALE 6.3.1, neutron flux and radionuclide inventories are calculated over 7,500 mesh elements within the concrete region. A total of 35 radionuclide inventory maps are produced, providing detailed visualization of radionuclide distributions. Among the analyzed radionuclides, 3 H, 41Ca, 60Co, 152Eu, 154Eu, and 134Cs exhibit the highest Specific activity levels. The analysis also performs sensitivity evaluations of the radionuclide inventory in the bioshield concrete concerning impurity content, neutron irradiation time, and cooling period, and it presents the resulting radial distribution characteristics of radionuclides in the reactor. In addition, a comparison between ORIGEN versions 6.1 and 6.3.1 showed differences in inventory estimations, underscoring the importance of using updated nuclear data. The results are expected to offer essential data for radioactive concrete waste classification and disposal planning.