Preliminary estimation of activation products inventory in reactor components for Kori unit 1 decommissioning

Based on the necessity to evaluate the activation products inventory during decommissioning for domestic nuclear power plants, a preliminary estimation of the activation products inventory for Kori unit 1, which is getting close to the end of lifetime, was carried out with ANISN and ORIGEN2 code. In order to calculate neutron flux using ANISN code, the reactor was divided into 8 zones from core to bioshield concrete for radial direction. Also the cross-section of main nuclides were calibrated with neutron flux in the Reactor Pressure Vessel(RPV) region. The results showed that 95% of the total radioactivity in RPV from reactor shutdown to 10 years came from the nuclides of 55Fe, 59Ni, 63Ni and 60Co. And the total radioactivity with cooling of more than 50 years after decommissioning was no more than 0.2% of at the time of shutdown. Considering the weight of RPV is 210 tons, the total radioactivity of RPV reached to 5.25x106 GBq at shutdown time. As compared with the total radioactivity of bioshield concrete at reactor shutdown time, the radioactivity after cooling more than 10 years was below 1 %