Validation of the Neutron Fluence Calculation on the VVER-440 RPV Support Structure

Abstract Measurements with activation detectors were carried out on Unit 4 of Kozloduy NPP in order to validate the fluence calculation data for the RPV support structure. Irradiation of iron, copper, and niobium detectors was performed during the 17th fuel cycle. The neutron fluence on the support structure and the activities of irradiated detectors were calculated by the three-dimensional transport code TORT with BGL440 multigroup cross section library. The history of local power distribution in the reactor core was taken into account. The measured and calculated induced activities are in good agreement in the area of the support structure. The calculated fluence evaluation in this area is conservative.