Neutron dosimetry on the full-core first generation VVER-440 aimed at reactor support structure load evaluation

Reactor support structures (RSS), especially ferritic steel wall of water tank, of VVER-440 of first generation are non-restorable reactor equipment and their lifetime may restrict plant-life at whole. All operated Russian first generation VVER-440 have a reduced core with dummy assemblies except reactor of Unit 4 of Novovoronezh NPP. In comparison with other reactors, the full-core loading scheme of this reactor provides the highest neutron fluence on the reactor pressure vessel (RPV) and RSS accumulated over design service-life and its prolongation. The radiation load parameters on the RPV and RSS resulted from this core loading scheme should be evaluated by means of precise calculations and validated by ex-vessel neutron dosimetry to provide the reliable assessment of embrittlement parameters of these reactor components. The results of different types of calculations and their comparison with measured data have been analyzed in this paper. The calculational analysis of RSS fluence rate variation in dependence on core loading scheme, including standard and low leakage core as well as dummy assemblies, has been presented in paper.