Advanced Neutron Dosimetry on VVER-440 Aimed to Reactor Equipment Load Evaluation during Lifetime Prolongation

摘要

The lifetime of nonrestorable reactor equipment (e.g., reactor pressure vessels, in-and ex-vessel constructions, reactor support structures) of a first-generation water-water energetic reactor, VVER-440, may restrict plant life as a whole. Service life extension has affected the first generation of VVER-440 type reactors. Today, all Russian first-generation VVER-440s that have been in operation more than 45 years run with reduced cores by using dummy assemblies, except reactor Unit 4 of the Novovoronezh nuclear power plant. In comparison with other power units, the full-core loading scheme of this unit results in the highest neutron fluence accumulated over the whole operation period. Another important aspect of dosimetry research on Unit 4 of the Novovoronezh nuclear power plant reactor is the verification and validation of calculational methods used for the prediction of the maximum neutron fluence on the VVER-440 pressure vessel.