Neutron Dosimetry for VVER Reactor Pressure Vessels in the Czech Republic

Abstract

The paper gives a description of the contemporary methods used for the fast neutron fluence determination applied to the reactors of the Dukovany VVER-440 nuclear power plant (NPP). Measurement methods include measurements in containers with supplementary surveillance program and in the reactor cavity. Retrospective dosimetry using scraps of reactor pressure vessel cladding material is being prepared. Information is also given about the analogous methods prepared for the reactors of the Temelin VVER-1000 NPP. The results at measured points (reactor cavity, surveillance) are recalculated to the reactor pressure vessel inner wall by using the conversion factors obtained in mock-up experiments carried out for both VVER- 440 and VVER-1000 at the LR-0 research reactor. The experimental works are completed with fluence calculations for which two methods have been developed. The DAVKA code is the LEPRICON system adaptation for the VVER reactors and the INCAL 3D code makes use of the influence functions of the given volume of the fuel element to the total fluence. Measurements can be completed by gamma scanning of surveillance specimens rest activities.