Evaluation of reactor pressure vessel metal state and life time at Kozloduy NPP Unit 1

The paper presents the results of studies aiming at determining the degree of Unit's 1 pressure vessel embrittlement. The following analysis performed are described in detail: 1) Determination of phosphorus and copper content in the shavings from weld. AES-ICP and two spectrophotometric methods are used independently; 2) Verification and evaluation of neutron fluence after 17-th refueling cycle. The calculations have been performed by the codes PYTHIA, REAC440, NETINP, NETDOT, 3D/ASYNT, DORT, FLUNG, IRDF-90. The results of the measurements have been used for evaluation of neutron fluence distribution. Activities of wire and foil detectors have been measured. The deviations between the calculated and measured values of activity are within 9%; 3) Evaluations of the shift of ductile to brittle transition temperature and embrittlement temperature are made, using the results obtained for Co and P- content; 4) Evaluation of the life time of Unit 1. It is established that for the core scheme of Unit 1 with dummy cassettes and 'low leakage' loading pattern for cycle's duration of 230 FPD the neutron fluence is below F=0.92.1018 cm-2, which satisfies the criteria for safety operation of WWER-440/230 pressure vessel