Results on research of templates from Kozloduy-1 reactor pressure vessel

The studies on the specimens manufaclured from the templales ciil oul from the weld 4 of Kozioduy NPP Unit 1 reactor vessel have been conducted. The data on chemical composition of the weld metal have been obtained. Neutron fluence, mechanical properties, ductile to brittle transition temperature (DBTT) using mini Charpy samples have been determined. The phosphorus and copper content averaged over all templates is U.046 and O.I wt.ʹXi, respectively. The fluence amounted up to 5 x 10^18 n cm ^-2 within 15-18 fuel cycles, and about 5 x 10^19 n cm ^-2 for the whole period of operation. These values agree well with calculated data. DBTT was determined after irradiation (T(k))to evaluate the vessel metal state at the present moment, then after heat treatment at the temperature of 475("C to simulate the vessel metal state after thermal annealing (T(an))). and after heat treatment at 560°C to simulate the metal stale in the initial stale (T(ko)). As a result of the tests the following values were obtained: T(k,) + 91.5°C; T(an;) + 63°C; and T(ko,) 54°C. The values of T(k) and 7(an) obtained by measurements were found to be considerably lower than those predicted in accordance with the conservative method accepted in Russia (177°C for T(k) and 100°C for T(an). Thus. the obtained results allowed to make a conclusion that it is nol necessary to anneal Kozioduy NPP Unit 1 reactor vessel for the second time. The fractographic and electron-microscopic research allowed to draw some conclusions on the embrittlement mechanism. © 1999 Elsevier Science S.A. All rights reserved.