SANS STUDY OF HIGH-COPPER RPV WELDS IN IRRADIATED AND ANNEALED CONDITIONS

摘要

Small-angle neutron scattering (SANS) has been used to study reactor pressure vessel (RPV) welds from the Heavy-Section Steel Irradiation (HSSI) Program. Each of the welds contains high bulk copper contents ranging from 0.26 to 0.40 wt %. The welds were irradiated in test reactors to fluences ranging from 0.5 to 1.9×10~(19) n/cm~2 (E > 1 MeV). SANS measurements were performed to determine number density, radius, and volume fraction of irradiation-induced scattering centers which were consistent with copper-rich precipitates (CRPs). The bulk copper content had no effect on CRP number density, volume fraction, and average radius. Postirradiation annealing (PIA) was performed on the welds for 168 h at 343, 399, and 454°C. SANS measurements on these samples show that high temperature PIA decreases the CRP number density and volume fraction while increasing the average radius. The SANS data obtained on these welds are consistent with the University of California, Santa Barbara, database and comparison is made with two A533B type model alloys irradiated to a similar fluence and following PIA. Evolution of the CRP scattering centers with irradiation and PIA is compared to the changes in mechanical properties.