ATOM PROBE CHARACTERIZATION OF COPPER SOLUBILITY IN THE MIDLAND WELD AFTER NEUTRON IRRADIATION AND THERMAL ANNEALING

摘要

An atom probe field ion microscopy characterization has been performed to determine the copper matrix concentration in a submerged are beltline weld of the Midland Unit 1 pressurized water reactor after 4 conditions: unirradiated, unirradiated and annealed for 168 h at 454 degrees C, neutron-irradiated in a test reactor to a fluence of 1.1 x 10(23) n m(-2) (E > 1 MeV) at a temperature of 288 degrees C, and neutron-irradiated and annealed for 168 h at 454 degrees C. Atom probe analysis of the unirradiated material revealed a substantial depletion of the copper in the matrix to 0.119 +/- 0.007 at% Cu from the bulk value of between 0.18 and 0.28 at% Cu. Annealing the unirradiated material produced intragranular copper-enriched precipitates and reduced the matrix copper level by similar to 25% to 0.088 +/- 0.012 at% Cu. Neutron irradiation also produced copper-enriched precipitates and reduced the matrix copper level by almost 50% over the stress relieved material to 0.058 +/- 0.008 at% Cu. Annealing the neutron-irradiated material reduced the matrix copper level further to 0.050 +/- 0.010+/-at% Cu. These results indicate that the annealing treatment coarsens the copper-enriched precipitates produced during neutron irradiation with a slight decrease in the matrix copper content. (C) 1997 Elsevier Science B.V. [References: 24]