Abstract
High-Cu weld material harvested from an ex service reactor pressure vessel (RPV) steel from Unit 1 of the decommissioned Zion Nuclear Generating Station has been characterized using atom probe tomography. Samples taken from 4 different positions through the thicknesses of the pressure vessel wall from the water-side to the air-side were characterized, along with an unirradiated baseline material. In the baseline material, no precipitates were found and the Cu was observed to be fully in solid solution; however, scanning transmission electron microscopy combined with energy dispersive spectroscopy (STEM-EDS) revealed the presence of ϵ-Cu that form during processing of the material and results in the concomitant decrease of matrix Cu. Following irradiation, a high number density of nano-scale Cu-rich precipitates (CRPs) were observed, uniformly distributed throughout the matrix. The Cu content within the CRPs was found to be ∼30-35 at.% regardless of location in the wall. No statistically significant variation in the compositions, mean radius, number density, or volume fraction as a function of location within the wall was observed. The measured matrix Cu level excluding CRPs contribution was found to be ∼90 appm higher than the solubility limit suggesting that further nucleation and growth of the CRPs under continued operations would have occurred. These results clearly demonstrate that the neutron energy attenuation has no significant effect on the precipitation kinetics of CRPs regardless of location in the wall in high-Cu RPV steels under irradiation. Notice: This manuscript has been authored by UT-Battelle, LLC under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (http://energy.gov/downloads/doe-public-access-plan).
| Original language | English |
|---|---|
| Article number | 152740 |
| Journal | Journal of Nuclear Materials |
| Volume | 545 |
| DOIs | |
| State | Published - Mar 2021 |
Funding
This work was supported by U.S. Department of Energy, Light-Water Reactor Sustainability Program of the Office of Nuclear Energy, under contract number DE-AC-05-00OR22725. APT was conducted at ORNL's Center for Nanophase Materials Sciences (CNMS), which is a U.S. DOE Office of Science User Facility. The Pressurized Water Reactor Owners Group (PWROG) is acknowledged for their provision of the unirradiated baseline material. FEI Talos F200X S/TEM instrument provided by US DOE, Office of Nuclear Energy, Fuel Cycle Research and Development and the Nuclear Science User Facilities. This work was supported by U.S. Department of Energy, Light-Water Reactor Sustainability Program of the Office of Nuclear Energy, under contract number DE-AC-05-00OR22725. APT was conducted at ORNL’s Center for Nanophase Materials Sciences (CNMS), which is a U.S. DOE Office of Science User Facility. The Pressurized Water Reactor Owners Group (PWROG) is acknowledged for their provision of the unirradiated baseline material. FEI Talos F200X S/TEM instrument provided by US DOE, Office of Nuclear Energy, Fuel Cycle Research and Development and the Nuclear Science User Facilities.
Keywords
- Atom probe tomography (APT)
- Copper rich precipitates
- Neutron irradiation
- Precipitation
- Reactor pressure vessel (RPV)
- Steel