Abstract
Stress corrosion cracking (SCC) caused by atmospheric deposition and deliquescence of aggressive compounds such as chloride-containing salts or oxidized sulfur species may pose a potential issue to the extended service life of spent nuclear fuel (SNF) storage canisters. When a chemically susceptible material is exposed to a hostile environment (e.g., coastal salt air) for a sufficient length of time, SCC may occur at locations on the canister which have undergone high tensile residual stress. These locations are often found in weld zones and the heat-affected zones (HAZ) of welded joints. Ideally, these cracks could be repaired by traditional fusion welding techniques, but the highly localized heat input of the repair welding may introduce additional high tensile residual stress and could increase the risk for future SCCs. This paper presents the results of neutron residual stress mapping of as-welded and repaired stainless steel specimens. The as-welded specimens were provided by Sandia National Laboratories from a canister mock-up manufactured using procedures similar to those used for actual canister production. ASME-qualified gas-tungsten arc welding (GTAW) was used to repair the specimens, and post-repair residual stresses were measured using neutron diffraction at the Oak Ridge National Laboratory (ORNL) High Flux Isotope Reactor (HFIR). As-welded and repaired specimen residual stress distributions are evaluated and compared. Significant residual stress profiles were identified from the received as-welded longitudinal weld sample. The generated residual stress profile from neutron diffraction is similar to that of the Sandia residual stress data obtained from deep-hole drilling. The GTAW-repaired specimen showed a notable redistribution in residual stresses and even introduced compressive stresses when compared with the as-welded condition. It appears that groove excavation and the well-controlled GTAW heat input resulted in a stress relief/annealing effect on the metal. The results of this comparison are expected to be used to guide improvements in future repair welding techniques.
| Original language | English |
|---|---|
| Pages | 249-253 |
| Number of pages | 5 |
| State | Published - 2019 |
| Event | 17th International High-Level Radioactive Waste Management Conference, IHLRWM 2019 - Knoxville, United States Duration: Apr 14 2019 → Apr 18 2019 |
Conference
| Conference | 17th International High-Level Radioactive Waste Management Conference, IHLRWM 2019 |
|---|---|
| Country/Territory | United States |
| City | Knoxville |
| Period | 04/14/19 → 04/18/19 |
Funding
For CISCC to initiate, residual tensile stresses must be of a sufficiently large magnitude. Of specific interest are fusion zones (FZ) and heat-affected regions associated with the welds on the canisters, since the welding process DISCLAIMERS: This technical paper does not take into account the contractual limitations under the Standard Contract for Disposal of Spent Nuclear Fuel and/or High-Level Radioactive Waste (Standard Contract; 10 Code of Federal Regulations [CFR] Part 961). Under the provisions of the Standard Contract, the Department of Energy (DOE) does not consider spent nuclear fuel (SNF) in multi-assembly canisters to be an acceptable waste form, absent a mutually agreed upon contract amendment. To the extent discussions or recommendations in this report conflict with the provisions of the Standard Contract, the Standard Contract provisions prevail. This material is based upon work supported by the US Department of Energy, Office of Nuclear Energy, under contract number DE-AC05-00OR22725. A portion of this research used resources at the High Flux Isotope Reactor, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory. The authors would also like to thank Paris Cornwell for his technical assistance in the experiments, Charles Bryan from Sandia, who provided the specimen, and Doug Kyle who performed the repair welding. NOTICE OF COPYRIGHT: This manuscript has been authored by UT-Battelle, LLC, under contract DE-AC05-00OR22725 with the US Department of Energy (DOE). The US government retains and the publisher, by accepting the article for publication, acknowledges that the US government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for US government purposes. DOE 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).
| Funders | Funder number |
|---|---|
| U.S. Department of Energy | |
| Office of Nuclear Energy | DE-AC05-00OR22725 |
| Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung |
