Abstract
As nuclear power plants (NPPs) approach or exceed 40–60 years of service, it may become necessary to repair damaged neutron-irradiated components to prolong longevity. However, fusion welding repair of irradiated steels and metallic materials is challenging because of helium-induced cracking. This study used friction stir welding (FSW) to address helium-related issues, such as helium bubble formation and grain boundary cracking. The microstructure, helium-induced degradation, and mechanical properties of a friction stir weld produced on neutron-irradiated 304L stainless steel with approximately 5.2 appm of helium were characterized. The analysis focused on variations in grain size, texture, and the morphology of helium-induced damage in the friction stir weld. Mechanical properties were characterized on the irradiated base metal (BM) and metallurgical zones of the friction stir weld: the stir zone (SZ), the thermo-mechanically affected zone (TMAZ), and the heat affected zone (HAZ). Only minor scattered porosity in the SZ and TMAZ and a few short microcracks (below 20 μm in length) in the TMAZ were observed, indicating limited helium-induced degradation. Tensile tests revealed good mechanical properties and fractography analysis demonstrated predominantly ductile fracture. The results highlight the immediate and substantial benefits of the FSW approach for repairing or joining helium-containing irradiated materials in NPPs.
| Original language | English |
|---|---|
| Article number | 113697 |
| Journal | Materials Characterization |
| Volume | 209 |
| DOIs | |
| State | Published - Mar 2024 |
Funding
This manuscript has been authored by UT-Battelle LLC and sponsored by the DOE Office of Nuclear Energy's Light Water Reactor Sustainability (LWRS) Program under contract DE-AC05-00OR22725 with UT Battelle LLC/ORNL . 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 ). The authors thank Dr. P. Doyle ( ORNL ) for reviewing the manuscript and providing valuable comments and suggestions. This manuscript has been authored by UT-Battelle LLC and sponsored by the DOE Office of Nuclear Energy's Light Water Reactor Sustainability (LWRS) Program under contract DE-AC05-00OR22725 with UT Battelle LLC/ORNL. 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). The authors thank Dr. P. Doyle (ORNL) for reviewing the manuscript and providing valuable comments and suggestions. The authors acknowledge and thank the people and teams who worked on the friction stir weld production and irradiated specimen transportation, handling, and preparation: ORNL's Radiochemical Engineering Development Center, Irradiated Material Examination and Testing Facility, Low Activation Materials and Development (LAMDA) facility, and Materials Joining group. We want to personally thank A. Smith, K. Kinney, C. Scott White, M. Delph, C. Morris, T. Davis, R. Bowman, S. Thurman, T. Muth, P. Tedder, S. Curlin, M. McAlister, N. Bibhanshu, Z. Feng, J. Chen, R. Miller, S. Clark, K. Leonard, and many others for their support. In addition, the authors would like to thank R. Roberts (ORNL) for her valuable help with the manuscript preparation.
| Funders | Funder number |
|---|---|
| DOE Office of Nuclear Energy's Light Water Reactor Sustainability | |
| DOE Public Access Plan | |
| LWRS | DE-AC05-00OR22725 |
| Oak Ridge National Laboratory | |
| UT-Battelle |
Keywords
- Cracking
- Friction stir welding
- Helium
- Neutron-irradiated steel
- Suppression of helium-induced embrittlement
