NSUF 25-5530: Effect of in situ Straining on Irradiation Induced Hardening in RPV Steel
Reactor pressure vessel (RPV) steels in commercial nuclear reactors are engineered for strength and irradiation resistance, but undergo embrittlement as neutron fluence increases, primarily via hardening mechanisms linked to the evolution of microstructural features. Early irradiation induces copper-rich precipitates (CRPs) and dislocation loops, while higher doses (>0.2 dpa) generate manganese-nickel-silicon-rich precipitates (MNPs) and late-blooming phases (LBPs), which pin dislocations and dominate embrittlement at high fluence. The role of operational stresses—particularly hoop stresses up to 300 MPa in reactor beltlines—remains poorly understood for their impact on defect evolution during irradiation, as such stresses drive dislocation glide and potentially reduce dislocation density, thereby influencing nucleation of irradiation-induced precipitates. This Super Rapid Turnaround Experiment aims to quantify the effects of applied straining during irradiation on the hardening and embrittlement of RPV steels. The central hypothesis is that straining during irradiation will decrease dislocation density and provide fewer nucleation sites for MNPs and LBPs, thereby mitigating irradiation-induced hardening. To accomplish this, in situ ion irradiation and nano-straining experiments will be performed at the IVEM facility at Argonne National Laboratory using the Gatan straining holder and push-to-pull (PTP) device across doses of 0, 0.1, 0.2, and 0.5 dpa at room temperature and 300°C. Transmission electron microscopy (TEM) will be used to directly observe dislocation and precipitate dynamics, while post-irradiation nano-tensile testing will generate stress-strain data. Microstructural and mechanical analyses will probe the relationships between applied stress, dislocation structure, nucleation and growth of irradiation defects, and resultant yield strength and plasticity. Convergent beam electron diffraction will enable lamella thickness measurement for accurate cross-sectional and density calculations. By correlating in situ defect evolution with mechanical properties, this work will provide foundational insight into how applied stress during irradiation fundamentally alters hardening pathways in RPV steels, guiding future design and operational strategies.
Additional Info
| Field | Value |
|---|---|
| Awarded Institution | University of Florida |
| DOI | 10.46936/NSUF/60015719 |
| Embargo End Date | 2028-01-22 |
| Facility Tech Lead | Wei-Ying Chen, Yong Yang |
| Irradiation Facilities | Intermediate Voltage Electron Microscopy (IVEM)-Tandem Facility |
| NSUF Call | FY 2025 Super RTE Call |
| PI | Brandon Bohanon |
| PIE Facilities | Intermediate Voltage Electron Microscopy (IVEM)-Tandem Facility |
| Prep Facilities | Nuclear Fuels and Materials Characterization Facility, Intermediate Voltage Electron Microscopy (IVEM)-Tandem Facility |
| Project Member | Professor Assel Aitkaliyeva, Assistant Professor - University of Florida (https://orcid.org/0000-0003-1481-6804) |
| Project Member | Dr. Wei-Ying Chen, Material Scientist - Argonne National Laboratory (https://orcid.org/0000-0002-6583-4204) |
| Project Member | Mr. Brandon Bohanon, PhD Graduate Research Assistant - University of Florida (https://orcid.org/0000-0002-7576-4916) |
| Project Type | RTE |