NSUF 20-2946: Unraveling the Mystery of Irradiation-Induced Void Closure
The objective of this project is to understand the intriguing and perplexing behavior of irradiation-induced void shrinkage in 304L stainless steels (SSs). Void nucleation and growth are well-established phenomena in nearly all nuclear reactor materials exposed to radiation – including structural alloys, cladding, and fuels – and can have a devastating effect on the functionality and integrity of nuclear components and fuels. It has long been accepted that voids grow without bound with increasing irradiation dose. However, recent studies suggest that the exact opposite behavior can occur under certain conditions! For example, Kr+ irradiation-induced densification has been reported in nanoporous Mg, Au, and Cu. In previously neutron-irradiated (i.e. neutron preconditioned) AISI 304L SS, we have also observed Fe2+ ion irradiation-induced transformation of voids into nanoprecipitates. Harnessing this unique phenomenon of irradiation-induced void closure could present a transformative pathway to control or repair voided materials, which could extend lifetimes of reactor components. Hence, there is a critical need to understand exactly how and why void closure occurs.
In our 304L SS, the depths at which the void-to-precipitate transformation occurs are not exactly coincident with the irradiation damage peak, nor with the ion implantation peak. Thus, we hypothesize the void closure is associated with the relative magnitudes of irradiation damage and ion implantation-induced chemical changes. Testing this hypothesis requires high-resolution chemical analysis capable of discerning the subtle composition changes introduced by Fe2+ ion irradiation. To this end, we propose to utilize atom probe tomography (APT) to evaluate chemistry at eight different depths along the damage and implantation profiles. Results will be corroborated with density functional theory (DFT) simulations and our existing transmission electron microscopy (TEM) analysis of irradiation damage. The project outcome will be an understanding of how chemistry and irradiation defects interact to close voids.
Additional Info
| Field | Value |
|---|---|
| Awarded Institution | None |
| Embargo End Date | 2023-03-30 |
| Facility Tech Lead | Mukesh Bachhav |
| NSUF Call | FY 2020 RTE 1st Call |
| PI | Janelle Wharry |
| PIE Facilities | Microscopy and Characterization Suite |
| Project Member | Professor Lin Shao, Professor - Texas A&M University (https://orcid.org/0000-0002-5703-1153) |
| Project Member | Dr. Frank Garner, President - Radiation Effects Consulting (https://orcid.org/0000-0003-4690-2205) |
| Project Member | Anter EL-AZAB - Purdue University |
| Project Member | Professor Janelle Wharry, Professor - University of Illinois (https://orcid.org/0000-0001-7791-4394) |
| Project Notes | Awarded on 02/05/2020 |
| Project Type | RTE |
| Publication | Elimination of remnant phases in low-temperature growth of wurtzite ScAlN by molecular-beam epitaxy Janelle Wharry, Amrita Sen, Mukesh Bachhav Journal of Applied Physics 132 2022-12-01 https://doi.org/10.1063/5.0118075 |
| RTE Number | 2946 |
| Sample Identifiers | 9294 |