NSUF 24-5012: The Role of Helium on Microstructure Evolution in A709
Significant effort has been underway to provide a code case for use of alloy A709 as a structural material in advanced nuclear reactors ranging from Sodium Cooled Fast Reactors (SFR’s) to High-Temperature Gas-cooled Reactors (HTGR’s). The hostile environments of these varied advanced reactor concepts will vary with respect to coolant/cladding compatibility criteria, stress/temperature combinations that may influence necessary experimentation regarding irradiation creep, and irradiation-induced and environmentally-assisted cracking; however, the effect of irradiation on the microstructure and mechanical properties of A709 as a function of temperature is a fundamental requirement for all systems. Unfortunately, the United States’ test reactors are limited to either the Advanced Test Reactor (ATR) or the High Flux Isotope Reactor (HFIR) for any irradiation campaign aimed at qualifying A709. Both have high thermal neutron fluxes and the associated high levels of He-production from the Ni content of A709. Thus, the objective of this work is to quantify differences in cavity distributions following irradiation of advanced austenitic stainless steel A709 as a function of varied Helium (He) production and damage rates. We hypothesize that, due to the significantly higher He-production rate in thermal test reactors, cavity distributions will be dominated by nanoscale He-bubbles that will fundamentally change post-irradiation measurements of strength and ductility following low-dose neutron irradiation compared to anticipated fast reactor spectra. Ion irradiations may provide an alternative solution to examine the differences in expected cavity nucleation in A709 between thermal and harder neutron spectra in an accelerated manner. We propose to perform a systematic ion irradiation study spanning two relevant operating temperature conditions and two He-generation rates for comparison with neutron-irradiated A709 from HFIR. The proposing team seeks use, through the Nuclear Science User Facilities, one partner institution for dual ion irradiation (UM), one partner institution for sample preparation (ORNL), and two partner institutions for post-irradiation examination (UM, CAES). The A709 material is immediately available for ion-irradiations and PIE, while the neutron-irradiated material will be extracted from HFIR in May 2024 and ready for sample preparation in LAMDA by August 2024, providing the high-impact comparative datapoints with low risk during the 12 month period of performance. Microstructure examination will include dislocation loops, precipitates, and cavities conducted in parallel at the university and national laboratory NSUF partner facilities. The outcome of this work will provide a quantitative analysis of the irradiation microstructure, with an emphasis on the cavity/He bubble distribution at low displacement damage levels (~2 dpa) anticipated for A709’s structural use case. The availability of this dataset will inform subsequent decisions on qualification-relevant neutron irradiations for A709 and enable a more realistic interpretation of the advanced austenitic alloy in fast-reactor operating environments.
추가 정보
| 필드 | 값 |
|---|---|
| Award Announced Date | 2024-08-15T09:35:52.333 |
| Awarded Institution | Oak Ridge National Laboratory |
| Facility Tech Lead | Kevin Field, Kory Linton, Yaqiao Wu |
| Irradiation Facility | Michigan Ion Beam Laboratory |
| PI | Caleb Massey |
| PI Email | [email protected] |
| Project Type | RTE |
| RTE Number | None |