NSUF 25-5202: Atom probe tomography of HT-9 to evaluate the effect of neutron irradiation temperature, alloying element and heat treatment
Ferritic-martensitic steels are being considered as candidate structural materials for fast reactors and advanced LWR due to their excellent resistance to radiation-induced void swelling, microstructural stability, thermal conductivity, and superior irradiation creep properties. HT-9 was selected as the fuel clad and duct material in FFTF and EBR-II, and it is still the first-choice candidate core material for several advanced reactor concepts due to its service performance and the relatively large database on it. Currently, commercial nuclear power companies such as TerraPower has rejuvenated the manufacturing of HT-9. To address the issue of low-temperature (~425°C) neutron irradiation hardening and embrittlement, it is necessary to conduct systematic investigations on the mechanical behavior and microstructure of HT-9 with slight variations in chemical composition and heat treatment over a wide range of doses and temperatures. Three HT-9 heats (ORNL, LANL and EBR II) with variations in manufacturing process, chemical composition and heat treatment were neutron irradiated (~4 dpa) in the ATR at different temperatures (241-469C). Our team recently won RTE award and completed microhardness and tensile testing of these HT-9 variants. Maximum impact of this work will be obtained by performing TEM and APT characterization of these neutron irradiated samples present at PNNL to correlate the measured hardening with microstructural features. We recently completed APT study on HT-9 (ORNL) at CAES. Currently, efforts are ongoing to perform APT study on HT-9 (EBRII) at CAES. Considering the RTE funding availability, we limited the number of samples by choosing one HT-9 heat/RTE to study a range of temperatures that is relevant for α′ precipitation studies and LWR/advanced reactor applications. We propose to employ APT to enhance the understanding of the underlying mechanisms for α′ and Ni/Mn/Si precipitate evolution in HT-9 (LANL heat) upon neutron irradiation. The objective of this RTE proposal (follow-up APT study #3) is to compare the formation of α′ and Ni/Mn/Si precipitates in neutron irradiated HT-9 heats since these have a significant variation in heat treatment, alloying elements (Ni, Mn, Si and W) and mechanical properties. Since these heats were side-by-side irradiated (identical conditions) in the ATR, the overall objective is to evaluate the formation of second phase precipitates in neutron irradiated (~4 dpa) HT-9 as a function of irradiation temperature (241°C, 388°C and 452°C; range of temperatures that is relevant for α′ precipitation studies and LWR/advanced reactor applications), heat treatment and alloying elements (Ni, Mn, Si, W). By doing this work, our team can contribute to filling the gap in the literature on understanding the irradiation effects on HT-9 and F-M steels in general. The proposed work will benefit the NE R&D programs involved in developing advanced structural materials with greater radiation resistance. The project performance is expected to take place during Feb-Sep 2025 and will result in one conference presentation and one journal article publication.
Additional Info
| Field | Value |
|---|---|
| Award Announced Date | 2025-06-26T09:03:21.277 |
| Awarded Institution | Pacific Northwest National Laboratory |
| Facility Tech Lead | Mukesh Bachhav, Stuart Maloy |
| Irradiation Facility | |
| PI | Ramprashad Prabhakaran |
| PI Email | [email protected] |
| Project Type | RTE |
| RTE Number | None |