NSUF 26-5612: Characterization of Irradiated Yttrium-hydride Solid State Moderator Materials
Microreactors with High-Assay Low Enriched Uranium (HALEU) fuel require solid-state neutron moderators, such as hydrides of Y and Zr, for operation at elevated temperatures. **The performance of the entire reactor depends crucially on the H concentration and its local variation as a response to e.g. temperature, temperature gradients, irradiation, or fabrication. Few data points exist for irradiated metal hydride pellets and the non-destructive measurements probing entire irradiated pellet samples proposed here will therefore provide unique data on irradiation performance that complement other data collected to develop fabrication routes and understand, predict and control the moderator performance during operation and excursions. The sensitivity of neutrons to H and their ability to penetrate the relevant geometries make neutrons an ideal probe to study such systems. We propose to apply neutron diffraction and energy-resolved neutron imaging (ERNI), where each pixel represents an entire neutron transmission spectrum, to quantify the H concentration in 2D and 3D. Compared to gray-scale white beam radiography, ERNI allows to fit parameters such as areal density of H atoms but also crystallographic parameters such as lattice parameters to the transmission spectra, enabling greatly improved accuracy and precision. We will use H site occupation factors measured by neutron diffraction to determine the H/Y ratio as well as verify whether additional phases formed during irradiation e.g. if irradiation caused H to dissociate and leave H containing yttrium metal. **
Additional Info
| Field | Value |
|---|---|
| Awarded Institution | Los Alamos National Laboratory |
| DOI | 10.46936/NSUF/60017673 |
| Embargo End Date | 2028-04-22 |
| Facility Tech Lead | Alex Long, Gordon Kohse |
| NSUF Call | FY 2026 RTE 1st Call |
| PI | Sven Vogel |
| PIE Facilities | Manuel Lujan Jr. Neutron Scattering Center at the Los Alamos Neutron Science Center |
| Prep Facilities | Massachusetts Institute of Technology Nuclear Reactor Laboratory |
| Project Member | Dr. Sven Vogel, Scientist-5 - Los Alamos National Laboratory (https://orcid.org/0000-0003-2049-0361) |
| Project Member | Dr Caitlin Kohnert, Scientist - Los Alamos National Laboratory (https://orcid.org/0000-0002-0614-7236) |
| Project Member | Dr Arunkumar Seshadri, Research Scientist - Massachusetts Institute of Technology (https://orcid.org/0000-0003-1388-3810) |
| Project Type | RTE |