Open AccessChemical and elemental mapping of spent nuclear fuel sections by soft X‐ray spectromicroscopy
Author(s) -
Ditter Alexander Scott,
Smiles Danil E.,
Lussier Daniel,
Altman Alison B.,
Bachhav Mukesh,
He Lingfeng,
Mara Michael W.,
Degueldre Claude,
Minasian Stefan G.,
Shuh David K.
Publication year - 2022
Publication title -
journal of synchrotron radiation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.172
H-Index - 99
ISSN - 1600-5775
DOI - 10.1107/s1600577521012315
Subject(s) - uranium , nuclear fission product , atom probe , non negative matrix factorization , chemical state , plutonium , analytical chemistry (journal) , ion , ion beam , oxidation state , materials science , oxide , uranium oxide , irradiation , spectral line , nuclear fuel , matrix (chemical analysis) , chemistry , fission products , x ray photoelectron spectroscopy , nuclear magnetic resonance , radiochemistry , matrix decomposition , crystallography , nuclear physics , nuclear chemistry , microstructure , physics , metal , metallurgy , chromatography , quantum mechanics , eigenvalues and eigenvectors , organic chemistry , astronomy , composite material
Soft X‐ray spectromicroscopy at the O K ‐edge, U N 4,5 ‐edges and Ce M 4,5 ‐edges has been performed on focused ion beam sections of spent nuclear fuel for the first time, yielding chemical information on the sub‐micrometer scale. To analyze these data, a modification to non‐negative matrix factorization (NMF) was developed, in which the data are no longer required to be non‐negative, but the non‐negativity of the spectral components and fit coefficients is largely preserved. The modified NMF method was utilized at the O K ‐edge to distinguish between two components, one present in the bulk of the sample similar to UO 2 and one present at the interface of the sample which is a hyperstoichiometric UO 2+ x species. The species maps are consistent with a model of a thin layer of UO 2+ x over the entire sample, which is likely explained by oxidation after focused ion beam (FIB) sectioning. In addition to the uranium oxide bulk of the sample, Ce measurements were also performed to investigate the oxidation state of that fission product, which is the subject of considerable interest. Analysis of the Ce spectra shows that Ce is in a predominantly trivalent state, with a possible contribution from tetravalent Ce. Atom probe analysis was performed to provide confirmation of the presence and localization of Ce in the spent fuel.