Characterization and Optimization of a Spectral Window for Direct Gaseous Uranium Hexafluoride Enrichment Assay Using Laser-Induced Breakdown Spectroscopy

Journal Article · Fri Jul 15 00:00:00 EDT 2022 · Applied Spectroscopy

DOI:https://doi.org/10.1177/00037028221112953· OSTI ID:2204568

Chan, George C. Y.  ^[1]; Martin, Leigh R. ^[2]; Russo, Richard E. ^[3]

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1. Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)
2. Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
3. Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States); Applied Spectra, West Sacramento, CA (United States)

Through a systematic scanning of ²³⁵U and ²³⁸U emission lines between 280 nm and 745 nm, the optimal emission line for direct gaseous uranium hexafluoride (UF₆) enrichment assay using laser-induced breakdown spectroscopy (LIBS) was found. Screening for spectral features that are potentially useful for U isotopic analysis was gauged from the magnitude of the ²³⁵U–²³⁸U isotopic shift and the signal-to-background ratio of the emission line through a parameter termed ΔSBR _235U–238U. The ΔSBR spectrum shows peaks at wavelength positions where there are strong lines with significant ²³⁵U–²³⁸U shifts. The screening identified 13 spectral-window candidates, which were down selected based on their overall accuracy in predicting the ²³⁵U enrichment of three UF₆ samples of natural (0.720 atom% ²³⁵U) and low-enriched (4.675 atom% and 9.157 atom% ²³⁵U) grades. The U(I) 646.498 nm emission line, with a determined ²³⁵U–²³⁸U isotopic shift of -17.7 pm, was found to be the optimal spectral window for direct UF₆ enrichment assay. The root mean square error for enrichment assays on the three natural and low-enriched UF₆ samples, with each sample measured in six replicates, was 0.31% in absolute ²³⁵U content. Each measurement comprised LIBS signals accumulated from 3000 laser shots. In conclusion, the analytical bias and precision were better than 0.5% and 0.3%, respectively, in absolute [²³⁵U/(²³⁵U + ²³⁸U)] ratios. Specific for the two low-enriched UF₆ samples, the relative standard deviations from six replicated measurements were around 2%.

• Research Organization: Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA)
• Grant/Contract Number: AC05-00OR22725; AC02-05CH 11231
• OSTI ID: 2204568
• Journal Information: Applied Spectroscopy, Vol. 77, Issue 8; ISSN 0003-7028
• Publisher: Society for Applied Spectroscopy
• Country of Publication: United States
• Language: English

Related Subjects

47 OTHER INSTRUMENTATION
Uranium hexafluoride
enrichment assay
isotopic analysis
isotopic shift
laser-induced breakdown spectroscopy
nuclear safeguards