Gamma spectrometry in the ITWG CMX-4 exercise

Abstract

Low enriched uranium samples of unknown origin were analyzed by 16 laboratories in the context of a Collaborative Materials Exercise (CMX), organized by the Nuclear Forensics International Technical Working Group (ITWG). The purpose was to compare and prioritize nuclear forensic methods and techniques, and to evaluate attribution capabilities among participants. This paper gives a snapshot of the gamma spectrometric capabilities of the participating laboratories and summarizes the results achieved by gamma spectrometry.

Analytical considerations in the determination of uranium isotope ratios in solid uranium materials using laser ablation multi-collector ICP-MS

“…During CMX-4, organised by the International Technical Working Group on Nuclear Forensics (ITWG), two low-enriched UO 2 pellets were delivered to each participating laboratory [ 3 ]. After initial non-destructive analysis using high resolution gamma spectrometry [ 9 ], fragments of ∼1.3 g of these two UO 2 pellets were dissolved in 8 M HNO 3 and subsequently analysed for their U isotopic composition using TIMS, following accredited analytical procedures [ 5 ]. These TIMS results served as a basis for the comparison to the LA-MC-ICP-MS measurements.…”

“…Moreover, such an analytical approach, results in an average U isotopic composition of the bulk material. The same applies for non-destructive high resolution gamma spectrometry [ 9 ]. Information on potential sample inhomogeneity, however, is not measurable by these methods.…”

Fourth Collaborative Materials Exercise of the Nuclear Forensics International Technical Working Group

“…Within this special section, the reader will find major outcomes from CMX-4 contained within one of seven technical articles organized by technical area [10][11][12][13][14][15][16], and one additional article briefly describing the experiences of seven of the laboratories participating in the CMX series of exercises for the first time [17]. The latter chronicles the challenges these newcomers faced, from the receipt and handling of special nuclear materials, to the timely analysis and reporting of results under operational timelines-all made possible by transforming often ''general use'' radioanalytical laboratories to execute analytical plans and quality assurance/quality control processes of a sufficient rigor for a court of law.…”

“…Within this timeframe no analytical tool is more valuable to nuclear forensic scientists than HRGS. Demonstrated by all participants during CMX-4 within the first 24 h of the exercise (as summarized by Lakosi et al [12]), this rapid and relatively accurate isotopic analysis technique has been a mainstay for the ITWG Network of Forensics Laboratories in every CMX conducted thus far [6][7][8]18]. Measuring isotopic abundance of special nuclear materials using HRGS is an advanced skill requiring participants to estimate detection efficiency as a function of gamma energy using commercial or in-house modeling software.…”

“…Attempts to utilize HRGS results for radiochronometric applications during CMX-4 were reported in [12]. While radiochronometry using HRGS has been demonstrated with exercise materials enriched in 235 U to greater than 90% [8] in the past, similar attempts to calculate process age during CMX-4 were unsuccessful due to the nature of the material (LEU).…”