4H-SiC alpha spectrometry for nuclear forensics with electrodeposited sources

The alpha emission spectrum of electrodeposited thin film ²³²Th and depleted uranium sources, including the alpha emitting ²³²Th decay chain daughters and ²³⁸U daughter nuclide ²³⁴U, have been measured using a thin film 4H-SiC alpha detector. The energy resolution of this detector was proved suitable for the identification of many of the major characteristic alpha emissions associated with the ²³²Th daughter isotopes. The identification of the lower energy daughter isotopes made from the 4H-SiC detector measurements was confirmed using a silicon surface barrier detector. A depleted uranium source was fabricated using electrodeposition in a molten salt and the alpha spectrum was acquired with a 4H-SiC detector. The ²³⁴U/²³⁸U activity ratio and atomic enrichment of ²³⁴U in the sample were determined. A method of determining the ²³⁵U enrichment in the product stream of the enrichment process used to produce the depleted uranium source was developed. This method makes use of the ²³⁴U and ²³⁵U waste stream enrichments, as indicated by the depleted uranium source, and a mass balance equation to determine the product ²³⁵U enrichment. Since the ²³⁵U spectrum was obscured in the electrodeposited source by peak broadening of ²³⁸U and ²³⁴U, a table of common ²³⁵U waste enrichment values was used to compute ²³⁵U product enrichments, thereby resulting in a plausible identification of the enrichment process as a Department of Energy HEU enrichment process. (author)