Enrichment measurement by passive γ-ray spectrometry of uranium dioxide fuel pellets using a europium-doped, strontium iodide scintillator

The performance of a europium-doped strontium iodide scintillator for uranium enrichment measurement of a variety of sintered uranium dioxide fuel pellets is described and compared to that of caesium iodide and sodium iodide. Enrichment has been determined via passive γ-ray spectrometry of the 186 keV line from uranium-235 using gross count, net count, and peak ratio analyses. The 38 mm Ø x 38 mm strontium iodide crystal demonstrates superior energy resolution (3.43 ± 0.03% at 662 keV) and competitive detection efficiency for its size in the energy range of interest for uranium enrichment analysis (<250 keV). It demonstrates better χv2 and coefficient of determination values than caesium iodide and sodium iodide when measuring uranium enrichment using the gross- and net-count from the 186 keV emission. It is shown to have the least measurement variance of the three scintillators studied in determining the uranium enrichment of pellets in a blind test, with a relative error comparative to sodium iodide and smaller than caesium iodide. This research heralds the potential of strontium iodide in passive γ-ray uranium enrichment applications.