Application of cadmium-zinc-telluride detectors in U-235 enrichment measurements

摘要

High-resolution, gamma- and x-ray spectrometry are used routinely in nuclear safeguards verification measurements of plutonium and uranium in the field. These measurements are mostly performed with high-purity germanium (HPGe) detectors, that require cooling to liquid-nitrogen temperatures, thus limiting their utility in field and unattended safeguards measurement applications. NaI scintillation detectors do not require cooling, but their moderate energy resolution (10% at 122 keV) is insufficient in most cases for reliable verification measurements. Semiconductor detectors that operate at room temperature, such as cadmium-zinc-telluride (CdZnTe) detectors, with energy resolution performance reaching 2.0% at 122 keV may complement HPGe detectors for certain safeguards verification applications. The authors used a 5x5x5 mm CdZnTe detector to measure U-235 enrichments ranging from 3% to 75%. They use a spectrum analysis technique that fits U-235, U-238, and U K x-ray response profiles to data in the 89- to 100-keV region of gamma-ray spectrum. From the relative magnitudes of the U-235 and U-238 profiles they determine the U-235 enrichment with an accuracy of about 10% with CdZnTe detectors.