APPLICATION OF CADMIUM ZINC TELLURIDE DETECTORS IN U-235 ENRICHMENT MEASUREMENTS

High-resolution, gamma- and X-ray spectrometry are used routinely in n uclear safeguards verification measurements of plutonium and uranium i n the field. These measurements are mostly performed with high-purity germanium (HPGe) detectors, that require cooling to liquid-nitrogen te mperatures, thus limiting their utility in field and unattended safegu ards measurement applications. NaI scintillation detectors do not requ ire cooling, but their moderate energy resolution (10% at 122 keV) is insufficient in most cases for reliable verification measurements. Sem iconductor 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 sa feguards verification applications. We used a 5 X 5 X 5 mm CdZnTe dete ctor to measure U-235 enrichments ranging from 3% to 75%, We use a spe ctrum analysis technique that fits U-235, U-238, and U K X-ray respons e profiles to data in the 89- to 100-keV region of a gamma-ray spectru m. From the relative magnitudes of the U-235 and U-238 profiles we det ermine the U-235 enrichment with an accuracy of about 10% with CdZnTe detectors.