Nondestructive Uranium Enrichment Determination in Process Holdup Deposits

A new technique has been developed for analyzing the gamma-ray spectra of uranium compounds to determine the relative abundance of all gamma-ray-emitting isotopes present. The technique works well for samples whose gamma-ray absorption properties are not well defined and has become an invaluable tool for characterizing inventory samples and residual uranium held up in process equipment. The gamma rays in a spectrum obtained with a hyperpure germanium detector are corrected for self-absorption, container attenuation, and branching ratios. The technique is being used (1) to calculate the relative abundance of uranium isotopes (i.e., 232U, 234U, B5U, and 238U) contained in nuclear materials, (2) to calculate the specific neutron activity emanating from deposits quantitatively measured using nondestructive neutron measurement techniques, and (3) to identify and correct for interference from other neutronemitting isotopes (e.g., ^'Np). The technique works well on a variety of deposits (e.g., UO2F2 and UF6) even if the deposits are \"infinitely thick\" to 186-keV gamma rays or are contained in thick-walled pipes. To date, results indicate excellent agreement between calculated and assigned enrichment values.