Confirmatory Measurements for Uranium in Nuclear Weapons by High-Resolution Gamma-Ray Spectrometry (HRGS)

High-resolution gamma-ray spectrometry (HRGS) measurement techniques have been developed to confirm HEU in the presence of plutonium in US nuclear weapons and have now been tested with all types of weapons in the enduring stockpile. A combination of high-resolution spectral features assures that both uranium and plutonium components are present. The most useful spectral features for uranium are the ratio of the 186-, 1001 keV peaks associated with the decay of 235U and 238U; the profiles of the 186-, 1001- and 2614-keV gamma-ray peaks versus position along the axis of a device' and the peak area of the 2614-keV gamma-ray from decay of 232U (a contaminant from processing reactor-irradiated uranium in gaseous diffusion cascades). Using design information quantitative acceptance-rejection criteria can be established. Battery powered HRGS equipment meets rigorous safety standards for use with nuclear weapons containing conventional high explosives. Portable HRGS equip,ent cane be operated either in process buildings or in the field bunkers used for storage of nuclear weapons at Pantex. HRGS techniques disrupt normal operations minimally. HRGS provides additional assurance, beyond low-resolution measurements, regarding the presence of all SNM in nuclear weapons being transferred to or from the Department of Energy;s (DOE) custody,