HEU (Highly Enriched Uranium) Drum Monitor Manual (For Confirmatory Measurements)

摘要

This manual describes the operation of the highly enriched uranium (HEU) drum monitor. The drum monitor measures the passive gamma-ray emissions from a sealed shipping container of HEU. These emissions are from sup 235 U and from daughters of sup 238 U. These radiations span a wide range of energy; consequently, each is susceptible to attenuation and shielding to a different degree. The combination of these measured gamma-ray rates with a weight measurement provides a unique signature for each item. These unique signatures can be determined with similar instruments at both ends of a material transfer between Department of Energy facilities. A consistent result from the two instruments indicates material control has been achieved, specifically that no material was lost or diverted. An additional objective of this instrument is to separate the material control issue from the measurement control issue. This is achieved by not calibrating the instrument and by reporting count rates instead of masses. Consequently, the results do not include calibration uncertainties, and therefore they are more precise. In addition, there are no sampling errors. A signal unique to the special nuclear material (SNM) is obtained nondestructively from the entire item. This instrument complements traditional containment and surveillance techniques by providing a precise measurement of an attribute unique to the SNM in the sample. 4 refs., 6 figs.