Gamma Ray Imaging for Qualitative Uranium Material Holdup Position Determination and Improved Quantitative Mass Determination

Two Gamma Ray Imaging Systems (GRIS) have been deployed at the Portsmouth Gaseous Diffusion Facility to improve the capabilities of nondestructive assay measurement systems for safeguard approaches. These systems are utilized in conjunction with other passive neutron and gamma based measurement techniques to provide an improved estimate of the location and mass of nuclear material in process equipment. This information can be used to explain inventory differences and by nuclear criticality safety personnel to evaluate criticality concerns pertaining to deposits. Although criticality safety is not a material control and accountability concern it is important because it can directly impact the application of safeguards at a facility. The GRIS systems are prototypes manufactured by Radiation Measurement Devices and are based on the earlier development work of Klaus Ziock, et al. The systems utilize a single Cesium Iodide detector coupled with a digital camera and a portable computer. These systems have been used to evaluate deposits located within a series of pipes, which run within a physically sealed header. A radiation image is integrated with mechanical drawings to indicate the location and extent of deposits. This data is then used to refine calculations for quantitative estimates of enriched uranium mass.