Technology development on nuclear material accountability

A portable HPGe, MCA and gamma-ray spectrometer has been used passive non-destructively for the rafid field measured of U-235 enrichment. Measurement of the 185.7 keV gamma-ray emitted by U-235 appeared most promising for this application. The factors influencing this measurement were identified as the effect of source to detector distance, self-absorption effect by various sample composition, attenuation effect by the wall thickness of sample container, collimation effect and counting efficiency. These factors were separately evaluated, and adjusted to obtain the optimized total counting system. The selected samples which of 55 gal. natural and depleted UO2 powder, and type 48Y depleted UF6 cylinder were measured and resulted in relative errors of 2.67%, 4.93% and 5.52% at 95% confidence level respectively from Tag values. As a result of this study the quantitative non-destructive assay method could be applied not only to uranium sample but to any radio-isotope sample which emits signature gammas provided inherent instrumental error ranges are acceptable. In addition, the computer program developed in 1987 for nuclear material accountings at both facility and state levels, was updated and reinforced particularly in the error checking function to minimize the errors caused by computer key-board operations. (Author)