Year
2004
Abstract
The results of the first phase of quantification of sources of uncertainty for MGA isotopic ratios are presented. Currently non-destructive Nuclear Materials Measurements require accurate isotopic ratios to get good results. Estimates of amounts of special nuclear material are a result of combining isotopic information (from gamma spectroscopy information) with absolute estimates of heat or neutron production. The uncertainties associated with the results are determined by the uncertainties from the two NDA contributors (gamma spectroscopy, and either neutron counting or calorimetry). This work is intended to allow a more accurate assessment of the errors associated with mass determinations via calorimetry or neutron counting. The study uses the off-the- shelf Multigroup Analysis program to analyze spectra from systems perturbed in ways to isolate sources of error in the analysis. Perturbations include changes in peak resolution and tailing, sample inhomogeneity, absorber materials, sample matrix , and efficiency curve shapes. The magnitudes (and for biases, the signs) of contributions to uncertainties will be presented. Replicate sample uncertainties will be compared with calculated uncertainties, as a gauge of statistical validity of the calculated uncertainties.