PRACTICAL GAMMA SPECTROSCOPY ASSAY TECHNIQUES FOR LARGE VOLUME LOW-LEVEL WASTE BOXES

摘要

A study was conducted at the Los Alamos National Laboratory (LANL) to evaluate thernperformance of the SNAPu0001 (Spectral Nondestructive Assay Platform) analytical software forrnmeasurements of known standards in large metal waste boxes (2.5 m3 volume). The trials wererndesigned to test the accuracy and variance of the analytical results for low-density combustiblernmatrices and higher-density metal matrices at two discrete gamma-ray energies: 121.78 keV andrn411.12 keV. For both matrix types the measurement method that produced the most accuraternresults with the lowest associated standard deviation involved combining four individualrnmeasurements taken at the geometric center of each of the box’s four vertical sides. With thisrnmethod the overall bias and the standard deviation amongst 24 individual results for the 121.78rnkeV and 411.12 keV gamma rays were as follows: 3.38% (u0002 20.19%) and 3.68% (u0002 15.47%) forrnthe combustible matrix and 37.88% (u0002 67.64%) and 9.38% (u0002 33.15%) for the metal matrix. Thernpersistent positive bias from measurements of the metal box is believed to be a result of a nonhomogenouslyrndistributed matrix.