Comparison of Gamma and Passive Neutron Non-Destructive Assay Total Measurement Uncertainty Using the High Efficiency Neutron Counter

Since 1997, the High Efficiency Neutron Counter (HENC) has been employed by the Los Alamos National Laboratory (LANL) to assay and ship to the Waste Isolation Pilot Plant (WIPP) plutonium waste using passive neutron methods. During 2004 and early 2005, the HENC has undergone a modification and recertification to add a Canberra broad energy germanium detector (BEGe), DSA- 1000 digital spectrum analyzer, and JSR-14 neutron analysis shift register so as to conduct simultaneous gamma and passive neutron measurements. The BEGe detector provides both isotopic and quantitative measurement data to complement the neutron detectors. The assay is under the control of Canberra’s NDA-2000 software suite that provides acquisition control and analysis. As part of the recertification effort, the total measurement uncertainty (TMU) is being evaluated. A comparison of the gamma and the passive neutron TMU will be provided and the NDA 2000 settings used to achieve the results will be summarized and reported.