Year
1999
Abstract
Research using the Combined Thermal/Epithermal Neutron (CTEN) instrument has been ongoing at Los Alamos National Laboratory to develop methods to improve the accuracy of both active and passive measurements uses in waste assay. A number of techniques used in the calibration studies such as generalized regression neural network and emission tomography required a large data set of over 1400 passive and active assays. Although CTEN measurement capabilities are extensive, only gross indicators are available to describe the neutron energy spectrum. A MCNP model of the CTEN instrument was constructed to determine not only interrogating neutron spectra as a function of matrix and position, but self-shielding and self-multiplication correction factors for the calibration sources. Calculated and measured values for detector efficiency and dieaway in the passive mode, and thermal flux dieaway and relative intensities in the active mode were used in model verification. This paper will provide an overview of the model and present results of benchmarking tests.