Year
1997
Abstract
The differential dieaway techniqu (DDT) is an active interrogation method that uses themalized neutrons form a 14-MeV pulsed source to irradiate radioactive waste drums. Prompt neutrons from induced fissions are detected and thus provide a direct measure of the fissile content of the drum. While the measurement technique is extremely sensitive to fissile material, its accuracy depends on significant corrections to compensate for the effects of the matrix material. Research using the combined thermal/epithermal neutron (CTEN) instrument has been ongoing at Los Alamos National Laboratory to develop methods to improve the overall accuracy of the differential dieaway technique. A series of mock waste drums with high and low moderating and absorbing abilities and combinations thereof have been measured in both the active and passive modes. New methods of data acquisition and analysis have resulted in improvements in matrix corrections and the detection of self shielding in some cases. Teh result of this research and the development of the algorithms for the active assay will be discussed.