Year
1998
Abstract
Prior to disposal, nuclear waste must be accurately characterized to identify and quantify the radioactive content. The DOE Complex faces the daunting task of measuring nuclear material with both a wide range of masses and matrices. Similarly daunting can be the selection of a nondestructive assay (NDA) technique(s) to efficiently perform the quantitative assay over the entire waste population. In fulfilling its role of a DOE Defense Programs nuclear User Facility/Technology Development Center, the Los Alamos National Laboratory Plutonium Facility recently tested three commercially built and owned, mobile nondestructive assay (NDA) systems with special nuclear materials (SNM). Two independent commercial companies financed the testing of their three mobile NDA systems at the site. Contained within a single trailer is Canberra Industries segmented gamma scanner/waste assay system (SGS/WAS) and neutron waste drum assay system (WDAS). For this test program, LANL operated the Canberra systems. The third system is a BNFL Instruments Inc. (formerly known as Pajarito Scientific Corporation) differential die-away imaging passive/active neutron (IPAN) counter. As part of this commercial trailer testing program, 25 Plutonium Facility waste drums were selected to be measured on these instruments. These included six different matrices: combustible, glass, HEPA, metal, plastics, and salts. Because this waste is continually generated over time and shipped from the site; only a limited supply of drums are available at any one time. These items are measured in our NDA Analytical Laboratory within the Plutonium Facility. Two primary techniques have been used on these wastes. For low-density waste, a segmented gamma scanner is used. For high-density waste a neutron coincidence counter is used. In an effort to improve the facility’s ability to measure this waste, the Plutonium Facility has taken the approach of measuring each waste item prior to loading into the 55 gal (208 liter) drum. These items are in cans ranging from 1 quart to 5 gallons. The assay value for each can in a drum is then summed to generate the total drum contents. In an effort to increase the value of this comparison, additional NDA techniques at LANL were also used to measure these same drums. These are comprised of three Tomographic gamma scanners (one mobile unit and two stationary) and one developmental differential die-away system. Although the drums are not certified standards, the authors hope that the comparisons will provide valuable data for those considering these different NDA techniques to measure their wastes. The results of the tests may also benefit the developers of these techniques.