APPLICATION OF MOBILE APNEA SYSTEM TO CHARACTERIZATION OF TRU WASTE AT DOE SITES

A trailer-borne Active Passive Neutron Examination and Assay nondestructive analysis system is being used in support of US Department of Energy transuranic waste characterization needed for the Waste Isolation Pilot Plant. This system can be relocated to a site requiring NDA for TRU and be operational in less than a week. In the passive mode, APNEA employs a high efficiency 4π neutron detector to measure autocorrelated neutrons emerging from 55-gallon TRU waste drums. In the active mode, the same neutron detector, plus a 14 MeV neutron generator are used to measure the thermal neutron induced fission rate of fissionable materials in the drums. By combination with isotopic ratio information, for example, from gamma ray spectroscopy, these active and passive neutron measurements yield assays for the TRU content of the drums. Both assay modes are needed for characterization of TRU waste ‐the passive assay is more accurate but the higher sensitivity of the active assay is needed to attain the minimum detection limit required for WIPP waste characterization. APNEA also employs a 252 Cf-neutron source to determine the waste type of the unknown drum, independently of prior knowledge. Waste heterogeniety effects are reduced by assay analyses using spatially dependent neutron-detection efficiencies and spatially dependent thermal neutron fluxes to match the measured waste drum. This APNEA system has been characterized using waste drum surrogates representing waste types from metals through sludge. It has participated and passed the Performance Demonstration Program (PDP) through cycle 5 and has been certified by participation in Carlsbad Area Office and Environmental Protection Agency audits.