Year
1998
Abstract
A boxed waste assay system, developed by BNFL Instruments Inc. (BII), was installed at the Waste Receiving and Packaging (WRAP) facility in Hanford, Washington in early 1997. The system combines imaging passive/active neutron (IPAN) techniques with gamma-ray energy analysis (GEA) to assay crates up to 2.5m x 2.5m x 6.5m in size. Two separate gamma-ray measurements are accomplished utilizing 16 arrayed NaI detectors and a moveable HPGe detector, while 3He detectors acquire both active and passive neutron data. These neutron measurements employ the differential die-away technique and coincidence analysis, respectively. Both neutron measurements use BII’s proprietary imaging methodology. Acceptance testing of the system was conducted at Hanford in January 1998. The system’s operating performance was evaluated based on accuracy and sensitivity requirements for three different matrix types. For a “Medium” matrix, testing results include an average 13% active mode accuracy for 10 nCi/g loadings of Pu waste and 5% passive mode accuracy for 10g loadings of Pu waste. Sensitivity testing demonstrated an active mode lower limit of detection (LLD) of less than 5 nCi/g of 239Pu for the medium matrix and less than 20 pCi/g of fission and activation products at 3s above background. The results of the acceptance test program and the intended application of the system are discussed in this report.