Year
2008
Abstract
The Canberra Box Counter Nondestructive Assay (NDA) System consists of two mobile subsystems: a Box Segmented Gamma Scanner (BSGS) and a separate Box Neutron Assay System (BNAS). The counter is to be used to assay transuranic (TRU) waste packaged in large containers for shipment to the Waste Isolation Pilot Plant (WIPP). The system was designed and fabricated by Canberra Industries, Inc. under a research and development contract with the US Department of Energy. Plutonium and other radionuclides of importance to the TRU waste disposal program at WIPP will be quantified by the counter. The BSGS is suitable for quantification of 241Am, 238Pu, 239Pu, 240Pu, 241Pu, 233U, 235U, 238U, 137Cs, and other radionuclides using either a multi-density efficiencycorrected method or a transmission-corrected approach to account for matrix attenuation. Spectra from the BSGS are also used to determine relative plutonium and uranium isotopic ratios. The BNAS directly measures the time-correlated neutron signal from spontaneously fissioning isotopes (generally 238Pu, 240Pu, and 242Pu) using both coincidence and multiplicity counting methods. Canberra’s Genie 2000 and NDA 2000 software packages automate control of the acquisition and motion elements of the two components, manage data collection and storage, analyze the collected data, integrate the results from the two subsystems as needed, and identify problems with the assay data. Combined results from the BSGS and BNAS are used to determine the total alpha activity, fissile gram equivalent, decay heat, and other properties of the radioactive waste. Unique to the box counter is its capability to accurately characterize the radioactive contents of Contact-Handled TRU waste packaged in a wide variety of containers. These range in size from 208-liter (55-gallon) drums to 5.5’ x 5.5’ x 8.5’ boxes. Factory calibration of the system was performed for a broad assortment of simulated waste matrices contained in 208-liter drums, Standard Waste Boxes (SWB), the Standard Large Box - 2 (SLB-2), and Ten Drum Overpacks (TDOP). The larger containers are to be used to ship multiple drum assemblies or large volume waste without resizing and/or repackaging. Upon completion of the design and fabrication of the system, the two box counter subsystems were calibrated and tested at the Canberra facility in Meriden, CT. They were then shipped to the Solid Waste Management Facility at the Savannah River Site (SRS) where acceptance testing was performed. Following acceptance, system operation was turned over to Washington TRU Solutions LLC and Mobile Characterization Services for qualification of the system to meet the waste acceptance requirements at the WIPP disposal site. This report will discuss technical aspects of the qualification process for the counter including descriptions of the quality assurance program that has been established for the gamma and neutron components, confirmation of the original calibration parameters, verification of the calibration after relocation of the system to the Savannah River Site, determination of minimum detectable activity values, and corroboration of the system’s total measurement uncertainty algorithms.