Operational and Regulatory Performance of Waste Crate Assay Systems at RFETS

摘要

As Rocky Flats Environmental Technology Site (RFETS) approaches its closure target of 2006 emphasis for Non-Destructive Assay (NDA) has shifted from small waste package assay systems towards larger systems that are designed to accommodate Standard Waste Boxes (SWB) and larger Low Level Waste (LLW) containers. To this end, Kaiser Hill, with the support of BNFL Instruments, Inc. (BII) and Los Alamos National Laboratory (LANL), has recently deployed two new crate assay systems. These systems provide the capacity to meet the assay requirements associated with the Deactivation and Decommissioning (D&D) at RFETS. The Super High Efficiency Neutron Coincidence Counting System (SuperHENC) was designed and fabricated as a collaborative effort between RFETS, LANL and BII. The purpose of this counter is to provide a WIPP certified assay capability for SWBs with a sensitivity that allows for TRU/LLW sorting. The SuperHENC has been in operation since early 2001. The BII Multi-Purpose Crate Counter (MPCC) is based on the Imaging Passive Active Neutron (IPAN) technology. This counter was designed to provide diverse capacity for WIPP certified assay of SWBs and to provide assay capability for larger LLW crates that are generated at RFETS. The MPCC has been in operation since early 2002. In order to meet the requirement for measurement of the WIPP tracked radionuclides, both systems incorporate a BII Gamma Energy Analysis sub-system. The unique Energy Times Attenuation (ETA) method is used to provide isotopic mass fractions for diverse waste streams. These systems were the first, and at this time the only, waste crate assay systems that have achieved WIPP certification. This represents a significant achievement given that the performance criteria applied to the measurements of large crates is identical to the criteria for 55-gallon (208 liter) drums. They are now both fully operational at RFETS and continue to successfully support the site closure mission.