Instrumentation applications for radioassay of transuranic waste at the Idaho National Engineering and Environmental Laboratory

The Radioactive Waste Management Complex (RWMC) located within the Idaho National Engineering and Environmental Laboratory (INEEL) contains facilities and equipment to manage and characterize transuranic (TRU) radioactive waste currently stored at the INEEL. This waste was generated primarily at the Department of Energy (DOE) Rocky Flats Plant. A facility referred to as the Stored Waste Examination Pilot Plant (SWEPP) provides space for the systems that characterize and certify the various TRU waste forms for shipping and disposal. This paper describes the processes and instrumentation used to perform nondestructive radioassay on the TRU waste. The equipment includes a passive-active neutron (PAN) assay system used to interrogate the waste container for the presence of fissile materials and a gamma-ray spectrometer (GRS) system used for the identification of the gamma-ray emitting isotopes in the waste containers. The PAN assay system consists of a Zetatron-type pulsed neutron generator; active, passive, and interrogation flux neutron detectors and instrumentation packages, safety interlocks, and various assay chamber signal acquisition instrumentation and processing electronics. The GRS system uses high-resolution, high-purity germanium detectors, amplifiers, high-voltage power supplies, analog-to-digital converters, signal acquisition and interface modules, and the gamma spectra calibration pulsers. The data from these two systems are combined to calculate radionuclide quantities required for the TRU waste characterization, certification, shipping, and disposal at a centralized DOE disposal facility, such as the proposed Waste Isolation Pilot Plant facility in New Mexico. The wide variety of waste matrix types and isotopic distributions has posed a real. challenge to both our radioassay system hardware/software and the technical support personnel assigned to the project.