Low Level and Transuranic Waste Segregation and Low Level Waste Characterization at the 200 Area of the Hanford Site - 12424

This paper describes the waste measurement and waste characterization activities carried out by ANTECH Corporation (ANTECH) and CH2M Hill Plateau Remediation Company (CHPRC) at the 200 Area of the Hanford Site under Contracts No. 22394 and No. 40245 for the US Department of Energy (DOE). These include Low Level Waste (LLW) and Transuranic (TRU) Waste segregation and LLW characterization for both 55-gallon (200-litre) drums with gross weight up to 454 kg and 85-gallon over-pack drums. In order to achieve efficient and effective waste drum segregation and assay, ANTECH deployed an automated Gamma Mobile Assay Laboratory (G-MAL) at the trench face in both 200 Area West and East. The unit consists of a modified 40 foot ISO shipping container with an automatic flow through roller conveyor system with internal drum weigh scale, four measurement and drum rotation positions, and four high efficiency high purity Germanium (HPGe) detectors with both detector and shadow shields. The unit performs multiple far-field measurements and is able to segregate drums at levels well below 100 nCi/g. The system is sufficiently sensitive that drums, which are classified as LLW, are characterized at measurement levels that meet the Environmental Restoration Disposal Facility (ERDF) Waste Acceptance Criteria (WAC). Withmore » measurement times of between 20 and 30 minutes the unit can classify and characterize over 40 drums in an 8-hour shift. The system is well characterized with documented calibrations, lower limits of detection (LLD) and total measurement uncertainty. The calibrations are confirmed and verified using nationally traceable standards in keeping with the CHPRC measurement requirements. The performance of the system has been confirmed and validated throughout the measurement process by independent CHPRC personnel using traceable standards. All of the measurement and maintenance work has been conducted during the period under a Quality Assurance Plan (QAP) compliant with the applicable criteria of NQA-1 (2000). This includes not only the calibrations and measurements but also the data analysis activities of the ANTECH Subject Matter Experts (SME) and ANTECH support and maintenance activities as well as the activities of CHPRC staff who recover, transport and load waste drums and disposition measured and characterized drums. The overall processes of drum recovery and analysis are described in the paper. Specific spectral data is presented which illustrates the segregation, sentencing and assay process for different types of drums with different radionuclide profiles. The process of identifying and quantifying a wide range of non-TRU radionuclide isotopes is explained and illustrated with spectral examples. The difficulties associated with the measurement of drums with a high gamma ray background, usually arising from high levels of Cs-137 are considered. These drums, which would normally be declared indeterminate and treated as TRU, are addressed under contract No. 40245 by the deployment of the ANTECH Neutron Mobile Assay Laboratory. This is an Active-Passive neutron assay system housed in a modified ISO shipping container. The unit is designed for the measurement and assay of both drums and crates (including B-25 boxes and SWB containers) and will quantify the content of both plutonium and uranium. The neutron system has been employed to perform further evaluation on indeterminate drums to classify them to either LLW or TRU. The experiences of both gamma ray and neutron system operation in different conditions are described; as are the issues of throughput, drum handling and system maintenance. All of these are considered in the overriding context of safe drum handling and safe assay system operation. (authors)« less