Automated Drum Measurements for LLW-TRU Segregation and LLW Characterization
In the United States between 1970 and 1987 waste drums were retrievably stored in the Low Level Burial Grounds (LLBGs) in the 200 East and 200 West Areas on the Hanford Reserve. As part of an agreement between the Department of Energy, the Environmental Protection Agency and the state of Washington these drums must be retrieved, the low level waste (LLW) drums segregated from Transuranic (TRU) drums and the LLW drums characterized for final disposition. A semi-automatic drum assay system with sufficient sensitivity to perform measurements at specific activities below 60 nCi/g was required.
In order to meet the requirement, ANTECH designed, built and deployed a gamma ray based mobile assay laboratory (G-MAL) with the following features:
- The G-MAL is housed in a modified 40 foot ISO shipping container, which is transportable and designed for deployment into the field at the trench site. It can be easily re-located from site to site.
- Drums are loaded onto an input roller conveyor by forklift and transported automatically onto a weigh scale and then onto one of four measurement positions. Each drum is rotated in front of the detector during the measurement. After the measurement the drums are automatically transported to an external buffer conveyor from which they are recovered by a forklift.
- The G-MAL has four measurement positions so 4 drums can be measured simultaneously. Each far field measurement position has a shielded high purity Germanium (HPGe) detector with detection efficiency greater than 50%. Lead shadow shields are fitted to each detector to reduce the background arising from adjacent waste drums.
- The G-MAL ISO container is fitted with HVAC and has a small control room for the operators with a window through which the drums can be viewed during the automatic measurement process.
- Following a measurement and preliminary on-site analysis, the measurement data is transmitted to the ANTECH facility in Denver, Colorado where subject matter experts (SME) perform detailed analysis and the results are subjected to independent technical review (ITR). Quality assured electronic results data packs are provided to the customer typically within 24 to 48 hours.
The G-MAL provides a high throughput measurement solution that has been used to measure over 7,500 LLW and TRU drums since 2004. The system is capable of assaying more than 60 drums in a 10-hour period. It can also be used to measure high dose-rate drums at a lower throughput rate. The sensitive and efficient measurement process and rapid analysis and result reporting system has allowed the timely disposition of drums by the Hanford site customer.
Tom Donohoue, E. Ray Martin, John A. Mason, Ty Blackford, Michael Cahill, Michael Estes and William Jasen, “Low Level and Transuranic Waste Segregation and Low Level Waste Characterization at the 200 Area of the Hanford Site”, WM2012 Conference, February 26 – March 1, 2012, Phoenix, Arizona, USA. (WM12-12424a)