Thermo Nutech's Segmented Gate System at Los Alamos National Laboratory Technical Area 33, Los Alamos, New Mexico

Site Name:

Los Alamos National Laboratory

Location:

Los Alamos, New Mexico

Period of
Operation:

April 28 May 19, 1999
(soil processing on 15 days)

Cleanup
Type:

Full scale

Vendor:

Joe Kimbrell
Thermo NUtech
Albuquerque, NM
(505) 254-0935 ext. 209

Technology:
Segmented Gate System (SGS)
- SGS is a combination of conveyor systems, radiation detectors (primarily gamma radiation), and computer control used to segregate waste by contamination level
- Detectors monitored radioactivity content of soil traveling on belt and computer opened specified gates to separate portions of soil based on radioactivity criteria
- Contaminated soil on conveyor belt was diverted by segmented gates into stockpiles
- Operating parameters included a belt speed of 30 ft/min, belt length of 16 18 ft, soil layer thickness of 2 in by width of 30.75 in, and soil density of 1.02 g/cm3
- Total soil processing time was 91.1 hrs; average daily operational time was 6.48 hrs
- Oversize debris and rock pre-screened

Cleanup Authority:
Voluntary Corrective Action

Management Support:
Ray Patteson
Sandia National Laboratories
(505) 884-1904

John McCann
Los Alamos National Laboratory
(505) 665-1091

Contaminants:
Natural Uranium (NU) and Depleted Uranium (DU)
- Concentrations reported as high as 431.46 pCi/g

Waste Source:
Nuclear weapon production operations

Type/Quantity of Media Treated:
Soil and Debris
- 2,526 yds3 of soil were processed
- Soil moisture content estimated as 12-15%

Purpose/Significance of Application:
Use of a gate system to reduce soil volume requiring off-site disposal

Regulatory Requirements/Cleanup Goals:
- Reduce the volume of contaminated soil by separating soil that was above the specified criteria and that would require off-site storage and disposal, from soil that was below the criteria
- The sorting criterion was 50 pCi/g

Results:
- Overall volume reduction of contaminated soil was 91.64%; approximately 350 yds3 of above-criteria soil required off-site disposal
- Average activities for soil from Sites C33-003, C33-010, and C33-007b were: above-criteria 318, 431.46, and 165.89 pCi/g, respectively, and below-criteria soil: 3.2, 44.8, and 9.88 pCi/g

Cost Factors:
- Actual cost for SGS was $275,745, including $6,600 for pre-deployment activities, $46,000 for mobilization, $185,445 for processing, $35,000 for demobilization, and $2,700 for final report
- Additional costs incurred by LANL were $543,400, including for staff, prime contractor, G&A, and soil disposal
- Overall unit cost of SGS was $103/yd3 of soil processed ($67/yd3 for processing)

Description:
Los Alamos National Laboratory (LANL) is a 43-square mile multi-disciplinary research facility owned by the U.S. DOE and located in north-central New Mexico. Technical Area 33 (TA-33), located in the eastern portion of LANL, is an active testing area. TA-33 was used to test initiators (components of nuclear weapons) from 1947 to the 1950's. This report focused on remediation of uranium-contaminated soil and debris from Potential Release Sites (PRSs) 33-007(b), 33-010(c), and C33-003 in TA-33. Historical records indicate that natural uranium (NU) and depleted uranium (DU) are present at these sites.

A Segmented Gate System (SGS) was used to reduce the volume of contaminated soil that required off-site disposal. SGS is a combination of conveyor systems, radiation detectors, and computer control, where contaminated soil on a conveyor belt is diverted by segmented gates into stockpiles by contamination level. Detectors monitor the radioactivity content of the soil traveling on the belt and a computer opens specified gates to separate portions of the soil based on radioactivity criteria. At this site, the overall volume reduction was measured as 91.64%. The actual cost for the application was $275,745, including $185,445 for soil processing. This corresponded to an overall unit cost of $103/yd3, including $67/yd3 for operations. Lessons learned included results from safety and electrical inspections, and operational failures from hydraulic systems, causing delays.