Thermo Nutech's Segmented Gate System at Sandia National Laboratories, ER Site 228A, Albuquerque, New Mexico

Site Name:

Sandia National Laboratories


Albuquerque, New Mexico

Period of

July - November 1998
(soil processing from November 6-17, 1998)


Full scale


Thermo NUtech
A ThermoRetec Company
4501 Indian School Road NE, Suite G105
Albuquerque, NM 87110

Segmented Gate System (SGS)
- SGS is a combination of conveyor systems, radiation detectors (primarily gamma radiation), and computer control
- Contaminated soil on conveyor belt was diverted by segmented gates into stockpiles
- Detectors monitored radioactivity content of soil traveling on belt and computer opened specified gates to separate portions of soil based on radioactivity criteria
- 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 1.29 g/cm3
- Average daily processing time was 4.47 hrs, less than the target of 7 hrs
- Oversize debris and rock pre-screened using a field grizzly (vertical bar grate) and hammermill

Cleanup Authority:
Not identified

Site Contact:
Sandia Corporation
Technical Support:
Sue Collins
Sandia National Laboratories
(505) 284-2546

Depleted Uranium (DU)
- Concentration not provided

Waste Source:
Burial pits

Type/Quantity of Media Treated:
- 1,352 yds3 of soil were processed
- Extended 0.4 acres at a depth of 2 ft
- Soil identified as sandy, moisture content estimated as 10%

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 27 pCi/g

- Overall volume reduction was measured as 99.56%; 21 55-gallons drums of above-criteria soil required off-site disposal
- Average activity of above-criteria soil was 223 pCi/g and below-criteria soil 14.77 pCi/g
- 5.2 yds3 of soil from Burn Site showed volume reduction of 99.4%

Cost Factors:
- Actual cost was $220,040, including $29,000 for excavation and pre-screening, $41,300 for mobilization, $117,000 for operations, and $32,340 for demobilization
- Overall unit cost was $154/yd3, including $82/yd3 for operations, reflecting the relatively small quantity of soil processed
- Project contracted as a lump sum fixed price; did not include excavation, oversight labor, health physics support, water supply, fuel services, generator support, sample analysis, and waste disposal

Environmental Restoration (ER) Site 228A, the Centrifuge Dump Area and Tijeras Arroyo Operative Unit-ADS 1309, is located 500 ft east of Technical Area II, within Kirtland Air Force Base. In July 1997, heavy rains eroded a portion of a depleted uranium burial from the Tijeras Arroyo rim. Depleted uranium mixed with soil and debris washed down the slope.

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. 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 99.56%. The actual cost for the application was $220,040, including $29,000 for excavation and pre-screening, $41,300 for mobilization, $117,000 for operations, and $32,340 for demobilization. This corresponded to an overall unit cost of $154/yd3, including $82/yd3 for operations. Lessons learned included impacts from weather delays and equipment concerns, and difficulties with rocks that were 3 inches in diameter.