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 1.0 g/cm3
- Average daily operational time was 2.67 hrs
- Oversize debris and rock pre-screened
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Cleanup Authority:
RCRA Corrective Action
Site Contact:
Martin Amos
Battelle Pantex
(806) 477-6458 | Management Support:
Tom Burford
Sandia National Laboratories
(505) 845-9893
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Contaminants:
Depleted Uranium (DU)
- Concentrations reported as high as 567 pCi/g |
Waste Source:
Firing range for test shots of depleted uranium and explosives |
Type/Quantity of Media Treated:
Soil and Debris
- 294 yds3 of soil were processed
- Soil moisture content estimated as 17% |
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 38.5%; approximately 180.8 yds3 of above-criteria soil required off-site disposal
- Average activities ranged from 125 - 213 pCi/g for above-criteria soil and 20 - 54 pCi/g for below-criteria soil |
Cost Factors:
- Actual cost for SGS was $203,887, including $18,768 for regulatory and compliance issues, $103,015 for mobilization, $32,594 for soil processing, and $49,510 for demobilization
- Additional costs incurred by LANL were for site preparation, excavation, oversight labor, health physics support, sample analysis, and waste disposal (specific cost data not provided)
- Unit cost of SGS was $111/yd3 for soil processing |
Description:
Firing Site 5 (FS-5) is within the boundaries of the Pantex Plant, located northeast of Amarillo, Texas. The site was used to conduct test shots of combined explosives and depleted uranium. The firing site was surrounded on three sides by an earthen berm 10 ft high and 33 ft thick at the base. Soil at the site was contaminated with depleted uranium (DU).
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 based on 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 for the first 294 yds3 of soil treated was measured as 38.5%, and the results were determined to be unsatisfactory; processing was terminated at this time. The actual cost for the application was $203,887, including $32,594 for soil processing. This corresponded to a unit cost of $111/yd3 for soil processing. Lessons learned included problems with using a hand survey method for classifying soil, which resulted in misclassifying soil as above the SGS criterion, and the method used each day to cover and uncover the piles. |
