ATG Process for Stabilizing Mercury (<260 ppm) Contaminated Mixed Waste from U.S. DOE's Portsmouth, Ohio Facility

Site Name:

Portsmouth Gaseous Diffusion Plant

Location:

Portsmouth, Ohio

Period of
Operation:

1998

Cleanup
Type:

Field demonstration

Vendor:

Allied Technology Group
Fremont, CA

Technology:
Stabilization
- Stabilization reagents included proprietary dithiocarbamate (DTC), phosphate, polymeric reagents, and generic reagents such as magnesium oxide and activate carbon
- Bench-scale and field demonstration tests were conducted
- Bench-scale tests showed that DTC without other reagents provided the best results
- Field demonstration tests were conducted on three-33 kg batches of waste, using a 7 ft3 mortar mixer

Cleanup Authority:
Not identified

Contacts:
Thomas B. Conley
Oak Ridge National Laboratory
Telephone: (423) 241-1839
Fax: (423) 241-2973
E-mail: tbc@ornl.gov

William Owca
DOE Idaho Operations Office
Telephone: (208) 526-1983
Fax: (208) 526-5964
E-mail: owcawa@inel.gov

Contaminants:
Heavy metals and Radionuclides
- Mercury concentration was 1.06 mg/mL
- Technetium-99 present at 680 pCi/g
- Other heavy metals included barium, cadmium, and chromium

Waste Source:
Nuclear processing operations

Type/Quantity of Media Treated:
Ion exchange resin
- 160 kg of resin (liquid waste) containing <5% solids

Purpose/Significance of Application:
Demonstrate stabilization of low level mercury in radioactive wastes

Regulatory Requirements/Cleanup Goals:
- Universal treatment standard (UTS) for mercury of 0.025 mg/L

Results:
- Mercury concentrations were reduced on average from 1.06 to 0.0092 mg/L, below the UTS of 0.025 mg/L; 99% of the mercury was stabilized
- Cadmium, the other heavy metal present at concentrations higher than the UTS, was reduced on average from 0.371 to 0.053 mg/L, below the UTS of 0.11 mg/L; 86% of the cadmium was stabilized
- The average density of the treated waste was 1.17 kg/L, which was a 17% weight increase and a 16% volume increase from the untreated waste
- No mercury vapors or radioactivity was detected during the demonstration

Cost Factors:
- Projected costs for a 1,200 lb/hr stabilization system included capital costs of $30,000 and operating costs of $95/hr of operation
- These correspond to a life cycle cost of $1.73/kg, without decontamination and decommissioning

Description:
Allied Technology Group (ATG) conducted a demonstration of stabilization of mixed wastes containing less than 260 ppm of mercury. The ATG technology used dithiocarbamate (DTC) to stabilize 160 kg of ion exchange resin containing <5% solids. The resin was contaminated with heavy metals including mercury and cadmium.

The DTC formulation stabilized mercury and cadmium to concentrations lower than the UTS, with a relatively small increase in weight and volume. A life cycle cost of $1.73/kg of waste was projected for use of this technology at a full scale.