GTS Duratek (GTSD) Process for Stabilizing Mercury (<260 ppm) Contaminated Mixed Waste from U.S. DOE's Los Alamos National Laboratory

Site Name:

Los Alamos National Laboratory

Location:

New Mexico

Period of
Operation:

September 1997 to September 1998

Cleanup
Type:

Treatability studies

Vendor:

GTS Duratek
Kingston, Tennessee

Technology:
Stabilization
- Stabilization reagents involved addition of water and then cement to form a grout mixture; the mixture was then blended with sodium metasilicate and cured for two days
- Bench- and pilot-scale tests were conducted, at high and low waste loadings
- Pilot-scale tests were conducted in drums using a vertical in-drum 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, Volatile Organics, and Radionuclides
- Mercury concentration was 230 mg/kg; TCLP 0.0399 to 0.184 mg/L
- DCE concentration was 11,000 mg/kg, vinyl chloride 220 mg/kg, methylene chloride 12,000 mg/kg
- Radionuclides included plutonium and strontium

Waste Source:
Nuclear processing operations

Type/Quantity of Media Treated:
Sludge and Laboratory Wastes
- Four 55-gallon drums containing 1,253 lbs of sludge
- Three containers of lab packs from analysis of the sludge

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

Regulatory Requirements/Cleanup Goals:
- Land Disposal Restrictions for heavy metals (such as mercury - 0.025 mg/L) and organics
- Envirocare Waste Acceptance Criteria (WAC) for disposal

Results:
- At low waste loadings, mercury concentrations were reduced to values ranging from 0.00127 to 0.0169 mg/L, below the LDR standard of 0.025 mg/L; at high waste loadings, mercury was reduced to values ranging from 0.0024 to 0.0314 mg/L one sample contained mercury above the LDR standard
- Several organic compounds and radionuclides were higher than the LDR standards or Envirocare WAC after treatment, including 1,1,1-trichloroethane, 1,1-dichloroethane, methylene chloride, lindane, DDE, heptachlor epoxide, and methoxychlor, strontium, and americium
- The vendor indicated that these results re-emphasized the importance of accurate characterization data; the high levels of organics were not expected based on the original characterization data provided by LANL
- Bench-scale tests showed mercury met LDR level in all 3 low load and 2 of 3 high load samples

Cost Factors:
- Projected costs for a full-scale stabilization system using this technology were not developed

Description:
Sludge was generated at the Phase Separation Pits of the TA 35 facility of the Los Alamos National Laboratory (LANL) by addition of a caustic solution to the condensate and particulates removed from laboratory fume hood exhausts by the phase separators. The sludge and laboratory wastes from analysis of the sludge, were a mixed waste due to the presence of radionuclides, heavy metals, and RCRA-listed organic compounds.

Bench- and pilot-scale tests of the GTS Duratek process were conducted to stabilize the contaminants in the sludge and laboratory wastes. The GTS Duratek process includes addition of water, cement, and sodium metasilicate. The stabilized product met the LDR standard for mercury in all but one high load test sample. However, several VOCs, pesticides, herbicides, and radionuclides did not meet the LDR standards or Envirocare WAC after treatment. This result was attributed to inaccurate characterization data of the waste streams, which did not show the relatively high levels of organics.