Environmental Engineering Reference
In-Depth Information
contamination. For landfill and structural closures, stabilization is also intended to
provide structural stability to prevent future subsidence of overburden and in some
cases mitigation of inadvertent intruders.
13.4.4.2
Saltstone Facility
The Saltstone Facility was originally permitted in 1986 as a wastewater treatment
facility to treat and dispose of decontaminated salt solution from the In-Tank Pre-
cipitation process, which was intended to remove radioisotopes from dissolved high-
level waste salt prior to treatment and disposal in Z-Area. The permits were modified
in 1988 to provide for treatment of the residues from the Effluent Treatment Facility.
13.4.4.2.1 Treatability Studies
The waste is an aqueous solution that contains up to about 30 wt% dissolved sodium
salts. These salts are the result of sodium hydroxide neutralization of acids used in
the isotope extraction processes that were performed at the site.
13.4.4.2.2 Delivery System
The Saltstone Facility is located in Z-Area at the DOE Savannah River Site and is
operated by the Westinghouse Savannah River Company. The Saltstone Facility was
designed to process about 30,000 gallons of waste per day with an attainment of
about 6,000,000 gallons per year. The processing objective is to stabilize liquid
mixed waste so that the resulting waste form can be disposed of as low-level
radioactive waste in a Subtitle D landfill. A schematic of this facility is shown in
Figure 13.12.
The current Saltstone Processing Room is a hands-on-maintenance facility, as
shown in Figure 13.13. The processing equipment in this figure is viewed from the
control room. The facility as shown here is currently processing very low-activity
waste and is operated as a hands-on-maintenance facility. Modifications are planned
to add shielding so that the facility can treat waste containing up to 0.1 Ci waste.
Blending and transfer of the stabilizing reagents is also carried out from the control
room. The primary components of the processing facility in Figure 13.13 are a mixer,
the waste, solution feed stabilizing, the reagents, the waste form, a slurry tank, and
a pump.
13.4.4.2.3 Operations
The Saltstone Facility began processing radioactive waste in June 1990. Since then
approximately 3,500,000 gallons of radioactive hazardous liquid waste and 100,000
gallons of high-solids slurry have been processed through the facility. In 2002, SRS
submitted a permit change to allow processing salt solution with up to 0.1 Ci, an
increase of three orders of magnitude. In 2003, modifications were begun to enable
processing of the higher-activity waste for a new program referred to as Low Curie
Salt Processing. The Saltstone waste form is prepared by combining preweighed
and premixed binders with salt solution as illustrated in Figure 13.12. Processing
admixtures may also be added to the formulation. The nominal composition of
Saltstone is listed in Table 13.9. The facility treats about 100 gallons of waste solution
per minute. This production rate requires transfer and metering of about 35 tons of
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