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Stabilization/Solidification - 8.3 Case Study #3

8.3 Case History #3: Radioactive Waste Stabilization at the US Department of Energy Savannah River Site (SRS), SC

8.3.1 Background 

The Savannah River Site (SRS) is a nuclear reservation in the state of South Carolina, US. The Saltstone facilities, opened in 1990, are part of SRS and use S/S technologies to treat low-level radioactive liquid salt wastes. The facilities consists of two components: the Saltstone Production Facility (SPF) and the Saltstone Disposal Facility (SDF) ("Fact Sheet of Saltstone Facilities", 2012). The Saltstone Facility is located in the Z-Area at the SRS and it is designed to process about 30,000 gallons of waste per day. The objective of the facility is to stabilize liquid mixed waste to make the waste suitable for disposal in a Subtitle D landfill. (Conner, 2004). See the location and facility in figures 8.3 and 8.3.1 below.

8-2

Figure 8.3: Location of SRS (http://sti.srs.gov)

 

8-3-a

 (a) Saltstone Production Facility (SPF) 

 

8-3-b

(b) Slatstone Disposal Facility (SDF)

Figure 8.3.1: Overview of Saltstone facilities (www.flickr.com)

 

8.3.2 Components of the waste 

The waste is an aqueous solution containing about 30 wt% dissolved sodium salts with radioisotopes. The salts are the product of the neutralization reaction between sodium hydroxide and acids used in the isotope extraction processes. (Conner, 2004)

8.3.3 Delivery System 

The current Saltstone Processing Room is a hands-on-maintenance facility, as shown in Figure 8.3.3. A schematic of the facility is shown in Figure 8.3.3.1.

 8-4

Figure 8.3.3: Processing room for SRS Saltstone facility for Case Study #2 (Conner, 2004)

 8-5

Figure 8.3.3.1: Schematic of the SRS Saltstone Facility for stabilizing radioactive salt waste for Case Study #2 (Conner, 2004)

 

8.3.4 Operations 

The Saltstone Facility began operation to treat radioactive waste in June 1990 and about 3,500,000 gallons of radioactive hazardous liquid waste and 100,000 gallons of high-solids slurry have been processed. (Conner, 2004) 

The S/S treatment of Sandstone Facility is realized by combining S/S binders, cement, slag, and fly ash with waste solution. The nominal composition of the mixture is listed in Table 8.3.4. The facility processes about 100 gallons of waste solution per minute, which requires transferring about 35 tons of cementitious reagents per hour. The mixing process is executed by a twin-shaft Readco continuous processor. The waste product is pumped over 2000 ft through a 3-inch carbon steel line and is disposed in SDF.  

Table 8.3.4: Nominal composition of mixture - Case study #3      

Component

Wt% of the product

Waste salt solution with 29 wt% radioactive dissolved sodium salts

46

Premixed reagents

 

Portland cement

6

Gound granulated blast furnace slag

24

Fly ash

24

          Source: Conner, 2004

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