Waste Management
SRS Liquid Waste Program
Radioactive liquid waste is generated at SRS as a by-product from the processing of nuclear materials for national defense, research, medical programs, and outer space missions. The waste, totaling about 33 million gallons, is stored in the remaining 43 underground carbon-steel waste tanks grouped into two tank farms at SRS. The waste tanks nominally hold a million gallons each. The liquid waste program at SRS consists of high-hazard operations, which include complex engineering, operations, construction, waste treatment, grouting, and disposal in order to operationally close the radioactive liquid waste tanks.
Waste Disposition
Waste Retrieval & Operational Tank Closure
SRS is home to two Tank Farms, or the areas where the underground waste tanks are located. H Tank Farm receives the waste byproduct generated from chemical separations operations at H Canyon. There are 51 tanks total located in H Tank Farm and F Tank Farm, eight of which have been operationally closed. Operational tank closure means the waste has been removed from the tanks, cleaned the maximum extent practical, and filled with a specially formulated grout.
As the waste is stored in the tanks, it mostly separates into a dense sludge that settles at the bottom of the tank, a hardened saltcake, and a salt supernate (liquid) at the top. The highly radioactive sludge waste is transferred to the Defense Waste Processing Facility to be turned into a solid glass form. The less-radioactive salt waste is transferred to the Salt Waste Processing Facility for decontamination so it can be turned into a solid grout form.
Evaporators & Effluent Treatment Facility
In the waste tanks, water sits on top of the waste and is dispositioned through an evaporation process. The evaporators reduce the waste to about 30 percent of its original volume, making tank space available for continuing liquid waste operations. Creating tank space supports cleaning and closure of the tanks, as well as other SRS missions. The condensed evaporator “overheads” are transferred to the Effluent Treatment Facility for final cleanup prior to release to the environment.
Waste Solidification
Defense Waste Processing Facility
The sludge waste, the highly radioactive portion, is transferred to the Defense Waste Processing Facility (DWPF) where it is converted into a solid glass form suitable for long-term storage and disposal. This waste contains the majority of the radioactivity in the tank waste and requires permanent isolation from the environment.
Scientists have long considered this glassification process, called “vitrification,” as the preferred option for immobilizing high-level radioactive liquid into a more stable, manageable form. In this vitrification process, a sand-like borosilicate glass (called “frit”) is mixed with the waste and sent to the plant’s 75-ton melter, where the waste/frit mixture is heated until molten. This molten mixture is poured into stainless steel canisters to cool and harden to form a stabilized glass. Turning this waste into glass makes the sludge waste safe for long-term storage and disposal.
and the Defense Waste Processing Facility (background)
Salt Waste Processing Facility
The salt waste, the less radioactive portion but majority of the tank waste, is transferred to the Salt Waste Processing Facility (SWPF).SWPF is designed to significantly increase the site’s ability to empty and close the waste tanks and dramatically reduce the legacy environmental risk.
SWPF receives salt waste from the Tank Farms and decontaminates it by removing the highly radioactive contaminants through a two-step process using filtration and specialty solvents. The first step (called the Alpha Strike Process) removes strontium and actinides (like uranium and plutonium) from the waste. The second step (called Caustic Side Solvent Extraction, or CSSX), removes the highly radioactive cesium. After this separation process is completed, the decontaminated salt solution goes to the Saltstone Production Facility to form a grout that hardens, and the concentrated high-activity waste is sent to the nearby Defense Waste Processing Facility to form a glass.
Saltstone Production Facility
The decontaminated salt solution processed at SWPF is sent to the Saltstone Production Facility (SPF) forsafe treatment and disposal.After the waste is received at SPF, the salt solution is mixed with dry materials (fly ash and blast furnace slag) to form grout. The grout is pumped from SPF into above-ground saltstone disposal units, where it hardens into a monolithic, non-hazardous form called saltstone. This process makes the salt waste safe for permanent disposal.
Waste Disposal
Glass Waste Storage Buildings
The canisters poured at the Defense Waste Processing Facility are moved by a one-of-a-kind shielded transporter from the facility to one of two Glass Waste Storage Buildings nearby. These buildings consist of a below-grade, seismically qualified steel and concrete vault containing support frames for vertical storage of the canisters. The canisters will be stored safely in these buildings until a federal repository for high-level waste is established.
Saltstone Disposal Units
The Saltstone Disposal Units (SDUs) are large, circular concrete units used for permanent disposal of the decontaminated salt solution (DSS) at SRS. Before this material is put into the SDUs, it was decontaminated at the Salt Waste Processing Facility then mixed with dry materials at the Saltstone Production Facility to form the grout that hardens into saltstone.
The original circular SDUs at SRS are much smaller (a capacity of about 3 million gallons) than the mega-size ones you see aboveground today. The mega-size SDUs have about a 33-million-gallon capacity. SRS will be home to 7 mega-size SDUs once they are all built. The larger SDU design will result in substantial cost savings because of the economies of scale, requiring less infrastructure and materials to design and build.
Solid Waste Management
The Savannah River Nuclear Solutions (SRNS) Solid Waste Management (SWM) department at the Savannah River Site (SRS) supports the site’s national security, nonproliferation and environmental cleanup activities by managing newly generated and backlogged and legacy wastes that exist at various facilities throughout SRS. Our goal is to eliminate legacy waste left after the Cold War Era and treat, store and dispose of newly generated waste.
Each day SWM faces the challenge of reducing the volume of waste generated sitewide and safely treating, storing and disposing of waste in the most environmentally-efficient and cost-effective manner possible.
SRS’s waste is categorized as transuranic, low-level, hazardous, mixed, high-level or sanitary waste. SWM is responsible for managing all of these categories except for the high-level waste.
Transuranic Waste
Transuranic (TRU) waste is waste contaminated with radioactive isotopes that have decay rates and activities exceeding defined levels. It contains man-made elements that are heavier than uranium and decay slowly, thus requiring thousands of years of isolation. TRU wastes can include equipment, protective clothing and tools used in the production and management of these radionuclides. In FY2009, 115 shipments including over 490 cubic meters of legacy TRU waste were shipped to the Waste Isolation Pilot Plant in New Mexico.
Low-Level Waste
Low Level Waste is any radioactive waste not classified as high level or TRU waste. Examples include slightly contaminated soil, D&D debris, protective clothing, job-control waste, equipment, tools, filters, rags and papers. In FY2009, 5,476 cubic meters of solid Low Level Waste were accepted for on-site disposal.
Hazardous Waste
The Resource Conservation and Recovery Act defines hazardous waste as any toxic, corrosive, reactive or ignitable material that could damage the environment or negatively affect human health. Some examples of SRS hazardous waste include oils, solvents, acids, metals, and pesticides. In FY2009, SWM disposed 179 cubic meters of hazardous waste at Environmental Protection Agency-regulated offsite treatment and disposal facilities.
Mixed Low Level Waste
Mixed Low Level Waste (MLLW) is waste that is both radioactive and hazardous. This type of waste is subject to regulations governing both waste types. In FY2009, the Mixed Low Level Waste program met all of its Site Treatment Plan commitments. The Site Treatment Plan represents an agreement among SWM, the Department of Energy, and the South Carolina Department of Health and Environmental Control to properly treat SRS’s mixed waste on a specified schedule. During FY2009, SWM disposed offsite 407 cubic meters of MLLW.
Sanitary Waste
Sanitary Waste (SW) includes both non-radioactive and municipal wastes (office waste, food, garbage, refuse and other solid wastes that are similar to those generated by most households) and typical industrial wastes (construction debris, scrap metals, wood waste, etc). During 2009, more than 85,000 tons of Sanitary Waste were disposed from SRS.
SRS has a recycling program using the City of North Augusta’s Material Recovery Facility (MRF). The MRF recovered about 1,000 tons of the municipal-type waste stream material in 2009 including white office paper, newspaper and magazines, cardboard, plastic, steel cans, aluminum cans and glass. Using the MRF resulted in SRS recovering and recycling about 40 percent from this part of the sanitary waste stream.