19.1.1 Radioactive waste (RAW) policy

The Government of Canada has policies, legislation and responsible organi­zations that ensure safe management of radioactive waste in Canada. The Government of Canada’s Policy Framework for Radioactive Waste consists of a set of principles governing the institutional and financial arrangements for management of radioactive waste (Natural Resources Canada, 1996). A key principle within the Policy Framework is that waste generators and owners are responsible, in accordance with the principle of ‘polluter pays’, for the funding, organization, management and operation of long-term waste management facilities and other facilities required for their wastes. The Policy Framework recognizes that arrangements may be different for the different categories of radioactive waste in Canada. In the case of nuclear fuel waste, the Government of Canada determined that it would be in the best interests of Canadians to have a national long-term management approach. In 2002, the Government of Canada brought into force the Nuclear Fuel Waste Act (NFWA), which outlines a process for the development and implementation of a long-term management approach for Canada’s nuclear

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fuel waste and required that an organization, the Nuclear Waste Manage­ment Organization (NWMO), be established to carry out the work.

J. M. MIL L E R and P. C. F. W O N G, Atomic Energy of Canada Limited (AECL) Nuclear Laboratories, Canada

DOI: 10.1533/9780857097446.2.612

Abstract: This chapter provides an overview of the policy and regulatory frameworks for radioactive waste in Canada. The chapter then discusses the strategies and long-term management approaches for various classes of radioactive waste generated from selected nuclear sectors, such as nuclear power generation, nuclear research, fuel fabrication, uranium mining, milling, refining and conversion, and radioisotope production and use. Lastly, the chapter provides examples of contaminated site cleanup and decommissioning projects, as well as lessons learned from implementing these projects.

Key words: policy and regulatory frameworks for radioactive waste, contaminated site cleanup, decommissioning, radioactive waste.

18.9.1 Background

In 1977, the DOE identified Yucca Mountain, Nevada, as a potential reposi­tory site for future investigation to host the nation ’s first deep geological repository for the disposal of SNF and HLW (Fig. 18.3). Other potential sites included bedded salts in Texas and Utah, salt domes in Louisiana and Mississippi, and basalt in the State of Washington. In 1982, Congress passed the NWPA, which established an office within the DOE with the responsi­bility of providing for the permanent disposal of SNF and HLW, and laid out the process for siting, developing, licensing, and constructing a geologic repository. In 1987, the NWPA was amended and directed the DOE to

investigate only one potential repository site, at Yucca Mountain. The period from 1987 to 2002 was devoted to site characterization of the Yucca Mountain site for a geologic repository, and the following years were dedi­cated to engineering studies and license application (LA) activities. In February 2002, the Secretary of Energy recommended the site to the Presi­dent, and the President recommended the site to Congress. In July 2002, Congress granted the authority to the DOE to prepare and submit a LA for constructing a repository at Yucca Mountain. The LA was submitted to the NRC in June 2008, and it was subsequently accepted for review by the NRC.

In early 2009, the Obama Administration determined that a repository at Yucca Mountain was not a workable option and that the project should be terminated. On March 3, 2010, the DOE filed a motion with an NRC Atomic Safety and Licensing Board (ASLB), seeking permission to with­draw the license application for a HLW repository at Yucca Mountain. On June 29, 2010, the ASLB issued an Order denying the DOE ’s motion to withdraw. This decision was appealed to the NRC. In October 2010, the NRC commenced and continued with the orderly closure of Yucca Moun­tain LA review activities. In September 2011, the Commission announced that the commissioners were evenly divided on the question of whether the ASLB Order should be overturned but, for budgetary reasons, ordered the ASLB to complete all pending case management matters. The ASLB sus­pended the licensing proceeding and, as of April 2012, the proceeding remains suspended.

The most important part of the DOE cleanup program is safety, which is integral to every program and project. In addition, DOE EM is implement­ing DOE Standard 1189 (DOE, 2008), which requires that safety-related documents and reviews be completed in the initial stages of the design process. DOE EM expects that integrating safety analyses up front in project design will avoid costly changes later (DOE, 2009).

Technology development is another key element of the cleanup program. The technology program is designed to provide a best-in-class science and engineering foundation and develop new technologies to reduce technical risk and uncertainty, support cleanup decisions, improve opera­tional efficiency, reduce costs, and accelerate schedules. In addition, laboratory — and pilot-scale testing is an important part of the technology maturation process.

The EM program has a strong commitment to reducing the technical risk of its programs and projects, and it is implementing two efforts to reduce those risks. This first is to conduct a Technology Readiness Assessment (TRA) to reduce the risks of deployment of a new technology. TRAs provide a snapshot in time of the maturity of technologies and their readi­ness for inclusion in the project. The results of a TRA assist program and project managers in developing plans to mature the technologies and to make decisions related to technology insertion. Eleven TRAs had been completed by the end of 2012.

The second effort is to conduct an External Technical Review (ETR) as one of several steps to ensure timely resolution of engineering and technol­ogy issues. The results of the reviews serve as a basis for developing strate­gies for reducing identified technical risks, and providing technical information needed to support critical project decisions. Twenty-five ETRs had been completed by the end of 2012.

Adhering to sound project management practices is essential. This includes, but is not limited to, developing comprehensive plans with a clear end-state for the site, defining clear project scopes, identifying and assessing risks, conducting system analyses, conducting peer reviews, establishing firm performance objectives, and anticipating unexpected outcomes.

The cleanup program would not be nearly so successful without the full involvement of its stakeholders, who provide insights and advice on how best to implement and improve it. The program has citizen advisory boards chartered under the Federal Advisory Committee Act at eight cleanup sites. The DOE also supports working groups with the National Governors Asso­ciation, National Conference of State Legislators, Energy Communities Alliance representing local governments, and State and Tribal Government Working Group. The DOE also works closely with its federal and state regulators to ensure that cleanup is being conducted in accordance with applicable laws, regulations, and compliance agreements, and in ways and according to schedules that protect public health and the environment (DOE, 2010). Continuous and transparent communication with stakehold­ers is vital.

The DOE’s cleanup mission poses unique, technically complex, and costly challenges, which can be achieved only through an exceptional workforce. The program’s 40,000 federal and contractor employees have the necessary skills and experience such that it is a world leader in the safe management and disposition of RAW and nuclear materials, as well as the remediation of contaminated facilities, soil, and groundwater (DOE, 2010).

In summary, the United States has extensive experience in cleanup of nuclear waste and facilities resulting from half a century of nuclear activities. The cleanup program has solved environmental problems that, at one time, seemed unsolvable; it will continue to make progress in solving the complex challenges it still faces (DOE, 2009).

18.8.1 US experience

For over five decades, the United States generated a large quantity and variety of nuclear wastes. Significant progress has been made in the treat­ment and disposal of these wastes and the cleanup and closure of nuclear sites. Much has been accomplished, but work remains to be done before the cleanup mission is complete.

The DOE has over 20 years of experience in site cleanup. DOE EM manages the DOE cleanup program, which has:

• stabilized millions of liters/gallons of radioactive tank waste

• completed 11 waste tank closures, including two in 2012 at the SRS in South Carolina

• operated the DWPF at the SRS since 1996 making 5,850 metric tons of borosilicate glass, which stabilized 1.5 x 106 Tera-Becquerels of radioactivity

• operated and completed waste processing at the West Valley Demon­stration Project (WVDP) in New York from 1996 to 2002 making -500 metric tons of borosilicate glass which stabilized 9 x 105 Tera-Becquerels of radioactivity

• begun construction of three major tank waste processing facilities.

The tank waste processing facilities include the WTP in Washington (2003), SWPF in South Carolina (2005), and the Sodium Bearing Waste Treatment Facility in Idaho (2003). The IWTU at the Idaho facility is expected to begin operations in 2013. See Section 18.7.6 for more detail about these three construction projects.

In addition, the world’s first geological repository — WIPP — began opera­tions in 1999, and had received over 11,000 shipments as of February 2013. The first CH TRU waste shipment arrived at WIPP from Los Alamos in 1999, and the first RH waste shipment arrived at WIPP from Idaho in 2007.

The DOE has also treated 240 km2 of contaminated groundwater and stabilized more than 180 contaminated groundwater plumes. It has exten­sive experience in deactivation and decommissioning (D&D), including D&D of about 1,500 facilities. For example, it is in the process of decom­missioning and demolishing the K-25 facility in Tennessee, a building nearly one mile long used to enrich uranium from 1945 to 1964. It contained nearly 5 million ft2 of floor space. Demolition of the west wing, which comprises just under half of the entire facility, began in 2008 and finished in 2010.

Another example of a completed D&D activity is the P Reactor in South Carolina (which was entombed in place using concrete grout to fill the rooms below ground level), disassembly basin, and reactor vessel. Cleanup of the Experimental Breeder Reactor-II in Idaho, which operated for about 30 years from the mid-1960s to the mid-1990s, is currently in progress. The systems and structures above the reactor building will be demolished and most of the remaining systems and structures will be grouted in place.

Other D&D projects include the K-Basins project and N Reactor closure in Washington. The K-Basins stored spent fuel; they were demolished in 2009, and remediation of the nearby soil was completed in 2010. N-Reactor operated from 1963 to 1987; its support facilities have been demolished, and it is being placed into safe interim storage.

The DOE has experience in LLW disposal. At the Hanford site, the Environmental Restoration Disposal Facility began operation in 1996 to dispose of contaminated soils, D&D waste, asbestos, and hazardous waste from onsite cleanup. Waste is disposed in cells approximately 150 x 150 m in area and about 20 m deep. Another LLW disposal facility at the Oak Ridge Reservation in Tennessee, the Environmental Management Waste Management Facility, has been operating since 2002.

The DOE has closed two former nuclear sites: the Rocky Flats Plant in 2005 and the Fernald Site in 2006. The Rocky Flats Plant was established in 1951 as part of the US nuclear weapons complex to manufacture nuclear weapons components. The site covers about 6,500 acres near the Rocky Mountains northwest of Denver. Most of the land served as a security buffer around an approximately 400-acre industrial area near the center of the site. When production of weapons components ended at Rocky Flats in 1994, its mission changed to cleanup and closure.

Because of operational problems and practices during the plant’s history, facilities contained substantial amounts of hazardous materials and con­tamination. Liquids remained in process piping and in tanks in unknown quantities and chemical configuration, which resulted in a significant envi­ronmental cleanup and closure challenge for the DOE.

In October 2005, the DOE and its contractor completed an accelerated ten-year, $6.7 billion cleanup of chemical and radiological contamination left from nearly 50 years of production. The cleanup required the decom­missioning, decontamination, demolition, and removal of more than 800 structures, including six processing and fabrication building complexes; removal of more than 500,000 m3 of LLW; and remediation of more than 360 potentially contaminated environmental sites. The majority of the prop­erty at the site was transferred to the US Department of Interior for man­agement by the US Fish and Wildlife Service as the Rocky Flats National Wildlife Refuge in July 2007 (DOE, 2011a).

The Fernald site, formally known as Feed Materials Production Center, was a uranium processing facility that produced high-purity uranium metal products as the first step in the US nuclear weapons production cycle. The site ’s production mission began in 1951 and continued until 1989, when production operations ceased and Fernald’ s mission changed to environ­mental remediation. The comprehensive environmental remediation and ecological restoration of the site was completed in 2006, at a total cost of $4.4 billion.

The 1,050-acre site, now known as the Fernald Preserve, is open to the public as a nature preserve. The ecological restoration has made the Fernald Preserve attractive to a large number of nesting and migrating birds, including locally rare species. Restoration activities at the site have created one of the largest man-made wetlands, including open water, forests, 360 acres of grassland, and seven miles of trails that provide access to varied habitats (DOE, 2011b).

Significant challenges remain in the DOE cleanup program. The DOE must safely store, retrieve, and treat approximately 340 million L (about 90 million gallons) of liquid radioactive waste stored in 230 underground tanks, remediate approximately 6.5 trillion L of contaminated groundwater, reme­diate approximately 40 million m3 of contaminated soil, and D&D over 2,500 facilities.

In addition, the DOE has decommissioned and cleaned up uranium mines and mill tailings. For conventional US uranium mills, waste is primarily the onsite disposal of tailings (residual ore after the uranium was leached). UMTRCA classified the tailings as either residual radioactive material or 11e.(2) byproduct material depending on the status of the facility at the time UMTRCA was passed in 1978. Since passage of UMTRCA, activities at Title I sites have focused largely on decommission­ing and cleanup of residual radioactive material by US governmental entities.

UMTRCA Title I required the DOE to complete surface remediation and groundwater cleanup at the listed inactive uranium milling sites at which uranium was processed solely for sale to the US government. Resid­ual radioactive material, including any wind-blown dust, may have been consolidated into a single cell or perhaps relocated to a cell constructed on another site. These cells are now under long-term surveillance by the DOE (or possibly by the state or tribal governments in which the cell is located) and licensed by the NRC. Annual site inspections are performed as part of the long-term surveillance program at 22 Title I disposal sites.

LLW is radioactively contaminated material that is not HLW, SNF, TRU, byproduct material, or naturally occurring radioactive material (DOE, 2009). Under the AEA, the DOE is self-regulating with regard to LLW. Mixed low-level waste (MLLW) is LLW that also contains a hazardous component and is, therefore, subject to a dual regulatory framework, under the AEA, including DOE Order 435.1, Radioactive Waste Management, as well as federal or state hazardous waste requirements promulgated under RCRA (DOE, 1999 ).

The strategy to deal with LLW and MLLW is:

• continue to utilize a combination of DOE onsite, DOE regional, and commercial disposal facilities

• complete an Environmental Impact Statement (EIS) for commercial GTCC waste and issue ROD for GTCC disposal facility

• reuse/disposition contaminated nickel

• build new onsite CERCLA cells

• continue to pursue treatment alternatives for wastes currently inciner­ated at the Toxic Substances Control Act Incinerator at the Oak Ridge Reservation in Tennessee

• continue to develop disposition plans for remaining legacy MLLW and LLW, eliminating waste acceptance and/or transportation barriers.

The DOE produced the Final Waste Management Programmatic Environ­mental Impact Statement (EIS) for Management, Treatment, Storage, and Disposal of Hazardous Waste in 1997 (DOE, 1997). The associated complex­wide decisions for treatment and disposal of LLW and MLLW were issued in 2000. These documents described the approach EM would use to elimi­nate the inventory of legacy LLW and MLLW, the latter in accordance with applicable regulatory agreements. As Table 18.5 illustrates, the DOE has an estimated 1.2 million m3 of LLW and MLLW.

While treatment and disposal of most LLW and MLLW are now routine, the DOE has inventories of both that lack readily available disposition options. The DOE is focusing on developing pathways for this waste. One category of waste for which a disposal solution has been developed is ‘silo material’, generated at the Fernald Site in Ohio. This waste was a byproduct of uranium processing, and the radium it contained emitted large amounts of radon. As a result, it was stored in heavily shielded concrete silos. Because of the nature of this material and the regulatory framework surrounding it, it required a specialized license.

The DOE worked closely with a vendor and state regulators in Texas to allow storage of the Fernald silo material at a Texas commercial facility. Removal of the silo material allowed the DOE to close the Fernald site on schedule in 2006 and greatly reduce the environmental risk of continued storage there. The vendor subsequently applied for a disposal license for this type of material and received the requested permit from Texas regula-

tors in 2008. The disposition path for the Fernald silo material is now final­ized and approved.

To complete cleanup of the Rocky Flats Plant in Colorado, the DOE supported technology development to decontaminate 1,500 gloveboxes suf­ficiently to allow equipment to be disposed of as MLLW or LLW. Glove — boxes are sealed chambers in which workers handle plutonium using long rubber gloves that extend through portholes. They range in size and can be as large as a bus. Previous disposition plans called for the gloveboxes to be reduced in size (cut into smaller pieces), packaged, characterized, and certi­fied for disposal at WIPP. This revised approach significantly reduced work exposure to contamination, workplace hazards, and associated costs.

DOE EM has the lead for developing the EIS for the disposal of GTCC low-level radioactive waste and GTCC-like waste. GTCC waste is LLW resulting from US NRC-licensed activities with radionuclides that would be dangerous to humans beyond 500 years. This waste stream comprises materials such as radioactive sources commonly used to sterilize medical products, detect flaws and failures in pipelines and metal welds, and serve other industrial and medical purposes. These materials were generated, owned, or managed by commercial entities rather than the DOE. However, the Low-level Radioactive Waste Policy Amendments Act of 1985 assigned the federal government responsibility for the disposal of certain GTCC radioactive waste resulting from US NRC-licensed activities.

GTCC waste is the highest radiological activity waste with no planned disposition path. The DOE is preparing an EIS to evaluate disposal options for commercial GTCC LLW as well as LLW similar in character to GTCC generated by the DOE. The DOE issued a Notice of Intent to prepare the EIS in July 2007. A draft EIS was issued by the DOE in February 2011, and a final EIS is expected to be released in 2013. By law, before the DOE makes a final decision on the disposal alternative(s) to be implemented, the agency must submit a report to Congress and await Congressional action before making a final disposal decision.

Contaminated nickel from the shutdown of gaseous diffusion plants is a potentially valuable asset. The DOE is evaluating the feasibility of recover­ing the nickel for potential sale to an end user rather than disposing of it as LLW.

TRU waste is a type of RAW that contains elements with atomic numbers greater than uranium (DOE, 2009). This waste consists primarily of clothing, tools, rags, residues, soil, debris, and other materials contaminated with plutonium; it may also be mixed with hazardous components. There are two categories of TRU waste: CH TRU waste can be handled by workers under very controlled conditions with no shielding for radioactivity other than the container itself, while RH TRU waste must be handled and transported in lead-shielded containers and casks because it emits more penetrating radiation. CH TRU represents 96% of the total volume of TRU waste to be disposed of at WIPP, while RH TRU makes up the remaining 4%.

Before WIPP opened, 28 DOE sites were storing TRU waste in a variety of configurations, primarily below-grade to contain the radioactive ele­ments while also allowing for its eventual retrieval for disposal. After nearly 20 years of testing, scientific research, engineering and design, and regula­tory permitting, WIPP began receiving CH TRU waste in 1999. In 2006, WIPP received final authorization to begin accepting RH TRU and the first shipment, from INL, arrived in January 2007.

Located 2,150 feet below ground in a 250 million-year-old salt formation, WIPP is the world ’s only operating deep geological repository. An esti­mated 150,000 m3 of CH TRU and 7,000 m3 of RH TRU resulting from US Cold War defense activities will ultimately be disposed of there.

Between 2002 and 2008, the DOE de-inventoried all legacy TRU waste at 14 sites, thereby eliminating associated management costs at these sites as well as environment, safety, and health risks. TRU waste was also removed from facilities at the NNSS, Lawrence Livermore National Laboratory, and Argonne National Laboratory (ANL) so they can support other missions.

As of February 2013, WIPP had received 11,112 shipments of TRU waste since it opened in 1999. These years of experience and a streamlined regula­tory framework have resulted in more efficient and routine operations with each passing year. The DOE has a clear strategy for building on this past success to meet its TRU risk reduction goals:

• characterize a small quantity of waste in Idaho for shipment to WIPP

• expand use of Central Characterization Project (CCP)

• facilitate shipping sites in certifying waste for acceptance at WIPP

• expand number of sites certified for RH shipping

• deploy shielded containers for shipping RH TRU.

This strategy includes expanding the number of sites certified for RH TRU shipping. To support and enhance this strategy, the DOE continues to develop shielded containers for RH TRU lead-lined drums that allow RH TRU waste to be handled, shipped, and potentially disposed of in a manner similar to CH TRU waste. Currently, RH TRU waste is emplaced in bore­holes along the walls of the WIPP repository and CH TRU waste is placed on the floors.

Significant coordination is required for optimal and efficient emplace­ment of RH TRU and CH TRU waste. The use of shielded containers for placement of selected RH TRU waste on the floors of the repository could increase the efficiency of disposal operations at WIPP. The DOE is actively pursuing the necessary regulatory approvals needed to move forward with shipping and disposing of RH TRU waste in shielded contain­ers at WIPP.

Another TRU waste risk-reduction strategy is the characterization of small-quantity TRU waste sites in Idaho for shipment to WIPP. A Record of Decision (ROD) approved in February 2008 allows the DOE to send waste from small-quantity sites to INL for treatment, characterization, and shipment to WIPP, assuming the waste meets INL waste acceptance criteria. This reduces costs by eliminating the need to construct TRU waste treat­ment facilities at sites with small quantities of TRU waste. It also results in faster removal of TRU from these sites and a greater economy of scale for the TRU waste facility at INL.

The DOE is also expanding the use of the CCP at large sites. The project employs a modular waste characterization system consisting of full disposal characterization equipment for both CH TRU and RH TRU waste and a mobile loading system used to place drums of TRU waste into shipping containers for transport to WIPP. CCP has proven successful in character­izing waste more cost effectively through use of a standard suite of proce­dures, quality assurance documents, and equipment.

Another strategy includes the use of TRU waste expert teams to assist generator sites in certification and characterization planning for waste streams that are more difficult to manage, such as those requiring additional documentation, treatment, or packaging. These teams help to ensure all TRU waste is characterized, shipped, and disposed of at WIPP.

The DOE has designed a new cask, TRUPACT-III, for TRU waste pack­aged in large boxes that cannot be shipped in currently available transporta­tion casks due to their size. The strategy to ship and dispose of large-size containers at WIPP also requires the development, deployment, and regula­tory approval of equipment needed to determine the contents of large containers. With this knowledge, the potentially dangerous and costly task of reducing the size of large containers before shipment and disposal at WIPP can be avoided.

Until a repository for permanent disposal becomes available, the DOE will store canisters of solidified high-activity tank waste onsite. The stabilized product of LAW treatment at WTP and at Saltstone (facilities for safely stabilizing and disposing of low-level radioactive liquid salt wastes) will be disposed of onsite in stainless steel containers at Hanford and in concrete vaults at SRS, respectively. These wastes contain only 1-10% of the radio­activity present in the tank waste.

Tanks at INL and Hanford contain liquid wastes that are not radioactive wastes generated from the reprocessing of SNF. The DOE plans to pursue alternative but safe, compliant, and more cost-effective disposal paths for these wastes on a case-by-case basis. For example, some may meet the cri­teria for disposal at the WIPP.

Once the waste has been retrieved to the maximum extent practicable, the next step is to separate it chemically and physically into two fractions: the higher-volume portion that contains shorter-lived, less radioactive elements (i. e., LAW) and a much smaller fraction that contains longer-lived, radioac­tive elements (i. e., HAW). The two fractions are then treated separately to convert them to stable, solid forms. The LAW is proposed to be disposed of onsite, and the HAW is proposed to be disposed of offsite in a geological repository.

The Salt Waste Processing Facility (SWPF) and the Waste Treatment and Immobilization Plant (WTP) are being constructed at SRS and Hanford, respectively, to treat and immobilize radioactive tank waste. SRS is com­pleting the design and construction of the SWPF. The SWPF will separate the LAW and HAW fractions, solidifying the former as a grout in the exist­ing Saltstone facility for disposal onsite in large vaults. The HAW fraction will be sent to the Defense Waste Processing Facility (DWPF), which has operated since 1996, where it will be converted to a stable glass form using vitrification. DWPF has vitrified HAW into 3,325 canisters as of December 2011 that are stored onsite in special-purpose facilities awaiting disposal in a geological repository.

To maintain the compliance-driven schedule for closing SRS tanks and to address risk more quickly, SRS began operating two interim tank-waste processing facilities (the Actinide Removal Process and the Modular Caustic Side Solvent Extraction Unit) in advance of SWPF startup to sepa­rate out LAW for onsite disposal. The DOE continues to pursue strategies to optimize the capacity of these facilities to complete treatment of the tank waste in a cost-effective manner.

The WTP, now under construction at Hanford, will also separate the LAW and HAW tank fractions. It will then vitrify the two waste frac­tions, with the LAW disposed of onsite and the HAW disposed of in a geological repository. Operation of the WTP facility is scheduled to begin in 2019.

The remaining INL tank waste will be treated in the Integrated Waste Treatment Unit (IWTU) at the Sodium Bearing Waste Treatment Facility forming a crystalline ceramic (mineral) waste form by fluidized bed steam reforming for ultimate disposal at WIPP. A vitrification plant constructed at West Valley has converted the radioactive tank waste there into 275 canisters of glass.

The first step in mitigating the risks posed by the tanks is to remove the waste, particularly focusing on the older single-shell tanks (as opposed to an inner and outer double-shell tank with space in between for containing and monitoring any leakage). This was already accomplished at Hanford where nearly 11.3 million L (3 million gallons) of liquids that could be removed from single-shell tanks physically and cost-effectively were retrieved and moved into double-shell tanks. At other sites, tanks have been emptied to the maximum extent practicable and then backfilled with con­crete or grout to stabilize the small amount of contamination remaining. Since 2002, seven 1.1 million L (300,000 gallon) underground storage tanks and four smaller 111,000 L (30,000 gallon) ancillary tanks at the INL have been emptied, cleaned, and filled with concrete. In addition, two 4.9 million L (1.3 million gallon) SRS tanks were closed and grouted in 1997, and an additional two were filled with concrete in 2012.