The second workshop, held on January 9-10, 2014, focused on post-closure controls and assessment of long-term performance of site remedies. Additionally, best practices for risk-based remediation decisions for contaminated sites were discussed and highlighted. The agenda for this workshop can be found in Appendix E.
- Effective and efficient risk-informed decision making;
- Approaches for assessing long-term performance of site remedies;
- Effective post-closure controls, monitoring, and long-term stewardship; and
- Identification of best practices for improving remediation/closure/post-closure of challenging sites.
All but the fourth session followed a similar format: an expert introduced the subject matter and then presenters highlighted case studies on that subject. A discussion was held after each presentation. The fourth session involved a round-robin discussion, which allowed the invited speakers representing tribal, federal, state, regulatory, academic, and practitioners to express viewpoints on best practices for effective site remediation. The final chapter of this report, Chapter 6, summarizes the goals of the workshops and the participants’ perspectives on each.
All workshop presentations are available online: http://dels.nas.edu/Past-Events/Best-Practices-Risk-Informed-Remedy/AUTO-8-12-72G?bname=nrsb. This summary was written by a rapporteur to present the various ideas and suggestions that arose in the workshop discussion and to synthesize the main discussion items. It does not include conclusions or recommendations, nor does it cover the full spectrum of issues around this topic.
The remainder of this chapter is based on a white paper (Heimberg 2014) distributed to the workshop participants and is intended to provide the reader with background information regarding selected nuclear legacy
Definitions of Waste Types
Definitions of the types of radioactive wastes are listed below.
Waste Types Definitions
High-level Waste (HLW)
HLW is defined in U.S. Code, Title 42, Section 10101 as
(A) the highly radioactive waste material resulting from the reprocessing of spent nuclear fuel, including liquid waste produced directly in reprocessing and any solid material derived from such liquid waste that contains fission products in sufficient concentrations; and
(B) other highly radioactive material that the Commission, consistent with existing law, determines by rule to require permanent isolation.
It is current U.S. policy to dispose of HLW in a deep geologic storage facility.
Transuranic (TRU) Waste
TRU waste is defined in the Waste Isolation Pilot Plant Land Withdrawal Act, Public Law 102-579 as
waste containing more than 100 nanocuries of alpha emitting transuranic isotopes [atomic number greater than 92] per gram of waste, with half-lives greater than 20 years, except for:
- High-level radioactive waste;
- Waste that the Secretary [of Energy] has determined, with the concurrence of the Administrator [of the Environmental Protection Agency], does not need the degree of isolation required by the disposal regulations; or
- Waste that the Nuclear Regulatory Commission has approved for disposal on a case-by-case basis in accordance with part 61 of title 10, Code of Federal Regulations.
waste sites that are likely to require post-closure controls and long-term management.
1.1 REMEDIATION OF LEGACY WASTE SITES
Legacy wastes can be roughly grouped into four categories: contained and/or stored waste, buried waste, contaminated soil and groundwater, and contaminated building materials and structures. Examples of contained or stored waste are wastes in tanks, canisters, and stainless steel bins. For example, large quantities of high-level radioactive wastes are stored at Department of Energy (DOE) legacy sites in tanks. Buried wastes include radioactive and chemically contaminated wastes disposed of in near-surface pits and trenches (see Box 1.1). These wastes may or may not be stored in
It is current U.S. policy to dispose of TRU waste in a deep geologic storage facility. However, waste buried prior to issuance of the directive above (established in 1970) nonetheless meets the definition of TRU waste. This requires excavation of burial pits and trenches in order to retrieve the TRU waste.
Spent Nuclear Fuel (SNF)
SNF is defined in the Nuclear Waste Policy Act of 1987 (as amended, 2002) as
The term “spent nuclear fuel” means fuel that has been withdrawn from a nuclear reactor following irradiation, the constituent elements of which have not been separated by reprocessing.
Low-level Radioactive Waste (LLRW)
LLRW (also referred to as low-level waste or LLW) is defined in the Low-Level Radioactive Waste Policy Act of 1985 (P.L. 99–240) and the Nuclear Waste Policy Act of 1987 (as amended, 2002) as
The term “low-level radioactive waste” means radioactive material that—(A) is not high-level radioactive waste, spent nuclear fuel, transuranic waste, or by-product material as defined in section 11e(2) of the Atomic Energy Act of 1954 [42 U.S.C. 2014(e)(2)]; and
(B) the [Nuclear Regulatory] Commission, consistent with existing law, classifies as low-level radioactive waste.
Mixed Low-level Waste
Mixed LLW is defined as LLW determined to contain both source, special nuclear, or byproduct material and a hazardous component.
containers prior to burial (NRC 2005).1 Contamination of soil and groundwater occurred through intentional (following past environmental practices) and accidental (e.g., leaching of buried wastes or leaking of tanks) releases. Building materials that are considered waste were contaminated by nuclear material (e.g., pipes, filters, and pumps). The structures themselves may also be contaminated.
Remediation decisions for closure and post-closure controls are site specific because of the complexities of each site. Several factors contribute to a site’s remediation complexity, including its size, location, geology, and climate; activities associated with its original and current missions; relationships with local regulators and stakeholders; and the type and scope of the principal legacy wastes.2 Several DOE nuclear legacy sites provide background on the complexities and diversity of sites, wastes, and challenges related to long-term remediation issues (DOE 2001a, 2001b). The Hanford site, Savannah River Site (SRS), Idaho National Laboratory (INL), and the Oak Ridge Reservation (ORR) are discussed below.
The Hanford site is located in southeastern Washington and covers an area of about 580 square miles. The Colombia River passes through the north portion and borders the south-eastern quadrant of the site (see Figure 1-1). It is located within the Columbia Plateau between the Cascade Mountains (to the west) and the Rocky Mountains (to the east) (Horton 2000). The subsurface geology contains horizontal sedimentary layers and layered basalt lava flows, and vertical clay dikes cut across these horizontal layers in some areas of the site (NRC 2010). Hanford has a cold, desert climate with light and occasional moderate rain and snow.
Hanford was established in 1943 by the U.S. government with a mission to produce plutonium and perform research on plutonium production. Plutonium was produced at the site through three main steps: reactor fuel fabrication, irradiation of the fuel in reactors to produce plutonium, and chemical processing of the irradiated fuel to separate and recover the plutonium. Fuel fabrication took place in the southeastern portion of the site, near the Columbia River, in a location designated as the 300 Area (see Figure 1-1). The fuel was irradiated in nine production reactors located in
1 In 1970 the U.S. Atomic Energy Commission identified transuranic (TRU) waste as a separate category of radioactive wastes (see definitions in Box 1.1). Prior to this determination, wastes meeting the definition of TRU waste were often buried with low-level wastes (LLW). After 1970, TRU wastes were placed in retrievable storage (DOE 2000).
2 Legacy wastes are wastes generated during the development, production, and testing of nuclear weapons for the Manhattan Project and the Cold War. They can contain a wide range of radioactive materials and/or hazardous chemicals.
FIGURE 1-1 A map of the Hanford site showing the locations of the major legacy production facilities described in the text. The 100 Area housed the production reactors. The 200 Area (also called the Central Plateau) housed the chemical processing plants. The 100 Area housed the fuel fabrication facilities.
the north portion of the site along the Columbia River (100 Area). Chemical processing of the irradiated fuel took place in the 200 Area, also referred to as the Central Plateau. The plutonium production mission at Hanford ended in 1989 (DOE 2001b). The site is currently undergoing environmental remediation by DOE’s Office of Environmental Management (EM).
The chemical separation processes in the 200 Area generated the largest volume of stored legacy waste at Hanford (DOE 2001b). Several hundred thousand metric tons of chemical and radioactive waste were produced, most of which is contained in large underground storage tanks (DOE 2001b). The tanks currently store approximately 56 million gallons of
high-level waste (HLW) and await final remediation (DOE 2013a). This waste is stored in 149 single-shell and 28 double-shell tanks. The acidic HLW was neutralized with sodium hydroxide and has segregated into two main components: a thick hydroxide sludge (the HLW fraction) and a liquid salt solution. The salt solution is rich in sodium nitrite-nitrate and sodium hydroxide but also contains radioactive elements (cesium and strontium). Additional tank wastes and wastes from chemical processing operations were intentionally or accidentally discharged into the subsurface (DOE estimates that up to 67 of the single-shell tanks have leaked waste into the subsurface). Starting in the 1980s, the drainable salt solution was pumped from the single-shell tanks into the double-shell tanks to reduce the risk of further leaks.
The tank waste is a significant remediation challenge. Under current plans it will be retrieved and stabilized into high activity waste (HAW) and low activity waste (LAW) (once the cesium and strontium are removed from the salt solution). The former will be disposed of off site and the latter on site; both will be stabilized in glass (i.e., vitrified). Once the waste has been removed, the tanks will be stabilized and entombed in place. Processing facilities to separate the wastes between high and low activity and convert each to a stable form have yet to be built and made operational. The Waste Treatment and Immobilization Plant (WTP) is the intended solution for this challenge but its construction has experienced numerous delays.
Hanford’s waste burial grounds include both lined and unlined trenches. Burial of solid wastes—low-level waste (LLW), mixed LLW (MLLW) and, prior to 1970, transuranic (TRU) waste—occurred primarily in open pits and near-surface trenches. An estimated 25 million cubic feet of solid waste was buried in 175 trenches (Brockman 2010).
Radioactive and chemical contaminants are present in surface and subsurface soils and groundwater throughout the site. At the start of cleanup in the late 1980s, DOE estimated that 25 to 35 percent of groundwater under the Hanford site was contaminated (DOE 2001b). More than 350 billion gallons of liquid were discharged to the ground in the 200 Area, resulting in an estimated 32,000 cubic meters of TRU-contaminated soil (DOE 2000). Groundwater contamination is being actively remediated in some cases and monitored in others. It is anticipated that residual soil and groundwater contamination will remain at Hanford after cleanup activities have been completed and will require long-term stewardship.
A large number of buildings containing radioactive or chemical materials were located throughout the Hanford site at the start of cleanup activities (DOE [2001b] estimated up to 800 buildings). The 100, 200, 300, and 400 Areas house shut-down reactors, chemical separation plants, waste-handling facilities, and various support facilities no longer in use. Since 1989, many of these facilities have gone through deactivation and
decommissioning (D&D). Six of the nine production reactors have been placed in interim safe storage (through a process called “cocooning”3); two of the three remaining reactors are also planned for cocooning. The cocooned reactors will remain on site until the radioactivity decays to safer levels and decisions can be made on final disposition. The remaining reactor, B Reactor, has been partially decommissioned and preserved as a national landmark.
Issues Related to Long-Term Remediation
Most of the wastes generated by the EM cleanup program will be disposed of on site. Two large Resource Conservation and Recovery Act (RCRA)-compliant waste storage facilities have been built to dispose of these wastes. The Environmental Restoration Disposal Facility (ERDF) is located in the Central Plateau (see Figure 1-1). It became operational in 1996 and currently stores 14 million tons of contaminated waste, LLW and MLLW.4 The ERDF’s current capacity is 18 million tons of waste; it is designed to be expanded as needed.
The Integrated Disposal Facility (IDF) will be used to dispose of the LLW and MLLW from tank treatment operations (e.g., vitrified LAW) and other on-site remediation activities (such as D&D) (DOE 2013b). The IDF’s capacity is 165,000 cubic meters. A 7-foot-thick liner at its base has been designed to collect leachate to reduce the risk of soil contamination beneath the containment facility. The IDF is not yet operational.
The wastes stored at the ERDF and IDF will remain on site with long-term post-closure controls and monitoring. Planning the size of these facilities based on current predictions of waste volumes can be difficult. Many of the DOE sites share the same key challenges including unpredicted compaction of the stored waste and accurate forecasting of waste volumes (Benson 2008).
Final retrieval and remediation decisions have not yet been made for much of Hanford’s tank waste. For example, EM is in the process of proposing remediation decisions for the Waste Management Area C (WMA C) in the 200 Area. This decision requires consideration of different tank waste retrieval technologies in contaminated soil.5 The WMA C decisions may impact future single-shell tank farm remediation decisions.
After active remediation activities of the full site are completed, wastes
3 The cocooning process leaves the reactor core intact after it is encased with concrete. The surrounding reactor building is decontaminated and demolished and a safe storage enclosure roof is installed.
5 For more information, see http://www.hanford.gov/files.cfm/WMA-C%20INFO%20SHEET.pdf.
will remain on site in LLW and MLLW disposal facilities (e.g., the ERDF and IDF), in the residual contamination of soil and groundwater, and as entombed buildings and structures. Post-closure control and monitoring to ensure effectiveness of the remedies will be part of the final remediation of this site.
At 310 square miles, the Savannah River Site is slightly smaller than the area within the Washington, DC, beltway. It is located in rural south central South Carolina, 20 miles south of Aiken and 25 miles northeast of Augusta (see Figure 1-2). The Savannah River defines its southwest border. The site, located on the Atlantic coastal plain (Denham 1995), is dissected by tributaries to the Savannah River. The subsurface contains heterogeneous coastal-plain sediments. SRS has a warm, humid temperate climate with hot summers and no dry season.
SRS produced tritium and plutonium for the U.S. government beginning in the early 1950s. Five production reactors, two chemical separation plants, and fuel fabrication facilities were designed and built to produce plutonium for the nation’s nuclear arsenal. Additionally, a heavy water extraction plant was built to supply heavy water for SRS reactor operations. From 1953 to 1988, SRS produced approximately 36 metric tons of plutonium (DOE 2001b). SRS no longer produces plutonium but continues to process, store, and recycle nuclear material. None of the original five production reactors is active; two are used for nuclear material storage. One chemical processing plant (H Canyon) is still in operation. The Tritium Extraction Facility (TEF), operational in 2007, is a critical source of tritium for the U.S. nuclear weapons stockpile. SRS remains an active DOE research site with research and development activities conducted at the Savannah River National Laboratory (SRNL) and other laboratories on site.6
At the start of cleanup activities in the late 1980s, SRS reported approximately 35 million gallons of liquid high-level waste stored in 51 underground tanks (DOE 2001b). These wastes were created as a result of SRS’s past chemical (plutonium and irradiated fuel) separation activities. Wastes within the tanks were neutralized with sodium hydroxide and have since separated into HLW sludge and a salt solution (similar to the tanks at the Hanford site). Current mission activities also produce additional HLW
6 Other laboratories and research organizations include a timber and forestry center run by the U.S. Forest Service and the Savannah River Ecology Laboratory run by the University of Georgia.
FIGURE 1-2 A map of the Savannah River Site. The triangles indicate locations of SRS’s five production reactors (the C-, K-, L-, P-, and R-reactors). Circles indicate location of other major facilities including A: the Savannah River National Laboratory and the Savannah River Ecology Laboratory, M: fuel fabrication facilities, E: onsite disposal of low-level waste, H: H-canyon and the Tritium Extraction Facility (TEF), F: chemical processing (F-Canyon and FB Line) and tank farms, S: the Defense Waste Processing Facility (DWPF), and Z: the Saltstone facilities.
waste. More than half of the tanks are double shelled (27 are double-shell tanks, 24 are single-shell tanks; notably, all of the tanks at SRS have a secondary containment sump). Six of the single-shell tanks have been grouted and closed;7 12 are suspected of leaking.
SRS has built and operated several large-scale facilities to process stored tank wastes: the Defense Waste Processing Facility (DWPF, see Area S in Figure 1-2) and two Saltstone facilities (see Area Z in Figure 1-2). The DWPF has been used to stabilize the HLW fraction of the tank waste (i.e., the HLW sludge) by vitrifying it in a glass matrix form (completed in April 1996); the vitrified waste is stored at SRS awaiting a federal repository. The saltwaste solution is currently being processed by the Actinides Removal Process (ARP) and Modular Caustic-side Solvent Exchange Unit (MCU). The removed actinides and cesium are fed to the DWPF for vitrification; the decontaminated salt solution is treated in the Saltstone Production Facility (SPF) through grouting and disposed of as LAW in the Saltstone Disposal Facility (SDF). The ARP/MCU is a pilot for the Salt Waste Processing Facility (SWPF), which has been designed to address the remaining radioactive salt waste within the tanks but it is not yet operational. This remediation decision is notably different from the vitrification of LAW at the Hanford site (which requires LAW to be stabilized in a glass matrix).
Radioactive and chemically contaminated wastes were disposed of in basins and burial grounds. One of the largest burial grounds, the Old Radioactive Waste Burial Grounds (ORWBG), covers roughly 76 acres (the ORWBG is located in area E in Figure 1-2). Currently an interim remediation measure is in place for the ORWBG—a 4-foot-thick soil cover to reduce ground-level radiation exposure, contact with rain water, and leaching waste into groundwater. DOE estimates that there are 4,500 cubic meters of buried TRU-waste at SRS (DOE 2000, Table 1).
Radioactive and chemically8 contaminated waste has been identified in soil, surface water, and groundwater. Approximately 300 million cubic meters of groundwater and nearly 9 million cubic meters of soil and sediment have been contaminated (NRC 1999). Contamination is treated in a number of ways at SRS including pump and treat and monitoring. Residual contamination will remain on site after active remediation is complete.
SRS also has waste from contaminated building materials and structures. Contaminated legacy waste facilities have been identified for deactivation and decommissioning (D&D). Some have already completed D&D activities creating contaminated waste. They include a portion of the tank farms, the heavy water and fuel fabrication facilities, one of the chemical
7 The following tanks in the F area have been closed: 5, 6, 17, 18, 19, and 20.
8 Most of the chemical contamination was trichloroethylene (TCE).
processing plants, and three of the five production reactors (C, P, and R reactors).
Issues Related to Long-Term Remediation
Some legacy wastes will remain on site at SRS as mentioned previously. Most of the LLW generated during remediation activities will remain on site at the SDF and a facility in Area E (see Figure 1-2).9 This LLW, residual contamination of soil and groundwater, and entombed buildings and structures (e.g., the underground storage tanks) will remain on site with long-term post-closure controls.
Remedies at SRS include waste stabilization (e.g., vitrification, salt-stone), capping, waste removal, grading, monitoring, and assessments. Monitoring programs are in place or planned throughout the site. Some of the remaining remediation challenges for SRS are the processing of salt waste, SNF, and plutonium10 remaining on site.
Idaho National Laboratory
The Idaho National Laboratory (INL) occupies approximately 890 square miles in a remote desert area along the western edge of the upper Snake River Plain. The closest population center, Idaho Falls, is approximately 25 miles to the east (see Figure 1-3). The site is flat, high-desert terrain with buttes and an average elevation of 5,000 feet; the subsurface geology is comprised of fractured basalt lava flows and sediment (Anderson 1999) that hosts the Snake River Plain Aquifer.11 The site has a cold and semi-arid (steppe) climate with light rain and snow and summertime thunderstorms.
U.S. government activities at the site have a long history. The government established the Naval Proving Ground in the 1940s to test fire World War II Pacific Fleet guns.12 In 1949, the site was expanded and converted to the Nuclear Reactor Testing Station, where approximately 100 reactor concepts were built, tested, and operated including reactors for naval nuclear propulsion. From 1953 to 1992, the Idaho Chemical Processing Plant reprocessed and extracted uranium and plutonium from U.S. government
10 A Mixed Oxide (MOX) Fuel Fabrication Facility (MFFF) will process plutonium into fuel for nuclear power facilities. The MFFF is delayed and not yet operational.
11 The Snake River Plain Aquifer is a sole source aquifer supplying water to most of Idaho’s 300,000 southeastern residents (see http://www.deq.idaho.gov/media/552772newsletter_0505.pdf).
FIGURE 1-3 A map of Idaho National Laboratory. Waste Area Groups (WAGs) correspond to the site’s major facilities. Notable WAGs related to legacy waste activities are WAG 2 (test reactors), WAG 3 (the Idaho Chemical Processing Plant and the Idaho CERCLA [Comprehensive Environmental Response, Compensation, and Liability Act] Disposal Facility), and WAG 7 (the Radioactive Waste Management Complex [RWMC]).
spent fuel. The spent fuel currently stored at INL has come from multiple sources: naval reactors, onsite test reactors, commercial, Three Mile Island core debris, West Valley Demonstration Project, and foreign research reactors (Provencher 2010). In addition to these activities, the Radioactive Waste Management Complex (RWMC) was established in 1952 to dispose of wastes from other sites (e.g., Rocky Flats). INL no longer reprocesses spent fuel or accepts wastes from other sites. Its current mission is to conduct research and testing of new nuclear fuel concepts and to conduct a safe environmental remediation of the legacy wastes within the site.
INL has actively addressed its tank wastes on site. A tank farm stored the waste generated from the chemical separation process. The waste calcining facility was built to treat and stabilize the HLW from this tank farm.13 The resulting calcine is stored in a total of 43 stainless steel bins within 6 concrete bin sets, rated to be safe for several hundred years. The bin sets are stored on site awaiting a federal repository.14 Eleven of the 15 HLW tanks have been emptied and grouted, but sodium bearing waste (SBW) tanks remain. A new facility, the Integrated Waste Treatment Unit (IWTU), has been built to process sodium bearing waste; it is a Fluidized Bed Steam Reformer (FBSR). During initial system testing in 2012, the IWTU experienced a pressure control shutdown event. In March 2014 the ITWU facility underwent an Operational Readiness Review and a Technology Readiness Assessment. Spent nuclear fuel from a variety of sites is stored in ponds and dry casks within INL.
Waste disposal ponds and ditches and subsurface disposal were used at all nine WAGs (DOE 2001b). In one of the largest current remediation activities on site, sections of the RWMC are being exhumed to retrieve buried TRU waste (primarily from Rocky Flats, see Box 1.1) to be packaged and transported to the Waste Isolation Pilot Plant (WIPP) in New Mexico. DOE estimates nearly 37,000 cubic meters of TRU waste has been buried at INL (DOE 2000).
Due to past practices, groundwater and soil contamination has occurred throughout the site. Amounts of radioactive and chemical contami-
13 The calcining process converts liquid HLW to a granular solid by a combined high-temperature drying, denitrating (nitrogen removal), and evaporation process. Calcining reduces the volume of HLW by a factor of approximately seven. This waste was calcined as a nitrate; unlike the waste tanks at the Hanford site, NaOH was not added to neutralize the HLW. The calcining facility operated from 1963 to 1987. The aboveground structures have been decontaminated and demolished; the underground structures have been grouted and entombed.
14 It is not clear whether a future repository will accept calcined waste so INL has been investigating the stabilization of the calcine into glass ceramic via hot isostatic pressing (HIPing).
nation have been estimated at 7.6 × 105 cubic meters of groundwater and 6.5 × 105 cubic meters of soil and sediment (NRC 1999). Contaminated groundwater from WAGs 1, 3, and 7 (see Figure 1-3) placed INL on the National Priorities List.
Many of the reprocessing and waste storage facilities are no longer needed and have been decommissioned. These include some of the fuel storage pools, hot cells and hot shops, a fuel reprocessing plant, warehouses, and waste storage buildings.15 Three nuclear reactor vessels have been disposed of in the Idaho CERCLA Disposal Facility (ICDF), located in WAG 3. The ICDF stores INL-generated LLW and MLLW.
Issues Related to Long-Term Remediation
Remediation of the TRU waste within the RWMC is one of the challenges at INL. After active remediation of the site is completed, wastes will remain through controlled LLW facilities (the ICDF and the RWMC), residual contamination of soil and groundwater, and entombed buildings and structures. Groundwater remediation and ecological monitoring currently take place throughout the site.16 Challenges to post-closure monitoring include adequate stabilization of residual contamination on site (in the soil and groundwater), and evaluation on long-term performance of current passive remedies (e.g., caps and grout).
Oak Ridge Reservation
The Oak Ridge Reservation (ORR) is located about 25 miles west of Knoxville, Tennessee, and is approximately 60 square miles in area. Three major watersheds within the site form parallel northeast to southwest trending valleys: Melton Valley, Bear Creek, and Bethel Valley. The Clinch River defines the eastern and southern borders of the site (see Figure 1-4), and the Tennessee River is downstream. The site contains low-permeability soils and fractured rock above bedrock. The climate at the site is temperate with hot summers and no dry season. Rain is the most likely form of precipitation, ranging from light to heavy.
ORR was established by the U.S. government in the early 1940s. The reservation had three major facilities: the X-10 research facility, the Y-12 Plant, and the K-25 Plant (see Figure 1-4). X-10 was originally constructed as a research and development facility to support plutonium production technology. The Y-12 and K-25 plants were built to produce highly enriched uranium (HEU). The Y-12 Plant enriched uranium by electromagnetic
FIGURE 1-4 ORR site map indicating original facilities. X-10 was originally used to research plutonium production; it is now the Oak Ridge National Laboratory (ORNL). Y-12 was originally used to enrich uranium using electromagnetic separation; it is now the Y-12 National Security Complex. K-25 was also known as the Oak Ridge Gaseous Diffusion Plant; it is now the East Tennessee Valley Technology Park (ETTP).
separation; the K-25 Plant used gaseous diffusion. Of the three mission goals, the enrichment of uranium encompassed the most area, energy, and resources.
ORR is currently a multi-mission site. It is used for nuclear material storage but no longer carries out nuclear material production.17 The Oak Ridge National Laboratory (ORNL) has replaced X-10; it is a national laboratory conducting research in materials, alternative fuels, and supercomputing. The Y-12 Plant is now the Y-12 National Security Complex
17 “It [ORR] is the only field site that performs every mission under the DOE’s portfolio—energy research, environmental restoration, national security, nuclear fuel supply, reindustrialization, science education, science and technology, and technology transfer” (see http://www.oakridge.doe.gov/external/Home/AboutUs/tabid/24/Default.aspx).
with a current mission of reducing worldwide nuclear stockpiles, storing nuclear material, and improving defense systems. The K-25 Plant area, now known as the East Tennessee Technology Park (ETTP), is being demolished. The site will eventually become a private industrial park.
Legacy wastes at ORR are stored in both above- and below-ground storage. Depleted uranium hexafluoride, or DUF6, is a by-product of uranium enrichment through gaseous diffusion. DUF6 had been stored as a solid in steel, above-ground cylinders (approximately 5,000 cylinders were stored at the ETTP). All of these cylinders have been transported to Portsmouth for further processing. Underground tanks containing legacy waste remain on site including 12 gunite tanks18 (containing wastes from plutonium separation research and pilot experiments) and 5 storage tanks (constructed as feed tanks for the Hydrofracture Facility, see below).19
Wastes have been buried throughout the ORR site (Webster and Bradley 1987). At the start of cleanup, it was estimated that there were up to 1,100 acres of unlined buried waste, facilities, inactive tanks, and unlined ponds (DOE 2001b). Pits and trenches were used for disposal of intermediate-level wastes.20 Intermediate-level wastes were also combined with grout and pumped into the subsurface at the Hydrofracture Facility (this practice was later discontinued). Solid LLW was disposed of in shallow trenches and auger holes near the X-10 and Y-12 facilities. DOE estimates that approximately 570 cubic meters of waste has been buried near the surface and 8,800 cubic meters of waste is buried at intermediate depths (via hydrofracture) (DOE 2000, Table 1).
Contamination of soil and groundwater has been detected throughout the site and in the surrounding areas. As a result of past operations, nearly 4,000 acres either were or had the potential to be contaminated (DOE 2001b).21 The main contaminants are mercury and PCBs (from metal work and electricity generation for enrichment), and cesium and strontium (Cs-137 and Sr-90 are fission products of U-235, DOE 2001b). These
18 Gunite is a mixture of cement and sand sprayed over a frame of steel-reinforced wire mesh. The gunite tanks on the ORNL campus have been closed. They were constructed to support X-10 R&D activities to support plutonium production at Hanford. Tanks in Melton Valley are used to recover wastes from R&D and chemical separations operations.
20 There is no formal regulatory definition for intermediate-level waste in the United States. The International Atomic Energy Agency (IAEA) describes intermediate-level waste as radioactive waste that requires remote handling (see http://www.iaea.org/OurWork/ST/NE/NEFW/_nefw-documents/LILWaste2011.pdf).
21 For a relative comparison, the total area of ORR is 35,000 acres.
contaminants—especially mercury—can be found in soils, sediment, and groundwater at the site and in onsite and offsite waterways.
Contaminated buildings and building materials existed throughout the three major areas within ORR. The largest buildings were in the K-25 and Y-12 areas. The gaseous diffusion facility (K-25) was the largest building under one roof (44 acres in area) at the time it was constructed. Recently, DOE announced its final demolition of K-25.22
Issues Related to Long-Term Remediation
ORR’s waste disposition for LLW and MLLW generated through remediation activities on site is the Environmental Management Waste Management Facility (EMWMF). TRU waste is to be addressed in the TRU Waste Processing Facility (not yet operational) and transported to WIPP or other sites (Gelles 2013). Some TRU wastes from ORR have already been shipped to WIPP. It is expected that other wastes will remain on site through residual contamination, buried wastes (e.g., hydrofractured wastes), and entombed facilities.
Long-term monitoring of the site will be required after active remediation is complete incurring costs for years to come. The State of Tennessee has a potential best practice for ensuring a constant source of funds for long-term stewardship (Benson 2008): long-term monitoring and remediation activities will be paid for in part by Tennessee’s perpetual care trust fund—a trust established by the U.S. government over several years ($1 million/year for 14 years). Once remediation has been completed, the $14 million will be returned.23