Research Opportunities for Managing the Department of Energy's Transuranic and Mixed Wastes (2002)

The accumulation of radioactive waste materials began in the 1940s with the development of the atomic bomb and continued with the large-scale refining and production of fissile materials such as uranium and plutonium during the Cold War. Processes included separation and enrichment of special isotopes, reactor fuel fabrication, dissolution and chemical separation of irradiated materials, and fabrication (casting, machining, plating) of weapons components. During this period, emphasis was placed on production and little attention was given to reducing the volume or variety of wastes. The wastes were managed using practices analogous to those used in other process industries, including on-site disposal in landfills and the use of ponds and lagoons to manage large volumes of wastewater.

Wastes generated by production operations ranged from slightly contaminated trash to highly radioactive liquids from processing irradiated fuels. Frequently these wastes contained both radioactive and hazardous chemical substances. This chapter provides a context for the Department of Energy’s (DOE’s) challenges in managing wastes contaminated with both hazardous chemicals and low levels of radioactive fission products (mixed low-level waste [MLLW]) and wastes contaminated with transuranic isotopes (TRU waste)—see Sidebar 2.1. Research challenges for managing DOE’s high-level radioactive waste and spent nuclear fuels and for remediating subsurface contamination are described elsewhere (NRC, 2000a, 2001a, 2002a) and are not dealt with in this report.

During most of the time this study was in progress, the Transuranic and Mixed Waste Focus Area (TMFA), a part of the DOE Environmental Management Office of Science and Technology (EM-OST), was responsible for ensuring that technologies were available to manage this waste. Organizational changes within EM-OST that occurred as this report was being finalized are described in Appendix A.

The Department of Energy’s challenges in managing and disposing its transuranic and mixed wastes (TM wastes) arise primarily from three factors. One is the large and diverse waste inventory, which is incompletely characterized. A previous study (NRC, 1999a, p. 18) of TM wastes found:

Another challenge is the complex and evolving regulatory constraints that are applied to these wastes. The earlier study (NRC, 1999a, p. 22) noted:

There is public concern about, and often opposition to, technologies that are unfamiliar or that might change agreed-upon cleanup plans. An international review of waste management programs (NRC, 2001c, p. 3) found the following:

Based on its fact finding, the committee believes that these conclusions remain valid. Through their impact on site technology needs, challenges arising from the diverse waste inventory, multiple evolving regulations, and public concerns will significantly affect any research agenda developed by the Environmental Management Science Program (EMSP). These factors, which frame DOE’s TM waste challenges, are discussed in this chapter.

Managing and disposing of DOE’s TM waste inventory presents technical challenges and research opportunities because the inventory is large and diverse. This section provides an overview of the inventory with emphasis on wastes that led the committee to its research recommendations. Appendix B gives a detailed description of the inventory.

Information on DOE’s waste inventory is given in a summary report published in April 2001 (DOE, 2001a). DOE compiled much of the inventory data from its fiscal year 2000 Central Internet Database.¹

FIGURE 2.1 Before 1970, transuranic and mixed wastes were buried in near-surface trenches. The waste was considered to be permanently disposed, and inventory data are lacking.

Source: http://web.ead.anl.gov/techcon/images/ineel3.jpg.

TM wastes are described in two categories, transuranic and MLLW. The summary report does not distinguish between TRU and mixed transuranic waste (MTRU) (see Sidebar 2.1). All inventory data refer to the waste volume unless noted otherwise.

Since 1970, DOE sites have stored most TM wastes retrievably in 55-gallon drums or larger containers for future treatment, if needed, and disposal. Before 1970, DOE sites buried TM wastes in “shallow land” facilities, within about 30 meters of the surface.² Most waste was buried in 55-gallon drums, some was buried in other containers, and some had no durable container (e.g., burial in plastic bags, cardboard boxes, or without containment); see Figures 2.1 and 2.2. At the time, DOE generally considered buried waste to be permanently disposed. Recently, DOE has recognized that at least some of its buried waste inventory may require retrieval and treatment (DOE, 2001a).

Contaminated soils and sediments have resulted from previous DOE practices of discharging low-level liquid wastes to retention basins or

FIGURE 2.2 Since 1970, DOE has required that sites store TRU waste so that it can be retrieved easily. TRU wastes at Hanford, which is in a very dry region, are stored in earthen mounds.

Source: DOE Richland Operations Office.

from leaks. DOE recognizes that some of these soils and sediments are sufficiently contaminated to warrant retrieval and describes these as “ex situ contaminated media” in its summary report. If they are retrieved, both the pre-1970 buried waste and the ex situ media will be considered newly generated waste (DOE, 2001a).

Table 2.1 gives an overview of DOE’s current and expected inventories of TM wastes. Disposing of retrievably stored TRU waste, which contains an estimated 2.6 million curies of radioactivity, in the Waste Isolation Pilot Plant (WIPP) is a top priority for DOE (Triay, 2001). Buried TRU waste, with a volume comparable to the stored TRU, is estimated to contain about 400,000 curies. A large volume of buried MLLW is contaminated with alpha-emitting isotopes at levels below the regulatory threshold for TRU waste and is designated as α-L LW.³ DOE expects to continue generating TRU waste until about 2034 and MLLW until about 2070, mainly from facility deactivation and decommissioning. In addition, DOE expects to produce ex situ waste by recovery of a portion of the more contaminated soils and sediments at some of its sites.

The diversity of the TM waste inventory is described in the Mixed Waste Inventory Report (MWIR [DOE, 1995]). This report was based on data compiled by DOE sites as a basis for developing their site treat-

ment plans as mandated under the Federal Facility Compliance Act of 1992. The inventory was divided into five treatment groups: debris, inorganic homogeneous solids and soils, organics, unique wastes, and wastewaters (see Sidebar 2.2). The treatment technologies for these groups were reviewed in a previous NRC (1999a) report.

Table 2.2 shows the relative amounts of retrievably stored wastes that fit into each of the treatment groups. Debris waste, which is very heterogeneous, comprises by far the largest category. Unique wastes make up a small fraction of the inventory. However, many unique wastes are problematic to treat and dispose, and their small volumes make them economically unattractive to site cleanup contractors.⁴

No information is available concerning the treatment needs for the previously buried waste. DOE’s production processes did not change with the prohibition of burial in 1970, so these materials are expected to have a composition similar to retrievably stored waste. The distribution profile of wastes into the treatment groups is unlikely to change appreciably if buried wastes are retrieved.

The 1995 inventory also indicates DOE’s level of confidence in how well the wastes were characterized. In general terms, DOE has high or medium confidence that the physical nature (i.e., soil or sludge) of most wastes is correctly identified but lacks confidence in the existing quantitative data on the wastes’ chemical and radioactive constituents (see Appendix B for details).

The current and projected volume of TRU waste will pose significant challenges for disposing of this waste. Several hundred thousand drums will have to be shipped to WIPP (see Table 2.1). The characterization required for shipping and acceptance at WIPP currently requires several hours and costs about four thousand dollars for each drum (DOE, 2001d).⁵

Methods to streamline characterization are likely to save large amounts of time and money (see Chapter 3).⁶

Characterizing and treating MLLW, which has received relatively little attention compared to TRU waste, to meet Resource Conservation and Recovery Act (RCRA) disposal requirements will be a challenge. In spite of the lack of quantitative chemical characterization, most of the

MLLW inventory is known to contain chemicals that are difficult to treat—heavy metals, solvents and other organics, and mercury (see Table 2.3). Further, there is considerable comingling of these classes of waste materials, making the selection of treatment options complicated.

Some components in TRU waste are problematic for shipping or disposal in WIPP (see Appendix B). About half of DOE’S TRU waste contains organic materials that have posed shipping problems due to potential gas generation, especially hydrogen. However, recent revisions to the Safety Analysis for TRUPACT-II shipping containers have reduced but not eliminated the concern about hydrogen accumulation during shipment. Under the new revision, only about 2 percent of the TRU waste inventory (about 14,200 drum equivalents) continues to face shipping restrictions.⁷ Reactive and corrosive chemicals (including paint

FIGURE 2.3 Manual sorting of waste inside a containment (glovebox) facility is required to remove items that are prohibited by shipping or disposal restrictions. Sorting and repacking the waste are time-consuming, expensive, and present risks to workers.

Source: DOE Richland Operations Office.

spray cans, which are often found in waste drums) cannot be accepted at the WIPP, and they are removed by sorting through the waste (see Figure 2.3). Waste that is contaminated with polychlorinated biphenyls (PCBs), about 1 percent of the inventory, cannot currently be accepted by the WIPP.

Approximately 2 to 4 percent of the TRU waste inventory produces enough penetrating radiation from fission product contaminants that it requires remote handling (RH-TRU), rather than hands-on operator contact. The requirement for remote handling greatly increases the difficulty of characterizing, treating, and packaging or repackaging this waste. Meeting per-drum limits on heat generation and fissile material content can require repackaging the waste (Curl et al., 2002; Moody, 2002). In addition to increasing the waste volume, repackaging to meet drum limits is expensive, time consuming, and creates a potential for worker exposure.

All waste handling and disposal operations are governed by regulatory requirements. However, DOE faces a particular challenge in

managing TM waste due to the number of agencies that regulate this waste and the generally prescriptive nature of their regulations. At the federal level, TM wastes are the regulatory responsibility of DOE, the Environmental Protection Agency, and the U.S. Nuclear Regulatory Commission. Department of Transportation requirements apply to shipping the waste as well as packaging the waste for shipment.

The Federal Facility Compliance Act of 1992 (FFCA) requires that DOE facilities comply with all federal, state, and local laws and regulations pertaining to hazardous waste. TM waste is thus subject to hazardous waste requirements promulgated by EPA under the Resource Conservation and Recovery Act of 1976 and subsequent revisions. The EPA has delegated its authority to many states, which may add additional requirements of their own.

The FFCA did not alter the separation between DOE and the USNRC. DOE is legally self-regulating for radioactive wastes (or the radioactive components of wastes) according to the Atomic Energy Act of 1954. However, DOE follows USNRC guidelines as a practical matter.⁸ Additionally, the USNRC has licensing authority over commercially operated waste disposal facilities in which DOE is disposing of MLLW. For some of this waste, the states regulate in place of the USNRC.⁹

Currently, DOE’s TRU waste disposal efforts are focused on maximizing the utility of the Waste Isolation Pilot Plant, which is located deep underground in a salt formation in southeastern New Mexico. In 1992, the WIPP Land Withdrawal Act transferred control of the land at the site from the Department of Interior to the DOE. Subsequent amendments exempted WIPP from RCRA treatment standards and land disposal regulations (NRC, 1996).

WIPP operates under a permit issued by the State of New Mexico, which allows it to receive only TRU waste resulting from the nation’s defense programs. DOE has committed in its permit application to manage all TRU waste as though it were mixed waste. In fact, the WIPP Waste Acceptance Permit (the Permit) specifically prohibits DOE from

disposing non-mixed TRU waste unless the waste has been characterized in compliance with applicable provisions of the Permit. This is to avoid any question of New Mexico’s having authority to regulate radioactive waste that is not subject to RCRA.

The Permit recognizes two classes of TRU waste: retrievably stored and newly generated. Retrievably stored refers to waste generated after 1970 but before the characterization requirements of the Permit were implemented at DOE sites (in about 1999). Newly generated refers to waste generated more recently. If wastes buried before 1970 or contaminated soils are retrieved, they will be considered as newly generated waste upon retrieval (see Table 2.1). Within each waste class, the Permit further categorizes three broad groups related to the physical form of the waste: homogeneous solids, soils and gravels, and heterogeneous debris (see Table 2.2).

Under the Permit, every retrievably stored waste container undergoes either radiography or visual examination to identify the physical form of the waste and to ensure that prohibited materials are absent.¹⁰ Headspace gas analysis to determine the presence of volatile organic compounds (VOCs) must be performed on every container. Containers are assayed to be sure that their heat generation and fissile material content are within Permit limitations. In addition, some homogeneous solids and soil or gravel wastes must be sampled to establish the concentrations of VOCs, semi-VOCs, and metals for hazardous waste characterization.

Currently, the Permit is limited to wastes that produce a radiation dose rate of less than 200 millirem per hour at the surface of the container. This waste is called contact-handled TRU waste (CH-TRU) because it is deemed safe for direct handling by workers. Waste that produces more then 200 millirem per hour, about 2 to 4 percent of the TRU inventory, is designated remote-handled TRU waste. Because RH-TRU presents a potential hazard to workers, DOE is seeking regulatory changes to simplify its characterization. The State of New Mexico and the EPA have not yet approved a DOE plan to characterize RH-TRU waste.¹¹ As noted later in this chapter, EMSP research will be especially important if DOE’s expected regulatory changes to simplify characterizing RH-TRU and dealing with other problematic wastes are not forthcoming.

Unlike TRU waste, MLLW has no special exemptions from regulatory controls. DOE is relying primarily on private contractors and commercial facilities to meet EPA and USNRC requirements for treating and disposing of its MLLW. MLLW cannot be disposed in WIPP because it does not qualify as TRU waste.¹²

The EPA has developed regulations for hazardous waste management and disposal principally under the authority of RCRA enacted in 1976.¹³ RCRA has been amended several times, with the most significant amendments passed in 1984 as the Hazardous and Solid Waste Amendments. RCRA provides for cradle-to-grave control of hazardous wastes by imposing management requirements on generators and transporters of hazardous waste and on owners and operators of treatment, storage, and disposal facilities.

The Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA, also known as Superfund) of 1980 addresses threats to public health and the environment from abandoned or active sites contaminated with hazardous or radioactive materials. Reauthorized by Congress in the Superfund Amendments and Reauthorization Act (SARA) of 1986, CERCLA gives EPA the authority to require remediation of hazardous waste previously disposed at DOE sites. Compliance with CERCLA may require the retrieval of some previously buried mixed wastes.

The EPA’s hazardous waste regulations apply to more than 500,000 companies and individuals throughout the United States (Case, 1991). Thus, the EPA uses a prescriptive approach to develop regulations that are almost universally applicable and contain straightforward numerical criteria that are relatively easy to understand and enforce. The EPA defines hazardous waste, specifies treatment standards that must be met prior to disposal, and specifies standards for construction and operation of hazardous waste disposal sites. For DOE MLLW, which includes relatively small quantities of many wastes that are diverse and heterogeneous, this universal prescriptive approach poses problems.

A Memorandum of Understanding (MOU) between DOE and EPA to help resolve these problems was signed in February 2000 (Eaton and Carlson, 2002). Under the auspices of this memorandum, DOE and EPA have established several joint agency work groups to address issues

such as alternatives to incineration, mercury-waste treatment and disposal, HEPA (high-efficiency particulate arresting) filter monitoring, and generally difficult technical issues where mixed waste does not fit well with the land disposal restriction treatment standards. The MOU also lists a number of recent EPA regulations that are likely to affect DOE’s plans and technical needs for managing MLLW (see Sidebar 2.3).

USNRC regulations that affect the management of MLLW include the Low-Level Waste Disposal Regulations (10 CFR 61) and Radiation Protection Standards (10 CFR 20). The USNRC regulates the radioactive characteristics of low-level waste materials acceptable for near-surface land disposal through a combination of prescriptive and performance-based requirements. Performance assessment is required to calculate worker and public exposure risks associated with waste disposal. According to the USNRC, a near-surface disposal facility is one in which radioactive waste is disposed within the upper 30 meters of the land surface. Institutional control of access is required for 100 years, and within 500 years, wastes must decay to a sufficiently low level that the remaining radioactivity will not pose unacceptable hazards to an intruder or the general public.

To meet this latter requirement, further prescriptive regulations define three classes of waste that are deemed suitable for near-surface disposal. Classification as Class A (the easiest to dispose), Class B, or Class C depends on which radionuclides are present and their concentrations (see Table 2.4). If the waste qualifies as TRU or is contaminated above certain limits with long-lived radionuclides, it is not suitable for near-surface disposal.¹⁴

DOE expects to use Envirocare’s Utah facility to dispose of about 30 percent of its MLLW (DOE, 1997). This is a commercial facility located in Tooele County, Utah, which is permitted for the disposal of several types of waste. This facility also provides some treatment capabilities, including stabilization by converting the waste to a solid material, macroencapsulation, and microencapsulation (see Chapter 3).

The State of Utah has permitting authority for low-level waste and hazardous waste using USNRC and EPA rules, respectively. Currently the facility is licensed to receive only USNRC Class A radioactive waste and naturally occurring or accelerator-produced material. Disposal of Class B or C waste requires additional approvals by the Utah Radiation Control Board (already issued), the governor, and the Utah legislature. However, it is not clear at this time if Envirocare will pursue these approvals.

Along with using commercial disposal facilities, DOE sites can establish on-site facilities. Both the DOE Hanford Site and the Nevada Test Site are developing RCRA-compliant facilities for their own wastes and might receive waste from other sites in the future (see Figure 2.4).¹⁵

In summary, MLLW that contains certain specified materials is pro-

hibited from near-surface disposal under current EPA and USNRC regulations. These include the following:

• liquids,

• reactive or explosive materials,

• flammable material,

• untreated biological material,

• materials that may emit toxic gases or fumes,

• other materials subject to EPA’s LDR, as listed in 40 CFR 268,

FIGURE 2.4 RCRA requirements for disposal of MLLW include use of an impermeable liner and leachate collection system to provide total containment of hazardous chemicals for at least 30 years. Here, a large box of macroencapsulated waste is being placed in a RCRA-compliant disposal facility at Hanford.

Source: DOE Richland Operations Office.

and

• radioactive isotopes in amounts that exceed USNRC Class C.

In order to be disposed, these wastes require treatments that may be technically difficult and expensive, as described in Chapter 3.

In establishing criteria for accepting waste at the Waste Isolation Pilot Plant, DOE attempted to combine complex regulatory programs with what were expected to be the performance characteristics of the WIPP system, even as WIPP was being designed and built. In hindsight, as actual operation experience is gained, some of the self-imposed and rather restrictive requirements are proving impractical and perhaps even irrelevant from a health and safety perspective, such as the PCB limitations and the lengthy characterization protocols. A previous NRC report (2001d) concluded that the requirements should be reviewed and updated so that the criteria (referred to as waste acceptance criteria, WAC) are kept relevant to long-term performance of the repository and to safety, technical, and legal considerations.

DOE has focused its efforts on simplifying the regulatory requirements for wastes that might be prohibited from disposal at WIPP or that might be sidelined due to failure to meet the WAC, particularly because of characterization difficulties. For example, DOE has prepared a draft request for authorization to allow the disposal at WIPP of TRU wastes containing PCBs. Approval of this request would allow DOE to dispose of approximately 88,000 cubic feet (2,500 cubic meters) of TRU wastes containing PCBs subject to regulation under the Toxic Substance Control Act (TSCA). In addition, DOE is also drafting requests for options for waste characterization being conducted at its sites that send waste to WIPP for management and disposal. DOE is particularly interested in simplifying the requirements for characterizing its RH-TRU waste (NRC, 2002b).

EPA requirements that will affect DOE’s management of MLLW for the next three to five years are identified in the MOU (see Sidebar 2.3). Given EPA’s broad responsibility to regulate hazardous waste, additional future regulations affecting MLLW are inevitable.

The views and concerns of members of the public will play an important role in establishing needs for improved technologies or changing agreed-upon plans for managing TM wastes. The statement of task for this report included evaluating treatment technologies for categories of TM waste for which current treatment technologies are not adequate, “in particular due to new or tightened regulatory requirements or other non-technical considerations such as nascent public opposition to incineration” (see Sidebar 2.4 and Appendix C).

During its site visits the committee heard from citizen groups at the Idaho National Engineering and Environmental Laboratory (INEEL), the Oak Ridge Reservation, and the Savannah River Site (see Appendix E). The committee did not hear a consistent opposition to incineration, but it did hear concerns about air emissions, buried waste retrieval, and monitoring. These broader concerns indicated that citizens are generally well informed about potential technology-related problems near their communities. Importantly, they expected DOE to address their concerns.

The committee believes that the key is not simply to develop new technologies to replace those that have raised public concern—to try to stay technologically one step ahead of the public—but rather to involve the public in the selection of technologies. The need for public participation is well documented (Chopayk and Levesque, 2002; Cohn, 2002; see also Busenberg, 1999). An earlier NRC study emphasized the importance of involving the public in choosing among technical options (NRC, 2001c, p. 24):

The committee agrees with this assessment. Any new technologies or changes in accepted cleanup plans are likely to encounter public concerns or opposition unless convincing scientific evidence for their adoption can be presented and citizens are involved in decision making. Providing a scientific basis for decision making that can be understood in the public forum is as important a role for the EMSP as providing routes to new technology.

DOE’s efforts are focused on removing TM wastes from its sites as rapidly as possible. Although the focus is on near-term accomplishments, in the broader perspective DOE’s waste inventory is large and diverse and wastes will continue to be produced by both site cleanup and new activities. During the course of DOE’s several-decades-long, multibillion-dollar cleanup program, there are certain to be many changes as technology and regulations evolve and citizens express their concerns through the political process. There are both time and opportunity for EMSP research to produce new technologies to significantly

enhance safety and reduce costs and uncertainties in DOE’s management and disposal of its TM wastes.¹⁶

TRU waste disposal in the Waste Isolation Pilot Plant will require handling and characterizing hundreds of thousands of drums as well as larger containers during the next 20 or more years. DOE is working with pertinent regulators to reduce or eliminate restrictions that may not be necessary for reducing risk and that interfere with waste shipments or disposal. DOE expects this regulatory relief to help accelerate site cleanup and closure.

Conversely, DOE has encountered legal, economic, and public concerns about incineration, a technology that was expected to treat a large fraction of the TM waste inventory. Some buried wastes and contaminated soils, which DOE previously considered disposed, may have to be retrieved and treated as new wastes. Monitoring WIPP and other waste disposal facilities will continue for many years.

In view of the changes and challenges that DOE will be facing for decades, there are two clear roles for EMSP-funded research in DOE’s TM waste management efforts:

1. To provide the scientific basis for new technologies that will be necessary for improving management and disposal of TM wastes during at least the next 20 years, especially if the regulatory changes that DOE expects to simplify dealing with problematic wastes are not forthcoming.

2. To enhance the scientific information available for regulatory decision making and public involvement, including evidence that disposal systems are operating as intended.