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

Incineration has been a tool for managing wastes containing low levels of radioactive contamination since the early stages of the nuclear industry. A review published almost 30 years ago described radioactive waste incineration in the United States and eight foreign countries (Perkins, 1976). In 1992, WASTECH, a multi-organization cooperative project managed by the American Academy of Environmental Engineers with grant assistance from the Environmental Protection Agency (EPA), Department of Defense (DOD), and Department of Energy (DOE), conducted a two-year study resulting in an eight-volume monograph series on innovative site remediation technologies. One volume was devoted to thermal processes, including a variety of incinerator designs and alternatives to incineration.

Recent public opposition to incinerators has forced DOE and other organizations to investigate alternative technologies. As a result, the DOE and several advisory groups have reviewed various technologies and written numerous reports. In April 1997, the Idaho National Engineering and Environmental Laboratory (INEEL) published a detailed report Evaluation of Alternative Nonflame Technologies for Destruction of Hazardous Organic Wastes (Schwinkendorf et al., 1997). The report evaluated technologies that are alternatives to open-flame, free-oxygen combustion. Alternative technologies were defined as those that have the potential to destroy organic materials without use of open-flame reactions with free gas-phase oxygen as the reaction mechanism, reduce the off-gas volume and associated contaminants emitted under normal operating conditions, eliminate or reduce the production of dioxins and furans, and reduce the potential for excursions in the process that can lead to accidental release of harmful levels of chemical or radioactive materials.

The report identified 23 technologies and rated them for performance; readiness for deployment; and environmental, safety, and health risks.

The top 10 technologies resulting from this evaluation are

1. steam reforming,

2. electron beam oxidation,

3. ultraviolet (UV) photo-oxidation,

4. ultrasonic destruction,

5. Eco Logic (hydrogen) reduction,

6. supercriticial water oxidation,

7. cerium mediated electrochemical oxidation,

8. DETOX (iron-catalyzed, low-temperature oxidation),

9. direct chemical oxidation, and

10. neutralization or hydrolysis.

The study recommended continuing research to improve incineration and other thermal systems, including air pollution control systems and continuous air emission monitors because none of the evaluated alternative technologies alone has the capability of thermal systems to treat the large variety of mixed low-level waste (MLLW) in the DOE complex in a single process. In addition, all of the evaluated alternative technologies have difficulty in treating organically contaminated inorganic matrices such as soils, inorganic sludges, and debris.

In 1997-1998, DOE’s Mixed Waste Focus Area published a number of Innovative Technology Summary Reports on acid digestion of organic waste and direct chemical oxidation. More recently, the Transuranic and Mixed Waste Focus Area published brief descriptions of several technologies including mediated electrochemical oxidation, plasma arc systems and direct-current (DC) arc melters, reverse polymerization, solvated electron dehalogenation, steam reforming, and supercritical water oxidation.¹

In April 2000, following a dispute over the proposed construction of an incinerator for treatment of radioactive mixed waste at INEEL, DOE appointed a blue-ribbon panel of independent experts to explore alternatives to incineration that might become available for use at DOE facilities nationwide (DOE, 2000b). The panel evaluated technologies in five general categories: (1) thermal treatment without incineration; (2) aqueous-based chemical oxidation; (3) dehalogenation; (4) separation (soil washing, solvent extraction, and thermal desorption); and (5) biological treatment. Among the alternatives, the panel considered the most promising to be

• thermal (vacuum) desorption of polychlorinated biphenyls, hydrocarbons, and water;

• direct steam reforming to destroy or remove problem contaminants; and

• DC arc and plasma torch melters to destroy contaminants.

The panel found that while there are promising technological alternatives to incineration, none of the alternatives is ready for immediate implementation; all need to be further developed, adapted, and tested with actual waste. The panel therefore recommended a DOE program to demonstrate commercial technologies, nurture the development of next-generation technologies, and guide basic and applied research for future technical advances.

In January 2001, the Secretary of Energy accepted the recommendations of the panel and directed the Office of the Assistant Secretary for Environmental Management to develop an action plan. Action Plan for Emerging Technological Alternatives to Incineration was published in June 2001 (DOE, 2001c). The Alternatives to Incineration Committee (ATIC) was formed to examine emerging alternatives and interface with concerned citizens (see Chapter 2, Sidebar 2.4).

The committee reviewed the Action Plan and noted that DOE sites have been largely successful in obtaining relief from regulations that restricted shipment of untreated wastes to the Waste Isolation Pilot Plant (WIPP), which was a principal strategy described in the Action Plan. For example, following a recent revision of the safety analysis for the TRUPACT-II shipping container, the amount of TRU waste that cannot be shipped due to potential hydrogen generation from untreated (nonincinerated) organics is only about 2 percent of the TRU waste inventory (Curl et al., 2002). DOE sites have also been successful in finding alternatives to incineration for most other special case wastes, for example, stabilizing organic liquids on polymers or clays. Because its emphasis is on sending TRU wastes to WIPP, DOE perceives few current incentives to develop true replacement technologies for incineration—those that would destroy essentially all organic materials in a wide variety of wastes and provide large volume reductions of combustible wastes. Developing these technologies, which may be required to treat large volumes of MLLW to meet EPA disposal requirements, remains a challenge as discussed in Chapter 3.