Waste classification system disposal requirements

This Section discusses the historical development and current approaches to classification and disposal of radioactive waste. Classification and requirements for disposal of different radioactive wastes in the United States are emphasized, particularly the relationship between waste classification and requirements for disposal much of this discussion is adapted from a previous paper (Kocher, 1990). Proposals for alternative radioactive waste classification systems are reviewed. Classification systems developed by the International Atomic Energy Agency (IAEA) and the relationship between waste classification and disposal requirements in IAEA recommendations are discussed in some detail. Waste classification systems developed in other countries are briefly mentioned. 

Management and disposal of the wide variety of hazardous wastes has been aided by the development of waste classification systems. The term waste classification refers to broadly defined waste categories related, for example, to properties of waste materials, potential risks to human health that arise from waste management or disposal, or the source of the waste. Ideally, hazardous wastes in the same class should pose similar risks to human health and, thus, require similar approaches to safe management and disposal. 

This Report is concerned with classification of hazardous waste for purposes of disposal. However, the principles and concepts embodied in the waste classification system could be applied in classifying hazardous materials for any other purpose. The classification system is intended to be applied to hazardous waste prior to disposal. It is not intended to be applied to screening or ranking of contaminated sites, including existing hazardous waste disposal sites, because these activities involve site-specific considerations that cannot be included in a generally applicable waste classification system. However, any wastes exhumed from contaminated sites that then require disposal would be included in the waste classification system. 

Exempt Radioactive Wastes. The radioactive waste classification system in the United States does not include a general class of exempt waste (see Table 1.1). Rather, many products and materials that contain small amounts of radionuclides (e.g., specified consumer products, liquid scintillation counters containing 3H and 14C) have been exempted from requirements for use or disposal as radioactive material on a case-by-case basis. The various exemption levels are intended to correspond to low doses to the public, especially compared with dose limits in radiation protection standards for the public or doses due to natural background radiation. However, the exemption levels are not based on a particular dose, and potential doses to the public resulting from use or disposal of the exempt products and materials vary widely. 

Development of a waste classification system based on considerations of risks to the public requires assumptions about generic exposure scenarios (i.e., exposure scenarios that are generally applicable at any disposal site). 

Many details would need to be considered in developing a new waste classification system based on the framework presented in this Report. Assumptions about generic scenarios for exposure of hypothetical inadvertent intruders at waste disposal sites to be used in classifying waste and the time frames for applying the scenarios would be required. Decisions would need to be made about negligible and acceptable (barely tolerable) doses or risks that would be used in classifying waste as exempt or low-hazard, respectively. 

In summary, a hazardous waste classification system is needed because (1) disposal of the composite unclassified waste would be prohibitively expensive and (2) the differences in timing between waste generation (now) and the development of treatment and disposal facilities (the future) require that wastes be segregated in anticipation of cost-effective means of waste management and disposal. Waste classification also allows consistent communication of the information needed to develop adequate treatment and disposal capacity and to develop appropriate regulations. 

A risk-based waste classification system must focus on the inherent characteristics of waste, representative facilities, and generic events, because the system necessarily presumes that specific disposal sites and related waste treatment and disposal technologies have not yet been identified and characterized. NCRP emphasizes that the principles, framework, and implementation details of a risk-based waste classification system do not provide a substitute for site-specific risk assessments. The two most important cases where site-specific risk must be estimated are (1) an assessment of risk for the spectrum of actual wastes at a specific disposal site for the purpose of establishing site-specific waste acceptance criteria, and (2) an assessment of risk posed by a prior waste disposal at a site for the purpose of determining whether the risk is unacceptable and, thus, whether remedial action is required at the site. 

Section 4 presents detailed information on existing classification systems for radioactive and hazardous chemical wastes, the relationships between waste classification and requirements for waste disposal, and the impacts of waste classification systems on management and disposal of mixed wastes. This Section also summarizes previous NCRP recommendations relevant to waste classification. 

Fourth, the definitions of waste classes in the United States are not related to requirements for disposal. In IAEA s waste classification system, there is some linkage between the definitions of waste classes and the types of disposal technologies that would be required, particularly for high-level waste. However, not all waste classes in IAEA s system are linked to required disposal technologies, because low-and intermediate-level waste could be acceptable for near-surface disposal or could require disposal in a geologic repository depending, for example, on the concentrations of long-lived radionuclides. 

The provision of the National Energy Policy Act (NEPA, 1992) that prohibits NRC from establishing dose criteria that could be used to exempt radioactive wastes from licensing requirements for disposal clearly is an impediment to development of generally applicable exemption levels for radioactive waste. An exempt class of radioactive and hazardous chemical waste is the cornerstone of the risk-based waste classification system developed in this Report, and any legal and regulatory impediments to establishment of generally applicable exemption levels would need to be removed. 

A risk-based waste classification system would be established by focusing on risks that arise from disposal of hazardous wastes. Thus, the amounts of hazardous chemical wastes that would be acceptable for near-surface disposal over the longer term would need to be evaluated. While NCRP believes that many hazardous chemical wastes would continue to be acceptable for near-surface disposal, it should be anticipated that this will not be the case for some wastes that contain high concentrations of heavy metals e.g., see Okrent and Xing (1993). As a result, some hazardous chemical wastes could be classified as high-hazard (see next section), and such a classification also could also mean that perpetual institutional control will be required at some existing burial sites. 

At the present time, there is essentially only one class of hazardous chemical waste (i.e., a waste either is hazardous or it is not), without regard for the amounts of hazardous substances in the waste. Establishment of a risk-based waste classification system would allow for the possibility of two classes of hazardous chemical waste based on the amounts of hazardous substances, consistent with the present situation for radioactive waste, with the attendant implication that high-hazard chemical waste that contains the highest amounts of hazardous substances would require a disposal technology substantially more isolating than a near-surface system. 

The classification system lacks a set of principles for determining when a waste contains sufficiently small amounts of radionuclides that it can be exempted from regulatory control as radioactive material. The lack of a general class of exempt waste increases in importance as the resources required for management and disposal of radioactive waste increase compared with the resources required for management and disposal of these materials as nonradioactive waste, and it may foreclose possible beneficial uses of slightly contaminated materials. 

Thus, the basic elements of the proposed classification system are, first, that there should be a general class of waste that contains sufficiently small concentrations of radionuclides or hazardous chemicals that it can be exempted from regulatory control as hazardous material and, second, that there should be two classes of nonexempt waste that contain increasing concentrations of hazardous substances and require dedicated disposal systems that provide increased waste isolation. 

Inclusion of NARM waste in the same classification system with radioactive waste that arises from operations of the nuclear fuel cycle would require a change in the scope of AEA, because management and disposal of commercial NARM waste cannot be regulated under AEA. 

Wastes have been classified for decades for a variety of purposes. This Section discusses the historical development of classification systems for radioactive and hazardous chemical wastes and the resulting classification systems in use at the present time. The relationship between waste classification and requirements for disposal of different classes of hazardous waste is emphasized. The framework for this discussion is the top-level system for waste classification in the United States shown in Figure 4.1. Within this framework, it is first determined whether a waste is nonhazardous (e.g., municipal waste) these wastes are not addressed in this Report. If a waste is deemed hazardous, it is so classified due to the presence of radionuclides or hazardous chemicals. Mixed radioactive and hazardous chemical waste is not a separate class of waste. However, mixed waste has been an important concern as a result of differences in requirements for management and disposal of radioactive and hazardous chemical wastes. Section 4.1 addresses classification and disposal of radioactive waste, and is followed by discussions of classification and disposal of hazardous chemical waste in Section 4.2 and approaches to management of mixed radioactive and hazardous chemical waste in Section 4.3. Finally, Section 4.4 summarizes previous NCRP recommendations relevant to waste classification. 

Characteristics of the system for classification and disposal of fuel-cycle waste. The current classification system for radioactive waste that arises from operations of the nuclear fuel cycle in the United States and the current requirements for disposal of waste in the different classes have the important characteristics discussed below. 

Requirements for Disposal and Their Relationship to Waste Classification. Under current laws and regulations, spent fuel, high-level waste, transuranic waste, and low-level waste generally do not require particular disposal systems. However, only certain types of disposal systems are authorized for some types of waste (see Table 4.1). In particular (1) spent fuel, high-level waste, transuranic waste, and greater-than-Class-C low-level waste normally are intended for disposal in a geologic repository, such as the proposed Yucca Mountain facility and the Waste Isolation Pilot Plant and... 

These considerations lead to an important conclusion regarding the relationship between classification of fuel-cycle wastes and requirements for their disposal—namely, that the selection of acceptable systems for disposal of fuel-cycle wastes does not depend on the definitions of waste classes. Rather, the types of disposal systems that are expected to provide adequate protection of public health (e.g., a near-surface facility or a geologic repository) are selected based on the radiological properties of waste, essentially without regard for how the waste is classified. Thus, general requirements for disposal are not affected by the qualitative, source-based, and ambiguous definitions in the classification system for fuel-cycle waste. 

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