Waste classification system

Based on these principles, the hazardous waste classification system recommended by NCRP includes three classes of waste exempt, low-hazard, and high-hazard waste. Each waste class is defined in relation to the type of disposal system (technology) that is expected to be generally acceptable in protecting public health as follows ... 

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. 

The primary purpose of this Report is to present NCRP s recommendations on classification of hazardous wastes. The Report is directed at a multidisciplinary audience with different levels of technical understanding in the fields of radiation and chemical risk assessment and radioactive and chemical waste management. Anew hazardous waste classification system is proposed that differs from the existing classification systems for radioactive and hazardous chemical wastes in two fundamental respects. First, hazardous waste would be classified based on considerations of health risks to the public that arise from disposal of waste. Hazardous waste would not be classified based, for example, on its source. Second, the classification system would apply to any hazardous waste, and separate classification systems for radioactive and hazardous chemical wastes would not be retained. In the proposed system, waste would be classified based only on its properties, and the same rules would apply in classifying all hazardous wastes. 

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. 

This Report presents the foundations and technical principles for development of a generally applicable and risk-based hazardous waste classification system. Recommendations on suitable approaches to establishing boundaries of different waste classes are discussed these boundaries could be expressed, for example, in terms of limits on concentrations of hazardous substances. However, a particular implementation of the proposed waste classification system in terms of quantifying the boundaries of different waste classes is not presented. 

Fig. 1.1. Current radioactive waste classification system in the United States.

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. 

Deficiencies in the Radioactive Waste Classification System. The classification system for radioactive waste in the United States summarized in Table 1.1 is based primarily on the earliest descriptions of different classes of waste that arises from chemical reprocessing of spent nuclear fuel and subsequent processing of nuclear materials that were developed beginning in the late 1950s. These wastes were considered to be the most important in regard to potential radiological impacts on workers. 

The radioactive waste classification system is complex, it is not transparent to the public, who are increasingly involved in decisions about management and disposal of waste, and it is not understandable by anyone but a studied expert. 

As part of this study, proposed radioactive waste classification systems that differ from the existing classification system in the United States were reviewed and evaluated. Of particular interest is the classification system currently recommended by the International Atomic Energy Agency (IAEA). This classification system and the disposal options for each waste class are summarized in Table 1.2. The basic waste classification system consists of exempt waste, low-and intermediate-level waste, and high-level waste. 

The basic waste classification system includes a general class of exempt waste, which is defined in terms of a dose to an individual member of the public, resulting from waste disposal, that is regarded as negligible. 

The basic waste classification system does not distinguish between radioactive waste associated with the nuclear fuel-cycle and other waste i.e., fuel-cycle and NARM wastes are included in the same classification system. 

Table 1.2—Summary of characteristics of radioactive wastes and disposal options in waste classification system... 

Waste is not part of basic waste classification system, but large volumes of waste that contains long-lived, naturally occurring radionuclides are given additional consideration. 

The system for classification and disposal of hazardous chemical waste developed by EPA under RCRA does not apply to all wastes that contain hazardous chemicals. For example, wastes that contain dioxins, polychlorinated biphenyls (PCBs), or asbestos are regulated under the Toxic Substances Control Act (TSCA). In addition, the current definition of hazardous waste in 40 CFR Part 261 specifically excludes many wastes that contain hazardous chemicals from regulation under RCRA, including certain wastes produced by extraction, beneficiation, and processing of various ores and minerals or exploration, development, and use of energy resources. Thus, the waste classification system is not comprehensive, because many potentially important wastes that contain hazardous chemicals are excluded, and it is not based primarily on considerations of risks posed by wastes, because the exclusions are based on the source of the waste rather than the potential risk. 

NCRP s approach to addressing these difficulties is to develop a single hazardous waste classification system that is comprehensive and risk-based. 

Basic Elements of Hazardous Waste Classification System... 

Given the basic elements of a new waste classification system described in the previous section, NCRP proceeded with development of the system on the basis of several assumptions. 

The waste classification system should be based on the distinct concepts of negligible and acceptable ii.e., barely tolerable) risks to the public that arise from waste disposal. Precedents for specifying negligible or acceptable risks that could be used in classifying waste, such as other NCRP recommendations, would be cited, but specific recommendations would not be presented in this Report. 

Legal impediments to development of a new waste classification system would be ignored. These include, for example, the distinction between radioactive waste that arises from operations of the nuclear fuel-cycle and NARM waste, which is based on provisions of AEA, the distinction between radioactive and hazardous chemical wastes, which is based on provisions of AEA and RCRA, and the provision in the National Energy Policy Act that prohibits NRC from establishing a general class of exempt radioactive waste. 

Thus, NCRP s recommendations focus on the technical foundations for a generally applicable and risk-based waste classification system. 

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). 

For the purpose of developing the waste classification system described in Section 1.4.1, a simple method of evaluating risks to the public posed by radionuclides and hazardous chemicals in waste is needed. The term risk generally refers to the probability of harm, combined with the potential severity of that harm. In the context of hazardous waste disposal, risk is the probability of a response in an individual or the frequency of a response in a population taking into... 

Table 1.4—Framework for the recommended risk-based waste classification system. 

Classification system applies to any waste that contains radionuclides or hazardous chemicals. Waste classification system does not provide a substitute for site-specific risk assessments in developing waste acceptance criteria at particular disposal facilities or in developing criteria for remediation of particular contaminated sites. 

Fig. 1.2. Depiction of waste classes defined in relation to acceptable disposal systems in recommended risk-based waste classification system.

Risk Index for Mixtures of Hazardous Substances. For the purpose of developing a comprehensive and risk-based hazardous waste classification system, a simple method of calculating the risk posed by mixtures of radionuclides and hazardous chemicals is needed. The method should account for the linear, nonthreshold dose-response relationships for radionuclides and chemical carcinogens (stochastic effects) and the threshold dose-response relationships for noncarcinogenic hazardous chemicals (deterministic effects). 

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