Waste classification, general

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 ... 

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. 

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. 

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. 

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... 

A general class of exempt waste, which could be regulated as nonhazardous material, would be established. Development of an exempt class of waste that contains low levels of hazardous substances has been controversial and currently is banned by law in the case of radioactive waste. Some radioactive and hazardous chemical wastes have been exempted on a case-by-case basis, but general principles for exempting radioactive or hazardous chemical wastes have not been established. In spite of these difficulties, however, a meaningful risk-based waste classification system must include a general class of exempt waste. 

The waste classification system presented in this Report would apply to all radioactive and hazardous chemical wastes from any source, and it would be based on considerations of health risks to the public that arise from waste disposal. The recommended classification system differs from the existing waste classification systems in three respects radioactive and hazardous chemical wastes would be included in the same classification system all waste would be classified based on its properties, rather than its source and the classification system would include a general class of exempt waste. 

Report thus, the phrase risk-based waste classification system. The desirability of basing a waste classification system on risk has been recognized for many years (DOE, 1980). While risk will be defined more precisely in subsequent sections, the following general definition is useful at this point (Garrick and Kaplan, 1995) ... 

The waste classification system developed in this Report includes a general class of exempt waste. Waste in this class would contain sufficiently small amounts of hazardous substances that it could be managed in all respects as if it were nonhazardous (e.g., as household trash). NCRP intends that exempt materials could be used or disposed of in any manner allowed by laws and regulations addressing disposition of nonhazardous materials. However, exempt waste would not necessarily be exempt for purposes of beneficial use without further analysis of the risks associated with anticipated uses. Materials could be exempted for purposes of disposal or beneficial use based on similar considerations of acceptable risk. However, based on differences in exposure scenarios for the two dispositions, limits on the amounts of hazardous substances that could be present in exempt materials intended for beneficial use could be substantially lower than the limits for disposal as exempt waste. Thus, disposal may be the only allowable disposition for some exempt materials based on considerations of risk. In addition, some exempt materials may consist of trash, rubble, and residues from industrial processes that would have no beneficial uses and must be managed as waste. 

In most cases, evaluations of ecological impacts are site-specific and, as a consequence, are not considered when establishing a generally applicable waste classification system. These impacts normally are addressed in disposal site selection, design, and operation, and they may be used in establishing waste acceptance criteria for the site. To the extent that ecological impacts can be evaluated generi-cally, NCRP believes that the principles and framework for risk-based waste classification presented in this Report are sufficiently flexible to take them into account. 

A proper reconciliation of the radiation and chemical paradigms for risk management is important to the development of a comprehensive and risk-based hazardous waste classification system. In particular, the proposed waste classification system developed in Sections 6.2 and 6.3 of this Report is based fundamentally on the concept that an acceptable risk generally can be substantially greater than a negligible risk. This distinction is used to define different classes of waste that pose an increasing hazard. 

Deterministic responses from exposure to hazardous chemicals generally are of concern in health protection of the public because many of the exposure limits derived from the assumed thresholds and the applied safety and uncertainty factors fall within the range of potential routine exposures. However, the possibility that the large safety and uncertainty factors normally used in setting exposure limits are quite conservative (pessimistic) could be taken into account in developing a risk-based waste classification system. Deterministic responses from exposure to radionuclides should not be of concern in health protection of the public or in classifying waste, because the dose limits intended to prevent deterministic responses are substantially higher than the dose limit intended to limit the occurrence of stochastic responses. 

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... 

Generally applicable waste classification system proposed by Kocher and Croff. In response to the definition of high-level waste in Clause (B) of NWPA (1982) discussed in Section 4.1.2.3.1, Kocher and Croff (1987 1988) developed a proposal for a quantitative, generally applicable, and risk-based radioactive waste classification system that addresses the definitions of high-level waste in... 

Not discussed in this Section are radioactive waste classification systems developed in other countries, particularly in Europe. Waste classification systems in European countries are discussed, for example, in a report of the Commission of the European Communities (CEC, 1990), and waste classification systems in a number of countries have been reviewed by Numark et al. (1995). The waste classification systems developed in other countries often have been based, at least in part, on the source-based classification system in the United States or the various IAEA recommendations discussed in this Section they generally do not include any new concepts of waste classification. 

A number of alternatives to the qualitative and source-based classification system for radioactive waste in the United States have been proposed. The alternative waste classification systems have three important features in common. First, they are comprehensive, in that NARM waste and nuclear fuel-cycle waste are included in the same classification system. Second, they are based on the concept that waste classes should be defined primarily on the basis of risk, particularly the risk resulting from waste disposal. Finally, to some degree, they associate waste classes with particular disposal systems that are expected to be generally acceptable. None of these features is embodied in the radioactive waste classification system in the United States. In addition, some proposed classification systems include an exempt class of radioactive waste that contains negligibly small amounts of radionuclides. Waste in this class would be regulated in all respects as if it were nonhazardous. A general class of exempt waste is not included in the radioactive waste classification system in the United States. 

The existing waste classification systems for radioactive and hazardous chemical wastes clearly are not comprehensive. At a fundamental level, entirely separate and quite different classification systems have been developed for the two types of hazardous waste. In addition, each classification system is not comprehensive in the context of the general type of waste to which each system applies. In the existing radioactive waste classification system, waste that arises from operations of the nuclear fuel cycle is classified separately from NARM waste. The existing classification system for hazardous chemical waste excludes many potentially important wastes that contain hazardous chemicals. 

Some existing waste classification systems are quantitative. For example, the concentrations of radionuclides defining the different subclasses of low-level radioactive waste that is generally acceptable for near-surface disposal are clearly stated in the regulations (NRC, 1982a), as are the quantitative conditions defining ignitable, corrosive, reactive, and toxic hazardous chemical wastes (see Section 4.2.1.1). 

Existing waste classification systems are generally compatible with available data. Compatibility is the result of the databases having been acquired to meet the needs of the waste classification... 

---