Waste classification system technologies

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 ... 

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. 

To address the limitations of the waste classification system described above, new recommendations on waste classification were developed (IAEA, 1994). A particular aim of the new system was to associate waste classes with intended disposal technologies (options), at least to some degree. The recommended classification system includes the following three major classes of waste exempt waste, low- and intermediate-level waste, and high-level waste. These waste classes and the associated disposal options are summarized in Table 4.2 and described as follows. 

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. 

Another desirable attribute of a waste classification system that is a corollary of the system being risk-based is that it treat wastes that pose similar health risks consistently. A chemically hazardous waste estimated to pose a certain risk should be in the same waste class as a radioactive waste that poses an equivalent risk, and similarly for mixed waste. Consistency also implies that wastes posing similar risks could be disposed of using essentially the same technology (municipal/industrial landfill, licensed near-surface facility for hazardous waste, or geologic repository). 

The basic framework for the waste classification system developed in this Report is depicted in Figure 6.1. Starting with the objectives that the classification system should apply to any waste that contains radionuclides or hazardous chemicals and that all such waste should be classified based on risks to the public posed by its hazardous constituents, the fundamental principle of the proposed system is that hazardous waste should be classified in relation to disposal systems (technologies) that are expected to be generally acceptable in protecting public health. This principle leads to the definitions of three classes of waste, and to quantification of the boundaries of the different waste classes based on considerations of risks that arise from different methods of disposal. The boundaries normally would be specified in terms of limits on concentrations of hazardous substances. At the present time, nearly all hazardous and nonhazardous wastes are intended for disposal in a near-surface facility or a geologic repository, and these are the two types of disposal systems assumed in classifying waste. The three waste classes and their relationship to acceptable disposal systems are described in more detail in Section 6.2. 

NCRP reiterates that the risk-based waste classification system developed in this Report does not, and cannot, obviate the need to establish waste acceptance criteria at each hazardous waste disposal site based on the characteristics of the site, the particular disposal technology, and characteristics of the wastes that are intended for disposal at the site. NCRP expects that most waste that would be assigned to a particular class will be acceptable for disposal using the associated type of disposal technology indicated in Figure 6.1. However, the disposal capabilities of particular sites and engineered systems can vary substantially and can depend on the waste characteristics. The primary function of any waste classification system is to facilitate development of cost-effective approaches to waste management and disposal and effective communication on waste matters (see Section 2.1.2). 

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. 

Existing hazardous waste classification systems frequently include subclassifications of basic waste classes to facilitate waste management (see Sections 2.2.4, 4.1.2 and 6.6). Examples include Class-A, -B, and -C commercial low-level waste and remotely-handled and contact-handled transuranic waste. These waste subclassifications are not expected to be significantly affected by a risk-based classification system unless particular wastes would not be generally acceptable for the disposal using the intended technology. For example, there is no inherent incompatibility with the system... 

Based on these objectives, the fundamental principle embodied in the proposed classification system is that waste should be classified in relation to disposal systems (technologies) that are expected to be generally acceptable in protecting public health. The types of disposal systems assumed in classifying waste should represent current or planned practices for radioactive or hazardous chemical wastes. 

Classification of a given waste is based on an evaluation of the risk index specified in Equations 6.4, 6.5 and 6.6 for assumed types of disposal systems. If the risk index is less than unity, the waste is acceptable for inclusion in the associated waste class otherwise, the waste generally requires a more protective disposal system and would be placed in a class for more hazardous wastes. The appropriate classification depends on the level of protection required which, in turn, depends on the characteristics of the waste relative to the capabilities of assumed disposal technologies. This concept is a fundamental part of the risk index. General assumptions about... 

Table II contains a categorization of sources of contamination developed by the USEPA (1976) and Office of Technology Assessment (1984) as referenced by Canter et al. (1988). The categories are based on a functional classification of various activities. It is evident from the previously cited categorization that many engineered systems designed to contain potentially toxic or hazardous products and wastes need to be considered in the inventory of somces. This point is borne out by the detailed listing...

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