Subclassifications of Basic Waste Classes

There often are valid reasons for developing subclassifications of basic waste classes (i.e., classifications subordinate to those based 

The principles of waste classification presented in this Report do not address a framework for subclassification of hazardous wastes. However, the relationship of existing subclassifications to the proposed framework is discussed. 

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. 

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Issues related to subclassification of basic waste classes, incorporation of conservative assumptions in applying the system, and future development needs regarding waste classification are discussed. 

Recommendations on subclassifications of the basic classes of exempt, low-hazard, and high-hazard waste defined in Section 6.2.2 are not developed in this Report. However, NCRP acknowledges that subclassifications of basic waste classes would be reasonable, particularly in the case of low-hazard and high-hazard wastes. NCRP believes that any such subclassifications should be consistent with the physical, chemical, radiological, and toxicological properties of waste, and with requirements for safe management and disposal. NCRP believes that extrinsic and non-risk-related factors, such as the source of a waste, should not be used in subclassifying risk-based waste classifications. 

Volumes of particular wastes are relevant to subclassification of basic waste classes, especially when the very large volumes of some wastes in a particular class necessitate different approaches to management and disposal than the much smaller volumes of other wastes... 

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... 

As indicated by the current subclassifications of existing waste classes summarized above, a variety of waste properties could be used to develop meaningful subclassifications of broadly defined waste classes. These properties include, for example, waste volumes, levels of decay heat and external radiation, and the long-term persistence of the hazard posed by waste constituents. Subclassifications of waste classes also could be based on the presence of particular hazardous substances. However, if the broadly defined waste classes are based on risk, as in the classification system proposed in this Report, the intrinsic toxicity of hazardous substances normally would not provide a basis for subclassification, because this property already is accounted for in determining the basic classification of any waste. Examples of possible approaches to subclassifying the basic waste classes are discussed in the following paragraphs. 

The recommended risk-based waste classification system has important implications in three areas (1) the resulting classification of existing radioactive and hazardous chemical wastes, (2) subclassification of the basic waste classes, and (3) changes in existing laws and regulations that would be required to implement such a classification system. 

NCRP believes that subclassification of the basic waste classes would be appropriate as long as it is based on properties of waste that are related to health risks from disposal or considerations of the cost-benefit of different options for waste management and disposal. Other factors that have influenced waste classification in the past should not be used as a basis for waste subclassification. For example, the present distinction between radioactive waste that arises from operations of the nuclear fuel cycle and NARM waste should not be maintained in subclassifying waste, because this distinction is based solely on the source of the waste rather than significant differences in health risks from waste disposal or considerations of cost-benefit in waste management and disposal. 

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