Waste classification system assumptions

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. 

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. 

Development of a comprehensive and risk-based hazardous waste classification system requires assumptions about the measure or measures of response (adverse health effects) from exposure to radionuclides and hazardous chemicals that should be used in classifying waste. Possible measures of response discussed in Section 3.2.3 include fatalities, incidence, or some combination of the two, such as total detriment (ICRP, 1991). The following sections discuss the measures of response from exposure to hazardous subtances that... 

Development of a comprehensive and risk-based hazardous waste classification system requires assumptions about thresholds in the... 

Assumptions about exposure scenarios are required in developing a risk-based waste classification system. These scenarios would be used to calculate potential risks posed by hazardous wastes for purposes of waste classification. An exposure scenario essentially is a set of assumptions about events and processes that could result in exposure of humans. 

The basic element of the recommended framework for a comprehensive and risk-based waste classification system is the assumption that any waste that contains sufficiently small amounts of radionuclides or hazardous chemicals should be classified as exempt, or essentially nonhazardous. Waste that contains greater amounts of hazardous substances then would be classified as nonexempt, and further classification of nonexempt wastes, based also on the amounts of hazardous substances present, would be appropriate. 

In general, degrees of conservatism could be incorporated in a risk-based waste classification system to account for such factors as uncertainties in assumptions, models, and data, as well as the need to protect sensitive population groups (e.g., infants and children). If... 

This Section provides example applications of the recommended risk-based waste classification system to a variety of hazardous wastes to illustrate its implementation and potential ramifications. Disposal is the only disposition of waste considered in these examples. In Section 7.1.1, a general set of assumptions for assessing the appropriate classification of hazardous wastes is developed, including a variety of assumed exposure scenarios for inadvertent intruders at waste disposal sites and assumed negligible and acceptable risks or doses from exposure to radionuclides and hazardous chemicals. Subsequent sections apply the methodology to several example wastes. 

It is not NCRP s intent to recommend specific boundaries between waste classes. Rather, the examples illustrate that the recommended framework has the potential to be practical and to result in an implementable waste classification system when a variety of plausible assumptions are used. Many assumptions are made in developing the examples. NCRP endorsement or disapproval should not be construed from the use or absence of specific assumptions about exposure scenarios and allowable doses or risks. It is the responsibility of the appropriate regulatory authorities to develop and guide implementation of any waste classification system. 

The RESRAD code was used to illustrate implementation of the proposed waste classification system. NCRP did not evaluate the code or its underlying assumptions and database, and its use should not be construed to constitute endorsement. 

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. 

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... 

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