High-hazard waste

3 High-Hazard Waste. Waste classified as high-hazard would contain such high concentrations of radionuclides or hazardous chemicals that it would not be generally acceptable for nearsurface disposal in a dedicated facility for hazardous waste, but would require disposal in a facility located well below the ground surface. At the present time, geologic repositories are intended for 

An important characteristic of acceptable disposal facilities for high-hazard waste is that inadvertent intrusion into a facility, such as by drilling, must be unlikely. Therefore, assessments of risk or dose to hypothetical inadvertent intruders based on exposure scenarios that are assumed to occur do not provide a suitable basis for determining acceptable disposals in facilities located well below the ground surface. 

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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 ... 

High -hazard waste any nonexempt waste that generally requires a disposal system more isolating than a dedicated nearsurface facility for hazardous wastes (e.g., a geologic repository). 

High-hazard waste Any nonexempt waste that generally requires disposal system more isolating than dedicated near-surface facility for hazardous wastes1 Concentrations of any hazardous substances that exceed limits for low-hazard waste... 

HIGH-HAZARD WASTE (GEOLOGIC DISPOSAL OR EQUIVALENT)... 

Most radioactive waste currently classified as low-level waste and most hazardous chemical waste would be classified as low-hazard waste, based on the expectation that these wastes would be generally acceptable for disposal in dedicated near-surface facilities for hazardous wastes. A possible exception is hazardous chemical waste that contains relatively high concentrations of heavy metals, which could be classified as high-hazard waste. 

In many respects, the system for classifying and managing hazardous chemical waste under RCRA makes no distinction between highly hazardous waste and virtually innocuous waste that contains very low levels of hazardous substances. Furthermore, many wastes that contain hazardous chemicals, as well as radionuclides not regulated under AEA, are excluded from the definition of hazardous waste based on the source of the waste, even though the excluded wastes can be just as hazardous as other wastes that are deemed hazardous under RCRA. 

High-Hazard Waste - Risk from disposal in dedicated near-surface hazardous waste facility would exceed acceptable levels... 

The basic definitions of exempt, low-hazard, and high-hazard waste shown in Figure 6.1 are considered in the following sections. Recommendations on approaches to calculating the risk from waste disposal in the numerator of the risk index and recommendations on specifying allowable risks in the denominator of the risk index for the purpose of classifying waste are discussed in Section 6.3. 

Nonexempt Waste. NCRP recommends that nonexempt waste—i.e., waste that contains amounts of radionuclides, hazardous chemicals, or both greater than the allowable amounts in exempt waste—be placed in one of two classes, called low-hazard waste and high-hazard waste. 

High-hazard, waste. NCRP recommends that high-hazard waste be defined to include any nonexempt waste with concentrations of hazardous substances greater than those that are generally acceptable for disposal in a dedicated near-surface facility for hazardous wastes. High-hazard waste would require a disposal system considerably more isolating than a near-surface facility for hazardous waste. 

Classification as High-Hazard Waste. Waste that would not be generally acceptable for near-surface disposal in dedicated... 

For the purpose of illustrating how the composite risk index in Equation 6.6 would be used to classify a hypothetical waste, it is helpful to simplify Equations 6.4 and 6.5. This is done by assuming that the summation over all responses (index r) has been calculated, that only one waste classification boundary represented by the index j is being considered (i.e., the boundary between exempt and low-hazard waste, based on a negligible risk, or the boundary between low-hazard and high-hazard waste, based on an acceptable risk), and that the modifying factor (F) is unity. Further, the calculated dose in the numerator of the risk index is denoted by D and the allowable dose in the denominator is denoted by L. Then, the composite risk index for all hazardous substances in the waste, expressed in the form of Equation 6.6, can be written as ... 

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. 

The exposure scenario described in the previous example of domestic uranium mill tailings was used to classify the high-radium residues. The risk and dose assessments indicated a probability of radiation-induced cancer incidence of about 0.6, potential doses in excess of 10 Sv, and a risk index between 50 and 100. Thus, these residues would be classified as high-hazard waste, even under conditions of perpetual institutional control over near-surface disposal sites, and they would require some form of greater confinement disposal well below the ground surface. This conclusion is consistent with recommendations for disposition of these residues (NAS/ NRC, 1995b). 

The analysis for chemicals that induce deterministic effects presented in Section 7.1.7.4 and summarized in Table 7.8 indicates that lead is the most important such constituent. Furthermore, the risk index for lead of about 0.7 is only marginally below the value of unity used to define the boundary between low-hazard and high-hazard waste. Therefore, the assumption that an acceptable dose of... 

These types of questions will undoubtedly complicate our use of the metric and the interpretation of the results as we attempt to put it into routine use. In addition, this metric does not consider the degree of hazard of the waste that is being created for instance, is it better to generate 100 kg of non-hazardous waste that is difficult to treat, or 50 kg of highly hazardous waste ... 

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