Waste classification system characteristics

Table 1.2—Summary of characteristics of radioactive wastes and disposal options in waste classification system... 

The existing waste classification systems are becoming increasingly complex as additional waste streams are incorporated into a patchwork system that is not based on a consistent set of principles. Some wastes are classified based on their source (i.e., the nature of the process or facility that produces them), some based on their composition, and some based on their physico-chemical characteristics. 

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. 

Section 7 then addresses the implications of the recommended risk-based waste classification system. By assuming key parameters (e.g., values of acceptable risk, characteristics of exposure scenarios) and applying the system to a variety of example waste streams, the question of how existing wastes would be classified in the new system is investigated. This Section also summarizes the legal and regulatory ramifications of the proposed hazardous waste classification system. 

Discussion of EPA s Hazardous Waste Classification System. Waste that is hazardous because it is ignitable, corrosive, or reactive, as defined above, must be treated to remove these characteristics prior to disposal. Examples of appropriate treatment methods... 

Significant parts of the existing waste classification systems are based on intrinsic properties of waste. The system for subclassifying low-level waste in 10 CFR Part 61 (NRC, 1982a) and the determination of whether a chemical waste is characteristically hazardous (see Section 4.2.1.1) are examples of waste classification based on intrinsic properties. 

It is highly desirable that a waste classification system be expressed in quantitative terms. More specifically, the intrinsic waste characteristics that define the boundaries between waste classes should be stated numerically. Qualitative definitions of waste classes, such as the definition of high-level radioactive waste discussed in Section 4.1.2.3.1, simply defer the issue of waste classification to a subsequent definition of the qualitative terms or to case-by-case determinations that typically occur after waste is generated. 

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). 

Development of a comprehensive and risk-based hazardous waste classification system, in which waste classes are defined in relation to types of disposal systems that are expected to be generally acceptable in protecting public health, would not obviate the need to establish waste acceptance criteria at each disposal site based on the characteristics of the site and engineered disposal facility and the properties of wastes intended for disposal therein. The primary purposes of a hazardous waste classification system are to facilitate cost-effective management and disposal of waste and effective communication on waste matters. 

The popularity of this waste classification system is enhanced by the fact that most of the incinerator manufacturers rate their equipment in terms of these waste types. However, it should be noted that actual average waste mixtures rarely have the exact characteristics delineated for any of these indicated waste types. ... 

Management and disposal of many wastes that contain hazardous chemicals are regulated by the U.S. Environmental Protection Agency (EPA) under authority of the Resource Conservation and Recovery Act (RCRA). In the classification system for hazardous chemical wastes specified in 40 CFR Part 261, waste is classified as hazardous by its characteristics or by listing. 

Characteristics of the system for classification and disposal of fuel-cycle waste. The current classification system for radioactive waste that arises from operations of the nuclear fuel cycle in the United States and the current requirements for disposal of waste in the different classes have the important characteristics discussed below. 

The classification system for fuel-cycle waste in the United States has the following important characteristics ... 

For hazardous chemical waste, there is no federal classification system other than a specification that the waste is hazardous or that it can be managed as if it were nonhazardous because it has been shown not to be characteristically hazardous or has been delisted or specifically excluded.14 Hazardous chemical waste that is not... 

The proposed framework for risk-based classification of all radioactive and hazardous chemical wastes developed in Section 6.2.2 represents waste classification in its broadest, most general terms. Thus, this classification system can be viewed as the highest level of a possible hierarchy of hazardous waste classifications (e.g., see Figure 4.2). Further subclassification of these broadly defined waste classes may be desirable for such purposes as protection of workers during waste operations, protection of public health and the environment following waste disposal, and development of efficient methods of waste management taking into account the characteristics of actual wastes. 

One of the most promising technical approaches to regulation of hazardous wastes (and one that already seems in progress for evaluation and response to old problem sites) is the development of a degree of hazard system of waste classification. The current RCRA approach and, to a slightly lesser degree, the Louisiana approach tend to treat all hazardous wastes as about equal. In fact, however, it is apparent that waste materials differ very greatly over a spectrum of intensity of the characteristics that make them hazardous. This is particularly so for the characteristic of toxicity. 

Classifications systems have been developed for commonly encountered waste compositions. These systems identify average characteristics of waste mixtures, including such properties as ash content, moisture, and heating value. The classification system published in the IIA Incinerator Standards is the most widely recognized and is almost always used by the incinerator manufacturers to rate their equipment. In this system, shown in Table 4.22, wastes are classified into seven types. Types 0 through 4 are mixtures of typical, general waste materials, and Types 5 and 6 (not listed in table) are industrial wastes requiring special analysis. 

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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