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Mixed Waste
Waste Management: 

Guidance on the Definition and Identification of Commercial Mixed Low-Level Radioactive and Hazardous Waste


The following information is based on guidance for identifying low-level mixed-waste developed jointly by the Nuclear Regulatory Commission and EPA. A join NRC/EPA memo was published with the guidance.

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Mixed, low-level radioactive and hazardous waste or more simply, mixed, low-level waste (LLMW) has two components:

  1. radioactively contaminated industrial or research waste such as paper, rags, plastic bags, or water-treatment residues. Its categorization does not depend the level of radioactivity it contains. (See the regulatory definition in the Low-Level Radioactive Waste Policy Amendments Act of 1985 (LLRWPAA) It is waste that does not meet the criteria for any of three other categories of radioactive waste:
    • spent nuclear fuel and high-level radioactive waste
    • transuranic radioactive waste
    • uranium mill tailings.
  2. hazardous waste that falls into either of the following classes under the Resource Conservation and Recovery Act (RCRA):
    • listed hazardous wastes (Subpart D of 40 CFR Part 261)
    • characteristic hazardous wastes (Subpart C of 40 CFR Part 261).

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Identification Methodology

Identification of Mixed LLW

Under current federal law, LLMW is subject to regulation by NRC under the Atomic Energy Act (AEA), as amended, and by EPA under RCRA, as amended, or equivalent state regulations.

The EPA/NRC guidance provides a methodology, illustrated in Figure 1, that generators of commercial LLW can use to identify mixed LLW. Its application in identifying mixed LLW highlights the complexity of the definition. For specific questions about whether LLW is mixed LLW, contact the appropriate agencies.

  1. Is the waste LLW?
    If the waste meets the definition provided above, then it is potentially LLMW. If not, then the waste cannot be LLMW because it is not LLW. However, the waste may be another radioactive or hazardous waste regulated under the Atomic Energy Act (AEA), RCRA, or both statutes.

  2. Does it contain a "listed" hazardous waste?
    "Listed" hazardous wastes include hazardous waste streams from specific and non-specific sources listed in 40 CFR Parts 261.31 and 261.32 and discarded commercial chemical products listed in 40 CFR Part 261.33. Generators are responsible for determining whether LLW contains listed hazardous wastes. Their determination should be based on knowledge of the process that generates the waste. For example, if a process produces LLW that contains spent solvents that are specifically listed in the tables of Subpart D of Part 261, the generator should suspect that the waste is mixed LLW. If the LLW contains a listed hazardous waste it is LLMW. If not, it may still be LLMW if one or more components are "characteristic" hazardous wastes.

  3. Do non-Atomic Energy Act components cause the waste to exhibit hazardous "characteristics?"
    "Characteristic" hazardous wastes exhibit any of the characteristics identified in Subpart C of 40 CFR Part 261. These characteristics include ignitability (Section 261.21), corrosivity (Section 261.22), reactivity (Section 261.23), and Extraction Procedure (EP) toxicity (Section 261.24). The determination can be based on either the generator's knowledge of the materials or processes used in generating the LLW or on testing using the methods identified in Subpart C of Part 261.

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Questions and Answers

As a supplement to the "Guidance on the Definition and Identification of Commercial Mixed Low-Level Radioactive and Hazardous Waste (Mixed LLW)," answers to anticipated questions are included to clarify obscure points and to respond to public comments.

Are my low-level radioactive wastes exempt from RCRA because they are source, special nuclear, or byproduct materials as defined under the AEA?

Except for certain ores containing source material, which are defined as source material in 10 CFR 40.4(h), and uranium and thorium mill tailings or wastes, NRC and EPA consider that only the radionuclides themselves are exempt from RCRA. Section 1004(27) of RCRA excludes source, special nuclear, and byproduct material from the definition of "solid waste." RCRA defines solid waste as:

"any garbage, refuse, sludge from a waste treatment plant, water supply treatment plant, or air pollution control facility and other discarded material, including solid, liquid, semisolid, or contained gaseous material resulting from industrial, commercial, mining, and agricultural operations, or from community activities, but does not include solid or dissolved materials in irrigation return flows or industrial discharges which are point sources subject to permits under section 402 of the Federal Waster Pollution Control Act, as amended (86 Stat. 880), or source, special nuclear, or byproduct material as defined by the Atomic Energy Act of 1954, as amended (68 Stat. 923)."

Since "hazardous waste" is a subset of "solid waste," RCRA also excludes source, special nuclear, and byproduct materials from the definition of hazardous waste and, therefore, from regulation under EPA's RCRA Subtitle C program. Section 11 of the Atomic Energy Act, as amended, defines these radioactive materials as follows:

Source material means:

  1. uranium, thorium, or any other material which is determined by the Atomic Energy Commission (AEC) pursuant to the provisions of section 61 of the AEA to be source material, or
  2. ores containing one or more of the foregoing materials, in such concentration as the AEC may by regulation determine from time to time.

Special nuclear material means:

  1. plutonium, uranium enriched in the isotope 233 or in the isotope 235, and any other material which the AEC, pursuant to the provisions of Section 51 of the AEA, determines to be special nuclear material; or
  2. any material artificially enriched by any of the foregoing, but does not include source material.

Byproduct material means:

  1. any radioactive material (except special nuclear material) yielded in or made radioactive by exposure to radiation incident to the process of producing or utilizing special nuclear material, and
  2. the tailings or wastes produced by the extraction or concentration of uranium or thorium from any ore processed primarily for its source material content.

Source, special nuclear, and byproduct materials, however, may be mixed with other radioactive or non-radioactive materials that are not source, special nuclear, or byproduct materials. For example, tritium may be contained in toluene, a nonhalogenated aromatic solvent. Consistent with the definition of byproduct material, the tritium may be considered a byproduct material, while the toluene that contains the tritium would not be byproduct material. Mixtures of toluene and tritium could satisfy the definition of Mixed LLW because they contain listed hazardous waste (spent toluene) and tritium that may qualify as LLW if it has been produced by activities regulated by NRC under the AEA.

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What are some examples of Mixed LLW?

A preliminary survey performed for the NRC identified two potential types of Mixed LLW:

The preliminary survey concluded that potential Mixed LLW comprises a small percentage of all LLW. For example, LLW containing organic liquids accounted for approximately 2.3% by volume of LLW reported in the preliminary survey (Bowerman, et al., 1985). An earlier survey identified a more diverse universe of potential Mixed LLW including wastes that contained aldehydes, aliphatic halogenated hydrocarbons, alkanes, alkenes, amino acids, aromatic hydrocarbons, chelating agents, esters, ethers, ketones, nitrosamines, nucleotides, pesticides, phenolic compounds, purines, resins, steroids, and vitamins (General Research Corporation, 1980). NRC also anticipates that additional LLW may be identified as Mixed LLW in the future, as generators implement the definition of Mixed LLW and as EPA revises the definition of hazardous waste.

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Could some "exempt" wastes be considered Mixed LLW?

A determination that radioactive wastes are exempt for radioactivity may affect how the wastes are managed or discarded, but it does not affect the legal status of the wastes. Specifically, their status with respect to the definition of Mixed LLW does not change. Exempt waste is still LLW because it satisfies the definition of LLW in the LLRWPAA and is within the NRC's jurisdictional authority under the AEA.

When radioactive waste contains sufficiently low concentrations or quantities of radionuclides, NRC may find that they do not need to be managed or disposed of as radioactive wastes. For NRC to make such a finding, management and disposal of the waste must not pose an undue radiological risk to the public and the environment. However, NRC's determination that the radioactive content of the wastes is exempt does not relieve licensees from compliance with applicable rules of other agencies governing non-radiological hazards (e.g., regulations of EPA or the Department of Transportation).

Therefore, some exempt wastes may still be considered Mixed LLW if they contain hazardous wastes that have been listed in Subpart D of 40 CFR Part 261 or that cause the LLW to exhibit any of the hazardous characteristics described in Subpart C of 40 CFR Part 261. Exempt Mixed LLW may be managed without regard to its radioactivity (but it must still be managed as a hazardous waste in compliance with EPA's regulations for hazardous waste generation, storage, transportation, treatment, and disposal (cf. 40 CFR Part 262 through Part 266).

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If I use chemicals in my process that are identified by EPA as hazardous constituents, should I assume that my LLW is Mixed LLW?

No. Low-level radioactive waste that contains hazardous constituents may not necessarily be Mixed LLW. As defined above, Mixed LLW is LLW that contains a known hazardous waste (i.e., a listed hazardous waste) or that exhibits one or more of the hazardous characteristics because it contains non-AEA materials. For wastes that are not listed in Subpart D of 40 CFR Part 261, testing is not necessarily required to "determine" whether the LLW exhibits any of the hazardous characteristics. A generator may be able to determine whether the LLW is Mixed LLW based on knowledge of the waste characteristics or the process that generates the LLW.

Furthermore, if the generator normally segregates LLW from hazardous and other types of wastes, there is no need to assume that hazardous wastes may have been inadvertently mixed with LLW or to inspect each container or receptacle to ensure that inadvertent mixing has not occurred. Although the generator is subject to RCRA inspections and must follow the manifest, pre-transport, and other requirements of 40 CFR Part 262, the generator is not required to demonstrate that every LLW container does not contain hazardous waste.

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How can I obtain representative samples of heterogeneous trash included in LLW to perform the hazardous characteristics tests?

Before discussing the collection of representative samples of waste, generators are reminded that they are not required to test LLW to determine if the waste contains hazardous wastes. Generators and handlers of mixed-waste and hazardous waste can declare their wastes hazardous or nonhazardous based on knowledge of the process/production of the waste, in lieu of testing for a characteristic.

Representative samples of waste should be collected for testing in accordance with EPA's regulations in 40 CFR 261.20(c), which state that waste samples collected using applicable methods specified in Appendix I of Part 261 will be considered as representative samples for hazardous characteristics testing. This appendix has been included in its entirety in Appendix II of this guidance. The sampling techniques described in Appendix I of Part 261 apply to extremely viscous liquids, fly ash-like material, containerized liquid wastes, and liquid wastes in pits, ponds lagoons, and similar reservoirs. In the absence of guidance about sampling heterogeneous wastes, generators should use appropriate portions of the sampling methods described in Appendix, I of Part 261 and EPA's manual entitled Test Methods for Evaluating Solid Waste, Third Edition (i.e., SW-846) in combination with other methods to collect, to the maximum extent practicable, representative samples of the waste to be tested.

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Are lead containers whose primary use is for shielding in disposal operations, hazardous waste under RCRA?

No. While lead containers and lead container liners may exhibit the hazardous characteristic for lead, those containers whose primary use is for shielding in low-level waste disposal operations are not considered wastes and thus, are not subject to the hazardous waste rules. These same containers and liners if disposed of or discarded would be considered wastes and if they exhibit the hazardous characteristic, would be subject to the hazardous waste rules.

It should be noted that EPA recognizes that all lead containers and liners may be equally hazardous to human health and the environment when placed in the ground independent of its legal classification as a waste or container. Therefore, EPA recommends that all lead containers and lead liners be managed in an environmentally safe manner (e.g., managed in a permitted hazardous waste facility or treated such that it no longer exhibits its characteristic).Encapsulation may be a viable mechanism to mitigate lead migration from these containers and liners. The EPA has not evaluated specific containers or encapsulation methodologies using the EP Toxicity test.

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If a waste contains any of the constituents listed on Appendix VIII of Part 261, is it a hazardous under RCRA?

No. Under RCRA, a waste is hazardous if it is a "listed" waste or it exhibits a hazardous characteristic. Wastes are listed by EPA if they contain significant amounts of toxic constituents identified in Appendix VIII, and the Agency has determined that these toxic constituents are persistent and mobile to some degree such that they pose a potential and substantial threat to human health and the environment. (Factors outlined in 40 CFR 261.11(a)(3)(i)-(xi), which include nature of the toxicity present and potential degradation products, may be considered when determining whether or not a waste should be listed). However, until the Agency lists the wastes in Subpart D of Part 261, they would not be considered hazardous by EPA (even if the waste contains one or more of the hazardous constituents listed on Appendix VIII) unless the waste would exhibit one or more of the hazardous waste characteristics.

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