United States 		Environmental Protection Agency

U.S. EPA Mixed Waste Team

NRC/EPA Draft Storage Guidance

The policies discussed herein are not final agency actions, but are intended solely as guidance. They are not intended, nor can they be relied upon, to create any rights enforceable by any party in litigation with the United States. Environmental Protection Agency or Nuclear Regulatory Commission officials may decide to follow the policies provided in this guidance or to act at variance with the policies, based on an analysis of specific site circumstances. The Agencies also reserve the right to change these policies at any time without public notice.

Note to readers:

The information contained in this guidance is intended for use by Nuclear Regulatory Commission licensees who may not be familiar with the hazardous waste storage requirements that apply to mixed waste. However, much of the document may also be useful for Federal facilities that generate mixed waste. The guidance assumes that the reader already possesses a valid NRC or Agreement State radioactive materials license, but may not possess an Environmental Protection Agency or authorized state storage permit.

EPA and NRC recognize that the radioactive component of mixed waste may pose hazards from external radiation and from potential internal exposures. Individuals that may be exposed to radiological and non-radiological hazards from mixed waste should be trained in radiation and chemical safety. In addition, mixed waste generators should ensure that the hazards associated with the mixed waste are fully evaluated Prior to generating the waste.

This guidance presumes that both radiological and industrial hygiene safety programs are in place and will be followed by the reader. The Agencies did not consult with the Occupational Safety and Health Administration or States agencies responsible for workplace safety in developing this guidance. However, nothing in this guidance supersedes the OSHA safety requirements. NRC licensees are expected to comply with OSHA requirements, as well as all other applicable regulations.


Draft for Comment
August 1995


Mixed low-level radioactive and hazardous waste (mixed waste) is waste that satisfies the definition of low-level radioactive waste in the Low-Level Radioactive Waste Policy Amendments Act of 1985 (LLRWPAA) (1) and contains hazardous waste that either: 1) is listed as a hazardous waste in Subpart D of 40 CFR Part 261; or 2) causes the waste to exhibit any of the hazardous waste characteristics identified in Subpart C of 40 CFR Part 261. Persons who generate, treat, store or dispose of mixed wastes are subject to the requirements of the Atomic Energy Act of 1954, as amended (AEA) and the Solid Waste Disposal Act (SWDA) as amended by the Resource Conservation and Recovery Act (RCRA), and the Hazardous and Solid Waste Amendments of 1984 (HSWA). The Federal agencies responsible for ensuring compliance with the implementing regulations of these two statutes are the Nuclear Regulatory Commission (NRC) and the Environmental Protection Agency(EPA) (2). In October 1992, Congress enacted the Federal Facilities Compliance Act (FFCA) which, among other things, added a definition of mixed waste to RCRA. Mixed waste is defined in the FFCA as "waste that contains both hazardous waste and source, special nuclear, or byproduct material subject to the Atomic Energy Act of 1954" (RCRA 1004(41), 42 USC 6903(41)).

The LLRWPAA established a series of milestones, penalties and incentives to ensure that States or Regional Compacts provide for the disposal of radioactive waste. Although mixed waste was not specifically addressed in the LLRWPAA , States must ensure adequate disposal capacity for all low-level radioactive wastes, including mixed wastes. To date, progress in meeting the milestones in the LLRWPAA has been limited. In addition, uncertainties about the amounts and types of mixed waste, along with the complexities in complying with the regulations for these wastes, have hindered development of treatment and disposal facilities for mixed waste. As a result, licensees may be required to store mixed waste on-site until adequate treatment and disposal capacity has been established.

This guidance is designed to assist persons currently storing mixed waste to meet the regulatory requirements of both the AEA and RCRA. However, many of the requirements and procedures discussed in this guidance may not be applicable to nuclear power reactor facilities. The guidance describes procedures that are generally acceptable to both NRC and EPA that resolve issues of concern which have been identified to the agencies by licensees. It also addresses similar storage issues identified by the Department of Energy (DOE). The guidance first summarizes the general requirements that licensees must meet to store mixed waste in accordance with NRC and EPA regulations, then addresses specific storage issues that have been brought to the Agencies' attention by mixed waste generators. Finally, the guidance discusses EPA's RCRA enforcement policy for mixed waste in storage.


a . Regulatory Authority

In general, NRC or Agreement State licensed facilities that manage mixed waste are subject to the RCRA Subtitle C requirements for hazardous waste in 40 CFR Part 124 and Parts 260-270 implemented by EPA, or to comparable regulations implemented by States or Territories that are authorized to implement RCRA mixed waste authority. EPA asserted its regulatory authority over the hazardous portion of mixed waste in Federal Register Notices on July 3, 1986 and September 23, 1988 (see 51 FR 24504 and 53 FR 37045). The RCRA Subtitle C program was primarily developed for implementation by the States, and oversight by EPA. As of April 1995, EPA regulates mixed waste in Alaska, Hawaii, Iowa, Wyoming and all U.S. Trust Territories except Guam. Thirty-eight states and one territory (Guam) have been authorized to implement the base RCRA hazardous waste program (i.e., authorized states), and to regulate mixed waste activities (see 51 FR 24504, July 3, 1986). Nine states are authorized for the RCRA base hazardous waste program, but have not been authorized to regulate mixed waste (3). In these 9 States mixed waste is not regulated by EPA but may be regulated by States under the authority of State law. To understand the roles of EPA and the States in regulating the hazardous portion of mixed waste, the following categories of States or Territories are discussed below:

  • States and Territories whose hazardous waste program has not been authorized under RCRA to act "in lieu of" the federal RCRA program; these are called "unauthorized States or Territories";

  • States and Territories with RCRA authorization that have adopted mixed waste authority; and

  • States and Territories with RCRA authorization that have not adopted mixed waste authority .

As a subset of hazardous waste, mixed waste is regulated by EPA in unauthorized States and Territories (i.e., States and Territories that have not been authorized to implement the RCRA Subtitle C program). Where States and Territories are RCRA authorized and have adopted mixed waste authority, mixed waste is subject to the State's or Territory's authorized hazardous waste program (which may contain regulations more stringent than those in the Federal RCRA program). See Table 1 for a list of States with mixed waste authority as of June 30, 1995. In States or Territories with RCRA authorization that have not yet adopted mixed waste as part of the base RCRA program, mixed waste may be regulated under State or Territorial regulation, but not as a hazardous waste under an authorized RCRA program.

Facilities in RCRA authorized States (whether the State has mixed waste authority or not) should contact their respective State agency to ascertain what State regulations may apply to mixed waste. In addition, facilities in RCRA authorized States should be aware that EPA Regions may share responsibility for implementing the RCRA program with the State, particularly with respect to certain requirements promulgated under the Hazardous and Solid Waste Amendments of 1984 (e.g., corrective action and land disposal restriction requirements), for which the State may not yet be authorized to implement (4).

Twenty-nine States have signed agreements with NRC enabling the various "Agreement States" to regulate source, byproduct, and small quantities of special nuclear material within their boundaries. (see Table 2). Most facilities located in Agreement States are subject to regulatory requirements for radioactive material under State law. This applies to all source, special nuclear, and byproduct material except that from nuclear utilities and fuel cycle facilities, which are subject to NRC's requirements and DOE facilities, which are subject to DOE Orders. While States are required to adopt programs that are comparable with the NRC program, States may have requirements that are more stringent, or are in addition to those from the Federal program. Facility managers should determine whether their State is an NRC Agreement State and determine the scope of the program that has been relinquished by NRC to the State.

In addition to NRC regulated facilities, many DOE facilities may store mixed waste. These facilities are subject to the RCRA Subtitle C requirements or comparable State regulations. DOE Order 5820.2A, "Radioactive Waste Management," and DOE Order 5400.3, "Hazardous and Radioactive Mixed Waste Program," establish policies, guidelines, and minimum requirements under which DOE facilities must manage their radioactive and mixed waste and contaminated facilities. DOE Order 5400.3 excludes byproduct material unless it is mixed with RCRA hazardous waste. Because the storage issues discussed in this document may arise at either NRC-licensed or DOE facilities, this guidance may be useful in addressing mixed waste storage at DOE facilities. However, the primary focus of this guidance is a discussion of the requirements for the storage of mixed waste at NRC-licensed and RCRA-regulated facilities. As summarized in Table 3, regulation of mixed waste may be the responsibility of the State in which a facility is located. To ensure compliance, licensees and permittees should contact their State agencies in RCRA authorized or NRC Agreement States to determine if this or other guidance is applicable.

b. Applicability of RCRA Storage Requirements

NRC licensees who store mixed waste must comply with the requirements of RCRA. Under RCRA regulations, storage is defined as "the holding of hazardous waste for a temporary period at the end of which the hazardous waste is treated, disposed of, or stored elsewhere." The specific RCRA storage requirements that apply to licensees are determined by the quantity of hazardous waste generated, how long the licensee stores hazardous waste (including mixed waste) on-site (5), and the type of unit in which the waste is stored. Licensed facilities are considered RCRA storage facilities that require a RCRA Permits (6) (40 CFR 262.34) if they store the waste for:

  • more than 90 days, and if the facility's generation rate (both hazardous and mixed waste) is greater than 1000 kilograms per month (or greater than 1 kilogram of acutely hazardous waste/month (7); or

  • more than 180 days, and if the facility's waste generation rate (both hazardous and mixed waste) is between 100 and 1000 kilograms/month (in addition, the on-site waste accumulation cannot exceed 6000 kilograms); or

  • longer than 270 days, if the facility's waste generation rate (both hazardous and mixed waste) is between 100 and 1000 kilograms/month, and if the hazardous waste management facility to which the waste must be shipped is over 200 miles from the licensee's facility.

Licensees have asked questions about the applicability of RCRA regulated quantities. If a facility generates a quantity of low-level mixed waste that, combined with on-site RCRA non-mixed hazardous waste generation, does not exceed 100 kg/mo (or one kilogram of acutely hazardous waste as defined in 40 CFR 261.11(a)(2) and listed in 40 CFR 261.31-33), it qualifies as a conditionally exempt small quantity generator (SQG). As a result, it can dispose of the low-level mixed waste as low-level radioactive waste, if these materials meet the disposal site's waste acceptance criteria (40 CFR 261.5).

RCRA permit requirements are unit-specific and are described in 40 CFR Part 264 for permitted facilities and 40 CFR Part 265 for interim status facilities. Interim status requirements are self-implementing waste management requirements which are limited to facilities that were already in existence on the date that a new regulation or statutory requirement took effect and which subjected the facility to RCRA. For mixed waste facilities in authorized states, this date generally corresponds to the date that the State received authorization for a mixed waste program, although State requirements may differ.

Under RCRA, persons who store the prescribed quantities of hazardous wastes for less than the times outlined above are considered generators only and need not obtain a storage permit. However, such generators are still subject to the storage requirements of 40 CFR Part 262.34(a) or (d) (8), unless they qualify for the conditionally exempt small quantity generator (SQG) exemption in 40 CFR 261.5. A generator qualifies for this exemption if he generates no more than 100 kilograms of hazardous waste (including mixed waste) per month or 1 kilogram of acutely hazardous waste/month. Conditionally exempt SQGs are generally not subject to RCRA regulation as long as they meet the generation and accumulation limits, properly characterize their waste and ensure its proper management. If a SQG accumulates more than 1000 kilograms on-site or if its generation rate exceeds 100 kilograms in any given month, that SQG is no longer conditionally exempt and is subject to RCRA (9).

Generators may also store up to 55 gallons of hazardous waste (or 1 quart of acutely hazardous waste) in containers at or near the site of generation without a RCRA permit and without regard to the storage time limits. This is known as "satellite accumulation" and is governed by 40 CFR 262.34(c)(1). However, any waste in excess of the SS gallons (or 1 quart of acutely hazardous waste) must be removed from this area within three days of the date that these volumes were exceeded to a central storage area at which time the accumulation times mentioned above take effect. For example, a facility that generates over 1000 kg of hazardous waste per month has up to three days to remove any waste that exceeds the satellite accumulation limit of SS gallons from the satellite accumulation container and, following that three day period (or after waste is moved to the generator storage area), may store the waste for up to 90 days in accordance with the generator storage provisions of 40 CFR Part 262.34(a). If the waste is stored longer than 90 days, RCRA interim status or a RCRA storage permit is required.

Secondary materials that are stored or accumulated prior to being recycled (used, reused, or reclaimed) may be considered "accumulated speculatively" (see 40 CFR sections 261.1(c)(7), 261.1(c)(8), and 261.2 and (e)) and thus may be identified as hazardous waste unless the generator or facility accumulating the material can demonstrate that:

  • the material is potentially recyclable;

  • the material has a feasible means of being recycled; and

  • at least 75 percent by weight or volume is recycled or transferred tn a different site for recycling during the calendar year.

The EPA Regional Administrator or State Director has authority to approve accumulation that does not meet these limits, upon request for a variance (see 40 CFR 260.31(a)).

These restrictions on speculative accumulation may bring materials into the hazardous waste universe that have in the past been considered recyclable (see 40 CFR 261.2(d) and 261.2(e)). The intent of having such a requirement is to prevent the long term storage and mismanagement of hazardous materials under the guise that they may have some potential for being reused or recycled. Readers are encouraged to review 40 CFR 261.2 and 261.6 for further information on accumulation.

c. Storage Time Limitations under the Land Disposal Restrictions and Variances

EPA's Land Disposal Restriction (LDR) regulations (i.e., the requirements in 40 CFR 268.50 that prohibit the land disposal of hazardous wastes without prior treatment) prohibit the storage of LDR restricted hazardous wastes (including mixed wastes) except when storage is "solely for the purpose of accumulation of such quantities of hazardous waste as necessary to facilitate proper recovery, treatment, or disposal." Wastes that satisfy this accumulation requirement, may be stored in tanks, containers, or containment buildings on-site (10). Waste may be stored without regard to the storage prohibition if it has been treated to meet EPA treatment standards or if the waste is not subject to, or is exempt from, the LDRs because of an extension or a specific exemption from the LDRs (e.g., conditionally exempt small quantity generator wastes). In addition, wastes that have been placed into storage prior to an applicable LDR effective date are not subject to the prohibitions on storage. However, once such wastes are removed from storage, these wastes are subject to treatment standards and other applicable LDR requirements (51 FR 40577, November 7, 1986).

The storage prohibition also is not in effect for waste subject to a variance from the Land Disposal Restrictions. EPA grants three general types of variances from the LDRs: 1) variances that delay the effective date of a prohibition (e.g., a variance based on the lack of capacity to treat, recover or dispose hazardous waste); 2) variances from the prohibition based on a "no migration" determination; and 3) a treatability variance from a specific treatment standard. For more information on these variances, please consult the EPA guidance document entitled "Guidance on the Land Disposal Restrictions' Effects on Storage and Disposal of commercial Mixed Waste" (OSWER Directive 9555.00-01, September 28, 1990) available from NRC or EPA.

d. RCRA Permits and NRC License Amendments

Storage of all radioactive waste, including mixed waste, should be carried out in such a manner that ensures that the stored waste does not create a radiological hazard to surrounding areas, increase the potential for a release of radioactive materials to unrestricted areas, or pose an increased hazard to facility personnel. The physical, chemical, and radiological characteristics of the waste, as well as any other characteristics that could pose a potential health and safety problem in the storage area should be identified and evaluated by the licensee prior to developing the NRC license application or amendment request. Provisions for material security and inventory, fire protection, effluent controls, effluent monitoring, shielding and area radiological controls should be included in the NRC license application or amendment request. This application or request should include written procedures for radiological surveys, periodic audits, and inspections, as well as an effective contingency plan to address the repackaging of damaged or deteriorating containers. The elements of the plan should take into account the isotopes, waste forms, and quantities to be stored.

In order to remain in compliance with all regulatory requirements for mixed waste storage, some licensees may need to obtain an EPA (or authorized State) storage permit and/or amend their NRC (or Agreement State) licenses. Examples of instances where an NRC license amendment may be needed include:

  • If the total activity of the radioactive material at the facility (both in use, storage, or in waste) would exceed the activity authorized by the facility license;

  • If the licensee intends to store the waste in a portion of the facility not authorized by the license;

  • If the chemical or physical form of the waste is not authorized by the license; or

  • If the storage program is not specifically included within the scope of the authorization.

If a licensee is required to amend its radioactive materials license, NRC will require the licensee to provide sufficient information to evaluate the request and determine if the proposed amendment impacts on the level of protection afforded by the existing license.

NRC License Amendments

While EPA regulations concerning the storage of hazardous waste (40 CFR Part 264, Subpart I and J) are fairly prescriptive, NRC regulations regarding the storage of radioactive waste, other than spent fuel, are more performance based. NRC licenses incorporate conditions specific to a facility or licensee that prescribe acceptable practices for the storage of radioactive material. Typically, licensees propose materials management practices to NRC and an evaluation of the proposed practice is performed by NRC prior to approving (or disapproving) the request. These license conditions are then enforceable conditions under which the licensee must conduct his operations.

Those facilities already possessing a radioactive materials license may need to amend their license to store mixed waste. Currently, NRC guidance on LLW storage is contained in several Generic Letters and Information Notices. Appendix A lists these Generic Letters and Information Notices. Licensees contemplating storing mixed waste should review the NRC guidance and contact NRC to determine the information that should be included in a request to store mixed waste at their facility.

[In a memorandum to the Commission dated August 1, 1994 (SECY 94-198), NRC staff provided the Commission with revisions to the existing guidance for on site storage of low-level radioactive waste. NRC staff expects to finalize the guidance in late 1995. Until the revised guidance is finalized licensees should refer to the guidance discussed in Appendix A. NRC staff expects to include the revised LLW storage guidance in the final joint guidance on mixed waste storage].

If licensees store mixed waste containing special nuclear material, they must address the special properties of the fissile radioisotopes in this waste. Their mixed-waste storage program must address the spatial distribution, geometry, volume, and the concentration of this waste at the storage facility. Strict controls are to be implemented and documented that assure the safe storage of mixed waste containing special nuclear material. Appropriate security measures are to be taken, and documented, to ensure the physical security of special nuclear material at the storage facility. The licensee must comply with all requirements stipulated in their license and with the requirements in 10 CFR Part 70, "Domestic Licensing of Special Nuclear Material."

RCRA Permits

Licensees who require a RCRA permit for storage must submit an EPA permit application. The application, which is described in 40 CFR Part 270, consists of two parts (Parts A and B). Part A consists of pages 1 and 3 of the Consolidated Permit Applications Form. There is no form for a Part B application. Rather, the Part B application is submitted in narrative form and should contain the information set forth in the applicable sections of 40 CFR Parts 270.14 through 270.29. For new facilities, Parts A and B of the permit must be submitted at least 180 days before physical construction of any new facility is expected to commence.

For existing facilities (i.e., existing on the date that RCRA applicability is established), timely submission of the Notification of Hazardous Materials Activity and a Part A application qualifies the facility for interim status under RCRA section 3005(e). Facilities with interim status are treated as having been issued a RCRA permit until EPA, or a State, makes a final determination on the permit application.

Facilities with interim status still must comply with the interim status regulations set forth in 40 CFR Part 265 or with their State's regulations if it is an EPA authorized State. For such existing facilities the EPA Regional Administrator shall set a date, giving the facility at least six months notice, for submission of the Part B application.


Most mixed waste at operating facilities will be stored in containers or, less frequently, in tanks. EPA requirements for waste stored in tanks and containers are outlined in RCRA Subparts J and I, respectively. In addition, 40 CFR 268.50 addresses the storage of hazardous wastes restricted from land disposal under Subpart C of RCRA. Unlike EPA regulations, NRC's requirements for waste storage are not specific with respect to the type of storage unit (i.e., container, tank, waste pile, etc.), except for tanks at nuclear power reactors, but are based on the type of waste (i.e, wet or dry) and are outlined in 10 CFR Parts 20, 30, 40, 50, 70, and 73. Licensees will be required to comply with container and tank requirements of both EPA and NRC.

Licensees have identified a variety of issues associated with the storage of mixed waste that have caused them concern. Licensees have indicated to both NRC and EPA that they believe strict adherence to the regulations of both agencies may not be possible because of perceived inconsistencies between the two sets of regulatory requirements. (11) Where radioactive wastes (or wastes suspected of being radioactive) are involved in storage, it has been suggested that the NRC's storage requirements may run counter to the aims of RCRA. Neither EPA nor NRC is aware of any specific instances where RCRA compliance has been inconsistent with the AEA. However, both agencies acknowledge that an inconsistency may occur. A licensee or applicant who suspects that an inconsistency may exist should contact both NRC, EPA, or any other AEA and RCRA regulatory agencies. These regulatory agencies should deliberate and consult on whether there is an unresolvable inconsistency and, if one exists, they should attempt to fashion the necessary relief from the particular RCRA provision that gives rise to the inconsistency. However, all other RCRA regulatory requirements would apply. That is, a finding by the regulatory agencies that an inconsistency exists does not relieve a hazardous waste facility owner/operator of the responsibility to ensure that the mixed waste is managed in accordance with all other applicable RCRA regulatory requirements. Owners/operators of mixed waste facilities are encouraged to address and document this potential situation and its resolution in the RCRA facility waste analysis plan which must be submitted with the Part B permit application, or addressed in a permit modification.

Licensees have identified four issues where compliance with both agencies regulations has caused concern or confusion. These issues are:

  1. Decay-in-storage of mixed waste;

  2. Inspection/surveillance requirements for mixed waste in storage;

  3. Allowable storage practices for stored mixed waste; and

  4. Waste compatibility, segregation and spacing requirements.

Decay-in-Storage of Mixed Waste

A large portion of the radioactive waste (and mixed waste) generated by medical and biomedical research institutions contains radionuclides with relatively short half-lives. These short lived radionuclides are especially prevalent in the combustible dry waste, aqueous wastes, and animal carcass wastes generated by medical and academic institutions. NRC generally allows medical facilities to store waste containing radionuclides with half-lives of less than 65 days until 10 half-lives have elapsed and the radiation emitted from the unshielded surface of the waste, as measured with an appropriate survey instrument, is indistinguishable from background levels. The waste may then be disposed of as non-radioactive waste after ensuring that all radioactive material labels are rendered unrecognizable (see 10 CFR 35.92). Radioactive waste may also be stored for Decay under certain circumstances in accordance with 10 CFR 20.2001. For mixed waste, storage for Decay is particularly advantageous, since the waste may be managed solely as a hazardous waste after the radionuclides Decay to background levels. Thus, the management and regulation of these mixed wastes are greatly simplified by the availability of storage for decay.

Before disposing of the waste after Decay, the licensee must survey the waste using an appropriate survey instrument, and technique, and demonstrate that the radiation emitted from the waste is indistinguishable from representative background levels. Licensees, not already authorized to hold wastes for Decay-in-storage, that wish to hold mixed waste for Decay-in-storage may need to obtain a license amendment from NRC prior to storing the mixed waste. Many licensees in possession of mixed waste and who use Decay-in-storage will be required to obtain an amendment to store the mixed waste for Decay prior to disposal as hazardous waste. The following should be included in a license amendment request to NRC:

  • a description of the survey procedures to be used during storage and prior to release of the waste to a hazardous waste-only facility,

  • a description of the procedures for segregating and tracking waste from placement in storage to release to a hazardous waste-only facility,

  • a commitment that waste will be held for a minimum of ten half-lives prior to performing the final radiation survey before release to a hazardous waste-only facility and

  • a statement that the decayed radioactive waste will not be released to a hazardous waste-only facility unless the radiation emitted from the waste is indistinguishable from background radiation.

While NRC licensing amendments address the management of the radioactive component of these wastes, they generally have no effect on the applicable RCRA storage provisions. Storage requirements under RCRA should ideally be implemented in a manner that provides appropriate protection of health and the environment, without setting up undue impediments to well conducted decay programs.

Under RCRA, a storage permit (or interim status) is generally required to manage the wastes during the Decay period if this storage period exceeds 90 days. However, even with such a permit, a question has been raised as to whether accumulation of mixed wastes during the Decay period violates the Land Disposal Restrictions (LDR) storage prohibition in RCRA section 3004(j). This latter provision, and regulations at 40 CFR 268.50, generally prohibit generators and owner/operators of hazardous waste treatment, storage, or disposal facilities from storing hazardous wastes that are restricted from land disposal under the LDR program, except when storage is "solely for the purpose of accumulation of such quantities of hazardous waste as necessary to facilitate proper recovery, treatment, or disposal." Exceptions are recognized for hazardous wastes that have been treated to LDR treatment specifications, and for wastes exempted by virtue of one of the LDR variance authorities, i.e., a capacity variance, a no migration variance, or a case-by-case extension. In addition, RCRA and regulations at 40 CFR 268.50(a) define a conditional exception for on-site storage in tanks or containers, where the generator complies with the regulations at 40 CFR 262.34 requirements, and the storage is solely for the purpose of the accumulation of such quantities of hazardous waste as are necessary to facilitate proper recovery, treatment, or disposal.

EPA believes that the limited periods of approved Decay-in-storage of mixed waste do not violate the RCRA section 3004(j) storage prohibition. EPA believes this interpretation is supported by the following consideration.

EPA considers decay-in-storage a necessary and useful part of the best demonstrated available technology (BDAT) treatment process. "Decay-in storage" meets the definition of "treatment" in 40 CFR 260.10, insofar as it is a method or technique designed to change the physical character or composition (amount of radioactivity) in the mixed wastes. Decay-in-storage subsequently makes the treatment of the hazardous constituents safer, and renders them safer for transport.

As a result, the LDR storage prohibition does not apply to mixed waste held pursuant to an NRC approved Decay-in-storage program during the period of Decay. EPA emphasizes that the inapplicability of the storage prohibition is coincident with the period of Decay; once the waste has decayed to levels that are indistinguishable from background levels, the RCRA 3004(j) and 40 CFR 268.50 provisions apply fully to any additional storage that occurs prior to completing the required BDAT treatment.

Inspection/Surveillance Requirements for Stored Mixed Waste

Under RCRA, waste storage containers must be inspected on a weekly basis (40 CFR 264.174) and certain above-ground portions of waste storage tanks on a daily basis (40 CFR 264.195(b)(1)). The purpose of these inspections is to detect leakage from or deterioration of containers. NRC recommends that waste in storage be inspected on at least a quarterly basis. Licensees have expressed concerns that daily or weekly "walk-through" inspections of high activity mixed waste may result in increased exposures to workers at their facilities and thus violate their As Low as Reasonably Achievable (ALARA) programs.

The RCRA regulations and permit guidance do not require that inspections of mixed waste in storage must be "walk-through" inspections. NRC and EPA recognize that increased exposures to workers may result from daily or weekly "walk through" inspections and suggest that licensees consider using methods other than walk-through inspections as a means to inspect high-activity mixed waste in storage. Alternative methods for inspection could include the use of remote monitoring devices to determine if a waste container is leaking or television monitors, or other means that are capable of detecting leakage or deterioration. Such alternative methods would comply with the RCRA regulation and would avoid the additional exposures of walk-through inspections. However, these measures should be coupled with a means to promptly locate and segregate or remediate leaking containers.

Flexibility does exist in the RCRA regulations to allow use of such alternative inspection procedures at frequencies specified in the hazardous waste regulations and in the facility's waste analysis plan. Once a facility receives a RCRA permit, these procedures and frequencies are included in the permit. Facilities with existing RCRA permits may have to request a permit modification to change stated inspection procedures (40 CFR 270.42).

NRC licensees that have incorporated specific inspection procedures in their radioactive materials licenses or procedures referred to in license conditions should contact the appropriate NRC or State office to determine if the alternative inspection procedure will require the license to be amended.

Allowable Storage Practices - Dense packing Practices

NRC currently allows containers with low exposure rates to be used to provide radiation shielding for containers with higher exposure rates. Licensees have expressed concerns that RCRA inspection requirements (40 CFR 264.174, 264.195(b)(1), 265.174, and 265.195(a)(1)) may restrict this use of low exposure rate containers and that such a restriction could cause an increase in worker exposures.

The agencies agree that using low-exposure rate containers for radiation shielding is a reasonable practice. However, concerns about the potential consequences of a container leaking liquid high-activity mixed waste must also be addressed. Containers may be used for radiation shielding, so long as a licensee is capable of detecting, locating the source, and responding to a release within 24 hours of detection to mitigate any significant release . An example of such a capability might include a remote monitoring capability coupled with a means for promptly locating and responding to such a release.

So long as the container configuration does not compromise the ability to detect or respond to container leakage or deterioration, the configuration complies with RCRA requirements.

Waste compatibility. Segregation and Spacing Requirements

In general, any facility that treats, stores or disposes of RCRA hazardous wastes (including mixed waste) must take special measures in handling ignitable, reactive, and potentially incompatible wastes. These measures are outlined in 40 CFR 264.17, including placing "No smoking" signs in areas where ignitable or reactive wastes present hazards, separating or protecting wastes from sources of ignition or reaction, and taking special precautions to avoid explosive, heat or gas generating reactions. Facilities must document their compliance with these measures (40 CFR 264.17(c)).

Additional requirements for ignitable, reactive, and incompatible wastes managed in tanks and containers are found in Subparts I and J of 40 CFR Parts 264 and 265. For example, 40 CFR 264.177 and 265.177 require that wastes managed in containers that are stored close to incompatible wastes or other materials "must be separated from the other materials or protected from them by means of a dike, berm, wall, or other device" to prevent ignition or reaction. This separation, however, can occur in the same storage facility and does not necessitate the construction of an entirely separate storage unit. Hazardous wastes also may not be placed in unwashed or contaminated units that previously contained incompatible wastes or materials (40 CFR 264.177(b)). Appendix V of 40 CFR Part 264 contains examples of potentially incompatible wastes.

RCRA storage facilities must also maintain sufficient aisle space in waste storage areas "to allow the unobstructed movement of personnel, fire protection equipment, spill control equipment, and decontamination equipment to any area of the facility operation in an emergency, unless it can be demonstrated to the EPA Regional Administrator that aisle space is not needed for these purposes" (40 CFR 264.35). In situations where high activity mixed wastes are monitored by remote means and/or stored using dense packing, a new facility has the flexibility to make such a demonstration to the Regional Administrator based (or authorized State) on the need to control the radiation hazard (40 CFR 264.35). Facilities with interim status have the same opportunity to justify why aisle space is not required (40 CFR 265.35). In either case, alternative systems or plans to contain spills, prevent fire and decontaminate equipment may be required by the Regional Administrator. The determination to waive or alter the aisle space requirement will be made on a case-by-case basis and be incorporated into the facility's RCRA permit.


EPA has recognized that a shortage of adequate treatment and disposal capacity for mixed waste has existed for some time, and that the LDRs present a problem for generators that are unable to treat or dispose of this waste. Accordingly, on August 29, 1991 EPA announced, in the Federal Register (56 FR 42730) a policy of giving a reduced priority to civil enforcement of the storage prohibition in section 3004 (j) of RCRA at facilities which generate mixed waste. The policy was limited to civil enforcement and administrative actions resulting solely from the act of storing mixed waste in violation of RCRA section 3004 (j) and to those waste streams for which adequate treatment is not available. The policy was limited in duration and expired on December 31, 1993. On April 20, 1994, EPA announced a two year extension of this policy (59 FR 18813).

This policy applies to facilities which generate less than 1,000 cubic feet per year of land disposal restricted mixed waste and are operated in an environmentally responsible manner. EPA will consider a variety of factors in determining if a facility is conducting its operations in an environmentally responsible manner including:

  • Whether the facility can demonstrate that its mixed waste storage areas are in compliance with all applicable RCRA storage facility standards found in 40 CFR 264.73/265.73 and inspection standards found in 40 CFR 264.15/265.15;

  • Whether the facility has identified and kept records of its mixed wastes in accordance with 40 CFR 264.73(b)/265.73(b), including sources, waste codes, generation rates and volumes in storage;

  • Whether the facility has developed a mixed waste minimization plan (see 58 FR 31114, May 28, 1993) and;

  • Whether the facility is prepared to demonstrate the good faith efforts it has undertaken to ascertain the availability of treatment capacity for its wastes.

    Licensees are encouraged to review this policy as presented in the Federal Register to determine if the flexibility contained in the policy may be appropriate for the operations at their facilities.


    NRC and EPA recognize that until adequate treatment and disposal capacity is developed, mixed waste generators will face difficulties when storing their mixed waste. Compliance with both agencies' regulatory requirements will require that mixed waste generators become familiar with and take advantage of the flexibility in the existing regulations. Methods to ensure compliance with these regulations may include the use of remote monitoring equipment and shielding high exposure rate containers with low exposure rate containers. Generators that manage land disposal restricted waste and that are unable to find treatment and disposal capacity are likely to meet the conditions for the lower enforcement priority policy described above. If a generator locates adequate treatment and disposal capacity, this capacity should be used rather than engaging in unnecessary storage.

    Generators should make every effort to determine if treatment or disposal capacity currently exists for their mixed waste. In order to provide mixed waste generators with information on commercial treatment and disposal capacity, the agencies published NUREG/CR-5938, the National Profile on Commercially Generated Low-Level Radioactive Mixed Waste in December 1992. This NUREG presents information on the volumes, characteristics, and treatability of commercially generated mixed waste and provides valuable information on facilities that currently offer treatment services for mixed waste. Finally, generators should minimize, to the maximum extent practicable, the amount of mixed waste being generated at their facilities. EPA's Risk Reduction Engineering Laboratory (RREL), in coordination with DOE, is currently conducting research in waste minimization techniques that should provide generators with general strategies to minimize their hazardous and mixed waste generation. Mixed waste generators should contact RREL at (513) 569-7391 to obtain information on these general waste minimization techniques. (For addition guidance, refer to 58 FR 31114, May 28, 1993, Guidance to Hazardous Waste Generators on the Elements of a Waste Minimization Pr w ram, or NRC Information Notice 94-23, Guidance to Hazardous. Radioactive and Mixed Waste Generators on the Elements of a Waste Minimization Program, March 25, 1994).

    NRC and EPA believe that through cooperation with the regulatory authorities, the use of innovative storage practices, minimizing mixed waste generation, and treating mixed waste to the maximum extent possible, mixed waste generators will be able to manage their mixed waste in a manner that protects the public and the environment until adequate disposal capacity is developed.

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    Last Updated: March 4, 1998.

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