8
Legal and Regulatory Factors for Waste Form Performance
The second charge of the statement of task for this study (see Box 2.1 in Chapter 2) calls for the identification and description of “Scientific, technical, regulatory, and legal factors that underpin requirements for waste form performance.” This chapter describes some key legal and regulatory requirements and agreements that apply to the DOE-EM cleanup program and their implications for waste form performance requirements.
In the context of this report, the term waste form performance has a very specific meaning: It is the ability of a waste form to sequester and retain its radioactive and chemically hazardous constituents. As discussed in Chapters 6 and 7, the performance of a waste form depends crucially on the physical and chemical conditions in the near-field environment of the disposal facility into which it will be emplaced. The committee interprets the phrase requirements for waste form performance to mean the legal and regulatory requirements that govern how a waste form must perform in a particular disposal environment.
The Department of Energy’s (DOE’s) cleanup and waste disposal programs operate under a large number of legal and regulatory requirements. These requirements are formalized in contracts, DOE orders, federal agency regulations, and in some cases state agreements and regulations. They include laws and regulations that apply to radioactive, hazardous, and mixed (radioactive and hazardous) wastes as well as agreements and orders that govern specific cleanup and disposal actions. These laws, regulations, and agreements have common objectives—to protect the worker, public health, and the environment.
Two DOE offices are responsible for waste management and disposal. The DOE-Office of Environmental Management (EM) is responsible for cleanup of radioactive and hazardous waste at DOE sites that are part of the cleanup program (see Figure 2.1). DOE-EM is also responsible for disposal of waste at its sites (i.e., low-level waste and the low-activity fraction of high-level waste) as well as for defense transuranic waste at the Waste Isolation Pilot Plant in New Mexico. The DOE-Office of Civilian Radioactive Waste Management1 (OCRWM) is responsible for disposal of spent nuclear fuel (SNF) and high-level radioactive waste (HLW) from the DOE-EM cleanup program (as well as for disposal of commercial spent nuclear fuel). As noted previously, these activities are carried out under a number of different laws, orders, regulations, and agreements.
8.1 LAWS AND DOE DIRECTIVES
There are several sets of laws and other governmental directives that apply to the DOE-EM cleanup program and have actual or potential implications for waste form performance. These include:
- Atomic Energy Act of 1954
- Nuclear Waste Policy Act of 1982
- Energy Policy Act of 1992
- DOE Order 5400.1
- DOE Order G 435.1
- National Defense Authorization Act Section 3116
These laws and directives are described briefly in the following sections.
8.1.1 Atomic Energy Act of 1954
The Atomic Energy Act of 1954, as amended, designates DOE as responsible for the safe management and final disposal of all radioactive wastes arising from its operations. DOE Order G 435.1, which is described in Section 8.1.5, establishes the technical basis for decisions on the classification, management, and disposal of DOE wastes except SNF and HLW. In some cases Order G 435.1 references other laws and regulations that govern DOE activities.
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1 OCRWM was established by the Nuclear Waste Policy Act and has responsibility for managing and disposing of spent nuclear fuel and high-level radioactive waste. However, the Obama Administration’s budget request for Fiscal Year 2011 eliminates funding for this office. Its responsibilities for spent fuel management are currently being handled by DOE’s Office of Nuclear Energy.
8.1.2 Nuclear Waste Policy Act of 1982
The Nuclear Waste Policy Act of 1982 (NWPA), as amended, establishes the current structure for the final disposal of SNF and HLW in a deep geological repository. The NWPA defines the roles and responsibilities for DOE as the implementing organization, the U.S. Environmental Protection Agency (EPA) to develop the safety standards for disposal, and the U.S. Nuclear Regulatory Commission (USNRC) to establish licensing procedures and regulations for a geological repository.
Following the Atomic Energy Act definitions, the NWPA states
The term ‘high-level radioactive waste’ means:
(A) the highly radioactive material resulting from the reprocessing of spent nuclear fuel, including liquid waste produced directly in reprocessing and any solid material derived from such liquid waste that contains fission products in sufficient concentrations; and
(B) other highly radioactive material that the [Nuclear Regulatory] Commission, consistent with existing law, determines by rule requires permanent isolation.
The definition of defense HLW in the NWPA is source based (as opposed to radioactivity based) and is rather vague (e.g., “… sufficient concentrations”). A broad interpretation of this term could have required the disposal in a geologic repository of approximately 140,000 defense HLW canisters from the Savannah River Site alone. To provide additional clarity to this source-based and vague definition, DOE promulgated Order G 435.1 in 1999 that uses risk criteria to determine what defense wastes actually need to be disposed of in a geologic repository. Using Order G 435.1, DOE was able to reduce the number of Savannah River Site defense HLW canisters requiring geologic disposal to between 6,000 and 8,000.
The NWPA established a statutory capacity limit of 70,000 metric tons of heavy metal for the nation’s first repository, until a second repository is in operation. That limit is not based on technical considerations. The 1987 Amendments to the NWPA directed the Secretary of Energy to focus site characterization activities only at Yucca Mountain, Nevada.
DOE’s OCRWM, also referred to as DOE-RW, was established to research, site, license, and construct a deep geological repository for disposal of commercial and defense spent fuel and defense HLW.2 As part of
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2 In an April 30, 1985, memorandum, President Ronald Reagan determined that there was no basis for establishing a separate repository for defense HLW. He directed then-Secretary of DOE John Harrington to arrange for the disposal of these wastes in repositories developed for disposal of civilian SNF and HLW.
its responsibilities, DOE-RW developed Waste Acceptance Criteria (WAC), which are described in Section 8.4, for accepting SNF and HLW for disposal at a U.S. repository.3
8.1.3 Energy Policy Act of 1992
The Energy Policy Act of 1992, Section 801, required EPA to develop a site-specific health and safety standard for a geologic repository at Yucca Mountain, Nevada. Section 801 also required EPA to contract with the National Academy of Sciences (NAS) to provide findings and recommendations on reasonable standards for protection of the public health and safety. The Energy Policy Act required EPA to promulgate a regulation that would be “based upon and consistent with” the NAS recommendations. The NAS recommendations, which were published in 1995 (NRC, 1995), were considered and implemented by EPA in Title 40, Part 197 of the Code of Federal Regulations (40 CFR 197). That regulation is described in Section 8.3.2 (see also http://www.epa.gov/radiation/yucca/regs.html).
8.1.4 DOE Order 5400.1
DOE Order 5400.1 establishes requirements, authorities, and responsibilities for DOE operations to ensure compliance with environmental protection laws, regulations, executive orders, and internal DOE policies. The most important part of this order for the purposes of this report is the order’s policy statement (emphasis added):
It is DOE policy to conduct its operations in an environmentally safe and sound manner…. DOE is firmly committed to ensuring incorporation of national environmental protection goals in the formulation and implementation of DOE programs…. Accordingly, it is DOE policy to conduct the Department’s operations in compliance with the letter and spirit of applicable environmental statutes, regulations, and standards. … [I]t is DOE’s policy that efforts to meet environmental obligations be carried out consistently across all operations and among all field organizations and programs. (emphasis added)
Through this order, DOE’s waste management and disposal activities are subject to federal, state, and local laws and regulations.
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3 OCRWM was being disbanded when this report was being finalized. The Obama Administration is withdrawing the license application to construct a repository at Yucca Mountain, Nevada, and has established a Blue Ribbon Commission on America’s Nuclear Future to evaluate alternative approaches for managing SNF and HLW.
8.1.5 DOE Order G 435.1
Defense HLW is defined in DOE Order G 435.1 similar to the definition in the NWPA, but it also defines a new classification of Waste Incidental to Reprocessing4 (WIR), which is:
Waste resulting from reprocessing spent nuclear fuel that is determined to be incidental to reprocessing is not high-level waste, and shall be managed under DOE’s regulatory authority in accordance with the requirements for transuranic waste or low-level waste, as appropriate.
WIR that will be managed as low-level radioactive waste (LLW) must meet three criteria (USNRC, 1999):
- Criterion 1: The waste must receive processing to remove key radionuclides to the maximum extent that is technically and economically practical.
- Criterion 2: The waste must be shown to be managed to meet the performance objectives in 10 CFR Part 61, Subpart C.5
- Criterion 3. The waste must be incorporated in a solid physical form at concentrations that do not exceed the concentration limits for Class C commercially generated LLW.
DOE Order G 435.1 recommends that the USNRC should be consulted for all determinations of whether a waste is LLW using these criteria.
DOE Order G 435.1 also provides guidance for the near-surface disposal of DOE-EM LLW at DOE sites. This guidance includes the following performance objectives, which are not stated as requirements:
- For off-site members of the public, a limit of an annual effective dose equivalent from all releases and exposure pathways of 0.25 millisieverts per year (mSv/year), excluding dose from radon and its progeny in air.
- For off-site members of the public, a limit on annual effective dose equivalent from releases to the atmosphere of 0.1 mSv/year, excluding the dose from radon and its progeny.
- A limit on release rate of radon at the surface of a disposal facility of 0.7 becquerels per square meter per second (Bq m–2 s–1) or, alternatively, a limit on the concentration of radon in air at the boundary of the disposal facility of 20 Bq m–3.
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4 The definition, evaluation, and impact of WIR from DOE Order G 435.1 are reviewed in Appendix C of NRC (2006).
5 Title 10, Part 61 of the Code of Federal Regulations provides regulations for the management and disposal of LLW. See Section 8.3.1.
Note that these objectives apply to the performance of the disposal system, not to waste form performance in the disposal system. These performance objectives are similar to those established previously in DOE Order 5820.2A, which was superseded by Order G 435.1. However, if DOE-EM LLW were to be sent to a facility licensed by the USNRC or an Agreement State,6 performance objectives and other criteria established by those authorities would apply (see Section 8.3.1).
DOE Order G 435.1 specifically states that performance objectives for disposal of DOE LLW apply for 1,000 years after disposal. Calculations of dose beyond 1,000 years should only be considered as qualitative for DOE sites, and only for comparison of disposal alternatives that are otherwise not distinguishable in their dose impacts.
There are additional requirements in DOE Order G 435.1 regarding the conduct of performance assessments, but these are not explicitly stated as performance objectives. For example, performance assessments must include a demonstration that releases from a disposal facility will be maintained as low as reasonably achievable (ALARA). Also, site-specific assessments of potential doses to inadvertent intruders are required for the purpose of establishing limits on concentrations of radionuclides to be disposed of at each site. These performance measures for inadvertent intruders are the same as those established in the superseded DOE Order 5820.2A. Furthermore, an analysis of potential impacts on water resources is required for the purpose of establishing limits on quantities of radionuclides that are acceptable for disposal at each site, based on site-specific criteria. Also, DOE Order G 435.1 specifies that disposal must comply with all other DOE environmental protection requirements.
8.1.6 National Defense Authorization Act Section 3116
Section 3116 (a) of the National Defense Authorization Act (NDAA) states that the Secretary of Energy can determine that radioactive waste resulting from the reprocessing of nuclear fuel is not HLW if it meets specific criteria. The Secretary must consult with the USNRC in making this determination by preparing a Waste Determination Basis Document. The USNRC will review this document and provide a Technical Evaluation Report to inform the Secretary’s decision.
The criteria for consideration in waste determinations include:
- Waste does not require permanent isolation in a deep geologic repository
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6 That is, a state that has signed an agreement with the Nuclear Regulatory Commission authorizing it to regulate certain uses of radioactive materials.
- Waste has had highly radioactive radionuclides removed to the maximum extent practical
- Waste does not exceed concentration limits for USNRC’s Class C LLW and will be disposed of:
— in compliance with the performance objectives set out in Subpart C of 10 CFR 61
— pursuant to a state-approved closure plan or a state-approved permit
- If waste exceeds concentration limits for Class C LLW it will be disposed of:
— in compliance with the performance objectives set out in Subpart C of 10 CFR 61
— pursuant to a state-approved closure plan or a state-approved permit
— pursuant to plans developed by the Secretary in consultation with the USNRC
8.2 STATE AND AFFECTED PARTIES AGREEMENTS
DOE has entered into agreements and consent orders, hereafter referred to simply as Agreements, with EPA, states, and in some cases with other affected local parties regarding the disposition of radioactive wastes on sites within these states, mostly notably South Carolina, Idaho, and Washington. The purpose of these Agreements is to ensure that the environmental impacts associated with releases or potential releases of hazardous substances at various DOE sites are thoroughly investigated and that appropriate response actions are undertaken and completed as necessary to protect the public health, welfare, and the environment. Each Agreement establishes a framework and schedule for developing, prioritizing, implementing, and monitoring appropriate response actions at these DOE sites in accordance with CERCLA, RCRA, and state HWMA7 requirements. Implementation of the Agreements is intended to facilitate cooperation, exchange of information, and participation of the parties in such actions. Where appropriate, interim action alternatives are to be identified at specific sites to promote cooperation among parties prior to the implementation of final actions.
DOE-EM has negotiated with the other parties to these agreements to establish specific characteristics for the waste forms that will be produced as a result of cleanup at its sites. For example, DOE and the state of South
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7 CERCLA is the Comprehensive Environmental Response, Compensation, and Liability Act; RCRA is the Resource Conservation and Recovery Act; HWMA is the Hazardous Waste Management Act. RCRA is described in Section 8.3.4.
BOX 8.1
Good as Glass
The Draft Tank Closure and Waste Management Environmental Impact Statement for the Hanford Site, Richland, Washington (DOE, 2009) contains a forward written by the Washington State Department of Ecology, which states that “Ecology’s measuring stick for a successful supplemental treatment technology has always been whether it is ‘as good as glass’ (from the WTP [Waste Treatment Plant]).” To the Committee’s knowledge, quantitative metrics for “as good as glass” have not been explicitly defined in any formally approved document.
A review of the literature reveals that the statement “as good as glass” has been interpreted in several ways. For example, the Draft Dangerous and/or Mixed Waste Research, Development, and Demonstration Permit (RD&D): Demonstration Bulk Vitrification System (DBVS Facility) notes that DOE intends to “evaluate the ability of bulk vitrification to produce immobilized low-activity waste (ILAW) that is comparable to that proposed for the Hanford Site Waste Treatment and Immobilization Plant (WTP) immobilized low-activity waste form” (ECY, 2004). In a notice requesting public comments on the draft permit,a the Washington State Department of Ecology noted, “The permittee [the U.S. Department of Energy] intends to demonstrate that the bulk vitrification technology is viable and as protective of the environment as the vitrified (glasslike) waste that will be produced by the Waste Treatment Plant (as good as glass).” In a 2005 letter to EPA (DOE, 2005), DOE suggests a set of performance criteria to support a determination of comparable treatment for bulk vitrification of the Hanford tank waste by showing that bulk vitrification is equivalent to High-level Waste Vitrification (HLVIT), which is considered by EPA to be Best Demonstrated Available Technology (BDAT). A September 2009 Government Accountability Office report makes the following statement (GAO, 2009, p. 43): “[T]he state [of Washington] has maintained that any supplemental treatment technology [for LAW at Hanford] must be shown to
Carolina have agreed that low-activity waste disposed of at the Savannah River Site will be in a grouted waste form (Saltstone). DOE-EM and the State of Washington have agreed that the waste form selected for immobilizing low-activity waste at the Hanford Site will be glass or “as good as glass” (see Box 8.1).
8.3 REGULATIONS
EPA and the USNRC have issued regulations for the management and disposal of HLW, TRU waste, and LLW. These are described briefly in the following sections.
be ‘as good as glass,’ which means that it must meet or exceed all the same performance standards and disposal criteria to protect human and ecological health that apply to the approved glass form.”
How would one demonstrate that an alternative waste form is as good as glass? One approach would be to demonstrate that the alternative waste form meets the same chemical durability performance measure (e.g., long-term fractional dissolution rate, see Chapter 5) as the current baseline Low-Activity Waste Reference Material (LRM) glass (see McGrail et al., 2003). Another approach would be to demonstrate that the disposal system, including the alternative waste form, meets the facility’s applicable performance requirements. Such a systems approach, which considers waste form performance in the context of a shallow subsurface disposal facility, appears to have been the basis for the processing, product acceptance, and chemical durability performance measures imposed by DOE for immobilized low-activity waste glass (Mann et al., 2001). This approach allows DOE to take credit for the other engineered and natural barriers in the near-field environment of the disposal facility, which could provide more flexibility in the selection of alternative waste forms. For example, based on a performance assessment, DOE could ensure that the system performance is “as good as glass” in a specific disposal facility either by establishing restrictions on waste loading for specific waste form products that are not limited to glass, or by minimizing the requirements on the durability of the waste form by modifying the facility design to incorporate engineered barriers such as hydraulic barriers that divert water from the waste and getters to trap important radionuclides (Mann et al., 2001, sections ES4 and 7.6.4).
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a See http://listserv.wa.gov/cgi-bin/wa?A3=ind0407&L=HANFORD-INFO&E=quoted-printable&P=12240&B=------_%3D_NextPart_001_01C46F91.659F3450&T=text%2Fhtml&XSS=3.
8.3.1 USNRC: 10 CFR Part 61 and Related Guidance for LLW Disposal
Title 10, Part 61 of the Code of Federal Regulations (10 CFR 61) was promulgated by the USNRC to regulate the disposal of low-level waste (LLW) generated at USNRC-licensed facilities except for Greater-Than-Class-C Waste.8 These regulations would also apply to DOE wastes that are
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8 Under the Low-Level Radioactive Waste Policy Act, the federal government has responsibility for the disposal of Greater-Than-Class-C (GTCC) Waste from Nuclear Regulatory Commission and Agreement State-licensed activities as well as GTCC-like waste from its own activities. DOE recently issued a draft environmental impact statement (DOE, 2011) that examines four alternative methods for disposing of this waste: (1) geologic disposal in the Waste Isolation Pilot Plant, and/or land disposal in (2) intermediate-depth boreholes; (3) enhanced near-surface trenches, and (4) above-grade vault facilities.
disposed of in commercial facilities. They would not apply to wastes that are disposed of at DOE sites.
Part 61.56 (Waste Characteristics) establishes requirements for the structural stability of waste forms. It states that a waste form
… will generally maintain its physical dimensions and its form, under expected disposal conditions such as weight of overburden and compaction equipment, the presence of moisture, and microbial activity, and internal factors such as radiation effects and chemical changes.
Furthermore, Part 61.7 (Concepts) requires that for Class B and C LLW, the waste form must maintain its gross physical properties and identity for 300 years, and that a concrete cover must be provided as an intruder barrier with an effective life of 500 years. These time scales, although long compared to human life spans and regulatory time scales applied to the disposal of chemically hazardous wastes, are much shorter than the 104- to 106-year regulatory time scales that apply to the disposal of HLW (see Section 8.3.2). It is also notable that Part 61.51 (Disposal Site Design for Land Disposal) stresses that the disposal system must be designed to complement the natural system, reinforcing the need to consider waste form performance in the context of a system of barriers (see Chapter 7) rather than in isolation.
The USNRC has produced several technical position and contractor reports on LLW waste form test methods and results acceptable to the USNRC staff for implementing 10 CFR 61. Appendix A of USNRC (1991) addresses cement waste form characterization and qualification, including test-sample preparation, sampling, and analysis. More recently, the USNRC has published technical guidance for the disposal of decommissioning LLW within engineered disposal systems (USNRC, 2006) and waste incidental to reprocessing (USNRC, 2007). The latter report provides guidance to DOE for conducting WIR determinations (see Section 8.1.6) at the Savannah River Site (SRS) in South Carolina and the Idaho National Laboratory (INL) in Idaho pursuant to the NDAA, as well as at the Hanford Site in Washington and the West Valley Site in New York. The document discusses the background and history of waste determinations; applicable criteria and how they are applied and evaluated; review of associated performance assessments for disposal systems and inadvertent intruder analyses; removal of highly radioactive radionuclides; and USNRC monitoring activities that will be performed at SRS and INL in accordance with the NDAA.
The Center for Nuclear Waste Regulatory Analyses (CNWRA, 2009) recently issued the report titled Review of Literature and Assessment of Factors Relevant to Performance of Grouted Systems for Radioactive Waste Disposal. This report focuses on potential time-dependent changes
in chemical, hydraulic, and structural properties of LLW cements and how they might affect the overall release performance of LLW disposal systems.
8.3.2 EPA: 40 CFR Parts 191 and 197 for HLW Disposal
EPA promulgated Title 40, Part 191 of the Code of Federal Regulations (40 CFR 191), as required under the NWPA, as the environmental protection standard for the geological disposal of SNF, HLW, and TRU waste. SNF and HLW are specifically defined in the Atomic Energy Act, whereas TRU waste is defined in 40 CFR 191 as waste containing more than 100 nanocuries per gram (nCi/g) of alpha-emitting transuranic isotopes having half lives greater than 20 years, except for (1) HLW; (2) wastes that DOE has determined, with the concurrence of the USNRC, do not need the same degree of isolation required for HLW (e.g., WIR); or (3) wastes that the USNRC has approved for disposal on a case-by-case basis in accordance with 10 CFR 61. EPA developed 40 CFR 191 in the early 1980s, when the understanding of geological disposal of long-lived nuclear wastes was in its infancy. Accordingly, EPA developed rather stringent safety standards to assure the safety of the overall repository system.
The standards in 40 CFR 191 establish three specific types of performance objectives to be met by a repository: (1) an individual protection requirement, (2) a containment requirement, and (3) a groundwater protection requirement.
- The individual protection requirement states that there must be reasonable expectation that “any member of the public” in the accessible environment will not receive a dose in excess of 15 millirems per year during a compliance period of 10,000 years.
- The containment requirements are defined probabilistically such that there must be less than a 0.1 probability that the release limits are exceeded and less than a 10–3 probability that they are exceeded by a factor of 10. The release limits were established for individual radionuclides based on cumulative activity released per 1,000 metric tons of heavy metal.
- The groundwater standard provides a tabulated allowable concentration for various radionuclides at the compliance boundary.
All of these performance objectives apply to the disposal system as a whole and impose no performance requirements on waste forms. It should be noted that these three separate safety requirements (individual protection, cumulative release, and groundwater concentration limits) within 40 CFR 191 are not necessarily self-consistent with each other.
The final 40 CFR 197, which was promulgated by EPA as required
under the Energy Policy Act of 1992, establishes a dose limit of 15 millirems per year for a reasonably maximally exposed individual for an initial period of 10,000 years after repository closure, and 100 millirems per year allowable dose rate for the period between 10,000 and 1 million years, in response to the NAS recommendations (NRC, 1995). The EPA drinking water standard is also to be applied. As with 40 CFR 191, the Yucca Mountain-specific safety standard sets performance requirements on the total repository system but places no performance requirements on waste forms.
8.3.3 USNRC: 10 CFR Parts 60 and 63 for HLW Disposal
The NWPA directed the USNRC to develop licensing procedures for geological repositories for SNF and HLW that are consistent with the environmental standards developed by EPA. Much of the USNRC’s regulation applies to licensing procedures and acceptable levels of evidence, rather than establishing additional requirements. The USNRC’s licensing procedures for a generic repository, which are contained in Title 10, Part 60 of the Code of Federal Regulations (10 CFR 60), do not differ significantly from the USNRC’s Yucca Mountain-specific licensing procedures, which are contained in Title 10, Part 63 of the Code of Federal Regulations (10 CFR 63). However, as discussed below, there are differences in the applicable safety standards.
Like 40 CFR 191, however, 10 CFR 60 was developed in the early 1980s when there was less complete knowledge of the properties and processes that are most important for long-term isolation of nuclear waste in geological disposal systems. Accordingly, one element of 10 CFR 60 that was not included in 10 CFR 63 was the set of provisions from 10 CFR 60, Subpart E (Technical Criteria). Part 60.113 (Waste Package Performance Objective) established so-called “subsystem” performance objectives for individual barrier components of the repository system in addition to the overall performance requirements established in the draft 40 CFR 191. Part 60.113 stated that “assuming anticipated processes and events,” containment within the waste packages would be “substantially complete” for a period between 300 and 1,000 years after permanent closure. Further, Part 60.113 set forth an engineered barrier system release objective, requiring that after the containment period, the release of each radionuclide from the engineered barrier system (EBS) cannot exceed 10–5 parts per year of the inventory calculated to be present 1,000 years after permanent closure.
The context for this 10–5 parts per year release rate from the EBS is important, in part because of subsequent efforts in the United States to link waste form performance to this EBS performance value. In the early 1980s,
preliminary studies (e.g., Crandall, 1983) on the dissolution behavior of borosilicate glass as a matrix for defense HLW showed a range of fractional dissolution rates between 10–4 to 10–6 parts per year (at these rates the glass waste form would totally dissolve in 10,000 to 1 million years). In the early 1980s there were no specific disposal concepts, no system-level performance analyses, and only draft disposal safety standards. In the absence of a specific disposal system context, the USNRC decided to set a sub-system performance target for the EBS (but not the waste form per se) based on a waste form fractional dissolution rate that was both known to be achievable and likely to aid in long-term performance of any disposal concept.
At that time, DOE was seeking to make decisions on the selection and qualification of a waste form for its defense HLW. Borosilicate glass was selected on the basis of industrial simplicity of the process, extensive nuclear experience in Europe with vitrifying HLW, adequate waste loading, reasonable processing rates, reasonable processing costs, reasonable durability, and a number of other factors. DOE wanted to develop a testing basis to show that borosilicate glass would be acceptable in any of the several geologically diverse repository host rocks (salt, basalt, granite, tuff, and argillite) then being considered. The difficulty was that EBS designs were still under development and there was considerable divergence among such designs for different host rocks. Moreover, the understanding that repository performance was dominated by radioelement solubilities was also just being developed (NRC, 1983; see Chapter 7).
Therefore, a conservative approach was taken to construe Part 60.113 as a benchmark for borosilicate glass waste forms; if it could be shown that the long-term fractional dissolution rate was equal to or less than 10–5 parts per year for the most soluble and long-lived radionuclides such as selenium-79, technetium-99, cesium-135, and iodine-129, then borosilicate glass should provide acceptable performance for any repository site or concept. This conservative approach was extended to include consideration of phenomena such as glass cracking and crystallization, which could increase the leach rates above 10–5 parts per year. Without accounting for these effects, it was judged that a homogeneous glass with a leach rate of 10–5 parts per year should perform adequately in a systems analysis.
Subsequent analyses by the USNRC showed that the assumption that a 10–5 parts per year sub-system performance target would meet safety regulations for disposal systems was not justified (USNRC, 1999): “[US]NRC was not able to demonstrate, however, that compliance with the subsystem criteria alone was sufficient to meet the assumed EPA standards, nor that compliance with the assumed EPA standards would suffice to assure compliance with the subsystem criteria.”
Furthermore, there was widespread criticism of the sub-system approach in 10 CFR 60 both in the United States and internationally;
application of such sub-system requirements was seen as unduly restricting the options and isolation strategies available for achieving a safe yet optimized disposal system. Sub-system performance objectives were criticized as overly prescriptive, lacking a strong technical basis, lacking a clear link to overall performance measure, and unclear in wording and implementation. No other nation has safety regulations that impose such sub-system performance objectives; it is left to the institution implementing the repository to develop and qualify a set of multiple barriers that, in concert with specific waste forms and site characteristics, will comply with system-level safety requirements.
In addition, the NAS specifically concluded that “because it is the performance of the total system in light of the risk-based standard that is crucial, imposing subsystem performance requirements might result in suboptimal design” (NRC, 1995). This conclusion was directed specifically to the USNRC, in the context of revisions that the USNRC needed to make to its new 10 CFR 63 regulations to be consistent with a new EPA standard for Yucca Mountain. Following these observations from the NAS, the USNRC made the following comment in promulgating its revised 10 CFR 63 (USNRC, 1999):
Identification of such subsystem performance measures was expected to be helpful input to DOE’s design process, without being overly restrictive. It is now recognized that [US]NRC attempted to define such criteria on the basis of limited, existing knowledge, without benefit of research and site-specific information that only later was acquired during characterization of a specific site at Yucca Mountain. (p. 8643)
and
More specifically, [the 1992 Energy Policy Act, EnPA-Public Law 102-486] and NAS [NRC, 1995] have specified an approach that would require the performance of a Yucca Mountain repository to comply with a health based standard established in consideration of risk to a hypothetical critical group, and further, that this would be the only quantitative standard for the post-closure performance of the repository. This approach is incompatible with the approach taken in the existing generic criteria that relies on quantitative, subsystem performance standards. The Commission proposed to leave the existing generic requirements intact and in place, if needed, for sites other than Yucca Mountain. Although their application could be expected to be difficult, the Commission assumes that it would be afforded adequate time and resources in future years to amend its generic regulations for any additional repository site that might be authorized. (p. 8648)
Based on the technical reasoning provided by both the NAS report (NRC, 1995) and the USNRC’s own analysis, the USNRC abandoned subsystem performance objectives in 10 CFR 63—thus eliminating specific requirements for waste form performance. It can be reasonably expected that this same decision to omit sub-system performance objectives would be adopted by the USNRC for any revisions to 10 CFR 60 as applied to other repository sites.
Part 60.135 establishes requirements for HLW packages and components. It requires that wastes be in solid, consolidated form and shall not contain explosive, pyrophoric, or chemically reactive materials in an amount that could compromise the ability of the geologic repository to satisfy performance objectives. It also requires that the waste package shall not contain free liquids in an amount that could compromise performance objectives or result in spillage and spread of contamination in the event of waste package perforation during the period through permanent closure. None of these requirements specifically relate to waste form performance in disposal systems.
8.3.4 Resource Conservation and Recovery Act
RCRA9 gives EPA cradle-to-grave authority to regulate the generation, transportation, treatment, storage, and disposal of hazardous waste10 to protect human health and the environment. RCRA was established in 1976 and has been amended several times since enactment.
RCRA gives EPA the authority to establish land disposal requirements (LDRs) for hazardous wastes. The requirements (promulgated in Title 40, Part 268 of the Code of Federal Regulations) require that hazardous wastes be treated to meet specific treatment standards prior to land disposal. The treatment standards are expressed in terms of specific contaminant levels, or specific treatment technologies that must be applied to reduce the toxicity or mobility of hazardous constituents. If a waste is listed or characteristically hazardous it must be treated to meet specific contaminant levels which
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9 42 U.S.C. §6901 et seq, promulgated in 40 CFR 260 et seq.
10 EPA defines hazardous waste as waste with properties that make it dangerous or potentially harmful to human health or the environment. There are three classes of hazardous wastes that are relevant to this discussion: wastes that are listed as hazardous (i.e., listed wastes) because of their process history; wastes that are characteristically hazardous (i.e., characteristic wastes) because they exhibit one or more of the following four characteristics: ignitability, corrosivity, reactivity, or toxicity; and wastes that contain both radioactive and hazardous constituents (i.e., mixed wastes). There are four types of hazardous wastes: (1) mixed listed waste; (2) characteristically hazardous mixed waste; (3) listed hazardous waste; or (4) characteristically hazardous waste. HLW at Savannah River and West Valley fall into the second category, whereas HLW at Idaho and Hanford fall into the first category.
are referred to as universal treatment standards (UTS). EPA can also define treatment standards for specific wastes; the specific treatment technologies are referred to as best demonstrated available technology (BDAT). Wastes that do not meet one of these treatment standards are prohibited from land disposal unless EPA has granted a variance or exclusion or the waste is managed under an EPA-approved no-migration petition.
SNF or HLW generated during the reprocessing of SNF are hazardous for one (or more) of the RCRA metals. EPA has established a BDAT for treatment of HLW generated during the reprocessing of fuel rods: HLW vitrification, referred to as HLVIT. DOE-EM has established that HLW vitrification at the Savannah River Site and West Valley is BDAT and therefore meets EPA’s LDRs. Consequently, vitrified HLW at these sites currently qualify for disposal.
HLW at Idaho and HLW/LAW at Hanford do not currently qualify for disposal because they contain listed wastes. Moreover, even if the Federal EPA approves HLVIT of these wastes as BDAT, a state EPA can still require that the waste meet more stringent standards—for example, that it be delisted prior to disposal. DOE-EM will likely need to consult with its regulators (EPA and states hosting the disposal facilities for these waste streams) to clarify this issue.
8.4 WASTE ACCEPTANCE CRITERIA
Waste acceptance criteria (WAC) are established by the owners/operators of waste disposal facilities. They provide specific requirements that waste must meet to be acceptable for disposal. WAC include such specifications as the types of waste accepted, including its physical and chemical forms; the container to be used for disposal, including its packaging and labeling; and allowable contamination levels on the outside of the container.
Within the DOE system WAC have been established for disposal of SNF and HLW in a geologic repository; TRU waste at the Waste Isolation Pilot Plant in New Mexico; and LLW and mixed waste in land-disposal facilities at DOE sites. The WAC for the Waste Isolation Pilot Plant is discussed in some detail in NRC (2001, 2002a, and 2004) and is not repeated here. The remainder of this section will focus on WACs for SNF and HLW.
OCRWM published a Waste Acceptance System Requirements Document (WASRD) to establish waste acceptance criteria imposed by the Civilian Radioactive Waste Management System (CRWMS) on SNF and defense HLW delivered into the CRWMS (DOE, 2008). The purpose of the WASRD is to ensure that the characteristics and properties of waste forms received into the CRWMS would not hinder or prevent safe handling, emplacement, and final disposal into a repository.
With respect to acceptance of SNF for disposal, uranium oxide fuels
present few issues, unless there has been significant deterioration or alteration of the fuel, as was the case for some of the spent fuel in wet storage at the Hanford Site.11 Metallic uranium SNF, however, presents key WAC issues with respect to both pyrophoric behavior and reactivity to groundwater under repository disposal conditions. To address WAC concerns for DOE’s damaged oxide SNF and metallic SNF, DOE has been studying various treatment options to generate acceptable reprocessed waste forms, most notably electrometallurgical methods leading to a Fe/Zr (cladding) metal waste form and a glass-bonded zeolitic waste form (NRC, 2000b).
Section 4.8 of the WASRD specifically addresses acceptance criteria and specific requirements for HLW, which at that time was taken to be borosilicate glass sealed inside an austenitic stainless steel canister. There are various requirements regarding the dimensions, weight, labeling, thermal output, criticality potential, radionuclide content, and handling characteristics of the HLW. With respect to dangerous properties, the WASRD states
The HLW canister materials shall preclude chemical, electrochemical, or other reactions (such as internal corrosion) of the canister or waste package such that there will be no adverse effect on normal handling, transportation, storage, emplacement, containment, isolation, or on performance under abnormal occurrences such as a canister drop accident and premature failure in the repository.
Section 4.8.1 (B) on Product Consistency states
1. The Producer shall demonstrate control of waste form production by comparing production samples or process control information, separately or in combination to the Environmental Assessment benchmark glass (Jantzen, 1993) using the Product Consistency Test (ASTM C1285-97 or equivalent.
2. For acceptance, the mean concentrations of lithium, sodium, and boron in the leachate, after normalization for the concentrations in the glass, shall be less than those of the benchmark glass.
Product Consistency Test A (PCT-A) is specifically used to evaluate whether the chemical durability and elemental release characteristics of nuclear, hazardous, and mixed waste glass waste forms have been consis-
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11 About 2,300 tonnes of spent fuel in wet storage in the K-Basins at the Hanford Site have been retrieved, dried, and packaged in steel canisters. This spent fuel is now in interim storage at the site.
tently controlled during production.12 It is a seven-day leach test performed at 90°C to simulate the heat of radioactive decay and involves the measurement of release rates of lithium, sodium, and boron from borosilicate glass waste forms. These soluble elements were chosen because they are released at the same rate (i.e., congruently; see Chapter 5, Box 5.2) as the most soluble, long-lived radionuclides (e.g., technetium-99, iodine-129, and cesium-135).
The applicability of PCT for quality control was determined by extensive testing of both simulated and radioactive glass waste forms. These tests may or may not be applicable to alternative HLW waste forms, such as ceramics or metals, when these elements are not present or their release mechanisms are different, as stated in the procedure’s documentation. Mechanistic testing is required to determine the adequacy of this test to other waste forms, and often this mechanistic testing is not performed before the PCT-A test is applied to different waste forms. PCT-A is not a performance requirement in the sense that it provides any information about the long-term (104-106 year) radionuclide-release performance of such a waste form in a multiple-barrier geological disposal system.
The PCT response can be useful, however, in the following manner: If a glass is made in a consistent manner and within a consistent range of composition by process control, then the imposed process control leads to composition control that, in turn, leads to consistent dissolution rate (hence, performance) control, within certain bounds (see Chapter 5). In this way, waste form producers have demonstrated that composition control can be used to bound acceptable performance. Also the PCT-B test can provide information about the longer-term radionuclide-release performance in a multiple-barrier geological disposal system when used in conjunction with the durability response of other kinetically based tests, such as the Single-Pass Flow-Through Test (SPFT) and the Pressure Unsaturated Flow (PUF) Test. The use of testing for these purposes is discussed in more detail in Chapter 5.
There are no requirements in the WASRD on waste form performance with respect to meeting long-term, post-closure regulatory safety standards for radionuclide release rates. This purposeful absence of waste form performance requirements by the repository implementer reflects (1) the understanding that the safety of a multiple barrier repository system does not rely on the performance of any one sub-system barrier, including
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12 PCT methods A and B evaluate the chemical durability of homogeneous glasses, phase-separated glasses, devitrified glasses, glass ceramics, and/or multiphase glass-ceramic waste forms, collectively referred to as “glass waste forms,” by measuring the amounts of the chemical species released to a specified volume of test solution over a specified time interval. These tests are described in more detail in Chapter 5.
the waste form, and (2) the desirability for the repository implementer to retain flexibility in the design, safety, and optimization of the overall disposal system.
8.5 DISCUSSION
The DOE-EM program operates under an extensive set of legal and regulatory requirements, key features of which were described in this chapter. Some of these requirements have been imposed by outside entities, including the U.S. Congress, state legislatures, and Federal and state regulatory authorities. Other requirements have been self imposed by DOE and appear in DOE orders and in Agreements with states and other agencies.
As noted in this chapter, some laws, regulations, orders, and Agreements establish requirements for the production and use of waste forms in the cleanup program. For example, RCRA waste intended for land disposal must be processed to meet specific treatment standards. The treatment standards are expressed in terms of specific contaminant levels (UTS) or specific treatment technologies (BDAT) (see Section 8.3.4). Additionally, DOE has Agreements with states that specify the characteristics of waste forms that are suitable for disposal (e.g., see Box 8.1), and DOE has in some cases established its own criteria for accepting waste forms for disposal (e.g., see Section 8.4 on Waste Acceptance Criteria).
However, the committee was unable to identify any specific requirements for waste form performance in disposal systems. Performance requirements have been established for disposal systems as a whole, but the committee could not identify any sub-system performance requirements that apply specifically to waste forms.
The RCRA requirements for disposal of hazardous waste, which DOE has agreed to follow under Order 5400.1, could reduce DOE-EM’s flexibility to pursue optimization of its overall waste management system, especially for disposal of Hanford HLW/LAW at Idaho HLW. Vitrified HLW from Savannah River and West Valley currently qualify for geological disposal because they meet EPA’s BDAT requirements. However, is not clear whether immobilized Hanford HLW/LAW and Idaho HLW would also satisfy RCRA requirements under a BDAT rationale. DOE-EM will need to consult with its regulators (EPA and states hosting the disposal facilities for these waste streams) to clarify this issue.
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