Alternative High-Level Waste Treatments at the Idaho National Engineering and Environmental Laboratory (1999)

A major consideration in deciding whether to process any radioactive waste for long-term conditioning is that of the risk(s) being mitigated. The fundamental purpose of environmental regulations [such as those of the Resources Conservation and Recovery Act (RCRA); the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA); and U.S. Nuclear Regulatory Commission (USNRC) directives] and radioactive waste policy legislation is minimization of risk to human health and the environment. In the absence of other clear and concise criteria and guidance, a driving consideration in deciding on a radioactive waste management strategy should be the comparative risks of the alternatives being considered (including those of limited or no processing). Comparative risk assessment calculations provide quantitative information about risk reduction strategies, and these calculations are required to choose among alternative approaches in a fully informed and objective way.

Once a decision to process waste has been made, key issues¹ to be considered in choosing among treatment alternatives include the following:

1. applicable regulatory requirements, such as RCRA requirements on hazardous chemical constituents, U.S. Environmental Protection Agency (EPA) maximal achievable controlled technology (MACT) role restrictions on mercury and other effluents, and transportation regulations;

2. disposal options, that is, the availability of present and possible furore repositories and their associated waste acceptance criteria;

3. worker and public safety, particularly for process steps with potential hazards such as radiological exposure;

4. technological risk, that is, the probability of technical success of a sequence of process steps, particularly if the limits of existing technology are taxed; and

5. considerations of total life-cycle cost.

Integral to a decision to select among processing options is consideration of the types and quantities of the final waste form products, whose classification and material properties (e.g., chemical durability) will affect, at least in part, how these five issues are handled.

This chapter addresses issues 1, 2, and 5. Issues 3 and 4 are not discussed in this chapter because they have been treated in the context of specific process steps in the preceding chapters, with further comments offered in the chapters to follow. This chapter begins by pro-riding an overview of the regulatory and other legal requirements (issue 1) for which the Idaho National Engineering and Environmental Laboratory (INEEL) high-level waste (HLW) program plans must account. The chapter continues with an overview of disposal options (issue 2) because of the importance of an available disposition pathway to the formulation of program plans. The chapter concludes with a brief discussion of cost considerations (issue 5) that are relevant to deciding among various processing alternatives.

The INEEL HLW contains not only radioactive constituents, as defined and regulated in the Atomic Energy Act (AEA) and its Amendments, but also hazardous chemical constituents, as defined and regulated in RCRA. While these regulations are briefly discussed below, this discussion does not encompass all relevant regulations, such as the EPA's MACT role providing air quality permitting restrictions.²

The AEA regulation and classification of HLW requires that the ultimate disposal of the high-level fraction be in a geologic repository, whose waste acceptance criteria must be met. Transport to such a repository requires that all applicable transportation regulations be met, and that states through which wastes travel are willing to allow these shipments (Wichmann et al., 1996; Wichmann, 1998a, b). The full suite of rules regulating radioactive waste classification and disposal are promulgated by EPA rulemakings, USNRC regulations, and DOE Orders, under the provisions of the AEA and its amendments, the EPA charter, the Low-Level Radioactive Waste Policy Act, and the Nuclear Waste Policy Act.

RCRA regulation requires that mixed (low-level) wastes that are to be disposed of in the shallow subsurface must be either delisted or adequately characterized and treated, by approved methods, for disposal in facilities that meet the terms and conditions of the Land Disposal Restrictions (LDRs). Closure of tanks and bins would be clone under guidance provided by RCRA or the EPA's CERCLA.

Regulatory constraints on treatment options are augmented by nonregulatory legal agreements DOE makes with other signatory parties, and by court orders, which have in the past established schedules and deadlines for the completion of certain tasks. Specifically, compliance agreements have been established with the EPA and the state of Idaho (see Appendix G).

Any waste forms produced from the treatment and immobilization of INEEL HLW will likely be disposed of, probably after a period of interim storage. The current suite of DOE disposal sites are briefly listed here, with more detail provided in Russell et al. (1998) and Russell and Taylor (1998). Each disposal site, when operational, will have ''waste acceptance criteria" (WAC) that specify the requirements that waste forms must meet to be accepted for disposal.

The high-activity waste (HAW) from treatment of INEEL HLW calcine could be immobilized in a waste form suitable for acceptance and disposal at a geologic repository. As specified in the Nuclear Waste Policy Amendments Act of 1987 (P.L. 100-203), the candidate repository at Yucca Mountain is the only site for DOE to currently study and characterize to ascertain its suitability. The Nuclear Waste Policy Act of 1982 (P.L. 97425) limits this repository to 70,000 MTHM³ of spent nuclear fuel (SNF) or an equivalent amount of HLW (Office of Civilian Radioactive Waste Management, 1998: p. 13). Because 70,000 MTHM is less than the total projected inventory of commercial SNF (ORNL, 1996), a second repository program (i.e., an extension of Yucca Mountain's legal limit, or another repository) will be needed to dispose of the remainder of the commercial SNF.

To dispose of DOE SNF and other forms of DOE HLW, a "co-disposal" strategy has been proposed (DOE, 1985, 1987) and pursued to date, in which 10 percent of the Yucca Mountain repository's capacity (i.e., 7,000 MTHM) would be reserved for inventories of DOE HLW. Even in this case, because the total DOE inventory of HLW exceeds 7,000 MTHM, a second repository program also would be needed for the remainder of the DOE HLW. DOE plans show the first repository to be filled by 2035, with an undetermined amount of INEEL HLW included in this first repository's inventory (Office of Civilian Radioactive Waste Management, 1998: pp. 7, 10-11; Wichmann et al., 1996: p. 2). Therefore, some, or perhaps all, of the INEEL HLW calcine is one of the candidate DOE HLW streams for disposal in a second repository, particularly if processing is not completed until close to 2035 or later.

The plans for disposal of commercial SNF in the Yucca Mountain repository stipulate use of a waste package container whose design would be tailored to provide adequate long-term containment. Unconditioned spent fuel would be the waste form within the waste package. The DOE SNF and other forms of HLW from defense-related activities within the former DOE weapons complex that would be co-disposed with commercial SNF would be placed in a similar waste package container. Current disposal concepts consider DOE and commercial SNF as unconditioned, with other DOE HLW (such as INEEL calcine) processed into suitable waste forms.

A vitrified HLW form is being produced for DOE HLW at both the West Valley Demonstration Facility in New York and the Defense Waste Processing Facility at the Savannah River Site in South Carolina. The Yucca Mountain WAC (Russell et al., 1998; Office of Civilian Radioactive Waste Management, 1998; DOE, 1996c) are still under development and will ultimately specify the requirements for these HLW forms. Although the HLW form is nominally to be borosilicate glass (DOE, 1996c: p. 7; Office of Civilian Radioactive Waste Management, 1998: p. 21), the current Yucca Mountain WAC make provision for other waste forms to be considered for disposal (Office of Civilian Radioactive Waste Management, 1998: pp. 15-16). To the committee's knowledge, the Nuclear Waste Policy Act (P.L. 97-425) specifies only that the DOE HLW be solidified; therefore, the solid waste form(s) of DOE HLW would seem to be a matter of DOE policy only and if so, use of nonborosilicate glass waste forms would not require any change of law.

Neither a second repository program nor definitive WAC for this repository exists. In the absence of any WAC for a second repository program, one approach could be to use the Yucca Mountain WAC as a surrogate. However, two potential problems arise with the use of the Yucca Mountain WAC to guide the INEEL HLW program.

The first potential problem is that using the Yucca Mountain WAC could be challenged insofar as the current Yucca Mountain WAC (1) may not be proper for a different geologic site, and/or (2) are likely to change over time.⁴ In support of the potential for change, the current "Systems Requirements Document" (Office of Civilian Radioactive Waste Management, 1998) is on its fourth revision, and the current "Waste Acceptance Product Specifications" (DOE, 1996c) is on its second revision, and the Yucca Mountain site has yet to be licensed by the USNRC. Unduly restrictive or lenient WAC could have significant consequences in setting the processing specifications for the waste form to be produced from the INEEL HLW calcine.

The second potential problem is that the Yucca Mountain WAC exclude RCRA constituents (Office of Civilian Radioactive Waste Management, 1998: pp. 11, 19; Wichmann et al., 1996). However, INEEL HLW calcine and SBW have both characteristic and listed RCRA hazardous constituents (Wichmann et al., 1996; Wichmann, 1998).⁵ Any disposal of these wastes must involve either of the following:

1. treating them to the terms of the RCRA LDRs, using a method equal to or better than the appropriate "Best Demonstrated Available Technology" (BDAT), or

2. obtaining suitable treatment variances (40 CFR 268; Wichmann et al., 1996) from the state of Idaho.

Following this treatment, the RCRA-characteristic wastes are "out of RCRA' and therefore qualify for disposal in a facility outside of RCRA controls. However, the RCRA-listed constituents must be disposed of in a facility with RCRA controls. The Yucca Mountain repository WAC does not allow such RCRA-listed constituents.

Two solutions to this problem are possible. One is to assume that the appropriate repository for INEEL HLW will comply with RCRA disposal requirements. In the absence of a repository complying with RCRA controls for disposal, the second solution would involve "delisting" the RCRA-listed components (Wichmann et al., 1996; Russell et al., 1998). For this second strategy to succeed, the DOE would present delisting petitions to each state through which the waste would be transported. All these states would have to approve such petitions (i.e., approve of the transport and disposal of the waste in the form in which it is proposed to be packaged) (Wichmann et al., 1996).

In the early 1960s, a waste management decision was made at INEEL to solidify acidic waste by calcination and to store this calcine in bins. At that time the current suite of regulations (i.e., from regulations promulgated since the 1960s, such as from the EPA and USNRC) that apply (or potentially apply) to storage of this kind did not exist. It is of course conceivable, if not likely, that the future might involve further changes in regulatory requirements.

With respect to the capacity of the first geologic repository as well as the development of a second repository, there are many current uncertainties, including how to express the disposal capacity for DOE HLW. This is an issue of equivalency between the measure (MTHM) used for commercial SNF and that for DOE defense waste co-disposed with it. No legal guidance defines this equivalent measure (Knecht et al., 1999); therefore, any change to it would seem to be a matter of DOE policy only and if so, would not require any change of law. The current method (DOE, 1985, 1987) planned for the first repository provides for this conversion by making 0.5 MTHM of SNF equivalent to one Savannah River-size (approximately 0.7 m³) (Russell et al., 1998: pp. 5, 23-24) canister of glass made from DOE HLW, a mass-to-volume conversion. This implies that DOE HLW waste destined for repository storage is to be measured by volume.

Consequences of Using Various Conversion Methods. As noted previously, DOE plans (Office of Civilian Radioactive Waste Management, 1998, p. 11) call for 7,000 MTHM, representing 10 percent of Yucca Mountain's capacity, to be filled with "co-disposed" DOE HLW rather than by commercial SNF. This 7,000 MTHM has been subdivided into two other "planning" figures: 4,667 MTHM for DOE HLW that is not SNF⁶ and 2,333 MTHM for DOE SNF. Using the mass-to-volume conversion introduced above, the 4,667 MTHM of non-SNF DOE HLW is equivalent to 9,334 Savannah-River-size canisters, or approximately 7,000 m³. This represents disposal in the first repository of less

than half (approximately 46 percent) of the projected estimate of DOE HLW that is not SNF (Knecht et al., 1999); therefore, a second repository (or expansion of the first) would be required.

However, other conversions are possible that would affect the amount of DOE HLW that can be co-disposed wire commercial SNF (Knecht et al., 1999). One would be to consider that DOE has processed at all of its sites over time approximately 177,000 metric tons of SNF (Kimmel, 1999a), and therefore to count the sum of all DOE HLW as equivalent to 177,000 MTHM. This conversion method would only permit 3 percent (4,667 MTHM of a total 177,000 MTHM) of all DOE non-SNF HLW to be disposed in the first repository, regardless of its volume.

Another possible conversion could be based on radioactivity as measured in curies, using the fact that I MTHM of SNF with a burnup of 30,000 megawatt-days contains approximately 300,000 curies (Ci) after 10 years of cooling. As a result, 0.5 MTHM would correspond to approximately 150,000 Ci of HLW (rather than to one Savannah River-size canister). Still another conversion could be based on radiotoxicity, using regulatory release limits in the USNRC's 10 CFR pan 20 to compare the long-term performance of commercial SNF to DOE HLW based on how the long-lived radionuclides in each contribute to the radiotoxicity after 1 to 10 millennia (Knecht et al., 1999). In each of the last two conversions, all of the DOE non-SNF HLW is represented by an equivalent MTHM number that is less than 4,667 MTHM. Therefore, in these last two conversion methods, the complete inventory of DOE HLW that is not SNF could be disposed of in the first repository, regardless of its volume (Knecht et al., 1999).

Conclusions. With respect to the capacity of the first geologic repository as well as the development of a second repository, there are many current uncertainties, including how to express the disposal capacity for DOE HLW. Some of these uncertainties—such as the solid waste form for DOE HLW and the equivalency between the measure (MTHM) used for commercial SNF and that for DOE defense waste co-disposed with it—seem to be matters of DOE policy only and if so, adjustments would not require any change of law.

Uncertainty in the conversion of MTHM to an equivalent measure for DOE HLW would affect both the amount of DOE HLW disposed of in a first repository and the importance of its volume. If the DOE defense waste destined for the repository is accounted for not by volume but by some other unit (e.g., the MTHM of reprocessed SNF that it represents, or its curie or radiotoxic content), then its volume will not be the unit of measure for determining how much DOE HLW enters the repository.

The general conclusion is that the current regulatory framework, particularly for the second repository program, is uncertain at present and subject to change in the long term. In particular, this uncertainty tempers the advantages of reducing the volume of the HLW fraction. Although minimizing the volume of defense HLW has benefits in reducing off-site transportation and disposal costs that are dependent on volume, the adaptation of a different measure by which INEEL HLW is to be disposed may make volume reduction a less important planning criterion.

The Greater Confinement Disposal Facility (GCDF), a DOE facility at the Nevada Test Site (NTS), is a disposal site that consists of boreholes into arid alluvium (Cochran et al.,

1999). High-activity low-level waste (LLW) and classified transuranic (TRU) waste⁷ have been disposed in these boreholes in the 1980s (Bonano et al., 1991; Cochran et al., 1999). This form of disposal is proposed for consideration for the mixed HLW form generated from any cementitious processing of HLW calcine and SBW (Russell et al., 1998). This disposal concept may have merit, but as noted in Chapter 4, such a use of the GCDF is outside the current regulatory approach for HLW disposal.

The Waste Isolation Pilot Plant (WIPP) near Carlsbad, New Mexico, is the DOE repository for defense-related TRU wastes, and would be a suitable disposal site for INEEL waste streams that meet this classification. The WIPP-WAC specify that both contact-handled (CH) and remote-handled (RH) TRU wastes are to be accepted. WIPP has legal limits on the total volume and total curies that can be accepted in each of these classification categories. The distinction between RH-TRU and CH-TRU, which are terms derived from operational considerations in the handling of TRU waste, is that waste is classified as RH-TRU if the contact dose rate exceeds 200 millirem per hour at the surface of the waste container. For waste to be defined as TRU, the concentration of transuranic isotopes must exceed 100 nanocuries per gram (nCi/g). The WIPP-WAC contain further specifications, such as limits on the total curie content of a waste container, and prohibition of excessive hydrogen-gas generation (via alpha-induced radiolysis of organic material co-disposed with TRU waste) during transport to the site in a sealed package (DOE, 1996a). WIPP can receive mixed (i.e., RCRA) waste according to the terms of the RCRA Part B permit, which was issued in October 1999. The WIPP facility began CH-TRU operations in March 1999.

WIPP's suitability as a TRU repository for these wastes would involve resolution of several issues, including the following:

1. Because WIPP accepts only TRU waste, any waste sent to WIPP would have to obtain regulatory approval as TRU waste.

2. Because WIPP can legally accept waste only of defense origin, these wastes would have to be judged as defense wastes to gain entry into WIPP.

3. WIPP is already overcommitted in RH-TRU wastes from all DOE sites; therefore, a legal change is required in order to allow more RH-TRU inventory to be disposed of in WIPP.

4. Adequate consideration should be given to the repository's ability to safely store all the waste components, particularly the gamma (γ) emitters and fission products. For example, ²⁴¹Am (with a 60 keV γ-ray), ²³³U, and ²³²U are three γ-emitting radionuclides that could be contained within some plutonium waste. A suitable TRU repository would provide adequate shielding for workers during waste handling operations and adequate long-term containment given the potential for gaseous daughter progeny. Similarly, the constituents of INEEL TRU waste streams should be examined for their impact on the modeled long-term

performance of the WIPP repository. In support of this statement, the EPA's Certificate of Compliance for WIPP in 1998 was based on an assessment of the projected inventory of radionuclides. This issue is mentioned for completeness and is not meant to be alarmist; indeed, the committee believes that there is no problem meeting the technical requirements of the current WIPP-WAC with the TRU waste streams under consideration here.

Currently, a few options exist for off-site disposal of a non-TRU LLW stream generated from INEEL. Commercial sites are either precluded from accepting DOE LLW or receive only low-activity waste (Russell et al., 1998). The only currently available off-site DOE options are the disposal facilities at the NTS and the Hartford Reservation.

The DOE LLW disposal site at the NTS can in general accept LLW from other DOE sites, but currently waste equivalent to the commercial category of Greater-than-Class C is accepted only on a case-by-case basis (DOE, 1997: p. 3-7; Russell et al., 1998, Vol. 1: p. 38). Mixed (i.e., RCRA-regulated) LLW waste is also accepted (DOE, 1997), but the WAC for these wastes are not yet finalized, and wastes generated at INEEL are not approved for disposal there at tiffs time (Russell et al., 1998, Vol. 1: p. 38; Vol. 2: p. 53).

The DOE LLW disposal site at the Hanford Reservation accepts waste with specific activity at or below the USNRC Class C designation (Russell et al., 1998, Vol. 2: p. 56). Certain mixed wastes are accepted (Fluor Daniel Hanford, Inc., 1998⁸). Non-Hartford waste generators can use the Hartford disposal site subject to the approval of the DOE Richland Office (Fluor Daniel Hanford, Inc., 1998).

On-site disposal of LLW can occur in suitable disposal sites. Currently DOE is self-regulating for the radionuclide constituents, based on DOE LLW disposal criteria that are both general and specific to the INEEL site (Russell et al., 1998; Bonano et al., 1991: p. 56), but the USNRC is increasing its regulatory authority at DOE sites and may be the future regulator. The USNRC disposal regulations (i.e., 10 CFR 61) require that a performance assessment calculation be done to model the fate and transport of radionuclides in the subsurface environ-mere, and to achieve a certain level of performance in the design of the disposal facility.⁹ When disposal operations are completed, the facility would be capped and monitored and institutional controls emplaced for 100 years.

Some constituents of HLW calcine and SBW are governed by the RCRA regulation of the EPA. The RCRA LDRs specify disposal site requirements, which include the use of liners and caps for "Subtitle C" landfills. These LDR requirements can be avoided if the DOE were successful in obtaining "delisting petitions" to exempt the waste from RCRA regulatory protocols.

There is some published guidance for how HLW of sufficiently low activity can be disposed of in a site that is not a geologic repository. A regulatory decision is needed to exempt waste, such as the low-activity waste (LAW) fraction from processing, from further management as HLW.

This problem was encountered at DOE's Hanford site, in the context of which the USNRC provided guidance regarding incidental waste classification for the contents of waste in underground tanks. In the Federal Register of March 4, 1993, it was written that, ". . . the USNRC indicated that spending vast sums of money without expectation of benefit to health and the environment would not be prudent . . ." (Wichmann et al., 1996: p. 10).

Near-surface disposal is possible if the following conditions/criteria are met:

• the waste activity is less than or equal to the USNRC Class C LLW limit(s);

• a performance assessment shows that disposal will not represent a hazard to public health or safety;¹⁰

• the majority of the radioactivity will be in a HAW form sent to a geologic repository; and

• technical and economic feasibility is supported, as by a cost/benefit analysis of separations options (Wichmann et al., 1996: p. 10).

It is not certain at present that INEEL waste products can be disposed of in most of the disposal options outlined above. This may be because of uncertainties in whether these repositories will be available for INEEL waste products and/or whether the INEEL wastes are properly qualified to meet the WAC. Only the LLW disposal sites, and WIPP for TRU LLW, are operational at present. The only off-site disposal option immediately available for INEEL wastes (i.e., without the need for a regulatory petition or special ruling) is DOE's Hartford site for nonmixed LLW. The committee's conclusion is that, with disposition pathways uncertain, efforts to develop a viable repository option are warranted. The requirements (e.g., repository waste acceptance criteria) so derived from a viable disposal pathway are an important input that should precede any decision among treatment alternatives for the HLW calcine and SBW.

Although HLW from some other sites likely will go to Yucca Mountain (presuming it is eventually licensed and opened), under current restrictions this repository will not accept mixed waste (i.e., containing untreated RCRA constituents) such as the current INEEL HLW calcine. Moreover, Yucca Mountain, if operational, is by DOE plans to be filled by 2035.

For all non-HLW streams, the USNRC would have to role on any waste reclassification as incidental waste. TRU waste could go to WIPP, which has recently opened, but which faces capacity limitations due to the amount of defense wastes at other sites. LLW in principle could go to commercial disposal sites in Washington or Nevada, but both of these sites have capacity and regulatory problems to contend with. Whatever the nature of radioactive wastes to be shipped offsite, transportation issues loom as significant problems to be resolved. The INEEL HLW program thus is faced with high uncertainty as to where, and whether, its wastes can be disposed off site.

At its meeting in Idaho Falls in August 1998, the committee was presented with cost estimates for 27 waste disposal options. These options involved various types and degrees of separation prior to different approaches to immobilization. The present value costs ranged from about $2.5 billion to between $9 billion and $10 billion. The committee gave little credibility to these estimates, largely because of the limited data on which they were based. Many of the cost differences were the result of differing estimates of disposal costs, which are highly uncertain at best. One contribution to the uncertainty of disposal costs is that the disposal locations are not established and developed sufficiently to permit an accurate estimate. Uncertainties as to when actions would actually be taken in the waste disposal options were another unknown that would affect cost figures calculated by discounting to a present value (see Appendix B).

With significant uncertainties represented in the information on which these cost estimates were based, the committee was forced to rely on simplistic, qualitative principles, such as:

• Do not spend money until the task is well defined and the route to its accomplishment identified.

• Low-temperature processes (e.g., evaporation, cementation) are usually less expensive than high-temperature processes (e.g., vitrification and production of ceramics).

• Each additional process step adds to the uncertainty in cost.

While no preliminary numbers were derived for the recommendations in this report, principles of this kind certainly influenced the committee's views.