1

Context and Setting

As described in previous National Academies’ review reports, the Hanford Nuclear Reservation is the site of the largest and most complex nuclear cleanup challenge in the United States (for background on the complexity of the cleanup challenge, see (NASEM, 2020, 2022b)).

The U.S. Department of Energy’s Office of Environmental Management (DOE-EM) is responsible for managing and cleaning up the waste and contamination under a legally binding Tri-Party Agreement (TPA) with the Washington State Department of Ecology (the Department of Ecology) and the U.S. Environmental Protection Agency (EPA). DOE-EM has proposed to retrieve the waste from the Hanford site’s tanks to produce two waste streams, high-level waste (HLW) and low-activity waste (LAW), by removing several specific radionuclides that constitute most of the radioactivity from the liquids and dissolved salt cake in the tanks, yielding liquid LAW, and then combining the removed radionuclides with the HLW solids. DOE-EM estimates that the HLW will contain more than 90 percent of the radioactivity and less than 10 percent of the total volume, while the LAW will consist of less than 10 percent of the radioactivity and more than 90 percent of the volume. Note, the two waste streams are complicated by the fact that they can be considered mixed-waste that includes regulated organics and other metals. The 90-10 separation is primarily accomplished by processing (also known as pretreating) waste retrieved from the tanks to route most of the radionuclides to the HLW stream and most of the non-radioactive chemicals (some of which are chemically hazardous resulting in mixed waste) to the LAW stream in the Waste Treatment and Immobilization Plant (WTP), which has been under construction for the past two decades at the Hanford site.

To treat these two waste streams, the current plan is to use vitrification i.e., immobilization in glass waste forms) for all of the HLW stream and for at least one-third of the direct (primary) LAW stream. Secondary waste from LAW processing comprised of liquid wastes, off-gas filters, and other internally generated wastes is expected to be grouted (i.e., immobilized in a cementitious waste form). Due to capacity limits in the recently completed LAW vitrification facility portion of the WTP, DOE-EM anticipates that there will be substantial amounts of LAW that the WTP cannot process. Note, the LAW vitrification facility is currently undergoing startup and commissioning.

To increase the LAW treatment capacity, DOE-EM intends to decide on a supplemental treatment approach and to implement it. The supplemental LAW (SLAW) to be treated would be similar in composition to the LAW to be treated in the WTP. The immobilized LAW—whether from the WTP LAW vitrification facility or the SLAW facility—was long expected to be disposed of in the existing near-surface Integrated Disposal Facility (IDF) at Hanford, though more recently (NASEM, 2020) preliminary analysis has been done regarding off-site disposal locations such as the Waste Control Specialists (WCS) facility near Andrews, Texas for the disposal of SLAW,

particularly if SLAW is not to be vitrified. It is still expected that vitrified output of the WTP LAW facility will be disposed at the IDF.

Presently, to keep the treatment of the HLW in the WTP on track to meet the amended TPA milestones, DOE’s plan is to have a supplemental treatment plant for the portion of the LAW that will exceed the capacity of the WTP (SLAW), because the SLAW must be treated concurrently to allow the HLW to be treated at the WTP’s full potential capacity. In DOE’s 2013 Record of Decision on Hanford tank waste management, DOE stated that it “does not have a preferred alternative regarding supplemental treatment for the LAW; DOE believes it is beneficial to study further the potential cost, safety, and environmental performance of supplemental treatment technologies” (Office of the Federal Register, 2013).

1.1 CONGRESSIONAL MANDATE TO CONTINUE THE ANALYSIS AND REVIEW OF SUPPLEMENTAL TREATMENT APPROACHES

DOE-EM has yet to formally select a supplemental treatment approach, although the Department of Ecology and some stakeholders assert that DOE has previously promised to use vitrification. To help with the selection, Congress directed DOE in Section 3125 of the Fiscal Year 2021 National Defense Authorization Act (Public Law 116-283, Sec. 3125) to enter a contract with a federally funded research and development center (FFRDC) to “conduct a follow-on analysis to the analysis required by section 3134 of the National Defense Authorization Act for Fiscal Year 2017 (Public Law 114-328; 130 Stat. 2769) with respect to approaches for treating the portion of low-activity waste at the Hanford Nuclear Reservation, Richland, Washington, intended for supplemental treatment.” The analysis “shall be designed, to the greatest extent possible, to provide decision makers with the ability to make a direct comparison between approaches for the supplemental treatment of low-activity waste at the Hanford Nuclear Reservation based on criteria that are relevant to decision making and most clearly differentiate between approaches.” For the criteria that Congress wanted to be considered, see Appendix A, which provides the complete texts of Sec. 3125 and Sec. 3134.

As specified in Sec. 3134, the SLAW treatment approaches considered should at a minimum include:

1. Vitrification,
2. Grouting, and
3. Fluidized bed steam reforming (FBSR).

Note that the three treatment alternatives result in different final waste forms. Vitrification produces glass waste forms either using Joule-heated melters, as are to be used in the WTP, or bulk vitrification. Grouting results in a cementitious waste form. FBSR produces calcined granules (often analogized to the consistency of puffed rice) or a monolithic crystalline ceramic waste form.

Sec. 3125 also asks for additional analysis of the grout treatment options identified in the FFRDC’s report for Sec. 3134.

In the previous Sec. 3134 study, the FFRDC considered in its final report five cases: (1) vitrification for disposal at the IDF, (2) grouting for disposal at the IDF, (3) grouting for disposal at a Texas facility known as WCS, (4) FBSR for disposal at the IDF, or (5) FBSR for disposal at WCS. In addition, secondary wastes, which were assumed to be grouted in all cases and disposed of in the IDF, are produced in amounts that depend on the treatment alternative, and these can contribute significantly to the dose rates resulting from long term disposal. To implement the alternatives, additional waste processing might be needed, for example, to remove certain radionuclides, or adjust the composition of the waste to make it more suitable or less costly for treatment and disposal.

In parallel to selecting an FFRDC, DOE was directed in Sec. 3125 to contract with the National Academies of Sciences, Engineering, and Medicine (the National Academies) to conduct a concurrent, iterative review of the FFRDC report as it develops to inform and improve the FFRDC’s work.¹ DOE contracted with Savannah River

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¹ For clarity, this review report uses the nomenclature of team for the FFRDC’s investigators, committee for the National Academies committee, report for the FFRDC team’s work, and review or review report for the committee’s work.

National Laboratory (SRNL), an FFRDC, and then SRNL formed a team of experts from SRNL and other DOE national laboratories as well as from outside the laboratories’ network. The charge to the FFRDC team from Sec. 3125 is in Appendix A. The Statement of Task (SoT) for the National Academies’ committee is in Appendix B.

The FFRDC team’s task is to provide DOE and Congress with a side-by-side comparison of the alternative treatment approaches and disposal options to aid decision making. As the committee has emphasized, its role in this iterative process was “to evaluate the technical quality and completeness” of the FFRDC report. In effect, the committee’s function is that of peer reviewer only. While the committee finds that the FFRDC’s recommendation, outlined in their report and discussed herein, has explanatory value and advance transparency, it was not within the committee’s scope to review the recommendation as such. Consequently, the committee does not express an opinion on, much less ratify or endorse, the FFRDC’s recommendation.

1.2 STUDY PROCESS

In the first review report, this National Academies committee published a peer review of the FFRDC’s draft framework report of 74 pages and a set of 71 slides produced by the FFRDC and presented at the public meeting on October 20–21, 2021,² titled “Hanford NDAA 3125 FFRDC Working Draft Compilation,” dated September 30, 2021. The committee also took into account presentations at the two public meetings and comments submitted by stakeholders and other interested members of the public (NASEM, 2022b). The committee’s review was published in January 2022 (NASEM, 2022b). Following the publication, the DOE sponsor of the study and other stakeholders were briefed by the co-chairs of the committee. The FFRDC committee was also briefed to clarify the findings and recommendations and answer any questions concerning the review.

On April 12, 2022, the National Academies committee was provided with the second report from the FFRDC committee for review. The report was titled Follow-on Report of Analysis of Approaches to Supplemental Treatment of Low-Activity Waste at the Hanford Nuclear Reservation (Bates, 2022b), a 191-page report with 579 pages of supporting information (Bates, 2022a). It is also publicly available on the National Academies website.

A public meeting was held in Richland, Washington, on April 26–28, 2022. The meeting included an update from the DOE Hanford Office of River Protection and Washington River Protection Solutions (WRPS), a restricted site tour of the Hanford site to show the progress being made at several of their facilities, presentations from the FFRDC team, invited presentations from the U.S. Government Accountability Office, the Department of Ecology for the State of Washington (WA Ecology), the Oregon Department of Energy, and the Yakama Nation. Regional stakeholders were also given opportunities for presentations and a 60-day public comment period was available from April 12 to June 12. The public comments are included in Appendix C of the committee’s second review. Also, Sec. 3134 highlights the necessity of consultation with the State of Washington and an opportunity for it to comment on the FFRDC’s draft reports. The committee appreciates the on-going input from WA Ecology.

The committee released the pre-publication version of Review of the Continued Analysis of Supplemental Treatment Approaches of Low-Activity Waste at the Hanford Nuclear Reservation Review: #2 in October 2022 and published the review in December 2022. This second review assisted the FFRDC in preparing its final report, which was released January 16, 2023, and is available on the National Academies website and in the Public Access Files for this consensus study (Bates et al., 2023), again a two volume set totaling 829 pages.³ Following the release of the final FFRDC report, a public meeting was held in Richland, Washington, on January 31–February 1, 2023. This meeting included updated presentations from the FFRDC team discussing changes to the final report based on the National Academies review, invited presentations from WA Ecology, the Oregon Department of Energy, and public comments from community and regional stakeholders.

An updated schedule is shown in Table 1-1 for the FFRDC’s work, the committee’s review, the public meetings, and the briefings to stakeholders. The final public meeting, in Richland, Washington, and with an online

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² To access all these documents and presentations from the public meetings, please go to nationalacademies.org and enter the search terms “Review of the Continued Analysis of Supplemental Treatment of Low-Activity Waste at the Hanford Nuclear Reservation.” This search will show the hyperlinks to the public meetings and provide access to the recordings of the events as well as the FFRDC draft documents and other presentations.

TABLE 1-1 Study Schedule

connection option, is planned for June 2023. The National Academies will publicly announce the specific dates for the meeting once these have been determined.

To perform its peer review task, the National Academies formed a committee composed of 14 experts and one technical consultant whose expertise spans the issues relevant for reviewing the FFRDC’s analysis, including risk assessment, cost estimation, cost-benefit analysis, decision analysis, waste pretreatment, supplemental treatment approaches, legal and regulatory requirements, and large-scale nuclear construction projects. Several of the committee members have prior experience in studying cleanup activities at the Hanford Nuclear Reservation, as well as at other DOE-EM sites. Appendix H contains biographical information about the committee members’ qualifications and experiences. Any information learned by the committee during additional fact-finding is available in the study’s Public Access File.³

The committee’s review is constrained by the SoT (Appendix B), which expressly calls for the committee to “evaluate the technical quality and completeness” of the FFRDC report on the treatment options for SLAW. The SoT also requires that the committee’s report be “technical,” providing feedback to the FFRDC team in an iterative process resulting in three FFRDC reports and three National Academies expert reviews.

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³ To request information in the Public Access File for this project, see https://www8.nationalacademies.org/pa/managerequest.aspx?key=DELS-NRSB-21-01.

1.3 REVIEW REPORT ORGANIZATION

The remainder of this review consists of the committee’s assessment, findings, and recommendations to respond to the three questions in the SoT.

1. Does the FFRDC’s report clearly lay out a framework of decisions to be made among the treatment technologies, waste forms, and disposal locations?
2. Does the FFRDC’s report consider in its analysis all the elements, criteria, and factors specified in Section 3125 of the National Defense Authorization Act of 2021?
3. Does the FFRDC’s report provide additional analysis for the grout treatment approach as identified in the FFRDC report for Section 3134 of the National Defense Authorization Act of 2017?

The findings and recommendations presented in the remaining chapters were prepared recognizing that the final review has audiences beyond the authors of the FFRDC report, including stakeholders and decision makers, such as DOE-EM and Congress. The committee’s review of the FFRDC report is divided into three chapters. Chapter 2 contains the committee’s findings and recommendations that are directly responsive to the questions contained in the committee’s SoT above. Chapter 3 contains the committee’s assessment of the strengths of the FFRDC’s report; and Chapter 4 contains the committee’s assessment of its limitations. Taken together, Chapters 3 and 4 can be seen as the committee’s reflections on the most appropriate ways decision makers and stakeholders could make use of the extensive data, analysis, and conclusions of the FFRDC report.

To aid the reader of this review, findings and recommendations from previous reviews (NASEM, 2022a, b) have been referenced in the narrative and re-printed in this review in Appendices D and F.

1.4 TERMINOLOGY

It is helpful in understanding the issues addressed in the FFRDC report and this review to distinguish two important concepts that often become confused in discussions of SLAW decisions: SLAW and direct-feed low-activity waste (DFLAW).

Hanford tank waste is essentially high-level waste (HLW), transuranic waste (TRU), and low-activity waste (LAW) as currently defined in DOE regulatory documents. LAW is tank waste that, by convention,

• has a relatively low level of radioactivity as a result of pretreatment or without pretreatment if the characteristics meet the criteria for processing in the LAW facility,
• is different than low-level waste (LLW) because LLW is defined legally for regulatory agencies whereas LAW is not, and
• “LAW is primarily the liquid portion of the tank waste that remains after as much radioactive material as is technically and economically practical has been removed. DOE uses the term LAW to mean the waste that, when solidified and properly classified as low-level radioactive waste, may be disposed of as low-level radioactive waste in a near-surface facility.” (GAO, 2021)

DOE uses the LAW label at Hanford to identify those tank waste streams with lower radioactivity to minimize the cost of pretreatment, immobilization shielding, packaging, transportation, and disposal that apply to higher activity waste that will be treated in the WTP HLW vitrification facility. Examples of LAW sources are (a) some wastes from tank-side pre-treatment of supernatant liquids, (b) liquids from WTP HLW vitrification such as off-gas processing, and (c) some liquid waste streams from the WTP LAW pretreatment facility after it begins operation. The relative contribution of the LAW volume needed to be treated will substantially increase once the WTP HLW vitrification facility begins operation. SLAW is additional capacity for treating LAW beyond the capacity of the WTP LAW vitrification facility. The amount of SLAW capacity needed will vary considerably over time and is forecast to significantly exceed the capacity of the existing LAW facility.

Accordingly, in the final FFRDC report, SLAW is defined as follows: “The volume of LAW to be treated and disposed of following waste retrieval and WTP operations that will exceed the planned processing capacity of the WTP LAW Vitrification Facility. ORP-11242, River Protection Project System Plan, estimates a shortfall in LAW treatment capacity of approximately 56 Mgal,⁴ approximately 50 percent of the projected LAW volume expected to be processed. To maintain the planned tank waste processing mission schedule, the U.S. Department of Energy (DOE) will require additional LAW treatment capacity (termed ‘supplemental LAW’) external to the WTP process.” (Bates et al., 2023, Vol. I, p. vii, footnotes omitted). SLAW treatment could involve a large facility, mobile or temporary capabilities, or both that would be integrated into WTP operations when the time comes either within the WTP or externally as a separate facility.

The disposition of SLAW becomes important because, as DOE-Office of River Protection (DOE-ORP) and the FFRDC have clearly stated, the constraining factor to meet future mission requirements in the DOE-ORP tank cleanup system planning documents was the insufficient WTP LAW vitrification throughput to be able to run the WTP plant at full capacity once the HLW vitrification facility is operational. Reemphasizing the previous paragraph, what constitutes SLAW is “the excess LAW treatment throughput requirements compared to what the [one] WTP LAW vitrification facility can provide.” (It might be roughly analogized to the peaking capacity that some electricity power plants provide to handle high summer air conditioning loads.) In general, a SLAW treatment facility or facilities would be handling LAW with some variations in specifics concerning volumes and compositions depending on what is occurring in feeder facilities. (This is why swings are predicted throughput requirement of the SLAW process selected [Bates, 2022b, Vol. 1, Fig 1.3-2]).

Shifting to DFLAW, DFLAW is a different operational concept, and there may be some confusion about its definition because the definition has expanded over time, and the term is not always used precisely. For the purposes of this report, the DFLAW project is a treatment pathway for LAW that involves a number of interconnected facilities that allows the WTP LAW vitrification plant to operate sooner, before the HLW vitrification facility is ready to operate, by operating all of the WTP facilities and capabilities except the WTP HLW vitrification and the pretreatment facilities (see Figure 1-1, a schematic describing the facilities that constitute DFLAW). By starting to operate before HLW vitrification can start, the tank waste contents can be reduced faster, and also the amount of supplemental LAW treatment capacity needed may be somewhat reduced. The DFLAW project required some WTP facility modifications to enable the WTP LAW vitrification facility to operate. The committee uses the above definitions of SLAW and DFLAW in this review of waste treatment at the Hanford site.

An additional point of terminology: the FFRDC was charged by Congress with analyzing “approaches for the supplemental treatment of low-activity waste at the Hanford Nuclear Reservation.” The term “approaches” refers to the three currently feasible technologies for treatment: vitrification, FBSR, and grouting. In this review the narrative will refer to these approaches as “technology alternatives.” Within each technology alternative, there are a number of potential means of implementation beginning with pretreatment and ending with disposal, which will be called options. Thus, the FFRDC analyzed in detail two options (Grout 4B and 6) within the grout technology alternative. This nomenclature is slightly different than terminology used by the FFRDC but is consistent in this review and provided clarity to the committee.

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⁴ The total capacity requirement is about twice the amount of waste now in the tanks because water must be added to sluice the waste from the tanks and for other purposes in the process.

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