2

The Committee’s Technical Review of the FFRDC’s Final Draft Analysis

For this review, the Statement of Task (see Appendix B) requires the committee to provide its overall assessment of the Federally Funded Research and Development Center’s (FFRDC’s) report in final draft form, as also required by Section 3134 (Sec. 3134) of the National Defense Authorization Act of Fiscal Year 2017 (see Appendix A). In this chapter, the committee gives its technical review of the FFRDC’s report dated April 5, 2019. That report’s chapters are listed in Table 2-1, and the report is available on the National Academies of Sciences, Engineering, and Medicine’s (the National Academies’) website.¹ The committee has also included in its review the set of slides presented by the FFRDC team at the May 16, 2019, public meeting in Kennewick, Washington. Those slides are available on the National Academies’ website.² The committee’s technical review follows the topical elements—specified in the major section headings—in study charges one through four in the Statement of Task.

TABLE 2-1 List of the Chapters and Appendixes in the FFRDC Final Draft Report, “Report of Analysis of Approaches to Supplemental Treatment of Low-Activity Waste at the Hanford Nuclear Reservation,” Dated April 5, 2019

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¹ See http://dels.nas.edu/resources/static-assets/nrsb/miscellaneous/ffrdc-2019-4.pdf.

² See http://dels.nas.edu/Past-Events/Meeting-Supplemental-Treatment/DELS-NRSB-17-02/10052.

GENERAL OBSERVATIONS

This section examines the FFRDC report as a whole and from the perspective of its intended audience. The committee notes favorably that the FFRDC has done a considerable amount of useful analytic work and that the FFRDC’s analysis has evolved and improved over the course of the team’s work. However, as may be evident from the list of chapters and appendixes (see Table 2-1), the report is lengthy (278 pages) and parts of it are highly technical.

It is understandable, and unavoidable, that the FFRDC report is lengthy and highly technical, because treatment of supplemental low-activity waste (SLAW) is a complicated and technically challenging matter. Several consequences, however, arise from the technical content and length of the FFRDC report. First, the lengthy technical content does not explicitly address the concerns that people in the Hanford region have faced in the past, face today, and will face in decades to come. In fairness to the FFRDC, its task was to review existing waste disposal technologies for supplemental treatment of low-activity waste (LAW). Moreover, to the credit of the report’s authors, they mention the urgency of the schedule for waste treatment and call this out in their Executive Summary. Even so, a reader easily could miss the pressing concerns about the waste tanks, the potential for future failures, and the hazards of the tank waste to current and future generations. Notably, extending tank cleanup schedules—whether it be the result of seeking better technologies, funding limitations, or technology or project management inadequacies—increases the chance that additional tanks will fail and release radionuclides and hazardous chemicals into the air or subsurface environment. Such an event is likely to cause even more delays and funding shortfalls as resources are diverted to address the consequences of the failure.

Second, as a consequence of the length and the technical nature of the report, the Executive Summary takes on increased importance as a means to guide the reader, especially a reader without extensive technical expertise in radioactive waste and disposal technologies. In all likelihood, the Executive Summary will be read by the largest number of people. Likewise, the report might also be improved by an introductory chapter or a “Reader’s Guide” (similar to what long technical documents such as Environmental Impact Statements have included), using to the extent possible laypersons’ terms.

In this chapter, the committee describes its primary findings concerning the FFRDC’s final draft analysis report. The narrative text of the chapter is organized to reflect the committee’s Statement of Task, but with formal findings collected at the end of the chapter because they often incorporate material from multiple parts of the Statement of Task and text. The analysis in this chapter’s text and findings are informed by the following questions:

• Does the FFRDC analysis rise to a level that it is useful to the decision-maker, and if so how?
• Does the FFRDC analysis describe a framework of decisions that need to be made?
• Does the FFRDC report provide a strong technical basis in support of the major decisions to be made?

This chapter is informed by the committee’s understanding of its fundamental task as a peer review of a report that describes alternative courses of action, and neither the FFRDC’s report nor the committee’s review is intended to select a preferred approach.

METHODS USED TO ASSESS RISKS, COSTS, BENEFITS, SCHEDULE, AND REGULATORY COMPLIANCE AND HOW THEY WERE IMPLEMENTED

Risk Analysis

Risk Assessment Methodology

The portion of the report on “Risks” (section 2.1, p. 23) includes the following statement on the FFRDC team’s methodology for risk analysis:

The FFRDC team considered a range of risks³ and candidate mitigation strategies. The FFRDC team used a semi-quantitative methodology to characterize the risks associated with each of the SLAW cases. A full quantitative risk assessment was not feasible because design and operational specifics currently available would not support that depth of analysis. The semi-quantitative approach adhered to a formal risk structure based on subject-matter expert analysis of the following triplet:

1. Scenario: The combinations of events that would result in deviations from design/operational/programmatic intent.
2. Probability: The likelihood of occurrence of each combination of events.
3. Consequences: The impacts of each combination of events.

The consequence metrics on which the study primarily focused were the incremental cost and the required extension in duration of the tank waste treatment mission associated with each scenario. Following the analysis of the risks associated with the individual SLAW cases, the team performed a side-by-side comparison among the alternatives. [Note that the committee has inserted the footnote on the definition of “risk.”]

Appendix E of the report goes on to explain that it used expert elicitation with team members as the subject-matter experts in a process that “involved team brainstorming to systematically identify and characterize risks associated with each technology option.” The team’s intent was “to establish a basis for preliminary risk-informed comparison between options as currently defined.” Moreover, the team sought “to obtain approximate, comparative risk rankings of the technology options considered.”

Appendix E identifies the scenarios that were considered in the exercise and reports their qualitative likelihoods. However, it does not provide any narrative explaining what the overall evaluation results mean for readers who are not familiar with risk analysis methods. Instead, it quickly follows the listing of the scenarios with a list of reasons to consider the exercise incomplete. In Appendix E, the FFRDC team describes two principal reasons why the scope of the scenarios it considered were incomplete (as paraphrased and quoted from p. 148 of the FFRDC report):

• Intended scope limitations, or known unknowns, mean that the convened experts did not have the ability to assess certain classes of risk. For example, a class of risks includes those beyond the control of the project. These classes of risk were mentioned in a list of programmatic risks, for example, the risk that there is inadequate funding appropriated for the project, but not analyzed further.
• Unintended scope limitations, or unknown unknowns, refer to possible scenarios that could adversely affect the tank waste cleanup mission but that the FFRDC did not identify. Such limitations are inherent in any risk assessment. However, “the strength of risk assessment as a specific approach resides in its ability to provide a systematic and transparent basis for decision-making in light of the information and knowledge available.”

The committee notes that the list of known unknowns, or system risks (in Table E-3 on pp. 150-151 of the report) could cause the reader to question the usefulness of the analysis done under constraints, and that the reader’s questions could unnecessarily undermine the insights from this part of the FFRDC’s work. The committee also notes that, setting aside the unavoidable presence of intended and unintended scope limitations, the list of scenarios that would reasonably fall within the intended scope may not be as complete

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³ In this context, “risk” is used in its general sense: “A probability or threat of damage, injury, liability, loss, or any other negative occurrence that is caused by external or internal vulnerabilities, and that may be avoided through preemptive action” (www.businessdictionary.com). It is not used in the context of human health risk.

as it could have been. For example, while Appendix E does consider the scenario where the grout formulation does not meet the performance expectations and permitting requirements of the state regulator, it does not appear to consider the scenario that the regulator rejects the Performance Assessment (PA) performed by the U.S. Department of Energy (DOE) for the vitrified LAW per se and the grouted secondary waste for the Integrated Disposal Facility (IDF). This gap in the analysis is problematic, because such a rejection would affect the ability to dispose of vitrified LAW or SLAW, and the associated grouted secondary waste in the IDF. The committee does not discount the usefulness of the FFRDC’s risk evaluation, but believes that the report would benefit from better integrating the risk assessment insights into a discussion of uncertainties in the main report.

Discussion of Uncertainties

The FFRDC has not properly presented the uncertainties elicited in the team’s risk assessment. Uncertainties are large and fundamental to nearly every aspect of the risk analysis, yet the report is relatively terse in identifying the various sources of uncertainty and, especially, the probability distributions that characterize each source. Given the high degree of sensitivity to risk in Hanford decision-making, it is important to understand, even if only in qualitative terms, whether the uncertainty is clustered around a central value, or whether it ranges across a wide spectrum of values. Similarly, it is also important to understand whether the uncertainty is symmetrically distributed above and below a central value, or whether the range is wider to the high or low side of the central value.

In the FFRDC report, after listing the risk scenarios evaluated, and assigning them qualitative likelihoods and consequences, the only summary provided in Appendix E is in Figure E-4 (on p. 150). This figure is a bar chart of expected values for the cost and schedule risks of each of the five technology options.⁴ The committee notes that the purpose of a risk assessment is to characterize the full range of uncertain values and the relative likelihood of outcomes over that full spectrum. Expected values are summary metrics that mask all of that subsumed information on uncertainty and risk, and so they are only useful when making decisions on a risk-neutral basis (i.e., when making a decision that is insensitive to the scale or tendency of the risks as compared to other factors). Risk neutrality has certainly not been a defining attribute of decision-making regarding the disposition of wastes at Hanford. Table E-2 and the cost-risk equation below this table on p. 146 of the report indicate how the FFRDC used the elicitation results quantitatively to develop the expected values presented in Figure E-4. It would, in addition, have been useful in Figure E-4 to indicate the full range of potential cost and schedule outcomes around those expected values, for example, in the form of a diagram that indicates the minimum, lower quartile, median, upper quartile, and maximum values (a box-and-whisker plot).

The committee also notes that the information in Appendix E mentions the potential that each technology option may cost more than one would estimate from the standard engineering-based evaluation that is presented in the cost section of the report (which is the source of the cost ranges in Table 2 of the report), and it is likely that these cost risks would have to be layered onto the cost ranges presented in the summary tables, Tables 2 and 10 of the report. The same is true of the schedule uncertainties.⁵ However, the report provides no acknowledgment of the presence of greater uncertainty than is reported as apparent cost and schedule uncertainties in Tables 2 and 10. Thus, the FFRDC report does not represent the full range of uncertainties in costs and schedules that the FFRDC team has actually assessed.

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⁴ The chart in the FFRDC report uses the term “expectation values,” which is a term more common to physics than to risk analysis, and itself lends to the overall opacity of the discussion. The committee prefers to use the more common term “expected value.”

⁵ During a question-and-answer session at the May 16, 2019, public meeting, the FFRDC confirmed that the cost ranges in Table 2 do not reflect the cost uncertainties explored in Appendix E.

Analysis of Costs and Benefits

Full Consideration of Benefits

In Section 2.2 of the report (p. 24), the FFRDC mentions the assessed benefits or advantages of each approach to treating Hanford SLAW, including waste form volume of both primary and secondary wastes, pre-treatment requirements, ease of operation, and flexibility, and notes that the “benefits of the individual treatment options are summarized in Section 3.0 and detailed in Appendices A-D.”

For the benefits of vitrification of the SLAW, Section 3.2.4 (p. 38 of the report) mentions (a) that design of the SLAW facility can be leveraged from the existing design for the primary LAW treatment facility in the WTP and thus is the “most technically mature technology;” (b) the waste form “has been studied extensively, so minimal further research is required;” (c) the high-temperature process destroys land disposal requirement (LDR) organics and most nitrates; and (d) the primary waste volume is comparatively low. The committee questions the claim that LAW vitrification is the most mature of the three treatment technologies. While it will undoubtedly be possible to capitalize on the research and design work underpinning the WTP LAW vitrification facility, this facility has itself neither been completed nor has it operated, and its scale is greater than any other experience with waste similar to Hanford LAW. In contrast, the Savannah River Site (SRS) has been grouting and disposing of similar LAW at an industrial scale for years with apparent success.

For the benefits of grouting of the SLAW, Section 3.3.4 on pp. 43-44 mentions that (a) it is the least complex process of the three options; (b) the process occurs at ambient temperatures and thus would not have the safety hazards to workers that high-temperature processes have; (c) it has the capability for relatively quick startup and shutdown that would more effectively accommodate variations in the SLAW feed rate; and (d) it has the lowest volume of secondary waste volume because the low operating temperature results in minimal off-gas. The committee notes that having start/stop capability may be particularly important because the SLAW is planned to receive the excess LAW that WTP cannot process and the receipt rate is projected to be highly variable (see Figure J-7 on p. 267 in the FFRDC report).

For the benefits of steam reforming of the SLAW, Section 3.4.4 on p. 50 mentions that (a) this process can tolerate variations in the SLAW feed rate and compositions and thus could give the flexibility to shut down temporarily or be operated with reduced feed rate; (b) it can efficiently destroy hazardous organics, nitrates and nitrous oxides, and ammonium compounds; (c) recent waste form durability tests indicate that this process can produce a durable waste form that would not increase waste volume during treatment and would not have liquid secondary wastes; and (d) because this process has a somewhat lower temperature as compared to vitrification, it reduces the amount of semi-volatiles that would be sent to off-gas and thus minimizes the recirculation in the treatment system of volatile and semi-volatile effluents. The committee notes that a high-temperature process such as steam reforming would entail an extensive off-gas processing system that would still produce some “secondary wastes” (e.g., see Figures D-2 and D-7 in the report). The report states that technetium and iodine will be completely removed by scrubbing and internally recycled (see Figure D-1); no separation process is complete. Also, the FFRDC analysis assumed that the carbon sorbents and high-efficiency particulate air (HEPA) filters do contain some technetium and iodine, even considering the effect of the recycle loop of the off-gas technology.

Section 4.1.2 on (pp. 57-58) provides the FFRDC’s high-level summary and comparison of the benefits of these options, which addresses an observation in the committee’s previous review (NASEM, 2018b) by “discuss[ing] or list[ing] the benefits for consideration of each treatment option,” which the previous FFRDC draft report did not do.

Consideration of Costs

The FFRDC report on p. 25 states that cost estimates for each SLAW technology “are full life-cycle costs, which include technology development, construction, operations, transport, and deactivation and decommissioning.” Sections 3.2.5, 3.3.5, and 3.4.5 provide summaries of the cost estimates for vitrification,

grouting, and steam reforming. Appendix H provides a detailed discussion of cost estimation methodology. Section 4.1.3 on (pp. 58-59) has a brief discussion about cost comparison among the technology options. Cost and schedule estimation ranges are listed in Tables 2 and 10. The FFRDC’s final draft analysis concluded that:

• The vitrification technology would take 10 to 15 years to implement and would cost $20 billion to $36 billion.
• The grouting technology would take 8 to 13 years to implement and would cost $2 billion to $8 billion.
• The fluidized bed steam reforming technology would take 10 to 15 years to implement and would cost $6 billion to $17 billion.

The cost estimates are based on technologies that, for the most part, have not yet been fully developed or deployed, and are based on costs from similar technologies, as well as assuming ideal funding conditions (i.e., no funding caps) and no redirection during a multi-year effort. Thus, there are large attendant uncertainties, suggesting that costs could be much higher than estimated, but are unlikely to be much lower. However, as discussed in this review’s section on “Risk Analysis,” these cost ranges provide the reader with a potentially incomplete view of the full range and nature of cost uncertainty.

Cost-Benefit Reasoning

Sec. 3134 (see Appendix A) calls for an “analysis” of the “benefits and costs of such [treatment] approaches,” but not a cost-benefit analysis per se. As the committee has noted in prior reports (NASEM, 2018a,b), Sec. 3134 does not call for a comprehensive comparative analysis that would identify a preferred alternative. The distinction is important, as the preferred alternative analysis requires crucial judgments by decision-makers that are in no way factual, but rather involve values, legal and regulatory compliance, policies, and many other considerations. This is beyond the scope of Sec. 3134 and thus the task set out for the FFRDC and the committee. Moreover, a comprehensive preferred-alternative analysis would invade the province of the elected and administrative bodies (DOE, state regulators, and Congress) that are established to make such choices on behalf of the public.

The FFRDC team made some initial steps along the lines of performing a preferred-alternative analysis in an earlier report, but withdrew them from the current draft after the committee cautioned against it. Instead, the committee recommended (NASEM, 2018b) and the FFRDC team provided a qualitative comparison of relevant considerations. It is summarized in a large table (see Table 10, p. 61 of the FFRDC report), whose contents are drawn from the report and appendixes. What is currently missing, however, which would help to inform the ultimate selection of a preferred alternative by decision-makers using the FFRDC report is a summary of findings in a format that reflects the “marginal analysis” perspective that is fundamental to the logic of cost-benefit analysis. A cost-benefit optimum occurs when the marginal cost of “doing more” is equal to or greater than the marginal benefit gained by that increment in cost. Such an analysis is particularly appropriate when selecting among SLAW treatment alternatives that represent a discrete part of a larger system that is mostly well established (e.g., Hanford tank cleanup), and the differences in their costs are very large. This is a perfect setting for “cost-benefit thinking” of the type called for by Sec. 3134. For example, as one considers adopting a higher-cost option over a lower-cost option, one should ask how much the benefits of the higher-cost option are improved, and furthermore, to directly consider whether those incremental benefits are significant enough to be “worth” the incremental cost that would be absorbed. In addition, because the differences in benefits among the technology options at issue here are not along a single continuum, but have multiple attributes [as discussed in “Full Consideration of Benefits” above], an incremental approach to comparison of options could be extremely useful in bringing clear insight to a complex and uncertain situation.

Ultimately, a preferred-alternative analysis will be required by decision-makers, who are the ultimate audience of the FFRDC report. It will be for them to choose and explain the reasoning for a particular technology (or technologies), and an analysis of costs and benefits, as required by Sec. 3134, will be an essential component of that preferred alternative analysis. More could be done to summarize the information in the FFRDC report in a manner that would be consistent with that decision process, even if it is to be initiated by and completed in the future under the oversight of the decision-makers using the FFRDC report as input.

Schedule

Schedule Considerations

In Section 2.4 (p. 25), the report states: “Schedules were developed in conjunction with cost estimates for each case. The schedules reflect team experience in process development and recent DOE capital projects.” In Section 3.0, the team provides its summaries of the schedule estimates for each technology option. For vitrification in Section 3.2.6 (p. 39), the estimated time is 10 to 15 years considering the time to complete additional research and development, design, construction, and cold and hot start up. For grouting in Section 3.3.6 (p. 44) the estimated time is 8 to 13 years considering the same factors. For steam reforming in Section 3.4.6 (p. 51), the estimated time is 10 to 15 years, and that section points out that the technology maturation plan and full-scale design are expected to benefit greatly from the experience at Idaho National Laboratory (INL) in developing the Integrated Waste Treatment Unit, “though that potential benefit is not assumed in the current cost and schedule estimates.” Likewise, comparison with previous Hanford high-level waste (HLW) vitrification plant time estimates and actual results (see “Brief Historical Context” section in Chapter 1 of this review) could be informative of the potential gap between expectations and reality.

Impact of System Integration Failures

While the FFRDC has provided a rationale for its schedule estimates based on recent DOE capital projects, it has not considered the effects on the schedule of a technology functioning well as an individual component and not as a part of the larger integrated system. For example, an efficient and cost-effective method for removing iodine from the LAW being fed to the SLAW may exist or be found, but it could introduce chemicals into the product stream that are incompatible with the selected immobilization process. Given the complexity, interdependencies, and relative novelty of Hanford processes, system integration would have to be considered a significant technology risk.

Funding Risks

On pp. 24-25, the report provides information about annual funding requirements to complete the Hanford tank waste treatment mission beginning with current funding levels. This information shows the substantial increase in projected funding requirements to complete the WTP, to build tank farm infrastructure required to retrieve the tank waste and move it to the WTP via pipeline, and to build the SLAW facility using vitrification technology. In a nutshell, the estimated funding requirements increase from the current approximately $1.3 billion per year to a maximum of about $4.7 billion per year. Figure 2-1, reprinted from the FFRDC’s report, shows the stacked estimated costs for the annual estimated budget. These costs are almost totally driven by the capital costs for the WTP, tank farm infrastructure, and the SLAW treatment plant. The FFRDC report states that meeting the funding requirements is one of the major challenges in successfully treating the SLAW, and the committee agrees. The committee also notes that these annual funding requirements do not include requirements to continue aspects of Hanford cleanup other than tank waste, such as facility decontamination and decommissioning, managing contaminated subsurface water plumes, and maintaining and operating common site infrastructure (e.g., water, roads, electricity, effluent treatment, waste evaporators), with costs that vary but are around $1 billion per year.

The FFRDC’s analysis assumes that funding would be made available to meet the schedule’s order and scale of operations indicated in the annual funding requirement graph. However, on p. 24, the report points out “project funding has often been ‘capped,’ i.e., annual funding limited, independent of the project estimate.” If this continues to be the case, SLAW technology development, facility design, and facility construction would compete for priority and funding with other large capital expenditures at Hanford including Direct Feed Low-Activity Waste treatment, WTP’s major construction projects, tank waste retrieval, and other operations involving the tanks. Thus, the duration of the Hanford tank cleanup mission would inevitably be substantially increased.

Regulatory Compliance

The FFRDC report (see Section 3.2.7, p. 39; Section 3.3.7, p. 45; Section 3.4.7, pp. 51-52; and corresponding sections in Appendixes B, C, and D) considers the three waste form options from the perspective

of their capabilities to meet applicable regulatory standards.⁶ For disposal in the IDF, the regulatory drivers for determining compliance are groundwater concentration limits for radionuclides developed by the U.S. Environmental Protection Agency (EPA) under the Safe Drinking Water Act, which are part of the DOE orders under which the IDF is regulated. Such requirements are not applicable at the Waste Control Specialists (WCS) site because this site is licensed under the U.S. Nuclear Regulatory Commission’s regulations (10 CFR part 61), which do not require compliance with the Safe Drinking Water Act. Both sites will be required to meet disposal standards (LDRs) under the Resource Conservation and Recovery Act (RCRA) concerning wastes containing hazardous chemicals. Meeting the RCRA requirements typically requires waste treatment to destroy or immobilize hazardous chemicals. The FFRDC team in its report did not directly discuss environmental and human health risks but in effect considered these in its analysis of regulatory compliance.

The use of the radionuclide drinking water concentration limits is a reasonable surrogate for human health risk as a first order of approximation. Moreover, for any of the alternatives to be feasible, it must be capable of complying with the applicable regulations such as drinking water standards. A thorough risk assessment and cost-benefit analysis would need to evaluate other exposure pathways (even if only to assure that the drinking water concentration is at least as protective), and to evaluate the benefits to be gained from additional protective actions or lost by other alternatives.

WASTE CONDITIONING AND SUPPLEMENTAL PRE-TREATMENT APPROACHES CONSIDERED IN THE ASSESSMENTS, INCLUDING ANY APPROACHES NOT IDENTIFIED BY CONGRESS

Sec. 3134 directed the FFRDC to perform an analysis of the risks, benefits, costs, schedules, and obstacles for removal of iodine-129 and technetium-99 from the SLAW for immobilization with the HLW. This highlights the fact that the identified approaches—vitrification, grouting, and steam reforming—are part of a larger system that provides the LAW feed and considers multiple potential disposal locations. In addition to the LAW feed from other parts of the tank waste remediation system, the SLAW facility will produce and have to manage its own secondary wastes and may include pre-treatment to make the SLAW more suitable for treatment or disposal. While these aspects precede and follow the central treatment approach, respectively, they can have a profound impact on the risk, cost, and benefit of the central approach.

Broader Waste Management System

The SLAW treatment technology is a relatively small part of a large, interrelated system that includes subsystems for treatment of the HLW and primary LAW, as well as tank operations. Following the congressional mandate, the FFRDC has focused its analysis within this relatively narrow scope of supplemental treatment of the LAW. The FFRDC team has analyzed three immobilization technologies identified in Sec. 3134: vitrification, grouting, and steam reforming.

Vitrification

This is a high-temperature technology that blends the SLAW with glass forming materials at about 1,150 °C, incorporating most of the radionuclides and metals into a glass waste form. The vitrification and off-gas systems destroy the LDR organics and some of the nitrates. Water is not incorporated into the glass, so it is treated in an effluent management facility to yield a large volume of grouted secondary waste. Solid secondary wastes (e.g., off-gas filters) that are generated are grouted (see separate discussion of secondary wastes below).

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⁶ See Appendix A of this review report for the list of relevant standards as specified in the congressional mandate and Appendixes F and I of the FFRDC report for more detailed information.

Grouting

Grouting technology operates at room temperature (§25 °C) and blends the liquid SLAW with dry inorganic materials to produce a cementitious waste form. All radionuclides, metals, and organics are incorporated into the grout, producing a very small amount of secondary wastes from filters and used equipment. Pre-treatment (see separate discussion below) to remove or destroy LDR organics may be needed.

Steam Reforming

This high-temperature technology blends the liquid SLAW with dry inorganic materials at 750 °C, forming dry granular mineral particles with a chemical structure that retains the radionuclides and metals. The particles can be mixed with additives to produce a monolithic solid waste form. This process also generates secondary wastes that the FFRDC assumed would be grouted.

In previous reviews, the committee accepted the FFRDC’s choice to study only these three primary treatment options. As implied by the congressional directive to study these particular technologies, they are familiar and relatively well understood—which is not to say completely understood—technologies, and so the FFRDC’s choice has merit especially given the looming Tri-Party Agreement milestones. At the same time, it is inevitable that further use of these technologies over time, whether at Hanford or elsewhere, will result in better understanding and improvements in the process and output—all the more so because the Hanford cleanup project is to last for decades. Moreover, given the need for waste disposal in many settings (beyond DOE, beyond nuclear), it is entirely possible, even likely, that entirely or partially new technologies will emerge that would be useful for the SLAW. Therefore, because new technologies, improved existing technologies, or new combinations of existing, improved, and new technologies may represent the best way to address the SLAW as the project develops over the next decades, it would behoove DOE to make choices now that do not foreclose the testing and adoption of treatment approaches that are not apparent or whose large-scale adoption is not yet warranted.

In addition to the three primary treatment options, the FFRDC also identified two near-surface land disposal options to analyze and compare. The IDF located at Hanford is considered as the “baseline” LAW disposal facility. In this baseline option, the liquid LAW will be solidified using vitrification, and the secondary waste will be grouted. DOE plans to dispose of both types of waste at the IDF, but the Washington State Department of Ecology (the Department of Ecology) has yet to approve waste acceptance criteria that would allow disposal of grouted secondary waste or even the primary vitrified LAW. The second disposal site analyzed is operated by WCS, located near Andrews, Texas. WCS is sited in an arid and isolated region of western Texas and has become an active commercial low-level waste disposal facility in recent years. Also, the report briefly mentions (see Appendix F, p. 155) the possible use of the EnergySolutions facility near Clive, Utah, especially if pre-treatment to remove sufficient strontium-90 can produce Class A waste, which is required for acceptance at that facility.

The Major Role of Pre-Treatment

Sec. 3134 directed the FFRDC to perform an analysis of the risks, benefits, costs, schedules, and obstacles for removal of iodine-129 and technetium-99 from the SLAW for immobilization with the HLW. (See sidebars on iodine-129 and technetium-99 for contextual discussion about characteristics of these radionuclides.) Instead, the FFRDC performed an analysis of whether removal of these radionuclides is needed to comply with the relevant waste acceptance criteria and examined the status of technologies for removing these radionuclides from the SLAW feed stream. Section 3.1 and Appendix A of the FFRDC report has a fairly complete review of the pre-treatment techniques and options that are available for these waste streams.

Besides the possibility of pre-treatment to remove technetium (Tc) and iodine (I) as specified by Sec. 3134, there is discussion of the need to pre-treat for organic materials to meet the LDR for waste acceptance of grouted SLAW, as well as the pre-treatment of the SLAW to remove strontium-90 to reclassify as Class A low-level waste for off-site disposal to possibly reduce disposal cost at the WCS site.

During the information-gathering meeting on May 16, 2019, slide #37 presented by the FFRDC team concluded:

• Treatment for LDR organics may be required for some of the waste for both on-site and out-of-state disposal.
• Technetium and iodine removal is not needed for out-of-state disposal of grouted or steam reformed waste forms.
• Technetium and iodine removal is not needed for on-site disposal of grouted or steam reformed waste forms, assuming high-performing grouted and steam-reformed waste forms.

For radioactive waste disposal, the committee notes that the two mobile and long-lived radionuclides iodine-129 and technetium-99 are consistently important risk contributors. Two important questions for this analysis are (1) whether it makes sense to remove these two radionuclides from the SLAW and immobilize them with the HLW streams, and (2) whether technetium and iodine will meet EPA’s drinking water standard and, presumably, the yet to be determined waste acceptance criteria for the IDF.

Both the unpublished IDF PA and the FFRDC’s Performance Evaluation (PE) attempted to answer the second question. According to the PA results described by Pat Lee of Orano Federal Services at the information-gathering meeting on February 28, 2018 (Lee, 2018), and the summary of those results in the FFRDC report (see p. 166), the immobilized (vitrified) low-activity waste form “is projected in the PA to contain the majority of ⁹⁹Tc and ¹²⁹I.” Moreover, the report (p. 166) notes: “No performance objectives or measures were exceeded within the 1,000-year DOE compliance period.” However, according to the PA’s simulations, the release of iodine-129 would exceed the drinking water standard approximately 7,000 years after site closure. In comparison, the FFRDC’s PE concluded that on-site IDF disposal would not require the removal of these radionuclides. The differing conclusions in the PA and PE analyses concerning iodine-129 point to the importance of revealing the modeling assumptions. In particular, the committee believes there are large uncertainties associated with the unvalidated waste form degradation models and data used in the FFRDC’s PE analysis. Furthermore, what differentiates a “low-performing grout” from a “high-performing grout” from a “projected best” grout would have to be specified. Therefore, the conclusions from the FFRDC’s PE that removal of iodine-129 and technetium-99 for on-site IDF disposal are not necessary would benefit from further evaluation and validation. If it turns out that iodine-129 can be removed from the current LAW or otherwise mitigated by engineered disposal barriers such as getters (which are added materials that can retain contaminants of concern) or isotopic dilution, resulting in much more benign LAW streams, other disposal options may open up for the disposal of these radionuclides as well as the waste from the treatment process.

Similarly with respect to selenium-79 (see sidebar for contextual discussion), without the proper supporting documentation for the FFRDC PE, or the IDF PA on which the PE was based, the committee is unable to assess the potential significance of ⁷⁹Se and any other long-lived fission products. It would have been useful for the FFRDC to include the risk over time for ⁷⁹Se and all of the long-lived radionuclides that are indicated in Table F-2 of the report.

The Major Role of Secondary Waste

While the FFRDC report mentions the challenges of secondary waste in the Executive Summary and explains its origins in Appendix F, the committee believes that the FFRDC does not emphasize strongly enough to decision-makers the central role that secondary waste plays in meeting disposal waste acceptance criteria. Secondary waste is produced during the treatment (and pre-treatment if used) of the SLAW in differing amounts depending on the treatment method used and can include solid (such as HEPA filters) and liquid wastes produced during primary processing which are then assumed to be grouted. In particular, high-temperature processes volatize iodine and a small fraction of it is present in the grouted secondary waste forms.

Indeed, the grouted secondary waste has a disproportionate impact on the IDF performance and results in it being the dominant contributor to calculated dose during a 10,000-year period. Specifically, long-lived and mobile iodine-129 dominates the long-term health risks for all three treatment technologies. As shown in Lee’s presentation from the February 28, 2018, public meeting on the IDF PA, the time of peak dose for iodine-129 occurs in the 7,000 to 8,000 year period after emplacement in the IDF (Lee, 2018). Thus, the production of secondary waste streams for high-temperature processes (vitrification and steam reforming)—if left unmitigated—becomes an important decision factor among the alternatives.

Given the fact that the grouted secondary waste streams drive IDF performance (except for grout, where less iodine is in the secondary wastes and the dose from the primary waste dominates), it is surprising that the FFRDC did not spend more time analyzing mitigation actions both on the secondary waste form, but also in the IDF design (which, for example, takes no credit for using engineered fill materials as a radionuclide migration barrier). Accomplishing either of these mitigation actions could have a significant impact on performance of the IDF LAW disposal system (including waste form, fill material, liners, and caps) and potentially streamline the decision-making process. However, the FFRDC’s report does mention the possibility of shipping grouted secondary waste to WCS while keeping vitrified primary waste at the IDF. Waste acceptance criteria at WCS are less restrictive than at the IDF because, in contrast to the IDF, WCS lacks an aquifer containing potable water under the disposal site.

OTHER KEY INFORMATION AND DATA USED IN THE ASSESSMENTS

Performance Assessment and Performance Evaluation of Waste Disposal

The compliance of primary (WTP) vitrified LAW disposal at the IDF relies on PA calculations (as specified in DOE Order 435.1; DOE, 2011b). The PA evaluated the performance of vitrified primary waste and grouted secondary wastes in the IDF, but did not address the performance of the IDF containing waste from the grouting and steam reforming alternatives. The report on p. 166 states the PA results for vitrified LAW as follows:

• No [DOE] performance objectives or measures were exceeded within the 1,000-year DOE compliance period. The highest calculated dose projected was for the chronic inadvertent intruder scenario where interception of four ILAW [immobilized low-activity waste] glass cylinders occurs from well drilling at the end of the institutional control period. In this case the dose is <50% of the 100 mrem/yr [milli-roentgen equivalent man/year] maximum dose rate performance objective.
• For the air and groundwater exposure pathways, the predicted dose during the DOE compliance period, is dominated by the air pathway for gaseous radionuclides, but is a factor of 50 below the 10 mrem/yr performance objective.
• Only the groundwater protection measure (beta-gamma dose equivalent) is exceeded during the post-compliance period (>1,000 years), where dose calculated using the EPA dosimetry method projects a dose rate of 4.9 mrem/yr (versus 0.4 mrem/yr beta-gamma standard) resulting from ⁹⁹Tc and ¹²⁹I within solid secondary waste, specifically the grouted granular activated carbon (GAC) and HEPA filters solid secondary waste (SSW).

To assess potential compliance of the SLAW and secondary waste disposal at the IDF from the grouting and steam reforming options, the FFRDC team conducted PE analyses that are similar to the PA methodology, and they validated the PE against the PA. The FFRDC team also conducted a PE of vitrified SLAW and secondary waste disposal using its own waste form models and assumptions. As discussed on p. 166 of the report, the results of the PE for all three waste disposal systems at the IDF extending to 500,000 years were that the calculated peak dose was less than 50 percent of the 100 mrem/yr dose rate performance objective. “After more than 200,000 years, radium-226 becomes a dominant dose contributor, but less so than the earlier peak doses from technetium-99 and iodine-129.”⁷ Thus, iodine-129 and technetium-99 were the only significant contributors to the peak dose, which occurred several thousand years after disposal site closure. The committee notes that preparation and release of PAs is beyond the scope of the FFRDC’s charge or resources. However, it is evident from the most recent report that the FFRDC has had access to draft PA analyses and results. The committee did not have access to the PA data and analyses, thereby, making it impossible for the committee to critically review the disposal performances of the three waste disposal systems. Moreover, the technical bases for waste degradation models and mechanisms used in the PE analyses for the IDF by the FFRDC team are not well documented and justified.

Consideration of Experience at Relevant Sites

In a number of places the report mentions experience relevant to the SLAW, especially at DOE sites other than Hanford. Examples include the vitrification and grouting at the SRS, vitrification at the West Valley Demonstration Project, and the steam reforming unit under development at INL. However, the mentions are just that. There is no analysis of what aspects of the experience are relevant to the SLAW or not, why this is the case, and the implications for the readiness of the various technologies for deployment. For example, extensive information exists on the design, cost, production, and performance of Saltstone at the SRS accumulated over nearly three decades. This information was used by the FFRDC to inform their cost

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⁷ Page 166 of the FFRDC report.

estimates for the grout alternative. Because of the similarities in some of the wastes, the committee believes that there are lessons to be learned from the activities at other sites that are not reflected in the FFRDC report, not only regarding the design and operation of these similar facilities, but also regarding the performance of the grout waste form, which has been widely used to immobilize radioactive and chemically hazardous wastes. Discussion of this experience would help inform decision-makers. In addition, it would help to consider other useful, relevant experience at non-DOE sites to include commercial facilities, such as the operating steam reforming facility in Erwin, Tennessee. This would include analysis of pre-treatment and treatment alternatives for operations similar to those being consider for treatment of SLAW at Hanford.

While there undeniably are relevant differences among the sites’ respective waste streams, physical environments, regulatory requirements, and other factors, there are also similarities. Success or lack of success at another site does not directly translate to the same outcome at Hanford, but every experience offers lessons to be learned, and the FFRDC report would be strengthened by a candid assessment of such lessons. The committee recognizes that there is often cultural resistance to assessments, but DOE, like all other organizations, would benefit from learning from its own experiences across the DOE complex. Moreover, as suggested in Recommendation 3-1 (see Chapter 3), the long duration of the Hanford cleanup lends itself to a concerted effort to learn from experience at other DOE sites, at locations in other countries where these technologies are used, and from Hanford’s own experience over multiple decades.

In a similar vein, the report has a brief comparative discussion of differences among the current efforts and previous performance assessments (see Appendix F.4.3.3) and a very brief acknowledgment of previous comparative evaluations of technologies relevant to the SLAW treatment (Sec. 3.5). A few documents in both categories are referenced in the report. The committee believes that there is a need to systematically and transparently identify and compare the differences among the various historical documents at both levels to provide the basis for determining the credibility and shortcomings of the current analysis.

Other Needed Information

Meeting the Requirements of the Resource Conservation and Recovery Act of 1976

An important aspect of regulatory compliance is meeting the requirements of the RCRA. Some metals and organic chemicals that are known or suspected to be in the SLAW waste stream are regulated under the RCRA, which sets stringent land disposal restrictions for these materials based on their potential to leach into groundwater. Other chemicals suspected to be in the SLAW, such as nitrates, are regulated to prevent groundwater contamination. If these materials are destroyed or removed during the processing of the waste, or adequately immobilized in waste form, then near-surface disposal is not an LDR issue. However, if they remain, the LDRs represent a regulatory hurdle, and one which is in the control of state regulators under the terms of the Federal Facilities Compliance Act. Although the FFRDC report mentions the possibility that the LAW might require pre-treatment to meet LDR, its analysis of mitigation options is terse, and it is unclear whether or when mitigation will be needed and how the need will be assessed.

Enhanced Engineered Barriers for Iodine-129

Because of its characteristics (see sidebar), iodine-129 poses a particular challenge for disposal in either a near-surface facility or a geologic repository. Over the very long term, iodine-129 becomes an important contributor to dose calculations. For this reason, there has been a substantial amount of research, mostly funded by DOE, to investigate new materials for the selective removal of iodine from the HLW waste streams, its incorporation into durable waste forms, and the development of getters to capture released iodine in the near-field of the disposal environment.

Although the report raises the possibility of using getters in the grout, the report does not provide an explanation or analysis of the materials that would be used, nor is the possibility of isotopic dilution discussed. Finally, the report does not consider a strategy for augmenting the design of the disposal site, for example, the IDF, to use getters in the fill material as a barrier to iodine release.

PRESENTATION OF ASSESSMENT RESULTS

Comparative Assessment of Waste Form Performance

In Review #2, the committee emphasized the need for a comparative assessment (NASEM, 2018b). One distinct element of the decision-making process will be to answer the question of whether the performance of the different waste forms has a significant impact on the performance of the disposal system. The answer to this question lies in an evaluation of the comparative material properties of the waste forms, their performance in the near-surface, disposal environment, and an understanding of how all of the elements of the disposal system actually functions individually and how they interact.

The FFRDC’s final draft analysis attempts to do this, but there are deficiencies to the FFRDC’s approach. Most noteworthy is the lack of a truly parallel analysis of the three waste forms. A parallel, comparative analysis would consist of three clearly presented and discussed steps:

• A clear definition of the waste feed stream (also called a feed vector) for each waste form. Although some data are given (e.g., Tables F-1 and F-2), these data represent examples at a specific time or global averages. In order to understand waste form performance, particularly of key radionuclides like iodine-129 and technetium-99, the analysis has to provide envelopes of composition that capture variations in the waste stream during processing. This may be important in determining whether the waste form can incorporate or encapsulate the waste stream’s radionuclides. More importantly, the type of processing, such as high-temperature vitrification versus low-temperature grouting, can change the immobilized waste stream composition. In the case of vitrification, small fractions of volatile elements, such as I (a few to 25 percent) and Tc (a fraction of a percent), are projected to be in the secondary waste streams, which are assumed to be grouted. Thus, the final disposal evaluation needs to consider not only the performance of the three waste forms, but also the performance of radionuclides in the secondary waste streams. Options for the treatment of the secondary waste streams also need to be described and evaluated.
• A comparison of material properties of the three waste forms. This should consist of four types of information:
  • A description of the basic waste form properties (e.g., waste loading and density), particularly properties that will affect performance, such as the composition of the glass, whether additional engineered barriers will be used in the grout, the permeability of the grout, and the microtexture of the glass ceramic that will result from steam reforming.
  • A description of the distribution and chemical speciation of key radionuclides within each waste form, particularly their redox state and the identification of other components that may change or control the redox state within the waste form.
  • A description of the radionuclide release mechanisms for each waste form, and a discussion of alternative mechanisms and why they were not adopted. The understanding of the mechanisms of release and retardation is a critical aspect of the models that were used in the PA.
• The last step in the comparison is the performance assessments of the waste forms in the disposal environment. If the PA and the PE calculations for the IDF had been available for the committee’s review, four issues would have been of critical interest:
  • How is the waste form’s release of radionuclides modeled?
  • What other near-field geochemical or hydrologic processes (e.g., solubility limits or sorption) slow the release and/or decrease the mobility of radionuclides?
  • How do assumptions about future conditions, e.g., climate or the geologic medium, affect the PA results?
  • How do the principal components in the IDF interact with one another? The scenario analyzed in the PA involves two types of waste in the IDF: glass for primary LAW and grout for secondary waste. Are there coupled mechanisms at play, such as the effect of grout on the pH of water

The committee notes the following key points:

• A modeled demonstration of compliance is only the first step in a performance assessment or a performance evaluation. One also needs to develop a strong understanding of how the disposal system functions as a whole and be able to make a compelling argument for the selection of one waste form over another (what is sometimes known as the safety case). Even if all three waste forms comply with the regulations, that still does not mean that the differences in waste form performance have been captured by the analysis. Other parameters, such as the time to reach the peak radiation dose rate and the time for dose rates to diminish, may be relevant to the decision-maker’s consideration of the three technologies and their waste forms. The committee acknowledges that the FFRDC has made a valiant effort to compile and compare data on the different waste forms. Still, the lack of a fully transparent comparison between the three waste forms hinders the analysis.
• As noted above, the FFRDC report has very limited discussion of the Saltstone that is in use at the SRS (see pp. 93-94 in Appendix C). More details on the similarities and differences between the grout to be used at Hanford and the Saltstone at SRS would have added greatly to understanding how the grout is being modeled at the IDF at Hanford.

In summary, the FFRDC report fails to muster the extensive data in the literature on the different waste forms and present a comparison that highlights the pros and cons of each. The committee notes that this is attempted, as an example for grout (p. 92 in Appendix C), but this bulleted list is really just composed of assertions without reference to data or citations to relevant literature.

The “As Good as Glass” Conundrum

Much has been made, particularly by the Department of Ecology, of a supposed commitment by DOE that any treatment technology for the SLAW be “as good as glass.” While not found in so many words in federal or state law or regulation, the “as good as glass” concept has taken on a life of its own at Hanford. Some stakeholder groups advocate for it; the Department of Ecology and others have developed a set of legal arguments for “as good as glass”; and the Department of Ecology has offered some tentative criteria (see the presentation of Alex Smith, Washington State Department of Ecology, at the July 23, 2018, public meeting) by which another technology might be determined to be as good as (or not as good as) glass. In theory, the “as good as” formulation would allow DOE to pursue a treatment technology other than glass (vitrification). In practical terms, however, “as good as glass” forces DOE to adopt vitrification because the content and contours of the concept are undefined. The conundrum is that “as good as glass” can mean different things—often without a clear awareness of the differences by users of the term. The committee has heard discussions during its information-gathering meetings that imply at least three different meanings, as follows:

• First, in its narrow technical sense, it refers to the waste isolation capacity of the SLAW immobilization medium (e.g., glass or grout). This is fundamentally a question of materials science and chemistry. It is informed by laboratory experiment and mechanisms of isolation, and it can be evaluated based on a considerable technical literature with varying degrees of uncertainty.
• Second, in a technical but broader sense, “as good as glass” refers to the disposal system—not just the waste form itself, but the waste isolation effectiveness of the waste form, packaging, fill material surrounding the packages in the disposal trenches, the engineered barriers such as liners and caps that surround the trenches, and the natural environment surrounding this engineered system.

• Thus, the engineering of the waste disposal facility is relevant, as is the geology, geochemistry, climate, and hydrology of the environment in which the disposal facility is located.

• Third, “as good as glass” can refer to the overarching decision that DOE has to make among treatment technologies and disposal locations. That is, it can refer to the comparison of the baseline alternative involving vitrified SLAW, grouted secondary waste, and disposal in the IDF to grouting and steam reforming alternatives with disposal in the IDF and/or WCS on a multi-attribute basis. This, however, requires consideration of not only the physical characteristics of the waste, its form, and its placement, but all of the factors that will be considered by the decision-makers when selecting a preferred alternative. This means that, in addition to physical characteristics of the waste form and disposal site identified in the previous two bullets, one has to consider a range of quasi-technical factors including cost, reliability of technology, technological readiness, schedule, and safety, and their relative importance, i.e., “all things considered.” Additionally, it is important to note that there are secondary wastes from the vitrification and steam reforming processes that were projected to contain significant amounts of ⁹⁹Tc and ¹²⁹I, so this waste stream is the most important contributor to calculated dose rate as compared to the immobilized SLAW per se. In other words, “as good as glass” could mean the primary and secondary waste forms.

As can be understood from the above steps in the analysis of waste form performance, the judgment of whether other waste forms are “as good as glass” may be made at different levels: (1) the evaluation and comparison of the release rates from each of the waste forms based on laboratory data; (2) the waste form performance in the disposal system modeled over time; and (3) multi-attribute comparison of alternative disposal systems that include consideration of quasi-technical factors. At each step, the factors to be considered are different and increase in number.

The committee believes that waste form performance would have to be based on the comparison of waste form performance in the disposal sites over relevant periods, e.g., out to the time of the peak dose rate. All other points of comparison, e.g., materials properties, are components of the larger PA analysis. It is essential that the analyses supporting the selection of a preferred threatment alternative clearly distinguish among, and provide the necessary information for, analyzing all of these meanings of “as good as glass.” The technical assessment of the waste form per se and the technical assessment of the waste form in situ are essential elements of the larger decision but are far from the only elements that need to be considered.

The committee also notes that there may be opportunities to engage productively with the Department of Ecology to reach an agreement on the “as good as glass” issue. While this issue falls outside the scope of the FFRDC’s mandate, it is germane to the committee’s scope because Sec. 3134 requires the National Academies to “provide an opportunity for public comment, with sufficient notice, to inform and improve the quality of the review.” The Department of Ecology is a major stakeholder and a decision-maker because of its role as the state regulator with the authority to issue permits for the Hanford Site’s facilities such as the IDF, the WTP, and the SLAW treatment—or not. Department of Ecology representatives have provided substantive comments at every public meeting that the committee has held in the Hanford area. At the most recent public meeting on May 16, 2019, Suzanne Dahl, section manager of tank waste for the Department of Ecology, described the FFRDC’s final draft report as a “feasibility study” and as a “potential first stepping stone to changing SLAW treatment.” She also noted several new pieces of information in the report, including the “cost of nearly complete LAW vitrification plant,” (sic) “WCS as new candidate waste disposal site,” “new high performance grout waste form performance data,” and “new FBSR [fluidized bed steam reforming] crystalline ceramic waste form performance data.” As to the high performance grout, she noted that the report indicates that this type of grout performs “better than the vitrification waste form performance.” She mentioned that these “results are contrary to 30 years of previous results” and that “Ecology has no comment on these results. Ecology has not completed evaluation of underlying studies and would need to complete a significant effort before concurring with the latest results.” The committee observes that Ms. Dahl’s remarks suggest an opportunity for DOE and the Department of Ecology to work together to take the next steps that she has outlined.

THE COMMITTEE’S FINDINGS

Overall Assessment

Finding 1-1

The purpose of the committee’s review is to advise whether DOE, Congress, regulators, and other stakeholders can rely on the FFRDC report to evaluate and decide on a treatment approach for the SLAW. The committee finds that, in its current iteration, the FFRDC’s analysis:

1. When taken alone, does not yet provide a complete technical basis needed to support a final decision on a treatment approach;
2. Does not yet clearly lay out a framework of decisions to be made among treatment technologies, waste forms, and disposal locations; but
3. Can form the basis for further work as described below in the committee’s findings and recommendations.

Analysis of Costs, Benefits, and Risks

Finding 2-1

The cost estimates in the FFRDC report are based on technologies that, for the most part, have not yet been fully developed, tested, or deployed for Hanford’s particular, and particularly complex, tank wastes, and instead use costs from similar technologies. As a result, there are large attendant uncertainties, suggesting that costs could be much higher than estimated, but are unlikely to be much lower.

Finding 2-2

The cost estimates in the FFRDC report are based on continuing funding at and beyond current levels to optimize the waste treatment technologies and speed of progress. These involve very large annual appropriations, which are inevitably uncertain over the planned decades of activity, especially because current planning assumptions anticipate a two- or three-fold increase in expenditures at certain points in the SLAW treatment process. This, too, introduces the possibility that funding shortfalls will lead to longer schedules, increased total costs, and higher chances of additional tank leaks or structural failures, which will themselves increase costs as well as health and environmental risks.

Finding 2-3

The report’s analysis of costs does not enable the reader to analyze key trade-offs among specific alternatives or variations of major alternatives.

Disposal Risk Assessment

Finding 3-1

Assessment of the waste forms’ performance would have to include consideration of the characteristics of the disposal sites and the transport pathways to receptors over the relevant periods of time, as well as be based on the inherent characteristics of the waste form.

Finding 3-2

The committee did not have access to the 2017 IDF Performance Assessment (PA) that has been prepared by DOE or to the Performance Evaluation (PE) data and analysis prepared by the FFRDC. Therefore, it was impossible for the committee to critically review the differences in the performances of the three waste forms and their associated disposal systems over time. Additionally, the technical bases for waste degradation models and mechanisms used in the PE analyses for the IDF by the FFRDC team are not well documented and justified.

Finding 3-3

Without the proper supporting documentation for the FFRDC’s PE, or the IDF PA on which it was based, the committee is unable to assess the potential significance of mobile, long-lived fission products such as iodine-129, technetium-99, and other long-lived radionuclindes (possibly selenium-79 and others). It would have been useful for the FFRDC to include the human health risk estimates (dose) over time for all of the long-lived radionuclides that are listed in Table F-2 of their report, not just iodine-129 and technetium-99.

Finding 3-4

The FFRDC report gives little consideration in its analysis to the environmental, health, and safety consequences of hastening or further delaying remediation of the Hanford waste storage tanks, which is related to the probability that additional tank leaks or structural failures will occur over the long time period expected for the removal and treatment of the waste in the tanks.

Pre-Treatment to Remove Iodine-129 and Technetium-99

Finding 4-1

The FFRDC performed an analysis of whether removal of iodine-129 and technetium-99 was needed to comply with the disposal waste acceptance criteria, and examined the status of technologies for removing these radionuclides from the SLAW feed stream, but the FFRDC report does not respond fully to the congressional direction (in Sec. 3134) because the report does not address immobilization of the iodine-129 and technetium-99 recovered from the LAW as part of the separate high-level glass waste form to be produced in the WTP.

Other Observations

Finding 5-1

The report makes little use of the experience with grouting and other technologies at other DOE sites and commercial operations. While there are unquestionably meaningful differences among the waste forms, technologies, and disposal environments as compared to Hanford, the extensive experience gained at Savannah River Site, in particular, is an invaluable source of insight.

Finding 5-2

The committee was repeatedly told that the selection and implementation of an approach to tank waste was hampered by the insistence by the State of Washington and some other stakeholders that any approach other than vitrification must be “as good as glass.” The term “as good as glass” is not defined in law, regulation, or agreement, and it is only tentatively defined by its advocates. The analysis in and the public

presentations of the draft FFRDC reports offer a follow-on opportunity for DOE to engage with its regulators and stakeholders to identify performance standards based on existing regulatory requirements for waste form disposal and to pursue a holistic approach to selecting a treatment technology.

Comparisons

Finding 6-1

Over multiple iterations, the FFRDC report has increasingly enabled side-by-side comparisons among the SLAW treatment approaches, exemplified by the table of alternatives and criteria. It remains difficult, however, for the reader to see comparisons and trade-offs in the supporting narrative.

The FFRDC Report’s Steps Forward

Finding 7-1

The report represents useful steps forward by:

1. Confirming that versions of vitrification, grouting, and steam reforming are treatment technologies that merit further consideration for the SLAW;
2. Establishing the likelihood that vitrification, grouting, or steam reforming are capable of meeting existing or expected regulatory standards for near-surface disposal albeit with varying amounts of pre-treatment being required;
3. Highlighting the important contribution of the iodine-129 in the secondary waste streams disposed at the IDF to the total estimated radiation dose rate to the receptors;
4. Underscoring the regulatory and acceptance uncertainties regarding approaches other than vitrification technology for processing the SLAW; and
5. Opening the door to serious consideration of other disposal locations, specifically the WCS facility near Andrews, Texas, and possibly the EnergySolutions facility near Clive, Utah.