4

Report Limitations

While the National Academies committee concludes that the FFRDC report meets the Statement of Task criteria (Recommendation A) and that the FFRDC report should be actively used by decision makers (Recommendation B), there remain specific limitations that decision makers should consider in their use of the report.

Finding 16. The FFRDC report has been completed during—but separately from—an ongoing “holistic review” of the Hanford facility construction, waste recovery, and disposition schedule, which is related to a review of the Tri-Party Agreement (TPA) and revision of the federal district court’s consent decree regarding Hanford cleanup. While these proceedings are almost entirely opaque to the committee (inevitably so, given the confidential nature of the discussions), the FFRDC stated to the committee that they had access to some of the technical underpinnings, such as the Analysis of Alternatives (AoA) that the U.S. Department of Energy (DOE) released publicly just a few days before the committee’s last meeting.

Recommendation C. The FFRDC report should not be used in a vacuum. Rather, decision makers must integrate the AoA, consent decree, holistic negotiations, and especially the regulatory approval and public acceptance criteria, in reaching a final decision on how to manage supplemental low-activity waste (SLAW).

Analysis of the Regulatory Requirements for Processing and Disposal of SLAW

The FFRDC stated (Bates et al., 2023, Vol. I, p. 16) that the team “examined regulatory requirements associated with the” technical standards referenced under NDAA 2017 Section 3134, as well as the Atomic Energy Act of 1954 as amended, the National Environmental Policy Act of 1969, the Hanford Federal Facility Agreement and Consent Order Tri-Party Agreement, and the Washington State Resource Conservation and Recovery Act of 1976 (RCRA) regulations. Based on the FFRDC team’s review of these and related federal laws, agreements, and regulations, it was concluded:

1. The interpretation and implementation by regulators will be the means by which the SLAW treatment options will be differentiated.
2. The likelihood that any given approach for SLAW treatment would be acceptable to or approved by regulators could not be determined. Of note by the FFRDC team, the uncertainty of regulatory acceptance

1. “could be resolved in a number of different ways, including by negotiation, legislative or agency action, or judicial decision.”

This approach by the FFRDC reflects the lack of agreement between the DOE and the State of Washington Department of Ecology (WA Ecology) on whether grouted SLAW can be disposed of in the Hanford Integrated Disposal Facility (IDF) under current regulations or whether issues will arise with regulators in states hosting transportation corridors and off-site disposal facilities. A key consequence of this lack of agreement is that the FFRDC cannot presently advise on the likelihood of success in this key area. The issue is important because, absent regulatory issues, disposal of grouted SLAW in the IDF is the least costly disposal option. Option 6 (which couples off-site disposal initially with IDF disposal at some uncertain future date) presumes that disposal of grouted SLAW in an IDF has not been excluded.

The report also presents a rather positive and even optimistic view of the logistics associated with rail transport of wastes—whether grouted before transport or being transported for grouting—than was reflected in the view of the previous National Academies committee report (NASEM, 2022a, Finding 13, Recommendation J) and the WA Ecology public response (Bates et al., 2023, Vol. II, Appendix J). With respect to the source, constituents, and campaign duration of the waste shipments, previous experience is only a partial guide to SLAW’s regulatory approval and public acceptance. The FFRDC’s confidence that off-site transportation of liquid SLAW for treatment and/or disposal is based almost entirely on the fact that this is accepted practice for similar and more hazardous liquid and solid low-level waste (LLW), the off-site facilities have advised the FFRDC they anticipate no serious objections to the transport of liquid SLAW, the facilities having prior experience accepting large volumes of waste, and the SLAW liquids meeting (and complying with) all the applicable regulatory requirements for transport. The committee has less confidence than was presented by the FFRDC team, and similar concerns were expressed by others from affected communities. The concern being that the transport issues are not conventional, potentially constitute a major hurdle, and this is more-so for out-of-state transport. Transport will be even more challenging if the waste is transported as liquid rather than grout. While it may well be that waste similar to SLAW can be and has been transported safely by rail with little or no public concern, even a single salient event, such as the recent derailment of a train carrying hazardous chemicals in East Palestine, Ohio, can create a level of public awareness and concern leading to impediments to SLAW transportation, and possibly expose weaknesses in rail safety. Despite transport of liquid and solid low-level waste by rail and truck long distances being an accepted practice, decision makers might need to expect that transportation of large quantities of liquid SLAW off the Hanford site will meet with heightened scrutiny and concern by transportation corridor and recipient state regulators and citizens.

Limitations concerning transportation of SLAW are considered in the FFRDC report (Bates et al., 2023, Vol. I, Sect. B.1.3; Vol. II, Sect. D.2.12). Moreover, the report states through much of Vol. I, Sect. B, and Vol. II, Sect. D that off-site transportation risks are moderate and risks from off-site spills are low. This also seems optimistic given the length of the campaign (Niles, 2014). The report indicates that there will be a National Environmental Policy Act (NEPA) assessmentand environmental impact statement, and transportation risks will need to be considered in that analysis (Bates et al., 2023, Vol. I, Appendix D.3.7).

Finding 17. The FFRDC chose to exclude Criterion 5 (regulatory approval) and Criterion 6 (public acceptance) from its analysis of the four options it identified, limiting its analysis to purely technical considerations (Criteria 1–4). While this exclusion is preferable to having the FFRDC speculate on the probability of regulatory and public responses, these criteria will inevitably have to be considered in the future by decision makers in order to implement any option chosen. Moreover, the conditions and likelihood of regulatory approval and public acceptance are likely to vary considerably among options, e.g., off-site disposal of grouted SLAW versus disposal of grouted SLAW in an IDF. The exclusion of Criteria 5 and 6 from the analysis thus represents a significant, albeit deliberately considered, limitation on the FFRDC’s decision framework.

Finding 18. Based on the necessity of regulatory approval and public acceptance for any final SLAW decision, assumptions about regulatory approval and public acceptance appear frequently in the FFRDC report, despite its disclaiming consideration of Criteria 5 and 6. For example, there are many generalizations about specific regulatory

standards (e.g., that non-organic land disposal restrictions (LDRs) can be met, that every alternative is capable of being permitted), and public acceptance of LLW transportation has not been a problem. In addition, regulatory standards will determine when the project is “done,” in that the project cannot be completed until such standards are met.

Recommendation D. The FFRDC’s decision framework excludes regulatory approval and public acceptance (Criteria 5 and 6), which are essential considerations for the success of the mission. Decision makers should immediately begin a thorough assessment of these two criteria to provide input to their consideration of how to manage SLAW.

Evaluation of Cost Estimates

To capture the main take-away messages from the life-cycle cost presentations, the committee combined the information from slide 66 with slide 160 (FFRDC presentation January 31, 2023). Plotted in Figure 4-1 are the FFRDC’s estimates of life-cycle costs discounted to the present value against the estimated year of start-up. From right to left, vitrification with on-site disposal at IDF (black square) has the highest life-cycle costs and latest projected start date. The green diamonds are fluidized bed steam reforming (FBSR) with on- and off-site disposal. The red diamonds are the grout options with on-site disposal and blue circles are grout options with off-site disposal. (Grout 3A/3B, the tank-side treatment options were not evaluated by the FFRDC and cannot be included

on the plot because cost estimates and start dates were not provided in the report.) In this area of the graph, the grout options have the same anticipated start date. Note plotted with the blue data points for Grout 1B, Grout 2B, Grout 4B, and Grout 6, costs for off-site disposal are somewhat more than the on-site grout options, but not nearly enough to make the grout alternative come close to closing the gap with vitrification on either cost or timeline grounds. While FBSR also has significant advantages over vitrification concerning life-cycle costs and start-up date, the analysis makes it clear that FBSR is a much lower level of technical readiness for application to Hanford’s wastes than either grout or vitrification. While FBSR may have advantages and applications in other areas of the DOE complex, applying it to Hanford tank waste remains an overall challenge. Consequently, all of the grouting options dominate FBSR options concerning cost and timing, as well as technical readiness in the Hanford context.

The vertical ordering of the dots for on-site and off-site disposal alternatives for grout (red and blue dots, respectively) appear to suggest that on-site disposal options are overall better on the basis of the two key technical criteria reflected in this figure, however, the committee cautions readers not to assume that means that the on-site disposal options for grout dominate those for off-site disposal in all important dimensions. First, the committee notes that the on-site and off-site categories of grouting alternatives are, in relative terms, quite close to each other. Thus, other decision criteria not directly graphed here could play a role in a final decision. Second, both categories of the grouting alternatives involve regulatory and public acceptance risks, and furthermore the nature of these risks is qualitatively dissimilar for the various grouting alternatives graphed in the figure. These additional criteria need to be carefully considered as well by decision makers before selecting any of the specific grouting options.

In brief, this single graph makes a defensible technical case in favor of the FFRDC’s recommendation to expeditiously move in the direction of developing grouting as a pathway for managing SLAW. The primary question left for decision makers, therefore, is to evaluate whether issues of regulatory approval hurdles or public acceptance are so significant in the case of grout to overcome the technical advantages of every one of the various grouting options in the FFRDC report (or other variants not actually in the FFRDC evaluation such as grouting through modular facilities on-site, followed by on-site or off-site disposal) vis-a-vis vitrification or FBSR. If not, the refining and choosing among the various grouting options can then become the subject of further study and deliberation.

The committee concluded that the predicted costs should be treated as qualitative, not quantitative. No matter how the alternatives are analyzed, the grout options all have very similar costs. If the discounting used in the estimates changes, the rankings all increase or decrease together because the timing of the costs that add up to the present value are the same, more or less. That is not true for vitrification because the start-up time is further into the future. The large cost gap visible in the figure would narrow if one were to use a higher discount rate than the 3 percent real discount rate used by the FFRDC. However, reasonable alternative choices of real discount rates for federally-funded projects would not likely cause the vitrification option to become less costly on a present value basis than any of the grout options. Furthermore, the discount rate will not affect the gap in timing between the grouting and vitrification options. Where the choice of discount rate becomes a more important analytical concern is if costs were to be compared to a monetized estimate of benefits; this is not a comparison that is considered in the FFRDC’s decision framework.

Finally, while the FFRDC decision framework does not contain a traditional cost-benefit analysis, the benefits are implicit, qualitatively, in several of its criteria other than cost. For example, a shorter time until completion of cleanup (used in the figure above) is a benefit of grout relative to vitrification or FBSR. Also, if an option has greater environmental and safety risk after disposal, that would be a benefit of one option over another. This leads the committee to view the FFRDC decision framework as a qualitative, yet valuable, multi-attribute decision analysis and not a traditional cost-benefit analysis.

Finding 19. Because of a number of limitations noted in Box 4-1, the committee finds that the cost estimates are usable as indicators of relative costs but are not suitable for predicting actual costs and or establishing budgets. The cost estimates also can be useful as a constraint on the timing of various alternatives and a relative basis for comparison among alternatives.

Finding 20. The cost estimates are sufficiently robust to demonstrate that there is a very significant gap between the costs of vitrification and FBSR on the one hand and the various grout options on the other. The costs of the former and the latter, even after accounting for the wide ranges of cost estimation uncertainty also identified in the FFRDC report, do not come close to overlapping.

Thus, the committee concludes that the FFRDC cost estimates, despite their limitations, are sufficient to provide useful insights for the relative evaluation of the three general types of SLAW management alternatives. The committee is more concerned with the use of a notional (NASEM, 2022a, Finding 3) benchmark budget constraint in the FFRDC analysis, particularly as to how this affects the design of options and the estimates of timelines. The report uses $450 million/year as a benchmark budget and the FFRDC constrains its cost estimates to this budget number. The budget constraint itself is necessarily imprecise (since congressional appropriations cannot be predicted with certainty from year to year, to say nothing of decades) and thus unreliable as a single benchmark. In recognition of this lack of precision, the FFRDC analysis included sensitivity analysis over alternative budget levels and cost estimates for each of the four selected alternatives. This sensitivity analysis established that the FFRDC qualitative findings with regard to Criteria 3 and 4 (schedule and cost consequences) are robust over a broad range of estimates and potential budgets. However, it is important to know by how much the benchmark is exceeded in each case. Tables F-1 through F-9 of FFRDC report Appendix F show the total overage a few sensitivity scenarios from which the following insights can be gleaned, focusing on results the last column of the row labeled “Funding (Overage/ Shortfall).” With regard to the assumed $450 million/year budget constraint, and assuming a 4 percent escalation factor for capital expenditures (CAPEX), vitrification is estimated to exceed that budget by $10 billion by 2070, as reported in the main FFRDC report (Table F-1). The comparable estimates for FBSR and Grout 1A are budget surpluses (relative to the notional $450 million/year budget) of $20 billion for FBSR (Table F-5) and “more than” $23 billion for Grout 1A (from Table F-7).

Sensitivity of these budget overage/shortfall estimates to the 4 percent CAPEX escalation factor assumption is provided only for FBSR (using 4 percent in Table F-5 and 8 percent in Table F-6). This comparison shows that FSBR’s budget surplus of $20 billion under a 4 percent escalation rate assumption falls to $17 billion under an 8 percent escalation rate assumption—a reduction of $3 billion, or 13 percent, and still a surplus. The surplus

for Grout 1A with the 8 percent escalation rate is $23 billion (Table F-7). Although the report does not provide a CAPEX sensitivity case for vitrification, one can readily infer that increase in total project cost (and hence decrease in potential budget surplus) due to a higher CAPEX escalation rate assumption will be greater for projects with longer capital expenditure periods, and hence more years of cumulative escalation. Thus, the effect of an 8 percent CAPEX escalation rate on the project cost for vitrification estimate will be larger—potentially much larger because of vitrification’s additional 10 years of cost escalation beyond that assumed for FBSR. This indicates that the estimated $10 billion of budget shortfall estimated for vitrification under a 4 percent escalation assumption would increase to a shortfall of more than $20 billion under an 8 percent CAPEX escalation factor.

Clearly if the notional annual budget is increased, the degree of surplus for grout and FBSR will increase (all other assumptions unchanged), and the degree of deficit for vitrification will decline. Table F-2 provides a sensitivity case that shows that (all else equal) the $10 billion budget exceedance of vitrification could be reduced to about zero for flat funding of $555 million/year. In effect, this simply increases the total cumulative funding by about $10 billion, and thus shifts the “budget overage/shortfall” for all alternatives upward by $10 billion. Thus, while it is a sufficient flat funding level to achieve a net budget neutrality for the vitrification alternative, assuming the 4 percent CAPEX escalation rate, it also would increase the estimated budget surpluses for grouting and FBSR upward by another $10 billion. The committee also notes that if the CAPEX escalation factor assumption is 8 percent, vitrification would still have an estimated budget deficit of $10 billion or more, just as it does for the case in which the funding is $450 million/year with an escalation rate of 4 percent. No annual or total shortfall figures are provided for the +100 percent cost estimate sensitivity cases.

In conclusion, no systematic table or chart of total/maximum overages/shortfalls by sensitivity case is provided. While the sensitivity analysis results provided in Appendix F are also not structured in a systematic manner, careful study of Tables F-1 through F-9 indicates that all of the grouting options and FBSR could fit comfortably within a flat budget of far less than $450 million per year over a wide range of assumptions about CAPEX escalation rates, while vitrification would require a budget of more than $555 million/year to ensure no budget shortfall provided capital expenditures rise at more than 4 percent per year, and higher still if they were to rise more rapidly than 4 precent.

An analysis of budget constraints could add utility in the sense of the time until completion estimate, because it constrains the timing of construction and/or the rate at which waste can be managed. If the budget constraint selected is grossly wrong, or if the absolute expenditures are significantly in error in either direction, this analysis could produce incorrect inferences about relative timelines. However, upon questioning by committee members, the FFRDC revealed that its assumed budget constraint is not the sole reason for the longer timeline for vitrification. Instead, the analysis also included (undocumented) assumptions about the ability of DOE and its contractors to manage the construction of multiple large facilities simultaneously including a SLAW vitrification plant (presentation February 1, 2023). Apparently, that undocumented constraint was a key reason for the long timeline for completing the construction and startup phases of a SLAW vitrification plant, and this would remain unchanged even if the assumed annual budget constraint were to be increased so the timeline for the vitrification plant would remain unchanged. Whether this additional constraint (which was said to be tied to inherent limits on available labor and materials delivery) is correct or not cannot be evaluated by the committee. However, it is an important aspect of the entire timeline analysis that the committee believes was not clearly explained in the report and appears to have eliminated other innovative on-site grouting approaches.

Finally, decision makers need to be cognizant of the fact, established in the first iteration of the FFRDC’s report and repeated here, that no matter what option is chosen, the costs of retrieval and treatment of the tank waste are projected to exceed the current annual budget for cleanup at Hanford. Thus, decision makers need to reconcile any plans for SLAW management with this continuing challenge, as well as the needs of other elements of the DOE Office of Environmental Management’s (DOE-EM’s) overall program.

Finding 21. The timing estimates in the FFRDC report depend on assumptions concerning available funding, and thus they must be used cautiously as a rationale for choosing among technological options. It is nevertheless clear based on their respective technical characteristics that grouting of SLAW would need far less lead time for operational use than either vitrification or FBSR.

Evaluation of Grout Options

The FFRDC analyzed two favored options for grout: 4B (ship liquid to off-site vendor for grouting; dispose containerized grout off-site) and 6 (phased approach of off-site vendor grouting and off-site disposal, followed by on-site grouting and on-site disposal) (Bates et al., 2023, Vol. I, p. 26). To a large extent the two grout options were selected for comparison because they dominated other grout options on the four top-level (technical) decision criteria (Bates et al., 2023, Vol. I, p. 45, and FFRDC presentation slides 157-159, January 31, 2023) but other grout options were close contenders, especially within the uncertainties in the analyses. One example of this is that the FFRDC preliminarily explored other grout options and discarded them for various reasons (e.g., Grout 3A/3B were deemed cost prohibitive because of added construction time). This effectively resulted in the FFRDC team ruling out DOE exploring near-term on-site commercial grout capabilities.

Despite not exploring the contracting options for acquiring an on-site grout facility from an existing commercial nuclear liquid LLW grout vendor or other contractual arrangements, the committee notes that the FFRDC found that such capabilities exist today at two or more commercial sites including the sites at Clive, Utah, and Andrews, Texas [Gene Ramsey presentation on January 31, 2023, 3:45 hr:min]. However, pursuing this option would enable DOE to avoid its complex design and construction requirements utilized primarily for designing and building one-of-a-kind DOE facilities (DOE Order 413.3) and consider a direct acquisition of an existing commercial system to be built on the Hanford site and operated by DOE or private sector personnel. This could lead to the possibility of meeting or bettering the FFRDC’s early grout timeframe, giving DOE the flexibility of providing SLAW without transporting liquid SLAW offsite to grout. In addition, an on-site or parallel grout capability would preserve DOE’s SLAW capability by eliminating the risk of mission interruption in the future were restrictions to be placed on transportation or disposition of DOE’s SLAW in the future.

The FFRDC’s charge and the committee’s Statement of Task focused on the choice between alternative technical approaches, that is, the choice between vitrification, FBSR, and grout. The FFRDC’s analysis of two options within the grout alternative was an appropriate and helpful way to illustrate the choice among the treatment options as well as to meet the statutory requirement for extra analysis of grout. However, the upshot of the previous two paragraphs is that the FFRDC analysis and its recommendation were not intended to, nor should be taken as, suggesting the identification of a final, detailed grout option or options. Other considerations will have to be considered before arriving at a final selection (e.g., regulatory, public acceptance, uncertainties in the evaluation of the technical criteria), and the considerations and priorities can expect to change over the long-term mission that cleanup entails.

The foregoing narrative represents important limitations on the use of the FFRDC’s report—one which the committee believes the FFRDC would endorse as discussed during the round table discussions on February 1, 2023—and decision makers will need to develop further technical detail related to the FFRDC’s recommendation (in addition to full consideration of the previously mentioned regulatory and public acceptance criteria, which were excluded from the FFRDC analysis) before making a decision.

Finding 22. Before reaching a decision on the FFRDC recommendation, there will still be the need for detailed analysis of a wider variety of grout options than 4B and 6, including but not limited to:

• the location of the grouting plant(s): on-site vs off-site, tank-side versus tank farm versus regional (west/ east) versus central;
• the possibility of building commercial SLAW facilities on the Hanford site and then the possibility of operating them; and
• detailed assessment of the waste acceptance criteria, cost, and other aspects of off-site treatment or disposal, including regulatory and public acceptance.

Recommendation E. DOE should promptly turn attention to a thorough review of all types of grout options—not limited to FFRDC options 4B and 6, and also extending the set of grout options that the FFRDC initially considered to include some of the additional ways that grouting can conform with the general attributes of the FFRDC

recommendation that the committee has noted, while perhaps reducing some of the regulatory and public acceptance features of options 4B and 6. Specifically, the options considered should include on- and off-site grouting facilities, nearby and distant treatment options, commercial and public vendors (or public-private partnerships), commercial versus government facilities, and parallel strategies driven by structured analysis of technology status and technology maturation requirements.

Transportation of SLAW

The FFRDC’s first analysis of approaches to SLAW treatment focused mainly on treatment and disposal of SLAW in the IDF on the Hanford site with only a brief discussion of other transportation and treatment options. However, based on National Academies’ recommendations concerning that report, the drafts of the FFRDC’s current report considered a number of options that involve on-site pretreatment of SLAW followed by off-site transport and disposal of monolithic grout or FBSR waste forms. Within these options, are some that involve offsite transport, treatment, and disposal of pretreated liquid SLAW to form the monolithic grout waste forms. The FFRDC analysis reviewed here contains a much more detailed analysis of off-site transportation of SLAW for disposal and possible treatment than in the prior FFRDC report.

The FFRDC analysis considered off-site options involving grout and FBSR waste forms. For FBSR only on-site treatment was considered whereas both on-site and off-site treatment were considered for grout. That is, off-site transportation of monolithic SLAW waste was considered for both FBSR and grout, but off-site transportation of pretreated liquid SLAW was only considered for grout.

The amount of SLAW to be transported could entail substantial cost and involve challenging logistics. Depending on assumptions about the timing of the options and feed vectors, the volume of waste to be transported ranges from about 200,000 to 350,000 cubic meters (Bates et al., 2023, Appendix H, Table H-6, Figure H-49). To reduce packaging and transportation costs the FFRDC conducted analyses to determine whether the SLAW would qualify as low-specific activity (LSA) waste (see Box 4-2 on the Nuclear Regulatory Commission’s (NRC’s) graded approach and LSA). If it qualifies, it could be shipped (a) in standard industrial packages such as double-walled tanks (Figure 4-2, Figure H-12 reproduced here from the FFRDC Report Vol. II) for liquids and soft-sided packages for solid waste forms, (b) in bulk quantities (package volumes ranging from 8 to 15 cubic meters), and (c) in unit trains containing many packages per shipment, which would substantially reduce the cost. Truck transport is possible but the applicable weight limits make it less attractive than trains.

Transportation of low-level waste by waste generators to waste processing and disposal facilities, including LSA waste which must have radionuclide concentrations at the low end of the low-level waste spectrum, is accepted

practice (Bates et al., 2023, Vol. II, Fig. H-27). Bulk quantities of liquid and solid LSA wastes have been transported for many years under longstanding NRC and U.S. Department of Transportation (DOT) regulations (U.S. Department of Energy, 2020). Transportation of radioactive wastes has involved engaging state, local, and tribal jurisdictions along transportation routes including providing training and tools to these jurisdictions. The fact that high-level waste (HLW) and spent nuclear fuel (SNF) transportation has an exemplary safety record is assumed by the FFRDC to apply to LSA waste, and on this basis the report concludes that transporting LSA waste will be safe and less difficult with respect to technical and societal challenges (Bates et al., 2023, Vol. II, pp. H-6–H-7). The committee notes that accidents involving HLW and SNF have occurred (Connolly and Pope 2016) but the accidents had no significant consequences due to the use of Type B packages, which are much more robust than industrial packages used for LSA waste. Similar accidents with liquid LSA wastes would be more likely to result in a release because of the nature of the package (basically a double-wall tank) but the waste being released is much less hazardous waste than SNF (Box 4-2 describes NRC and DOT transportation regulations are based on a graded approach for LSA waste).

In the previous draft analysis, the FFRDC assumed that liquid SLAW would be transported in 5,000-gallon tanks and concluded “…that untreated supplemental LAW liquids…can be transported in IPs in all off-site disposal options with considerable margin.” (Bates, 2022b, Vol. I, p. D-16). The current FFRDC report contains a more complete analysis of five criteria that have to be considered for liquid SLAW to qualify as LSA. The following items discuss the results of the FFRDC analyses for each of the five criteria, which were based on two feed vectors providing two average compositions of the SLAW transported each month based on different modeling assumptions.

1. Criterion 1 Specific Activity: The specific activity (Ci/g) of the mixture of radionuclides in the liquid SLAW has to be less than the specific activity limit for liquid LSA using a standard sum-of-the-fractions approach. The FFRDC concluded that liquid SLAW would be at least one order of magnitude below the LSA-II limit for liquids with a few exceptions and the evidence presented in the analysis supports this conclusion.
2. Criterion 2 Non-Fissile Material Exemption: The amount of fissionable material in a package of liquid SLAW is limited to 2 grams. The FFRDC analyzed the two SLAW feed vectors in the current analysis and determined that this criterion would require 99 percent and 87 percent (depending on the feed vector assumed) of the liquid SLAW to be transported in tanks containing less than 4,000 gallons of SLAW, and

2. 82 percent and 59 percent to be transported in tanks containing less than 2,000 gallons (values taken from Bates et al., 2023, Vol. II, Fig. H-6).
3. Criterion 3 External Dose Rate: The external dose rate from the tank is limited at multiple distances from the tank surface. The FFRDC calculated the dose rates from a 5,000-gallon tank having the maximum liquid SLAW radionuclide concentrations across all of the monthly feed streams for the two feed vectors. The calculated dose rates at one meter from the tank surfaces (side and bottom) ranged from 7 to 9.5 mrem/hr (depending on which vector and which tank surface), which is close to the 10 mrem/hr limit at 1 m from the tank surface with the dominant contributor being Cs-137 gamma radiation¹ (Bates et al., 2023, Vol. II, Table H-2). An exception to this is that for one of the feed vectors there is a “tail” having a Cs-137 concentration that is high enough for about 6 percent of the liquid SLAW (Bates et al., 2023, Vol. II, Fig H-14) to exceed the dose limit unless the amount of SLAW in a tank were reduced. The amount of Cs-137 in a tank that would exceed the limit begins at 2.3 Ci and extends to about 80 Ci (Bates et al., 2023, Vol. II, Fig H-14). This means the amount of Cs-137 in a tank would have to be reduced by up to a factor of 35, which translates to a maximum of about 143 gallons of liquid SLAW per tank for a small number of tanks.
4. Criterion 4 Homogeneity: The radioactivity in liquid SLAW must be uniformly distributed for it to qualify as LSA. This criterion is met assuming that solids do not form in the liquid SLAW. Solids might form as a result of precipitates from reaction of chemicals dissolved in the SLAW or from cooling of marginally soluble species in the SLAW, or possibly from less-than-expected efficiency of SLAW filtration during pretreatment. Washington River Protection Solutions (WRPS) conducted a preliminary evaluation and concluded there was a very low probability of precipitation occurring (Daniel et al., 2020).
5. Criterion 5 Total Activity in a Unit Train: The total radioactivity in all the liquid SLAW in a unit train is also limited and the extent to which this would constrain the number of rail cars in a unit train was analyzed by the FFRDC. The FFRDC concluded that Criterion 2 was usually more constraining but Criterion 5 might limit the number of cars in 5 to 8 percent of the unit trains (Bates et al., 2023, Vol. II, Fig. H-8).

Based on the more thorough analyses underpinning the LSA determination in the current FFRDC analysis as summarized above, it appears that their conclusion “…that untreated supplemental LAW liquids…can be transported in IPs in all off-site disposal options with considerable margin” (Bates, 2022b, Vol. I, p. D-16) is no longer the case because some of the criteria now appear to be close to limits, be limiting, or have significant uncertainties as discussed below.

During the public meeting at Hanford leading to this review, the FFRDC staff was questioned about whether constraints on non-fissile isotope concentration (Criterion 2) and total activity in a unit train (Criterion 5) meant that significant fractions of liquid SLAW would not qualify as LSA and would require smaller and more expensive Type A packages. The FFRDC indicated that their approach to avoiding reliance on significant numbers of Type A packages would be to (a) standardize on a 4,000-gallon tank, (b) partially fill the tank with liquid SLAW to meet Criteria 1, 2, and 3,² (c) limit the total amount of SLAW in a unit train when needed to meet Criterion 5, and (d) use a relatively small number of much smaller tanks (e.g., ~350 gallon) (Bates et al., 2023, Vol. II, Fig. H-18) to address outlier situations such as the “tail” described in Criterion 2 above. The FFRDC also mentioned the possibility of reworking some of the SLAW to allow Criteria 1–3 to be met by pretreating the SLAW again to lower Cs-137 or fissionable isotope concentrations.

Regarding Criterion 4, the FFRDC stated in their report that only a preliminary evaluation of the potential for precipitating solids could be conducted within the time and knowledge available, and that WRPS plans to test samples of tank waste to further evaluate the potential for precipitation of solids into the future.

In addition to the foregoing specifics, the committee notes an overarching assumption that could affect whether and how all of the criteria could be met: composition averaging. The feed vectors that the FFRDC assumed are

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¹ The FFRDC assumed that pre-treatment would remove 99 percent of the cesium from the SLAW.

² The committee observes that partially filled tanks may not be an appropriate safety practice (see https://www.international-tank-container.org/en/technical/technical-guidance-for-shipping-bulk-liquids), and this should be taken into account in the transportation analysis.

based on calculated average SLAW compositions for each month over the life-cycle of tank remediation for two scenarios because more granular information was not available. Because this assumption could have affected whether and how all of the criteria could be met, a sensitivity analysis was conducted (Bates et al., 2023, Vol. II, Section H.10). The analysis concluded that all the requirements could be met with the higher-than-average concentrations (30 percent higher each month of waste generation) of the major contributors. The calculated number of unit trains per month is fewer than five 79–93 percent of the time but can range into the dozens of unit trains per month in the remainder of cases (Bates et al., 2023, Vol. II, Figs. H-30, H-31). The number of tanks per unit train ranges from 10 to 1,000 but the most frequent values are in the 50–30 range (Bates et al., 2023, Vol. II, Fig H-8). Based on these considerations and assuming three-unit trains per month and 40 tanks per unit train as representative values leads to an average production rate of four tanks per day. This production rate has an important implication that deserves consideration.

Given the variation in the compositions of the feeds to the SLAW treatment facility, it is possible that some of the treated supernatant liquids sent to SLAW will have radionuclide content at the high end of the expected composition that requires a change in the transportation protocols from normal operations. This leads to the need to determine an approach to manage those that do not meet the qualification criteria.

Finding 23. The FFRDC analysis in their previous report led to a conclusion that liquid SLAW would easily qualify as LSA that would allow it to be transported at low cost in bulk quantities. This opens the door to more cost-effective SLAW management options involving off-site treatment and disposal. The revised analysis in the current FFRDC report indicates that the liquid SLAW may still qualify as LSA but only with careful attention to the composition of the SLAW going into each tank and then using measures such as partially filling the tanks, adjusting the number of tanks in a unit train, and/or additional pretreatment to comply with regulatory requirements. Even then, ensuring that precipitates will not form in variable SLAW compositions of wastes from different sources and possibly for tanks needing to be mostly full or mostly empty will be an operational and regulatory challenge.

Recommendation F. The fact that low-level liquid radioactive and mixed waste is and has been routinely qualified as LSA waste and transported in bulk over long distances and across multiple states in other contexts should not be seen as unconditional defense that all transport of the SLAW is acceptable. However, this is not a conclusive prediction of how much of and how readily the SLAW can qualify as LSA and the operational difficulties of doing so. Additionally, the assurances (however sincere) of receiving facilities (Bates et al., 2023, Vol. II, Appendix K) that such transport and receipt is accepted practice should not be viewed as meaning regulatory approval and public acceptance of sustained transport of large amounts of liquid SLAW would be acceptable without question or contention. DOE should conduct additional and more detailed investigations and assessments of operational feasibility, regulatory approval, and public acceptance at receiving sites and the transportation corridors to improve understanding of the advantages and disadvantages of transporting liquid SLAW before definitely settling on offsite pathways as the solution.

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