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Developments Since Publication of Review #3

AVAILABILITY OF THE PERFORMANCE ASSESSMENT FOR THE INTEGRATED DISPOSAL FACILITY

Since publication of Review #3 on August 15, 2019, the committee has received access to the Performance Assessment (PA) for the Integrated Disposal Facility (IDF) at Hanford.¹ In Review #3 (see Appendix A), the committee mentioned in Finding 3-2 that it did not have access to the PA or to the Performance Evaluation (PE) data and analysis prepared by the Federally Funded Research and Development Center (FFRDC), and thus, “it was impossible for the committee to critically review the differences in the performance of the three waste forms and their disposal systems over time.” In addition, Finding 3-3 specified,

While the committee had limited time to review the PA, which runs to more than 1,800 pages, during this final review, it has focused on searching the PA for information and data relevant for the concerns expressed in above findings from Review #3. In its October 31, 2019, meeting, the committee was told by Pat Lee, a co-author of the PA, that the final PA results do not differ from those provided to the committee at the February 28, 2018, public meeting.

First, the committee reminds readers that in Review #3 and in the FFRDC’s final draft report, it was emphasized that the PA applies only to a vitrified primary low-activity waste (LAW) form as well as grouted secondary waste forms. However, the grout assumed for the PA for secondary wastes is not the same grout as would be used for primary waste forms, according to the analysis in the FFRDC’s final draft report. In addition, the PA does not address steam reformed or grout waste forms for the primary supplemental LAW (SLAW). It is these considerations that led the FFRDC to develop a performance evaluation for primary SLAW that consistently addressed all three treatment alternatives.

Second, the committee assesses that the information that it was able to review in the PA does not change the findings or recommendations in Review #3 as they relate to the vitrified waste alternative. But as noted below, the committee has added a new recommendation.

Third, the committee underscores that the U.S. Department of Energy’s Office of River Protection (DOE-ORP) has to meet multiple regulatory requirements as described in the PA (although not concisely) and addressed for the baseline (primary vitrification and secondary grouted waste) alternative. As far as the committee can ascertain from its time-limited review of the PA, there are three important requirements: meeting (a) DOE dose limits to the public, (b) land disposal restriction (LDR) requirements, and (c) the drinking water standard (DWS) limits.

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¹ While the PA was released by DOE on July 31, 2019, the study director was notified on August 14, 2019, and then received a copy of the PA on August 24, 2019. Even if the PA had been received on July 31, 2019, it would have been too late for the committee’s consideration for Review #3.

1. DOE dose limits are risk-based, and the disposed material must meet the prescribed dose limit. The analysis was done, and the calculated doses were well below requirements. The committee notes two interesting points within the analysis. First, a number of radionuclides other than iodine-129 and technetium-99 were the most important determinants of compliance in many instances, which makes the primacy of the DWS and these particular radionuclides suspect. Second, the most important dose scenario to a public receptor was inadvertent intrusion by a farmer and not the infiltration-leaching-radionuclide transport scenario that underlies the DWS. In both ways, the PA’s analysis may be inapposite to the analysis undertaken in the FFRDC report.
2. LDR requirements are definitely not risk-based in the sense of the risk of their presence in a particular disposal site; rather, they are based on specified leachate concentrations of statutory and regulatory lists of chemicals. Hanford tank waste may contain a number of these chemicals, but their concentrations are very uncertain because of the difficulty and cost of sampling tanks containing heterogeneous wastes. All of this is acknowledged in the FFRDC’s final draft and final reports. The committee observes that this uncertainty may pose an opportunity for a hybrid approach (along the lines of Recommendation 4-1 in Review #3) in which the retrieved waste is analyzed a batch at a time and then routed to an appropriate treatment process that includes treatment for LDR constituents or not, as needed.
3. The DWS is ostensibly risk-based in that the limits on the amount of the two key radionuclides in drinking water (iodine-129 and technetium-99) are expressed in terms of dose. The committee notes that the National Drinking Water Standards, as promulgated by the U.S. Environmental Protection Agency’s (EPA’s) 40 CFR 141, limits beta and gamma emitting radionuclides as a class in terms of dose in 40 CFR 141.66(d). The maximum contamination levels or MCLs (EPA, 2002) are based on Handbook 69 (NBS, 1959); however, Handbook 69 is based on dosimetry guidance found in International Commission on Radiological Protection’s (ICRP’s) Publication 2, published in 1959. Thus, the committee observes that this guidance would benefit from updating to the current international radiological dosimetry practices. Additionally, the committee notes that DOE assumes the point-of-compliance for the DWS is 100 meters from the edge of the IDF by rule. These observations lead to the following recommendation:

Recommendation 5-1

The committee believes it would behoove DOE to consult with its regulators (particularly EPA and Washington State Department of Ecology) to determine whether risk-informing the current drinking water standard in terms of its underlying dosimetry and the assumed point-of-compliance is appropriate for application to SLAW disposal, or whether a more up-to-date standard for drinking water should be adopted. In view of the extent to which disposal decisions are driven by this standard, such a re-assessment would be well worth the effort.

See Chapter 1 for a brief discussion of risk-informed decision-making with reference (GAO, 2019).

PUBLICATION OF THE FFRDC’S FINAL REPORT AND COMMENTS RECEIVED FROM THE FFRDC

FFRDC Final Report

On October 18, 2019, the FFRDC published its final report, and it is available on the National Academies website.² In addition, Appendix B of this review reproduces the executive summary and conclusions of that report. The final report contains numerous significant changes, and the committee appreciates the substantial effort that the FFRDC team made to respond to the committee’s Review #3. As explained in Chapter 1 of this review, the committee is not required to conduct a further peer review. Nevertheless, out

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² See http://dels.nas.edu/resources/static-assets/nrsb/miscellaneous/SRNL-RP-2018-00687-Final-Report-Hanford-SLAW.pdf.

of respect for the FFRDC’s efforts and to assure the completeness of this Review #4, the committee highlights in this section notable changes in the final report.

The committee observes, first, that the final report has a substantially revised executive summary, and that is now written in a manner more accessible to a non-technical readership. Likewise, the executive summary and the introductory chapter provide a set of clearly stated conclusions. The committee also notes that the final report has additional useful information about cost comparisons and provides updated summary tables that help show the comparisons of the relevant factors useful for decision-makers who need to decide among the treatment and disposal options. In these and other ways, the FFRDC final report contributes valuably to the understanding of the leading alternatives for SLAW treatment and disposal, which should “be accepted as a pilot or scoping study for a full comparative analysis of the SLAW treatment alternatives,” as stated in Recommendation 1-1 of Review #3.

FFRDC Comments on the Committee’s Review #3

During the public comment period, the FFRDC submitted to the National Academies its comments on Review #3. Here the committee summarizes those comments and provides its views.

The team notes that the committee’s Finding 1-1 implies that the FFRDC team has failed to provide a decision framework, but the team believes that such a framework is not in the scope of the team’s task. The committee stands by Finding 1-1 that the FFRDC’s analysis “does not yet provide a complete technical basis needed to support a final decision on a treatment approach.” This should not be construed as a failure on the part of the FFRDC because it was not within their scope, and if it were, it would have been infeasible, given the team’s limited time for completion, to do more than an overview or scoping study. As suggested by a comparison with the scope and detail of the PA for just one alternative, full analysis of each alternative will be a very significant undertaking. Rather, the FFRDC was tasked with providing a foundation for comparison of possibilities, and the committee stands by its assessment of the valuable contributions of the team’s analysis, as noted in Finding 7-1.

The team suggests that in Finding 2-1, “it would be more correct to say: The cost estimates are based on technologies that, for the most part, have not yet been fully developed or deployed for treating Hanford SLAW, and are based on costs from similar applications of these technologies” [emphasis was present in the submitted comments]. The committee appreciates this clarification from the team. The committee stands by its larger point about the uncertainties about the technical maturity and capacity of each treatment approach.

The team states that in Finding 2-2 it “is not clear how this finding is different from the descriptions and conclusions in the FFRDC [final draft] report.” Also, the team notes that in Finding 2-3, “the cost delta between the different variants of each technology was too small to be accurately assessed. It is not clear how the committee intends the FFRDC team to address this finding.” The committee observes that the FFRDC final report has come closer to Finding 2-2 and that it has shown responsiveness to Finding 2-3.

In commenting on Finding 3-2, the team acknowledges that it has provided additional details in its final report about how the performance evaluation (PE) was conducted. The committee recognizes this additional information, but it stands by Finding 3-2 that it did not have access to the PA and did not receive much of the data on the PE during the time of its review. Moreover, as described above, the PA only details one of the alternative approaches. The committee observes that the team in the final report is responsive to Finding 3-3.

The team comments that Finding 3-4 points to an evaluation concerning how delays in waste treatment could lead to tank failures, but the team believes this analysis is outside of its scope. The team, however, notes that its report “does state that delays will result in extension of tank duration and risk.” This is a fair point, and the committee (in Review #3) has previously praised the FFRDC report for specifically acknowledging the consequences in time, cost, and risk of an unaffordable path forward for SLAW, as that it is absolutely fundamental to the decisions that DOE must make.

The team notes that Recommendation 1-1 implies that “additional studies would significantly change the conclusions reached by the FFRDC study” and that the committee did not state which of the main conclusions are “inadequately supported.” In Recommendation 2-1, the team comments that it “is not clear from the recommendation what additional information is needed versus when the committee is simply requesting the existing information be reorganized.” While, as mentioned above, the committee recognizes the laudable effort in the revised report, it stands by these recommendations that lay out the detailed questions and factors that need to be fully addressed and placed in a format to support a decision framework. The committee underscores that the FFRDC final draft report and its latest revision provide a useful scoping study that identifies many practical findings, as noted in Recommendation 1-1, and gives a basis for a follow-on study and decisional document. This is not a case of damning with faint praise; the FFRDC team has provided valuable analysis, even if not the final technical analysis that will ultimately be required for decision-makers. The committee has added to Recommendation 1-1 the text: This comprehensive analysis should adopt a total systems approach (one that includes addressing relevant externalities to SLAW that were outside the FFRDC’s scope) to provide a substantially complete basis for decision-making.

Notably, as discussed below and shown in Appendix B of this review, the team itself recommends several items for further study. The committee also observes that the team provides in the final report new and better organized information that is responsive to Recommendation 2-1; however, it still does not clearly show the trade-offs, as outlined in the committee’s recommendation. The committee has added to Recommendation 2-1 the text: The committee notes the limited amount of information and pervasiveness of uncertainty in many aspects of the decisions to be made. Although it may seem counter-intuitive, the committee suggests that probabilistic approaches be used in future analyses because, when information is limited, the result is in the form of uncertainties, which are very useful to decision-makers.

The team points to several places in Chapter 2 of Review #3 where the committee highlights several items that are outside the scope of the FFRDC’s analysis. The team requests that these items not be considered “deficiencies in the report.” The committee’s intent is to underscore that the scope is limited and that the system for SLAW treatment is just one part of a much bigger, complex system for treating Hanford tank waste that would have to be considered in an integrated manner in future studies.

The team itself makes clear in its revised executive summary (see Appendix B) and updated final report that:

The committee in Review #3 pointed out:

• HLW Definition Clarifications, [and]
• Improved LAW glass or process models.

Any of these examples would result in direct or indirect impacts on the assumptions in this analysis. It is not possible in this study to evaluate each potential future scenario as many of the scenarios have not been defined sufficiently well to allow a definitive impact evaluation. If these scenarios progress, the impact on the SLAW mission needs to be considered.

Also, as the committee stated in Review #3: