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Suggested Citation:"4 The Committee's Observations and Responses to Comments." National Academies of Sciences, Engineering, and Medicine. 2020. Final Review of the Study on Supplemental Treatment Approaches of Low-Activity Waste at the Hanford Nuclear Reservation: Review #4. Washington, DC: The National Academies Press. doi: 10.17226/25710.
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4

The Committee’s Observations and Responses to Comments

In this chapter, the committee provides its views on selected themes of the comments relevant to its Review #3 and does not provide a one-to-one response to every specific comment or theme. Also, the committee follows the ground rules as described in Chapter 3.

CONCEPT OF “AS GOOD AS GLASS”

As to the comments on “as good as glass,” the committee appreciates that the Washington State Department of Ecology (Department of Ecology) acknowledges in its written comments that objective criteria still need to be developed. The committee also recognizes the Consortium for Risk Evaluation with Stakeholder Participation (CRESP) members’ comment that there is no legally binding agreement that supplemental low-activity waste (SLAW) be treated with vitrification (see Appendix E, p. 106). The committee does not state in Review #3 that there is a “perceived agreement” that has some legal or regulatory basis; rather, Finding 5-2 states in part, “The term ‘as good as glass’ is not defined in law, regulation, or agreement, and it is only tentatively defined by its advocates.” Review #3 also points out that some stakeholders strongly hold the view that there is an agreement on “good as glass,” an observation that is demonstrated by the comments described in Chapter 3. In addition, the committee appreciates CRESP members’ comment that “the focus should not be on any specific waste form (e.g., glass versus others) but instead on defining the necessary technical performance requirements of any waste form that would be used for low-level waste burial in the IDF” (see Appendix E, p. 106). The committee notes that Review #3 adequately addresses the committee’s comments about the need for a stepwise comparison.

In Review #3, the committee also discusses the (lack of) maturity of vitrification as a waste form by focusing primarily on the unique and uniquely challenging nature of the Hanford waste. It is worth repeating that vitrification has an inconsistent history of success, and that even where successful it has high operating and maintenance costs, as well as significant periods of planned and unplanned unavailability.

GROUT WASTE FORMS, RETENTION OF LONG-LIVED RADIONUCLIDES, AND CONCERNS ABOUT RELEASES OF IODINE-129 AND TECHNETIUM-99 INTO THE ENVIRONMENT

Concerning releases of long-lived radionuclides, in particular, iodine-129 and technetium-99, into the environment, stakeholders such as the Oregon Department of Energy, the Oregon Advisory Board (citing the letter prepared by the Oregon Department of Energy), the Department of Ecology, Hanford Challenge, tribal nations, and other individual members of the public raise concerns about grout’s capability to sufficiently retain these radionuclides for possible disposal at the Integrated Disposal Facility (IDF) at Hanford. The committee notes that the Oregon Department of Energy’s letter contains a detailed review of the literature on this topical area, and here, the committee provides its response on the main themes of that letter.

The letter from the Oregon Department of Energy raises two main points related to the disposal of grout at Hanford: (1) the lack of rigorous public review of the Performance Assessment (PA) for the IDF, and (2) the use of short-term laboratory performance data on reducing grout and grout with getters, and extrapolation of these data to predict long-term waste form performance in a dynamic storage environment.

Suggested Citation:"4 The Committee's Observations and Responses to Comments." National Academies of Sciences, Engineering, and Medicine. 2020. Final Review of the Study on Supplemental Treatment Approaches of Low-Activity Waste at the Hanford Nuclear Reservation: Review #4. Washington, DC: The National Academies Press. doi: 10.17226/25710.
×

The committee has addressed aspects of both items during public meetings and interim review reports. Finding 3-2 of Review #3 specifically highlights the committee’s inability to review the draft PA for waste form comparisons (see Chapter 2 of this review for the committee’s comments on aspects of the PA). In Review #3, the committee also notes that the Federally Funded Research and Development Center’s (FFRDC’s) evaluation did not include a scenario where the PA was rejected by the Washington State regulator. In interim and the final FFRDC reports, the FFRDC team mentioned that it used information from the draft PA and included it in the team’s analysis. Complete review of the PA will likely occur as the disposal options mature and as the U.S. Department of Energy’s Office of Environmental Management (DOE-EM) and DOE’s Office of River Protection take the next steps toward reaching a decision on SLAW treatment and disposal.

The reliance on short-term, condition-specific studies on waste forms is also a subject of interest to the committee, and one that is coupled with the PA. Obviously, extrapolation from short-term studies is unavoidable in predictions of the long-term behavior of any waste form. Nevertheless, the committee recognizes that the inclusion of degradation models, chemical reaction mechanisms, and radionuclide speciation to describe waste form behavior would improve data usage and applicability for analysis of disposal options and anticipated long-term behavior. In Review #3, the committee calls for the waste forms to be compared with respect to waste loading, density, composition, radionuclide speciation, and radionuclide release mechanisms. Within a waste form composition, the addition of getters to the grout is noted as a topic requiring further assessment. The need for detailed understanding of radionuclide speciation highlights the oxidation state behavior, and how this property is influenced, stabilized, or altered by other waste form components. As noted in the Oregon Department of Energy’s letter, the oxidation state of the radionuclides strongly influences solubility and mobility. Radionuclide speciation is also coupled to radionuclide release and retention mechanisms in the waste form. In Review #3, the committee highlights these waste form material properties as a means to promote further research that will provide the scientific foundations for understanding long-term behavior of radionuclides in a disposal environment.

The committee also notes that Hanford Challenge in its submitted comments asserts that “the grout form proposed by the FFRDC report is itself toxic and a potential threat to the environment” because of the use of fly ash from coal combustion. In response, the committee observes that in April 2015, the U.S. Environmental Protection Agency published in the Federal Register its final ruling on “Hazardous and Solid Waste Management System; Disposal of Coal Combustion Residuals From Electric Utilities.” This ruling, in part, discusses that an “encapsulated beneficial use is one that binds the CCR [coal combustion residual] into a solid matrix that minimizes mobilization into the surrounding environment.” A major example of an encapsulated beneficial use is: “Fly ash used as a direct substitute for Portland cement during the production of concrete” or grout (EPA, 2015).

ADVANTAGES OF WASTE CONTROL SPECIALISTS VERSUS THE INTEGRATED DISPOSAL FACILITY

The Waste Control Specialists (WCS) facility near Andrews, Texas, has a number of advantages over the IDF at Hanford for any waste form, but it is mainly relevant for non-vitrified waste forms. As mentioned in Chapter 2, the PA for the IDF is for a primary low-activity waste (LAW) that is vitrified. But the secondary waste from that treatment process would be grouted. The Department of Ecology has yet to issue a permit based on the PA, and in the Department of Ecology’s submitted written comments, it states that since the 2012 Tank Closure and Waste Management Environmental Impact Statement, it has been known that “some of the secondary waste would have to be treated with improved grout formulations. Vitrification alternatives analysis should not be unfairly penalized by treating the secondary waste with lesser performing grout.” In contrast, the WCS facility has an approved PA and waste acceptance criteria as part of a license to operate. The committee notes that the FFRDC final draft report and final report mention the possibility of shipping the grouted secondary waste to WCS. Many commenters support that option. In particular, Pam Larsen, executive director of the Hanford Communities, emphasized in her presentation on October 31, 2019, and her written comments, that the Test Bed Initiative has provided a demonstration of treating LAW

Suggested Citation:"4 The Committee's Observations and Responses to Comments." National Academies of Sciences, Engineering, and Medicine. 2020. Final Review of the Study on Supplemental Treatment Approaches of Low-Activity Waste at the Hanford Nuclear Reservation: Review #4. Washington, DC: The National Academies Press. doi: 10.17226/25710.
×

as grout and successfully sending it to WCS. WCS has the main advantage of having no drinking water aquifer underneath its disposal facility; moreover, there is no nearby river and no potential for flooding.1 That site also appears to have a stable geology, although the committee notes that it never received a detailed presentation on the geological and hydrological characteristics of WCS. All of these physical features of WCS could mitigate the concerns of many commenters about releases of iodine-129 and technetium-99 from non-vitrified waste forms. This is why the committee emphasizes in Review #3 that one of the principal contributions of the FFRDC study is to “[open] the door to serious consideration of other disposal locations, specifically the WCS facility near Andrews, Texas, and possibly the EnergySolutions facility near Clive, Utah.”

Concerning additional engineered changes to the IDF, the committee acknowledges the Department of Ecology’s comment that Review #3 “appeared to advocate consideration of enhancing the disposal facility design to enhance the performance of each waste form…. If there is a proven basis for considering these kinds of disposal facility enhancements in relation to long term performance, (e.g., substantially greater than 1,000 years),” (see Appendix E, p. 103) the Department of Ecology asks for the committee to refer to that basis and that if there is none, it requests that the committee rescind those comments. In Review #3, the committee simply states the obvious point that, in principle, performance of the entire waste disposal system could be extended either by improvements to the waste form or by improvements to the disposal facility or both. The committee was not tasked with, and did not, perform an engineering analysis of the IDF, but it stands to reason that realistic improvements to the disposal facility, if they exist, should be explored. As an example and as a reference, the committee notes that DOE submitted a request to the U.S. Environmental Protection Agency (EPA) in 2006 for emplacing magnesium oxide in the Waste Isolation Pilot Plant (WIPP) repository for transuranic waste. EPA notes that magnesium oxide “is an engineered barrier that DOE included as part of the original WIPP Certification Decision that ensures repository releases will be well within the EPA’s regulatory limits” (EPA, 2006). As in Review #3, the committee would not support ruling out a priori a category of potential improvements to the disposal system.

BULK VITRIFICATION

Early in the FFRDC’s analysis, the team considered about 22 variants. Bulk vitrification in a metal container was one of them. This treatment method was tested at Hanford between 2003 and 2008, and subsequent plans called for construction and operation of a demonstration facility. However, DOE cancelled the project and related development work in 2008 after an independent technical review (Independent and External Team of Experts, 2006) that identified 19 technical issues that could result in the failure of the demonstration to meet performance requirements and 26 areas of concern that might have resulted in a change to design or require additional testing, followed by a U.S. Government Accountability Office (GAO) report (GAO, 2007) that was critical of the proposed demonstration because of concerns about technical and project management.

During its work, the FFRDC developed flowsheets for bulk vitrification and conducted analyses to assess bulk vitrification (e.g., Sect. B.2 and p. 169 of the final FFRDC report). However, in an effort to make its results more transparent and comprehensible, the FFRDC reduced the number of variants from 22 to the five now considered in its final report. Those five did not include bulk vitrification, noting the need for “additional development and testing to resolve key process issues” for bulk vitrification (p. 169). The committee agrees with this approach because (a) it did contribute to making the FFRDC’s report more transparent and comprehensive, (b) the issues that need to be resolved indicate that substantial time would be required to advance the technology so that it could be confidently deployed, and (c) the vitrification

___________________

1 The WCS website notes: “The WCS site in Andrews County, Texas was selected due to its location atop a ridge of 600-ft. thick red-bed clay in a relatively remote, semi-arid, sparsely inhabited area of far west Texas, with the nearest residence approximately 3.5 miles to the west in New Mexico and annual rainfall of less than 16 inches.” That website also notes that the nearest aquifer is 6 miles north of the site. In addition, water would have to travel up a gradient to reach the site. See http://www.wcstexas.com/about-wcs/environment.

Suggested Citation:"4 The Committee's Observations and Responses to Comments." National Academies of Sciences, Engineering, and Medicine. 2020. Final Review of the Study on Supplemental Treatment Approaches of Low-Activity Waste at the Hanford Nuclear Reservation: Review #4. Washington, DC: The National Academies Press. doi: 10.17226/25710.
×

alternatives that are addressed in the FFRDC report and the committee’s reviews are applicable to the essential features of bulk vitrification with the exception being that bulk vitrification was to be deployed as a set of connected modules in the field and not in a large concrete and steel structure.

EXAMINE THE ENTIRE SYSTEM

As the committee has mentioned in previous reviews, the scope of this study is limited to analyzing treatment approaches for SLAW, but the committee has also drawn attention in earlier reviews to the fact that SLAW is one part of a much bigger, complex waste treatment system. Moreover, this system is interconnected to the even larger system of the surrounding environment, including the Columbia River and the regional ecosystem. Furthermore, the timescales are immense—consider the half-life of 15.7 million years for iodine-129—that have to be taken into account when examining the impacts on human health and the other parts of the living environment.

In light of these interrelated systems across the landscape, network of rivers and wetlands, and the long temporal period for some radionuclides, the committee recognizes the serious concerns of many stakeholders and members of the public. In particular, the committee calls attention to concerns about climatic impacts, risks of major flooding, and seismic events that have not yet been taken into account for all waste forms.

The committee acknowledges the Department of Ecology’s comments that one cannot look at the IDF in isolation, and specifically,

while it may be possible to control future releases of chromium, nitrate, Tc-99, and I-129 from IDF (by controlling the waste forms, limiting [what] is disposed of in IDF, or both), there is little to no possibility of controlling the future release of [these contaminants] from waste already disposed of to the soils across the Hanford Site. These additional contributions are why the State is looking for results that are significantly lower than the EPA drinking water MCLs [maximum contaminant levels]. (see Appendix E, p. 103)

As noted above, the current MCLs may warrant reconsideration, as they are based on outdated methodologies. In any event, the FFRDC’s and the committee’s scope is limited to the contribution of SLAW treatment and disposal, and the committee has insufficient information (and it may be that no one does) to translate the legitimate overall concern into practical guidance for performance levels for SLAW disposal. Indeed, this kind of overarching assessment is precisely why clean-up decisions are committed to DOE, which has the widest overview of the Hanford situation.

When considering the entire system, experience has confirmed that a rigorous assessment of the uncertainties fills the gap of the lack of information. In particular, it is possible to do a probabilistic analysis of risks and cost regardless of the state of the design or the process. In situations where little is known, the result of the analysis is in the form of uncertainty, which can always be quantified with evidence-based probabilities. Thus, this would be a calibration of the areas of uncertainty that are exposed and can be ranked by importance. Information on uncertainties and their distribution can be very useful to decision-makers. Such results might be applied to SLAW using the risk-informed decision-making framework suggested by the GAO (2019) as described in Chapter 1.

SPRINGBOARD CONCEPT

Some commenters (five) express support for the concept in Recommendation 4-1 that the FFRDC’s analysis could be used as a “springboard” to considering the possibility of hybrid approaches, or approaches that permit consideration of new or improved technologies. It seems inevitable that the management of Hanford’s tank waste will take decades to complete, and rather than fighting the timeline, it may be possible to take advantage of it. Technologies of waste treatment and disposal systems are constantly evolving.

Suggested Citation:"4 The Committee's Observations and Responses to Comments." National Academies of Sciences, Engineering, and Medicine. 2020. Final Review of the Study on Supplemental Treatment Approaches of Low-Activity Waste at the Hanford Nuclear Reservation: Review #4. Washington, DC: The National Academies Press. doi: 10.17226/25710.
×

Novel techniques are gaining maturity with additional use. Also, our understanding of pathways of contaminants, their effects, and means of protection are constantly improving. An approach to SLAW treatment and disposal should be open to, and if possible encourage, such opportunities. This would be a novel approach at Hanford and elsewhere within DOE, but the sheer size and complexity of the Hanford site may be the strongest argument for considering the possibilities.

Areas for Additional Study

As the committee noted in Chapter 2, the FFRDC team has already identified some areas for additional study:

  • Treatment of organics restricted from land disposal (for the grout waste form cases of disposal at the IDF and WCS)
  • Treatment of technetium and iodine (for the case of grout waste form disposal at the IDF)
  • Treatment of liquid secondary wastes (for vitrification case of disposal at the IDF)
  • Performance of grouted waste forms (for the case of disposal at the IDF)
  • Performance of steam reformed waste forms (for the case of disposal at the IDF)

When assessing the readiness of various technologies, the committee suggests that assessors use a rigorous structured assessment process such as that described in DOE’s Technology Readiness Assessment Guide (DOE, 2011b).

The committee also points out the need for researching improvements in secondary waste forms, enhancements for engineered barriers at the IDF to be tailored for the particular waste forms instead of treating as one size fits all, and methods to place the technetium and iodine into high-level waste forms. In addition, the committee notes the need for more research and development on the best performing grout and the getters, which are added materials that can better retain the contaminants of concern. Finally, the committee underscores Recommendation 4-1 from Review #3 on development of hybrid options.

Suggested Citation:"4 The Committee's Observations and Responses to Comments." National Academies of Sciences, Engineering, and Medicine. 2020. Final Review of the Study on Supplemental Treatment Approaches of Low-Activity Waste at the Hanford Nuclear Reservation: Review #4. Washington, DC: The National Academies Press. doi: 10.17226/25710.
×
Page 26
Suggested Citation:"4 The Committee's Observations and Responses to Comments." National Academies of Sciences, Engineering, and Medicine. 2020. Final Review of the Study on Supplemental Treatment Approaches of Low-Activity Waste at the Hanford Nuclear Reservation: Review #4. Washington, DC: The National Academies Press. doi: 10.17226/25710.
×
Page 27
Suggested Citation:"4 The Committee's Observations and Responses to Comments." National Academies of Sciences, Engineering, and Medicine. 2020. Final Review of the Study on Supplemental Treatment Approaches of Low-Activity Waste at the Hanford Nuclear Reservation: Review #4. Washington, DC: The National Academies Press. doi: 10.17226/25710.
×
Page 28
Suggested Citation:"4 The Committee's Observations and Responses to Comments." National Academies of Sciences, Engineering, and Medicine. 2020. Final Review of the Study on Supplemental Treatment Approaches of Low-Activity Waste at the Hanford Nuclear Reservation: Review #4. Washington, DC: The National Academies Press. doi: 10.17226/25710.
×
Page 29
Suggested Citation:"4 The Committee's Observations and Responses to Comments." National Academies of Sciences, Engineering, and Medicine. 2020. Final Review of the Study on Supplemental Treatment Approaches of Low-Activity Waste at the Hanford Nuclear Reservation: Review #4. Washington, DC: The National Academies Press. doi: 10.17226/25710.
×
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The U.S. Department of Energy's Office of Environmental Management is responsible for managing and cleaning up the waste and contamination at the Hanford Nuclear Reservation, the nation's biggest and most complex nuclear cleanup challenge. At the site, 177 underground tanks collectively contain about 211 million liters of waste that includes high-activity and low-activity materials.

At the request of Congress, Final Review of the Study on Supplemental Treatment Approaches of Low-Activity Waste at the Hanford Nuclear Reservation: Review #4 focuses on approaches for treatment and disposal of the supplemental portion of the low-activity waste from the tanks. This review report discusses developments since the publication of Review #3 and provides a summary of public comments on the third committee review report. The authoring committee then shares their views on these comments and whether they change any of the findings or recommendations in the third review report.

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