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Review of the Analysis of Supplemental Treatment Approaches of Low-Activity Waste at the Hanford Nuclear Reservation: Review #1 (2018)

Chapter: 3 Committee's Review of the FFRDC's Draft Assessment of Waste Conditioning and Supplemental Treatment Approaches

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Suggested Citation:"3 Committee's Review of the FFRDC's Draft Assessment of Waste Conditioning and Supplemental Treatment Approaches." National Academies of Sciences, Engineering, and Medicine. 2018. Review of the Analysis of Supplemental Treatment Approaches of Low-Activity Waste at the Hanford Nuclear Reservation: Review #1. Washington, DC: The National Academies Press. doi: 10.17226/25093.
×

3

Committee’s Review of the FFRDC’s Draft Assessment of Waste Conditioning and Supplemental Treatment Approaches

The committee’s second charge in the Statement of Task is to evaluate the technical quality and completeness of waste conditioning and supplemental treatment approaches considered in the Federally Funded Research and Development Center’s (FFRDC’s) assessments, including any approaches not identified by the U.S. Department of Energy’s Office of Environmental Management (DOE-EM).

THREE PRIMARY SUPPLEMENTAL TREATMENT TECHNOLOGIES

Key Points in the FFRDC’s Work

In Documents 4, 5, and 6 and Presentations 3, 4, and 5, the FFRDC discusses the three primary supplemental treatment technologies, vitrification, grouting, and fluidized bed steam reforming, and the FFRDC does not identify any other primary supplemental low-activity waste (SLAW) treatment technology.

Vitrification

In Document 4 and Presentation 3, the FFRDC describes two vitrification methods: “traditional” Joule-heated ceramic-lined melter and in-container, or bulk vitrification. (Joule-heating passes an electric current through a mixture of glass forming materials and waste; the internal resistance of these materials results in the electrical energy being dissipated as heat, thereby melting the material to form glass.) The Joule-heating method has two options: one that “mimics” the flowsheet for the immobilized LAW (ILAW) treatment system within the Waste Treatment and Immobilization Plant (WTP) (Document 4, p. 1), and another that uses the ILAW system design but with two next generation melters rather than the four melters planned for the ILAW system. The next generation melters would have increased throughput as compared to the WTP’s melters because of larger surface area and thicker refractory liners. The next generation melters would be able to operate at higher temperatures due to the increase in the refractory material’s resistance to heat. In addition, the next generation melter system would be expected to use simultaneously both of its pour spouts as compared to the ILAW melters’ capacity to only use one pour spout at a time. Thus, the draft flowsheet for this advanced system projects that two next generation melters can meet the production rate of four WTP LAW melters (Document 4, p. 3). For either the current or next-generation melters, it could be possible to increase throughput using improved glass formulation as has occurred in the Savannah River Site’s HLW melter during its operating life (e.g., Kruger et al., 2013).

The method of bulk vitrification is also known as in-container vitrification because dried feed material and glass forming chemicals are added to a melt container. Heating is provided through Inconel electrodes that transfer the electrical current through the molten glass pool which is heated through resistance effects.

In Presentation 3, the FFRDC provides its estimates, as of the end of February 2018, for the technology readiness levels (TRLs) for the vitrification options. For all flowsheets, the waste feed system is rated as a high TRL because of common commercial equipment that would be used. But the batching and blending systems for the glass forming chemicals are rated as TRL medium because they would be more complicated at Hanford’s proposed SLAW system than most dry material blending and transfer operations that have

Suggested Citation:"3 Committee's Review of the FFRDC's Draft Assessment of Waste Conditioning and Supplemental Treatment Approaches." National Academies of Sciences, Engineering, and Medicine. 2018. Review of the Analysis of Supplemental Treatment Approaches of Low-Activity Waste at the Hanford Nuclear Reservation: Review #1. Washington, DC: The National Academies Press. doi: 10.17226/25093.
×

been demonstrated elsewhere. It is assumed that SLAW vitrification facility construction (if this approach is selected) would begin after LAW vitrification was initiated and would thus likely then have a high TRL rating if the LAW vitrification works successfully. As to the next generation melters, the TRL is assessed as medium due to the need to incorporate modifications that have yet to be demonstrated. As to in-container vitrification, the TRL is rated as medium because it has been demonstrated only in limited testing.

Grouting

Document 5, p. 1, notes that grouting technology has a long track record of transforming radioactive aqueous liquid and sludge waste into solid waste forms, and it has been used to encapsulate radioactive particulate matter and debris. Grouting for radioactive waste treatment can use hydraulic cements or acid-based cements. For details on the cementitious grouts that can be used, see Document 5. The FFRDC notes also that there are several advantages to using grout technology to treat and condition radioactive waste, including relatively inexpensive cementitious materials, low-cost processing at ambient temperatures, multiple demonstrated remote processing options, capability of incorporating slag cement to reduce the mobility of toxic heavy metals, suitability for a wide-range of aqueous compositions, alkaline chemistry to reduce the solubility of many radionuclides, flexible formulations to accommodate various waste feeds, and limited secondary waste volume (Document 5, p. 1).

In Document 5 and Presentation 4, the FFRDC specifically calls attention to some demonstrations and successful applications of grout technology for waste form encapsulation. At the Savannah River Site, since 1991, more than 17 million gallons of liquid decontaminated tank waste (i.e., LAW) have been grouted and disposed in near-surface concrete vaults on site. The grouted material is known locally as Saltstone. At the West Valley Demonstration Project, the supernate tank waste in more than 19,000 square bins holding 71 gallons each were grouted and then shipped to the Nevada National Security Site (NNSS). At the Oak Ridge Reservation, an in situ grouting disposal method was used and aqueous tank low-level waste were also grouted and shipped to NNSS.

Document 5 and Presentation 4 mention that the FFRDC team will consider in its analysis: (1) keeping technetium-99 and iodine-129 in the grouted waste forms, (2) removing these radionuclides, (3) pre-treatment for removal of strontium-90 to lower the transportation costs, (4) pre-treatment for organics in the waste to meet waste classification and treatment standards, and (5) disposal on-site at IDF or off-site at the WCS facility, taking into account the waste acceptance criteria at these facilities.

Fluidized Bed Steam Reforming

Document 6, p. 2, defines fluidized bed steam reforming (FBSR) as a process that uses superheated steam to crack and oxidize organic chemicals in order to generate more free radical chemicals that can accelerate decomposition of hydrocarbons and reactions with other solids and gaseous chemicals. The end products (p. 5) are mineralized waste forms such as nepheline, carnegieite, and sodalite that can incorporate non-volatile and semi-volatile waste chemicals and radionuclides in the mineral structure or inside “cages.” Document 6, p. 1, notes that FBSR “has been researched, developed, and used commercially for over two decades for processing low level radioactive wastes.” In particular, it notes the experience of the commercial Studsvik Processing Facility that began operations in the late 1990s for treating radioactive wastes in ion-exchange resins, as well as the small-scale testing at Idaho National Laboratory (INL) for treating liquid, highly acidic, radioactive sodium bearing waste. This testing provides the basis for the full-scale Integrated Waste Treatment Unit (IWTU) for treating up to 900,000 gallons of sodium-bearing waste in tanks at INL. Document 6, pp. 1-2, notes that the IWTU is presently in non-radioactive startup operations to be readied for beginning radioactive waste treatment although this is occurring after modification of the facility over a period of years to address operational problems. Presentation 5 mentions that some key components of a potential SLAW treatment system for Hanford have already been demonstrated at the Engineering Scale Test Demonstration Fluidized Bed Steam Reformer at the Hazen Research Inc. facility in Golden, Colorado.

Suggested Citation:"3 Committee's Review of the FFRDC's Draft Assessment of Waste Conditioning and Supplemental Treatment Approaches." National Academies of Sciences, Engineering, and Medicine. 2018. Review of the Analysis of Supplemental Treatment Approaches of Low-Activity Waste at the Hanford Nuclear Reservation: Review #1. Washington, DC: The National Academies Press. doi: 10.17226/25093.
×

Presentation 5 outlines two options for potential application of FBSR for SLAW treatment at Hanford. The first option would use two Denitration Mineralizing Reformer (DMR) vessels to create a dry granular solid product. The DMR “contains a bed of particles that are the right size and density to be continually fluidized [circulated within a vessel] by a superheated flow of steam that enters the bottom of the vessel” (Document 5, p. 2). This option would use a 500,000 gallon waste holding tank upstream of the SLAW treatment system, but a ≈1,000,000 gallon additional delay tank plus two 250,000 gallon waste feed/mix tank capacity would be needed for the first approximately three years of SLAW treatment to accommodate the high initial feed rates calculated by the One System Integrated Flowsheet and then the throughput would decrease afterwards. The two identical DMRs would have shared waste staging, mixing, and feed systems. Option 2 would use two DMR systems to produce a solid monolith product to eliminate dust and provide for more compression strength. This option would have the same waste feed, FBSR, off-gas, and product handling systems as in Option 1 and would have two completely identical product monolith systems.

The FFRDC’s estimate of the FBSR’s TRL is that technology maturation is needed for some operations. Presentation 5 lists some advantages as (1) the use of moderate temperatures and pyrolysis in the DMR to destroy organics and nitrous oxides, (2) production of a durable, mineralized waste form, (3) the capability to retain radionuclides, halogens, and hazardous metals with efficient loading in the waste forms, and (4) no liquid secondary wastes and thus no volume increase. But some disadvantages, which the FFRDC notes might be resolved with applied research and development, are (1) that it is a complex, integrated thermal process, (2) the need for design details specific to Hanford SLAW, and (3) the need for integrated pilot-scale demonstration of that design.

Committee’s Observations and Suggestions

The committee understands that the FFRDC has focused on the three primary technologies listed in Sec. 3134 as the technologies to analyze. Based on the FFRDC’s draft report and presentations, the committee is not aware of any other primary technologies that are sufficiently developed or likely of success to warrant detailed analysis.

Regarding each of the three primary treatment technologies, the committee suggests that the FFRDC clarify the relationship between the low-medium-high TRL levels used in the FFRDC report to the traditional nine-level TRL scale (DOE, 2011b) and the reason the traditional scale was not used. The committee suggests that the FFRDC give its assessment of the potential problems and technical challenges of each of these treatment technologies as well as the potential barriers to acceptance of any of these technologies and the resulting waste forms for disposal sites under consideration.

In general, the committee notes that the relevant consideration in analyzing the human health risks from various treatment options is the performance of the entire disposal system (natural and engineered components), not just the waste form per se and that leaching measures need to account for containers. The committee offers the following observations concerning each of the three primary technologies.

Vitrification

Vitrification, while a known and successful technology, is still technologically challenging, and thus technologically risky, especially when applied to variable feed mixtures, and at the unprecedented scale envisioned for Hanford. To reckon a sense of the larger scale, consider that the first-of-a-kind LAW melter for Hanford that was assembled last year has a capacity that is five times bigger than the Defense Waste Processing Facility (DWPF) melter at the Savannah River Site (Cary, 2017). Notably, the DWPF at Savannah River has operated successfully since 1996; only two melters have been used so far, the second of which lasted nearly 13 years. Nonetheless, the Hanford LAW melters are significantly larger.

Previous analysis by several researchers at national laboratories has underscored the variability of the LAW at Hanford. “The composition of the LAW will vary from tank to tank because of the variability in types and sources of wastes stored in the individual tanks and the processes used to separate the wastes into

Suggested Citation:"3 Committee's Review of the FFRDC's Draft Assessment of Waste Conditioning and Supplemental Treatment Approaches." National Academies of Sciences, Engineering, and Medicine. 2018. Review of the Analysis of Supplemental Treatment Approaches of Low-Activity Waste at the Hanford Nuclear Reservation: Review #1. Washington, DC: The National Academies Press. doi: 10.17226/25093.
×

HLW and LAW fractions” (PNNL and SRNL, 2013). These challenges point to potential benefits of blending of the tank waste. Notably, the FFRDC mentions that “it should be expected that tanks that would challenge the treatment technology would not be selected for individual treatment (i.e., the waste would be blended as needed to meet the specified limits for Supplemental LAW)” (Document 1, p. 10).

Grouting

The grouting treatment approach would require high quality constituent materials. Another consideration is the potential of various chemicals in some parts of the heterogeneous SLAW feed being possible impediments to use of grouting as a treatment method. The committee suggests that the FFRDC evaluate whether this is an impediment. As mentioned previously, some, or even most, of these materials could become less available or more expensive at the time when the SLAW plant would become operational (in several years) and during the decades’ long time of operations. For instance, while there are many stockpiles of fly ash, not all fly ash is suitable for use in cementitious systems; some fly ash is incompatible with admixtures; some will cause premature setting; and some is too variable. As a byproduct material, fly ash is subject to quality variations that are beyond the control of DOE. The alternatives to fly ash, slag cement, and other constituents need to be tested. Some potential alternatives are calcined clay and natural pozzolans. Consideration also needs to be given to what happens if a grouting batch fails to set, as well as the effect (if any) of alternatives on the leaching properties of the resulting grout.

Fluidized Bed Steam Reforming

The IWTU at INL may not be a useful model because it has yet to operate successfully and has experienced several technical problems since 2012 (DOE-OIG, 2016; Trevellyan, 2017). The waste treatment challenge at Idaho is much smaller than at Hanford—approximately 900,000 gallons versus 56 million (a greater than 60× scale-up)—and the waste composition at Idaho is more homogeneous and well characterized as compared to Hanford’s wastes. The committee also notes that while the FFRDC does mention commercial, large-scale industrial experience in this technology, it would be useful to understand this experience in more depth in order to find out if it is more applicable to Hanford especially in terms of technological maturity and scalability. Also of note is that high-quality coal is used in the FBSR process; thus, there might be a supply chain concern about the source of such coal if likely to come from outside the United States.

IDENTIFICATION AND ANALYSIS OF OTHER PRE-TREATMENT AND TREATMENT TECHNOLOGIES

Key Points in the FFRDC’s Work

In Document 3 and Presentation 6, the FFRDC presents a preliminary identification of “other” options for review. Presentation 6, in particular, lists in a table a dozen options; nine of those are conditioning (pretreatment) options and the additional three consist of immobilization options (treatment). In Presentation 6, the FFRDC also states that it will perform a literature review of these other options and that the review will look at the “rationale for the options’ earlier disposition (e.g., screened out, or further consideration recommended).” Presentation 8 discusses that the team will assess “subsequent development or evaluation of the technology option (since its previous evaluation).” Moreover, the FFRDC will “evaluate the current relevance of the option to:

  • Scope of the study,
  • Potential benefits to the supplemental treatment mission, and
  • Likelihood that benefits could be realized if pursued.”
Suggested Citation:"3 Committee's Review of the FFRDC's Draft Assessment of Waste Conditioning and Supplemental Treatment Approaches." National Academies of Sciences, Engineering, and Medicine. 2018. Review of the Analysis of Supplemental Treatment Approaches of Low-Activity Waste at the Hanford Nuclear Reservation: Review #1. Washington, DC: The National Academies Press. doi: 10.17226/25093.
×

Committee’s Suggestions

Because it was not clear to the committee whether the FFRDC considers these technologies to be major alternatives to the three major SLAW options, or variations within one or more of these three, the committee suggests that the FFRDC clarify whether there are other major alternatives or a variation of or supplement to one of the major three baseline SLAW approaches. Clarity in this regard will both highlight opportunities to vary the major approaches to optimize operations or output, and assist decision-makers in their assessment of the alternatives provided.

COMMON ISSUES FOR THE SUPPLEMENTAL TREATMENT APPROACHES

Committee’s Observations

The committee notes that DOE may find that the development of two treatment approaches, instead of just one, would be useful as a hedge against technological or programmatic risks. For example, if vitrification is chosen as the main approach, it might be useful to develop grouting or another approach on a smaller scale in order to mitigate and diversify risk, because then there would be a backup approach. (The analogy is imperfect, but the Manhattan Project itself followed multi-track approaches to its novel engineering challenges: a two-track approach [uranium-235 and plutonium] for the designs of the weapons, and a three-track approach [thermal diffusion, gaseous diffusion, and electromagnetic separation] for uranium enrichment.) Viable alternatives could be especially important if supplemental LAW becomes a rate-limiting step.

Variability in volume, composition, and timing of the feed vector is a pervasive concern in design, according to the FFRDC’s draft report and presentations. Upstream waste blending (which could occur in the SLAW facility, the tank farm, or facilities associated with the WTP) could potentially address the variation and result in a more reliable, more effective production process. The committee understands that much of the uncertainty is traceable to the limited or complete absence of successful experience with the technologies and processes. The SLAW treatment is planned to be connected to other components of the HLW and LAW portions of the WTP, and thus a comprehensive plan is the preferred management approach. Indeed, for this reason, comprehensiveness has been DOE’s consistent approach to planning for waste treatment at Hanford. Given the novelty, complexity, and the many and substantial uncertainties surrounding the waste and the treatment technologies, there might be opportunities to stage decisions and construction so as to (a) learn from the results of actual operations (e.g., “direct feed” LAW vitrification), (b) revisit primary technologies if upstream/previous aspects of the project do not operate as expected, or (c) other key variables (e.g., funding or regulatory environment) change fundamentally. This is an adaptive management approach.

Committee’s Suggestions

The committee suggests that the team could usefully consider, at least briefly, whether certain combinations of primary treatment technologies could confer particular advantages.

FURTHER “UPSTREAM” TECHNOLOGIES

Committee’s Observations

In addition to considering variations in the principal SLAW alternatives themselves, consideration can be given to “upstream” opportunities that can optimize these alternatives. Notably, the FFRDC’s draft report and presentations identify several opportunities that may improve SLAW treatment or disposal by making certain upstream changes part of the conditioning (pre-treatment) of SLAW. Without expanding

Suggested Citation:"3 Committee's Review of the FFRDC's Draft Assessment of Waste Conditioning and Supplemental Treatment Approaches." National Academies of Sciences, Engineering, and Medicine. 2018. Review of the Analysis of Supplemental Treatment Approaches of Low-Activity Waste at the Hanford Nuclear Reservation: Review #1. Washington, DC: The National Academies Press. doi: 10.17226/25093.
×

the FFRDC’s scope, the committee believes that it would be useful to identify a limited number of promising upstream technologies or processes and use them to do a sensitivity analysis on the FFRDC report’s ultimate findings. Consideration can be given to removal of particular elements of concern, especially technetium and iodine and maybe strontium, and blending of tank wastes. This consideration would benefit from laying out clearly the reasons for such pre-treatment, for example, to remove certain radionuclides and other hazardous chemicals to meet waste acceptance criteria at certain disposal sites.

Suggested Citation:"3 Committee's Review of the FFRDC's Draft Assessment of Waste Conditioning and Supplemental Treatment Approaches." National Academies of Sciences, Engineering, and Medicine. 2018. Review of the Analysis of Supplemental Treatment Approaches of Low-Activity Waste at the Hanford Nuclear Reservation: Review #1. Washington, DC: The National Academies Press. doi: 10.17226/25093.
×
Page 17
Suggested Citation:"3 Committee's Review of the FFRDC's Draft Assessment of Waste Conditioning and Supplemental Treatment Approaches." National Academies of Sciences, Engineering, and Medicine. 2018. Review of the Analysis of Supplemental Treatment Approaches of Low-Activity Waste at the Hanford Nuclear Reservation: Review #1. Washington, DC: The National Academies Press. doi: 10.17226/25093.
×
Page 18
Suggested Citation:"3 Committee's Review of the FFRDC's Draft Assessment of Waste Conditioning and Supplemental Treatment Approaches." National Academies of Sciences, Engineering, and Medicine. 2018. Review of the Analysis of Supplemental Treatment Approaches of Low-Activity Waste at the Hanford Nuclear Reservation: Review #1. Washington, DC: The National Academies Press. doi: 10.17226/25093.
×
Page 19
Suggested Citation:"3 Committee's Review of the FFRDC's Draft Assessment of Waste Conditioning and Supplemental Treatment Approaches." National Academies of Sciences, Engineering, and Medicine. 2018. Review of the Analysis of Supplemental Treatment Approaches of Low-Activity Waste at the Hanford Nuclear Reservation: Review #1. Washington, DC: The National Academies Press. doi: 10.17226/25093.
×
Page 20
Suggested Citation:"3 Committee's Review of the FFRDC's Draft Assessment of Waste Conditioning and Supplemental Treatment Approaches." National Academies of Sciences, Engineering, and Medicine. 2018. Review of the Analysis of Supplemental Treatment Approaches of Low-Activity Waste at the Hanford Nuclear Reservation: Review #1. Washington, DC: The National Academies Press. doi: 10.17226/25093.
×
Page 21
Suggested Citation:"3 Committee's Review of the FFRDC's Draft Assessment of Waste Conditioning and Supplemental Treatment Approaches." National Academies of Sciences, Engineering, and Medicine. 2018. Review of the Analysis of Supplemental Treatment Approaches of Low-Activity Waste at the Hanford Nuclear Reservation: Review #1. Washington, DC: The National Academies Press. doi: 10.17226/25093.
×
Page 22
Next: 4 Committee's Review of the Information and Data Used by the FFRDC »
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In 1943, as part of the Manhattan Project, the Hanford Nuclear Reservation was established with the mission to produce plutonium for nuclear weapons. During 45 years of operations, the Hanford Site produced about 67 metric tonnes of plutonium—approximately two-thirds of the nation's stockpile. Production processes generated radioactive and other hazardous wastes and resulted in airborne, surface, subsurface, and groundwater contamination. Presently, 177 underground tanks contain collectively about 210 million liters (about 56 million gallons) of waste. The chemically complex and diverse waste is difficult to manage and dispose of safely.

Section 3134 of the National Defense Authorization Act for Fiscal Year 2017 calls for a Federally Funded Research and Development Center (FFRDC) to conduct an analysis of approaches for treating the portion of low-activity waste (LAW) at the Hanford Nuclear Reservation intended for supplemental treatment. The first of four, this report reviews the analysis carried out by the FFRDC. It evaluates the technical quality and completeness of the methods used to conduct the risk, cost benefit, schedule, and regulatory compliance assessments and their implementations; waste conditioning and supplemental treatment approaches considered in the assessments; and other key information and data used in the assessments.

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