NUCLEAR WASTE

Opportunities Exist to 

Reduce Risks and 

Costs by Evaluating 

Different Waste 

Treatment 

Approaches at 

Hanford 

Report to Congressional Addressees

May 2017

GAO-17-306

United States Government Accountability Office
United States Government Accountability Office

Highlights of GAO-17-306, a report to 

congressional addressees

May 2017

NUCLEAR WASTE

Opportunities Exist to Reduce Risks and Costs 

by Evaluating Different Waste Treatment 

Approaches at Hanford

What GAO Found

The Department of Energy (DOE) chose different approaches to treat the less 

radioactive portion of its nuclear weapons waste stored in tanks (tank waste)—

which DOE refers to as “low-activity waste” (LAW)—at its two main cleanup 

sites, primarily in response to input from the two states. At the Savannah River

Site, DOE and South Carolina agreed to use an existing facility to grout the site’s 

LAW, a method that DOE determined could treat the waste faster and therefore 

address risks posed by prolonged storage of liquid waste in tanks sooner. Grout 

immobilizes waste in a concrete-like mixture. At Hanford, DOE is required by an 

agreement with the state and the Environmental Protection Agency to treat at 

least one-third to one-half of the site’s LAW with a process called vitrification, 

which immobilizes the waste in glass. DOE chose vitrification in the 1990s with 

input from Washington state because studies at that time indicated that

vitrification would be the most effective treatment approach for the conditions at 

Hanford. However, DOE has not yet determined how it will treat the remaining 

one-half to two-thirds of Hanford’s LAW, known as “supplemental LAW,” a 

decision it has proposed making by 2018. Congress passed legislation in 2004 

that clarified DOE’s authority to manage the LAW at the Savannah River Site as 

low-level waste. Clarifying DOE’s authority at Hanford, in a manner that does not 

impair the regulatory authorities of Washington state, to determine whether some 

portions of the supplemental LAW can be managed as low-level waste, could

enhance DOE’s ability to make risk-based decisions for supplemental LAW.

At the Savannah River Site, DOE has grouted about 4 million gallons of LAW

and has effectively addressed minor technical challenges, but at Hanford DOE

has not yet treated any LAW and faces significant unresolved technical 

challenges. In addition, the best available information indicates that DOE’s 

estimated costs to grout LAW at the Savannah River Site are substantially lower 

than its estimated costs to vitrify LAW at Hanford, and its schedule for 

completing LAW treatment at the Savannah River Site is decades shorter than 

its schedule at Hanford.

According to the 21 experts that attended GAO’s meeting convened by the 

National Academies of Sciences, Engineering, and Medicine (National 

Academies), both vitrification and grout could effectively treat Hanford’s LAW.

These experts stated that current information shows that grout will perform better 

than was assumed when DOE made its decision to vitrify Hanford’s LAW. 

According to some of the experts, using grout for supplemental LAW could help 

DOE complete its treatment mission sooner, reducing the environmental risks of

leaving waste in tanks for long periods. Experts at GAO’s meeting stated that 

developing updated information on the performance of treating Hanford’s 

supplemental LAW with other methods, such as grout, may enable DOE to 

consider waste treatment approaches that accelerate DOE’s tank waste 

treatment mission, thereby potentially reducing certain risks and lifecycle 

treatment costs. However, DOE has not developed current information on the 

performance of treating LAW with grout, or alternate methods, at Hanford, which 

View GAO-17-306. For more information, is inconsistent with guidance developed by the National Research Council.

contact David C. Trimble at (202) 512-3841 or 

trimbled@gao.gov or Timothy M. Persons at 

(202) 512-6412 or personst@gao.gov.

Why GAO Did This Study

DOE oversees the treatment and 

disposal of about 90 million gallons of 

radioactive waste from the nation’s 

nuclear weapons program. Most of this 

waste is stored in tanks at DOE sites in 

Hanford, Washington, and Savannah 

River, South Carolina. The less 

radioactive portion of the tank waste, 

called LAW, comprises more than 90 

percent of the waste’s volume but less 

than 10 percent of the total 

radioactivity. DOE has chosen different 

approaches for treating LAW at the two 

sites, but it has not made a final 

decision on how to treat Hanford’s 

supplemental LAW.

GAO examined (1) DOE’s reasons for 

choosing its treatment approaches for 

LAW at the Savannah River and 

Hanford Sites, (2) the status of DOE’s 

treatment of LAW at these sites, and 

(3) experts’ views on the likely

performance of approaches for treating

Hanford’s LAW. GAO reviewed 

technical reports on DOE’s waste 

treatment strategies at the two sites, 

interviewed DOE officials at 

headquarters and the sites, and 

convened an experts’ meeting through

the National Academies to discuss the 

effectiveness and risks of vitrification 

and grout.

What GAO Recommends

Congress should consider specifically 

authorizing DOE to classify Hanford’s

supplemental LAW based on risk, 

consistent with existing regulatory 

authorities. GAO also recommends

that DOE develop updated information 

on the performance of treating LAW

with alternate methods, such as grout, 

before it selects an approach for 

treating supplemental LAW. DOE 

agreed with both recommendations.
Page i GAO-17-306 Nuclear Waste

Letter 1

Background 6

DOE Chose Different Treatment Approaches at the Savannah 

River and Hanford Sites Primarily to Address Different State 

Input 15

DOE Has Treated Some LAW at the Savannah River Site but 

None Yet at Hanford 24

Experts Believe That Both Vitrification and Grout Can Treat 

Hanford’s LAW and Identified Options to Accelerate Cleanup 

and Reduce Future Costs 41

Conclusions 51

Matter for Congressional Consideration 52

Recommendations for Executive Action 52

Agency Comments and Our Evaluation 53

Appendix I Objectives, Scope, and Methodology 56

Appendix II DOE’s Current Plans for Treating Low-Activity 

Waste at the Hanford Site 65

Appendix III Timeline of Treatment Plans at the Hanford Site 66

Appendix IV Experts’ Views on the Technical Benefits and 

Shortcomings of Vitrification and Grout for Treating 

Hanford’s Low-Activity Waste 67

Appendix V Comments from the Department of Energy 75

Appendix VI Comments from the U.S. Nuclear Regulatory Commission 77

Contents
Page ii GAO-17-306 Nuclear Waste

Appendix VII GAO Contacts and Staff Acknowledgments 78

Tables

Table 1: Types of Radioactive Mixed Waste Contained in Tanks at 

the Department of Energy’s Hanford and Savannah River 

Sites 9

Table 2: Comparisons of Total Estimated Costs for Grouting LowActivity Waste (LAW) at the Savannah River Site and 

Vitrifying LAW at the Hanford Site, Based on Best 

Available Information 40

Table 3: Experts Participating in GAO’s May 2016 Experts’ 

Meeting 60

Table 4: Technical Benefits and Shortcomings Associated with 

Vitrification and Grout at the Hanford Site, According to 

Experts 67

Figures

Figure 1: Overview of the Department of Energy’s Tank Waste 

Treatment Status and Approaches at the Hanford and 

Savannah River Sites 27

Figure 2: Current Treatment Milestones at the Department of 

Energy’s Hanford and Savannah River Sites 30

Figure 3: A Risk-Informed Approach to Decision Making 62
Page iii GAO-17-306 Nuclear Waste

Abbreviations

DOE Department of Energy

EIS environmental impact statement

EPA Environmental Protection Agency

HLW high-level waste

LAW low-activity waste

National Academies National Academies of Sciences, 

Engineering, and Medicine 

NRC Nuclear Regulatory Commission

RCRA Resource Conservation and Recovery Act

TPA Tri-Party Agreement

WTP Waste Treatment and Immobilization Plant

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Page 1 GAO-17-306 Nuclear Waste

441 G St. N.W.

Washington, DC 20548

May 3, 2017

Congressional Addressees

The Department of Energy (DOE) is responsible for the treatment and 

disposal of radioactive and hazardous waste created as a byproduct of 

producing nuclear weapons. In 2016, DOE estimated that cleanup of the 

nation’s former weapons production sites would cost $257 billion and 

would last for decades. The majority of this cleanup responsibility and 

expense involves treating about 90 million gallons of waste currently 

stored in underground tanks at DOE sites in Hanford, Washington; 

Savannah River, South Carolina; and near Idaho Falls, Idaho. At its 

Hanford Site, in particular, DOE manages one of the world’s largest 

environmental cleanup programs. The U.S. government built and 

operated nine nuclear reactors at Hanford—including the world’s first 

operating large-scale reactor, developed as part of the Manhattan Project 

during World War II—to produce plutonium and other special nuclear 

materials for the country’s nuclear weapons program. A significant 

amount of hazardous and radioactive waste resulted from nuclear 

materials production at Hanford, and 54 million gallons of this waste is 

now stored in 177 large underground storage tanks and must be treated 

before disposal. Because multiple processes were used for plutonium 

production at Hanford, its tank waste contains a more complex mixture of 

radioactive and hazardous components, or constituents, than the tank 

waste at other DOE sites. The volume and complexity of the tank waste 

have been a persistent challenge for DOE—since beginning its mission to 

treat and dispose of Hanford’s waste over 25 years ago, DOE has spent 

more than $19 billion on several different tank waste treatment strategies, 

but DOE has yet to treat any of Hanford’s tank waste.1

Much of DOE’s tank waste is “high-level waste” (HLW) mixed with 

hazardous chemicals that, under current law, must be vitrified—a process 

in which the waste is immobilized in glass—prior to land disposal. “Lowactivity waste” (LAW) is DOE’s term for the portion of this tank waste with 

 1

This cost figure is not adjusted for inflation.

Letter
Page 2 GAO-17-306 Nuclear Waste

low levels of radioactivity.2 LAW is primarily the liquid portion of the tank 

waste that remains after as much radioactive material as technically and 

economically practical has been removed.3 Cleanup of the Hanford Site is 

governed by two main compliance documents: (1) the 1989 Hanford 

Federal Facility Agreement and Consent Order, or Tri-Party Agreement 

(TPA), an agreement among DOE, the Washington State Department of 

Ecology, and the Environmental Protection Agency (EPA);4 and (2) a 

2010 Consent Decree, amended in 2016.5 The Consent Decree currently 

requires DOE to begin vitrifying LAW by the end of 2023, and the TPA 

requires DOE to complete waste treatment by 2047.6

The Waste Treatment and Immobilization Plant (WTP) is DOE’s current 

planned approach to treating Hanford’s tank waste. The WTP includes 

several waste treatment facilities, including a facility to vitrify Hanford’s 

HLW and a facility to vitrify its LAW. Before treatment, DOE plans for the 

WTP to separate the tank waste into two streams: the HLW portion, which 

DOE estimates will contain more than 90 percent of the radioactivity but 

less than 10 percent of the volume, and the LAW portion, which will 

 2

DOE uses the term “low-activity waste” to mean the waste that remains after as much 

radioactivity as technically and economically practical has been separated from tank 

waste that, when solidified, may be disposed of as low-level radioactive waste in a nearsurface facility. At its Savannah River Site, DOE refers to the low-activity portion of its 

waste as low-level waste or “salt waste.” For the purpose of this review, we will refer to the 

low-activity portion of the waste at both the Hanford and Savannah River Sites as LAW.

3

Vitrification and grout are commonly referred to as immobilization methods. For the 

purposes of this report, we refer to them as treatment approaches because the scope of 

our review includes the entire process of treating the tank waste, not just the final 

immobilized waste form.

4

Hanford Federal Facility Agreement and Consent Order, EPA Docket No. 1089-03-04-

120, Ecology Docket No. 89-54, as amended through August 1, 2016. The agreement as 

available at: http://www.hanford.gov/page.cfm/TriParty/TheAgreement.

5

Washington v. Chu, Civ. No. 08-05085 (E.D. Wash), entered October 25, 2010, amended 

in March and April 2016.

6

The TPA lays out a series of legally-enforceable milestones for completing major 

activities in Hanford’s waste treatment and cleanup process. The purpose of the TPA is to 

ensure that Hanford’s cleanup activities comply with the Comprehensive Environmental 

Response, Compensation, and Liability Act; Resource Conservation and Recovery Act 

(RCRA); and Washington’s Hazardous Waste Management Act. DOE entered into the 

TPA pursuant to the Comprehensive Environmental Response, Compensation, and 

Liability Act; Executive Order 12580; and the Atomic Energy Act of 1954. The Consent 

Decree addresses a subset of these cleanup activities: completing the construction and 

achieving initial operations of the Waste Treatment and Immobilization Plant and retrieving 

waste from 12 single-shell tanks.
Page 3 GAO-17-306 Nuclear Waste

contain less than 10 percent of the radioactivity and more than 90 percent 

of the volume. The WTP, however, is currently designed to treat all of 

Hanford’s HLW but only one-third to one-half of the LAW, including some 

that DOE intends to treat using a “direct feed” process.7 DOE will need to 

identify and select another approach for treating the remaining LAW. The 

portion of the LAW remaining in the tanks for which DOE has yet to select 

a treatment approach is commonly referred to as “supplemental LAW.”

Our report focuses on possible treatment and disposal pathways for the 

supplemental LAW. It does not otherwise address DOE’s responsibilities 

under the compliance agreements.

Independent reviews conducted over the last 15 years have noted that 

DOE’s approach to treating LAW is not consistent across its cleanup sites 

and does not appear to be based on the degree of risk the waste poses 

for treatment, storage, and disposal.8 These reviews have noted that 

DOE plans to treat Hanford’s LAW using vitrification, but DOE treats LAW 

at its Savannah River Site by grouting it—a process in which the liquid 

waste is combined with a concrete-like or grout mixture, called saltstone, 

which then hardens to immobilize the waste.9 In 2006, the National 

Research Council found that these different approaches to treating LAW 

were not always based on a systematic consideration of risks and, as a 

result, waste having similar physical, chemical, and radiological 

characteristics may be managed in disparate ways.10 Moreover, the 

 7

DOE intends to feed a portion of Hanford’s LAW directly into the LAW vitrification facility 

that is part of the WTP, which would bypass the pretreatment component of the WTP. By 

doing so, DOE believes that waste treatment can begin years earlier than if it waits until all 

of the Pretreatment facility’s technical issues are resolved.

8

Committee on Risk-Based Approaches for Disposition of Transuranic and High-Level 

Radioactive Waste, National Research Council of the National Academies, Risk and 

Decisions About Disposition of Transuranic and High-Level Radioactive Waste 

(Washington, D.C.: National Academies Press, 2005). National Research Council of the 

National Academies, Improving the Regulation and Management of Low-Activity 

Radioactive Wastes, (Washington, D.C.: National Academies Press, 2006). Committee on 

Waste Forms Technology and Performance, National Research Council of the National 

Academies, Waste Forms Technology and Performance: Final Report (Washington, D.C.: 

National Academies Press, 2011). Omnibus Risk Review Committee, A Review of the Use 

of Risk-Informed Management in the Cleanup Program for Former Defense Nuclear Sites

(August 2015). 

9

We did not include the Idaho Site in our analysis because DOE does not plan to manage 

any of the site’s waste as low-level waste. Because DOE does not consider any waste at 

Idaho as LAW, we determined that it is not practical to compare the Idaho Site’s treatment 

approach with that of the Hanford Site. 

10Improving the Regulation and Management of Low-Activity Radioactive Wastes.
Page 4 GAO-17-306 Nuclear Waste

National Research Council stated that because DOE’s nuclear wastes are 

regulated primarily by their origins—the nature of the process that 

produced them—rather than by the actual radiological hazards they 

present, DOE may select relatively expensive treatment and disposal 

options for relatively low-risk waste.

We prepared this report under the authority of the Comptroller General to 

assist Congress with its oversight responsibilities, in light of broad 

congressional interest in DOE’s plans for treating supplemental LAW at 

the Hanford Site. We examined (1) DOE’s reasons for choosing its 

treatment approaches for LAW at its Savannah River and Hanford Sites, 

(2) the status of DOE’s treatment of LAW at its Savannah River and 

Hanford Sites, and (3) experts’ views on the likely performance of 

vitrification compared with grout for treating Hanford’s LAW.

To conduct our work, we gathered and reviewed information on DOE’s 

waste treatment strategy at the Savannah River and Hanford Sites, 

including DOE technical reports and internal and external reports on the 

sites’ histories, treatment approaches, schedules, and cost estimates. 

Specifically, we did the following work.

• To examine DOE’s reasons for choosing its treatment approaches for 

LAW at its Savannah River and Hanford Sites, we reviewed 

documents describing how DOE’s tank waste cleanup strategy has 

evolved, and we reviewed DOE’s environmental impact statements 

(EIS), which evaluate the potential environmental effects of different 

waste treatment approaches.11 We also reviewed applicable legal and 

regulatory requirements governing the cleanup of hazardous and 

radioactive wastes. In addition, we interviewed officials at DOE 

headquarters, as well as officials at the Hanford Site’s Office of River 

Protection and at the Savannah River Site, about the status of 

treatment at the two sites. We also interviewed officials from the 

Washington State Department of Ecology and the South Carolina 

Department of Health and Environmental Control, which are the state 

agencies that help regulate DOE’s cleanup programs at its Hanford 

and Savannah River Sites, respectively.

 11Under the National Environmental Policy Act of 1969, agencies evaluate the potential 

environmental effects of projects they are proposing using an environmental assessment 

or, if the projects likely would significantly affect the environment, a more detailed 

environmental impact statement.
Page 5 GAO-17-306 Nuclear Waste

• To examine the status of DOE’s treatment of LAW at the Savannah 

River and Hanford Sites, we reviewed numerous reports and studies 

on DOE’s plans to treat its tank waste at these two sites, including the 

amount of LAW that has been and will be treated; the schedule for 

constructing and operating the LAW treatment facilities; the cost of 

treating LAW; and technical challenges, if any. We also visited (1) the 

Hanford Site, where we observed tank farms and the WTP 

construction site, and (2) the Savannah River Site, where we 

observed tank farms, LAW treatment facilities, and the construction 

site for its future LAW treatment facility. We also analyzed available 

information on the costs of treating the Hanford and Savannah River 

Sites’ LAW, and we interviewed DOE officials on the estimated or, if 

available, actual costs of constructing and operating the LAW 

treatment facilities at the Hanford and Savannah River Sites. Because 

precise information on the costs of treatment options at Hanford is 

unavailable, we used the best available information to provide a 

rough, order-of-magnitude estimate.

• To examine experts’ views on the performance of vitrification 

compared with grout for treating Hanford’s LAW, we worked with the 

National Academies of Sciences, Engineering, and Medicine (National 

Academies) to select 21 experts and convene a 2-day meeting with 

those experts. We asked the experts to discuss (1) the state of 

research on the performance of vitrification and grout; (2) the longterm disposal risks associated with vitrified and grouted waste forms; 

and (3) economic, technological, and logistical factors that may affect 

decisions about the treatment of Hanford’s supplemental LAW. The 

experts’ meeting focused on the treatment of all of Hanford’s LAW 

because DOE has not yet determined which tanks’ waste will be 

treated by the WTP and which tanks’ waste will be treated with a 

supplemental treatment approach. After the meeting, we analyzed the 

transcripts to characterize the experts’ responses and to identify major 

themes.

Additional details on our objectives, scope, and methodology can be 

found in appendix I.

We conducted this performance audit from July 2015 to May 2017 in 

accordance with generally accepted government auditing standards. 

Those standards require that we plan and perform the audit to obtain 

sufficient, appropriate evidence to provide a reasonable basis for our 

findings and conclusions based on our audit objectives. We believe that 

the evidence obtained provides a reasonable basis for our findings and 

conclusions based on our audit objectives.
Page 6 GAO-17-306 Nuclear Waste

This section provides an overview of nuclear materials production at the 

Hanford and Savannah River Sites, the composition of the Hanford and 

Savannah River Sites’ tank waste, the regulatory framework governing 

waste treatment and disposal, and the requirements for the disposal of 

LAW.

Established in 1943, the Hanford Site produced plutonium for the world’s 

first nuclear device and continued producing nuclear materials for 

decades, generating millions of gallons of radioactive and hazardous 

chemical waste in the process. Some of this waste was deposited directly 

into the soil; some liquids were evaporated; and some waste was stored 

in 177 large, underground tanks, which are clustered together in 18 

locations called tank farms. In total, these tanks contain about 54 million 

gallons of waste. Most of these tanks are operating decades past their 

original design life, and DOE estimates that 62 of these tanks may have 

already leaked over 1 million gallons of waste into the ground.

The Savannah River Site was established in the 1950s to produce 

nuclear materials, such as tritium and plutonium, which were needed to 

manufacture nuclear weapons. It did so by dissolving highly radioactive 

spent nuclear fuel from the site’s nuclear reactors in large, heavily 

shielded separation facilities. Nuclear materials production at the site from 

1954 to the present has resulted in about 160 million gallons of waste. 

About 42 million gallons of this waste have been stored in 51 

underground tanks.12 The Savannah River Site’s tanks continue to 

receive additional waste from ongoing activities at the site.

Hanford’s tanks contain a complex mix of radioactive and hazardous 

components in both liquid and solid form. Waste that contains both types 

of components is called mixed waste.13 Hanford’s tank waste also 

includes various metals.

 12The volume of the Savannah River Site’s waste was reduced over the years as a result 

of operating a series of evaporators.

13Specifically, the term “mixed waste” means waste that contains both, (1) hazardous 

waste subject to the Resource Conservation and Recovery Act or authorized state 

programs that operate in lieu of the federal program; and (2) source, special nuclear, or 

byproduct material subject to the Atomic Energy Act of 1954.

Background

Nuclear Materials 

Production at the Hanford 

and Savannah River Sites

Composition of the 

Hanford and Savannah 

River Sites’ Tank Waste
Page 7 GAO-17-306 Nuclear Waste

• Radioactive component. About 46 different radioactive 

constituents—byproducts of chemically separating plutonium from 

uranium for use in nuclear weapons—account for the majority of the 

radioactivity in the Hanford Site’s tanks. The atoms of a radioactive 

constituent disintegrate, or decay, over time, releasing their radiation.

Some of these constituents decay to a stable (or non-radioactive) 

form in a relatively short time, while others remain radioactive for 

millions of years. The rate of radioactive decay is measured in halflives—that is, the time required for half the unstable atoms in a 

radioactive material to decay. The vast majority (98 percent) of the 

radioactivity of the tank waste comes from two constituents, strontium90 and cesium-137, which have half-lives of about 29 and 30 years, 

respectively. The remaining radioactive constituents, which account 

for about 2 percent of the waste’s total radioactivity, have much longer 

half-lives. For example, the half-life of technetium-99 is 213,000 

years, and that of iodine-129 is 15.7 million years.

• Hazardous component. The tanks also contain large volumes of 

hazardous chemical waste. Altogether, about 240,000 tons of 

hazardous chemicals were added to Hanford’s tanks from the 1940s 

to the mid-1980s. A majority of the chemicals were added to 

neutralize acids in the waste. Other chemicals, such as solvents and 

several organic compounds, were added during various waste 

extraction operations to help recover selected radioactive constituents 

(uranium, cesium, and strontium) for reuse. These hazardous 

chemicals are dangerous to human health, and they can remain 

dangerous for thousands of years.

The Savannah River Site’s tank waste also contains both radioactive and 

hazardous components in both liquid and solid form, as well as various 

metals.

• Radioactive component. The Savannah River Site’s waste contains 

about 60 radioactive constituents. As in the case at the Hanford Site, 

about 96 percent to 98 percent of the radioactivity comes from 

strontium-90 and cesium-137. Long-lived constituents—such as 

technetium-99 and iodine-129—account for about 1 percent of the 

radioactivity.

• Hazardous component. The tanks also contain hazardous chemical 

waste. Before waste generated during reprocessing was transferred 

to the tank farms, a chemical called sodium hydroxide was added to 
Page 8 GAO-17-306 Nuclear Waste

the waste to neutralize acids.14 One tank also contains organic 

constituents that were added during a demonstration project.

At both the Hanford and Savannah River Sites, DOE’s plan for treating its 

tank waste resulting from reprocessing centers on separating the various 

components of the waste so that the majority of the key or highly 

radioactive radionuclides are retained in the portion managed as HLW 

and the remainder are managed as low-level waste, where DOE makes a 

determination to that effect under applicable procedures. Waste that DOE 

determines can be managed as low-level waste is called waste incidental 

to reprocessing.

Table 1 describes the two main types of radioactive mixed waste 

contained in tanks at DOE’s Hanford and Savannah River Sites.

 14Reprocessing extracts isotopes from spent (or used) nuclear fuel so they can be used

again as reactor fuel.
Page 9 GAO-17-306 Nuclear Waste

Table 1: Types of Radioactive Mixed Waste Contained in Tanks at the Department of Energy’s Hanford and Savannah River 

Sites

Waste Type Description

High-level waste (HLW) HLW is defined by the Nuclear Waste Policy Act as (1) the highly radioactive material resulting 

from the reprocessing of spent nuclear fuel, including liquid waste produced directly in 

reprocessing and any solid material derived from such liquid waste that contains fission products 

in sufficient concentrations; and (2) other highly radioactive material that NRC, consistent with 

existing law, determines by rule requires permanent isolation.a

Low-activity waste (LAW) The term “low-activity waste” is not specifically defined in statute or regulation.b It is DOE’s term 

for the portion of tank waste with low levels of radioactivity. LAW is primarily the portion of the tank 

waste that remains after as much radioactive material as technically and economically practical 

has been separated. At the Hanford and Savannah River Sites, DOE estimates that LAW contains 

less than 10 percent of the radioactivity of the tank waste but more than 90 percent of the tank 

waste by volume, according to DOE.

Source: GAO analysis of Department of Energy (DOE) documents and the Nuclear Waste Policy Act. | GAO-17-306

a

42 U.S.C. § 10101(12).

b

Specifically, DOE uses the term “low-activity waste” to mean the waste that remains after as much 

radioactivity as technically and economically practical has been separated from the tank waste that, 

when solidified, may be disposed of as low-level radioactive waste in a near-surface facility. In 1997, 

DOE requested the Nuclear Regulatory Commission (NRC) to review DOE’s proposal to vitrify 

Hanford’s LAW. Based on the information available at the time, NRC reviewed DOE’s proposal, 

including the anticipated concentrations of radionuclides in the resultant waste, and determined that if 

the waste was vitrified, it would meet one of NRC’s criteria for being considered waste incidental to 

reprocessing. If DOE decided to use a different waste treatment process for the LAW, it was to reinitiate consultations with NRC staff.

The treatment and disposal of tank waste at DOE sites are governed by a 

number of federal laws—some of which establish state responsibilities—

that define the roles of federal agencies and states in managing mixed 

waste, as well as cleanup agreements among DOE, EPA, and the 

relevant state that implement these laws.

Radioactive components of the tank waste are regulated primarily by 

DOE under the Atomic Energy Act of 195415 and the Nuclear Waste 

Policy Act of 1982.16 These acts define HLW to include (1) the highly 

radioactive waste material resulting from the reprocessing of spent 

nuclear fuel, including liquid waste produced directly in reprocessing and 

any solid material derived from such liquid waste that contains fission 

products in sufficient concentrations; and (2) other highly radioactive 

material that is determined, consistent with existing law, to require 

permanent isolation. Under the Nuclear Waste Policy Act, DOE must 

 1542 U.S.C. § 2011 et. seq.

1642 U.S.C. § 10101 et. seq.

Regulatory Framework 

Governing DOE’s Tank 

Waste
Page 10 GAO-17-306 Nuclear Waste

send HLW to a geologic repository for disposal. The act does not 

establish a specific disposal path for radioactive waste other than HLW.

Hazardous components of the tank waste are regulated by EPA under the 

Resource Conservation and Recovery Act (RCRA) or, under limited 

circumstances, the Clean Water Act.17 Where EPA has authorized states 

to implement hazardous waste programs, those state programs operate 

in lieu of the federal programs.18

• RCRA. Under RCRA, high-level mixed waste—waste with a 

hazardous component regulated under RCRA and a radioactive 

component regulated under the Atomic Energy Act—that was 

generated during the reprocessing of fuel rods must be vitrified prior 

to disposal.19 Other mixed waste must generally be physically, 

chemically, and/or thermally treated to substantially diminish its 

toxicity or to reduce the mobility of the hazardous constituents 

according to waste-specific regulatory levels. This waste may then be 

disposed of in a near-surface landfill meeting requirements 

established under RCRA, including that it have a double liner and a 

leachate collection system, which collects any liquids that leach from 

the disposal unit.

 17RCRA regulations governing the treatment, storage, and disposal of hazardous waste 

generally do not apply to wastewater treatment units, defined to include units that (1) are 

part of a wastewater treatment facility that is subject to regulation under the permit 

provisions of the Clean Water Act; (2) receive and treat or store influent wastewater that is 

a hazardous waste; and (3) meet the definition of a tank or tank system under RCRA. See 

40 C.F.R. § § 260.10, 264.1(g)(6).

18Under RCRA, EPA may authorize a state to implement its own hazardous waste 

management program in lieu of the respective federal program, so long as the state 

program is at least as stringent. State programs may be more stringent than the federal 

program. EPA has authorized Washington and South Carolina to administer their own 

hazardous waste programs.

19Specifically, the hazardous component of mixed waste is subject to applicable RCRA 

requirements, which include compliance with land disposal restrictions. This means that 

generated waste must be treated to specific regulatory levels or according to specified 

methods of treatment prior to land disposal. Treatment either substantially decreases the 

toxicity of the mixed waste or reduces the likelihood that hazardous constituents (e.g., 

metals) will migrate from the mixed waste and contaminate the environment. Under 

RCRA’s land disposal requirements program, certain mixed wastes have specific 

treatment standards. For example, radioactive high-level wastes generated during the 

reprocessing of fuel rods that exhibit specified hazardous waste characteristics must be 

vitrified in compliance with all applicable radioactive protection requirements under control 

of NRC before the waste can be land disposed. 40 C.F.R. § § 268.42, 268.40(a).
Page 11 GAO-17-306 Nuclear Waste

• Clean Water Act. Under the Clean Water Act, the discharge of 

pollutants from certain sources, such as industrial facilities, into U.S. 

waters is prohibited without a permit; facilities obtain permits from 

authorized states or from the applicable EPA region. Wastewater 

treatment facilities are among the facilities regulated under the Clean 

Water Act.

The Federal Facilities Compliance Act of 1992 specifically made federal 

facilities, including DOE sites, subject to state hazardous waste 

regulations described below.20

• The Hanford Site. Under RCRA, EPA has authorized the state of 

Washington to administer its own hazardous waste regulatory 

program. The state has issued a dangerous waste permit under its 

authorized RCRA program that establishes requirements for the 

treatment, storage and disposal of mixed waste, including the 

construction and operation of the WTP complex.21 As previously 

noted, many of DOE’s activities at Hanford are carried out under the 

Hanford Federal Facility Agreement and Consent Order among DOE, 

EPA, and the Washington State Department of Ecology. Commonly 

called the Tri-Party Agreement (TPA), this document was signed in 

May 1989 and has been amended numerous times since then. The 

document lays out a series of legally enforceable milestones for 

completing major activities in Hanford’s waste treatment and cleanup

process. In 2010, DOE entered into an agreement, called a Consent 

Decree, to resolve a lawsuit by the state of Washington. The 2010 

Consent Decree required DOE to retrieve waste from 19 tanks and 

 2042 U.S.C. § 6961.

21Washington issued this site-wide permit under the state’s Hazardous Waste 

Management Act and associated regulations. Rev. Code Wash. Title 70, Ch. 70.105; 

WAC Ch. 173-303. The permit is currently undergoing revision.
Page 12 GAO-17-306 Nuclear Waste

begin operating the WTP and treating waste by 2022.22 In 2016, the 

relevant federal district court amended the Consent Decree by 

revising the schedule for startup and commissioning of the WTP, 

modifying tank waste retrieval milestones and enhancing DOE’s 

reporting obligations under the Decree. Under this Amended Consent 

Decree, DOE must complete the specified tank waste retrievals for 12 

tanks by March 2024 and must achieve initial plant operations of the 

WTP by the end of 2036.

• The Savannah River Site. Under RCRA, EPA has authorized the 

state of South Carolina to administer its own hazardous waste 

regulatory program. The state of South Carolina elected to manage 

DOE’s tanks at the Savannah River Site as wastewater treatment 

units under the Clean Water Act, an option that RCRA regulations 

authorize under certain conditions.23 Cleanup at the Savannah River 

Site is carried out under industrial wastewater permits issued by the 

state of South Carolina; a Site Treatment Plan approved by the state 

of South Carolina; the Consent Order for the treatment and disposal 

of mixed waste; and the 1993 Federal Facility Agreement among 

DOE, EPA, and the state of South Carolina.24 For example, DOE is 

 22See Consent Decree, Washington v. Chu, Civ. No. 08-05085 (E.D. Wash), October 25, 

2010, available at 

http://pdw.hanford.gov/arpir/index.cfm/viewDoc?accession=1011110420 (last visited April 

21, 2017). The TPA lays out a series of legally enforceable milestones for completing 

major activities in Hanford’s waste treatment and cleanup process. The purpose of the 

TPA is to ensure that Hanford cleanup activities comply with the Comprehensive 

Environmental Response, Compensation, and Liability Act; RCRA; and Washington’s 

Hazardous Waste Management Act. DOE entered into the TPA pursuant to the 

Comprehensive Environmental Response, Compensation, and Liability Act; Executive 

Order 12580; and the Atomic Energy Act of 1954. The TPA has been modified numerous 

times. The Consent Decree addresses a subset of these cleanup activities: completing the 

construction and achieving initial operations of the WTP and retrieving waste from 12 

single-shell tanks. The Consent Decree arose out of a lawsuit by the state alleging that 

DOE had missed, or was certain to miss, 10 TPA milestones related to WTP construction 

and tank waste retrieval and has been amended twice, both in 2016.

23See 40 C.F.R. § § 260.10, 264.1(g)(6).

24The Federal Facility Agreement lays out a series of legally enforceable milestones for 

the comprehensive remediation of the Savannah River Site. One of its purposes is to 

ensure that Savannah River Site cleanup activities comply with RCRA and the 

Comprehensive Environmental Response, Compensation, and Liability Act. The Federal 

Facility Agreement specifies milestones for the removal of waste from, and operational 

closure of, tanks, which do not meet full secondary containment standards specified in the 

Federal Facility Agreement. The Federal Facility Agreement has been modified several 

times. According to DOE, it has operationally closed 8 of the required 24 tanks.
Page 13 GAO-17-306 Nuclear Waste

required to complete tank waste treatment at the Savannah River Site 

by 2028.

At Hanford, DOE plans to dispose of vitrified LAW in an on-site landfill 

called the Integrated Disposal Facility. At the Savannah River Site, DOE 

disposes of grouted LAW on site in large concrete structures called 

saltstone disposal units. DOE has used two processes to determine that 

portions of its tank waste can be managed as low-level waste (referred to 

as a determination that the waste is incidental to reprocessing).

• DOE Order. DOE Order 435.1 and Manual 435.1-1 provide that DOE 

can manage tank wastes as waste incidental to reprocessing if, 

among other things, the wastes have been processed to remove 

radionuclides to the maximum extent practicable and will be managed 

in a manner comparable to the performance objectives established in 

Nuclear Regulatory Commission (NRC) regulations for the nuclear 

waste disposal facilities.25

• Section 3116. Section 3116 of the National Defense Authorization Act 

for fiscal year 2005 authorizes the Secretary of Energy, in consultation 

with NRC, to determine that certain waste from reprocessing is not 

HLW if it meets the criteria set forth in that section: that it does not 

require disposal in a deep geologic repository, has had highly 

radioactive radionuclides removed to the maximum extent practical, 

meets concentration limits and/or dose-based performance objectives 

for near-surface disposal of radioactive waste set out in subpart C of 

part 61 of title 10, Code of Federal Regulations, and will be disposed 

of pursuant to a state-issued permit or state-approved closure plan.26

Section 3116 applies only to Idaho and South Carolina.

 25Under Order 435.1, DOE manages waste incidental to reprocessing as either low-level 

waste or transuranic waste based on the waste’s specific radioisotopic inventory. DOE 

defines transuranic waste as waste that is contaminated with alpha-emitting radionuclides 

(greater than uranium on the periodic table) with half-lives greater than 20 years and 

concentrations greater than 100 nanocuries per gram.

26Pub. L. No. 108-375, Div. C, Title XXXI, § 3116, 118 Stat. 2162 (2004). As noted above, 

HLW is the highest-activity primary waste that results from reprocessing spent nuclear 

fuel. It must be disposed in a deep geologic repository licensed by NRC. Under Section 

3116, on the other hand, DOE may dispose of its low-level waste in a near-surface DOE 

facility subject to state approval and NRC monitoring, but not subject to NRC licensing.

LAW Disposal

West Valley Demonstration Project: 

Example of DOE’s Treatment of LowActivity Waste with Grout 

From 1966 to 1972, Nuclear Fuels Services 

operated the Western New York Nuclear 

Service Center—later renamed the West 

Valley Demonstration Project—in West Valley, 

New York. This is the only commercial spent 

nuclear fuel reprocessing plant to have 

operated in the United States. Spent fuel is 

the used fuel removed from nuclear power 

plants. Nuclear Fuels Services reprocessed 

this fuel to recover uranium and plutonium to 

be used again as reactor fuel. During 

operations, the plant generated 660,000 

gallons of liquid high-level waste (HLW) that 

was stored in two underground storage tanks. 

In 1988, the Department of Energy (DOE) 

began to separate out the low-activity portion 

of the tank waste to reduce the amount of 

waste to be vitrified. To treat this low-activity 

waste (LAW), DOE mixed it with grout and 

poured it into square drums. Treatment was 

completed in 1995. The drums containing 

treated, cemented waste were shipped to,

and disposed of at, the Nevada National 

Security Site. After completing treatment of 

the LAW, DOE vitrified the remaining HLW, 

which is stored on site until a geologic 

repository becomes available for its 

permanent disposal. 

DOE officials explained that DOE chose to 

mix the LAW with cement because it would 

minimize the amount of tank waste to be 

vitrified, thereby reducing costs. According to 

DOE officials, it cost $216.2 million to produce 

19,900 70-gallon drums of grouted LAW, and 

$616.8 million to produce 275 canisters of

vitrified HLW (roughly 1/20th the volume of the 

treated LAW). 

Sources: GAO analysis of DOE documents and data and 

interviews with DOE officials. Image source: DOE. | GAO17-306
Page 14 GAO-17-306 Nuclear Waste

DOE’s requirements and NRC guidance establish different periods of 

performance for low-level waste disposal.

• DOE requirement. According to DOE Manual 435.1-1, a low-level 

waste disposal site must conduct a performance assessment 

demonstrating that the site meets DOE performance objectives, 

including demonstrating that the dose to a member of the public will 

not exceed 25 millirems from all exposure pathways during any 1 

year, over the course of a 1,000-year post-closure period. DOE 

officials told us that this requirement for low-level waste disposal 

applies to the treatment and disposal of Hanford’s LAW, and waste 

from reprocessing will only be disposed of as low-level waste if a 

determination under Order 435.1 has been issued. Hanford intends to 

dispose of this treated low-level waste at its on-site Integrated 

Disposal Facility.

• NRC guidance. The 2004 legislation authorizes DOE to manage 

certain waste at its Savannah River and Idaho Sites as low-level 

waste. According to NRC guidance implementing Section 3116, NRC 

recommends using a 10,000-year period of performance. DOE used 

the 10,000-year period of performance in its 2012 EIS on the Hanford 

Site for its assessment of the long-term impacts for groundwater, 

human health, and ecological risks. NRC is currently considering 

changing its period of performance.27

 27In 2016, NRC staff issued a draft final rule that would provide for either a 1,000-year or 

10,000-year compliance period—depending on the quantities of long-lived radionuclides 

that have been or plan to be disposed of at the site—followed by a performance period. 

According to NRC staff, for waste incidental to reprocessing, most waste forms would be 

expected to contain significant quantities of long-lived radionuclides, and therefore, a 

10,000-year compliance period would most likely be used. For sites using a 10,000-year 

performance period—because the waste contains significant quantities of long-lived 

radionuclides—the draft final rule would also establish a post-10,000-year performance 

period to evaluate how the disposal system could mitigate the risk from the disposal of 

significant quantities of long-lived radionuclides after the compliance period. NRC has not 

yet taken a vote on the draft final rule.
Page 15 GAO-17-306 Nuclear Waste

DOE chose to treat LAW differently at the Savannah River and Hanford 

Sites—with grout at the Savannah River Site and with vitrification at 

Hanford—primarily to address input from South Carolina and Washington, 

respectively, and the different environmental laws that state regulators 

chose to apply to tank waste management at each site. DOE chose to 

grout LAW at its Savannah River Site because the state viewed grout as 

a method that would allow DOE to treat LAW sooner than other methods, 

thereby reducing environmental and human health risks posed by 

prolonged waste storage in the tanks. DOE chose to vitrify Hanford’s 

LAW primarily because, in studies conducted at the time, vitrification was 

shown to perform better (i.e., more effectively immobilize the waste) than 

grout for disposal in the environmental conditions at the Hanford Site. 

DOE’s choice was also influenced by input from EPA and the state of 

Washington, as well as public concerns about the long-term effectiveness 

of grout. DOE has not formally selected a treatment method for 

supplemental LAW—the portion of the LAW not currently planned to be

treated in the WTP.

According to officials from the Savannah River Site, DOE chose to grout 

LAW at the Savannah River Site for several reasons, primarily because 

DOE had determined that grouted LAW would meet human health and 

environmental requirements and because DOE could treat LAW sooner 

with grout than with other methods, thereby reducing the risk to 

groundwater posed by possible leaks in the underground tanks.28

According to DOE officials, DOE found that grout was safe for human 

health and the environment and met applicable environmental 

 28At the Savannah River Site, LAW is called “salt waste,” but for the purpose of this report, 

we refer to it as LAW. The Savannah River Site uses a grout mixture, called “saltstone,”

but for the purpose of this report, we refer to it as grout. Also, as previously noted, at its 

Savannah River Site, DOE refers to the low-activity portion of its waste as low-level waste 

or “salt waste.” For the purpose of this review, we refer to the low-activity portion of the 

waste at both the Hanford and Savannah River Sites as LAW.

DOE Chose Different 

Treatment 

Approaches at the 

Savannah River and 

Hanford Sites 

Primarily to Address 

Different State Input

DOE Chose to Grout LAW 

at the Savannah River Site 

Primarily Because of the 

State’s Desire to Address 

Environmental Risks 

Sooner Than It Could 

Using Other Methods
Page 16 GAO-17-306 Nuclear Waste

requirements, as described in its 1982 EIS for the Savannah River Site.29

DOE documents30 stated that grouted LAW would safely retain hazardous 

constituents at levels below EPA’s current drinking water standards for at 

least 1,000 years.31

South Carolina chose a legal approach that gave DOE the flexibility to 

use grout, according to an official from the South Carolina Department of 

Health and Environmental Control. Specifically, South Carolina chose to 

permit the tanks and waste treatment facilities separately from the

disposal site. The site’s LAW treatment facilities are permitted as 

wastewater facilities under the Clean Water Act because, according to 

this official, the Clean Water Act is more flexible and would allow DOE to 

treat the waste faster than RCRA would allow, while still achieving the 

same environmental safeguards as RCRA would have required.32

According to this official, one of the state’s top priorities was for DOE to 

begin treatment as soon as possible and remove the liquid waste from the 

tanks to reduce the risk to groundwater at the site from potential leaks in 

the underground tanks. This official noted that by using grout, DOE was 

able to begin treatment sooner and at a lower cost than if it had used a 

more complicated treatment approach, such as vitrification.

DOE officials told us that as they learned more about the performance of 

grout at the Savannah River Site, they added additional safeguards to the 

disposal site to ensure that human health and the environment would be 

protected from contaminant exposure over the long term. For example, in 

1988, DOE research identified the potential for nitrates—a hazardous 

contaminant of concern in LAW—to leach from grout when it was poured 

into underground trenches at the site. In response, DOE added 

engineered barriers—which are structures intended to improve the 

 29Department of Energy, Final Impact Statement Defense Waste Processing Facility, 

Savannah River Plant, Aiken, S.C., DOE/EIS-0082 (Washington, D.C.: February 1982).

30Department of Energy, Final Supplemental Environmental Impact Statement Defense 

Waste Processing Facility, DOE/EIS-0082-S (Washington, D.C.: November 1994); 60 

Fed. Reg. 70 (Apr. 12, 1995). The 1995 Record of Decision stated that the peak 

radiological dose from groundwater contamination would occur 2,000 years after closure 

and would be 100 times less than current EPA dose limits for drinking water.

31According to DOE Manual 435.1-1, a low-level waste disposal facility must conduct a 

performance assessment demonstrating that the site meets DOE performance objectives, 

such as the dose to the public not exceeding 25 millirems from all exposure pathways 

during any 1 year, over a 1,000-year post-closure period.

32See 40 C.F.R. § § 260.10, 264.1(g)(6).

Idaho National Laboratory: Example of 

How DOE will Treat the Site’s Liquid HighLevel Waste with the Integrated Waste 

Treatment Unit

The Department of Energy (DOE) does not 

have low-activity waste (LAW) at its Idaho Site 

because it did not separate out a lower activity 

portion from the site’s high-level waste (HLW). 

DOE officials stated that they will have to 

petition the Environmental Protection Agency 

to be able to consider any disposal method 

other than vitrification because only 

vitrification has been demonstrated to meet 

Resource Conservation and Recovery Act

requirements for high-level mixed waste

disposal. At the Idaho Site, 11 underground 

stainless steel tanks originally stored about 9 

million gallons of HLW. This waste was 

primarily liquid and resulted from reprocessing 

spent nuclear fuel for defense and other 

purposes. DOE treated nearly 8 million 

gallons of the liquid waste through a process 

called calcination, which converts liquid waste 

to a granular solid form. The calcined waste is 

currently stored on site in 43 bins where,

according to a DOE official, it is awaiting final 

treatment with another process that has not 

yet been determined. 

About 900,000 gallons of liquid waste remain 

in 3 tanks. DOE plans to treat the remaining 

waste in the tanks using a process called 

steam reforming. DOE is currently 

constructing a facility called the Integrated 

Waste Treatment Unit for this purpose. This 

first-of-a-kind facility will dry the liquid waste 

into a solid granular material. The treated 

waste will then be packaged into stainless 

steel containers and transported out of state 

for final disposal. 

Sources: DOE and Idaho state documents and interviews 

with Idaho National Laboratory official. Image source: DOE. | 

GAO-17-306
Page 17 GAO-17-306 Nuclear Waste

disposal site’s ability to retain waste—to the Savannah River Site’s waste 

disposal approach, rather than pouring the treated waste into trenches.33

Later DOE studies confirmed that grouted LAW would meet human health 

and environmental safety requirements, particularly when the engineered 

barriers were used for disposal of the treated waste.34 According to DOE 

officials, DOE has evaluated the effects of multiple barriers, both 

collectively and independently, to provide reasonable assurance that 

DOE’s performance objectives will be met to protect human health and 

the environment.35 The barriers evaluated include the grout waste form, 

engineered disposal structures, closure caps, and the natural 

environment. In a 2016 study conducted at the Savannah River Site, DOE 

predominantly affirmed assumptions used in earlier contaminant leaching 

models that found contaminants would be safely contained for the 1,000-

year period of performance.36

Another factor also influenced the department’s decision to grout LAW at 

the Savannah River Site, according to a DOE official. DOE already had 

some infrastructure that had previously been used to grout other wastes 

at the site, and that infrastructure could be used to grout the LAW. For 

example, DOE treated contaminated soils from its nuclear materials 

production program with grout.37 Already having certain infrastructure in 

place made it more cost-effective and faster to begin waste treatment with 

grout than to build a new facility to vitrify LAW or pursue another 

alternative.

 33The Savannah River Site currently uses an engineered barrier called a saltstone 

disposal unit, which is a large, cylindrical concrete tank—about 150 feet in diameter—

intended to keep precipitation from reaching the grout.

34See, for example, Department of Energy, Savannah River Site Salt Processing 

Alternatives Final Environmental Impact Statement, DOE/EIS-0082-S2 (Aiken, SC: June 

2001); Department of Energy, Supplement Analysis Salt Processing Alternatives at the 

Savannah River Site, DOE/EIS-0082-S2-SA-01 (Aiken, SC: January 2006); and Savannah 

River Remediation, Performance Assessment for the Saltstone Disposal Facility at the 

Savannah River Site, SRR-CWDA-2009-00017 (Aiken, SC: October 2009).

35Savannah River Remediation LLC, FY2014 Special Analysis for the Saltstone Disposal 

Facility at the Savannah River Site, SRR-CWDA-2014-00006, rev. 2 (Aiken, SC: 

September 2014).

36Savannah River Remediation LLC, Property Data for Core Samples Extracted from SDU 

Cell 2A, SRR-CDWA-2016-00051 (Aiken, SC: April 2016).

37Contaminated soils in the Old F-Area Seepage Basin were stabilized in-situ with grout.
Page 18 GAO-17-306 Nuclear Waste

DOE chose in 1994 to vitrify the LAW at Hanford in part because studies 

from the early 1990s showed that vitrification would be safer for long-term 

disposal than grout, given the conditions at the Hanford Site.38 DOE’s 

choice was also influenced by input from the state of Washington, and to 

a lesser extent from EPA in its role of providing support to and oversight 

of the state’s authorized RCRA program, as well as public concerns about 

the long-term effectiveness of grout. According to DOE and Washington 

State Department of Ecology documents, vitrification was viewed as 

preferable to grout for several reasons.

• Ability of grout to set. In the early 1990s,39 the state identified 

technical concerns with the ability of grout to set properly or uniformly 

because of the heat released by radioactive constituents within the 

grout.40

• Volume of waste. The state also raised concerns in the early 1990s 

that grout would produce a larger volume of waste that would need to 

be disposed of than vitrification would. This would have resulted in the 

need to use a larger area of land to dispose of the waste. In turn, local 

governments, tribes, and regional groups expressed concerns about 

possible restrictions on future land use at the site if grout was used 

and disposed of at Hanford.

• Ease of retrieval. The state conveyed public concerns that it would 

be more difficult to retrieve grouted waste than vitrified waste.41

 38Since plutonium production ended at Hanford in the late 1980s, DOE has tried 

developing various approaches for treating and disposing of its tank waste. In 1989, 

DOE’s initial strategy called for treating only the waste in the double-shell tanks—the HLW 

would have been vitrified, and the LAW would have been grouted. In 1993, DOE 

developed a new strategy aimed at treating the waste in all 177 tanks with vitrification, but 

DOE found that the planned treatment facility would not have had sufficient capacity to 

treat all the waste in a time frame acceptable to EPA and the Washington State 

Department of Ecology. In 1994, the TPA was amended to reflect a new goal of vitrifying 

both the LAW and HLW, instead of treating the LAW with grout.

39Washington State Department of Ecology, History of Grout as Waste Form for Hanford 

Tank Waste White Paper (Richland, WA: February 2015).

40We previously reported on the problems that DOE had at Rocky Flats in Colorado with 

mixing cement to treat pond sediment contaminated by radioactive material, nitrates, and 

heavy metals. This material, known as pondcrete, was improperly mixed and did not set 

properly, resulting in pondcrete blocks that crumbled, cracked, and were soft enough to be 

dug into with a stick. See GAO, Nuclear Health and Safety: Problems Continue for Rocky 

Flats Solar Pond Cleanup Program, GAO/RCED-92-18 (Washington, D.C.: Oct. 17, 1991).

41Washington State Department of Ecology, “Agencies Propose Changes to the Tri-Party 

Agreement,” Hanford Update, vol. 5, no. 1 (1993).

DOE Chose to Vitrify a 

Portion of LAW at Hanford 

Largely Because Initial 

Studies Showed It to Be 

Safer Than Other Methods
Page 19 GAO-17-306 Nuclear Waste

Members of the public wanted DOE to have the ability to retrieve 

waste if DOE developed more advanced treatment methods in the 

future or if the waste form failed.42

• Safety. One 1995 study indicated that vitrified waste was more likely 

than grouted waste to retain radioactive and hazardous constituents.43

Specifically, vitrified waste was the best-performing waste form during 

leach testing and was less likely to be considered a “hazardous 

waste” under RCRA because vitrification would destroy hazardous 

organic constituents. In addition, several communities in Washington 

and Oregon expressed concern that their groundwater could be 

affected by certain radioactive and hazardous constituents leaching 

from grout.

It is unclear to what extent costs were considered in DOE’s 1994 decision 

to choose vitrification over grout for Hanford LAW. Various studies 

conducted around that time and since then have provided differing 

information on the cost of grout compared with the cost of vitrification.

• A 1995 Westinghouse report reviewed alternatives for treating all of 

Hanford’s LAW.44 This report concluded that vitrification was the best 

treatment option when risk, cost, and other factors were considered. 

Among other things, the report found that grout and vitrification both 

adequately met NRC’s environmental requirements for disposal but 

that vitrification would perform better. In addition, the report noted that 

grout would cost about $1 billion less than vitrification over the 

lifecycle of treatment, but the report concluded that vitrification would 

be more cost effective because the contractor that produced the study 

believed that grout would require an extensive pretreatment process 

 42Any repository constructed on a site approved under the Nuclear Waste Policy Act must 

be designed and constructed to permit spent nuclear fuel retrieval for any reason 

pertaining to public health and safety or the environment, among other reasons, during 

operation of the facility. According to Hanford officials, there is no requirement for 

Hanford’s LAW to be retrievable.

43Westinghouse Hanford Company, Evaluation of Low-Level Waste Forms for 

Immobilization of Hanford Site Tank Wastes, WHC-SD-WM-ES-319 (Richland, WA: June 

1995).

44Evaluation of Low-Level Waste Forms for Immobilization of Hanford Site Tank Wastes. 

The Westinghouse report compared three treatment approaches: glass, grout, and 

polyethylene—a process in which the waste is dried to a powder and then mixed with 

molten polyethylene, a plastic, and cast into containers for final disposal.
Page 20 GAO-17-306 Nuclear Waste

to separate certain radioactive constituents from LAW, which was not 

included in the cost estimate.45

• In 2003, DOE’s Office of River Protection analyzed alternatives for 

treating all of Hanford’s LAW under three scenarios: all grout, all 

vitrification, or a combination of both.46 This study found that all 

vitrification was the most cost-effective approach. The study found 

that the higher cost to grout the waste was largely driven by the costs 

associated with stopping the current approach of vitrifying LAW and 

switching to a new approach.

• Another 2003 study by a DOE contractor compared three different 

potential treatment approaches for a portion of Hanford’s LAW.47 This 

report found that grout was the least expensive approach from the 

standpoint of designing, constructing, and operating the treatment 

facilities, but when transportation to the disposal site and disposal 

costs were included, grout would cost approximately $100 million to 

$200 million more than the other alternatives.

• Finally, DOE’s 2012 EIS examined four technologies, including grout 

and vitrification, for treating Hanford’s supplemental LAW,48 and our 

analysis of the information provided in the EIS found that grouting the 

supplemental LAW could cost about $2.6 billion less than vitrifying it.49

 45The cost figure is in 1995 dollars.

46Department of Energy, Assessment of Low-Activity Waste (LAW) Treatment and 

Disposal Scenarios for the River Protection Project (Richland, WA: Apr. 14, 2003).

47CH2M HILL Hanford Group, Inc., Draft Supplemental Technologies Cost Summary 

Report (Richland, WA: Sept. 19, 2003). The CH2M HILL report compared three treatment 

approaches: cast stone (grout), bulk vitrification, and steam reforming. The bulk 

vitrification process would convert LAW into solid glass by drying the waste, mixing it with 

Hanford soils, and applying an electric current within a large steel container. Steam 

reforming is a process that dries liquid waste into a solid granular material.

48Department of Energy, Final Tank Closure and Waste Management Environmental 

Impact Statement for the Hanford Site, Richland, Washington, DOE/EIS-0391 (Benton 

County, WA: November 2012).

49Estimated cost differences have been inflation-adjusted to fiscal year 2015 dollars. The 

estimated cost difference included about $806 million in reduced pre-treatment storage 

costs, $45 million in reduced retrieval costs because of more rapid treatment completion 

with the grouting alternative, and $1.8 billion in reduced treatment plant construction and 

operations costs for the LAW grouting alternative relative to the vitrification-only 

alternative. Disposal costs for the LAW grouting alternative would be $89 million higher 

than for the vitrification-only alternative, according to DOE’s estimates.
Page 21 GAO-17-306 Nuclear Waste

Other factors may have also influenced DOE’s decision to vitrify LAW at 

the Hanford Site. For example, in its foreword to the 2012 EIS, the 

Washington State Department of Ecology noted that in the mid-1990s 

DOE delayed construction of Hanford’s vitrification facility because other 

DOE sites were competing for the same budgetary resources.50 Officials 

from the Washington State Department of Ecology told us that they 

agreed to accept a delay in treating Hanford’s tank waste and, in 

exchange, DOE committed to the Washington State Department of 

Ecology that it would vitrify Hanford’s LAW in light of public concerns 

about the use of grout.

According to DOE documents and officials, DOE has not selected a 

treatment method for the supplemental LAW—the portion of the LAW that 

cannot be treated in the WTP as it is currently designed. As previously 

discussed, the WTP is currently designed to treat only one-third to onehalf of Hanford’s LAW, meaning that DOE will have to modify the WTP or 

build another facility to treat the supplemental LAW, whether or not 

vitrification is chosen as the treatment method. In its Record of Decision 

accompanying its 2012 EIS, DOE discussed four alternatives for 

supplemental LAW treatment, including vitrification and cast stone, which 

is a form of grout.51 DOE stated that it had not selected a method for 

treating supplemental LAW and that it would be beneficial to further study 

the potential cost, safety, and environmental performance of technologies 

to treat supplemental LAW.52

There is disagreement, however, between DOE and the state of 

Washington about whether DOE has the legal authority to select a 

treatment method other than vitrification for supplemental LAW. 

Washington state officials told us that they acknowledge that DOE has 

not yet selected a supplemental treatment method, but in the foreword to 

the 2012 EIS, the Washington State Department of Ecology stated that 

glass is the only acceptable waste form for immobilized LAW that is going 

to be disposed of at Hanford. The foreword states that the 2012 EIS 

 50Final Tank Closure and Waste Management Environmental Impact Statement for the 

Hanford Site, Richland, Washington.

51DOE also analyzed bulk vitrification and steam reforming.

52Department of Energy, Record of Decision: Final Tank Closure and Waste Management 

Environmental Impact Statement for the Hanford Site, Richland, Washington, 78 Fed. 

Reg., 75913 (Dec. 13, 2013).

DOE Has Not Yet Chosen 

a Waste Treatment 

Approach for 

Supplemental LAW at 

Hanford
Page 22 GAO-17-306 Nuclear Waste

clearly supports vitrification as the only environmentally protective option 

for treating supplemental LAW and that the Washington State Department 

of Ecology therefore disagrees with DOE’s decision not to identify a 

treatment method for supplemental LAW. Further, the Washington State

Department of Ecology states that it believes the cost comparisons in the 

EIS show that all the various options are similar in cost, so any 

assumptions about potential cost savings in choosing other treatment 

options are invalid.

Regardless of uncertainty about DOE’s ability to consider alternative 

options, the TPA requires DOE to take a set of specific actions in 

selecting a treatment method for supplemental LAW. Specifically, the 

TPA required DOE to select a treatment method for supplemental LAW 

no later than April 30, 2015. However, DOE has not yet selected a 

treatment method, and this issue is currently in a dispute resolution 

procedure between DOE and the state of Washington. Negotiations 

began on September 8, 2016, on a number of milestones that require 

negotiation within 6 months after DOE’s System Plan is updated, 

including the DOE decision on supplemental treatment. DOE has 

proposed setting a deadline of April 30, 2018, for the completion of the 

negotiations related to this milestone in order to be consistent with other 

agreements, allowing for 6 months after its System Plan is updated for 

negotiations to be completed. The TPA requires that the next revision to 

DOE’s System Plan—which is scheduled to be released by October 31, 

2017—outline specific options for treating supplemental LAW.53 For 

example, vitrification options could include modifying the WTP to increase 

capacity to treat supplemental LAW or building another vitrification facility 

to treat the supplemental LAW. According to DOE officials, DOE may also 

consider other treatment options, such as grout. The waste treatment 

schedule for supplemental LAW has yet to be finalized, but a senior DOE 

 53The primary purpose of the System Plan at Hanford is to evaluate scenarios, including 

underlying assumptions, selected and defined by DOE and the Washington State 

Department of Ecology, for the disposition of all tank waste. As noted above, DOE and the 

state of Washington disagree on whether these options can include waste treatment 

methods other than vitrification. 
Page 23 GAO-17-306 Nuclear Waste

official told us that if DOE must vitrify supplemental LAW, completing 

treatment will take at least until 2061.54

In considering different approaches to treating supplemental LAW at 

Hanford, DOE faces regulatory and legal challenges. Specifically, DOE 

may be limited in its ability to employ different treatment methods unless it 

succeeds in managing some tank waste as low-level waste.55 DOE’s 

authority to apply Order 435.1 and the associated manual to certain tank 

waste in Idaho was challenged in a 2002 lawsuit.

56 The federal district 

court held that the relevant provisions of the Order and Manual were 

inconsistent with the Nuclear Waste Policy Act, but a federal appeals 

court reversed that decision on procedural grounds in October 2004 and 

ordered dismissal of the suit without ruling on the underlying claim. While 

the 2002 litigation was pending, DOE sought legislation clarifying its 

authority to manage portions of tank waste that have low levels of 

radioactivity as low-level waste. In response, Congress passed Section 

3116 of the National Defense Authorization Act in October 2004. 

However, the legislation did not apply to Hanford. Our previous work has 

found that DOE could be open to further legal challenges if it attempts to 

use Order 435.1 to manage tank waste as low-level waste at Hanford.57

However, in commenting on a draft of this report, DOE noted that it has 

successfully used the Order 435.1 process twice since the 2002 lawsuit to 

determine that certain wastes associated with the West Valley 

Demonstration Project in New York can be managed as low-level wastes. 

As we have previously recommended, legislation specifically authorizing 

DOE to manage some of the waste at Hanford as low-level waste would 

 54Section 3134 of the National Defense Authorization Act for Fiscal Year 2017 contains a 

provision requiring DOE to enter into an arrangement with a federally funded research and 

development center to carry out an analysis of approaches for treating the portion of 

Hanford’s LAW currently intended for supplemental treatment. Pub. L. No. 114-328, § 

3134 (2016).

55Hanford officials told us that the site could classify certain tank waste as “transuranic”

waste. The word “transuranic” is used for elements that have atomic numbers greater than 

that of uranium. Transuranic waste could be treated and sent to the DOE Waste Isolation 

Pilot Plant near Carlsbad, New Mexico, which serves as the only deep geologic repository 

in the United States for the disposal of defense-related transuranic nuclear waste. 

56Natural Resources Defense Council v. Abraham, 271 F.Supp.2d 1260 (D. Idaho 2003), 

vacated as unripe 388 F.3d 701 (9th Cir. 2004).

57GAO, Nuclear Waste: Uncertainties and Questions about Costs and Risks Persist with 

DOE’s Tank Waste Cleanup Strategy at Hanford, GAO-09-913 (Washington, D.C.: Sept. 

30, 2009) and Nuclear Waste: Challenges to Achieving Potential Savings in DOE’s HighLevel Waste Cleanup Program, GAO-03-593 (Washington, D.C.: Jun. 17, 2003).
Page 24 GAO-17-306 Nuclear Waste

insulate DOE from legal challenges regarding its authority to make 

treatment decisions based on the actual radioactivity of the waste, which 

in turn could allow DOE to consider potentially less costly and less 

complicated treatment approaches for supplemental LAW.58

DOE has treated about 4 million gallons of LAW at its Savannah River 

Site but has not yet treated any tank waste at the Hanford Site.59 In 

addition, DOE is likely to complete its LAW treatment sooner, with fewer 

technical challenges, and at lower costs at the Savannah River Site than 

at Hanford.

DOE officials told us that it has grouted about 4 million gallons of the 

Savannah River Site’s approximately 36 million gallons of LAW since 

2007 and has disposed of this waste on site in large concrete vaults

pursuant to a determination DOE made under Section 3116 of the 

National Defense Authorization Act for Fiscal Year 2005.

60 DOE 

estimates that about 36 million gallons of waste remains in the Savannah 

River Site’s underground tanks, of which DOE estimates that about 32 

million gallons is LAW.61 DOE recently completed construction of a new 

 58See GAO-09-913 and GAO-03-593. DOE implemented two recommendations in 

GAO-09-913 but disagreed with our recommendation that they seek clarification from 

Congress about DOE’s authority at Hanford to determine whether some tank waste 

managed by DOE can be treated and disposed of as a waste type other than HLW. DOE 

implemented all three recommendations in GAO-03-593; however, the Hanford Site was 

not covered by Section 3116.

59The 4 million gallons represents waste that was originally in the tanks but that has now 

been treated. The treatment process necessarily increases the volume of the waste 

treated because water and other constituents are added during the process. 

Consequently, the total amount of LAW grouted at the Savannah River Site thus far is 

about 8.3 million gallons.

60As previously noted above, HLW is the highest-activity primary waste that results from 

reprocessing spent nuclear fuel. It must be disposed of in a deep geologic repository 

licensed by NRC. Under Section 3116, on the other hand, DOE may dispose of its lowlevel waste in a near-surface DOE facility subject to state approval and NRC monitoring, 

but not subject to NRC licensing.

61DOE has also treated about 4 million gallons of HLW at the Savannah River Site. DOE 

began treating this tank waste in 1996 by vitrifying it in a facility called the Defense Waste 

Processing Facility.

DOE Has Treated 

Some LAW at the 

Savannah River Site 

but None Yet at 

Hanford

DOE Is Successfully 

Treating LAW at the 

Savannah River Site but 

Has Not Yet Begun to 

Treat LAW at Hanford
Page 25 GAO-17-306 Nuclear Waste

waste processing facility—called the Salt Waste Processing Facility—that 

will replace the Savannah River Site’s existing facility and will process the 

remaining LAW faster than DOE could have done with the site’s existing 

facility.62 Specifically, this new facility is designed to remove most of the 

highly radioactive constituents—such as cesium and strontium—from the 

liquid waste, which according to agency officials, will enable DOE to treat 

the Savannah River Site’s waste more quickly.63

At the Hanford Site, DOE has not yet treated any of the approximately 54 

million gallons of radioactive waste stored in its 177 underground tanks. 

DOE has delayed the start of waste treatment numerous times, in part 

because of project management challenges.64 In 2000, DOE awarded a 

contract to Bechtel National, Inc., to design, construct, and commission a 

prototype plant to demonstrate the technology that was to treat 10 

percent of the waste by volume and 25 percent by radioactivity. At the 

time, DOE’s plans called for the WTP to begin treating waste in 2011 and 

complete waste treatment by 2028. In 2002, DOE began an initiative to 

accelerate the schedule for, and reduce the costs of, cleaning up 

radioactive and hazardous waste at its sites. This included increasing the 

WTP’s capacity to vitrify waste and using supplemental technologies to 

 62DOE’s existing LAW processing facility is known as the Actinide Removal Process and 

Modular Caustic Side Solvent Extraction Unit. DOE has finished construction of and has 

begun system testing for the new Salt Waste Processing Facility. DOE grouts its LAW in 

the Savannah River Site’s Saltstone Production Facility. 

63Once the tanks are empty, DOE plans to fill them with grout. To date, eight tanks have 

been grouted in this way.

64In 1993, we reported that DOE was moving ahead with design and site work for the 

vitrification facility before uncertainties were resolved and before a complete design was 

prepared. We recommended that DOE begin construction of the facility only after the 

design was sufficiently complete. GAO, Nuclear Waste: Hanford Tank Waste Program 

Needs Cost, Schedule, and Management Changes, GAO/RCED-93-99 (Washington, 

D.C.: Mar. 8, 1993). As we reported most recently in May 2015, DOE’s use of the designbuild approach—in which the construction, technology development activities, plant 

design, and construction occur simultaneously rather than sequentially—has led to cost 

and schedule overruns. DOE discourages use of this approach for complex, first-of-a-kind 

facilities but has continued to use it for the WTP. GAO, Hanford Waste Treatment: DOE 

Needs to Evaluate Alternatives to Recently Proposed Projects and Address Technical and 

Management Challenges, GAO-15-354 (Washington, D.C.: May 7, 2015).
Page 26 GAO-17-306 Nuclear Waste

treat LAW.65 However, DOE did not implement the acceleration initiative 

at the Hanford Site. In 2012, DOE stopped construction on parts of the 

WTP until the contractor could demonstrate that the systems were 

aligned with DOE nuclear safety requirements.66

In September 2013, DOE proposed the current waste treatment strategy, 

which is intended to allow some LAW to be treated before WTP’s 

technical challenges are resolved. This new strategy (known as directfeed LAW) includes the construction of a new LAW pretreatment system 

to directly feed a portion of Hanford’s LAW to the LAW treatment facility to 

be vitrified.67 According to DOE officials, direct-feed LAW will be used to 

treat about 13 million gallons of LAW, which represents about 25 percent 

of the total LAW to be treated. Nevertheless, DOE will still require the 

successful construction of the WTP and its specific components, such as 

the Pretreatment facility, to treat the remaining portion of LAW that was 

originally planned to be treated in the WTP. In addition, as previously 

discussed, DOE has not yet chosen a waste treatment approach for 

supplemental LAW—the LAW that the WTP was not designed to treat. 

See appendix II for an illustration of DOE’s proposed waste treatment 

plans at the Hanford Site and key facilities involved in each process, and 

see appendix III for a timeline of treatment plans at the Hanford Site.

Figure 1 provides an overview of the status of treatment at the Savannah 

River and Hanford Sites.

 65Under this initiative, Hanford tank waste treatment was planned to have been completed 

by 2028 and to cost up to $20 billion less than the estimated baseline. In its August 2002 

report, Performance Management Plan for the Accelerated Cleanup of the Hanford Site, 

DOE noted that many tanks contain wastes that are less well suited for vitrification 

because of high sulfate content, among other things. DOE also noted in this report that 

treating all of the LAW streams by vitrification has the potential to unnecessarily constrain 

the rate of waste treatment.

66DOE resumed construction on a portion of the WTP in 2014, but according to DOE 

officials, as of December 2016, construction had not yet fully resumed.

67The direct-feed LAW treatment process also requires DOE to build a new Effluent 

Management Facility to receive secondary waste—that is, waste generated during the 

treatment process—from the LAW treatment facility.
Page 27 GAO-17-306 Nuclear Waste

Figure 1: Overview of the Department of Energy’s Tank Waste Treatment Status and 

Approaches at the Hanford and Savannah River Sites

a

The Savannah River Site has treated about 4 million gallons of LAW from the tanks. The treatment 

process necessarily increases the volume of the waste treated because water and other constituents 

are added during the process. Consequently, the total amount of LAW grouted at the Savannah River 

Site so far is about 8.3 million gallons.

b

According to the Site Treatment Plan, the Savannah River Site must complete tank waste treatment 

by 2028, but according to DOE documents, DOE currently estimates that it will complete treatment by 

2032.

c

According to the Tri-Party Agreement, Hanford must complete tank waste treatment by 2047, but a 

senior DOE official stated that internal planning documents estimate that supplemental LAW 

treatment will last until at least 2061.
Page 28 GAO-17-306 Nuclear Waste

Under a plan developed pursuant to its Federal Facility Agreement with 

South Carolina, DOE is required to complete tank waste treatment at the 

Savannah River Site by 2028, but according to DOE documents, DOE 

aims to complete the majority of LAW treatment in 2032.68 Site officials 

are exploring ways to treat the Savannah River Site’s LAW more quickly. 

For example, according to the Savannah River Site’s System Plan—

which is a DOE plan that is periodically updated and documents the 

activities required to treat and dispose of the Savannah River Site’s tank 

waste—the site plans to employ an additional waste processing 

technology, called “Tank Closure Cesium Removal,” to selectively remove 

cesium from liquid waste so that the waste can be processed more 

quickly.69 DOE plans to initiate Tank Closure Cesium Removal at the site 

in 2018. According to the Savannah River Site’s Treatment Plan, if DOE 

does not complete tank waste treatment by 2028, it is subject to financial 

penalties under the Savannah River Site’s Federal Facility Agreement.

Under the TPA, DOE is required to complete tank waste treatment at the 

Hanford Site by 2047, but according to DOE officials and planning 

documents, DOE is unlikely to complete LAW treatment, in particular, by 

this date. DOE currently plans to begin treating some of the waste in 

2023, after the WTP’s LAW treatment facility is completed. DOE officials 

told us that because of pending decisions regarding LAW treatment, 

uncertainties about the amount of LAW that the LAW facility can vitrify, 

and ongoing technical challenges, DOE does not know how long waste 

treatment will take. However, in a December 2016 letter to the 

Washington State Department of Ecology, the manager of DOE’s Office 

of River Protection stated that the site is likely to miss milestones 

governing waste retrieval from 9 tanks because vapors present at tank 

farms may require the adoption of additional worker protections that will 

 68The Savannah River Site’s System Plan notes that DOE will continue to treat HLW until 

2036. Because treating HLW generates a low-level waste stream as a byproduct, the LAW 

that is created as a byproduct will need be treated, and such treatment will be completed 

when HLW treatment is complete in 2036. 

69Savannah River Remediation LLC, Liquid Waste System Plan Revision 20, SRR-LWP2009-00001 (Aiken, SC: March 2016). According to DOE, the Tank Closure Cesium 

Removal system is a new technology that will help process tank waste in the tank by 

pumping the waste into a unit designed to collect cesium. When it becomes loaded with 

cesium, a column within the unit will be removed and replaced. The “spent,” or used, 

column will then be stored for disposition, such as in the HLW Defense Waste Processing 

Facility or using a disposal alternative that will be determined in the future.

DOE Faces Schedule 

Delays at Both the 

Savannah River and 

Hanford Sites, but the 

Savannah River Site Will 

Likely Complete LAW 

Treatment Sooner
Page 29 GAO-17-306 Nuclear Waste

slow waste retrieval from the tanks.70 Difficulties in retrieving waste from 

the tanks may delay the start of treatment at the WTP LAW facility, 

according to the Hanford tank farms contractor, although DOE stated that 

other options may exist to keep the start of LAW treatment on schedule. 

Under the TPA, Hanford is subject to penalties if it does not complete the 

treatment of all tank waste by December 31, 2047. However, DOE 

officials told us that the state of Washington has agreed that the current 

tank waste treatment dates are unrealistic, and DOE plans to forecast 

more realistic tank waste treatment dates after it updates its System Plan 

in October 2017.71 A senior DOE official told us that internal planning 

documents estimate that supplemental LAW treatment will not be 

completed until at least 2061.

Figure 2 shows the timeline of the Savannah River and Hanford Sites’

current treatment milestones.

 70On July 11, 2016, the Hanford Atomic Metal Trades Council—a labor organization 

composed of unions whose members work on the Hanford Site—issued a “stop work”

order because of concerns about exposure to chemical vapors emanating from Hanford’s 

tank farms. The Hanford Atomic Metal Trades Council demanded that all workers 

performing work within certain areas at the Hanford Site wear supplied air. On August 31, 

2016, the Council agreed to lift its stop work order provided that all work within certain 

areas was performed with supplied air. The use of supplied air in specific areas of the 

Hanford Site is under litigation. Specifically, the state of Washington alleged in a motion 

for preliminary injunction that over 50 Hanford tank farm workers were sickened by toxic 

vapors shortly after a DOE contractor reduced safety protections at the site, including 

reductions in the use of supplied air. On November 15, 2016, after consolidating cases 

brought by the state and other plaintiffs, the court denied the state’s and other plaintiffs’

motions for a preliminary injunction against DOE. Hanford Challenge, et al. v. Moniz et al., 

Civ. No. 15-05086 (E.D. Washington), filed November 15, 2016. The court held, among 

other things, that because of the agreement of the parties regarding the use of supplied 

air, there was little to no chance of an imminent and substantial endangerment present 

that would warrant preliminary injunctive relief. The court stated, however, that arguments 

of DOE and its contractor seeking to minimize the Hanford employees’ health related 

claims were unpersuasive. The consolidated case is still pending, with trial currently 

scheduled for March 5, 2018. 

71Changing a TPA milestone requires the approval of DOE, the Washington State 

Department of Ecology, and in some cases, the EPA. DOE officials told us that they plan 

to use revision 8 of the System Plan during the schedule renegotiation process.
Page 30 GAO-17-306 Nuclear Waste

Figure 2: Current Treatment Milestones at the Department of Energy’s Hanford and Savannah River Sites

Note: According to DOE officials at both sites, treatment completion dates for both the Savannah 

River and Hanford Sites are likely to be delayed.

a

According to DOE officials, the Savannah River Site began treating waste from contaminated storm 

water and residual waste from tank waste evaporators using saltstone in 1990. The site began to 

vitrify its high-level waste in 1996, and it began grouting low-activity waste (LAW) in 2007.

b

DOE is required to complete tank waste treatment at the Savannah River Site by 2028; however, 

according to internal planning documents, DOE expects to have the majority of the Savannah River 

Site’s LAW treatment competed by 2032.

c

DOE plans to start tank waste treatment at the Hanford Site for a portion of its LAW by 2023, but 

DOE has not yet chosen a waste treatment approach for Hanford’s remaining portion of LAW, called 

supplemental LAW. According to a court document, DOE is to have technical issues related to the 

high-level waste facility resolved by 2019 and the facility redesigned by 2021. The high-level waste 

facility is to begin tank waste treatment by 2033.

d

DOE is required to complete tank waste treatment at the Hanford Site by 2047, but according to 

DOE officials and internal planning documents, LAW treatment will not be completed until at least 

2061.
Page 31 GAO-17-306 Nuclear Waste

According to DOE officials, they have not faced major technical 

challenges treating LAW at the Savannah River Site, and they have 

addressed minor technical challenges as they have arisen. For example, 

NRC identified a potential technical challenge at the Savannah River Site 

related to the ability of grout to retain a certain radioactive constituent 

over a long period of time. Specifically, in 2012, NRC sent a letter to DOE 

expressing concern that the Savannah River Site’s grouted LAW may 

leach technetium-99 at levels exceeding NRC’s limit at some point within 

10,000 years after the site is closed.72 DOE officials told us that NRC had 

expressed concern that DOE’s model indicated that radiation doses could 

reach about 100 millirems at some point within 10,000 years.73 According 

to NRC officials, in response to their 2012 letter of concern, DOE has 

reduced the concentration of technetium-99 in the Savannah River Site’s 

LAW before it is grouted. Savannah River Site officials also told us that a 

multi-year study examined core samples from one of the site’s grout 

vaults and found that DOE’s assumptions about radiation releases from 

grout have mostly been affirmed.74 NRC officials told us that they agreed 

with this assessment but that other studies raised questions about other 

assumptions that DOE had made with respect to technetium and iodine 

releases. DOE officials and NRC officials appear to have different 

opinions on the extent to which engineered barriers were accounted for in 

the model that prompted NRC’s concerns. DOE officials told us that the 

model prompting this concern was based on a “worst case scenario” that 

did not use engineered barriers and assumed that all of the grout in the 

site’s grout vaults instantaneously failed. However, NRC officials told us 

 72According to DOE’s Radioactive Waste Management Manual (DOE M 435.1-1), 

performance assessments must show that members of the public will not be exposed to 

radiation doses of greater than 25 millirems per year for 1,000 years after closure of a 

disposal facility. However, NRC Staff Guidance for Activities Related to U.S. Department 

of Energy Waste Determinations (NUREG-1854) states that the period of performance for 

DOE radioactive waste disposal facilities is generally 10,000 years. 

73According to NRC, the average American receives a radiation dose of approximately 

620 millirems per year. Half of this dose comes from natural background radiation, and the 

other half comes from man-made sources of radiation including medical, commercial, and 

industrial sources. For example, according to NRC, each year the average person 

receives an average internal dose of about 30 millirems of radiation from radioactive 

potassium and radium in the food and water we eat and drink.

74Property Data for Core Samples Extracted from SDU Cell 2A.

DOE Has Addressed 

Minor Technical 

Challenges It Has Faced 

at the Savannah River Site 

but Continues to Face 

Significant Unresolved 

Technical Challenges at 

Hanford
Page 32 GAO-17-306 Nuclear Waste

that the model included both optimistic and pessimistic assumptions.75

DOE officials also told us that NRC does not license or regulate DOE’s 

low-level waste disposal sites, including the Savannah River Site’s grout 

vaults.

76 NRC has not yet determined whether it will rescind its 2012 

letter, according to NRC officials, but it may consider doing so in the 

future because DOE is taking actions to address NRC’s concerns. NRC 

officials told us that DOE plans in 2017 to continue studying grout’s ability 

to retain technetium-99 and other constituents, and NRC will continue to 

monitor the results of DOE’s studies.

According to site officials, the Savannah River Site may face future 

technical challenges related to one tank that contains 250,000 gallons of 

waste with organic constituents.77 According to DOE’s disposal permit 

with South Carolina, the organic constituents in this tank must be 

destroyed before the waste is disposed of. DOE officials stated they have 

not yet selected a method to destroy the organic constituents. According 

to the site’s 2016 Liquid Waste System Plan, DOE expects to begin the 

process of selecting a method in 2022.

 75In commenting on a draft of this report, NRC staff stated that, while it may not have been 

intended to represent engineered barriers, the model derived significant projected dose 

reduction from the disposal structure floors. Other disagreements focused on the 

projected performance that the model derived from issues related to the timing of the grout 

degradation.

76However, NRC staff noted that Section 3116 does apply to wastes incidental to 

reprocessing, which includes certain grout vaults at the Savannah River Site. Wastes 

governed by Section 3116 must be disposed in compliance with the performance 

objectives set out in subpart C of part 61 of title 10, Code of Federal Regulations.

77An organic (i.e., carbon containing) constituent was added to this tank in 1995 as part of 

an effort to separate cesium, strontium, and plutonium from the tank waste. DOE 

suspended use of this process (called the “in-tank precipitation process”) in 1998 because 

of concerns about the amount of explosive, toxic benzene gas that the facility was 

generating.
Page 33 GAO-17-306 Nuclear Waste

In contrast, DOE faces significant technical challenges at the Hanford Site 

that are not yet resolved.78 Based on our analysis of DOE documents and 

interviews with DOE officials, we identified three key technical challenges 

associated with DOE’s plans to vitrify Hanford’s LAW that remain 

unresolved.

• Glass formulation. During the vitrification process, DOE may 

encounter challenges developing precise glass formulations. DOE will 

need to develop different glass formulations to treat different batches 

of Hanford’s LAW because there are several different chemical 

mixtures present in the tanks.79 If the wrong formulation is used, the 

glass that immobilizes the waste may not meet disposal requirements, 

or the glass may not encapsulate all of certain waste constituents.

80

For example, according to a 2015 DOE report, if too much sodium—

the main constituent in Hanford’s LAW—is present in the vitrified 

waste form, it will have poor durability and will fail to meet site 

disposal requirements.81 According to DOE officials, DOE plans to 

adjust the amount of waste placed in the glass to ensure glass 

performance, and DOE will establish waste acceptance criteria to 

apply to each batch of waste before treatment to ensure that the 

vitrified LAW will meet disposal requirements.

 78For the purpose of this review, we focus only on challenges related to the vitrification of 

LAW; however, DOE faces other challenges with the WTP more broadly, which we have 

previously reported on. For example, in May 2015, we found that significant technical and 

management challenges continued to affect the WTP and hinder its completion, 

particularly at the Pretreatment facility and HLW facility. Specifically, we noted that DOE 

experienced persistent challenges with pulse-jet mixing that could lead to an uncontrolled 

nuclear chain reaction known as a criticality incident, as well as challenges with erosion 

and corrosion of piping that could lead to equipment damage and leaks. See GAO, 

Hanford Waste Treatment: DOE Needs to Evaluate Alternatives to Recently Proposed 

Projects and Address Technical and Management Challenges, GAO-15-354 (Washington, 

D.C.: May 7, 2015).

79Because of the highly heterogeneous chemical and radiological composition of the 

Hanford tank wastes, DOE will need to vitrify the waste in batches, calibrating the 

composition of each batch of waste to be vitrified to maximize waste treatment 

effectiveness. According to the 2012 EIS, Hanford’s Best Basis Inventory, which 

establishes the chemical inventory of the tanks, may have uncertainties of 50 percent to 

400 percent for selected constituents of concern in the tanks. Final Tank Closure and 

Waste Management Environmental Impact Statement for the Hanford Site, Richland,

Washington.

80In comparison, the Savannah River Site uses one grout formulation for the treatment of 

its LAW.

81Department of Energy, Office of River Protection Advanced Low-Activity Waste Glass 

Research and Development Plan, ORP-59500 rev. 0, (Richland, WA: November 2015). 

United Kingdom: Treating Low-Activity 

Defense Waste with Grout

The United Kingdom is one of a limited 

number of countries that have defense 

nuclear waste as a byproduct of nuclear 

weapons production. Such waste was 

produced at the Sellafield site beginning in the 

1950s and has been separated into highlevel, “intermediate-level,” and low-level waste 

streams.

High-level waste in the United Kingdom, as in 

the United States, is treated using vitrification. 

However, the country’s less radioactive waste 

has been treated using grout for the last 20

years. Officials from the United Kingdom told 

us that they chose grout because it is 

effective, less costly, and suitable for a wide 

range of radioactive wastes. 

According to officials from the United 

Kingdom, intermediate-level waste contains 

constituents similar to Hanford’s low-activity 

waste, including technetium-99 and iodine129. Officials told us that technetium and 

iodine are more likely to be effectively 

retained in a low-temperature treatment 

method, such as grout, than high-temperature 

methods, such as vitrification. Officials also 

told us that they would not recommend using 

vitrification to treat intermediate-level waste 

because the technology is much more 

complex and expensive than grout.

Sources: GAO analysis of Sellafield and International Atomic 

Energy Association documents and interviews with officials 

from the United Kingdom. Image shown courtesy of: United 

Kingdom Nuclear Decommissioning Authority. | GAO-17-

306
Page 34 GAO-17-306 Nuclear Waste

• Off-gas treatment systems. During the vitrification process, DOE 

may encounter issues with its LAW off-gas treatment systems, which 

confine and treat radioactive and hazardous gases that are a 

byproduct of the vitrification process. According to a 2015 DOE report, 

without mitigating actions, the LAW off-gas treatment systems may 

chronically limit the LAW facility’s overall production capacity.82 For 

example, the report states that DOE will need to cease operating its 

melters—which produce the vitrified waste—in order to safely perform 

maintenance on the off-gas system, which may in turn reduce the 

 82Department of Energy, Office of River Protection, Waste Treatment and Immobilization 

Plant Low-Activity Waste Facility Design and Operability Review and Recommendations,

15-WTP-0151 Attachment 2, (Richland, WA: Sept. 4, 2015).
Page 35 GAO-17-306 Nuclear Waste

facility’s production capacity.83 This report also notes that the off-gas 

systems do not have redundant back-up systems, which may cause 

the equipment to fail more frequently.84

• Tank space. After DOE begins vitrifying Hanford’s LAW, it may not 

have sufficient tank space if additional tanks leak or if a higher-thanexpected amount of effluent—which is the liquid waste generated 

from the LAW facility—needs to be returned to the tanks. Specifically, 

the vitrification process will generate liquid waste that is created by 

the off-gas system. A portion of this waste will be returned to the 

tanks.85 However, according to a 2015 DOE document, if the waste 

that is returned to the tanks does not meet certain criteria, it could 

cause corrosion in the tanks.86 DOE officials told us that the portion of 

the effluent that is returned to the tanks will undergo chemical 

adjustments in order to prevent tank corrosion, but this will require 

expanding the volume of waste returned to the tanks by two or more 

times the effluent volume. According to this 2015 DOE document, 

discharging this waste back into the tank farms is a short-term 

solution because space constraints will severely impact the tank 

system.87

These and other challenges may prevent DOE from vitrifying Hanford’s 

LAW with the WTP at the rate required by the Consent Decree, which 

 83Melters are used to produce vitrified waste. Waste, in combination with glass-forming 

materials, is heated to high temperatures by an electrical current that passes through the 

molten glass-forming materials and waste in the melter. The waste and the glass-forming 

materials melt, forming a vitrified product that is poured into containers.

84According to DOE officials, the contractor has agreed to resolve all issues identified in 

the Design and Operability Review, including vulnerabilities associated with the off-gas 

system, and has “closed out” 499 of 516 vulnerabilities. DOE officials stated that DOE’s 

Office of River Protection is verifying the accuracy of the contractor’s assessments and 

expects to “close out” most of the remaining vulnerabilities in 2017.

85To support direct-feed LAW operations, DOE is building the Effluent Management 

Facility, which will evaporate and concentrate the liquid waste that results from the 

vitrification process. After initial treatment, the effluent will either be (1) sent to the Effluent 

Treatment Facility—a different facility from the Effluent Management Facility—for further 

treatment, (2) recycled back into the LAW facility to be vitrified, or (3) returned to the 

tanks. According to a 2015 DOE plan, of the effluent that is not sent to the Effluent 

Treatment Facility, 15 percent will be returned to the tanks, while 85 percent will be 

recycled back to LAW facility. See: Advanced Low-Activity Waste Glass Research and 

Development Plan.

86Department of Energy, River Protection Project Technology Roadmap, RPP-PLAN43988, rev. 1 (Richland, WA: Jun. 30, 2015).

87River Protection Project Technology Roadmap.

Oak Ridge National Laboratory: Example 

of DOE Treating Low-Level Waste with 

Low Temperature Drying

Oak Ridge National Laboratory was 

constructed during World War II, in part, as a 

pilot-scale facility to support nuclear energy 

research. Since the 1940’s, the site has 

generated transuranic waste, low-level waste, 

and mixed waste during nuclear materials 

production and research and development 

activities. In 1995, the Tennessee Department 

of Environment and Conservation issued an 

order that mandated specific requirements for 

Oak Ridge’s waste treatment and disposal.

Oak Ridge reviewed several options for 

treating its low-level waste, including 

vitrification, grout, and low-temperature 

drying. According to a former Department of 

Energy (DOE) project manager who oversaw 

waste treatment, the estimated cost for 

treating the waste with low-temperature drying 

was about $250 million, while the estimated 

cost for grout was $350 million, and the 

estimated cost for vitrification was $1 billion.

In August 2000, Oak Ridge decided to treat 

the waste with low-temperature drying. 

According to the former DOE project 

manager, this method used a low-temperature 

dryer to concentrate the liquid portion of the 

waste before it was mixed with metasilicate—

which, according to this DOE official, is a 

material that sets like cement but can be 

dissolved if needed by adding water—and fed 

into storage casks for shipment to the Nevada 

National Security Site for disposal. By treating 

the low-level waste through low-temperature 

drying and combining it with metasilicate, the 

volume of waste disposed of was reduced to 

about a quarter of the original volume.

Sources: GAO analysis of DOE documents and interviews. 

Image source: DOE. | GAO-17-306
Page 36 GAO-17-306 Nuclear Waste

could result in additional future schedule delays and increased costs. 

According to the WTP contract and the Consent Decree, the LAW 

treatment facility must produce vitrified waste at an average rate of 70 

percent of its stated design capacity.88 DOE’s 2015 LAW facility Design 

and Operability Review states that there is significant evidence that this 

rate is an overly optimistic assessment of the LAW treatment facility’s 

production capabilities.89 Moreover, the report notes that this required rate 

significantly exceeds what vitrification facilities at other DOE sites and 

those in the United Kingdom have been able to achieve. For example, the 

Savannah River Site’s Defense Waste Processing Facility, which vitrifies 

HLW, has operated at an average of 36 percent of design capacity, and 

the West Valley Demonstration Project operated its HLW vitrification 

facility at a rate of about 17 percent of design capacity.90 Also according 

to the report, HLW vitrification facilities in the United Kingdom have 

sustained an operating capacity of less than that of the Savannah River 

Site.

Although existing information is incomplete, the best available information 

suggests that DOE’s costs to grout LAW at the Savannah River Site may 

be substantially lower than its approximate costs to vitrify LAW at 

Hanford.91 As discussed previously, at the Savannah River Site, DOE 

began grouting LAW in 2007 using existing grouting facilities while 

constructing a new, higher capacity facility to prepare the LAW to be 

grouted.

• Construction of the Savannah River Site’s LAW treatment 

facilities. In 2016, DOE completed construction on the new Salt 

Waste Processing Facility, which DOE expects will allow it to process 

 88To produce vitrified waste at that rate, the LAW treatment facility—which has a design 

capacity of 30 metric tons of glass per day—must produce, on average, 21 metric tons of 

glass per day.

89Department of Energy, Office of River Protection, Waste Treatment and Immobilization 

Plant Low-Activity Waste Facility Design and Operability Review and Recommendations,

15-WTP-0151 Attachment 2, (Richland, WA: Sept. 4, 2015).

90The West Valley Demonstration Project is the only commercial spent fuel reprocessing 

plant to have operated in the United States. The site produced tank waste that was 

separated into a HLW stream and a LAW stream. The HLW was treated with vitrification, 

and the LAW was treated with grout.

91All costs and cost estimates in this section are presented in 2015 dollars, unless 

otherwise noted.

DOE’s Costs to Grout 

LAW at the Savannah 

River Site May be 

Substantially Lower than 

Its Approximate Costs to 

Vitrify LAW at Hanford
Page 37 GAO-17-306 Nuclear Waste

the Savannah River Site’s LAW at a faster pace than its existing 

facilities could. Construction of this new facility cost $2.3 billion 

(adjusted to $2.4 billion in 2015 dollars), and DOE plans to begin 

using this facility in 2018 to prepare the Savannah River Site’s 

remaining LAW to be grouted.92 However, DOE could not provide us 

complete information on the cost to construct the existing facilities that 

have been in use for years. According to officials from the Savannah 

River Site, DOE does not have the information because the work was 

done in the 1980s by different contractors than the ones currently 

employed by the site. Our review of DOE documents indicates that 

DOE spent about $45 million ($85 million in 2015 dollars) to construct 

the existing facilities in the late 1980s.93 In addition, a 2007 DOE 

budget document noted that DOE spent about $160 million ($190 

million in 2015 dollars) to modify the existing facilities at the Savannah 

River Site to prepare the first 4 million gallons of LAW to be grouted.

• Operation of the Savannah River Site’s LAW treatment facilities. 

The estimated cost to operate the Savannah River Site’s existing 

grout facilities for the duration of the treatment mission, including the 

approximately $250 million already spent to grout the first 4 million 

gallons of LAW, will be about $1.2 billion. DOE estimates that 

operating the new Salt Waste Processing Facility to prepare the rest 

of the Savannah River Site’s LAW to be grouted will cost about $1.6 

billion.

Based on the information available to us, DOE’s total cost to modify and 

construct the Savannah River Site’s existing and newly constructed 

facilities was about $2.7 billion, and DOE’s total costs for operating these 

facilities is estimated to be about $2.8 billion.

With regard to the Hanford Site, as previously discussed, DOE has not 

yet completed construction of Hanford’s LAW vitrification facility, nor has 

it selected an approach for treating Hanford’s supplemental LAW. As a 

result, DOE does not have complete estimates for the costs of 

constructing and operating LAW treatment facilities at Hanford, but the 

 92According to DOE officials, this includes the total project cost to design, construct, 

perform startup testing, and commission the new Salt Waste Processing Facility.

93We obtained information from various DOE and budget documents. According to these 

documents, construction of the existing Saltstone Facility and the first two disposal vaults 

was completed between February 1986 and July 1988 at a cost of $45 million. The 

documents do not discuss how the costs were allocated for the Saltstone Facility and the 

two vaults. To be conservative in our analysis, we are reporting the full $45 million for the 

construction of the Saltstone Facility.
Page 38 GAO-17-306 Nuclear Waste

cost information that is available indicates that the costs to vitrify LAW at 

Hanford may be substantially more than the estimated costs to grout LAW 

at the Savannah River Site.

• Construction of Hanford’s LAW treatment facilities. At Hanford, 

DOE estimates that constructing the WTP’s LAW treatment facility, 

along with the ancillary facilities needed for LAW treatment, will cost 

about $6.5 billion.94 This estimate accounts for DOE’s original 

estimate of $1.4 billion (in 2006 dollars) to construct the LAW 

vitrification facility, as well as $316 million for construction of 

additional facilities to support LAW treatment. In addition, in 2016, 

DOE estimated that inflation adjustment and additional modifications 

needed to treat LAW will add $4.8 billion in construction costs. DOE 

has not yet selected an approach to treat the supplemental LAW at 

Hanford and therefore does not have an estimate for the costs to 

complete LAW treatment. However, DOE’s current life-cycle estimate 

assumes that DOE will build and operate a second LAW vitrification 

facility with the same technical assumptions as the first one. In 

addition, senior DOE officials told us that if DOE chooses to vitrify 

supplemental LAW, the costs to construct and operate a second 

vitrification facility for supplemental LAW would be roughly as much 

as the costs associated with constructing and operating the existing 

LAW facility.

• Operation of Hanford’s LAW treatment facilities. Construction of 

the WTP’s LAW treatment facility is not complete, and according to 

DOE officials, they do not yet have an estimate for how much it will 

cost to operate the facility because they have not selected a 

contractor to operate it. However, according to January 2017 

estimates from the DOE contractor that is constructing the WTP, the 

cost for commissioning and operating the LAW facility is currently 

estimated at about $600 million per year ($530 million in 2015 

dollars). According to DOE officials, LAW treatment would likely not 

be completed until 2061, requiring the facility to operate for 39 years 

 94Available information indicates that it will cost about $6.5 billion to construct the facilities 

needed for LAW treatment. However, in a March 2017 internal monthly status report, DOE 

estimated that the direct feed LAW approach, which encompasses the WTP LAW facility 

and other infrastructure needed for treating the initial portion of LAW, will cost $8.3 billion. 

We did not include this higher figure in the estimated construction costs because we were 

unable to review the source documents associated with it. Nevertheless, if the cost to 

construct the facilities needed for LAW treatment is $8.3 billion, this will increase the cost 

per gallon figure for vitrifying LAW. As noted above, DOE will still require the successful 

construction of the WTP and its components to treat the remaining portion of LAW that 

was originally planned to be treated in the WTP.
Page 39 GAO-17-306 Nuclear Waste

for a total of about $20 billion. As discussed above, DOE’s life cycle 

estimates assume that it will cost the same to operate a second 

vitrification facility for supplemental LAW, and senior DOE officials 

confirmed that it would cost roughly as much to operate a second 

LAW facility.

Overall, DOE officials indicated that $13 billion is their best estimate for 

the total cost to construct (1) the LAW treatment facility currently under 

construction and (2) a new vitrification facility for supplemental LAW. DOE 

officials indicated that their best estimate for the costs to operate these 

facilities is about $40 billion.

Table 2 compares best available cost information for treating LAW at the 

Savannah River and Hanford Sites. These estimates indicate that the 

costs to vitrify LAW at Hanford may be substantially higher than the costs 

to grout LAW at the Savannah River Site. This is consistent with DOE’s 

assessment of treatment costs at the Savannah River Site: senior DOE 

officials estimated in 2004 that by grouting LAW at the Savannah River 

Site, DOE would have saved at that time about $55 billion (in constant 

2004 dollars) over the lifecycle of waste treatment operations, when 

compared with vitrification.95

 95This estimate was developed by a senior official in DOE’s Office of Environmental 

Management in 2004; officials from the Savannah River Site were not able to reproduce 

this estimate for us at the time of this review. 
Page 40 GAO-17-306 Nuclear Waste

Table 2: Comparisons of Total Estimated Costs for Grouting Low-Activity Waste (LAW) at the Savannah River Site and 

Vitrifying LAW at the Hanford Site, Based on Best Available Information

Savannah River Site Hanford Site

Existing and new salt waste 

processing facilities

LAW Treatment 

facility

Vitrification facility for 

supplemental LAWa Total

Estimated cost to construct treatment 

facilities (millions of dollars)

$2,700 $6,500b $6,500 $13,000

Estimated cost to treat LAW (millions 

of dollars)

$2,800 $20,000c $20,000 $40,000

Total estimated cost

(millions of dollars)

$5,500 $53,000

Total LAW (gallons)d 36 million 49 million

Estimated average cost per gallon 

of LAW treated (dollars)

$153/gallon $1,081/gallon

Source: GAO analysis of Department of Energy (DOE) data and interviews. | GAO-17-306

Note: All costs and cost estimates in this table are presented in 2015 dollars. In addition, the 

estimates for both sites do not include costs to dispose of the treated waste. We did not evaluate 

whether the grouted waste form at the Savannah River Site would meet Washington State’s 

hazardous waste management requirements. Further, because DOE does not have complete 

information on the costs of various treatment options, nor has it precisely specified the treatment 

options it will pursue, our analysis is based on the best information we could obtain. In particular, the 

precise costs of vitrifying Hanford’s LAW are not known. To the extent possible, we corroborated 

estimated costs with available budget documents, DOE reports, and DOE officials. Because some of 

DOE’s estimated costs were approximations, we conducted a sensitivity analysis by examining the 

cost-per-gallon difference between the Hanford and Savannah River Sites under different scenarios. 

This helped us assess how, if at all, imprecise information could affect the results of this comparison. 

For example, if DOE operated Hanford’s LAW treatment facility and a vitrification facility for 

supplemental LAW for 20 years, rather than its projected 39 years—which would cost about $10 

billion in total—DOE’s costs would be about $673 per gallon. In this scenario, DOE’s costs per gallon 

to vitrify all of Hanford’s LAW would still be about four times the costs to grout the Savannah River 

Site’s LAW.

a

DOE has not yet made a decision on how it will treat supplemental LAW. However, DOE’s current 

life-cycle estimate assumes that a second LAW vitrification facility will be built and operated with the 

same technical assumptions as the first one.

b

Until 2016, DOE had estimated that construction of the LAW facility would cost $1.4 billion. 

According to DOE’s December 2016 estimates, additional modifications to DOE’s approach to 

treating LAW have added $4.8 billion. In addition, DOE is building a new $316 million facility to 

prepare the tank waste before it is brought into the LAW treatment facility ($6.5 billion total). However, 

although available information indicates that it will cost about $6.5 billion to construct the facilities 

needed for LAW treatment, DOE estimated in a March 2017 internal monthly status report that the

direct feed LAW approach—which encompasses the WTP LAW facility and other infrastructure 

needed for treating the initial portion of LAW—will cost $8.3 billion. We did not include this higher 

figure in the estimated construction costs because we were unable to review the source documents 

associated with it. Nevertheless, if the cost to construct the facilities needed for LAW treatment is 

$8.3 billion, this will increase the cost per gallon figure for vitrifying LAW.

c

DOE does not have an estimate for the cost to treat LAW. However, according to contractor 

estimates, the cost for commissioning and operating the LAW facility and associated support systems 

is currently estimated at about $600 million per year ($530 million when adjusted for inflation). DOE is 

currently planning to begin operating the facility in 2022, and treatment is not expected to finish until 

2061 (39 years) (about $20 billion total).

d

These figures reflect the total amount of waste previously treated and currently stored in the tanks. 

However, the total amount of waste treated will be significantly higher because the waste will need to 

be diluted before it can be treated.
Page 41 GAO-17-306 Nuclear Waste

According to experts who participated in our meeting convened by the 

National Academies, both vitrifying and grouting Hanford’s LAW could be 

protective of human health, including limiting the risk of exposure over the 

long term.96 These experts also noted that new information since DOE 

made its decision to vitrify Hanford’s LAW suggests that grout will perform 

better than assumed in previous studies. Moreover, these experts stated 

that by adopting a risk-informed decision-making approach to treating 

Hanford’s supplemental LAW, DOE could address certain risks sooner 

and avoid significant costs.97

According to experts who participated in our meeting, both vitrification 

and grout could effectively treat Hanford’s LAW and be protective of 

human health by, for example, limiting the risk of exposure over the long 

term.98 Many experts who participated in our meeting asserted that the 

risk posed to human health and the environment by both vitrified and 

grouted waste is small at a modern disposal site, such as the one that will 

be used at Hanford. A few experts noted that the long-term risks of 

vitrified and grouted LAW in a modern disposal site are so low that the 

difference in exposure risk between the two forms might not be 

measurable.99 One expert noted that a 2013 DOE report that studied 

grout formulations found that for the range of parameters studied, all 26 of 

 96The experts did not address issues related to the construction and operation of the 

WTP. In addition, the experts’ meeting focused on the treatment of all of Hanford’s LAW 

because DOE has not yet determined which tanks will be treated by the WTP and which 

tanks’ waste will be treated with a supplemental treatment approach.

97In November 2016, several months after our experts’ meeting, Congress passed the 

National Defense Authorization Act for Fiscal Year 2017. Pub. L. No. 114-328 (2016). 

Section 3134 of the act requires DOE to enter into an arrangement with a federally funded 

research and development center to conduct an analysis of approaches for treating the 

portion of LAW at Hanford intended for supplemental treatment. The analysis is to include 

an assessment of the benefits and costs of various treatment approaches, including 

vitrification, grouting, and steam reforming, and other alternative approaches identified by 

DOE. DOE has not yet entered into the agreement required by this section.

98DOE plans to dispose of its treated LAW on site in Hanford’s Integrated Disposal 

Facility, a RCRA-permitted landfill with two separate expandable cells.

99However, some experts stated that while both waste forms would meet requirements, 

vitrification might perform slightly better than grout over the long term.

Experts Believe That 

Both Vitrification and 

Grout Can Treat 

Hanford’s LAW and 

Identified Options to 

Accelerate Cleanup 

and Reduce Future 

Costs

According to Experts, 

Vitrification and Grout 

Could Both Effectively 

Treat Hanford’s LAW
Page 42 GAO-17-306 Nuclear Waste

the grout formulations tested met the land disposal standards for 

hazardous constituents and met the anticipated waste acceptance criteria 

for on-site disposal at Hanford.100 Appendix IV provides a detailed 

summary of experts’ views on the performance of vitrification and grout, 

including the benefits and shortcomings of each in treating LAW with

certain constituents at Hanford.

Some experts who participated in our meeting also stated that recent 

studies have shown significant improvement in the performance of grout. 

This view is underscored by a 2015 DOE report, which stated that 

grouted LAW has been shown to effectively immobilize waste and retain 

constituents of concern, including technetium-99 and iodine-129.101 The 

report further stated that grouted LAW has been shown to meet the 

RCRA waste treatment standards for land disposal of hazardous waste. 

Moreover, a 2016 study of the long-term performance of the Savannah 

River Site’s grout in its Saltstone Disposal Facility showed that the grout 

will retain constituents of concern for the required period of time.102

When accounting for the environment in which LAW is planned to be 

disposed of at Hanford, experts who participated in our meeting viewed 

the long-term exposure risks of vitrified LAW and grouted LAW as low 

and nearly identical. A few experts said that Hanford is a favorable place 

for the long-term disposal of LAW with either vitrification or grout. Experts 

explained that Hanford is an arid climate with low rainwater soil infiltration 

rates, which will slow down the rate at which waste would be released 

into the soil if the vitrified or grouted waste form and the engineered 

 100Department of Energy, Supplemental Immobilization of Hanford Low-Activity Waste: 

Cast Stone Screening Tests, PNNL-22747, (Aiken, SC and Richland, WA: September 

2013). Each of the 26 formulations was characterized based on its processing properties 

including gel time, hardening time, and the heat generated during curing; and cured waste 

properties including compressive strength, density, leaching, and chemical composition. 

The report noted that, to be acceptable for disposal at the Integrated Disposal Facility on 

the Hanford Site, cast stone containing hazardous metals must pass EPA’s toxicity 

characteristic leaching protocol. RCRA’s land disposal restrictions require that the 

concentration of the metals in the leachate be below the treatments standards contained 

in 40 C.F.R. part 268. 

101Department of Energy, Technical Approach for Determining Key Parameters Needed 

for Modeling the Performance of Cast Stone for the Integrated Disposal Facility 

Performance Assessment, PNNL-24022 rev. 0 (Richland, WA: March 2015).

102Additionally, this report noted that while the grout did not encapsulate iodine as well as 

had been modeled, the leaching of iodine would not affect the risk of exposure to the 

surrounding environment. Property Data for Core Samples Extracted from SDU Cell 2A.

Nevada National Security Site: DOE’s 

Disposal of Low-Level Waste in the Arid 

Nevada Environment

The Nevada National Security Site accepts 

low-level waste and mixed low-level waste—

which is low-level radioactive waste that also 

contains hazardous constituents regulated 

under the Resource Conservation and 

Recovery Act—for disposal from the 

Department of Energy (DOE), as well as 

certain waste from the Department of 

Defense. According to an official from the 

National Nuclear Security Administration who 

is an environmental management operations 

manager for the low-level waste facility at the 

Nevada National Security Site, the waste 

disposal site is ideal for radioactive waste 

disposal because of its arid environment, 

deep groundwater table, and low likelihood of 

rain reaching the groundwater. In addition, the 

Nevada National Security Site facilities sit 

atop deep aquifers and potential leaks have 

no pathway to the groundwater. 

To be accepted at the site, waste must meet 

specific criteria, such as limits on the amount 

of free liquids, and the waste must adhere to 

applicable packaging criteria. The official 

stated that the site does not require a certain 

waste form and that waste has been accepted 

in grouted and other forms. The official was 

not aware of any vitrified waste having been 

disposed of at the site.

Sources: Interview with NNSA official and GAO analysis of 

DOE documents. Image source: DOE. | GAO-17-306
Page 43 GAO-17-306 Nuclear Waste

barriers were not effective. As a result, these experts stated that there is a 

very low risk that waste treated with either grout or vitrification would 

contaminate the groundwater. One expert noted that even if waste from 

the vitrified or grouted waste form leached from the disposal site, it could 

take approximately 2,000 years for any waste to enter the groundwater, 

and a few experts stated that any waste that reached the groundwater 

after that period of time would be significantly diluted so as to pose 

virtually no risk.

Moreover, some experts who participated in our meeting stated that the 

engineered barriers planned for use at the Hanford disposal site will 

further reduce risks. Specifically, these experts stated that the 

engineering of the disposal site plays a role in minimizing risks and that 

engineered barriers—such as adding a cap to prevent water infiltration 

into the disposal site—could help to limit the possible spread of some 

contaminants from grouted waste forms for up to the 1,000-year period of 

performance.103 For example, one expert explained that engineered 

barriers greatly reduce the amount of water that flows through a disposal 

site. A few experts noted that such barriers can be maintained to preserve 

their effectiveness over time.

Some experts who participated in our meeting stated that some of the 

research on the effectiveness of grout and vitrification included in early 

studies—as well as DOE’s 2012 EIS, which supported DOE’s decision to 

vitrify at least some of Hanford’s LAW—relied on assumptions that are no 

longer viewed as accurate or that no longer apply. According to multiple 

experts, DOE used overly conservative models in assessing the longterm risk of grouting LAW for its 2012 EIS, which underestimated the 

long-term performance of grout. A few of these experts stated that when 

models are overly conservative, they do not accurately reflect site 

conditions. For example, according to the 2012 EIS, approximately 0.14 

inches (3.5 millimeters) of rain infiltrates the soil at the Hanford Site each 

year, but a few experts stated that the rain infiltration rate is probably 

 103According to DOE Manual 435.1-1, low-level waste containment facilities must conduct 

a performance assessment demonstrating that the site meets performance objectives 

such as the dose to the public not exceeding 25 millirems from all exposure pathways 

during any 1 year, over the course of a 1,000-year after-closure period of compliance. 

According to NRC, the average American receives a radiation dose of approximately 620 

millirems per year. 

Experts Stated That New 

Information Shows Grout 

Will Perform Better than 

Was Assumed When DOE 

Made Its Decision to Vitrify 

Hanford’s LAW
Page 44 GAO-17-306 Nuclear Waste

closer to 0.04 inches (1 millimeter) each year.104 As a result, less water 

may reach the waste form than the EIS indicated, thereby reducing the 

likelihood of contaminating groundwater. One expert further explained 

that Hanford’s 2012 EIS used conservative assumptions on how well 

grout would retain technetium-99 that were based on outdated research, 

and the EIS used more realistic assumptions on how well a vitrified waste 

form would retain technetium-99. Another expert noted that when such 

overly conservative assumptions are all accounted for, they become 

collectively significant. The expert noted that the performance of grout in 

the 2012 EIS could have been misleading, and that if DOE had used 

more realistic assumptions, it might have reached different conclusions 

about the ability of grout to safely and effectively treat Hanford LAW.

A few experts who participated in our meeting noted that engineered 

barriers also help to improve waste form performance, but their impacts 

were not fully accounted for in the models used for the Hanford Site. 

According to the 2012 Hanford EIS, the site’s engineered barriers are 

assumed to last for 500 or 1,000 years—depending on the type of barrier 

used—before failing.105 In contrast, a 2009 DOE report on the 

performance of the Savannah River Site’s Saltstone Disposal Facility 

found that the performance of engineered barriers used there is assumed 

to degrade slowly over more than 5,000 years.106

 104DOE Final Tank Closure and Waste Management Environmental Impact Statement for 

the Hanford Site, Richland.

105DOE Final Tank Closure and Waste Management Environmental Impact Statement for 

the Hanford Site, Richland.

106Performance Assessment for the Saltstone Disposal Facility at the Savannah River 

Site.
Page 45 GAO-17-306 Nuclear Waste

Experts who participated in our meeting noted that current scientific 

information should be used as part of a risk-informed decision-making 

process. Some of these experts suggested that using grout could 

significantly reduce the costs of treating Hanford’s supplemental LAW. 

Moreover, experts stated that under a risk-informed decision-making 

process, options exist that could help DOE reduce certain risks in treating 

Hanford’s supplemental LAW.

According to experts who participated in our meeting, DOE would benefit 

from incorporating information on significant advances in grout 

performance as part of a risk-informed decision-making approach to 

treating Hanford’s supplemental LAW. The National Research Council 

has reported several times that DOE’s cleanup strategy could benefit 

from a risk-informed process—in essence, a process that aligns treatment 

approaches with the risk the waste poses. In a 2005 report, the National 

Research Council found that an effective and credible risk-informed 

decision-making process is one that is consistent with current scientific 

knowledge and practice, reasonably independent of decision makers, and 

subjected to thorough independent peer review.107 A 2011 National 

Research Council report asserted that incorporating new science and 

technology does not have to halt a cleanup program’s progress and that 

by incorporating new science and technology, a cleanup program can 

increase efficiencies and reduce life-cycle costs and risk.108 By 

developing updated information on the likely performance of alternate 

methods for treating Hanford’s supplemental LAW, such as grout, DOE 

may be able to develop waste treatment approaches that would 

accelerate the tank waste treatment mission, thereby reducing certain 

risks, and may reduce tank waste treatment costs.

 107Specifically, the report stated that such a decision-making process is (1) participatory; 

(2) logical; (3) consistent with current scientific knowledge and practice; (4) transparent 

and traceable; (5) structured with reasonable independence of the decision authority from 

the petitioner; (6) subjected to thorough, independent peer review; (7) technically credible 

with believable results; and (8) framed to address the needs of the decision process. Risk 

and Decisions About Disposition of Transuranic and High-Level Radioactive Waste. 

108Waste Forms Technology and Performance: Final Report. This study was performed at 

the request of DOE’s Office of Environmental Management.

Some Experts Noted That 

a Risk-Informed DecisionMaking Process Could 

Help DOE Possibly Avoid 

Significant Costs and 

Develop Options to 

Address Certain Risks 

Sooner

Experts Noted that Recent 

Scientific Information Should 

Be Used as Part of a RiskInformed Decision-Making 

Process
Page 46 GAO-17-306 Nuclear Waste

Experts who participated in our meeting stated that DOE could consider 

other options for treating supplemental LAW at Hanford that may better 

align treatment approaches with the risks the waste poses, which could 

reduce certain risks and possibly avoid significant costs. These experts 

noted that the greatest risks to human health and the environment arise 

from leaving the waste in the tanks for prolonged periods of time and that 

this risk is far greater than those associated with possible leaching of 

waste from a disposal site. According to some experts, the longer the 

waste stays in the tanks, the greater the risk that potential tank leaks 

pose to human health and the environment, and one expert noted that the 

longer that tank farms continue to operate, the greater the risk to 

workers.109 According to another expert, a significant risk could arise if the 

dome of one of the aging tanks were to collapse because this could 

cause the contamination to become airborne. This point was also 

underscored in a 2015 Omnibus Risk Review Committee report, which 

found that important infrastructure systems at Hanford are operating past 

their designed lives and are showing the stress of extended operations 

and that failures of infrastructure could lead to unforeseen major human 

health risks.110 We have also previously reported that Hanford’s tanks are 

aging and that 153 of the 177 tanks are beyond their design life.111

According to a 2014 DOE document, tank leaks could extend tank waste 

treatment efforts by 25 years and cost an additional $91 billion.112

 109According to DOE officials, 61 of DOE’s 149 single-shell tanks at Hanford are assumed 

to be leaking. In October 2012, DOE announced that nuclear waste at the Hanford site 

had leaked into the space between the inner and outer shell of one of its double-shell 

tanks. Four months later, in February 2013, DOE announced that waste was leaking into 

the environment from at least one single-shell tank. More recently, in April 2016, DOE 

reported that Hanford officials detected a major leak of waste from the inner shell of one 

double-shell tank, and DOE reported that it was investigating whether a second tank had 

also developed a leak from the inner shell. 

110A Review of the Use of Risk-Informed Management in the Cleanup Program for Former 

Defense Nuclear Sites.

111GAO, Hanford Cleanup: Condition of Tanks May Further Limit DOE’s Ability to 

Respond to Leaks and Intrusions, GAO-15-40 (Washington, D.C.: Nov. 25, 2014). In this 

report, we recommended that DOE assess the alternatives for creating new RCRAcompliant tank space for the waste from the single-shell tanks, including building new 

double-shell tanks.

112Department of Energy, Office of River Protection, River Protection Project System Plan 

Revision 7 (Richland, WA: October 2014). This cost figure is from a budget document and 

includes escalation.
Page 47 GAO-17-306 Nuclear Waste

Experts who participated in our meeting explained that employing a multipronged approach to treating Hanford’s LAW could allow DOE to avoid 

significant costs. Several experts indicated that, on the basis of their 

professional experience and opinion, vitrifying LAW—in general and at 

the Hanford Site in particular—would likely be more expensive than 

grouting it. For example, one expert said that cost estimates for the 

treatment of LAW at Hanford indicated that grouting the waste could be 

20 percent to 50 percent cheaper than vitrifying it. Other experts pointed 

out that the costs of maintaining Hanford’s tanks influence long-term lifecycle costs, and shortening the length of time that DOE must manage the 

tanks could save significant costs.113 Another expert suggested that 

DOE’s major opportunity for avoiding future costs is to “dump the onesize-fits-all approach for the remainder of the waste” (i.e., supplemental 

LAW) and adopt a risk-based approach because the hazardous and 

radioactive constituents in the waste vary by tank, and different treatment 

options may be more efficient for different tanks. Certain experts did not 

fully agree that grouting Hanford’s LAW would be cheaper than vitrifying 

it. For example, a few experts stated that it may be costly to disrupt 

DOE’s current plans to vitrify Hanford’s LAW and change treatment 

approaches. However, other experts noted that DOE does not necessarily 

need to curtail its current approach and that, by grouting supplemental 

LAW while continuing the direct-feed LAW approach, DOE would not 

incur costs associated with abandoning its vitrification plans.

While the precise costs of grouting or vitrifying Hanford’s LAW are not 

known, experts who participated in our meeting stated that to inform a 

risk-based approach to Hanford’s tank waste treatment mission, DOE 

should have reliable cost data for the various LAW treatment options that 

could be considered at Hanford. Several experts who participated in our 

meeting noted that DOE’s estimates for treating LAW are outdated and 

unreliable. For example, a few experts stated that the cost estimates 

included in DOE’s 2012 EIS are not useful because the data underlying 

the EIS are out-of-date and have since been revised. Specifically, in 

December 2016, DOE updated its estimate for constructing just one 

portion of the WTP and stated that this portion alone will cost about $4.5 

billion more than the previous $12.3 billion estimate that was developed in 

2006.114 In addition, some experts stated that DOE’s current cost 

 113In November 2014, we reported that DOE spends nearly $500 million each year 

managing the underground waste storage tanks at Hanford, including monitoring them for 

leaks and assessing their integrity. See: GAO-15-40.

114The cost figures come from a budget estimation document and include escalation.

Some Experts Suggested That 

Using Grout Could Significantly 

Reduce Costs at Hanford

Waste Isolation Pilot Plant: DOE’s 

Disposal of Transuranic Waste 

The Waste Isolation Pilot Plant is a waste 

repository located near Carlsbad, New 

Mexico, where the Department of Energy 

(DOE) disposes of defense-related 

transuranic waste. The term “transuranic”

refers to those elements with an atomic 

number greater than that of uranium, and 

transuranic waste generally includes 

radioactive wastes containing more than 100 

nanocuries of alpha-emitting transuranic 

isotopes per gram of waste, with half-lives 

greater than 20 years. The site also accepts 

transuranic mixed waste, which is transuranic

waste that also contains hazardous 

constituents regulated under the Resource 

Conservation, and Recovery Act and the New 

Mexico Hazardous Waste Act. 

The Waste Isolation Pilot Plant is located in a 

semiarid climate that was selected because of 

its deep, thick salt formations; minimal 

groundwater; low population density; and 

geological stability. The disposal facility is 

located about 2,150 feet below the surface in 

a 2,000-foot-thick salt deposit. 

The site began disposing of waste in 1999 

and is the only operating U.S. defense 

nuclear waste repository. However, 

operations were suspended in February 2014 

because of two unrelated underground 

incidents: (1) a fire on a salt-hauling truck and 

(2) a radiological release from a waste 

container that contaminated portions of the 

underground facility and released a small 

amount of radiation into the environment 

above ground. In response to these two 

events, DOE issued a recovery plan and has 

undertaken recovery efforts. DOE resumed 

limited operations at the Waste Isolation Pilot 

Plant in January 2017. 

Sources: DOE and analysis of DOE documents. Image 

source: DOE. | GAO-17-306
Page 48 GAO-17-306 Nuclear Waste

estimates are unreliable and therefore of limited use in making treatment 

decisions. Another expert stated that DOE’s lack of a reliable cost 

estimate for different treatment options is “unconscionable” and 

recommended that DOE obtain an independent cost estimate before 

making additional decisions on treating LAW. According to our Cost 

Estimating and Assessment Guide, when done correctly, an independent 

cost estimate provides decision makers with additional insight into a 

program’s potential costs—in part, because independent cost estimates 

frequently use different methods and are less burdened with 

organizational bias.115 Moreover, our guide notes that independent cost 

estimates tend to incorporate risk and, therefore, tend to be more 

conservative than program offices that develop cost estimates by 

forecasting high costs. To be of value, however, an independent cost 

estimate must be performed by entities far removed from the acquiring 

program office and must also be accepted by management as a valuable

risk reduction resource that can be used to minimize unrealistic 

expectations.

Experts who participated in our meeting stated that DOE should not 

discontinue its current treatment plan for direct-feed LAW, which involves 

vitrification. Rather, these experts stated that DOE should consider 

treating at least some of the supplemental LAW with alternatives, such as 

grout, which would allow DOE to treat the waste sooner than the currently 

projected WTP start date of 2036 and with less costly methods, reducing 

both risks and costs.116 Numerous experts stated that by considering 

multiple treatment methods, DOE would have the flexibility to treat 

different portions of the waste with different treatment methods best 

suited for the radioactive and hazardous constituents of the waste. These 

experts described several options that could be used in parallel to treat 

and dispose of Hanford’s supplemental LAW and address the risks 

associated with leaking tanks sooner:

• Vitrify LAW in certain tanks. A few experts noted that certain 

constituents in LAW might be better candidates for vitrification. For 

 115GAO, GAO Cost Estimating and Assessment Guide: Best Practices for Developing and 

Managing Capital Program Costs, GAO-09-3SP (Washington, D.C.: March 2009).

116One expert further stated that the waste treatment facilities at the Hanford Site should 

be constructed closest to the tanks they are intended to treat, which may help to reduce 

the fixed costs. Hanford’s tank farms are located in two areas, 200 East and 200 West, 4 

miles apart. The WTP is located in the 200 East area. According to DOE officials, the 

transfer line that moves tank waste between the two areas is 7 miles long. 

According to Experts, Options 

Exist That Could Help Reduce 

Certain Risks
Page 49 GAO-17-306 Nuclear Waste

example, a few experts noted that waste containing high 

concentrations of organics, which one expert said could include about 

18 to 20 tanks, may be better treated by vitrification.

• Grout LAW in certain tanks. A few experts noted that certain types 

of waste might be better candidates for grout, particularly a portion of 

the LAW that contains especially low levels of radioactivity. According 

to one expert, for example, a grout facility can be constructed faster 

and is less capital-intensive than a vitrification facility. Another expert 

noted that grouting is a simple process that can be employed on a 

relatively small scale. This expert further stated that grout could treat 

waste that contains elevated concentrations of constituents that can 

be problematic to immobilize in glass, such as sulfate and halogens, 

which include fluorine and chlorine.117 A 2002 DOE report noted that 

68 of Hanford’s 149 single-shell tanks, were—as part of Hanford’s 

2002 mission acceleration initiative118—considered as candidates for 

having their waste treated by a supplemental treatment technology, 

such as grout.119 Agency officials told us that this waste remains in 

these 68 tanks.

• Ship transuranic waste to another facility. A few experts stated 

that some tanks could contain transuranic waste and should not be 

 117Sulfate may limit the amount of waste that can be loaded into glass, which can increase 

the amount of glass that must be made. If too much sulfate is present in the waste stream, 

a layer of molten sulfate can form on the surface of the molten glass during the vitrification 

process which could damage the melter. Halogens, such as fluorine and chlorine, reduce 

the amount of waste that can be loaded into the glass. Most of the halogens will not be 

incorporated in the glass and will instead be emitted from the melter as a gas. 

118In 2002, DOE began an initiative to accelerate the schedule and reduce the costs of 

cleaning up HLW at its sites including the Hanford and Savannah River Sites. At Hanford, 

this plan would have accelerated the site cleanup completion date from 2070 to 2035 and 

reduced risk. This plan included employing supplemental technologies—such as grout and 

bulk vitrification—to treat Hanford’s LAW, but the plan was never fully implemented. 

Department of Energy, Hanford Mission Acceleration Initiative—Draft Preliminary Testing 

Recommendations for Supplemental Treatment, PNNL-14005 (Richland, WA: August 

2002).

119In 2003, to accelerate the treatment of Hanford’s LAW, DOE decided to proceed with 

development of bulk vitrification technology—a process similar to the technology planned 

for the LAW vitrification facility except that in the case of bulk vitrification, the melter 

serves as the final disposal container. However, DOE did not pursue additional funding for 

the project for fiscal year 2009 because bulk vitrification was more technologically difficult 

to develop and costly than previously envisioned. GAO, Nuclear Waste: Uncertainties and 

Questions about Costs and Risks Persist with DOE’s Tank Waste Cleanup Strategy at 

Hanford, GAO-09-913 (Washington, D.C.: Sept. 30, 2009).

Waste Control Specialists: Federal and 

Commercial Entities’ Disposal Facility

Waste Control Specialists is a commercial 

disposal facility in Texas that accepts lowlevel waste and mixed low-level waste—which 

is low-level radioactive waste that contains 

hazardous constituents regulated under the 

Resource Conservation and Recovery Act—

for disposal from federal government 

generators, such as the Department of 

Energy. The site also accepts low-level waste 

from Texas and Vermont commercial waste 

generators, such as nuclear power plants, 

hospitals, and research centers. Additionally, 

Waste Control Specialists accepts low-level 

commercial waste from generators in 34 other 

states whose waste has been approved by 

the Texas Compact Commission for disposal. 

According to a Waste Control Specialists 

official, the site is ideal for radioactive waste 

disposal because of its remote location, arid 

environment, and no drinkable groundwater. 

The site’s disposal license with the state of 

Texas was modified in August 2014 to remove 

limits on the amount of iodine-129 and 

technetium-99 that the site can accept.

Waste accepted at the site for disposal must 

meet applicable waste acceptance criteria, 

such as limits on the amount of free liquids. 

According to a Waste Control Specialists 

official, the site grouts waste containers in 

modular concrete canisters that weigh over 

100,000 pounds. The official noted that the 

site did not consider vitrifying waste because 

vitrification is expensive and complex, and 

grout exceeds federal and state 

environmental requirements.

Sources: GAO analysis of Waste Control Specialists and 

Department of Energy documents and interviews. Image 

source: Waste Control Specialists. | GAO-17-306
Page 50 GAO-17-306 Nuclear Waste

considered HLW.120 Specifically, according to agency officials, the site 

has 4 million gallons of waste stored in 11 tanks that may be able to 

be managed as transuranic waste. A few experts stated that this 

waste could then be treated in ways that would cost less than 

vitrification, and if the state of New Mexico allowed it, DOE could send 

this waste to its Waste Isolation Pilot Plant in New Mexico.121

• Consider alternate disposal sites. A few experts noted that much of 

Hanford’s LAW could be treated and disposed of at an alternate 

location. DOE is currently conducting a demonstration project that 

would grout some of Hanford’s LAW and transport it to the Waste 

Control Specialists’ site in Texas for permanent disposal. According to 

DOE officials, disposal of grouted Hanford LAW at the Waste Control 

Specialists’ site has the potential to save significant costs associated 

with the construction and operation of an additional vitrification 

facility.122 According to an estimate conducted by Waste Control 

Specialists, disposal of Hanford’s LAW at the site in Texas could save 

DOE up to $16.5 billion when compared with the costs of constructing 

and operating a second vitrification facility for the treatment of 

supplemental LAW.123

 120The word “transuranic” is used for elements that have atomic numbers greater than that 

of uranium. The DOE Waste Isolation Pilot Plant near Carlsbad, New Mexico, serves as 

the only deep geologic repository in the United States for the disposal of defense-related 

transuranic nuclear waste.

121The federal legislation governing the Waste Isolation Pilot Plant bans the disposal of 

HLW in the repository. Pub. L. No. 102-579, § 12, 106 Stat. 4791 (1992). In addition, 

according to DOE officials, the Waste Isolation Pilot Plant’s permit with the state of New 

Mexico prohibits the site from taking Hanford’s transuranic tank waste. DOE officials told 

us that they would need to go through a detailed process to modify the Waste Isolation 

Pilot Plant’s permit with New Mexico in order to accept this waste at the site.

122The demonstration project would involve removing certain constituents—cesium-137 

and strontium-90—and grouting the waste and then transporting it for disposal at the 

Waste Control Specialists’ site in Texas. According to a senior official from Waste Control 

Specialists, the site is well-suited for LAW disposal because of its deep groundwater; arid 

climate; and clay soil, which acts like a dense barrier to prevent any waste from reaching 

the groundwater. A DOE official told us that this option could eliminate the need for 

supplemental treatment and has the potential to cost significantly less than building and 

operating a second vitrification facility. 

123This cost figure includes escalation.
Page 51 GAO-17-306 Nuclear Waste

Treatment of DOE’s tank waste at Hanford is among the world’s largest 

environmental cleanup programs. Because multiple processes were used 

for plutonium production, Hanford’s tank waste contains a more complex 

mixture of radioactive and hazardous constituents than the tank waste at 

other DOE sites. Nearly 25 years ago, when DOE chose vitrification as 

the treatment approach for Hanford’s LAW, it did so based on the best 

available information at that time, which showed that vitrification was 

better than other methods at encapsulating the radioactive and hazardous 

waste at Hanford in a way that protects human health and the 

environment over the long term. Since that time, DOE has experienced 

significant technical challenges at Hanford, unforeseen when it made the 

treatment decision, and has spent more than $19 billion on tank 

management and plant construction without yet treating any waste. 

Conversely, at its Savannah River Site, DOE has successfully treated 

about 4 million gallons of LAW with grout at a substantially lower cost 

than Hanford’s estimated costs for vitrification.

As both grout and vitrification technologies matured at DOE sites over the 

last 25 years, new scientific information on the ability of grout and 

vitrification to immobilize radioactive and hazardous waste at the Hanford 

Site has also been developed. This new information, combined with the 

statements of many experts who participated in our meeting convened by 

the National Academies, has shed new light on the assumptions about 

grout performance at Hanford that were used in the early 1990s to inform 

DOE’s waste treatment approach for LAW and that were reiterated in 

DOE’s 2012 EIS describing waste treatment options for supplemental 

LAW. These assumptions no longer appear to be accurate, particularly 

when considering the engineered and natural barriers at the site that are 

designed to help ensure long-term safe disposal. The National Research 

Council has advised DOE to make risk-informed decisions when selecting 

waste treatment approaches. Because DOE must soon make a decision 

on how to treat supplemental LAW at Hanford, incorporating current 

scientific information on the performance of grout would help DOE ensure 

that it identifies potential treatment approaches that align the costs of 

treatment and disposal pathways with the relatively low long-term risk of 

LAW. With more than $250 billion in estimated costs to clean up the 

nation’s former weapons production sites, DOE must seek ways to 

address risks nation-wide under a limited budget.124 But until DOE 

 124The cost estimate is in 2016 dollars.

Conclusions
Page 52 GAO-17-306 Nuclear Waste

develops information that reflects what is now known about the 

performance and costs of alternate treatment and disposal methods, such 

as grout, congressional and agency decision makers will not have access 

to current scientific and cost information as they decide how to best 

allocate limited financial resources among many competing needs. 

Moreover, having updated information on the effectiveness of alternate 

methods for treating supplemental LAW will help to inform DOE’s 

discussions with the state of Washington. Given the Savannah River 

Site’s experience of saving billions of dollars by grouting its LAW rather 

than vitrifying it, DOE may have an opportunity to also save costs at 

Hanford while beginning sooner to remove waste from the aging Hanford 

tanks. As experts asserted, by taking a hybrid approach to LAW treatment 

at Hanford, DOE may be able to target different portions of the waste with 

different treatment methods based on the radioactive and hazardous 

constituents of the waste, thereby reducing both short-term risks and 

long-term costs.

While the state of science may suggest alternatives for DOE to consider 

when selecting a treatment approach for supplemental LAW, DOE may 

be vulnerable to legal challenge if it attempts to manage Hanford’s 

supplemental LAW as low-level waste. In 2004, Congress specifically 

authorized the Savannah River and Idaho Sites to manage some of their 

low-activity tank waste as low-level waste, but this specific authority was 

not extended to Hanford. Without the specific authority to manage 

Hanford’s supplemental LAW as low-level waste, DOE may face 

challenges to taking a risk-based approach and treating and disposing of 

the supplemental LAW as a waste type other than HLW.

To enhance DOE’s ability to make risk-based decisions for the treatment 

of Hanford supplemental LAW, Congress should consider clarifying, in a 

manner that does not impair the regulatory authorities of EPA and the 

state of Washington, DOE’s authority at Hanford to determine, in 

consultation with NRC, whether portions of the supplemental LAW can be 

managed as a waste type other than HLW.

To help ensure that DOE’s treatment of Hanford’s supplemental LAW is 

risk based and cost effective, we are making two recommendations to the 

Secretary of Energy. In implementing these recommendations, DOE 

should take into account the results of the analysis required by Section 

3134 of the National Defense Authorization Act for Fiscal Year 2017.

Matter for 

Congressional 

Consideration

Recommendations for 

Executive Action
Page 53 GAO-17-306 Nuclear Waste

1. Develop updated information on the effectiveness of treating and 

disposing of all the different portions of Hanford’s supplemental LAW 

with alternate methods or at alternate disposal sites, and based on 

this information, identify potential treatment and disposal pathways for 

different portions of Hanford’s supplemental LAW, considering the 

risks posed by the LAW.

2. Have an independent entity develop updated information on the 

lifecycle costs of treating and disposing of Hanford’s supplemental 

LAW with alternate methods or at alternate disposal sites.

We provided a draft of this report to the Department of Energy, 

Environmental Protection Agency, and Nuclear Regulatory Commission 

for comment. In its comments, reproduced in appendix V, DOE agreed 

with our two recommendations. DOE made one substantive comment on 

our report about our use of the phrase “low-activity waste.” We did not 

make this change because the primary focus of our report is on the lowactivity waste stream at Hanford. We specifically alert the reader to the 

differences in terminology used at each site, and our report recognizes 

that there are some differences in the composition of the lower 

radioactivity waste streams at the Savannah River and Hanford Sites. 

For consistency and comparative purposes, however, we refer to the lowactivity portion of DOE’s tank waste at all sites as LAW. We have added 

an additional footnote at the beginning of our first objective reminding the 

reader that the Savannah River Site refers to its low-activity waste stream 

as low-level waste. Following the agency comment period, we slightly 

modified our recommendations to add further clarity. We also received a 

written response from NRC, which is reproduced in appendix VI. DOE 

and NRC both provided technical comments, which we incorporated as 

appropriate. EPA did not provide comments on the draft report.

Agency Comments 

and Our Evaluation
Page 54 GAO-17-306 Nuclear Waste

We are sending copies of this report to the appropriate congressional 

committees, the Secretary of Energy, the EPA Administrator, the NRC 

Chairman, and other interested parties. In addition, this report is available 

at no charge on the GAO website at http://www.gao.gov.

If you or your staff members have questions about this report, please 

contact David C. Trimble at (202) 512-3841 or trimbled@gao.gov or 

Timothy M. Persons at (202) 512-6412 or personst@gao.gov. Contact 

points for our Offices of Congressional Relations and Public Affairs may 

be found on the last page of this report. Key contributors to this report are 

listed in appendix VII.

David C. Trimble

Director, Natural Resources and Environment

Timothy M. Persons, Ph.D.

Chief Scientist
Page 55 GAO-17-306 Nuclear Waste

List of Addressees

The Honorable John McCain

Chairman

The Honorable Jack Reed

Ranking Member

Committee on Armed Services

United States Senate

The Honorable Maria Cantwell

Ranking Member

Committee on Energy and Natural Resources

United States Senate

The Honorable Mac Thornberry

Chairman

The Honorable Adam Smith

Ranking Member

Committee on Armed Services

House of Representatives

The Honorable Greg Walden

Chairman

The Honorable Frank Pallone, Jr.

Ranking Member

Committee on Energy and Commerce

House of Representatives

The Honorable Patty Murray

United States Senate
Appendix I: Objectives, Scope, and 

Methodology

Page 56 GAO-17-306 Nuclear Waste

The objectives of our review were to examine (1) the Department of 

Energy’s (DOE) reasons for choosing its treatment approaches for lowactivity waste (LAW) at the Savannah River and Hanford Sites, (2) the 

status of DOE’s treatment of LAW at these sites, and (3) experts’ views 

on the likely performance of vitrification compared with grout for treating 

Hanford’s LAW.

For the purpose of this review, we focused on the Savannah River and 

Hanford Sites because these are DOE’s two sites with the most 

radioactive tank waste. The Idaho Site, near Idaho Falls, Idaho, also has 

some radioactive tank waste. We did not include the Idaho Site in our 

analysis because DOE currently does not plan to manage the waste at 

this site as low-level waste. For this reason, we determined that it was not 

practical to compare the Idaho Site’s treatment approach with the Hanford 

Site or the Savannah River Site.

To inform and provide context for all three objectives, we reviewed 

numerous reports and technical studies. We first identified reports and 

studies using sources cited in our prior work, as well as through literature 

searches (using key words, such as grout, vitrification, low-activity waste, 

Hanford, and Savannah River Site) of sources including national 

laboratories; DOE contractors; academic institutions; research journals; 

and the National Academies of Sciences, Engineering, and Medicine 

(National Academies). We also obtained reports and documents 

requested from and provided by DOE, as well as studies suggested by 

experts who participated in our May 2016 experts’ meeting (see below for 

information on our experts’ meeting). We selected studies for further 

review that were peer reviewed or were from credible sources that were 

relevant to our focus on the treatment of LAW at the Hanford and 

Savannah River Sites. We reviewed the studies to gather information 

about the performance of vitrification and grout, technical challenges 

facing the Savannah River and Hanford Sites, the costs of treatment, the 

evolution of decision making on treatment at the two sites, and the 

advancement of science on vitrification and grout. After reviewing each 

selected study, we identified and obtained the major sources that were 

cited in the studies and reviewed the additional studies, as appropriate. 

We repeated this process several times until we determined that we had 

identified the major themes related to the topics listed above. We also 

used these studies to corroborate information obtained from interviews 

with DOE officials and from experts who participated in our May 2016 

experts’ meeting.

Appendix I: Objectives, Scope, and 

Methodology
Appendix I: Objectives, Scope, and 

Methodology

Page 57 GAO-17-306 Nuclear Waste

To determine DOE’s reasons for choosing its treatment approaches for 

LAW at the Hanford and Savannah River Sites, we reviewed numerous 

reports and studies addressing DOE’s overall plan to retrieve, treat, and 

dispose of its tank waste at the Hanford and Savannah River Sites. We 

reviewed documents to understand how DOE’s tank waste cleanup 

strategy has evolved, as well as DOE’s environmental impact statements. 

Because we found that precise information on DOE’s estimated costs of 

treating Hanford’s LAW with different treatment approaches is not 

available, we present the cost estimates from various studies to illustrate 

the evolution of cost estimates over time, rather than to imply that any of 

these estimates are precise. To identify the legal and regulatory reasons 

for DOE’s chosen treatment approaches, we reviewed applicable legal 

and regulatory requirements and guidance documents governing the 

cleanup of hazardous and radioactive wastes, as well as information on 

past and pending lawsuits (as cited in our report). We also reviewed 

documents analyzing DOE’s need for supplemental LAW treatment 

capacity at the Hanford Site and DOE’s analysis of potential options for 

treating LAW. In addition, we interviewed officials from DOE’s Office of 

Environmental Management, as well as DOE officials from the Hanford 

Site’s Office of River Protection and the Savannah River Site. We also 

visited (1) the Hanford Site, where we observed Hanford’s tank farms and 

waste treatment plant construction site, and (2) the Savannah River Site, 

where we observed its tank farms, operating high-level waste (HLW) and 

existing LAW treatment facilities, and the construction site for its future 

LAW treatment facility. We interviewed officials from other agencies—

specifically, the Washington State Department of Ecology, the South 

Carolina Department of Health and Environmental Control, the 

Environmental Protection Agency, and the Nuclear Regulatory 

Commission. We selected these agencies because they play a role in 

LAW treatment at the Hanford and Savannah River Sites.

To determine the status of LAW treatment at DOE’s Savannah River and 

Hanford Sites, we examined DOE reports and studies, environmental 

impact statements, budget and financial documents, and other relevant 

DOE documents. Specifically, we sought information on the amount of 

LAW that has been and will be treated, the schedule for constructing and 

operating the LAW treatment facilities, the cost of treating LAW, and 

technical challenges, if any. To identify DOE’s timeline for treating waste 

at each site, we reviewed milestones DOE agreed to under its Federal 

Facility Agreement with South Carolina and the Tri-Party Agreement 

(TPA) and Consent Decree, as well as modifications made to the 

milestones since 1989 when the TPA was initially signed. We also asked 

officials from the Savannah River and Hanford Sites to review our 
Appendix I: Objectives, Scope, and 

Methodology

Page 58 GAO-17-306 Nuclear Waste

identified schedule milestones for accuracy. To identify technical 

challenges at each site, we reviewed reports and technical studies 

prepared by DOE and contractors as well as academic reports. We also 

interviewed DOE officials and officials at both the Savannah River and 

Hanford Sites. We identified challenges based on key themes identified 

across the documents and on whether challenges could affect the sites’

costs and/or schedules.

Further, we analyzed available information on the costs of treating 

Hanford’s LAW, such as internal cost estimates and estimates included in 

DOE’s 2012 Environmental Impact Statement. We also reviewed DOE’s 

budget justification documents, Hanford’s System Plan, DOE contractor 

estimates, and project cost and schedule baselines. We asked DOE 

officials at the Hanford and Savannah River Sites to provide expenditures 

and planned costs related to the construction and operation of LAW 

treatment facilities. To the extent possible, we took steps to corroborate 

estimated costs with available budget documents, DOE reports, and DOE 

officials, but the estimates we present are based only on available 

information and rough estimates provided by DOE. Because precise 

information on the costs of treatment options at Hanford is unavailable, 

we used the best available information to provide a rough, order-ofmagnitude estimate. We adjusted budget numbers for inflation and 

reported all figures in 2015 dollars, unless otherwise noted. Because 

some of DOE’s estimated costs were approximations, we conducted a 

sensitivity analysis by examining the cost-per-gallon difference between 

the Hanford and Savannah River Sites under different scenarios. This 

helped us assess how, if at all, imprecise information could affect the 

results of this comparison. For example, we assessed how DOE’s costs 

would change if the estimates provided by DOE officials were incorrect 

(e.g., if Hanford’s vitrification facilities operated for 20 years, rather than 

its projected 39 years). In this scenario, DOE’s costs per gallon to vitrify 

all of Hanford’s LAW would still be more than four times the costs to grout 

the Savannah River Site’s LAW. We believe that the information 

presented in our report provides an approximate order-of-magnitude 

comparison and is sufficiently reliable to suggest that DOE’s cost to treat 

Hanford’s LAW with vitrification appears to be substantially more than 

DOE’s costs to treat the Savannah River Site’s LAW with grout.

To determine experts’ views on the likely performance of vitrification 

compared with that of grout for treating LAW at the Hanford Site, we 

convened an experts’ meeting, as described below. In order to 

corroborate statements made by the experts on this topic, to the extent 

possible, we also identified and analyzed technical studies and reports by 
Appendix I: Objectives, Scope, and 

Methodology

Page 59 GAO-17-306 Nuclear Waste

DOE, contractors, and academic institutions regarding the use of 

vitrification, grout, and other treatment approaches to treat LAW. During 

and after the meeting, several experts provided us with information on 

published studies and information on how other sites treat their 

radioactive waste. To the extent possible, we collected and analyzed this 

information on the performance of vitrification compared with other 

treatment methods.

We collaborated with the National Academies to convene a 2-day 

meeting with 21 experts on the treatment of Hanford’s LAW. The meeting 

was held on May 3 and 4, 2016. We collaborated with staff from the 

National Academies to select a broad mix of experts from state and 

federal government agencies, academia, national laboratories, and 

industry with scientific expertise in nuclear waste treatment, 

immobilization, or disposal. We also sought experts with knowledge about 

issues that may help to inform decisions related to treating Hanford’s 

LAW, such as experts with a background in the treatment and disposal of 

radioactive and hazardous waste as it pertains to economics, risk 

analysis, and the environment. We sought to obtain a balance of experts 

with expertise in vitrification (glass) and expertise in grouting (or saltstone 

or cement). We asked the experts to disclose any potential conflicts of 

interest, such as any current financial or other interest that might conflict 

with their service. The 21 experts were determined to be free of conflicts 

of interest, and the group as a whole was judged to have no inappropriate 

biases.1 The views of these experts cannot be generalized to everyone 

with expertise on LAW or Hanford; they represent only the views of the 

experts who participated in our meeting hosted by the National 

Academies. The experts who participated in our study are listed in table 

3.

 1

Two of the experts noted that, while they did not have any conflicts of interest, they are 

periodically involved in work associated with DOE. Both experts told us that they did not 

believe this work would interfere with their ability to provide an unbiased perspective 

during our experts’ meeting. We evaluated their statements and determined that they did 

not have any inappropriate biases.

Selection of Experts
Appendix I: Objectives, Scope, and 

Methodology

Page 60 GAO-17-306 Nuclear Waste

Table 3: Experts Participating in GAO’s May 2016 Experts’ Meeting

Expert Affiliation

George Apostolakis Massachusetts Institute of Technology, Emeritus

John Applegate Indiana University 

Arden L. Bement, Jr. Purdue University 

Craig H. Benson University of Virginia

Paul Black Neptune and Company, Inc.

Thomas Brouns Pacific Northwest National Laboratory

Patricia J. Culligan Columbia Universitya

David Esh U.S. Nuclear Regulatory Commission

Fred Glasser University of Aberdeen

Carol Jantzen Savannah River National Laboratory

David W. Johnson, Jr. Journal of the American Ceramic Society

David S. Kosson Vanderbilt University

Igor Linkov Army Corps of Engineers

Graham Mitchell State of Ohio Environmental Protection Agency (retired)

Ian Pegg Catholic University of America

Eric Pierce Oak Ridge National Laboratory

James Rispoli North Carolina State University 

Rebecca Robbins International Atomic Energy Agency

David J. Swanberg Washington River Protection Solutionsb

Catherine Veyer AREVA

Chris Whipple Environ (retired)

Source: GAO. | GAO-17-306

a

Patricia Culligan participated via teleconference.

b

David Swanberg participated via video-teleconference.

During this meeting, we asked the experts to discuss issues related to the 

treatment and disposal of LAW and how these issues fit into the riskinformed decision-making process. We designed the meeting to follow the 

structure of a 2006 National Research Council report addressing the 

regulation and management of LAW.2 According to this report, a risk 

assessment provides a framework for organizing information in a form 

that is meant to provide input to risk-management decision making. The 

National Research Council developed a framework for the relationship 

 2

Improving the Regulation and Management of Low-Activity Radioactive Wastes.

Meeting Content
Appendix I: Objectives, Scope, and 

Methodology

Page 61 GAO-17-306 Nuclear Waste

among scientific information, risk assessments, and risk management; 

this framework and the basic risk terminology supporting it have served 

as the basis for environmental health risk assessment, both regulatory 

and non-regulatory, since the mid-1980s. According to the framework, 

scientific data provide the basis for performing an environmental risk 

assessment, which in turn provides input to a risk management decision. 

The results of a risk assessment are used by regulators and other 

decision makers, along with information about economics, technological 

feasibility, politics, and the law, to determine how best to manage a risk.3

See figure 3 for a graphic depiction of a risk-informed approach to 

decision making, as applied to our review of the treatment of Hanford’s 

LAW. Using this framework, we divided the 2-day meeting into four 

sessions: (1) the state of research on vitrification and grout; (2) the longterm disposal risks associated with vitrification and grout; (3) how other 

factors—such as economic, technological, and logistical factors—may 

affect decisions about the treatment of Hanford’s LAW; and (4) an openended discussion of other issues related to the treatment of Hanford’s 

LAW and topics and themes that arose during the prior three sessions. 

The experts’ meeting focused on the treatment of all of Hanford’s LAW 

because DOE has not yet determined which tanks’ waste will be treated 

by the Waste Treatment and Immobilization Plant (WTP) and which tanks’

waste will be treated with a supplemental treatment approach. In addition, 

the experts did not address issues related to the construction and 

operation of the WTP.

 3

The National Research Council report notes that the origin of waste is not relevant in 

determining risk.
Appendix I: Objectives, Scope, and 

Methodology

Page 62 GAO-17-306 Nuclear Waste

Figure 3: A Risk-Informed Approach to Decision Making

The meeting was recorded and transcribed to ensure that we accurately 

captured the experts’ statements. In addition, after each session during 

the meeting, we summarized the key points and themes that arose during 

that session and invited the experts to offer any additional themes that 

they believed should be included. Before and after the experts’ meeting, 

we also conducted targeted interviews with certain experts to ask 

questions pertaining to the experts’ specific areas of expertise or to follow 

up about specific comments they made during our May 2016 experts’

meeting.

After the meeting, we analyzed the transcripts to characterize the experts’

responses and to identify major themes. Specifically, we used a software 

program for qualitative analysis to assist with coding the comments using 

categories that we identified based on (1) the overall structure that we 

established for the experts’ meeting and (2) topics highlighted during 

each session of the experts’ meeting. To assess the content of the 

transcripts, we classified experts’ statements into a preliminary set of 

Content Analysis
Appendix I: Objectives, Scope, and 

Methodology

Page 63 GAO-17-306 Nuclear Waste

categories, and then refined this into a final categorization of themes that

included the following.4

• Effectiveness. We also considered terms related to effectiveness, 

such as “encapsulate,” “retain,” “perform,” “immobilize, “technetium99,” and “iodine-129.”

• Risks. We also considered terms related to risks, such as “hazards,”

“threats,” “contaminate,” “mitigate,” and “likely.”

• Costs. We also considered terms related to costs, such as 

“economic,” “savings,” “comparison,” “expensive,” “cheap,” and 

“feasible.”

• Benefits of starting or completing treatment sooner. We also 

considered related issues, such as the risks or costs of delaying 

treatment.

• Regulatory factors. We also considered comments about the 

considerations and impacts of regulatory factors on cleanup.

• Comparisons to other sites. We also considered comparisons 

between the sites, such as the Savannah River and Hanford Sites.

To code sensitive and prominent key terms—such as on concepts related 

to cost—we had three different analysts check the coding. Each analyst 

reviewed the comments falling under each theme for completeness and 

level of detail, as well as for areas of potential bias, and made a judgment 

about appropriate codes that described the themes in the experts’

comments. The analysts compared their decisions and reconciled any 

disagreements regarding appropriate codes by refining the criteria used 

to categorize the responses. We also conducted a word frequency count 

of the transcript to identify terms that were most commonly used during 

our experts’ meeting. We reviewed these terms to ensure that our content 

analysis of the transcript accounted for each of the key terms. We then 

identified key themes that arose from the experts’ meeting by looking for 

patterns and comparing comments made by different experts.

For reporting purposes, we chose to include experts’ comments that (1) 

captured the essence of a perspective that was raised more than once; 

(2) provided illuminating detail or illustrative examples; (3) cited specific 

evidence, such as a specific study or research; (4) were within the core of 

the commenting expert’s base of knowledge; and (5) were well-

 4

In all applicable cases, we used variations of the key word. For example, we considered 

both “risk” and “risks.” As another example, we considered both “hazard” and “hazardous.”
Appendix I: Objectives, Scope, and 

Methodology

Page 64 GAO-17-306 Nuclear Waste

articulated. We also considered the strength of evidence presented by the 

experts, such as whether they cited any reports to support their views and 

the level of details included in their statements. For reporting purposes, 

we cannot include a complete list of themes and comments made by the 

experts—because, for example, of the technical complexities of this 

subject and the various ways that each theme could be articulated—but 

we believe we were able to identify the main themes that emerged from 

the experts’ meeting, note areas of disagreement, and select specific 

comments to include in our report to serve as illustrative examples of the 

key themes. To the extent possible, we corroborated experts’ statements 

with technical literature. For reporting purposes, “a few experts” refers to 

two or three experts, “some experts” refers to four or five experts, “several 

experts” refers to six to eight experts, and “numerous experts” refers to 

nine or more experts.5 The general use of the term “experts” refers to four 

or more experts and is used to set up a broad concept that the experts 

discussed. When practical and appropriate, we note where there were 

dissenting views.

We provided information on the technical benefits and shortcomings of 

vitrification and grout for treating Hanford’s LAW to the experts who 

participated in our meeting to review for technical accuracy. We 

incorporated experts’ technical comments as appropriate. We also 

provided a full draft of our report to two experts who participated in our 

meeting. We selected experts who are members of the National 

Academies or who were former senior leaders in the federal government. 

We incorporated their technical comments as appropriate.

We conducted this performance audit from July 2015 to May 2017 in 

accordance with generally accepted government auditing standards. 

Those standards require that we plan and perform the audit to obtain 

sufficient, appropriate evidence to provide a reasonable basis for our 

findings and conclusions based on our audit objectives. We believe that 

the evidence obtained provides a reasonable basis for our findings and 

conclusions based on our audit objectives.

 5

Not all experts were able to offer informed views on every topic of the two-day meeting. 

Therefore, it would be unreasonable to expect all 21 experts to comment on every issue 

discussed.
Appendix II: DOE’s Current Plans for Treating 

Low-Activity Waste at the Hanford Site

Page 65 GAO-17-306 Nuclear Waste

Notes: LAW comprises about 90 percent of the total volume of tank waste, while HLW comprises the 

remaining 10 percent. DOE estimates that supplemental treatment will be needed to treat about onehalf to two-thirds of the LAW at Hanford. The supplemental LAW treatment path has not yet been 

defined. DOE could, for example, modify the existing Waste Treatment and Immobilization Plant to 

accommodate the additional capacity, or DOE could construct a new waste treatment facility.

Appendix II: DOE’s Current Plans for 

Treating Low-Activity Waste at the Hanford 

Site
Appendix III: Timeline of Treatment Plans at 

the Hanford Site

Page 66 GAO-17-306 Nuclear Waste

Note: The $418 million figure has not been adjusted to 2015 dollars. The cost estimates from 2005 

forward are from budget and contract documents and include escalation.

Appendix III: Timeline of Treatment Plans at 

the Hanford Site
Appendix IV: Experts’ Views on the Technical 

Benefits and Shortcomings of Vitrification and 

Grout for Treating Hanford’s Low-Activity 

Waste

Page 67 GAO-17-306 Nuclear Waste

According to experts who participated in our meeting convened by the 

National Academies of Sciences, Engineering, and Medicine (National 

Academies), both vitrification and grout could effectively treat Hanford’s 

low-activity waste (LAW). These experts noted that there are benefits to 

treating the waste with either vitrification or grout but that both vitrification 

and grout have some key shortcomings that the Department of Energy 

(DOE) would need to address. Table 4 provides a summary of the 

benefits and shortcomings associated with each method, as identified by 

these experts.

Table 4: Technical Benefits and Shortcomings Associated with Vitrification and Grout at the Hanford Site, According to 

Experts

Benefits Shortcomings

Vitrification • More research has been done on vitrification than 

on grout at the Hanford Site.

• Organics and nitrates are destroyed during the 

high-heat vitrification process.

• The vitrification process requires high temperatures, 

which increases the complexity of the treatment 

process.

• Radioactive constituents—such as technetium-99 

and iodine-129—may not be completely retained 

during the vitrification process.

• Certain constituents—such as technetium-99 and 

iodine-129—will need to be recycled through the 

vitrification facility or treated with a secondary waste 

form, which will likely be grout.

Grout • Grout has been optimized in recent years.

• Grout is a “well established” and mature process.

• Grout has been used successfully at the Savannah 

River Site and by commercial disposal sites.

• Grout may face technical challenges related to its 

ability to retain radioactive constituents—particularly 

technetium-99 and iodine-129—over long periods of 

time.

• Organics could prevent grout from setting.

• Smaller blocks of grouted waste degrade more 

quickly.

Source: GAO analysis of experts’ views. | GAO-17-306

Experts who participated in our meeting discussed the benefits of both 

vitrification and grout. According to one expert, one reason it may be 

beneficial to vitrify LAW at Hanford is that much more is known about 

designing LAW glass formulations than grout formulations for the 

particular chemical compositions of Hanford’s LAW. This expert explained 

that because DOE chose to vitrify Hanford’s LAW in the 1990s, more 

Appendix IV: Experts’ Views on the Technical 

Benefits and Shortcomings of Vitrification 

and Grout for Treating Hanford’s Low-Activity 

Waste
Appendix IV: Experts’ Views on the Technical 

Benefits and Shortcomings of Vitrification and 

Grout for Treating Hanford’s Low-Activity 

Waste

Page 68 GAO-17-306 Nuclear Waste

research has been done on vitrification than on grout at the site.1 One 

expert stated that high-level waste (HLW) has been successfully vitrified 

in other countries, including France and Germany. A few experts also 

noted that it may be beneficial to vitrify LAW because organics and 

nitrates are destroyed during the high-heat vitrification process, which 

means that these chemicals would not be a concern for disposal.

According to a few experts who participated in our meeting, it may be 

beneficial to grout LAW because there have been significant advances in

the use of grout that enable grout to perform much more effectively than it 

was assumed to perform when DOE made its decision to vitrify Hanford’s 

LAW. One expert stated that grout is a “well established” and mature 

process. A second expert explained that grout is a less complex process 

than vitrification. Another expert stated that recent studies have shown 

that grout performs significantly better than indicated in DOE’s 2012 

Environmental Impact Statement (EIS).2 This expert also explained that 

recent studies on grouted secondary waste—the waste generated during 

the treatment process—have demonstrated that grout retains waste 

almost as well as vitrified LAW.3 Specifically, grout testing has focused on 

several aspects of its performance, including increasing the amount of 

waste loaded into the grout and adding materials to increase the retention 

of technetium and iodine in grouted wastes. A 2015 DOE report stated 

that grouted LAW has been shown to have acceptable waste form 

properties, such as its leachability indexes—which measure the mobility 

of constituents from a waste form—for technetium and iodine.4 The report 

further stated that grouted LAW test mix had been shown to meet the 

treatment standards for land disposal of hazardous waste. Experts also 

 1

This expert also noted that Hanford’s testing of the LAW pilot melters was conducted 

using four different sized melters. According to this expert, after testing on the largest 

LAW pilot melter—which operated for nearly 5 years—was completed, the melter was 

shut down, disassembled, and subjected to extensive testing to validate the melter’s 

design lifetime and performance.

2

Department of Energy, DOE Final Tank Closure and Waste Management Environmental 

Impact Statement for the Hanford Site, Richland, Washington, DOE/EIS 0391 (November 

2012).

3

Specifically, the expert stated that grout has been demonstrated to perform at least two 

orders of magnitude better than was presented in the 2012 EIS.

4

Department of Energy, Technical Approach for Determining Key Parameters Needed for 

Modeling the Performance of Cast Stone for the Integrated Disposal Facility Performance 

Assessment, PNNL-24022 rev. 0 (Richland, WA: March 2015
Appendix IV: Experts’ Views on the Technical 

Benefits and Shortcomings of Vitrification and 

Grout for Treating Hanford’s Low-Activity 

Waste

Page 69 GAO-17-306 Nuclear Waste

noted that DOE’s Savannah River Site has been successfully treating its 

LAW with grout with few challenges.

According to experts who participated in our meeting, there are some 

shortcomings associated with vitrification, including process complexity,

waste retention, and recycling.

• Process complexity. Vitrification is a process by which glass is made 

at high-temperatures, and experts noted that high temperatures 

increase the complexity of the treatment process in several ways, 

including by creating the potential for radionuclide constituents to 

become volatile.5 According to a 2011 DOE report, most vitrification 

issues occur, in part, because of the high operating temperature.6

According to this report, high operating temperatures can cause 

equipment failure, but the potential for such failure is low. More 

specifically, this report states that molten glass is corrosive, and at 

high enough operating temperatures, the molten glass can corrode 

internal melter components or breach the melter walls.7 One expert 

suggested that DOE may need to acquire a more sophisticated melter 

to improve reliability and processing versatility. A few experts noted 

that vitrification uses a complex off-gas system, which captures waste 

constituents that volatilize during the vitrification process.8 According 

to a 2015 DOE report, without mitigating actions, the LAW off-gas 

systems may chronically limit the LAW treatment facility’s overall 

production capacity.9 In addition, experts noted that DOE may 

encounter challenges developing precise glass formulations to treat 

 5

Some volatile chemicals may vaporize into gasses at the relatively high temperatures 

involved in the vitrification process

6

Department of Energy, Office of River Protection, A Joule-Heated Melter Technology for 

the Treatment and Immobilization of Low-Activity Waste, RPP-48935, rev. 0 (Richland, 

WA.: March 2011).

7

Melters are used to produce vitrified waste glass. Waste, in combination with glass 

forming materials, is heated to high temperatures by passing an electrical current through 

the melter. The waste and glass forming materials melt, forming a vitrified waste glass 

product that is poured into containers.

8

Off-gasses must be treated prior to release to remove radioactive and hazardous 

components to protect personnel, the public and the environment from radionuclide and 

chemical exposure. In the off-gas system, some liquid will become part of the secondary 

liquid waste stream instead of being vitrified.

9

Department of Energy, Office of River Protection, Waste Treatment and Immobilization 

Plant Low-Activity Waste Facility Design and Operability Review and Recommendations,

15-WTP-0151 Attachment 2, (Richland, WA: Sept. 4, 2015).
Appendix IV: Experts’ Views on the Technical 

Benefits and Shortcomings of Vitrification and 

Grout for Treating Hanford’s Low-Activity 

Waste

Page 70 GAO-17-306 Nuclear Waste

different batches of Hanford’s LAW, which has numerous different 

chemical mixtures in the tanks.10 One expert noted that, in order to 

encapsulate waste during the vitrification process, the formulation of 

the vitrification materials—such as sugar and silica, which is found in 

sand—must be matched to specific types of chemicals in the waste. If 

the wrong formulation is used, the glass that immobilizes the waste 

might not meet the disposal requirements, or the glass might not 

encapsulate all of certain waste constituents. Moreover, one expert 

also noted that not all types of waste contained in Hanford’s tanks 

have been demonstrated to be effectively vitrified in the facility as 

designed. According to the 2015 DOE report on Hanford’s LAW 

vitrification process, if a certain glass-forming component is not added 

to a batch of waste to be vitrified, it could, over time, lead to the melter 

failing prematurely.11 One expert also stated that concerns about the 

melters failing prematurely apply specifically to Hanford’s vitrification 

process because Hanford uses a different chemistry than the 

Savannah River Site’s HLW vitrification process does.12

• Waste retention. Experts stated that radioactive constituents, such 

as technetium-99 and iodine-129, as well as non-radioactive 

constituents, such as sulfate, may be volatilized at the high 

temperatures used in the vitrification process, meaning that the glass 

may not completely retain these constituents. One expert also noted 

that certain chemicals, such as sulfate, technetium, and iodine, are 

not well retained in glass.13 Experts described techniques that can be 

 10Because of the highly heterogeneous chemical and radiological composition of the 

Hanford tank waste, DOE will need to vitrify the waste in batches, calibrating the 

composition of each batch of waste to be vitrified to maximize waste treatment 

effectiveness. According to the 2012 EIS, Hanford’s Best Basis Inventory, which 

establishes the chemical inventory of the tanks, may have uncertainties of 50 to 400 

percent. Final Tank Closure and Waste Management Environmental Impact Statement for 

the Hanford Site, Richland, Washington.

11Department of Energy, Office of River Protection, Waste Treatment and Immobilization 

Plant Low-Activity Waste Facility Design and Operability Review and Recommendations,

15-WTP-0151 Attachment 2, (Richland, WA: Sept. 4, 2015).

12According to this expert, Hanford plans to operate a “oxidizing flowsheet,” while 

Savannah River’s HLW facility operate a “reducing flowsheet.” This expert explained that 

an oxidizing flowsheet reduces the lifespan of a melter and increase waste volatility.

13According to a 2015 DOE report on LAW glass development, the amount of technetium 

retained in LAW glass can vary depending on factors, such as waste chemistry and how 

the melter is operated. Department of Energy, Office of River Protection Advanced LowActivity Waste Glass Research and Development Plan, ORP-59500 rev. 0 (Richland, WA: 

November 2015).
Appendix IV: Experts’ Views on the Technical 

Benefits and Shortcomings of Vitrification and 

Grout for Treating Hanford’s Low-Activity 

Waste

Page 71 GAO-17-306 Nuclear Waste

employed to increase waste retention, such as controlling the waste 

chemistry or adding a layer of waste plus glass-forming chemicals that 

float on top of the melter’s molten glass (called a cold cap), creating 

conditions to enhance the mixing of waste. According to one expert, 

during HLW vitrification and LAW immobilization with grout, the 

Savannah River Site employs chemistry designed to keep 

constituents in their least volatile state to more effectively encapsulate 

waste. This expert stated that Hanford does not plan to use this 

chemistry to the extent that the Savannah River Site does.14 In 

November 2015, the Office of River Protection issued a report 

describing its glass research program, which aims to develop 

advanced glass formulations that will increase the amount of waste 

encapsulated in the glass while meeting waste form performance 

requirements.15

• Recycling. Experts noted that certain constituents will not be 

incorporated into the molten glass by the vitrification process and will 

need to be recycled through the vitrification facility or treated with a 

secondary waste form.16 Experts stated that recycling can increase 

the amount of certain constituents, such as technetium and iodine, 

incorporated in the glass.17 However, according to a 2015 DOE 

report, recycling technetium also decreases the amount of tank waste 

that can be immobilized in each glass canister because of increased 

amounts of chemicals from the recycling process.18 Those 

constituents that are not immobilized are captured by the off-gas 

system and must be treated with a secondary waste form, such as 

low-temperature waste forms, including grout, that are being 

considered or developed for liquid secondary wastes; however, a 

treatment method has yet to be selected. At the Hanford Site, DOE is 

working to create glass formulations designed to better retain certain 

constituents. One expert explained that although recycling is a 

 14According to the Office of River Protection Advanced LAW Glass Research and 

Development Plan, Hanford is studying controlling the waste chemistry to increase the 

retention of technetium during vitrification.

15Office of River Protection Advanced Low-Activity Waste Glass Research and 

Development Plan.

16In order to retain more of certain constituents (such as technetium) in glass, the liquid 

stream from off-gas treatment may be recycled back through the melter.

17For any one pass of waste through the melter, approximately 20 percent to 70 percent of 

the technetium is expected to be retained by the glass.

18Office of River Protection Advanced Low-Activity Waste Glass Research and 

Development Plan.
Appendix IV: Experts’ Views on the Technical 

Benefits and Shortcomings of Vitrification and 

Grout for Treating Hanford’s Low-Activity 

Waste

Page 72 GAO-17-306 Nuclear Waste

common practice in chemical processing—and vitrification is a type of 

chemical processing—recycling reduces the amount of waste that can 

be loaded into each glass canister, thereby increasing the volume of 

vitrified waste.

According to experts who participated in our meeting, there are also some 

shortcomings associated with grout, including ones related to radionuclide 

retention, organic constituents, and waste form stability.

• Radionuclide retention. A few experts noted that grout may face 

technical challenges related to its ability to retain radioactive 

constituents—particularly technetium and iodine—over long periods of 

time. One expert stated that grout is a porous material, meaning that 

water can enter more easily and leach out the technetium and iodine. 

In contrast, another expert noted that the grout recently developed for 

secondary waste has technetium release rates almost equivalent to 

those of Hanford’s LAW glass. According to a third expert, it is 

possible to retain technetium and iodine in grout by adding in other 

materials that decrease leaching. Another expert noted that grout 

improves in its ability to retain constituents after long periods of 

curing. Other experts suggested that by removing the technetium from 

LAW, Hanford could create a viable waste form that meets 

performance requirements. DOE officials from the Savannah River 

Site and a few experts also stated that the Savannah River Site has 

been successfully grouting its LAW, which contains both technetium 

and iodine.19 According to a January 2016 DOE report, the tank waste 

at the Savannah River Site has more technetium than Hanford—

41,500 curies at the Savannah River Site compared with 26,500 

curies at Hanford.20 Moreover, DOE officials from the Savannah River 

Site noted that initial results of a multi-year study of core samples 

from one of the Site’s vaults—conducted to address uncertainties 

about grout’s long-term performance—show that radiation releases 

 19One expert presented a different view, noting that the environment at Hanford is arid, 

whereas the environment at the Savannah River Site is very humid and wet and is 

therefore a better location to dispose of treated LAW. The expert further noted that 

Hanford could face additional challenges because of these environmental differences. As 

discussed earlier in this report, several experts disagreed with this perspective and stated 

that Hanford is an optimal location to dispose of LAW, compared with the Savannah River 

Site, because of its arid climate and low rainfall levels. 

20Department of Energy, Office of Environmental Management, Technetium Management 

Program Plan (January 2016).
Appendix IV: Experts’ Views on the Technical 

Benefits and Shortcomings of Vitrification and 

Grout for Treating Hanford’s Low-Activity 

Waste

Page 73 GAO-17-306 Nuclear Waste

from grout will not exceed those allowed for protection of the public.21

This study showed that the assumptions for leach rates used in the 

Savannah River Site’s Saltstone Disposal Facility performance model 

were sufficiently conservative and that the grout will retain the waste 

for the required period of time.22

• Organic constituents. Experts stated that organic hazardous 

constituents could prevent grout from setting, thereby reducing the 

grout’s effectiveness.23 One expert noted that organics could also 

interfere with the strength of the grouted product.24 According to a few

experts, waste with high levels of organic constituents could require 

thermal treatment, such as vitrification. One expert noted that prior to 

grouting waste that contains organics, the site would need to conduct 

tests to make sure that the organics did not interfere with the groutsetting process. This expert further noted that some organics in the 

waste may be present at low enough concentrations that they may be 

within site limits. According to another expert, grout can be formulated 

to tolerate organic constituents without affecting its ability to set. 

According to a 2002 DOE report, approximately 20 percent of the tank 

waste at Hanford contains soluble organic compounds.25 One expert 

stated that waste containing these organic constituents is mostly 

concentrated in two double-shell tanks and that the remaining waste 

with organic constituents is segregated from other waste that does not 

 21The Savannah River Site’s grout testing is ongoing. According to agency officials, the 

site has been conducting studies on grouted waste forms for its low-level and low-activity 

waste since the late 1970s.

22The report noted that the grout did not encapsulate iodine-129 as well as had been 

modeled, but leaching of iodine-129 from grout would not impact the magnitude or timing 

of the peak dose in the surrounding environment. Department of Energy, Property Data for 

Core Samples Extracted from SDU Cell 2A, SRR-CWDA-2016-00051 rev. 0 (Aiken, SC: 

April 2016). 

23Grout is a low-temperature process. It does not destroy organics and nitrates. However, 

one expert noted that nitrates may accelerate the set of grout without causing any adverse 

impacts to the final grout product, and another noted that the release of nitrates into the 

environment can be controlled by facility design.

24To meet disposal criteria, grout must achieve a minimum compressive strength. If the 

grout does not achieve this compressive strength, it may not withstand the disposal 

facility’s overlying deposit of materials.

25Department of Energy, Recommendation for Supplemental Technologies for Potential 

Mission Acceleration, RPP-11261, rev. 0 (Richland, WA: July 26, 2002). According to one 

expert, 18 to 20 of Hanford’s tanks contain 40 percent to 50 percent of Hanford’s total 

organic content.
Appendix IV: Experts’ Views on the Technical 

Benefits and Shortcomings of Vitrification and 

Grout for Treating Hanford’s Low-Activity 

Waste

Page 74 GAO-17-306 Nuclear Waste

contain organic constituents.26 According to the Savannah River Site’s 

Liquid Waste System Plan Revision 20, the site has not yet 

determined how it will treat the waste in its one tank that contains 

organic constituents and plans to begin the technology selection 

process around the 2022 time frame.27

• Waste form stability. According to one expert, the size of the grouted 

waste form impacts its performance. Specifically, this expert noted 

that large blocks of grout retain waste for longer periods of time, 

whereas smaller blocks of both vitrified and grouted waste forms 

degrade more quickly. A second expert explained that by increasing 

the size of the grouted waste form, the grout will degrade more slowly, 

thereby reducing the rate that constituents are released into the 

environment. Savannah River Site officials told us they decided to use 

large units with engineered barriers, called saltstone disposal units, 

instead of underground trenches because models indicated that 

nitrate, a hazardous contaminant of concern, may leach into the 

groundwater from a smaller disposal unit. According to agency 

officials, the Savannah River Site’s saltstone disposal units also serve 

to prevent precipitation from reaching the grout and leaching iodine, 

as well as to prevent technetium from leaching. Containerized grout, 

which is a smaller-sized waste form, was used in Hanford’s more 

recent assessments, such as DOE’s 2012 EIS in which containerized 

grout did not meet requirements, and a 2003 DOE assessment of 

LAW treatment in which the containerized grout did not meet 

requirements.28 One expert also noted that containerized grout 

substantially increases the cost of treatment, compared with large 

grout disposal units.

 26At the Hanford Site, waste contained in single-shell tanks will be transferred to doubleshell tanks prior to waste treatment.

27Savannah River Remediation LLC, Liquid Waste System Plan Revision 20, SRR-LWP2009-00001 (Aiken, SC: March 2016).

28DOE Final Tank Closure and Waste Management Environmental Impact Statement for 

the Hanford Site, Richland. Also see, Department of Energy, Office of River Protection, 

Assessment of Low-Activity Waste Treatment and Disposal Scenarios for the River 

Protection Project (Richland, WA: Apr. 14, 2003). Containerized grout has met 

requirements at West Valley, which grouted its waste into containers before shipping the 

grouted containers to the Nevada National Security site. According to an official at the 

Nevada National Security Site, the grout was determined to meet the site’s waste 

acceptance criteria and was disposed of on site without special instruction.
Appendix V: Comments from the Department 

of Energy

Page 75 GAO-17-306 Nuclear Waste

Appendix V: Comments from the Department 

of Energy
Appendix V: Comments from the Department 

of Energy

Page 76 GAO-17-306 Nuclear Waste
Appendix VI: Comments from the U.S. Nuclear 

Regulatory Commission

Page 77 GAO-17-306 Nuclear Waste

Appendix VI: Comments from the U.S. 

Nuclear Regulatory Commission
Appendix VII: GAO Contacts and Staff 

Acknowledgments

Page 78 GAO-17-306 Nuclear Waste

David C. Trimble, (202) 512-3841 or trimbled@gao.gov

Timothy M. Persons, (202) 512-6412 or personst@gao.gov

In addition to the individuals named above, Nathan Anderson, Assistant 

Director; Charlotte E. Hinkle; Richard Johnson; Amanda K. Kolling; 

Jeffrey Larson; and Katrina Pekar-Carpenter made key contributions to 

this report. Also contributing to this report were Mark Braza, Ellen Fried,

Andrew Stavisky, Sara Sullivan, and Jack Wang.

Appendix VII: GAO Contacts and Staff 

Acknowledgments

GAO Contacts

Staff 

Acknowledgments

(100208)
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