From 1943 to 1989, the Hanford Nuclear Reservation produced weapons-grade plutonium and approximately 212,000 cubic meters of mixed radioactive and hazardous chemical waste, filling 177 aging underground tanks. It is assumed that 90% of this waste is “Low Activity Waste” after cesium, strontium, and transuranics are removed. In late 2025, the Direct Feed Low Activity Waste facility began vitrification, i.e., mixing liquid waste with molten glass at 1150 °C, thereby destroying hazardous organic chemicals. To continuously maintain heat in the two 300-ton melters, approximately 200,000 megawatt-hours of electricity are required annually. Over their 40-year lifetimes, these vitrification melters generate approximately 3,000,000 tonnes of carbon dioxide. This carbon footprint could be reduced by “grouting” a substantial portion of the waste, i.e., mixing the waste with Portland cement, granulated slag, and fly ash. In a recent agreement, the Washington State Department of Ecology agreed in principle to grouting, provided that the resulting grout is shipped to a dedicated off-site radioactive waste disposal facility. This would reduce Hanford’s carbon footprint even after accounting for the CO2 from transportation.

• Vitrification

• Grouting

• Radioactive waste

• Carbon dioxide

• Hanford

Rothwell GS (2026) The Carbon Footprint of Radioactive Waste Immobilization. Chem Eng Process Tech 11(1): 1110.

DFLAW: Direct Feed Low Activity Waste facility; JHCM: Joule-Heated Ceramic Melters; LAW: Low Activity Waste, MWh: Megawatt-hour; SRS: Savannah River Site; TPA: Tri-Party Agreement; WTP: Waste Treatment and Immobilization Plant 

What is to be done with “supplemental” waste at the Hanford Site?

From 1943 to 1945, the Hanford Nuclear Site hosted the Manhattan Project’s plutonium production facilities, culminating in the production of the fissile material used in the bomb that exploded over Nagasaki in August 1945. During the Cold War, much of the U.S. arsenal’s plutonium was produced at Hanford, with nine plutonium production reactors and five reprocessing plants (with lesser amounts produced at Idaho National Laboratory and the Savannah River National Laboratory). Until 1989, 212,000 cubic meters (m3, or 56,000,000 gallons) of mixed hazardous and radioactive waste filled 177 underground tanks. It is assumed that 90% of this waste is “Low Activity Waste”(LAW) after cesium, strontium, and transuranics have been removed, i.e., approximately 191,000 m3 (50,000,000 gallons).

In 1989, the U.S. Department of Energy (DOE), the U.S. Environmental Protection Agency (EPA), and the Washington State Department of Ecology signed the Tri Party Agreement (TPA) to set milestones for Hanford tank waste remediation. The facility for treating the waste, known as the Waste Treatment and Immobilization Plant (WTP), has been under construction for 25 years. The TPA was updated in 2025 (Ecology, 2025) [1].

The Hanford Field Office of DOE-Environmental Management manages the WTP construction and operations contracts. WPT includes the High-Level Waste (HLW) facility, the Pre-Treatment (PT) facility, the Direct Feed Low Activity Waste system (DFLAW; GAO, 2022 [2]), the Analytical Laboratory, and the Balance of Facilities, including the Tank-Side Cesium Removal (TSCR) facility.

In late 2025, the DFLAW facility began vitrification (mixing waste with molten glass at 1150 °C (2100 °F), which also destroys hazardous organic chemicals) at an average daily production rate of 21 metric tons (5300gallons), or 875 kg/hr. Once fully operational (expected in 2027), the facility is projected to produce approximately 1,100 stainless-steel containers of vitrified waste annually. Each container holds about 2.5 m3 of glass product and will be disposed of onsite in the Integrated Disposal Facility. DFLAW consists of two “300-ton” melters and an off-gas treatment facility. The 300-ton designation refers to the physical weight of the melter assembly, including its refractory lining and steel casing, rather than its processing capacity. These are Joule-Heated Ceramic Melters (JHCM), which use submerged electrodes to pass current directly through the molten glass. This technology is described in GAO (2023) [3] and Gutta (2019) [4].

To accelerate disposal, the latest TPA envisions “grouting” to solidify “supplemental” LAW by mixing it with concrete-like materials for off-site disposal, e.g., at the Clive Radioactive Waste Disposal Facility in Utah and/or the Waste Control Specialists’ facility in Texas. See NASEM (2023) [5], which reviews Bates et al. (2023) [6]. But there is disagreement over whether grouting is “as good as glass” (NASEM 2019 [7]). While the Washington State Department of Ecology does not agree that grouting is as good as vitrification for long-term storage, it has agreed in principle to grouting supplemental LAW for off-site disposal.

Before 2017, discussions about whether to grout LAW assumed that vitrification would cost about $53 billion and grouting about $5.5 billion (Table 1).

Table 1: Total Estimated Costs for Grouting LAW at the SRS and Vitrifying LAW at the Hanford Site, Based on Best Available Information

Many calculations have been performed to estimate these values. However, there has been no discussion of the greenhouse gas footprint of grouting or vitrification.

In contrast to high-temperature vitrification, grouting operates at room temperature (about 25°C). It blends the liquid supplemental LAW with dry inorganic materials to produce a concrete-like product (in which gravel is replaced by recycled ground slag from steel production) for disposal in polypropylene-lined, reusable steel boxes. This paper proposes a method for determining the energy input to the LAW solidification processes and for calculating the resulting greenhouse gas emissions.

How much electricity does radioactive waste immobilization consume?

Although the electricity required to power the two 300-ton electrical/joule-heated melters (the Liquid-Fed/ Joule-Heated Ceramic Melters, LF/JHCMs, the largest in the nuclear industry) is not publicly available, this section estimates the megawatt-hours consumed by DFLAW to maintain 1150 °C during 5 years of continuous operation within a 40-year life cycle (i.e., through 16 melters each operating for 5 years).

DOE (2024) [8] states, “When the WTP begins operating, it will roughly double Hanford's energy demands. Addressing emissions at these facilities is key to Hanford's net-zero approach and helps create a waste treatment process less impactful to global climate change.” The explicit assumption is that DFLAW is operating in equilibrium, i.e., that the facility has been commissioned as explained in Cary (2023) [9]. (Electricity used during commissioning is excluded from this paper’s calculation.)

The Glass Material Oxidation and Dissolution System (GMODS) was evaluated as a potential technology for treating surplus fissile materials and spent nuclear fuel at the Savannah River Site (SRS). It was designed to convert various fuel types directly into glass forms and to potentially integrate with the SRS DWPF (Defense Waste Processing Facility). Forsberg et al. (1995, p.13) [10], described the construction and operation of the GMODS facility: “This site plan is essentially identical to the DWPF at the SRS because the GMODS facility would be about the same size and produce similar quantities of [High-Level Waste] glass.”

The DWPF uses a 75-ton JHCM melter to mix radioactive sludge with glass frit (see the photograph of glass frit in Cary 2023 [9]) and pour the molten mixture into stainless steel canisters. Since March 1996, it has produced over 4000 canisters. The two DFLAW melters are 4 times larger than the DWPF and the proposed GMODS. According to Forsberg et al. (1995, p.45) [10], the annual average electricity consumption of GMODS would have been 25,000 MWh. Therefore, one would expect the annual electricity consumption at DFLAW to be about 200,000 MWh, or about 8,000,000 MWh over a 40-year operating life for the two melters. This does not include electricity used by [1], the DFLAW off-gas recovery system, [2] the Effluent Management Facility (EMF), (Figure1), which treats gases and liquids produced during the vitrification process, or [3] many of the support systems discussed in U.S. GAO (2023, pp. 7-8) [3].

Figure 1: Effluent Management Facility (EMF) under construction

The most frequently cited estimate of operating expenses appears in GAO (2017, p. 40) [11], reproduced as (Table 1). The $40B estimate for the “Estimated operating cost for vitrification at Hanford” is accompanied by a footnote that states,

“DOE does not have an estimate for the cost to treat LAW. However, according to contractor estimates [Bechtel National, Inc.], the cost for commissioning and operating the LAW facility and associated support systems is currently estimated at about $600 million per year… 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).”

Although the facility did not begin operations until late 2025, and it is unclear whether the 2015-dollar estimate accounts for inflation, escalation, or discounting (Rothwell, 2025 [12]), Congressionally allocated funding for fiscal year 2026 is $460 million. However, U.S. GAO (2023, p.1) [3], later re-estimated the cost of vitrification: “The Hanford Site in Washington State is one of the largest and most expensive environmental cleanup projects worldwide. We estimated in 2022 that the cleanup will cost between $300 billion and $640 billion and take decades.” DOE-RL (2019, p. D-14) [13] estimated that “Radioactive Liquid Tank Waste Disposition” would cost $213.9 billion (see discussion in Rothwell, 2026 [14]).

On the other hand, the cost of grouting LAW at Hanford is based on a specific grouting technique used to treat LAW at SRS. According to research at SRS (Hill and Langton, 2025, p. 4 [15]), mixing one liter (1250 g) of liquid LAW (after cesium, strontium, and suspended transuranic solids have been removed) with Portland cement (55.5 ml, 172 g), granulated slag (348.5 ml, 1010.5 g), and fly ash (368 ml, 967.5 g) yields a total volume of 1772 ml (a 77% increase) and a total mass of 3400 g (a 272% increase).

What might be the CO2 emissions of LAW immobiliza tion at Hanford?

Because DFLAW's electricity is drawn from the grid (although a nuclear power plant and hydroelectric dams are near the site), the Energy Information Administration (EIA) carbon calculator indicates that generating a MWh of electricity in the U.S. produces, on average, 0.37 metric tonnes of CO2, tCO2 (EIA, 2024 [16]). Assuming an average of 0.37 tCO2/MWh, vitrification at DFLAW using 8,000,000 MWh would produce approximately 3,000,000 tCO2. (Because many of the subsystems in the grouting alternative would also be required in the vitrification alternative, the electricity use in these subsystems is excluded from the carbon footprint calculations; they cancel out in a comparison.)

Assuming half of the LAW is vitrified and half is grouted, the electricity required for vitrification is reduced to 4,000,000 MWh over its lifetime, thereby lowering CO2 emissions to 1,500,000 tCO2. Assuming 95,400 m3 of LAW is grouted, the volume would increase by 77% to 170,000 m3, and the mass would be 315,325 t (or 347,586 tons). The most recent TPA agreement requires that this grout be moved off-site 1045 km (640 miles) to Utah (330,000,000 tkm or 222,500,000 ton-miles) or 2560 km (1590 miles) to Texas (807,000,000 tkm or 553,000,000 ton-miles). Moving 1,000,000 ton-miles of freight by truck in the U.S. generates approximately 161.8 tCO2. The total carbon footprint of moving grout by truck ranges from 32,256 to 80,086 tCO2. The total CO2 footprint of vitrifying half of Hanford’s LAW and grouting the other half ranges from 1,532,000 to 1,580,000 tCO2.

Because vitrifying low-level radioactive waste is energy intensive, the carbon footprint of this waste immobilization method is enormous. Because the Department of Energy has not yet determined how it would grout this waste, it is not possible to determine the optimal amount of waste to grout. However, it appears that any amount of grouting would reduce carbon dioxide emissions during Hanford tank waste remediation. Further research is required to better understand the CO2 reductions from grouting.

This research is based on committee work for the National Academies of Sciences, Engineering, and Medicine (NASEM). All errors are the author’s responsibility, who thanks N. Anderson, J. Applegate, L. Dysert, S. Fraizinger, G.E. Gibson, R. Graber, J. Hollmann, D. Korn, D. Melamed, P. O’Sullivan, C. Pescatore, R. Prieto, W.G. Ramsey, T. Wood, and committee members for their comments and support, and reviewers of this and companion papers. This paper reflects the views and conclusions of the author, not those of NASEM committee members or staff.

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