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The Basics

What does the nuclear fuel cycle look like?

The nuclear fuel cycle refers to what takes place before and after fuel is used in a commercial nuclear reactor. The “front end” of the nuclear fuel cycle refers to all the steps that prepare fuel to go into a reactor. The “back end” is the set of procedures that safely manage used nuclear fuel. 

Just like fossil fuels and critical minerals like lithium and cobalt are mined from the earth, miners extract uranium to fuel nuclear reactors. But freshly mined, natural uranium cannot power most nuclear reactors. While some reactors can run on natural uranium, U.S. nuclear reactors work differently. They need a higher blend of certain uranium isotopes to operate. Some of these isotopes are “fissile,” or able to sustain nuclear reactions because the atoms are easier to split apart. For nuclear reactors, the most important of these isotopes is U-235, which only makes up about 0.73% of freshly mined uranium (most of the rest is U-238). Because freshly mined uranium doesn’t contain enough U-235, it has to undergo a few more steps to be fit for use in a reactor. These steps include refining, conversion, enrichment, and fuel fabrication. Typically, when the fuel finally enters a power reactor, the uranium will have been enriched to between 3% and 5% U-235. 

Graphic depiction of the percentage of U-235 and U-238 in Mined Uranium and Reactor Fuel.

Inside the reactor, uranium atoms split apart through fission, releasing a lot of energy and creating heat. Unlike coal or gas, fuel that powers nuclear reactors isn’t burned. Instead, it’s transformed by the fission process, with only a tiny fraction of the mass disappearing. Heat from the reactor is used to produce steam, which spins a turbine and generates electricity for the grid. After spending 12–18 months in the reactor, used fuel can no longer sustain the fission chain reaction that generates heat. Nuclear plant workers put 27 tons of fresh uranium fuel into a reactor, and after a multi-year-long cooling period, they pull out 27 tons of spent fuel minus a few ounces.

Today, reactor operators remove spent fuel from the reactors, cool it in pools for a few years, and then store it in concrete dry casks awaiting permanent burial at a repository. Today, more than 88,000 metric tons of spent nuclear fuel is in pools and dry-cask storage at reactor sites nationwide. This is the “once-through nuclear fuel cycle, where interim or permanent nuclear fuel storage or disposal occurs after the fuel has only been in a reactor once.

Graphic depiction of the percentage of Pu, U-235, other, and U-238 in Spent Fuel.

So what’s in that spent fuel? It’s still mostly U-238, but it also contains other fissile materials, including some plutonium (Pu) and U-235. After producing heat in the reactor, more than 90% of the potential energy still exists in the fuel assembly.

What is spent-fuel reprocessing and recycling? 

FAQ: RECYCLING NUCLEAR WASTE / NUCLEAR FUEL CYCLE / Graphic showing recycling process of nuclear fuel /

Instead of storing spent nuclear fuel in dry casks in a once-through fuel cycle, another option is to reprocess the used fuel. This is called the “twice-through or the “closed nuclear fuel cycle. Although the terms are often used interchangeably, “reprocessing” specifically refers to separating plutonium and uranium from spent fuel. In contrast, “recycling” means using reprocessed material to create new fuels for commercial power reactors. Reprocessing and recycling spent fuel extracts more usable energy from the original fuel.

What is the process for recycling spent fuel?

Graphic depiction of the percentage of reprocessed material and U-238.

The most common method of reprocessing is PUREX, or plutonium uranium reduction extraction. This is the only technology used commercially globally today. The PUREX process separates spent-fuel byproducts from uranium and plutonium, which can then be used to create new fuel for certain nuclear reactors. The uranium and plutonium from reprocessing facilities are usually combined to create a “mixed oxide fuel,” or MOX. However, the PUREX process isolates very pure plutonium, which raises nuclear weapons proliferation concerns. Fuel reprocessors handle these materials carefully with extensive oversight from domestic and international nuclear safety regulators. 

PUREX is not the only method available to recycle spent nuclear fuel. Other techniques have been researched and developed as potential alternatives. One such technique is electrometallurgical processing, or “pyroprocessing.” Several companies are interested in pyroprocessing to fuel a new generation of reactors. Pyroprocessing and similar techniques differ from PUREX because they do not isolate pure plutonium. Pyroprocessing is more straightforward and less expensive than traditional reprocessing methods and does not pose the same weapons proliferation concerns. However, it typically results in impurities within the resulting fissile materials and does not create suitable recycled fuel for the existing reactor fleet. A different nuclear reactor type called a fast reactor can generate energy from pyroprocessed recycled nuclear fuel.

What is the difference between nuclear safety, nuclear safeguards, and nuclear security?

Nuclear experts distinguish between nuclear safety, nuclear safeguards, and nuclear security. Nuclear safety practices ensure that the operation and design of a facility that works with nuclear material protect its surroundings from unintended releases of radiation. Nuclear security measures enable these facilities to withstand terrorist events, such as sabotage and external or internal attacks. Finally, nuclear safeguards ensure that nuclear materials are not misused and diverted to weapons proliferation or other non-peaceful uses.

Which countries currently recycle spent fuel?

While there is no law banning reprocessing in the United States, the country does not currently engage in national reprocessing efforts. 

Two countries are actively reprocessing and recycling their spent nuclear fuel for their commercial reactors, and another is about to start. All three use the PUREX process. France reprocesses about 1,700 metric tons of spent fuel annually. MOX fuel powers about 10% of France’s nuclear output. The only other currently operating commercial recycling facility is in Russia and has a much smaller annual production capacity of around 400 metric tons.

Japan is nearly finished with a reprocessing plant, which is expected to reprocess around 800 metric tons of used fuel every year. The United Kingdom reprocessed 55,000 metric tons of spent fuel until 2022 when it closed its recycling facility.

Why don’t we recycle our spent fuel in the United States?

At the start of the commercial nuclear industry, the United States was a clear nuclear technological leader, including on reprocessing. At the West Valley Demonstration Project in New York and the Savannah River Site in South Carolina, the government pursued the commercial reprocessing of spent fuel. The West Valley plant recovered 1,926 kilograms of plutonium and 620 metric tons of uranium during its operation from 1966 to 1972. The Hanford site in Washington state housed a PUREX reprocessing facility for military applications, which operated intermittently from 1956 to 1988. The Barnwell reprocessing site in South Carolina was also under construction in the early 1970s until the national stance toward reprocessing changed. 

The PUREX technique concerned domestic nuclear nonproliferation experts due to the purity of the plutonium created. A 1977 Carter Administration executive order diverted federal funding and support away from recycling as a component of the fuel cycle. The administration hoped to set a global precedent against recycling fuel, attempting to set clear boundaries between the power sector and weapons production. In the following years, support for reprocessing and recycling flip-flopped between presidents, creating an inconsistent environment of governmental support for reprocessing. This political environment, along with low prices for uranium and stagnated demand, led to the lack of a comprehensive U.S. spent fuel recycling program.

The situation may be changing. Several projects are evaluating the technologies and feasibility of spent-fuel recycling in the United States. ARPA-E, a research agency within the U.S. Department of Energy, has funded 12 reprocessing-related research projects through its CURIE program to research novel reprocessing technologies and 11 projects through its ONWARDS program to optimize the waste streams from new reactor designs.

The Implications

How does recycling change the conversation about nuclear waste?

By recycling and reusing existing domestic nuclear waste, the country could power itself for thousands of years with fast reactor technologies. Likewise, the U.S. could power its existing reactor fleet with recycled fuel using PUREX reprocessing for 30 years without the need for any new uranium mining. 

Recycling spent fuel could also decrease current spent nuclear fuel stockpiles and lower long-term radioactivity. The high-level waste produced from the recycling process must only be contained for 500 years (rather than tens of thousands of years) until it no longer poses a meaningful threat to human health. 

However, recycling spent nuclear fuel comes with challenges. First, while high-level waste generated from the recycling process is only radioactive for a few hundred years, it is “hotter,” or more dangerous to manage. Second, while reprocessing can reduce the quantity of waste, it can also create more complex waste forms and result in different byproducts that require different storage methods.

Whether the United States or private companies start reprocessing spent fuel, the United States has a statutory responsibility to build a long-term, deep geological repository for existing nuclear waste from commercial reactors. The U.S. must meet that commitment in an environmentally just way. And nuclear developers will need to plan ahead for how to manage spent fuel from new reactors.

Are there justice implications for recycling spent nuclear fuel?

Recycling domestic spent fuel could demonstrate a commitment to good nuclear stewardship. Recyclers could source their spent nuclear fuel from the 70-plus sites in over U.S. states where commercial nuclear waste currently sits next to operating and decommissioned nuclear power plants. Communities hosting this stranded spent fuel never agreed to host nuclear waste indefinitely, and they deserve federal support for actions that result in the spent fuel’s removal from their neighborhoods. Recycling could complement the federal government’s ongoing work toward an integrated management system for nuclear waste by closing the fuel cycle. 

Recycling spent fuel could also reduce the amount of fresh uranium ore that must be mined to produce new fuel. In the U.S., most of the highest-quality domestic uranium lies on or near tribal lands. The U.S. government has a documented, scarred history of supporting uranium mining that mistreated and inadequately protected indigenous communities.

Today, the U.S. does not mine much domestic uranium, but the business case for mining U.S. uranium has recently improved. The U.S. sources most fresh uranium from allies like Canada and Australia, and Kazakhstan, an ally of Russia. But as the global uranium supply has tightened, buyers have greater uncertainty about their future access to Russian uranium. The U.S. is also actively considering limiting or banning imports of Russian uranium, as proposed by Wyoming Senator John Barrasso (S.3856). As a result of these factors, more companies plan to renew mining and milling in the coming years. 

Some unknowns remain. We don’t yet know where a domestic recycling facility would get built, or what its potential environmental impact would be. Recycling project developers will need to engage local communities to make sure people on the ground understand the risks and can exercise willing and informed consent.

Is recycling more expensive?

Historically, domestic recycling faced prohibitive costs. The facilities, processes, and infrastructure that can recycle spent fuel are expensive. Companies are unlikely to invest in recycling if the resulting fuel is not cost-competitive with a once-through fuel cycle. Until recently, global uranium prices were low amid abundant supply and declining demand. In the U.S., the historic Megatons to Megawatts program of weapons disarmament also kept uranium costs artificially low. 

For certain recycling processes, the economics may not make sense. While recent economic analyses of reprocessing are scarce, a 2003 report from Harvard’s Kennedy School found that PUREX reprocessing would create fuel at an estimated $1,000 per kilogram — significantly costlier than the current uranium price, which hovers around $40 per kilogram. As a result, absent motivating factors other than fuel costs, recycling using the PUREX technique for traditional, light-water reactors is likely not economically competitive for private industry to pursue. 

But as global uranium prices increase, as concerns grow around supply, and as recycling technologies improve, the business case for recycling spent fuel could improve. France has shown that long-term commitment to PUREX recycling can decrease costs. In the last 10 years, the cost of recycling in France has decreased by 40%. However, the average household in France pays an extra $10 per year in electricity costs to keep the recycling plant operational.

Pyroprocessing may offer a different story. A 2018 Argonne National Laboratory report determined that a pyroprocessing facility could produce fuel for a new generation of reactors at a cost similar to alternatives. Where the current market rate for high-assay low-enriched uranium, or HALEU, hovers around $8,000 per kilogram, a pilot reprocessing facility could produce reprocessed fuel for somewhere between $5,000 – $10,000 per kilogram. According to the report, this recycled fuel would be cost-competitive with (or cheaper than) new fuel. In addition, the facility could achieve further cost reductions if scaled past a pilot project. 

It is unlikely that the recycling of light-water reactor fuel will take place soon, mainly because the economics of manufacturing fuel through the PUREX process provides little incentive for private industry to invest in the construction of a facility. It will take significant federal support to jumpstart or maintain a recycling program, and many U.S. reactors would need to undergo further licensing procedures to run on the most common type of resulting fuel, MOX. More likely, pyroprocessing will be used to create fuel for different, new types of nuclear reactors; many projects funded through the ARPA-E CURIE program focus on these alternative techniques. 

Are any private sector companies looking to recycle spent fuel?

A few private sector companies have indicated a desire to construct and operate a commercial waste recycling facility, including Oklo, Moltex Energy, and SHINE Technologies. Perhaps most publicly, Oklo is working with the U.S. Nuclear Regulatory Commission to license a pyroprocessing-based recycling facility and manufacture fuel for their Aurora reactor. Canadian-based Moltex Energy is developing a similar approach, hoping to recycle spent fuel from Canadian design reactors to run in their reactor “Stable Salt Reactor — Wasteburner.” However, the companies may face extensive capital expenses, uncertain regulatory environments, and fluctuating political support that could complicate the licensing of recycling facilities.

How is reprocessing connected to nuclear weapons proliferation?

Different recycling technologies present different risks for weapons proliferation. For instance, pyroprocessing does not separate pure plutonium, and there is a general agreement that pyroprocessing facilities cannot produce weapons-grade materials, reducing proliferation risks.

Opponents of spent nuclear fuel recycling often point to concerns about nuclear weapons proliferation as a point of contention against expanding the technology. PUREX facilities are fundamentally the same facilities that militaries use to produce weapons-grade plutonium: If improperly managed or monitored, materials from reprocessing facilities could be diverted to build nuclear weapons. The U.S. has extensive experience applying strong nuclear safeguards to managing radioactive materials and nuclear weapons stockpiles. However, concerns about expanding a recycling program still need to be addressed. 

Many concerns about reprocessing center around moral hazard: Will U.S. reprocessing encourage other countries to engage in reprocessing? Many countries don’t have the same experience protecting nuclear materials. Absent an expansion and enhancement of safeguarding capabilities, a global expansion of reprocessing facilities could theoretically increase the risk of state-based proliferation. The global norm against reprocessing has significantly eroded since the 1970s. France, Japan, and Russia already engage in recycling — activities that did not lead to the mass adoption of nuclear fuel recycling worldwide, as was feared. 

While reprocessing poses an increased risk of stockpiling weapons-grade plutonium, the safeguards the International Atomic Energy Agency has put in place, such as continuous remote sensors and consistent and surprise facility inspections, have prevented extensive weapons proliferation. For countries like the U.S. and France that cooperate with global nuclear agencies and adhere to strong safeguards and security norms, a domestic facility would likely keep concerns about weapons proliferation the same.