When you think about nuclear waste, you might have in mind something like the creeping blobs of green goo, as on “The Simpsons.” In reality, though, it is a lot cleaner and easier to manage than that. It isn’t the most dangerous waste, or even the longest-lived; a lot of it isn’t even waste, [see Conca (here)]. It’s just the most misunderstood of all the types of leftovers that an industrial society produces.
And it is a political football.
To meet our decarbonization goals, which will require ramping up nuclear energy, we’ll need to correct our misperceptions of nuclear waste, understand what the real challenges are, and address the political factors standing in the way of safe, zero-carbon energy. [For more on approaching zero-carbon energy, see (here)]
Some Nuclear Contamination Isn’t a Problem
Radioactive waste from nuclear power reactors takes many forms. Some of it is lightly contaminated, like tools or protective gloves and coveralls—or even filter material used to purify the cooling water. Those materials can be safely buried in engineered landfills, where they will be isolated until their radioactivity declines to the point that it is no longer a risk to human health. That process can take a few hundred years.
The reactor, too, develops radioactive parts because some of the neutrons, the sub-atomic particles that are set loose when an atom is split (and which are used to split other atoms), end up being captured by atoms of the plant’s concrete, or the reactor’s metal walls. When these atoms absorb the extra neutron, they are “activated,” or made unstable, but they gradually return to stability by giving off radiation and reverting to a harmless non-radioactive form. The most common activation product, Cobalt-60, will be gone after a few decades, which is why owners of reactors that will be decommissioned sometimes propose waiting for years to do the work.
Likewise, some concrete and other building material are also contaminated. But these, too, have been successfully buried in environments where they remain until they are not a health issue. Decommissioning a reactor will produce more than 100,000 tons of material, most of it slightly radioactive. Some of it is not radioactive and will go to an industrial landfill.
The Nuclear Waste Problem
The bulk of the radioactivity from any given nuclear plant, and the material which is the subject of a dispute in this country, is spent fuel. That fuel is the best inventoried, best protected, and best sealed-up used material of any industry, but its final disposition has been the subject of a decades-long standoff.
So what is going on? To explain, we need to first understand what spent nuclear fuel really is. The current generation of nuclear power reactors in the United States runs on uranium, formed into a ceramic somewhat like the material that makes up a coffee mug. The ceramic comes in the form of pellets about the size of a pencil eraser, and these are stacked in long, thin tubes. The tubes are bundled together into fuel assemblies that are up to 15 feet long and weigh about 1,000 pounds each. When they are new, they are barely radioactive, and technicians can handle them wearing cotton gloves. That’s to protect the fuel, not the technicians.
The fuel goes into a reactor, where it typically lasts for four and a half to six years. Upon removal, the bundles look the same, rather like a flashlight battery looks the same after its battery is fully run down. Inside the long, thin metal tubes, the ceramic has often broken up, but like a broken coffee mug, it’s still a solid. But also, like a battery in a flashlight, the chemical makeup of the fuel is altered. As the reactor runs, it splits a small fraction of the uranium atoms, creating fragments that are unstable. They return to stability by giving off a particle or an energy wave, i.e., radiation. Some of the fragments go through several steps, morphing from one unstable form to another until they reach stability.
A reactor also creates new elements by planting one or more stray neutrons in some of the uranium atoms, which results in radioactive “transuranic” elements, of which plutonium is the most common. Some of that plutonium is also split, but a lot remains in the reactor.
Some radioactive atoms return to stability in a few seconds or a few minutes, some in decades, and some in millennia. The transuranics are in the millennia category. The longevity of radioactive materials is measured by the time it takes half the atoms in a sample to degrade to another form is called a “half-life.” (Sometimes, the radioactive atom degrades into a harmless stable form; sometimes, it changes into another radioactive element, which has its own half-life, and will degrade yet again, in a long chain of events.)
“Half-life” is a term in common use, but it is widely misunderstood. Intuitively, it might seem like a long half-life would be a bad thing, but short half-lives are actually the hardest to handle in fuel when it is removed from a reactor. Materials with short half-lives are extremely radioactive but reach stability quickly. Materials with a long half-life, like plutonium, are barely radioactive, but continue emitting radiation for extended periods.
In terms of spent fuel, after a few hundred years (which is a period short enough to make it easy for engineers and geologists to predict the performance of a repository), most of the fragments have lost their radioactivity.
The fragments giving off the most radiation in the first few years—types of cesium and strontium, with half-lives of about 30 years—have been through so many half-lives that they are almost entirely gone. But the transuranics, which were only ever slightly radioactive, are still emitting. Yet from a substance that was initially too radioactive to stand near, now the spent fuel is safe to be around, but probably unwise to eat (and definitely something we want to keep out of drinking water sources).
How to Manage Spent Nuclear Fuel?
Unlike some chemical pollutants like arsenic or mercury, which are eternal, spent nuclear fuel becomes easier to handle over time. Initially, it is extremely radioactive, and it generates a lot of heat. So, it is plucked out of the reactor by a crane, kept underwater, and moved to a spent fuel pool, where it sits for several years. Spent fuel pools are very deep, and the water shields workers from radiation. Heat exchangers remove heat from the water. If the pool’s cooling systems were lost, because of a loss of electric power, for example, technicians would eventually have to add water to the pool to make up for evaporation or to prevent boiling. The pools are built to withstand earthquakes and other natural hazards.
At reactors, spent fuel pools are quiet places, with a whirr of pumps in the background. The water is very clear but tinted a Ty-D-Bol shade of blue because plant workers have added boron, a chemical that absorbs stray neutrons. (Boron is not toxic; in fact, it is the main ingredient of boric acid eyewash.) Because the water blocks the radiation, technicians walk through the area in street clothes.
After five years or so in the pool, the materials with the shortest half-lives have disappeared, and the spent fuel’s heat production is way down. At that point, it can be lifted by a crane and moved into a steel cask with other fuel assemblies. The cask is drained, and when it is dry, it is filled with an inert gas, so there is no possibility of corrosion.
Once the cask is sealed, it is put inside a small concrete silo. The silo has vent holes at the bottom and top, so air can flow in, around the sealed steel canister, and carry off the heat that is still being generated. These are called “dry casks,” and at power plants around the country, they sit on extra-strong concrete pads, surrounded by barbed wire. The pads look a little like basketball courts at a maximum-security prison.
Most of the casks have no moving parts at all, and some have pressure gauges that monitor the gas inside. Maintenance requirements are quite modest. Over the years, they have been known to shift during earthquakes, or be partially covered with water in floods, but they are designed to withstand being completely submerged or knocked over. After the terrorist attacks of 9/11, some nuclear opponents said they could be breached by armor-piercing shells, but it is not clear if that is true, and in any case, the materials inside are not likely to be a hazard to the public. There are some gases, which would disperse quickly, but nearly all the radioactive material is in ceramic form, not creeping globs of goo, green or otherwise, and would not spread beyond where it sits in the nuclear facility.
Outside the silos, radiation levels are near the background levels anywhere else. But the concrete can be slightly warm to the touch. Dry casks can be licensed for 40 years, and those licenses can be renewed for 40 years, but as with all nuclear licenses, there are inspection and performance requirements. No casks are yet approaching 80 years of age yet, but it appears likely that they could last much longer. In fact, some casks are at locations where the reactors have long since been demolished and returned to “green field” conditions. So the equipment to empty the casks is no longer readily at hand, and they just sit in place, as inert as a concrete and steel monument. But they are guarded and monitored.
How Much Spent Fuel Is There in the United States?
The national inventory is about 90,000 metric tons, growing by 2,000 tons a year. But this isn’t a big volume because uranium is extremely heavy, about one and a half times denser than lead and two and a half times denser than steel. If the whole volume of spent fuel were stacked on a football field, it would pile up to a depth of fewer than 10 yards, according to the Department of Energy.
In the future, the volume of spent fuel created per unit of electricity produced may go down because the utilities are seeking a uranium blend that is richer in U-235, the type that splits easily, so each assembly would generate heat in a reactor for a longer time. And some of the advanced reactor designs produce waste in other forms, some of which are easier to handle. The bottom line, though, is that spent nuclear fuel is already securely and safely managed—and it will only get easier to handle over time. But this is not the way the reactor builders initially expected the fuel to be handled.
Part 2:
Where the U.S. stands on nuclear waste storage and how we got here.
In the early years of nuclear energy, uranium was thought to be scarce, and the industry was afraid it would run out. (This was very wrong, but no more so than similar predictions about oil or gas or coal.)
The reactor designers knew that after months in a reactor, the fuel would need replacing because the reactor had fissioned most of the easy-to-split atoms, but it still had a lot of useable uranium in it—plus plutonium, an element created when one type of uranium captured a stray neutron let loose by an atom that split. If the plutonium and other usable materials could be harvested, they could yield a lot more energy.
And so, engineers came up with a plan. The idea, briefly put into practice, was to let the used fuel cool for a while and then take it to a factory where it would be mechanically chopped up and dissolved in acid. The reusable elements could be chemically separated from the waste—fragments from uranium that had been split and various other ingredients—and fashioned into new fuel. The waste would still have to be buried somewhere, but the volume would be smaller, and some of the transuranics, whose radioactivity lasted the longest, would go into new fuel. But this “reprocessing” ran into two problems. One was economics; as often happens in mining and drilling, plenty of raw material was soon found. Using virgin uranium turned out to be much cheaper than scavenging unused uranium and plutonium from spent fuel.
The other was fear; if the United States was able to reprocess spent fuel, it might set a bad example for countries around the world that wanted nuclear weapons and thought they could pull off something similar. From a technical standpoint, many nuclear experts doubted the likelihood of such plans, because many of the plutonium atoms in spent fuel pick up more than one neutron and become a mix of plutonium types that is not good bomb fuel. (It is generally referred to as “civil grade” plutonium, not “weapons grade.”) And at any rate, the invention and continuous improvement of centrifuges for uranium enrichment in the years since have created a path to a uranium bomb that is simpler and cheaper than using spent reactor fuel.
Nonetheless, President Gerald Ford and then President Jimmy Carter banned the technology in the United States. This had the effect of increasing the quantity and longevity of used fuel that would require burial.
But where to bury spent nuclear fuel?
In the 1960s, the Atomic Energy Commission set about looking for a burial site, and its successor agency, the Department of Energy, continued the search. Then, in 1982, Congress passed the Nuclear Waste Policy Act, which instructed the DOE to study five particular sites, recommend three to the president by 1985, and build a repository and open it by January 1998, at which point the Energy Department would have to start picking up spent fuel for burial. A state could block the selection, but Congress could override that block, according to the legislation. To pay for the facility, Congress told the DOE to collect a fee from the nuclear utilities, which was later set at a tenth of a cent per kilowatt-hour produced at reactors. Some members of Congress, notably from Texas and Washington State, sought to make political points by taking their states or districts off the target list. And so, in 1987, Congress amended the law, to tell the DOE to concentrate on Yucca Mountain, a volcanic structure about 100 miles from Las Vegas. That change drew support from all the other candidate sites, and Nevada, politically isolated, wasn’t able to stop the process.
In February 2002, U.S. Secretary of Energy Spencer Abraham recommended Nevada to President George Bush, Nevada objected, and Congress overruled. Burial at Yucca remains the law of the land, and the Nuclear Waste Trust Fund, including interest earned, has a balance of over $43 billion from the nuclear utilities. But there has been no progress on building the repository because, over the years, Nevada gained political muscle. In turn, the utilities and an organization representing state public service commissions sued the Federal government, and a judge ruled in 2013 that they no longer had to pay the tenth-of-a-cent fee. The utilities also sued the government because it did not, in fact, start picking up the fuel for burial in 1998. It still hasn’t.
The courts ruled that the government violated the contracts it signed and would have to pay for the cost to build dry casks, where much of the spent fuel is now stored, and other expenses. The government has so far paid out more than $8.6 billion, but not from the waste trust fund that was created with the money it got by collecting rents from the nuclear utilities. Instead, the money comes from a standing account at the Treasury called the Judgment Fund, the same fund used to pay simpler damages, like re-imbursing a driver whose car was rear-ended by a government vehicle.
What went so wrong with Yucca?
As part of its work in the 1980s and 1990s, the Energy Department conducted substantial research on Yucca Mountain, and, following the law, applied in 2008 to the Nuclear Regulatory Commission for a license to build and operate it. Like a lot of DOE projects, this one was way behind schedule, but the scientific and engineering evaluations of Yucca indicated that the combination of the containers and the geology of the site could contain the wastes until they were no longer radioactive enough to cause a problem. Two developments torpedoed the Yucca project.
One was that then-Senator Barack Obama, fighting hard for Nevada’s electoral votes, promised to stop the project. He cut funding soon after he came into office. Second, Harry Reid, a Senator from Nevada, became the Democratic leader in 2005 and the majority leader in 2007, and he bottled up funding for the project and managed to install an opponent of Yucca, and an opponent of nuclear power generally, as chairman of the Nuclear Regulatory Commission.
At one point, President Donald Trump then promised to restart Yucca, but he apparently changed his mind. President Biden has not revived the project. Before Congress stopped funding the licensing process, the Nuclear Regulatory Commission, began its evaluation of the suitability of Yucca, and the commission staff found that the site appeared to be suitable. But the loss of funding blocked the NRC’s next step, an adjudicatory hearing where the staff, the applicant (the DOE), opponents, and other interest parties get to make arguments about its technical merits.
So the spent fuel sits in deep pools of water, safe from earthquakes and other natural hazards, with redundant cooling systems, inside the security perimeter of the nuclear plants where it was used. In most plants, much of the fuel has been moved out of the pools, and sealed up in steel canisters, filled with inert gas to prevent rust, and fitted into small concrete silos. These “dry casks” dissipate heat passively; they do not need pumps, fans, or other mechanical equipment. But in some cases, the dry casks are orphaned because the reactor at the site was decommissioned years ago.
At the sites, maintenance workers check that no animals have built nests in the vent holes at the bottom of the concrete silos, because this might reduce the airflow around the steel canisters. But there is hardly any other maintenance requirement. The casks are inspected regularly. Over the years, they have already survived floods and earthquakes.
Radiation outside the silos is very low; workers approach in street clothes. The concrete is warm to the touch. The fact that snow won’t stick to them is a clue to what’s inside. They are quite boring.
But centralized storage, and eventual burial, would be more economical.
The problem with burial is that opponents of nuclear energy have so thoroughly seized on the waste issue that it will be hard for any administration to make progress. It isn’t even clear that spent fuel is the concern of opponents. Rather, it is just a convenient way to build public resistance to nuclear energy. Opponents have argued that the dry casks can’t be safely shipped, for example, although there is a long history, in the United States and abroad, of safe transport of spent fuel.
It is also not clear that spent fuel is even waste. The Nuclear Energy Policy Act requires that the material be retrievable, so that if the economics change, it is available for re-use. In fact, the coming commercialization of “fast reactors” makes it somewhat more likely that there will be economic value to materials in the spent fuel. Fast reactors might also make it practical to put the longest-lived materials right back into a reactor and destroy them. They would be broken up and thus converted into elements that were more radioactive, but that would make disposal easier because they would burn out sooner; essentially, they would be converted from a log to a pile of crumpled newspaper.
Who has incentives to solve the nuclear waste problem?
Aside from wanting to end payments to the utilities for breach of contract, the federal government has another incentive to find a solution: It sits on a substantial volume of military nuclear waste. This includes liquids that have been “vitrified,” or mixed into a very strong form of glass. The lack of a permanent repository continues to be a talking point against the development of advanced reactors, on which the government has promised to spend billions of dollars.
With Yucca’s future uncertain, attention has turned to another concept, championed by a federal commission organized to study the issue: “consent-based siting.” That essentially means finding a place where residents will volunteer to host the project, perhaps in exchange for payments for local infrastructure or other emoluments. In September 2022, the Energy Department said it would offer $16 million to communities interested in learning about consent-based siting.
The idea is not simple, however, because there is a dispute about who would have to consent. In the Yucca case, some communities in Nevada favor the project, but the state government does not. The same split developed in Texas and New Mexico when interim storage of dry casks was proposed. Local people see economic benefits, but state-level elected officials with broader constituencies have found it good politics to oppose the projects.
Some impetus for opening a repository may come from developments in Sweden and Finland, though. Both countries are proceeding expeditiously to dig storage tunnels in granite formations. But both have a governmental structure unlike the one in the United States; they have strong national governments, and local governments. There is no equivalent of America’s sovereign states.
A growing public acceptance of nuclear energy as essential to preventing radical climate change may translate into less national opposition to nuclear energy, but it seems unlikely to change local reactions to a radioactive waste repository. But local feelings could change.
Success in Scandinavia will go a long way to refute one argument, that building a repository is impossible. And it will buttress the argument for consent-based siting. In Sweden, several towns competed to host the project. In Finland, the utility negotiated with the municipality, offering benefits to win local approval.
In the meantime, the national inventory is growing, But in the early years, most of the radiation comes from varieties of cesium and strontium that have half-lives in the range of 30 years; that is, every 30 years, their radiation output drops by half. That means that the oldest fuel is now substantially less radioactive, and somewhat simpler to transport and bury.
[For more discussions on nuclear waste and on the status of nuclear power in general, see a recent radio podcast (here)].
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