President-elect Joe Biden comes into office at a time when phasing out fossil fuels is critical. The Intergovernmental Panel on Climate Change (IPCC) has warned that we must keep the planet from warming more than 1.5˚C above pre-industrial levels by 2030. Every pathway the IPCC envisioned to achieve this goal requires an increase in nuclear energy—of 59 to 106 percent more than 2010 levels by 2030. Biden’s $2 trillion climate plan, recognizing this urgency, includes support for the development of nuclear energy. What is the current state of nuclear energy in the U.S., and what role could it play in a decarbonized future?
Nuclear energy’s role in fighting climate change
Nuclear power is the second largest source of clean energy after hydropower. The energy to mine and refine the uranium that fuels nuclear power and manufacture the concrete and metal to build nuclear power plants is usually supplied by fossil fuels, resulting in CO2 emissions; however, nuclear plants do not emit any CO2 or air pollution as they operate. And despite their fossil fuel consumption, their carbon footprints are almost as low as those of renewable energy. One study calculated that a kilowatt hour of nuclear-generated electricity has a carbon footprint of 4 grams of CO2 equivalent, compared to 4 grams for wind and 6 grams for solar energy — versus 109 grams for coal, even with carbon capture and storage.
In the last 50 years, nuclear energy has precluded the creation of 60 gigatons of carbon dioxide, according to the International Energy Agency. Without nuclear energy, the power it generated would have been supplied by fossil fuels, which would have increased carbon emissions and resulted in air pollution that could have caused millions more deaths each year.
The state of nuclear energy today
Around the world, 440 nuclear reactors currently provide over 10 percent of global electricity. In the U.S., nuclear power plants have generated almost 20 percent of electricity for the last 20 years.
Most of the nuclear plants operating today were designed to last 25 to 40 years and with an average age of 35 years, a quarter of them in developed countries will likely be shut down by 2025. After the Fukushima meltdown, a number of countries began to consider phasing out their nuclear programs, with Germany expected to shut down its entire nuclear fleet by 2022.
The U.S. has 95 nuclear reactors in operation, but only one new reactor has started up in the last 20 years. Over 100 new nuclear reactors are being planned in other countries, and 300 more are proposed, with China, India, and Russia leading the way.
How nuclear reactors work
All commercial reactors generate heat through nuclear fission, wherein the nucleus of a uranium atom is split into smaller atoms (called the fission products). The splitting releases neutrons that trigger a chain reaction in other uranium atoms.
As the atoms split, they release a tremendous amount of energy—a kilogram of uranium undergoing fission releases three million times more energy than a kilogram of coal being burned. Coolant, often water, circulates around the reactor core to absorb the heat that fission creates; the heat boils the water, creating pressurized steam to turn a turbine and generate electricity.
Reactor fuel is usually uranium in pellets that are placed in fuel rods and arranged in the reactor’s core. A 1,000MW nuclear reactor might contain as many as 51,000 rods with over 18 million pellets.
After it fuels the reactor for four to six years, the spent fuel is replaced with new fuel rods. The highly radioactive and hot spent fuel rods are transferred to a pool of water on-site that cools and shields them.
After about five years, when enough of the energy has decayed, the fuel is transferred to dry casks that are stored on-site in concrete bunkers. This is how most of the nuclear waste that has been produced over the years is currently stored.
The challenges facing nuclear energy
The nuclear industry in the U.S. faces resistance due to a number of factors.
The American public has misgivings about nuclear power because of three nuclear accidents that occurred: the Three Mile Island partial meltdown in 1979, the Chernobyl meltdown and explosion in 1986, and the Fukushima meltdown in 2011 precipitated by an earthquake and a tsunami.
Both the Three Mile Island and Fukushima accidents began after the reactors were shut down and a lack of power prevented the pumps from circulating water to cool the decaying fuel. Similar light water reactors, cooled with ordinary water, make up the majority of the nuclear reactors in use.
While nuclear accidents are rare, the consequences are catastrophic. Fukushima’s meltdown drove over 200,000 people from their homes. Chernobyl’s reactor site will be radioactive for tens of thousands of years.
The uranium found in nature consists of mostly uranium-238, and a tiny amount of uranium-235, which is what is needed for fission. The process of concentrating and increasing the U-235 in relation to U-238 is called enrichment. However, enrichment is controversial because the process can sometimes be used to create uranium for nuclear weapons, as can reprocessing spent fuel to recover uranium and plutonium to recycle them for fresh fuel.
“The U.S. position since the Ford administration has been to not reprocess fuel, because we don’t really want other countries reprocessing their fuel,” said Matt Bowen, a research scholar focusing on nuclear energy at Columbia University’s Center on Global Energy Policy.
To prevent nuclear proliferation, most countries have signed onto international agreements to limit nuclear weapons, and the International Atomic Energy Agency regularly inspects nuclear facilities to monitor their nuclear materials.
There is still no viable way to permanently dispose of the radioactive material that is produced at every stage of a nuclear power plant’s life, from the mining and enrichment of uranium through operation to the spent fuel. Of this radioactive material, three percent—mostly spent fuel—is considered high-level waste, meaning that it is extremely dangerous and will be radioactive for tens of thousands of years; it needs to be cooled, then safely contained virtually forever. Seven percent is intermediate waste, material from the reactor’s core and other reactor parts; this is also dangerous but can be contained in canisters. The rest, made up of building materials, plastics and other miscellany, is considered low-level waste, but also needs to be stored.
A Greenpeace report estimates that there are 250,000 tons of high-level waste in 14 countries that are sitting in temporary storage. The U.S. itself has almost 90,000 tons of high-level waste awaiting permanent disposal. While governments and industry agree that deep burial is the best solution for nuclear waste, no country has a site for deep burial in operation. One nuclear expert said that “there is no scientifically proven way” of disposing of high- and intermediate- level waste.
In 1987, Yucca Mountain in Nevada was selected to be a disposal site for U.S. nuclear waste, but it has been opposed by state leaders and residents, and its fate is in limbo.
New nuclear reactors can cost over $7 billion, which makes them expensive propositions, especially when natural gas is so cheap. Some of the newest nuclear projects have gone far over schedule and over budget. Bowen said that Westinghouse’s failure to build two of four new-and-improved AP1000 reactors planned for South Carolina and Georgia has had serious consequences for the whole nuclear industry. After costing $9 billion dollars, the two South Carolina reactors were canceled. “It’s not the materials that are resulting in the high costs, but a doubling of the construction time,” he said. “For the AP1000s, it is widely acknowledged that the construction was begun at a relatively low design maturity. It’s not that Westinghouse wasn’t completely aware that they were beginning construction before they finished the design, and [that] there was some risk involved. They just didn’t think it would go as badly as it went.”
Bowen added that he thinks the cancellation of South Carolina’s AP1000s is “the shadow that’s cast over the whole U.S. industry. It took down a utility—which should make other utilities more cautious about building a first-of-a-kind nuclear reactor.”
The Georgia reactors, also late and over budget, are scheduled to begin operation in 2021 and 2022.
The evolution of nuclear reactors
The first generation of nuclear reactors was developed in the 1950s; by 2015, these had all shut down. Generation II reactors are the ones mostly in operation today. While they were designed to last only 40 years, as of 2018, the Nuclear Regulatory Agency had granted license renewals to 89 reactors for an additional 20 years. (Three of those reactors have since shut down.) A few plants have been relicensed out to 80 years. Relicensing usually involves upgrading or replacing old equipment and technology, and is less costly than constructing a brand-new reactor.
Advanced reactors, sometimes called Generation III and III+, are operating in Japan and being built in other countries. Generation IV reactors are still in the design stage.
Many of the new nuclear plant designs that are in advanced planning stages, under construction, or being researched in North America, Europe, Japan, Russia and China address the main challenges of nuclear energy. They incorporate improvements in safety and cost, as well as in reliability, proliferation resistance and waste reduction.
Whereas traditional reactors depended on mechanical systems to deal with malfunctions, many new reactors utilize passive safety measures that don’t need outside operators. This entails systems that rely on gravity, convection or tolerance of high temperatures to prevent accidents. Some are designed more simply, which means there are fewer components that can malfunction. Others have a more standardized design so that modular components, which can be manufactured in a factory, can be used, reducing construction time and costs; older nuclear reactors usually had to be fabricated on-site. Many new reactors also use fuel more efficiently and produce less waste, and some are designed to consume nuclear waste as fuel.
Some new reactors
Here are just a few of the many new reactors being planned with a variety of technologies and designs. The first two listed were chosen by the Department of Energy’s (DOE) Advanced Reactor Demonstration Program. They each will receive $80 million this year and an additional $400 million to $4 billion over the next five to seven years. The DOE also plans to make two to five more awards totaling $30 million for advanced reactor designs by December.
TerraPower, co-founded by Bill Gates, and GE Hitachi Nuclear Energy are developing a 345MW Natrium reactor that will use molten sodium metal as a coolant. Sodium has a much higher boiling point than water so the coolant would not need to be pressurized, making operation simpler. Moreover, it saves on costs because there is no need to construct a large containment structure. The heat in the sodium will be transferred to molten salt, to either drive a steam turbine or be stored for later use. This allows the system to boost its output to 500MW for over five and a half hours if necessary. The Natrium will also use more highly enriched uranium, which would enable it to burn fuel more efficiently. The Natrium reactor is expected to be operational in the late 2020s.
The 80MW high temperature reactor, Xe-100, developed by X-Energy, uses fuel in pebble form, which cannot melt down. The 220,000 balls of graphite filled with ceramic uranium-filled kernels slowly make their way down through the core and exit out the bottom when they are spent. They are cooled by pressurized helium, which heats up to 750˚C to produce steam for electricity. The reactor’s simpler design uses components that can be manufactured in a factory then assembled, and due to its modular design, it can be combined with other 80MW reactors to produce 320MW or more. Bowen noted that the higher efficiency of this reactor means it can produce a smaller amount of waste per megawatt-hour generated.
Terrapower’s traveling wave reactor is a liquid sodium cooled reactor operating at atmospheric pressure. It uses fuel made from depleted uranium, a byproduct of the fuel enrichment process that is often disposed of. The used fuel is kept in the core so there is no need for storage. Terrapower claims that the traveling wave reactor will eventually eliminate enrichment and reprocessing, thus reducing proliferation risk. Over its 60-year lifetime, the total amount of waste it produces would fill only one and a half rail cars. With the design almost complete and engineering begun, it’s expected to begin operation in the mid-2020s.
NuScale is developing a small modular light water reactor that will generate 77MW. It will occupy the space of only one percent of a conventional reactor. The design has been simplified to eliminate pumps and other moving parts, which makes it safer, and the reactor can shut itself down and cool itself without any need for an outside operator. Its compact size enables it to be used for communities that need less power as well as for medical and military installations. Twelve small modular reactors could be placed together to form a 924MW power plant, with some modules producing electricity while others provide heat for industry. The Department of Energy has partnered with NuScale and Utah Associated Municipal Power Systems to develop this reactor, but recently eight of the 36 utilities involved backed out. Nevertheless, NuScale is scheduled to bring the first module online by mid-2029 and the remaining 11 modules by 2030 to align with when UAMPS’ coal-fired plants retire, according to NuScale’s Diane Hughes. The total budget is projected to be $6.1 billion.
There are many designs of fast neutron reactors in development with sodium, lead, gas, and molten salt coolants. Because these coolants enable neutrons to move faster than water does, fast reactors have the potential to yield 60 times more energy from uranium than traditional light water reactors. In any reactor, some of the U-238 is turned into different forms of plutonium during its operation, and some then undergo fission to produce heat. Fast neutron reactors can optimize this process so that it actually “breeds” more fuel. While fast reactors have been around since the 1950s, there is more interest in them today because of the pileup of nuclear waste, and the ability of these reactors to destroy through fission the elements in spent fuel that make it highly radioactive for so long—instead of the waste being toxic for tens of thousands of years, it is toxic for a hundred years.
Microreactors that can fit in the back of a semi-truck could produce from one to 20MW of power and be used for heat or electricity. Their small size makes them able to generate energy for industrial processes along with heating and cooling in remote areas, natural disaster areas, and military bases around the world; in addition they can be easily integrated with renewable energy in microgrids. Oklo Power is developing its Aurora micro modular fast reactor, which will deliver 1.5MW of power and heat at Idaho National Laboratory. The compact design incorporates solar panels, and will use a new kind of “high-assay, low-enriched uranium” fuel called HALEU. This means the uranium is enriched to have a higher concentration of the U-235 needed for fission, which allows the reactor to get more power from the fuel and be refueled less often. HALEU isn’t yet commercially available.
Other uses for nuclear energy
Nuclear energy will need to play a key role in decarbonizing the economy because it is difficult for renewable energy to muster the intense heat needed in industrial processes, such as steel and cement production. These kinds of industrial processes comprise 10 percent of global emissions, according to Columbia University’s Center on Global Energy Policy. Some advanced reactors, such as the high-temperature gas-cooled reactor, can provide both electricity and heat for petroleum refining, or for the production of fertilizer and chemicals. Nuclear reactors could also be used to produce the electricity needed to split water into hydrogen and oxygen; clean hydrogen could then be used to generate heat for steel manufacturing and other industrial activities, to fuel vehicles, produce synthetic fuel, or store energy for the grid.
Most desalination plants that convert seawater into drinking water require a great deal of energy that usually comes from fossil fuels. Small modular reactors located by the ocean could generate the electricity needed for desalination.
The prospects for nuclear energy
Biden’s climate plan supports research into “affordable, game-changing technologies to help America achieve our 100 percent clean energy target,” with a focus on small modular reactors and the issues that challenge nuclear energy development: cost, safety and waste disposal. Biden could potentially get Republican buy-in for climate legislation through nuclear energy, since nuclear energy bills have received bipartisan support in the past. Since 2018, two acts that would speed the modernization of the Nuclear Regulatory Commission, support the development of advanced reactor fuel, and help nuclear developers collaborate with universities and the national labs, received bipartisan support in Congress and were signed into law. The bipartisan Nuclear Energy Leadership Act introduced in 2019 would help advanced nuclear reactor concepts go from research to commercialization by matching private capital to build two demo reactors by 2025 and potentially five more by 2035. The Nuclear Waste Administration Act of 2019 was introduced by a bipartisan group of senators to create a new entity to focus on nuclear waste management.
“It makes sense from a risk management point of view to have investments in nuclear be part of the solution [to climate change],” said Bowen. “But the generation that we’re talking about is going to need years to sort of mature and they will still have to build their first unit relatively close to on time and on budget. Otherwise, there isn’t going to be a second unit.” And despite the Congressional acts and the many plans for new reactors, he thinks we may not see many new reactors in the U.S. unless Congress passes a federal clean energy standard. Bowen believes relicensing may actually be the key to more nuclear energy. “I have more confidence that there will be measures to maintain the existing fleet, which is just a much lighter lift,” he said. “I’m optimistic that there’s going to be more and more of the subsequent relicensing where we’re extending the plant operations from 60 to 80 years.”
As for new reactors, Nuscale’s small modular reactors are farthest along and won’t be operating until 2030 at this point. But if the company can successfully bring the project in reasonably on time, and if there is a national climate policy driving us to zero carbon emissions, Bowen thinks more nuclear power plants could get built to substantially support the decarbonization of the electric grid by the 2050s.