Can Nuclear Power Offer a Way Out of the Climate Crisis?

“The construction of nuclear power plants makes no sense economically,” says Christoph Pistner of the Institute for Applied Ecology in Darmstadt. In some cases, he says, nuclear plants are being decommissioned even before the end of their planned operating life because of competition from cheap wind or solar power, and without state subsidies, the technology would never be profitable. “New construction is only happening now in places where the state finances it or at least subsidizes it massively — in Russia, China or India, for example,” he says.

The problems associated with nuclear power are reflected in the fact that nuclear power now supplies only 10.2 percent of the global energy mix, down from 17 percent in 1997. Just when the world could use more carbon-neutral electricity, use of nuclear energy is in decline. The International Energy Agency estimates that by 2040, total output from nuclear power plants could fall by a further two-thirds because a growing number of plants are becoming uneconomical to operate, are too old or are no longer desired by society.

New Reactors for a New Era

Conditions could hardly be worse for proclaiming a renaissance of nuclear energy. So, why are some companies pursuing it anyway? José Reyes, wearing a gray jacket and pink shirt in his office in Corvallis, Oregon, is keen to take a stab at that question.

Reyes was a professor at Oregon State University for 30 years before he began developing his own nuclear reactor. The company is called NuScale and it is widely viewed as the most interesting startup in the rebooted nuclear power industry.

“We asked ourselves what a reactor would look like for a modern power grid that relies a lot on renewables like wind or solar power,” says Reyes. What they came up can be seen in model form next to his desk. It’s a conventional pressurized water reactor, but with a capacity of only 60 megawatts. It has very little in common with the giants of the past, which were vaulted by concrete domes and had an output of more than 1,000 megawatts.

A nuclear reactor is like an extremely complicated water kettle. The nucleus of a uranium is split in the reactor, a process which releases neutrons. Those neutrons, slowed by water molecules, go on to split additional uranium nuclei. This chain reaction, a series of nuclear fissions, generates heat, which is absorbed by the water. Steam is formed in a second cooling circuit, which drives the turbines.

Problems arise when the cooling system fails — either due to a power failure and the consequential failure of the cooling water pumps, or from a leak in one of the cooling circuits. Modern reactors contain technology that brings the chain reaction to a halt when the cooling system fails. But even then, sufficient residual heat can build up to melt the core. That is what happened in 2011 in Fukushima, where a tsunami flooded the cooling pumps, rendering them inoperative.

The reactor in the Chernobyl disaster, meanwhile, exploded because its output continued to increase uncontrollably. The design of modern reactors, including all those operating in Germany, prevents that from happening.

NuScale’s reactor reduces the risk even further. Reyes and his colleagues have packed the reactor into a cigar-shaped steel shell only 23-meters long and four-and-a-half meters in diameter. This module is placed vertically in a large water basin. The engineers intend to incorporate several such modules in a plant that resembles an indoor swimming pool.

“The safety is unprecedented,” says Reyes. “Even if all systems fail, the reactor will shut itself down automatically — without operator action, without computer action, without AC or DC power, it’s physics.”

The engineer demonstrates how to do this in the dim control room on the top floor of the NuScale building. The simulated data measured from 12 reactors flicker there simultaneously on large screens. One reactor is now meant to survive a serious incident as part of a test. The engineers send a command to the reactor to close a series of valves so that the reactor is completely isolated from the outside world — a nightmare scenario for normal nuclear power plants.

Red warning lamps light up immediately and, as expected, the temperature in the core begins rising. But then the safety systems kick in: Control rods fall between the fuel rods, slowing the fission reaction, while valves open automatically to counteract the increasing pressure in the reactor. Steam flows from the cooling circuit into the containment vessel. This in turn releases the heat into the reactor pool. The temperature of the core stabilizes.

Reyes is pleased. “We are looking at events that happen once in a billion years,” he says, “and even if all systems fail, there’s enough water in the pool to cool the reactor down.”

The test was only a simulation. NuScale’s reactor hasn’t been built yet. But the computer models are based on real data. In a warehouse at Oregon State University, Reyes and his team built a test reactor at a scale of 1:3. Further tests will be carried out on an eight-meter high model that is true to the original.

The NuScale reactor has no pumps and few moving parts. The steel shell is more pressure-resistant than a concrete dome and also easier to build. Ultimately, Reyes hopes to be able to build three of these plants per month, which would drive down prices. The entirely prefabricated nuclear reactors are to be delivered to customers straight from the factory.

“We have interest from around 20 countries,” says Reyes. In Europe, both Romania and the Czech Republic are interested in NuScale’s compact nuclear power plants. And in the U.S., the company is in talks with 29 different electric utility companies. Several U.S. states have set the goal of becoming climate neutral by 2050, prompting the American energy industry to seek options for replacing aging coal-burning plants.

One utility company has already decided to go with NuScale. Utah Associated Municipal Power Systems has expressed its intent to order 12 modules from Reyes as soon as the U.S. nuclear regulatory authority has given the plant its approval. In contrast to Germany, where such plants currently stand no chance of approval, the U.S. authorities have already confirmed the passive safety of the plant.

Like two oversized six-packs, the reactors are to be placed in a water basin the size of a soccer field. Reyes is confident he’ll be able to deliver soon. The 12 units, which are expected to cost a total of $3 billion, are set to go online in 2026. NuScale expects to be able to generate electricity at cost of about six cents per kilowatt hour, which would even allow the reactor to compete with cheap gas-fired power plants in some places.

Nuclear Power’s Potential as a Back-Up

Do small, modular reactors like these really have the potential to fuel a nuclear power renaissance? The broader question is which energy mix will prevail in order to achieve climate targets at the lowest possible cost.

There is one thing almost all model calculations do agree on: Moving forward, the majority of electricity will be supplied by a mix of solar, biomass, wind and hydro power. The Berlin-based think tank Agora Energiewende has forecasted that, in Europe, that mix will be responsible for 57 percent electricity production in just 10 years. There is, however, still disagreement over the best design for an electricity system that is dependent on the forces of nature.

Sometimes the wind is strong, and at others it doesn’t blow at all. And the sun only shines during the day, sometimes more and sometimes less. The worst case scenario is referred to as the “dark doldrums,” the complete absence of wind and sun.

Some experts believe that energy storage systems and a sufficiently flexible pan-European electricity market will be enough to manage those fluctuations. But the more realistic and cheaper option appears to be reliance on back-up power plants that go online when there’s no wind or sun.

Patrick Graichen, executive director of Agora Energiewende, believes natural gas-fired power plants are ideally suited as backups. They can increase or decrease their output very quickly, just like a gas stove at home. “We have gas-fired power plants with a capacity of 30 gigawatts on the grid in Germany,” says Graichen, “but they are only operating at half capacity.” The combustion of natural gas, though, also generates CO2. Graichen is calling for the fossil fuel to be replaced in the future by hydrogen or synthetically produced methane. But enormous amounts of energy would be required to produce those alternatives.