Designers of small modular reactors hope their time has come

nUKLAR POWER never quite kept his promise. Reactors have turned out to be much more expensive than hoped. Accidents and leaks have earned it a reputation for being risky, despite its zero-carbon credentials. (Attempts to suggest that coal-fired power plants kill far more people than nuclear power plants failed to convince many voters.) Nuclear power’s share of global electricity generation fell from 17.5% in 1996 to 10.1% in 2020.

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But governments committed to ambitious climate change targets have given the technology a second look. In January, the European Union included nuclear power in a list of projects eligible for green funding. Russia’s invasion of Ukraine, meanwhile, has pushed up fossil fuel prices and put energy security high on the political agenda in Europe, which currently relies heavily on Russian natural gas. The nuclear industry believes it has the answer: a new generation of small modular reactors (SMRs) that are designed to be cheaper, faster, and less financially risky to build.

In 2019 Russia closed the Academic Lomonosov– an experimental ship SMR– to its power grid. China, which has more large reactors under construction than anywhere else, is hoping for its first commercial success SMR Operation in Hainan by 2026. Last year the UK government said it would accelerate plans to build 16 SMRIt was designed by Rolls Royce. NuScale Power, an American company, is hoping for its first SMRto be built at the Idaho National Laboratory will provide electricity through 2029. The International Atomic Energy Agency estimates “about 50” SMR Drafts are being worked on worldwide.

Henry Ford and nuclear fission

As the name indicates, SMRs are smaller than conventional nuclear power plants. Normally they are supposed to produce fewer than 300MW Power, about a fifth of what a standard reactor could do. Because of their size, their designers, like cars, toasters, and food cans, aim for mass production in factories to save costs.

“In a typical large reactor, you assemble most things on site,” says Chris Colbert, NuScale Power’s chief strategy officer. “They have maybe 8,000 people working on the site.” NuScale, with facilities to produce 77MW of electricity, hopes to move as much of this work as possible to dedicated factories for later assembly on site. Factories provide protection from weather delays, he says. And a regular supply of work in one place means that a new batch of construction workers does not have to be trained for each plant. “Something that takes 17 hours in a field may only take an hour in a factory,” he says. Instead of tying up capital for decades to build a large plant, customers could see a return on investment much sooner.

NuScale’s design consists of a 23-meter-high, diamond-shaped reactor vessel sitting in a steel-lined underground cooling water basin (see diagram) and capped by a reinforced concrete reactor building. Several systems can be combined to form a large power plant or a few can be used to supply one location. Such modularity also implies redundancy, since individual reactors can be shut down for refueling while the others continue to run.

Going smaller also offers opportunities to simplify the design, which helps keep costs down. The cooling water in NuScale’s plant circulates through the core by simple convection and requires no pumps or moving parts. And smallness, says Mr. Colbert, brings security benefits too. Even if the internal cooling fails, the external water in the pond has enough capacity to absorb the heat produced by the tiny reactor. In addition to its putative Idaho facility, NuScale has received expressions of interest from Kazakhstan, Poland and Romania.

Other SMRs stretch the definition of “small”. Rolls-Royce is designed to produce 470MW Electricity – more than most of the first generation Magnox nuclear power plants that Britain began building in the 1950s. That requires the kind of active safety systems found in ordinary nuclear power plants, like coolant pumps and backup generators, to ensure constant operation if something goes wrong. This increases complexity and therefore cost.

But most analysts assume that larger size means economies of scale and therefore cheaper power. “The reason we are at 470MW That’s the greatest performance we can squeeze from our footprint while fitting every component on a truck,” said Alastair Evans, a spokesman for Rolls-Royce. The company hopes that if and when their production line is up and running, each of their jumbo SMRs are expected to cost £1.8bn ($2.4bn) and take around four years to build. It has attracted interest from America, the Czech Republic and Turkey.

NuScale, Rolls-Royce and the China National Nuclear Corporation, which is building the Hainan plant, are sticking to proven designs. All of their proposed plants are light water reactors (LWRs) that use plain water to both cool the core and dampen the rate of the nuclear chain reaction. There are also most of the world’s existing reactors LWRs, they hope sticking to the same general design will speed up regulatory approvals. (NuScale’s design was approved by the US Nuclear Regulatory Commission in 2020, four years after it was submitted.)

Other designs are more exotic, relying on molten lead or sodium or gaseous helium instead of water to cool their cores. x-energy and u-Battery, American and British companies rely on helium-cooled miniature reactors. These operate at much higher temperatures than LWRS. The helium inside u-The battery’s reactor will reach temperatures of around 750°C, says Tim Abram, the company’s chief engineer.

This means that such reactors could also sell heat in addition to electricity. Many industrial processes take place at high temperatures. This is currently mainly due to the burning of fossil fuels. u-Battery hopes its reactors could one day find a home in industries ranging from glass and ceramics to steel, cement and paper. They could even be used, says Mr Abram, to produce hydrogen for energy storage via a process called thermochemical fission, which uses heat instead of electricity to split water into oxygen and hydrogen.

Everything looks good on paper. But history advises a degree of skepticism. Previous attempts to build commercially SMRs that go back to the 1960s failed on the twin rocks of economy and technology. The biggest difficulty, says MV Ramana, a physicist at the University of British Columbia’s School of Public Policy and Global Affairs, is that small reactors are at a disadvantage compared to their larger cousins. The cost of building a reactor grows more slowly than its output, he says. Other things being equal, bigger means cheaper.

Whether mass production can overcome this disadvantage remains to be seen. Nu Scale’s Idaho facility is funded in part by federal grants. But the cost, according to Dr. Ramana increased from $3.6 billion in 2017 to $6.1 billion in 2020. Several trading partners of the company withdrew from the project in 2020. That’s not encouraging for a technology that has to compete for low-carbon investments in solar and wind power, the cost of which continues to fall.

If it doesn’t work the first time…

However, nuclear power looks cheaper these days than it used to. A large under construction facility in the UK, on ​​the Somerset coast, had to be promised an inflation-linked electricity price from £92.50 per MWh in 2013. This deal was judged to be too expensive at the time. But amid gas shortages and lack of wind, UK electricity costs have been above these levels for most of the last six months.

The International Energy Agency points out that taking into account storage needs or backup generation, renewables are more expensive than their sticker price suggests. And, as Russia’s invasion of Ukraine shows, energy policy needs to weigh factors beyond bean counting. If SMRs can contribute to making nuclear power attractive again remains to be seen. But its supporters are unlikely to get a better chance to make their case.

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This article appeared in the Science & Technology section of the print edition under the heading Pint-sized Power Plants.

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