Nuclear energy is coming back into focus, not only due to U.S. President Donald Trump’s interest in the largest nuclear power plant on European soil—Zaporizhzhia (in Ukraine, under Russian control). Tech giants Amazon, Google, and Meta recently announced plans to use Small Modular Reactors (SMRs) in data centers, while Microsoft signed a 20-year electricity purchase agreement with a company that plans to bring an existing nuclear reactor back online. Both the UN and the EU are now classifying nuclear energy as a green form of energy. Thus, we’re witnessing a broad shift toward this energy source, which has long been imprinted in the collective subconscious as dangerous.

Is nuclear energy misunderstood?

We asked for insight from Georgios Laskaris, a nuclear physicist and president of the Deon Policy Institute, a think tank based in Boston, USA, to answer some of the most current questions on the topic. And we began with the question of the "color" of nuclear energy.

“The EU classified nuclear energy as green because it has a low carbon footprint. Nuclear power plants do not produce greenhouse gases, which is expected to help achieve decarbonization targets, and specifically, carbon neutrality by 2050,” the Greek scientist told us, adding that the EU also considered the benefit of nuclear energy in ensuring stable energy production, which will help reduce our dependence on Russian natural gas.

Waste Management

While nuclear plants may not emit greenhouse gases, what about nuclear waste?

“Radioactive or nuclear waste is a byproduct of various human activities involving the use of radioactivity in hospitals, research centers, and nuclear power plants. Nuclear waste is categorized into three levels based on their radioactivity: (1) low-level, (2) intermediate-level, and (3) high-level. The overwhelming majority of waste globally—about 90% of total volume—consists of slightly contaminated items, such as work clothing and tools, which contain only 1% of total radioactivity. In contrast, high-level waste, including spent nuclear fuel, makes up only 3% of total waste volume but contains 95% of the radioactivity,” Laskaris noted.

He explained: “When spent fuel is removed from the reactor, it’s hot and radioactive and must be stored in water to cool down. After initial cooling, it can be temporarily stored in either wet or dry conditions. Temporary storage allows for further reduction of temperature and radioactivity, thus making recycling or final disposal easier.”

Recycling and Vitrification

The Greek scientist appears reassuring regarding the issue of nuclear waste. In fact, he argues that the term “waste” is not entirely accurate: “About 97% of spent fuel—mostly uranium—can be reused and provide vast amounts of energy.” Indeed, many countries—including France—recycle nuclear fuel, thereby reducing the radioactive footprint of their waste. “Recycling extracts plutonium and uranium, which can be remixed with uranium to produce new fuel rods. The byproducts (about 4%), which mainly contain fission fragments, require permanent storage. These are usually mixed with glass (vitrification) for safe storage. In the U.S., spent fuel is placed in metal barrels that are stored in underground facilities.”

As for the volume of this waste, Laskaris explains: “The U.S., which has about 100 large reactors, produces enough spent nuclear fuel annually to fill just half an Olympic-sized swimming pool. As you can imagine, if Greece, which has no nuclear reactors, were to operate even one or two Small Modular Reactors (SMRs), the volume of high-level nuclear waste it would generate would be extremely limited and manageable, especially given today's technological advances in containment and recycling.”

Technological Advancements

Given that there are currently 36 countries worldwide that have or are soon expected to acquire nuclear reactors, it’s clear that the design of new reactors is a thriving technological field. Particular emphasis is being placed on the development of Small Modular Reactors (SMRs), which are already in use in Russia and China.

"SMRs are an advanced type of nuclear reactor that are smaller in size and have an output of up to 300 MW (about one-third the power of traditional nuclear reactors). They are described as 'modular' because they can be manufactured in factories and then transported to the site where they will operate and be assembled there. This allows for the gradual addition of more reactors to meet changing energy needs," explains Mr. Laskaris, adding that the SMRs currently in design are classified into six different groups based on their technical characteristics.

Potential Applications

As for their potential uses, the Greek scientist explains that "the different groups of SMRs reflect the various applications these reactors will have in the field. For example, water-cooled reactors can be used to produce clean base-load electricity, support the fluctuating power supply of renewable energy sources, and replace old lignite-fired power plants. Floating Nuclear Power Plants (FNPPs) at sea can generate electricity for powering data centers and desalinating seawater, which is needed to cool these centers. These same reactors can also be used to supply power to ports and produce green fuels such as hydrogen and ammonia near harbors. Floating molten salt-cooled reactors (Molten Chloride Fast Reactors) are ideal for nuclear propulsion of ships, such as tankers making transoceanic voyages. Finally, high-temperature gas-cooled reactors can be used in industrial applications that require high temperatures, such as oil refining and cement production, while microreactors can supply electricity to remote areas like islands."

Flexibility and Safety

Mr. Laskaris estimates that SMRs will become commercially viable by the mid-2030s and expects that this technology will be widely adopted in the decades that follow. He attributes this confidence to both their technological superiority and flexibility, as well as the enhanced safety they offer.

"SMRs have many technological and safety advantages that make them a serious alternative to traditional reactors. Their modular design allows for factory production and rapid on-site assembly, which is expected to reduce nuclear plant development time from 8–15 years to just 3–5 years. Moreover, their smaller size and output allow them to be installed in remote locations. Many SMRs incorporate advanced technologies that offer greater fuel efficiency and produce less waste. As we mentioned earlier, some SMRs use alternative cooling systems such as air or liquid metals, reducing their reliance on water resources," says Mr. Laskaris.

He adds that the enhanced safety of SMRs is due to a range of factors. Specifically, "SMRs incorporate passive safety systems, which allow the reactor to cool down and shut off automatically without human intervention, thereby reducing the risk of core meltdown. Unlike traditional reactors that depend on pumps and generators, SMR safety systems rely on natural processes like gravity, natural circulation of the coolant, and thermal conductivity to dissipate heat—eliminating the risk of active cooling system failure, as occurred at Fukushima in 2011. Additionally, their smaller size requires smaller exclusion zones, making it possible to install them closer to populated areas. Lastly, the use of advanced fuels ensures the minimization of nuclear waste."

Economic Considerations

Of course, deploying any technology comes with economic considerations. If an SMR were ready today, how much would it cost? How many years would it take to break even? How long would it operate?

“No one can accurately estimate the total capital cost of an SMR because it varies greatly depending on design, location, and project scale. What I can say is that for a prototype SMR, the capital cost could range from half a billion dollars to nine billion dollars. In contrast, the capital cost of traditional large reactors ranges from $24 billion (Barakah, UAE) to $40 billion (Hinkley Point C, UK),” says Mr. Laskaris.

He adds, however, that “while the total capital cost of SMRs is lower than that of large nuclear power plants, the cost per megawatt currently appears to be higher for SMRs. We’re in a transitional period, as SMRs are still in the early stages of development, and the cost reductions expected from mass production and economies of scale have not yet materialized.”

As for the lifespan of these reactors, no one can say for certain. The same goes for the payback period of an SMR investment. “Since there are currently no SMRs in commercial operation in the West, we can’t say definitively. But based on the experience of large reactors (1–1.6 GW), the lifespan of a reactor ranges from 60 to 80 years, and the payback period is around 20 to 30 years. I believe we can expect similar lifespans and returns for SMRs.”

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International Acceptance with Strict Safety Standards

The UN, the EU, the USA, and the International Maritime Organization all consider nuclear energy to be green.

• The Intergovernmental Panel on Climate Change (IPCC) of the UN includes nuclear energy — as a low-carbon emission source — in its strategies for reducing global greenhouse gas emissions. The reasoning is that nuclear energy supports the Sustainable Development Goals (SDGs), specifically Goal 7 (Affordable and Clean Energy) and Goal 13 (Climate Action). The IPCC thus recognizes that nuclear energy can contribute to reducing carbon emissions.

• This is why the International Atomic Energy Agency (IAEA) — an organization closely affiliated with the UN — actively promotes nuclear energy as part of the global clean energy mix.

• In July 2022, the European Commission classified nuclear energy as a “green” and sustainable energy source, on the condition that it meets strict safety and environmental protection standards. These standards involve the safe management of nuclear waste and the use of specific third- and fourth-generation reactor technologies, including Small Modular Reactors (SMRs). The operation of these new reactors must be approved by 2045, while existing nuclear plants can continue functioning provided they upgrade their systems with modern safety technologies.

• In the United States, nuclear energy is also considered green. In 2024, the former president passed the Atomic Energy Advancement Act with overwhelming bipartisan support, aiming to accelerate the development of nuclear technologies like advanced reactors. The Trump administration also intends to further support nuclear energy, especially through Small Modular Reactors (SMRs), and to speed up the licensing processes.

• The International Maritime Organization (IMO) has confirmed, through its chairman, its active interest in nuclear propulsion. Through its subcommittee on maritime transport safety, it is working closely with the IAEA to revise the outdated 1981 safety code for nuclear-powered commercial ships.