While the return to nuclear power is being discussed in Italy, mini modular reactors are already a reality in various parts of the world. What they are and why they are controversial
Since the Chamber of Deputies approved the enabling law on the possible resumption of energy production from nuclear sources on Italian soil, giving rise to a provision that will now pass to the Senate, there has been a lot of talk about small modular reactors (SMRs). According to the opposition, they do not exist, they are not available on the commercial market and they do not solve the problem.
Let’s try to clarify: they are called “small” because in terms of size and energy produced they constitute a fraction of what we mean by a nuclear power plant, even if they are to all intents and purposes mini-power plants. They were invented in the military sector more than sixty years ago, to provide energy to aircraft carriers and submarines, they have evolved and today they are installed in prefabricated modules – hence modular, the more elements correspond to the more energy supplied – after being transported directly to the site, greatly reducing construction times, complexity and costs. They therefore take up less space than traditional nuclear power plants and are installed in dimensions that satisfy energy demand, while also being able to be enlarged when needed.
The history of small modular reactors
So, although SMRs are often presented as a novelty, their history begins at the dawn of the atomic age. As early as the 1950s, the US military operated eight small reactors to power remote bases in Antarctica and Greenland; later mini-reactors were also tested in civilian environments in the United Kingdom (Magnox plants). However, it was realized that demand was growing too rapidly and that small plants were proving uneconomical compared to large power plants. And, in 1977, the US military ended the program, decommissioning the existing reactors.
However, technology has evolved since then: Many SMR projects today have passive safety systems that use physics and gravity rather than mechanical pumps, to prevent core meltdowns. This helps to make them safer, but there is no shortage of skeptics who argue that the small size still cancels out the economic advantages, and that the evolution of plants for renewable sources is, or will soon become, competitive. But one fact is certain: renewables are not constant: sun, wind and tides are not always available. Regarding how safe SMRs are, their operating procedures comply with safety standards similar to those applied in third generation nuclear power plants.
The operation of small modular reactors
Like the traditional ones, they have a “core” that contains nuclear fuel (usually uranium), which releases large quantities of heat through nuclear fission. This heats water transforming it into steam, and the latter moves one or more turbines connected to generators, which in turn produce electricity. On military ships, obviously, they rotate the propellers for propulsion, create steam for the catapults to launch aircraft or, on submarines, power the torpedo launch systems.
Civil installations are obviously different from military ones (sea water is a free and always available refrigerant), so the size of the land needed to host them is larger, typically slightly smaller than that of a couple of football fields, however a hundred times smaller than a traditional nuclear power plant. The smaller size also means less energy producednormally between 100 and 500 megawatts, far from the gigawatts produced by a modern conventional power plant, but also less waste to dispose of. The downside: The cost per kilowatt is obviously higher, but remains constant in the long run, like production.
Where they are scattered around the world
Another piece of false news concerns the fact that there are no functioning civil plants, since there are already some active in China, Uzbekistan And Russiawhile there is news of a specimen under construction also in Argentina. On the dedicated website of Siemens Energia, we read that there is also a European industrial alliance for SMRs, which aims to accelerate the development of these systems within a decade. It is stated that in early 2026, Rolls-Royce Smr received an order from Great British Energy – Nuclear for the construction of three plants to be installed at Wylfa, Wales; and that in April 2026 a contract was signed with the Čez Group for the design of an SMR at the Temelín nuclear power plant, in Czech Republic.
Small nuclear reactors in the USA
President Donald Trump’s executive order “14299” is being implemented in the USA. This is the implementation of advanced nuclear reactor technologies for national security, which has directed the War Department to begin operating an Army-regulated nuclear reactor at a national military installation by September 30, 2028. Recently, Buckley Space Base (Colorado) and Malmstrom Air Base (Montana) have been selected by the United States Department of the Air Force as potential locations for the installation of microreactors, as part of the Advanced Nuclear Power for Installations (Anpi) program, born in 2024 with the aim of installing advanced nuclear microreactors at the installations of the Department of the Air Force, in collaboration with private companies in the sector.
It is expected that these companies will be responsible for the location, licensing, construction, operation and dismantling of end-of-life facilities. Among the companies selected by the Department of Defense for this program are giants such as Antares Nuclear, General Atomics ES, Westinghouse Government Services and X-Energy. All will be able to apply for funding under a program to supply fixed micro reactors on site at military installations.
