Good News for Small Nuclear Reactors!

Small modular nuclear reactors are being pitched as a fix for two long-running nuclear bottlenecks—slow construction and high costs—but the record so far is mixed, with multiple flagship projects cancelled after spending overruns. Even so, governments and utilities across Europe and North America are accelerating plans for new deployments, suggesting the technology’s biggest near-term impact may be political momentum rather than electricity generation.

The core promise is straightforward: build reactors in factories, ship them to sites, and scale output by combining multiple modules. Typical designs target roughly 100 megawatts per unit, compared with about 1 gigawatt for conventional nuclear plants—so around ten modules could match the output of a standard facility. That modularity also opens a potential market beyond the grid, including energy-intensive industries such as steel, chemicals, and AI data centers, where reactors might supply power directly without utility interconnection.

Yet the transcript highlights why the economics have been harder than the concept. First, shielding requirements don’t shrink proportionally when reactors are split into smaller units. Ten smaller cores still demand substantial radiation shielding, increasing the amount of material and undermining cost reductions—an analogy is offered: physics works either way, but “who pays for the boxes” becomes the problem. Second, shrinking the reactor core changes the reaction geometry. A smaller core has a larger surface-to-volume ratio, letting more neutrons escape; maintaining the same fission rate typically requires higher-enriched fuel, which again runs counter to cost goals.

The “faster to build” argument also hasn’t held up in practice. The mPower project, launched in 2009, was cancelled in 2017 after costs ballooned. NuScale announced its small modular reactor in 2016, but that effort was terminated in 2024 following further cost explosions. NuScale’s own estimate put Levelized Cost of Energy at $89 per megawatt-hour, including a $30 subsidy—slightly cheaper than standard nuclear but still more expensive than gas, and likely optimistic. Independent assessments often found small modular reactors would be as expensive as full-sized plants or more, and even completed projects tended to take longer and cost more than promised.

Despite that track record, the political push is expanding. The International Atomic Energy Agency lists only two small modular reactors in operation plus two test units, but the European Commission has a dedicated small modular reactor strategy. EDF plans to bring 30 small nuclear reactors online by 2050; Finland is selecting sites; the UK government wants two in Wales; Sweden’s prime minister announced new nuclear construction after 50 years, specifically small reactors. In the U.S., Donald Trump has called for at least three small modular reactors operational by next year, while NuScale has proposed a new design plan approved in May after its cancellation.

The Nuclear Energy Agency reports 98 current plans to build small nuclear reactors, with dozens of designs, mostly in North America and then Europe. Interest comes primarily from utility owners, followed by national laboratories and industry. The transcript’s bottom line: small modular reactors may not yet be delivering electricity at scale, but they are already generating a measurable field of political enthusiasm—raising the question of whether future overruns will be treated as prototype growing pains or whether the same cost and schedule failures will repeat.