Technology · Future technologies
SMR: Are Nuclear Reactors Now Built in a Factory?
Small Modular Reactors promise nuclear power from the factory line, not the mega-construction site. What SMRs are, and how realistic the timeline is.
By Boaz Lichtenstein
Nuclear power has a problem that has nothing to do with physics: large reactors are decades-long mega-construction sites with runaway costs. Small Modular Reactors are meant to solve that – not with new physics, but with a different manufacturing principle. Hardly any other field is currently attracting so much capital and attention at once. Time for a sober look behind the promise.
Key takeaways
- SMRs are conventional nuclear reactors in miniature, meant to be built as standardised modules in a factory and shipped to site.
- The driving force behind the current wave of capital is mainly data centres for AI training, which need reliable round-the-clock baseload power.
- Western SMR projects are still mostly in permitting and early construction – not routine operation.
- The promised cost advantages of series production remain unproven, because no meaningful series has actually been built yet.
- Realistic timeline for a noticeable contribution to electricity supply: the 2030s, and initially only in a handful of pioneer countries.
The factory thesis
What makes an SMR technically different from a conventional power plant? At its core, an SMR is a conventional nuclear reactor, just much smaller – roughly in the range of a few tens to a few hundred megawatts, instead of over a gigawatt for conventional plants. The real idea isn’t a physical one, but an industrial one: instead of casting each power plant as a one-off on site, SMRs are meant to be built as standardised modules in a factory and then shipped to the construction site – more like aircraft manufacturing than bridge building. Series production is meant to cut the cost and build time that conventional nuclear power has recently blown through almost everywhere. Whether factory learning effects can actually be transferred to this degree onto such a strictly regulated product is the central open bet behind the entire SMR promise.
SMR versus conventional large reactor, compared
| Criterion | Conventional large reactor | Small Modular Reactor |
|---|---|---|
| Output | over 1,000 megawatts | a few tens to a few hundred megawatts |
| Build principle | one-off mega-construction on site | standardised factory production |
| Build time (targeted) | often a decade or more | markedly shorter, per manufacturer plans |
| Safety concept | mostly active cooling systems | passive safety often targeted |
| Track record | decades of routine operation | first prototypes and pilot plants |
Why Big Tech has suddenly piled in
Where has the sudden surge of capital for a technology that stagnated for decades come from? Less from energy policy than from data centres: AI training and operation need enormous, extremely reliable baseload power – round the clock, independent of the weather. Large tech companies have therefore announced offtake agreements and investments in SMR developers in recent years. That gives the industry capital and attention, but changes nothing about the underlying timing problem: a contract is not a running reactor.
Who’s leading SMR development worldwide
Which countries and companies are leading the race? The US currently has the most projects in permitting and early construction, with several competing reactor designs using different cooling technologies. Canada has advanced pilot projects early on thanks to a comparatively swift permitting process. Britain is pursuing its own SMR development through established energy companies, while in Asia, China and South Korea in particular are pushing forward their own programmes, in some cases with state backing and shorter permitting routes than in the West. What’s common to all these locations: announced capacity is many times larger than what has actually been built – a pattern that repeats with almost every new energy technology.
The honest state of play
How far along are the projects actually, beyond the press releases? Western SMR projects sit mostly between permitting procedures and initial construction work, not routine operation. The promised cost advantages of series production remain unproven so far – the maths only becomes solid once several units of the same design have actually been built. The contrast with the world of large reactors makes the problem tangible: flagship projects such as Vogtle in the US or Flamanville in France have run years behind schedule and, in some cases, blown their budgets several times over – exactly the experience SMR advocates want to break through with factory manufacturing. Whether that succeeds can only be judged once the first production units actually exist. The realistic timeline for a meaningful contribution is the 2030s. SMR power should be placed alongside two other works in progress in the energy transition: storage technologies such as in our sodium-ion battery article, which make renewables more baseload-capable, and nuclear fusion, whose status we assess in our nuclear fusion reality check – both with similarly long timescales. The same pattern also applies to perovskite solar cells: promising physics, but a real-world proof that still has to be delivered.
The most common misconceptions about SMRs
- “SMR is a new, safer nuclear technology.” Only partly true – the nuclear reaction itself is the same physics as in large reactors; what’s new is primarily the size and the manufacturing principle.
- “If a company signs an SMR contract, the plant will soon be running.” Wrong – between signing a contract and a running reactor typically lie permitting, construction and test operation over several years.
- “SMR makes conventional large reactors obsolete.” Not necessarily – for countries with an established nuclear industry, large reactors often remain competitive on pure electricity cost per megawatt; SMR targets sites and applications where a gigawatt unit is too big.
- “The cost advantages of series production are already proven.” Premature – without an actually built series of identical reactors, that remains a forecast, not a solid figure.
The German context
Where does Germany stand in this development? Germany took the opposite path with its 2023 nuclear phase-out; SMRs are currently a non-issue politically and legally for grid expansion here, but they keep resurfacing as an argument in public debate – usually detached from the actual construction progress abroad. Anyone trying to make sense of the discussion should clearly separate announcement from operation: permitted projects and announced contracts are not running power plants.
When SMR becomes realistically relevant
What stages still need to be completed before SMR power flows at scale? A rough but realistic sequence: first, approval of the reference design by regulators – largely not yet complete. Second, construction and commissioning of the first unit per design, with the usual risk of delays. Third, several years of test operation showing whether the promised safety and availability hold up in everyday use. Fourth, only then the shift to genuine series production, which is what could actually deliver the promised cost advantages. Currently, the majority of projects sit between steps one and two – step four is still a long, multi-year road away.
The bottom line
SMR is a plausible answer to a real problem – the runaway costs of conventional nuclear mega-projects – but it is nowhere near a proven concept yet. Anyone who keeps the 2030s in view rather than short-term headlines assesses SMRs realistically: as a possible but still unproven piece of the energy transition puzzle, alongside storage technologies and other future technologies with similarly long timescales. Contracts and announcements signal capital interest, not a substitute for a running reactor.
From experience: anyone reading an SMR headline should specifically look for three pieces of information before assessing it: the actual project status (permitting, construction or operation – not merely “announced”), the concrete site with a timeline, and whether it’s the first unit of a design or already a genuine series. If all three are missing, it’s usually a statement of intent, not solid news about actual construction progress.