☢️ Small Modular Reactors Explained: Why AI Data Centers Are Driving a Nuclear Revival

Why Nuclear Power Is Suddenly a Data Center Story

AI training and inference workloads have pushed data center electricity demand to a scale that is genuinely straining grid infrastructure — global data center power demand is forecast to rise by roughly 50% by 2027 and by as much as 165% by the end of the decade, and individual hyperscale AI campuses are now being designed around gigawatt-scale power draws that a single conventional substation interconnection often can't deliver on the developer's timeline. Utility interconnection queues in many regions now run years long, and the practical constraint on building new AI data center capacity has shifted from capital and chip supply to a more basic question: where does the electricity actually come from, and how fast can it be delivered. Nuclear power, and small modular reactors specifically, entered this conversation because they offer a path to large, reliable, carbon-free, always-on power that doesn't depend on the same grid queue as everything else — at least in principle.

What Actually Makes a Reactor "Small" and "Modular"

A conventional nuclear power plant is a large, custom-engineered, site-built facility — typically 1,000+ megawatts of capacity, built over many years with a construction process that's substantially unique to each site. A small modular reactor is defined by two specific engineering choices rather than just being a physically smaller version of the same thing. "Small" means a much lower power output per unit, generally under 300 megawatts and often well below that (many designs target 50–100 MW), which fundamentally changes the safety case: a smaller reactor core has less total decay heat to manage after shutdown, which enables passive safety systems that rely on natural physical processes like convection and gravity rather than active pumps and operator intervention to keep the reactor safe during an incident — a meaningful simplification compared to the active safety systems conventional large reactors depend on.

"Modular" means the reactor components are manufactured in a factory and shipped to the site for assembly, rather than being built entirely on-site the way conventional nuclear plants are. This is the more economically significant of the two properties: factory manufacturing enables standardized designs built repeatedly with the same tooling and workforce, capturing the kind of learning-curve cost reductions that on-site, bespoke construction never achieves. This is the core economic bet behind SMRs — that manufacturing reactors like a repeatable industrial product, rather than constructing a unique megaproject each time, can bring nuclear power's cost and schedule under control in a way conventional large-reactor construction has struggled to do for decades.

Why Data Centers Specifically Are Driving This

Data centers have a specific set of power requirements that make nuclear an unusually good match on paper, even though the industry pairing is new. AI training and inference workloads run continuously, need extremely high power-supply reliability (an unplanned outage during a large training run is expensive and disruptive), and increasingly need carbon-free power to meet corporate sustainability commitments that predate the current AI buildout — nuclear checks all three boxes in a way that intermittent renewables paired with battery storage don't fully match at this scale and reliability requirement today, without significantly larger storage buildouts. This has led to a wave of direct deals: Microsoft's agreement to restart Three Mile Island's undamaged reactor unit (rebranded Crane Clean Energy Center) specifically to supply a data center, Amazon's investment in SMR developer X-energy alongside a direct power purchase agreement, and Google's agreements with Kairos Power for SMR-supplied data center power are the clearest public examples of hyperscalers moving from exploring nuclear as a talking point to signing real commercial agreements.

The other structural driver is the interconnection queue problem. Connecting new generation — or new large loads — to the existing grid requires a lengthy utility study and approval process that in many US regions now takes multiple years due to a backlog of pending requests. A "behind-the-meter" or co-located power arrangement, where a data center's power comes from a generation source built specifically for it rather than being drawn through the general grid interconnection queue, sidesteps a meaningful part of that delay — which is precisely why hyperscalers are pursuing direct generation deals (nuclear, but also on-site gas turbines and renewables) rather than simply waiting in the standard interconnection queue like a conventional large industrial customer would.

The Regulatory and Timeline Reality

The economic case for SMRs depends on the standardized-factory-manufacturing thesis actually playing out, and that requires regulatory approval processes that can keep pace with a genuinely different construction and licensing model than conventional nuclear plants were designed around. In the US, the Nuclear Regulatory Commission has been developing streamlined licensing pathways specifically for SMR designs, and several designs (NuScale, X-energy, Kairos Power, TerraPower) have received or are pursuing NRC design certification — a necessary but not sufficient step, since design certification doesn't build an actual operating reactor. NuScale's own experience is instructive here: its Utah-based small modular reactor project, once the furthest along in the US commercial SMR pipeline, was cancelled in 2023 due to rising costs and insufficient subscriber commitment, a concrete reminder that SMR economics remain unproven at commercial scale despite genuine engineering and regulatory progress.

The honest timeline picture as of 2026 is that no US commercial SMR is yet operating and supplying power to a data center — announced projects generally target operational dates in the late 2020s to early 2030s, and every one of those dates carries real execution risk given the industry's historical track record of nuclear construction delays and cost overruns, even accounting for the different, factory-based construction model SMRs are betting on. The Three Mile Island restart is a partial exception, since it involves restarting an existing, previously licensed conventional reactor unit rather than a new SMR build — which is precisely why it's the nearest-term of the major hyperscaler nuclear deals, targeted for the mid-2020s to 2027 timeframe, while the genuinely new SMR-based projects sit further out.

What This Means for Engineers Working Near This Space

For power systems, electrical, and data center infrastructure engineers, the practical takeaway is that nuclear-powered data centers are a real, well-funded, actively-progressing direction rather than a hypothetical — but they are not yet an available power source for a project being designed today. Near-term data center power strategy for most projects still runs through conventional grid interconnection, on-site gas generation, and renewables-plus-storage, with SMR and restarted-nuclear power purchase agreements functioning as a multi-year-out strategic hedge for the largest hyperscale developers rather than a general-purpose option available to a typical data center project. Engineers tracking this space should watch NRC design certification milestones and first-of-a-kind construction progress (not just power purchase agreement announcements, which represent a commercial commitment rather than a completed engineering and licensing milestone) as the more meaningful signal of how close SMR-powered data centers actually are to operational reality.