The Community of Madrid has turned its focus to next-generation nuclear energy. The regional government led by Isabel Díaz Ayuso has announced a strategy to increase research in nuclear technologies —including small modular reactors (SMRs)— aimed at strengthening supply security and attracting scientific and industrial talent into the Madrid ecosystem. The plan, presented during the State of the Region debate, mobilizes specific programs to attract researchers and aligns centers like IMDEA Energy with European sector partnerships, amid friction with the national policy of phased nuclear plant closures between 2027 and 2035.
While Madrid explores research pathways, other countries are already making regulatory and commercial moves. United Kingdom has selected Rolls-Royce SMR as the preferred bidder to build the country’s first SMRs, within the Great British Energy – Nuclear program, with the goal of connecting projects by the mid-2030s. Meanwhile, the digital sector is beginning to align SMRs with AI peak power needs: Google has signed an agreement to purchase electricity generated from Kairos Power SMRs in the U.S., with plans to start meeting data center demand around 2030 (Oak Ridge, Tennessee, in collaboration with TVA).
From here, a guide to understanding what SMRs are, how they work, what they promise, and what questions remain open.
What exactly is an SMR?
Small Modular Reactors are nuclear reactors of up to 300 megawatts electrical (MWe) per unit —roughly one-third the power of a conventional reactor— designed to be manufactured in modules in factories and assembled on site, with shorter construction times and series economies. The IAEA and the European Commission place their typical range between 20 and 300 MWe and estimate a daily output of up to 7.2 million kWh, compared to the 24 million kWh/day of a large plant exceeding 1,000 MWe.
Although the “SMR” umbrella covers diverse technologies (light water, molten salts, liquid metals), Rolls-Royce SMR favors a PWR (pressurized water reactor) “classic” design with key innovations, including a boron-free primary circuit, reducing corrosion, water usage, and secondary waste generation.
Note: despite the standard definition (≤300 MWe), Rolls-Royce’s British design reaches ≈470 MWe per unit — the company maintains the SMR label because of its industrial modularity and construction cycle.
How it works: fission, two circuits, and industrial packaging
The physical principle is the same as conventional nuclear: uranium fission produces heat, high-pressure water extracts this energy in the primary circuit, and an independent second circuit creates steam to drive turbines. The difference lies in the scale (lower power per reactor), the compact design, and the high level of prefabrication that allows for standardized safety, operation, and maintenance. For Rolls-Royce, the planned fuel is uranium enriched to 4.95%, typical of commercial PWRs, with the mentioned operation without soluble boron.
What they promise: speed, cost, safety, and uses beyond kilowatts
1) Faster, predictable deployment.
Modularity shifts most tasks to factories (repetitive, tested modules), reduces civil works, and enables planning for block scale-up. The UK estimates three initial units after the preferred bidder award, with grid connection by mid-30s if contracts and licenses are finalized on time.
2) Lower costs through series production.
Instead of one-off, complex mega-projects, the industrial model favors long series, learning effects, and more controllable capex. (However, this promise relies on actual costs being verified when commercial operation begins.)
3) “Passive” safety and favorable inertia.
Lower power, compactness, and “passive” systems (which do not require external energy or human intervention to reach safe states) improve fault tolerance. Standardization — same design, tests, training — reduces variability and uncertainty compared to bespoke plants.
4) Flexible heat uses.
Beyond electricity, an SMR can provide process heat for hydrogen, desalination, or synthetic fuels, making industrial decarbonization more feasible. The EU recognizes these co-products as part of the technology’s strategic appeal.
5) Integration with data centers and AI.
Large “campus” data centers require 24/7 energy and grid stability. Hence, the PPA agreements announced by Google with Kairos Power: multiple SMRs to meet AI data center base load in the U.S., with TVA as a public partner and initial goals toward 2030. Ecosystem partnerships are also emerging (e.g., Oklo–Vertiv) to couple nuclear heat and data center cooling.
What questions remain open?
Licensing and real timelines.
The UK’s “mid-2030s” target is ambitious: it involves regulatory procedures, funding, supply chain, and public acceptance. Demonstrating industrial series — the key to cost efficiency — is still to be proven outside prototypes.
Fuel and cycle considerations.
Many light water SMRs use standard fuels (LEU ~4–5%), but advanced designs are aiming for HALEU (up to 19.75%), with limited supply. Planning supply chain and waste management remains as strategic as civil works. (Sector overview: World Nuclear Association).
Levelized cost vs. alternatives.
SMR investment competes with renewables + storage, flexible cycles, and demand response. The value lies in carbon-free firm energy and heat utilization; the key will be the final MWh price.
Local acceptance and grid coordination.
Smaller footprint and less cooling water facilitate siting, but public perception and grid planning (avoiding “islands”) are as important as engineering.
What does this mean for Madrid?
The regional initiative does not propose building reactors but rather boosting research, talent, and collaboration with European hubs to avoid being late if the technology proves viable. Madrid has already announced new university projects and innovation districts linked to industry, aerospace, and energy, which can create a critical mass in materials, simulation, safety, and regulation.
A robust scientific-industrial ecosystem would position the region in three areas:
- R&D (resilient materials, instrumentation, digital twins, cybersecurity),
- modular engineering (series manufacturing of components),
- coupled applications (hydrogen, desalination, urban heat, AI campuses), even if nuclear operation in Spain remains dependent on national and European frameworks.
How much do they produce and how much space do they take?
As an institutional benchmark, a typical SMR (≤300 MWe) can generate ≈7.2 million kWh daily; a large plant exceeding 1,000 MWe produces around 24 million kWh/day. At the upper end, the Rolls-Royce SMR (≈470 MWe) claims enough capacity to supply about 1 million homes for decades in their nominal operation.
The compact packaging, reduced cooling water needs, and modular construction minimize footprint and onsite work. The industrial goal is to perform most assembly indoors and limit on-site intervention to integration, testing, and grid connection.
Are they safer?
The safety of an SMR relies on:
- Passive designs: the reactor reaches a safe state by physical principles (natural convection, dissipation, relief valves) without depending on external energy.
- Lower power per unit: reduces thermal inventory and simplifies design accident management.
- Standardization: identical modules, tests, and training lead to fewer engineering surprises at each site.
- Chemical innovations: for example, Rolls-Royce’s boration elimination reduces corrosion and liquid waste.
Absolute safety does not exist — in nuclear nor other forms of energy — but intrinsic design + passive systems and series manufacturing aim to improve the margin over large, bespoke plants.
What about timelines?
nationally, United Kingdom aims to allocate sites this year and connect by the mid-2030s if processes and contracts are finalized on time. On a corporate level, Google–Kairos–TVA target the start of supply around 2030 for data centers. In Spain, Madrid’s path today is focused on research, talent, and value chains, not operational construction.
What’s next?
For Madrid—and Spain—the debate is not only technological but also industrial, regulatory, and educational. If SMR waves solidify in the UK and U.S., the greatest risk isn’t “testing” or failing but not being in the supply chain, in standards, and in decision-making capacity. The regional initiative reads as: position yourself for the coming decade through applied research and international partnerships, while national energy policy sets its nuclear horizon.
FAQs
What exactly is an SMR, and how much energy does it produce?
A small modular reactor is an ≤300 MWe unit (per IAEA/EU definition), built in modules for quick assembly. It can generate around 7.2 million kWh/day; a large plant exceeding 1,000 MWe produces about 24 million kWh/day.
Why are the UK and major tech companies betting on SMRs?
For faster deployment, carbon-free reliable energy, and compatibility with uses like data centers. The UK chose Rolls-Royce as the preferred partner; Google has signed PPAs with Kairos Power and TVA.
Are they safer than traditional plants?
They incorporate passive designs, smaller power levels, and modular standardization. Rolls-Royce’s approach features a primary circuit without boric acid, reducing corrosion and waste. Total safety cannot be guaranteed, but they improve inertia and safety margins.
What role would Madrid play if it does not build reactors?
The regional plan emphasizes research, talent development, and supply chain, involving IMDEA and universities, and vying for European alliances and pilot projects. It’s a pathway to talent attraction and industry positioning, even if nuclear operations in Spain remain tied to national and European rules.
Sources: Gov.uk, NuclearWire, El Español, and El País. Archival photo of the Kairos SMR.