SMR

by Sérgio Granato de Araújo

Small in size and with a simple integration plan, small modular reactors (SMR) are advanced nuclear reactors w/ a power capacity of up to 300 MWe per unit, which is about one-third of the generating capacity of conventional nuclear power reactors.  Some intermediate designs (between 300 and 700 MWe) are also often included in this classification [WNA, 2023].

Fuel requirements in SMR technologies can vary depending on the reactor design.  While SMRs based on conventional light-water technology typically use uranium enriched to levels similar to current reactors (around 3%–5% U-235), several advanced SMR concepts require higher enrichment levels, commonly referred to as HALEU (High-Assay Low-Enriched Uranium), ranging from 5%-20%.  This higher enrichment enables longer fuel cycles, more compact cores, and alternative cooling and moderation strategies.

This interest in small and medium-sized nuclear power reactors is driven both by a desire to reduce the impact of capital costs and to provide power away from large grid systems, as well as by the growing energy demand of hyperscale data centers for AI applications [WNA, 2023], [IEA, 2025].  More than 80 commercial SMR designs are being developed around the world, targeting varied outputs and different applications, such as electricity generation, hybrid energy systems, heating, water desalination, and steam for industrial applications [IAEA, 2021].

Advantages of SMR [EG, 2021]

• Fuel Security: SMRs can store 2 years of fuel on-site, and in some cases, several decades’ worth.

• Ramp Up & Ramp Down: certain SMR designs, like that of NuScale Power, LLC (“NuScale”), allow for output to be varied over days, hours, or even minutes.

• Islanding: SMR can operate connected to the grid or independently.

• Black Start: SMR can start up from a completely de-energized state without receiving energy from the grid.

• Underground Construction: SMR can be built underground, making them less vulnerable to natural phenomena, EMP, and other intentional destructive acts.

Schematic of a SMR

A key feature of the SMR is that all the main components such as i) pressurizer, ii) steam generators, and iii) reactor coolant pumps are installed inside the reactor pressure vessel, as shown in Figure 1.

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Key players

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Small Modular Reactor Market worth USD 7.14 billion by 2030 [M&M, 2026].  Key player are:

• Westinghouse Electric Company LLC (USA) – AP300 SMR

• NuScale Power, LLC (USA) – VOYGR SMR

• GE Hitachi Nuclear Energy (GEH) (USA/Japan) – BWRX-300

• X-energy, LLC (USA) – Xe-100 (HTGR)

• Terrestrial Energy Inc. (Canada) – IMSR (Molten Salt Reactor)

• Moltex Energy Canada Inc. (Canada) – SSR-W (Molten Salt Reactor)

• Rolls-Royce SMR Ltd. (United Kingdom) – PWR-based SMR

• Rosatom State Atomic Energy Corporation (Russia) – RITM-200, KLT-40S

• China National Nuclear Corporation (CNNC) (China) – ACP100 (Linglong One)

• Korea Atomic Energy Research Institute (KAERI) / Hyundai E&C (South Korea) – SMART

SMRs in commercial operation 

As of Jan/2026, only two SMR projects are in commercial operation worldwide.  In Russia, the Akademik Lomonosov, the world’s first floating nuclear power plant, has been supplying electricity & heat to the remote Arctic town of Pevek since May 2020, using two KLT-40S reactor modules rated at 35 MWe each. In China, the HTR-PM high-temperature gas-cooled reactor demonstration plant at Shidao Bay entered commercial operation in late 2023, delivering approximately 200 MWe from two modular reactor units.

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Micro-reactors 

On the other hand, micro-reactors are a subset of SMRs designed to generate electrical power typically up to 10 MWe, featuring ultra-compact designs, factory fabrication, and transportability, which make them particularly suitable for deployment in remote, isolated, or infrastructure-constrained regions, as well as for providing resilient backup power and replacing diesel-based generation.  As of Jan/2026, no commercial nuclear micro-reactors are in operation; all remain in demo, licensing, or early construction.

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Final remarks

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1. Reality vs. Hype: Current Landscape

• Commercial Operation: Reality. Russia operates the Akademik Lomonosov floating plant (two KLT-40S reactors) since 2020. China has grid-connected the HTR-PM high-temperature reactor and is finalizing commercial operation for its Linglong One (ACP100) PWR SMR.

• Western Markets (US, Europe, Canada): Transitioning from Licensing to Construction. Despite setbacks like NuScale’s project cancellation in Idaho due to inflation and interest rates, progress continues toward site preparation.

• AI & Big Tech Catalyst: Massive 24/7 power demand for AI data centers has injected renewed commercial momentum, unlocking billions in public and private capital for SMR manufacturing.​​

2. Key Leaders and Developers

• China (Onshore Deployment Leader): CNNC's Linglong One (ACP100) and the operational HTR-PM demonstrate fast-track construction driven by strong state support.

• Russia (Remote & Floating Leader): Rosatom leads with the Akademik Lomonosov floating unit and land-based RITM-200 projects targeting remote mining operations in Yakutia.

• U.S. (Design & Licensing Leader): GE Hitachi: Developing the BWRX-300, selected for Canada's Darlington plant and Poland's OSGE; NuScale Power: Holds the first NRC-certified SMR design, pivoting to international deployments like Romania's RoPower; Advanced Concepts: TerraPower, X-energy, Westinghouse (AP300), and Holtec are advancing liquid-metal, molten-salt, and PWR designs with US DOE backing.

• Canada & UK (Western Deployment Hubs): Canada is set to deploy the West's first commercial SMR (BWRX-300 at Darlington), while the UK’s Great British Nuclear initiative funds leading designs like Rolls-Royce SMR.

Figure 1: Schematic of a SMR