Small Modular Reactors

Small Modular Reactors (SMRs) are compact nuclear power units typically producing ≤ 300 MW(e) and designed for factory fabrication, transport, and on‑site assembly. Their reduced footprint, modular scalability, and emphasis on passive safety distinguish them from conventional gigawatt‑scale reactors, promising faster deployment and lower upfront capital. The concept gained prominence after the 2012 International Atomic Energy Agency (IAEA) definition, which framed SMRs as “nuclear power reactors of 300 MWe or less that can be manufactured at a plant and shipped to a site for installation.”

Origins and Early Development

The modern SMR movement traces back to the 1990s when the United States Department of Energy (DOE) launched the “Advanced Small Modular Reactor” program to diversify the nuclear fleet after the 1979 Three‑Miles Island incident. In 2007, the DOE’s $70 million grant to NuScale Power catalyzed the first commercial‑grade design, an 60‑MW(e) integral pressurized water reactor (iPWR) that integrates primary coolant loops within the reactor vessel. By 2010, the Canadian Nuclear Laboratories (CNL) introduced the “SLOWPOKE‑2” prototype, demonstrating a 0.5‑MW(e) SMR for remote applications. These early projects established the regulatory and engineering foundations that later enabled the International Atomic Energy Agency’s 2018 “SMR Roadmap,” which identified 70 SMR projects across 15 countries.

Technical Design and Safety Features

SMRs employ a variety of coolant technologies, but the most mature design is NuScale’s iPWR, which uses light‑water coolant at 155 °C and a natural‑circulation loop that eliminates the need for active pumps during normal operation. The reactor core, containing 25 fuel assemblies, is housed in a steel pressure vessel that also serves as the primary heat exchanger, thereby reducing the number of large penetrations and simplifying the containment structure. Passive safety is achieved through gravity‑driven cooling and a steel‑in‑steel containment that can withstand a 10‑minute loss‑of‑coolant accident without operator intervention. The modular architecture allows a single 60‑MW(e) module to be scaled up to 12 modules, delivering 720 MW(e) while preserving the same safety envelope.

International Landscape

The United States remains the leading SMR developer; in August 2020 the Nuclear Regulatory Commission (NRC) issued a final safety evaluation report approving NuScale’s design, clearing the path for the first commercial unit at the Idaho National Laboratory slated for 2029. Europe has followed suit: the United Kingdom’s Office for Nuclear Regulation granted a design acceptance order for the Rolls‑Royce‑led “UK SMR” in February 2023, targeting a 470 MW(e) plant at Sizewell C by 2032. Russia’s Rosatom has deployed the 300‑MW(e “KLT‑40S”) floating SMR on the Akademik Lomonosov vessel since 2019, supplying electricity to the Murmansk region. According to the 2023 IAEA SMR Outlook, the global market is projected to reach US$30 billion by 2030, driven by the combined capacity of 70 projects under construction or licensing.

India’s SMR Programme

India’s Department of Atomic Energy (DAE) announced its SMR ambition in the 2022 “Nuclear Power Programme” document, earmarking ₹10,000 crore (≈ US$1.2 billion) for research, design, and demonstration. The Bhabha Atomic Research Centre (BARC) partnered with the Nuclear Power Corporation of India Limited (NPCIL) to develop a 200‑MW(e) sodium‑cooled fast reactor, leveraging indigenous fuel‑fabrication capabilities and targeting a pilot plant at Kalpakkam by 2035. In March 2023, DAE signed a memorandum of understanding with NuScale Power and the DOE to explore a 60‑MW(e) SMR deployment in the state of Gujarat, aligning with the Gujarat Energy Development Agency’s goal of adding 5 GW of clean capacity by 2030. The Indian Nuclear Regulatory Authority (INRA) issued its first draft safety guidelines for SMRs in July 2024, stipulating a maximum core damage frequency of 10⁻⁶ per reactor‑year and mandating on‑site emergency response teams trained within 48 hours of installation. These regulatory steps, coupled with the 2025 launch of a joint Indo‑U.S. SMR research hub at the Indian Institute of Technology Delhi, position India to become one of the world’s earliest large‑scale SMR adopters.