Understand Small Modular Reactors

Stanford University | September 30, 2025

What you need to know

Significance: SMRs, like large-scale fission reactors, are zero carbon, but they also have the potential to be faster and cheaper to deploy with lower capital costs and efficient mass production in factories. SMRs can provide 24/7 electricity and potentially be co-located with heavy energy users like data centers or industrial facilities. Additionally, some proposed SMR designs would be able to produce high-temperature heat to power hard-to-decarbonize industries like steel and cement.

Only two SMRs are operating commercially: KLT-40S in Russia has been operating since 2020 and HTR-PM in China has been operating since 2023. Both projects had longer development timelines, higher costs, and lower initial capacity factors than expected. But this industry is in its early stages: 74 new SMR projects are in development worldwide. The Nuclear Energy Agency (NEA) is tracking $15.4 billion of financing toward SMRs, with private capital playing an increasingly important role.

What are small modular reactors (SMRs)? SMRs are exactly what the name suggests: small and modular fission reactors. Industry organizations typically use these criteria:

• Small: 50-300 MW capacity (up to one-third the size of a conventional reactor)

• Modular: Built with components manufactured in factories to achieve economies of scale

Keep in mind that “small” is relative: 300 MW is enough to power 300,000 homes! An SMR power plant still takes up a lot of land as shown in the image below.

Read the entire Stanford report here.