Small Modular Nuclear Reactors

Chor Seng Tan
December 11, 2015

Submitted as coursework for PH240, Stanford University, Fall 2015


Fig. 1: Illustration of how small modular reactor can be deployed to meet our energy needs (Courtesy of the US Department of Energy)

According to a report by the International Panel on Climate Change (IPCC), renewable energy needs to grow to about 80% of the power sector from about 30% currently for the world to avoid "severe, pervasive and irreparable" damage. [1] In order to meet this challenge, all forms of low-carbon energy technologies need to be on the table, including nuclear power. According to estimates by the Organization for Economic Co-operation and Developement (OECD)'s energy agency, nuclear energy has already avoided the release of over 60 gigatonnes of CO2 emissions since 1980, assuming that the power would otherwise have been generated by burning coal or oil. [2] Climate scientist James Hansen called for a larger focus on nuclear energy in the 2015 Paris climate negotiations due to its "tremendous potential to be part of the solution to climate change". [3]

What Are Small Modular Nuclear Reactors?

Small modular reactors are part of a new generation of nuclear power plants being developed today with the aim of providing a flexible, cost-efficient means of clean energy generation in order to enhance energy supply security.

According to the International Atomic Energy Agency (IAEA), small modular reactors (SMRs) are defined as nuclear reactors with electricity output lower than 300 megawatt (MWe) (traditional reactors generate about 1000 MWe), designed to be built in factories and shipped to utilities for installation as demand arises. Fig. 1 is an illustration of how they are deployed. [4]

Advantages of Small Modular Reactors

SMRs offer several benefits over traditional large nuclear reactors. Because they are mainly fabricated in a factory environment before being shipped to the point of use, SMRs require limited on-site preparation and can greatly reduce the lengthly construction times of larger units. They also offer simplicity of design, enhanced safety features, and the superior quality afforded by factory production. For example, the Westinghouse small modular reactor is designed to shut down automatically and keep itself cool without human intervention, making it about 100 times safer than existing nuclear plants. [5]

SMRs require significantly lower capital costs due to their smaller size. Nuclear reactors that generate over 1000 MWe of power can cost more than $10 billion to construct, compared to SMRs that are expected to cost a few billion dollars. [6]

SMRs can be deployed in areas that lack the infrastructure to support a larger plant, or that do not require the energy generation of a larger plant. This allows smaller electrical markets, isolated areas, and sites with limited land and water resources access to nuclear power. A large nuclear plant requires an emergency planning zone that extends 10 miles around the plant, whereas a SMR may require a zone as small as half a mile around it. [6]

SMRs can be added incrementally to load centers as demand increases to match supply with demand. Another advantage of having multiple small reactors is that other reactors can stay online when one needs to go off-line for refueling, allowing for power to be generated continuously whereas for a conventional plant, the entire plant has to go offline for refueling. [7]

SMRs also provide safety benefits due to their nonproliferation nature. Most SMRs are built below grade for security purposes, hence minimizing the risks of sabotage or hazards that may arise due to natural disasters.

Current Status and Future Outlook

Because of its many advantages, SMRs have attracted the attention of many countries. In 2012, the US Department of Energy announced that $450 million would be made available towards the development of SMRs. [8] More recently, UK announced that 250 million pounds would be put into SMR research. [9] Currently, there are more than 45 SMR designs under development for various purposes or applications. [4]

According to Dr. Christina Back, a physicist at General Atomics, nuclear remains the largest source of clean, sustainable, and reliable energy. In order to play a bigger role in reducing carbon emissions, future advanced nuclear reactors must address four core challenges: they have to be safer, produce less radioactive waste, pose a lower risk of nuclear proliferation, and be cheaper. [10] SMRs have the potential to tick all the boxes, and holds promise for a clean and sustainable energy future.

© Chor Seng Tan. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.


[1] R. K. Pachauri and L. A. Meyer, eds., "Climate Change 2014: Synthesis Report," Intergovernmental Panel on Climate Change, 2015, p. 2.

[2] G. Souvant, "Nuclear Power as Panacea for Climate Change? Experts Divided," Agence France-Presse, 4 Dec 15.

[3] G. Vaidyanathan, "Nuclear Power Must Make a Comeback for Climate's Sake", Scientific American, 4 Dec 15.

[4] D. Carrington, "George Osborne Puts UK at the Heart of Global Race for Mini-Nuclear Reactors ," The Guardian, 24 Nov 15.

[5] S. Dotson, "The Promise of Small Modular Reactors," Power Engineering, 5 Feb 15.

[6] K. Bullis, "Can Small Reactors Ignite a Nuclear Renaissance?," Technology Review, 28 Mar 13.

[7] N. Cunningham, "Small Modular Reactors: A Possible Path Forward for Nuclear Power," American Security Project, October 2012.

[8] D. Biello, "Small Reactors Make a Bid to Revive Nuclear Power," Scientific American, 27 Mar 12.

[9] E. Gosden, "UK Plans Small Modular Nuclear Reactor 'in 2020s'," The Telegraph, 25 Nov 15.

[10] C. Flavelle, "Eight Eight Ways to Save the Planet", Bloomberg View, 30 Nov 15.