Last updateTue, 02 Jun 2020 7pm

Small Modular Nuclear Reactors: Gaining Momentum

NuScaleInterior of the NuScale Power small modular reactor. (Image courtesy of NuScale Power)The concept of small nuclear reactors may seem new, but small reactors have been around for more than 50 years, used in naval vessels such as submarines, aircraft carriers and ice breakers. A new generation of land-based small modular reactors (SMRs) has been under development for the last several years. Learning from the advantages and problems of traditional, large reactors, the designers of these new SMRs are making them more economical to build and safer to operate.

The basic principle is to make a reactor small enough that it can be built in a factory and shipped to its installation location. In addition, these reactors are self-contained and incorporate features to protect them when natural disasters or power outages happen.

According to the U.S. Office of Nuclear Energy, the SMRs currently under development in the U.S. represent a variety of sizes, technology options and deployment scenarios. They can help provide safe, clean, affordable nuclear power. These advanced reactors may produce one or two megawatts or up to hundreds of megawatts of electricity; a conventional nuclear power plant might produce up to two or three thousand megawatts. In addition to power generation, SMRs can be used for process heat, desalination, and other industrial uses. Many of the SMRs under development use water as a coolant; others use gas, liquid metal or molten salt.

Each SMR has a much lower power output than a conventional nuclear plant, but multiple SMRs will typically be installed together to achieve higher output, as needed. They could also be installed individually to meet low power demand, in isolated areas, for example.


multiple reactor installationA multiple-reactor installation. (Image courtesy of NuScale Power)Safety features are intrinsic to the designs. For example, some SMRs use the natural circulation of water to cool the reactor. No electric power is needed to keep the cooling going, so a power outage would not pose a problem. Many of the SMRs are designed to be walk-away safe; if there is a problem such as a power outage or a failure inside the module, nothing needs to be done; essentially, the operator can just walk away. Many of these SMRs are installed below grade, also for safety. Other features include extended refueling schedules, in some SMRs 20 months or longer.

An in-depth study by staff at Boise State University, Jacksonville (FL) University and Idaho Public Utilities Commission showed that an installed multiple-SMR power plant would likely cost about 40 percent less per kilowatt capacity than a conventional nuclear plant. Also, in a 2018 paper the U.S. Energy Information Administration showed the levelized cost of electricity from advanced nuclear sources, such as SMRs, was in the ballpark of other sources: about twice the cost of natural gas power plants, but less than offshore wind.

Part of the economics of SMRs is that they have fewer moving parts than conventional nuclear plants. This is good for cost cutting, but may mean less demand for valves and other components. However, multiple SMRs will be deployed in each power plant, so perhaps the additional modules will make up for some of the reduction in the number of components in each reactor.


In the U.S., several companies and partnerships are developing SMRs.

One company that has been getting a lot of attention is NuScale Power, Portland, OR. In April 2018, NuScale Power’s design for a 60 MWe (megawatts of electricity) SMR completed the first phase of review for design certification by the U.S. Nuclear Regulatory Commission. After the necessary approvals, NuScale plans an installation at the Idaho National Laboratory and foresees commercial operation of its NuScale Power Module in 2026. A further series of projects is on the drawing board for five other Western states. NuScale is also in talks with utilities in other countries, notably Canada and Jordan as of February 2019.

The U.S. Department of Energy’s Office of Nuclear Energy awarded NuScale $40 million in cost-sharing financial assistance under its “U.S. Industry Opportunities for Advanced Nuclear Technology Development” funding. This federal award supports early-stage research and development and the industry’s acceleration of these technologies to promote U.S. energy independence, electricity grid resiliency, national security and clean baseload power.

Westinghouse Electric Company, Cranberry Township, PA, is developing two small reactors. The Westinghouse SMR is a >225 MWe integral pressurized water reactor with all primary components located inside the reactor vessel. The eVinci micro reactor is a very small modular reactor intended for decentralized power generation markets. Westinghouse received funding from DOE’s Advanced Research Projects Agency-Energy (ARPA-E) for development of a self-regulating solid core block that employs solid materials (instead of bulk liquid flow or moving parts) to inherently self-regulate the reaction rate in a nuclear reactor. This is a key component of the eVinci micro reactor concept.

The SMR-160 from Holtec, Jupiter, FL, is a 160 MWe pressurized light water reactor. In February 2018, GE Hitachi Nuclear Energy, Global Nuclear Fuel, Holtec International and SMR LLC announced a collaboration to advance the SMR‐160.

Advanced Reactor Concepts, LLC, Chevy Chase, MD, is developing ARC-100, an advanced small modular nuclear reactor. This reactor will produce 100 MWe of energy, be factory-built and offer the customer fixed fuel costs for 20-plus years.

The Generation IV International Forum is a co-operative international endeavor developing a sodium-cooled fast reactor. A small size (50 to 150 MWe) modular-type reactor with uranium-plutonium-minor-actinide-zirconium metal alloy fuel.

Other countries have their own programs. In Russia, half a dozen SMRs are in the works. They range in size from small, transportable models to 100 MWe. They are integral pressurized-water reactors and high-temperature gas-cooled reactors.

In China, Chinergy has already started building the 210 MWe HTR-PM, which consists of twin 250 MWt (megawatts thermal) high-temperature gas-cooled reactors (HTRs). China is also developing small reactors specifically to produce heat, 100 to 200 MWt, which can serve the heat market in northern China where use of coal has caused serious air pollution.

Other countries, such as Canada, India and Sweden, have SMRs under development as well.


In addition to the naval vessels using nuclear power, the military is looking into having SMRs developed for use on land. In January 2019, the Strategic Capabilities Office (SCO) at the Department of Defense issued an RFI (request for information) for a small, mobile nuclear reactor. After identifying key gaps in energy systems for remote operations, SCO is also interested in such a design to support domestic operations to make them resilient to an electrical grid attack. Also, a small mobile nuclear reactor would support humanitarian assistance and disaster relief operations. 

The requirements for this SMR are similar to those in the commercial world (inherent safety, self-contained, transportable), with some additional specifications, such as a 3-year refueling cycle. This RFI’s Phase I development effort will fund up to three different reactor designs in an anticipated 9- to 12-month effort.


As development of these different SMRs continues, some will soon reach the testing and installation stage. If they succeed and fulfill their promise, they could provide affordable, clean, safe power and heating capacity to supplement and maybe supplant existing energy sources.

This email address is being protected from spambots. You need JavaScript enabled to view it. is Web editor at VALVE Magazine

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