NuScale’s reactors are designed to generate 40 megawatts each, compared to over 1,000 megawatts for conventional reactors. They can be linked together on site to generate larger amounts of electricity. Traditionally, nuclear power plants have been built large to take advantage of economies of scale. But the large size of the projects leads to long construction times, and delays and cost overruns are common, heightening the risk for investors and increasing financing costs.
Smaller reactors, which can be built in factories rather than assembled on site, could be faster to build, lowering financing costs. The designs can also be simpler, and thus cheaper than conventional nuclear power plants, since the smaller reactors require lower pressures, for example, and their small size makes it practical to combine multiple elements into one containment vessel. Some experts have calculated that costs per megawatt could be comparable to large nuclear reactors, but no one really knows because no small, modular commercial nuclear power plants have been built yet.
Even if costs per megawatt prove higher than with conventional plants, their small size might make them attractive in areas that lack the power lines and other infrastructure needed to distribute power from a large reactor, and that may not immediately have demand for the full power output of a large reactor. The modular design could allow utilities to gradually add more reactors as demand increases. Several rural electric cooperatives in the United States have expressed interest in using NuScale’s small nuclear reactors to replace aging coal plants—the small size of the plants would eliminate the need to upgrade existing transmission lines.
Critics of small nuclear reactors, such as the Union of Concerned Scientists, say that large numbers of small reactors could be more difficult to manage during an accident, and could pose greater risk of nuclear materials falling into the hands of terrorists or rogue states.