Today, every nuclear power plant is unique, custom-built and run by site-specifically trained employees. This makes reactor construction expensive and, some argue, less safe because repairs require custom parts and one-off solutions. In recent years, nuclear energy advocates have been promoting an alternative—smaller, modular reactors that could be mass-produced. These cheaper, smaller, and standardized units could be a power solution for industries and municipalities that are looking to lower their carbon dioxide footprint.

But a paper by Ahmed Abdulla, Inês Lima Azevedo, and M. Granger Morgan finds that the small module reactor solution may not actually be cost effective yet.

The small modular designs have several advantages over traditional nuclear plants. Average construction time for a small module reactor should be about three years, compared to five for a traditional reactor. The new designs also have potential to be sited in places where a traditional nuclear reactor could not be located.

Several American companies are actively developing this technology, but without a sample of active small reactors to study, there was no hard economic data for the researchers to use. Instead, the researchers careful quantified the average opinions of industry experts. The researchers presented 16 experts with a variety of installation scenarios and asked them to estimate the cost per kilowatt of reactor capability and the time required for construction.

As you might expect, opinions varied widely. Although the experts remain anonymous, most work for companies developing smaller reactor technology. The median cost estimates for a kilowatt of electricity produced by a single 45 MWe reactor ranged from $4,000 to $16,000. For comparison, the cost estimates for 1000-MWe large light water reactor ranged from $2,600 to $6,600.

One problem is that as a reactor shrinks, it loses the economy of scale for key components like the pressure vessel that holds the coolant and the reactor core. Five of the 16 experts “argued that costs rise rapidly as reactors become smaller, with the result that the 45-MWe reactor is especially disadvantaged,” Abdulla et al wrote.

Another problem is that current law prohibits more than two reactors from being operated from the same control room, making it illegal to site lots of the small modular reactors together. However, most of the experts believed that, if legal, installing a series of the small reactors could increase economies of scale and reduce costs.

The experts agreed that the main advantage to a small module reactor is the standardized factory production, which would certainly be cheaper than custom components. However, a majority of those interviewed “were skeptical that such economies would completely offset the diseconomies of scale in reactor size,” Abdulla et al. wrote.

While this study shows significant uncertainty about the competitiveness of small module reactors in today’s energy economy, the experts certainly aren’t ready to rule them out. As pilot projects come online, better data will be available. Designs will undoubtedly become more efficient. And if reducing carbon dioxide emissions becomes more of a priority, the economy might become more favorable to nuclear power. If that happens, small module reactors could be a solution.

PNAS, May, 2013. DOI: 10.1073/pnas.1300195110 (About DOIs.)