Small may be beautiful for the nuclear power industry So argue a host of would-be builders of novel nuclear reactors. While the U.S. government has not given up on investing in large units that boast conventional designs, the Department of Energy has also announced the availability of $450 million in funds to support engineering and licensing of so-called "small modular reactors."

"The Obama Administration and the Energy Department are committed to an all-of-the-above energy strategy that develops every source of American energy, including nuclear power," said Secretary of Energy Steven Chu in a statement announcing the funding, which aims to get such modular reactors hooked into the grid by 2022. "The Energy Department and private industry are working to position America as the leader in advanced nuclear energy technology and manufacturing."

Globally, large reactor designs remain the predominant technology. One alternative to cut costs could be small, novel reactors, appropriate for areas with smaller electricity demands or as part of a flexible power production facility that could scale up quickly as necessary. Small reactors would have a maximum capacity of 300 megawatts of electricity, or enough to power more than 200,000 U.S. homes for a year. In addition, the reactors would be modular—made in factories and shipped to sites—to reduce costs.

But such reactors still require the same electricity-generating, safety, and waste disposal systems as the hulking light-water reactors presently being built as well as identical rigorous licensing requirements, at least in the U.S.—and that may cost them. "Yeah, there's less concrete and, yeah, there's less steel in the reactor vessel," says nuclear engineer Eric Loewen, chief consulting engineer at GE Hitachi Nuclear Energy, which is proposing a modular fast reactor to help the U.K. with its plutonium problem. But the list of other expenses associated with nuclear will not change with the new designs and "that gives pause to small modular reactors."

Mini-nuke

A modern pressurized water reactor, like the two being built in Georgia, can pump out more than 1,000 megawatts worth of power using the heat from fission to boil water to spin a turbine. Babcock & Wilcox—one-time builder of large pressurized water reactors as well as smaller ones suitable for the submarines of the U.S. Navy—would like to shrink those down to just 180 megawatts. "It's not for lack of knowledge of how to build big reactors," says Chris Mowry, president of B&W Modular Nuclear Energy.

Instead, B&W suggests that the fundamental problem facing the adoption of nuclear power is not the technology itself, but the financial risk of committing to a build a big nuclear reactor. Simply put, even the largest utilities do not have the capital to build a $7 billion reactor, and such large projects have a tendency to see costs balloon as projects are delayed. A case in point is the Tennessee Valley Authority's bid to complete a second reactor at its Watts Bar Nuclear Power Plant. The reactor, first begun in the 1970s and resumed in 2007, is behind schedule and "will cost more than forecast," admits TVA spokesman Terry Johnson. "It's a size issue," Mowry argues.

So B&W has designed an integral pressurized-water reactor that it can manufacture in a factory and ship to a site. "We wanted to be able to put it on a rail car," Mowry says, and so the self-contained reactor is 25 meters tall and 4 meters wide. Operating at high pressure and temperature, such reactors are not truly novel, having propelled the first commercial nuclear ships, such as the nuclear-powered cargo ship named Savannah, in past decades.

Shrinking the reactor and putting its parts (such as the control rods that regulate the fission process) inside the reactor vessel, also reduces the need for redundant safety systems to deal with problems such as leaky pipes. The pipes in and out of the reactor sit above the nuclear fuel rods themselves, ensuring that any leaks do not result in uncovered fuel. In addition, the pipes are much smaller than those required for a larger reactor. "You have a hell of a lot more water in the reactor relative to the size of the breaks that can happen," Mowry explains. External tanks hold enough additional water to cool the reactor for two weeks in the event of a loss of power as well. In addition, the reactor—in essence, a nuclear battery because it is largely self-contained—is buried, rendering it "immune from external events like tornadoes, hurricanes or tsunamis."

The smaller reactor uses the same nuclear fuel rods—albeit slightly shorter in length to fit—but fissions them more slowly, operating for four years before fresh fuel is needed. A test facility near Lynchburg, Va. is up and running to ensure that what looks good on paper will also work in practice and B&W already has one potential customer in the U.S.—the TVA—expressing an interest in building as many as six of the small modular reactors at its Clinch River site, former home of a failed effort to build a fast breeder reactor in the 1970s.

The B&W mPower reactor is not the only such small modular design moving forward: Westinghouse Electric, NuScale and Holtec—a company better known for making the hulking concrete and steel casks to store used nuclear fuel—have similar designs of varying sizes. "The advantage of the smaller one is: even if you need 1000 megawatts you can put investment in piecemeal and generate money while the next unit is put in," says Westinghouse CEO Aris Candris.

But multiple reactor sites proved problematic at Fukushima Daiichi, where an accident in one rapidly became a crisis for multiple reactors and spent fuel pools. "If you're going to have multiple reactors, are you going to gain in safety or lose in safety?" asks physicist M.V. Ramana of Princeton University. "We don't know."

"Early in the discovery of any new technology you have this rosy picture that is formed," Candris admits of small modular reactors. "In the early days of nuclear, there were people out there saying it would be too cheap to meter. We found out otherwise."

Alternative fuel?

Small modular reactors may help with two of the biggest challenges facing the nuclear industry: the growing stores of waste from existing reactors and residue from the mass production of nuclear weapons as well as the overall safety of nuclear power. GE's PRISM fast reactor, General Atomic's helium-cooled fast reactor, or Hyperion Power's liquid lead-bismuth cooled reactor could all turn waste into fuel. Hyperion hopes to demonstrate its reactor, capable of generating 25 megawatts of electricity, at the Savannah River National Laboratory in South Carolina. The site has also signed memorandums of understanding to host prototypes of the NuScale and Holtech reactors.

Such nuclear batteries could in principle be sealed, placed in the ground, and run for a decade before being swapped out for an entirely new modular reactor. And if manufactured in a factory, they could also be cheap. "There is no inherent reason why nuclear power needs to be expensive," Bill Gates, who has invested in the novel reactor proposed by TerraPower, told the ARPA–e summit on February 28, noting that nuclear's relative expense largely derives from building in safety features.

Evaluating the safety of such new reactors will take time, of course, and the U.S. Nuclear Regulatory Commission has yet to receive an application from any of the would-be vendors of small modular reactors, whether fast reactors or scaled-down light-water reactors. And staffing requirements, emergency planning and clean-up funds, among other issues, remain to be worked out between the reactor makers and the NRC—a key component of reducing the cost of such reactors. "The staff has contended pretty much all along that they will have to meet the same security requirements as all of the large reactors," says Michael Mayfield, director of the Division of Advanced Reactors and Rulemaking in the NRC's Office of New Reactors, noting that a timeline for licenses could be expedited if such reactors are simply scaled down versions of existing light water reactors that do not require new regulations. "Why would it take so long to review something that is substantially smaller with fewer parts? That however is based on the notion that vendors submit complete, high quality applications and address staff concerns more quickly than we have been able to do with some of the large [reactor] designs."

By eliminating human intervention—through passive safety features that kick in without the help of operators—staffing requirements might be cut. And if buried or otherwise hardened, the need to pay security guards might also be reduced. "If you need humans to do something, that is not a good design," Gates argued at the ARPA-e conference.

Ultimately, the success or failure of such scaled-down designs may relate to manpower. "If you need the same overhead to run 100 megawatts as you do to run a 1000, that's economically problematic," notes William Johnson, CEO of Progress Energy, a utility considering whether to build new nuclear power plants in future.

The Homer Simpson factor

Of course, human error has yet to be eliminated from either operating reactors or those that exist only on paper. And, much as in airplane or pharmaceutical development, government decisions will determine whether these reactors succeed. Small modular reactors "becoming a reality are dependent on government and the nuclear industry," said NRC commissioner William Ostendorff in a speech to the American Nuclear Society conference this past November. "With respect to new reactor licensing, 'the devil is in the details.'"

Regardless of how cheap such small modular reactors may allow nuclear to be in future, it is unlikely to be as cheap as natural-gas-fired turbines in the present. In fact, low natural gas prices stalled the U.S. nuclear renaissance outside Georgia and South Carolina, long before the reactor meltdowns at Fukushima Daiichi in Japan. "Because of an unanticipated abundance of natural gas in the United States, nuclear energy, in general, is facing tough competition," noted an analysis of the prospects for small modular reactors from the University of Chicago published last November. The analysis also suggested that small reactors would be more expensive than large reactors on a per-megawatt basis until manufacturing in significant quantities has happened. "It [is] unlikely that SMRs will be commercialized without some form of government incentive."

But the Department of Energy funding may only support two designs. Innovation spurred by competition seems unlikely. And that may ultimately erode the current U.S. nuclear industry advantage—from design to operation to regulation.

That means that the rest of the world—particularly China, which is building almost every type of reactor on offer, and Russia—may well inherit the promise and peril of nuclear power, whether small or large. "China and India lead the world in nuclear safety today," NRG CEO David Crane told the Bloomberg New Energy Finance Summit on March 20. NRG initiated and abandoned plans to build at least two new large reactors in the last five years, thanks to falling natural gas prices and uncertainty surrounding U.S. government policy. "The U.S. cannot lead the world in safety, if we're not building new nuclear power plants."