U.S. Energy Secretary Ernest Moniz has alluded to the promise of small modular reactors (SMRs) multiple times over the past few months, noting that they may offer benefits in terms of financing, costs and security, while also warning that realistic expectations suggest these reactors are unlikely to come onstream for almost a decade.
“We remain very interested in pursuing small modular reactors as a technology option for the future,” he said in Washington, D.C. in June. “We don’t know at this stage what the cost is, and that’s why we’re helping to move some new technologies toward licensing,” but, he added, “this would change a lot of the dynamics around how nuclear power’s deployed, particularly the financing structure.”
At a late August event in New York, he reiterated that SMRs may offer a new way forward for nuclear power in the U.S., but with a bit more caution about the technology's viability.
“There is some promise -- I emphasize it’s only promise at this stage -- about a new generation of reactors called small modular reactors,” Moniz said. “These would be much smaller units, maybe 200 megawatts, maybe even smaller. And if these are economical, they generally have very attractive safety features, and they could be an important part of a nuclear future.”
“We won’t know until we build some,” Moniz added. “The target date would be a first modular reactor operating in 2022.”
To get a sense of what differentiates SMRs from traditional nuclear plants, we spoke to one company, NuScale, that is angling to prove that SMRs can be both safe and cost-effective, as are several of its competitors, such as Westinghouse and Babcock & Wilcox.
A Different Scale
NuScale aims to claim a share of the emerging SMR nuclear generation market. The company is seeking Department of Energy funding in an effort to bring its scalable modular reactors to market.
Each NuScale reactor has a capacity of 45 megawatts. A single “plant” could hold up to 12 modules, immersed in 10 million gallons of water, bringing total capacity to 540 megawatts, about half of the typical U.S. nuclear power plant’s 1,000 megawatts, said Mike McGough, NuScale’s chief commercial officer.
“When you think of the existing fleet, you often see the large, dome-shaped structure. That’s the containment building, with a four-foot concrete wall that serves to encapsulate components and piping systems,” McGough said. NuScale’s modules, which include a containment vessel and a reactor vessel as an integrated component, “are significantly simpler and smaller, and do not require the multitude of large vessels, pumps, motors, and electrically driven valves and piping systems.”
Unlike traditional plants, the modules can be manufactured in a factory and transported by truck, rail or barge. “The idea was, instead of using these very large monolithic structures to make a containment vessel that could house the reactor pressure vessel within it, make [the reactor] small enough that the whole thing can be built under controlled conditions and transported via common modes of conveyance to where it’s going to be installed,” McGough said.
Another key difference between traditional plants and NuScale’s SMRs is safety features. The company’s design sought “to solve the most vexing problem of the commercial nuclear industry: what happens to your plant in the event of a station blackout that caused the problems of Fukushima,” McGough said. The solution NuScale came up with was to eliminate the need for electricity to implement a plant shutdown.
If a NuScale plant loses power, all its valves revert to a “safe” position, which allows cooling through natural circulation, using convection (the tendency of a fluid, when heated, to become less dense and rise), conduction (the tendency of heat to transfer through a metallic surface), and gravity. “Those things will work all the time, whether there’s electricity or not.” Heat is released into a common 10-million-gallon pool of water in which the modules are immersed.
“Our plant, in the case of a complete loss of offsite power, will shut itself down and cool itself off indefinitely with no operator action,” McGough said. “The plant is able to maintain itself, and to cool itself until it has reached ambient temperatures.”
McGough estimates that the cost for electricity generation will be in the range of $0.08-$0.09 per kilowatt-hour. “If you look at costs of electricity generation at today’s natural gas prices in the $4.00 per MMBtu range, frankly, nuclear will have a difficult time competing,” McGough said.
But McGough pointed both to expectations that natural gas prices will not stay that low forever, and to much higher gas prices abroad -- in the $18/MMBtu range in Japan, for example -- as indications that NuScale’s SMRs could be competitive by the time they hit the market. “At $6-$7/MMBtu [for natural gas], our plants will be very competitive,” he said.
And if by the time NuScale’s reactors come on-line, there is a cost associated with carbon dioxide emissions, they will be even more competitive with gas-fired generation. “Nuclear generates zero GHG emissions, and although natural gas emits less than coal, it’s still about two-thirds of coal’s emissions,” he said.
“SMRs are an option for a hedge against carbon,” McGough said.
NuScale’s timeline for getting a plant up and running roughly conforms to Secretary Moniz’s 2022 target, with regulatory compliance eating up the most of the next nine years.
“The long pole in the tent is obtaining design certification and the construction operating license from the NRC [Nuclear Regulatory Commission],” McGough said. “You have to apply for the license first, and developing an application for design certification is a daunting task.”
“It costs about $1 billion to get through the process required to get a design certification. Today, we are about $160 million into that.”
NuScale intends to submit a design certification application -- a document of about 10,000 pages -- in the second half of 2015. The company expects the certification process to last around 39 months, and to receive a construction operating license roughly six months after that. “That takes you into the second half of 2019,” McGough said.
At that point, NuScale will be able to begin safety-related construction on the first plant, which will take an additional 36 months. “That would put us in the 2022 timeframe,” McGough said.