NuScale Reactor Nears One Milestone, With More to Follow

Artist's concept of a NuScale nuclear power facility
Illustration: NuScale Power

The U.S. Nuclear Regulatory Commission (NRC) is expected to decide by mid-March whether to accept an application with no fewer than 12,000 pages of technical details that support a design for a small modular nuclear reactor design from NuScale Power.

As Winston Churchill might say, the milestone may not mark the beginning of the end but, just maybe, the end of the beginning.

That’s because the NRC’s act of accepting the application does nothing more than trigger a license certification review for the reactor. (The modular reactor might one day generate electric power for small cities, large hospitals, industrial facilities, and even remote water desalination plants.)

As part of its certification review, the NRC will follow a design-specific standard that lays out multiple requirements NuScale's design must meet. Completing that review and certification process could consume anywhere from 30 to 40 months.

It may be no surprise, then, that NuScale is the first small modular reactor (SMR) to have made it this far in the U.S. regulatory process. And it’s had some help.

Development of the reactor concept dates back to 2000, with origins as a project involving Oregon State University (OSU), the Idaho National Engineering and Environmental Laboratory, and Nexant. That concept, designated as the Multi-Application Small Light-Water Reactor, was refined by OSU and became the basis for the current design.

In 2013, NuScale was the sole winner of a Department of Energy funding program aimed at refining SMR technology and advancing the design certification process with the NRC. As part of the award, NuScale took home $226 million in federal funding over a five-year period.

NuScale Power was originally financed by a group of strategic partners and capital venture investors. In October 2011, Fluor Engineering became the majority investor and a partner for engineering, procurement, and construction services. To date, Fluor has invested more than $170 million in NuScale.

Defining SMR

Small modular reactors are defined as nuclear reactors delivering 300 megawatts of electric power equivalent or less. They are designed to include modular technology and use factory fabrication techniques that offer the promises of economies of scale and shorter construction times.

SMR designs include water-cooled reactors, high temperature gas-cooled reactors, as well as liquid metal cooled reactors with fast neutron spectrum. Some SMRs, like NuScale’s advanced light-water reactor, are designed to be deployed as multiple-module power plants.

In paractice, each 50 MW NuScale module is intended to be a self-contained unit that operates independently within a multi-module configuration. Up to 12 of the 50-MW modules can be monitored and operated from a single control room. Each reactor measures 17.1 meters tall and 2.7 meters in diameter, and sits within a containment vessel.

Construction Cost

Tom Mundy, a NuScale executive vice president, says that a facility with 12 reactor modules of 50 MW each would have an estimated net overnight construction cost of around $5,078 per kilowatt equivalent.

“One of our initiatives for this year will be looking for additional ways to drive costs down even further, such that the overnight capital cost on a per-kilowatt basis is even more competitive to gigawatt-size advanced nuclear,” says Mundy. 

The Energy Department’s Energy Information Administration estimates that a 2,200-MW advanced nuclear unit currently has an overnight construction cost of around $5,945/kW.

By comparison, a 700-MW natural gas–fired combined cycle unit has an overnight construction cost of about $978/kW. And a 650-MW ultra-supercritical coal-fired plant equipped with carbon capture and sequestration equipment could cost $5,084, roughly on par with a 600-MW NuScale plant.

Natural Circulation

The NuScale reactor and containment vessel operate inside a water-filled pool that is built below grade. The reactor operates using the principles of natural circulation. The company says that no pumps are needed to circulate water through the reactor. Instead, the system uses a convection process by which water is heated as it passes over the core.

As the water temperature rises, so does the water itself. It rises within the interior of the vessel, and once it reaches the top of the riser, it is drawn toward to the steam generators, where it is cooled. Because the water that has passed through the steam generators is cooler, and therefore more dense, than the heated water, it is pulled by gravity back down to the bottom of the reactor where it is again drawn over the core.

Water in the reactor system is kept separate from the water in the steam generator system to prevent contamination. As the hot water in the reactor system passes over the hundreds of tubes in the steam generator, heat is transferred through the tube walls and the water in the tubes turns to steam. The steam turns turbines which are attached by a single shaft to the electrical generator. After passing through the turbines, the steam loses its energy. It is cooled back into liquid form in the condenser, then pumped by the feed water pump back to the steam generator where it begins the cycle again.

SMR Deployment

The International Atomic Energy Agency expects that new SMR designs will be ready for deployment somewhere between now and the 2025–2030 timeframe. The agency counts more than 45 SMR designs under development. A handful of SMR-category reactors have so far been deployed in China, India, Russia, and Argentina.

In the U.S., Utah Associated Municipal Power Systems’ (UAMPS) Carbon Free Power Project (CFPP) is considering developing a NuScale plant, possibly at the federally operated Idaho National Laboratory in Idaho Falls.

Energy Northwest, owner and operator of the 1,190-MWe Columbia Nuclear Generating Station, has the option to operate the proposed plant. In August 2015, DOE awarded $16.6 million to NuScale to prepare a combined construction and operating license application for the proposed facility.

The company says that its module design is sufficiently complete that a number of detailed studies have been completed for additional applications beyond generating electricity. These include supporting industrial applications, and powering facilities that need a highly reliable electricity supply like healthcare and national security facilities.

Receiving certification from the NRC is essential if a unit is to be built in the U.S. But it also will be useful if the company is to fully realize its plans to market the technology internationally.

“While we see success in the United States as our starting point, we project that about half of our sales will be overseas, to both existing and ‘new to nuclear’ nations,” says Mundy.

Many nations look to the NRC and its licensing process in much the same way that U.S. Federal Aviation Administration approval of aircraft design helps aerospace companies sell internationally.

NuScale also lends its support to efforts through the IAEA and other global organizations to move toward standardization in licensing.

“A certification that might extend beyond U.S. borders would be even more important,” Mundy says. Such certification would boost U.S. trade and help reduce the burden for nations “struggling against energy poverty.”

So yes, Mundy says, “our pending certification by the NRC is very important.” 

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