Over the past two years, the Department of Energy has pledged nearly half a billion dollars in financing to the development of small modular nuclear reactors, technology that supporters say could usher in a new era of flexible, cost-effective nuclear power.
The department's selection of companies to receive the funds -- veteran manufacturer Babcock & Wilcox in 2012 and Oregon-based NuScale Power last month -- also reaffirms the prominent role of the light water reactor (LWR) in the United States. Like the vast majority of functioning U.S. reactors, the designs proposed by both NuScale and B&W would use light water technology (ClimateWire, Dec. 13, 2013).
Many experts believe that other reactor designs, such as the molten salt reactor that competed with the LWR design in the early days of U.S. nuclear power, offer the potential for more efficient, less polluting nuclear power generation. But the focus on LWRs by both industry and government indicates that, in the near term at least, the next generation of nuclear power plants will look a lot like the last one, albeit on a somewhat smaller scale.
This is due, in part, to a constrained climate of investment. Commercialization of next generation nuclear reactors isn't anticipated for a decade or more, and investors are wary of placing long-term bets on untried technology. But a more pressing consideration may well be the regulatory process by which reactors are evaluated and approved -- a process that, in the United States at least, emerged along side the existing reactor fleet.
"If you step back for a moment and ask how to fast-track SMRs into the field, I think the most likely path is a design that goes through the regulatory process smoothly," said Rob Rosner, co-director of the Energy Policy Institute at the University of Chicago. "If that's your criteria, the most plausible reactor types are the ones that, from a technology level, are already-approved designs."
Peering into the future
The federal agency responsible for design certification, the Nuclear Regulatory Commission, "has a great deal of faith, based on its own experience and lots of years of data, that the design codes it's created for LWRs can accurately predict performance," he added. "The NRC may not be in a position anymore to build design tools for new kinds of reactors."
NRC works with DOE to plan and administer nuclear power in the United States, with DOE playing the role of developer and promoter and NRC ensuring standards and safety. But years of constrained budget may have reduced NRC's ability to be a coequal partner in the relationship, Rosner said.
The agencies were not immediately available for comment, but documents published by DOE indicate that the department has considered the need for new standards and design codes for some time. In a report for the House Energy and Water Development and Related Agencies Appropriations Subcommittee, NRC lays out the need for expanded research into next generation nuclear design, as well as funding for the same.
"The evolution of advanced reactor technologies from the status quo to commercialization will require extensive investment in research and, correspondingly, the extensive use of resources -- both personnel and facilities," the report notes.
A simpler design
One way to smooth the regulatory process is to simplify the reactor's design, an objective the makers of NuScale's SMR had in mind from the project's earliest days.
"There are a lot of pipes, a lot of pumps that operate in a conventional reactor," said chief commercial officer Mike McGough. Each of those is a potential point of failure, he said, requiring its own contingency plan in order to meet regulatory approval. A simpler design means fewer points of failure and thus an easier approval.
The NuScale reactor eliminates the need for heat pumps and associated equipment by relying on the reactor's natural conduction and convection to dissipate the energy generated by the core. Such a design is only possible in a small reactor, since the unit needs to be factory-assembled and transported to the reactor site in one piece.
Passive safety features, such as reactors that automatically flood or shut down in the event of a station blackout, are key components of most proposed SMR designs.
These characteristics would seem to fall in line with NRC's objectives. The commission's "Policy Statement on the Regulation of Advanced Reactors" notes that "advanced reactors will provide enhanced margins of safety and/or use simplified, inherent, passive or other innovative means to accomplish their safety and security functions."