Bold Visions for the Future of Nuclear Power

Mar 13, 2017

Pilgrim Nuclear Power Plant is scheduled to close in 2019, and there are many who would like to see it shut down sooner. But that leaves a significant gap in southern New England’s energy supply. And, love it or hate it, nuclear power is a source of electricity with a much smaller carbon footprint than fossil fuels.
The public debate about the role of nuclear power often pits climate change concerns against the safety records of existing power plants. But those facilities are, quite frankly, old - decades old. According to the Energy Information Administration, the average age of a nuclear power plant in the United States is 36 years.
Pilgrim is almost a decade beyond that – what’s known as first generation technology. The few nuclear power plants being built today are third generation designs. And what nuclear engineers are working on now is the fourth generation.  
Up through generation three, the changes are incremental. Jacopo Buongiorno, director of MIT’s Center for Advanced Nuclear Energy Systems, calls them “evolutionary.” But fourth generation technology is different.
“What really changes the design radically in a nuclear reactor is when you change the coolant,” he said.
All the power plants in the U.S. are water-cooled. A different coolant - a gas, like helium or carbon dioxide, a liquid metal, or molten salt – can be far more efficient, allowing the reactor to operate at a higher temperature.
“According to the laws of thermodynamics, higher temperatures mean higher efficiency of converting heat into electricity,” Buongiorno explained.
Buongiorno himself is working on a design that a conventional water-cooled reactor, but is radical, nonetheless. The idea is to put a reactor inside a modified oil rig and float it ten miles offshore, so that no land is within the evacuation zone.
Safety isn’t actually the primary driving factor for Buongiorno. Cost is. He says that an offshore nuclear power plant could be built in a shipyard equipped to service nuclear submarines, then towed offshore, all in less time and for less than the cost of a land-based nuclear plant.
China and Russia both have floating nuclear plants in the works, but none are currently planned in the United States.
What is moving forward is a different idea, from Oregon-based startup Nuscale Power. Their concept is combine small reactors – like eggs in a carton – to create modular power plants that are safer, more efficient, and more cost-effective. A major benefit of the design is that no outside power is needed to cool the reactor.
“We’re using the laws of physics, basically,” said Jose Reyes, co-founder and chief technology officer at NuScale Power. “When you shrink things down, what happens in a cylinder is that the surface area to volume really grows significantly. That means we have a lot of surface area for heat removal with a relatively small amount of thermal input.”
Reyes says the natural movement of water against the inside of the containment vessel is enough to cool the reactor.
Nuscale is building its first plant at Idaho National Lab, and expects to be online in several years.
David Lochbaum, director of the Nuclear Safety Program at the Union of Concerned Scientists, says both ideas have merit. In fact, the floating nuc idea isn’t new. Back in the 1970s, Westinghouse started working on offshore nuclear power plants, but the deals fell through due to lack of demand.
Financial constraints have dogged the nuclear power industry. Existing plants have faced rising costs to maintain and upgrade aging facilities, as the costs of natural gas and renewables, like solar, have fallen.
“We’re seeing more power plants being shut down due to unfavorable economics than we’re seeing being built,” said Lochbaum “And the ones that are being built are way over budget.”
What makes a nuclear power plant so expensive? One reason is as mundane as it is surprising.
“These nuclear power plants need a lot of concrete for shielding and to support a lot of the safety equipment,” said Lochbaum. “Concrete is surprisingly expensive, and it’s a large share of the construction cost for nuclear power plants.”
That’s another attraction of Nuscale’s modular design. Construction costs for a smaller reactor pose less of a barrier, and revenue from the first reactor can be used to help build additional reactors, as demand builds. Smaller reactors can also be ramped up and down more easily to help balance the variable supply of renewable energy.
Still, Lochbaum says he doubts that the nuclear industry will find a way to make the finances work on a scale that could really address climate change.
“Clearly, nuclear does have some environmental benefits – a much smaller carbon footprint,” he said. “But the price of that is too high. Nuclear power is very expensive.”

NuScale Power has designed a small (50 Megawatt) plant that can be scaled up by adding more units.
Credit Courtesy nuscalepower.com