The little reactors that could
Billed as safe and cheap, NuScale's small reactors aim to revive the ailing nuclear industry and help save a warming planet.
To a world facing the existential threat of
global warming, nuclear power would appear to be a lifeline. Advocates
say nuclear reactors, compact and able to deliver steady, carbon-free
power, are ideal replacements for fossil fuels and a way to slash
greenhouse gas emissions. However, in most of the world, the nuclear
industry is in retreat. The public continues to distrust it, especially
after three reactors melted down in a 2011 accident at the Fukushima
Daiichi Nuclear Power Plant in Japan. Nations also continue to dither
over what to do with radioactive reactor waste. Most important, with new
reactors costing $7 billion or more, the nuclear industry struggles to
compete with cheaper forms of energy, such as natural gas. So even as
global temperatures break one record after another, just one nuclear
reactor has turned on in the United States in the past 20 years.
Globally, nuclear power supplies just 11% of electrical power, down from
a high of 17.6% in 1996.
Jose Reyes, a nuclear engineer
and cofounder of NuScale Power, headquartered in Portland, Oregon, says
he and his colleagues can revive nuclear by thinking small. Reyes and
NuScale's 350 employees have designed a small modular reactor (SMR) that
would take up 1% of the space of a conventional reactor. Whereas a
typical commercial reactor cranks out a gigawatt of power, each NuScale
SMR would generate just 60 megawatts. For about $3 billion, NuScale
would stack up to 12 SMRs side by side, like beer cans in a six-pack, to
form a power plant.
But size alone isn't a panacea. “If I
just scale down a large reactor, I'll lose, no doubt,” says Reyes, 63, a
soft-spoken native of New York City and son of Honduran and Dominican
immigrants. To make their reactors safer, NuScale engineers have
simplified them, eliminating pumps, valves, and other moving parts while
adding safeguards in a design they say would be virtually impervious to
meltdown. To make their reactors cheaper, the engineers plan to
fabricate them whole in a factory instead of assembling them at a
construction site, cutting costs enough to compete with other forms of
energy.
Spun out of nearby Oregon State University (OSU)
here in 2007, NuScale has spent more than $800 million on its
design—$288 million from the Department of Energy (DOE) and the rest
mainly from NuScale's backer, the global engineering and construction
firm Fluor. The design is now working its way through licensing with the
Nuclear Regulatory Commission (NRC), and the company has lined up a
first customer, a utility association that wants to start construction
on a plant in Idaho in 2023.
NuScale is far from alone.
With similar projects rising in China and Russia, the company is riding a
global wave of interest in SMRs. “SMRs as a class have a potential to
change the economics,” says Robert Rosner, a physicist at the University
of Chicago in Illinois who co-wrote a 2011 report on them. In the
United States, NuScale is the only company seeking to license and build
an SMR. Rosner is optimistic about its prospects. “NuScale has really
made the case that they'll be able to pull it off,” Rosner says.
For
now, NuScale's reactors exist mostly as computer models. But in an
industrial area north of town here, the company has built a full-size
mock-up of the upper portion of a reactor. Festooned with pipes, the
8-meter-tall gray cylinder isn't exactly small. It resembles the conning
tower of a submarine, one that has somehow surfaced through the dusty
ground. NuScale built it to see if workers could squeeze inside for
inspections, says Ben Heald, a NuScale reactor designer. “It's a great
marketing tool.”
Not everyone thinks NuScale will make
the transition from mock-up to reality, however. Dozens of advanced
reactor designs have come and gone. And even if NuScale and other
startups succeed, the nuclear industry won't build enough plants quickly
enough to matter in the fight against climate change, says Allison
Macfarlane, a professor of public policy and geologist at George
Washington University in Washington, D.C., who chaired NRC from 2012
through 2014. “Nuclear does not do anything quickly,” she says.
A NUCLEAR REACTOR
is a glorified boiler. Within its core hang ranks of fuel rods, usually
filled with pellets of uranium oxide. The radioactive uranium atoms
spontaneously split, releasing energy and neutrons that go on to split
more uranium atoms in a chain reaction called fission. Heat from the
chain reaction ultimately boils water to drive steam turbines and
generate electricity. Designs vary (see sidebar, p. 809),
but 85% of the world's 452 power reactors circulate water through the
core to cool it and ferry heat to a steam generator that drives a
turbine.
The water plays a second safety role. Power
reactors typically use a fuel with a small amount of the fissile isotope
uranium-235. The dilute fuel sustains a chain reaction only if the
neutrons are slowed to increase the probability that they'll split other
atoms. The cooling water itself serves to slow, or moderate, the
neutrons. If that water is lost in an accident, fission fizzles,
preventing a runaway chain reaction like the one that blew up a
graphite-moderated reactor in 1986 at the Chernobyl Nuclear Power Plant
in Ukraine.
Even after the chain reaction dies, however,
heat from the radioactive decay of nuclei created by fission can melt
the core. That happened at Fukushima when a tsunami swamped the
emergency generators needed to pump water through the plant's reactors.
NuScale's
design would reduce such risks in multiple ways. First, in an accident
the small cores would produce far less decay heat. NuScale engineers
have also cut out the pumps that drive the cooling water through the
core, relying instead on natural convection. That design eliminates
moving parts that could fail and cause an accident in the first place,
says Eric Young, a NuScale engineer. “If it's not there, it can't
break,” he says.
NuScale's new reactor housings offer
further protection. A conventional reactor sits within a reinforced
concrete containment vessel up to 40 meters in diameter. Each
3-meter-wide NuScale reactor nestles into its own 4.6-meter-wide steel
containment vessel, which by virtue of its much smaller diameter can
withstand pressures 15 times greater. The vessels sit submerged in a
vast pool of water: NuScale's ultimate line of defense.
For
example, in an emergency, operators can cool the core by diverting
steam from the turbines to heat exchangers in the pool. During normal
operations, the space between the reactor and the containment vessel is
kept under vacuum, like a thermos, to insulate the core and allow it to
heat up. But if the reactor overheats, relief valves would pop open to
release steam and water into the vacuum space, where they would transfer
heat to the pool. Such passive features ensure that in just about any
conceivable accident, the core would remain intact, Reyes says.
To
prove that the reactor will behave as predicted, NuScale engineers have
constructed a one-third scale model. A 7-metertall tangle of pipes,
valves, and wires lurks in the corner of a lab at OSU's department of
nuclear engineering. The model aims not to run exactly like the real
reactor, Young says, but rather to validate the computer models that NRC
will use to evaluate the design's safety. The model's core heats water
not with nuclear fuel but with 56 electric heaters like those in curling
irons, Young says. “It's like a big percolator,” he says. “We set up a
test and watch coffee being made for 3 days.”
Making a
reactor smaller has a downside, says M. V. Ramana, a physicist at the
University of British Columbia in Vancouver, Canada. A smaller reactor
will extract less energy from every ton of fuel, he argues, driving up
operating costs. “There's a reason reactors became larger,” Ramana says.
“Inherently, NuScale is giving up the advantages of economies of
scale.”
But small size pays off in versatility, Reyes
says. One little reactor might power a plant to desalinate seawater or
supply heat for an industrial process. A customized NuScale plant might
support a developing country's smaller electrical grid. And in the
developed world, where intermittent renewable sources are growing
rapidly, a full 12-pack of reactors could provide steady power to make
up for the fitful output of windmills and solar panels. By varying the
number of reactors producing power, a NuScale plant could “load follow”
and fill in the gaps, Reyes says.
SUCH VISIONS
point to another key aspect of NuScale's plans: Designers want to
dramatically change how nuclear plants are organized and run. Under NRC
regulations, a control room can operate no more than two reactors, in
which case it must have a staff of at least six operators. NuScale wants
permission to run a dozen of their simpler, safer reactors from such a
control room. “People have laughed at me when I said I could run this
plant with six people,” says NuScale senior operations engineer Ross
Snuggerud.
To show that it's possible, NuScale engineers
built a fully operational control room to run a virtual power plant.
The control room, locked away on the second floor of NuScale's building
in an industrial park along the Willamette River, has a wall of jumbo
high-resolution monitors that display the 12 virtual reactors'
performance. On a recent day, Snuggerud manipulates a touch screen to
cook up a mock crisis. Reactivity spikes in one of the 12 virtual
reactors. Graphite control rods, which should drop into the core to
absorb neutrons and stop the reaction, fail to respond.
An
alarm sounds. Lights flash. The core's temperature surges. But the
NuScale reactor handles the crisis with ease. Within minutes,
temperatures fall as the reactor automatically shunts heat into the
pool. So is melting the core impossible? “No responsible engineer would
say ‘never,’” Snuggerud says. “But we've done a lot of things right to
ensure the core's integrity.”
NuScale engineers must convince NRC that a real
plant would run as placidly. Two years ago, the company submitted its
12,000-page application, and the review should conclude by September
2020. The NuScale team has plenty of experience with such reviews. While
Reyes was at OSU, he helped NRC certify two conventional Westinghouse
designs. If approved, NuScale's design would be the first that NRC has
licensed since 2014.
NuScale has responded to more than
1500 formal requests for more information, about a third of the typical
number, says Carrie Fosaaen, a licensing specialist at NuScale. “I think
that speaks volumes about what we put together up front,” she says.
Still, Fosaaen says, “Our design is so different that it's a challenge
even for people who have done a lot of licensing.”
If
interpreted strictly, Fosaaen says, NRC regulations would push NuScale
engineers toward building a miniature version of a conventional
reactor—exactly what they don't want to do. So the task, she says, is to
explain to regulators how the NuScale design is safe without having to
add back layers of complexity.
Some of NuScale's
requests are bold. The company has asked NRC to eliminate a requirement
for backup electrical power because its reactors can shut down without
power. Similarly, NuScale wants to avoid a requirement for an emergency
evacuation zone 32 kilometers wide, arguing its reactors pose no risk of
spreading radiation beyond the plant boundary. Such a rule change would
enable a utility to replace an aging coal plant with a NuScale plant in
a populated area. “That's something that utilities really want,” Reyes
says.
Such requests strike one prominent critic as
hubris. Nuclear safety relies on layers of protection, says Edwin Lyman,
a physicist with the Union of Concerned Scientists in Washington, D.C.,
and NuScale is peeling them away to cut costs. “To say that you know so
well how a new reactor will work that you don't need an emergency
evacuation zone, that's just dangerous and irresponsible,” he says.
However, Jacopo Buongiorno, a nuclear engineer at the Massachusetts
Institute of Technology (MIT) in Cambridge, says NuScale's requests are
reasonable and likely to win approval. “I would disagree that they're
removing safety features,” he says. “Quite the opposite.”
NUSCALE ENGINEERS ARE ITCHING
to build a real plant. The company has a tentative deal with Utah
Associated Municipal Power Systems (UAMPS), a consortium of 46 public
utilities in six western states, to build a 12-pack plant at DOE's Idaho
National Laboratory near Idaho Falls as part of UAMPS's carbon-free
power project. As DOE's lead nuclear energy lab, Idaho National
Laboratory would use one module for research and another to supply the
lab with power. The other 10 modules would feed the grid. UAMPS should
decide this year about the plant, which would be built by 2027.
NuScale
expects other customers to follow. “There are many companies that don't
want to be first but would clearly like to be second in line,” says Tom
Mundy, NuScale's chief commercial officer. According to a 2014 report
by the National Nuclear Laboratory in Sellafield, U.K., by 2035 SMRs
could provide 65 to 85 gigawatts of power globally, a building spree
worth between $320 billion and $510 billion. Engineers in Argentina,
China, Russia, and South Korea have all developed SMR designs. However,
because of the quality of its design, “internationally, NuScale is going
to be a formidable competitor,” Rosner predicts.
To
succeed, NuScale will have to compete with cheap natural gas. The
company aims to produce electricity at a total cost, including
construction and operations, of $65 per megawatt-hour. That's about 20%
higher than the current cost of energy from a gas-powered plant.
However, Rosner says, “The price of gas isn't going to stay low
forever.” Countries also could put a price on carbon emissions, which
would drive up the cost of fossil-fuel power. In fact, a September 2018
report from MIT indicated that a carbon tax could make nuclear
competitive with gas.
Nuclear power could face even
stiffer competition from renewable sources of energy such as wind and
solar power, which are getting cheaper and cheaper, Ramana says. And
given the numbers, Lyman says he expects NuScale will find few
customers—and that's only if DOE subsidizes the deals, as it has for
UAMPS. “I just don't see this tsunami of small reactors around the
world,” he says, “and it's because the economics is so bad.” But like
many experts, Reyes argues that an energy economy based on renewables
will require some form of steady “baseload” power—and nuclear, unlike
gas, can deliver it without carbon emissions.
Although
NuScale is eager to break ground in the United States, an indicator of
its prospects may come from across the Atlantic. To reduce carbon
emissions, the United Kingdom has committed to shuttering its remaining
seven coal-fired power plants by 2025. It could replace them with
gas-fired plants, but NuScale is trying to persuade U.K. government
officials to make a bolder choice and opt for its nuclear plants. “We
are not a concept, we are not a technology that is still on the drawing
board,” Mundy says. “We're real.” A few years should tell whether that's
true.
