Fast reactors, whose high-speed neutrons
can break down nuclear waste, are on the road to commercialization. That
message has been advanced forcefully by Russia, China, and India.
At a global conference sponsored by the
International Atomic Energy Agency last week in Paris, Russia and India
described large demonstration plants that will start operating next year and
further deployments that are still in the design phase. China, meanwhile,
described a broad R&D effort to make fast reactors comprise at least
one-fifth of its nuclear capacity by 2030.
By breaking down the longest-lasting and
hottest components of spent fuel from light-water reactors, fast reactors would
need only 2 percent of the space required by a conventional reactor to store
spent fuel. Fast reactors would also reduce the time that the waste must remain
in storage from roughly 300,000 years to just 300. “Are they going to eliminate
the need for geological repositories? No. But it will reduce the burden,” says
Thierry Dujardin, acting deputy director general for the Organization for
Economic Cooperation and Development’s Paris-based Nuclear Energy Agency.
Despite that enticing promise, however,
the inherent hazards of today’s state-of-the-art fast reactors also loomed
large at the Paris confab, which concluded a few days before Monday’s two-year
anniversary of the Fukushima accident in Japan. At the conference, Dujardin
said that fuel safety and prevention of severe accidents need to be “high
priorities” for fast reactor research.
The problem with most fast reactors in
construction or development is the molten sodium that cools their cores. Molten
sodium is highly corrosive and explodes on contact with water and oxygen. Most
dangerous, however, is that the sodium-cooled fast reactor, or SFR, exhibits
what physicists call positive reactivity. Unlike conventional reactors, which
experience their fastest possible chain reaction when operating at full power,
the SFR’s chain reaction is capable of further acceleration than its equipment
is designed to handle. This puts such reactors at greater risk of a runaway
reaction that could cause a core meltdown or breach its steel containment
vessel.
Many technical presentations at last
week’s meeting focused on improved materials and designs intended to protect
SFRs from the most extreme accidents imaginable. But alternative core designs
were also well represented, and some countries are hedging their bets by
testing the alternatives. A U.S. company, Transatomic Power, recently revealed designs for a new kind of molten salt reactor, which
has different safety characteristics than a reactor cooled by molten sodium
metal and should be compact and cheap to manufacture (see “Safer Nuclear Power at Half the
Price”).
This dual approach is visible within the
fast reactor program of Rosatom, Russia’s state nuclear corporation. Valery
Rachkov, scientific director of the Leipunski Institute of Physics and Power
Engineering within Rosatom, says Russia needs fast reactors to sustain its
nuclear power program. Light-water reactors under construction in Russia will
give the country an additional 10 gigawatts of nuclear power capacity by 2020—a
42 percent jump—but further growth will become difficult unless Russia can
manage its spent fuel, Rachkov says.
Hence Rosatom’s 2.5-billion-euro
($3.25-billion) investment directed not only at fast reactor technology but
also facilities to recycle spent fuel into fuel for fast reactors. Rosatom has
operated its BN-600, a 600-megawatt fast reactor, since 1980 at the Beloyarsk
nuclear power plant. Rosatom expects to start operating an upgraded
880-megawatt version at Beloyarsk next year. That would be close to the
1,000-megawatt size of some commercial nuclear reactors.
Ivanovitch Zagorulko, a fast reactor
specialist at Rosatom’s Leipunski Institute, says the BN-600 experienced
serious sodium leaks only during its first four years of operation. And he says
a 1987 incident—in which particle contaminants building up in the sodium
coolant caused an acceleration of its chain reaction—was solved with an
improved purification system and tighter airflow control during maintenance to
keep contaminants out. He adds that the BN-800 provides further safety
enhancements.
But Zagorulko says there is still a “big
gap” between the BN-800’s design and the international safety criteria that
Rosatom intends to meet with a 1,200-megawatt commercial-scale fast reactor,
the BN-1200, now in the design phase. Sergey Shepelev, a representative of Afrikantov
OKBM, a subsidiary of Rosatom, refused to discuss the BN-600’s 1987
incident during an open-panel session. When questioned after the session,
Shepelev said there were “many versions” of the incident and that it was not
known “which is right,” but that he was certain the BN-1200 was “absolutely a
safe” design.
Rosatom is also developing another fast reactor
cooled with molten lead. Lead coolant is less corrosive than sodium and
chemically inert to water and air. It has never been used in a power plant, but
the reactors in Russia’s nuclear submarines have long been cooled with a lead
alloy. Rosatom’s plan calls for a 300-megawatt lead-cooled demonstration plant
to be operating at Beloyarsk by 2020.
Some countries are more devoted to
existing fast reactor technology. Indian researchers argued vehemently for the
safety of sodium-cooled reactors at the Paris meeting. India’s 500-megawatt SFR
demonstration plant is nearing completion at Kalpakkam, and the state-owned
Indian Nuclear Power Corporation has a green light to build two more
500-megawatt SFRs at the site.
Redundant passive safety systems are one
answer, according to Narayanasamy Mahendran, an engineer with Indian Nuclear
Power. Backup cooling loops, for example, use convection alone to draw heat
from the reactor and dump it into the air above the reactor building. Their
plant has four such loops of two distinct designs. Any two should be capable of
keeping a reactor cool in the event of a station blackout like the one that
upended Fukushima. Similarly, he says, the core control rods are suspended by
electromagnets and can thus passively drop by gravity to instantaneously scram
the reactor during a station blackout.
European, Japanese, and U.S. researchers
at Paris had research advances to note but no funding to support large
demonstration projects. For the U.S., the focus is on finding repositories for
interim and long-term waste storage. “The U.S. will be focused on geologic
disposal for at least a few decades,” says Peter Lyons, the U.S. assistant
secretary of energy for nuclear energy.
Absent funding in Japan and Europe is
largely due to the corrosive impact of Fukushima. France is going it alone on
Europe’s only well-funded fast-reactor program: a 650-million-euro design
called Astrid that incorporates some bold next-generation components. For
example, solid-state electromagnetic pumps move sodium coolant. They are
expected to be more efficient and reliable than pumps with moving parts.
However, Astrid’s future hangs on a French
energy policy review that got underway last month that could yet see the
country turn away from nuclear power (see “Will France Give Up Its Role as a
Nuclear Powerhouse?”). Pierre Le Coz, the project’s manager at France’s Atomic Energy
Commission, says that if France has begun pulling away from nuclear energy in
five years, when Astrid’s design is mature, they probably won’t get the green
light to build.
Japan’s fast reactor program once led the
world, but it’s now frozen—along with all but two of Japan’s nuclear reactors.
Successive Japanese prime ministers seek to redefine Japan’s energy policy in
the wake of the Fukushima accident. Each of the Japanese speakers last week
began their talks with a reminder of the over 100,000 people who are still
displaced from their homes—some of whom will never return—and of the fisheries
and large forests that are still contaminated.
They were just as mindful of the
accident’s impact on their colleagues’ efforts to advance nuclear energy. As
Shunsuke Kondo, chairman of the Japanese Atomic Energy Commission, put it in
his address: “The fact that this accident has raised concerns around the world
about the safety of nuclear power generation is something Japan takes with
great seriousness.”
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