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.
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.
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.
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