Friday, February 12, 2016

China Could Have a Meltdown-Proof Nuclear Reactor Next Year

Two high-temperature, gas-cooled reactors under construction in Shandong will make up the first commercial-scale plant of its type in the world.

Schematic representation of the spherical fuel element of a pebble bed reactor (Credit: Click to Enlarge.
In what would be a milestone for advanced nuclear power, China’s Nuclear Engineering Construction Corporation plans to start up a high-temperature, gas-cooled pebble-bed nuclear plant next year in Shandong province, south of Beijing.  The twin 105-megawatt reactors—so-called Generation IV reactors that would be immune to meltdown—would be the first of their type built at commercial scale in the world.

Construction of the plant is nearly complete, and the next 18 months will be spent installing the reactor components, running tests, and loading the fuel before the reactors go critical in November 2017, said Zhang Zuoyi, director of the Institute of Nuclear and New Energy Technology, a division of Tsinghua University that has developed the technology over the last decade and a half, in an interview at the institute’s campus 30 miles south of Beijing.  If it’s successful, Shandong plant would generate a total of 210 megawatts and will be followed by a 600-megawatt facility in Jiangxi province.  Beyond that, China plans to sell these reactors internationally; in January, Chinese president Xi Jinping signed an agreement with King Salman bin Abdulaziz to construct a high-temperature gas-cooled reactor in Saudi Arabia.

“This technology is going to be on the world market within the next five years,” Zhang predicts.  “We are developing these reactors to belong to the world.”

Pebble-bed reactors that use helium gas as the heat transfer medium and run at very high temperatures—up to 950 °C—have been in development for decades.  The Chinese reactor is based on a design originally developed in Germany, and the German company SGL Group is supplying the billiard-ball-size graphite spheres that encase thousands of tiny “pebbles” of uranium fuel.  Seven high-temperature gas-cooled reactors have been built, but only two units remain in operation, both relatively small:  an experimental 10-megawatt pebble-bed reactor at the Tsinghua Institute campus, which reached full power in 2003, and a similar reactor in Japan.

During a recent visit to the Tsinghua facility, technologists were testing the huge helium blower that will circulate the gas coolant at the Shandong site once it starts up.  Such high-temperature reactors are immune to meltdown because they don’t require elaborate external cooling systems of the sort that failed at Fukushima, Japan, in 2011.  The graphite coating protects the fuel from breaking down, even at temperatures well beyond those found in the reactor core during operation, and once the interior temperature passes a certain threshold, the nuclear reactions slow, cooling the reactor and making it essentially self-regulating.  And while pebble-bed reactors do not totally solve the problem of nuclear waste, the fuel’s form also gives rise to multiple options for waste disposal.  China’s eventual goal is to eliminate or greatly reduce waste by recycling the spent fuel.

One of the main hurdles to building these reactors is the cost of the fuel and of the reactor components.  But China’s sheer size could help overcome that barrier.  “There have been studies that indicate that if reactors are mass-produced, they can drive down costs,” says Charles Forsberg, executive director of the MIT Nuclear Fuel Cycle Project.  “The Chinese market is large enough to make that potentially possible.”

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