Sunday, 27 March 2011

Nuclear Reactors in China, a difference & safer too!





A Different Kind of Nuclear Reactor in China
 
Rather than using fuel rods encased in water as in most reactors, engineers in China are building pebble-bed reactors that use billiard ball-size fuel spheres known as pebbles. Amassing these pebbles inside the reactor creates nuclear fission, which heats a gas. The gas in turn heats water into steam, driving a turbine. The reactor core consists of 420,000 of these fuel spheres, and every 15 seconds one is removed and replaced by another one. Experts say these reactors offer a safer nuclear alternative.


China can guarantee nuclear power plants safety: official

(Xinhua)
BEIJING - An official overseeing nuclear safety in China has said that the safety of the country's nuclear power facilities is guaranteed, while reaffirming its goal of developing nuclear power as a clean energy source.

"There is a guarantee for the safety of China's nuclear power facilities and (China) will not abandon (its nuclear power plan) for fear of slight risks," said Tian Shujia in response to reports that China will become more prudent toward developing nuclear power.

Tian, director of two nuclear safety centers under the Ministry of Environmental Protection, made the remarks in an interview with the People's Daily.

He said there are strict laws, regulations, and technical standards which govern site selection, design, construction, testing, operation, and retirement of nuclear power plants in China. He added that these codes are stringently enforced by the Chinese government.

China drew up these codes by taking developed countries' nuclear standards and the safety recommendations of the International Atomic Energy Agency into full account, he said.

China took lessons from previous nuclear power accidents and adopted time-tested technology in designing and building its nuclear power plants, he added.

According to Tian, no notable defects have been found in China's seven operational nuclear power plants, and the safety statistics for most of these plants are higher than the global average.

In addition, China has an emergency-response mechanism in place for its nuclear power plants, he said.

Tian's interview was the latest official remark on nuclear safety in China after a quake-triggered explosion led to radioactive leakage at a Japanese nuclear power plant earlier this month.

One day after the deadly quake jolted Japan, Vice Minister of Environmental Protection Zhang Lijun said that China would not change its plans for developing nuclear power.

Although China suspended its approval process for new nuclear power stations on March 16, officials have not indicated any possible suspension of the national nuclear energy plan set in the country's development plan for the next five years.

Under the 12th Five-Year Plan approved by China's top legislature on March 14, China will launch new nuclear energy projects with a combined generative capacity of 40 million kilowatts.

In the interview, Tian said nuclear energy, as a form of clean energy, is a necessary choice for China if the country will meet its 2020 goal. Currently, non-fossil fuels account for 8 percent of China's total energy consumption.

China plans to have 66 nuclear power plants by 2020 with a total generating capacity of 66 million kilowatts, which will account for 6 percent of China's total power capacity, according to Tian.

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China is building reactors touted as safer




SHIDAO, China • While engineers at Japan's stricken nuclear power plant struggle to keep its uranium fuel rods from melting down, engineers in China are building a radically different type of reactor that some experts say offers a safer nuclear alternative.

The technology will be used in two reactors here on a peninsula jutting into the Yellow Sea, where the Chinese government is expected to let construction proceed even as the world debates the wisdom of nuclear power.

Rather than using conventional fuel rod assemblies of the sort leaking radiation in Japan, each packed with nearly 400 pounds of uranium, the Chinese reactors will use hundreds of thousands of billiard-ball-size fuel elements, each cloaked in a protective graphite layer.

The coating moderates the pace of nuclear reactions and is meant to ensure that if the plant had to be shut down in an emergency, the reaction would slowly stop on its own and not lead to a meltdown.

The reactors will also be cooled by nonexplosive helium gas instead of depending on a steady source of water — a critical problem with the damaged reactors at Japan's Fukushima Daiichi power plant. And unlike those reactors, the Chinese reactors are designed to gradually dissipate heat on their own, even if coolant is lost.

If the new plants here prove workable, China plans to build dozens more of them in coming years.
So-called pebble-bed reactor technology is not new. Germany, South Africa and the United States have all experimented with it.

Germany led the initial research into pebble-bed nuclear reactors and built its own research version in the 1960s. That reactor closed after an accident, caused by a jammed fuel pebble that released traces of radiation — coincidentally nine days after the Chernobyl accident in 1986, at a time of greatly increased worry about nuclear safety. Xu said China, learning from the German mishap, had designed its reactors to keep the pebbles from jamming.

South Africa tried hard until last summer to build a pebble-bed reactor but ran into serious cost overruns.
In the United States, the federal government and companies have spent heavily on pebble-bed research. But there has been little appetite for actually building new nuclear reactors.

But as in many other areas of alternative energy, including solar panels and wind turbines, China is now taking the lead in actually building the next-generation nuclear energy technology. The government has paid for all of the research and development costs for the two pebble-bed reactors being built here, and will cover 30 percent of the construction costs.

"China epitomizes the stark choices that we face globally in moving away from current forms of coal-based electricity," said Jonathan Sinton, the top China specialist at the International Energy Agency in Paris. 

"Nuclear is an essential alternative" to coal, he said. "It's the only one that can provide the same quality of electricity at a similar scale in the medium and long term."

Despite Japan's crisis, China still plans to build as many as 50 nuclear reactors over the next five years — more than the rest of the world combined. Most of this next wave will be of more conventional designs.

But if the pebble-bed approach works as advertised, and proves cost effective, China hopes it can eventually adopt the technology on a broad scale to make nuclear power safer and more feasible as it deals with the world's fastest-growing economy and the material expectations of its 1.3 billion people.

Western environmentalists are divided on the safety of pebble-bed nuclear technology.

Thomas Cochran, the senior scientist on nuclear power for the Natural Resources Defense Council, an American group, said such reactors would probably be less dangerous than current nuclear plants, and might be better for the environment than coal-fired plants.

"Overall, in terms of design," he said, "it would appear to be safer, with the following caveat: The safety of any nuclear plant is not just a function of the design but also of the safety culture of the plant."

The executives overseeing construction of the new Chinese reactors say that engineers are already being trained to oversee the extensively computerized controls for the plant, using a simulator at a test reactor that has been operating for a decade near Beijing, apparently without mishap.

But Greenpeace, the international environmentalist group, opposes pebble-bed nuclear reactors, questioning whether any nuclear technology can be truly safe. Wrapping the uranium fuel in graphite greatly increases the volume of radioactive waste eventually requiring disposal, said Heinz Smital, a Greenpeace nuclear  technology specialist in Germany. But he said the waste was far less radioactive per ton than spent uranium fuel rods — one of the big sources of trouble at the Fukushima Daiichi plant.