Japan plans controlled meltdown to help learn from Fukushima disaster

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Japans controlled meltdown
Image courtesy of the Yomiuri Shimbun

In 2014, for the first time, Japan will carry out an experiment which will involve allowing a fuel rod to undergo a rapid fission process and meltdown, in order to improve their abilities to deal with problems stemming from the Fukushima Daiichi disaster and other potential severe accidents in the future.

The project will be conducted north of Tokyo by the Japan Atomic Energy Agency, a government-funded organization, at the Nuclear Safety Research Reactor in Tokai, Ibaraki Prefecture.

A spokesman for the agency said that the planned experiment will not be specifically designed to analyze the progression of the three reactor meltdowns at the Fukushima Daiichi complex, rather will allow officials to study how and when meltdowns happen.  The data however will be used to enhance computer calculations of the meltdowns at Fukushima Daiichi.

Workers will place a fuel rod about a foot long inside of a stainless steel enclosure, which will prevent cooling water from coming in contact with the rod.    Additional fuel rods will then surround the capsule, releasing neutrons which will cause the test rod to melt once temperatures rise high enough.

Workers will record temperature, pressure, and water level information from the test.  They will also place a camera in the capsule to record the melting process.

Once the fuel rod melts down the operators will allow the fission process to cease, and allow the molten materials to return to a solid state.  Once solidified the fuel can be analyzed.

After the experiment the solidified fuel will be stored in a spent fuel pool.

When analyzing the Fukushima Daiichi reactor meltdowns, Japanese calculations assumed that the whole fuel rod would melt after temperatures reach 2,000 C.  An assumption that admittedly is not precise.  TEPCO was not able to confirm the temperatures and water levels in each reactor when the meltdowns occurred at Fukushima Daiichi reactors 1, 2, and 3.

The research will help experts understand how different materials which make up the fuel rod start melting, as each material used has a different melting point.

Similar experiments have been carried out by other nuclear nations, like the United States and France.

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1 Comment

  1. Note that neither the TMI nor the Fukushima meltdowns involved criticality. In both cases the heating causing melting was due to the radioactive decay of fission products from reactor operation while the reactor cores were sub-critical. The experiment can give useful data, but we should not jump to the conclusion that meltdowns were caused by nuclear chain reactions.

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