Improved nuclear fuel-rod cladding might prevent future Fukushimas

Improved nuclear fuel-rod cladding might prevent future Fukushimas
David L. Chandler, MIT News Office

In the aftermath of Japan’s earthquake and tsunami in March 2011, the Fukushima Daiichi nuclear plant was initially driven into shutdown by the magnitude 9.0 quake; its emergency generators then failed because they were inundated by the tsunami. But the greatest damage to the complex, and the greatest release of radiation, may have been caused by explosions of hydrogen gas that built up inside some of the reactors.

That hydrogen buildup was the result of hot steam coming into contact with overheated nuclear fuel rods covered by a cladding of zirconium alloy, or “zircaloy” — the material used as fuel-rod cladding in all water-cooled nuclear reactors, which constitute more than 90 percent of the world’s power reactors. When it gets hot enough, zircaloy reacts with steam to produce hydrogen, a hazard in any loss-of-coolant nuclear accident.

A team of researchers at MIT is developing an alternative that could provide similar protection for nuclear fuel, while reducing the risk of hydrogen production by roughly a thousandfold. Tests of the new cladding material, a ceramic compound called silicon carbide (SiC), are described in a series of papers [1|2] appearing in the journal Nuclear Technology.

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