New fuel rod coating may prevent future nuclear disasters
A new ceramic coating around nuclear fuel rods may prevent the chemical reaction that caused a build-up of hydrogen in the Fukushima nuclear reactor and later led to an explosion and spreading of nuclear material.
In 2011, Japan’s Fukushima nuclear power plant suffered the worst nuclear disaster since Chernobyl. When both an earthquake and tsunami hit the region, the cooling system for the plant was knocked out and as the plant heated, a build up of hydrogen eventually caused an exploded. This explosion is thought by experts to be the main reason cause of radiation spreading after the disaster. The incident has sparked the creativity of MIT researchers, who believe they have a solution that may prevent similar accidents in the future. Their solution is a special coating which can be added to the fuel rods to prevent the hydrogen build-up.
To understand how the coating works, we must first understand where the hydrogen comes from: In a normal nuclear power plant, nuclear fuel rods made of uranium are used to heat water. This water turns to steam and then flows through a turbine which generates electricity. The water is then cooled and returned to the reactor where it can be heated again. When the cooling system for a nuclear plant shuts down however, new water never re-enters the reactor, and without water to draw heat from the fuel rods, they begin to overheat. The hydrogen is formed when the zirconium casing around the fuel rods begins to react with super-heated steam.
Here’s how nuclear fuel looks
The new MIT-developed coating is made from silicone carbide. It would replace the zirconium alloy casing entirely, and according to two recently published papers, we won’t be missing the zirconium any time soon: The silicone carbide coating shows 100 to 1,000 times less corrosion at meltdown temperatures. In addition, during meltdown, there is no loss of strength in the material (unlike with zirconium). Since silicone carbide is also more durable, it would lead to longer service time for for fuel rods, and less nuclear waste. Sounds like a winner to me.
Unfortunately, we still have a ways to go before we see silicone carbide enter service in nuclear plants: while zirconium can be closed off at the ends of the fuel rod through welding, there is as of yet no way to cap the ends of the silicone carbide coating. In addition, the way the material fractures under stress is still being studied.