
In March 2011 at Fukushima, the fuel’s cladding, a zirconium alloy used to contain the fuel and radioactive fission products, reacted with boiling coolant water to form hydrogen gas, which then exploded, resulting in the biggest nuclear power-related disaster since Chernobyl. Challenged by this event, two research teams have made progress in developing fuel claddings that are capable of withstanding the high temperatures resulting from a Loss of Coolant Accident (LOCA), like that at Fukushima.
http://www.sciencedaily.com/releases/2015/10/151019104151.htm