Formation of zirconium hydrides is an important factor in the operation of several types of nuclear reactors , such as boiling water reactors Fukushima I and II , which suffered from a series of explosions caused by the 2011 Tōhoku earthquake and tsunami . Their uranium fuel pellets are enclosed in metal rods made from Zircaloy – an alloy of typically about 98.25 % zirconium with 1.5 % tin and minor amounts of other metals . Zircaloy is used because of its small absorption cross-section for thermal neutrons and superior mechanical and corrosion properties to those of most metals , including zirconium . The rods are cooled by streaming water which gradually oxidizes zirconium , liberating hydrogen . In Fukushima reactors , the reactor cooling system failed because of the tsunami . The resulting temperature increase accelerated chemical reactions and caused accumulation of significant amounts of hydrogen , which exploded upon reaction with oxygen when the gas was released to the atmosphere
2011 Tōhoku earthquake and tsunami
2011 Tōhoku earthquake and tsunami
Zirconium hydride