Zirconium alloys above 620 ° c (depending on the composition) will be transformed into body centered cubic zirconium. After the transformation, the mechanical properties and corrosion resistance of the alloy will be greatly reduced, which will make it impossible to maintain the safe operation of the nuclear reactor. The famous event was the accident at the fukushima nuclear power plant in Japan. Affected by the east Japan earthquake, fukushima nuclear power plant water leakage, the temperature of cladding increased significantly, zirconium alloy cladding quickly softened, and the leakage of air into brittle material, resulting in the leakage of nuclear fuel. A large amount of water contaminated by nuclear pollution enters the sea, causing great damage to the ecology of the world.
As a nuclear reactor cladding material, it is required to have a small thermal neutron capture cross section, which leads to the zirconium alloy can not be highly alloyed, so the zirconium alloy's high-temperature performance is doomed to be difficult to break through. At present, countries attach great importance to this problem, on the one hand, they are trying to make a breakthrough in the high-temperature performance of zirconium alloy, on the other hand, they are seeking alternative products of existing fuel cladding, such as SiC composite materials, molybdenum alloy, cobalt alloy and so on. Molybdenum and cobalt alloys were originally considered structural materials for nuclear fusion reactors, and although they do not have the same low thermal neutron absorption cross section as zirconium alloys, their high-temperature stability is excellent.
