Explanation

Encapsulates and seals the outer shell of nuclear fuel. It is used to protect nuclear fuel (core or pellet) from the impact of environment with active chemical properties, contain nuclear fuel and radioactive products generated by fission, and provide structural support. fuel cladding is one of the main components of fuel element. The fuel cladding materials shall have the following properties: ① Small thermal neutron absorption cross section (limited to thermal reactor). Low induced radioactivity: ② Good corrosion resistance in the coolant; ③ Good compatibility with nuclear fuel; ④ High thermal conductivity; ⑤ Having sufficient strength and plasticity; ⑥ Irmdiatiem damage is small; ⑦ Easy to process; ⑧ Easy for post-processing; ⑨ Cheap prices, etc. The fuel element usually uses aluminum and aluminum alloy, magnesium and magnesium alloy, zirconium and zirconium alloy, stainless steel, etc. as the materials of fuel cladding, and the research and test reactor with fuel cladding surface working temperature lower than 200 ° C generally uses aluminum and aluminum alloy as the cladding, and the cladding and nuclear fuel use an intermediate layer (such as nickel layer) to achieve metallurgical bonding; Magnox type reactor uses magnesium alloy as fuel cladding, and the surface working temperature is 450-500 ° C. The cladding and nuclear fuel are generally mechanically combined. To enhance heat release. Ribbed fuel cladding surface; Water cooled power reactors generally use Zirconium-2 or zircaloy-4 as fuel cladding. Fill helium with certain pressure between cladding and nuclear fuel; The fast breeder reactor uses stainless steel as the cladding; High temperature gas cooled reactor (HTGR) uses pyrolytic carbon and pyrolytic silicon carbide composition cladding layer.

Classification