The effect of dissolved hydrogen on the high pressure steam oxidation of Zircaloy-4

Zr-alloys have been used as a cladding material for the nuclear fuel for several decades. The cladding is the first barrier against the release of radioactive fission products to the outside. The behaviors of the cladding under the accidental conditions have to be well analyzed, since the safety of nuclear power plants becomes one of main issues after Fukushima accident. Hydrogen is generated from the oxidation of the cladding by water and dissolves into the cladding during operation. The dissolved hydrogen becomes hydrides when the concentration of hydrogen exceeds the solubility limit at low temperatures. Due to the quite different mechanical properties of the hydride, the effect of hydrides on the maintenance of the fuel during operation and storage has been main concerns. However, the dissolved hydrogen also affects high temperature oxidation, even though the hydrogen is fully dissolved into the matrix at high temperatures (above 700C). In this study, we observed the effect of dissolved hydrogen on the high pressures steam oxidation of Zry-4 claddings