Effect of the inner liner on the hydrogen distribution of zircaloy-2 nuclear fuel claddings

Abstract

Hydrides precipitation has been induced by slow cooling of hydrogen-charged specimens of three different Zircaloy-2 claddings commonly used in boiling water reactors. The resulting hydrides distribution has been analysed by optical and scanning electron microscopy and neutron radiography. With the latter technique, it is possible to quantify radially the hydrogen concentration with a resolution of ±10 wppm and a spatial resolution of 10 µm. Hydrogenated samples were subjected to a temperature of 400°C and afterwards a cooling rate of 0.3°C/h and 10°C/h showed that practically a complete migration of the hydrogen towards the liner-cladding interface took place, leading to very high local hydrogen concentrations exceeding 2000 wppm.