Effect of the hydrogen contents on the circumferential mechanical properties of zirconium alloy claddings

The circumferential mechanical properties of zirconium alloy cladding were investigated with a variation of the hydrogen content. Hydrogen was charged onto zirconium alloy cladding such as HANA-4 (Zr-1.5Nb-0.4Sn-0.2Fe-0.1Cr), HANA-6 (Zr-1.1Nb-0.05Cu), and Zircaloy-4 (Zr-1.3Sn-0.21Fe-0.1Cr). Then the ring tension test and the burst test were carried out for the hydrogen charged specimens. The results showed that the maximum stress for the ring tension test increased with the hydrogen content, which is assumed to be the effect of a solute strengthening caused by the hydrogen. As the tin content increases, the fraction of the alpha phase increased so that the effect of a solute strengthening increased. At a high temperature such as 350 °C, dissolved hydrogen inside the zirconium matrix increased the magnitude of a dynamic strain aging of the zirconium cladding. While tin offered a vacancy site to accommodate a migration of solute atoms, hydrogen itself acted as another medium besides oxygen to lock the moving dislocation.