On the effects of heat treatment and surface orientation on corrosion and hydrogen ingress of Zr-2.5Nb pressure tube material

The influences of surface orientation and heat treatment on the corrosion and hydrogen pickup of Zr-2.5Nb pressure tube material have been investigated. Following a prefilm treatment in 673 K steam and exposure to lithiated water (pH 10.5) at 583 K, the increase in oxide thickness and the pickup of hydrogen during a 120-day exposure at 583 K were monitored. In addition to being sensitive to the heat treatment given, the corrosion and hydrogen pickup were affected by the alignment of β-Zr with respect to the oxide surface. An enhanced oxide growth is associated with the initially undecomposed β-Zr aligned primarily perpendicular to the oxide surface. A minor effect on oxide growth is attributed to changes in the dislocation substructure due to heat treatment. A reduced hydrogen pickup is associated with β-Zr initially in the partially or fully decomposed states and aligned primarily perpendicular to the oxide surface. (orig.)