Hydrogen uptake and corrosion behavior of Zr–2.5Nb pressure tubes in Wolsong Unit 1

The hydrogen uptake behavior of Zr–2.5Nb pressure tubes in Wolsong Unit 1 was analyzed in terms of reactor operating factors including the longitudinal location, coolant temperature and time, and compared with those obtained from other CANDU reactors. The amount of deuterium uptake was higher at the outlet of the pressure tubes which were subjected to a higher coolant temperature and became enhanced with increasing reactor operation time. The Zr–2.5Nb pressure tubes in Wolsong Unit 1 showed stable hydrogen uptake behavior up to 13 effective full power years (EFPY). However, scattering of the deuterium uptake tends to increase with increasing operation time. Furthermore, the hydrogen charged Zr–2.5Nb specimens were subjected to corrosion at 400°C under 10 MPa H2O with an aim of evaluating the effect of absorbed hydrogen on the corrosion of pressure tubes in the later stage of life. The absorbed hydrogen seems to have a negligible effect on the corrosion behavior of Zr–2.5Nb pressure tubes.