Deuterium Ingress at the Rolled Joints in CANDU Reactors: Where Does It Come From and How Can It Be Reduced?

Abstract

Simple, small-scale, experiments demonstrate that the initial protium in stainless-steel end fittings contributes to the high deuterium concentrations found in the zirconium pressure tubes at CANDU rolled joints. This protium isotopically exchanges becoming deuterium that is then gettered by the zirconium pressure tube. We propose to reduce the concentration of hydrogen isotopes at the ends of pressure tubes in heavy-water nuclear reactors with yttrium getters placed in the outer regions of the stainless-steel end fittings away from the heat-transport heavy water. Simple, small-scale, experiments demonstrate the operating principle showing that yttrium can getter hydrogen isotopes from the zirconium through the stainless steel.