Corrosion of Zr-2.5 wt% Nb pressure tube material in D2O steam: Deuterium depth distributions measured by nuclear reaction analysis

The corrosion of Zr-2.5 wt% Nb pressure tube material in D2O steam at 763 K has been studied by nuclear reaction and backscattering spectrometry. The oxide thicknesses - ranging from 3-7 μm - were determined by backscattering of 2.5 MeV protons. The deuterium depth distributions from the surface to beneath the oxide have been determined using the d(3He, p)4He nuclear reaction. The oxide contains high deuterium concentrations (0.003-0.005 D/Zr). Samples which have been 'pickled' prior to corrosion have slightly thinner oxides, increased deuterium levels in the metal, and the deuterium depth profiles show a micrometer-wide depletion in deuterium, which may reflect an interfacial region with stress and plastic deformation. (orig.)