CORROSION OF ZR-2.5 WT-PERCENT 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-mu-m - 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(He-3,p)He-4 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.