ON THE STRUCTURE OF OXIDE LAYERS OF STAINLESS STEELS FORMED IN SIMULATED LIGHT WATER REACTOR CONDITIONS.

The oxide layers of AISI 304 and 321 formed under conditions typical of boiling water (BWR) dand pressurized water (PWR) reactors have been studied by X-ray photoelectron spectroscopy, Auger electron spectroscopy, scanning electron microscopy, energy and wave length dispersive X-ray microanalysis and X-ray diffraction. The oxide layers had a two-layer structure: the outer layer consisted of large crystals and the inner uniform layer of small crystals. Divalent and traivlent iron, trivalent chromium and divalent and metallic nickel were found in the layers. The oxide layers formed under PWR-conditions consisted of M//3O//4 (M equals Fe, Cr, Ni) spinels and those formed under BWR-conditions, M//3O//4 spinels and hematite ( alpha -Fe//2O//3). Enrichment of nickel and depletion of chromium was found in the oxide layers of AISI 304 under BWR-conditions and enrichment if iron was found in the oxide layers of AISI 304 under PWR-conditions. Sensitization and plastic deformation had no effect on the structure of the layers. Electrolytically polished surfaces exhibited thinner oxide layers than mechanically finished ones.