The Compatibility of Tellurium with Austenitic Stainless Steels

Abstract

During the nuclear fission of plutonium fuels a number of volatile elements are produced that may corrode the surrounding cladding material. Of these elements, tellurium has been shown (67, 68) to have a corrosive effect on stainless steels that are potential fuel cladding materials. In the present research the effects of tellurium on a particular alloy, namely an A.I.S.I. 316L austenitic stainless steel were studied at temperature of 650°C and 750°C. Liquid tellurium was found to corrode the steel surface and reaction resulted in the formation of an intermediate phase. The corrosion embrittled the stainless steel with a consequent loss in mechanical properties as found by torsion tests at room and elevated temperature. The loss in mechanical properties increased with increased corrosion. The degree of reaction was determined initially by the amount of tellurium in the compatibility couple. With a small amount of tellurium the reaction saturated and limited the corrosion, while a consistent, high concentration gradient stimulated the reaction which then depended upon tellurium diffusion through the intermediate phase. The extent of the corrosion can be reduced by the preferential formation of a telluride, which will prevent liquid tellurium from wetting the alloy surface.