The effects of a number of variables on the stress corrosion cracking behavior of two different heats of Type 347 stainless steel were examined in simulated aqueous homogeneous reactor fuel solution containing low concentrations of chloride ions. The fuel solution consisted of uranyl sulfate, sulfuric acid and copper sulfate. Tests were conducted in the temperature range of 50 C to 101 C. Although the two heats of stainless steel were nearly identical in composition, specimens from one heat were consistently more susceptible to cracking than specimens from the second heat.
Chloride concentrations of 25 to 500 ppm were equally effective in producing cracks. The higher the dissolved oxygen content in solution, the more numerous and intensive were the cracks. Cracking was still observed, however, in the absence of oxygen. Uranyl sulfate concentration was an important variable; at concentrations of 0.40M and greater, no cracking took place with chloride present. Sodium dichromate was found to be an effective cracking inhibitor. Pretreatment of specimens in chloride-free fuel solution either before or after stressing greatly reduced cracking susceptibility during subsequent exposure in the fuel solution containing added chloride.
