Intergranular corrosion mechanism of ultra-low carbon type 304 stainless steel in a nuclear reprocessing plant

Ueno, Fumiyoshi  ; Kato, Chiaki   ; Motooka, Takafumi; Ichikawa, Shiro*; Yamamoto, Masahiro 

Authors were aimed for development of life evaluation method of components and clarification of corrosion mechanism of the components in nuclear reprocessing plant. Corrosion behavior of heat exchanger tubes in the reduced pressure evaporator made by ultra-low carbon type 304ULC stainless steel was studied. A simplified mock-up test apparatus was used for corrosion test with long-term test duration. Following results were obtained. The corrosion rates were increased from beginning of the test to more than 25,000 hours and then corrosion rate was reached to constant. From the measurement results of intergranular penetration depths, it was thought that intergranular corrosion was progressed on entire grain boundary around a grain and then the grain dropped out to the solution.