Highly corrosion-resistant Type 304ULC stainless steel for nuclear fuel reprocessing plants

In view of the widespread application of 304 stainless steel for most facilities and pipework in nuclear fuel reprocessing plants, research into improving its corrosion resistance has been undertaken. The current objective has been to optimize the chemical composition of the steel within the frame of the JIS standard specifications using a system of components involving an increase in the Cr and Ni contents as far as the SUS304L specification at an ultralow C content. The corrosion resistance has also been investigated through variation in the contents of Si, N, P, etc. within the component specification. The resulting optimized steel offers a corrosion resistance 20-30% better than conventional steels. Investigations of the effects of heat treatments show, however, that when the P and C contents are limited to a suitable range and the steel is suitably aged, it has a corrosion resistance equivalent to that of 310 stainless steel. (author)