CORROSIONOne of the major concerns

CORROSIONOne of the major concerns for wet pool spent fuel storage and cask designs is the resistance of the materials to corrosion and intergranular stress corrosion cracking.Intergranular corrosion resistance testing was accomplished for 1.12 and 1.75% Grade A borated stainless steels utilizing ASTM A262, Practice C and Practice E. The results presented in Tables3-15 and 3-16 indicate that intergranular corrosion resistance under acidic conditions decreases with increased boron content. While the material is generally susceptible to light attack under acid conditions at the boron contents of interest, it should not present a problem for its intended applications in that exposure to acid conditions are not considered a design application condition.To further evaluate borated steels in environments of concern testing was done for 1.0 and 1.75% borated steel in aqueous solution of H3B03. The results of this test indicate that there is no difference in corrosion resistance for 1.0g boron to that of 1.75% boron for H3BO3 concentrations typical of PWR spent fuel pools of 2000ppm when tested for six months at 154 degrees F. The results of this testing are presented in Table 3-17.Testing also has indicated that borated stainless steel is more susceptible to salt spray corrosion and pitting than conventional Type 304 stainless steel. While salt spray may only apply to transport cask applications, the introduction of chlorides is of potential concern. The results of the spray testing are as indicated in Table 3-18. In addition this product may experience higher corrosion rates in a design which is susceptible to galvanic or crevice conditions.Corrosion resistance to acids is not of concern for the application of borated stainless steel for spent fuel storage. The corrosion resistance to ferric sulfate and sulfuric acid are shown in Table 3-19. While the material does show significant corrosion suseptability to these solutions, corrosion resistance is not a factor for borated stainless steel use in spent fuel racks.