Corrosion and mass transfer of steels for FBR in sodium loop for 10,000 hours

In order to clarify quantitatively the corrosion and mass transfer of steels for FBR in sodium loop and obtain useful data for establishing their allowable stress values and corrosion rates, a special sodium loop for material testing was designed and fabricated by MHI and 304, 321 H stainless steels and 2 1/4 Cr-1 Mo steel were given 10,010 hours exposing test in the sodium loop. The results of the test are as follows: (1) The maximum corrosion rate of 304, 321 H stainless steel and 2 1/4 Cr-1 Mo steel in sodium was less than 1.4 μm/year. Local corrosion such as grain boundary corrosion was not detected in these steels up to 10,010 hours exposure at 5700C. From these results, it is considered that it is not necessary to specifically provide corrosion allowances of steels used for secondary coolant system of FBR. (2) The decarburization rate constant of 2 1/4 Cr-1 Mo steel in sodium satisfied the design curve recommended by J.L. Krankota, et al. and the effect of decarburization on the tensile properties of 2 1/4 Cr-1 Mo steel was very small. (author)