Chemical interaction between granular B₄C and 304L-type stainless steel materials used in BWRs in Japan

Chemical reactions between stainless steel and boron carbide were investigated using the materials applied for control rods in BWRs in Japan, specifically 304L-type stainless steel and granular boron carbide. The reaction region consisted of 2–4 layers, in which the significant composition variation of each element was detected, especially for B and C. Assuming that the reaction layer growth obeys the parabolic law, the effective rate constant between 304L-type stainless steel and granular boron carbide was evaluated to be approximately one order of magnitude smaller than the previously reported values for boron carbide pellets or powers. This difference might originate from the loose contact between the stainless steel and the granular boron carbide in the present study. Regarding liquefaction progress, the stainless steel components were selectively dissolved in the melt; consequently, the unreacted boron carbide tended to remain. (author)