Study on eutectic melting behavior of control rod materials in severe accidents of sodium-cooled fast reactors, 3; Material analysis of boron carbide immersed in molten stainless steel

Takai, Toshihide  ; Emura, Yuki; Yamano, Hidemasa   

Interest in eutectic reaction between boron carbide, which used as control rod material and stainless steel, which used as cladding tubes, etc. is growing from a perspective to improve analysis accuracy of severe accidents analysis codes. Immersion experiment of boron carbide pellet into molten stainless steel were carried out in the temperature range between 1773 and 1973 K. The eutectic melting behavior of the pellet were investigated by observing the cross section of the pellet using an optical microscope, a scanning type electron microscope. And elemental distribution in there and crystal structure were analyzed to clarify the eutectic reaction behavior. Based on the thickness reduction of the pellet cross section, the reaction rate constants between boron carbide and stainless steel were evaluated under various conditions of contact temperature and contact time.