End plug welding of fuel elements for prototype advanced thermal reactor FUGEN

Some experiments were performed to improve the procedure of the end plug welding of plutonium fuel elements for the advanced thermal prototype reactor FUGEN. The optimum welding conditions were sought in these experiments to minimize the thermal deformation and the gap size of non-weld section. The outline of the normal welding procedure and the method of experiments are presented in the first part. The following items were included in the experiments: the effects of pushing force applied to an end plug on the increase of diameter of a cladding tube; the effect of rotating speed and chill position on the deformation of a cladding tube; the relation between the cleaning method and welding defects (the cleaning with acetone, surfactant, and alumina was tested): the effect of heat input conditions on the welding defects (two-step and three-step heat input procedures were tested). The combined effects of these items were also investigated. The results of experiments are presented. (Aoki, K.)