FATIGUE CHARACTERISTICS OF LASER WELDED ZIRCALOY THIN SHEET

The spacer grid is one of the main structural components in a fuel assembly. It supports fuel rods, guides cooling water and maintains geometry from external impact load and cyclic stress by the vibration of nuclear fuel rod, it is necessary to have sufficient strength against dynamic external load and fatigue strength. In this study, the mechanical properties and fatigue characteristics of laser beam welded zircaloy thin sheet are examined. The fatigue strength under cyclic load was evaluated by staircase method at stress ratio R=0.1. The most appropriate distribution for probabilistic characteristics of fatigue strength at 2×106 cycles was 2-paramer Weibull distribution. Results show that reliability analysis strength was derived from the strength-stress interference model. As a result of the experimental approach, the design guide of fatigue strength for laser welded joint is proposed and the results obtained in this are to be the useful data for spacer gird design.