Control rod for nuclear reactor

Hafnium rods made of a long-life absorber are filled in containing holes at an upper portion of a blade, while boron carbide powder is filled in containing holes at other portion of the blade. A partition wall is disposed between the upper portion and the other portions of the blade, and both wing ends of the blade are welded to seal each of the absorbers. In addition, each of the upper portion and the other portions of the blade is formed as a unit, in which each of the absorbers is sealed. Since the absorbers of hafnium and boron carbide powder are sealed separately, 3T formed by reaction of 10B with neutrons moves freely in the B4C powder region, but does not intrude into the Hf region. Therefore, possibility of hydrogenation of Hf by 3T is decreased, to reduce occurrence of stress-induced cracks due to stresses generated by swelling. The control rods are not dominated by mechanical lifetime, but it is only necessary to consider the neutron life time. (N.H.)