Patent Number: 051805448
Section: claims

1. A control blade for use in nuclear reactors comprising: an upper structure means provided with a handle for handling of the control blade;  a lower structure means provided with a speed limiter;  a central tie rod means for connecting integrally said upper and lower structure means together, having radial projections so as to exhibit a substantially cross-shaped cross section;  a sheath plate means having a substantially U-shaped cross-section and secured to the end of each projection of said central tie rod means;  a hafnium neutron absorber means disposed in each sheath plate means and divided into a plurality of neutron absorber elements along the axis of said central tie rod means, each neutron absorber element being composed of a pair of substantially parallel adjacent neutron absorber plates or sheets spaced from and opposing each other so that a space is defined therebetween and an end tie rod means provided between outer facing end portions of the respective neutron absorber plates so as to close an outer end opening of the space, said end tie rod means being disposed for effectively increasing reactivity, each of said neutron absorber plates being provided with an inner facing end adjacent to said central tie rod, said inner facing ends of each pair of adjacent neutron absorber plates being curved to approach each other and said inner facing ends are spaced from each other so that thermal expansion of the neutron absorber plates is absorbed, the respective adjacent ones of said neutron absorber elements being arranged with gaps therebetween in the axial direction of said central tie rod means so that axial ends of the absorber elements of adjacent neutron absorber plates occupy different horizontal planes; and  supporting spacer means provided inbetween said adjacent opposing neutron absorber plates at a predetermined interval in the axial direction of said central tie rod means so as to define the space as a water gap for guiding flow of a moderator.