Patent Number: 039473210
Section: claims

1. In combination with a neutronic reactor having a mass of moderator in which is disposed fissionable material enclosed in a biological shield of sufficient radiation absorption characteristics and thickness to protect living organisms outside it by absorbing neutrons, gamma rays and other radiation emanating from the mass, a lateral face on said biological shield having a plurality of apertures to pass only a plurality of control rods, said control rods being of equal length and comprising neutron absorbing material, said mass having passages aligned with said apertures, linear extensions on said control rods at the ends opposite to the ends disposed toward the mass, and driving means associated with said extensions adapted to impart movement to said control rods into and out of said passages in the mass, the improvement comprising a second shield of hydrogenous concrete forming a complete enclosure over said lateral face of the biological shield and having a wall parallel with said lateral face distant therefrom the length of the neutron absorbing portions of the control rods and a small part of their extensions, said parallel wall having apertures aligned with said passages in the mass to permit said extensions to pass between said complete enclosure and said driving means, shield gates comprising movable plugs mounted in front of each of the plurality of apertures in the biological shield and shield gates comprising movable plugs mounted in front of each of the apertures in the second shield, and means for moving said plugs laterally to open and close said apertures. 2. The improved structure of claim 1 wherein the second shield is at least 5 feet thick. 3. The improved structure of claim 1 wherein the passages in the mass are horizontal and the movement imparted to said extensions is horizontal. 4. The improved structure of claim 1 wherein the biological shield gates are enclosed in frames and the means for moving the plugs to open and close the apertures in the biological shield comprises double acting pneumatic pistons fixed to the frames of the gates with piston rods movably fixed to the plugs.