Abstract: A wall for a fluid container which includes a pair of vertically extending side beams between a pair of horizontally extending upper and lower beams. An arcuate panel is secured in the area defined by the vertically and horizontally extending beams. When the fluid container is filled iwth a fluidic material, fluid pressure applied to the arcuate inner surface deflects the panel downwardly in tension to force the upper beam downwardly to thereby compress the side beams between the upper and lower beams and thereby add significant static structural integrity to the wall.

Abstract: A radioactive fuel cell storage rack is comprised of structural elements including elements which are hollow and cruciform in section. Each leg of the cruciform structural element includes a neutron shield therein. The free end of the legs of the cruciform structural element converge so as to have an included angle of approximately 90.degree.. The rack is comprised of such cruciform elements as well as cooperating elements which are generally T and L shaped in section.

Abstract: A shell and tube type heater exchanger is disclosed for withstanding cyclic changes in temperatures of fluid without suffering failure by removing metal from the outer periphery of a tube sheet. The central portion of the tube sheet is a smooth arching contour mating with portions of the adjoining shell proximate to the tube sheet periphery without abrupt changes of section so that the surfaces blend with one another.