Abstract: In a nuclear reactor of the pool kind the primary vessel and fuel assembly are carried from the roof of the containment vault by tie straps. The primary vessel incorporates an annular yoke of `K` cross-section the tie straps being attached to the upwardly directed vertical leg and the downwardly directed inclined leg. The upper and lower strakes of the primary vessel are extensions of the remaining legs. Load supporting welds therefore are of intermittent nature thereby limiting the effects of weld crack propagation.

Abstract: The reactor core is carried from the base region of the primary vessel by a strongback. An annular foot is attached to the inside surface of the leak jacket leaving a clearance of 6 mm between the foot and the outer surface of the base region of the primary vessel. In the event of deflection of the primary vessel, downward displacement of the core relative to the control rods is limited thereby avoiding serious reactivity instability.

Abstract: The primary vessel of a pool type fast reactor is open at its upper end and is suspended from the roof of the vault by ties. The vessel is enclosed within a fluid tight leak jacket containing an inert cover gas for the pool of coolant.Because of the unrestrained open end of the vessel severe stress concentrations in the upper strake are avoided. The problem does not occur in the leak jacket because the cover gas, supplemented by thermal insulation cladding and cooling coils, avoids excessive temperature differentials.

Abstract: The fuel assembly in a nuclear reactor construction is supported from the wall of a primary vessel on a strongback and there is secondary support means for the fuel assembly the means comprising a secondary strongback supported from the roof structure of a containment vault by ties. The secondary support means provides a safety device whereby in the event of relaxation of the primary support relative movement between the fuel assembly and control rods is limited. Alternative secondary support means comprise a series of ties supporting the diagrid and a support stool beneath the fuel assembly.