Abstract: A liquid metal cooled nuclear reactor of the kind wherein a fuel assembly is supported on a diagrid and submerged in a pool of coolant. The diagrid comprises a plenum supported on a load bearing undershell and has an array of resilient spikes upstanding from the upper face of the plenum each for locating a fuel sub-assembly. The load of the fuel assembly is distributed over the upper face plate of the plenum and transmitted to the undershell by an array of strut members.

Abstract: A reusable system for removably attaching the lower end 21 of a nuclear reactor fuel assembly duct tube to an upper end 11 of a nuclear reactor fuel assembly inlet nozzle. The duct tube's lower end 21 has sides terminating in locking tabs 22 which end in inwardly-extending flanges 23. The flanges 23 engage recesses 13 in the top section 12 of the inlet nozzle's upper end 11. A retaining collar 30 slides over the inlet nozzle's upper end 11 to restrain the flanges 23 in the recesses 13. A locking nut 40 has an inside threaded portion 41 which engages an outside threaded portion 15 of the inlet nozzle's upper end 11 to secure the retaining collar 30 against protrusions 24 on the duct tube's sides.

Abstract: A nuclear reactor of the type including a reactor vessel and a core assembly to be maintained in a fixed position within the vessel is disclosed herein along with a structural arrangement also located in the vessel, for supporting the core assembly in its fixed position. The structural arrangement disclosed utilizes a plurality of components including a grillage of I-beams interconnected to one another by welded joints so as to define a unitary structure capable of supporting the core assembly within the vessel. These components including the I-beams are also mechanically interlocked such that a total failure of the welded joints will result in a limited but readily detectable downward deflection of the unitary structure, thereby indicating such a failure while, at the same time, retaining sufficient structural integrity to maintain the core assembly in a supported position.