Abstract: The fuel assembly includes an arrangement for quickly fixing the guide thimble into an opening passing through the adaptor plate of a dismountable nozzle of the assembly. This arrangement includes at least two bearing stops inside the opening of the nozzle, a bearing sleeve integral with the end of the guide thimble and a locking ring which includes stops for bearing on bearing surfaces of the stops inside the opening of the nozzle and deformable elastic parts capable of being accommodated in cavities of the opening of the adaptor plate or of the bearing sleeve, in order to place the ring in a position in which the guide thimble is locked or unlocked. The sleeve includes a rim for bearing on a bearing surface of the adaptor plate at the periphery of the opening.

Abstract: Improved efficiency process for preparing or breeding tritium gas from dense molten lithium alloy by bombardment of the alloy as a target material using a linear accelerator emitting a high energy proton beam to generate a neutron flux. The invention involves using a dense eutectic molten lead lithium alloy as the target material, directing the impact area within the body of molten target material, such as to a depth of about 2 meters of the target material, and continuously circulating the molten alloy past the impact area to dissipate the heat of reaction to provide a substantial lead source for maximum neutron production and to provide an effective lithium source to absorb the neutrons, to produce the highest possible amount of tritium per proton applied by the high energy proton beam. The formed tritium gas is insoluble in and separates from the molten alloy.

Abstract: The lower end of each of a plurality of fuel rods is supported by a fuel supporting portion of a lower tie plate. The fuel supporting portion includes a plurality of second coolant paths for supplying a coolant from below the fuel supporting portion to a first coolant path defined above the fuel supporting portion and between the fuel rods. The total cross-sectional area of all the second coolant paths is smaller than the cross-sectional area of the first coolant path.