Abstract: The core is constituted by detachable assemblies (21) disposed vertically and maintained in position by a support or bolster (22) receiving the lower part or foot (21a) of the assemblies (21) inside sleeves having a vertical axis (25). Each of the sleeves (25) includes at least one orientation configuration (31) for the assembly (21) and each of the assemblies (21) includes on its foot (21a) at least one orientation configuration (30) adapted to cooperate with the orientation configuration (31) of the sleeve (25). The charging of the first core of the reactor may be carried out in a simple operation without a prior charging of false assemblies in an air atmosphere.

Abstract: A nuclear reactor has a pressure vessel containing a core supported by the bed-plate. The bed-plate is arranged for admitting an upward flow of coolant into the core. The coolant, generally pressurized water, collects in an outlet plenum. The core comprises fuel assemblies each having a lower end piece. The bed-plate defines an inner volume containing coolant at a pressure lower than the coolant pressure under said bed-plate; the lower end piece of each of said fuel assemblies has a lower extension having a cross-sectional area smaller than the cross-sectional area of the fuel assembly above the bed-plate, cooperating with said bed-plate to define a passage for said flow of coolant into said core; and said extension is surrounded by an annular chamber communicating with said volume and defined by a downwardly facing external surface of said lower end piece.

Abstract: The fuel assembly is supported by means of a cylindrical supporting member which is introduced into a shore of the cross-member. The foot of the fuel assembly is introduced into the upper part of the cross-member. Orifices, coinciding with those made with the shore permit the introduction of the liquid metal into the supporting member and from there into the actual assembly. The supporting member is closed at its lower end.Application to the construction of the core of a fast neutron nuclear cooled with liquid sodium.