Patent GB-785928-A (GB)
Title: Improvements in nuclear reactors including horizontal graphite bars
IPC: G21C5/08
Filed: 1956-06-14
Abstract: 785,928. Nuclear reactors. COMMISSARIAT A L'ENERGIE ATOMIQUE. June 14, 1956 [June 16, 1955], No. 18451/56. Class 39(4). A nuclear reactor which comprises a multiplicity of juxtaposed contiguous parallel rows of horizontal graphite bars, each row consisting of a plurality of bars disposed end to end, the whole of the rows forming a graphite block provided with a multiplicity of horizontal channels parallel to the rows of bars for housing slugs of fissile material, the block being supported by suitable means on the ground and being surrounded by a shielding structure fixed to the ground, is characterized in that resilient means are interposed between the shielding structure and the ends of the rows of bars located near the structure, the resilient means being strong enough to overcome the friction forces between the bars of each row and the rows of bars adjoining the row. Figs. 1 and 2 show sections of a reactor at right angles to each other. The moderator/reflector structure comprises graphite bars 1 arranged in layers, the area within the circle 2, Fig. 1, comprising the moderator and the remainder comprising the reflector. Within the moderator section channels 3 are provided to receive uranium bars, and each such channel is constituted by two longitudinal grooves of semi-circular cross-section in adjacent layers. A central gap 4 is located at the middle of the rows of graphite bars and is fed with a cooling gas. The width of the gap is kept constant by struts 5 of beryllium or zirconium which are located at the junction of three rows of bars as shown in Fig. 4, and by pressure on the ends of the rows of bars. At the ends of the rows comprising the reflector section leaf springs 8 are provided between the rows and fixed supports 11 ; at the ends of the rows of the moderator section springs 12, Fig. 5, exert pressure on the rows through a female conduit 15, a connection 20, and a conduit 17 mounted to these members through swivel joints, the conduits allowing uranium bars to be passed through them into the channels 3. The moderator/reflector block is surrounded by resilient belts, the lower portion of each belt being constituted by a plate 22 having a coefficient of expansion equal to that of graphite. The spaces between the plates 22 and the oblique faces of the block are filled, inside the belt, by horizontal graphite bars 23 perpendicular to the bars of the blocks. Each plate 22 rests on a further plate 27 resting on supports 43 mounted on the floor 21 of the surrounding shield. The plates 27 carry side plates 28 to keep the graphite bars 23 in position, and are inter-connected by tie-rods 45. The belts comprise girders 30, 31 and tie rods 32 which exert pressure on shoes 33, 34 and 35. The girders 30 are connected to plates 22 through hinges 36 slidable with respect to plates 22 and subjected to pressure by springs 37. Girders 31 are pushed towards the block by springs 38 bearing on the shield, and the upper ends of tie members 32 are fixed, through springs 41, to tie rods 39 hinged at 40. The belts are interconnected by tie rods 46 similar to tie rods 45.