Patent GB-1121430-A (GB)
Title: Nuclear reactor plant
IPC: G21C1/00
Filed: 1967-07-14
Abstract: 1,121,430. Reactors. SULZER BROS. Ltd. 14 July, 1967 [14 July, 1966], No. 32479/67. Heading G6C. A reactor core has tubes containing fuel or control rods which extend out of the top of the core and by means of which the core is suspended within a pressure vessel. As shown in Fig. 1, an intermediate floor 5 consisting of a central fixed part 8 and a yielding peripheral part 9 is suspended within a concrete pressure vessel 1 from tie-rods 10, the part 9 abutting the side wall 3. A reactor core 11 and a plurality of heat exchangers 12 are located beneath the floor 5, the heat exchangers 12 being supported on the floor 4 by a structure 13. The core 11 includes a tank 14 filled with a liquid moderator 50 and tubes 15 accommodating fuel rods 16 and control rods (not shown). The tubes 15 are welded to the bottom 17 of the tank and are each connected to the ceiling 18 by a bellows 19, one end of which is welded to the tube 15 and the other end to the ceiling 18. The part of each tube 15 within the tank 14 is lined with a heatinsulating tube 37. Flanges 38 at the top ends of the tubes 15 are anchored in the floor 5. The floor 5 forms an upper biological shield, and a shield against lateral radiation is provided by a shield wall 23 surrounding the core 11 and secured to the floor 5. A lower biological shield 24 provided with angled coolant passages is secured to the bottom ends of the tubes 15. For each fuel rod-accommodating tube 15, the lower shield 24 carries a bracket 29 the upper end 30 of which supports a fuel rod 16. A cylindrical wall 26 is suspended from the fixed part 8 of the floor 5, its lower edge being adjacent the lower ends of the heat exchangers 12 and above the floor 4 A flange 27 at the base of the tank 14 is connected to the cylindrical wall 26 through a movable seal 28. Above the floor 5 there is a horizontal partition wall 31 which includes a movable seal 32 abutting the side wall 3 and which contains apertures 34 accommodating plugs 35 inserted into the tubes 15. Helical grooves in the plugs 35 allow passage of a gaseous coolant which enters a distribution chamber 6 below the floor 5 through a duct 56 from a circulating blower 53. The coolant emerges from the tubes 15 through apertures 20 and after passing through the heat exchangers 12 flows up between the side wall 3 and the cylindrical wall 26 to a duct 52 leading to the blower 53. The duct 56 is so constructed that it has a greater flow resistance and hence a greater pressure drop than a parallel duct 57 leading to a fuel rod-changing ohamber 41 above the partition wall 31, so that any leakage through the latter is into the distribution chamber 6. Within the chamber 41, secured to the tie-rods 10, is a ring 42 outside the area occupied by the tubes 15 and forming a track for a wheeled-carriage 44 on which is movably mounted on rollers 45 a frame 46 supporting a fuel rod-changing apparatus 47. In a modification (Fig. 2, not shown) in which the liquid moderator is circulated through a heat exchanger, a regulating device is provided to ensure that the pressure inside the moderator tank is maintained approximately equal to that within one of the fuel rod-containing tubes.