GB1249331A - Improvements in or relating to liquid metal cooled fast breeder nuclear reactors - Google Patents

Abstract

1,249,331. Fast reactors. UNITED KINGDOM ATOMIC ENERGY AUTHORITY. 9 Jan., 1969 [30 Jan., 1968; 21 Feb., 1968], Nos. 4847/68 and 8535/68. Heading G6C. A large power-producing fast breeder reactor comprises a sodium-filled tank 1 within a vault 2 closed by a roof 3. The sodium level is denoted by chain-line L and disposed in the sodium are the reactor core 4, four primary heat exchangers 6, four sodium-coolant pumps 7 and interconnecting ducts 15, 16, 17. The core 4 is disposed in an open-topped vessel 50 having thermal insulation 9 and neutron shielding 10 and closed by a lid 11 having neutron shielding 22. A platform 12 constituting the bottom of the vessel 50 is supported by beams 13 suspended by a cylinder 14 from the roof 3, the lid 11 being suspended by a pillar 44. The ducts 15 penetrate the side wall 8 of the vessel 50 and conduct hot coolant from the upper region of the core to the heat exchangers 6. The ducts 16 lead the coolant from the exchangers 6, to the inlet of pumps 7, the coolant being returned to the lower end of the core by the ducts 17. The ducts 17 extend through platform 12 and terminate at a junction with the inlet ends of fuel element support tubes (not shown) carried by the diagrid 18. Leakage or flow-back of sodium from the junction mentioned above collects in a tank 20 and is returned by ducts 21 to a pump 7. Additionally, (not shown) the ducts 21 can be branched to the upper end of the core to scavenge cool sodium from the sodium pool in the tank which may otherwise be able to leak through the lid 11. A fuel store 24 for irradiated fuel sub-assemblies 27 has thermal insulation 26 and is disposed adjacent the vessel 50, these subassemblies being cooled by convection flow of sodium in the pool. The fuel sub-assemblies are transferred from the core 4 to the store 24 by tubes 23 provided at their upper ends with transfer machines (not shown), the upper ends of the pipes terminating in a rotatable inner shield 32. The inner shield 32 is eccentrically mounted in an outer rotatable shield 33 and the axis of the shield 32 may be aligned with the axis of the core 4. A refuelling machine 31 on the outer shield 33 may be connected at its upper end to a flask (not shown) whereby new fuel sub-assemblies may be loaded into the store 24 and irradiated fuel sub-assemblies may be removed to a remote facility. The inner shield 32 also supports the lid 11 through the pillar 44 and carries equipment 36 for operating the control elements 37. Further equipment 41, 42 43 carried by the shield 32 serves to monitor the coolant and measure the fuel temperature. Jacking means (not shown) are provided for lifting the shield 32 relatively to the shield 33 prior to rotation of the shield 32 or 33. In a modification described with reference to Figs. 3-5 (not shown) the tank 1 is elliptical in plan view, the reactor core being situated at the centre of the major axis but displaced off-centre on the minor axis to provide space for the fuel store. The space at each end of the ellipse is occupied by the primary heat exchangers and pumps.