GB1196915A - Nuclear Reactors - Google Patents

Abstract

1,196,915. Reactors. ENGLISH ELECTRIC CO. Ltd. 6 Sept., 1967 [9 Sept., 1966; 24 Jan., 1967], Nos. 40491/66 and 3453/67. Heading G6C. A nuclear reactor comprises a pressure vessel having an internal wall surface enclosing two spaces separated from each other by a membrane having a peripheral edge disposed substantially in a plane, the membrane being sealed at its edge to the internal wall surface of the pressure vessel by a peripheral resilient seal which allows movement in the plane of the edge relative to the internal wall surface. In one example, the membrane separates an inlet space for relatively cool coolant, which space includes the reactor core, from a " hot box " or coolant outlet chamber in a split-flow reactor. The junction between the membrane and the pressure vessel wall is liable to substantial relative movement. As shown in Fig. 1, a concrete pressure vessel 10 is divided by a membrane 11 into a coolant outlet chamber 12 and a larger core chamber 13 in which there is a reactor core 14 (supported on means not shown) having longitudinal fuel channels 15. Each fuel channel 15 includes a fuel stringer 43 comprising a stack of fuel elements, each of which is in the form of a graphite sleeve containing nuclear fuel pins, and connected with a plug (not shown) in a standpipe 17 penetrating the roof 18 of the pressure vessel 10, by means passing through an open-ended connecting tube assembly 29 which extends from the corresponding standpipe 17 down through the hot box 12 to a joint with the top end of an extension tube 16 fixed to and passing through the membrane 11. Coolant gas enters the core chamber 13 through an inlet 21 and some of the gas enters the lower ends of the fuel stringers 43, the remainder by-passing the core 14 and entering the top ends of the fuel channels 15, passing down the channels and into the fuel stringers 43 through openings 20. All the gas passes up inside the fuel stringers 43, extension tubes 16 and tube assemblies 29, through openings 19 into the hot box 12 and then through outlets 22. The pressure vessel wall is maintained at a relatively low temperature by suitable thermal insulation and cooling arrangements, and since the membrane 11 is at a much higher temperature during operation, it is liable to undergo substantial expansion and contraction. Further movement may arise due to pressure differences between the gas in the hot box 12 and that in the core chamber 13, and due to external forces such as may be imposed by prestressing means in the concrete. The membrane 11 is therefore joined by a resilient peripheral seal 32 to a frusto-conical skirt 33 fixed to the steel liner of the pressure vessel 10. Suitable thermal insulation is provided over the whole internal surface of the hot box 12, and over the steel liner and the underside of the skirt 33 in the core chamber 13. The seal could be between the pressure vessel wall and the skirt, instead of between the skirt and the membrane. The skirt is preferably frusto-conical, though it may also be frusto-spherical or cylindrical, and may itself be resilient. The invention may relate to dividing walls other than between a coolant inlet space and a coolant outlet chamber, e.g. the latter may have such a dividing wall on the side remote from the core, separating the interior of the chamber from a space through which coolant fluid is passed for cooling the adjacent part of the pressure vessel. Yet again, the dividing wall may form part of the core support structure below the core, separating a coolant inlet chamber above the membrane from a coolant outlet space below it, or vice versa. 1,196,936. Multipliers. GENERAL ELECTRIC CO. 16 Jan., 1967 [10 Jan., 19671, No. 37801/67. Heading G4G. [Also in Divisions H2 and H3] A D.C. to A.C. converter comprises at least one shunt switch 18 arranged to clamp a circuit between D.C. input and A.C. output E2 to a predetermined potential, said switch 18 being controlled by pulses the duration of which is modulated at the required output frequency. Preferably a pair of shunt switches 18, 19, operating alternately, are employed so as to minimise the D.C. level at the output. Switches 18, 19 may each consist of a transistor connected between the junctions of resistors R4, R5; R7, R8 to earth. A multiplying function may be provided by modulating the 400 Hz. signal fed to the pulse width modulator 12.