GB917606A - Improvements in or relating to pressurised fluid-cooled nuclear reactors - Google Patents

Abstract

917,606. Nuclear reactors. SIMON-CARVES Ltd., and GENERAL ELECTRIC CO. Ltd. Nov. 2, 1961 [Nov. 8, 1960], No. 38328/60. Class 39 (4). A pressurized fluid-cooled nuclear reactor in which the reactor core is housed within a concrete pressure vessel whose inner surface is adapted to be cooled by coolant flowing in heat exchange relationship with the surface independently of the main reactor coolant. The reactor comprises a graphite core 1 within a concrete pressure vessel 3. Pressurized coolant gas enters the core through the ducts 4, flows through the vertical fuel elements, and is exhausted by way of ducts 5 to four heat exchangers (not shown). Access to the core is provided by standpipes 7, while further standpipes (not shown) are placed at the side of the reactor to enable samples of gas to be extracted for monitoring purposes. The whole of the inner surface of the vessel 3 is lined with a gasimpervious steel membrane 9, and spaced from this membrane, forming an annulus, is another steel membrane 14 constituting a heat insulator. Heat is removed from the walls of the vessel by three primary circuits each of which is provided with auxiliary circuits. In the first circuit gas enters the vessel through six inlets 17 and passes up the sides of the vessel in the annular space between the membranes 9 and 14. At the crown of the vessel the gas is guided radially inwards and is extracted through twelve nozzles (not shown) disposed between the standpipes 7 in two circular patterns. The main reactor and coolant pressures are equalized by providing small holes 22 in the membrane 14, however interchange of gases is discouraged by placing screens 23 in front of the holes. Gas entering the pipe 24 and leaving the pipe 27 provides a parallel auxiliary coolant circuit for the duct 5. The second primary circuit, which cools the bottom of the vessel and the ducts 4, enters the space between the membranes through the pipe 28, is guided by baffles 29 and leaves through the pipe 30. Again the membrane 14 is provided with holes to equalise the adjacent pressures. Parallel auxiliary circuits cool the ducts 4, inlet pipes 32 and outlet pipes 33 being used for this purpose. The third primary circuit cools the standpipes 7 by allowing the coolant gas to flow in the annulus formed between the standpipe and its sleeve. The standpipes are arranged in groups of eight, the coolant of those in the same group flows in series, while that of different groups flows in parallel and is connected to headers 41 and 42. The pressure of this circuit is less than the reactor coolant so that contamination of the latter is avoided.