GB1013544A - Improvements in gas-cooled nuclear reactors - Google Patents

Abstract

1,013,544. Cooling arrangements for gascooled nuclear reactors. BABCOCK & WILCOX Ltd. June 26, 1962 [June 26, 1961], No. 24497/62. Heading G6C. A gas-cooled nuclear reactor having fuel elements disposed in channels in moderating material has solid heat conducting means arranged to transfer heat from the fuel elements to the moderator, which is arranged to be cooled during the operation of the reactor, the thermal conducting properties of the solid heat-conducting means being such that, upon shut-down of the reactor, heat is transferred from the fuel elements to the moderator at a rate approximately equal to the rate of heat generation in the fuel elements as a result of the disintegration of radio-active fission products after the chain reaction has ceased. The principle of the arrangement is illustrated by Fig. 1, where heat generated in nuclear fuel 1 is conducted mainly to the passing coolant indicated by arrows 2 and partly through heatconducting body 3 in the direction of arrows " q " to the moderator 4. The moderator 4 gives off this heat and any other produced in the moderator to coolant stream 5. Coolant streams 2 and 5 may be separate systems or they may be a common circuit as indicated by arrow 6, where the coolant gas first cools the moderator before passing over the fuel element. If the cooling system fails and the reactor is shut down, the heat generated in 1 by radioactive decay is conducted away from the fuel elements by bodies 3 and is stored in the moderator. Figs. 2 to 8 (not shown) illustrate various embodiments of this principle. Figs. 2 and 3 illustrate a liquid moderated reactor with separate moderator and fuel element cooling systems, the fuel element being enclosed in a heat-conducting material which is in close contact with the fuel channel wall. Fig. 4 illustrates a fuel element, having central cooling channels, but which is insulated externally from the coolant stream, thus providing separate channels for cooling the moderator and the fuel elements, the heat conducting means being fins which are insulated from the coolant stream but in contact with the moderator. Figs. 5 and 6 illustrate dished fuel elements with central apertures, the fuel element being equipped with spaced radial flanges which contact the moderator and Figs. 7 and 8 show fuel elements which are frusto-conical shells supported on flanges in grooves in the moderator. In the last two embodiments the construction of the fuel elements provides the passages for coolant flow, and, if desired, the radial surfaces of the fuel elements may be equipped with a helical fin extending coaxially of the central aperture to induce spiral flow of the coolant over the surface. The flanges mentioned above serve as the heat conducting means.