GB820579A - Improvements in and relating to nuclear reactors - Google Patents

Abstract

820,579. Nuclear reactors. PARSONS & CO. Ltd., C. A. Oct. 16, 1957 [Dec. 28, 1956], No. 39410/56. Class 39(4). In a liquid moderated liquid cooled reactor, the nuclear fuel is housed in a plurality of re-entrant tubes each comprising an inner tube and an outer tube, the inner tube containing the fuel, and the liquid coolant being circulated through a space between the inner and outer tube and thence through the inner tube to cool the surface of the fuel. In the reactor shown in Fig. 1 re-entrant tubes each comprising an outer tube 3a and an inner tube 3b are disposed in a liquid moderator 2 which may be heavy water. A cooling liquid, preferably a diphenyl or a triphenyl, is introduced at an inlet 4 to each tube 3a and flows downwardly between the inner and outer tubes and then upwardly through the inner tube 3b past fuel element 6. Preferably the liquid has a lower velocity when flowing downwards than when flowing upwards to reduce heat transfer to the moderator ; the tubes 3a may incorporate gas spaces to further reduce the heat transfer to the moderator. The heat transfer to the moderator may thus be kept at a level which prevents boiling without the need for pressurizing. The re-entrant tubes may be connected in parallel to supply and exhaust mains through which coolant is circulated by a pump in a closed pressurized system.