GB960678A - Nuclear power reactor with rod-shaped fuel elements - Google Patents

Abstract

960,678. Reactors. BETEILIGUNGS-UND PATENTVERWALTUNGSGESELLSCHAFT. Oct. 22, 1962, No. 39943/62. Heading G6C. A nuclear reactor with no bottom grid has horizontally rod shaped fuel elements the ends of which are connected to longitudinal members to form a number of ladder-like groups in which the fuel elements form the rungs of the ladders. The invention is applicable to boiling water and gas cooled reactors and provides a single zone within the reactor in which superheating takes place. The fuel may be metallic or ceramic compounds of circular or elliptical cross-section. A further feature of all the embodiments described is that one of the longitudinal members of each "ladder" is movable in a direction parallel to the fuel element axes in order to accommodate thermal expansion. The water cooled reactor shown in Fig. 7 comprises two heating zones, the first heating the water, which may be heavy water acting as coolant, moderator and shield, and the second superheating the resultant steam. Each ladder-like fuel assembly is immersed in the liquid coolant, and the steam thereby generated accumulates above the water level in the reactor before passing into the first hollow longitudinal member 6 of the fuel assemblies From the member 6 the steam passes through the interiors of the hollow fuel elements 5, out through the second longitudinal member 7 and into a steam accumulator 8. Superheated steam passes from the accumulator either to a heat exchanger or direct to a turbine. The superheating coolant circuit may be modified by placing a divider at approximately the mid point of the longitudinal member 6, such that the entire steam flow passes from left to right in the upper half of the "ladder", and from right to left in the lower half. The upper end of the longitudinal member 7 is closed, and the steam accumulator is connected to the lower end of the member 6. In a modified form of boiling water reactor, solid fuel elements are used, there being no circulation of coolant within the "ladder". In this case, the superheating takes place in a zone above the water level into which the "ladder" ends project. The gas cooled reactor shown in Fig. 11 utilizes a solid fuel element surrounded by two spaced apart concentric graphite tubes (Figs. 8, 9, not shown). Provision is made for circulating a scavenging gas (entirely independent of the coolant circuit) through the graphite annulus surrounding each fuel element via inlet and outlet connections made to the two longitudinal members 24, 25. Gas . enters the reactor through an annulus 29 and passes dpward, cooling the reflector 28. The thus preheated gas then passes down through the core and out through a pipe 32. An advantageous feature of both the boiling water and gas cooled reactors described is that the "ladder" construction of the fuel assemblies obviates the need for a bottom grid plate. The weight of fuel is supported through the longitudinal members on an annular ring positioned in the bottom of the reactor.