GB978159A - Solid moderator stack for nuclear reactors - Google Patents

Abstract

978,159. Moderator structures. COMMISSARIAT A L'ENERGIE ATOMIQUE. July 4,1961 [July 4, 1960], No. 24092/61. Heading G6C. A moderator structure comprising prismatic columns 1 of beryllium or beryllium oxide stacked side-by-side and connected by keys 8 oriented parallel to at least three directions passing through the axes of the columns 1 and engaged in longitudinal grooves machined in the lateral faces of the columns, is characterized in that each of the columns 1 is made up of superposed tubular elements of polygonal external outline each element consisting of separate indentical prisms, such as prisms 5, 6 and 7 in Fig. 1, one longitudinal face of each of which forms part of the duct which passes axially through the columns 1. The dividing of the elements into separate prisms prevents inadmissible stresses from being set up due to the difference in temperature existing between the internal and external surfaces of the elements, beryllium and beryllium oxide having an appreciable modulus of elasticity, a low tensile strength and a high coefficient of thermal expansion. Each element is angularly displaced with respect to its neighbours so that the planes in which the prisms in one element are in contact do not merge with those of adjacent elements. Columns 2, 3 form a reflector with metal stabilizing posts 4 disposed in the columns 3. As shown in Fig. 2, centring pieces 9 are provided on the upper faces of the prisms and engage corresponding recesses 10 in the lower faces of the prisms. Embodiments are described in which the columns 1 are of regular hexagonal, flattened hexagonal, and square cross-section. Specifications 913,818 and 977,019 are referred to.