GB1090587A - Improvements in or relating to moderator structures for heterogeneous nuclear reactors - Google Patents

Abstract

1,090,587. Moderator structures. COMMISSARIAT A L'ENERGIE ATOMIQUE. March 17, 1966 [March 17, 1965], No. 11689/66. Heading G6C. A solid moderator, e.g. graphite, bar is formed with at least one helical slot which is cut in a lateral surface of the bar. Where the bar includes a bore, the outside surface and/or the inside surface can be formed with helical slots. Preferably, slots are formed in both the outside and the inside surfaces and are of the same pitch and hand. From the point of view of bar strength, the outer slots should be offset from the inner slots. The slots should be very narrow in order to limit loss of moderator material. The region of the cross-section of the bar in which the stresses due to the Wigner effect have not been interrupted is reduced by this means to that between two cylinders of revolution on which the bases of the outer and inner slots lie. Alternatively, the outer slots may be of the same pitch as the inner slots but of opposite hand, or the slots in any one surface may be in the form of two series of helices which have the same pitch and opposite hands. In zones where axial or circumferential stresses are severe, the outer or inner slots can have veryshort-pitch or very-long-pitch slots, respectively, superimposed on them.