GB890520A - Improvements in nuclear reactors and in restraint garters therefor - Google Patents

Abstract

890,520. Nuclear reactors. BABCOCK & WILCOX Ltd. June 3, 1960 [June 3, 1959], No. 1.8948/59. Class 39(4) In a nuclear reactor having a temperature compensated restraint garter surrounding a stack of material providing the moderator and reflector of the nuclear reactor core, the garter includes a series of circumferentially distributed levers adapted to rock under the differential thermal expension of lever actuating means and arranged and dimensioned to give a circumferential expansion or contraction of the garter substantially equal to the circumferential thermal expansion or contraction of the adjacent part of the stack. The garter of which part is shown in Fig. 2 comprises a plurality of channel-shaped stays extending along sides of the stack within recesses (not shown) in the stack; mild steel tie rods 6 extend along alternate stays 5, and along the other stays 7 extend pairs of rods 8 and 9, the rod 8 being a stainless steel tube in compression and the rod 9 being of mild steel in tension. Rods 8 and 9 are pivoted at their ends to the longer arms of cranked levers 22, the pivot pin 25 connecting each rod 8 and lever 22 also passing through enlarged apertures in a pair of side plates 13 (of which only the upper is shown in Fig 2) welded to the base plate 11 of the stay 7. The shorter arm of each lever 22 is pivoted to a tie rod 6 by a pin 45 which also passes through an aperture in a swing link 48 and through enlarged apertures in two similar balance lever plates 52 (of which only the upper is shown in Fig. 2). The outer end of each swing link 48 is pivoted by a pin 61 to the pair of balance lever plates 52. Each pair of balance lever plates 52 is coupled to the side plates 12 of adjacent stays 5, 7 by pins 68, 74 passing through apertures in the balance lever plates and through apertures in the side plates which are elongated in a direction parallel to the stay. Thus a radially inward force produced by the tie rods 6, compression rods 8 and tension rods 9 is transferred to the swing links 48 by the pin 45, from the swing link 48 to the balance lever plates 52 by the pin 61, and from the balance lever plates to the stays by pins 68 and 74. The rods 8 have a greater coefficient of expansion than rods 6 and 9 and the dimensions are chosen so that the rocking of levers 22 on thermal expansion is such that overall expansion of the garter is equal to that of the stack. The rods 8 may be tubular and may be internally threaded on to stems of the associated clevises, the threads of the two ends being of opposite hand so that the initial tension of the garter may be adjusted by rotating rods 8. A nuclear reactor core may be surrounded by one such garter at the top and two at the bottom, the intermediate garter being as described in Specification 890,523.