Cylindrical pressure chamber for nuclear reactor or the like

Abstract

A cylindrical pressure chamber, designed to contain a hot expanding fluid in a nuclear reactor, has a refractory peripheral wall provided with a cooled metal lining surrounding a ceramic insulating layer which is shielded from the fluid by an inner metallic shell. The shell is separated from the ceramic layer, in the nonoperating state, by an annular clearance allowing its expansion under internal fluid pressure to pretension that shell so as to reduce the thermally induced stress to less than the yield point of the metal. The ceramic layer is anchored to the lining by radial bolts and has radial bores slidably engaged by guide studs welded to the shell. FIELD OF THE INVENTION My present invention relates to a cylindrical pressure chamber designed to contain a hot expanding fluid, more specifically a pressure chamber used in a nuclear reactor. BACKGROUND OF THE INVENTION Conventional pressure chambers of this kind comprise a cylindrical structure forming a refractory peripheral wall, this wall being internally provided with a first metallic lining surrounding a ceramic insulating layer of low thermal conductivity. The insulating layer, in turn, is provided with a second, inner metallic lining protecting it from the confined fluid. The insulating layer may consist of concrete, for example; the tubular linings coaxially bracketing that layer are usually made of steel. In operation, the inner lining undergoes considerable heating and tends to expand radially as well as axially. Its radial distension is blocked, however, by the insulating layer whose thermal coefficient of expansion is substantially lower than that of steel. This places the inner lining under considerable stress, often exceeding its yield point and leading to an early destruction thereof, particularly if the pressure chamber is repeatedly taken out of service so that the lining undergoes recurrent cooling and heating. OBJECT OF THE INVENTION The object of my present invention, therefore, is to provide an improved construction for such a pressure chamber which avoids the aforestated disadvantages and increases the service life of its peripheral wall structure. SUMMARY OF THE INVENTION I realize this object, pursuant to my present invention, by replacing the conventional inner metallic lining with a metal shell or tube separated from the insulating layer, in an unoperated state of the assembly, by an annular clearance enabling radial expansion of the shell under pressure of the confined fluid as soon as operations are started. This expansion is, of course, limited by the depth of the clearance, which is sufficient to enable pretensioning of the shell in peripheral direction for reducing the thermally induced stresses therein to less than the yield point of the metal. If the outer peripheral wall surrounding the insulating layer is provided with a cooled metallic lining as in conventional nuclear reactor chambers, this lining may carry anchor means engaging that layer. On the other hand, the layer is provided with countersunk guide means bridging the intervening clearance and engaging the inner metallic shell to facilitate its radial displacement relative to the layer. The guide means may comprise a number of sleeves seated in radial bores of the layer and a corresponding number of studs slidably received in these sleeves, the studs preferably having retaining heads of larger diameter than the sleeves limitedly displaceable in extensions of the bores beyond the sleeves. The insulating layer may be axially subdivided into tiers of sectoral blocks with interlocking trapezoidal profiles in an axial plane, the profiles of adjoining tiers converging alternately toward the periphery and toward the axis. In such a case I prefer to anchor the outwardly converging blocks firmly to the outer wall, advantageously via its cooled lining as mentioned above, and to provide the inwardly converging blocks with lost-motion couplings of the aforedescribed kind linking them with the inner metallic shell to act as the aforementioned guide means. In order to facilitate thermal distension of the shell in an axial direction, the same may be subdivided into axially separated sections interconnected by expansion joints.

Dependencies are inferred from the claim text.