Abstract: In a known design of liquid metal cooled fast fission nuclear reactor, the primary pumps (22) plug into the outboard ends of the high pressure pipes (28), leading to the development of a vertical load which has to be supported by substantial additional structure to avoid subjecting the reactor diagrid (18) to significant bending moments. The invention resides in connecting the inboard ends of the high pressure pipes (28) to the diagrid (18) via spigot and socket joints (40) so that the pipes are not rigidly connected at either end. With this arrangement loads are developed at each end of the pipes which combine to produce radial reaction loads acting on smaller moment arms whereby the total moments imposed on the diagrid are reduced.

Abstract: A baffle (12) is provided for the gaps between a pair of surfaces (10, 14). The baffle has a lantern configuration and comprises a number of spring steel foils (15) arranged in side-by-side relation with overlap between adjacent foils. Each foil (15) is of shallow V-configuration. The ends of the V are attached by stud and slot connections (22, 24, 26, 28) to one of the surfaces separated by the gap at axially spaced locations and the midpoint of the V bears against the opposing surface. The stud and slot connections afford limited axial movement of the ends of the V to compensate for irregularities in the gap width.

Abstract: A roof shield for a nuclear reactor comprises a normally fixed radially outer portion, a radially inner portion rotatable about a vertical axis, and a connection between the inner and outer portions which permits relative angular movement between the portions without loss of containment, the connection comprising a radially inner wall of the outer portion, an upper portion of the inner wall being so arranged that on upward movement of the inner portion the upper wall portion receives substantially no angular movement, the lower end of the upper portion being at a position below the level of the upper surface of the outer portion.

Abstract: In a nuclear reactor of the type in which the vault has a roof in which inner and outer rotatable shields are mounted, coolant is supplied to the roof and shields via duct penetrations which extend in the plane of rotation and can be brought into alignment and connected together by slidable connectors when relative rotation between the shields and roof is not required. When such rotation is to be effected, the connectors can each be retracted into a respective duct so that rotation is not obstructed thereby.

Abstract: The combination in a nuclear reactor of a concrete containment and thermal insulation for the roof of the containment, the thermal insulation being secured to the roof by hangers each of which has a linkage connector at its upper end by means of which it is secured to the roof, the linkage connector permitting movement of the hanger in two dimensions, and means at the lower end of each hanger serving to support the thermal insulation from beneath and permitting lateral movement of the insulation in two dimensions.

Abstract: In a liquid metal cooled nuclear reactor with a nuclear fuel assembly in a coolant-containing primary vessel housed within a concrete containment vault, there is thermal insulation to protect the concrete, the insulation being disposed between vessel and concrete and being hung from metal structure secured to and projecting from the concrete, the insulation consisting of a plurality of adjoining units each unit incorporating a pack of thermal insulating material and defining a contained void co-extensive with said pack and situated between pack and concrete, the void of each unit being connected to the voids of adjoining units so as to form continuous ducting for a fluid coolant.

Abstract: A liquid metal cooled nuclear reactor of the kind in which the reactor core is disposed in a pool of liquid metal contained in the inner vessel of a double-walled steel tank supported in a vault having a roof the reactor has the roof supported by a conical support skirt carried by the wall of the vault, a single annular weld securing a main roof member to the skirt, and the conical skirt including a forked part providing inner and outer annular skirt portions from which the inner and outer vessels of the tank are carried respectively.