Abstract: A latching device for use in nuclear reactors. The device is used to latch outer housing assemblies to the reactor core. The device contains a shear pin which does not break under normal loading imposed by movement of absorber rod assemblies, but which shears when it is desired to remove the housing from the core.

Abstract: A tube-in-shell heat exchanger wherein the tube bundle has a central spine which carries a series of bracing grids for the tubes. The grids are resiliently mounted on the spine so that differential thermal expansion of one group of tubes relative to other groups of tubes and structure can be accommodated without inducing severe thermal stress.

Abstract: A remotely controlled vehicle capable of roving over the outer surface of a nuclear reactor primary vessel carrying inspection instrumentation. The vehicle comprises an elongate bridge having a pair of suction support pads. Each pad carries gas thrusters for acting in opposition to the suction effort thereby to reduce adherence of the pads and enable displacement of the vehicle over the surface. The vehicle is supported by a services conducting umbilical.

Abstract: A suction pad for adhering a load to a surface and comprising a disc having an extensible annular seal on one face and a radial vacuum inducer mounted on the other. The inducer is capable of evacuating the interior region bounded by the seal to anchor the disc to the surface. There are gas thrusters disposed outside the seal for opposing the vacuum by extending the seal when it is required to reduce adhesion to allow lateral displacement of the suction pad without breaking the annular seal.

Abstract: A liquid metal cooled fast breeder nuclear reactor comprising a nuclear fuel assembly submerged in a pool of coolant contained in a primary vessel is housed in a concrete vault. A core cover structure suspended from the roof of the vault and immersed in the pool of coolant comprises a plurality of vertical tubes braced apart by perforated grid plates. An intermediate grid plate has a permeable shroud which constrains coolant passing through the perforations in the grid plate to flow transversely over the upper surface to reduce the transient temperature differential.

Abstract: In a nuclear reactor of the pool kind the primary vessel and fuel assembly are carried from the roof of the containment vault by tie straps. The primary vessel incorporates an annular yoke of `K` cross-section the tie straps being attached to the upwardly directed vertical leg and the downwardly directed inclined leg. The upper and lower strakes of the primary vessel are extensions of the remaining legs. Load supporting welds therefore are of intermittent nature thereby limiting the effects of weld crack propagation.

Abstract: A liquid metal cooled fast breeder nuclear reactor comprising a fuel assembly supported on a diagrid and submerged in a pool of liquid metal coolant within a containment vessel. The diagrid is of triple component construction comprising a short cylindrical plenum mounted on a conical undershell and loosely embraced by a fuel store carrier. The plenum merely distributes coolant through the fuel assembly the load of the assembly being carried by the undershell by means of struts which penetrate the plenum. The fuel assembly, fuel store carrier and undershell provide secondary containment for the plenum.

Abstract: The vault of a liquid metal cooled nuclear reactor is lined with thermal insulation. The insulation is in two layers, a first layer cladding the vault surface is of solid ceramic material while a second layer cladding the first layer is of fibrous or metallic material. In the event of a breach of the vessel leakage of liquid metal is absorbed by the second layer providing a conduction path to the first layer thereby enhancing heat loss to the concrete of the vault and maintaining the internal temperature at a safe limit.

Abstract: A liquid metal cooled fast breeder nuclear reactor wherein the fuel assembly includes some breeder fuel sub-assemblies having electromagnetic brakes and fluidic valves of the controlled vortex kind for controlling the coolant outlet temperature. The coolant flow through each breeder sub-assembly is divided into a major flow fraction by way of the fluidic valve and fuel pins a minor flow fraction by way of the electromagnetic brake which is sensitive to the temperature of coolant flow. A control component of force for the fluidic valve is derived from the back pressure of the brake so that as the power output of the sub-assembly increases the braking effect diminishes and flow of coolant through the fluidic valve is increased.

Abstract: The core tank of a liquid metal cooled fast breeder reactor of the pool kind has thermal insulation cladding its inner wall surface. The thermal insulation comprises a plurality of spaced layers of stainless steel sheet material each layer comprising rectilinear panels in spaced array in vertical and horizontal rows. Closure members of cruciform shape close the spaces between adjacent panels.

Abstract: The primary vessel of a pool type fast reactor is open at its upper end and is suspended from the roof of the vault by ties. The vessel is enclosed within a fluid tight leak jacket containing an inert cover gas for the pool of coolant.Because of the unrestrained open end of the vessel severe stress concentrations in the upper strake are avoided. The problem does not occur in the leak jacket because the cover gas, supplemented by thermal insulation cladding and cooling coils, avoids excessive temperature differentials.

Abstract: The fuel assembly in a nuclear reactor construction is supported from the wall of a primary vessel on a strongback and there is secondary support means for the fuel assembly the means comprising a secondary strongback supported from the roof structure of a containment vault by ties. The secondary support means provides a safety device whereby in the event of relaxation of the primary support relative movement between the fuel assembly and control rods is limited. Alternative secondary support means comprise a series of ties supporting the diagrid and a support stool beneath the fuel assembly.

Abstract: In a liquid metal cooled fast breeder nuclear reactor of the pool kind the inner wall surface of the core tank has continuous fins inclined upwardly to form troughs through which cool liquid metal drawn from the outer region of the pool of coolant can cascade and thereby jacket the wall surface with relatively cool coolant.

Abstract: In a nuclear reactor (e.g. one having coolant down-flow through a core to a hearth below) thermal insulation (e.g. of a floor of the hearth) comprises a layer of bricks and a layer of tiles thereon, with smaller clearances between the tiles than between the bricks but with the bricks being of reduced cross-section immediately adjacent the tiles so as to be surrounded by interconnected passages, of relatively large dimensions, constituting a continuous chamber extending behind the layer of tiles. By this arrangement, lateral coolant flow in the interbrick clearances is much reduced.The reactor core is preferably formed of hexagonal columns, supported on diamond-shaped plates each supported on a pillar resting on one of the hearth-floor tiles.

Abstract: In a nuclear reactor installation comprising a fluid-cooled nuclear heat source within a primary pressure vessel, the latter is enclosed within a secondary containment means which comprises a lower wall portion surrounding the primary pressure vessel, an annular portion extending out from the lower wall portion, and an upper portion integral with the annular portion and extending over it and over the primary pressure vessel and housing handling means for lifting fuel and other reactor components through normally sealed vertical penetrations in the roof of the primary pressure vessel (giving access to the reactor core) and in the said annular portion (giving access to new and spent fuel stores and other auxiliary facilities disposed outside the secondary containment and wholly or partly below the said annular portion).