Abstract: A guide tube flow restrictor for use on an upper guide tube housing support plate of a nuclear reactor, for guiding of a control rod drive shaft through an aperture in the support plate and restriction of flow of coolant therethrough, has an outer ring seatable on the support plate, the outer ring having a flange member from which there depends a plurality of flexible members, the flexible members having inwardly disposed deflectors thereon, and extending through the bore of the outer ring and the aperture of the support plate. An axially insertable sleeve, upon insertion into the outer ring, between the flexible members, contacts the deflectors thereon to radially force the flexible members outwardly to secure the same with the walls of the aperture of the support plate. Baffles are provided on the flexible segments and additional locking members provided between the outer ring and inner sleeve.

Abstract: Apparatus is disclosed for introducing a low neutron moderating fluid into the reactor vessel of a spectral shift pressurized water nuclear reactor and for distributing the moderating fluid through the lower core support plate into the fuel assemblies in the core.

Abstract: To preclude failure of components of control-rod assemblies or of unprotected control rods (WDRC's) a calandria is provided above the upper internals. The calandria includes hollow tubes through which the drive rods for the various control rods pass and which protect the drive rods. The guides for the control rods are closed except at the top so that the coolant flows vertically through the guides into the calandria. In the calandria, the coolant flows transversely to the hollow tubes and out through the outlet nozzle. The tubes have a mass and stiffness and strength such that they resist failure by reason of the transverse flow of the coolant to which they are subjected.

Abstract: Device for the homogeneous mixing of liquids flowing at different temperatures comprising a member connected to an inlet tube and to an outlet tube of a main circuit in which circulates a hot liquid, a cylindrical inlet of the member being connected to a secondary tube of a secondary circuit in which circulates a cold liquid, a cylindrical circuit sealingly fixed to the member on the outlet side thereof and having openings on the inlet tube side, wherein (1) an envelope formed, as from the inlet tube, by a cylindrical part, a frustum-shaped part and a cylinder surrounds the cylindrical pipe providing an annular space with the latter over part thereof located on the side of the inlet tube and having the said openings; (2) the envelope forms a first annular channel with the member; (3) a connecting tube connected to the secondary tube and to the cylinder forms, with a cylindrical inlet of the member, a second annular channel linked to the first annular channel; and (4) the cylindrical pipe has a series of holes

Abstract: A method and apparatus for eliminating leakage spaces between the partitions (1) surrounding the core of a pressurized water nuclear reactor, after it is brought into operation. Operations are carried out under water, during shutdown of the reactor. The defective joins (12) between the partitions (1) are identified. For each join, the partitions (1) are pierced, the hole inside a partition (1) is screw-threaded, the swarf is recovered, a screw with diametrical expansion is introduced and screwed into the hole and the screw is expanded by displacement of a rod in the longitudinal direction of the screw. Moving location, the operations are repeated for each defective join (12). The apparatus comprises a case (25) containing a drum (36) bearing tools for boring (54-65), screw-threading, and screwing, a cleaning tube and a punch for locking the screw.

Abstract: Cover-plug for the core of a fast neutron nuclear reactor, comprising a support-plate (6), a cylindrical shell (8) having a vertical axis fixed integrally to the support plate (6) and braces (14) which are transverse relative to the shell (8). Vertical tubes fixed to the support plate (6) at their upper part are joined to the braces (14), which consist of at least two conical webs (14) having their axes coincident with the axis of the shell (8). These conical webs have a top angle greater than 120.degree. and a diameter which is slightly smaller than the diameter of the shell (8), at their base. The brace (14a) situated in the lowest position in the shell (8) ensures the deflection of the reactor cooling fluid. The invention applies, in particular, to fast neutron nuclear reactors of the integrated type.

Abstract: A plenum separator system for separating the hot plenum from the cold plenum and from the reactor vessel wall in a pool-type nuclear reactor. One or more intermediate plena containing substantially stagnant and thermally stratified coolant provide axial separation of the hot and cold plena. A dual pass forced bypass flow through annuli at the upper portion of the reactor vessel wall, in conjunction with the intermediate plenum and an annular gas space adjacent the reactor vessel wall, provide radial separation of the hot plenum and the vessel wall.

Abstract: Control cluster guide devices, for light water cooled nuclear reactors, including housings. The reactor includes means outside the core for guiding control clusters (7) during their movements.The housings (12) are associated respectively with the several control clusters (7) and comprise plates which ensure discontinuous guidance at intermediate levels for the individual pencils and an associated spider, each housing including for continuous of the individual pencils, tubes which connect two tube plates for the pencils to pass through, which are proper to the housing, the one terminating it and the other forming a positioning flange on the core plate.

Abstract: A device which controls coolant flow through a nuclear reactor assembly comprises a baffle means at the exit end of said assembly having a plurality of orifices, and a bimetallic member in operative relation to the baffle means such that at increased temperatures said bimetallic member deforms to unblock some of said orifices and allow increased coolant flow therethrough.

Abstract: Nuclear reactor with a radiation-emitting core including a container for conducting a coolant, the radiation-emitting container having a wall formed with a plurality of slots disposed parallel to one another, the slots having a depth within the wall equal to at least one-fourth the thickness of the wall, the slots being spaced from one another a distance which is at most as great as the depth thereof.

Abstract: The invention comprises a core barrel plug capable of being remotely installed in a port of a core barrel of a pressurized water nuclear reactor for converting the reactor from a by-pass downflow configuration to a by-pass upflow configuration. The plug comprises a body having an expandable cylindrical portion with a movable mandrel disposed in the body. Remote fluid pressurization causes the mandrel to be advanced thus expanding the body into contact with the port. The plug also comprises a locking mechanism to prevent inadvertent release of the plug and a venting mechanism to prevent inadvertent overpressurization of the plug.

Abstract: A pressurized water nuclear reactor of the type with vertical control rods passing through the core surrounded by control rod guide tubes. A major portion of the water flow is passed directly to the bottom of the core for upward flow therethrough. A minor portion pressurizes a volume at the top of the vessel and passes downwardly through the control rod guide tubes to join the major portion of flow at the lower end of the core.

Abstract: Device for producing steam by heat exchange between a heat-transfer liquid metal and feed water, comprising a cylindrical casing (31) receiving liquid metal in its upper part through at least one nozzle (35, 36). The liquid metal enters in a space bounded by a central sleeve (38), a lower perforated distribution plate (40) and a first perforated plate (45). A second perforated plate (46) parallel to the latter is separated therefrom by perforated crosspieces (47). The perforated plates (45 and 46) are disposed between the sleeve (38) and a peripheral sleeve (39). The three plates (40, 45 and 46) have identical perforations which are aligned in the vertical direction. The distribution plate (40) is provided with stiffening ribs (44) ensuring the distribution of the liquid metal thereon. The invention applies, in particular, to fast breeder nuclear reactor steam generators cooled by liquid sodium.

Abstract: In a cluster of nuclear fuel rods cooled by liquid metal an obstruction to coolant flow results in overheating in the wake of the obstruction. By the provision of open ended heat transfer tubes in the flow channels, a guaranteed supply of coolant is maintained and this supply holds the temperature to below saturation. Heat transfer via the tubes is highly efficient and ensures that a sufficient temperature rise occurs at the cluster exit to provoke a response from the outlet temperature transducer sensing average temperature.

Abstract: A device which mitigates against the effects of a failed coolant loop in a nuclear reactor by restricting the outflow of coolant from the reactor through the failed loop and by retaining any particulated debris from a molten core which may result from coolant loss or other cause. The device reduces the reverse pressure drop through the failed loop by limiting the access of coolant in the reactor to the inlet of the failed loop. The device also spreads any particulated core debris over a large area to promote cooling.

Abstract: Method of producing a core baffle with a plurality of horizontally disposed, parallel profile-rib rings for enclosing the fuel assemblies of a pressurized-water reactor, the profile-rib rings being formed with respective cutouts having a polygonal contour corresponding to that of the reactor core and with baffle plates secured vertically to the profile-rib rings and forming a casing matching the contours of the cutouts, which includes fastening to the profile-rib rings, by welding, one end of a plurality of ribs having a height corresponding to a mutual spacing of the profile-rib rings; successively welding the profile-rib rings to one another by the respective ribs thereof into a cage; assembling baffle plates bent partly into profile sections into the form of casing by bracing the plates against the cage; successively welding the baffle plates to the profile-rib rings of the cage; and welding the baffle plates to one another into a tight casing.

Abstract: Integrated nuclear reactor cooled by a liquid metal and incorporating a main vessel sealed in its upper part by a slab, an inner vessel containing the core, the latter resting on a system for the positioning and supply of the core with liquid metal and which is called the support, the latter itself resting on a supporting structure bearing on the bottom of the main vessel of the reactor, wherein it comprises an inner baffle cladding the side wall and bottom of the main vessel and defining with the latter an intermediate space filled with the liquid metal, tubes for supplying a liquid metal to the intermediate space below the bottom of the main vessel and tubes for returning said liquid metal to an auxiliary exchanger in order to remove heat from the intermediate space.

Abstract: A reusable system for removably attaching the lower end 21 of a nuclear reactor fuel assembly duct tube to an upper end 11 of a nuclear reactor fuel assembly inlet nozzle. The duct tube's lower end 21 has sides terminating in locking tabs 22 which end in inwardly-extending flanges 23. The flanges 23 engage recesses 13 in the top section 12 of the inlet nozzle's upper end 11. A retaining collar 30 slides over the inlet nozzle's upper end 11 to restrain the flanges 23 in the recesses 13. A locking nut 40 has an inside threaded portion 41 which engages an outside threaded portion 15 of the inlet nozzle's upper end 11 to secure the retaining collar 30 against protrusions 24 on the duct tube's sides.

Abstract: A nuclear reactor assembly including a substantially cylindrically-shaped and vertically extending pressure vessel. A uniquely constructed bracket assembly is arranged for mounting a water distributor against an inner wall of the cylindrically-shaped pressure vessel, with the bracket assembly including a spring assembly capable of biasing an inlet conduit of the water distributor into abutting contact with an inlet nozzle extending through a wall of the pressure vessel.