Abstract: A cask for loading at least one nuclear fuel assembly in a transport container, including a body with a longitudinal axis (X) capable of sealably covering an upper end of a container, at least one aperture (10) for letting through a fuel assembly, at least one means for connecting to pneumatic confinement means and at least one means (56) capable of maintaining a means (58) for sealing a chamber of the container inside the cask and at a distance from an entrance of said chamber during loading, wherein the maintaining means (56) includes a first arm (60) rotationally mobile around a first axis and a second arm (62) attached to the first arm (60) and rotationally mobile relatively to the first arm, said cask also including external means for controlling the arms (68,86), and wherein the second arm (62) includes a housing (76) for receiving the sealing means.

Abstract: The present invention is used to reduce thermal load itself, being the cause to generate stress, which develops near liquid surface in a nuclear reactor wall and to contribute to further improvement of safety. A partition member (5) is arranged above a coolant liquid surface (9) in an annulus space (3) between a reactor vessel (1) and a guard vessel (2), a low-temperature gas is circulated through the annulus space above the partition member to cool down, the gas is circulated through the annulus space from under the coolant liquid surface to the partition member, and the high-temperature gas heated under the coolant liquid surface is used to raise the temperature above the coolant liquid surface.

Abstract: A device for suspending a core cover from a sealing slab of a fast neutron nuclear reactor of the type comprising a vertically axed vessel structure filled with liquid metal, closed by the slab and containing the reactor core. The device comprises an upper row and a lower row of superimposed, generally flat, planar, metal plates enabling the rows to be joined to the slab and to the core cover, each row of plates defining a closed convex envelope. The plates are flexible in a direction radial relative to the envelope, while being rigid in a direction circumferential with respect to the envelope. The two rows of flexible plates are interconnected by a lattice of rigid bars in an "X" or "V" form. The upper row plates have upper edges rigidly fixed in position relative to the slab and lower edges rigidly fixed in position relative to the lattice. The lower row plates have upper edges rigidly fixed in position relative to the lattice and lower edges rigidly fixed in position relative to the core cover.

Abstract: Core cover plug for a liquid metal-cooled nuclear reactor.It comprises a structure constituted in part by suspension elements fixed to the lower plate of the small rotary plug, and in part by control rod sleeve elements and a conical deflecting plate positioned directly above the core. The suspension elements, which can either be rod sleeves or rigid tie rods, support the sleeve elements by means of one or more grids constituted by intersecting vertical plates. The deflecting plate, which itself carries a group of sampling tubes, is fixed to certain sleeve elements by a connection permitting radial sliding.

Abstract: A rotating, radiation shielded crane system for use in a high radiation test cell, comprises a radiation shielding wall, a cylindrical ceiling made of radiation shielding material and a rotatable crane disposed above the ceiling. The ceiling rests on an annular ledge intergrally attached to the inner surface of the shielding wall. Removable plugs in the ceiling provide access for the crane from the top of the ceiling into the test cell. A seal is provided at the interface between the inner surface of the shielding wall and the ceiling.

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: A liquid metal cooled fast breeder reactor which permits a closer installation of a fuel handling mechanism relative to an upper reactor core structure of the reactor. The fuel handling mechanism has a fuel handling body without a housing, and has a rotational driving device on a rotating plug of a shield plug device of a reactor vessel. The fuel handling mechanism has an aseismatic support extending outwardly from the upper reactor core structure. The fuel handling mechanism is supported, at its upper portion, by the rotational driving device, and secured, at its lower protion, by the aseismatic support.

Abstract: A nuclear reactor refueling system for a liquid metal-cooled fast breeder reactor includes a large rotatable plug (18) eccentrically mounted relative to the reactor core (12), and a small rotatable plug (24) mounted within the large plug (18). A fuel handling machine (28) is rotatably mounted upon the small plug (24), and the eccentric mounting of the large plug (18) permits the fuel handling machine (28) to access all areas of the reactor core (12) as well as a fuel transfer station or port (34) located externally of the reactor core barrel (16) yet internally of the reactor pressure vessel. A unique six-fingered star-shaped upper internals structure (36) is eccentrically mounted upon the large plug (18) so as to be concentrically disposed relative to the core (12) when the reactor is in operation yet permitting access to the central-most fuel assemblies (14) of the core (12) as the large rotatable plug (18) is rotated during refueling operations.

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: Slab for closing a fast neutron nuclear reactor, comprising a first central annular part (10) the diameter of which is substantially equal to the diameter of the reactor vessel (5) and a second peripheral annular part (11) connected to the first part (10) by its outer shell (14). Both parts of the slab are made in the form of steel caissons enclosing concrete. The central part (10) is strengthened by two frusto-conical shells (20, 21). The peripheral part (11) is strengthened by flat axial webs. The inner shell coincides with the outer shell (14) of the central part. The invention applies in particular to fast neutron nuclear reactors cooled with liquid sodium, of an integrated type.

Abstract: Installation for handling the assemblies of a fast neutron nuclear reactor comprising a core located in a vertically axed vessel and constituted by a group of assemblies positioned in a supporting grid, a horizontal slab over the vessel, a large rotary plug in the slab, a small rotary plug in the large rotary plug and off-centered with respect to the latter, and a handling pot or container making it possible to remove the fuel elements from the vessel, wherein the small rotary plug has a handling poker and the large rotary plug positioned coaxially with respect to the core has a handling arm, the poker making it possible to reach a fraction of assemblies, particularly those in the central part of the core and to transfer them into a take-up station of the supporting grid, the assemblies placed in the take-up station, as well as those in the peripheral area downwardly accessible to the handling arm being deposited by the latter in the handling pot or container.

Abstract: The invention relates to a nuclear reactor cooled by a liquid metal contained in a vessel obturated by upper closing means, said latter essentially being constituted by a slab and rotating plugs. The upper closing means comprise at least one circuit for circulation of a cooling gas or liquid, this circuit being provided with means for maintaining the closing means at a homogeneous temperature at least equal to 100.degree. C. and preferably close to 120.degree. C. The invention is applicable to the production of less cumbersome and less expensive fast neutron nuclear reactors.

Abstract: A jacking mechanism for raising the upper internals structure of a liquid metal nuclear reactor which jacking mechanism uses a system of gears and drive shafts to transmit force from a single motor to four mechanically synchronized ball jacks to raise and lower support columns which support the upper internals structure. The support columns have a pin structure which rides up and down in a slot in a housing fixed to the reactor head. The pin has two locking plates which can be rotated around the pin to bring bolt holes through the locking plates into alignment with a set of bolt holes in the housing, there being a set of such housing bolt holes corresponding to both a raised and a lowered position of the support column. When the locking plate is so aligned, a surface of the locking plate mates with a surface in the housing such that the support column is then supported by the locking plate and not by the ball jacks.

Abstract: A nuclear reactor having integral heat exchangers comprises intermediate heat exchangers (35) which are entirely contained within the reactor vessel (1) and bear on the support (4) for the reactor core (5) at the periphery of the latter. Each one of the intermediate heat exchangers (35) is connected to the secondary liquid sodium circuit by a conduit (50) which passes through a slab (8) closing off the top of the reactor. An upper rotating stopper (15) includes an opening (53) of a size which is comparable to that of the cross-section of an intermediate heat exchanger (35), the opening being located at such a distance from the axis of rotation (12) of the stopper that the opening (53) can be brought into vertical alignment with each one of the intermediate heat exchangers (35) in succession. The invention particularly relates to fast neutron reactors which are cooled with liquid sodium.

Abstract: A cable handling system for use in an installation such as a nuclear reactor is disclosed herein along with relevant portions of the reactor which, in a preferred embodiment, is a liquid metal fast breeder reactor. The cable handling system provides a specific way of interconnecting certain internal reactor components with certain external components, through an assembly of rotatable plugs. Moreover, this is done without having to disconnect these components from one another during rotation of the plugs and yet without interfering with other reactor components in the vicinity of the rotating plugs and cable handling system.

Abstract: Tubes or cables designated as ducts and extending through a movable component which is capable of rotational motion about a vertical axis are supported between a fixed point located externally of the movable component and a second point which is located on the vertical axis of rotation of the component and constitutes the extremity of the supporting means. The portions of ducts located between the extremity of the supporting means and the center of rotation of the movable component are guided and maintained in uniformly spaced relation on a ruled surface of revolution about the axis of said movable component so that the duct portions thus form a bundle-type assembly. Means are further provided for securing the lower extremity of the guiding means to the movable component at the center of rotation of this latter.

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.