Abstract: The invention relates to a paste, preferably for joining components of power electronics modules, the paste comprising a solder powder, a metal powder and a binder, wherein the binder binds solder powder and metal powder before a first heating. According to the invention, the binder is free of flux or is a flux having only low activation. In this way, a joining layer which exhibits only few included voids and good mechanical and electrical stability can be provided between a first and a second component.

Abstract: The invention relates to a plug device for jet pumps installed in nuclear power plant vessels, which comprises two covers (1-2) that form two independent plug units, one fitted on the even pump, which incorporates two plugs (6), and the other on the odd pump of each jet pump assembly, which incorporates three plugs (6), both mounted on a common base (3) at the end of respective arms (4), articulated in the central area, which are actuated by mechanical or hydropneumatic means. The plugs may be blind, in which case they are used to seal the five outlets of the nozzle of the jet pump, or channeled, being used to close the decontamination circuit of the recirculation loops, preventing the cleaning solution from being dispersed in the reactor.

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: A temporary cover is plugged into an open handhole or inspection port in a steam generator or another pressure vessel of a nuclear power plant after bolted covers are removed for maintenance inside the generator or vessel. The temporary cover may be locked to prevent foreign objects from entering the generator or vessel. The cover is vented at inclined angles so that air or gas may pass therethrough but is shielded so that gamma rays, which are the most penetrating type of radiation, are greatly reduced and dispersed away from personnel.

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 nuclear power plant comprising a casing which encloses a primary space, a reactor vessel arranged in the primary space, and a reactor core provided in the reactor vessel. The plant further comprises an upper space provided above the casing. The reactor core is separated from the upper space by means of an openable cover arrangement. The casing is designed in such a manner that the primary space is completely closed against the environment to at least the level corresponding to the most highly located part of the reactor core. The upper space is arranged to house a volume of a liquid sufficiently large to permit the filling of the primary space with the liquid to a level located above the most highly located part of the reactor core.

Abstract: A nuclear reactor having a pressure vessel which is open at the top. The open top of the pressure vessel is closed by a steel dome. A containment, which is open at the top, extends upward from and is joined to the top of the pressure vessel and has an open containment head at the top thereof. The open top of the containment is closed by a steel dome, thereby forming a containment well bounded laterally by the containment, on the bottom by the vessel closure and on the top by the containment closure. The pressure vessel can be a steel-lined prestressed concrete vessel, while the containment is formed by an extension of the prestressed concrete vessel. Alternatively, the pressure vessel and the containment are parts of a unitary steel vessel. Isolation valves are installed on each penetration pipeline to isolate the system in the event of a loss-of-coolant accident.

Abstract: In order to reduce the time and difficulty of disassembling a seal arrangement in a cramped radioactive environment, a nozzle assembly hub is provided with a step bore which receives a seal arrangement, a compression collar, and a retaining nut which presses the seal arrangement into engagement with an inner wall portion of the hub and an outer wall portion of an ICI (in-core instrument) seal plug assembly. The ICI units remain connected to the seal plug assembly during normal disassembly operations. In this manner, the nozzle assembly may be disassembled by merely removing the retaining nut, compression collar, and seal arrangement and lifting the reactor head, along with the nozzle assembly, over the ICI units. The compression collar extends outside the retaining nut such that the collar can be engaged and compressed by an hydraulic loading tool while threading the retaining nut onto the hub.

Abstract: Extrusion-resistant seal assembly for sealing a gap defined between a first structure spaced-apart from a second structure, which first structure and second structure may be an annular first flange and an annular second flange belonging to an instrumentation column of the kind typically found penetrating nuclear reactor pressure vessels. The seal assembly includes an annular retainer disposed in a gap defined between the first flange and the second flange, the first flange and the second flange capable of being moved into close proximity to reduce the gap therebetween. The retainer includes a first surface thereon having a first recess extending therearound. The retainer also has a second surface thereon having a second recess extending therearound. An annular first gasket is retained in the first recess and an annular second gasket is retained in the second recess.

Abstract: A system is directed for remotely securing a canopy seal about a broken omega seal site between the control drive mechanism and the adapter tube of a nuclear reactor vessel so as to contain any radioactive leakage therebetween. The system includes a stalk measuring device for initially measuring the diameter of the adapter tube, a split canopy installation fixture which is adjusted according to the measurement detected by the stalk measuring device to position a two-piece canopy seal about the omega seal site, and a robotic weld arm for performing the upper and lower radial welds about the canopy seal as well as C-shaped vertical welds between the two-piece canopy seal.

Abstract: The device comprises a threaded rod (11a) capable of being screwed into the threaded bore (10') traversing the core (10) and solid, at one of its ends, with a blocking element (11b) the external diameter of which is greater that the diameter of the rod (11a) and which comes into engagement in that end (7) of the casing (4) of the plug (3) opposite the closure base (5) of the plug when the threaded rod (11a) is screwed into the core (10). The blocking element (11b) cooperates with the end of the casing (4) of the plug to achieve the blocking, against rotation and/or translation, of the obturating device (11). The threaded rod (11a) may comprise a transverse orifice in which a braking part is engaged.

Abstract: The feed device comprises a housing (10) of sufficient size to contain a cylindrical piece (15), equipped with a removable cover (20), through which passes a nozzle (24) connected to a compressed-air distribution source (25, 26). A flexible pipe (11) is fastened at one of its ends to the housing (10). A loading unit (12) consisting of a fixed part (28) and of a rotary arm (29) is connected to the end of the flexible pipe (11) opposite the housing (10). The pieces (15) can, in particular, be plugs for plugging the tubes of a steam generator of a pressurized-water nuclear reactor.

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: A fast neutron nuclear reactor having a vessel filled with liquid metal and sealed in its upper part by a box slab having a central opening in which is placed a plug-cover-core overhanging the core of the reactor. The central opening is surmounted by a cell containing the handling and storage mechanism for the plug-cover-core and a mechanism for handling the assemblies. The latter can be moved on annular rails and can be collapsed against the wall of the cell, in order to permit the manipulation of the plug-cover-core. A radial passage connects the cell to a transfer station.

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: 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: 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 liquid metal-cooled nuclear reactor sealing system. The nuclear reactor includes a vessel sealed at its upper end by a closure head. The closure head comprises at least two components, one of which is rotatable; and the two components define an annulus therebetween. The sealing system includes at least a first and second inflatable seal disposed in series in an upper portion of the annulus. The system further includes a dip seal extending into a body of insulation located adjacent a bottom portion of the closure head. The dip seal comprises a trough formed by a lower portion of one of the components, and a seal blade pendently supported from the other component and extending downwardly into the trough. A body of liquid metal is contained in the trough which submerges a portion of the seal blade.

Abstract: Heat exchanger of a nuclear reactor, whose vessel is sealed by a slab, the exchanger being of the type which has within a vertically axed outer ferrule a plurality of heat exchange modules with substantially straight tubes, each of the said modules having a secondary fluid inlet chamber and a secondary fluid outlet chamber and means for introducing and removing the primary fluid with respect to the exchange modules, wherein it comprises a base plate peripherally fixed to the said outer ferrule, means for supporting the outer ferrule by the slab, supporting ferrules for the modules, each ferrule traversing the base plate and being connected on the one hand to the upper end of the module and on the other to the said base plate, a plurality of pipes for the supply and removal of the secondary fluid sealingly traversing the base plate, a supply manifold and a discharge manifold for the secondary fluid positioned within the outer ferrule above the base plate, said manifolds being respectively connected to the supp

Abstract: Arrangements for sealing cover gas from the clearance spaces among primary vessel head structure components in a liquid metal cooled fast breeder nuclear reactor including a dip seal having a trough and blade respectively suspended from adjacent head structure components, such as rotatable plugs, the trough and blade extending downward to an elevation below the operating level of coolant within the vessel. A vent pipe equalizes pressure during power operation among the separate cover gas regions formed by the dip seal.