Abstract: Device for the emergency removal of the heat dissipated by a fast breeder nuclear reactor when shut down, comprising a liquid-liquid heat exchanger immersed in the vessel of the reactor and a liquid-air exchanger for the cooling of the secondary liquid of the latter exchanger. The liquid-liquid comprises a casing composed of a sleeve (18,19) having openings (21,22) for the natural circulation of the cooling fluid of the reactor in contact with the tubes (25) of a nest (20) disposed in the casing of the exchanger. Each of the tubes (25) includes a straight input section and a long straight return section, separated by a helically wound section forming a loop with a low number of turns, inclined to a small extent with respect to the horizontal plane. The coil diameter of the tubes (25) is constant and identical for all the tubes and very slightly less than the interior diameter of the sleeve (18,19).The invention applies in particular to liquid sodium-cooled fast breeder nuclear reactors.

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: Heat exchanger comprising a bundle (35) with straight vertical tubes, whose inner wall serves as the entry duct (46) for the fluid to be heated. This inner wall consists of a first shell (45) having a vertical axis, welded to the lower tube plate (39), a second shell (46) coaxial with the first and similarly fixed to the tube plate (39) and a third shell (47) fixed to the upper tube plate (40) and extended downwards between the two plates (39 and 40). The three shells are joined to the upper part of the exchanger so as to form two chambers (54 and 55) filled with inert gas. The inner shell (45) is joined to an entry duct (48) for the fluid to be heated. The invention applies, in particular, to intermediate heat exchangers of fast neutron nuclear reactors of an integrated type.

Abstract: A device for providing protection against heat and radiation for an intermediate heat exchanger immersed in the vessel of a nuclear reactor. In its upper part, the exchanger has an inner sleeve (8a) inside which a liquid metal circulates, and an outer sleeve (8b), these sleeves being joined by a Y-shaped connector (25). A peripheral space is provided around the outer sleeve (8b), inside the passage (3) through the slab (2) covering the reactor vessel. The protection device comprises a sleeve (27) fixed under the flange (18) and carrying, in its lower part, a solid piece (30) occupying the greater part of the peripheral space around the sleeve (8b). In its upper part, under the flange (18), the sleeve (27) carries a heat insulation means (32) of annular shape. The Y-shaped connector (25) is located in the central part of the sleeve (27), between the solid piece (30) and the heat insulation means (32). The invention is applicable, in particular, to fast neutron nuclear reactors cooled by liquid sodium.

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: Steam outlet connection for connecting the outlet (5) of a tube of the bank of tubes of a steam generator to the pipe (8) connecting it to a steam header. The connection is of the T type with a straight portion (10) closed at one end and a side branch (19) connected to the pipe (8). The closed end of the straight portion (10) has an end wall (14) having a zone of sufficiently slight thickness to permit its perforation for the purpose of injecting a gas into the tube.

Abstract: Annular slab for closing the vessel of a fast nuclear reactor, comprising at least one downwardly divergent frusto-conical sleeve coaxial with the inner and outer sleeves delimiting the slab, dividing the slab envelope into upper and lower parts respectively filled with concrete incorporating metal reinforcements and with concrete for radiation protection.

Abstract: Device for removing cooling fluid and for locating defective fuel arrays in a nuclear reactor in operation by detection of fission products in the cooling fluid. The device consists of at least two independent locating modules (12, 14) and of sampling pipes (17, 24) associated with each of the arrays and connected to the modules. For each of the arrays of the core, there is at least one adjacent array in contact with the first array via one of its lateral faces, connected by its sampling pipe (24) to a locating module (14) which differs from the module (12) to which the first array is connected by its pipe (17). The device is particularly applicable to fast fission nuclear reactors cooled by liquid sodium.

Abstract: Apparatus for the production of steam by heat-exchange between a heat-transfer liquid metal and feed-water, comprising an envelope (1) containing a tube bundle (8) which occupies only part of the internal volume of the envelope with the bundle (8) in which the feed water is passed in. At least two superposed compartments (18, 28), in communication with the internal volume of the envelope (1) by their lower part, are located inside the envelope (1). Each of the compartments (18, 28) communicates with the compartment located thereabove by means of a first tube (23), and with the compartment located therebelow by means of a second tube (21). The compartment (28a) located at the lowest level is fed with inert gas through the establishment of liquid/inert gas interfaces in each of the compartments (18, 28). The invention applies particularly to the steam generators of fast neutron nuclear reactors, in which it is desired to avoid the harmful effects of pressure waves in case of a sodium/water reaction.

Abstract: A junction device between the delivery duct of a primary pump and a duct joined to the core support of a liquid metal cooled fast neutron nuclear reactor comprises a frusto-conical sleeve (6) widening out towards the inlet (2) of the duct joined to the core support, a connecting member (7) joined to the sleeve (6), a sealing device (18) interposed between the outlet end of the sleeve (6) and the inlet (2) of the duct joined to the core support, and an elastic means (6) interposed between the outlet end of the sleeve (6) and a support member joined to the core support. In its central portion the connecting member (7) carries the movable portion (14) of an articulated connection element the fixed portion (16) of which is carried by the pump. On its periphery this member (7) is connected sealingly and articulatedly to the delivery duct of the pump at the level of a spherical surface (9).

Abstract: The annular space (19) delimited by the main vessel (3) and an internal shell (16) is in communication with the zone (15) of the reactor vessel, in which the cold primary liquid is located. The annular space (20) delimited by the shell (16) and by an internal shell (17) is in communication with the lower part of the core (7) via tubes (31). Thus, the cold primary liquid is injected into the space (20), where it circulates from bottom to top, and flows into the space (19), where it circulates from top to bottom while at the same time cooling the main vessel (3).The invention applies, in particular, to fast fission nuclear reactors cooled by liquid sodium.

Abstract: The invention relates to an emergency shut-off device, in the case of leakage, of a tube of a steam generator where the heat of vaporization is contributed by a liquid metal circulating in contact with the outer surface of the tube. The device includes on the terminal portion of the tube connected to the water supply device a tubular bush interposed in the path of the feed water. The bush contains a valve connected to the bush by a rupture part. The breakage of the part under the effect of an increased flow of water, in the case of a leakage, enables the closing of the outlet of the bush. The device includes also, in the terminal portion of the tube connected to the steam collector a bush containing a free valve enabling the steam outlet to be closed in the case of a leakage in the tube. The invention is applied in particular to steam generators of fast breeder nuclear reactors cooled by liquid sodium.

Abstract: Apparatus for loading and unloading fuel assemblies, for fast neutron nuclear reactors, and in particular for groups of fast neutron nuclear reactors cooled by liquid sodium located on one and the same site. The apparatus is removable as a unit and comprises a lock chamber (25) in the form of a removable and transportable vessel. The vessel (25) contains a pivoting ramp (35) allowing transfer of assemblies between the primary ramp (28) and the secondary ramp (29) of the nuclear reactor. Apertures (26) and (27) corresponding to the ramps (28) and (29) respectively are provided in the wall of the vessel (25) and connecting and isolating apparatuses (30) and (31) allow the lock chamber to be placed in communication with the ramps of the reactor, or conversely to be separated from the reactor and isolated.

Abstract: A dismountable and movable device for the transfer of fuel assemblies for a breeder nuclear reactor, comprising a platform (11) mounted for rotation on a support (12) resting on the structure of the reactor. The platform is provided with apertures (19, 20) and carries a hopper (23) which can contain a fuel assembly (5) in vertical position, at the level of one of the apertures (19). The apertures can be brought into correspondence with vertical shafts (14, 15) permitting access to storage (5a) and evacuation (5b) positions for the assemblies (5). The hopper (23) contains a winch (37) for the vertical displacement of the assemblies in the hopper and the shafts when they are in correspondence. The shafts and the platform comprise complementary connecting and sealing devices to assure the connection between the hopper and the shafts. The device is particularly useful for reactors grouped on one and the same site where transport of the assemblies is effected by modules displaced on the site.

Abstract: Apparatus for measuring a parameter relating to at least one substance possibly present in at least one chamber of a set of measurement chambers kept under very low residual pressure. The chambers (12) are connected, on the one hand to a single vacuum pump installation (14), by low conductance elements (18) offering great resistance to the passage of molecules, and on the other hand, to a device (23) for measuring the parameter common to the set of chambers (12) by a selector (20) allowing each of the chambers (12) to be put in communication successively with the device (23) for measuring the parameter. The invention is particularly suited for measurement of the hydrogen content of the liquid sodium in a steam generator of a fast neutron nuclear reactor.

Abstract: A refractory material and the process for its manufacture, designed particularly for contacting molten aluminum. The material is composed of an aggregate constituted by silicon nitride, and a binder. Preferably, the silicon nitride enters into the composition of the material in a proportion comprising between 70% and 80% of the total weight of the final product, and it is in addition obtained by reaction sintering. In the process for manufacturing the material, the silicon nitride and the binder are first mixed dry and then kneaded in a wet kneader.

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: Nuclear reactor exchanger which assures the transfer of heat between two streams of coolant sodium. It includes an outlet connector which channels coolant sodium leaving a bundle of exchanger tubes traversed on the inside by the sodium and immersed externally in coolant sodium, and an inner tubular jacket forming a surface of revolution about a vertical axis and an outer tubular jacket. The wall of the inner jacket has a folded portion distinguished by at least one flank in the form of a crown.

Abstract: An electromagnetic conduction pump for liquid metal, including a part of refractory material; two magnetic circuits each including a horizontal arm embedded in the refractory material, the first having a gap and the other being closed; a rising channel arranged in the refractory material for pumping of the liquid metal passing through the gap in the first magnetic circuit and a closed turn of liquid metal communicating with the rising pumping channel at the place where it passes through the gap. The turn consists of a channel of inverted-U shape the legs of which dip into the bath of metal, one of the legs consisting of a section of the rising channel and the other leg partially interlacing the horizontal arm of the second magnetic circuit.

Abstract: The apparatus comprises an annular cup (5) solid with the component (1) and surrounding its outer wall, a frusto-conical support surface (9) having as axis the vertical axis (2) of the component (1) fixed at the perimeter of its large base to the passage (4) into which the component (1) passes and a closure element (14) with rotational symmetry. The closure element (14) has an upper part (15) which rests on the support surface (9) so as to totally close the annular space (18) at the top and a part directed downwards constituted by a sleeve whose lower part goes into the cup (5). The cup (5) fills up with liquid metal (17) which condenses when the reactor is operating, which ensures sealing between the sleeve (4) and the cup (5).The invention is particularly applicable to fast neutron nuclear reactors cooled by liquid sodium.