Framatome & Cie.

Framatome Gmbh

Jean-Paul Millot

Guy Desfontaines

Patrice Alibran

Michel Babin

Claude Leroy

Jean-Luc Leroy

Pol Dejeux

Eric Gonse

Pierre Deroubaix

Jean Damezin

Michel Trouble

Dominique Hittner

The device comprises a mobile probe which can be displaced inside thimbles. A plurality of ducts (20) for the passage and support of a thimble are disposed in the partitioning (6) of the reactor, around the core (4) along an axial direction and substantially over the entire height of the core. The ducts (20) are distributed circumferentially around the core (4). A plurality of feed-through sleeves in the cover of the vessel are each disposed along the axial extension of a duct (20) for the passage of a thimble. Guide columns each disposed along the axial extension of a duct and each engaged in a feed-through sleeve in the cover of the vessel form, with the corresponding duct (20) and feed-through sleeve, a channel for the reception of a thimble. An arrangement for the guidance, displacement, switching and parking of the mobile probe is disposed outside the vessel (1) and fixed on to the cover of the vessel. This arrangement comprises a plurality of guide tubes each connected at one of its ends to the apparatus for displacement, guidance and switching of the mobile probe and, at its other end, to a thimble. The device with mobile probe enables a readjustment to be carried out to the measurements of neutron flux made by a set of fixed instruments comprising in particular external multi-stage fission chambers (40).

Device and method for the measurement of the neutron flux in the core of

A method is disclosed for controlling a PWR comprising a plurality of control bars selectively and individually positioned in the reactor core. The current value of an operating parameter indicative of the power level (for instance the average temperature of the core) is measured as well as the current positions of the control bars and the axial power offset in the core. When the difference between the current value of the operating parameter and the set value exceeds a predetermined deadband interval or the axial power offset in the core exceeds a reference value, the amount by which the reactivity of the core should be modified is computed. Through a simulation process on a model of said reactor, it is determined which ones of the bars may be moved and which are the amounts of travel to be given to the bars for bringing the difference within the deadband and the offset toward the reference value while minimizing a core enthalpy increase factor.

Method of controlling a pressurized water nuclear reactor

The invention relates to a nuclear reactor with improved efficiency. The nuclear reactor comprises a massive partition (18) of material reflecting high energy neutrons at the circumference of the core (7) of the reactor, two layers (19 and 20) of material absorbing low energy neutrons and containing fertile material arranged one at the lower part and one at the upper part of the core (7) and an assembly of neutron energy spectrum variation rods (27). The rods (27) are associated with mechanisms permitting them to be either fully inserted into the core (7), or fully extracted. These rods (27) consist of a material absorbing low energy neutrons and permit a shift of the neutron spectrum towards the high energies. The invention is particularly applicable to pressurized water nuclear reactors.

Nuclear reactor with improved efficiency

For operating a PWR with spectral shift during all combustion cycles and with undermoderation during some cycles only, the reactor structure is designed for receiving either one of two types of fuel assemblies, having the same geometry. All fuel assemblies have guide tubes for receiving spectral shift clusters containing fissile material but with different elements bundles so as to be able to choose the type of operation.

Spectral shift light water nuclear reactor

A control device for a PWR includes a plurality of clusters arranged for insertion into and removal from the core and each having a plurality of rods connected to a common carrier vertically slidable in a stationary guide structure and connectable to a drive shaft. First clusters contain neutron absorbing material and are each individually associated with electromagnetic actuation means for adjusting the amount of insertion of the associated one of the first clusters. Second clusters contain a different material and are each individually associated with hydraulic actuation means controllable to cause upward and downward movement. A set of one first cluster and one second cluster is associated with some of said fuel assemblies, with the drive shafts of the two clusters in each set being arranged symmetrically with respect to the axis of a single stationary structure located above the associated fuel assembly and arranged for authorizing mutually independent movement of the first and second clusters.

Device for control of the core of a nuclear reactor

Fuel array for an undermoderated nuclear reactor, comprising rods (6) arranged in a prism-shaped casing (1) parallel to the height of this casing (1). The internal surface of each of the walls (2) of the casing (1) is provided with channels (5) each of the channels (5) is located opposite a rod (6) arranged at the periphery of the array. The projecting parts (9) of the walls (2), between two channels (5), occupy part of the space between two peripheral rods (6). In this way, the moderating level remains constant throughout the cross-section of the array. The invention applies, in particular, to pressurized water reactors.

Fuel array for an undermoderated nuclear reactor

A modular lining for adapting the containment to the core of a pressurized water nuclear reactor, consisting of juxtaposed modular blocks (5) placed between the core containment (1) and the outer surface of the core (3). Arranged between the adjacent faces of the blocks (5), there are thin packing pieces (8) maintaining a certain gap between the undrilled solid blocks (5). The blocks (5) are fixed non-contiguously to the core containment (1) by screw devices (10) cooled by water circulation. The invention applies in particular to pressurized water nuclear reactors of improved efficiency and with a varying neutron spectrum.

Modular lining for adapting the containment to the core of a pressurized

The invention relates to a fuel assembly with cooled guide tubes for a nuclear reactor. It consists of a bundle of parallel fuel tubes (1) held in a structure comprising spacer grids, guide tubes (6) and end plates. At least a part of the guide tubes (10) comprises a set of guiding surfaces (16) projecting towards the interior of the tubes (10) over the whole of their length. The projections (16) are formed by embossing of the wall of the tube (10) and permit the guidance of the rod of absorbing material which is moved in the tube and the provision of circulating spaces for the cooling fluid between the tube and the rod of absorbing material. The invention applies in particular to pressurized water reactors and to reactors with neutron spectrum variation.

Fuel assembly with cooled guide tubes for a nuclear reactor

The invention relates to a core for a nuclear reactor cooled with water under pressure. The core comprises a first group of zones (1, 2) extending over its entire height and over a fraction of its transverse section where the fuel rods contain mainly enriched uranium oxide, and a second group of zones (3) inserted between the zones (1, 2) of the first group where the rods contain mainly plutonium. The rods of zones (1, 2) of the first group emit neutrons and maintain the neutron reactions. The energy spectrum of the neutrons is in the thermal region in the zones (1, 2). The rods of the zones (3) of the second group are spaced at a distance which is appreciably smaller than the distance separating the rods of the zones (1, 2) so that the neutrons produced therein are in the high energy region. The invention applies, in particular, to nuclear reactors with spectral shift control.

Core for a nuclear reactor cooled by water under pressure

A nuclear fuel assembly has fuel rods connected to the lower end plate of the assembly. The connecting structure comprises an attachment plate which is superimposed on the lower end plate and which is formed with openings corresponding to the rods. The openings lead out into parallel grooves machined on the lower surface of the plate. Each rod comprises a lower part having three radial branches at 120.degree., each formed with an end extension projecting radially outwardly from the outline of the rod. The extensions engaged in a groove have a height substantially equal to the depth of the groove. Axial fixing and locking against rotation of the rods are thus ensured.

Fuel assembly for a nuclear reactor

Fuel assembly for a pressurized water nuclear reactor, comprising a peripheral zone (1) consisting of a first group of rods (2) containing mainly enriched uranium oxide and a central zone (4) consisting of a second group of rods (5) containing mainly plutonium or uranium depleted in fissile uranium. The rods of the first zone (1) are spaced sufficiently so that the neutrons are slowed down to the thermal region. The rods of the second zone (4) are spaced by a distance which is appreciably smaller so that the neutrons produced in this zone (4) are in the high-energy region. The invention applies, in particular, to nuclear reactors with spectral shift.

Fuel assembly for a pressurized water nuclear reactor

A complementary shutdown device for an undermoderated nuclear reactor, comprising, inside certain arrays (3) of the core, guide tubes (7) of which the cross-section is at least equal to the sum of the cross-sections of three rods (6), and which are surrounded by at least one row of fertile rods (8), and a set of shutdown rods, the cross-section of which matches the cross-section of the guide tubes (7). The shutdown is obtained by allowing the shutdown rods, containing a neutron-absorbing material, to fall into the arrays (3) of the core, in the position of maximum insertion. The invention applies, in particular, to pressurized water nuclear reactors.

Complementary shutdown device for an undermoderated nuclear reactor

Upper internal equipment of a pressurized water nuclear reactor, comprising guide tubes containing guide plates and sleeves adapted to two different types of charge of the reactor core, one for obtaining a thermal neutron spectrum and the other for obtaining an epithermal spectrum. The plates (20) and the sleeves (33, 34) have, for each of the guide tubes, a first set of perforations (31, 36) and a second set of perforations (30,35) for guiding the control rods in either case. The invention applies to a pressurized water reactor operating either as a conventional reactor or as an undermoderated reactor.

Upper internal equipment of a pressurized water nuclear reactor

The invention relates to an actuating device for two clusters of control rods movable vertically in one and the same fuel array of the core of a nuclear reactor. The first cluster, used for running the reactor, is connected to a first actuating rod (2), the movements of which are effected by a mechanism (27, 28, 29, 30, 34). This rod (2) carries hooking fingers (41), the operation of which is effected by a device (45) mounted slidingly on the end of the rod (2). The device (45) causes the closing of the fingers by means of a spring (46), or on the contrary their opening by overstroke movement towards the top of the rod (2). The second cluster remaining fully inserted into the assembly during a part of the operating cycle of the reactor is connected to a second actuating rod (3). This second rod (3), fitted coaxially within the rod (2), forms a piston (3b) in this rod (2) driven for its upward movement by the opening of a pressure relief valve (65) of the fluid-tight enclosure (1) in which the actuating rods (2 and 3) move. The rod (3) in the top position can be connected to the rod (2) by the fingers (41) engaging in a groove (53) of the rod (3). The invention is applicable particularly to nuclear reactors with improved efficiency employing neutron spectrum variation clusters.

Actuating device for two clusters of control rods movable vertically in

When the control parameter (.DELTA.T) is within its deadband, a correction of the axial deviation of power (DA) is effected by movement of at least one group of control rods, when DA is outside a predetermined range or deadband straddling a reference value DA ref. The group which is moved is chosen as a function of the sign of .DELTA.T, of the position of .DELTA.T with respect to its deadband and of the position of the other groups. When .DELTA.T is outside its deadband, the differences between the amplitudes of insertion of the groups participating in the control of the reactor are made to vary by stopping or starting of groups selected as a function of the positions of the groups of rods (G1, G2, N1, N2) in the core of the reactor and of the position of DA either with respect to its deadband if DA is outside this deadband, or with respect to DA ref, if DA is within this deadband. The invention is in particular applicable to pressurized-water nuclear reactors.

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Elancourt, France

Jean-Paul Millot