Classifications

• • G—PHYSICS
  • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
  • G21C—NUCLEAR REACTORS
  • G21C13/00—Pressure vessels; Containment vessels; Containment in general
  • G21C13/02—Details
  • G21C13/032—Joints between tubes and vessel walls, e.g. taking into account thermal stresses
• • G—PHYSICS
  • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
  • G21C—NUCLEAR REACTORS
  • G21C13/00—Pressure vessels; Containment vessels; Containment in general
  • G21C13/02—Details
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16L—PIPES; JOINTS OR FITTINGS FOR PIPES; SUPPORTS FOR PIPES, CABLES OR PROTECTIVE TUBING; MEANS FOR THERMAL INSULATION IN GENERAL
  • F16L13/00—Non-disconnectible pipe-joints, e.g. soldered, adhesive or caulked joints
  • F16L13/02—Welded joints
• • G—PHYSICS
  • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
  • G21C—NUCLEAR REACTORS
  • G21C13/00—Pressure vessels; Containment vessels; Containment in general
• • G—PHYSICS
  • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
  • G21C—NUCLEAR REACTORS
  • G21C7/00—Control of nuclear reaction
  • G21C7/06—Control of nuclear reaction by application of neutron-absorbing material, i.e. material with absorption cross-section very much in excess of reflection cross-section
  • G21C7/08—Control of nuclear reaction by application of neutron-absorbing material, i.e. material with absorption cross-section very much in excess of reflection cross-section by displacement of solid control elements, e.g. control rods
  • G21C7/12—Means for moving control elements to desired position
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E30/00—Energy generation of nuclear origin
  • Y02E30/30—Nuclear fission reactors

Definitions

• the invention relates to a device for moving a control bar of a nuclear water reactor and a method for mounting the device on a vessel cover. under pressure and a method of mounting the device on a tank cover.
• Pressurized water nuclear reactors generally comprise a vessel of cylindrical overall shape arranged with its vertical axis enclosing the core of the nuclear reactor constituted by assemblies of straight prismatic form juxtaposed and placed with their axis parallel to the axis of the vessel .
• the tank has an upper end which is closed by a removable cover generally of hemispherical shape which is fixed on the tank in a watertight manner for cooling the high pressure and high temperature nuclear reactor which fills the tank during operation of the nuclear reactor.
• control rods constituted by clusters of rods made of absorbent material neutrons.
• the displacement of each of the control rods inside the core of the nuclear reactor, to adjust the reactivity of the core, is carried out by a displacement device making it possible to obtain displacements and precise positioning of the following control rod the height of the heart.
• Each of the displacement devices of a control bar comprises a very long control rod (greater than the height of the heart which is itself generally greater than 4 m) which comprises, at one of its longitudinal ends axial, removable means for fixing on the upper part of a control bar and along its length, on its external lateral surface, grooves regularly spaced along the axial direction of the control rod defining a toothing for engaging pawls for holding and moving the mechanisms of the movement device.
• the movement device comprises a closed enclosure which is connected to the tank in a leaktight manner ensuring the support and housing of the movement mechanisms and in which the very long control rod connected to a control bar can move between a position. extraction of the control bar outside the heart and a position for complete insertion of the control bar inside the heart.
• the enclosure of the displacement device comprises an adapter tube fixed inside an opening passing through the cover of the tank in an axial direction of the tank, a tubular casing supporting and containing the electromagnetic mechanisms for moving the bar control fixed in the axial extension of the adapter tube towards the outside of the tank and a sheath allowing to receive the upper part of the control rod during its movements fixed in the axial extension of the casing of the mechanisms towards the outside of the tank .
• the enclosure is fixed in the tank cover in a sealed manner by crimping and welding and the connections between the adapter tube and the casing, on the one hand, and between the casing and the sheath, on the other hand, are made so perfectly waterproof and resistant to water under nuclear reactor cooling pressure.
• the sheath fixed on the end of the casing opposite its end connected to the adapter tube has a first end sealed with a plug and a second open end, at which the sheath is connected coaxially and end to end with the mechanism housing.
• the enclosure in which the control rod moves in the axial direction thus constitutes a completely sealed enclosure extending the tank in the axial direction, above the cover.
• the sealed enclosure of a device for moving a control rod comprises an adapter made of nickel alloy 690 which is fixed in the factory, during the construction of the nuclear reactor on the vessel cover, to the inside an opening passing through the cover, by a welding process with filler metal perfectly controlled as to the metallurgical quality of the weld.
• the adapter has at its free end outside of the tank cover, a expansion which is threaded on its outer surface and the housing of the mechanisms.
• nisms comprises, at its end intended to be assembled to the adapter, a threaded bore corresponding to the threaded part of the adapter, so that the casing of the mechanisms is engaged by screwing on the end part of the adapter, in a perfectly coaxial arrangement with the adapter.
• the seal between the adapter and the mechanism housing is ensured by lips in the form of toroid or cylinder portions integral with the external surface of the adapter and of the mechanism housing in their part, one engaging with the other, the sealing lips each comprising an annular free end surface in a plane perpendicular to the axis of the adapter or of the mechanism housing.
• the two free end surfaces of the sealing lips face each other, after the screwing of the mechanism housing on the end part of the adapter.
• the connection is sealed by welding the two sealing lips at their opposite annular free surfaces by making an annular weld joint in a direction perpendicular to the axis common to the adapter and to the mechanisms housing.
• the tubular sheath the first end of which is generally closed by a plug engaged and fixed to the sheath by welding, has, at a second open axial end for engagement and fixing on the casing, a threaded end part on its external surface intended to be assembled by screwing with a threaded bore part at the corresponding end of the casing opposite its end connected to the adapter tube.
• the seal is formed between these two elements by welding of surfaces facing a sealing lip secured to the outer surface of the mechanism housing and a sealing lip secured to the outer surface of the tubular sheath.
• the sealing lips have a wall in the form of a torus portion and the junction surfaces of the two sealing lips facing each other after screwing the tubular sheath into the casing of the mechanisms are cylindrical surfaces having for axis the axis common to the tubular sheath and the casing.
• the welding of the two sealing lips one on the other can be carried out with an electrode having a direction parallel to the axis of the two parts to be joined, above the sealing lips to form a welded sealing joint having an ⁇ -shaped section.
• this seal is generally referred to as an OMEGA seal.
• the mounting of the control rod displacement devices on the nuclear reactor vessel covers is generally carried out entirely in the factory, the tubular sheath being closed by a welded plug fixed at its first end then screwed by its second end into the corresponding end of the mechanism housing (which were previously mounted on and in the housing).
• the sealing lips are welded together to make the OMEGA seal and the casing is screwed by its end opposite the tubular sheath on the upper part of an adapter. Sealing is then carried out between the adapter and the mechanism casing by welding on opposite sealing lips.
• This welding must be carried out with an electrode perpendicular to the axis of the adapter and of the mechanism housing, that is to say in a horizontal position, the tank cover being in a position similar to its closed position of the tank.
• the production of this welded joint is therefore considerably more delicate than the production of the OMEGA joint.
• pressurized water from the nuclear reactor penetrates inside the sealed enclosure of the mechanism displacement device and comes into contact with the inner surface of the welded joints of the lips of seal.
• the contact of high pressure water at high temperature with the internal part of the welded joints can cause some corrosion, in particular on the lower joint between the adapter and the mechanism housing which is closer to the inside the tank and therefore at a higher temperature.
• the adapter tube and the mechanism housing in one-piece form.
• the casing integral with the adapter tube generally called an integrated casing, is fixed to the tank cover in factory, when mounting and fixing the adapter tube on the tank cover.
• the assembly of the tubular sheath on the casing of the mechanisms which is carried out as described above can be carried out in the factory with careful production and control of the OMEGA seal.
• the object of the invention is therefore to propose a device for moving a bar for controlling the reactivity in the core of a nuclear reactor cooled by pressurized water, inside a tank containing the reactor core closed by a tank cover, comprising a control rod provided with means for fixing the control bar to an axial end, electromechanical means for moving the control rod in an axial direction and a sealed enclosure fixed on the tank cover following a through opening comprising an adapter tube fixed by welding in the opening of the cover and a casing of the mechanisms, tubular, integral with the adapter on which the electromechanical means for moving the control rod are mounted, and a tubular sheath allowing the axial displacement of the control rod between two extreme positions, closed at a first end and open at a second end, fixed in the axial extension of the casing towards the outside, by its second open end, characterized in that the adapter and the casing of the mechanisms are produced in one piece, that the casing of the mechanisms comprises, an axial end opposite to the adapter, an internal thread and a sealing lip in
• the tubular adapter and the casing of the mechanisms are welded end to end in a coaxial arrangement to form an integrated casing fixed to the tank cover via the adapter tube
• - the adapter tube is made of nickel alloy and the casing of the mechanisms is made of stainless steel
• - the tubular sheath is made of stainless steel
• the sealing lips of the integrated casing and the tubular sheath produced in one piece, respectively with the casing and the tubular sheath are made of stainless steel.
• the invention also relates to a method of mounting a device for moving a bar for controlling the reactivity in the core of a nuclear reactor cooled by pressurized water inside a vessel.
• a tank cover comprising a control rod provided with means for fixing the control bar to an axial end, electromechanical means for moving the control rod in an axial direction and a sealed enclosure fixed to the tank cover following a through opening comprising an adapter tube fixed by welding in the opening of the tank cover and a casing of mechanisms, tubular, integral with the adapter on which the electromechanical means for moving the control rod and a tubular sheath allowing the axial displacement of the control rod between two extreme positions, closed at a first end and open at a second end, the car- ter being integral with the adapter and placed in its axial extension towards the outside of the tank and the tubular sheath being fixed in the axial extension of the casing towards the outside, at its second open end, characterized in that carries out mounting and fixing by welding in a through opening of the tank cover of an integrated casing comprising the adapter and the casing of the mechanisms in one piece, which is carried out by screwing the tubular sheath end part threaded
• Figure 2 is a partial sectional view of a tank cover and sealed enclosures of control rod displacement devices according to the invention.
• Figure 3 is an enlarged view of detail 3 of Figure 2.
• Figure 4 is an axial sectional view of an integrated mechanism housing of a displacement device according to the invention.
• Figure 5 is an enlarged sectional view of the sealing lips of the mechanism housing and the tubular sheath of a displacement device according to the invention during an operation for producing the sealing weld.
• FIG. 1 there is seen a device for moving the control rods of a pressurized water nuclear reactor generally designated by the reference 1.
• the adapter 1 is produced according to a prior art described above and has been shown in a mounting position on an adapter tube 2 fixed in a through opening of a cover of a tank of a pressurized water nuclear reactor.
• the adapter 2 constitutes the lower part of the sealed enclosure of the displacement device 1 which further comprises a casing 3 and a tubular sheath 4.
• the adapter 2, the casing 3 and the sheath 4 produced in tubular form are assembled in coaxial arrangements and in axial extension of one another.
• the mechanism housing 3 carries three magnetic coils 5a, 5b and 5c for controlling the mechanisms contained in the mechanism housing 3 allowing the displacement of a control rod 6 in the axial direction common to the adapter and to the housing and to the tubular sheath.
• the control rod 6 has at its lower axial end a means 6a for fixing a control rod of the nuclear reactor.
• the lateral surface of the control rod 6 has grooves defining a toothing 8 for the stepwise movement of the control rod actuated by the mechanisms contained in the casing 3.
• the mechanisms include in particular a retaining pawl 7a and a pawl transfer 7b corn- mandated, respectively, at the opening to release the pawls of the toothing 8 of the control rod, by the windings 5a and 5b arranged around the casing 3.
• the winding 5c is a winding for lifting the control rod (and the control bar fixed to the end of the control rod), when the transfer pawls 7b are engaged in the toothing 8 of the control rod.
• the threaded lower part 4a of the tubular sheath 4 is screwed inside a tapped part corresponding 3a of the mechanism housing 3 then the welding along a weld joint 9 of an O-ring sealing lip 3b of the mechanism housing 3 and of a corresponding sealing lip also of O-shaped 4b of the tubular sheath 4.
• the annular weld joint 9 has for axis the axis common to the tubular sheath 4 and to the mechanism casing 3.
• the weld 9 can be carried out in a preparation workshop comprising means suitable for producing a quality weld .
• the assembly comprising the tubular sheath and the mechanism housing carrying and enclosing the electromechanical control mechanisms is then screwed onto the threaded end part of the adapter 2, the sealing being ensured by welding of surfaces facing each other.
• two sealing lips 2a and 3c produced respectively on the external surface of the adapter and on the casing 3.
• the disadvantage of the mounting method according to the prior art is that the production of the weld between the lips of sealing 2a and 3c is deli- due to the position of the surfaces to be welded, the small thickness of the sealing lips and the fact that the adapter and the mechanism housing 3 are made of different materials (nickel alloy for the adapter and, generally , 304 stainless steel for the mechanism housing 3).
• the cover 10 shows the cover 10 of the tank of a nuclear reactor cooled by pressurized water on which are sealed envelopes of devices for moving control rods.
• the cover 10 comprises a very thick flange 10a which is crossed by openings 11 for the passage of fixing studs for the cover 10 on an upper end flange of a nuclear reactor vessel.
• the cover 10 comprises a central convex part 10b in the form of a spherical cap which is crossed by openings such as 9a and 9b in the direction of the axis 10 'of the cover of the tank which is intended to be fixed in position centered on the 'upper end of the tank, so that the axis 10' of the cover is arranged along the vertical axis of the tank in the service position.
• FIG. 2 there is shown a sealed enclosure of a first device for moving control bars 1a in the fully assembled state and part of an enclosure of a second device for moving control bars 1b without its upper part constituted by a tubular sheath for displacement of a control rod.
• the upper part of the device 1a has also been shown in enlarged form on the left of the figure.
• the adapter tube 12 fixed in the tank cover and the casing 13 of the mechanisms of the movement device are made in one piece and fixed to the tank as a whole, the adapter tube 12 and the casing of the mechanisms 13 constituting an integrated casing which will be generally designated by the reference 15.
• FIG. 4 there is shown, on a larger scale, an integrated casing 15 of the sealed enclosure of a device for moving control rods according to the invention.
• the integrated casing 15 comprises a lower part 12 constituted by an adapter tube of constant diameter which can advantageously be made of a nickel alloy such as alloy 690 resistant to corrosion.
• the upper part of the integrated casing 13 comprises, on the one hand, the casing of the mechanisms proper 13a and a lower part 13b of connection to the adapter 12.
• the tubular adapter 12 is assembled end to end in a coaxial arrangement (according to the axis 16 of the integrated casing) with a section of the lower end portion 13b of the casing 13 having a diameter substantially equal to the diameter of the adapter tube.
• the end-to-end assembly of the adapter tube 12 and the casing 13 is carried out in the factory by a joining process making it possible to produce a high-quality metallurgical assembly between the adapter tube of nickel alloy and the casing of mechanisms 13 which is generally made of 304 stainless steel.
• a single piece is therefore obtained, comprising the adapter tube 12 and the mechanism housing 13 assembled end to end constituting the integrated housing 15.
• the adapter tube 12 is engaged and fixed by welding in a through opening of the tank cover, so that the axis 16 of the integrated casing is parallel to the axis 10 'of the tank cover.
• a thermal sleeve 17 is placed inside the integrated casing 15, then the mechanisms inside the bore of the part. upper part 13a of the integrated casing 15.
• the upper part 13a of the integrated casing is machined so as to receive the windings of the mechanisms on its external surface.
• the integrated casing has a threaded part
• FIG. 3 which is intended to receive a lower threaded part of the tubular sheath 14 which is screwed in a coaxial arrangement inside the integrated casing, as shown in FIG. 2.
• a sealing lip in the shape of a torus portion 14b produced on the outer surface of the tubular sheath, at -above its threaded part 14a of engagement by screwing in the integrated casing comes opposite a lip in the form of a torus portion 13d provided on the upper part of the integrated casing, above the tapped part 13c.
• a tight junction between the tubular sheath 14 and the casing 13 is provided by an annular weld bead 18 joining the two edges facing the lips in the form of toroid portions 14b and 13d.
• the upper end of the tubular sheath 14 is closed by a plug 19 comprising a lifting ring which is screwed into a threaded end part of the sheath 14.
• the weld bead 18 must be made in situ ensuring the seal between the lips 13d and 14b.
• This operation can be carried out either in the factory, during the manufacture of a cover, or on site, in the case of a replacement of a tank cover of a nuclear reactor.
• you can transport between the manufacturing plant and the site and introduce into the reactor building the cover of the tank on which the integrated casings are fixed 15 containing the mechanisms for moving the control rods, the tubular sheaths not being put in place on the integrated housings.
• the total height of the cover is significantly reduced, which considerably facilitates the operations of transport and introduction into the reactor building of the replacement cover.
• the tubular sheaths are supplied independently of the cover comprising the integrated casings and put in place on the site by screwing into the upper ends of the integrated casings.
• the sealing weld bead 18 is produced on site between the lips 13d of the integrated casing and 14b of the tubular sheaths.
• the tubular sheath is dismantled after machining the weld bead joining the sealing lips, the replacement or repair of the mechanisms, then a tubular sheath is replaced by screwing into the integrated casing.
• the weld bead 18 for joining the sealing lips is produced.
• the sealing lips and the method of welding these sealing lips have been adapted so that they can be produced on site without difficulty and with entirely satisfactory production conditions.
• FIG. 5 shows, in an enlarged view, the respective sealing lips 13d of an integrated casing 13 and 14b of a tubular sheath 14, after screwing the tubular sheath 14 into the integrated casing and when the sealing weld joint is made 18.
• the sealing lips 13d and 14b have respective free end surfaces 13'd and 14'b of cylindrical shape which are opposite after screwing of the tubular sheath and which have as axis the axis common to the integrated casing 13 and to the tubular sheath 14 in the assembled position by screwing.
• the lips 14b and 13d have walls delimited by toric surface portions whose cross section, visible in FIG. 6, corresponds to lays about a quarter of a circle.
• the lips 14b and 13d are produced so that there remains an annular space of width I between the free end surfaces facing 14'b and 13'd of the toric lips, when the integrated casing 13 and the tubular sheath 14 have been assembled by screwing.
• the weld joint 18 is produced by placing, between the free facing surfaces 14'b and 13'd of the sealing lips, an annular piece 21 of a metal compatible metallurgically with the metal of the lips 14b and 13d and by performing, using an electrode 22 of an automatic orbital welding machine, the fusion of the part 21 made of filler metal and heating of parts of the lips 14b and 13d in contact with the part 21 to achieve a good metallurgical bond. As shown in FIG.
• the section of the annular piece 21 of filler metal can advantageously have a part of width I which engages practically without play between the lips to be joined by welding and an enlarged part to ensure the maintenance of the part above the lips which is welded.
• the sealing lips 14b and 13d and the welding joint 18 constitute an OMEGA type joint of perfect quality, when an automatic orbital welding machine is used whose conditions were determined beforehand by calibration on samples.
• the seal 21 is made of filler metal generally used for welding stainless steels and the electrode 22 is a tungsten electrode of an orbital TIG welding machine, the fusion of the filler metal 21 being carried out in a gas atmosphere. inert.
• the welding machine comprises means for guiding the welding head comprising the electrode 22 which can be engaged around the tubular sheath and the upper part of the integrated casing, by means of particular support means.
• the welding parameters which are preset include in particular the orbital displacement speed of the tungsten electrode 22, the welding voltage and current and the distance from the tip of the electrode to the upper surface of the annular part 21 in filler metal.
• the adjustment of the automatic welding conditions and the use of a filler metal seal of perfectly defined shape and dimensions relative to the space between the sealing lips makes it possible to produce a welding seal 18 of perfect quality. and perfectly constant along the entire periphery of the sealing lips. We can thus guarantee the production of a welded joint of perfect quality and therefore a perfect seal of the OMEGA type joint.
• the invention therefore makes it possible to mount devices for moving control rods on a cover of a nuclear reactor vessel, with the installation of tubular enclosures on the site of the nuclear reactor, with very good performance of the alignment of the tubular enclosures with respect to the integrated casings fixed on the tank cover and with a very good seal.
• the invention is not limited to the embodiment which has been described. It is thus possible to imagine the use of other types of welding than TIG orbital welding to produce the welded joint of the sealing lips.
• sealing lips having a shape different from that which has been described, from the moment when these sealing lips have junction surfaces facing each other after screwing the tubular sheath of cylindrical shape. and coaxial having for axis the axis common to the integrated casing and to the tubular sheath.
• the invention applies to any nuclear reactor comprising devices for moving control rods having sealed enclosures fixed in openings passing through the cover of the nuclear reactor vessel.

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• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• General Engineering & Computer Science (AREA)
• Plasma & Fusion (AREA)
• High Energy & Nuclear Physics (AREA)
• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Mechanical Engineering (AREA)
• Butt Welding And Welding Of Specific Article (AREA)
• Monitoring And Testing Of Nuclear Reactors (AREA)

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• 2004
  • 2004-02-10 FR FR0401292A patent/FR2859308B1/fr not_active Expired - Lifetime
• 2005
  • 2005-02-03 BR BRPI0506559-3A patent/BRPI0506559A/pt not_active IP Right Cessation
  • 2005-02-03 WO PCT/FR2005/000236 patent/WO2005083718A2/fr not_active Application Discontinuation
  • 2005-02-03 KR KR1020067016067A patent/KR20060129378A/ko not_active Application Discontinuation
  • 2005-02-03 US US10/588,941 patent/US20070140406A1/en not_active Abandoned
  • 2005-02-03 EP EP05717548A patent/EP1714295A2/de not_active Withdrawn
  • 2005-02-03 CN CNA2005800044600A patent/CN1918665A/zh active Pending
• 2006
  • 2006-07-10 ZA ZA200605730A patent/ZA200605730B/xx unknown

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