WO1995026553A1 - Dispositif d'etancheite autour d'un obturateur dans un canal de combustible de reacteur nucleaire - Google Patents

Dispositif d'etancheite autour d'un obturateur dans un canal de combustible de reacteur nucleaire Download PDF

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Publication number
WO1995026553A1
WO1995026553A1 PCT/SE1994/000281 SE9400281W WO9526553A1 WO 1995026553 A1 WO1995026553 A1 WO 1995026553A1 SE 9400281 W SE9400281 W SE 9400281W WO 9526553 A1 WO9526553 A1 WO 9526553A1
Authority
WO
WIPO (PCT)
Prior art keywords
sealing device
sealing
plug
fuel channel
graphite
Prior art date
Application number
PCT/SE1994/000281
Other languages
English (en)
Inventor
Olle Eriksson
Original Assignee
Abb Atom Ab
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Abb Atom Ab filed Critical Abb Atom Ab
Priority to PCT/SE1994/000281 priority Critical patent/WO1995026553A1/fr
Publication of WO1995026553A1 publication Critical patent/WO1995026553A1/fr

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Classifications

    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21C—NUCLEAR REACTORS
    • G21C3/00—Reactor fuel elements and their assemblies; Selection of substances for use as reactor fuel elements
    • G21C3/02—Fuel elements
    • G21C3/04—Constructional details
    • G21C3/06—Casings; Jackets
    • G21C3/10—End closures ; Means for tight mounting therefor
    • 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 refers to a sealing device in a nuclear reactor of graphite-moderated light water-cooled type. More precisely, the invention refers to a sealing device arranged around a plug, which in its turn is arranged in a fuel channel where the sealing device is intended to seal between the plug and the channel.
  • a graphite-moderated light water-cooled nuclear reactor comprises a plurality of fuel assemblies, each fuel assembly comprising a plurality of fuel rods in the form of sealed Zircaloy tubes which are filled with uranium dioxide pellets. Further, each fuel assembly is enclosed by a fuel channel. A plurality of fuel channels are arranged in a graphite stack which moderates the neutrons.
  • each fuel channel Removal of irradiated fuel elements, their handling and charge of fresh elements are performed by means of a refuelling machine working from the upper portion of each fuel channel.
  • the upper part of each channel is provided with a plug. Between the fuel channel and the plug a gap arises.
  • a sealing device is arranged in the gap to prevent leakage of cooling water through the gap.
  • the sealing device is positioned between sealing surfaces arranged on the outer surface of the plug and the inner surface of the channel, respectively.
  • a known sealing device is formed from a plurality of metal rings, each having a cross section formed, in principle, as an inverted U and a plurality of correspondingly shaped rings of asbestos which are arranged between the metal rings in such a way that one asbestos ring separates two metal rings. Both the metal rings and the asbestos rings have a sealing effect.
  • the lower end of the plug is provided with a gland.
  • the gland is arranged in such a way that, when the plug is tightened, the gland presses the metal rings in the axial direction so that the metal rings, as well as the sealing as a whole, due to the axial force transformed to a radial selaing pressure, expand the sealing device in the radial direction effecting sealing between the sealing surfaces.
  • the problem is that the known sealing device, arranged between the plug and the channel, leaks, at least after some refuellings which require untightening and retightening of plugs in the reused fuel channel.
  • the problem is due to the fact that the metal rings during sealing are pressed by the sealing pressure in the radial direction towards the metal channel and the metal plug, using the principle metal against metal sealing.
  • the metal rings cause damage to the sealing surfaces due to cold hardening effects that occur.
  • the sealing surface on the fuel channel wall is more or less damaged and the sealing effect is no longer present or at least not satisfying. Since there are many fuel channels, there are many potentially leaking regions.
  • FIG. 1 schematically shows a nuclear reactor 1 of graphite- moderated light water-cooled type.
  • the reactor 1 comprises a plurality of fuel assemblies 2, each fuel assembly 2 containing a plurality of fuel rods 3 in the form of sealed Zircaloy tubes which are filled with uranium dioxide pellets (not shown) .
  • each fuel assembly 2 is enclosed by a fuel channel 4.
  • a plurality of fuel channels 4 are arranged in a graphite stack 5 which moderates the neutrons.
  • the light water is circulated through the channels .
  • the heat from the fuel assemblies during the fission process forms a mixture of water and saturated steam.
  • the mixture is transported to a steam separator 7 where the steam is separated from the water and then fed to a turbine 8.
  • Figure 2a schematically shows the upper part of the fuel channel 4, a plug 9 arranged and tightened in the fuel channel 4, and a sealing device 10, according to prior art, arranged in a gap 11 provided between the fuel channel 4 and the plug 9. Sealing surfaces 12, 13 are arranged on the outer surface of the plug 9 and the inner surface of the channel 4, respectively.
  • the lower end of the plug 9 is provided with a gland 14.
  • the gland 14 is arranged in such a way that, when the plug 9 is tightened, the gland 14 is pressed against the sealing device 10 in the axial direction so that the sealing device 10 expands in the radial direction effecting sealing pressure between the sealing surfaces 12, 13.
  • FIG 2b schematically shows the sealing device 10, according to prior art, before tightening.
  • the sealing device 10 comprises a plurality of metal rings 15, each having a cross section in principle shaped as an inverted U and a plurality of rings 16 formed of asbestos.
  • the asbestos rings 16 are arranged between the metal rings 15 in such a way that one asbestos ring 16 separates two metal rings 15.
  • Figure 2c schematically shows the sealing device 10, according to the prior art, during tightening. During tightening, the metal rings 15, due to the axial force via the plug 9, as well as the asbestos rings 16, are expanded in the radial direction.
  • the plug 9 Upon tightening, the plug 9 is placed in the fuel channel 4 and the upper part 9c of the plug is rotated.
  • the plug 9 comprises an outer nut 17 and an inner screw 18.
  • the nut 17 is secured to the screw 18 by two break pins 19 (pins 19 are already broken in Figure 2a) .
  • the nut 17 in its turn is rotated together with the break pins 19 and the parts 9a, 9b and 9c of the plug 9, until the nut 17 stops against a facing surface 20 in the fuel channel 4, whereby the pins 19 break.
  • the rotation of the part 9a and 9c of the plug 9 is continued, as well as its movement downwards.
  • the screw 18 is rotated until the plug 9, i.e.
  • the gland 14 reaches the sealing device 10 resting on a heel 21, said heel being arranged on the plug 9, part 9a, whereby the rotation stops and the plug 9 is arranged in its sealing position.
  • the received force from the rotation stop in the axial direction is transformed via the sealing device 10 into a sealing pressure in the radial direction
  • the part 9c of the plug 9 Upon untightening, the part 9c of the plug 9 is turned the other way around. The plug 9 moves upwards and separates the gland 14 from the sealing device 10. A flange 22, which is arranged around the part 9c of the plug 9 reaches the nut 17 and causes the nut 17 to rotate whereby the plug 9 (parts 9a, 9b and 9c) is free to move upwards and leave the fuel channel .
  • the object of the invention is to provide a sealing device for sealing between a fuel channel and a plug arranged in the upper part of the fuel channel in a nuclar reactor of graphite- moderated light water-cooled type.
  • a further object of the invention is to provide a sealing device with a sufficient sealing effect both before and after a certain number of untightenings and retightenings of plugs in the reused fuel channels.
  • a sealing device is formed of one or more annular bodies arranged in the axial direction one after the other and making direct contact with each other. Each body is plastically deformable for transforming the force in the axial direction obtained via the plug into a sealing pressure in the radial direction achieving a sealing effect of the sealing device. At least that part of the sealing device which is arranged facing the sealing surfaces is made of a monolithic sealing material, i.e. the part of the sealing device which is arranged facing the sealing surfaces is made of one and the same material. The monolithic sealing material achieves a uniform surface pressure. Further, at least part of the sealing material is plastically deformable in such a way that the axial force, provided via the plug, is converted into radial sealing pressure causing the sealing device to expand in the radial direction and provide a tight sealing between surfaces.
  • the sealing material can, for example, be graphite, asbestos, silver or a metallic ring with a silver or graphite coating.
  • the sealing device can at its upper and/or lower parts comprise means, for example metal strips, for preventing, during tightening, the annular body or bodies from trickling into the gap between the plug and the channel. These means are not involved for sealing purposes.
  • sealing device according to the invention is that sealing effect is achieved after a certain number of untightenings and retightenings of plugs in the reused fuel channel, since no damaging hard-metal parts are involved for sealing purposes.
  • a further advantage is that a sealing device according to the invention can be arranged in existing reactors without certain modifications of the fuel channels or the plugs.
  • Figure 2a according to prior art comprises an area surrounded by a broken line. This area is shown in greater detail in Figures 3-7.
  • Figure 3 shows a sealing device according to the invention.
  • Figure 4a shows an alternative of an embodiment of a sealing device according to the invention provided with an upper and a lower metal strip.
  • Figure 4b shows an alternative embodiment of the sealing device in Figure 4a, where the sealing device is arranged in three annular bodies.
  • Figure 5 shows an alternative embodiment of a gland with an edge which has a pointed cross section and a sealing device where only the lower part is provided with a metal strip.
  • Figure 6 shows a further alternative of an embodiment of a sealing device according to the invention provided with an upper metal strip and a lower vaulted cross section.
  • Figure 7 shows a further alternative of an embodiment of a sealing device according to the invention where the plastically deformable part and the monolithic part are separated and made of different materials.
  • FIG 3 shows schematically and in a cross section the sealing device 10 according to the invention.
  • the sealing device 10 comprises one annular body, of which the part arranged facing the sealing surfaces is made of a monolithic sealing material.
  • the body also comprises a part which is plastically deformable in such a way that the axial force provided via the plug 9 is transformed into radial sealing pressure providing pressure in the radial direction to such an extent that the sealing device 10 is tight.
  • FIG 4a shows schematically and in a cross section an alternative of an embodiment of a sealing device 10 according to the invention.
  • This sealing device 10 is formed as an annular body and made of graphite.
  • the sealing device 10 is provided with an upper and a lower metal strip 23 preventing the graphite from trickling out into the gap 11 between the sealing surfaces 12, 13 below and above the sealing device 10, since the graphite has properties similar to a fluid.
  • These metal strips 23 do not have any sealing effect and have no harmful effect on the sealing surfaces 12, 13.
  • the fact that the graphite has a lubricating effect also prevents the metal strips 23 from damaging the sealing surfaces 12, 13.
  • Figure 4b shows an alternative embodiment of the sealing device in Figure 4a.
  • This sealing device is arranged in three annular bodies 10a, 10b, 10c. This embodiment is preferable when the sealing device is made of graphite only.
  • This embodiment is also provided with metal strips 23 at the upper and the lower parts, respectively.
  • FIG. 5 shows schematically and in a cross section an alternative of an embodiment of a sealing device 10 according to the invention.
  • This sealing device 10 is shaped as an annular body and made of graphite.
  • the sealing device 10 is provided with a lower metal strip 23 only.
  • the upper part of the sealing device 10 is adapted to receive a gland 14 which is provided with a wedge-shaped edge 14a for exerting a radial sealing pressure in the sealing device.
  • FIG. 6 shows schematically and in a cross section an alternative of an embodiment of a sealing device according to the invention.
  • This sealing device 10 is shaped as an annular body and made of graphite.
  • the sealing device 10 has an upper metal strip 23 which has a plane view in the radial direction and a lower metal strip 23 which has a vaulted cross section.
  • the monolithic and the plastically deformable part are either the same part or different parts depending on which material/s is/are chosen.
  • a preferred material to use for the monolithic part is graphite.
  • the graphite is also preferred as the material in the plastically deformable part.
  • Other usable materials for monolithic and/or plastically deformable parts are asbestos and silver. According to Figure 7 it is also possible to have different combinations where the plastically deformable part and the monolithic parts are separated and of different materials, for example an inner plastically deformable part lOd consisting of metal which is covered by an outer monolithic part lOe of silver or graphite.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Plasma & Fusion (AREA)
  • General Engineering & Computer Science (AREA)
  • High Energy & Nuclear Physics (AREA)
  • Gasket Seals (AREA)

Abstract

L'invention concerne un dispositif d'étanchéité (10) dans un réacteur nucléaire modéré au graphite et refroidi à l'eau légère (1). Le réacteur (1) comprend une pluralité de canaux de combustible (4) et chaque canal (4) enferme un obturateur (9) au niveau de sa partie supérieure. Un espace (11) se trouve entre ledit canal de combustible (4) et ledit obturateur (9) et des surfaces d'étanchéité (12, 13) sont disposées respectivement, de façon à correspondre entre elles, sur la partie intérieure du canal de combustible (4) et sur la partie extérieure de l'obturateur (9). Le dispositif d'étanchéité (10) se trouve dans l'espace (11) entre lesdites surfaces d'étanchéité (12, 13) et il est caractérisé par le fait qu'il est composé d'un ou de plusieurs corps annulaires disposés successivement dans un sens axial en contact réciproque direct. Chaque corps est déformable plastiquement, de façon à transformer la force, dans un sens axial, obtenue par l'intermédiaire de l'obturateur (9) en pression d'étanchéité dans le sens radial, ce qui permet au dispositif (10) d'exercer un effet d'étanchéité. De plus, le dispositif d'étanchéité (10) est caractérisé par le fait qu'il est au moins partiellement monolithique au niveau de sa partie opposée aux surfaces d'étanchéité (12, 13).
PCT/SE1994/000281 1994-03-29 1994-03-29 Dispositif d'etancheite autour d'un obturateur dans un canal de combustible de reacteur nucleaire WO1995026553A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
PCT/SE1994/000281 WO1995026553A1 (fr) 1994-03-29 1994-03-29 Dispositif d'etancheite autour d'un obturateur dans un canal de combustible de reacteur nucleaire

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/SE1994/000281 WO1995026553A1 (fr) 1994-03-29 1994-03-29 Dispositif d'etancheite autour d'un obturateur dans un canal de combustible de reacteur nucleaire

Publications (1)

Publication Number Publication Date
WO1995026553A1 true WO1995026553A1 (fr) 1995-10-05

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Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/SE1994/000281 WO1995026553A1 (fr) 1994-03-29 1994-03-29 Dispositif d'etancheite autour d'un obturateur dans un canal de combustible de reacteur nucleaire

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CH382863A (de) * 1959-03-11 1964-10-15 Atomic Energy Authority Uk Einrichtung zum Abschliessen der Bohrung eines Rohres, insbesondere des Standrohres eines Kernreaktors
GB1154780A (en) * 1967-05-03 1969-06-11 Commissariat Energie Atomique Device for Hermetically Closing a Nuclear Reactor Fuel Element
SE381358B (sv) * 1974-11-22 1975-12-01 Babcock & Wilcox Ag Tetning for tillslutningen pa tryckkerl
EP0164524A1 (fr) * 1984-05-14 1985-12-18 Combustion Engineering, Inc. Joint d'étanchéité limite pour organe de pénétration dans une cuve
EP0244669A2 (fr) * 1986-05-05 1987-11-11 Combustion Engineering, Inc. Pénétration d'un tube d'instrument pour cuves à haute pression

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CH382863A (de) * 1959-03-11 1964-10-15 Atomic Energy Authority Uk Einrichtung zum Abschliessen der Bohrung eines Rohres, insbesondere des Standrohres eines Kernreaktors
GB1154780A (en) * 1967-05-03 1969-06-11 Commissariat Energie Atomique Device for Hermetically Closing a Nuclear Reactor Fuel Element
SE381358B (sv) * 1974-11-22 1975-12-01 Babcock & Wilcox Ag Tetning for tillslutningen pa tryckkerl
EP0164524A1 (fr) * 1984-05-14 1985-12-18 Combustion Engineering, Inc. Joint d'étanchéité limite pour organe de pénétration dans une cuve
EP0244669A2 (fr) * 1986-05-05 1987-11-11 Combustion Engineering, Inc. Pénétration d'un tube d'instrument pour cuves à haute pression

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