EP0065922B1 - Primary pump for a pressurized water reactor, having a seal arrangement for its shaft - Google Patents

Primary pump for a pressurized water reactor, having a seal arrangement for its shaft Download PDF

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Publication number
EP0065922B1
EP0065922B1 EP82400929A EP82400929A EP0065922B1 EP 0065922 B1 EP0065922 B1 EP 0065922B1 EP 82400929 A EP82400929 A EP 82400929A EP 82400929 A EP82400929 A EP 82400929A EP 0065922 B1 EP0065922 B1 EP 0065922B1
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EP
European Patent Office
Prior art keywords
seal
chamber
shaft
pressure
upstream
Prior art date
Legal status (The legal status 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 status listed.)
Expired
Application number
EP82400929A
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German (de)
French (fr)
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EP0065922A1 (en
Inventor
Nicolaas Bonhomme
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Areva NP SAS
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Framatome SA
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Publication of EP0065922A1 publication Critical patent/EP0065922A1/en
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
    • F04D29/00—Details, component parts, or accessories
    • F04D29/08—Sealings
    • F04D29/10—Shaft sealings
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
    • F04D29/00—Details, component parts, or accessories
    • F04D29/08—Sealings
    • F04D29/10—Shaft sealings
    • F04D29/106—Shaft sealings especially adapted for liquid pumps
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
    • F04D13/00—Pumping installations or systems
    • F04D13/02—Units comprising pumps and their driving means
    • F04D13/06—Units comprising pumps and their driving means the pump being electrically driven

Definitions

  • the invention relates to a primary pump of a pressurized water nuclear reactor comprising a device for sealing its drive shaft.
  • the cooling circuit of the reactor core, or primary circuit comprises at least two cooling loops each comprising a steam generator and a primary pump.
  • the primary pumps consist of a volute inside which rotates an impeller rigidly attached to the lower end of a drive shaft connected to a motor.
  • Sealing along the drive shaft is ensured by a set of seals arranged in an annular space between the shaft and a housing which surrounds this shaft from its exit from the volute to the drive motor.
  • the sealing device of the drive shaft of the primary pumps generally consists of three seals comprising a fixed part secured to the housing and a mobile part secured to the shaft.
  • the facing surfaces of these sealing elements are either in rubbing contact, the seal is then of the mechanical type, or separated by a layer of fluid in circulation between the surfaces of the seal, the seal is then of the hydrostatic type.
  • the water circulated by the pump is at a very high pressure, of the order of 150 bars.
  • the seal placed most upstream on the drive shaft, that is to say closest to the internal part of the pump, is therefore a hydrostatic seal which allows a significant pressure drop between its upstream part and its downstream part, while the seals arranged downstream are generally mechanical type seals.
  • a high pressure cold water supply circuit makes it possible to bring into the annular space limited by the housing, upstream of the hydrostatic seal, water, part of which is discharged towards the volute of the pump and of which another part supplies the hydrostatic seal leakage current. After passing through the hydrostatic seal, this water is also used to cool the mechanical seals.
  • a pump for a high pressure fluid such as the primary water of a pressurized water nuclear reactor and its drive motor
  • the pump drive shaft is placed in a cylindrical housing which provides an annular space around the shaft receiving the pressurized fluid.
  • a hydrostatic seal is arranged between the drive shaft and the housing, at the end through which the drive shaft exits, in order to prevent leaks of high pressure fluid towards the outside and in particular towards the engine. Coolant of the hydrostatic seal at a pressure slightly higher than the pressure of the fluid circulated by the pump is introduced into the annular space, upstream of the hydrostatic seal, that is to say in the part of the annular space located towards the pump.
  • a hydrostatic seal as used on primary pumps as an upstream seal has for example been described in patents FR-A-1,435,568 and FR-A-2,049,690.
  • this pressure limit is of the order of 14 bars.
  • the cooling water of the reactor is at a pressure of the order of 150 bars and the cold water injected upstream of the hydrostatic seal is at a slightly higher pressure, so that the pressure drop across the hydrostatic seal is very high and generally around 150 bars. The proper functioning of the hydrostatic seal is then ensured.
  • the injection pressure upstream of the hydrostatic seal is no longer sufficient to ensure such a ⁇ P greater than 14 bars and the hydrostatic seal can no longer function correctly.
  • the object of the invention is therefore to propose a primary pump for a pressurized water nuclear reactor comprising a drive shaft, a housing surrounding this shaft so as to provide an annular space around the shaft and a device for '' seal made up of a set of seals placed one after the other along the length of the shaft in the annular space, at least one of which, disposed most upstream, that is to say say towards the inside of the pump, is of the hydrostatic type with liquid leakage between two elements limiting this leakage, one connected to the shaft and the other to the housing, the part of the annular space which is located upstream of the seal and which constitutes a chamber in communication with the internal part of the pump being supplied with water at a pressure higher than the primary pressure of the reactor by a circuit, this primary pump being able to remain in operation even if the pressure of the fluid which is carried out the pumping reaches low values, for example the lower than 26 bars.
  • FIG. 1 we see a pump comprising a pump body or volute 1 pierced with a suction opening 2 and a delivery opening 3.
  • a diffuser 4 Inside this volute is arranged a diffuser 4 inside which rotates the impeller 5 secured to the drive shaft 7 connected to the drive motor of the pump not shown.
  • the upper part of the pump body has a coupling flange 8 making it possible to connect the pump to its motor unit.
  • the shaft 7 is surrounded by a housing 9 which provides an annular space 10 around it.
  • the housing 9 includes a flange 12 for connection to the pump drive motor.
  • seals 14 making it possible to seal along the shaft 7.
  • the shaft 7 carries at its end entering the volute the impeller 5 and exits from this volute at a labyrinth seal 16 at which is also placed a thermal barrier 17 traversed by a cooling coil.
  • the shaft 7 then passes through a bearing 15 ensuring its maintenance and its guidance.
  • the seal 14 disposed most upstream, that is to say towards the inside of the pump, and therefore placed closest to the bearing 15, is of the hydrostatic type, cold water under a pressure slightly higher than the water pressure in the pump being injected by injection pipes 19, into the annular space 10 in which the seals are placed.
  • FIG. 2 we see a schematic representation of the sealing device associated with a primary pump of the same type as the pump shown in FIG. 1.
  • the impeller 25 integral with the end of the shaft 27 is rotated by means of this tree.
  • the shaft passes through a set of two labyrinth seals 26 themselves surrounded by the thermal barrier 28 traversed by a coil 29 supplied with cooling water.
  • the shaft 27 then passes through the annular space 30 delimited by a housing arranged around the shaft along its entire length until it is connected to the drive motor 31.
  • the first seal 33 disposed upstream is of the hydrostatic type with liquid leakage between its rotating part linked to the shaft 27 and its fixed part linked to the housing.
  • the seals 34 and 35 are of the mechanical type comprising two floating parts, one of which is integral with the shaft and the other of the housing.
  • a cold pressurized water supply circuit 36 makes it possible to bring this cold water to a pressure slightly higher than the pressure of the water circulated by the pump, in the annular space 30, upstream of the seal 33.
  • the pressure of this cold water is adjusted by means of a bypass valve 38 and a charge pump 39 placed in bypass on the main line of the circuit 36.
  • a pressure gauge 40 makes it possible to check the pressure in the circuit 36. Lines 41, 42 and 43 make it possible to recycle the water recovered downstream of the seal 33 in the supply circuit 36.
  • the sealing device according to the invention further comprises an auxiliary seal 45 disposed upstream of the hydrostatic seal 33 in the part of the annular space 30 constituting a chamber 46 in communication with the internal part of the volute 21, by means of the labyrinth seals 26.
  • the auxiliary seal 45 is a mechanical seal with rubbing surfaces which separates the chamber 46 into two parts, 46a situated upstream of the seal 45 and 46b situated downstream of the seal 45 and upstream of the seal 33.
  • a pipe 47 makes it possible to join the two parts 46a and 46b of the chamber 46.
  • a valve 48 is arranged on the pipe 47 to isolate or put the two parts of the chamber 46 into communication.
  • a valve 49 is placed in bypass with respect to the valve 48.
  • the auxiliary seal 45 consists of a fixed part 50 secured to the housing 29 and a movable part 51 secured to the shaft 27, the surfaces of which are placed in facing contact are in rubbing contact.
  • the hydrostatic seal 33 consists of a floating lining and a rotating lining separated by a film of water with controlled leakage.
  • the thickness of the water film (water filtered and injected upstream of the seal 33 in the chamber 46b by the circuit 36) is regulated by the geometric profile of the active parts as a function of the pressure in the chamber 46b.
  • the water leak from this seal 33 is partly evacuated through the seal 34 and the rest towards the circuit 36 via the pipe 41 (FIG. 2).
  • the nuclear reactor During normal operation of the pump, the nuclear reactor being in service, it causes the circulation of the water in the primary circuit which is at a pressure of the order of 150 bars and at a temperature above 300 ° C.
  • the valve 48 disposed on the pipe 47 connecting the two parts of the chamber 46 is open. Cold water is brought by the circuit 36 in the part 46b of the chamber, at a pressure slightly higher than the pressure of the primary circuit.
  • the placing in communication of the two parts 46a and 46b of the chamber 46 by the pipe 47 produces a pressure balancing between these two parts of the chamber, so that the pressure difference across the auxiliary seal 45 is negligible. It is therefore possible to provide a rubbing contact between the surfaces facing the seal 45, with a low application pressure so that the wear of this seal is very limited.
  • the seal 45 is cooled by the water of the circuit 36 and works at moderate temperature.
  • the sealing device then operates like the devices of the prior art, the pressure difference across the hydrostatic seal 33 being practically equal to the overpressure of the primary circuit.
  • the pressure in the primary circuit can drop to a low value, for example less than 26 bars.
  • this pressure will be chosen equal to 26 bars so as to be just above the minimum threshold of ⁇ p allowing the operation of the seal 33.
  • the pressure difference between the chamber 46b subjected to a pressure close to 26 bars and the chamber 46a subjected to a pressure close to that of the primary circuit is at most equal to 26 bars, so that the pressure drop of on either side of the joint 45 is at most equal to this value.
  • the seals with rubbing surfaces of the sealing device shown in FIGS. 2 and 3 operate in good conditions because the pressure drops on either side of these seals are weak and the circulation of water coming from in contact with these seals allows lubrication of the friction surfaces.
  • the seal 45 is cooled and lubricated by the water injected by the circuit 36 while the seals 34 and 35 are cooled and lubricated by a part of the water passing through the seal 33. This water allowing the cooling and the lubrication is finally recycled by lines 41, 42 and 43.
  • valve 49 placed in bypass with respect to the valve 48 is designed to remain closed as long as the pressure in the chamber 46a is lower than the pressure in the chamber 46b.
  • This valve opens only in the case of an overpressure in the chamber 46a relative to the chamber 46b. During normal operation of the reactor, this valve therefore remains closed since the circuit 36 introduces water at slight overpressure relative to the water in the primary circuit.
  • the pressure in the chamber 46a becomes higher at the pressure in the chamber 46b which is no longer supplied and the valve 49 opens, so that the water of the primary circuit cooled by the thermal barrier 28 can penetrate into the chamber 46b and perform the cooling and lubrication of seals with rubbing surfaces to replace the cold water injected by circuit 36.
  • an advantage of the device according to the invention is to allow the operation of the primary pumps of a nuclear reactor at low pressure. During the reactor shutdown phases it becomes possible to continue circulating the water in the primary circuit without using auxiliary means to maintain its pressure above 26 bars.
  • the reactor cooling circuit which makes it possible to lower the temperature and the pressure of the primary circuit during the cold shutdown phases of the reactor can be used at pressures below 26 bars, which was not the case. not possible previously since circulation of primary water must be maintained during the shutdown phases.
  • this cooling circuit can be used until the final phases of the cold shutdown of the reactor.
  • the hydrostatic seal disposed upstream of the sealing device can be associated with seals of any type and the number of these seals is not limited.

Description

L'invention concerne une pompe primaire d'un réacteur nucléaire à eau sous pression comportant un dispositif d'étanchéité de son arbre d'entraînement.The invention relates to a primary pump of a pressurized water nuclear reactor comprising a device for sealing its drive shaft.

Dans les réacteurs nucléaires à eau sous pression, le circuit de refroidissement du coeur du réacteur, ou circuit primaire, comporte au moins deux boucles de refroidissement comportant chacune un générateur de vapeur et une pompe primaire.In pressurized water nuclear reactors, the cooling circuit of the reactor core, or primary circuit, comprises at least two cooling loops each comprising a steam generator and a primary pump.

Les pompes primaires sont constituées par une volute à l'intérieur de laquelle tourne une roue à aubes fixée rigidement à l'extrémité inférieure d'un arbre d'entraînement relié à un moteur.The primary pumps consist of a volute inside which rotates an impeller rigidly attached to the lower end of a drive shaft connected to a motor.

L'étanchéité le long de l'arbre d'entraînement est assurée par un ensemble de joints disposés dans un espace annulaire compris entre l'arbre et un boîtier qui entoure cet arbre depuis sa sortie de la volute jusqu'au moteur d'entraînement.Sealing along the drive shaft is ensured by a set of seals arranged in an annular space between the shaft and a housing which surrounds this shaft from its exit from the volute to the drive motor.

Le dispositif d'étanchéité de l'arbre d'entraînement des pompes primaires est généralement constitué de trois joints comportant une partie fixe solidaire du boîtier et une partie mobile solidaire de l'arbre.The sealing device of the drive shaft of the primary pumps generally consists of three seals comprising a fixed part secured to the housing and a mobile part secured to the shaft.

Les surfaces en regard de ces éléments d'étanchéité sont soit en contact frottant, le joint est alors de type mécanique, soit séparées par une couche de fluide en circulation entre les surfaces du joint, le joint est alors du type hydrostatique.The facing surfaces of these sealing elements are either in rubbing contact, the seal is then of the mechanical type, or separated by a layer of fluid in circulation between the surfaces of the seal, the seal is then of the hydrostatic type.

Les joints de type mécanique sont généralement utilisés pour assurer l'étanchéité entre deux zones dont les pressions ne sont pas trop différentes, alors que les joints hydrostatiques peuvent être utilisés dans le cas d'une très grande différence de pression de part et d'autre du joint.Mechanical seals are generally used to seal between two zones whose pressures are not too different, while hydrostatic seals can be used in the case of a very large pressure difference on either side of the joint.

Dans le cas des pompes primaires, l'eau mise en circulation par la pompe est à une pression très élevée, de l'ordre de 150 bars. Le joint disposé le plus en amont sur l'arbre d'entraînement, c'est-à-dire le plus près de la partie interne de la pompe, est donc un joint hydrostatique qui permet une chute de pression importante entre sa partie amont et sa partie aval, alors que les joints disposés en aval sont généralement des joints de type mécanique.In the case of primary pumps, the water circulated by the pump is at a very high pressure, of the order of 150 bars. The seal placed most upstream on the drive shaft, that is to say closest to the internal part of the pump, is therefore a hydrostatic seal which allows a significant pressure drop between its upstream part and its downstream part, while the seals arranged downstream are generally mechanical type seals.

Un circuit d'alimentation en eau froide sous haute pression permet d'amener dans l'espace annulaire limité par le boîtier, à l'amont du joint hydrostatique, de l'eau dont une partie est refoulée vers la volute de la pompe et dont une autre partie fournit le courant de fuite du joint hydrostatique. Après être passée par le joint hydrostatique, cette eau sert également au refroidissement des joints mécaniques.A high pressure cold water supply circuit makes it possible to bring into the annular space limited by the housing, upstream of the hydrostatic seal, water, part of which is discharged towards the volute of the pump and of which another part supplies the hydrostatic seal leakage current. After passing through the hydrostatic seal, this water is also used to cool the mechanical seals.

Dans le brevet US-A-3.215.083, est décrite une pompe pour un fluide à haute pression, tel que l'eau primaire d'un réacteur nucléaire à eau sous pression et son moteur d'entraînement. L'arbre d'entraînement de la pompe est placé dans un boîtier cylindrique qui ménage autour de l'arbre un espace annulaire recevant le fluide sous pression. Un joint hydrostatique est disposé entre l'arbre d'entraînement et le boîtier, à l'extrémité par où sort l'arbre d'entraînement, afin d'éviter des fuites de fluide à haute pression vers l'extérieur et en particulier vers le moteur. Du fluide de refroidissement du joint hydrostatique à une pression légèrement supérieur à la pression du fluide mis en circulation par la pompe est introduit dans l'espace annulaire, en amont du joint hydrostatique, c'est-à-dire dans la partie de l'espace annulaire située vers la pompe.In patent US-A-3,215,083, a pump for a high pressure fluid, such as the primary water of a pressurized water nuclear reactor and its drive motor, is described. The pump drive shaft is placed in a cylindrical housing which provides an annular space around the shaft receiving the pressurized fluid. A hydrostatic seal is arranged between the drive shaft and the housing, at the end through which the drive shaft exits, in order to prevent leaks of high pressure fluid towards the outside and in particular towards the engine. Coolant of the hydrostatic seal at a pressure slightly higher than the pressure of the fluid circulated by the pump is introduced into the annular space, upstream of the hydrostatic seal, that is to say in the part of the annular space located towards the pump.

Un joint hydrostatique tel qu'utilisé sur les pompes primaires comme joint amont a par exemple été décrit dans les brevets FR-A-1.435.568 et FR-A-2.049.690.A hydrostatic seal as used on primary pumps as an upstream seal has for example been described in patents FR-A-1,435,568 and FR-A-2,049,690.

Pour qu'un tel joint hydrostatique puisse fonctionner correctement, c'est-à-dire sans que les éléments disposés en vis-à-vis limitant la fuite viennent en contact, il faut que la chute de pression à travers ce joint hydrostatique, appelée Δp, soit supérieure à une certaine limite.In order for such a hydrostatic seal to function properly, that is to say without the elements arranged facing each other limiting the leak coming into contact, the pressure drop across this hydrostatic seal, called Δp, ie greater than a certain limit.

Dans le cas des pompes primaires utilisées actuellement, cette limite de pression est de l'ordre de 14 bars.In the case of the primary pumps currently used, this pressure limit is of the order of 14 bars.

Dans le cas du fonctionnement normal du réacteur nucléaire, l'eau de refroidissement du réacteur est à une pression de l'ordre de 150 bars et l'eau froide injectée en amont du joint hydrostatique est à une pression un peu supérieure, si bien que la chute de pression à travers le joint hydrostatique est très élevée et généralement voisine de 150 bars. Le bon fonctionnement du joint hydrostatique est alors assuré.In the normal operation of the nuclear reactor, the cooling water of the reactor is at a pressure of the order of 150 bars and the cold water injected upstream of the hydrostatic seal is at a slightly higher pressure, so that the pressure drop across the hydrostatic seal is very high and generally around 150 bars. The proper functioning of the hydrostatic seal is then ensured.

Il n'en est plus de même lorsque la pression du circuit primaire diminue par exemple dans le cas d'un arrêt du réacteur, puisqu'on est amené à diminuer la pression d'injection de l'eau froide lorsque la pression du circuit primaire diminue. Il faut en effet équilibrer les débits injectés dans la volute et dans le joint et ces débits dépendent de la pression du circuit primaire.It is no longer the same when the pressure of the primary circuit decreases for example in the case of a reactor shutdown, since it is necessary to decrease the injection pressure of cold water when the pressure of the primary circuit decreases. It is indeed necessary to balance the flows injected into the volute and into the joint and these flows depend on the pressure of the primary circuit.

En deçà d'une certaine valeur de la pression dans le circuit primaire la pression d'injection en amont du joint hydrostatique n'est plus suffisante pour assurer un tel ΔP supérieur à 14 bars et le joint hydrostatique ne peut plus fonctionner correctement.Below a certain value of the pressure in the primary circuit, the injection pressure upstream of the hydrostatic seal is no longer sufficient to ensure such a ΔP greater than 14 bars and the hydrostatic seal can no longer function correctly.

Dans le cas des pompes primaires utilisées dans les réacteurs nucléaires à eau sous pression actuellement en service, on considère que la pression minimale du fluide primaire en deçà de laquelle on ne peut plus faire fonctionner le joint hydrostatique est de l'ordre de 26 bars.In the case of primary pumps used in pressurized water nuclear reactors currently in service, it is considered that the minimum pressure of the primary fluid below which the hydrostatic seal can no longer be operated is of the order of 26 bars.

Lors de l'arrêt d'un réacteur nucléaire à eau sous pression, il est nécessaire de laisser en fonctionnement au moins une pompe primaire pour permettre la circulation du fluide primaire et assurer un bon refroidissement.When shutting down a pressurized water nuclear reactor, it is necessary to leave at least one primary pump in operation to allow the circulation of the primary fluid and ensure good cooling.

En fin de refroidissement, on est en présence d'eau à 26 bars et à une température de 70 °C. A cette température, on ne peut plus maintenir la pression de 26 bars par utilisation de l'équilibre IiquideNapeur dans le pressuriseur du réacteur et on est obligé d'utiliser des pompes de charge d'un circuit auxiliaire pour maintenir la pression.At the end of cooling, we are in the presence of water at 26 bars and at a temperature of 70 ° C. At this temperature, the pressure of 26 bars can no longer be maintained by using the liquid-vapor equilibrium in the pressurizer of the reactor. and it is necessary to use charge pumps from an auxiliary circuit to maintain the pressure.

Le but de l'invention est donc de proposer une pompe primaire d'un réacteur nucléaire à eau sous pression comportant un arbre d'entraînement, un boîtier entourant cet arbre de façon à ménager un espace annulaire autour de l'arbre et un dispositif d'étanchéité constitué par un ensemble de joints placés l'un à la suite de l'autre suivant la longueur de l'arbre dans l'espace annulaire dont l'un au moins, disposé le plus en amont, c'est-à-dire vers l'intérieur de la pompe, est du type hydrostatique à fuite de liquide entre deux éléments limitant cette fuite reliés l'un à l'arbre et l'autre au boîtier, la partie de l'espace annulaire qui se trouve en amont du joint et qui constitue une chambre en communication avec la partie interne de la pompe étant alimentée en eau à une pression supérieure à la pression primaire du réacteur par un circuit, cette pompe primaire pouvant rester en fonctionnement même si la pression du fluide dont on effectue le pompage atteint des valeurs faibles, par exemple inférieures à 26 bars.The object of the invention is therefore to propose a primary pump for a pressurized water nuclear reactor comprising a drive shaft, a housing surrounding this shaft so as to provide an annular space around the shaft and a device for '' seal made up of a set of seals placed one after the other along the length of the shaft in the annular space, at least one of which, disposed most upstream, that is to say say towards the inside of the pump, is of the hydrostatic type with liquid leakage between two elements limiting this leakage, one connected to the shaft and the other to the housing, the part of the annular space which is located upstream of the seal and which constitutes a chamber in communication with the internal part of the pump being supplied with water at a pressure higher than the primary pressure of the reactor by a circuit, this primary pump being able to remain in operation even if the pressure of the fluid which is carried out the pumping reaches low values, for example the lower than 26 bars.

Dans ce but, le dispositif d'étanchéité suivant l'invention comporte en outre :

  • - un joint auxiliaire du type mécanique dont les pièces frottantes en regard sont liées, l'une à l'arbre et l'autre au boîtier, disposé dans là chambre, en amont du point de jonction du circuit et séparant cette chambre en une partie amont et une partie aval,
  • - et une canalisation disposée entre la partie amont et la partie aval de la chambre, sur laquelle est placée une vanne permettant d'isoler ou de mettre en communication les deux parties de la chambre.
To this end, the sealing device according to the invention further comprises:
  • - an auxiliary seal of the mechanical type, the facing rubbing parts of which are linked, one to the shaft and the other to the housing, arranged in the chamber, upstream of the junction point of the circuit and separating this chamber in part upstream and a downstream part,
  • - And a pipe arranged between the upstream part and the downstream part of the chamber, on which is placed a valve making it possible to isolate or to put the two parts of the chamber in communication.

Afin de bien faire comprendre l'invention, on va maintenant décrire, à titre d'exemple non limitatif, en se référant aux figures jointes en annexe, une pompe primaire d'un réacteur nucléaire à eau sous pression équipée d'un dispositif d'étanchéité suivant l'invention.In order to clearly understand the invention, a description will now be given, by way of nonlimiting example, with reference to the appended figures, a primary pump of a pressurized water nuclear reactor equipped with a device for sealing according to the invention.

  • La figure 1 représente dans une vue en perspective éclatée, une pompe primaire suivant l'art antérieur.Figure 1 shows in an exploded perspective view, a primary pump according to the prior art.
  • La figure 2 représente de façon schématique le dispositif d'étanchéité suivant l'invention.Figure 2 shows schematically the sealing device according to the invention.
  • La figure 3 représente dans une demi-vue en coupe par un plan vertical de symétrie, la partie supérieure d'une pompe primaire pour réacteur nucléaire comportant un dispositif d'étanchéité suivant l'invention.FIG. 3 shows in a half-view in section through a vertical plane of symmetry, the upper part of a primary pump for a nuclear reactor comprising a sealing device according to the invention.

Sur la figure 1 on voit une pompe comportant un corps de pompe ou volute 1 percée d'une ouverture d'aspiration 2 et d'une ouverture de refoulement 3.In FIG. 1 we see a pump comprising a pump body or volute 1 pierced with a suction opening 2 and a delivery opening 3.

A l'intérieur de cette volute est disposé un diffuseur 4 à l'intérieur duquel tourne la roue à aubes 5 solidaire de l'arbre d'entraînement 7 relié au moteur d'entraînement de la pompe non représenté.Inside this volute is arranged a diffuser 4 inside which rotates the impeller 5 secured to the drive shaft 7 connected to the drive motor of the pump not shown.

La partie supérieure du corps de pompe comporte une bride d'accouplement 8 permettant de relier la pompe à son groupe moteur.The upper part of the pump body has a coupling flange 8 making it possible to connect the pump to its motor unit.

L'arbre 7 est entouré d'un boîtier 9 qui ménage autour de celui-ci un espace annulaire 10.The shaft 7 is surrounded by a housing 9 which provides an annular space 10 around it.

A sa partie supérieure le boîtier 9 comporte une bride 12 de raccordement au moteur d'entraînement de la pompe.At its upper part, the housing 9 includes a flange 12 for connection to the pump drive motor.

Dans l'espace annulaire 10 sont disposés des joints 14 permettant d'assurer l'étanchéité le long de l'arbre 7.In the annular space 10 are arranged seals 14 making it possible to seal along the shaft 7.

L'arbre 7 porte à son extrémité pénétrant dans la volute la roue à aubes 5 et sort de cette volute au niveau d'un joint labyrinthe 16 au niveau duquel est également placée une barrière thermique 17 parcourue par un serpentin de refroidissement. L'arbre 7 passe ensuite dans un palier 15 assurant son maintien et son guidage.The shaft 7 carries at its end entering the volute the impeller 5 and exits from this volute at a labyrinth seal 16 at which is also placed a thermal barrier 17 traversed by a cooling coil. The shaft 7 then passes through a bearing 15 ensuring its maintenance and its guidance.

Le joint 14 disposé le plus en amont, c'est-à-dire vers l'intérieur de la pompe, et donc placé le plus près du palier 15, est du type hydrostatique, de l'eau froide sous une pression légèrement supérieure à la pression de l'eau dans la pompe étant injectée par des tubulures d'injection 19, dans l'espace annulaire 10 dans lequel sont placés les joints d'étanchéité.The seal 14 disposed most upstream, that is to say towards the inside of the pump, and therefore placed closest to the bearing 15, is of the hydrostatic type, cold water under a pressure slightly higher than the water pressure in the pump being injected by injection pipes 19, into the annular space 10 in which the seals are placed.

Sur la figure 2, on voit une représentation schématique du dispositif d'étanchéité associé à une pompe primaire du même type que la pompe représentée à la figure 1.In FIG. 2, we see a schematic representation of the sealing device associated with a primary pump of the same type as the pump shown in FIG. 1.

A l'intérieur de la volute 21 de cette pompe comportant une ouverture d'aspiration 22 et une ouverture de refoulement 23, la roue à aubes 25 solidaire de l'extrémité de l'arbre 27 est mise en rotation par l'intermédiaire de cet arbre. A sa sortie de la volute 21, l'arbre passe dans un ensemble de deux joints à labyrinthe 26 eux- mêmes entourés par la barrière thermique 28 parcourue par un serpentin 29 alimenté en eau de refroidissement.Inside the volute 21 of this pump comprising a suction opening 22 and a discharge opening 23, the impeller 25 integral with the end of the shaft 27 is rotated by means of this tree. On leaving the volute 21, the shaft passes through a set of two labyrinth seals 26 themselves surrounded by the thermal barrier 28 traversed by a coil 29 supplied with cooling water.

L'arbre 27 traverse alors l'espace annulaire 30 délimité par un boîtier disposé autour de l'arbre suivant toute sa longueur jusqu'à son raccordement avec le moteur d'entraînement 31.The shaft 27 then passes through the annular space 30 delimited by a housing arranged around the shaft along its entire length until it is connected to the drive motor 31.

A l'intérieur de cet espace annulaire sont disposés le palier 32 permettant le guidage de l'arbre et les joints 33, 34 et 35.Inside this annular space are arranged the bearing 32 allowing the shaft to be guided and the seals 33, 34 and 35.

Le premier joint 33 disposé en amont est du type hydrostatique à fuite de liquide entre sa partie tournante liée à l'arbre 27 et sa partie fixe liée au boîtier.The first seal 33 disposed upstream is of the hydrostatic type with liquid leakage between its rotating part linked to the shaft 27 and its fixed part linked to the housing.

Les joints 34 et 35 sont du type mécanique comportant deux parties flottantes dont l'une est solidaire de l'arbre et l'autre du boîtier.The seals 34 and 35 are of the mechanical type comprising two floating parts, one of which is integral with the shaft and the other of the housing.

Un circuit d'alimentation en eau froide sous pression 36 permet d'amener cette eau froide à une pression légèrement supérieure à la pression de l'eau mise en circulation par la pompe, dans l'espace annulaire 30, en amont du joint 33.A cold pressurized water supply circuit 36 makes it possible to bring this cold water to a pressure slightly higher than the pressure of the water circulated by the pump, in the annular space 30, upstream of the seal 33.

La pression de cette eau froide est réglée grâce à une vanne de dérivation 38 et à une pompe de charge 39 placée en dérivation sur la conduite principale du circuit 36. Un manomètre 40 permet de vérifier la pression dans le circuit 36. Des conduites 41, 42 et 43 permettent de recycler l'eau récupérée à l'aval du joint 33 dans le circuit d'alimentation 36.The pressure of this cold water is adjusted by means of a bypass valve 38 and a charge pump 39 placed in bypass on the main line of the circuit 36. A pressure gauge 40 makes it possible to check the pressure in the circuit 36. Lines 41, 42 and 43 make it possible to recycle the water recovered downstream of the seal 33 in the supply circuit 36.

Le dispositif d'étanchéité suivant l'invention comporte de plus un joint auxiliaire 45 disposé en amont du joint hydrostatique 33 dans la partie de l'espace annulaire 30 constituant une chambre 46 en communication avec la partie interne de la volute 21, par l'intermédiaire des joints labyrinthes 26.The sealing device according to the invention further comprises an auxiliary seal 45 disposed upstream of the hydrostatic seal 33 in the part of the annular space 30 constituting a chamber 46 in communication with the internal part of the volute 21, by means of the labyrinth seals 26.

Le joint auxiliaire 45 est un joint mécanique à surfaces frottantes qui sépare la chambre 46 en deux parties, 46a située à l'amont du joint 45 et 46b situé à l'aval du joint 45 et à l'amont du joint 33.The auxiliary seal 45 is a mechanical seal with rubbing surfaces which separates the chamber 46 into two parts, 46a situated upstream of the seal 45 and 46b situated downstream of the seal 45 and upstream of the seal 33.

Une conduite 47 permet de joindre les deux parties 46a et 46b de la chambre 46. Une vanne 48 est disposée sur la canalisation 47 pour isoler ou mettre en communication les deux parties de la chambre 46.A pipe 47 makes it possible to join the two parts 46a and 46b of the chamber 46. A valve 48 is arranged on the pipe 47 to isolate or put the two parts of the chamber 46 into communication.

Un clapet 49 est placé en dérivation par rapport à la vanne 48.A valve 49 is placed in bypass with respect to the valve 48.

En se reportant à la figure 3, on retrouve les mêmes éléments que ceux représentés sur la figure 2 et avec les mêmes repères, la pompe primaire étant du même type que la pompe représentée sur la figure 1.Referring to FIG. 3, we find the same elements as those represented in FIG. 2 and with the same references, the primary pump being of the same type as the pump represented in FIG. 1.

Sur la figure 3, le circuit 36 n'a cependant pas été représenté pour éviter de compliquer la représentation.In FIG. 3, the circuit 36 has not, however, been shown in order to avoid complicating the representation.

Le joint auxiliaire 45 est constitué d'une partie fixe 50 solidaire du boîtier 29 et d'une partie mobile 51 solidaire de l'arbre 27, dont les surfaces disposées en vis-à-vis sont en contact frottant.The auxiliary seal 45 consists of a fixed part 50 secured to the housing 29 and a movable part 51 secured to the shaft 27, the surfaces of which are placed in facing contact are in rubbing contact.

Le joint hydrostatique 33 consiste en une garniture flottante et une garniture tournante séparées par un film d'eau à fuite contrôlée.The hydrostatic seal 33 consists of a floating lining and a rotating lining separated by a film of water with controlled leakage.

L'épaisseur du film d'eau (eau filtrée et injectée en amont du joint 33 dans la chambre 46b par le circuit 36) est régulée par le profil géométrique des parties actives en fonction de la pression dans la chambre 46b. La fuite d'eau de ce joint 33 est évacuée en partie à travers le joint 34 et le reste vers le circuit 36 par la conduite 41 (figure-2).The thickness of the water film (water filtered and injected upstream of the seal 33 in the chamber 46b by the circuit 36) is regulated by the geometric profile of the active parts as a function of the pressure in the chamber 46b. The water leak from this seal 33 is partly evacuated through the seal 34 and the rest towards the circuit 36 via the pipe 41 (FIG. 2).

On va maintenant décrire, en se référant aux figures 2 et 3, le fonctionnement du dispositif d'étanchéité suivant l'invention.We will now describe, with reference to Figures 2 and 3, the operation of the sealing device according to the invention.

Pendant le fonctionnement normal de la pompe, le réacteur nucléaire étant en service, celle-ci provoque la circulation de l'eau du circuit primaire qui est à une pression de l'ordre de 150 bars et à une température supérieure à 300 °C. La vanne 48 disposée sur la conduite 47 mettant en communication les deux parties de la chambre 46 est ouverte. De l'eau froide est amenée par le circuit 36 dans la partie 46b de la chambre, à une pression un peu supérieure à la pression du circuit primaire. La mise en communication des deux parties 46a et 46b de la chambre 46 par la conduite 47 produit un équilibrage de pression entre ces deux parties de la chambre, si bien que la différence de pression à travers le joint auxiliaire 45 est négligeable. On peut donc prévoir un contact frottant entre les surfaces en regard du joint 45, avec une pression d'application faible si bien que l'usure de ce joint est très limitée. D'autre part, le joint 45 est refroidi par l'eau du circuit 36 et travaille à température modérée.During normal operation of the pump, the nuclear reactor being in service, it causes the circulation of the water in the primary circuit which is at a pressure of the order of 150 bars and at a temperature above 300 ° C. The valve 48 disposed on the pipe 47 connecting the two parts of the chamber 46 is open. Cold water is brought by the circuit 36 in the part 46b of the chamber, at a pressure slightly higher than the pressure of the primary circuit. The placing in communication of the two parts 46a and 46b of the chamber 46 by the pipe 47 produces a pressure balancing between these two parts of the chamber, so that the pressure difference across the auxiliary seal 45 is negligible. It is therefore possible to provide a rubbing contact between the surfaces facing the seal 45, with a low application pressure so that the wear of this seal is very limited. On the other hand, the seal 45 is cooled by the water of the circuit 36 and works at moderate temperature.

Le dispositif d'étanchéité fonctionne alors comme les dispositifs de l'art antérieur, la différence de pression à travers le joint hydrostatique 33 étant pratiquement égale à la surpression du circuit primaire.The sealing device then operates like the devices of the prior art, the pressure difference across the hydrostatic seal 33 being practically equal to the overpressure of the primary circuit.

Lors d'un arrêt du réacteur, la pression du circuit primaire peut s'abaisser jusqu'à une valeur faible, par exemple inférieure à 26 bars. Pour maintenir la pompe en état de marche, Il suffit alors de fermer la vanne 48 et de régler le débit et la pression de l'eau froide injectée par le circuit 36, en agissant sur la vanne 38 et la pompe 39, de façon à maintenir une pression suffisante dans la chambre 46b délimitée par le joint hydrostatique 33 et par le joint auxiliaire 45. De préférence, on choisira cette pression égale à 26 bars de façon à être juste au-dessus du seuil minimal du Δp permettant le fonctionnement du joint 33.When the reactor is shut down, the pressure in the primary circuit can drop to a low value, for example less than 26 bars. To keep the pump in working order, it is then sufficient to close the valve 48 and to regulate the flow rate and the pressure of the cold water injected by the circuit 36, by acting on the valve 38 and the pump 39, so as to maintain sufficient pressure in the chamber 46b delimited by the hydrostatic seal 33 and by the auxiliary seal 45. Preferably, this pressure will be chosen equal to 26 bars so as to be just above the minimum threshold of Δp allowing the operation of the seal 33.

Dans ces conditions, la différence de pression entre la chambre 46b soumise à une pression voisine de 26 bars et la chambre 46a soumise à une pression voisine de celle du circuit primaire est au plus égale à 26 bars, si bien que la chute de pression de part et d'autre du joint 45 est au plus égale à cette valeur.Under these conditions, the pressure difference between the chamber 46b subjected to a pressure close to 26 bars and the chamber 46a subjected to a pressure close to that of the primary circuit is at most equal to 26 bars, so that the pressure drop of on either side of the joint 45 is at most equal to this value.

Ceci est compatible avec un fonctionnement du joint 45 dans de bonnes conditions.This is compatible with operation of the seal 45 under good conditions.

Dans tous les cas, les joints à surfaces frottantes du dispositif d'étanchéité représenté aux figures 2 et 3 fonctionnent dans de bonnes conditions car les chutes de pression de part et d'autre de ces joints sont faibles et la circulation de l'eau venant en contact avec ces joints permet la lubrification des surfaces frottantes. Le joint 45 est refroidi et lubrifié par l'eau injectée par le circuit 36 alors que les joints 34 et 35 sont refroidis et lubrifiés par une partie de l'eau traversant le joint 33. Cette eau permettant le refroidissement et la lubrification est finalement recyclée par les conduites 41, 42 et 43.In all cases, the seals with rubbing surfaces of the sealing device shown in FIGS. 2 and 3 operate in good conditions because the pressure drops on either side of these seals are weak and the circulation of water coming from in contact with these seals allows lubrication of the friction surfaces. The seal 45 is cooled and lubricated by the water injected by the circuit 36 while the seals 34 and 35 are cooled and lubricated by a part of the water passing through the seal 33. This water allowing the cooling and the lubrication is finally recycled by lines 41, 42 and 43.

Le clapet 49 placé en dérivation par rapport à la vanne 48 est conçu pour rester fermé tant que la pression dans la chambre 46a est inférieure à la pression dans la chambre 46b. Ce clapet ne s'ouvre que dans le cas d'une surpression dans la chambre 46a par rapport à la chambre 46b. Pendant le fonctionnement normal du réacteur, ce clapet reste donc fermé puisque le circuit 36 introduit de l'eau en légère surpression par rapport à l'eau du circuit primaire.The valve 49 placed in bypass with respect to the valve 48 is designed to remain closed as long as the pressure in the chamber 46a is lower than the pressure in the chamber 46b. This valve opens only in the case of an overpressure in the chamber 46a relative to the chamber 46b. During normal operation of the reactor, this valve therefore remains closed since the circuit 36 introduces water at slight overpressure relative to the water in the primary circuit.

Lors d'un arrêt du réacteur, la pression étant amenée à une valeur faible dans le circuit primaire et la vanne 48 étant fermée, s'il se produit une avarie sur le circuit d'alimentation 36, la pression dans la chambre 46a devient supérieure à la pression dans la chambre 46b qui n'est plus alimentée et le clapet 49 s'ouvre, si bien que l'eau du circuit primaire refroidie par la barrière thermique 28 peut pénétrer dans la chambre 46b et assurer la fonction de refroidissement et de lubrification des joints à surfaces frottantes en remplacement de l'eau froide injectée par le circuit 36.During a shutdown of the reactor, the pressure being brought to a low value in the primary circuit and the valve 48 being closed, if damage occurs on the supply circuit 36, the pressure in the chamber 46a becomes higher at the pressure in the chamber 46b which is no longer supplied and the valve 49 opens, so that the water of the primary circuit cooled by the thermal barrier 28 can penetrate into the chamber 46b and perform the cooling and lubrication of seals with rubbing surfaces to replace the cold water injected by circuit 36.

On voit donc qu'un avantage du dispositif suivant l'invention est de permettre le fonctionnement des pompes primaires d'un réacteur nucléaire à basse pression. Pendant les phases d'arrêt du réacteur il devient possible de continuer à faire circuler l'eau du circuit primaire sans recourir à des moyens auxiliaires pour maintenir sa pression au-dessus de 26 bars.So we see that an advantage of the device according to the invention is to allow the operation of the primary pumps of a nuclear reactor at low pressure. During the reactor shutdown phases it becomes possible to continue circulating the water in the primary circuit without using auxiliary means to maintain its pressure above 26 bars.

D'autre part le circuit de refroidissement du réacteur qui permet d'abaisser la température et la pression du circuit primaire au cours des phases de mise en arrêt à froid du réacteur peut être utilisé à des pressions inférieures à 26 bars ce qui n'était pas possible antérieurement puisqu'une circulation de l'eau primaire doit être maintenue pendant les phases de mise à l'arrêt.On the other hand, the reactor cooling circuit which makes it possible to lower the temperature and the pressure of the primary circuit during the cold shutdown phases of the reactor can be used at pressures below 26 bars, which was not the case. not possible previously since circulation of primary water must be maintained during the shutdown phases.

Il en résulte que ce circuit de refroidissement pourra être utilisé jusqu'aux phases ultimes de l'arrêt à froid du réacteur.As a result, this cooling circuit can be used until the final phases of the cold shutdown of the reactor.

De façon générale, au joint hydrostatique disposé en amont du dispositif d'étanchéité peuvent être associés des joints d'un type quelconque et le nombre de ces joints n'est pas limité.Generally, the hydrostatic seal disposed upstream of the sealing device can be associated with seals of any type and the number of these seals is not limited.

Claims (3)

1. Primary pump of a pressurised water nuclear reactor incorporating a drive shaft (27), a casing surrounding this shaft (27) so as to form an annular space (30) around the shaft (27) and a sealing device consisting of a set of seals (33, 34, 35) placed one following another along the length of the shaft (27) in the annular space (30), at least one (33) of which, arranged furthest upstream, that is to say towards the inside of the pump, is of the hydrostatic type with leakage of liquid between two components which restrict this leakage and are connected one to the shaft (27) and the other to the casing, the part of the annular space (30) which is upstream of the seal (33) and which forms a chamber (46) communicating with the inner part of the pump being supplied with water at a pressure greater than the primary pressure of the reactor by a supply circuit (36), characterised in that the sealing device additionally incorporates :
- an auxiliary seal (45) of the mechanical type whose facing rubbing parts are connected one to the shaft (27) and the other to the casing, which is arranged in the chamber (46), upstream of the junction point of the circuit (36) and dividing this chamber (46) into an upstream part (46a) and a downstream part (46b),
- and a channel (47) arranged between the upstream part (46a) and the downstream part (46b) of the chamber (46), in which is placed a valve (48) making it possible to isolate or to bring into communication the two parts (46a and 46b) of the chamber (46).
2. Primary pump according to Claim 1, characterised in that a flap valve (49) is placed in the bypass in relation to the valve (48) making it possible to isolate or to bring into communication the two parts (46a and 46b) of the chamber (46), this flap valve (49) being designed to open when the pressure in the chamber part (46a) situated upstream is greater than the pressure in the chamber part (46b) situated downstream of the auxiliary seal (45).
3. Primary pump according to either of Claims 1 and 2, incorporating successively, around its drive shaft (27), from its volute (21) up to its drive motor (31), a thermal barrier (28), a bearing (32), the hydrostatic seal (33), a first mechanical seal with rubbing surfaces (34) and a second mechanical seal with rubbing surfaces (35), characterised in that the auxiliary mechanical seal (45) is placed between the thermal barrier (28) and the bearing (32).
EP82400929A 1981-05-21 1982-05-19 Primary pump for a pressurized water reactor, having a seal arrangement for its shaft Expired EP0065922B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8110128 1981-05-21
FR8110128A FR2506399A1 (en) 1981-05-21 1981-05-21 DEVICE FOR SEALING THE DRIVE SHAFT OF A HIGH PRESSURE FLUID PUMP

Publications (2)

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EP0065922A1 EP0065922A1 (en) 1982-12-01
EP0065922B1 true EP0065922B1 (en) 1985-07-17

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EP82400929A Expired EP0065922B1 (en) 1981-05-21 1982-05-19 Primary pump for a pressurized water reactor, having a seal arrangement for its shaft

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US (1) US4587076A (en)
EP (1) EP0065922B1 (en)
JP (1) JPS57198395A (en)
KR (1) KR880001267B1 (en)
CA (1) CA1193482A (en)
DE (1) DE3264764D1 (en)
EG (1) EG15240A (en)
ES (1) ES8406654A1 (en)
FI (1) FI71394C (en)
FR (1) FR2506399A1 (en)
YU (1) YU96682A (en)
ZA (1) ZA823471B (en)

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GB9008987D0 (en) * 1990-04-21 1990-06-20 David Brown Corp Limited Means for applying a back pressure to a shaft seal
FR2821978B1 (en) * 2001-03-12 2003-06-20 Jeumont Sa METHOD FOR REPAIRING THE LABYRINTH JOINT OF A DIFFUSER OF A PRIMARY PUMP OF A NUCLEAR POWER PLANT
US6599091B2 (en) * 2001-05-29 2003-07-29 James Nagle Modular submersible pump
US20020181325A1 (en) * 2001-06-05 2002-12-05 Engel David J Mixer seal and bearing apparatus and method
FI20050451A (en) * 2005-04-29 2006-10-30 Sulzer Pumpen Ag Centrifugal pump side-plate mounting sealing arrangement and mounting screw thereon
CN101403395B (en) * 2008-11-17 2011-01-12 浙江大农实业有限公司 Pressure-regulating device of high-pressure water pump
DE102013004908B3 (en) * 2013-03-22 2014-02-06 Ksb Aktiengesellschaft Valve and pump arrangement with valve
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Also Published As

Publication number Publication date
FI71394B (en) 1986-09-09
ES512345A0 (en) 1984-07-01
EP0065922A1 (en) 1982-12-01
EG15240A (en) 1987-04-30
JPS57198395A (en) 1982-12-04
CA1193482A (en) 1985-09-17
ES8406654A1 (en) 1984-07-01
FI71394C (en) 1986-12-19
ZA823471B (en) 1983-03-30
FR2506399A1 (en) 1982-11-26
KR880001267B1 (en) 1988-07-16
FR2506399B1 (en) 1983-10-07
YU96682A (en) 1986-08-31
US4587076A (en) 1986-05-06
JPH0361039B2 (en) 1991-09-18
DE3264764D1 (en) 1985-08-22
FI821802A0 (en) 1982-05-20
KR830010308A (en) 1983-12-30

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