Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
  • G01M3/00—Investigating fluid-tightness of structures
  • G01M3/02—Investigating fluid-tightness of structures by using fluid or vacuum
  • G01M3/26—Investigating fluid-tightness of structures by using fluid or vacuum by measuring rate of loss or gain of fluid, e.g. by pressure-responsive devices, by flow detectors
  • G01M3/32—Investigating fluid-tightness of structures by using fluid or vacuum by measuring rate of loss or gain of fluid, e.g. by pressure-responsive devices, by flow detectors for containers, e.g. radiators
  • G01M3/3236—Investigating fluid-tightness of structures by using fluid or vacuum by measuring rate of loss or gain of fluid, e.g. by pressure-responsive devices, by flow detectors for containers, e.g. radiators by monitoring the interior space of the containers
  • G01M3/3245—Investigating fluid-tightness of structures by using fluid or vacuum by measuring rate of loss or gain of fluid, e.g. by pressure-responsive devices, by flow detectors for containers, e.g. radiators by monitoring the interior space of the containers using a level monitoring device
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
  • G01M3/00—Investigating fluid-tightness of structures
  • G01M3/02—Investigating fluid-tightness of structures by using fluid or vacuum
  • G01M3/04—Investigating fluid-tightness of structures by using fluid or vacuum by detecting the presence of fluid at the leakage point
  • G01M3/16—Investigating fluid-tightness of structures by using fluid or vacuum by detecting the presence of fluid at the leakage point using electric detection means
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
  • G01M3/00—Investigating fluid-tightness of structures
  • G01M3/02—Investigating fluid-tightness of structures by using fluid or vacuum
  • G01M3/04—Investigating fluid-tightness of structures by using fluid or vacuum by detecting the presence of fluid at the leakage point

Definitions

• the invention relates to a detector for the presence of liquid in an element of an industrial installation and the use of this detector for detecting a leak, in particular on an instrumentation duct of a nuclear reactor.
• Pressurized water nuclear reactors have a core consisting of prismatic assemblies arranged vertically and resting on a core support plate, inside the reactor vessel.
• the instrumentation guide duct comprises a guide tube connecting a measurement room at the bottom of the reactor vessel, at the level of a sleeve for crossing the bottom of the vessel, and a vertical channel passing through the lower internal equipment of the reactor in the alignment of the guide tube of a fuel assembly into which the thermowell is introduced.
• the internal volume of the thermowell is subjected to a pressure which corresponds substantially to atmospheric pressure.
• the internal volume of the guide tube around the thermowell is, however, subjected to a pressure equal to the operating pressure of the reactor, that is to say a pressure of the order of 155 bars.
• a device In the measurement room, a device, called a nozzle, ensures the seal between the internal volume of the guide tube and the thermowell which extends beyond the nozzle.
• thermowell It is important to check that the joints of the nozzle ensuring the seal between the thermowell and the internal wall of the guide tube do not have any defects likely to cause leaks of coolant from the reactor in the measurement room.
• the open end of the thermowell is sometimes fitted with a ball valve, the function of which is to prevent coolant from leaking into the measuring room if the thermowell is pierced.
• This valve can only work in the case where the flow detector and its cable are not introduced inside the thermowell. When the flow detector and its cable are not in the thermowell, a motorized valve is closed automatically to close the open end of the thermowell.
• detection devices of known type which include two electrodes connected to a low voltage electrical circuit. When both electrodes are immersed in a liquid, contact is made between the electrodes to control a circuit which delivers an alarm signal. These devices are generally fixed on the body of the nozzle, inside the measurement room, so that the electrodes are in the internal space of the nozzle in which the coolant has flowed, in the event of flight.
• Such devices have the disadvantage of triggering nuisance alarms. Indeed, the temperature of the measurement room is relatively high, generally of the order of 25 “C and, at this temperature, the humidity of the air condenses on different parts of the instrumentation conduits and in particular, in the internal space of the nozzle, on the electrodes of the detection device.
• the electrodes which are very close to each other are easily brought into contact by the water which has condensed, so that the device delivers an alarm signal when there is no leak on the corresponding instrumentation pipe.
• the object of the invention is therefore to propose a detector for the presence of a liquid in an internal space of an element of an industrial installation, so as to detect a possible leak of liquid in the installation, this detector making it possible to '' avoid false alarms and perform detection regardless of the physical properties of the liquid.
• the detector according to the invention comprises a detector body delimiting a chamber, means for connecting the detector body to the element of the industrial installation so as to put the detector chamber and the space in communication internal of the element by fixing the detector body to the element and means for detecting the exceeding of a liquid level in the detector chamber.
• the detector comprises a float placed inside the chamber and the detection means are actuated by the movement of the float in the case where the detector chamber receives a leaking liquid. -.
• the invention applies in particular but not exclusively to the detection of leaks on an instrumentation pipe of a pressurized water nuclear reactor.
• FIG. 1 is a schematic elevational view in partial section of the building of a pressurized water nuclear reactor containing the reactor vessel and the instrumentation means of the vessel.
• Figure 2 is a side elevational view of an end portion of an instrumentation conduit placed in the measurement room.
• FIG. 3 is an enlarged sectional view of the nozzle of the instrumentation duct shown in FIG. 2.
• Figure 4 is an elevational view of a leak detector which may occur in the instrumentation conduit, produced according to the prior art.
• Figure 5 is a sectional view of a detector according to the invention.
• FIG. 6 is an exploded perspective view of the various components of the detector shown in FIG. 5.
• FIG. 1 there is shown the vessel 1 of a pressurized water nuclear reactor arranged inside a vessel well 2 in the lower part of the safety building 3 of a pressurized water nuclear reactor .
• the tank 1 encloses the core 4 of the reactor constituted by fuel assemblies into which the thermowells can be introduced inside guide tubes arranged vertically.
• Probes attached to the end of telescopic cables can be moved inside the thermowells to make neutron flux measurements or temperature measurements inside the core, from a measurement room 5 placed in an adjacent position relative to the tank well 2.
• Instrumentation guide conduits such as 6 provide the junction between the instrumentation room 5 and the bottom of the tank la at which the instrumentation conduits 6 are connected to sleeves crossing the bottom of the tank la.
• a manual safety valve 7 and a nozzle 8 are placed on each of the instrumentation guide conduits.
• thermowell The end 10 of the thermowell is accessible inside the measuring room 5 and the means 9 for closing automatic steps are arranged on an extension 16 of the thermowell, downstream of the nozzle 8.
• the assembly comprising the guide duct, the elements fixed to this duct in the instrumentation room, the thermowell, its extension and the extension means for closing constitutes a line of instrumentation of the reactor associated with an assembly of fuel.
• FIG. 2 shows on a larger scale the part of the instrumentation guide duct disposed inside the measurement room 5.
• the guide duct passes through the concrete wall of the instrumentation room, in a leaktight manner, inside a bushing 11 fixed to a penetrating plate 12, inside the room 5.
• the guide tube 6 constituting the internal part of the guide duct is connected to the manual valve 7 ensuring the opening and closing of the guide duct.
• the manual valve 7 is itself connected to the nozzle 8 by means of a conduit element on which is placed a pressurizing connection 13 of the instrumentation conduit.
• the nozzle 8 is fixed in the instrumentation room 5, by means of a nozzle support 14 and includes a leak detector 15.
• the thimble extension 16 which is connected to a non-return valve 17 fixed directly on a motorized valve 18.
• the non-return valve 17 and the motorized valve 18 constitute the means 9 for automatically closing the extension of the thermowell.
• the installation does not include a non-return valve 17 and the thermowell extension is connected directly to the motorized valve 18.
• the assembly shown in FIG. 2 which is arranged in the measurement room 5 makes it possible to ensure a sealed exit from the probe support cable introduced into the thermowell 10, to check the sealing of the guide duct and to avoid any coolant outlet from the reactor in the measurement room.
• the nozzle 8 which is a well-known element of the state of the art has internal sealing elements 19 and 19 ′ placed around the thimble 10 and the connection rings. by screwing 8a and 8b making it possible to connect the nozzle 8, respectively to the extension 6a of the guide duct, upstream, and to the extension 16 of the thimble 10, downstream.
• the guide tube 6a communicates with the interior volume of the vessel, so that, when the nuclear reactor is in service, the interior volume of the extension 6a of the guide conduit is subjected to the pressure inside the vessel which is around 155 bars.
• the interior volume of the thimble 10 which communicates with the interior of the measurement room by means of the extension 16 and of the valves 17 and 18 is at atmospheric pressure.
• the interior space 8c of the nozzle 8 is also at a pressure close to atmospheric pressure.
• the seals 19 therefore ensure the separation between cooling water at very high pressure and an area at atmospheric pressure.
• the reactor coolant flows, under the effect of the pressure, into the internal space 8c of the nozzle 8 which is located therefrom. brought to the pressure of the reactor coolant in service.
• the seals 19 ', 21 and 22 of the nozzle 8 are provided to resist the pressure of the coolant of the nuclear reactor; but in the event of a leak in the internal part of the nozzle, the latter is in a degraded operating situation.
• the primary coolant in the pressurized reactor containing radioactive fluids may spill into the measurement room 5.
• a detector 15 is used for this, which makes it possible to emit a signal when traces of humidity or a certain amount of liquid have entered the internal space of the nozzle.
• the primary coolant of the nuclear reactor flows into the measurement room through the interior of the thermowell. Normally, the primary coolant is blocked by the non-return valve 17 or the motorized valve 18.
• the motorized valve 18 is open and the non-return valve also opens, under the thrust of the flow measurement probe.
• the primary coolant flows into the measurement room as soon as the operator has inserted the measurement probe into the extension of the thermowell to the non-return valve.
• FIG. 4 shows a detector 15 according to the prior art which can be used to detect a leak by detecting the presence of liquid in the internal space of the nozzle or at the level of the non-return valve or of the motorized valve.
• the detector 15 can occupy positions 15, 15 ′ and 15 ′′ to detect the presence of liquid in the installation constituted by the elements arranged in the measurement room 5.
• the detector 15 comprises a body 15a having a threaded end portion 15b which can be screwed into a threaded opening passing through the wall of the nozzle 8 as it is visible in FIG. 3 or even in the body non-return valve 17 or motorized valve 18.
• the detector 15 comprises a central electrode 23 isolated from the metal body 15a of the detector 15 by an insulating sleeve 24.
• the electrode 23 is connected to a connecting cable 15c penetrating into the body 15a of the detector 15 through its lower part.
• the connecting cable 15c is connected, at its end opposite to the detector, to a device allowing the signaling of the fault, for example by emission of a sound or light signal perceptible by an operator located in the measurement room.
• the liquid When liquid flows either into the internal space 8c of the nozzle 8, or into the body of the non-return valve 17 or of the motorized valve 18, the liquid is caused to cover the electrode 23 of the detector very quickly. is engaged in the lower part of the body of the element on which monitoring is carried out.
• the conductive liquid establishes an electrical contact between the electrode 23 and the wall of the element to be monitored. This electrical contact is detected by the signaling device connected to the cable 15c of the detector.
• a detector such as the detector 15 shown in Figure 4 has the drawback of reporting faults in an untimely manner. Indeed, because the ambient temperature in the measurement room is relatively high, of the order of 25 °, the humidity of the air condenses in the element to be monitored, whether it is the nozzle 8, non-return valve 17 or motorized valve 18. The water condensed in the internal space of the element to be monitored is fixed around the electrode 23 and short-circuits the insulating part 24.
• the detector cannot differentiate between a fault in the seals or the thermowell causing a leak and the condensation of humid air in the measurement room, in particular in the case where the leak has a low flow.
• FIGS. 5 and 6 show a detector according to the invention designated by the reference 25.
• the detector 25 comprises a detector body consisting of a casing 26 of cylindrical-frustoconical shape and an internal body 27 delimiting between them a detector chamber 28 in which a float 29 is disposed.
• a sensitive electrical element 30 is mounted inside the internal body 27 of the detector produced in hollow form.
• the casing 26 has a cylindrical part with a large diameter, the internal bore of which has a threaded end part 26a as well as a part with a smaller diameter, the internal bore 26b of which is connected to the bore of the part of the envelope with large diameter, via a frustoconical surface.
• the bore 26b of small diameter of the casing 26 has, at its end opposite to the frustoconical part for connection to the large diameter part, one end opening at the upper end part of the casing 26.
• the smaller diameter portion of the casing 26 has on its outer surface a prismatic portion 31 constituting a gripping surface for a screwing and tightening tool and a threaded portion 32.
• the internal body 27 of the detector comprises a portion lower prismatic shape 33 allowing the body 27 to be taken up by a screwing and tightening tool, a cylindrical-frustoconical part 34 comprising a support shoulder 34a, a threaded part 35 and an element 36 having, from bottom to top , a cylindrical part 36a then ' ⁇ n flat 36b and finally a terminal part 36c flared in corolla and terminated by a flat circular end.
• the body 27 of the detector is hollow up to the upper end level of the cylindrical part 36a.
• the sensitive electrical element 30 which is engaged inside the hollow body 27 of the detector comprises a base 30a constituting a female electrical connector and a flexible blade switch 30b (ILS) coated in a radiation-resistant protective material such as by example of polypropylene.
• the flexible blade switch further comprises electrical contacts arranged so that the switch constitutes a reversing contactor which can switch, under the action of a magnetic field, from an open state to a closed state.
• the sensitive electrical element is housed inside the hollow internal body 27 of the detector, so that the flexible blade contactor 30b is disposed inside the cylindrical part 36a of the body 27.
• the float 29 is constituted by a polypropylene piece of annular shape having a cylindrical tubular part and a frustoconical bearing surface.
• the outside diameter of the float 29 is slightly less than the diameter of the bore of the large diameter part of the casing 26 of the detector 25.
• the diameter of the inside bore of the float 29 is greater than the diameter of the cylindrical part 36a of the hollow body 27.
• a permanent magnet 37 in the form of a torus is embedded in the wall of the float 29 and arranged coaxially with respect to this wall.
• the casing 26 and the internal body 27 constituting the detector body are made of a non-magnetic material such as austenitic stainless steel Z2CN18-10.
• the threaded part 35 of the internal body 27 of the detector is designed to be screwed into the threaded part 26a of the casing 26.
• the annular float 29 is engaged inside the casing 26 or on the cylindrical part 36a of the body 27 and the hollow body 27 in which the electrical element has been mounted is screwed sensitive 30 in the casing 26.
• a sealing weld 38 is made between the body 27 and the casing 26, at the bearing surface 34a abutting against the flat lower part of the casing 26.
• the upper part 36b of the internal body 27 in the form of a flat is housed within the bore 26b; the flat part makes it possible to provide a passage between the upper part of the internal body 27 and the small diameter internal bore 26b of the casing 26.
• the end part 36c of the body 27 whose diameter is less than the diameter of the bore 26b is disposed slightly above the through end of the bore 26b, so that there remains an annular passage between the end portion 36c of the body 27 and the through portion of the bore 26b.
• the threaded part 32 of the casing 26 is provided in order to be able to screw the end part of the detector into a tapped opening passing through the wall of an element such as the nozzle 8, the non-return valve 17 or the valve.
• the internal chamber 28 of the detector formed between the casing 26 and the body 27 is in communication with 1 !.
• space internal 8c of the nozzle 8 via the annular passage around the end portion 36c of the body 27, in the shape of a corolla.
• the detector 25 is screwed onto the element which is monitored inside a tapped opening located at the bottom of the element. Furthermore, the detector 25 is placed with the axis common to the casing 26 and to the internal body 27 in a vertical direction.
• An electrical signal is collected by the electrical conductor 39, one end of which constitutes a pin which is engaged in the electrical connector 30a of the electric sensitive element with flexible blade 30.
• the conductor 39 is connected to a signaling device which emits, for example , a light or sound signal to alert the operator of the presence of moisture in the nozzle 8.
• the detector according to the invention makes it possible to avoid triggering nuisance alarms, since the condensation of water vapor contained in the air of the measurement room cannot produce an accumulation of water in the chamber 28 of the detector and lifting the float 29 to trigger the electrical contactor with flexible blade.
• the float 29 abuts by its frustoconical end surface on the frustoconical surface of the internal bore of the casing 26.
• the chamber 28 of the detector 25 is closed in a sealed manner, when the detector is screwed onto an element to be checked. In the event that cooling water from the high pressure reactor enters the nozzle, this high pressure cooling liquid cannot leak into the room at the level of the liquid detector.
• the detector which has been described and which is shown in the figures can be produced in a miniaturized manner and can incorporate commercial elements, in particular, it can be used as a sensitive element. electric, a commercial switch, for example of the RA1UF type sold by the company LEMO.
• the flat 36b of the internal body 27 may have a small thickness, for example of the order of 1 mm.
• the permanent magnet 37 of toroidal shape can be made of any hard magnetic material having characteristics ensuring stable operation of the detector over long periods.
• the permanent magnet is embedded in the wall of the float, during the production by molding of the float.
• the float can be of any material having a density less than the density of the liquid.
• the invention is not limited to the embodiment which has been described.
• the envelope and the internal body of the detector can have different shapes from those which have been described and the detector can be produced from different parts of an envelope into which a hollow internal body is screwed.
• the level of liquid in the detector chamber can be detected by a level monitoring device other than a float incorporating a permanent magnet and associated with an electric switch.
• the invention applies not only to the detection of coolant leaks in an instrumentation duct of a pressurized water nuclear reactor but also to the detection of the presence of liquid in an element of a any industrial installation, in order to detect a liquid leak in the industrial installation.

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Monitoring And Testing Of Nuclear Reactors (AREA)

Applications Claiming Priority (3)

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• 1996
  • 1996-07-04 FR FR9608352A patent/FR2750765B1/fr not_active Expired - Fee Related
• 1997
  • 1997-07-02 EP EP97931850A patent/EP0909379A1/fr not_active Withdrawn
  • 1997-07-02 WO PCT/FR1997/001183 patent/WO1998001735A1/fr not_active Application Discontinuation
  • 1997-07-02 JP JP10504854A patent/JP2000514554A/ja active Pending
  • 1997-07-02 CA CA002259468A patent/CA2259468A1/fr not_active Abandoned
  • 1997-07-02 CN CN97196945A patent/CN1226963A/zh active Pending
  • 1997-08-01 TW TW086111020A patent/TW403915B/zh not_active IP Right Cessation
• 1999
  • 1999-01-04 KR KR1019997000004A patent/KR20000023561A/ko not_active Application Discontinuation

Non-Patent Citations (1)

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