Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
  • G01P13/00—Indicating or recording presence, absence, or direction, of movement
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
  • G01B17/00—Measuring arrangements characterised by the use of infrasonic, sonic or ultrasonic vibrations

Definitions

• the present invention relates to an acoustic sensor for measuring a linear displacement by means of an acoustic wave.
• the invention finds a particularly advantageous application in the field of nuclear reactors, in particular for measuring the displacements of the internal structures of a nuclear reactor, such as, for example, the so-called "core support" structure intended to receive the nuclear fuel.
• the document describes a measuring device formed by a first waveguide adapted to guide the acoustic transmission wave and by a second waveguide adapted to guide the acoustic wave reflected.
• the two waveguides communicate at one of their ends by the provision of a groove at the second waveguide.
• a movable piston positioned in contact with the part to be measured, modifies the opening of the groove as a function of the displacement of the part to be measured, thus modifying the characteristics of the wave reflected as a function of the linear displacement of the part.
• Such a device is relatively expensive and complex to achieve in particular for the number of elements necessary for the realization of the device.
• the document also describes a measurement method comprising a calibration step of the device consisting in measuring the reference signal without closing the groove by the piston in order to calibrate the sensor.
• a calibration method does not make it possible to obtain sufficiently precise measurements, the calibration being carried out periodically and the measurement conditions being able to vary between each calibration period, in particular when the sensor is used in an environment subject to significant temperature gradients along the measuring device.
• the object of the invention is to overcome the aforementioned drawbacks by proposing an acoustic sensor for measuring a linear displacement enabling precise measurements to be made whatever the environment in which the sensor is used, and in particular in a subject environment. at severe temperature conditions, typically of the order of 400 ° C.
• an acoustic sensor for measuring a linear displacement of an internal structure of a nuclear reactor by means of an acoustic wave comprising: an electroacoustic transducer adapted to emit said acoustic wave;
• a waveguide capable of guiding said acoustic wave emitted by said transducer towards a measuring zone of the internal structure
• said acoustic sensor being characterized in that said waveguide is adapted to guide the reflected wave; said waveguide being integral with said measurement zone of the internal structure and arranged to be able to extend or retract as a function of the displacement of said internal structure of the nuclear reactor.
• the sensor according to the invention uses a single waveguide for the propagation of the transmitted wave and the reflected wave thus making it possible to minimize the number of parts used for producing the sensor and to minimize the number of parts that are subject to to severe stress under severe temperature and radiation conditions.
• said waveguide is formed by a plurality of sections of which two consecutive sections have a different diameter so as to be able to measure under a temperature gradient;
• said waveguide is formed by three sections: a connecting section comprising said transducer, an intermediate standard section and a measuring section integral with said measurement zone;
• the standard section has a smaller diameter than the connecting sections and the measuring section situated on either side of the said standard section;
• said measurement section comprises means adapted to extend or retract said waveguide as a function of the displacement of the measurement zone;
• said means are formed by a metal bellows
• said means are formed by a piston integral with said measurement zone and sliding inside the measuring section;
• Said means are formed by a cylindrical tube having a bottom integral with said measuring zone, said cylindrical tube being adapted to cooperate by sliding with said measurement section;
• said electroacoustic transducer is a piezoelectric transducer.
• the invention also relates to a method for measuring a linear displacement of an internal structure positioned in the vessel of a nuclear reactor by means of an acoustic sensor according to the invention characterized in that it comprises a step of positioning said sensor so that said electroacoustic transducer, able to emit said acoustic wave and to receive the reflected wave, is positioned outside the vessel of said reactor; and in that said waveguide, adapted to guide said acoustic wave emitted by said transducer to a measurement zone and adapted to guide the reflected wave, is positioned in the tank of said reactor.
• the measurement method according to the invention comprises a calibration step of the acoustic sensor performed simultaneously during the measurement of the linear displacement of the internal structure.
• the measuring method according to the invention comprises a step of analyzing the reflection of said emitted wave so as to determine the displacement of the internal structure.
• FIG. 1 is a schematic representation of a first exemplary embodiment of an acoustic sensor for measuring a linear displacement of a core support structure of a nuclear reactor;
• FIG. 2 is a schematic representation of a second exemplary embodiment of an acoustic sensor for measuring a linear displacement of a core support structure of a nuclear reactor:
• FIG. 3 is a schematic representation of a third exemplary embodiment of an acoustic sensor for measuring a linear displacement of a core support structure of a nuclear reactor;
• FIG. 4 is a graph illustrating a history of the emitted and reflected signals recorded by the acoustic sensor according to the invention during a measurement of a linear displacement.
• FIG. 1 represents a first embodiment of an acoustic sensor for measuring a linear displacement of a structure 20 present in the tank of a nuclear reactor, such as, for example, a core support structure intended to receive the fuel rods.
• the acoustic sensor 10 according to the invention is formed by a waveguide 5 consisting of:
• a first section 1 1, referred to as a connecting section, of length L1 comprising a portion integrated in the reactor vessel and another part located outside the vessel, the delimitation of the vessel being shown in FIG. dotted line A1;
• a second section 12 called standard section 12, of length L2;
• variable length L3 which is integral with the part to be measured 20.
• the three sections thus form a continuous waveguide 5 capable of propagating an acoustic wave.
• the acoustic sensor 10 further comprises:
• a piezoelectric transducer 14 located at the end of the link section 1 1 positioned outside the tank, the transducer 14 being adapted to transmit and receive the acoustic signals propagating inside the waveguide 5; - Means 1 5 arranged at the measuring section 1 3 and adapted to extend or retract the length of the section 1 3 according to the displacement of the structure 20 which defines the measurement zone of the acoustic sensor 1 0.
• the means 1 5 adapted to extend or retract the waveguide 5 as a function of the displacement of the structure 20 are formed by a metal bellows making it possible to decouple the portion of the measurement section 13a in a stiff state, integral with the structure 20, with respect to the rest of the waveguide 5.
• the means 15 make it possible to adapt the shape and / or the length of the waveguide 5 as a function of the displacement of the structure 20.
• the displacement of the structure 20 modifies the length L3 of the measurement section 13 and thus modifying the response time of the signal reflected on the bottom 33 of the waveguide 5 traveling a distance in the waveguide 5 which is a function of the displacement of the structure 20.
• the waveguide 5 is formed by a sealed stainless steel tube filled with a neutral gas.
• the diameter of the sections 1 1, 12, 1 3 and the frequency of the acoustic wave are defined so as to fulfill the propagation conditions of an acoustic wave in a waveguide.
• the reference section 1 2 located between the connecting section 1 1 and the measurement section 1 3 has a smaller diameter than the sections 1 1 and 1 3 located on either side of the standard section 12.
• the difference in diameter between the different successive sections form geometrical breaks 31, 32 at the junction of the different sections 1 1, 12, 1 3. These breaks 31, 32 and the bottom 33 of the waveguide 5 thus form acoustic reflectors localized to inside the waveguide 5.
• FIG. 4 illustrates an example of results obtained during a measurement of a linear displacement of a structure by means of the acoustic sensor 10 according to the invention.
• the graph represents the transmission signal S1 emitted by the transducer 14 as well as the echoes E2, E3, E4, E5, E6 recorded by the transducer 14.
• the echo is the reflection of the acoustic transmission wave S1 whose amplitude and delay with respect to the emission wave are sufficient to be detected by the transducer 14.
• the analysis of the echoes by signal processing methods thus makes it possible to determine the value of the displacement at the transmitter. end of the acoustic sensor 10 integral with the structure 20.
• the three echoes E3, E4 and E5 make it possible to measure the displacement and echoes E3 and E4 make it possible to calibrate the sensor when the measurement is made simultaneously. Indeed, the echoes E3 and E4 make it possible to determine the celerity of the acoustic wave propagating in the waveguide 5 during the realization of the measurement.
• the calibration of the sensor 10 and the measurement of the displacement are carried out by means of the same acoustic wave emitted by the transducer.
• the sensor according to the invention thus makes it possible to determine for each measurement the celerity of the acoustic wave in the waveguide 5.
• the acoustic sensor according to the invention can be used under severe temperature conditions, such as, for example, in the internal tank of a nuclear reactor with large temperature gradients along the waveguide. Indeed, when performing the measurement, the temperature gradients along the waveguide 5 modifying the velocity of the wave are taken into account during the measurement by automatic and systematic calibration of the acoustic sensor.
• the acoustic sensor according to the invention is perfectly applicable to the measurement of a linear displacement of the internal structure of a nuclear reactor.
• the acoustic sensor according to the invention can be positioned in a nuclear reactor vessel without affecting the accuracy of the measurement.
• the electronic part sensitive to the temperature conditions and radiation ie the transducer
• Such a sensor makes it possible to obtain, whatever the temperature conditions, an accuracy of less than one millimeter and preferably less than 0.5 mm for a displacement of the order of one millimeter.
• the means arranged at the measuring section 1 3 and adapted to extend or retract the measuring section 1 3 as a function of the displacement of the structure 20 are formed by a piston 25 sliding inside the section 1 3.
• the piston 25 is integral with the structure so that the displacement of the structure 20 varies the position of the face 33 and therefore the reflector formed by the bottom of the waveguide 5.
• Sealing means 26 are arranged between the piston 25 and the section 13 so as to make the waveguide 5 tight to the external environment.
• the means arranged at the level of the measurement section 13 and adapted to extend or retract the measuring section 1 3 as a function of the displacement of the structure 20 are formed by a hollow cylindrical tube 35 sliding inside the section 13.
• the cylindrical tube 35 has a bottom 33 secured to the structure 20 so that the displacement of the structure 20 changes the position of the reflector formed by the bottom 33 of the cylindrical tube 35.
• Sealing means 36 are arranged between the cylindrical tube and the section 13 so as to make the waveguide 5 tight to the external environment.
• the cylindrical tube has a diameter greater than the third measurement section 13 so that the cylindrical tube slides outside the measuring section.
• the invention has been particularly described for the measurement of a displacement of an internal structure of a nuclear reactor, such as a structure heart support; however, the invention is equally applicable to the measurement of a displacement of any other type of part and is applicable to other areas of use.
• the acoustic sensor according to the invention is particularly well suited for measuring a linear displacement in an environment subjected to temperatures or large temperature gradients.

Landscapes

• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Monitoring And Testing Of Nuclear Reactors (AREA)
• Measurement Of Mechanical Vibrations Or Ultrasonic Waves (AREA)
• Length Measuring Devices Characterised By Use Of Acoustic Means (AREA)

Applications Claiming Priority (2)

Publications (1)

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• 2011
  • 2011-12-06 FR FR1161190A patent/FR2983573B1/fr not_active Expired - Fee Related
• 2012
  • 2012-12-05 RU RU2014127186A patent/RU2014127186A/ru not_active Application Discontinuation
  • 2012-12-05 WO PCT/EP2012/074440 patent/WO2013083603A1/fr active Application Filing
  • 2012-12-05 JP JP2014545228A patent/JP2015504154A/ja active Pending
  • 2012-12-05 EP EP12795444.4A patent/EP2788713A1/fr not_active Withdrawn
  • 2012-12-05 CN CN201280067954.3A patent/CN104067088A/zh active Pending
  • 2012-12-05 US US14/362,835 patent/US20140318256A1/en not_active Abandoned

Non-Patent Citations (1)

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