Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
  • G01B7/00—Measuring arrangements characterised by the use of electric or magnetic techniques
  • G01B7/34—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring roughness or irregularity of surfaces
  • G01B7/345—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring roughness or irregularity of surfaces for measuring evenness
• • G—PHYSICS
  • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
  • G21C—NUCLEAR REACTORS
  • G21C17/00—Monitoring; Testing ; Maintaining
  • G21C17/017—Inspection or maintenance of pipe-lines or tubes in nuclear installations
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E30/00—Energy generation of nuclear origin
  • Y02E30/30—Nuclear fission reactors

Definitions

• the object of the present invention is to measure the deformation of the nuclear fuel assembly guide tubes, making it possible to check their straightness.
• a fuel assembly can present deformations giving the guide tubes a non-rectilinear shape. It is important to detect the existence and the importance of such deformations before reloading in the reactor, in particular to guarantee the free passage of the adjustment cluster rods in the guide tubes.
• the invention aims to provide a device and a method for obtaining a plot of the external deformations of a guide tube, usable while the assembly is kept under water.
• FR-A-2 656 415) is already known a method for simultaneously measuring the distance between substantially parallel metal tubes constituting a sheet, in particular between tubes constituting the sheaths of the rods of a fuel assembly, and the thickness d oxide covering the tubes.
• an eddy current probe is moved parallel to the sheet, pressing it in passing on the tubes; an electrical signal is supplied by the probe and represents variations in the impedance of the probe; the distance between rods is deduced from the measurement of the displacement of the probe between values of the signal corresponding to successive extrema of impedance.
• This method is not applicable to the measurement of the deformation of guide tubes which do not constitute plies and which are not distributed at all equal intervals.
• the invention provides a method according to which: (a) a current probe is moved horizontally Eddy so as to pass it successively over a substantially vertical rectilinear reference, metallic and on the guide tubes of a first row of the assembly kept vertical, the output signal of the probe is measured and the positions of the probe are memorized corresponding to the signal extrema, with respect to said mark, (b) step (a) is reproduced at several altitudes on said row, (c) steps (a) and (b) are reproduced on the other rows, (d ) the steps (a), ⁇ b) and (c) are reproduced with a displacement of the probe in a direction orthogonal to the first, (e) from the stored positions, the amplitude and the direction of the position deviations are calculated by relative to the nominal position for a straight tube, at each of the altitudes. Steps (b), (c) and (d) can be performed in any order.
• Guide tubes unlike pencil sheaths, are generally not very oxidized. Measurement is made easier.
• the probe and the measuring chain which processes its output signal can be calibrated by passing the probe over a section of standard tube placed near the assembly.
• the method can be implemented using a device comprising elements common to that described in document FR-A-2 656 415.
• the device can then include means for moving an eddy current probe in a determined horizontal direction and measuring the displacements of the probe, said probe comprising means intended to rest on a sheet of rods, to push it elastically, transversely. to the direction of movement of the probe, and apply it successively on the tubes encountered and on a marker placed outside the assembly; processing means supplying a signal depending on the impedance of the probe and making it possible to determine the signal extrema and the corresponding locations of the probe with respect to the reference; and means for calculating the deformations of the tube from the determined locations, measured at several levels and in two mutually orthogonal horizontal directions.
• the fuel assembly guide tubes often have, at their lower part, an area of reduced diameter, little greater than that of a control cluster rod capable of descending into the tube.
• Deformations of the guide tubes are particularly critical in this area.
• the measurement can be carried out there in a particularly precise way by reference to a section of standard tube.
• FIG. 1 is a simplified elevational view of a device for implementing the invention
• FIG. 2 is a top view of ia Figure 1 with parts omitted;
• FIG. 3 and 4 show, respectively in front view and in top view, a bracket for mounting a vertical mark consisting of a stretched metal wire;
• FIG. 5 shows a constitution of a probe that can be used for implementing the invention
• FIG. 6 is a block diagram.
• the device shown in FIGS. 1 and 2 can be constructed in such a way that most of its mechanical elements, except for those intended for the actual measurement, are identical to those used for other checks on a fuel assembly.
• the device comprises a fixed frame resting on the bottom of a swimming pool, for example a deactivation swimming pool.
• This frame has a square support 10 forming a base, fixed to the bottom of the pool, intended to receive and hold in position the lower end piece 12 of an assembly 14.
• This assembly can be removed using a operating rod or pole (not shown) engaged on the upper end piece 16 of the assembly.
• the guide tubes, such as the guide tube 18 shown in FIG. 1, are then approximately vertical.
• the frame also comprises vertical rails, not shown in FIG. 1, forming a rolling cnemm 20 for a carriage 22 provided with rollers 24.
• the carriage is movable vertically by motor means provided with a device for measuring the vertical level.
• motor means can for example be constituted by a motor for driving a pair of rollers (or pinions) engaged with a rail, provided with an encoder providing, in digital form, an indication of the level of the carriage.
• the plate 26 can be moved from the position where it is shown in solid lines in FIG. 2 to the position shown in phantom, the distance between the two positions being at least equal to the width of the assembly 14.
• the plate 26 is for example provided with rollers 30 driven by a motor not shown and rolling on a horizontal rail 32 provided on the carriage. This motor is also provided with an encoder providing an indication of the movements in the y direction.
• the plate 28 is on its mobile side on a rail 34 secured to the plate 26.
• a blade 36 carrying a measurement probe 38, which will be designated later by the term "saber".
• This saber can have the constitution shown schematically in Figure 5, very similar to that already described in document FR-A-2 656 415 to which reference may be made.
• the saber crosses a guide 39 fixed to the plate 26, which imposes an orientation parallel to it on one of the sides of the assembly 14.
• a television camera 40 can be fixed on the guide to provide an operator, on a screen, an image of the area in which the measurement is made.
• the device also includes at least one vertical reference with respect to which measurements are taken.
• a first reference is constituted by a vertical wire 42 attached to a bracket carried by the edge of the coping 43 of the pool.
• This tensioned wire makes it possible to measure the deformations and / or to trace the deformation of the guide tube over its entire length.
• the bracket is formed by a horizontal section 44 whose position is adjustable on a carriage 45 which can also support the pole or rod handling the assembly.
• the lower end of the wire which is several meters long, is hooked to the base 10.
• a standard tube 46 with characteristics identical to those of a typical guide tube is fixed on the guide 39 at a location such that the measurement probe s 'presses him during the advancement of the plate 28, before arriving in one assemolage.
• the assembly guide tubes have a part of reduced diameter over a fraction of their length, it is preferable to provide the base 10 with a section of reference tube 48, of length equal to that of the part of reduced diameter, allowing identification of the measurement probe. This reference tube allows a measurement very precise deformation on this part of reduced diameter.
• the saber 36 is designed to be inserted between the appropriate rows of fuel rods 49, so that the measurement probe 38 can rest on the passage on the guide tubes 18.
• Two superimposed springs 50 provided on the saber 36 are supported on the rods 49 of the row adjacent to that in which the guide tubes 18 to be checked are located.
• the passage on a guide tube is detected by a maximum or a minimum of signal, as in the case already described in the document FR-A-2 656 415.
• the support on a guide tube can be differentiated from the support on a fuel rod due to the difference in signal and by comparison with the signal supplied by passing over standard 46.
• Figure 6 is a block diagram which shows a possible constitution of the signal processing system of the device.
• the output signals from the probe 38 are shaped by operating circuits 52 and transmitted to a computer 54 as well as possibly to a display 56 allowing an operator to determine the instant of passage in the median plane of a guide cube.
• the computer 54 is associated with a working working memory 57 and with a mass memory 58 making it possible to keep all the measurements made in two orthogonal directions of the assembly and to restore them to the computer 54 for the measurement of the deformations .
• the computer 54 also receives the indications provided by the encoder of a motor 60 for vertical displacement (motor in z) and the indications provided by the encoder of a motor 62 for displacement in x.
• the motors can be activated by the operator, so as to allow him to choose the levels at which the measurement is carried out and also to send an identification signal to the passage in the median plane of a guide tube 18.
• the process for checking the straightness of the guide tubes an assembly 14 can then be carried out as follows.
• the assembly 14 is put in place as shown in FIGS. 1 and 2, then the plate 23 is moved back so that the saber is entirely disengaged from the assembly, that is to say moved from the position where it is shown in Figures 1 and 2 at an extreme right position, which can be detected by a sensor, for example 66.
• the plate 26 is moved in the direction y so as to bring the saber in front of the gap between a row of pencils 49 of a row in which guide tubes 13 are inserted (FIG. 5).
• Servo-control systems can be provided to prevent this movement in y if the plate 28 is not in its extreme recoil position.
• the plate 28 is then moved in the direction x so that the measurement probe 38 comes to bear successively on the rods and the guide tubes, at a determined level.
• the passage of the probe in the median plane of a guide tube is identified on the screen by the user who can then send the computer an order to record the position in x in mass memory 58.
• This operation is carried out for all the rows comprising guide tubes (7 in number on a fuel assembly currently in use) and at several levels. Each time, the position of the guide tubes is identified with respect to the reference constituted by the tensioned wire 42.
• the assembly is rotated 90 ° and the same operations are carried out, at the same levels.
• the values thus acquired and stored in mass memory 58 are then processed offline, by the computer 54 or an offline computer, to determine the deformation by calculating the vector sum of the deformed in two directions at 90 °. It can be seen that the method and the device make it possible, at will, to measure and / or trace the deformation of the tube either over its entire length, or only in the part of reduced diameter.

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• Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• Plasma & Fusion (AREA)
• General Engineering & Computer Science (AREA)
• High Energy & Nuclear Physics (AREA)
• General Physics & Mathematics (AREA)
• Monitoring And Testing Of Nuclear Reactors (AREA)
• Measurement Of Length, Angles, Or The Like Using Electric Or Magnetic Means (AREA)

Applications Claiming Priority (3)

Publications (1)

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• 1996
  • 1996-09-30 FR FR9611871A patent/FR2754053B1/fr not_active Expired - Fee Related
• 1997
  • 1997-09-29 WO PCT/FR1997/001709 patent/WO1998014752A1/fr not_active Ceased
  • 1997-09-29 CN CN97198392A patent/CN1232541A/zh active Pending
  • 1997-09-29 EP EP97943016A patent/EP0929791A1/de not_active Ceased
  • 1997-09-30 ZA ZA9708746A patent/ZA978746B/xx unknown

Non-Patent Citations (1)

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