JP4968834B2 - Discrimination device and discrimination method for fuel rod cladding tube material - Google Patents

Description

  The present invention relates to an apparatus and a method for discriminating a fuel rod cladding tube, and in particular, to determine which zirconium alloy is used for a cladding tube used for a nuclear fuel rod by measuring conductivity. The present invention relates to a determination device and a determination method.

As a material for a reactor fuel rod cladding tube (hereinafter, referred to as “fuel rod cladding tube” or “cladding tube” in principle), ZWR is a base material of BWR (boiling water reactor). (Main material, base material), Sn 1.5% (weight%, the same applies hereinafter), Fe 0.13%, Ni 0.05%, Cr 0.1% In PWR (Pressurized Water Reactor), Zircaloy 4 (Zr is a base material, Sn is 1.5%, Fe is 0.21%, Cr is 0.1%) In recent years, Nb-containing Zircaloy with slightly improved composition and improved corrosion resistance has been used for high burnup fuel in PWR (Patent Document 1).
Therefore, in the production line of the fuel rod for PWR, the cladding tube of Zircaloy 4 and Nb-containing Zircaloy is used.

For this reason, at the fuel rod manufacturing site, a symbol identifying the material is engraved (engraved) on the cladding tube, so that not only the shape, size and weight but also the material composition is almost the same, so the color, gloss, texture, etc. It is discriminated which material is made of a similar cladding tube.
Japanese Patent No. 3389018

However, if the marking portion is cut off as the fuel rod manufacturing process progresses, it is difficult to visually identify which material the cladding tube is made of for the above reasons.
Although it is conceivable to stamp at a position where it is not cut off, it is necessary to confirm that the stamped place has sufficient corrosion resistance, for example, an evaluation test for that purpose because it is an object used in a nuclear reactor.
Furthermore, it cannot be stated that there is no error in engraving.
In addition, it is not practical to collect a sample from a cladding tube during the manufacturing process of a fuel rod and analyze and identify the composition because it takes too much time and time.

  For this reason, a destructive test such as analysis of the fuel rod is unnecessary during the production of the fuel rod, and it is desired to develop a technology capable of discriminating the material of the cladding tube without taking time and effort. .

  As a result of intensive research aimed at solving the above-mentioned problems, the inventors of the present application have found that materials for nuclear reactors have a stricter tolerance for the composition ratio of metal elements than metal materials in other technical fields. Even if the composition ratios are almost the same or only slightly different, it has been found that if the conductivity is accurately measured, it is possible to determine which material the cladding tube is made of The present invention has been accomplished. In addition, ingenuity has been devised for accurate measurement. The invention of each claim will be described below.

The invention described in claim 1
Conductivity measuring means ;
When measuring conductivity, temperature holding means for keeping the temperature of the measurement location constant,
A fuel rod cladding tube material discrimination device having
The conductivity measuring means includes
A stand on which the fuel rod cladding tube is put in place;
A probe,
A contact adjusting section for bringing the probe into contact with the fuel rod cladding tube under certain conditions;
Conductivity measurement for measuring conductivity while the tip of the probe is in contact with a fuel rod cladding tube placed at a predetermined position on the table under a certain condition under the action of the contact adjusting unit. Part
The contact adjusting unit is
A measuring column erected on the table;
A rubber ring attached to the outer periphery of the probe;
An elevating arm attached to the measuring column and capable of elevating the measuring column while holding the rubber ring;
The lifting arm is lowered, and the tip of the probe is brought into contact with the fuel rod cladding tube under certain conditions,
The probe is
A fixed part having the rubber ring attached to the outer periphery;
A spring having one end attached to the fixed part;
A probe body attached to the other end of the spring and movable in the vertical direction with respect to the fixed portion;
The rubber ring is interposed between the probe and the lifting arm,
The pressing of the probe tip to the fuel rod cladding tube is configured to be performed by the weight of the elevating arm that supports the probe via a double elastic structure of the rubber ring and the spring,
The temperature holding means is
The fuel rod cladding tube placed at a predetermined position on the table has a gas supply section that controls the temperature of the portion to 20 ± 5 ° C. by spraying gas to the portion where the probe contacts . This is an apparatus for discriminating a fuel rod cladding tube material.

In the invention of this claim, the conductivity measuring means accurately detects a slight difference in conductivity caused by slightly different materials, and based on the difference, the fuel rod cladding tube (as described above, In the description, it is possible to discriminate the material of “clad tube”.
In addition, during the production of the fuel rod, it is possible to determine the material of the cladding tube without taking time and effort such as a destructive test such as analysis of the fuel rod.
In the measurement of conductivity, for example, a probe for measuring conductivity is brought into contact with the cladding tube, and the deformation received by the original magnetic field line is amplified and discriminated by the magnitude of the eddy current induced in the cladding tube by the magnetic field line generated from the probe. That is, by measuring the change in impedance of the probe.

In the invention of this claim, since the temperature holding means for keeping the temperature at the measurement location constant is provided, the discrimination based on the slight difference in the conductivity due to the slight difference in the material becomes easier.
In addition, it is preferable to keep the temperature of a measurement location (measuring device and cladding tube) constant throughout the year.

  In the invention of this claim, since the probe contacts the upper part of the cladding tube under the action of the contact adjusting portion under a certain condition and the cladding tube is placed on the table, the cladding tube and the detection end are always constant. Since the contact is made with the same conditions, especially with a constant pressing force and a constant contact area, and the composition of the material and the metal structure are close, it is possible to accurately determine the cladding material even if the difference in conductivity is very small. Is possible.

  In the invention of this claim, since the raising / lowering arm descends and the tip of the probe comes into contact with the cladding tube, the contact condition between the cladding tube and the probe is always constant. Is ensured, and the reliability of the discrimination of the material by measuring the conductivity is further increased.

The “measurement column erected on the table” is provided for the probe to come into contact with a certain position of the cladding tube at a predetermined position on the table. As long as the lifting arm that holds the probe via the ring plays a role of ensuring that it is in a certain position on the table, the shape is not limited to a rod-shaped column, and a frame that performs positioning around the lifting arm Etc. are also included.
Further, it may be provided at the end portion (tip in the length direction) of the cladding tube or may be provided at the side portion.
Further, “attached to the measuring column” means that the position is fixed when measuring the conductivity.
Further, “raising and lowering” includes not only moving up and down the pillar but also fitting into a frame surrounding the lifting arm during measurement.

The rubber ring prevents the probe and the cladding tube from being excessively pressed during measurement, and the shape of the rubber ring is strict if it can be held elastically (flexibly) by the lifting arm. It is not limited to a ring shape, and may consist of a plurality of small pieces.

In the invention of this claim, since the probe is supported by a double elastic structure of a rubber ring and a spring, when the measurer holds the lifting arm in his hand and presses the probe against the cladding tube, the probe is measured. As a result, the contact condition with the cladding tube, that is, the contact with an appropriate pressing force and the uniformity of the contact area are further improved, and accurate measurement and material discrimination are possible.

In the invention of this claim, since the temperature is constant or substantially constant and clean gas is supplied from the gas supply unit to the location where the probe contacts the cladding tube, that is, in the vicinity of the measurement location, the temperature is always constant and As a result, the measurement accuracy is improved.
In terms of cost and safety, “gas” is preferably diverted from argon, nitrogen, clean air for air conditioning in the work room, compressed air for factory control, etc., and prevents condensation. In order to improve the accuracy as much as possible, it is preferable that the temperature is slightly higher than the room temperature of the measurement location, or that moisture is removed, and from the aspect where temperature correction is unnecessary, the reference temperature in IACS is 20 ° C. It is preferable to be within a range (within ± 5 ° C).

The invention described in claim 2
A method for discriminating a fuel rod cladding tube material that is discriminated using the fuel rod cladding tube material discrimination device according to claim 1,
Conductivity measurement recording step of measuring the conductivity of each material of the fuel rod cladding tube in advance and recording the measured value of conductivity for each material;
A determination step of measuring the conductivity of the material of the fuel rod cladding tube during manufacture of the fuel rod and determining the material of the fuel rod cladding tube in comparison with the measured value recorded in the measurement recording step,
A method for discriminating a fuel rod cladding tube material characterized by comprising:

  The invention of this claim is the invention of the object (apparatus), and is taken as the invention of the method.

The invention according to claim 3 is a method of discriminating the fuel rod cladding tube material,
In the conductivity measurement recording step and the discrimination step, when measuring the conductivity of the material of the fuel rod cladding tube, at least the measurement temperature and the contact state between the detection end of the device for measuring conductivity and the fuel rod cladding tube This is a method for discriminating a fuel rod cladding tube material, wherein one condition is the same.

According to the invention of this claim , more accurate discrimination becomes possible.

  In the present invention, in order to discriminate the material of the fuel rod cladding tube based on the slight difference in conductivity due to the slight difference in material, it is troublesome to discriminate the material of the cladding tube during the production of the fuel rod. It is not necessary to perform destructive tests such as analysis of fuel rods that take a long time.

  Hereinafter, the present invention will be described based on the best mode. Note that the present invention is not limited to the following embodiments. Various modifications can be made to the following embodiments within the same and equivalent scope as the present invention.

(First embodiment)
The present embodiment relates to the entire measuring apparatus.
FIG. 1 is a diagram showing the overall configuration of the measuring apparatus. In FIG. 1, 10 is a cladding tube, 20 is a measurement probe (probe), 30 is a measurement table on which the cladding tube is placed, 31 is a cladding tube receiver for positioning, 32 Is a rubber ring attached to the outer periphery of the probe, 33 is an elevating arm for holding the probe 20 via the rubber ring 32, 34 is a measuring column for elevating the elevating arm 33 during measurement, and 35 is a covering Reference numeral 40 denotes an end portion of the tube 10, 40 is a gas supply pipe, 50 is a conductivity measuring device, 51 is a measuring wire on the probe side, and 60 is a personal computer.

  As shown in FIG. 1, the measurement column 34 is erected at the end of the base 30, and the lifting arm 33 moves the measurement column 34 up and down while holding the probe 20 via the rubber ring 32. Is possible. Then, when measuring the conductivity of the cladding tube 10, the elevating arm 33 is raised to the upper part of the measurement column 34, and the cladding tube 10 is covered with the end portion of the cladding tube 10 being in contact with the end pad 35 of the measuring table 30. It is placed horizontally on the tube receiver 31, and then the elevating arm 33 is lowered, and the tip of the probe 20 held by the elevating arm 33 is brought into contact with the uppermost portion of the cladding tube 10. The movement of the probe 20 at this time is indicated by a thick double arrow.

Predetermined magnetic field lines are generated from the probe 20, and eddy currents are induced in the material of the cladding tube 10 by the magnetic field lines. Further, magnetic field lines in a direction that weakens the original magnetic field lines are generated by the eddy currents. The lines of magnetic force are deformed and the impedance changes. At this time, if the material of the cladding tube 10 is different, the conductivity is different, so the magnitude of the generated eddy current is also different, and hence the deformation of the magnetic lines of force of the probe 20 and the change in impedance are also different.
The conductivity measuring device 50 amplifies and discriminates the change, measures the conductivity of the material of the cladding tube 10, and sends the measured value to the personal computer 60.
Note that the upper surface of the base 30 and the end pad 35 are manufactured using a material that does not damage the cladding tube 10 and maintains good insulation, such as Teflon (registered trademark).

At this time, as shown by thin arrows, the upper surface of the cladding tube receiver 31 and the upper surface of the cladding tube 10 are supplied with nitrogen gas that is clean and slightly higher than the temperature of the measurement location and at a constant temperature. The measurement location of the cladding tube 10 has no condensation and is kept clean and at a predetermined temperature.
Moreover, if the force with which the probe 20 presses the cladding tube 10 is different for each measurement, the areas of the probe 20 and the contact portion between the cladding tube 10 and the contact portion between the cladding tube 10 and the cladding tube receiver 31 are different, and resistance is reduced. Measurements can be inaccurate due to changes. Therefore, the tip of the probe 20 at the time of measurement is pressed against the cladding tube 10 by the weight of the elevating arm 33 holding the probe 20 via the rubber ring 32. That is, the tip of the probe 20 lightly presses the cladding tube 10 (contacts by its own weight) by the weight of the probe 20, the rubber ring 32, and the lifting arm 33.

Therefore, no positive restraining means such as a latch or a gear is provided between the lifting arm 33 and the measurement column 34 at the measurement position, and the measurement wire connected to the probe 20 is as flexible as possible. It is said.
The role of the rubber ring 32 interposed between the probe 20 and the lifting / lowering arm 33 is to compensate for some differences in restraint conditions such as friction and distortion between the lifting / lowering arm 33 and the measuring column 34.

In addition, since no means, such as a gear mechanism, for positively restraining the vertical movement is provided between the lifting arm 33 and the measurement column 34 at the measurement position, the fuel assembly of the reactor to be used is not provided. Even if the diameter of the cladding tube is slightly different according to the standard, it is possible without difficulty to lower the lifting arm 33 to the lowest position, that is, the position where the tip of the probe 20 contacts the uppermost portion of the cladding tube 10. ing.
However, when the cladding tube 10 is placed on the table 30 or removed from the table 30, a mechanism for holding the elevating arm 33 on the upper part of the measuring column 34 so as not to get in the way, such as a latch, is provided. ing.

  The personal computer 60 is previously input with various data such as the thickness of the cladding tube 10 to be measured, the thickness of the cladding tube 10 and the like, and the threshold value of conductivity according to the material. Various input data and the measured conductivity value notified by the conductivity measuring device 50 are compared to determine the material of the cladding tube 10 and display it on the liquid crystal display. I do.

In this embodiment, the conductivity is measured by amplifying and discriminating the deformation received by the original magnetic field lines depending on the magnitude of the eddy current induced in the material by the magnetic field lines generated from the probe. It is not a flat plate of thickness. For this reason, if an accurate conductivity is to be measured, it is necessary to compensate for the eddy current attenuation due to the thickness and curvature (diameter) of the cladding tube. However, the conductivity measurement of the present invention is performed in order to determine the material of the cladding tube by comparing the measured value with a threshold value. For this reason, if the threshold value is also measured and created under the same conditions, there is no inconvenience.
As a result, there are various types of PWR, such as 17 × 17 type (type in which a horizontal cross section is a square 17 × 17 arranged in a fuel assembly), 14 × 14 type, and so on. In addition, it is easy to measure the conductivity and create a threshold value.

  Note that the type of fuel rod cladding tube, such as 17 × 17 type or 14 × 14 type, can be easily identified by measuring the plate thickness, curvature, and the like.

Finally, determination of threshold values, analysis of measurement data, and calibration of each part in the present embodiment will be described.
Take several samples for each cladding tube to be measured and supply from the gas supply pipe prior to measurement, how to contact the probe, ie contact by its own weight or contact by some pressure, temperature at the time of measurement The conductivity was measured by changing the gas supply time, temperature, and the like. In addition, the sample cladding tube is collected not only for the material (Zircaloy 2, Zircaloy 4, Nb-containing Zircaloy) but also for each material by changing the dimensions (outer diameter and wall thickness) to obtain reliable data, Then, the threshold was determined for each type and size of the cladding tube.

  Specifically, for example, in a 17 × 17 type cladding tube for PWR having a diameter of 9.5 mm and a wall thickness of 0.6 mm, the average value of measured conductivity is 1.25 when the material is Zircaloy 4. % IACS (the value of standard annealed copper at 20 ° C. is 100%), and in the case of Nb-containing Zircaloy, it was also 1.40% IACS. Therefore, in determining whether the material of the cladding tube is Zircaloy 4 or Nb-containing Zircaloy, if the conductivity is 1.35% IACS or less, it is determined as Zircaloy 4 and the conductivity is 1.35%. If it is larger than IACS, it is determined as Nb-containing Zircaloy.

Thus, for a 17 × 17 type cladding tube for PWR, by comparing the measured conductivity with a threshold value, it is possible to reliably determine whether the material is Zircaloy 4 or Nb-containing Zircaloy. Is possible.
In addition, when determining with a threshold value, it is preferable to set the threshold value within a range of 1.30 to 1.35% IACS.

Similarly, in the 14 × 14 type cladding tube for PWR, it has been found that the average value of the measured conductivity is preferably 1.6% IACS when the material is Zircaloy 4.
Therefore, in determining whether the material of the cladding tube is Zircaloy 4 or Nb-containing Zircaloy, if the conductivity is 1.6% IACS or less, it is determined as Zircaloy 4 and the conductivity is 1.6%. If IACS is exceeded, it will be judged as Nb-containing Zircaloy.

In other words, in the present embodiment, the conductivity measuring means amplifies and discriminates the deformation received by the original magnetic field lines due to the magnitude of the eddy currents induced in the material by the magnetic field lines generated from the probe. Conductivity is measured without compensating the thickness and curvature (diameter) of the rod cladding tube,
For each fuel rod cladding tube having the same plate thickness and curvature, a conductivity threshold corresponding to the material and not compensating for the plate thickness and curvature is prepared in advance, and the conductivity measured by the conductivity measuring means is measured. The fuel rod cladding tube material discriminating apparatus determines the material of the fuel rod cladding tube actually measured for each fuel rod cladding tube having the same thickness and curvature.

  Specifically, in the PWR 17 × 17 type fuel rod cladding tube, the conductivity threshold is set to any value between 1.30 and 1.35% IACS, for example, 1.35% IACS.

  Similarly, in the PWR 14 × 14 type fuel rod cladding tube, the conductivity threshold is set to 1.6% IACS.

That is, in the first embodiment,
For the fuel rod cladding tube of each plate thickness and curvature, measure the conductivity for each material in advance without compensating the plate thickness and curvature, record the measured value, create a threshold, etc.
During the production of fuel rods, the conductivity of the material of the fuel rod cladding tube with the plate thickness and curvature is measured without compensating the plate thickness and curvature, and the material of the fuel rod cladding tube is discriminated by comparing with the threshold value etc. It is. Thereby, the material of the cladding tube can be easily discriminated.

In addition, the temperature in the vicinity of the measurement location of the cladding tube is input to the personal computer from a temperature sensor (not shown), which makes it possible to collect the relationship between temperature and conductivity for each material and cladding tube size. Data for obtaining a threshold value for more accurate discrimination is created.
In addition, the temperature of the measurement room is also input to the personal computer, and the temperature of the gas ejected from the gas supply pipe 40 is adjusted to be slightly higher than the temperature of the measurement room from the data for both temperatures to prevent condensation at the measurement location. I try to do it.

(Second Embodiment)
The present embodiment relates to a measurement probe.
FIG. 2 shows the probe of this embodiment. In FIG. 2, 21 is a probe body, 22 is a probe outer cylinder, and 23 is a spring. The top view of FIG. 2 shows the side and the top shows the interior. The lower figure of FIG. 2 shows the AA cross section of the upper figure. In the present embodiment, the probe main body 21 fitted into the probe outer cylinder 22 plays the role of the original probe.

  The probe main body 21 is fitted into the probe outer cylinder 22 via a retractable spring 23. Therefore, the probe main body 21 can move in the vertical direction within the probe outer cylinder 22 with a small force, as shown by the double arrows in the upper diagram of FIG. For this reason, even if a slight pressure is required after contact with its own weight for some reason, such as collecting data for determining the threshold, or the measurer holding the lifting arm 33 makes an excessive press due to an error. Even in this case, since the probe main body 21 enters the upper probe outer cylinder 22, excessive pressure is not applied to the cladding tube 10, and there is no possibility of damaging the cladding tube 10.

It is a figure which shows the whole structure of the conductivity measuring apparatus in connection with this invention. It is a figure which shows the structure of the probe of the measuring device of the electric conductivity in connection with this invention.

DESCRIPTION OF SYMBOLS 10 Cladding tube 20 Probe 21 Probe main body 22 Probe outer cylinder 23 Spring 30 Stand 31 Cladding tube receiver 32 Rubber ring 33 Lifting arm 34 Measuring column 35 End pad 40 Gas supply tube 50 Conductivity measuring instrument 51 Measuring wire 60 Personal computer

Claims (3)

Conductivity measuring means ;
When measuring conductivity, temperature holding means for keeping the temperature of the measurement location constant,
A fuel rod cladding tube material discrimination device having
The conductivity measuring means includes
A stand on which the fuel rod cladding tube is put in place;
A probe,
A contact adjusting section for bringing the probe into contact with the fuel rod cladding tube under certain conditions;
Conductivity measurement for measuring conductivity while the tip of the probe is in contact with a fuel rod cladding tube placed at a predetermined position on the table under a certain condition under the action of the contact adjusting unit. Part
The contact adjusting unit is
A measuring column erected on the table;
A rubber ring attached to the outer periphery of the probe;
An elevating arm attached to the measuring column and capable of elevating the measuring column while holding the rubber ring;
The lifting arm is lowered, and the tip of the probe is brought into contact with the fuel rod cladding tube under certain conditions,
The probe is
A fixed part having the rubber ring attached to the outer periphery;
A spring having one end attached to the fixed part;
A probe body attached to the other end of the spring and movable in the vertical direction with respect to the fixed portion;
The rubber ring is interposed between the probe and the lifting arm,
The pressing of the probe tip to the fuel rod cladding tube is configured to be performed by the weight of the elevating arm that supports the probe via a double elastic structure of the rubber ring and the spring,
The temperature holding means is
The fuel rod cladding tube placed at a predetermined position on the table has a gas supply section that controls the temperature of the portion to 20 ± 5 ° C. by spraying gas to the portion where the probe contacts . An apparatus for discriminating a fuel rod cladding tube material. A method for discriminating a fuel rod cladding tube material that is discriminated using the fuel rod cladding tube material discrimination device according to claim 1,
Conductivity measurement recording step of measuring the conductivity of each material of the fuel rod cladding tube in advance and recording the measured value of conductivity for each material;
A determination step of measuring the conductivity of the material of the fuel rod cladding tube during manufacture of the fuel rod and determining the material of the fuel rod cladding tube in comparison with the measured value recorded in the measurement recording step,
A method for discriminating a fuel rod cladding material, comprising: In the conductivity measurement recording step and the discrimination step, when measuring the conductivity of the material of the fuel rod cladding tube, at least the measurement temperature and the contact state between the detection end of the device for measuring conductivity and the fuel rod cladding tube 3. The method for discriminating a fuel rod cladding tube material according to claim 2 , wherein one condition is the same.

Images