JP2012225859A - Temperature measurement body of control rod guide thimble, temperature measurement device of fuel assembly and temperature measurement method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a temperature measurement body of a control rod guide thimble, etc. capable of simultaneously and easily measuring temperature at a plurality of parts of each of an axis direction of the control guide thimble, and a direction perpendicular to the axis direction, easily and exactly measuring temperature distribution of a fuel assembly.SOLUTION: A temperature measurement body of a control rod guide thimble includes: a protective pipe with outer diameter dimensions smaller than inner diameters of the control rod guide thimble; an axis rod which is slidably stored in the protective pipe; a plurality of thermocouples attached to the outer peripheral surface of the protective pipe at proper intervals in a pipe axis direction; and a pressure body which projects from the outer peripheral surface on the side opposite to a position to which the thermocouples of the protective pipe are attached by pulling up of the axis rod, in which the pressure body which projects from the outer peripheral surface of the protective pipe presses the inner peripheral surface of the control rod guide thimble to bring the thermocouples into contact with the inner peripheral surface of the control rod guide thimble. A temperature measurement device of a fuel assembly includes a temperature measurement body. In a temperature measurement method of the fuel assembly, temperature of the fuel assembly is measured by using the temperature measurement device of the fuel assembly.

Description

  The present invention relates to a temperature measuring body for a control rod guide thimble, a temperature measuring device for a fuel assembly, and a temperature measuring method.

  The dimensions of uranium fuel, highly enriched uranium fuel, and MOX fuel assemblies change due to thermal expansion.

  In particular, unlike the uranium fuel, the temperature of the fuel assembly of the MOX fuel having a predetermined calorific value due to the decay of Pu is higher than the ambient temperature and rises with time. The specific calorific value of the MOX fuel assembly depends on the weight of the Pu isotope contained in the fuel assembly, but is about 600 to 1000 W in the case of the MOX fuel in practical use.

  For this reason, it is necessary to correct the influence of thermal expansion for the result of dimensional measurement performed as quality control, and in order to quantitatively evaluate the correction amount, the temperature distribution of the fuel assembly must be corrected. It is necessary to grasp accurately. Moreover, when storing in a manufacturing factory, in order to ensure the soundness of a fuel assembly, it is necessary to monitor temperature distribution.

  In addition, since the total length of the fuel assembly is almost determined by the length of the control rod guide thimble due to its structure, the total length of the fuel assembly can be determined by measuring the temperature distribution of the control rod guide thimble and knowing the temperature distribution of the fuel assembly. The measured value can be corrected accurately.

  In particular, the MOX fuel assembly includes 3 to 4 types of fuel rods having different Pu contents, the center portion is composed of fuel rods having a high Pu content, and the outer peripheral portion is a fuel having a low Pu content. Since it is composed of rods, a temperature distribution occurs in the fuel assembly. Furthermore, heat generated at the outer peripheral portion of the MOX fuel assembly is likely to escape to the outside of the MOX fuel assembly, but heat generated at the central portion is difficult to escape. For this reason, the temperature distribution of the MOX fuel assembly is high in the central portion in the horizontal direction and low in the outer peripheral portion. Further, since the total length is about 4 m, when the MOX fuel assembly is stored in an upright state, the fuel rods that generate heat raise the surrounding air by heating up, and the temperature rises toward the upper side of the fuel assembly. For this reason, simultaneous measurement at a plurality of locations of the MOX fuel assembly is required.

  However, although various proposals have been made as techniques for measuring the temperature of the fuel assembly, there has been no one that can easily measure the temperature distribution of the fuel assembly (for example, Patent Document 1).

Japanese Patent Laid-Open No. 8-94789

  Therefore, in view of the above problems, the present invention can easily perform temperature measurement simultaneously at a plurality of locations in the axial direction of the control rod guide thimble and in the direction orthogonal to the axial direction, and the temperature of the fuel assembly It is an object of the present invention to provide a temperature measuring body for a control rod guide thimble, a temperature measuring device for a fuel assembly, and a temperature measuring method capable of easily and accurately measuring the distribution.

  The present inventor has found that the above problems can be solved by the inventions described in the following claims, and has completed the present invention. Hereinafter, each claim will be described.

The invention described in claim 1
A temperature measuring body of a control rod guide thimble inserted into a control rod guide thimble of a fuel assembly, and a protective tube formed with an outer diameter smaller than the inner diameter of the control rod guide thimble;
A shaft bar slidably accommodated in the protective tube;
A plurality of thermocouples attached to the outer peripheral surface of the protective tube at appropriate intervals in the tube axis direction of the protective tube;
A pressing body that protrudes from the outer peripheral surface opposite to the position where the thermocouple of the protective tube is attached by pulling up the shaft rod;
The pressing body protruding from the outer peripheral surface of the protective tube presses the inner peripheral surface of the control rod guide thimble, so that the protective tube moves in the control rod guide thimble and moves the thermocouple to the control rod guide. It is a temperature measuring body of a control rod guide thimble which is brought into contact with the inner peripheral surface of the thimble.

  When a thermocouple is placed in the control rod guide thimble and temperature measurement is to be performed, a protective tube with a thermocouple on the outer peripheral surface is inserted into the control rod guide thimble and the thermocouple is connected to the inner periphery of the control rod guide thimble. By contacting the surface, the temperature distribution of the control rod guide thimble can be measured. However, if the outer diameter of the protective tube is the same as the inner diameter of the control rod guide thimble, the thermocouple and the control rod guide thimble will be damaged.

  In the present invention, since the protective tube having an outer diameter smaller than the inner diameter of the control rod guide thimble is provided, when the temperature measuring body is taken in and out of the control rod guide thimble, Contact with the inner peripheral surface can be avoided.

  On the other hand, a pressing body that protrudes from the outer peripheral surface of the protective tube opposite to the position where the thermocouple is attached by the lifting operation of the shaft rod is provided, and the pressing body that protrudes from the protective tube is the inner periphery of the control rod guide thimble By pressing the surface, the protective tube moves slightly in the control rod guide thimble and the thermocouple comes into contact with the inner peripheral surface of the control rod guide thimble.

  For this reason, when inserting the thermocouple into the control rod guide thimble, the inner surface of the control rod guide thimble at a predetermined position can be obtained by a simple operation of lifting the shaft rod without damaging the thermocouple or the control rod guide thimble. The temperature distribution of the control rod guide thimble can be measured easily and accurately.

  Therefore, by inserting the temperature measuring body of the control rod guide thimble of the present invention into the plurality of control rod guide thimbles of the fuel assembly, a plurality of axial directions of the control rod guide thimble and directions orthogonal to the axial direction are respectively provided. Temperature measurement can be performed simultaneously at the locations, and the temperature distribution of the fuel assembly can be measured easily and accurately. For this reason, it is possible to quantitatively evaluate the correction amount in consideration of the effect of thermal expansion in the dimensional measurement of the fuel assembly, including the MOX fuel assembly having the above characteristics, and to monitor the temperature distribution. it can.

The invention described in claim 2
The temperature measuring body of the control rod guide thimble according to claim 1,
A fuel assembly temperature measuring apparatus, comprising: a measuring unit that measures temperature based on a detection signal from the thermocouple of the temperature measuring body of the control rod guide thimble.

  According to the detection signal from the thermocouple of the temperature measuring body according to the first aspect, the accurate temperature measurement can be easily performed. Therefore, the temperature distribution of the fuel assembly can be easily and accurately measured.

The invention according to claim 3
A fuel assembly temperature measurement method using the fuel assembly temperature measurement device according to claim 2,
Inserting the temperature measuring body of the control rod guide thimble into each of a plurality of control rod guide thimbles arranged in the fuel assembly,
In a state where the thermocouple of the temperature measuring body is brought into contact with the inner peripheral surface of the control rod guide thimble by the pulling up operation of the shaft rod, the axial direction of the control rod guide thimble and the direction orthogonal to the axial direction A temperature measurement method for a fuel assembly, wherein temperature measurement is performed simultaneously at each of a plurality of locations.

  As described above, the temperature distribution of the fuel assembly can be easily and accurately measured by using the temperature measuring device according to claim 2. Specifically, the temperature measuring body is inserted into each of the plurality of control rod guide thimbles of the fuel assembly, and the thermocouple is measured in contact with the inner peripheral surface of the control rod guide thimble, and the control rod guide thimble is measured. The temperature is measured simultaneously at a plurality of locations in the axial direction of the above and a direction orthogonal to the axial direction. Thereby, the temperature distribution of the fuel assembly can be measured easily and accurately.

  According to the present invention, temperature measurement can be easily performed simultaneously at a plurality of locations in the axial direction of the control rod guide thimble and in a direction orthogonal to the axial direction, and the temperature distribution of the fuel assembly can be easily and accurately measured. Can be measured.

It is a figure which shows one Embodiment of the temperature measurement body of the temperature measurement apparatus of the fuel assembly of this invention. It is the figure which expanded a part of one Embodiment of the temperature measurement apparatus of the fuel assembly of this invention. It is a figure explaining operation | movement of one Embodiment of the temperature measurement apparatus of the fuel assembly of this invention.

  Hereinafter, the present invention will be specifically described based on embodiments.

1. FIG. 1 is a diagram showing an embodiment of a temperature measuring body of a temperature measuring apparatus for a fuel assembly according to the present invention. FIG. 2 is an enlarged view of a part of one embodiment of a temperature measurement device for a fuel assembly according to the present invention. FIG. 3 is a diagram for explaining the operation of an embodiment of the temperature measurement device for a fuel assembly according to the present invention.

  As shown in FIGS. 1 and 3, the fuel assembly temperature measuring apparatus 1 includes a temperature measuring body 10 that is inserted into a control rod guide thimble 60 of the fuel assembly and measures a temperature distribution, and a temperature measuring body 10. A measurement unit (not shown) that measures temperature based on a detection signal from the sheath thermocouple 20 is provided.

  The temperature measurement body 10 includes a protective tube 11 having an outer diameter smaller than the inner diameter of the control rod guide thimble 60, a shaft rod 12 slidably accommodated in the protective tube 11, and a plurality of sheath thermoelectric devices. A pair 20 and a pressing body 30 are provided.

  The temperature measuring body 10 is configured to project the pressing body 30 outward from the protective tube 11 by performing an operation (pull-up operation) for moving the shaft 12 relatively upward with respect to the protective tube 11. Has been.

  A plurality of openings (notches) 13 are formed on one side of the outer peripheral surface of the protective tube 11 at predetermined intervals in the axial direction. In the opening 13, the shaft rod 12 inserted into the protective tube 11 can be visually recognized. A plurality of sheathed thermocouples 20 are fixed to the outer peripheral surface on the other side of the outer peripheral surface of the protective tube 11 (that is, the side opposite to the position where the opening 13 is formed) at a predetermined interval in the axial direction. Yes.

  As shown in FIG. 2, the pressing body 30 includes a mounting plate 31 formed of an elongated thin metal plate having spring properties, and a mounting bracket 32 for projecting the mounting plate 31 from the outer peripheral surface of the protective tube 11. I have.

  The mounting bracket 32 is fixed to the outer peripheral surface of the shaft rod 12 located in the opening 13 of the protective tube 11 by spot welding or the like. In the state before the shaft rod 12 is lifted, the mounting bracket 32 is attached to the protective tube 11. Is slightly projecting from the opening 13 below the opening 13. Further, the mounting bracket 32 is inclined with respect to the axial direction of the shaft 12.

  The mounting bracket 32 slightly protrudes from the protective tube 11 through the opening 13, but the protruding length is set to a size that does not hinder the temperature measuring body 10 from being inserted into the control rod guide thimble. ing.

  The mounting plate 31 is fixed to the outer peripheral surface of the protective tube 11 by spot welding or the like, and the lower end (free end) of the mounting plate 31 extends toward the mounting bracket 32.

The dimensions of the protective tube 11 and the shaft rod 12 are set as follows when the inner diameter of the control rod guide thimble 60 is about 11 mm and the length is about 4 m, for example.
Protective tube outer diameter: about 5mm
Inner diameter of protective tube: about 3mm
Protective tube length: Approximately 3.5m
Vertical dimension of the opening: about 50mm
Width of opening: about 4mm
Shaft rod outer diameter: about 3mm

  Further, the temperature measuring device 1 includes a stainless stopper 40 and a regulating means 50 that regulates the moving distance of the temperature measuring body 10 by the pressing body 30.

  The stopper 40 is provided on the upper portion of the protective tube 11 in order to position the temperature measuring body 10 in the axial direction. When the temperature measuring body 10 is inserted into the control rod guide thimble 60 from the upper nozzle 61 of the fuel assembly, the temperature measuring body 10 is positioned at a predetermined position in the axial direction by the stopper 40 engaging with the upper nozzle 61. The

  The restricting means 50 includes a cap 51 that is fixed to the upper end of the protective tube 11 by welding, a stopper ring 52 that is fixed to the shaft 12, a spacer 53, and a bolt 54.

  By interposing a spacer 53 in a gap formed between the cap 51 and the stopper ring 52 when the shaft rod 12 is pulled up, the shaft rod 12 can be held in a lifted state.

  The cap 51, the stopper ring 52 and the spacer 53 are formed with vertical holes 57, 56 and 55, respectively. The vertical hole 57 of the cap 51 is a screw hole. Then, as shown in FIG. 3, the bolts 54 are inserted into the vertical holes 55 and 56 and screwed into the vertical holes 57 to fix the spacer 53. The bolt 54 shown in FIG. 1 is drawn sideways for convenience.

2. Fuel Assembly Temperature Measurement Method Next, a fuel assembly temperature measurement method using the fuel assembly temperature measurement apparatus 1 will be described.

(1) As shown in FIG. 3, the temperature measuring body 10 of the temperature measuring device 1 is inserted into the control rod guide thimble 60 from the upper nozzle 61 of the fuel assembly, and the stopper 40 is locked to the upper nozzle 61. The temperature measuring body 10 is positioned in the axial direction.

(2) Next, by pulling up the shaft rod 12, the mounting bracket 32 causes the mounting plate 31 to protrude from the protective tube 11 and press the inner surface of the control rod guide thimble 60. As a result, the temperature measuring body 10 translates in the control rod guide thimble 60 in a direction orthogonal to the axial direction, and brings the sheath thermocouple 20 into contact with the inner peripheral surface of the control rod guide thimble 60.

  At this time, since the sheath thermocouple 20 is pressed by the elastic force of the mounting plate 31 and elastically contacts the inner peripheral surface of the control rod guide thimble 60, the sheath thermocouple 20 contacts the control rod guide thimble 60. The shock of is eased.

(3) Next, a spacer 53 is interposed in the gap between the cap 51 of the regulating means 50 and the stopper ring 52, and this spacer is fixed with a bolt 54.

(4) Thereby, the plurality of thermocouples 20 of the temperature measuring body 10 are arranged at predetermined positions in the axial direction of the control rod guide thimble 60 so that the temperature distribution in the axial direction of the control rod guide thimble 60 can be measured. Become.

(5) Further, by inserting the temperature measuring body 10 into the plurality of control rod guide thimbles 60 of the fuel assembly, it is possible to measure the temperature distribution in the direction orthogonal to the axial direction of the control rod guide thimble 60.

  Further, it is possible to insert and measure a plurality of temperature measuring bodies 10 at the same time. However, since the stoppers 40 of the plurality of temperature measuring bodies 10 are integrated, a plurality of temperature measuring bodies 10 can be measured simultaneously. It can also be made into a simple structure.

  While the present invention has been described based on the embodiments, the present invention is not limited to the above embodiments. Various modifications can be made to the above-described embodiment within the same and equivalent scope as the present invention.

DESCRIPTION OF SYMBOLS 1 Temperature measuring apparatus of fuel assembly 10 Temperature measuring body 11 Protection tube 12 Shaft bar 13 Opening part 20 Sheath thermocouple 30 Pressing body 31 Mounting plate 32 Mounting bracket 40 Stopper 50 Control means 51 Cap 52 Stopper ring 53 Spacer 54 Bolt 55, 56, 57 Vertical hole 60 Control rod guide thimble 61 Upper nozzle

Claims (3)

A temperature measuring body of a control rod guide thimble inserted into a control rod guide thimble of a fuel assembly, and a protective tube formed with an outer diameter smaller than the inner diameter of the control rod guide thimble;
A shaft bar slidably accommodated in the protective tube;
A plurality of thermocouples attached to the outer peripheral surface of the protective tube at appropriate intervals in the tube axis direction of the protective tube;
A pressing body that protrudes from the outer peripheral surface opposite to the position where the thermocouple of the protective tube is attached by pulling up the shaft rod;
The pressing body protruding from the outer peripheral surface of the protective tube presses the inner peripheral surface of the control rod guide thimble, so that the protective tube moves in the control rod guide thimble and moves the thermocouple to the control rod guide. A temperature measuring body for a control rod guide thimble, which is brought into contact with the inner peripheral surface of the thimble. The temperature measuring body of the control rod guide thimble according to claim 1,
A fuel assembly temperature measuring apparatus, comprising: a measuring unit that measures temperature based on a detection signal from the thermocouple of the temperature measuring body of the control rod guide thimble. A fuel assembly temperature measurement method using the fuel assembly temperature measurement device according to claim 2,
Inserting the temperature measuring body of the control rod guide thimble into each of a plurality of control rod guide thimbles arranged in the fuel assembly,
In a state where the thermocouple of the temperature measuring body is brought into contact with the inner peripheral surface of the control rod guide thimble by the pulling up operation of the shaft rod, the axial direction of the control rod guide thimble and the direction orthogonal to the axial direction A temperature measurement method for a fuel assembly, wherein temperature measurement is performed simultaneously at a plurality of locations.

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