JPS5816457B2 - Method for manufacturing simulated fuel rods - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improved method for manufacturing simulated fuel rods.

In various nuclear reactors, the fuel rods are formed in approximately the same shape as the actual fuel rods in order to confirm their safety.

In addition, various tests are generally conducted using simulated fuel rods that are designed to emit approximately the same amount of heat by electrical means or the like.

Therefore, when conducting such a test, it is necessary to accurately measure the temperature at the point where the temperature should be measured, and for this reason, generally a temperature sensing element such as a thermocouple is attached to the temperature measurement point, and the temperature is measured. I try to do this.

However, in the past, for example, as shown in FIG.
When measuring the temperature at a predetermined location on the inner wall of the cladding tube C in a simulated fuel rod in which an insulating material d such as magnesium oxide is filled in the cladding tube C that fits the heating element connected between the ,
Either attach and fix the temperature sensing element C to the inner wall of the cladding tube C, or
Alternatively, as shown in FIG. 2, a temperature sensing element e is attached to the inner wall of the covered tube body C, and a thin inner fitting tube f is further provided from the inside thereof.

However, in the former method, particles of the insulating material d are inserted between the temperature sensing element e and the cladding tube C, and the two cannot be brought into close contact, making it impossible to accurately measure the temperature of the cladding tube C itself. There are some difficulties in the latter method, and the inner fitting tube f
An air layer g is interposed between the cladding tube C and the inner wall of the cladding tube C. Therefore, there is a problem in that the air layer g having poor thermal conductivity causes a large measurement error.

Therefore, as a means to solve this problem, cladding tube C
A recessed storage groove is formed on the outer wall of the housing, and a temperature sensing element e is placed in the groove.
There is also a proposed example of storing the cladding tube C and drawing the cladding tube C, but in the case of this method, the temperature sensing element e is placed inside the tube C.
Since the temperature-sensitive element e is located on the outer wall of the drawing die, contact between the temperature-sensing element e and the drawing die may damage the element e during the drawing process.

Temperature sensing element e due to lateral pressure generated during processing deformation of storage groove
There is a risk that the thermosensor e may escape from the storage groove, and even with products manufactured using this method, there is no guarantee that the temperature sensing element e will escape from the storage groove due to expansion of the cladding tube C that receives high heat during use. Otherwise, problems occur such that water flowing through the surface of the cladding tube flows into the storage groove.Furthermore, since the temperature sensing element e is located on the outer wall of the cladding tube C, the temperature sensing element e is exposed to the internal heating element. is moving away, and the temperature measurement performance is correspondingly reduced.

Therefore, in this proposed example, a simulated fuel rod with good performance cannot be manufactured.

In view of these problems, the present invention provides an extremely stable mounting state of the temperature sensing element.

Furthermore, the present invention aims to provide a manufacturing method that can ensure sufficient performance of the simulated fuel rod.

The configuration of the present invention will be explained below with reference to FIG. 3. This figure shows a simulated fuel rod configured to perform temperature tests, etc. As is known, 1 and 1 are designed to apply a desired voltage. A pair of conductors, 2 is a heating element connected between the conductors 1 and 1, and a part of these 1.1 and 2 are placed in a cladding tube 3 through an insulating material 4 such as magnesium oxide filled. Loaded.

Accordingly, in the present invention, first, concave-shaped storage grooves 5, 5, . . . are formed in the inner wall of the cladding tube 3, and the storage grooves 5 are
, 5... Temperature sensing elements such as thermocouples 6゜6.
..., and in the case shown, a plurality of storage grooves 5, 5... are formed in the inner wall of the cladding tube 3, and open grooves 5, 5...・One temperature-sensing element 6.
. . . As well, as is known, an inorganic insulating material 6' is attached to the jacket tube 6'.
A strand 6' is installed inside through /.

The cladding tube 3 in which the temperature-sensitive elements 6, 6, . The diameter and wall thickness of the cladding tube 3 squeezed in this way are narrowed, and along with this, the storage groove 5, The width and depth of 5... are narrowed and the temperature sensing elements 6, 6... are also stretched and squeezed, so that the temperature sensing elements 6.6...
・ is the storage groove 5°5... as shown in the opening of Figure 4.
It will be buried completely in the interior.

Next, specific examples of the present invention will be described.

A pair of conductors 1, 1 made of Ni-Cu alloy wire with an outer diameter of 6z
A heating element 2 made of a nichrome wire with a thickness Q of 6 mym and a width of 4.2 mrn is connected between them, and an Inconel 6 with a length of 4 m, an outer diameter of 11.7 da, and a thickness of 1.3 z is connected to the outer periphery of the heating element 2.
An insulating material 4 made of BN (or Mgo) is fitted between the cladding tube 3 and the heating element 2.
A storage groove 5 is provided in the longitudinal direction of the inner circumferential wall of the cladding tube 3.
, 5... are formed, and each storage groove 5, 5... is formed.
. . ., each thermocouple with an Inconel sheath of outer diameter o and 5 g was housed, and then the vaginal covering tube 3 was pulled out and stretched to a length of 4.78 m, and its outer diameter was set to 1.
I paid $1.0.

As a result of doing this, the thermocouple is placed in each storage groove 5,
No breakage or other damage occurred to the thermocouples during this process, and similar results were obtained when the thermocouples were hammered out using a staking machine. .

As explained above, in the method of the present invention, a recessed storage groove 5 is formed in the inner wall of the cladding tube 3 along the longitudinal direction of the tube, and a temperature sensing element 6 such as a thermocouple is stored in the storage groove 5. After finishing the step of placing the heating element 2 inside the cladding tube 3 and filling the insulating material 4, the cladding tube 3 is expanded and squeezed in the axial direction, thereby producing the temperature-sensitive material. A feature is that the element 6 is buried in the storage groove 5 in a close contact state.

Therefore, in the case of the present invention, the temperature sensing element 6 is housed in the housing groove 5 on the inner wall of the cladding tube, and the drawing process is performed in this state.
The temperature sensing element 6 on the inner wall side of the cladding tube 3 does not come into contact with the die etc., and the temperature sensing element 6 tends to escape out of the groove due to the lateral pressure of the storage groove 5 generated during processing. However, if the open groove surface of the storage groove 5 is closed with a layer of insulating material 4, such escape will not occur, and of course, even if the cladding tube 3 expands due to high heat during use, it will not be sensitive to temperature due to the above-mentioned reason. The element 6 is prevented from escaping, and the closer the temperature sensing element 6 is to the internal heating element 2, the better the temperature measurement performance becomes.
Since the outer wall of the cladding tube 3 has a smooth surface (no grooves) like an actual fuel rod, it does not have an unfavorable effect on the water flowing through the surface.

Therefore, when using the method of the present invention, a simulated fuel rod with a stable mounting state of the temperature sensing element 6 and good performance can be manufactured without failure.

[Brief explanation of the drawing]

Figures 1 and 2 show a conventional example of a simulated fuel rod to which a temperature sensing element is attached, A is a vertical cross-sectional side view, 10 is an enlarged cross-sectional view of the main part, and Figure 3 is a diagram showing the method of the present invention. FIG. 4 is an enlarged cross-sectional view of a main part showing the mounted state of the temperature-sensitive element, where A shows the state before stretching and the opening shows the state after stretching. 2... Heating element, 3... Cladding tube, 4...
····Insulating material. 5... Storage groove, 6... Temperature sensing element.

Claims (1)

[Claims] 1. A step of forming a concave storage groove along the longitudinal direction of the cladding tube in the inner wall of the cladding tube and accommodating a temperature sensing element such as a thermocouple in the accommodating groove, and arranging a heating element inside the cladding tube, and , after completing the step of filling the insulator, the cladding tube is stretched in the axial direction and squeezed, thereby embedding the temperature sensing element in the storage groove in a close state. Production method.