JPS5923430B2 - How to install a thermocouple on a rod-shaped sheathed heater - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a rod-shaped sheathed heater used as a simulated fuel rod of a nuclear reactor, in which a thermocouple used to measure the temperature etc. of the surface of the cladding tube is attached to the surface of the rod-shaped sheathed heater. Regarding the method.

BACKGROUND ART Conventionally, instead of using nuclear fuel rods, simulated fuel rods that simulate the dimensions, thermal output, etc. of nuclear fuel have been used in tests such as safety evaluation of reactors in nuclear power plants.

Rod-shaped sheathed heaters are widely used as simulated fuel rods due to their structure, and generally one or 100 of them are used.
It is used as a collection of ~200 pieces bundled together.

In order to simulate a nuclear reactor using such a rod-shaped sheathed heater and test the various behaviors of the reactor core, it is necessary to measure the temperature at various points on the surface of the simulated fuel rod cladding tube. is attached to the outer wall of the rod-shaped sheathed heater.

At this time, in order to improve the responsiveness of the thermocouple and make accurate measurements, it is necessary to reduce the heat capacity of the thermocouple itself, so in general, ultra-thin sheath type thermocouples with an outer diameter of O and from 5wL to 1.07FE are used. pairs are used.

Conventionally, in order to attach a thermocouple to the surface of a rod-shaped sheathed heater a, storage grooves b are provided intermittently in the longitudinal direction on the sheath surface of a rod-shaped sheathed heater a, as shown in FIGS. After the thermocouple c is housed in the groove b, the sheath a' is deformed and the thermocouple c is clamped and fixed in the groove b. However, the simulated fuel rod is required to have the ability to withstand repeated tests of severe thermal and cold cycles, and although the rod-shaped sheathed heat rod itself can withstand the above-mentioned usage conditions, the temperature measurement thermocouple attached to its surface cannot. According to the conventional installation method, the above-mentioned storage groove b is 100 times smaller than the outer diameter of the thermocouple c.
Since the sides are approximately U-shaped with a wide width of about rm and are recessed at right angles to the outer periphery of the sheath a', after embedding the thermocouple c, deforming the sheath a' will separate the thermocouple c and the sheath. Although a' is tightly attached, the width of the storage groove b is difficult to be smaller than the outer diameter of the thermocouple c, and even if the width becomes narrower, the opening and the bottom will be the same width. Thermocouple c is the third
As shown in the figure, when thermocouple c is installed using the conventional installation method, it is only deformed into an oval shape and does not have thermocouple c attached to it. If a temperature difference occurs between the sheaths a' and the expansion coefficients and storage ratios differ, the thermocouple will separate from the storage groove b due to repeated cooling and heating cycles, and even in the embodiment, the heating and cooling cycles will be repeated about 10 times. It was confirmed that the temperature measurement purpose could not be achieved due to the separation of the temperature sensor.

Therefore, as a result of studies in view of the above-mentioned conventional circumstances, the present invention is an installation method in which a storage groove is provided on the outer wall surface of a rod-shaped sheathed heater and the thermocouple is embedded therein, thereby making it possible to reliably embed the thermocouple. The purpose of this invention is to make it possible to make it durable and to withstand repeated use.

The drawings showing the embodiments of the present invention will be described in detail below.
4 to 6, a storage groove 3 is provided by recessing the outer wall of the sheath 2 of the rod-shaped sheathed heater 1 in the longitudinal direction using an appropriate tool. The depth t is approximately equal to the outer diameter of the pair 4, and the opening 3a
The width w is set approximately 10μ larger than that to make it convenient for embedding the thermocouple 4, and when the sheath 2 is squeezed, the two corners 3c, 3c of the bottom 3bVC are fixed points and face each other. The bottom portion 3b is tilted symmetrically with both side surfaces 3e, 3e so as to form tip opening edges 3d, 3d that can be deformed by
The width w of the opening 3a is set to be larger than the width w of the opening 3a, so that the storage groove 3 is omitted.

That is, the illustrated example shows a dovetail groove that satisfies the above conditions.

The thermocouple 4 is fitted into the storage groove 3 thus formed, and the width w of the opening 3a in the storage groove 3 is larger than the width w of the thermocouple 4.
As mentioned above, the outer diameter of the thermocouple 4 is slightly wider than the outer diameter of the groove 3, so the thermocouple 4 will not be damaged during fitting, and the depth is set to t, so the thermocouple 4 is The thermocouple 4 is fitted so as to be sunk in the groove, and there is a sufficient gap at the bottom for the thermocouple 4 to extend in the width direction of the groove.

When the sheath 2VC is then squeezed by applying an external force, the apical opening edges 3d, 3d are deformed inwardly using the left and right corners 3c, 3c of the bottom 3b as fixing points, so that the opening The width of the thermocouple 3a is narrowed from w in FIG. 5 to w' shown in FIG. 6, that is, smaller than the outer diameter of the thermocouple 4, so the thermocouple 4 is attached at this time.

In addition, due to the deformation of the tip opening edges 3d, 3d, the thermocouple 4
is sandwiched between the bottom part 3b and the bottom part 3b of the storage groove 3.
Since the width W is set larger than the outer diameter of the thermocouple 4, the thermocouple 4 is deformed into an elliptical shape in a direction perpendicular to the depth direction of the storage groove 3, that is, in the groove width direction, and is clamped. Therefore, by squeezing the sheath 2, the thermocouple 4 is wrapped without coming off from the storage groove 3.

The opening width w' of the storage groove 3 after squeezing the sheath 2 shown in FIG. 6 is the same as the opening width w shown in FIG. It goes without saying that the dimensions should be such that it does not expand to the extent that it does.

Although the thermocouple 4 buried in this way is slightly deformed, since a sheath type thermocouple is used, there is no problem in terms of performance even if the deformation occurs to about half of the outer diameter.

Since the present invention attaches the thermocouple 4 to the outer wall of the rod-shaped sheathed heater as described above, the thermocouple 4 is attached to the pointed opening edge 3 in the storage groove 3 recessed in the longitudinal direction of the outer wall of the sheath 2.
d and 3d are wrapped and buried in a state that can be easily installed by mechanical squeezing means without damage. Therefore, the rod-shaped sheave heater obtained by this method can withstand cold and hot cycles. Even if the adhesion between the sheath 2 and the thermocouple 4 is slightly damaged due to repeated steps, the thermocouple 4 will not physically separate from the sheath 2, thereby preventing an accidental disconnection of the thermocouple 4. It is possible to prevent this and improve reliability.

[Brief explanation of drawings]

Fig. 1 is a half-longitudinal cross-sectional view of a rod-shaped sheathed heater with a thermocouple attached using the conventional method, and Fig. 2 is an enlarged cross-sectional view taken along the - line in Fig. 1 and showing the thermocouple attachment state. , FIG. 3 is a partially enlarged cross-sectional view showing a state in which a thermocouple is attached to a rod-shaped sheathed heater using the conventional method, and FIG. FIG. 5 is a partially enlarged cross-sectional view showing the thermocouple in the middle of installation, and FIG. 6 is a cross-sectional view showing the thermocouple in a completed state. 1..... Sheathed sheathed heater, 2... Sheath, 3... Storage groove, 3a... Opening of storage groove.
3b...Bottom of the storage groove, 3c...Corner of the storage groove, 3d...Apical opening edge of the storage groove, 3e
...The side of the Nuno ditch, 4...The fuden pair, lol...
...Width of the opening that fits into the storage groove, t...Depth of the storage groove.

Claims (1)

[Claims] 1. In a method of attaching a thermocouple to a storage groove formed by recessing the outer wall of the sheath of a rod-shaped sheathed heater in the longitudinal direction,
When providing the storage groove, a pointed opening edge is formed that can be deformed in opposite directions using a corner portion at the bottom of the storage groove provided with an opening width and depth that is approximately the same as the outer diameter of the thermocouple. A housing groove is provided with both sides slanted approximately symmetrically and the bottom width is larger than that of the opening, and after housing the thermocouple in this housing groove, the sheath is squeezed and the edge of the pointed opening is inserted into the thermocouple. A method for attaching a thermocouple to a rod-shaped sheathed heater, characterized in that the thermocouple is attached to the rod-shaped sheathed heater.