JPS6046791B2 - Sheathed heater for nuclear fuel simulation heating element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sheath heater, and particularly to a sheath heater suitable for use in a high temperature range and as a nuclear fuel simulating heating element.

For example, a sheath heater used in a high temperature range such as a nuclear fuel simulating heating element is required to uniformly dissipate sufficient heat to the outer circumference with thermal efficiency and not to deform during use.

Furthermore, it is required to be easy to manufacture and inexpensive for use in various tests or applications, especially tests for destroying sheath heaters. Furthermore, in order to use it as a nuclear fuel simulating heating element, it is required that it be similar to actual nuclear fuel. The present invention
This was done to solve the above technical problem.

That is, the sheathed heater of the present invention has a structure including a jacket tube and a plurality of ceramic sintered bodies arranged in the axial direction inside the jacket tube. It has a plurality of through holes, and each through hole is equipped with an insulating material located at an equal distance from the wall of the jacket tube, and a plurality of heating elements mainly made of tungsten and provided through the through holes. It is characterized by The jacket tube may be made of any material that can withstand high temperatures, and stainless steel is usually used. In particular, it is preferable to use an alloy mainly composed of zirconium or stainless steel, which is equivalent to nuclear fuel, for use as a nuclear fuel simulating heating element.
The insulating material may be a dense ceramic sintered body, but oxide ceramics such as alumina, beryllia, and magnesium are usually used, and nitride ceramics such as silicon nitride and boron nitride can also be used. It is preferable to use alumina ceramic, which has properties similar to those of the fuel, to be used as a nuclear fuel simulating heating element. The heating element can be made of a high melting point metal such as tungsten or tantalum in order to be used at high temperatures, but for practical reasons it is mainly made of tungsten. That is, tungsten has the highest melting point and is most suitable for the sheath heater of the present invention, which requires high temperatures.
As the heating element, doped tungsten doped with alumina or the like, tungsten containing rhenium, or tungsten clad with platinum are industrially easily available and can be preferably applied. Note that it is best to use it in the form of a line or ribbon. Examples will be described below with reference to figures.

FIG. 1 is an enlarged partial cross-sectional view of a part of the sheath heater of the present invention, and FIG. 2 is a cross-sectional view of the sheath heater of the present invention taken along line A--A in FIG. 1 and viewed in the direction of the arrow. In the figure, a jacket tube 1 is made of Zircaloy, and a plurality of insulating materials 2 made of alumina sintered body are disposed inside the jacket tube. A plurality of through holes are provided in the insulating material 2 along the axial direction of the jacket tube, and a plurality of linear heating elements 3 made of rhenium-tungsten are disposed through the through holes. The sheath heater configured in this manner uses a plurality of linear heating elements mainly made of tungsten and is arranged concentrically, so that high temperature heat can be uniformly generated toward the outer periphery.

In order to uniformly generate high temperature heat around the outer circumference of the sheath heater, the alumina sintered body needs to be undivided cylindrical as shown in this example, and it is desirable to have six or more heating elements. . Furthermore, since the heating element is linear, the sheath heater can be used vertically and there is no risk of deformation such as sagging of the heating element even when the heating element is exposed to high temperatures. This shows that it is suitable for a nuclear fuel simulating heating element that is normally used in the vertical direction. Also, using tungsten, which is not easy to process, in a straight shape contributes to ease of manufacturing. Furthermore, since a ceramic sintered body is used as the insulating material, it has sufficient insulation even when used at high temperatures. Furthermore, this insulator has the advantage that it can be easily applied even when using a jacketed tube such as Zircaloy, which is difficult to roll. Furthermore, in a device used as a nuclear fuel simulating heating element, it is necessary to have an appropriate gap communicating with the inside of the sheath heater, and this condition can be easily satisfied by using this insulator. That is, the void inside the sheath heater is filled with helium gas, which is the same as the structure of the nuclear fuel rod, so that the results of various experiments will be accurate.

The above-mentioned sheath heater can be easily replaced with one using molybdenum disilicide as a heating element, which is used as a nuclear fuel simulating heating element.

Using the above sheath heater as a simulated nuclear fuel heating element,
When used in a cooling water loss test, it performed as well as nuclear fuel, and valid data was obtained.

As described above, the sheath heater of the present invention is suitable for use at high temperatures and has a wide range of practical applications.

[Brief explanation of the drawing]

FIG. 1 is an enlarged partial cross-sectional view of a part of the sheath heater of the present invention, and FIG. 2 shows the sheath heater of the present invention along line A-A in FIG.
It is a cross-sectional view taken along a line and viewed in the direction of the arrow. 1...Envelope tube, 2...Insulating material, 3...
...Heating element.

Claims (1)

[Claims] 1 A jacket tube and a plurality of through holes arranged inside the jacket tube and drilled along the axial direction of the jacket tube, each of these through holes being equidistant from the jacket tube wall. A cylindrical ceramic sintered body formed at equal distances from each other,
A sheath heater for a nuclear fuel simulating heating element, comprising a plurality of heating elements mainly made of tungsten and provided through the through hole.