JPS6339675Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to an in-reactor neutron flux measuring device with an improved neutron detection tube guide tube.

As this type of device shown in Fig. 1, there is a
There is one known as shown in Figure 1. In FIG. 1, 1 is a reactor vessel, and 2 is a guide tube for a neutron detector that penetrates the reactor vessel 1 and extends inside and outside the reactor vessel.

One end of the guide tube 2 inside the reactor vessel 1 is hermetically sealed, and the other end outside the reactor vessel 1 is open for insertion of a neutron detector.

Further, a heating and heat-retaining device 3 is provided around the guide tube 2 along the guide tube 2.
This is to keep the temperature at a high temperature.

Generally, carbon dioxide gas is injected into the guide tube to prevent oxidation of the guide tube 2, but this carbon dioxide gas, air, and hydrogen react in the guide tube inside the furnace vessel, and it becomes a gas at high temperatures, but at low temperatures. Foreign matter is produced that hardens. If this foreign material sticks to the inner wall of the guide tube,
It becomes difficult to insert and withdraw the neutron detector into the reactor vessel.

The heating and insulation device 3 is intended to prevent this foreign material from adhering to the inner wall of the low-temperature section guide tube outside the reactor vessel 1;
Disadvantages include the need to heat the entire length of the guide tube 2 located outside, which makes the heating device long, and foreign matter that comes out of the open end may adhere to nearby equipment and have an adverse effect. It was hot.

This idea was made in order to eliminate the above-mentioned drawbacks of the conventional method. By providing a branch pipe in the middle of the guide pipe outside the reactor vessel and cooling this branch pipe, the heating device of the guide pipe can be shortened. It is an object of the present invention to provide a neutron flux measurement device in a nuclear reactor that can trap foreign matter reliably.

Hereinafter, an embodiment of the in-reactor neutron flux measuring device of this invention will be described based on the drawings. FIG. 2 is a sectional view of a guide tube portion in one embodiment. In FIG. 2, parts that are the same as those in FIG. 1 are given the same reference numerals, and their explanation will be omitted, and the parts that are different from those in FIG. 1 will be mainly described.

In FIG. 2, the reactor vessel 1 and thermal protection device 3 are the same as in FIG. 1, and also in the guide tube 2, one end of the reactor vessel 1 is hermetically sealed as in FIG. The same is true. However, it differs from FIG. 1 in the following points.

That is, the guide tube 2 outside the reactor vessel 1
A branch pipe 4 is provided in the middle, and this branch pipe 4 is cooled by a cooling device 5.
A heating and heat-retaining device 3 is provided in the guide tube 2 between the position where the branch pipe 4 is provided and the portion where the guide tube 2 penetrates the reactor vessel 1 in the same manner as in the prior art.

With this configuration, reactor vessel 1
Foreign matter generated inside the guide tube 2 will not stick to the guide tube section where the heating and heat retention device 3 is installed.
Since the foreign matter is fixed when it touches the cooling part of the branch pipe 4, the foreign matter does not move further toward the open end of the guide pipe 2, and can be reliably deposited inside the branch pipe.

Note that if a large number of small metal pieces are placed inside the branch pipe 4, the effect of depositing foreign matter will be further improved.

Furthermore, in the above embodiment, the heating and heat-insulating device 3 is applied only to the guide pipe 2 between the position of the branch pipe 4 and the penetrating portion of the reactor vessel 1. can also be extended a little further toward the open end.

Furthermore, in an in-reactor neutron flux measuring device having a large number of guide tubes, a plurality of branch tubes provided in each guide tube 2 can be cooled by the same cooling device.

Further, since the solidification temperature of foreign matter is 45 to 50°C, depending on the ambient temperature, cooling of the branch pipes may be performed by natural cooling.

As described above, according to the in-reactor neutron flux measuring device of this invention, a branch pipe is provided in the middle of the guide pipe outside the reactor vessel, and this branch pipe is cooled. This has the effect of shortening the heating length of the reactor, and also ensuring that foreign matter generated inside the guide tube inside the reactor vessel is deposited in the branch pipe, allowing smooth insertion and withdrawal of the neutron detector.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a guide tube portion of a conventional in-reactor neutron flux measuring device, and FIG. 2 is a cross-sectional view of a guide tube portion in an embodiment of the in-core neutron flux measuring device of this invention. . 1... Nuclear reactor vessel, 2... Guide tube for neutron detector, 3... Heating and heat retention device, 4... Branch pipe, 5... Cooling device. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Scope of Claim for Utility Model Registration] (1) A reactor vessel, one end of which penetrates the wall of the reactor vessel and is hermetically sealed within the reactor vessel, and the other end is open outside the reactor vessel, and An in-reactor neutron flux measuring device comprising a guide tube for a neutron detection tube having branch tubes at predetermined locations, a cooling device for cooling the branch tube, and a heat insulating device or heating heat insulating device to keep the guide tube at a high temperature. (2) A nuclear reactor interior according to claim 1 of the utility model registration claim, characterized in that a plurality of guide pipes are provided, each having a large number of branch pipes, and the plurality of branch pipes are cooled by the same cooling device. Neutron flux measurement device. (3) The in-reactor neutron flux measuring device according to claim 1 or 2, wherein the branch pipe has a large number of metal pieces inserted therein.