JPS6027979Y2 - neutron detector - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a neutron detector used for measuring neutron flux in nuclear reactors, and in particular to an airtight sealing structure for the outer container of the detector and the cable.

Generally, neutron detectors for nuclear reactors are required to have extremely high reliability, and the outer container of the detector and the MI cable must be completely hermetically sealed.

A conventional device of this type is shown in FIG.

In the figure, 1 is a neutron detection element section, 2 is a ■cable for applying high voltage to the neutron detection element section 1 or taking out a signal, 3 is a connector for connecting the above ■cable 2 and an electric circuit, 4 5 is an outer container for keeping the neutron detection element section 1 and the M1 cable 2 in a dehumidified atmosphere, 5 is a joint for joining the outer container 4 and the MI cable 2 while maintaining vacuum tightness, and 6 is an insulator. .

The inside of the neutron detection element section 1 is filled with a substance that is sensitive to neutrons (for example, IOB, 235U) and an ionized gas for electrically extracting a signal by the energy generated by the nuclear fission reaction between the neutron-sensitive substance and the neutrons. has been done.

The neutrons to be measured pass through the outer container 4 and enter.

The MI cable 2 and connector 3 are used to apply voltage to the neutron detection element section 1 described above, take out signals from the detection element section 1, and connect to an electrical measurement system.

However, the signal from the seven neutron detection element section 1 is 10-12 [A
] It is a minute current on the order of
Because the voltage is as high as (V) 3 CKV), the insulation resistance of the insulators that make up these components is between 1σ2 [Ω] and 10" (
Ω] is required.

To this end, it is necessary to keep these insulators from the external atmosphere and prevent deterioration of insulation resistance due to moisture.

The neutron detection element section 1 and MI cable 2 for this purpose are hermetically sealed by an outer container 4 and a joint 5.

Further, a neutron detection element section 1, an outer container 4. The material used for the joint 5 is a material that is less activated by neutron flux (AJ
, Ti, Zr, etc.) are required.

The material used for the outer container 4 is neutron flux absorption 9
A material that has little reflection and can be airtightly sealed with the cable 2 is required.

In order to satisfy these requirements, the outer container 4 is conventionally made of Ti, and the joint 5 is made of brazed Ti and stainless steel. An airtight seal was achieved by welding the stainless steel part of the joint 5 to the stainless steel part of the joint 5.

However, since the outer container 4 of the conventional neutron detector is made of Ti, the absorption of neutrons is 9 compared to A/.
There is a lot of reflection, and the incidence rate of neutron flux to the neutron detection element 1 is poor.

Therefore, it becomes necessary to cut the outer periphery of the outer container 4 over the entire length of several hundred degrees to a wall thickness of approximately 0.5 mm.

However, the commonly used Ti pipes are welded pipes, so they have poor roundness and are particularly deformed near the welded joints.
It has drawbacks such as requiring advanced machining technology to machine to a certain degree and yield rate during machining is also poor.

This invention was developed to solve the above-mentioned drawbacks of conventional neutron detectors, and the outer container is made of aluminum or an alloy mainly composed of aluminum, which absorbs less neutron flux, and the outer container is made of aluminum or an alloy mainly composed of aluminum. The joint device for airtight sealing is made of aluminum or a first joint mainly composed of aluminum, stainless steel/L/, Fe-Ni
a second joint made of at least one of alloy, Fe-Ni-Co alloy, and Fe, and these joints are hermetically connected by a bonding material, and the first joint, the outer container, and the second joint are The joint and the stainless steel outer case of the MI cable are connected by welding, eliminating the need for machine processing to thin the outer case, reducing processing costs, improving processing yield, and improving reliability. The purpose was to obtain a neutron detector that could improve the

An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 2, 21 is an outer container made of Al; 22
is the first tube made of A/ that can be hermetically sealed with this outer container 21 by welding.
The joint 23 is a second joint made of stainless steel that can be welded to the stainless steel part of the MI cable 2.

The first joint 22 made by AJ and SuS (stainless steel)
The second joint 23, made of A.

Further, the second joint 23 is plated with Ni plating or the like in order to eliminate poor flow of the brazing material due to oxidation of Cr during Af brazing.

SuS and Al cannot be welded in normal welding, but by using the joint of the present invention, it is possible to weld the Al outer container 21 and the Al joint 22 with Af and similar metals, and to weld SuS and Al joints 22. The first joint 23 and the outer cylinder of the MI cable 2 are made of SuS, and the same metals are welded together, making it possible to vacuum-tightly seal the cable with highly reliable welding.

Next, the first joint 22 made of Al and the second joint 2 made of SuS
In the case of vacuum sealing in step 3, a highly reliable vacuum seal can be obtained by A/brazing, etc., but in this case, SuS is used as the material of the second joint 23, and Al brazing is performed using flux. When using flux, the optimum temperature for removing the metal oxide film differs depending on the metal, and compared to l', the oxide film removal efficiency of SuS is lower unless the temperature is higher.

Conversely, at the optimum temperature for SuS, the efficiency of removing the oxide film of Af decreases, and the problem of At' matrix melting also occurs.

Therefore, by plating a material such as SuS with a metal that requires a low oxide film removal temperature using Ni plating or flux, highly reliable brazing of Al and SuS can be obtained.

Note that in the above embodiment, the first. Although we have shown the case where Af brazing filler metal is used as the bonding material for joining the second joint, depending on the operating temperature of the neutron detector, epoxy adhesive or lubricant may be used.
'You may use hand soldering.

The material of the second joint 23 is SuS, which is the material of the Ml cable.
Hyperloy (Fe--Ni alloy), ] bar/L/ (Fe--Ni--Co alloy), Fe, etc., which can be melted with , may also be used.

Further, although an Al brazing material using flux is shown as the AI brazing material, an A/brazing material containing Mg may be used and brazing may be performed in a vacuum.

As described above, according to this invention, the outer container can be formed of aluminum or its alloy, and the outer container has a good neutron flux incidence rate, and the conventional thinning process of the outer container is no longer necessary. This has the effect of producing a highly reliable neutron detector with inexpensive parts and high yield.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional side view of a conventional neutron detector, and FIG. 2 is a cross-sectional side view showing a neutron detector according to an embodiment of the invention. In the figure, 1... neutron detection element, 2...
...■Cable, 3...Connector 4...
... Outer container, 5 ... Fitting, 21 ...
・Outer container, 22...First joint, 23...
...Second joint, 24...l' brazing metal, 6...
...It is an insulator. It should be noted that the same reference numerals in the drawings indicate corresponding parts.

Claims (1)

[Claims for Utility Model Registration] 1. An outer container housing a neutron detection element therein, a cable electrically connected to the neutron detection element and having an outer cylinder made of stainless steel, and the outer container and the cable. A neutron detector has a joint device that is coupled to an outer case to hermetically seal the inside of the outer case, wherein the outer case is made of aluminum or an alloy containing aluminum as a main component; and a first joint made of aluminum or an alloy containing aluminum as a main component, and the first joint is hermetically joined with a bonding material to stainless steel, Fe-Ni alloy, Fe-Ni-Co alloy,
and a second joint made of at least one of iron, the first joint and the outer container being joined by welding, and the second joint being joined to the outer case of the cable by welding. A neutron detector characterized by: 2 The second joint is nickel-plated, and the first joint and the second joint are hermetically joined by brazing with an aluminum brazing filler metal, as set forth in claim 1 of the utility model registration claim. neutron detector.