JPH0432358B2 - - Google Patents

Description

[Detailed description of the invention] [Object of the invention] (Industrial application field) The present invention relates to a neutron instrumentation guide tube in a nuclear reactor,
In particular, it relates to a neutron instrumentation guide tube inside a nuclear reactor with improved earthquake resistance.

(Prior Art) The in-reactor neutron instrumentation guide tubes of a boiling water nuclear power plant are a plurality of relatively long tubes that are arranged at the lower part of the nuclear reactor and guide the neutron instrumentation equipment from below.

The flow conditions for cooling water in the lower part of the reactor core are relatively severe, and if the neutron instrumentation guide tube were placed alone, rigidity would be an issue, so the support structure for these tubes was constructed by connecting the tubes with support metal fittings. ing.
Since the flow of cooling water in the reactor is axially symmetrical about the reactor center axis, vibration of the neutron instrumentation guide tubes due to this flowing water can be prevented by connecting the guide tubes together.

However, when the entire tube group vibrates greatly in the same phase due to vibrations in the same direction, such as during an earthquake, there is a risk of damaging other equipment, such as control rod guide tubes. In order to prevent this, it has been considered to connect and fix the instrumentation guide tube located on the outer periphery to the core shroud using a connecting member to improve rigidity.

An example of connecting and fixing the instrumentation guide tube to the core shroud using the connecting member will be described with reference to FIG. 9. Incidentally, FIG. 9 is a schematic cross-sectional view showing how the neutron instrumentation guide tubes in the nuclear reactor are connected.

As shown in FIG. 9, the plurality of neutron instrumentation guide tubes 1 are each connected to each other by an internal connecting member 9a, and the neutron instrumentation guide tube 1 (four corners in the figure) located at the outer peripheral end thereof and the core shroud 5 are relatively firmly connected and fixed by an external connecting member 9b.

With this configuration (a configuration in which all of the neutron instrumentation guide tubes 1 arranged on the outer circumferential side are fixed to the core shroud 5 with external connecting members) can improve the overall rigidity, The temperature conditions inside the furnace are harsh, and due to the high temperature, differences in thermal expansion caused by each material become a problem. In other words, the core shroud 5 is made of Inconel (trade name), which has excellent high-temperature strength, and the neutron instrumentation guide tube 1 and the connecting member 9 are made of Inconel, which is made of Inconel, which has excellent high-temperature strength.
SUS is commonly used.

Inconel has a smaller coefficient of thermal expansion than SUS (coefficient of thermal expansion of Inconel: 14.17×
10 ^-6 mm/mm℃, SUS thermal expansion coefficient: 17.62×10 ^-6
mm/mm℃) SUS is shown in the drawing, as shown in Fig. 9, the core shroud 5 made of Inconel apparently shrinks and deforms, and the connecting member 9 made of SUS
undergoes stress deformation.

In addition, in Figure 9, the solid line shows the state before deformation, and the broken line shows the state after deformation, and as mentioned above, it shows the relative thermal expansion deformation of Inconel based on SUS, and as a whole, it shows the state at high temperature. Although it expands against, it is omitted in the drawing. That is, although it expands as a whole, by showing the SUS after expansion and deformation in FIG. 9 as having the same size as the SUS before expansion, the core shroud 5 made of Inconel is shown to be apparently contracted and deformed.

Due to the shrinkage deformation of the core shroud 5, the external connecting member 9b, which is connected and fixed to the core shroud 5, is deformed as schematically indicated by the symbol A in FIG. )
However, there is a problem in that there is an extremely large possibility that the connecting member will be damaged as a result.

(Problems to be Solved by the Invention) As described above, the conventional in-reactor neutron instrumentation guide tube is relatively firmly fixed to the core shroud 5 by the connecting member, so the connecting member is damaged due to stress due to thermal expansion. There was a risk of damage.

The present invention has been made in order to solve the above problems, and is designed to alleviate the thermal stress applied to the connecting member that is connected and fixed to the reactor core shroud so that the in-reactor neutron instrumentation guide tube does not vibrate greatly due to disturbance. The purpose of the present invention is to obtain an in-reactor neutron instrumentation guide tube that prevents damage to connecting members.

[Structure of the Invention] (Means for Solving the Problem) The present invention provides a neutron instrumentation guide tube that serves as a guide trajectory for a plurality of neutron detectors provided between the bottom of a reactor pressure vessel and a core support plate. , an internal connecting member that interconnects these neutron instrumentation guide tubes, and an external connecting member that connects and fixes the neutron instrumentation guide tube located near the inner wall of the core shroud to the inner wall of the core shroud. In the in-reactor neutron instrumentation guide tube equipped with the above, an arbitrary row of the neutron instrumentation guide tubes connected by the internal connecting member is connected to only the neutron instrumentation guide tube located at one end side of this row and the reactor core. It is characterized in that it is configured to be connected and fixed to the inner wall of the shroud by the external connecting member.

(Operation) According to the present invention configured as described above, the first
As shown by the broken line in the figure, only a slight deformation of the relatively long neutron instrumentation guide tube does not generate local stress on the connecting members, and can prevent stress damage in the connecting members due to thermal expansion differences. It is preventable.

In other words, the connecting members do not deform or receive stress even during high-temperature operation, and
Even if vibrations of the same phase act, such as during an earthquake, the neutron instrumentation guide tubes will not collide with each other, or the neutron instrumentation guide tubes and other equipment will not collide.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

Embodiment 1 FIG. 1 is a schematic cross-sectional view showing how neutron instrumentation guide tubes in a nuclear reactor are connected. Also,
FIG. 2 is an explanatory diagram showing the installation location of the neutron instrumentation guide tube in the reactor, FIG. 3 is a schematic diagram showing the connection between the neutron instrumentation guide tube and the core shroud, and FIG. In FIGS. 2 and 3, the same parts as in FIG. 9 are designated by the same reference numerals, and detailed explanations are omitted.

The neutron instrumentation guide tube 1 is provided between the bottom of the reactor pressure vessel 2 and the core support plate 3 and between the control rod guide tubes 4 . In addition, this neutron instrumentation guide tube 1
serves as a guide trajectory for neutron flux detectors such as LPRM (Local Power Monitoring System) or TIP (Travelling Calibration System). In addition, the core shroud 5 in the figure
covers a reactor core consisting of a neutron instrumentation guide tube 1, a control rod guide tube 4, and a fuel assembly 6.

The feature of the present invention is that the external connecting member 9b
The structure is connected to the core shroud 5. The internal connecting member 9a has the function of connecting the neutron instrumentation guide tubes 1 to each other as described above, and the external connecting member 9 has the function of connecting these to the core shroud 5.

That is, as shown in FIG. 1, any row of neutron instrumentation guide tubes 1 connected by the internal connection member 9a is connected to only the neutron instrumentation guide tubes 1 located at one end of this row and the core shroud 5. It is constructed by connecting and fixing the inner wall with an external connecting member 9b.

The above feature points will be explained in more detail with reference to FIG.

For convenience of explanation, the symbols are set in FIG. 1 as follows.

As the rows of neutron _{instrumentation} guide tubes 1 connected by _the internal connecting member _9a , the vertical rows in _FIG . The _four columns are B ₁ , B ₂ , B ₃ , and B in order.

In addition, the neutron instrumentation guide tubes 1 arranged in a matrix in the figure are ₁₁₁ for the one located at the intersection of the _first rows A1 _and B, ₁₂₄ for the one located at the intersection of _{the four} rows _A2 and B, The one located at the intersection of A ₃ and B ₁ column is 1 ₁₃ ,
Let ₁₄₂ be the one located in _{the 2nd} column of A ₄ and B.

The external connecting members 9b are two from the neutron instrumentation guide tube ₁₁₁ upward and to the left in the figure, one from the neutron instrumentation guide tube ₁₂₄ downward in the figure, and one from the neutron instrumentation guide tube ₁₁₃ in the figure. One upward, neutron instrumentation guide tube 1
₄₂ to the right in the figure, neutron instrumentation guide tube 1 ₄₄
There are six in total, one downward in the figure.

In this embodiment, the idea of the arrangement of the external connecting member 9b is that among the rows of neutron instrumentation guide tubes 1 connected by the internal connecting member 9a, adjacent rows are arranged in directions that are approximately 180 degrees different from each other by the external connecting member 9b. It is connected and fixed to the inner wall of the core shroud 5. That is, pairs of adjacent columns (A ₁ and A ₂ ) (A ₃ and A ₄ )
(B ₁ and B ₂ ) are connected and fixed to the inner wall of the core shroud 5 in directions approximately 180 degrees different from each other by external connection members 9b.

With this configuration, the following actions and effects can be obtained.

That is, in FIG. 1, the solid line shows the state before deformation and the broken line shows the state after deformation, as in FIG. 9, but the neutron instrumentation guide tube 1 is only slightly deformed in the direction perpendicular to its length. (The positions appear shifted in FIG. 1), and the internal and external connecting members 9a and 9b
never deforms. When compared with FIG. 9, this shows that the external connecting member 9b indicated by the symbol A in FIG.
This is also clear from the fact that the local deformation does not occur in the configuration shown in FIG.

In other words, the relatively long neutron instrumentation guide tube 1
Even if the connecting member is slightly deformed, no local stress is generated in the connecting member, and stress damage to the connecting member due to a difference in thermal expansion can be prevented.

With the above configuration, the internal and external connecting members 9a and 9b will not be deformed or subjected to stress even during high temperature operation, and
Even if vibrations of the same phase act, such as during an earthquake, the neutron instrumentation guide tubes will not collide with each other, or the neutron instrumentation guide tubes and other equipment will not collide.

Note that which neutron instrumentation guide tube 1 is connected to the core shroud 5 is not limited to the embodiment shown in FIG. 1, and can be modified in various ways without departing from the gist of the present invention. .

The support fitting 7 for connecting the neutron instrumentation guide tubes 1 to each other with the internal connection member 9a is constructed by sandwiching the neutron instrumentation guide tube 1 between band plates 8 as shown in FIGS. 4 and 5. The plate 8 and the strip plate 8 of another neutron instrumentation guide tube 1 are connected by an internal connecting member 9a.

The external connection member 9b connected to the neutron instrumentation guide tube 1 located on the outer periphery is connected to the support 10 attached to the core shroud 5 as shown in FIGS. 6 and 7.
connected to.

Example 2 In the in-reactor neutron instrumentation guide tube configured as described above, internal and external connecting members 9a, 9
If the material of b and the core shroud 5 are the same or have the same coefficient of linear expansion, the internal and external connection members 9
This can be said to be a more desirable configuration since the stress applied to a and 9b can be made small or almost zero.

With this configuration, the connecting members are unlikely to deform or receive stress even during high-temperature operation, and even if vibrations of the same phase act, such as during an earthquake, the neutron guide tubes can be easily connected to each other. There will be no collision between the neutron instrumentation guide tube and other equipment.

Embodiment 3 The above embodiment shows an example in which the core shroud 5 is made of a single material, but as shown in FIG.
In the case where the core shroud 5 is made of a different material or more, the material of the internal and external connecting members 9a and 9b is also the same as that of the core shroud 5, or a material with a linear expansion coefficient equivalent to that of the core shroud 5. That is, in FIG. 8, the core shroud 5 and the internal and external connecting members 9a and 9b are made of the same material, and the core shroud 5'
The inner and outer connecting members 9a' and 9b' are made of the same material.

Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment.
Various modifications and embodiments can be made without departing from the gist of the invention.

[Effects of the Invention] As detailed above, according to the present invention, the connecting members are not deformed or subjected to stress even during high-temperature operation of the nuclear reactor, and the same phase does not occur during earthquakes, etc. Even if vibrations occur, the neutron instrumentation guide tubes will not collide with each other, nor will the neutron instrumentation guide tubes and other equipment collide.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view illustrating an embodiment of a structure in which in-reactor neutron instrumentation guide tubes of the present invention are connected by a connecting member, and FIGS. 2 and 3 are in-reactor neutron instrumentation guide tubes of the present invention. 4 and 5 are plan views showing how the connecting member is attached, and FIGS. 6 and 7 are cross-sectional views illustrating the schematic structure of the installation guide tube. FIG. 8, which is a plan view showing the situation, is a sectional view showing another embodiment of the present invention. FIG. 9 is a schematic cross-sectional view showing how neutron instrumentation guide tubes in a nuclear reactor are connected in a conventional example. 1... Neutron instrumentation guide tube, 2... Reactor pressure vessel, 3... Core support plate, 4... Control rod guide tube,
5, 5'... Core shroud, 6... Fuel assembly,
7... Support metal fittings, 8... Band plates, 9a, 9a'... Internal connection members, 9b, 9b'... External connection members, 10
...Support.

Claims (1)

[Claims] 1. A plurality of neutron instrumentation guide tubes that are provided between the bottom of the reactor pressure vessel and the core support plate and serve as a guide trajectory for a neutron detector, and these neutron instrumentation guide tubes are interconnected. An in-reactor neutron instrumentation guide tube comprising an internal connection member that connects and fixes the neutron instrumentation guide tube disposed close to the inner wall of the core shroud to the inner wall of the core shroud, In any row of the neutron instrumentation guide tubes connected by the internal connecting member, only the neutron instrumentation guide tubes located at one end of this row and the inner wall of the core shroud are connected and fixed by the external connecting member. What is claimed is: 1. A neutron instrumentation guide tube in a nuclear reactor, characterized by comprising: 2. The rows of neutron instrumentation guide tubes connected by the internal connecting member are connected and fixed to the core shroud inner wall in directions that differ by approximately 180 degrees between adjacent rows by the external connecting member. An in-reactor neutron instrumentation guide tube according to claim 1. 3. The in-reactor neutron instrumentation guide tube according to claim 1, wherein the core shroud and the internal and external connecting members are made of materials having substantially the same coefficient of linear expansion or the same material.