JPS5997092A - Supporting device for neutron instrumentation guide tube - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a support device for a neutron instrumentation guide tube provided below the core of a boiling water nuclear reactor.

[Technical background of the invention and its problems]

The conventional boiling water reactor neutron instrumentation guide tube support device is
In the lower core solenum, the neutron instrumentation guide tubes that stand in a forest within the core shroud wall are connected together in a lattice shape using coupling members to increase the natural frequency of the entire neutron instrumentation guide tube group and increase the rigidity of each guide tube. The guide tube was constructed to reduce vibrations of the guide tube due to the flow of coolant.

However, as the flow rate of the coolant below the reactor core increases, especially the flow rate of the coolant that flows into the lower solenum along the peripheral wall of the pressure vessel and flows perpendicularly to the neutron instrumentation guide tubes, the neutron instrumentation guide tubes become integrated. It is predicted that these vibrations will not be suppressed sufficiently by simply connecting the connecting member to the core shroud, and as a countermeasure, it is being considered to fix the end of the connecting member to the core shroud wall in order to further improve the rigidity.

However, in this case, during reactor operation, the coolant around the instrumentation guide tubes is at a high temperature, so thermal expansion occurs in the connecting members, causing distortion in the lattice of the guide tube group, and increasing thermal stress. was there.

[Purpose of the invention]

The present invention was made based on these circumstances, and
The purpose is to increase rigidity by connecting the neutron instrumentation guide tube group in a lattice shape with connecting members, and to increase the rigidity due to the flow of coolant. It is an object of the present invention to provide a neutron instrumentation guide tube support device that can reduce vibration and prevent damage due to distortion of the lattice due to thermal expansion of coupling members and increase in thermal stress.

[Summary of the invention]

The neutron instrumentation guide tube support device of the present invention divides a group of neutron instrumentation guide tubes arranged in a core shroud wall into at least a central guide tube group and a peripheral guide tube group surrounding this, The guide tube groups at the center and the periphery are connected independently in a lattice shape for each group using some connecting members, and only a part of the connecting member connecting the guide tube groups at the periphery is connected to the core shroud wall. It is configured in a fixed manner.

[Embodiments of the invention]

Hereinafter, a description will be given based on an embodiment shown in the drawings.

Figure 1 shows the lower blenum section of the boiling water reactor where the neutron instrumentation guide tube is installed.

That is, inside the reactor pressure vessel 1, there is a lower solenum surrounded by the searoud wall 3 that constitutes the reactor core 2, and there is a space between the peripheral wall of the reactor pressure vessel 1 and the shroud wall 3 (
Coolant is pumped in by the provided internal pump f4.

Further, in the lower plenum, a large number of neutron instrumentation guide tubes 5 containing built-in neutrons for measuring the neutrons of the reactor core 2 are arranged in a forest together with control rods (not shown). These neutron instrumentation guide tubes 5 are connected by band-like connecting members 6 assembled in one or more stages. As shown in FIG. 2, the coupling members 6 are connected to each other in a lattice shape to increase rigidity.

In addition, the neutron instrumentation guide tube 5... is shown in Figure 2 (■ in Figure 1).
As shown in the cross-sectional view taken along the line -■, the tube is divided into a guide tube group 5A in the center and a guide tube group 5B in the periphery, and each group is independently connected in a grid pattern. In addition, the second
7 in the figure schematically shows fuel assemblies that constitute the reactor core 2. In FIG.

The guide tubes 5 are connected to each other as shown in FIG.

That is, the guide tube 5 is sandwiched between a pair of joints 8, 8 whose center is curved into a semicircular shape, and the ends of the connecting member 6 are held between the ends of the side joints 8°8 to unite the king. Tightening is done using a fixing device 9 such as a bolt or rivet.

Regarding the peripheral guide tube group 5B, a part of the connecting members 6 at the end end is fixed to the shroud wall 3 by welding, but - a plurality of connecting members 6 connected in a straight line . . is designed so that neither end thereof is fixed to the shroud wall 3. This is connecting member 6...
By leaving at least one end side free, the increase in stress due to thermal expansion can be alleviated.

Furthermore, for the central guide tube group 5A, none of the coupling members 6 is fixed to the shroud wall 3.

By configuring as described above, the following effects can be obtained.

In other words, due to an increase in the flow rate of coolant in the lower core plenum, the neutron instrumentation guide pipes 5 that stand in the lower plenum
Strong lateral pressure acts on...

This side pressure is strong at the periphery, and as it approaches the center of the lower plenum, it is relieved by the guide tubes 5 and the control rods.

By the way, the guide tube 5 in the peripheral part is connected to the connecting member 6...
are connected in a lattice shape to form an integrated guide tube group 5B, and as a result of a part of the connecting members 6 being fixed to the sea loud wall 3, the rigidity of the guide tube group 5B is sufficiently increased. Therefore, even if the guide tubes 5 receive strong lateral pressure due to the flow of coolant, the vibrations of the guide tubes 5 can be suppressed to a small level.

Furthermore, even if thermal expansion occurs in the coupling members 6..., the plurality of coupling members 6..., which are coupled in a straight line, are still coupled to the central guide tube 5... Since at least one end is free, the thermal stress of the coupling member 6 can be suppressed to a low level, and the guide tube 5 as well as the coupling member 6 can be kept to a minimum.
... will not cause any distortion or breakage.

On the other hand, the guide tubes 5 in the center are also connected in a lattice shape by the connecting members 6 to form an integrated guide tube group 5A, thereby increasing the rigidity of the guide tubes, so that the coolant can be Vibrations caused by the flow can be suppressed to a small level. Note that since the guide tube group 5A in the center is not fixed to the sea loud wall 3, it has lower rigidity than the guide tube group 5A in the peripheral area, but as mentioned earlier, the lateral pressure due to the flow of coolant is generated in the center. Since it is weaker than the peripheral portion, the vibration of the guide tube group 5A can be suppressed to a sufficiently low level. Furthermore, since they are not fixed to the shroud wall 3, thermal stress can be suppressed to a low level, and there is no risk of distortion, breakage, etc. occurring in the guide tubes 5 and the coupling members 6.

Note that the present invention should not be limited to the above embodiments. For example, the neutron instrumentation guide tube may be divided into three guide tube groups: a central portion, a peripheral portion, and an intermediate portion.

〔Effect of the invention〕

As described above in detail, the neutron instrumentation guide tube support device according to the present invention divides the neutron instrumentation guide tube into at least a center guide tube group and a peripheral guide tube group, and Each group is independently connected in a lattice shape via a connecting member,
One structure is constructed by fixing only a part of the connecting member that connects the peripheral guide tube group to the core shroud wall. Therefore, the rigidity of the guide tube is increased, vibrations caused by the flow of the coolant can be suppressed to a small level, and desired effects such as being able to prevent damage due to strain caused by thermal expansion of the connecting member can be achieved.

[Brief explanation of drawings]

The figures show one embodiment of the present invention, in which Figure 1 is a vertical cross-sectional view of the area around the lower plenum of a boiling water reactor, and Figure 2 is a vertical cross-sectional view of the area around the lower plenum of a boiling water reactor.
FIG. 3 is a cross-sectional view taken along the shoreline ``■'' in the figure, and FIG. 3 is a plan view showing the connecting portion between the connecting member and the neutron instrumentation guide tube. DESCRIPTION OF SYMBOLS 1... Reactor pressure vessel, 2... Reactor core, 3... Shroud wall, 4... Pump, 5... Neutron instrumentation guide tube, 5A, 5B... Guide tube group, 6... ...Connection member. Applicant's agent Patent attorney Takeshi Suzue Hikoga 1 Figure 2 Figure 3

Claims (1)

[Claims] The neutron instrumentation guide tube group that stands in the core shroud wall is divided into at least a central guide tube group and a peripheral guide tube group surrounding this, and the central and peripheral guide tube groups are combined. A neutron instrumentation guide tube support characterized in that each group is independently connected in a lattice shape through members, and only a part of the connecting member that connects guide tube groups in the peripheral part is fixed to a core shroud wall. Device.