JPH0140315B2 - - Google Patents

Description

[Detailed Description of the Invention] <Technical Classification/Field> The disclosed technology belongs to the technical field of operation and control of control rods set inside a nuclear reactor vessel.

<Explanation of the gist> This invention is set in a container of a nuclear reactor such as a fast breeder reactor (FBR), and is linked to be able to move up and down by an upper drive device, and is provided in a guide tube. The control rods are immersed in the cooling liquid sodium, so that the control rods do not shake or shake due to the lateral vibrations of the flow force caused by the cooling liquid sodium, and the control rods do not shake horizontally with the guide pipe due to earthquakes, etc. This invention relates to a lateral vibration suppression device that can quickly scram without being affected by misalignment, and in particular, it is designed to ensure sufficient flow of liquid sodium for cooling between the control rod and the guide tube. A large number of flexible thin rods are fixed in a radial direction from the side surface of the control rod toward the inner surface of the guide tube, or conversely from the inner surface of the guide tube toward the side surface of the control rod. , the tip forms a set minute clearance with respect to the opposing surface to ensure circulation cooling of the cooling liquid sodium, prevent lateral vibration due to the flow force, and prevent interference with the guide pipe due to earthquakes etc. This invention relates to a control rod lateral vibration suppression device that prevents the descending function from being impaired even if there is misalignment or the like.

<Prior art> As is well known, in a nuclear reactor, in order to adjust the output during operation, the control rods set in the reactor core inside the vessel are raised and lowered with the control rods set in the guide tubes by a drive device located above the control rods. However, the functions of the control rods are generally to adjust the output during operation and to descend as quickly as possible to stop the reactor core in the event of an emergency such as an earthquake. be.

Usually, a single control rod serves both functions.

Briefly explaining this aspect based on the schematic diagram of FIG. 1, the reactor vessel 1 is sealed by a shielding plug 2 at the upper part, and the cooling which flows in through the inlet 3 at the lower part and the outlet 4 at the upper part. The liquid sodium 5 is stored up to the level of the outlet 4, and the upper guide tube 6 provided in the shielding plug 2 is connected to the control rod 8 suspended by the drive device 7 in the upper part to support the lower part. In addition to being provided in the mechanism 9, the in-core fuel 10
In the lower guide tube 11 set in the lower guide tube 11, as shown in the normal mode on the left side of FIG. In the event of an emergency such as an earthquake, the dart ram is scrammed and quickly lowered so that the dart ram is seated in the dart pot of the lower guide pipe 11.

By the way, the relationship between the control rod 8 and the guide tubes 6, 11 has the following problem.

That is, in the event of an earthquake such as the above-mentioned emergency, the lateral vibration may cause misalignment between the upper guide tube 6 and the lower guide tube 11 and between the control rod 8, as shown in FIG. If this occurs, if the diameters of the upper guide tube 6 and lower guide tube 11 are small, that is, if the gap between the inner surfaces of the guide tubes 6 and 11 and the side surface of the control rod 8 is small, the control rod 8 is difficult to perform, and it is difficult for the control rod to quickly ram its dart ram and sit in the dart pot of the lower guide tube 11 due to gravity or the like.

Therefore, in order to quickly scram in the event of an emergency, it is advantageous if the distance between the inner surfaces of the guide tubes 6 and 11 and the side surfaces of the control rods 8 is large, which facilitates scramming.

On the other hand, as mentioned above, during operation, the space between the guide tubes 6, 11 and the control rod 8 is filled with cooling liquid sodium 5, so that
Vibrations caused by the flow force, particularly lateral vibrations, cause regular lateral vibrations in the control rod 8, causing fluctuations in the output during normal operation.

For this purpose, it is better that the cross-sectional ring-shaped gap between the guide tubes 6, 11 and the control rod 8 be small.

There is a situation where it is necessary to give priority to one of the contradictory conditions between the two, and although it is natural to do so, in the past, priority was given to Scrum in an emergency, and the emergency stop function was Priority is given to the inner surface of the guide tube 8 and the control rods 6, 1.
There was a large gap between it and the side of 1.

Therefore, the lateral vibration behavior of the control rod 8 due to the flow force of the cooling liquid sodium flowing between the guide tubes 6, 11 and the control rod during normal operation cannot be absorbed, and therefore output fluctuations are likely to occur. There was a potential drawback.

To deal with this, for example, JP-A-58-11888
As in the invention disclosed in the above publication, a means for attaching a ball or roller to the above-mentioned gap has been devised. The disadvantage is that it is not in a state that is sufficient to prevent vibrations during normal operation.

As described above, the conventional technology has the disadvantage that no technology has been devised that provides both a means for keeping the control rods as still as possible during normal operation and a means for easily performing an emergency scram. .

<Objective of the invention> The object of the invention is to provide a stable stationary state of control rods for the core of a nuclear reactor such as a fast breeder reactor (FBR) during normal operation and a prompt and reliable scram formation in an emergency based on the above-mentioned conventional technology. As a technical issue to be solved, we decided to make the inner surface of the guide tube sized so that it would be possible to insert the control rod as quickly as possible in an emergency between the sides of the control rod. The object of the present invention is to provide an excellent control rod lateral vibration suppression device that is useful in the field of nuclear energy applications in the energy industry by absorbing the effects of vibration caused by the flow force of liquid sodium cooling during normal operation. be.

<Structure of the Invention> That is, the present invention is a lateral vibration suppressing device for a control rod that is vertically and vertically suspended inside a guide tube set in a nuclear reactor vessel. A large number of flexible thin rods are arranged in a radial direction from one surface to the other,
The tip of the flexible thin rod has a minute clearance a (D-d)/2>l≧(D-d-a)/2 with respect to the other surface defined by the following formula, where D: guide This is a control rod lateral vibration suppressing device characterized in that the pipe inner diameter d: the control rod outer diameter l: the length of a flexible thin rod. Therefore, even if the cooling liquid sodium filled in the container tries to apply lateral vibration to the control rod due to the flow force between the guide tube and the control rod, the large number of flexible thin rods The tip of the control rod comes into contact with the opposing surface to absorb the lateral vibration and prevent vibration of the control rod as much as possible, preventing output fluctuations and ensuring stable operation. This is a technical measure that allows the control rod to be inserted smoothly and scram easily by bending the thin flexible rod in case of an emergency.

<Embodiment - Configuration> Next, one embodiment of this invention will be described as follows based on the drawings from FIG. 3 onwards. Note that the same parts as in FIG. 1 will be explained using the same reference numerals.

In the embodiment shown in FIGS. 3 and 4, 11 is a lower guide pipe, and 8 is a control rod, which is a vessel of a nuclear reactor such as a fast breeder reactor (FBR), as in the conventional embodiment shown in FIG. 1 and set in the lower support device 9, and the gap 12 between the two is wide to facilitate scramming.

In this embodiment, stainless steel,
A large number of thin flexible rods 13, 1 made of carbon steel and having a set thickness.
3 are fixed through means such as welding so as to extend from the side surface of the control rod regularly or irregularly in multiple stages in the axial direction and radially to the inner surface of the guide tube 8. and are oriented perpendicularly to the inner surface of the guide tube 11.

The flexible thin rods 13 are arranged perpendicularly to the axial direction, and their lengths are set so that the axis of the guide tube 11 and the axis of the control rod have a minute clearance under the operating temperature conditions. If the inner diameter of the guide tube 11 is D, the outer diameter of the control rod 8 is d, and the allowable eccentricity is a, then the length l of the flexible thin rod is the fifth As shown in the figure, (D-d)/2>l≧(D-d-a)/2.

<Embodiment - Effect> In the above-described configuration, as in the embodiment on the left side shown in FIG. The control rod 8 is moved up and down in a predetermined manner to adjust its output, but in this state, the flow force of the cooling liquid sodium flowing between the inner surface of the guide tube 11 and the regular surface of the control rod 8 causes lateral vibrations in the control rod 8. is applied, and the control rod 8 attempts to vibrate in the lateral direction, but by absorbing the minute clearance a, the numerous thin flexible rods 13, 13, etc. in the vibration direction immediately come into contact with the inner surface of the guide tube, causing the guide tube to vibrate. 11, there will be no lateral vibration exceeding the set clearance, and as long as this occurs, no fluctuations will occur in the output.

In addition, if the control rod 8 falls out of alignment in an emergency, the flexible thin rod 13,
13... bends and the control rod 8 slides down the inner surface of the guide tube without resistance, so the scram is performed smoothly and easily.

Therefore, in this case, the large number of flexible thin rods 13, 13, . . . function as a kind of elastic spacer.

In the embodiments shown in FIGS. 4, 5, and 6, only a limited number of flexible thin rods 13 are shown in the horizontal direction, but in reality, they are used in the form of a mustache brush for washing bottles. Of course, a large number of them are arranged in multiple stages in the radial direction and the axial direction.

In addition, in the process of flowing the cooling liquid sodium through the space 12 between the inner surface of the guide tube and the side surface of the control rod, a large number of thin flexible rods are interposed. Since the diameter and volume are very small and the spacing 12 is relatively large, the flow path of the liquid sodium is virtually unobstructed and the flow resistance is not large.

Therefore, if an emergency such as an earthquake occurs during operation, a scram is immediately performed and the control rods 8 are inserted and lowered. As shown in FIG. 2, even if misalignment occurs, the inner diameter of the guide tubes 6 and 11 should be sufficiently large with respect to the outer diameter of the control rod 8, as shown in FIG. Therefore, it is easy to insert the dart ram, and the core seated in the dart pot of the guide tube 11 can be easily stopped.

In this case, as shown in FIG. 6, even if the thin flexible rod 13 interferes with the inner surface of the guide tube 11, it will easily warp and will not impede its downward insertion.

Furthermore, according to an experimental scale design example, D is 110
mm and d are 94 mm, which is (D-d)/2=about 8 mm, and the minute clearance a/2 of about 1 to several mm is sufficient.

It goes without saying that the embodiment of the present invention is not limited to the above-mentioned embodiment. For example, in the above-mentioned embodiment, the flexible thin rod is integrally extended and fixed from the side surface of the control rod, On the other hand, various embodiments can be used, such as conversely, a large number of thin flexible rods may be integrally fixed and inwardly extended in a kind of radial direction from the inner surface of the guide tube in a centripetal manner with respect to the control rod. Of course.

Regarding the axial arrangement of the flexible thin rod,
Although it may be arranged in one stage or in multiple stages, it is preferable to arrange them in multiple stages at random, since this produces an effect of suppressing vibrations caused by the flow.

Furthermore, the lengths of the flexible thin rods do not necessarily have to be exactly the same.

<Effects of the Invention> As described above, according to the present invention, a control rod that is movable by being inserted into a guide tube set in a vessel of a nuclear reactor such as a fast breeder reactor (FBR) can be operated during normal operation. Even if it receives vibration due to the flow force caused by the flow of the cooling liquid sodium inside it, the group of flexible thin rods comes into contact with the opposing surface and creates a buffering effect, absorbing the vibration. The excellent effect is that there is little movement, and as long as there is no output fluctuation. On the other hand, in an emergency such as an earthquake, even if the control rod and the guide tube become misaligned, the flexible thin rod can be used as the other side. Since the insert flexibly and elastically abuts against the insert, it is easy to insert the insert, and the insertion is performed smoothly.

In addition, during normal operation, since each flexible thin rod has a small diameter and small volume, it does not substantially impede the flow of the sodium metal liquid for cooling, and the flow resistance does not increase. There are also advantages.

As described above, according to the present invention, extremely excellent effects can be achieved in that both safety and stable operation can be expected in the use of nuclear power.

[Brief explanation of drawings]

Figure 1 is a schematic sectional view explaining the positional relationship between guide tubes and control rods set in a general nuclear reactor vessel, and Figure 2 is an explanation of misalignment of the upper and lower guide tubes and control rods during an earthquake. A schematic cross-sectional view, FIG. 3 and the following are explanatory views of one embodiment of the present invention, FIG. 3 is a cross-sectional view, FIG. 4 is a longitudinal cross-sectional view, and FIG. FIG. 6 is a partially enlarged sectional view illustrating the positional relationship of the guide tube, and FIG. 6 is a partially sectional view illustrating the action of the thin flexible rod in the event of an emergency fall when the control rod is misaligned with respect to the guide tube. 1... Reactor vessel, 7... Drive device, 6, 11
... Guide tube, 8 ... Control rod, 13 ... Flexible thin rod, a ... Setting clearance.

Claims (1)

[Scope of Claims] 1. A lateral vibration suppression device for a control rod that is suspended vertically and vertically inside a guide tube set in a reactor vessel, the device comprising either a side surface of the control rod or an inner surface of the guide tube. A large number of flexible thin rods are arranged in a radial direction from one surface to the other surface, and the tips of the flexible thin rods have a microscopic diameter defined by the following formula with respect to the other surface. Clearance a (D-d)/2>l≧(D-d-a)/2 In the formula, D: guide tube inner diameter d: control rod outer diameter l: length of flexible thin rod A control rod lateral vibration suppression device characterized by: