JPS60161588A - Inhibiting device for transverse vibration of control rod - 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 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> Therefore, this invention is set in the container of a nuclear reactor such as a fast breeder reactor (FBR), and is linked so as to be raised and lowered 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 due to the lateral vibration of the flow force due to the cooling liquid sodium, and the lateral centering with the guide tube due to earthquakes etc. This invention relates to a lateral vibration suppression device that is capable of quickly scramming without being affected by deviations, etc., and in particular, a system that sufficiently allows the flow of liquid sodium for cooling between the control rod and the guide tube. Maintain as much distance as possible,
A large number of thin flexible 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, and their tips are attached to the opposing surface. A small clearance is formed against the guide tube to ensure the flow of cooling liquid sodium, prevent lateral vibration due to the flow force, and prevent the drop even if there is misalignment with the guide tube due to earthquakes, etc. This invention relates to a control rod lateral vibration suppression device that does not impair functionality.

<Prior Art> As is well known, in a nuclear reactor, in order to adjust the output during operation, control rods set in the reactor core inside a vessel are raised and lowered while set in a guide tube by a drive device located above the control rods. However, the functions of the control rods generally include a power adjustment function during the operation and a function to lower the reactor core as quickly as possible in order to stop the reactor core in an emergency such as an earthquake.

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 cooling liquid sodium is introduced through an inlet 3 at the lower part and an outlet 4 at the upper part. 5 is stored up to the level of the outlet 4, and the upper guide pipe 6 provided in the shielding plug 2 is connected to the control rod 8 suspended by the drive device 7 in the upper part, and the support mechanism 9 in the lower part. In-core fuel 10
Normally, as shown on the left side of FIG. 1, it is moved up and down by the drive device 7 to adjust its output as described above. In the event of an emergency such as an earthquake, the dash ram is scrammed and quickly lowered so that the dash ram is seated on the dash pot of the lower guide pipe 11.

However, the relationship between the control rod 8 and the guide tube 6.11 has the following problem.

That is, in the event of an earthquake such as the above-mentioned emergency, due to the lateral vibration, the upper guide pipe 6 and the lower guide pipe 11 move horizontally as shown in FIG.
If misalignment occurs between the upper guide tube 6 and the control rod 8, if the diameter of the upper guide tube 6 and the lower guide tube 11 is small, that is, the inner surface of the guide tube 6.11 If the gap between the control rod 8 and the side surface of the control rod 8 is small, the control rod 8 will not be scrammed, and the control rod will dash ram into the dashpot of the lower guide pipe 11 due to gravity etc. The problem is that it is difficult to sit down.

Therefore, in order to quickly scram in the event of an emergency, it is advantageous for the distance between the inner surface of the guide tube 6.11 and the side surface of the control rod 8 to be large, since it facilitates scram.

On the other hand, as mentioned above, during operation, when the space between the guide tube 6.11 and the control rod 8 is filled with cooling liquid sodium 5, vibrations due to the flow force, among others, occur. There is a problem in that regular and irregular lateral vibrations occur in the control rod 8 due to the lateral vibrations, resulting in fluctuations in output during normal operation.

For this purpose, it is better that the cross-sectional ring-shaped gap between the guide tube 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 was given to the distance between the inner surface of the guide tube 8 and the side surface of the control rod 6.11.

Therefore, the lateral vibration behavior of the control rod 8 due to the flow force of the cooling liquid sodium flowing between the guide tube 6.11 and the control rod 8 during normal operation cannot be absorbed, and as a result, output fluctuations are likely to occur. There were potential drawbacks.

To deal with this, for example, a means for attaching a ball or roller to the above-mentioned gap has been devised, as in the invention disclosed in Japanese Patent Laid-Open No. 58-11888. There is a disadvantage that it is not in a sufficiently satisfactory state to prevent the emergency scram of the 8 and to prevent its lateral normal operation.

As described above, the conventional technology has the disadvantage that it has not devised a technology that has both a means for keeping the control rods as still as possible during normal operation and a means for easily performing an emergency scram. .

<Object of the invention> The object of the invention is to develop a fast breeder reactor (
The problem of inability to maintain a stable stationary state during normal operation of the control rods in the core of a nuclear reactor such as FBR) and the prompt and reliable appearance of a scram in an emergency has been identified as a technical issue to be solved. The space between the surface and the side of the control rod is set to a size that allows the control rod to be inserted as quickly as possible in an emergency, and during normal operation, it is designed to prevent vibrations caused by the flow force of liquid sodium for cooling. It is an object of the present invention to provide an excellent control rod lateral vibration suppressing device that absorbs the lateral vibration of the control rod, thereby benefiting the field of nuclear power application in the energy industry.

<Configuration of the Invention> In order to solve the above-mentioned problems, the configuration of the present invention is such that the inside of the guide tube set in the reactor vessel is linked to a guide tube drive device provided in the upper shielding plug of the vessel. The control rod suspended from the corresponding guide tube has a sufficient gap for emergency insertion, and the control rod is suspended from either the side surface of the control rod or the inner surface of the guide tube. A large number of flexible thin rods made of stainless steel or the like are provided by means such as welding in the radial direction across the opposing surface of the side, and between the tips of the flexible thin rods and the opposing surface of the other side. It has a set amount of minute clearance, and the cooling liquid sodium filled in the container will apply lateral vibration to the control rod due to the flow force between the guide tube and the control rod. However, the tips of the large number of flexible thin rods contact the opposing surface to absorb the lateral vibration and prevent vibration of the control rod as much as possible to prevent output fluctuations. Enables stable driving,
On the other hand, in the event of an emergency such as an earthquake, a technical measure has been taken in which the control rod can be smoothly inserted by bending the flexible thin rod, making it easy to perform a scram.

<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 FIG. 3.4, 11 is a lower guide pipe, 8 is a control rod, and as in the conventional embodiment shown in FIG. 1 and set in the lower support device 9, with a gap 1 between the two.
2 is provided sufficiently wide to facilitate scramming.

In this embodiment, a large number of thin flexible rods 13, 13, . Regularly or irregularly in multiple stages from the side of the control rod in the axial direction,
Further, it is fixed to the inner surface of the guide tube 8 by means such as welding so as to extend in the radial direction, and is oriented perpendicularly to the inner surface of the guide tube 11.

The flexible thin rods 13 are arranged so that they are perpendicular to the axial direction, and their lengths are such that the axis of the guide tube 11 and the axis of the control rod are within the allowable eccentricity based on the operating temperature conditions. The inner diameter of the guide tube 11 is determined to match D flint O
If the outer diameter of the il rod 8 is d, and the allowable eccentricity is a, the length l of the thin flexible rod is (D-d), /2>#≧, as shown in FIG. (D-d-a)/2.

<Embodiment - Effect> In the above-mentioned configuration, as in the embodiment on the left side shown in FIG. The control rod 8 is raised and lowered in a predetermined manner to adjust its output, but in this state, the control rod 8 is caused to vibrate horizontally due to the flow force of the cooling liquid sodium flowing between the inner surface of the guide tube 11 and the side surface of the control rod 8. The control rod 8 attempts to vibrate in the lateral direction due to the applied force, 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. There is no lateral vibration within the guide tube 11 that exceeds the set clearance, and as long as this occurs, no fluctuation occurs in the output.

In addition, in an emergency, if the control rod 8 falls out of alignment, the thin flexible rods 13, 13... bend as shown in Fig. 6, and the control rod 8 slides down the inner surface of the guide tube without resistance. Therefore, scrum is performed smoothly and easily.

Therefore, in this case, the plurality of flexible thin rods 13.1
3... will function as a kind of elastic spacer.

In addition, in the embodiment shown in FIG. 4.5.6, the flexible thin rod 1
3, only a limited number are shown in the lateral direction, but it goes without saying that in reality, a large number of them are arranged in multiple stages in the radial direction and the axial direction, like a so-called beard brush for washing a bottle. It is about.

In addition, in the process of flowing 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 of ... are extremely small,
Since the spacing 12 is relatively large, the liquid sodium flow path is not substantially obstructed and the flow resistance is not increased.

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. 8, as shown in FIG. 2, even if misalignment occurs, the inner diameter of the guide tube 6.11 is sufficiently large relative to the outer diameter of the control rod 8. Since it is easy to insert, the dashram can easily stop the reactor core seated on the dashpot of the guide tube 11.

In this case, as shown in FIG.
Even if the guide tube 3 interferes with the inner surface of the guide tube 11, it is easily bent and does not impede its downward insertion.

Furthermore, according to a general calculation example on an experimental scale, D is 110+++
m and d are 94IIll and (D-d)/2=8ml
11, and the minute clearance a/2 is 1 to several m1
About 1 liter is sufficient.

In addition, the fruit of this invention is 11il! Of course, the i-mode 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, but on the other hand, On the other hand, it goes without saying that various embodiments are possible, such as having a large number of thin flexible rods integrally fixed and extending inward in a kind of radial direction from the inner surface of the guide tube toward the control rod. .

Further, the thin flexible rods may be disposed in one or multiple stages in the axial direction, but it is preferable to arrange them in multiple stages at random, since this produces an effect of suppressing vibrations caused by 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, basically a fast breeder reactor (FBR)
) etc., the guides set in the reactor vessel and the control rods inserted into the pipes to make them movable are subject to vibrations due to the flow force caused by the flow of the cooling liquid sodium inside them. The group of flexible thin rods comes into contact with the opposing surface and creates a buffering effect, absorbing the vibration, so there is almost no vibration-induced behavior, and as long as that is the case, there is no output fluctuation, which is an excellent effect. On the other hand, even if the control rod and the guide tube become misaligned in an emergency on the ground MW, the thin flexible rod contacts the other side flexibly and elastically, making it easy to insert the control rod.
An excellent effect is achieved in that both functions are performed smoothly at the same time.

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 the drawing]

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. FIG. 3 is a cross-sectional view, FIG. 4 is a longitudinal cross-sectional view, and FIG. 5 is a flexible thin rod and a control rod. FIG. 6 is a partially enlarged cross-sectional view explaining the positional relationship between the control rod and the guide tube, and FIG. 1... Reactor vessel, 7... Drive device, 6.11.
... Guide tube, 8 ... Control rod, 13 ... Flexible thin rod, a ... Setting clearance Fig. 1 Fig. 2 Fig. 3 Fig. 5

Claims (1)

[Claims] In a lateral vibration suppression device using fluid force provided for a control rod that is set inside a reactor vessel and inserted into a guide tube in conjunction with an upper drive device, either one of the side surface of the control rod and the inner surface of the guide tube is provided. A large number of flexible thin rods are arranged in a radial direction from the surface to the other surface, and the tip thereof is arranged with a predetermined minute clearance with respect to the other surface. Lateral vibration suppression device for control rods.