JPH027378B2 - - Google Patents

Description

Detailed Description of the Invention <Industrial Application Field> This invention cools a liquid metal used as a nuclear reactor coolant, such as liquid sodium, and removes impurities in the sodium that becomes supersaturated and precipitates using a wire mesh or the like. Regarding cold traps captured with mesh bodies,
More specifically, the present invention relates to a cold trap improved to improve the impurity trapping capacity of the mesh body.

<Conventional technology> In cold traps, sodium containing impurities is cooled to approximately 120°C to become supersaturated and precipitated, and the impurities are collected and removed using a mesh body filled in a tank. When the trap reaches its full trapping capacity and reaches the end of its lifespan, it will be necessary to replace it with a new cold trap. However, only a portion of the entire mesh body placed in a relatively low temperature area traps a large amount of impurities and becomes clogged; the rest of the mesh body is not clogged. Not used effectively.

In order to eliminate these drawbacks, the mesh body filled in the cold trap tank is divided into multiple stages along the direction of sodium flow, and the sodium flow path is sequentially moved from the lower stage to the upper stage according to the clogging caused by impurities. A device that can be changed has been proposed (for example, Japanese Patent Publication No. 18062/1983). This device is the fourth
With the structure shown in the figure, the sodium containing impurities that flows into the tank 1 from the inlet 2 is once led to the lower part of the tank, and during this time, the cooling gas flowing outside the tank 1 (flows from the inlet 3 and exits the tank 1). 4). The mesh bodies 5a, 5b, and 5c are filled in the tank in multiple stages, and a sodium bypass flow path 6 extending from the bottom of the tank to the top is formed on the outer periphery of the mesh body, and this flow path 6 is arranged vertically as appropriate. It is partitioned by partition plates 7 at intervals, and an annular opening 8 is bored in each partition plate, and each annular opening is provided with a ring 9.
It can be opened and closed by a and 9b.

At the start of operation of a cold trap having such a structure, all the annular openings 8 are closed by the rings 9a and 9b as shown in the figure, so that the cooled sodium led to the bottom of the tank flows through the bottom mesh. After flowing through the mesh body 5a, the sodium flows out through the sodium outlet 10 extending upwardly through the center of the mesh body, and impurities that become supersaturated and precipitate during this time are captured. In this way, when the lowest mesh body 5a captures impurities to its full capture capacity and becomes clogged, for example, when the lowest ring 9a is lifted by pump pressure, the sodium flow bypasses the lowest mesh body 5a and becomes clogged. 2
The sodium flows to the mesh body 5b of the third stage, and impurities in the sodium continue to be captured in this stage. Further, when the second stage mesh body 5b becomes clogged, the second stage ring 9b is lifted to cause the third stage mesh body 5c to capture impurities in the sodium. Thus, the bottom mesh body 5a
By sequentially changing the sodium flow path to the uppermost mesh body 5c, the mesh bodies 5a, 5
This means that the entire impurity trapping capacity of b and 5c can be effectively utilized.

<Problems to be Solved by the Invention> However, in the conventional device as described above, when forming the bypass flow path, the ring 9
The lifting means must be operated from outside the tank by mechanical means such as pump pressure or a control rod. This type of operation from outside the tank generally requires high reliability and certainty because the inside of the tank cannot be directly seen, but lifting the ring by mechanical means as described above is not reliable or reliable. From this point of view, it was not necessarily satisfactory.

Therefore, the present invention provides a means for reliably and easily forming a sodium bypass flow path when necessary in a cold trap in which the sodium flow path can be sequentially changed from the lower stage to the upper stage of the mesh body in response to clogging caused by impurities. It was made with the purpose of providing.

<Means for Solving the Problems> In the present invention, the mesh body filled in the tank of the cold trap is divided into multiple stages, and a bypass flow path is formed in each stage of the mesh body by opening a partition plate. The partition plate is made of a shape memory alloy that operates in one direction with a transformation point at a temperature above the cold trap operating temperature or below room temperature. Then, when the partition plates of each bypass flow path are heated above the cold trap operating temperature or cooled to below room temperature, the shape memory alloy of each partition plate is designed to open sequentially from the lower stage to the upper stage. The transformation point is changed.

According to such a configuration, first, when the lowest stage of the mesh body becomes clogged due to the capture of impurities, the partition plate of the bypass flow path at this stage is heated or cooled to the transformation point of its shape memory alloy, and the bypass flow is opened. By forming the channel, the sodium flow can bypass the clogged bottom mesh body and directly flow to the second mesh body. Next, when the second stage mesh body becomes clogged with impurities, the second stage mesh body is heated or cooled to the transformation point of the shape memory alloy of the bypass flow path partition plate provided in the second stage mesh body. A bypass flow path is formed, which allows the sodium flow to bypass the bottom and second mesh bodies and flow directly to the third mesh body.

In this case, the shape memory alloy transformation point of each stage of the bypass flow path partition plate is different, and since the shape memory alloy that operates in one direction at the transformation point is used, the bypass flow path partition plate of the desired stage is changed. When you want to open the bypass flow path, you can open only the desired stage without opening the bypass flow path partition plates of other stages by changing the temperature in accordance with the transformation point of the shape memory alloy of the partition plate. However, once opened, the partition plate will not close again.

<Examples> The present invention will be described in detail below with reference to examples shown in the drawings. FIG. 1 shows an example in which the present invention is applied to the same type of cold trap as the conventional device shown in FIG. 4, and the same parts as the conventional device shown in FIG. The explanation will be omitted by adding it. In FIG. 1, instead of the annular opening 8 and ring 9 of the partition plate 7 in the conventional device shown in FIG. 4, the partition plates 17a and 17b themselves are made of a shape memory alloy. This shape memory alloy transforms at temperatures above the operating temperature of the cold trap (above the highest operating temperature in the system) (e.g. 360°C or higher) or below room temperature (below the lowest temperature in the system) (e.g. 20°C or lower). When such a transformation point is reached, the partition plate is deformed as shown in the figure, and the partition plate opens to form a bypass flow path 6. The reason for specifying the transformation point of the shape memory alloy as described above is to prevent the partition plate from deforming and opening in the temperature range from operating temperature to room temperature during use of the cold trap.

In addition, the transformation point of the shape memory alloy of each partition plate 17a, 17b is changed for each stage, and by heating or cooling to a predetermined temperature, the partition plate of a predetermined stage is opened, and the selected bypass flow path is opened. to be able to form. Furthermore, each shape memory alloy is of a unidirectional action type so that once each partition plate is opened, it will not deform again to the closed state even if the temperature changes.

The operation of the embodiment shown in FIG. 1 will be explained. At the start of operation of this cold trap, both the partition plates 17a and 17b are in a closed state. Therefore, the impurity-containing sodium flow that flows into the tank 1 from the inlet 2, is cooled, and is led to the lower part of the tank flows through the lowest mesh body 5a and flows out from the outlet 10, while being supersaturated. The precipitated impurities are captured by the mesh body 5a. In this way, when the lowest mesh body 5a captures impurities to its full capture capacity, clogging occurs. At this point, the flow of sodium into the tank is stopped, and the entire tank is heated to reach the transformation point (for example, 390°C) of the shape memory alloy of the partition plate 17a, or the entire tank is cooled and the partition plate 17a is heated. By setting the transformation point of the shape memory alloy (for example, 5°C),
The partition plate 17a is deformed and opened, bypassing the lowermost mesh body 5a and opening the second mesh body 5b.
A bypass flow path 6 leading to is formed.

As a means for heating the entire inside of the tank, an electric heater 50 attached to the outside of the tank can be used, while as a cooling means for cooling the entire inside of the tank,
A cooling device with an inlet 3 and an outlet 4 conventionally installed in a cold trap can be used as is.

Only the partition plate 17a is opened as described above,
By continuing operation again at the cold trap operating temperature with the partition plate 17b remaining closed,
The sodium flow bypasses the lowermost mesh body 5a and flows through the second mesh body 5a. When the mesh body 5b of the second stage becomes clogged, the flow of sodium into the tank 1 is stopped again, and the entire inside of the tank is heated to the transformation point (for example, 410° C.) of the shape memory alloy of the partition plate 17b. Alternatively, the partition plate 17b is deformed and opened by cooling the entire inside of the tank to the transformation point of the shape memory alloy of the partition plate 17b (for example, -10°C), and the bottom row 5a of the mesh body 5a and the second row 5b of the mesh body are opened. A bypass flow path 6 is formed which bypasses and leads to the uppermost mesh body 5c. In this way, the final stage of the cold trap operation can be continued until the uppermost mesh body 5c is clogged, and the impurity trapping capacity of the entire mesh bodies 5a, 5b, and 5c can be effectively utilized.

As mentioned above, the opening operation of the partition plates 17a and 17b may be performed by heating the entire inside of the tank above the transformation point of the shape memory alloy or by cooling it below the transformation point, but if the heating method is adopted. Since the temperature is raised above the cold trap operating temperature, it is expected that the precipitated impurities captured in the mesh body will be dissolved in the sodium again, and the clogging of the mesh body will be recovered to some extent.

In FIG. 2, there is no sodium outlet extending upward through the center of the mesh body, and the sodium flow led downward from the tank 1 is directed to the lowest stage 25 of the mesh body.
An embodiment in which the present invention is applied to a cold trap of the type in which the cold trap flows sequentially through the second stage 25b and the uppermost stage 25c and flows out from the outlet 20 will be shown. Bypass passages 26a and 26b in each stage of the mesh body are provided at different locations in the radial direction of mesh bodies 25a and 25b, and partition plates 27a and 27b made of shape memory alloy are provided at the upstream entrance of each bypass passage.
are arranged respectively. Also, gaps 28 are formed between each stage of the mesh body.

In the embodiment shown in FIG. 2, the opening operation of the partition plates 27a and 27b of each bypass flow path is performed by an electric heater (heating wire or heating coil, etc.) inserted near each partition plate, without heating the entire tank 1. )29a, 29
This is done by locally heating in step b. In this case, it may be inserted near the partition plate 27a on the outside of the bypass flow path 26a like the electric heater 29a, or it can be inserted into the bypass flow path 26b like the electric heater 29b.

To briefly describe the operation of the cold trap in the embodiment shown in FIG. 2, at the start of operation, all partition plates 27
a and 27b are closed, and the sodium flow containing impurities is passed from the bottom of the tank 1 to the bottom mesh body 25.
a, it sequentially passes through the second mesh body 25b and the uppermost mesh body 25c and flows out from the outlet 20. During this time, the precipitated impurities are captured and removed by the mesh body, but the lowest mesh body 25a becomes clogged most quickly. At this point, by activating the heater 29a and heating the shape memory alloy of the partition plate 27a to the transformation point, the partition plate 27a is deformed as shown in the figure, and a bypass flow path 26a is formed in the mesh body 25a. let By continuing to operate the cold trap in this state, the sodium flow bypasses the lowest mesh body 25a and flows directly to the second mesh body 25b, and impurities are captured in the second mesh body. Ru.
Note that since the shape memory alloy of the partition plate 27a is of a unidirectional operation type, it will not return to the closed state even if the heater 29a is turned off. When the second stage mesh body 25b becomes clogged, the heater 29b is further activated to heat the shape memory alloy of the partition plate 27b to the transformation point, thereby deforming the partition plate 27b into an open state as shown in the figure. A bypass flow path 26b is formed in the mesh body 25b. By operating the cold trap again in this state, the sodium flow bypasses the lowermost mesh body 25a and the second mesh body 25b and reaches the uppermost mesh body 25c.
The impurities are captured by the uppermost mesh body 25c.

Figure 3 shows that the sodium flow containing impurities that has flowed into the tank 1 is not guided downward into the tank.
The sodium is passed through the uppermost mesh body 35c, the second mesh body 35b, and the lowermost mesh body 35a in order as it is, and then flows out from the sodium outlet 30 extending upward through the center of the mesh body. An example to which the invention is applied will be shown. In this case as well, clogging of the mesh body due to impurity capture occurs in the lowest mesh body 3, which has the lowest temperature.
It first occurs in 5a. Therefore, the partition plates 37a, 3
7b is closed, and when the lowermost mesh body 35a first becomes clogged, the shape memory alloy of the partition plate 37a is deformed to open it, and the uppermost mesh body 35c and The sodium flow that has passed through the second mesh body 35b flows out to the outlet 30 through the gap in the open partition plate 37a without passing through the bottom mesh body 35a.
In other words, in this case as well, a bypass flow path for the lowermost mesh body 35a is formed. Next, when the second stage mesh body 35b becomes clogged, the partition plate 37
When the shape memory alloy b is deformed to open, the sodium flow flowing through the uppermost mesh body 35c flows out to the outlet 30 from the gap in the open partition plate 37b without passing through the second mesh body 35b. .

In each of the embodiments described above, an example was shown in which the mesh body was divided into three stages, but the number of stages is of course not particularly limited and can be any desired number. Further, if the uppermost mesh body becomes clogged with impurities, the cold trap must be replaced, so it is not necessary to provide a bypass flow path in the uppermost mesh body.

Further, the entire partition plate for forming the bypass flow path may be made of a shape memory alloy, but only the main portion of the partition plate may be made of a shape memory alloy.

<Effects of the Invention> As explained above, in this invention, a partition plate made of a shape memory alloy that can be deformed at a predetermined transformation point is used as a means for forming a sodium bypass flow path in each stage of the mesh body. The plate-opening operation can be performed by heating means or cooling means, rather than by conventional mechanical means.
This greatly simplifies the device structure, and at the same time allows the bypass flow path to be formed reliably and easily.As a result, the impurity capture capacity of the entire mesh body filled in the tank can be effectively utilized. It is possible.

[Brief explanation of drawings]

FIGS. 1, 2, and 3 are explanatory diagrams showing different embodiments of the cold trap according to the present invention, and only the left side from the center line is shown to simplify the drawings. FIG. 4 is an explanatory diagram showing a typical example of a conventional cold trap. 1...tank, 5a, 25a, 35b...bottom mesh body, 5b, 25b, 35b...second mesh body, 5c, 25c, 35c...top mesh body, 6, 26a, 26b...bypass Channel, 17a, 17b, 27a, 27b, 37a,
37b...Partition plate, 29a, 29b, 40...Heater.

Claims (1)

[Scope of Claims] 1. In a cold trap in which a mesh body filled in a tank captures impurities precipitated by supersaturation by cooling a liquid metal containing impurities, the mesh body is The mesh body is divided into multiple stages, and a bypass flow path is formed in each stage of the mesh body by opening a partition plate made of a shape memory alloy that operates in one direction with the transformation point at a temperature above the cold trap operating temperature or below room temperature. At the same time, a device is installed to heat the partition plates of each bypass flow path above their transformation point or cool them below their transformation point, so that the partition plate of each bypass flow path is heated above the cold trap operating temperature. A cold trap characterized in that the transformation point of the shape memory alloy of each partition plate is changed so that the partition plate sequentially opens from the lower stage to the upper stage when the trap is cooled to below room temperature. 2. The cold trap according to claim 1, wherein the heating device or the cooling device is provided outside the tank in order to heat or cool the entire inside of the tank. 3. Claim 1, wherein the heating device is an insertion type heater that locally heats the vicinity of each partition plate.
Cold trap as described in section.