JP2013029521A - Radioactive waste storage container heat removal structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance cooling efficiency in a storage shed by improving and working out a storage container stored in the storage shed.SOLUTION: When a wall thickness of a storage container 1 is varied according to a circumferential position, a thermal flow rate is increased at portions having thin wall thicknesses and the thermal flow rate is decreased at portions having thick wall thicknesses. Further, when differences in distribution of thermal flow rates occur due to the circumferential position, a rising speed of a rising air flow in a circumferential direction on a surface of the storage container 1 also becomes non-uniform, an air flow rising in an oblique direction occurs, disturbance of the air flow occurs and heat transfer is accelerated.

Description

The present invention relates to a heat removal structure for a cylindrical storage container that contains a heating element in which radioactive waste is sealed and is in a heated state.

Radioactive waste such as spent fuel in a nuclear power plant is sealed as a heating element, and the sealed heating element is stored in a dedicated storage container. And this storage container is stored in the inside of the store | warehouse | chamber formed with the reinforced concrete material etc. which have sufficient thickness to interrupt radiation.

Since the heating element formed by sealing the radioactive waste is hot, the storage container is in a heated state. Therefore, the temperature inside the storage is also increased considerably. However, since the heat-resistant temperature of the reinforced concrete material forming the storage is about 60 ° C. at most, it is necessary to suppress the inside of the storage from rising to a temperature higher than this.

And conventionally, measures such as suppressing the temperature rise inside the storage by a so-called natural cooling method by introducing air from outside into the storage and passing the introduced air through the cooling flow path formed inside the storage. It has been adopted (see, for example, Patent Document 1).

Japanese Patent Laid-Open No. 7-294697

However, since all of the measures that have been employed in the past are merely improvements and improvements to the internal structure of the storage, it has been difficult to improve the cooling efficiency of the natural cooling system to a certain level or more.

The present invention has been made in view of the above circumstances, and it is possible to remove a radioactive waste storage container that can improve the cooling efficiency in the storage by improving and devising the storage container stored in the storage. It aims to provide a thermal structure.

As a means for solving the above-mentioned problem, the invention according to claim 1 is a cylindrical storage container in which a heating element in which radioactive waste is sealed is stored and in a heated state, and the meat of the cylindrical storage container is The thickness is changed according to the position in the circumferential direction.

According to the present invention, since the storage container stored in the storage is improved and devised, the cooling efficiency in the storage can be improved.

It is explanatory drawing of the 1st Embodiment of this invention, (a) is a front view, (b) is a BB arrow line view of (a). It is explanatory drawing of the 2nd Embodiment of this invention, (a) is a longitudinal cross-sectional view, (b) is a BB arrow line view of (a). Explanatory drawing of the 3rd Embodiment of this invention. Explanatory drawing of the 4th Embodiment of this invention. Explanatory drawing of the 5th Embodiment of this invention. Explanatory drawing of the 6th Embodiment of this invention. It is explanatory drawing of the 7th Embodiment of this invention, (a) is a front view, (b) is a BB arrow line view of (a), (c) is a characteristic view of this embodiment. It is explanatory drawing of the conventional structure corresponding to 7th Embodiment of FIG. 7, (a) is a cross-sectional view, (b) is a characteristic view of a conventional structure. Explanatory drawing of the 8th Embodiment of this invention. Explanatory drawing of the 9th Embodiment of this invention. It is explanatory drawing of the 10th Embodiment of this invention, (a) is a front view, (b) is a BB arrow line view of (a).

1A and 1B are explanatory views of a first embodiment of the present invention, in which FIG. 1A is a front view and FIG. 1B is a BB arrow view of FIG. The storage container 1 is, for example, a cylindrical cylinder made of stainless steel having a diameter of 50 cm and a height of about 8 m. The storage container 1 is supported in a vertical posture by a suitable support member such as a grid spacer inside a storage that is not shown. It is stored in a heated state. The storage container 1 of the present embodiment has a cylindrical shape with a circular cross section, but the storage container of the present invention is not particularly limited, and may be a polygonal cylindrical shape. Absent.

Inside the storage container 1 is stored a heating element 2 formed by sealing high-temperature radioactive waste. A large number of conical protrusions 3 are formed on the surface of the storage container 1. Since the protrusion 3 is usually fixed to the surface of the storage container 1 by welding, the material thereof is the storage container 1.
The same stainless steel is preferable.

Next, the operation of the first embodiment will be described. Since the storage container 1 stores the heating element 2, it is in a heated state. Therefore, the air that comes into contact with the surface of the storage container 1 is heated and expands, and the density decreases, so that it becomes lighter and rises. That is, an upward air flow is generated near the surface of the storage container 1.

At this time, the rising air flow collides with a large number of protrusions 3 in the middle of the rising, so that the rising air flow is disturbed. The turbulence of the rising air flow causes an increase in the amount of air that contacts the storage container 1 and an increase in the contact time, thereby increasing the heat transfer rate from the storage container 1 to the rising air flow. become. Therefore, according to the storage container 1 of the present embodiment, it is possible to remove heat more effectively than a conventional storage container in which nothing is formed on the surface, and the cooling efficiency in the natural cooling system is improved. be able to.

In the present embodiment, the case where the shape of the protrusion 3 is conical has been described. However, the shape is not particularly limited as long as it causes disturbance in the ascending air flow. Therefore,
A shape convenient for manufacturing such as a cylindrical shape or a prismatic shape may be appropriately adopted. Further, the size of the protrusion 3 is not particularly limited, and a very small minute protrusion, or a micro-projection when the surface of the storage container 1 is finished to a rough rough surface is also used. It is included in the “projection” of the embodiment.

FIG. 2 is an explanatory view of a second embodiment of the present invention, where (a) is a longitudinal sectional view, and (b) is (a).
It is a BB arrow line view. In this embodiment, the hollow part 1a is formed in the center part of the cylindrical storage container 1. FIG. The plurality of heating elements 2 stacked in multiple stages are also formed with a hollow part 2a concentric with the hollow part 1a, and the plurality of heating elements 2 can be stored in the storage container 1.

According to this embodiment, the rising air flow not only rises along the outer peripheral surface of the storage container 1,
Since it raises through the hollow part 1a which functions as a hollow flow path, the heat transfer rate from the storage container 1 to an ascending air flow increases correspondingly, and the heat removal area of the storage container 1 increases. Therefore, according to the storage container 1 of the present embodiment, it is possible to remove heat more effectively than a conventional storage container in which no hollow portion is formed, and to improve the cooling efficiency in the natural cooling method. Can do.

In the present embodiment, the heating element 2 stored in the storage container 1 is divided into a plurality of layers and stacked in multiple stages. However, the heating element 2 has various forms and is integrated. Of course, there is a case where it is stored in the storage container 1.

FIG. 3 is an explanatory diagram of the third embodiment of the present invention. In this embodiment, streamline caps 4 are attached to the lower end and the upper end of the storage container 1. The streamline cap 4 is made of aluminum, for example, and is fixed to the storage container 1 by spot welding or the like.

According to this embodiment, since the flow resistance of the rising air flow is reduced on the lower end side and the upper end side of the storage container 1, the flow rate of the rising air flow is increased, and the heat transfer rate from the storage container 1 to the rising air flow is increased. Increase. Therefore, according to the storage container 1 of the present embodiment, effective heat removal can be performed as compared with the conventional storage container in which the streamline cap 4 is not attached, and the cooling efficiency in the natural cooling system is improved. Can be made.

In the present embodiment, the streamline cap 4 is attached to both the lower end and the upper end of the storage container 1, but only one of the lower end or the upper end depends on the environmental conditions such as space. It is good also as a structure which attaches the streamline cap 4.

FIG. 4 is an explanatory diagram of the fourth embodiment of the present invention. In this embodiment, for example, the surface of the storage container 1 is wrapped by a water absorbing member 5 formed of natural fibers or synthetic fibers such as cloth and sponge. And the lower end part of this water absorbing member 5 is the state immersed in the cooling water 7 with which the saucer 6 was filled. A cooling water supply tank 8 having a supply port 8a (provided with a valve capable of adjusting the supply amount) that is immersed in the cooling water 7 in the receiving tray 6 is provided above the receiving tray 6. It is arranged. The tray 6 is provided with a water level gauge (not shown). When the water level drops, the cooling water 7 is automatically supplied from the supply port 8a, and the water level of the cooling water 7 always filled in the tray 6 is provided. Is kept constant.

According to such a configuration of the present embodiment, the cooling water 7 filled in the receiving tray 6 ascends the water absorbing member 5 by capillary action and contacts the surface of the storage container 1. The water in contact with the surface of the storage container 1 and the water contained in the water absorbing member 5 are evaporated by the heat of the storage container 1. Therefore, since heat is removed from the storage container 1 by the evaporation of water at this time, the heat removal of the storage container 1 can be effectively performed.

FIG. 5 is an explanatory diagram of the fifth embodiment of the present invention. This embodiment can be said to be a modification of the fourth embodiment. The storage container 1 whose surface is wrapped by the water absorbing member 5 is disposed inside the container storage box 9. The bottom of the container storage box 9 is used as a tray, and the bottom is filled with cooling water 7. And the lower end part of this water absorbing member 5 is the state immersed in the cooling water 7 with which the bottom part of the container storage box 9 was satisfy | filled. Further, a cooling water supply tank 8 is disposed outside the container housing box 9, and only the supply port 8 a passes through the wall and is immersed in the cooling water 7.

An air inlet 9 a is formed near the bottom of the container housing box 9 and slightly above the water surface of the cooling water 7, and an air outlet 9 b is formed in the ceiling of the container housing box 9. . Around the air discharge port 9b, a radiating fin 10 made of a material having good thermal conductivity such as aluminum is attached.

According to the configuration of this embodiment, as already described in the fourth embodiment of FIG. 4, the water in contact with the surface of the storage container 1 and the water contained in the water absorbing member 5 are stored in the storage container. Therefore, the heat is removed from the storage container 1 by the evaporation of water at this time, and the heat removal of the storage container 1 can be performed effectively.

At this time, the inside of the container housing box 9 is highly humid due to evaporation of water, and the dry air introduced from the air inlet 9a tends to be discharged from the air outlet 9b after containing a large amount of moisture. To do. However, since the heat radiating fins 10 are attached around the air discharge port 9b, the moisture contained in the air to be discharged adheres to the inner wall of the air discharge port 9b as water droplets. The adhering water drops gradually fall along the inner wall, and eventually fall to the bottom of the container storage box 9.

In this way, the water contained in the water absorbing member 5 once evaporates into the air, but also drops as water droplets and returns to the bottom of the container housing box 9, so that the cooling supplied from the cooling water supply tank 8. The water 7 circulates in the container storage box 9. Therefore, the fluctuation of the water level at the bottom of the container housing box 9 does not become so large, and the water level can be easily managed.

Moreover, since most of the moisture in the exhausted air is removed by the action of the heat radiating fins 10, it is possible to suppress the humidity of the interior of the storage in which the container housing box 9 is installed.

FIG. 6 is an explanatory diagram of the sixth embodiment of the present invention. In this embodiment, a wire-like member 11 for guiding the rising air flow around the storage container 1 is spirally wound and fixed to the surface of the storage container 1.

The rising air flow is generated in a very thin layer on the surface of the storage container 1, and the air outside the layer hardly moves. However, as shown in FIG. 6, when the wire-like member 11 is spirally wound and fixed on the surface of the storage container 1, the ascending air flow hits the wire-like member 11 wound in a spiral, resulting in disturbance. The boundary between the high temperature rising air flow and the cold air that has stopped outside is disturbed and mixed, and the temperature of the rising air flow decreases. Therefore, the temperature difference between the surface of the storage container 1 and the rising air flow is increased, and heat transfer from the former to the latter is promoted, so that effective heat removal is performed.

FIGS. 7A and 7B are explanatory views of a seventh embodiment of the present invention, where FIG. 7A is a front view, FIG. 7B is a view taken along the line BB in FIG. It is.

In this embodiment, as shown in FIG.7 (b), the thickness of the storage container 1 shall be changed according to the circumferential direction position. That is, in the rotational coordinates temporarily set on the cross section, 0
The wall thickness near 90 ° (360 °) and 180 ° is increased, and the wall thickness near 90 ° and 270 ° is decreased.

In this way, if the thickness of the storage container 1 is changed according to the circumferential position, the heat transfer from the heating element 2 also changes, and as shown in FIG. The heat flow rate at the thin part increases, while the heat flow rate at the thick part decreases. And if a difference occurs in the distribution of the heat flow rate depending on the circumferential position, the rising speed in the circumferential direction of the rising air flow on the surface of the storage container 1 also becomes non-uniform. Due to this non-uniform ascent rate, pressure in the lateral direction acts on the air flow that has been straightly rising in the vertical direction, and an air flow that rises in an oblique direction is generated, as shown in FIG. To do. The oblique rising air flow and the vertical rising air flow collide with each other so that the air flow on the surface of the storage container 1 is disturbed, and heat transfer from the surface of the storage container 1 to the rising air flow is promoted. Heat removal is performed.

On the other hand, the wall thickness of the conventional storage container 1 is constant regardless of the circumferential position as shown in the cross-sectional view of FIG. As shown in b), it was the same at any circumferential position. Therefore, since the rising speed in the circumferential direction of the rising air flow on the surface of the storage container 1 is uniform and all the rising directions are also in the vertical direction, the air flow on the surface of the storage container 1 is not disturbed. The effect of heat could not be expected.

FIG. 9 is an explanatory diagram of the eighth embodiment of the present invention. In this embodiment, the storage container 1 has a plurality of metal materials A, B, so that materials having different thermal conductivities are distributed according to the circumferential position.
It is formed of C. For example, the metal material A has the highest thermal conductivity, such as copper and metal material B.
For example, aluminum having the next highest thermal conductivity, and iron or stainless steel having the lowest thermal conductivity may be used for the metal material C.

As described above, if the kind of the metal material forming the storage container 1 is changed according to the position in the circumferential direction, the heat conduction from the heating element 2 is also changed, and the metal having a high thermal conductivity. The heat flow rate in the material is increased, while the heat flow rate in the metal material having a small thermal conductivity is decreased. And if a difference occurs in the distribution of the heat flow rate depending on the circumferential position, the rising speed in the circumferential direction of the rising air flow on the surface of the storage container 1 also becomes non-uniform. Due to this non-uniform ascent rate, pressure in the lateral direction acts on the air flow that has been straightly rising in the vertical direction, and an air flow that rises in an oblique direction is generated. By the collision of the rising air flow in the oblique direction and the rising air flow in the vertical direction,
The air flow on the surface of the storage container 1 is disturbed, heat transfer from the surface of the storage container 1 to the rising air flow is promoted, and effective heat removal is performed. That is, according to the configuration of the present embodiment, it is possible to achieve the same effect as that of the seventh embodiment in which the thickness of the storage container 1 is changed according to the circumferential position.

FIG. 10 is an explanatory diagram of the ninth embodiment of the present invention. In this embodiment, for example, a plurality of ring members 12 made of stainless steel are attached to the outer peripheral surface of the storage container 1. The mounting intervals of the plurality of ring members 12 are not necessarily equal, and may be appropriately changed according to the state of the rising air flow.

According to the present embodiment, the ascending air flow can collide with the plurality of ring members 12 in the middle of the ascent and cause the ascending air flow to be disturbed, so that the first embodiment of FIG. 1 and the sixth embodiment of FIG. The substantially same effect as that of the embodiment can be obtained.

FIG. 11 is an explanatory diagram of a tenth embodiment of the present invention, where (a) is a front view and (b) is (a
It is a BB arrow line view of). In this embodiment, a plurality (four in the illustrated example) of storage containers 1 can be inserted, and a plurality of plate-like spacer members 13 having a hole portion 13a at the center are provided. A plurality of storage containers 1 are attached.

According to the present embodiment, the ascending air flow rises in the vicinity of the peripheral edge of each spacer member 13 and through the hole 13a, but hits the plurality of spacer members 13 in the middle of the ascent and disturbs the ascending air flow. Can be generated. Accordingly, the first embodiment of FIG. 1 and the sixth embodiment of FIG.
The substantially same effect as in the ninth embodiment and the ninth embodiment in FIG. 10 can be obtained.

1: storage container 1a: hollow part 2: heating element 2a: hollow part 3: projection part 4: streamline cap 5: water absorbing member 6: tray 7: cooling water 8: cooling water supply tank 8a: supply port 9: container Housing box 9a: Air inlet 9b: Air outlet 10: Radiation fin 11: Wire-like member 12: Ring member 13: Spacer member 13a: Hole

Claims (2)

In a cylindrical storage container that contains a heating element in which radioactive waste is sealed and is in a heated state,
The thickness of the cylindrical storage container was changed according to its circumferential position,
A heat removal structure for a radioactive waste container. The thickness of the cylindrical storage container is configured so that the thickness near 90 ° and 270 ° is thinner than the thickness near 0 ° and 180 ° in the rotation coordinates arbitrarily set as the center of the cross section. ,
2. The radioactive waste storage container heat removal structure according to claim 1, wherein an outer periphery of the cylindrical storage container is circular and an inner periphery is elliptical on the cross section.

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