JPS61202199A - Storage facility in base rock of radioactive waste - 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] [Industrial application field] The present invention relates to an in-rock storage facility for radioactive waste.

[Conventional technology]

High-level radioactive waste generated during the process of reprocessing spent nuclear fuel has high radioactivity over a long period of time.
Furthermore, the amount of heat generated is large.

Therefore, before final disposal to isolate it from the human environment, we must first take sufficient safety measures such as glass assimilation, and then store and manage it for a certain period of time to reduce its radioactivity and calorific value. It must be sufficiently attenuated. The storage and management of this radioactive waste is a long-term process involving tens to hundreds of pieces, and the facilities for this purpose are designed to keep the radioactive waste in good health during that period, and to prevent negative effects such as radioactive contamination on the surrounding environment. It is required to be able to cool radioactive waste and attenuate its radioactivity without causing any damage.

Facilities for storing such radioactive waste are currently being considered to be built in structures built above or semi-underground, and those built underground in bedrock. Among these, those installed in underground bedrock are intended to use stable bedrock as the structural framework, and the facility must have sufficient durability and be resistant to natural impacts (earthquakes, volcanic activity) and social impact. It is said to be particularly advantageous as a long-term storage facility because it can withstand high temperatures, has excellent radiation shielding performance, and has sufficient cooling capacity.

[Problem that the invention seeks to solve]

However, the above-mentioned storage facility in underground bedrock is still just an idea, and no information has been provided regarding its specific equipment, especially storage equipment that can efficiently cool radioactive waste. Because of this problem, it has been desired to provide such storage facilities.

This invention was made in view of the above circumstances, and an object thereof is to provide a rock-based storage facility that can efficiently cool and store radioactive waste.

[Means for solving problems]

This invention provides an upper shaft and a lower shaft that are spaced apart in the vertical direction in underground rock, and communicates the upper shaft and the lower shaft through one or more vertical shafts so that air can circulate inside the shaft. In addition, the shaft is equipped with cooling means for cooling the air in the upper shaft, and radioactive waste is stored in the direction of the shaft. The above cooling means are
A device that cools the air by spraying groundwater into the upper tunnel could be considered.

[Effect]

The rock-based storage facility of the present invention cools radioactive waste by circulating air within the mine shaft by natural convection.

That is, air flows around the radioactive waste stored in the vertical direction of the shaft to cool it, and the relatively heated air rises in the vertical direction and flows into the upper tunnel.

In the upper shaft, the air inside thereof is cooled by a cooling means, and the air whose temperature has decreased flows down the shaft, flows into the lower shaft, and is drawn from the lower shaft to the shaft again. As described above, the air inside the tunnel circulates and the radioactive waste is cooled.

〔Example〕

An embodiment of the present invention will be explained with reference to Fig. 1.〇 Fig. 1 is a diagram showing the overall schematic configuration of the storage facility of this embodiment when it is installed halfway up a mountain. Reference numeral 1 indicates a rock forming a mountain (1) An upper shaft 2 and a lower shaft 3 are excavated in this bedrock 1, which are spaced apart in the vertical direction and are substantially horizontal and substantially parallel to each other. This upper tunnel 2
Doors 4 and 5 are attached to the lower shaft 3 near the ground surface (slope), respectively, and are closed to prevent the air inside the shaft from flowing out to the outside.

The upper shaft 2 and the lower shaft 3 are in communication with each other through a ventilation shaft 6 excavated almost vertically and a plurality (in this embodiment, two) storage shafts 7...K. Also, storage shaft 7...
Inside, there is a solidified radioactive waste package 8...
is stored. Assimilate package 8... is made by vitrifying radioactive waste and placing it in a stainless steel container (
It is sealed in a canister) and has high heat generation properties due to the decay heat of radioactive waste. This assimilate pancake 8... is cylindrical in shape, and its outer diameter is slightly smaller than the inner diameter of the storage shaft 7...
... and the inner surface of the storage shaft 7... so that air flows through the gap between the storage shaft 7 and the inner surface of the storage shaft 7.

Further, a water spray device 9 is provided in the upper tunnel 2 near the upper part of the ventilation shaft 6. The water spray device 9 collects low-temperature groundwater that gushes out from within the bedrock 1 into a bit (not shown), pressurizes this groundwater with a pump (not shown), and sprays it. The head 10 sprays into the upper tunnel 2.

The sprayed groundwater passes through a filtration device (not shown) and is infiltrated into the bedrock 1 by an appropriate means of infiltration and diffused.

Based on the above configuration, in this storage facility, air generates natural convection and circulates as shown by the arrows in the figure, thereby cooling the assimilate pancakes 8 . In other words, storage shaft 7...
- The assimilate package 8, which is housed inside and has become hot due to its own heat generation ff1K, is cooled by the surrounding low-temperature air. The air relatively heated by cooling the solidified material packages 8 rises in the storage shafts 7 and flows into the upper shaft 2. In the upper shaft 2, low-temperature groundwater is sprayed by the water spray device 9Vc, so the air flowing into the storage shaft 7... is cooled and becomes low temperature, and the air descends inside the ventilation shaft 6. and flows into the lower tunnel 3. The low-temperature air that has flowed into the lower shaft 3 is attracted by the air rising inside the storage shaft 7 and flows into the storage shaft 7 again to cool the solidified material packages 8. As described above, as the air circulates within the tunnel by natural convection, the assimilate pancakes 8 are constantly cooled.

In addition, by cooling the air in the upper tunnel 2 and relatively heated groundwater penetrating into the bedrock 1 and diffusing,
It will be cooled by the heat capacity of the rock 1.

In this way, in the radioactive waste storage facility of this embodiment, since the tunnel is sealed, the air inside the tunnel does not leak into the atmosphere. In addition, since the air in the tunnel circulates through natural convection, there is no need for a blower, and easily available low-temperature groundwater is used as a cold source to cool the air, reducing operating costs.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments.

For example, in the above embodiment, the sprayed groundwater is allowed to permeate into the bedrock, but it may also be collected and reused. In addition, the cooling means for cooling the air in the upper tunnel is not limited to a device that sprays groundwater, for example, heat pipes can be used to perform heat exchange between the air in the upper tunnel and the atmosphere or groundwater. It may also be cooled.

〔Effect of the invention〕

As explained in detail above, 1.According to this invention, the upper shaft and the lower shaft are connected by a shaft, a means for cooling the air in the upper shaft is provided, and radioactive waste is stored in the shaft. The air inside the tunnel circulates through natural convection, which has the effect of efficiently cooling radioactive waste. Furthermore, if the cooling means is a device that sprays groundwater into the upper tunnel, a cold source can be easily obtained, which has the effect of reducing operating costs.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing the overall schematic configuration of an in-rock storage facility according to an embodiment of the present invention. 1... Bedrock, 2. Curved upper shaft, 3. Curved lower shaft, 6... Ventilation shaft (shaft shaft), 7. Curved storage shaft (shaft shaft), 8. ...Solid package (
Radioactive waste), 9...Water spray device (cooling means).

Claims (2)

[Claims] (1) An upper shaft and a lower shaft are provided vertically apart in the underground bedrock, and the upper shaft and the lower shaft are connected to one another.
The upper shaft is connected by two or more shafts to allow air to circulate therein, and is provided with cooling means for cooling the air in the upper shaft, and radioactive waste is stored in the shaft. An in-rock storage facility for radioactive waste characterized by: (2) The in-rock storage facility for radioactive waste as set forth in claim 1, wherein the cooling means is a device that cools the air in the upper tunnel by spraying groundwater into the upper tunnel. .