JP2510815B2 - HEPA filter processing method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating a contaminated HEPA filter used for filtering a gas containing radioactivity.

[0002]

2. Description of the Related Art A HEPA filter used for filtering a gas containing radioactivity has a large number of aluminum separators 2 arranged in parallel inside a metal frame 1 as shown in FIG. The filter paper 3 is arranged in a zigzag pattern between the separators 2. And its size is usually 610mm x 610mm x 300mm.

[0003] Such HEPA filters are widely used in nuclear facilities because they have extremely excellent filtration performance, but a method for treating contaminated HEPA filters has not been established, and conventionally, they are stored as they are. It had been. However, this method has the drawback of requiring a very large storage space. Therefore, attempts have been made to reduce the volume of contaminated HEPA filters either by leaving the frame or by separating it from the frame and then crushing it, but in the future it will be fixed with cement mortar like other miscellaneous solid waste. It is said that a disposal method that changes to a solid state is desirable.

However, when the HEPA filter is enclosed inside the container together with the cement mortar, the aluminum separator in the HEPA filter comes into contact with the cement mortar or the concrete buffer solution and reacts as follows to generate a large amount of hydrogen gas. 2Al ＋ Ca (OH) ₂ ＋ 2H ₂ O → Ca (AlO ₂ ) ₂ ＋ 3H ₂ ↑ The amount of hydrogen gas generated is about 1350 ml per 1 g of aluminum, and the above-mentioned normal size HEPA filter contains about 3.5 kg of aluminum. Because
The calculated amount of hydrogen gas is 4725 liters.

As a result, there is a risk that the internal pressure of the container in which the HEPA filter is enclosed rises and the container and the lid are deformed, or hydrogen gas is generated even after the container is disposed at the disposal site.
Therefore, this problem of hydrogen gas has been a technical obstacle in adopting a disposal method of fixing a contaminated HEPA filter with cement mortar.

[0006]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems of the prior art and makes it possible to fix a HEPA filter with cement mortar while avoiding an increase in the internal pressure of the container due to hydrogen gas. It has been completed to provide a processing method.

[0007]

SUMMARY OF THE INVENTION The present invention, which was made to solve the above-mentioned problems, provides a HEP contaminated with radioactivity.
Put the A filter in a closed container, inject cement mortar into it, measure the amount of hydrogen gas generated by contact with the aluminum separator, and confirm that a predetermined amount of gas has been generated, then close the closed container. The gist is a method of treating a HEPA filter characterized by tightening.

[0008]

The present invention will be described in more detail below with reference to the illustrated embodiments. In the first embodiment shown in FIG. 2, the HEPA filter contaminated by radioactivity is removed from the frame and placed in the closed container 11. The shape of the closed container 11 is not limited, but a container that can be used as it is as a storage container is preferable. And cement mortar is poured into the inside. As a result, as described above, a large amount of hydrogen gas is generated due to the contact between the aluminum separator and the cement mortar, but in the present invention, the amount of hydrogen gas generated from the closed container 11 is measured by the gas generation amount measuring device 12. The generated hydrogen gas is burned by the hydrogen gas processing device 13.

The aluminum separator generally has a thickness of 0.03 mm, and the amount of hydrogen gas generated changes with time as shown in the graph of FIG. And if the contact with the cement mortar is done well, the theoretical gas amount is reached in the first 24 hours, and there is no further generation. Therefore, in the present invention, after confirming that the hydrogen gas generation amount measured by the gas generation amount measuring device 12 has reached the theoretical gas amount, the closed container 11 is closed with the lid. As a result, there is no possibility that hydrogen gas will be generated after the lid is fastened, and it is possible to eliminate the risk of a rise in internal pressure or a fire caused by hydrogen gas.

As shown in FIG. 1, since the HEPA filter has a complicated structure, the cement mortar cannot completely contact the aluminum separator depending on how it is placed in the closed container 11, so that the The theoretical gas amount may not be reached even if left for a while. In order to solve this problem, it is preferable to arrange the HEPA filters so that the cement mortar can easily flow in and to use cement mortar having high fluidity.

To obtain a highly fluid cement mortar, extra water used for the reaction may be added and kneaded with the cement. Specifically, for 1 g of aluminum
It suffices to add 0.67 to 1 g of water.
100 parts by weight of sand and 36-45 parts of water to 100 parts by weight of cement
1 part by weight to 1 to 2 parts by weight of a high performance water reducing agent. Since the generated hydrogen gas causes the mortar to be in a porous state, it is desirable to use a lined container for the closed container 11. Further, since a HEPA filter having a size of 610 mm × 610 mm × 300 mm cannot fit in a usual 200 liter drum, it is preferable to use a large container as the closed container 11.

In the above embodiment, the HEPA filter was stored in the closed container 11 in the state of being taken out from the frame. However, the HEPA filter taken out from the frame and the HEPA filter already compressed are crushed. It is also possible to adopt a method of storing in the closed container 11.
By crushing in this way, the contact between aluminum and cement mortar is improved. Also in this case, it is needless to say that the closed container 11 is closed after confirming that the hydrogen gas generation amount measured by the gas generation amount measuring device 12 has reached the theoretical gas amount.

[0013]

As described above in detail, according to the present invention, the contaminated HEPA filter can be fixed with cement mortar while avoiding the problem of the increase of the internal pressure of the container due to hydrogen gas. . Therefore, the present invention is extremely effective as an HEPA filter processing method that solves the conventional problems and contributes to the industrial development.

[Brief description of drawings]

FIG. 1 is a partially cutaway perspective view showing the structure of a HEPA filter.

FIG. 2 is a block diagram showing steps of the present invention.

FIG. 3 is a graph showing a cumulative value of hydrogen gas generation amount.

[Explanation of symbols]

 1 Frame 2 Aluminum Separator 3 Filter Paper 11 Airtight Container 12 Gas Generation Measurement Device 13 Hydrogen Gas Treatment Device

Claims (1)

(57) [Claims] 1. A HEPA filter contaminated by radioactivity is placed in a closed container, cement mortar is injected into the container, and the amount of hydrogen gas generated by contact with an aluminum separator is measured. A method for treating a HEPA filter, which comprises closing a closed container after confirming that the HEPA filter has been generated.