Ventilation system and case for shelters

Abstract

The present invention provides a shelter ventilation system that prevents radiation emitted from radioactive materials accumulated in a filter unit that filters out dust containing radioactive materials from the outside air from leaking into the shelter room. [Solution] The shelter ventilation system according to the present invention is a shelter ventilation system that includes a filter unit configured to take in outside air, filter out dust containing radioactive materials contained in the outside air, and discharge purified air, wherein the outer wall which serves as a case for housing the filter unit inside comprises an inner circumferential wall made of lead, an outer circumferential wall containing water or a water-containing gel that covers the outer periphery of the inner circumferential wall, and an outermost circumferential wall that supports the outer circumferential wall.

Description

Technical Field

[0001] The present invention relates to a ventilation system and a case for a shelter, and particularly to a ventilation system and a case for a shelter that prevent leakage of radiation emitted from radioactive substances accumulated in a filter unit that filters dust containing radioactive substances contained in outside air to the outside.

Background Art

[0002] Shelters have been studied and developed assuming cases where radioactive substances are scattered into the atmosphere due to damage to facilities handling radioactive substances or the use of weapons containing radioactive substances, along with natural disasters and regional conflicts. The shelter serves to shield radiation emitted into the atmosphere by its outer wall, but in a sealed state, there is a shortage of air necessary for people taking refuge inside the shelter. Therefore, a ventilation system for taking in outside air is provided in the shelter. However, in a situation where radioactive substances are scattered into the atmosphere, outside air cannot be taken in as it is. Usually, a filter unit for filtering dust containing radioactive substances is attached upstream of a blower for taking in outside air in a ventilation system for a shelter so that clean air can be taken into the shelter.

[0003] Patent Document 1 discloses an NBC filtration system for a collective protection shelter including an NBC filter unit, an electric blower, and means for switching the NBC filtration system state between a ventilation mode effective during normal times or conventional disasters and an NBC protection mode effective during NBC disasters.

[0004] According to the invention described in Patent Document 1, under normal circumstances ventilation can be performed without going through the NBC filter unit, and in the event of a disaster, the ventilation circuit can be switched to supply air from which harmful substances have been removed via the NBC filter unit into the shelter. The NBC filter is a filter that can handle nuclear materials, biological materials, and chemical substances. In the case of biological materials and chemical substances, there is no problem even if the filtered material accumulates inside the NBC filter unit, but in the case of radioactive materials, they continue to emit radiation, so the NBC filter unit has the problem that it can become a source of radiation unless its outer case is formed to block radiation. The NBC filter unit in Patent Document 1 does not address this problem. In particular, when dealing with dust containing radioactive materials, it is desirable to provide a shelter ventilation system that takes into account the leakage of radiation from the filter unit.

[0005] Furthermore, while shelters are generally constructed as fixed structures, they can also be used as mobile structures. When used as a mobile structure, they are either constructed on top of a mobile body or formed to be towed by a mobile body. The basic configuration of the shelter itself is almost the same whether it is for fixed or mobile use. However, in the case of a mobile structure, consideration must be given to the vibrations that occur during movement. In particular, when block-shaped activated carbon is used in the filter unit, there is a risk that the block-shaped activated carbon will pulverize due to vibrations, reducing the filter performance. For this reason, when considering applications as mobile structures, it is desirable to provide a ventilation system and case for shelters equipped with a filter unit that is more resistant to vibrations. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Special Publication No. 2019-525115 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] The present invention has been made in view of the problems with the above-mentioned conventional ventilation systems and cases for shelters, and the object of the present invention is to provide a ventilation system and case for shelters that prevents the leakage to the outside of radiation emitted from radioactive materials accumulated in a filter unit that filters dust containing radioactive materials contained in the outside air. [Means for solving the problem]

[0008] To achieve the above objective, the present invention provides a shelter ventilation system comprising a filter unit configured to take in outside air, filter out dust containing radioactive materials contained in the outside air, and discharge purified air, wherein the outer wall, which serves as a case for housing the filter unit, comprises an inner circumferential wall made of lead, an outer circumferential wall containing water or a water-containing gel covering the outer periphery of the inner circumferential wall, and an outermost circumferential wall supporting the outer circumferential wall. The filter unit comprises, from upstream to downstream along the airflow path, a pre-filter, a HEPA filter, and an activated carbon filter consisting of block-shaped activated carbon. The filter unit is configured as a two-part filter unit, comprising a first filter unit comprising the pre-filter and the HEPA filter, and a second filter unit comprising the activated carbon filter. Each of the two-part filter units comprises an inner circumferential wall, an outer circumferential wall, and an outermost circumferential wall. It is characterized by the following:

[0009] To achieve the above objective, the present invention provides a shelter ventilation system comprising a filter unit configured to take in outside air, filter out dust containing radioactive materials contained in the outside air, and discharge purified air, wherein the outer wall, which serves as a case for housing the filter unit, comprises an inner circumferential wall made of lead, an outer circumferential wall containing water or a water-containing gel covering the outer periphery of the inner circumferential wall, and an outermost circumferential wall supporting the outer circumferential wall. The filter unit is individually housed in a housing section of a case having an inner wall and an outer wall, and includes a pre-filter, a HEPA filter, and a block of activated carbon, which are installed in order from the outside air intake side, with the block of activated carbon being fixed in a state where it is pressed down by a biasing means so as not to move within the housing section. Characterized by .

[0010] Preferably, the case is configured such that when storage is not ventilated, the inlet and outlet holes are covered to prevent air from entering or leaving, and when ventilation is required, the cover is removed to expose the inlet and outlet holes.

[0011] Preferably, the system further includes a housing that slidably houses the case containing the filter unit between a first and second installation position, wherein in the first installation position, which is the normal installation position when ventilation is not performed, a part of the housing acts as a cover to block the inlet hole and the outlet hole, and in the second installation position, which is the installation position when filter ventilation is performed, an external inlet hole provided in the housing communicates with the inlet hole, and an external outlet hole provided in the housing communicates with the outlet hole, thereby enabling ventilation through the filter unit.

[0012] To achieve the above objective, the present invention provides a case for covering a filter unit of a shelter ventilation system configured to take in outside air, filter out dust containing radioactive materials contained in the outside air, and discharge purified air, wherein the case has an outer wall comprising an inner circumferential wall made of lead, an outer circumferential wall containing water or a water-containing gel covering the outer periphery of the inner circumferential wall, and an outermost circumferential wall supporting the outer circumferential wall.

[0013] The outer wall of the case includes a plurality of partial outer walls configured to cover the filter unit when combined with each other, and it is preferable that overlapping portions are provided where the partial outer walls overlap each other in the combined portions of the plurality of partial outer walls to prevent the leakage of radiation from radioactive material inside the filter unit. [Effects of the Invention]

[0014] According to the shelter ventilation system and case of the present invention, the outer wall that forms the case of the filter unit included in the shelter ventilation system is composed of an inner circumferential wall made of lead and an outer circumferential wall containing water or a water-containing gel that covers the outer periphery of the inner circumferential wall. Therefore, even if radioactive material filtered from the outside air by the filter unit accumulates due to the operation of the shelter ventilation system, the radiation emitted from the radioactive material is blocked by the outer wall of the filter unit, making it possible to prevent leakage into the shelter.

[0015] Furthermore, according to the shelter ventilation system of the present invention, the filter unit includes a pre-filter, a HEPA filter, and a block of activated carbon. The block of activated carbon is fixed in a state where it is pressed down by a biasing means to prevent it from moving within the storage compartment. Therefore, even when this shelter ventilation system including the filter unit is used as a mobile facility, it is possible to prevent the block of activated carbon from becoming powdery even when subjected to vibrations associated with movement, thereby achieving stable filter performance.

[0016] Furthermore, according to the shelter ventilation system of the present invention, the filter unit is installed inside the housing so as to be slidable between a first installation position and a second installation position. In the first installation position, which is the normal installation position, the air intake and exhaust holes of the filter unit are covered by the inner wall of the housing. By simply sliding the filter unit to the second installation position inside the housing, ventilation through the filter unit becomes possible. This eliminates the need for complex valve structures and other such features, making it possible to realize a simple and easy-to-use shelter ventilation system. [Brief explanation of the drawing]

[0017] [Figure 1] This figure schematically shows the overall configuration of a shelter ventilation system according to an embodiment of the present invention. [Figure 2] This figure schematically shows the overall configuration of a shelter ventilation system according to another embodiment of the present invention. [Figure 3] This figure schematically shows the configuration of a portion of a shelter ventilation system including a filter unit according to yet another embodiment of the present invention. [Figure 4] This is an exploded perspective view schematically showing the structure of a filter storage container according to an embodiment of the present invention. [Figure 5] This figure schematically shows the structure of a filter retainer to be installed inside a filter storage container according to an embodiment of the present invention. [Figure 6] This figure schematically shows the internal structure of a filter unit according to an embodiment of the present invention. [Figure 7]It is a diagram schematically showing an attachment structure of a case of a filter unit according to an embodiment of the present invention.

Embodiments for Carrying Out the Invention

[0018] Next, a specific example of an embodiment for implementing a ventilation system for a shelter according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram schematically showing an overall configuration of a ventilation system for a shelter according to an embodiment of the present invention.

[0019] Referring to FIG. 1, a ventilation system 1 for a shelter according to an embodiment of the present invention includes a blower 20 that takes in outside air 80 and supplies it to the interior of the shelter, and a filter unit 10 that is installed in the middle of the flow path of the outside air 80 from the shelter outer wall 5 to the blower 20, filters the taken-in outside air 80, purifies it, and discharges it to the blower 20.

[0020] Although not shown in FIG. 1, inside the filter unit 10, there are three filter layers of a pre-filter, a HEPA filter (high-efficiency particulate air filter), and an activated carbon filter along the flow path of the outside air 80 from the upstream side. The pre-filter filters relatively large dust and contaminants in the introduced outside air 80 for the purpose of preventing performance degradation due to clogging of the HEPA filter, etc., and filters dust and contaminants of a size visible to the naked eye or slightly smaller, about a few μm. The HEPA filter is a filter having a performance of capturing 99.97% or more of particles of a size of 0.3 μm and can capture contaminants of a size of about 0.3 μm. The activated carbon filter captures smaller contaminants that cannot be captured by the HEPA filter. The activated carbon filter may use finely crushed material, but in the embodiment, block-shaped activated carbon formed in a block shape is used.

[0021] The shelter ventilation system 1 according to an embodiment of the present invention, having the arrangement shown in Figure 1, ensures that even if the outside air 80 contains dust and pollutants, clean air filtered by the filter unit 10 is supplied before reaching the blower 20, so that the blower 20 does not release dust and pollutants into the shelter.

[0022] On the other hand, dust and contaminants separated by filtration accumulate inside the filter unit 10. While the accumulation of ordinary dust and contaminants inside the filter unit 10 does not affect the surroundings, if the outside air 80 contains radioactive materials, the accumulation of radioactive materials inside the filter unit 10 will cause the radioactive materials to continue emitting radiation, potentially turning the filter unit 10 into a source of radiation and adversely affecting people sheltered inside the shelter.

[0023] The shelter ventilation system 1 according to an embodiment of the present invention is configured to eliminate the risk of adverse effects on people inside the shelter, even if the outside air 80 contains radioactive material. For this reason, the filter unit 10 according to an embodiment of the present invention is housed in a case 18 that surrounds the filter unit 10 and prevents radiation leakage so that radiation from accumulated radioactive material does not reach people inside the shelter.

[0024] Case 18 comprises an inner circumferential wall 11 whose outer wall is made of at least lead, an outer circumferential wall 12 containing water or a water-containing gel that covers the outer periphery of the inner circumferential wall 11, and an outermost circumferential wall 13 that supports the outer circumferential wall 12. In one embodiment, an innermost circumferential wall 14, such as a rubber layer, is further provided inside the inner circumferential wall 11.

[0025] The inner circumferential wall 11, made of lead, contributes primarily to shielding against gamma rays among radiation. The outer circumferential wall 12, containing water or a water-containing gel, contributes to shielding against beta rays. Since water or a water-containing gel cannot constitute an outer wall on its own, in the case 18 of the embodiment, an outermost circumferential wall 13 made of a metal plate such as stainless steel is provided, and the outer circumferential wall 12 is formed by filling the space between the inner circumferential wall 11 and the outermost circumferential wall 13 with water or a water-containing gel.

[0026] Water-containing gels can be produced, for example, by using water as the main component and adding a high-molecular-weight water-absorbing polymer to maintain the water in a gel-like state. Suitable high-molecular-weight water-absorbing polymers include cellulose-based polymers such as sodium polyacrylate, polyacrylamide, and carboxymethylcellulose. For simpler applications, cooling gels primarily using sodium polyacrylate can be used.

[0027] When water is used as the outer perimeter wall 12, as shown in Figure 1, the top surface of the case 18 is provided with an inlet 15 for filling with water, and an air vent 17 to prevent air from being trapped inside the outer perimeter wall 12 and remaining as bubbles when water is injected, and the bottom surface of the case 18 is provided with a drain 16 for changing the water. When a water-containing gel is used as the outer perimeter wall 12, the gel may be directly injected into the outer perimeter wall 12 from the inlet 15, similar to water, but in one embodiment, the gel packed in flexible resin bags is laid out and stacked to form the outer perimeter wall 12. The thickness of the outer perimeter wall 12 can be expected to have some effect even with a thickness of about 3 mm when considering low-energy radiation, but it is preferable to have a thickness of about 10 mm or more in order to cover high-energy radiation as well.

[0028] In Figure 1, the ventilation system 1 for the shelter is shown with the piping for introducing outside air 80 directly attached to the outer wall 5 of the shelter. However, if the shelter is to be used not only for emergency evacuation but also as a living space on a daily basis, a switching valve may be provided near the interior of the outer wall 5 to switch between the flow path for taking in outside air 80 via the ventilation system 1 and the flow path for taking in outside air 80 for daily use directly or through a simple filter.

[0029] Furthermore, the filtration performance of the filter unit 10 deteriorates during use due to clogging and other factors. Therefore, when a decrease in filtration performance is observed, replacement becomes necessary. To address this, a joint is provided in the piping connected to the case 18 in which the filter unit 10 is housed, and the connection of the piping is released at the joint during replacement, allowing the entire case 18 to be replaced. Although not shown in Figure 1, in one embodiment, shut-off valves are provided on the upstream and downstream sides of the joint to close the piping and prevent radioactive material from leaking out from the released piping connection during replacement.

[0030] Figure 2 is a schematic diagram showing the overall configuration of a shelter ventilation system according to an embodiment of the present invention. Referring to Figure 2, the shelter ventilation system 2 according to an embodiment of the present invention is the same as the embodiment shown in Figure 1 in that it comprises a blower 20 that takes in outside air 80 and supplies it to the interior of the shelter, and a filter unit 10 that is installed in the middle of the flow path of the outside air 80 from the outer wall 5 of the shelter to the blower 20, and filters and purifies the taken-in outside air 80 before discharging it to the blower 20. However, the embodiment shown in Figure 1 differs in that the filter unit 10 is divided into two parts: a filter unit 10-1 equipped with a pre-filter and a HEPA filter, and a filter unit 10-2 equipped with an activated carbon filter.

[0031] The three types of filters included in the filter unit 10 may have different replacement frequencies depending on the conditions of the incoming outside air 80. Therefore, by dividing the filter unit 10 into filter unit 10-1 and filter unit 10-2, it becomes possible to replace only the filter unit that needs replacing. If the outside air 80 contains radioactive material, the radioactive material will be captured in each of the divided filter units (10-1, 10-2). In the embodiment shown in Figure 2, cases 18 are provided for each filter unit (10-1, 10-2) to block radiation irradiated from the radioactive material. The configuration of the outer wall of the case 18 for each filter unit (10-1, 10-2) may be common, or the thickness and configuration of the outer wall may be changed according to the type and size of the expected radioactive material.

[0032] In the embodiments shown in Figures 1 and 2, the shelter ventilation systems (1, 2) are shown to be installed inside the shelter outer wall 5. However, the embodiments of the shelter ventilation systems (1, 2) are not limited to these, and they may be installed partially or entirely outside the shelter outer wall 5. For example, if filter unit 10-1 in shelter ventilation system 2 is installed outside the shelter outer wall 5 and filter unit 10-2 is installed inside the shelter outer wall 5, the case 18 installed around filter unit 10-2 prevents radiation leakage into the shelter room. The case 18 of the filter unit 10-1 installed on the outside does not directly prevent radiation leakage into the shelter room, but it prevents radiation exposure to workers when replacing or disposing of the filter unit 10-1 after use, etc.

[0033] Figure 3 is a schematic diagram showing the configuration of a portion of a shelter ventilation system including a filter unit according to yet another embodiment of the present invention. Referring to Figure 3, a portion of the shelter ventilation system 3 according to the embodiment is shown, including the filter unit 10-3 with the blower 20 omitted.

[0034] Unlike the stationary embodiment shown in Figures 1 and 2, the shelter ventilation system 3 according to this embodiment is designed for use in shelters as mobile facilities and is made to be small and lightweight. The filter unit 10-3 is formed to have a roughly rectangular parallelepiped shape and is housed in a case 18 which also has a rectangular parallelepiped shape. Furthermore, the case 18 is slidably housed in a housing 30 which also has a roughly rectangular parallelepiped shape.

[0035] The filter unit 10-3 houses a pre-filter 60, a HEPA filter 61, and an activated carbon filter 62 in order from the upstream side to the downstream side of the outside air 80 to be filtered, i.e., from left to right in Figure 3, within a roughly rectangular filter housing container 40. These filters have the same function and performance as the pre-filter, HEPA filter, and activated carbon filter described above with reference to Figure 1. The activated carbon filter 62 in this embodiment is a block-shaped activated carbon 62.

[0036] As a mobile facility, the shelter is intended to be mounted on or towed by a mobile body. Therefore, vibrations are applied to the shelter's ventilation system 3 as it moves. The block-shaped activated carbon 62 is also subjected to vibrations, but if it vibrates in such a way that relative motion occurs between the block-shaped activated carbon 62 and the filter storage container 40, the block-shaped activated carbon 62 may gradually pulverize, potentially reducing its filtration performance. Therefore, in the filter unit 10-3 of this embodiment, the block-shaped activated carbon 62 is fixed in a state where it is pressed down by a biasing means to prevent it from moving within the storage section. The biasing means will be explained in detail with reference to Figure 4, but Figure 3 shows the situation in which the block-shaped activated carbon 62 is pressed down and fixed toward the downstream side, i.e., the right side of Figure 3, by a filter retainer 51 which constitutes part of the biasing means.

[0037] The filter storage container 40 has an opening in the storage container lid 42 located upstream of the pre-filter 60 that forms part of the introduction hole 36 for introducing outside air 80, and an opening in the bottom of the storage container body 41 located downstream of the block-shaped activated carbon 62 that forms part of the discharge hole 37 for discharging purified air.

[0038] Case 18, similar to the embodiment shown in Figure 1, comprises an inner circumferential wall 11 made of at least lead, an outer circumferential wall 12 containing water or a water-containing gel that covers the outer circumference of the inner circumferential wall 11, and an outermost circumferential wall 13 that supports the outer circumferential wall 12. Case 18 also comprises an inlet 36 for introducing outside air 80 into the filter unit 10-3 and an outlet 37 for discharging the air purified by the filter unit 10-3. When the outer circumferential wall 12 is made of water, simply opening the inlet 36 and the outlet 37 will not be enough to stop the water, so circular pipes corresponding to the inlet 36 and the outlet 37 are installed to seal the gap between the inner circumferential wall 11 and the outermost circumferential wall 13 to prevent water leakage. Furthermore, an injection hole for injecting water into the outer circumferential wall 12 and a drain for drainage are also necessary. For this reason, in this embodiment, it is preferable to form the outer circumferential wall 12 by packing a bag of water-containing gel, which is easier to handle than water, between the inner circumferential wall 11 and the outermost circumferential wall 13.

[0039] Furthermore, since the case 18 is slidably housed inside the housing 30, it may be equipped with mounting parts such as hooks for attaching sliding means 31 such as handles to facilitate sliding. The sliding means 31 may be detachably provided via these mounting parts, or it may be fixedly provided for each case 18 in advance. In this case, considering the transportation of multiple cases 18 together, it is desirable that the sliding means 31 be provided in a foldable form.

[0040] The housing 30 houses a case 18 containing the filter unit 10-3, which is slidably positioned between a first installation position 32 and a second installation position 33. The first installation position 32 is the normal installation position when ventilation is not performed via the filter unit 10-3. Figure 3 shows the case 18 installed in the first installation position 32. In the first installation position 32, the opposing side walls of the housing 30 act as covers that block the inlet hole 36 and the outlet hole 37 of the case 18, so that outside air 80 is not introduced into the inside of the filter unit 10-3.

[0041] The second installation position 33 is the position where the case 18 is manually lifted by the sliding means 31, and is the installation position when ventilation is performed via the filter unit 10-3. The housing 30 is provided with an external inlet 34 for introducing outside air 80 into the filter unit 10-3, and an external exhaust 35 for discharging the clean air filtered by the filter unit 10-3 to the blower 20. In the second installation position 33, the external inlet 34 and the inlet 36 of the case 18 are in communication, and the external exhaust 35 and the exhaust 37 of the case 18 are in communication, enabling ventilation via the filter unit 10-3.

[0042] The case 18 and the inner wall of the housing 30 are required to be in contact to prevent air leakage. In this embodiment, an elastic body such as rubber is provided on the outer wall surface of the case 18 where the inlet hole 36 and discharge hole 37 are located, or on the inner wall surface of the housing 30 facing it. In another embodiment, an elastic body such as a packing is provided near the outer periphery of the inlet hole 36 and discharge hole 37 of the case 18 at the first installation position 32 and the second installation position 33 to prevent leakage of outside air 80 from the flow path. The elastic body may be provided on the housing 30 side, but it is preferable to provide it on the case 18 because it is effective regardless of the installation position of the case 18.

[0043] In Figure 3, the case 18 is shown installed in the first installation position 32, with both the external inlet 34 and the external exhaust 35 closed off by the outermost wall 13 of the case 18. However, the height of the housing 30, i.e., the vertical height in the figure, may be extended, so that when the case 18 housing the filter unit 10-3 is installed in the first installation position 32, both the external inlet 34 and the external exhaust 35 open above the case 18, allowing it to be used for daily ventilation without going through the filter unit 10-3. In this case, a removable filter separate from the filter unit 10-3 for filtering the outside air 80 introduced through the external inlet 34 may be provided on the inner wall surface of the housing 30 corresponding to the position of the external inlet 34.

[0044] As the filter unit 10-3 is used, its filtration efficiency may decrease due to clogging, etc., so it is preferable that it be installed inside the housing 30 so that it can be replaced. In this embodiment, the housing 30 is provided with an openable or removable lid, and is configured so that each case 18 can be replaced. Since the case 18 has two openings, an inlet hole 36 and an outlet hole 37, on two opposing sides, if the used unit is left unattended after being removed during replacement, there is a risk that the stored radioactive material may leak out. Also, even when storing unused units, there is a risk that dust and contaminants from the air may enter through the two openings. Therefore, when ventilation is not performed, a lid is attached to the inlet hole 36 and the outlet hole 37 to block the internal filter from the outside. Specifically, for example, female threads may be formed in the inner diameter of the inlet hole 36 and the outlet hole 37, and a lid having a male thread portion may be screwed on to cover the openings. In one embodiment, the filter unit 10-3 is built in, and the inlet hole 36 and the outlet hole 37 are covered with a lid, and this replacement filter unit is manufactured and supplied. The user can obtain this replacement filter unit and store it as a spare filter unit 10-3 with the cover still attached, or they can remove the cover and install it inside the housing 30 for immediate use in ventilation.

[0045] Figure 4 is an exploded perspective view schematically showing the structure of a filter storage container according to an embodiment of the present invention. Referring to Figure 4, the filter storage container 40 according to an embodiment of the present invention comprises a storage container body 41 having a space for storing a filter inside, and a storage container lid 42. The storage container lid 42 has an opening that is part of an inlet hole 36 for introducing outside air 80, and the bottom of the storage container body 41 has an opening that is part of an outlet hole 37 for discharging purified air.

[0046] Inside the storage container body 41, a block of activated carbon 62, a HEPA filter 61, and a pre-filter 60 are installed in order from the bottom side, i.e., the right side in the figure. As mentioned above, it is desirable to fix the block of activated carbon 62 in a pressed state by a biasing means in order to prevent it from becoming powdery during movement. In this embodiment, the biasing means 50 includes a filter holder 51, a coil spring 55, a spring sleeve 56, a spacer 57, and a pressure adjustment bolt 58. The filter holder 51 has a spring receiving portion 53 that contacts one end of the coil spring 55 and receives the compressive force of the coil spring 55, and uses this compressive force to maintain the pressed state against the block of activated carbon 62. In order to maintain the pressed state, the filter holder 51 needs to be slidable in the direction toward the block of activated carbon 62. The storage container body 41 is provided with a guide groove 54, and the spring receiving portion 53 formed on the filter holder 51 is installed to slide along the guide groove 54, so the filter holder 51 can slide in the direction toward the block of activated carbon 62.

[0047] The pressure adjustment bolt 58 is screwed into a female thread formed in a through hole provided in the storage container lid 42, and the tip of the pressure adjustment bolt 58, which penetrates the storage container lid 42, compresses the coil spring 55. The spacer 57 is located inside the spring sleeve 56 together with the coil spring 55 and transmits the force received from the pressure adjustment bolt 58 to the coil spring 55. In one embodiment, a graduated slit is provided on the side of the spring sleeve 56 so that the compression state of the coil spring 55 can be determined by the position of the spacer 57, thereby allowing confirmation of the pressing state against the block-shaped activated carbon 62.

[0048] In this embodiment, after inserting the block-shaped activated carbon 62 into the bottom of the storage container body 41, the filter retainer 51 is inserted, followed by the HEPA filter 61 and pre-filter 60 being installed inside the filter retainer 51 in order, and then the storage container lid 42 is attached to the storage container body 41 with fixing screws (not shown). Subsequently, with the spring sleeve 56, into which the spacer 57 and coil spring 55 are inserted, placed in the guide groove 54 of the storage container body 41, the pressure adjustment bolt 58 is screwed into the storage container lid 42. The pressure adjustment bolt 58 can be screwed in until the spacer 57 is pressed in, thereby applying compressive force to the coil spring 55. The compressive force of the coil spring 55 is transmitted to the filter retainer 51 by the spring receiving part 53, and this force maintains the pressing state of the filter retainer 51 against the block-shaped activated carbon 62.

[0049] The structure of the filter storage container 40 shown in Figure 4 is one embodiment for maintaining the pressing state on the block-shaped activated carbon 62, and the installation position and number of coil springs 55, the structure of the filter retainer 51, etc. are not limited to the structure shown in Figure 4, as long as it is possible to maintain the pressing state on the block-shaped activated carbon 62. Also, although the filter storage container 40 is shown in a roughly rectangular parallelepiped shape, it is not necessary to limit it to this shape, and for example, it may have a cylindrical outer shape, and the filter to be inserted and the filter retainer 51 may be shaped to fit the internal space.

[0050] Figure 5 is a schematic diagram showing the structure of a filter retainer installed in a filter storage container according to an embodiment of the present invention. Referring to Figure 5, the filter retainer 51 according to an embodiment of the present invention has a substantially rectangular parallelepiped shape with a space inside for housing a pre-filter 60 and a HEPA filter 61. The filter retainer 51 is positioned along the flow path of the outside air 80 to be filtered, with the left side in the figure being the upstream side and the right side being the downstream side. The upstream end of the filter retainer 51 is fully open, and a frame-shaped retaining frame 52 is provided on the downstream end face. The retaining frame 52 presses against the block-shaped activated carbon 62 which is housed downstream of the filter retainer 51 in the filter storage container 40. The filter retainer 51 is made of a metal material such as stainless steel, but an elastic material such as a frame-shaped rubber may be provided on the downstream side of the retaining frame 52 to allow for flexible contact with the block-shaped activated carbon 62. L-shaped spring receiving parts 53 are provided on the upstream outer walls of two opposing sides of the filter retainer 51 to receive force from a coil spring 55. Receiving a downstream force from the coil spring 55, the filter retainer 51 continues to press the block-shaped activated carbon 62 against the retaining frame 52.

[0051] Figure 6 is a schematic diagram showing the internal structure of a filter unit according to an embodiment of the present invention. Figure 6 shows a horizontal cross-section along the guide groove 54 of the filter unit 10-3 according to an embodiment of the present invention.

[0052] The filter unit 10-3 is formed by placing a block-shaped activated carbon 62, a HEPA filter 61, and a pre-filter 60 in order from the bottom inside the storage container body 41 of the filter storage container 40, and then attaching the storage container lid 42. The filter retainer 51, which presses and fixes the block-shaped activated carbon 62, is inserted into the storage container body 41 after the block-shaped activated carbon 62 has been inserted into the storage container body 41 but before the HEPA filter 61 has been inserted, and is positioned so that the block-shaped activated carbon 62 is pressed against the bottom side of the storage container body 41 by a frame-shaped retaining frame 52 at one end.

[0053] The HEPA filter 61 and pre-filter 60 are inserted in this order into the internal space of the filter holder 51 and installed, and then the storage container lid 42 is attached to complete the filter assembly. Subsequently, the spring sleeve 56 with the spacer 57 and coil spring 55 inserted is set so as to abut against the spring receiving portion 53 of the filter holder 51, and the pressure adjustment bolt 58 is screwed in from the storage container lid 42 side, and the tip of the pressure adjustment bolt 58 that penetrates the storage container lid 42 pushes the spacer 57 and applies compressive force to the coil spring 55. Due to the repulsive force of the coil spring 55 trying to return to its original position, the filter holder 51 continues to press against the block-shaped activated carbon 62. As a result, even when the filter unit 10-3 is used in a mobile facility, it is possible to prevent the block-shaped activated carbon 62 from being pulverized by vibration during transport.

[0054] Figure 7 is a schematic diagram showing the mounting structure of the filter unit case according to an embodiment of the present invention. Figure 7 shows a horizontal cross-section including the filter unit 10. Figure 7(a) shows an embodiment in which the outer wall 70 of the case 18 is formed as a single unit, and Figure 7(b) shows an embodiment in which the outer wall 70 of the case 18 is formed as a combination of partial outer walls 71. Note that the details of the filter unit 10, including its internal structure, are omitted.

[0055] When manufacturing a new shelter ventilation system (1, 2), the shape and positional relationship between the filter unit 10 and the case 18 can be set to a certain extent. For this reason, as shown in Figure 7(a), the filter unit 10 can be housed in the case 18 of the outer wall 70 which is formed as a single unit, and the outer periphery of the filter unit 10 can be covered without leakage.

[0056] However, many shelter ventilation systems have already been manufactured and put into practical use that do not take into account radiation leakage, such as the shelter ventilation system of the embodiment of the present invention, and are manufactured primarily for the purpose of filtering harmful chemical substances. Therefore, there is naturally a need for radiation leakage countermeasures in these shelter ventilation systems that do not have countermeasures against radiation leakage. Figure 7(b) shows an embodiment for realizing the configuration of the shelter ventilation system (1, 2) of the present invention by retrofitting the case 18 of the embodiment of the present invention to an existing shelter ventilation system in response to this need.

[0057] Referring to Figure 7(b), the outer wall 70 of case 18 includes partial outer walls (71-1, 71-2) configured to cover the filter unit 10 when combined with each other. The partial outer walls (71-1, 71-2) also consist of an inner circumferential wall 11 made of at least lead, an outer circumferential wall 12 containing water or a water-containing gel that covers the outer periphery of the inner circumferential wall 11, and an outermost circumferential wall 13 that supports the outer circumferential wall 12, as described with reference to Figure 1. In one embodiment, an innermost circumferential wall 14, such as a rubber layer, is further provided inside the inner circumferential wall 11, similar to the outer wall of case 18 described above.

[0058] Figure 7(b) shows the system composed of two partial outer walls, 71-1 and 71-2, but depending on the embodiment, there may be three or more. When combining partial outer walls 71-1 and 71-2, if they are combined so that their ends abut each other, there is a possibility that radiation may leak from the abutting boundary. Therefore, in one embodiment, when combining partial outer walls (71-1, 71-2), an overlapping portion 72 is provided at the combination point where the partial outer walls overlap. This makes it possible to cover the outer periphery of the filter unit 10 without leakage with an outer wall 70 that has a radiation shielding effect, even in an existing shelter ventilation system, and to reconstruct it as a shelter ventilation system (1, 2) according to the embodiment of the present invention. Note that in Figure 7(b), fastening means such as bolts or belts used to fasten the combined partial outer walls (71-1, 71-2) are omitted.

[0059] Although embodiments of the present invention have been described in detail above with reference to the drawings, the present invention is not limited to the embodiments described above, and can be modified in various ways without departing from the technical scope of the present invention. [Explanation of Symbols]

[0060] 1, 2, 3 Ventilation systems for shelters 5 Shelter exterior wall 10, 10-1, 10-2, 10-3 filter unit 11 Inner wall 12 Peripheral wall 13 Outermost wall 14 Innermost wall 15 Inlet 16 Drain 17. Bleeding the air 18 cases 20 Blower 30 cabinets 31 Sliding means 32 1st installation position 33 Second installation position 34 External entry holes 35 External drain hole 36 Inlet holes 37 Discharge hole 40 filter storage containers 41 Storage container body 42 Storage container lid 50. Biasing means 51 Filter holder 52 Retainer frame 53 Spring support section 54 Guide grooves 55 Coil spring 56 Spring Sleeves 57 Spacer 58 Pressure adjustment bolt 60 pre-filters 61 HEPA filter 62 Activated carbon filter (block-shaped activated carbon) 70 Exterior Wall 71, 71-1, 71-2 Partial exterior wall 72 Overlapping section 80 Outdoor air

Claims

1. A ventilation system for a shelter, comprising a filter unit configured to take in outside air, filter out dust containing radioactive materials contained in the outside air, and discharge purified air, The outer wall, which serves as a case for housing the filter unit, comprises an inner circumferential wall made of lead, an outer circumferential wall containing water or a water-containing gel covering the outer periphery of the inner circumferential wall, and an outermost circumferential wall supporting the outer circumferential wall. The aforementioned filter unit comprises, from upstream to downstream along the flow path of outside air, a pre-filter, a HEPA filter, and an activated carbon filter consisting of block-shaped activated carbon. The ventilation system for a shelter is characterized in that the filter unit is configured as a two-part filter unit comprising a first filter unit having the pre-filter and the HEPA filter, and a second filter unit having the activated carbon filter, and the case of each of the two-part filter units comprises the inner circumferential wall, the outer circumferential wall, and the outermost circumferential wall.

2. A shelter ventilation system comprising a filter unit configured to take in outside air, filter out dust containing radioactive materials contained in the outside air, and discharge purified air, The outer wall, which serves as a case for housing the filter unit, comprises an inner circumferential wall made of lead, an outer circumferential wall containing water or a water-containing gel covering the outer periphery of the inner circumferential wall, and an outermost circumferential wall supporting the outer circumferential wall. The ventilation system for shelters is characterized in that the filter unit is individually housed in a housing section of a case having an inner wall and an outer wall, and includes a pre-filter, a HEPA filter, and a block of activated carbon, which are installed in order from the outside air intake side, and the block of activated carbon is fixed in a state in which it is pressed by a biasing means so as not to move within the housing section.

3. The ventilation system for a shelter according to claim 2, characterized in that the case comprises an inlet for introducing outside air into the filter unit and an outlet for discharging air purified by the filter unit, and when storage is not performed, the inlet and outlet of air are prevented by a cover, and when ventilation is performed, the cover is removed to expose the inlet and outlet.

4. The case housing the aforementioned filter unit is further provided with a housing that slidably houses the case between a first installation position and a second installation position. The shelter ventilation system according to claim 3, characterized in that, in the first installation position, which is the normal installation position when ventilation is not performed, a part of the housing acts as a cover to block the inlet hole and the outlet hole, and in the second installation position, which is the installation position when filter ventilation is performed, the external inlet hole provided in the housing is in communication with the inlet hole, and the external outlet hole provided in the housing is in communication with the outlet hole, thereby enabling ventilation through the filter unit.

5. A case that encloses a filter unit of a shelter ventilation system configured to take in outside air, filter out dust containing radioactive materials contained in the outside air, and discharge purified air, The case is characterized by having an outer wall comprising an inner circumferential wall made of lead, an outer circumferential wall containing water or a water-containing gel covering the outer periphery of the inner circumferential wall, and an outermost periphery wall supporting the outer circumferential wall.

6. The case according to claim 5, wherein the outer wall of the case includes a plurality of partial outer walls configured to be combined with each other to cover the filter unit, and overlapping portions are provided at the combined portions of the plurality of partial outer walls so as to prevent leakage of radiation from radioactive material inside the filter unit.

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