WO2018110547A1 - Radioactive substance removal filter, radioactive substance removal filter unit in which said radioactive substance removal filter is used, and method for removing radioactive substance - Google Patents

Abstract

Provided are: a radioactive substance removal filter capable of suppressing the deterioration of radioactive substance removal capability even if an organic solvent, in particular a compound having a high boiling point of 120 degrees or higher, is present in the air; a radioactive substance removal filter unit in which the radioactive substance removal filter is used; and a method for removing radioactive substances. The radioactive substance removal filter is provided with an activated carbon fiber layer 2 on the downstream side and an activated carbon particle layer 3 on the upstream side. The activated carbon fiber layer 2 includes a fiber-like activated carbon to which an amine compound is attached, and the ratio of the amount of the amine compound attached in the activated carbon particles layer 3 and the amount of the amine compound attached in the activated carbon fiber layer 2 (amount of the amine compound attached in the activated carbon particles layer 3 / amount of the amine compound attached in the activated carbon fiber layer 2) is 0.1 or less (including 0).

Description

Radioactive substance removal filter, radioactive substance removal filter unit using the same, and radioactive substance removal method

The present invention relates to a radioactive substance removal filter, and more particularly to a radioactive substance removal filter that removes radioactive substances contained in a gas, particularly radioactive iodine and organic iodine compounds.

In facilities handling radioactive substances such as medical facilities and nuclear facilities, it is necessary to remove the generated gaseous radioactive substances from the air, and radioactive substance removal filters are used. As a radioactive substance removal filter for removing gaseous iodine, a processing method for collecting and removing gaseous iodine by allowing air to pass through an activated carbonized sheet-shaped charcoal filter is known (for example, Patent Documents). 1).

As a radioactive substance removal filter for removing organic iodine compounds together with gaseous iodine, the pore volume with a pore diameter of 3 to 30 nm is 0.15 cc / g or less and the pore diameter is 3 nm or less. There is known a radioactive substance removal filter having a filter medium formed by attaching an amine to a sheet made of activated carbon having a volume of 0.50 cc / g or more and laminating a protective sheet on at least one of the sheets made of activated carbon (for example, Patent Document 2).

JP 2003-66191 A JP 2004-205490 A

However, in facilities that handle radioactive materials such as these, liquid scintillation counters are used to measure radiation. In a liquid scintillation cocktail used for a liquid scintillation counter, an organic solvent having a boiling point of 120 ° C. or higher and a high boiling point compound such as 1,2,4-trimethylbenzene and linear dodecylbenzene is used. For this reason, the exhaust gas of the facility contains a trace amount of these organic solvents (VOC) in addition to gaseous radioactive substances. The organic solvent of a high boiling point compound adheres to the radioactive substance removal filter like patent document 1 and patent document 2, and becomes a reduction factor of the removal performance of the radioactive substance using these radioactive substance removal filters.

The present invention has been made in view of the above circumstances, and its purpose is to provide radioactive iodine and organic matter even when a gaseous organic solvent, particularly a high boiling point compound having a boiling point of 120 ° C. or more, is contained in the gas. An object of the present invention is to provide a radioactive substance removal filter that can suppress a reduction in the removal performance of radioactive substances such as iodine compounds, a radioactive substance removal filter unit using the radioactive substance removal filter, and a radioactive substance removal method.

The radioactive substance removal filter of the present invention that has been able to solve the above-mentioned problem comprises an activated carbon fiber layer on the downstream side and an activated carbon particle layer on the upstream side, and the activated carbon fiber layer is a fibrous material to which an amine compound is attached. It has activated carbon, and the ratio of the amount of amine compound attached to the activated carbon particle layer to the amount of amine compound attached to the activated carbon fiber layer (the amount of amine compound attached to the activated carbon particle layer / the amount of amine compound attached to the activated carbon fiber layer) is 0. .1 or less (including 0).

Since the radioactive substance removal filter of the present invention adsorbs the organic solvent in the gas in the upstream activated carbon particle layer, the activated carbon fiber layer on the downstream side deteriorates the removal performance of radioactive iodine and organic iodine compound by the organic solvent. Can be prevented.

In the radioactive substance removing filter of the present invention, the amine compound is preferably water-soluble, and more preferably triethylenediamine.

In the radioactive substance removing filter of the present invention, the amount of the amine compound attached to the activated carbon fiber layer is preferably 5% by mass or more and 20% by mass or less of the fibrous activated carbon.

In the radioactive substance removing filter of the present invention, the basis weight of the fibrous activated carbon of the activated carbon fiber layer is preferably 150 g / m ² or more and 900 g / m ² or less.

In the radioactive substance removal filter of the present invention, the basis weight of the granular activated carbon of the activated carbon particle layer is preferably 150 g / m ² or more and 900 g / m ² or less.

In the radioactive substance removal filter of the present invention, the fibrous activated carbon preferably has a BET specific surface area of 800 m ² / g or more.

In the radioactive substance removal filter of the present invention, the granular activated carbon preferably has a BET specific surface area of 800 m ² / g or more.

In the radioactive substance removing filter of the present invention, the total pore volume of the fibrous activated carbon is preferably 0.3 cc / g or more.

In the radioactive substance removing filter of the present invention, the total pore volume of the granular activated carbon is preferably 0.3 cc / g or more.

In the radioactive substance removing filter of the present invention, the average fiber diameter of the fibrous activated carbon is preferably 10 μm or more and 40 μm or less.

In the radioactive substance removal filter of the present invention, the average particle diameter of the granular activated carbon is preferably 200 μm or more and 700 μm or less.

In the radioactive substance removing filter of the present invention, the activated carbon fiber layer and the activated carbon particle layer are laminated and preferably have a pleated shape.

The present invention includes a radioactive substance removal filter unit characterized by having the radioactive substance removal filter and a radioactive substance removal method.

The radioactive substance removal filter of the present invention is characterized in that an activated carbon fiber layer having fibrous activated carbon to which an amine compound is attached is provided on the downstream side, and an activated carbon particle layer having granular activated carbon is provided on the upstream side. By having an activated carbon fiber layer on the downstream side and an activated carbon particle layer on the upstream side, the radioactive substance removal filter removes radioactive substances such as radioactive iodine and organic iodine compounds even if organic solvents are contained in the gas. It becomes possible to suppress that performance falls, and the radioactive substance removal effect of a radioactive substance removal filter can be exhibited over a long period of time.

The schematic of the radioactive substance removal filter in embodiment of this invention is represented. The schematic sectional drawing after the pleating process of the radioactive substance removal filter in embodiment of this invention is represented. The perspective view of the radioactive substance removal filter unit in embodiment of this invention is represented.

Hereinafter, the radioactive substance removal filter according to the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the illustrated examples, and is suitable as long as it can meet the purpose described above and below. It is also possible to carry out by modifying the above, and they are all included in the technical scope of the present invention.

The radioactive substance removal filter according to the present invention includes an activated carbon fiber layer on the downstream side and an activated carbon particle layer on the upstream side, and the activated carbon fiber layer includes fibrous activated carbon to which an amine compound is attached, and the activated carbon particle layer The ratio between the amount of the amine compound attached to the activated carbon fiber layer and the amount of the amine compound attached to the activated carbon fiber layer is 0.1 or less (including 0). Hereinafter, the downstream side, the upstream side, the activated carbon fiber layer, and the activated carbon particle layer in the present invention will be described.

In the present invention, the downstream side is the side after the gas passes through the filter, and means the gas outflow side. The upstream side is the side opposite to the downstream side, before the gas passes through the filter, and means the gas inflow side. The arrows in FIGS. 1 and 2 indicate the gas flow, and the upper side in FIGS. 1 and 2 is the upstream side, and the lower side is the downstream side.

The activated carbon fiber layer 2 is a layer having fibrous activated carbon to which an amine compound is attached. Fibrous activated carbon is fibrous activated carbon obtained by carbonizing natural fiber, regenerated fiber or synthetic fiber and performing an activation reaction by gas activation.

The activated carbon fiber layer 2 is obtained by laminating non-woven fabrics on both sides of a sheet-like fibrous activated carbon and performing an integration treatment.

The BET specific surface area of the fibrous activated carbon is preferably 800 m ² / g or more, more preferably 1000 m ² / g or more, and further preferably 1200 m ² / g or more. When the lower limit value of the BET specific surface area of the fibrous activated carbon is this value, the radioactive substance removing effect of the activated carbon fiber layer 2 can be enhanced.

The total pore volume of the fibrous activated carbon is preferably 0.3 cc / g or more, more preferably 0.4 cc / g or more, and further preferably 0.5 cc / g or more. When the lower limit value of the total pore volume of the fibrous activated carbon is this value, the effect of removing the radioactive substance in the activated carbon fiber layer 2 is enhanced.

The average fiber diameter of the fibrous activated carbon is preferably 10 μm or more, and more preferably 12 μm or more. When the lower limit value of the average fiber diameter of the fibrous activated carbon is such a value, the breathability of the activated carbon fiber layer 2 can be improved. The average fiber diameter of the fibrous activated carbon is preferably 40 μm or less, more preferably 35 μm or less, and further preferably 30 μm or less. When the upper limit value of the average fiber diameter of the fibrous activated carbon is such a value, the surface area of the activated carbon fiber layer 2 is increased, and the radioactive substance removal efficiency is improved.

The fibrous activated carbon is observed with an electron microscope at a magnification of 500 times, and the fiber diameter is measured. Arbitrary 100 fiber diameters are arithmetically averaged, and this average value is taken as the average fiber diameter of the fibrous activated carbon.

Specific examples of the amine compound include 1,4-diazabicyclo [2,2,2] octane (triethylenediamine), N, N′-bis (3-aminopropyl) piperazine, N, N-dimethylaminoethyl methacrylate, N, N-dimethylaminopropylamine, 3-aminopropyltrimethoxysilane, 1,5-diazabicycloundecene, polyethyleneimine, 1,5-diazabicyclo [4.3.0] nonene, 1,8-diazabicyclo [ 5.4.0] -7-undecene, 2-methyl-1,4-diazabicyclo [2.2.2] octane, phenylhydrazine, 2-cyanopyridine, diisopropylamine, N, N ′, N′-trimethylamino Examples include ethyl piperazine, hexamethylene tetramine, and polyalkyl polyamine. Among them, the amine compound used is preferably water-soluble, and more preferably 1,4-diazabicyclo [2,2,2] octane (triethylenediamine). By using a water-soluble amine compound, the activated carbon fiber layer 2 can be easily manufactured, and by using triethylenediamine, a high radioactive substance removing effect can be obtained.

The amount of the amine compound attached to the activated carbon fiber layer 2 is preferably 5% by mass or more, more preferably 7% by mass or more, and further preferably 10% by mass or more of the fibrous activated carbon. When the lower limit of the amount of the amine compound attached to the activated carbon fiber layer 2 is this value, the radioactive organic iodine compound can be sufficiently adsorbed. Further, the amount of the amine compound attached to the activated carbon fiber layer 2 is preferably 20% by mass or less, more preferably 17% by mass or less, and further preferably 15% by mass or less of the fibrous activated carbon. . When the upper limit value of the amount of the amine compound attached to the activated carbon fiber layer 2 is this value, the cost can be suppressed while maintaining a sufficient radioactive substance removing effect.

The method of attaching the amine compound to the activated carbon fiber layer 2 includes a method of immersing and drying a sheet-like fibrous activated carbon in an amine compound solution, a method of spraying and drying the amine compound solution on a sheet-like fibrous activated carbon, Examples thereof include a method in which fibrous activated carbon is immersed in an amine compound solution and dried to form a sheet. Especially, it is preferable to make an amine compound adhere to the activated carbon fiber layer 2 by the method of immersing a sheet-like fibrous activated carbon in the solution of an amine compound, and drying. By attaching the amine compound to the activated carbon fiber layer 2 in this way, the amine compound can be uniformly attached to the fibrous activated carbon, and the radioactive substance removing effect of the activated carbon fiber layer 2 is enhanced.

The basis weight of the fibrous activated carbon in the activated carbon fiber layer 2 is preferably 150 g / m ² or more, more preferably 200 g / m ² or more, and further preferably 400 g / m ² or more. When the lower limit value of the fibrous activated carbon in the activated carbon fiber layer 2 is this value, the radioactive substance removing effect of the activated carbon fiber layer 2 is sufficient. Moreover, the basis weight of the fibrous activated carbon in the activated carbon fiber layer 2 is preferably 900 g / m ² or less, more preferably 800 g / m ² or less, and further preferably 700 g / m ² or less. When the upper limit value of the fibrous activated carbon in the activated carbon fiber layer 2 is this value, the weight of the activated carbon fiber layer 2 can be reduced, and the pressure loss can be reduced.

The activated carbon particle layer 3 is a layer having granular activated carbon. The granular activated carbon is a granular activated carbon obtained by performing an activation reaction by gas activation or chemical activation on carbonized palm shell, sawdust, bamboo or the like, coal, pitch or the like. Examples of the granular activated carbon include crushed charcoal, granular charcoal, and formed charcoal, and any type can be suitably used. In addition to granular activated carbon, powdered activated carbon, which is powdered activated carbon, can be used, but granular activated carbon is preferably used in order to reduce pressure loss.

The activated carbon particle layer 3 is obtained by mixing granular activated carbon and a thermoplastic resin, sandwiching the mixture between nonwoven fabrics, and performing a heat treatment.

The BET specific surface area of the granular activated carbon is preferably 800 m ² / g or more, more preferably 900 m ² / g or more, and further preferably 1000 m ² / g or more. When the lower limit value of the BET specific surface area of the granular activated carbon is this value, the effect of the activated carbon particle layer 3 removing the organic solvent can be enhanced.

The total pore volume of the granular activated carbon is preferably 0.3 cc / g or more, more preferably 0.4 cc / g or more, and further preferably 0.5 cc / g or more. When the lower limit value of the total pore volume of the granular activated carbon is this value, the effect of removing the organic solvent from the activated carbon particle layer 3 is improved.

The average particle diameter of the granular activated carbon is preferably 200 μm or more, and more preferably 250 μm or more. When the lower limit value of the average particle diameter of the granular activated carbon is such a value, the air permeability of the activated carbon particle layer 3 can be improved. Further, the average particle diameter of the granular activated carbon is preferably 700 μm or less, more preferably 625 μm or less, and further preferably 550 μm or less. When the upper limit value of the average particle diameter of the granular activated carbon is such a value, the surface area of the activated carbon particle layer 3 is increased, and the efficiency of removing the organic solvent is improved.

The granular activated carbon is observed at a magnification of 35 times using an optical microscope, and the particle diameter is measured. Arbitrary 100 particle sizes are arithmetically averaged, and this average value is taken as the average particle size of the granular activated carbon.

The basis weight of the granular activated carbon in the activated carbon particle layer 3 is preferably 150 g / m ² or more, more preferably 200 g / m ² or more, and further preferably 250 g / m ² or more. When the lower limit value of the granular activated carbon in the activated carbon particle layer 3 is this value, the activated carbon particle layer 3 can have a sufficient organic solvent removing effect. Further, the basis weight of the granular activated carbon in the activated carbon particle layer 3 is preferably 900 g / m ² or less, more preferably 800 g / m ² or less, and further preferably 700 g / m ² or less. Since the upper limit of the basis weight of the granular activated carbon in the activated carbon particle layer 3 is this value, the activated carbon particle layer 3 can be made lightweight and the pressure loss can be reduced.

The ratio of the amount of amine compound attached to the activated carbon particle layer 3 and the amount of amine compound attached to the activated carbon fiber layer 2 (the amount of amine compound attached to the activated carbon particle layer 3 / the amount of amine compound attached to the activated carbon fiber layer 2) is: It is 0.1 or less, preferably 0.08 or less, and more preferably 0.06 or less. In addition, the ratio of the amine compound adhesion amount of the activated carbon particle layer 3 and the amine compound adhesion amount of the activated carbon fiber layer 2 includes 0. Since the ratio of the amine compound adhesion amount of the activated carbon particle layer 3 and the amine compound adhesion amount of the activated carbon fiber layer 2 is this value, the organic solvent in the gas is removed to the activated carbon particle layer 3 and the organic The solvent is prevented from adhering to the activated carbon fiber layer 2. Therefore, it is possible to suppress a decrease in the radioactive substance removal performance of the radioactive substance removal filter 1, and it is possible to extend the lifetime of the radioactive substance removal filter.

The activated carbon fiber layer 2 and the activated carbon particle layer 3 are preferably laminated in the thickness direction, and preferably have a pleated shape that is repeatedly folded and folded repeatedly. Since the activated carbon fiber layer 2 and the activated carbon particle layer 3 are laminated, the radioactive substance removal filter 1 can be downsized. In addition, since the activated carbon fiber layer 2 and the activated carbon particle layer 3 are pleated, the area in contact with the gas is increased, and the radioactive material in the gas can be efficiently removed.

The radioactive substance removal filter 1 according to the present invention can be used for the radioactive substance removal filter unit 11. As shown in FIG. 3, the radioactive substance removal filter unit 11 can be manufactured by housing the radioactive substance removal filter 1 in a frame 12 as an example of the embodiment. The material of the frame 12 is not particularly limited, and examples thereof include metals, synthetic resins, and wood. Among these, a metal is preferable. Since the frame body 12 is made of metal, the strength of the radioactive substance removal filter unit 11 can be increased.

In the method for removing a radioactive substance according to the present invention, a gas containing a radioactive substance such as gaseous iodine or an organic iodine compound is passed through the radioactive substance removal filter 1 of the present invention. Thereby, it becomes possible to remove radioactive substances from the gas. Even if an organic solvent is contained in the gas, the organic solvent is removed from the gas by the activated carbon particle layer 3 of the radioactive substance removal filter 1, so that the organic solvent does not easily adhere to the activated carbon fiber layer 2, and activated carbon. It can prevent that the radioactive substance removal performance of the fiber layer 2 falls.

This application claims the benefit of priority based on Japanese Patent Application No. 2016-243467 filed on Dec. 15, 2016. The entire contents of the specification of Japanese Patent Application No. 2016-243467 filed on December 15, 2016 are incorporated herein by reference.

Hereinafter, the effects of the present invention will be described more specifically by way of examples. The following examples are not intended to limit the present invention, and any design changes that fall within the spirit of the preceding and following descriptions are within the technical scope of the present invention.

(Production method of activated carbon fiber layer)
An activated carbon fiber layer was prepared by laminating a spunlace made of polypropylene (weight per unit area: 35 g / m ² ) on both sides of a sheet-like fibrous activated carbon or a laminate of a plurality of sheets and integrating them by needle punching. .

(Production method of activated carbon particle layer)
A mixed powder was prepared such that granular activated carbon and thermoplastic powder resin SK-PE20L (manufactured by Seishin Enterprise Co., Ltd.) had a granular activated carbon: powder resin = 10: 1. The prepared mixed powder was sprayed on a thermal bond nonwoven fabric (weighing 27 g / m ² ), and the same thermal bond nonwoven fabric was superimposed thereon, followed by heat treatment to produce an activated carbon particle layer.

(Measurement method of BET specific surface area and total pore volume)
About 100 mg of a sample was collected from each of the granular activated carbon and the fibrous activated carbon, vacuum-dried at 120 ° C. for 24 hours, and then weighed. Using an automatic specific surface area measuring device Gemini 2375 (manufactured by Micromeritics), the adsorption amount of nitrogen gas at the boiling point of liquid nitrogen (-195.8 ° C.) is within a relative pressure of 0.02 to 0.95. 40 points were measured while gradually increasing, and an adsorption isotherm of the sample was created. With the analysis software (GEMINI-PCW version 1.01) attached to the automatic specific surface area measuring device Gemini 2375, the surface area analysis range is set to 0.01 to 0.15 under the BET conditions, and the BET specific surface area [m ² / g]. Further, the total pore volume [cc / g] was determined from the data of the relative pressure 0.95.

(Measurement method of amine compound adhesion)
About 300 mg of a sample from granular activated carbon or fibrous activated carbon was collected and extracted with 10 mL of chloroform. The amine compound adhesion amount [mass%] was calculated by measuring and further dividing by the weight of the sample.

(Organic solvent load test)
The sample was set in a glass tube having an inner diameter of 44 mm, and air containing 25 ppm of 1,2,4-trimethylbenzene (boiling point 169 ° C.) at a temperature of 25 ° C. and humidity of 0% RH was continuously 270 at 6 L / min. Circulated for a minute.

(Measurement method of methyl iodide removal rate)
The sample was set in a glass tube having an inner diameter of φ25 mm, and air containing 10 ppm of methyl iodide and having a temperature of 25 ° C. and a humidity of 0% RH was continuously circulated at 5 L / min. Five minutes after the start of distribution, the gas at the inlet and outlet sides of the sample was collected, and the methyl iodide concentration was measured on a gas chromatograph with ECD (GC-2014, manufactured by Shimadzu Corporation), and the methyl iodide removal rate was determined from the ratio. [%] Was calculated.

Example 1
625 mg of triethylenediamine (manufactured by Tokyo Chemical Industry Co., Ltd.) was dissolved in 250 g of ion-exchanged water to prepare a triethylenediamine aqueous solution. Sheet of the fibrous activated carbon 6 g (BET specific surface area: 1460 m ² / g, total pore volume: 0.63cc / g, basis weight: 200 g / ^{m 2,} average fiber diameter: 13 .mu.m), and the aqueous solution previously prepared After the addition, the mixture was stirred at room temperature for 12 hours. Thereafter, the sheet-like fibrous activated carbon was separated by filtration and dried at 80 ° C. for 2 hours. As a result, a sheet-like amine compound-attached fibrous activated carbon having an amine compound adhesion amount of 10.3% by mass was obtained. Three sheets of the obtained sheet-like amine compound-attached fibrous activated carbon were laminated to produce an activated carbon fiber layer.
Coconut shell granular activated carbon with an amine compound adhesion of 0% by mass (below the detection limit) (BET specific surface area: 1350 m ² / g, total pore volume: 0.62 cc / g, particle diameter: 250 to 500 μm, average particle diameter: 320 μm ) Was used to prepare an activated carbon particle layer so that the granular activated carbon basis weight was 600 g / m ² .
The produced activated carbon particle layer was disposed on the upstream side, and the activated carbon fiber layer was disposed on the downstream side, and an organic solvent load test was performed. Then, the methyl iodide removal rate was measured using the sample after the organic solvent load test.

(Example 2)
An activated carbon fiber layer was produced in the same manner as in Example 1 except that the amount of triethylenediamine used was 1.88 g.
A triethylenediamine aqueous solution was prepared by dissolving 45 mg of triethylenediamine (manufactured by Tokyo Chemical Industry Co., Ltd.) in 8 g of ion-exchanged water. Further, 6 g of palm activated carbon activated carbon (BET specific surface area: 1350 m ² / g, total pore volume: 0.62 cc / g, particle diameter: 250 to 500 μm, average particle diameter: 320 μm) was mixed with the previously prepared aqueous solution. Then, it was dried at 80 ° C. for 2 hours. An amine compound-attached granular activated carbon having an amine compound adhesion amount of 0.7% by mass was obtained. The activated carbon particle layer was produced using the obtained amine compound adhesion granular activated carbon so that granular activated carbon basis weight might be 600 g / m < ² >.
The produced activated carbon particle layer was disposed on the upstream side, and the activated carbon fiber layer was disposed on the downstream side, and an organic solvent load test was performed. Then, the methyl iodide removal rate was measured using the sample after the organic solvent load test.

(Example 3)
The same operation as in Example 1 was conducted except that the amount of triethylenediamine used was 4.38 g. The amine compound adhesion amount was 14.8% by mass.

Example 4
The same procedure as in Example 1 was performed except that the activated carbon particle layer had a granular activated carbon basis weight of 300 g / m ² .

(Example 5)
The same procedure as in Example 3 was performed except that the activated carbon particle layer had a granular activated carbon basis weight of 300 g / m ² .

(Comparative Example 1)
An activated carbon fiber layer was produced in the same manner as in Example 3.
780 mg of triethylenediamine (manufactured by Tokyo Chemical Industry Co., Ltd.) was dissolved in 8 g of ion-exchanged water to prepare a triethylenediamine aqueous solution. Further, 6 g of palm activated carbon activated carbon (BET specific surface area: 1350 m ² / g, total pore volume: 0.62 cc / g, particle diameter: 250 to 500 μm, average particle diameter: 320 μm) was mixed with the previously prepared aqueous solution. Then, it was dried at 80 ° C. for 2 hours. An amine compound-attached granular activated carbon having an amine compound adhesion amount of 12.1% by mass was obtained. The activated carbon particle layer was produced using the obtained amine compound adhesion granular activated carbon so that granular activated carbon basis weight might be 300 g / m < ² >.
The produced activated carbon particle layer was disposed on the upstream side, and the activated carbon fiber layer was disposed on the downstream side, and an organic solvent load test was performed. Then, the methyl iodide removal rate was measured using the sample after the organic solvent load test.

(Comparative Example 2)
An activated carbon particle layer and an activated carbon fiber layer were prepared in the same manner as in Example 5, the activated carbon fiber layer was disposed on the upstream side, the activated carbon particle layer was disposed on the downstream side, and an organic solvent load test was performed. Then, the methyl iodide removal rate was measured using the sample after the organic solvent load test.

(Comparative Example 3)
An activated carbon particle layer similar to that in Example 4 is disposed on the upstream side, and the activated carbon particle layer is disposed on the downstream side in the same manner as in Comparative Example 1 except that the granular activated carbon basis weight is 600 g / m ^2. A load test was performed. Then, the methyl iodide removal rate was measured using the sample after the organic solvent load test.

As is apparent from Table 1, it can be seen that in Examples 1 to 5, the methyl iodide removal rate is high and the durability against high boiling point compounds is high. On the other hand, when the ratio of the amine compound adhesion amount of the activated carbon particle layer and the amine compound adhesion amount of the activated carbon fiber layer is greater than 0.1 (Comparative Example 1), the activated carbon fiber layer is disposed upstream. (Comparative Example 2) When the activated carbon fiber layer is not disposed on the downstream side (Comparative Example 3), it can be seen that all have low methyl iodide removal rate and low durability against high boiling point compounds.

When the amine compound is attached not only to the activated carbon fiber layer on the downstream side but also to the activated carbon particle layer on the upstream side, which is the sample of Comparative Example 1, the organic solvent in the gas can be removed only with the activated carbon particle layer. Instead, the organic solvent reaches the activated carbon fiber layer, and the organic solvent adheres to the activated carbon fiber layer. Therefore, the thing of the comparative example 1 compared with the thing of Example 5 which made the amine compound adhere only to the activated carbon fiber layer of the downstream, without attaching an amine compound to the activated carbon particle layer of the upstream, The removal effect of radioactive material is reduced. Therefore, it is preferable that the amine compound is not attached to the upstream layer, and the amine compound is attached only to the downstream layer.

In the case where the activated carbon fiber layer is disposed on the upstream side and the activated carbon particle layer is disposed on the downstream side, which is a sample of Comparative Example 2, the activated carbon fiber layer has better radioactive substance removal performance than the activated carbon particle layer. The organic solvent in the gas adheres, and the radioactive substance removal performance of the activated carbon fiber layer decreases. Therefore, the comparative example 2 is less effective in removing the radioactive substance than the example 5 in which the activated carbon particle layer is disposed on the upstream side and the activated carbon fiber layer is disposed on the downstream side. Yes. Therefore, it is preferable that the activated carbon particle layer is disposed on the upstream side and the activated carbon fiber layer is disposed on the downstream side.

In the case where the activated carbon fiber layer is not disposed on the downstream side and the activated carbon particle layer is disposed on both the upstream side and the downstream side, which is the sample of Comparative Example 3, the radioactive substance removal performance is superior to the activated carbon particle layer. Since the activated carbon fiber layer is not used, the radioactive substance removal effect is reduced. Therefore, it is preferable to use both the activated carbon particle layer and the activated carbon fiber layer instead of using only the activated carbon particle layer.

Further, in Comparative Example 3, the amine compound is attached to the downstream activated carbon particle layer, but compared to Examples 4 and 5 in which the amine compound is attached to the downstream activated carbon fiber layer, the radioactive compound is used. The substance removal effect is reduced. Therefore, it is preferable to attach the amine compound to the activated carbon fiber layer rather than attaching the amine compound to the activated carbon particle layer.

In addition, when the activated carbon fiber layer is disposed on both the upstream side and the downstream side, it is necessary to increase the basis weight of the activated carbon fiber layer in order to provide sufficient radioactive substance removal performance. When the basis weight of the activated carbon fiber layer is increased, the thickness increases, and the thickness of the radioactive substance removal filter also increases. As a result, there is a problem that the radioactive substance removing filter is enlarged and it is difficult to pleat the radioactive substance removing filter. Therefore, it is preferable to use both the activated carbon particle layer and the activated carbon fiber layer instead of using only the activated carbon fiber layer.

As described above, the radioactive substance removal filter of the present invention includes an activated carbon fiber layer on the downstream side and an activated carbon particle layer on the upstream side, and the activated carbon fiber layer has fibrous activated carbon to which an amine compound is attached, The ratio of the amount of amine compound attached to the activated carbon particle layer to the amount of amine compound attached to the activated carbon fiber layer (the amount of amine compound attached to the activated carbon particle layer / the amount of amine compound attached to the activated carbon fiber layer) is 0.1 or less (0 Including). By having such a configuration, even if an organic solvent, particularly a high boiling point compound having a boiling point of 120 ° C. or more is contained in the gas, it suppresses a decrease in the removal performance of radioactive substances such as radioactive iodine and organic iodine compounds. Can do.

1: Radioactive substance removal filter 2: Activated carbon fiber layer 3: Activated carbon particle layer 11: Radioactive substance removal filter unit 12: Frame

Claims (15)

Provided with an activated carbon fiber layer on the downstream side and an activated carbon particle layer on the upstream side,
The activated carbon fiber layer has fibrous activated carbon to which an amine compound is attached,
The ratio of the amount of amine compound attached to the activated carbon particle layer to the amount of amine compound attached to the activated carbon fiber layer (the amount of amine compound attached to the activated carbon particle layer / the amount of amine compound attached to the activated carbon fiber layer) is 0.1. A radioactive substance removing filter characterized in that it includes the following (including 0). The radioactive substance removing filter according to claim 1, wherein the amine compound is water-soluble. The radioactive substance removal filter according to claim 1 or 2, wherein the amine compound is triethylenediamine. The radioactive substance removal filter according to any one of claims 1 to 3, wherein the amount of the amine compound attached to the activated carbon fiber layer is 5 mass% or more and 20 mass% or less of the fibrous activated carbon. The radioactive substance removing filter according to any one of claims 1 to 4, wherein a basis weight of the fibrous activated carbon in the activated carbon fiber layer is 150 g / m ² or more and 900 g / m ² or less. The radioactive substance removal filter according to any one of claims 1 to 5, wherein a basis weight of the granular activated carbon in the activated carbon particle layer is 150 g / m ² or more and 900 g / m ² or less. The radioactive substance removal filter according to any one of claims 1 to 6, wherein the fibrous activated carbon has a BET specific surface area of 800 m ² / g or more. The radioactive substance removal filter according to any one of claims 1 to 7, wherein the granular activated carbon has a BET specific surface area of 800 m ² / g or more. The radioactive substance removal filter according to any one of claims 1 to 8, wherein the total pore volume of the fibrous activated carbon is 0.3 cc / g or more. The radioactive substance removal filter according to any one of claims 1 to 9, wherein a total pore volume of the granular activated carbon is 0.3 cc / g or more. The radioactive substance removal filter according to any one of claims 1 to 10, wherein an average fiber diameter of the fibrous activated carbon is 10 µm or more and 40 µm or less. The radioactive substance removal filter according to any one of claims 1 to 11, wherein an average particle diameter of the granular activated carbon is 200 µm or more and 700 µm or less. The radioactive substance removal filter according to any one of claims 1 to 12, wherein the activated carbon fiber layer and the activated carbon particle layer are laminated and have a pleated shape. A radioactive substance removal filter unit comprising the radioactive substance removal filter according to any one of claims 1 to 13. A method for removing a radioactive substance, comprising: passing a gas containing a radioactive substance through the radioactive substance removing filter according to any one of claims 1 to 13, and removing the radioactive substance from the gas.

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