JP6928928B2 - Radioactive material removal filter, radioactive material removal filter unit using it, and radioactive material removal method - Google Patents

Description

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

In facilities that handle 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 removing filter for removing gaseous iodine, a treatment method for collecting and removing gaseous iodine by passing air through an activated carbon sheet-shaped charcoal filter is known (for example, Patent Document). 1).

As a radioactive substance removing filter for removing an organic iodine compound as well as gaseous iodine, a pore having a pore volume of 3 to 30 nm and a pore volume of 0.15 cc / g or less and a pore diameter of 3 nm or less is used. A radioactive substance removal filter having a filter medium in which an amine is impregnated on a sheet made of activated carbon having a volume of 0.50 cc / g or more and a protective sheet is laminated on at least one of the sheets made of activated carbon is known (for example, See Patent Document 2).

Japanese Unexamined Patent Publication No. 2003-66191 Japanese Unexamined Patent Publication No. 2004-205490

However, facilities that handle radioactive materials such as these use liquid scintillation counters to measure radiation. In the liquid scintillation cocktail used for the liquid scintillation counter, an organic solvent having a boiling point of 120 ° C. or higher, such as 1,2,4-trimethylbenzene and linear dodecylbenzene, is used. Therefore, the exhaust gas of the facility contains a small amount of these gaseous organic solvents (VOCs) in addition to the gaseous radioactive substances. The organic solvent of the high boiling point compound adheres to the radioactive substance removing filters such as Patent Document 1 and Patent Document 2, and causes a decrease in the removal performance of the radioactive substance using these radioactive substance removing filters.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide radioactive iodine and organic substances even if the gas contains a gaseous organic solvent, particularly a high boiling point compound having a boiling point of 120 degrees or higher. It is an object of the present invention to provide a radioactive substance removing filter capable of suppressing deterioration of removal performance for a radioactive substance such as an iodine compound, a radioactive substance removing filter unit using the radioactive substance removing filter, and a method for removing the radioactive substance.

The radioactive substance removal filter of the present invention that has been able to solve the above problems is provided with 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 in the form of fibers to which an amine compound is attached. It has activated carbon, and the ratio of the amount of the amine compound attached to the activated carbon particle layer to the amount of the amine compound attached to the activated carbon fiber layer (the amount of the amine compound attached to the active carbon particle layer / the amount of the amine compound attached to the activated carbon fiber layer) is 0. It is characterized in that it is 1 or less (including 0).

Since the radioactive substance removal filter of the present invention adsorbs the organic solvent in the gas at the activated carbon particle layer on the upstream side, the activated carbon fiber layer on the downstream side deteriorates the removal performance of radioactive iodine and the 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 adhered 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 in the activated carbon fiber layer ^{is preferably 150 g / m 2} or more and 900 g / m ² or less.

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

In the radioactive substance removing filter of the present invention, the BET specific surface area of the fibrous activated carbon ^{is preferably 800 m 2} / g or more.

In the radioactive substance removing filter of the present invention, the BET specific surface area of the granular activated carbon ^{is preferably 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 removing filter of the present invention, the average particle size 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 also includes a radioactive substance removing filter unit characterized by having the radioactive substance removing filter and a method for removing radioactive substances.

The radioactive substance removing filter of the present invention is characterized by having an activated carbon fiber layer having fibrous activated carbon to which an amine compound is attached on the downstream side and an activated carbon particle layer having granular activated carbon 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, even if the gas contains an organic solvent, the radioactive substance removal filter removes radioactive substances such as radioactive iodine and organic iodine compounds. It is possible to suppress the deterioration of the performance, and the radioactive substance removing effect of the radioactive substance removing filter can be exhibited for a long period of time.

The schematic diagram of the radioactive substance removal filter in embodiment of this invention is shown. A schematic cross-sectional view of the radioactive substance removal filter according to the embodiment of the present invention after pleating is shown. The perspective view of the radioactive substance removal filter unit in embodiment of this invention is shown.

Hereinafter, the radioactive substance removing filter according to the present invention will be specifically described with reference to the drawings. It is also possible to make changes to the above, and all of them are included in the technical scope of the present invention.

The radioactive substance removal filter according to the present invention has 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 and is an activated carbon particle layer. The ratio of the adhering amount of the amine compound to the adhering amount of the amine compound in 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 has passed 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, with the upper side of FIGS. 1 and 2 being the upstream side and the lower side being the downstream side.

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

The activated carbon fiber layer 2 is obtained by laminating a non-woven fabric on both sides of a sheet-shaped 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 of the BET specific surface area of the fibrous activated carbon is this value, the effect of removing radioactive substances from 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 of the total pore volume of the fibrous activated carbon is this value, the effect of removing radioactive substances in the activated carbon fiber layer 2 is enhanced.

The average fiber diameter of the fibrous activated carbon is preferably 10 μm or more, more preferably 12 μm or more. When the lower limit of the average fiber diameter of the fibrous activated carbon is such a value, the air permeability 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 even more preferably 30 μm or less. When the upper limit 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 removal efficiency of radioactive substances is improved.

The fibrous activated carbon is observed with an electron microscope at a magnification of 500 times, and the fiber diameter is measured. Arithmetic mean of 100 arbitrary fiber diameters, 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-dimethylaminoethylmethacrylate, and the like. N, N-dimethylaminopropylamine, 3-aminopropyltrimethoxysilane, 1,5-diazabicycloundecene, polyethyleneimine, 1,5-diazabicyclo [4.3.0] nonen, 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 thereof include ethyl piperazine, hexamethylenetetramine, polyalkylpolyamine and the like. Among them, the amine compound used is preferably water-soluble, and more preferably 1,4-diazabicyclo [2,2,2] octane (triethylenediamine). By using the water-soluble amine compound, the production of the activated carbon fiber layer 2 becomes easy, and by using triethylenediamine, a high effect of removing radioactive substances 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, still more preferably 10% by mass or more of the fibrous activated carbon. When the lower limit of the amount of the amine compound adhered to the activated carbon fiber layer 2 is this value, the radioactive organic iodine compound can be sufficiently adsorbed. 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. .. Since the upper limit of the amount of the amine compound adhered to the activated carbon fiber layer 2 is this value, it is possible to suppress the cost while maintaining a sufficient effect of removing radioactive substances.

The method of adhering the amine compound to the activated carbon fiber layer 2 is a method of immersing a sheet-shaped fibrous activated carbon in a solution of the amine compound and drying it, a method of spraying the solution of the amine compound on the sheet-shaped fibrous activated carbon and drying it. Examples thereof include a method of immersing the fibrous activated carbon in a solution of an amine compound, drying it, and then forming it into a sheet. Above all, it is preferable to attach the amine compound to the activated carbon fiber layer 2 by a method of immersing a sheet-shaped fibrous activated carbon in a solution of the amine compound and drying it. By adhering the amine compound to the activated carbon fiber layer 2 in this way, the amine compound can be uniformly adhered to the fibrous activated carbon, and the effect of removing the radioactive substance from 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 of the basis weight of the fibrous activated carbon in the activated carbon fiber layer 2 is this value, the effect of removing radioactive substances from the activated carbon fiber layer 2 becomes sufficient. 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. Since the upper limit of the grain size 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. Granular activated carbon is granular activated carbon obtained by carbonizing coconut shells, sawdust, bamboo, etc., coal, pitch, etc., by performing an activation reaction by gas activation or chemical activation. Examples of the type of granular activated carbon include crushed charcoal, granular charcoal, and briquette, and any type can be preferably used. In addition to the granular activated carbon, it is possible to use the powdered activated carbon which is a powdered activated carbon, but it is preferable to use the granular activated carbon in order to reduce the pressure loss.

The activated carbon particle layer 3 is obtained by mixing granular activated carbon and a thermoplastic resin, sandwiching the mixture with a non-woven fabric, and performing 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 of the BET specific surface area of the granular activated carbon is this value, the effect of the activated carbon particle layer 3 on 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 of the total pore volume of the granular activated carbon is this value, the effect of removing the organic solvent in the activated carbon particle layer 3 is improved.

The average particle size of the granular activated carbon is preferably 200 μm or more, more preferably 250 μm or more. When the lower limit of the average particle size of the granular activated carbon is such a value, the air permeability of the activated carbon particle layer 3 can be enhanced. The average particle size of the granular activated carbon is preferably 700 μm or less, more preferably 625 μm or less, and even more preferably 550 μm or less. When the upper limit of the average particle size 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 with an optical microscope at a magnification of 35 times, and the particle size is measured. Arithmetic mean of 100 arbitrary particle sizes, 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 of the basis weight of the granular activated carbon in the activated carbon particle layer 3 is this value, it is possible to give the activated carbon particle layer 3 a sufficient organic solvent removing effect. 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 the amine compound attached to the active carbon particle layer 3 to the amount of the amine compound attached to the active carbon fiber layer 2 (the amount of the amine compound attached to the active carbon particle layer 3 / the amount of the amine compound attached to the active carbon fiber layer 2) is It is 0.1 or less, preferably 0.08 or less, and more preferably 0.06 or less. The ratio of the amount of the amine compound attached to the activated carbon particle layer 3 to the amount of the amine compound attached to the activated carbon fiber layer 2 is 0. When the ratio of the amine compound adhesion amount of the active carbon particle layer 3 to the amine compound adhesion amount of the active carbon fiber layer 2 is this value, the organic solvent in the gas is removed by the activated carbon particle layer 3 and is organic. The solvent is prevented from adhering to the activated carbon fiber layer 2. Therefore, it is possible to suppress the deterioration of the radioactive substance removing performance of the radioactive substance removing filter 1, and it is possible to extend the life of the radioactive substance removing filter.

The activated carbon fiber layer 2 and the activated carbon particle layer 3 are laminated in layers in the thickness direction, and preferably have a pleated shape in which mountain folds and valley folds are alternately repeated for bending. Since the activated carbon fiber layer 2 and the activated carbon particle layer 3 are laminated, the radioactive substance removal filter 1 can be miniaturized. Further, since the activated carbon fiber layer 2 and the activated carbon particle layer 3 have a pleated shape, the area in contact with the gas becomes large, and radioactive substances in the gas can be efficiently removed.

The radioactive substance removing filter 1 according to the present invention can be used in the radioactive substance removing filter unit 11. As an example of the embodiment, the radioactive substance removing filter unit 11 can be manufactured by housing the radioactive substance removing filter 1 in the frame body 12, as shown in FIG. The material of the frame body 12 is not particularly limited, and examples thereof include metal, synthetic resin, and wood. Above all, it is preferably metal. Since the frame body 12 is made of metal, the strength of the radioactive substance removing filter unit 11 can be increased.

In the method for removing radioactive substances 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 removing filter 1 of the present invention. This makes it possible to remove radioactive substances from the gas. Even if the gas contains an organic solvent, the active carbon particle layer 3 of the radioactive substance removing filter 1 removes the organic solvent from the gas, so that the organic solvent is less likely to adhere to the activated carbon fiber layer 2 and the activated carbon. It is possible to prevent the fiber layer 2 from deteriorating the radioactive substance removing performance.

Hereinafter, the effects of the present invention will be shown more specifically by way of examples. The following examples are not of a nature that limits the present invention, and any design modification according to the gist of the above and the following is included in the technical scope of the present invention.

(Method for producing activated carbon fiber layer)
A sheet-shaped fibrous activated carbon sheet or a plurality of sheets were laminated, and polypropylene spunlaces (meshing 35 g / m ² ) were laminated on both sides and integrated by needle punching to prepare an activated carbon fiber layer. ..

(Method for producing activated carbon particle layer)
A mixed powder of granular activated carbon and thermoplastic powder resin SK-PE20L (manufactured by Seishin Enterprise Co., Ltd.) was prepared so that the mass ratio of granular activated carbon: powder resin = 10: 1. The prepared mixed powder was sprayed on a thermal-bonded non-woven fabric (meetsuke 27 g / m ² ), and the same thermal-bonded non-woven fabric was further superposed on the thermal-bonded non-woven fabric, followed by heat treatment to prepare an activated carbon particle layer.

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

(Measuring method of amine compound adhesion amount)
Approximately 300 mg of a sample was taken from granular activated carbon or fibrous activated carbon, and the amine compound content of the solution extracted with 10 mL of chloroform was determined using GC / MS (7890A / 5975C, manufactured by Agilent Technologies). The amount of amine compound adhered [mass%] was calculated by measuring and further dividing it by the weight of the sample.

(Organic solvent load test)
The sample is set in a glass tube having an inner diameter of φ44 mm, and air containing 100 ppm of 1,2,4-trimethylbenzene (boiling point 169 ° C.) at a temperature of 25 ° C. and a humidity of 0% RH is continuously 270 at 6 L / min. It was 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, 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 on the inlet side and the outlet side of the sample was sampled, the methyl iodide concentration was measured with a gas chromatograph with ECD (GC-2014, manufactured by Shimadzu Corporation), and the methyl iodide removal rate was measured 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 an aqueous triethylenediamine 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 charging, the mixture was stirred at room temperature for 12 hours. Then, the sheet-shaped fibrous activated carbon was filtered off and dried under 80 ° C. conditions for 2 hours to obtain a sheet-shaped amine compound-adhered fibrous activated carbon having an amine compound adhering amount of 10.3% by mass. Three sheets of the obtained sheet-like amine compound-attached fibrous activated carbon were laminated to prepare an activated carbon fiber layer.
A palm-based granular activated carbon with an amine compound adhesion amount 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 grain was 600 g / m ^2.
The prepared activated carbon particle layer was arranged on the upstream side, and the activated carbon fiber layer was arranged on the downstream side, and an organic solvent load test was carried out. 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 prepared in the same manner as in Example 1 except that the amount of triethylenediamine used was 1.88 g.
45 mg of triethylenediamine (manufactured by Tokyo Chemical Industry Co., Ltd.) was dissolved in 8 g of ion-exchanged water to prepare an aqueous triethylenediamine solution. Further, 6 g of coconut shell-based granular 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) is mixed with the previously prepared aqueous solution. Then, it was dried under the condition of 80 ° C. for 2 hours. An amine compound-adhered granular activated carbon having an amine compound adhering amount of 0.7% by mass was obtained. Using the obtained amine compound-adhered granular activated carbon, an activated carbon particle layer was prepared so that the granular activated carbon basis weight was 600 g / m ^2.
The prepared activated carbon particle layer was arranged on the upstream side, and the activated carbon fiber layer was arranged on the downstream side, and an organic solvent load test was carried out. Then, the methyl iodide removal rate was measured using the sample after the organic solvent load test.

(Example 3)
The same procedure as in Example 1 was carried out except that the amount of triethylenediamine used was 4.38 g. The amount of the amine compound attached was 14.8% by mass.

(Example 4)
The same procedure as in Example 1 was carried out except that the granular activated carbon basis weight of the activated carbon particle layer was 300 g / m ^2.

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

(Comparative Example 1)
An activated carbon fiber layer was prepared 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 an aqueous triethylenediamine solution. Further, 6 g of coconut shell-based granular 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) is mixed with the previously prepared aqueous solution. Then, it was dried under the condition of 80 ° C. for 2 hours. An amine compound-adhered granular activated carbon having an amine compound adhering amount of 12.1% by mass was obtained. Using the obtained amine compound-adhered granular activated carbon, an activated carbon particle layer was prepared so that the granular activated carbon basis weight was 300 g / m ^2.
The prepared activated carbon particle layer was arranged on the upstream side, and the activated carbon fiber layer was arranged on the downstream side, and an organic solvent load test was carried out. 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 arranged on the upstream side, the activated carbon particle layer was arranged on the downstream side, and an organic solvent loading test was carried out. Then, the methyl iodide removal rate was measured using the sample after the organic solvent load test.

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

As is clear 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 adhering amount of the amine compound to the activated carbon fiber layer and the adhering amount of the amine compound to the activated carbon fiber layer is larger than 0.1 (Comparative Example 1), the case where the activated carbon fiber layer is arranged on the upstream side. In the case of (Comparative Example 2), when the activated carbon fiber layer is not arranged on the downstream side (Comparative Example 3), it can be seen that the methyl iodide removal rate is low and the durability against the high boiling point compound is low.

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 cannot be completely removed by the activated carbon particle layer alone. Instead, the organic solvent reaches the activated carbon fiber layer, and the organic solvent adheres to the activated carbon fiber layer. Therefore, the one of Comparative Example 1 was compared with the one of Example 5 in which the amine compound was not attached to the activated carbon particle layer on the upstream side and the amine compound was attached only to the activated carbon fiber layer on the downstream side. The effect of removing radioactive substances is reduced. Therefore, it is preferable not to attach the amine compound to the upstream layer, but to attach the amine compound only to the downstream layer.

When the activated carbon fiber layer is arranged on the upstream side and the activated carbon particle layer is arranged on the downstream side, which is the sample of Comparative Example 2, the activated carbon fiber layer having better radioactive substance removal performance than the activated carbon particle layer is obtained. , The organic solvent in the gas adheres, and the radioactive substance removal performance of the activated carbon fiber layer deteriorates. Therefore, in Comparative Example 2, the effect of removing radioactive substances is reduced as compared with that in Example 5 in which the activated carbon particle layer is arranged on the upstream side and the activated carbon fiber layer is arranged on the downstream side. There is. Therefore, it is preferable that the activated carbon particle layer is arranged on the upstream side and the activated carbon fiber layer is arranged on the downstream side.

When the activated carbon fiber layer is not arranged on the downstream side and the activated carbon particle layer is arranged 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 that of the activated carbon particle layer. Since the activated carbon fiber layer is not used, the effect of removing radioactive substances 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 was attached to the activated carbon particle layer on the downstream side, but it was more radioactive than in Examples 4 and 5 in which the amine compound was attached to the activated carbon fiber layer on the downstream side. The effect of removing substances is reduced. Therefore, it is preferable to attach the amine compound to the activated carbon fiber layer instead of attaching the amine compound to the activated carbon particle layer.

When the activated carbon fiber layer is arranged 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 have sufficient radioactive substance removal performance. Increasing the basis weight of the activated carbon fiber layer increases the thickness and also increases the thickness of the radioactive substance removal filter. As a result, there are problems that the radioactive substance removal filter becomes large and that pleating of the radioactive substance removal filter becomes difficult. 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 has 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 the amine compound attached to the active carbon particle layer to the amount of the amine compound attached to the active carbon fiber layer (the amount of the amine compound attached to the active carbon particle layer / the amount of the amine compound attached to the active carbon fiber layer) is 0.1 or less (0). Includes). With such a configuration, even if the gas contains an organic solvent, particularly a high boiling point compound having a boiling point of 120 degrees or higher, deterioration of the removal performance of radioactive substances such as radioactive iodine and organic iodine compounds can be suppressed. Can be done.

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

Claims (12)

An activated carbon fiber layer is provided on the downstream side and an activated carbon particle layer is provided on the upstream side.
The activated carbon fiber layer has a fibrous activated carbon to which an amine compound is attached, and has.
The ratio of the amount of the amine compound attached to the activated carbon particle layer to the amount of the amine compound attached to the activated carbon fiber layer (the amount of the amine compound attached to the active carbon particle layer / the amount of the amine compound attached to the activated carbon fiber layer) is 0.1. Below (including 0),
In the activated carbon particle layer, a mixture of granular activated carbon and a thermoplastic resin is arranged on a non-woven fabric.
All SANYO being further arranged nonwoven over the mixture,
The 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 BET specific surface area of the granular activated carbon is 800 m ² / g or more.
Total pore volume of the granular activated carbon, radioactive substances removing filter, characterized in der Rukoto least 0.3 cc / g. The radioactive substance removing filter according to claim 1, wherein the amine compound is water-soluble. The radioactive substance removing filter according to claim 1 or 2, wherein the amine compound is triethylenediamine. The radioactive substance removing filter according to any one of claims 1 to 3, wherein the amount of the amine compound adhered to the activated carbon fiber layer is 5% by mass or more and 20% by mass or less of the fibrous activated carbon. The radioactive substance removing filter according to any one of claims 1 to 4, wherein the fibrous activated carbon has a texture of 150 g / m ² or more and 900 g / m ^{2 or less in the activated carbon fiber layer.} The radioactive substance removing filter according to any one of claims 1 to 5 , wherein the fibrous activated carbon has a BET specific surface area of 800 m ² / g or more. The radioactive substance removing filter according to any one of claims 1 to 6 , wherein the total pore volume of the fibrous activated carbon is 0.3 cc / g or more. The radioactive substance removing filter according to any one of claims 1 to 7 , wherein the average fiber diameter of the fibrous activated carbon is 10 μm or more and 40 μm or less. The radioactive substance removing filter according to any one of claims 1 to 8 , wherein the average particle size of the granular activated carbon is 200 μm or more and 700 μm or less. The radioactive substance removing filter according to any one of claims 1 to 9 , wherein the activated carbon fiber layer and the activated carbon particle layer are laminated and have a pleated shape. A radioactive substance removing filter unit according to any one of claims 1 to 10. A method for removing a radioactive substance, which comprises passing a gas containing the radioactive substance through the radioactive substance removing filter according to any one of claims 1 to 10 to remove the radioactive substance from the gas.

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