JPWO2016104553A1 - Filter vent filler and filter vent device - Google Patents

Abstract

Provided are a filter vent filler and a filter vent device that can cope with severe accidents capable of adsorbing radioactive iodine more effectively than before. A filter vent filler 1 obtained by granulating X-type zeolite, wherein a part of the ion exchange site of the X-type zeolite is replaced with silver, and the remainder is selected from the group consisting of lead, nickel, and copper Of the ion exchange sites substituted with at least one kind of metal, the composition ratio (a / b) of the ion exchange site (a) substituted with silver and the ion exchange site (b) substituted with a metal other than silver ) Is set to 60/40 to 80/20. The silver content is set to 17 to 26% by weight.

Description

  The present invention relates to a filter vent filler formed by granulating X-type zeolite and a filter vent apparatus for treating radioactive iodine.

  Conventionally, a filter for removing radioactive iodine has been installed in a nuclear facility such as a nuclear power plant. The vapor containing radioactive iodine generated in the nuclear facility is passed through the filter to adsorb and remove the radioactive iodine, and then discharged outside the nuclear facility. Since this process is very important, research and development have been conducted on the adsorption effect of radioactive iodine by a filter, and several radioactive iodine adsorbents using zeolite have been developed as such a filter. As one of them, there is a radioactive iodine adsorbent in which silver is supported on zeolite having a molar ratio of silica to alumina of 15 or more (see, for example, Patent Document 1). According to Patent Document 1, the radioactive iodine removal efficiency is improved while the amount of silver supported is small.

JP-A-60-225638

  The adsorbent disclosed in Patent Document 1 utilizes the crystal structure of zeolite, and selectively adsorbs radioactive iodine using the molecular sieve effect due to the pore size. This adsorbent is considered to have a certain effect on the adsorption of radioactive iodine. However, it is required to develop a higher performance radioactive iodine adsorbent so that radioactive iodine is not leaked to the outside without fail.

  In addition, if an abnormal situation (severe accident) such as a nuclear accident occurs at a nuclear facility, a large amount of radioactive material containing radioactive iodine will be scattered over a wide area, so a nuclear accident must be prevented in advance. If an accident occurs, it must be dealt with promptly. Therefore, a plan is underway to install a filter vent in the reactor building that reduces the internal pressure of the reactor when an abnormal situation occurs in the reactor. However, the radioactive iodine adsorbent described in the above-mentioned Patent Document 1 is not supposed to cope with an abnormal situation that requires a filter vent or the like. In addition, the nuclear accident is considered to be caused by hydrogen generated in the nuclear reactor. However, there is no description in Patent Document 1 for dealing with this hydrogen. Further research and development is needed in the future for radioactive iodine adsorbents that can be used in the event of an abnormal situation.

  The present invention has been made in view of the above problems, and provides a filter vent filler and a filter vent device that can cope with severe accidents capable of adsorbing radioactive iodine more effectively than before. Objective.

The characteristic configuration of the filter vent filler according to the present invention for solving the above problems is as follows.
A filter vent filler formed by granulating X-type zeolite,
Part of the ion exchange site of the X-type zeolite is replaced with silver, and the remainder is replaced with at least one metal selected from the group consisting of lead, nickel, and copper,
Among the ion exchange sites, the composition ratio (a / b) between the ion exchange site (a) substituted with silver and the ion exchange site (b) substituted with a metal other than silver is 60 / 40-80. Is set to / 20.

The filter vent filler of the present invention uses a granulated X-type zeolite as a base. There are various types of zeolite, and their crystal structures are different, but each crystal structure has a characteristic of having a uniform pore diameter. Due to this characteristic pore size, zeolite is used for molecular sieves and selective adsorption of molecules.
In the filter vent filler according to the present invention, among zeolites, X-type zeolite having a relatively large pore diameter is used, and a part of the ion exchange site of the X-type zeolite is replaced with silver, and the remainder is lead, nickel. And at least one metal selected from the group consisting of copper (such a zeolite is referred to herein as "AgMX zeolite"). Furthermore, as a configuration for this AgMX zeolite to effectively exhibit the ability to adsorb radioactive iodine, among the ion exchange sites of the X-type zeolite, an ion exchange site (a) substituted with silver and a metal other than silver It was also found that the composition ratio (a / b) with the ion exchange site (b) exchanged in step (b) must be set to 60/40 to 80/20. Here, the said structural ratio is corresponded to the ratio (atomic ratio) of the number of the silver atoms contained in AgMX zeolite, and the number of metal atoms other than a silver atom. In the event of an abnormal situation such as a nuclear accident (severe accident), it is important to deal with it immediately after the accident so that radioactive iodine does not scatter around. Therefore, if a filter vent filler composed of AgMX zeolite with the composition ratio (atomic ratio) set in the above range is used, radioactive iodine is surely adsorbed and the radioactive iodine is scattered outside the reactor facility. Can be prevented. Note that lead, nickel, and copper are less expensive materials than silver. For this reason, AgMX zeolite obtained by substituting a part of the ion exchange site of X-type zeolite with at least one metal selected from the group consisting of lead, nickel, and copper is advantageous from the viewpoint of cost. is there.

In the filter vent filler according to the present invention,
It is preferable that a part of the ion exchange site of the X-type zeolite is replaced with silver and the rest is replaced with lead.

  Since the filter vent filler of this configuration includes an ion exchange site substituted with silver and an ion exchange site substituted with lead, it is a low cost and excellent filter for adsorbing radioactive iodine. It can be used as a filler for venting.

In the filter vent filler according to the present invention,
The silver content is preferably set to 17 to 26% by weight.

  Since the content of silver is set to 17 to 26% by weight, the filter vent filler of this configuration can be a filter vent filler excellent in the adsorption effect of radioactive iodine.

The characteristic configuration of the filter vent device according to the present invention for solving the above-described problems is
A filter vent device for continuously processing radioactive iodine,
A silver-containing filler in which almost all of the ion exchange sites of the X-type zeolite are substituted with silver is disposed in front of any one of the above-mentioned fillers for filter vents.

Since the filter vent apparatus is installed outside the nuclear reactor, the AgMX zeolite in the filter vent apparatus is usually in a normal temperature state. Here, when a severe accident occurs and high-temperature steam containing radioactive iodine and hydrogen flows into the filter vent device, the steam is cooled on the surface of the AgMX zeolite, and moisture condensation occurs. As a result, the hydrogen concentration and the oxygen concentration are relatively high in the filter vent device, and the risk of hydrogen explosion increases.
Therefore, in the filter vent apparatus according to the present invention, almost all of the ion exchange sites of the X-type zeolite are replaced with silver in the front stage of the filter vent filler composed of AgMX zeolite (such zeolite is described in this specification). In the description, it is referred to as “AgX zeolite”.) A silver-containing filler is arranged. In this way, if a two-stage configuration of AgX zeolite and AgMX zeolite is used, when high-temperature steam containing hydrogen flows into the filter vent device, most of the steam is condensed in the former stage of AgX zeolite and moisture is removed. In the latter stage AgMX zeolite, water condensation hardly occurs, and a relative increase in hydrogen concentration or oxygen concentration can be avoided. In addition, since the AgX zeolite in the previous stage can adsorb not only radioactive iodine but also hydrogen well, an increase in relative hydrogen concentration is suppressed. This reduces the risk of hydrogen explosion. Further, the gas passing through the latter AgMX zeolite has already been reduced in hydrogen concentration. Therefore, if it is a filter vent apparatus of this structure, hydrogen and radioactive iodine can be reduced effectively from the initial stage of severe accident. Moreover, even if the processing capacity of the former stage AgX zeolite declines after a predetermined time has elapsed, the latter stage AgMX zeolite can adsorb radioactive iodine even in the presence of hydrogen, so that it can cope with severe accidents for a long time. It becomes possible. In this way, if AgX zeolite and AgMX zeolite are installed in two stages in the filter vent device, an increase in the hydrogen concentration in the filter vent device can be suppressed, and radioactive iodine can be reliably scattered in the surrounding environment. It can prevent and improve safety more.

FIG. 1 is a schematic configuration diagram of a boiling water reactor including a filter vent device according to the first embodiment. FIG. 2 is a schematic configuration diagram of a boiling water reactor including a filter vent device according to the second embodiment. FIG. 3 is a graph showing changes in temperature when a gas containing hydrogen is allowed to flow through AgMX zeolite according to the filter vent filler of Example 1. FIG. 4 is a graph showing a state of temperature change when a gas containing hydrogen is passed through AgMX zeolite related to the filter vent filler of Example 2. FIG. 5 is a graph showing changes in temperature when a gas containing hydrogen is allowed to flow through AgMX zeolite according to the filter vent filler of Example 3. FIG. 6 is a graph showing a change in temperature when a gas containing hydrogen is passed through the silver-lead zeolite according to the filter vent filler of Comparative Example 1.

  Hereinafter, the embodiment regarding the filler for filter vents of this invention is described with reference to FIGS. However, the present invention is not intended to be limited to the configuration described below.

  As mentioned above, when a severe accident occurs in a nuclear reactor facility, radioactive iodine is scattered in the surrounding environment and the risk of hydrogen explosion is high. Therefore, in preparation for a severe accident, a plan is underway to install a filter vent device in the reactor building that reduces the internal pressure of the reactor. The inventors of the present invention can install a zeolite obtained by replacing the ion exchange site of the X-type zeolite with silver or a metal other than silver (lead, nickel, copper) as a filter vent filler in this filter vent apparatus. It was thought that iodine scattering and hydrogen explosion could be reliably prevented.

<AgMX zeolite>
First, the X-type zeolite serving as a base for the filter vent filler of the present invention will be described. Zeolite is a kind of silicate, and the basic unit of the structure is tetrahedral (SiO ₄ ) ^4- and (AlO ₄ ) ^5- , and these basic units are connected one after another three-dimensionally to form a crystal structure. Form. Various crystal structures are formed depending on the form of connection of the basic units, and each formed crystal structure has a unique uniform pore diameter. Since it has this uniform pore size, the zeolite has characteristics such as molecular sieve, adsorption, and ion exchange ability. The filter vent filler of the present invention is based on X-type zeolite, which is a kind of zeolite, and in particular, 13X-type zeolite can be suitably used. 13X type zeolite is a zeolite widely used industrially, and its composition is Na ₈₆ [(AlO ₂ ) ₈₆ (SiO ₂ ) ₁₀₆ ] · 276H ₂ O. By replacing a part of the sodium site, which is an ion exchange site of the 13X type zeolite, with silver and replacing the remaining part with at least one metal selected from the group consisting of lead, nickel, and copper, preferably with lead, The filter vent filler of the present invention is prepared. Such a filter vent filler is referred to herein as "AgMX zeolite".

  AgMX zeolite has an excellent ability to adsorb radioactive iodine, and in the present invention, this property is used to prevent the radioactive iodine from being scattered outside the reactor facility. As described above, AgMX zeolite is at least one metal selected from the group consisting of lead, nickel, and copper, preferably lead, in which part of the ion exchange site of 13X zeolite is replaced with silver, and the remainder is preferably lead. Since it is substituted and lead, nickel, and copper are cheaper than silver, it is advantageous in terms of cost to use AgMX zeolite as a filter vent filler.

  AgMX zeolite is a constituent ratio (a / b) of ion exchange sites (a) substituted with silver and ion exchange sites (b) exchanged with a metal other than silver, among the ion exchange sites of 13X type zeolite. Is prepared in the range of 60/40 to 80/20, preferably 65/35 to 75/25. Here, the said structural ratio is corresponded to the ratio (atomic ratio) of the number of the silver atoms contained in AgMX zeolite, and the number of metal atoms other than a silver atom. When the composition ratio (a / b) is smaller than 60/40, the ion exchange sites substituted with silver are insufficient, so that the adsorption effect of radioactive iodine is insufficient. On the other hand, when the composition ratio (a / b) is greater than 80/20, the proportion of silver in the AgMX zeolite increases, and thus the reaction with hydrogen becomes remarkable. As a result, the AgMX zeolite is likely to be overheated by the reaction heat, which may reduce the safety. In addition, since silver is an expensive material, it will become disadvantageous in terms of cost if the silver content is too high. Therefore, if the ion exchange site of 13X zeolite is replaced with silver and metals other than silver (lead, nickel, copper) so as to be in the above range, radioactive iodine is stabilized while preventing overheating of AgMX zeolite. Thus, an adsorbable filter vent filler can be obtained. In particular, a material obtained by substituting the ion exchange site of 13X zeolite with silver and lead can be used as a filter vent filler having an excellent effect of adsorbing radioactive iodine at a low cost.

  Incidentally, the filter vent filler (AgMX zeolite) prepared as described above has a silver content of 17 to 26% by weight. When the silver content is set within this range, the function of the ion exchange site by silver contained in the filter vent filler and the function of the ion exchange site by metals other than silver (lead, nickel, copper) are balanced. Even when it is exhibited effectively and severe accidents occur, it is possible to reliably avoid scattering of radioactive iodine while maintaining safety.

  As the filler for the filter vent, one obtained by molding AgMX zeolite into an appropriate shape, for example, a granular type or a pellet type, is preferably used. In the case of the granular type, the particle size is adjusted to 4 × 100 mesh (JIS K 1474-4-6), preferably 10 × 20 mesh (JIS K 1474-4-6). Here, the “mesh” representing the particle size will be described. For example, “10 × 20 mesh” means that the particles pass through the 10 mesh sieve but do not pass through the 20 mesh sieve, that is, the particle size is 10 to 20 mesh. Means that. The hardness of the particles is adjusted to 20% or more (JIS K 1474-4-7). Further, the water content of the particles is adjusted to 15% by weight or less, preferably 12% by weight or less as the water content when the drying loss is performed at 150 ° C. for 3 hours.

  In the case of the pellet type, the pellet length is adjusted to 1 cm or less, preferably 0.8 cm or less. The pellet diameter is adjusted to 3 mm or less, preferably 2 mm or less. The pellet type hardness and water content can be adjusted in the same range as the granular type. If the filler for filter vents adjusted in this way is used, the above-mentioned excellent radioactive iodine adsorption ability can be exhibited more effectively.

  By the way, since the filler for filter vents is exposed to harsh environments (high temperature, high pressure, high humidity), a certain level of strength (shape retention) is required. Therefore, the filter vent filler according to the present invention has a wear degree of 10% or less (ASTM D-4058), preferably 5% or less (ASTM D-4058), more preferably 3% or less (ASTM D-4058). It is adjusted to become. Thereby, even if it puts on severe conditions, such as a filter vent, the filler for filter vents can maintain the shape, and can continue exhibiting high radioactive iodine adsorption ability.

<AgX zeolite>
In the filter vent apparatus of the present invention, AgX zeolite in which almost all of the sodium sites in the X-type zeolite are ion-exchanged with silver is disposed in the preceding stage of the AgMX zeolite, as will be described in the following embodiments. As the X-type zeolite serving as the base of the AgX zeolite, the 13X-type zeolite is preferably used in the same manner as the AgMX zeolite. The 13X zeolite ion-exchanged with silver has a smaller pore size than the original 13X zeolite. Specifically, the pore size (about 0.4 nm) of 13X zeolite having sodium sites before being ion-exchanged with silver is too large to capture hydrogen molecules (molecular size: about 0.29 nm). However, when the sodium site is ion-exchanged with silver, an optimum pore diameter (about 0.29 nm) is obtained in which hydrogen molecules are tightly accommodated. As a result, the 13X zeolite ion-exchanged with silver can adsorb not only radioactive iodine but also hydrogen molecules with high efficiency and efficiency.

<Filter vent device>
[First embodiment]
The AgMX zeolite prepared as described above and the filter vent device of the present invention using the AgX zeolite will be described. FIG. 1 is a schematic configuration diagram of a boiling water reactor 100 including a filter vent device 50 according to the first embodiment of the present invention. As shown in FIG. 1, the boiling water reactor 100 includes a filter vent device 50, a reactor building 3, a reactor containment vessel 4, and a reactor pressure vessel 5. The filter vent device 50 includes a filter vent filler 1 and a filter vent portion 2. The filter vent part 2 of the present embodiment employs a scrubber type wet vent system. The filter vent device 50 is installed outside the reactor building 3 in case an accident occurs in the reactor and the reactor containment vessel 4 is damaged. When the internal pressure of the reactor containment vessel 4 increases, the steam in the reactor containment vessel 4 is sent to the filter vent device 50 through the pipe 6 as shown by the solid line arrow in FIG. 1. In the filter vent device 50, radioactive iodine in the vapor is collected by the filter vent portion 2, and then discharged from the exhaust pipe through the filter vent filler 1 to the outside.

  As shown in FIG. 1, the filter vent filler 1 is housed in a case 7 and connected to the subsequent stage of the filter vent portion 2. The case 7 is preferably made of a material having heat resistance and corrosion resistance because water vapor and gas generated from the reactor containment vessel 4 flow therethrough. Examples of the material of the case 7 include stainless steel and titanium alloy, and aluminum alloy or the like can also be used. The case 7 is provided with a plurality of minute holes so that steam and gas can flow inside. Filling the case 7 with the filter vent filler 1 makes it easy to handle the filter vent filler 1. Here, since the nuclear facility requires the utmost attention to safety, it is desirable that the human work be performed as easily and in a short time as possible. In this respect, in this embodiment, since the case 7 has a simple configuration in which the filter vent filler 1 is filled, when the filter vent filler 1 is replaced, it is simply removed from the case 7 and replaced with a new one. It can be done with simple work. Therefore, the burden on the worker can be reduced, and safety can be ensured.

  By the way, when a severe accident occurs, not only radioactive iodine but also a large amount of hydrogen is generated from the reactor facility, and these are included in the steam discharged from the reactor containment vessel 4. If hydrogen remains in the nuclear reactor facility, there is a risk of hydrogen explosion, so it is necessary to perform hydrogen treatment together with radioactive iodine treatment. Since AgMX zeolite can adsorb radioactive iodine even in the presence of hydrogen, the filter vent filler 1 made of AgMX zeolite is filled in the case 7 and installed in the subsequent stage of the filter vent portion 2. When the filter vent device 50 is configured, it is considered that radioactive iodine is successively adsorbed by the AgMX zeolite and the radioactive iodine in the vapor is removed. However, since the filter vent part 2 is installed outside the reactor building 3, the AgMX zeolite (the filter vent filler 1) in the case 7 arranged downstream of the filter vent part 2 is usually at room temperature. It is in the state of. In this state, when high-temperature steam containing hydrogen flows into the filter vent device 50, when the steam enters the case 7, it is cooled on the surface of the filter vent filler 1 and moisture condensation occurs. Thereby, in the filter vent apparatus 50, hydrogen concentration and oxygen concentration become relatively high, and the danger of hydrogen explosion increases. For this reason, when the filter vent filler 1 is applied alone to the filter vent device 50, the safety may be lowered depending on the situation, particularly in the initial stage of severe accident.

  Therefore, the present invention has come up with an optimal filter vent device configuration for reliably removing not only radioactive iodine but also highly explosive hydrogen. As such a configuration, in the present embodiment, as shown in FIG. 1, substantially all of the ion exchange sites of the 13X zeolite are replaced with silver in the front stage of the filter vent filler 1 made of the AgMX zeolite of the present invention. The silver-containing filler 8 made of AgX zeolite prepared in this manner was arranged. Thus, if the silver-containing filler 8 (AgX zeolite) and the filter vent filler 1 (AgMX zeolite) are configured in two stages in the case 7, high-temperature steam containing hydrogen is generated in the filter vent device 50. Even if it flows into the case 7, most of the vapor is condensed in the front-stage silver-containing filler 8 and the water is removed, so that the water-condensation hardly occurs in the rear-stage filter vent filler 1, and the relative hydrogen concentration And an increase in oxygen concentration can be avoided. And since the silver containing filler 8 of the front | former stage can adsorb | suck not only radioactive iodine but hydrogen well, the raise of a relative hydrogen concentration is suppressed. This reduces the risk of hydrogen explosion. In addition, the gas passing through the latter filter vent filler 1 has already been reduced in hydrogen concentration. Therefore, if it is the filter vent apparatus 50 of this embodiment, hydrogen and radioactive iodine can be reduced effectively from the initial stage of severe accident. Moreover, even if the processing capacity of the former silver-containing filler 8 is lowered after a predetermined time has elapsed, the latter filter vent filler 1 can adsorb radioactive iodine even in the presence of hydrogen. This makes it possible to deal with severe accidents. Thus, in the filter vent apparatus 50, the filter vent part 2, the silver-containing filler 8, and the filter vent filler 1 are continuously arranged to share the respective functions, thereby increasing hydrogen and radioactive iodine. It becomes possible to adsorb efficiently and effectively. As a result, an increase in the hydrogen concentration in the filter vent device 50 can be suppressed, and radioactive iodine can be reliably prevented from being scattered in the surrounding environment, thereby improving safety.

[Second Embodiment]
FIG. 2 is a schematic configuration diagram of a boiling water reactor 100 including a filter vent device 50 according to the second embodiment of the present invention. In the first embodiment described above, in the filter vent device 50, the case 7 in which the filter vent filler 1 and the silver-containing filler 8 are stored is not directly adjacent to the reactor containment vessel 4, that is, the filter vent portion 2. Arranged downstream. On the other hand, in 2nd embodiment, as shown in FIG. 2, in the filter vent apparatus 50, the case 7 which accommodates the silver containing filler 8 and the filler 1 for filter vents adjoins the reactor containment vessel 4 It was made to install in. At this time, the steam discharged from the reactor containment vessel 4 contains hydrogen in addition to radioactive iodine, and the steam is sent to the filter vent device 50 through the pipe 6 as shown by the solid line arrow in FIG. In the second embodiment, the steam flows through the silver-containing filler 8 in the case 7 before the processing by the filter vent portion 2, and then flows through the filter vent filler 1. When the filter vent device 50 is configured in this manner, the adsorption of radioactive iodine and the treatment of hydrogen are performed before the vapor is sent to the filter vent portion 2, and thus the silver-containing filler 8 and the filter vent filler 1 are accommodated. The gas coming out of the case 7 has a reduced load, and can be processed smoothly by the filter vent portion 2.

[Another embodiment]
The first to second embodiments described above are all embodiments relating to a boiling water reactor, but the filter vent filler 1 of the present invention can also be applied to a pressurized water reactor. As with the boiling water reactor, the filter vent filler 1 and the silver-containing filler 8 are accommodated in the case 7 and connected to the subsequent stage of the filter vent portion 2 as a countermeasure when the nuclear reactor is damaged by a severe accident. The filter vent device 50 arranged as described above can be installed in a pressurized water reactor. In the filter vent device 50, the case 7 containing the silver-containing filler 8 and the filter vent filler 1 is placed in the pressurized water reactor. It can also be installed at a position adjacent to the reactor containment vessel 4 (not shown). Furthermore, the filter vent filler 1 of the present invention is combined with not only a wet vent system in which the filter vent portion 2 described in each of the above embodiments is a scrubber system, but also, for example, a metal fiber filter or a sand filter. It is also applicable to the Dora event system.

  In order to confirm the performance of the filter vent filler of the present invention, in the filter vent filler, among the ion exchange sites of the X-type zeolite, the ion exchange site (a) substituted with silver, and other than silver What set appropriately the composition ratio (a / b) with the ion exchange site (b) substituted with the metal (Examples 1-3), and the ion exchange site (a) substituted with silver other than silver A sample (Comparative Example 1) which was set excessively with respect to the ion exchange site (b) substituted with the above metal was prepared, and the temperature change was measured when a gas containing hydrogen was passed through each.

[Example 1]
By preparing a nitrate mixed aqueous solution having a silver concentration of 63.2 g / L and a lead concentration of 42.2 g / L, an appropriate amount of 13X zeolite was added to the mixed aqueous solution, and the mixture was maintained at room temperature and stirred for about 1 day. Ion exchange treatment was performed. The 13X zeolite after the ion exchange treatment was filtered off, washed with pure water, and dried to obtain AgMX zeolite. After this AgMX zeolite is heated and dissolved in a mixed solution of hydrofluoric acid and nitric acid, the contents of silver and lead are analyzed with an ICP emission spectroscopic analyzer (ICP emission spectroscopic analyzer iCAP-6200Duo manufactured by Thermo Fisher Scientific Co., Ltd.). As a result, the silver content (dry weight) was 23.6% by weight, and the lead content was 15.8% by weight. The ratio (atomic ratio) of silver and lead constituting the ion exchange site of 13X zeolite was 74/26.

[Example 2]
By preparing a nitrate mixed aqueous solution with a silver concentration of 52.6 g / L and a lead concentration of 52.6 g / L, an appropriate amount of 13X zeolite was added to the mixed aqueous solution, and the mixture was maintained at room temperature and stirred for about 1 day. Ion exchange treatment was performed. The 13X zeolite after the ion exchange treatment was filtered off, washed with pure water, and dried to obtain AgMX zeolite. This AgMX zeolite was heated and dissolved in a mixed solution of hydrofluoric acid and nitric acid, and then analyzed for the contents of silver and lead with an ICP emission spectroscopic analyzer. The silver content (dry weight) was 19.7% by weight, lead The content of was 19.3% by weight. The ratio of silver and lead constituting the ion exchange site of 13X type zeolite was 66/34.

[Example 3]
By preparing a nitrate mixed aqueous solution having a silver concentration of 63.8 g / L and a copper concentration of 42.1 g / L, an appropriate amount of 13X zeolite was added to the mixed aqueous solution, and the mixture was maintained at room temperature and stirred for about 1 day. Ion exchange treatment was performed. The 13X zeolite after the ion exchange treatment was filtered off, washed with pure water, and dried to obtain AgMX zeolite. This AgMX zeolite was heated and dissolved in a mixed solution of hydrofluoric acid and nitric acid, and then analyzed for the contents of silver and copper with an ICP emission spectroscopic analyzer. The silver content (dry weight) was 25.4% by weight, copper The content of was 4.7% by weight. The ratio of silver and copper constituting the ion exchange site of 13X type zeolite was 76/24.

[Comparative Example 1]
By preparing a nitrate mixed aqueous solution having a silver concentration of 78.9 g / L and a lead concentration of 26.3 g / L, and adding an appropriate amount of 13X type zeolite to the mixed aqueous solution, and maintaining it at room temperature, stirring for about 1 day, Ion exchange treatment was performed. The 13X zeolite after the ion exchange treatment was filtered off, washed with pure water, and dried to obtain a silver-lead zeolite. This silver-lead zeolite was heated and dissolved in a mixed solution of hydrofluoric acid and nitric acid, and then the silver and lead contents were analyzed with an ICP emission spectroscopic analyzer. The silver content (dry weight) was 28.2% by weight. The lead content was 10.0% by weight. The ratio of silver and lead constituting the ion exchange site of 13X type zeolite was 84/16.

[Temperature change measurement test]
Subsequently, the temperature change when the gas containing hydrogen was passed through the AgMX zeolite prepared in Examples 1 to 3 and the silver-lead zeolite prepared in Comparative Example 1 was measured. The test conditions are as follows.

[Examples 1-2]
With respect to the AgMX zeolite of Examples 1 and 2 heated to about 150 ° C., (A) only dry air is allowed to flow for 10 minutes from the start of flow, and (B) 10 minutes to 40 minutes after the start of flow. The dry gas, water vapor, and hydrogen mixed gas were allowed to flow through until (C), and only dry air was allowed to flow from 40 minutes to 50 minutes after starting the flow. FIG. 3 is a graph showing changes in temperature when a gas containing hydrogen is passed through the AgMX zeolite of Example 1. FIG. 4 is a graph showing changes in temperature when a gas containing hydrogen is passed through the AgMX zeolite of Example 2.

[Example 3]
For the AgMX zeolite of Example 3 heated to about 150 ° C., (A) Only the dry air was allowed to flow for 10 minutes from the start of flow, and (B) from 10 minutes to 58 minutes after the start of flow. During the period, a mixed gas of dry air, water vapor, and hydrogen was allowed to flow, and (C) only dry air was allowed to flow from 58 minutes to 70 minutes after the start of the flow. FIG. 5 is a graph showing changes in temperature when a gas containing hydrogen is passed through the AgMX zeolite of Example 3.

[Comparative Example 1]
For the silver-lead zeolite of Comparative Example 1 heated to about 150 ° C., only dry air is allowed to flow for 10 minutes after the start of flow (A), and (B) 10 minutes to 40 minutes after the start of flow. The dry gas, water vapor, and hydrogen mixed gas were allowed to flow through until (C), and only dry air was allowed to flow from 40 minutes to 50 minutes after starting the flow. FIG. 6 is a graph showing a change in temperature when a gas containing hydrogen is passed through the silver-lead zeolite of Comparative Example 1.

  As shown in FIG. 3, the AgMX zeolite related to the filter vent filler in Example 1 was maintained at about 150 ° C. during the period (A) in which only dry air was passed. During the period of (B), a mixed gas (by volume percentage, including dry air (27.0%), water vapor (68.0%), and hydrogen (5.0%)) was passed. The contact time of the mixed gas with respect to AgMX zeolite at this time was set to 0.20 seconds. Then, the temperature of the AgMX zeolite gradually increased within about 10 to 25 minutes from the start of the test. It can be presumed that this temperature rise is caused by the heat of adsorption generated when the silver zeolite part of AgMX zeolite adsorbs hydrogen or the heat of reaction due to some reaction between hydrogen and oxygen. However, after that, the temperature gradually decreased, and in the period (C), the temperature decreased to about 150 ° C. at the start of flow.

  As shown in FIG. 4, the AgMX zeolite according to the filter vent filler of Example 2 was maintained at about 150 ° C. during the period (A) in which only dry air was passed. During the period of (B), a mixed gas (containing dry air (44.0%), water vapor (50.0%), and hydrogen (6.0%) in volume percentage) was passed. The contact time of the mixed gas with respect to AgMX zeolite at this time was set to 0.34 seconds. Then, the temperature rose immediately after 10 minutes from the start of the test. Similar to the AgMX zeolite of Example 1 (FIG. 3), the heat of adsorption generated when the silver zeolite part adsorbs hydrogen in the AgMX zeolite of Example 2 and some reaction between hydrogen and oxygen. It can be inferred that this is due to the generation of reaction heat. However, the degree of the temperature increase was slight, and thereafter, the increased temperature was maintained, and even during the period (C), the temperature became around 150 ° C. at the start of flow without any temperature change.

  As shown in FIG. 5, the AgMX zeolite related to the filter vent filler in Example 3 was maintained at about 150 ° C. during the period (A) in which only dry air was passed. A mixed gas (containing dry air (89.3%), water vapor (8.2%), and hydrogen (2.5%) as a percentage by volume) was allowed to flow during the period of (B). The contact time of the mixed gas with respect to AgMX zeolite at this time was set to 0.29 seconds. Then, although the temperature gradually increased after 15 minutes from the start of the test, it gradually decreased to around 150 ° C. at the start of flow. Thereafter, when 30 minutes, 50 minutes, and 55 minutes passed after the start of flow, a temperature increase was observed, but immediately returned to about 150 ° C. at the start of flow. This is similar to the AgMX zeolite of Examples 1 and 2 (FIGS. 3 to 4), and also in the AgMX zeolite of Example 3, the adsorption heat generated when the silver zeolite part adsorbs hydrogen, and hydrogen and oxygen. It can be inferred that this is because heat of reaction due to some reaction occurs. Even during the period (C), the temperature was about 150 ° C. at the start of the flow without any temperature change.

  As shown in FIG. 6, the silver-lead zeolite according to the filter vent filler of Comparative Example 1 was maintained at about 150 ° C. during the period (A) in which only dry air was passed. During the period (B), a mixed gas (by volume percentage, including dry air (40.0%), water vapor (55.0%), and hydrogen (5.0%)) was passed. The contact time of the mixed gas with the silver-lead zeolite at this time was set to 0.31 seconds. Then, the temperature rose rapidly after 10 minutes from the start of the test. And in the period of (C), temperature fell rapidly. Such a rapid temperature change is caused by the fact that, in the silver-lead zeolite of Comparative Example 1, the silver zeolite part adsorbs hydrogen one after another and heat of adsorption is generated continuously. It is presumed that reaction heat is generated by the reaction.

  Thus, among the ion exchange sites of the X-type zeolite, the composition ratio (a / b) of the ion exchange site (a) substituted with silver and the ion exchange site (b) substituted with a metal other than silver. When the gas containing hydrogen was allowed to flow through the AgMX zeolites of Examples 1 to 3 in which the gas was appropriately set, no significant temperature change was observed in the AgMX zeolite. From this, it can be judged that the AgMX zeolites of Examples 1 to 3 have low heat of adsorption generated during hydrogen adsorption and low heat of reaction due to the reaction between hydrogen and oxygen, that is, low hydrogen adsorption capacity. On the other hand, the silver-lead zeolite of Comparative Example 1 in which the ion exchange site (a) substituted with silver is excessively set with respect to the ion exchange site (b) substituted with a metal other than silver is hydrogen or the like. When flowing through, the temperature increased rapidly, and after stopping the hydrogen flow, the temperature decreased rapidly. From this, it can be judged that the silver-lead zeolite of Comparative Example 1 has a large heat generated by hydrogen adsorption, that is, has a large hydrogen adsorption capacity.

  From the above test results, in the case of AgMX zeolite according to the present invention, since the temperature change when the gas containing hydrogen is passed is slight, there is a concern that the AgMX zeolite is overheated and the safety is lowered. It is not considered. By the way, when the radioactive iodine adsorption test was performed on the AgMX zeolites of Examples 1 to 3 separately from this test, all of them showed a high adsorption rate of 97% or more. For this reason, when the filler for filter vents containing AgMX zeolite of the present invention is arranged in the filter vent device together with the silver-containing filler containing AgX zeolite, most of the hydrogen and radioactive iodine are adsorbed by the silver-containing filler in the previous stage. Thereafter, a trace amount of radioactive iodine that has not been adsorbed in the former stage can be reliably adsorbed by the latter-stage filter vent filler. Thus, with the filter vent device of the present invention, it is possible to suppress an increase in the hydrogen concentration in the filter vent device while reliably preventing radioactive iodine from being scattered to the surrounding environment, thereby further improving safety. It becomes possible.

  The filter vent filler and filter vent apparatus of the present invention are used in nuclear facilities such as nuclear power plants, but the safety of facilities (housing, stores, schools, etc.) existing around the nuclear facilities. It is also possible to use for the purpose of protecting. It can also be used in ships equipped with nuclear reactors, research facilities, factories, and the like.

DESCRIPTION OF SYMBOLS 1 Filter vent filler 2 Filter vent part 3 Reactor building 4 Reactor containment vessel 5 Reactor pressure vessel 6 Piping 7 Case 8 Silver containing filler 50 Filter vent apparatus 100 Boiling water reactor

Claims (4)

A filter vent filler formed by granulating X-type zeolite,
Part of the ion exchange site of the X-type zeolite is replaced with silver, and the remainder is replaced with at least one metal selected from the group consisting of lead, nickel, and copper,
Among the ion exchange sites, the composition ratio (a / b) between the ion exchange site (a) substituted with silver and the ion exchange site (b) substituted with a metal other than silver is 60 / 40-80. Filter vent filler set to / 20.   The filter vent filler according to claim 1, wherein a part of the ion exchange site of the X-type zeolite is substituted with silver and the remainder is substituted with lead.   The filler for filter vents according to claim 1 or 2, wherein the silver content is set to 17 to 26% by weight. A filter vent device for continuously processing radioactive iodine,
A filter vent device in which a silver-containing filler in which substantially all of the ion exchange sites of the X-type zeolite are substituted with silver is disposed in the front stage of the filter vent filler according to any one of claims 1 to 3. .

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