JP2013181838A - Radioactive secondary waste treatment method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the volume of radioactive secondary waste including synthetic resin material carrying an absorbent used for decontamination and to secure safety from collection of the radioactive secondary waste to intermediate storage.SOLUTION: A decontamination filter 1 is nonwoven cloth having coarse polyethylene fiber containing iron ferrocyanide, and a used decontamination filter 1 is put in a radioactive shielding bag 3 using polypropylene (PP) for base material to be collected. Collected radioactive secondary waste is compressed by a compression packing machine and bound with a band made of polypropylene (PP), and stored in a radioactive shielding metal box in a disposal facility 10. Next, the prescribed number of radioactive shielding metal boxes are stored in a radioactive shielding container, and the container is transported to an intermediate preservation place, and layered in many steps for preservation outdoors.

Description

  The present invention relates to a radioactive secondary waste processing method capable of safely performing a process until the volume of an adsorbent used for decontamination of radioactively contaminated water or air is reduced.

  In Patent Document 1, ion exchange resins and hollow fiber membranes are used to purify waste liquids from nuclear power generation facilities, nuclear fuel reprocessing plants, and radioactive isotope handling facilities. Pointing out the fact that the membrane has become a large amount of secondary waste, in order to reduce the volume of this secondary waste, we have proposed a multi-function filtration membrane with both ion adsorption function and particulate removal function .

  The accident at the Fukushima nuclear power plant that occurred in conjunction with the 2011 off the Pacific coast of Tohoku earthquake and tsunami continued to release a large amount of radioactive material into the environment. The radioactive substances released into the environment include cesium 134 and cesium 137. The half-life of cesium 134 is about 2 years and the half-life of cesium 137 is about 30 years. Environmental pollution is a serious social problem.

  Radioactive materials that continue to diffuse widely due to accidents at the Fukushima nuclear power plant are scattered in a wide variety of locations, so effective decontamination techniques have been proposed for each decontamination target. The “coagulation sedimentation method” proposed by Areva in France was adopted to purify highly-contaminated water in the Fukushima nuclear power plant. This “aggregation precipitation method” is a decontamination method in which an adsorbent containing nickel ferrocyanide is introduced into contaminated water to adsorb radioactive substances, and the adsorbent that has captured the radioactive substances is precipitated with the flocculant and removed. It is.

  It is known that zeolite is effective for adsorption of radioactive substances, and mesh filters containing zeolite are commercially available. This filter is used by being attached to an air purifier, a dehumidifier, a ventilation fan or the like. A mesh filter containing activated carbon has also been developed, and this mesh filter containing activated carbon has been applied to masks and the like.

  Patent Document 2 teaches an effective adsorbent for each radionuclide in addition to activated carbon. Specifically, as an adsorbent for cobalt (Co), inorganic ion exchangers (layered phosphate compounds) manufactured by Toa Gosei Co., Ltd., chelate resins manufactured by Unitika Co., Ltd., and oxine-impregnated coal manufactured by Johoku Chemical Industry Co., Ltd. are representative examples. As an adsorbent for cesium (Cs), a ferrocyanide compound-added hydrous titanium oxide adsorbent manufactured by Asahi Engineering Co., Ltd., a ferrocyanide compound adsorbed carbon manufactured by Johoku Chemical Industry Co., Ltd., an inorganic ion exchanger manufactured by Teika Co. Phosphate compounds) are illustrated as representative examples.

  After the accident at the Fukushima nuclear power plant, the National Institute of Advanced Industrial Science and Technology, in collaboration with Kanto Chemical Co., Ltd., has a fine powder (particle size: about 10 nanometers (nm)) Prussian blue (ferrocyanide) : Various types of cesium adsorbing materials using bitumen) are published. Tokyo Institute of Technology is conducting a public experiment on water purification using ferrocyanide.

JP 2001-239138 A Japanese Patent Laid-Open No. 11-183691

  The accident at the Fukushima nuclear power generation facility has not yet converged, and as described above, since radioactive contamination covers a wide area, immediate and long-term thorough radioactive decontamination is required. From this, it is expected that the development of the right adsorbent for the right material will continue.

  However, even if the radioactive substance is captured by an appropriate adsorbent, disposal of the adsorbent and the material supporting the adsorbent, that is, secondary waste becomes a problem. Although Patent Document 1 proposes volume reduction as described above, the invention of Patent Document 1 is a proposal related to limited and controlled contamination of a nuclear power generation facility or the like. The radioactive contamination associated with the accident at the Fukushima nuclear power plant is so large that it cannot be compared with other scales, and the disposal of radioactive secondary waste is an urgent issue. It is an urgent issue.

  The object of the present invention is to reduce the volume of radioactive secondary waste containing the synthetic resin material carrying the adsorbent used for decontamination and to ensure safety from collection of radioactive secondary waste to intermediate storage. An object of the present invention is to provide a method for treating radioactive secondary waste that can be secured.

According to the present invention, the above technical problem is
A decontamination adsorbent comprising a synthetic resin as a base material and containing an adsorbent that adsorbs radioactive substances;
A radioactivity shielding bag or container containing a synthetic resin for containing a used decontamination adsorbent as a base material and containing a substance that shields radioactivity;
Radioactivity shielding metal box with radioactivity shielding function;
Prepare a radiation shielding container with a radiation shielding function and capable of logistics,
Decontamination with the decontamination adsorbent,
Sealing the used decontamination adsorbent in the radiation shielding bag or container; and
Transporting the sealed radioactive shielding bag to a processing facility;
In the treatment facility, a radioactive secondary waste volume reducing step for reducing the volume in a sealed state without taking out the decontamination adsorbent from the sealed radioactive shielding bag or container; and
Placing the reduced radioactive secondary waste in the radioactive shielding metal box;
Storing the radioactive shielding metal box containing the radioactive secondary waste in the radioactive shielding container;
This is achieved by providing a method for treating radioactive secondary waste, comprising the step of transporting the radioactive shielding container storing the radioactive shielding metal box to an intermediate storage site.

  That is, since the used decontamination adsorbent is carried in a radioactive shielding bag or container, safety in the recovery process including this conveyance can be ensured. In the treatment facility, radioactive secondary waste is reduced in volume and placed in a radioactive shielding metal box in a reduced volume, and a plurality of radioactive shielding metal boxes are stored in a radioactive shielding container. The radioactive secondary waste inside is double shielded. Thereby, the radiation dose emitted from the container can be suppressed to a low level, and can be stored in the middle for a long time outdoors.

  Further objects and advantages of the present invention will become apparent from the following detailed description of embodiments of the present invention.

It is a figure for demonstrating the process of a series of Examples until it reduces the volume of the air-conditioning filter used for radioactive decontamination, and carries out intermediate storage.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 shows a decontamination filter 1 as a decontamination adsorbent. The decontamination filter 1 has a thin sheet-like form made from a non-woven fabric with relatively coarse synthetic fibers. The size of the decontamination filter 1 is set for an air conditioner (for an air conditioner). The sheet-like decontamination filter 1 is preferably attached with an accumulated radioactivity measurement sheet 2 and an IC chip for traceability. As is known, the accumulated radioactivity measurement sheet 2 has a characteristic that the indicator changes color according to the accumulated amount of radioactivity and does not return to its original state once the color changes. In the IC chip, the track from the manufacture to the collection of the filter 1, such as the number of the filter 1, the date of manufacture, the filter distribution date and time, and the filter collection date and time, is recorded. Thereby, it is possible to confirm that all the filters 1 to be shipped have been reliably collected.

  As raw materials for synthetic fibers of the decontamination filter 1, in addition to polypropylene resin (PP resin) and polyethylene resin (PE resin), polyethylene terephthalate resin (PET resin), acrylonitrile-butadiene-styrene copolymer synthetic resin (ABS resin), polyamide Adopting a general-purpose resin such as a resin (PA resin) is effective in reducing the cost. As will be described later, the melting temperature is used to melt and reduce the volume of the decontamination filter 1 that has adsorbed a radioactive substance. Is desirably a relatively low resin, and it is preferable to select a polyethylene (PE) resin from this viewpoint.

  The decontamination filter 1 contains fine powder of iron ferrocyanide (particle size: about 10 nanometers (nm)). As a method of incorporating ferric ferrocyanide into the decontamination filter 1, it is preferable to knead the ferric ferrocyanide fine powder into the resin material when the synthetic fiber of the decontamination filter 1 is made.

  The decontamination filter 1 is supplied to the user together with the radiation shielding bag 3. The radioactive shielding bag 3 may be made by using, for example, a sheet made of shielding material powder and an organic polymer material (synthetic resin material) as disclosed in JP 2007-85865 A (P2007-85865A). You may make using the sheet | seat which consists of a polyolefin resin or a thermoplastic resin or a thermoplastic elastomer which barium sulfate added disclosed by Kaihei 11-133184 and Unexamined-Japanese-Patent No. 2007-212304.

  When the decontamination filter 1 that is a radioactive adsorbent is incorporated into an air conditioner, an air purifier, a ventilation fan, etc. to perform decontamination in the air, typically, the decontamination filter 1 after decontamination is collected. Polypropylene (PP) bags, polyethylene (PE) bags and paper bags to which radiation shielding materials such as barium sulfate and barium oxide are added or applied may be adopted, but preferably polypropylene (PP) kneaded with barium oxide. A radioactivity shielding bag 3 created using a resin sheet is employed.

  It is convenient for the user to be provided as a decontamination filter set in which the decontamination filter 1 and the radiation shielding bag 3 are combined. By assembling the decontamination filter 1 to the air conditioner, the user can adsorb the radioactive substance (typically cesium) in the air to the decontamination filter 1 by the circulation of indoor air accompanying the operation of the air conditioner.

  After the decontamination filter 1 is set in the air conditioner, when a predetermined period (for example, 2 months) has elapsed or when it is time to replace the indicator of the indicator of the accumulated radioactivity measurement sheet 2, the decontamination filter 1 from the air conditioner The filter for setting a new decontamination filter 1 is removed, and the used decontamination filter 1 that has been removed is accommodated in the radiation shielding bag 3 and sealed. Instead of this radioactive shielding bag 3, barite, barium oxide, barium sulfate, cerium oxide, tungsten oxide, gadolinium oxide, deteriorated uranium oxide, leaded glass powder and fiber, zeolite, clinoptilolite, celestite, etc. You may have the form of the airtight container shape | molded by selecting one type or multiple types from the material provided with the radiation shielding function, and knead | mixing with the synthetic resin of a base material.

  In the embodiment, as described above, polypropylene (PP) resin is adopted as the synthetic resin constituting the base material of the radiation shielding bag 3, but in order to reduce leakage of radioactivity even slightly, high density polypropylene ( High density PP) resin has been selected. Instead of attaching the IC chip for traceability described above to the filter 1, an IC chip may be attached to the radiation shielding bag 3.

  Replacing and collecting the used decontamination filter 1 from the air conditioner is left to the processing contractor. The processor can safely transport the collected decontamination filter 1 to the treatment facility 10 in the radioactive shielding bag 3 in a sealed state. Moreover, the radioactive diffusion to the surrounding environment in the process of conveying to the processing facility 10 can be prevented. In the treatment facility 10, the decontamination filter 1 contained in the collected radiation shielding bag 1 is reduced in volume by the compression packing machine (baler) 5 without taking out from the radiation shielding bag 3, and the decontamination filter 1 and the volume reduced. The mass of the radiation shielding bag 3 is banded using a binding band.

  This banded mass is stored in a dedicated radioactive shielding metal box in two ways. The first method is to store the banded mass as it is in a radioactive shielding metal box. The second method is a method in which a banded mass is heated and melted, put in a radioactive shielding metal box in a molten state, and solidified in the radioactive shielding metal box. In this second method, banding may be omitted from the process of the compression packing machine prior to that.

  By adopting the first and second methods, not only decontamination and the material carrying the adsorbent used for this, that is, the filter 1 but also the radiation shielding bag 3 is reduced in volume together with the radiation. It can be changed into secondary waste, and the radioactivity can be kept in a state of being shielded by the radioactivity shielding metal box.

  Regarding the second method, that is, melting the filter 1 and the radiation shielding bag 3 together, it is known that polyethylene (PE) resin, which is the base material of the filter 1, generates gas when heated. In addition, the amount of gas generated by the polyethylene (PE) resin can be reduced by melting the radiation shielding bag 3 and the binding band using polypropylene (PP) resin. Therefore, it is possible to reduce the deterioration of the working environment in the facility that implements the second method.

  The dedicated radioactivity shielding metal box is a hexagonal sealed metal box with a rectangular cross section made of stainless steel plate or steel plate, and a lead plate with an appropriate thickness having a certain radioactivity shielding effect is provided on the inner surface. It is attached. In order to reduce the cost, it is preferable to use a hexagonal sealed box made of a steel plate, which is used in many cases for transportation of 100cm x 100cm x 60cm automobile parts overseas. Examples of the thickness of the lead plate attached to the inner surface of the sealed box include 0.3 to 3 mm. A tungsten sheet may be used instead of the lead plate. A radiation shielding mat in which a lead plate is coated with a resin such as polyethylene is commercially available. However, the radiation shielding mat may be attached to the inner surface of the above-described sealed box for transporting automobile parts to overseas.

  Radioactive shielding metal boxes containing radioactive waste are housed in a dedicated radioactive shielding container. Prepare a dedicated radioactive shielding container for land transportation or sea transportation (preferably a sea transportation container with a relatively strong structure), and a lead plate is preferably attached to the inner surface of the container. Is preferred. Examples of the thickness of the lead plate attached to the inner surface of the container include 0.3 to 3 mm. A tungsten sheet may be used instead of the lead plate. The radiation shielding mat described above may be attached to the inner surface of a container for land or sea transportation.

  Adopting containers that are used in large quantities in logistics is suitable for reducing costs. By storing the reduced volume of radioactive secondary waste in a double container of a radioactive shielding metal box and a radioactive shielding container, the radiation dose emitted from the radioactive shielding container can be suppressed to a low level. It is possible to prevent the rainwater from entering the radioactivity shielding metal box and its outflow for a long time. Therefore, the radioactive shielding container can be intermediately stored outdoors without being buried in the soil. In the intermediate storage using this radioactive shielding container, the ground transportation container or the marine transportation container as a base has a structure and strength that can be stacked one above the other. It can be stored in a stacked state of three, four, five, and six stages. In addition, since the ground-based or sea-based containers that are used as the base for radioactive shielding containers are made for transportation, radiation shielding is performed using existing forklifts and trucks as soon as the final disposal site is determined. Containers can be transported to the final disposal site.

  As described above, a series of processing methods related to the filter 1 for space decontamination installed in the air conditioner has been described. However, this also applies to a filter applied to a device that circulates indoor air such as a dehumidifier, a circulator, and a fan. The invention can be applied. It can also be used as a screen door in the form of a synthetic resin mesh. Moreover, if the decontamination filter 1 is accommodated in a mask and used, it can be decontaminated at the mouth. Further, the filter 1 may be used to decontaminate radioactively contaminated water.

  Further, the present invention is not limited to air and water decontamination using the decontamination filter 1. A decontamination adsorbent formed by kneading iron ferrocyanide into a synthetic resin such as polypropylene (PP) resin and molding it into a porous or solid arbitrary shape such as beads, particles, and threads, for example, polyethylene (PE) You may make it decontaminate by putting in the water-permeable bag like a resin-made mesh bag, and putting this in a radioactive contamination water. Further, in the same manner, it is possible to decontaminate the soil by putting radioactively contaminated soil into a water tank and stirring the soil.

  The decontamination adsorbent used was collected in a radioactive shielding bag 3 made using a sheet made of polypropylene (PP) resin kneaded with barium oxide together with a polyethylene mesh bag, and Reduce the volume of radioactive secondary waste in the same manner as described with reference to 1 and store it in a radioactive shielding metal box, and store this radioactive shielding metal box in a radioactive shielding container for intermediate storage. It may be. To reduce the volume of porous or solid decontamination adsorbents such as beads, the used decontamination adsorbents are collected in the radioactivity shielding bag 3 or a radioactivity shielding container made of the same material. In the same manner as described above with reference to FIG. 1, it is preferable to heat and melt this as it is to fill the radioactive shielding metal box and solidify in the radioactive shielding metal box. .

  For the traceability of this decontamination adsorbent, the IC chip is attached to the radioactivity shielding bag 3 or the radioactivity shielding container in the same manner as the filter 1 described above, so that the total recovery of the decontamination adsorbent can be confirmed. It is preferable to do this.

  Although ferric ferrocyanide was exemplified as the adsorbent contained in the decontamination adsorbent, the radioactive adsorbent is not limited to ferric ferrocyanide, and zeolite, activated carbon and ferrocyan which are conventionally known as radioactive adsorbents It may be a chemical compound-impregnated carbon, nickel ferrocyanide, or an adsorbent that will be developed in the future. Of course, a plurality of these adsorbents may be mixed and used. Moreover, although the nano-level fine powder was employ | adopted as the particle size of the adsorption agent in the decontamination adsorbent 1, the particle size should just determine an optimal value by experiment according to the decontamination object.

1 Decontamination filter (decontamination adsorbent)
3 Radioactive shielding bag 10 Treatment facility

Claims (8)

A decontamination adsorbent comprising a synthetic resin as a base material and containing an adsorbent that adsorbs radioactive substances;
A radioactivity shielding bag or container containing a synthetic resin for containing a used decontamination adsorbent as a base material and containing a substance that shields radioactivity;
Radioactivity shielding metal box with radioactivity shielding function;
Prepare a radiation shielding container with a radiation shielding function and capable of logistics,
Decontamination with the decontamination adsorbent,
Sealing the used decontamination adsorbent in the radiation shielding bag or container; and
Transporting the sealed radioactive shielding bag to a processing facility;
In the treatment facility, a radioactive secondary waste volume reducing step for reducing the volume in a sealed state without taking out the decontamination adsorbent from the sealed radioactive shielding bag or container; and
Placing the reduced radioactive secondary waste in the radioactive shielding metal box;
Storing the radioactive shielding metal box containing the radioactive secondary waste in the radioactive shielding container;
And a step of transporting the radioactive shielding container storing the radioactive shielding metal box to an intermediate storage site.   The radioactive secondary waste processing method according to claim 1, wherein the volume reduction step includes a step of heating and melting the decontamination adsorbent in a state where the decontamination adsorbent is put in the radioactive shielding bag or container. The decontamination adsorbent is a filter;
The radioactive secondary waste processing method according to claim 1, wherein the volume reduction step includes a step of compressing the filter in a packing compressor while the filter is in the radioactive shielding bag.   The method for treating radioactive secondary waste according to claim 3, wherein the filter is made by kneading iron ferrocyanide powder in polyethylene (PE) resin.   The radioactive secondary waste processing method according to claim 4, wherein the radioactive shielding bag is made of a sheet of polypropylene (PP) resin containing a radioactive shielding material.   The radioactive secondary waste processing method according to claim 5, wherein the radioactive secondary waste compressed by the packing compressor is bound by a band made of polypropylene (PP) resin.   The radioactive secondary waste according to claim 6, wherein the volume reduction step includes a step of heating and melting the radioactive secondary waste compressed by the packing compressor and bound by a band made of polypropylene (PP) resin. Processing method.   The radioactive secondary waste processing method according to claim 7, wherein the radioactive secondary waste melted by heating is filled in the radioactive shielding metal box and solidified in the radioactive shielding metal box.

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