JP2015045562A - Decontamination method of radioactive contaminated soil, etc. - Google Patents

Abstract

PROBLEM TO BE SOLVED: To decontaminate soil, etc., contaminated with a radioactive material (cesium) by biology means.SOLUTION: The decontamination method of a radioactive contaminated soil, etc., comprises: adding an aqueous solution containing a microorganism group for promoting fermentation decomposition to wastes derived from deforestation trees including a bark of 50% or more to perform primary crushing; adding and mixing an organic fertilizer to chips obtained by the primary crushing to perform crushing again; filling the secondary crushing object in a bag formed by a material poor in water permeability and gas permeability; mixing and agitating a base member manufactured by fermenting and aging the secondary crushing object for an appropriate period of time and an object to be decontaminated, such as radioactive contaminated soil at an appropriate ratio; mixing an appropriate amount of a fermentation accelerator therewith; and maturing the resultant mixture in the state that ventilation is limited.

Description

  The present invention relates to a decontamination method for radioactively contaminated soil and the like in which radioactive substances are contained by using microorganisms in soil or forest contaminated with radioactive cesium to reduce radiation.

  Radioactive materials are widely diffused due to accidents at nuclear power plants, penetrate into the soil from the surface of the diffused soil, and are absorbed by trees together with moisture in the soil.

  As a means for decontaminating these radioactive substances, particularly radioactive cesium, a method of decontaminating them by incorporating them into microorganisms (radioactive bacteria) has been proposed. For example, Patent Document 1 (Japanese Patent Laid-Open No. 2013-68556) discloses that cells are electrically adsorbed to a specific strain, collected together with the cells remaining alive, and discarded after the collection. Has been.

  In Patent Document 2 (Japanese Patent Laid-Open No. 2013-130574), a decontaminating agent containing a photosynthetic bacterium is dispersed in a contaminated area, the photosynthetic bacterium takes a radioactive substance into the body, and the radiation is sucked as growth energy. Means for reducing the amount are disclosed.

  It is also known that about 1/10 of the bacteria present in the soil have the ability to concentrate cesium. These bacteria are concentrated by the same mechanism as the potassium concentration mechanism (incorporation into cells) (Non-patent Document 1: National Institute for Environmental Studies, Vol. 15, No. 1, 1996, Noriko Tomioka, “Environmental Pollutants by Microorganisms” Concentration "). Furthermore, it is widely known that the actinomycetes Rhodococcus erythropolis takes in the radioactive substance cesium 137.

JP2013-68556A. JP2013-130574A.

National Institute for Environmental Studies, 1996 Volume 15 No.1 by Noriko Tomioka “Enrichment of Environmental Pollutants by Microorganisms”

  It is widely known that various microorganisms take in radioactive substances (radiocesium) into cells, but if the microorganisms take in many radioactive substances, they are killed by the radiation of the substances, and eventually Radioactive material will return. For this reason, as shown in Patent Document 1, it is necessary to recover the bacteria in a living state. As the recovery means, it is described that water containing the cells is recovered, or that the cells are immobilized on a porous carrier coated with iron, and recovered with a magnet.

  However, even if radioactive substances in the environment are taken into predetermined cells, the recovery of the viable bacteria is complicated, and the collected radioactive substances still require a predetermined containment process.

  Therefore, the present invention finds a phenomenon in which, when a predetermined fermentation treatment base member is used, a radiation substance is taken into a microorganism and radiation is blocked (contained) even after it is assumed that the microorganism has been killed. Proposed a new decontamination method for radioactively contaminated soil.

  In the decontamination method for radioactively contaminated soil and the like according to the present invention, an aqueous solution containing a group of microorganisms that promote fermentation decomposition is added to waste derived from a felled tree containing 50% or more of bark, and primary pulverization is performed. A base member manufactured by adding organic fertilizer to the chip obtained by primary pulverization, pulverizing it again, filling the secondary pulverized product in a bag formed of a material having poor water permeability and air permeability, and fermenting and aging as appropriate. And an object to be decontaminated such as radioactively contaminated soil at a suitable ratio, and a suitable amount of a fermentation accelerator is mixed and ripened in a state in which aeration is restricted. .

  It is known that radioactive substances are taken in from a group of microorganisms in the natural world (in the soil), and it is difficult to identify the exact microorganisms. However, in the verification test, it has been confirmed that the external radiation amount of γ rays has been halved. .

  The decontamination principle can be estimated as follows. The base material is wood-based bark compost, which is a radio-resistant bacterium (such as Deinococcus radiodurance, Rhodococcus erythropolis, etc.) and other various effective microorganisms, organic glass components, and aluminum components contained in trees When the base member and the object to be treated are mixed and ripened, the radioactive bacterium takes up radioactive cesium into the cells in the same manner as the uptake of potassium.

  On the other hand, the organic glass component is polyacrylamide converted into polyacrylamide, and the replaceable aluminum accumulated in the tree is converted into soluble aluminum by touching the air by making it into crushing chips etc. when producing the base member. To do. Radioactive cesium is electrically captured by the mediation of Al, and the radioactive bacterium (which is molten by fermentation heat) is taken up by the radioactive resistant bacterium, and the water-soluble resin polyacrylamide coats the radioactive resistant bacterium, Even if the Bacillus bacteria are attracted to the Al film and sulfuric acid is released from the spore bag provided outside the body to form the polyacrylamide film, the radioactive bacterium that has taken in the radioactive cesium is killed. Is coated to reduce the emission of gamma rays.

  The present invention is as described above, and it is possible to decontaminate soil contaminated with radioactive substances (contaminated soil, contaminated livestock excrement, contaminated trees) by the action of microorganisms. As a soil improvement material for agricultural land, it can be recycled and can provide a decontamination method that does not require re-fixation after decontamination.

Table 1 shows the temperature course of the processing object in the demonstration test data of the present invention. Measurement values of the contaminated soil: Table 2. Table 3 shows measured values of the contaminated cow manure compost. Table 4 shows measured values of the contaminated wooden raw chips. It is a graph which shows the change of the radiation dose of the process target object, the lower part of each graph shows an actual measurement value, and the upper part shows a dry matter conversion value. Addition table of supplements for promoting fermentation of the microorganism.

  The verification test of the present invention was performed as follows. The base member used is an aqueous solution containing a group of microorganisms that promote fermentation decomposition (compost solution obtained by composting various organic wastes) to the waste derived from felled trees containing 50% or more of the bark. Then, organic fertilizer is added to the chip obtained by the primary pulverization, pulverized again, and the secondary pulverized product is packed in a bag formed of a material having poor water permeability and air permeability, and is appropriately timed. It is a woody bark compost produced by fermentation and aging.

  The treatment objects contaminated with radioactive materials are “A: top soil in the contaminated area (peeled contaminated soil)”, “B: cattle dung collected from the cow dung accumulation site in the contaminated area”, “C: trees breeding in the contaminated area Wood chips felled and crushed.

  In the demonstration test, the processing object and the base member are set to a volume ratio of 4: 6 (400 liters and 600 liters), and 120 g of urea and 1 liter of zeolite are added and mixed to further promote the fermentation reaction. A cubic flexible container bag (hereinafter referred to as “flexible bag”) was filled and fermented.

Confirmation of the verification test results is as follows.
1. The progress of fermentation was confirmed by the temperature measured by inserting a temperature sensor into the center of the processing object from a position 50 cm from the upper layer in a state where the processing object was packed (Table 1). The outside air temperature at the time of measurement was 10 to 14 ° C., and the progress of fermentation was recognized higher than the outside air temperature from the next day when the object to be treated was filled into the flexible container bag on May 12. Since the melting point of radioactive cesium is 28 ° C., it is assumed that radioactive cesium is ionized and present in the moisture of the object to be treated, and is taken into the fungus like potassium ions.

  2. Concentration of radioactive material is 1 kg of sample collected from the flexible container filling, and the measurer is a general incorporated association, Niigata Prefectural Institute of Environmental Health, with a measurement time of 1000 seconds and a gamma ray spectrometer (germanium semiconductor detector). It was measured. A measurement result is as Tables 2-4, and has five days. In addition, additives were added on May 31 to supplement microbial fermentation accelerating energy in Table 4.

  From the above demonstration experiment, radioactive cesium was taken up by radiation resistant bacteria and decreased to 1/3 or more in 5 days. Moreover, fermentation progresses and the additive (microorganism energy source) which accelerates | stimulates fermentation progress is added, fermentation is continued and the reduction | decrease of a radioactive substance is not recognized. That is, although the growth of the radioactive resistant bacteria which take in a radioactive substance is not recognized, it is dying, but it is supported that the radioactive cesium is contained without dissolving again in a processing target object because the said bacterium died.

  As described above, the method of the present invention can be applied to radioactive pollutants (contamination targets), radioactive bacteria and useful bacteria (bacteria that contain radioactive bacteria), organic glass components that promote the action of the useful bacteria, and aluminum. When fermented and matured by mixing with compost derived from trees containing, radioactive cesium is contained by the action of microorganisms to achieve decontamination.

Claims (2)

  An aqueous solution containing a group of microorganisms that promote fermentation decomposition is added to the waste derived from the felled tree containing 50% or more of the bark to perform primary pulverization, and organic fertilizer is added to and mixed with the chips obtained by the primary pulverization. Regrind again, pack the secondary pulverized product into a bag made of a material with poor water permeability and air permeability, and appropriately prepare a base member manufactured by fermentation and aging for an appropriate period and a decontamination target such as radioactively contaminated soil. A method for decontamination of radioactively contaminated soil or the like, characterized by mixing and stirring at a proper ratio, adding an appropriate amount of a fermentation accelerator and mixing the mixture, and ripening in a state where aeration is restricted.   The method for decontamination of radioactively contaminated soil according to claim 1, wherein the organic fertilizer is animal manure or chicken manure soaked in an aqueous solution containing a microorganism group that promotes fermentation decomposition,

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