JP7010098B2 - Storage treatment equipment and storage treatment method for radioactive material-containing fly ash - Google Patents

Description

The present invention relates to a storage treatment device and a storage treatment method for radioactive substance-containing fly ash discharged from an incinerator of combustible waste containing radioactive substances.

When combustible waste containing radioactive substances is incinerated using an incinerator such as a stoker furnace, a kiln furnace, or a fluidized bed furnace, main ash and flying ash containing radioactive substances are generated. Fly ash has a higher concentration of radioactive substances than main ash, so it is stored in a storage container.

A drum can is generally used as a container for storing waste containing radioactive substances. In drums, radioactive waste generates harmful gas due to radiolysis, and the internal pressure inside the drums rises, which may cause damage.

Therefore, Patent Document 1 proposes a drum can as a storage container that releases gas generated from radioactive waste to prevent damage.

In the drum can of Patent Document 1, an opening is provided in the lid covering the drum can body, an inclined portion toward the opening is formed on the inner surface of the lid, and a filter is attached to the opening. Under such a structure, even if gas is generated in the drum can, the gas is guided toward the opening at the inclined portion and discharged to the outside through the filter. At that time, dust and the like of waste are captured by the above filter and only gas is released.

On the other hand, it is reported in Non-Patent Document 1 that metallic aluminum contained in incinerator ash of waste containing metallic aluminum reacts with water to generate hydrogen gas. When the fly ash stored in the storage container reacts to generate hydrogen gas, it causes an increase in the internal pressure inside the container.

Japanese Patent Laid-Open No. 3-231200

28th Research Conference of Waste Recycling Resources Society Lecture Manuscript 2017 C 2-2 Basic research on hydrogen gas generation characteristics from general waste incinerator ash

Therefore, if metallic aluminum is contained in the radioactive substance-containing flying ash discharged from the incinerator of combustible waste containing radioactive substances and stored in the storage container, the metallic aluminum reacts with water and hydrogen gas. If the storage container is a closed type, hydrogen gas is generated during storage and the internal pressure inside the storage container rises, causing the storage container to expand and break, and flying ash containing radioactive substances is around. There is a risk of leaking to the gas.

In the current situation where there is such a problem, it is appropriate to consider the possibility of hydrogen gas generation for the container that houses the fly ash generated when waste containing radioactive substances is incinerated, and to grasp the presence or absence of hydrogen gas generation. The storage processing technology for storage processing has not yet been established.

In view of such circumstances, the present invention accurately determines in a short time whether or not there is a risk of hydrogen gas generation when storing fly ash containing radioactive substances, and appropriately stores the fly ash according to the presence or absence of hydrogen gas generation. An object of the present invention is to provide a storage processing apparatus and a storage processing method capable of processing.

According to the present invention, the above-mentioned problems are solved by a storage treatment device for radioactive substance-containing fly ash, a storage treatment method, and a storage container, which are configured as follows.

<Storage processing equipment>
A fly ash pretreatment device that pre-treats the fly ash that is discharged from the incinerator of combustible waste containing radioactive substances and contains the radioactive substances prior to the storage of the fly ash, and the fly ash that stores the fly ash after the pretreatment. Has a storage device and
The fly ash pretreatment device receives a part of the fly ash from the fly ash storage tank and the fly ash, and adds a reactant that reacts with the metallic aluminum in the fly ash to the fly ash to generate hydrogen gas. It has a hydrogen gas generation determination device that determines the presence or absence of
The fly ash storage device is a closed storage container that stores the fly ash that is determined not to generate hydrogen gas by the hydrogen gas generation determination device, and the fly ash that is determined to have generated hydrogen gas by the hydrogen gas generation determination device. Equipped with a ventilated storage container to store
The ventilation type storage container has a double structure of an inner storage part having a plastic layer for storing fly ash and a metal outer storage part for storing the inner storage part, and also allows ventilation of hydrogen gas. Have a mouth,
A storage treatment device for fly ash containing radioactive substances.

In the present invention having such a configuration, the ventilated storage container may be a plastic container having an inner accommodating portion with a vent and a metal container having an outer accommodating portion having a vent.

Further, in the present invention, in the ventilated storage container, the inner surface of the metal container as the outer accommodating portion may be covered with a plastic coating as the inner accommodating portion.

<Storage processing method>
A fly ash pretreatment step in which fly ash discharged from an incinerator of combustible waste containing radioactive substances is pretreated prior to storage of the fly ash, and a fly ash in which the fly ash after the pretreatment step is stored. Has an ash storage process
The fly ash pretreatment step is an ash storage step of storing the fly ash in an ash storage tank, and a reactant that receives a part of the fly ash from the fly ash and reacts with metallic aluminum in the fly ash is added to the fly ash. Has a hydrogen gas generation determination step to determine the presence or absence of hydrogen gas generation.
In the fly ash storage step, when it is determined that no hydrogen gas is generated in the hydrogen gas generation determination step, the fly ash is stored in a closed storage container, and it is determined that hydrogen gas is generated in the hydrogen gas generation determination step. If so, store the fly ash in a ventilated storage container.
The aerated storage container has a double structure of an inner accommodating portion having a plastic layer for accommodating fly ash and a metal outer accommodating portion accommodating the inner accommodating portion, and also allows aeration of hydrogen gas. A method for storing and treating radioactive substance-containing fly ash, which has a mouth and discharges hydrogen gas from the vent of a ventilated storage container to the outside of the container in the fly ash storage step.

In the present invention, the additive can be an alkaline solution.

In the present invention, the vented storage container is a plastic container having an inner accommodating portion having a vent, and a metal container having an outer accommodating portion having a vent. , Can be discharged to the outside of the container through the vents of the outer accommodating portion in sequence.

In the present invention, the ventilated storage container can be such that the inner surface of the metal container as the outer accommodating portion is covered with a plastic coating as the inner accommodating portion.

<Storage container>
A fly ash storage container that stores fly ash that is discharged from an incinerator of combustible waste containing radioactive substances and contains radioactive substances.
The fly ash storage container has a double structure of an inner accommodating portion having a plastic layer for accommodating fly ash and a metal outer accommodating portion accommodating the inner accommodating portion, and also allows aeration of hydrogen gas. A ventilated storage container with a mouth,
A storage container for fly ash containing radioactive substances.

In the present invention, the ventilated storage container can be such that the inner storage portion is a plastic container with a vent and the outer storage portion is a metal container with a vent.

In the present invention, the ventilated storage container may be provided with a plastic coating as an inner storage portion on the inner surface of the metal container as the outer storage portion.

<Principle of operation>
In the storage treatment device and storage treatment method of the present invention, a part of the fly ash in the ash storage tank is collected and brought to the hydrogen gas generation determination device, and the reaction agent is added in the hydrogen gas generation determination device. Therefore, it is determined whether or not hydrogen gas is generated. When it is determined that no hydrogen gas is generated, the fly ash in the ash storage tank is stored in a normal closed storage container, and when it is determined that hydrogen gas is generated, it is stored in a ventilated storage container. .. As the reactant, for example, an alkaline solution such as an aqueous solution of calcium hydroxide or an aqueous solution of sodium hydroxide or an acid solution is used.

Since the flying ash stored in such a ventilation type storage container is stored in the inner storage portion having a plastic layer in the storage processing device, the storage processing method, and the storage container of the present invention, leakage of flying ash and moisture is prevented. Further, when the inner accommodating portion is protected by the metal outer accommodating portion and the metallic aluminum in the flying ash reacts with the moisture in the flying ash to generate hydrogen gas, the hydrogen gas is released into a ventilated storage container. Since it is discharged to the outside from the vent of the storage container, the internal pressure inside the storage container does not increase and there is no risk of damage to the storage container.

As described above, in the storage treatment apparatus and storage treatment method of the present invention, a part of the flying ash in the ash storage tank is sampled and a reaction agent is used to determine whether or not hydrogen gas is generated, and hydrogen gas is generated. It is decided to store the flying ash without hydrogen gas in a normal closed storage container, and only the flying ash with hydrogen gas generation needs to be stored in the ventilation type storage container having the vent of the present invention, and there is a risk of damage to the storage container. In addition to ensuring safety in storage, it is possible to reduce the number of ventilated storage containers that are expensive compared to ordinary closed storage containers.

In the storage treatment apparatus and storage treatment method of the present invention, since the storage container has an inner storage portion having a plastic layer and an outer storage portion made of metal, fly ash and moisture leak from the inner storage portion. As a result of preventing damage to the inner accommodating portion in the outer accommodating portion, safety in storage can be surely obtained.

It is a schematic block diagram of the storage processing apparatus of the radioactive substance-containing fly ash as one Embodiment of this invention. FIG. 1 shows a storage container used for a storage processing device, (A) is a closed type storage container, and (B) is a ventilation type storage container.

Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

The fly ash storage treatment device for radioactive substances shown in FIG. 1 as an apparatus according to an embodiment of the present invention includes a fly ash pretreatment device I and a fly ash storage device II, and the fly ash pretreatment device I is a fly ash pretreatment device I. The fly ash collected from the exhaust gas discharged by incinerating the waste containing radioactive substances in the incinerator 1 is received, and the fly ash is pretreated and delivered to the fly ash storage device II.

A dust collector 2 for removing exhaust gas, for example, a bag filter, is connected to the incinerator 1, the exhaust gas is sent to the dust collector 2, fly ash in the exhaust gas is collected by the dust collector 2, and the exhaust gas after dust removal is next. It is discharged for the exhaust gas detoxification treatment in the process, while the collected fly ash is sent to the kneader 4 by the feeder 3.

Water is added to the kneader 4 to prevent the fly ash from scattering and to facilitate kneading, and a chelating agent is added to prevent the elution of heavy metals in the fly ash. The fly ash kneaded by the kneader 4 is sent to the fly ash pretreatment device I.

In the fly ash pretreatment device I, hydrogen gas is generated by the reaction between the metallic aluminum contained in the fly ash and water, and the internal pressure inside the storage container rises during the storage of the fly ash, causing damage to the storage container. It is a device for determining whether or not there is a risk of occurrence before storage, and has an ash storage tank 5 for receiving fly ash from the kneader 4 and storing the fly ash, and a hydrogen gas generation determination device 6.

The hydrogen gas generation determination device 6 has a reaction device 6A and a hydrogen gas concentration measuring device 6B. The reaction device 6A has a stirring member in the container, and is connected to the ash storage tank 5 to collect a part of the fly ash in the ash storage tank 5 as a sample fly ash. A reactant is added to this sample fly ash and stirred. As the reactant, for example, an alkaline solution such as an aqueous solution of calcium hydroxide or an aqueous solution of sodium hydroxide has been used. Further, the reactant may be an acid solution.

The hydrogen gas concentration measuring device 6B receives the generated gas generated by the reaction between the flying ash and the reactant in the reaction device 6A from the reaction device 6A, and the hydrogen gas in the generated gas is received by, for example, a gas chromatographer or a detector tube. It is designed to measure the concentration.

When metallic aluminum is contained in the flying ash, since the metallic aluminum is an amphoteric metal, it reacts with an alkaline solution or an acid solution to generate hydrogen gas. In the present invention, the presence or absence of hydrogen gas generation is measured based on the result of hydrogen concentration measurement by the hydrogen gas concentration measuring device 6B. If the measured hydrogen concentration value exceeds 0, it is determined that hydrogen gas is generated even if the hydrogen concentration is low.

The fly ash storage device II is configured to include a plurality of storage containers, and has two types of containers, a closed type storage container 7 and a ventilation type storage container 8. The closed storage container 7 is composed of one or more closed storage containers 7-1, 7-2, ..., And the ventilated storage container 8 is one or more ventilated storage containers 8-1, 8-2. , 8-3, ...

In the present embodiment, as seen in FIG. 1, the closed storage containers 7-1, 7-2, ... Are all of the same embodiment, but are designated by reference numerals 7-1, 7-2 in the order of the array standby position. Similarly, the ventilation type storage containers 8-1, 8-2, 8-3, ... Are all of the same form, but are attached in the order of the arrangement position standby position 8-1, 8-2. , 8-3, ... are attached separately.

In FIG. 1, one of the closed storage containers 7-1, 7-2, ... And the ventilated storage containers 8-1, 8-2, 8-3, ... (Ventilation in FIG. 1). The mold storage container 8-1) is arranged directly under the ash storage tank 5 to receive the supply of fly ash falling from the ash storage tank 5, and others (sealed storage containers 7-1, 7-2). , ... And the ventilated storage container 8-2, 8-3, ...) Is in a standby position away from the position directly below the above-mentioned ash storage tank 5 shown in the figure.

As seen in FIG. 2A, the closed storage container 7 is a plastic bag made of polyethylene or the like in the outer accommodating portion 7A of a metal container having strength such as a drum can, and is a liquid from fly ash. An inner accommodating portion 7B capable of preventing leakage is housed. The inner accommodating portion 7B may be in the shape of a case or a bottle, and may be integrated with the outer accommodating portion 7A. For example, the inner surface of the metal container as the outer accommodating portion 7A may be formed. It can also be formed as a plastic coating on the surface.

On the other hand, in the case of the present embodiment, the ventilated storage container 8 has an outer storage portion 8A and an inner storage portion which are made of the same material and form as the outer storage portion 7A and the inner storage portion 7B of the closed type storage container 7. Although it has 8B, in this ventilation type storage container 8, both the outer storage portion 8A and the inner storage portion 8B have a ventilation port 8A-1 and a ventilation port 8B-1, respectively. The outer accommodating portion 8A also has a filter 8A-2 in the vent 8A-1.

When the fly ash contained in the inner accommodating portion 8B reacts with moisture to generate hydrogen gas, the vents 8B-1 and 8A-1 use this hydrogen gas in the inner accommodating portion 8B and the outer accommodating portion 8A. Small-sized pores sufficient to be released from each of them are formed or made of a porous material. The filter 8A-2 attached to the vent 8A-1 of the outer accommodating portion 8A allows hydrogen gas to permeate and does not allow fly ash to permeate. It is preferable to use a HEPA filter as the filter 8A-2.

Next, a procedure for storing fly ash by the present embodiment device having such a configuration will be described.

Waste containing radioactive substances is incinerated in incinerator 1. The incinerator ash is discharged from the lower part of the incinerator 1, and the exhaust gas is discharged from the upper part of the incinerator 1 and sent to the dust collector 2. The exhaust gas contains fly ash, and the dust collector 2 collects the fly ash, and only the gas component is sent to the next step for exhaust gas detoxification treatment. In the present embodiment, it is assumed that the fly ash contains heavy metals in addition to the radioactive substance, and the fly ash is sent to the kneader 4 via the feeder 3.

Water and a chelating agent are supplied to the kneading machine 4, and the kneading machine 4 is kneaded with the fly ash so that the heavy metals in the fly ash are not eluted by the chelating agent.

The kneaded fly ash is sent to the ash storage tank 5 of the fly ash pretreatment device I and stored in the ash storage tank 5 until it is stored in the storage containers 7 and 8. A part of the fly ash in the ash storage tank 5 is collected as sample fly ash and sent to the reaction device 6A of the hydrogen gas generation determination device 6. A reactant is added to the fly ash 1 to the reactor 6A. If metallic aluminum is contained in the fly ash, hydrogen gas is generated by reacting with the water content in the fly ash. However, since this reaction progresses gradually, it is not possible to grasp the presence or absence of this hydrogen gas when filling the container with fly ash, and hydrogen gas is generated during long-term storage, and the internal pressure inside the storage container gradually increases. It may rise and cause damage to the storage container. Therefore, in the present invention, in order to find out the presence or absence of hydrogen gas generation at an early stage, the above-mentioned reactant is added to the sample fly ash to promote the hydrogen gas generation, and the hydrogen gas is charged before filling the fly ash container. It was decided to determine whether or not it had occurred. As the reactant, an alkaline solution (for example, calcium hydroxide aqueous solution, sodium hydroxide aqueous solution) or an acid solution is used, but an alkaline aqueous solution is preferable. The reason is as follows.

Exhaust gas from the incinerator contains acidic gas, so in order to neutralize it, alkaline chemicals such as slaked lime (calcium hydroxide) are added to the exhaust gas flowing through the flue, and a dust collector is used. The collected fly ash contains alkaline chemicals. Therefore, when water is added to fly ash, the pH of fly ash is about 10 or more, which is alkaline. By adding an alkaline solution such as an aqueous solution of calcium hydroxide or an aqueous solution of sodium hydroxide to such flying ash in a relatively small amount, the hydrogen gas generation reaction is promoted and generated, and the presence or absence of hydrogen gas generation is present. Can be confirmed. On the other hand, if it is attempted to oxidize and react metallic aluminum with an acid solution to determine the presence or absence of hydrogen generation, a large amount of acid solution is required. On the other hand, as described above, when an alkaline solution is added, the presence or absence of hydrogen gas generation can be confirmed with a relatively small amount of addition, which is not an acid solution but an alkaline solution in the present embodiment. Is the reason for using as a reactant.

The generated gas generated by the reaction between the metallic aluminum in the flying ash and the reactant in the reactor 6A is sent to the hydrogen gas concentration measuring device 6B, where the hydrogen concentration in the generated gas is measured and the hydrogen gas in the generated gas. Is checked to see if it is included. The hydrogen concentration in the generated gas is measured by a gas chromatograph or a detector tube.

In addition to the above, it is conceivable to quantify the metallic aluminum contained in the fly ash as a method for determining whether or not hydrogen is generated from the fly ash. The quantification method includes a bromine-halogen dissolution method, a powder X-ray diffraction method, and an electron microscopy method. However, the bromine-halogen dissolution method takes a long time to measure and cannot be quantified in a short time. Since the lower limit of detection is about several percent, the measurement accuracy is low. In addition, electron microscopy has problems such as poor quantification because only local samples can be observed. Therefore, in the present embodiment, it is decided to measure the hydrogen concentration of the generated gas by using the generated gas extracted from the reaction device as a gas chromatograph or a detector tube as the hydrogen gas concentration measuring device 6B.

In the present embodiment, when hydrogen gas is detected from the generated gas by the hydrogen gas concentration measuring device 6B, hydrogen is generated and the internal pressure of the container is increased when the flying ash is stored in the storage container for a long period of time regardless of the concentration thereof. It was decided that the storage container could rise and be damaged.

Next, when the hydrogen gas generation determination device 6 detects the generation of hydrogen gas, the flying ash from the ash storage tank 5 is arranged in the flying ash storage device II regardless of the concentration thereof. It is housed and stored in the container 8, and when the generation of hydrogen gas is not detected at all, it is stored in the closed storage container 7. In the fly ash storage device II, a plurality of closed type storage containers 7 (7-1, 7-2, ...) And a plurality of ventilated storage containers 8 (8-1, 8-2, 8-3, ...) (・) Are arranged respectively, and either the closed type storage container 7 or the aerated type storage container 8 is selected based on the determination result by the hydrogen gas generation determination device 6 and brought to the position directly below the ash storage tank 5. Then, fly ash is received from the ash storage tank 5.

When it is determined that no hydrogen gas is generated from the sample fly ash, the fly ash is stored in the closed storage container 7 from the ash storage tank 5, and there is no risk of damage to the storage container even if it is stored for a long period of time. So there is no problem.

When the generation of hydrogen gas is detected in the sample fly ash, the fly ash is stored in the aeration type storage container 8 from the ash storage tank 5 regardless of the concentration of the hydrogen gas. When hydrogen gas is generated from fly ash as a result of long-term storage, the hydrogen gas passes through the vent 8B-1 of the inner accommodating portion 8B of the ventilated storage container 8 and the vent 8A-1 of the outer accommodating portion 8A. It is released to the outside.

In this way, the flying ash that is expected to generate hydrogen gas during storage is stored in the ventilation type storage container 8, so that the hydrogen gas when it is generated is vent 8A-1,8B-. Since it is discharged from 1 and does not remain in the container, the internal pressure of the container rises and the container does not expand or break, the flying ash does not scatter out of the container, and the flying ash safely contains radioactive substances. Ash can be stored. When hydrogen gas is released from the vent 8A-1 of the outer accommodating portion 8A, the fine powdery fly ash accompanying the hydrogen gas is filtered by the filter 8A-2, so that the fly ash is sure to leak to the outside. Is prevented.

5 Ash storage tank 6 Hydrogen gas generation determination device 7 Sealed storage container 8 Ventilated storage container 8A Outer storage part 8B Inner storage part I Fly ash pretreatment device
II Fly ash storage device

Claims (7)

A fly ash pretreatment device that pre-treats the fly ash that is discharged from the incinerator of combustible waste containing radioactive substances and contains the radioactive substances prior to the storage of the fly ash, and the fly ash that stores the fly ash after the pretreatment. Has a storage device and
The fly ash pretreatment device receives a part of the fly ash from the fly ash storage tank and the fly ash, and adds a reactant that reacts with the metallic aluminum in the fly ash to the fly ash to generate hydrogen gas. It has a hydrogen gas generation determination device that determines the presence or absence of
The fly ash storage device is a closed storage container that stores the fly ash that is determined not to generate hydrogen gas by the hydrogen gas generation determination device, and the fly ash that is determined to have generated hydrogen gas by the hydrogen gas generation determination device. Equipped with a ventilated storage container to store
The ventilation type storage container has a double structure of an inner storage part having a plastic layer for storing fly ash and a metal outer storage part for storing the inner storage part, and also allows ventilation of hydrogen gas. Have a mouth,
A storage treatment device for fly ash containing radioactive substances. The storage processing device for radioactive substance-containing fly ash according to claim 1, wherein the ventilated storage container is a plastic container having a vent in the inner accommodating portion and a metal container having a vent in the outer accommodating portion. The storage treatment device for radioactive substance-containing fly ash according to claim 1, wherein the ventilation type storage container is provided with a plastic coating as an inner storage portion on the inner surface of the metal container as the outer storage portion. A fly ash pretreatment step in which fly ash discharged from an incinerator of combustible waste containing radioactive substances is pretreated prior to storage of the fly ash, and a fly ash in which the fly ash after the pretreatment step is stored. Has an ash storage process
The fly ash pretreatment step is an ash storage step of storing the fly ash in an ash storage tank, and a reactant that receives a part of the fly ash from the fly ash and reacts with metallic aluminum in the fly ash is added to the fly ash. Has a hydrogen gas generation determination step to determine the presence or absence of hydrogen gas generation.
In the fly ash storage step, when it is determined that no hydrogen gas is generated in the hydrogen gas generation determination step, the fly ash is stored in a closed storage container, and it is determined that hydrogen gas is generated in the hydrogen gas generation determination step. If so, store the fly ash in a ventilated storage container.
The aerated storage container has a double structure of an inner accommodating portion having a plastic layer for accommodating fly ash and a metal outer accommodating portion accommodating the inner accommodating portion, and also allows aeration of hydrogen gas. A method for storing and treating radioactive substance-containing fly ash, which has a mouth and discharges hydrogen gas from the vent of a ventilated storage container to the outside of the container in the fly ash storage step. The method for storing and treating fly ash containing a radioactive substance according to claim 4, wherein the additive is an alkaline solution. The ventilation type storage container is a plastic container with an inner storage part with a vent and a metal container with an outer storage part with a vent. The method for storing and treating radioactive substance-containing flying ash according to claim 4, wherein the gas is sequentially discharged to the outside of the container through the vents of the above. The method for storing radioactive material-containing fly ash according to claim 4, wherein the ventilated storage container is covered with a plastic coating as an inner container on the inner surface of the metal container as the outer container.

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