JP2015007577A

JP2015007577A - Storage method and storage system of contaminated water

Info

Publication number: JP2015007577A
Application number: JP2013132862A
Authority: JP
Inventors: 石井　徹哉; Tetsuya Ishii; 徹哉石井; 和平与野; Kazuhira Yono
Original assignee: Sekisui Chemical Co Ltd
Current assignee: Sekisui Chemical Co Ltd
Priority date: 2013-06-25
Filing date: 2013-06-25
Publication date: 2015-01-15

Abstract

PROBLEM TO BE SOLVED: To store a large amount of contaminated water containing radioactive contaminant stably for a long period.SOLUTION: A storage method of contaminated water includes: dissolving a solute 4 such as sodium chloride into contaminated water 2 in a high-specific gravity processing unit 12 to cause the contaminated water 2 to have higher specific gravity than that of environmental water 3A (sea water, and lake water) in an underwater environment 3; and storing the contaminated water 2A having high specific gravity at the bottom (sea bottom, and lake bottom) of the underwater environment 3 while being encapsulated in encapsulation means. The encapsulation means is preferably a flexible bag 20.

Description

本発明は、汚染水を貯蔵する方法及びシステムに関し、特に放射性汚染物質を含んだ汚染水を長期間にわたって貯蔵するのに適した汚染水貯蔵方法及び汚染水貯蔵システムに関する。 The present invention relates to a method and system for storing contaminated water, and more particularly to a contaminated water storage method and a contaminated water storage system suitable for storing contaminated water containing radioactive pollutants over a long period of time.

例えば原子力発電所の事故などで放射性汚染物質を含んだ放射性汚染水が生活環境に排出されることは社会的に受け入れられていない。しかし、大量の放射性汚染水を陸上に貯蔵することは、漏れたときの環境汚染をどのように防止するかが問題になるし、そもそも貯蔵施設の建設場所の確保が問題になる。 For example, it is not accepted socially that radioactive water containing radioactive pollutants is discharged into the living environment due to an accident at a nuclear power plant. However, storing a large amount of radioactively contaminated water on land is a problem of how to prevent environmental pollution when it leaks, and in the first place, securing a construction site for the storage facility becomes a problem.

特許文献１には、沿岸海域の護岸を廃棄物処分場として用いることが記載されている。しかし、護岸は耐波浪強度などを確保する必要がある。
特許文献２には、フレキシブルなコンテナを海底に設置し、このコンテナに雨水等の淡水を貯蔵することが記載されている。しかし、貯蔵水の浮力でコンテナが浮かないようにコンテナを海底に固定する手段が必要になる。 Patent Document 1 describes using a seawall in a coastal sea area as a waste disposal site. However, the revetment needs to secure the strength of wave resistance.
Patent Document 2 describes that a flexible container is installed on the seabed, and fresh water such as rainwater is stored in the container. However, a means for fixing the container to the seabed is necessary so that the container does not float due to the buoyancy of the stored water.

特開２００５−２８８４１９号公報JP 2005-288419 A 特表２００８−５０８４５４号公報Special table 2008-508454 gazette

本発明は、上記事情に鑑み、放射性汚染水等の汚染水を大量に、かつ長期間にわたって安定的に貯蔵する方法を提供することを目的とする。 In view of the above circumstances, an object of the present invention is to provide a method for stably storing a large amount of contaminated water such as radioactively contaminated water over a long period of time.

上記課題を解決するため、本発明方法は、汚染水を水中環境に貯蔵する汚染水貯蔵方法であって、前記汚染水が前記水中環境の環境水より高比重になるように、前記汚染水に溶質を溶解させ、前記高比重の汚染水を閉じ込め手段にて閉じ込めた状態で前記水中環境の底部に貯蔵することを特徴とする。また、本発明システムは、汚染水を水中環境に貯蔵する汚染水貯蔵システムであって、前記汚染水が前記水中環境の環境水より高比重になるように、前記汚染水に溶質を溶解させる高比重化処理部と、前記高比重の汚染水を閉じ込めた状態で前記水中環境の底部に配置される閉じ込め手段と、を備えたことを特徴とする。これによって、汚染水を大量にかつ長期間にわたって安定的に貯蔵できる。
前記溶質としては、塩化ナトリウム（ＮａＣｌ）、塩化カリウム（ＫＣｌ）、糖等が挙げられる。前記溶質は、塩化ナトリウム（ＮａＣｌ）を含むことが一層好ましい。前記溶質は、ガスを発生させないものであることが好ましい。
前記水中環境としては、海、湖、池等が挙げられる。
前記水中環境が海であることが好ましい。前記溶質は、貯蔵場所の海水（前記水中環境の底部における環境水）から採取したものであることが好ましい。 In order to solve the above problems, the method of the present invention is a contaminated water storage method for storing contaminated water in an underwater environment, wherein the contaminated water has a higher specific gravity than the environmental water of the underwater environment. The solute is dissolved, and the high specific gravity contaminated water is stored in the bottom of the underwater environment in a state of being confined by a confinement means. The system of the present invention is a polluted water storage system for storing polluted water in an underwater environment, wherein the polluted water has a higher specific gravity than the environmental water of the underwater environment. And a confining means disposed at the bottom of the underwater environment in a state where the high specific gravity contaminated water is confined. Thereby, a large amount of contaminated water can be stably stored for a long period of time.
Examples of the solute include sodium chloride (NaCl), potassium chloride (KCl), and sugar. More preferably, the solute includes sodium chloride (NaCl). It is preferable that the solute does not generate gas.
Examples of the underwater environment include a sea, a lake, and a pond.
The underwater environment is preferably the sea. The solute is preferably collected from seawater at the storage location (environmental water at the bottom of the underwater environment).

前記水中環境の底部に設けられた凹地に前記閉じ込め手段を配置することが好ましい。これによって、汚染水が水中環境を水平方向に拡散するのを防止できる。 It is preferable to arrange the confinement means in a depression provided at the bottom of the underwater environment. Thereby, it is possible to prevent the contaminated water from diffusing in the underwater environment in the horizontal direction.

前記閉じ込め手段が、可撓性の袋を含むことが好ましい。これによって、閉じ込め手段の製造、運搬、設置等を簡易化でき、施工コストを低減できる。袋は、内部の高比重の汚染水の重みで水中環境の底部に安定的に配置されるから、袋が浮かないように水中環境の底部に袋を固定する固定手段を設けなくても済む。また、前記凹地に配置する場合、閉じ込め手段（袋）を凹地の形状に倣うように変形させることができる。 Preferably, the containment means comprises a flexible bag. Thereby, manufacture, transportation, installation and the like of the confinement means can be simplified, and the construction cost can be reduced. Since the bag is stably placed at the bottom of the underwater environment with the weight of the contaminated water having a high specific gravity, there is no need to provide a fixing means for fixing the bag to the bottom of the underwater environment so that the bag does not float. Moreover, when arrange | positioning to the said depression, a confinement means (bag) can be deform | transformed so that the shape of a depression may be followed.

前記袋にガス抜き管が接続されており、前記ガス抜き管が前記環境水より低比重であることが好ましい。これによって、ガス抜き管を環境水中において自立姿勢にすることができる。貯蔵中の汚染水内でガスが発生した場合、このガスを袋の内部からガス抜き管を経て水中環境等の外界に排出できる。これによって、袋が浮いたり、袋の内圧が過度に上昇したりするのを防止できる。 It is preferable that a gas vent pipe is connected to the bag, and the gas vent pipe has a specific gravity lower than that of the environmental water. Thereby, the degassing pipe can be in a self-supporting posture in the environmental water. When gas is generated in the contaminated water being stored, this gas can be discharged from the inside of the bag to the outside environment such as an underwater environment through a gas vent pipe. This can prevent the bag from floating or the internal pressure of the bag from rising excessively.

前記汚染水を液輸送船にて前記水中環境における貯蔵場所上の水面まで運搬し、この水面に浮遊させた前記袋に前記汚染水を前記液輸送船から送液管を介して注入することが好ましい。これによって、前記袋に注入した高比重の汚染水の重みによって、前記袋を水中環境の底部に向けて沈降させることができ、袋の設置作業を簡易に行うことができる。 The contaminated water is transported to a water surface on a storage place in the underwater environment by a liquid transport ship, and the contaminated water is injected from the liquid transport ship through a liquid feed pipe into the bag suspended on the water surface. preferable. As a result, the bag can be settled toward the bottom of the underwater environment by the weight of the high specific gravity contaminated water injected into the bag, and the bag can be installed easily.

前記汚染水は、例えば放射性汚染物質を含んでいる。この場合、前記高比重の汚染水と前記環境水との比重差が、前記放射性汚染物質の崩壊熱による前記汚染水の比重低下量の収束値よりも大きくなるように、前記溶解を行なうことが好ましい。これによって、汚染水の貯蔵期間中に放射性汚染物質の崩壊によって汚染水が加温されることで汚染水の比重が低下したとしても、汚染水が環境水よりも低比重になることを防止できる。したがって、汚染水を一層安定的に貯蔵できる。
前記溶解前に、前記汚染水から放射性物質を分離除去することによって、前記汚染水の放射性汚染物質濃度を低下させておくことが好ましい。 The contaminated water contains, for example, radioactive contaminants. In this case, the dissolution may be performed so that the specific gravity difference between the high specific gravity contaminated water and the environmental water is larger than the convergence value of the specific gravity decrease due to the decay heat of the radioactive pollutant. preferable. This prevents the contaminated water from having a lower specific gravity than the environmental water even if the contaminated water is heated by the decay of radioactive pollutants during the storage period and the specific gravity of the contaminated water decreases. . Therefore, the contaminated water can be stored more stably.
Prior to the dissolution, it is preferable to reduce the concentration of radioactive contaminants in the contaminated water by separating and removing radioactive substances from the contaminated water.

本発明によれば、汚染水を大量にかつ長期間にわたって安定的に貯蔵できる。 According to the present invention, a large amount of contaminated water can be stably stored for a long period of time.

本発明の第１実施形態に係る汚染水貯蔵システムの概略を示す断面図である。It is sectional drawing which shows the outline of the contaminated water storage system which concerns on 1st Embodiment of this invention. 第１実施形態における貯蔵部を示す断面図である。It is sectional drawing which shows the storage part in 1st Embodiment. 本発明の第２実施形態における貯蔵部を示す断面図である。It is sectional drawing which shows the storage part in 2nd Embodiment of this invention.

以下、本発明の実施形態を図面にしたがって説明する。
図１及び図２は、本発明の第１実施形態を示したものである。本発明は、汚染水を水中環境に貯蔵するものである。貯蔵対象の汚染水は、例えば原子力発電所１から出る放射性の汚染水２である。汚染水２は、汚染物質としてセシウム１３７等の放射性物質を含む。更に、汚染水２は、微生物や細菌等の生物やその餌等の有機系の汚染物質をも含んでいる場合がある。 Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1 and 2 show a first embodiment of the present invention. The present invention stores contaminated water in an underwater environment. The contaminated water to be stored is, for example, radioactive contaminated water 2 emitted from the nuclear power plant 1. The contaminated water 2 contains a radioactive substance such as cesium 137 as a contaminant. Furthermore, the contaminated water 2 may also contain organic pollutants such as organisms such as microorganisms and bacteria and their baits.

図２に示すように、貯蔵場所となる水中環境は海３である。詳細には、海底３ｂ（水中環境の底部）が貯蔵場所となる。好ましくは、貯蔵場所は、海水３Ａ（環境水）が十分に長期間にわたって殆ど入れ替わることのない深海の海底であり、より好ましくは、汚染水中の放射性物質の半減期より十分長い期間にわたって海水の入れ替えが起きない深海の海底である。また、貯蔵場所は、火山活動などによって温水等が吹き出されることがない場所であることが望ましく、そのような温水等に含まれる塩分等の養分を摂取する海底生物がほとんどいない場所であることが望ましい。さらに貯蔵場所は、望ましくは周辺よりも水深が深い場所である。好ましくは、海底３ｂに凹地３ｃが設けられており、この凹地３ｃが貯蔵場所になっている。凹地３ｃは、天然の海底凹地であってもよく、人工的に構築したものであってもよい。 As shown in FIG. 2, the underwater environment serving as a storage place is the sea 3. Specifically, the seabed 3b (the bottom of the underwater environment) serves as a storage location. Preferably, the storage location is a deep sea floor where seawater 3A (environmental water) hardly changes over a sufficiently long period of time, and more preferably replacement of seawater over a period sufficiently longer than the half-life of radioactive material in contaminated water. It is the deep sea floor where no wakes up. The storage location is preferably a location where warm water is not blown out due to volcanic activity, etc., and there are few submarine organisms that ingest nutrients such as salt contained in such warm water. Is desirable. Further, the storage location is preferably a location where the water depth is deeper than the surroundings. Preferably, a recess 3c is provided on the seabed 3b, and this recess 3c is a storage place. The depression 3c may be a natural seabed depression or an artificially constructed one.

図１に示すように、貯蔵対象の汚染水２は、前処理として除染処理（汚染度合の低減化処理）及び高比重化処理を施されたうえで貯蔵場所３ｃに貯蔵される。汚染水貯蔵システム１０は、貯蔵のための前処理部として、除染処理部１１と、高比重化処理部１２とを含む。詳細な図示は省略するが、除染処理部１１は、汚染水２の汚染度合（放射性汚染物質濃度や有機系汚染物質の含有量）を低減するものであり、逆浸透膜等の分離膜、吸着剤、沈殿処理槽等を含む。高比重化処理部１２は、汚染水２を高比重化処理するものであり、溶解槽１３と、溶質供給部１４を含む。溶解槽１３は、除染処理部１１の後段に設けられている。溶解槽１３に溶質供給部１４が接続されている。溶質供給部１４の溶質４としては、塩化ナトリウム（ＮａＣｌ）が用いられている。貯蔵場所の海底３ｂから海水を採取し、この海水から塩分を析出させ、この塩分を上記溶質４として用いることが望ましい。
以下、高比重化処理部１２を経た汚染水２を適宜「高比重汚染水２Ａ」又は「汚染水２Ａ」と称す。 As shown in FIG. 1, the contaminated water 2 to be stored is stored in the storage place 3c after being subjected to decontamination processing (processing for reducing the degree of contamination) and high specific gravity processing as pretreatment. The contaminated water storage system 10 includes a decontamination processing unit 11 and a high specific gravity processing unit 12 as a preprocessing unit for storage. Although detailed illustration is omitted, the decontamination processing unit 11 reduces the degree of contamination of the contaminated water 2 (the concentration of radioactive contaminants and the content of organic contaminants). Includes adsorbents, precipitation tanks, etc. The high specific gravity processing unit 12 performs high specific gravity processing on the contaminated water 2 and includes a dissolution tank 13 and a solute supply unit 14. The dissolution tank 13 is provided in the subsequent stage of the decontamination processing unit 11. A solute supply unit 14 is connected to the dissolution tank 13. Sodium chloride (NaCl) is used as the solute 4 of the solute supply unit 14. It is desirable to collect seawater from the seabed 3b of the storage location, deposit salt from the seawater, and use this salt as the solute 4.
Hereinafter, the contaminated water 2 that has passed through the high specific gravity treatment section 12 is appropriately referred to as “high specific gravity contaminated water 2A” or “contaminated water 2A”.

貯蔵システム１０は、閉じ込め手段として袋２０を含む。高比重汚染水２Ａが袋２０に閉じ込められた状態で海底凹地３ｃに貯蔵されている。袋２０は、例えばポリエチレン等の樹脂やゴム等のシートにて構成され、可撓性及び液密性を有している。袋２０の材質は、好ましくは、内部の汚染水２Ａ中の放射性物質の半減期（例えばセシウム１３７は３０年）よりも十分に長い時間の貯蔵耐久性を有している。好ましくは、袋２０は、複数のシートを積層した複層シートにて構成されている。各シートの厚みは、例えば数十μｍ〜数百μｍであり、ここでは１００μｍ程度であるが、これに限られるものではない。シートの積層枚数は、例えば数枚から数十枚であり、ここでは１０枚程度であるが、これに限られるものではない。袋２０の容量は、例えば１ｍ^３〜１０００００ｍ^３程度である。ハンドリングのしやすさ等を考えると、袋２０の容量は、１００００ｍ^３以下が好ましく、破損時の影響を小さくするためには、１０ｍ^３程度が好ましい。 The storage system 10 includes a bag 20 as a containment means. The high specific gravity contaminated water 2A is stored in the seabed depression 3c in a state of being confined in the bag 20. The bag 20 is made of, for example, a resin such as polyethylene or a sheet of rubber, and has flexibility and liquid tightness. The material of the bag 20 preferably has a storage durability for a time sufficiently longer than the half-life of the radioactive substance in the contaminated water 2A inside (for example, cesium 137 is 30 years). Preferably, the bag 20 is comprised by the multilayer sheet which laminated | stacked the some sheet | seat. The thickness of each sheet is, for example, several tens μm to several hundreds μm, and is about 100 μm here, but is not limited thereto. The number of stacked sheets is, for example, several to several tens, and is about 10 here, but is not limited thereto. Capacity of the bag 20 is, for example, ^1m ³ ^~100000m 3 about. Considering ease of handling and the like, the capacity of the bag 20 is preferably 10,000 m ³ or less, and about 10 m ³ is preferable in order to reduce the influence at the time of breakage.

上記貯蔵システム１０において、汚染水２を袋２０に貯蔵する迄の貯蔵方法を説明する。
＜除染処理工程＞
原子力発電所１から発生した放射性汚染水２を除染処理部１１に導入する。除染処理部１１において、汚染水２から放射性汚染物質や有機系汚染物質を分離して除去する。これによって、汚染水２の汚染度合が低減される。つまり、汚染水２の放射性物質濃度が低下される。除染処理後の汚染水２の放射性物質濃度は、１００００Ｂｑ／ｋｇ以下であることが好ましい。また、除染処理部１１の逆浸透膜等によって汚染水２中の有機系汚染物質をほとんど除去できる。 A storage method until the contaminated water 2 is stored in the bag 20 in the storage system 10 will be described.
<Decontamination process>
The radioactive polluted water 2 generated from the nuclear power plant 1 is introduced into the decontamination processing unit 11. In the decontamination processing unit 11, radioactive pollutants and organic pollutants are separated and removed from the contaminated water 2. Thereby, the degree of contamination of the contaminated water 2 is reduced. That is, the radioactive substance concentration in the contaminated water 2 is reduced. The radioactive substance concentration in the contaminated water 2 after the decontamination treatment is preferably 10000 Bq / kg or less. Moreover, almost all organic pollutants in the contaminated water 2 can be removed by the reverse osmosis membrane or the like of the decontamination processing unit 11.

＜高比重化処理工程（溶解工程）＞
上記除染処理後の汚染水２を高比重化処理部１２の溶解槽１３に導入する。また、溶質供給部１４の溶質４（塩化ナトリウム）を溶解槽１３に投入し、攪拌機１５にて汚染水２と溶質４とを混合攪拌する、これによって、溶解槽１３内において、溶質４が汚染水２に溶解される。そのため、汚染水２の比重が高まる。ここで、汚染水２が貯蔵場所の海水３Ａより高比重になるように、汚染水２の目標比重（溶質４の溶解量）を設定する。例えば、海水の比重は通常１．０２５ｇ／ｃｃ程度であるから、汚染水２の比重は、少なくとも１．０２５ｇ／ｃｃを上回るようにし、好ましくは１．０５ｇ／ｃｃ（海水３Ａの比重の１．０２５倍）以上になるようにし、より好ましくは１．０７５ｇ／ｃｃ（海水の比重の１．０５倍）以上になるようにする。 <High specific gravity treatment process (dissolution process)>
The contaminated water 2 after the decontamination treatment is introduced into the dissolution tank 13 of the high specific gravity treatment section 12. Further, the solute 4 (sodium chloride) of the solute supply unit 14 is put into the dissolution tank 13, and the contaminated water 2 and the solute 4 are mixed and stirred by the stirrer 15, whereby the solute 4 is contaminated in the dissolution tank 13. Dissolved in water 2. Therefore, the specific gravity of the contaminated water 2 is increased. Here, the target specific gravity (dissolution amount of the solute 4) of the contaminated water 2 is set so that the contaminated water 2 has a higher specific gravity than the seawater 3A at the storage location. For example, since the specific gravity of seawater is usually about 1.025 g / cc, the specific gravity of the contaminated water 2 should be at least 1.025 g / cc, and preferably 1.05 g / cc (1. 025 times) or more, and more preferably 1.075 g / cc (1.05 times the specific gravity of seawater) or more.

好ましくは、高比重化処理時の汚染水２の温度と貯蔵場所の温度との温度差を考慮して、汚染水２の目標比重を設定する。温度によって水の体積が変化し、その結果、比重が変化するからである。ここで、貯蔵場所の上記温度は、海底３ｂの海水３Ａの平均温度ないしは予測される最低温度である。
更に好ましくは、高比重汚染水２Ａと海水３Ａとの比重差が、汚染水２Ａ中の放射性汚染物質の崩壊熱による汚染水２Ａの比重低下量の収束値よりも大きくなるように、溶質４の溶解を行なう。つまり、上記崩壊熱が汚染水２Ａに吸収されることで、汚染水２Ａが昇温されると、汚染水２Ａの体積が膨張し、その結果、汚染水２Ａの比重が小さくなる。一方、汚染水２Ａの放射能は時間の経過とともに減衰するため、上記崩壊熱の積算量はある大きさに収束し、汚染水２Ａの比重低下量はある値に収束する。そこで、上記崩壊熱のすべてが汚染水２Ａに吸収されたと仮定した場合でも、収束時（半減期よりも十分長い期間の経過時、好ましくは無限時間経過時）の汚染水２Ａが海水３Ａより高比重になっているように、汚染水２の目標比重を設定することが好ましい。なお、汚染水２Ａ中の放射性汚染物質がセシウム１３７（半減期３０．１年、１回の崩壊エネルギー１．１７６ＭｅＶ）であり、かつその初期濃度（上記除染処理終了時の濃度）が１００００Ｂｑ／ｃｃ程度である場合、崩壊熱の無限時間分の積算量は、水１ｃｃあたり２．５Ｊ程度であり、この熱量の全部が汚染水２Ａの加温に使われたとしても汚染水２Ａの温度は０．６℃程度しか上昇しないから、汚染水２Ａの比重はほとんど変化しない。したがって、汚染水２Ａの放射性汚染物質濃度が１００００Ｂｑ／ｃｃ程度であれば、放射性汚染物質の崩壊熱による汚染水２Ａの比重低下は実質的に考慮しなくてもよい。 Preferably, the target specific gravity of the contaminated water 2 is set in consideration of the temperature difference between the temperature of the contaminated water 2 during the high specific gravity treatment and the temperature of the storage location. This is because the volume of water changes with temperature, and as a result, the specific gravity changes. Here, the said temperature of a storage place is the average temperature of the seawater 3A of the seabed 3b, or the lowest temperature estimated.
More preferably, the difference in specific gravity between the high specific gravity contaminated water 2A and the seawater 3A is larger than the convergence value of the decrease in specific gravity of the contaminated water 2A due to the decay heat of radioactive pollutants in the contaminated water 2A. Dissolve. That is, if the decay water is absorbed by the contaminated water 2A and the temperature of the contaminated water 2A is increased, the volume of the contaminated water 2A expands, and as a result, the specific gravity of the contaminated water 2A decreases. On the other hand, since the radioactivity of the contaminated water 2A decays with time, the integrated amount of decay heat converges to a certain magnitude, and the specific gravity decrease amount of the contaminated water 2A converges to a certain value. Therefore, even when it is assumed that all of the decay heat is absorbed by the contaminated water 2A, the contaminated water 2A at the time of convergence (when a period sufficiently longer than the half-life, preferably at an infinite time) is higher than the seawater 3A. It is preferable to set a target specific gravity of the contaminated water 2 so as to have a specific gravity. The radioactive pollutant in the contaminated water 2A is cesium 137 (half-life 30.1 years, decay energy 1.176 MeV once), and its initial concentration (concentration at the end of the decontamination process) is 10000 Bq / If it is about cc, the cumulative amount of decay heat for an infinite time is about 2.5J per cc of water, and even if all of this heat is used to heat the contaminated water 2A, the temperature of the contaminated water 2A is Since it rises only about 0.6 degreeC, the specific gravity of contaminated water 2A hardly changes. Therefore, if the concentration of the radioactive pollutant in the contaminated water 2A is about 10,000 Bq / cc, it is not necessary to substantially consider the decrease in the specific gravity of the contaminated water 2A due to the decay heat of the radioactive pollutant.

＜輸送工程＞
次に、溶解槽１３の近くの港湾にタンカー等の液輸送船５を配船し、高比重汚染水２Ａを溶解槽１３から液輸送船５に移す。この液輸送船５によって汚染水２Ａを貯蔵場所３ｃの真上の海面（水面）まで運搬する。なお、液輸送船５自体が高比重化処理部１２を構成していてもよい。つまり、除染処理後の汚染水２を液輸送船５に貯め、かつ液輸送船５内において、汚染水２に溶質４を溶解させることによって汚染水２を高比重化してもよい。 <Transport process>
Next, the liquid transport ship 5 such as a tanker is arranged at the harbor near the dissolution tank 13, and the high specific gravity contaminated water 2 A is transferred from the dissolution tank 13 to the liquid transport ship 5. The liquid transport ship 5 transports the contaminated water 2A to the sea level (water surface) just above the storage place 3c. The liquid transport ship 5 itself may constitute the high specific gravity processing unit 12. That is, the contaminated water 2 may be increased in specific gravity by storing the contaminated water 2 after the decontamination treatment in the liquid transport ship 5 and dissolving the solute 4 in the contaminated water 2 in the liquid transport ship 5.

＜貯液工程＞
次に、液輸送船５の近くの海面又は海中に袋２０を浮かべ、この袋２０と液輸送船５とを送液管２２で繋ぐ。そして、汚染水２Ａを液輸送船５から送液管２２を介して袋２０に注入する。この汚染水２Ａは海水３Ａよりも高比重であるから、袋２０が内部の汚染水２Ａの重みで沈降する。この袋２０を海底３ｂの凹地３ｃに導いて凹地３ｃ内に設置する。
凹地３ｃに予め袋２０を配置しておき、その真上の海上に配船した液輸送船５から汚染水２Ａを、送液管２２を経由して凹地３ｃの袋２０に充填してもよい。
高比重汚染水２Ａの充填後、袋２０から送液管２２を外し、かつ袋２０を密封する。 <Liquid storage process>
Next, the bag 20 is floated on the sea surface or in the sea near the liquid transport ship 5, and the bag 20 and the liquid transport ship 5 are connected by the liquid feeding pipe 22. Then, the contaminated water 2 A is injected into the bag 20 from the liquid transport ship 5 through the liquid supply pipe 22. Since this contaminated water 2A has a higher specific gravity than seawater 3A, the bag 20 sinks with the weight of the contaminated water 2A inside. The bag 20 is guided to the depression 3c on the seabed 3b and installed in the depression 3c.
The bag 20 may be placed in the depression 3c in advance, and the contaminated water 2A may be filled into the bag 20 in the depression 3c via the liquid feeding pipe 22 from the liquid transport ship 5 arranged on the sea directly above the depression. .
After the high specific gravity contaminated water 2A is filled, the liquid feeding pipe 22 is removed from the bag 20, and the bag 20 is sealed.

高比重汚染水２Ａは海水３Ａ（環境水）よりも比重が大きいから、袋２０が海底３ｂ（水中環境の底部）に安定的に載置される。これによって、高比重汚染水２Ａを安定的に貯蔵できる。袋２０を浮かないように海底に固定する固定手段は不要である。しかも、深海の海底３ｂは海流がほとんどないため、袋２０ひいては高比重汚染水２Ａを一層安定して貯蔵できる。
高比重汚染水２Ａを袋２０（閉じ込め手段）の内部に閉じ込めることで、高比重汚染水２Ａが拡散するのを防止できる。
さらに、袋２０ひいては高比重汚染水２Ａを凹地３ｃに貯蔵することによって、たとえ高比重汚染水２Ａが袋３０から漏れた場合でも、高比重汚染水２Ａが水平方向に広がるのを確実に防止できる。
溶質４として、貯蔵場所の海水から採取した塩分を用いることによって、汚染水２Ａが袋２０から漏れた場合でも、周辺環境における海水の塩分組成の変化等の、汚染物質による影響以外の影響を小さくすることができる。 Since the specific gravity of the high specific gravity contaminated water 2A is larger than that of the seawater 3A (environmental water), the bag 20 is stably placed on the seabed 3b (bottom of the underwater environment). Thereby, the high specific gravity contaminated water 2A can be stably stored. A fixing means for fixing the bag 20 to the sea floor so as not to float is unnecessary. Moreover, since there is almost no ocean current in the deep sea bottom 3b, the bag 20 and thus the high specific gravity contaminated water 2A can be stored more stably.
By confining the high specific gravity contaminated water 2A inside the bag 20 (confining means), it is possible to prevent the high specific gravity contaminated water 2A from diffusing.
Furthermore, by storing the bag 20 and thus the high specific gravity contaminated water 2A in the recess 3c, even if the high specific gravity contaminated water 2A leaks from the bag 30, it is possible to reliably prevent the high specific gravity contaminated water 2A from spreading in the horizontal direction. .
By using the salinity collected from the seawater at the storage location as the solute 4, even if the contaminated water 2A leaks from the bag 20, the influence other than the influence of the pollutants, such as changes in the salinity composition of the seawater in the surrounding environment, is reduced. can do.

高比重汚染水２Ａ中の放射性物質が放射性崩壊すると、その崩壊熱によって高比重汚染水２Ａの温度が上昇する。これに伴って、高比重汚染水２Ａの体積が膨張し、ひいては高比重汚染水２Ａの比重が低下する。一方、上記高比重化処理時の目標比重の設定によって、上記崩壊熱のすべてが汚染水２Ａに吸収されたとしても、高比重汚染水２Ａの比重が海水３Ａの比重を十分に長期間にわたって、好ましくは永続的に上回るようにすることができる。これによって、袋２０ひいては高比重汚染水２Ａが浮くのを防止できる。 When the radioactive substance in the high specific gravity contaminated water 2A is radioactively decayed, the temperature of the high specific gravity contaminated water 2A is increased by the decay heat. Along with this, the volume of the high specific gravity contaminated water 2A expands, and as a result, the specific gravity of the high specific gravity contaminated water 2A decreases. On the other hand, even if all of the decay heat is absorbed by the contaminated water 2A by setting the target specific gravity at the time of the high specific gravity treatment, the specific gravity of the high specific gravity contaminated water 2A is sufficient for the specific gravity of the seawater 3A for a sufficiently long period of time. Preferably it can be permanently exceeded. This can prevent the bag 20 and thus the high specific gravity contaminated water 2A from floating.

除染処理部１１における低放射能化処理によって汚染水２Ａの放射性物質濃度が低下されているために、汚染水２Ａが拡散したとしても、環境に与える影響を実質的に無くすことができる。また、汚染水２Ａ中の放射性物質等の反応によるガスの発生量を抑制できる。したがって、袋２０が浮いたり、袋２０の内圧が高くなったりするのを防止できる。さらに、除染処理部１１における有機系汚染物質の除去処理によって、汚染水２Ａには微生物等の生物やその餌となる有機物がほとんど存在しないために、有機物の分解によるガスの発生量を十分に少なくできる。したがって、袋２０が浮いたり、袋２０の内圧が高くなったりするのを一層確実に防止できる。 Since the radioactive substance concentration in the contaminated water 2A has been lowered by the low-activity treatment in the decontamination processing unit 11, even if the contaminated water 2A diffuses, the influence on the environment can be substantially eliminated. In addition, the amount of gas generated due to the reaction of radioactive substances or the like in the contaminated water 2A can be suppressed. Therefore, it is possible to prevent the bag 20 from floating or the internal pressure of the bag 20 from increasing. Furthermore, due to the removal processing of organic pollutants in the decontamination processing unit 11, the contaminated water 2A contains almost no organisms such as microorganisms or organic matter serving as food for it, so that a sufficient amount of gas is generated due to decomposition of the organic matter. Less. Therefore, it can prevent more reliably that the bag 20 floats or the internal pressure of the bag 20 becomes high.

次に、本発明の他の実施形態を説明する。以下の実施形態において、既述の実施形態と重複する内容に関しては、図面に同一符号を付して説明を省略する。
図３は、本発明の第２実施形態を示したものである。第２実施形態の袋２０にはガス抜き管２３が設けられている。ガス抜き管２３の基端部（下端部）が袋２０の上端部に接続されている。ガス抜き管２３の内部が袋２０の内部に連なっている。ガス抜き管２３の材質は、海水３Ａよりも低比重の樹脂等にて構成されている。そのため、ガス抜き管２３は、海中において袋２０から上へ向かって延びている。ガス抜き管２３の先端部（上端部）は、海中に開口されている。
なお、ガス抜き管２３の先端部が、海面に達していてもよい。 Next, another embodiment of the present invention will be described. In the following embodiments, the same reference numerals are attached to the drawings for the same contents as those of the above-described embodiments, and the description thereof is omitted.
FIG. 3 shows a second embodiment of the present invention. The bag 20 of the second embodiment is provided with a gas vent pipe 23. The base end portion (lower end portion) of the gas vent pipe 23 is connected to the upper end portion of the bag 20. The inside of the gas vent pipe 23 is connected to the inside of the bag 20. The material of the gas vent pipe 23 is composed of a resin having a specific gravity lower than that of the seawater 3A. Therefore, the gas vent pipe 23 extends upward from the bag 20 in the sea. The distal end portion (upper end portion) of the gas vent pipe 23 is opened into the sea.
In addition, the front-end | tip part of the gas vent pipe 23 may have reached the sea surface.

ガス抜き管２３の内部には海水３Ａが入り込んでいる。ガス抜き管２３の内径は、ガスと液とが管２３の内部で上下に入れ替わることができ、かつ袋２０内の汚染水２Ａが管２３を伝って漏れ出ることがないような大きさであることが好ましく、たとえば１０ｍｍ〜５０ｍｍ程度である。ガス抜き管２３の内径が小さすぎると、ガスと液とが管２３の内部で上下に入れ替わることができず、袋２０内からのガスが管２３の内部の液を押し上げてしまう。また、ガス抜き管２３の内径が大きすぎると、袋２０内の汚染水２Ａが管２３内に拡散して、外部に漏れ出るおそれがある。ガス抜き管２３の長さは、袋２０内の汚染水２Ａが管２３を伝って漏れ出ることがない程度に長くすることが好ましく、例えば１０ｍ以上である。ガス抜き管２３の数は、１つに限られず、複数であってもよい。 Sea water 3 A enters the gas vent pipe 23. The inner diameter of the gas vent pipe 23 is such that the gas and liquid can be exchanged up and down inside the pipe 23, and the contaminated water 2A in the bag 20 does not leak through the pipe 23. For example, it is about 10 mm to 50 mm. If the inner diameter of the gas vent pipe 23 is too small, the gas and the liquid cannot be exchanged up and down inside the pipe 23, and the gas from the bag 20 pushes up the liquid inside the pipe 23. If the inner diameter of the gas vent pipe 23 is too large, the contaminated water 2A in the bag 20 may diffuse into the pipe 23 and leak out. The length of the gas vent pipe 23 is preferably long enough to prevent the contaminated water 2A in the bag 20 from leaking through the pipe 23, for example, 10 m or more. The number of the gas vent pipes 23 is not limited to one and may be plural.

第２実施形態によれば、袋２０の汚染水２Ａ内でガスが発生した場合、このガスを袋２０の内部からガス抜き管２３を経て外界（海中）に排出できる。これによって、袋２０が浮いたり、袋２０の内圧が過度に上昇したりするのを防止できる。 According to the second embodiment, when gas is generated in the contaminated water 2 A of the bag 20, this gas can be discharged from the inside of the bag 20 to the outside (underwater) through the gas vent pipe 23. This can prevent the bag 20 from floating or the internal pressure of the bag 20 from rising excessively.

本発明は、上記実施形態に限定されるものではなく、その趣旨を逸脱しない範囲において種々の改変をなすことができる。
例えば、水中環境は、海に限られず、湖でもよく、池でもよい。汚染水２を湖水より高比重にして湖底に貯蔵してもよい。汚染水２を池の水より高比重にして、池底に貯蔵してもよい。
閉じ込め手段として、袋２０に代えて、金属製容器、タンク、コンクリート製貯蔵室等を適用してもよい。
溶質４として、塩化ナトリウムに代えて、塩化カリウム（ＫＣｌ）や、糖等を用いてもよい。２以上の溶質の混合物を汚染水２に溶解させることにしてもよい。溶質４は、ガスを発生させないものであることが好ましい。
貯蔵場所は、海底３ｂ（水中環境の底部）における必ずしも凹地３ｃである必要はなく、海底３ｂ（水中環境の底部）の平地であってもよい。凹地３１に貯蔵すれば袋２０が破損しても高比重汚染水２Ａを凹地３ｃに留めることができる。 The present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.
For example, the underwater environment is not limited to the sea, and may be a lake or a pond. The contaminated water 2 may be stored at the bottom of the lake with a specific gravity higher than that of the lake water. The contaminated water 2 may be stored at the bottom of the pond with a specific gravity higher than that of the pond water.
As a confinement means, instead of the bag 20, a metal container, a tank, a concrete storage room, or the like may be applied.
As the solute 4, potassium chloride (KCl), sugar, or the like may be used instead of sodium chloride. A mixture of two or more solutes may be dissolved in the contaminated water 2. It is preferable that the solute 4 does not generate gas.
The storage place does not necessarily need to be the concave 3c on the seabed 3b (bottom of the underwater environment), and may be a flat ground on the seabed 3b (bottom of the underwater environment). If stored in the depression 31, the high specific gravity contaminated water 2 A can be retained in the depression 3 c even if the bag 20 is damaged.

本発明は、例えば原子力発電所から排出された放射性物質を含む放射性汚染水を貯蔵するのに適用可能である。 The present invention is applicable to storing radioactively contaminated water containing radioactive material discharged from, for example, a nuclear power plant.

１原子力発電所
２放射性汚染水
２Ａ高比重汚染水
３海（水中環境）
３Ａ海水（環境液）
３ｂ海底（水中環境の底部）
３ｃ凹地（貯蔵場所）
４塩化ナトリウム（溶質）
５液輸送船
１０汚染水貯蔵システム
１２高比重化処理部
１３溶解槽
２０袋（閉じ込め手段）
２２送液管
２３ガス抜き管 1 Nuclear power plant 2 Radioactive contaminated water 2A High specific gravity contaminated water 3 Sea (underwater environment)
3A Seawater (environmental fluid)
3b Seabed (bottom of the underwater environment)
3c depression (storage place)
4 Sodium chloride (solute)
5 Liquid transport ship 10 Contaminated water storage system 12 High specific gravity processing section 13 Dissolution tank 20 Bag (containment means)
22 Liquid feed pipe 23 Gas vent pipe

Claims

A contaminated water storage method for storing contaminated water in an underwater environment,
Dissolving the solute in the contaminated water so that the contaminated water has a higher specific gravity than the environmental water of the underwater environment,
The contaminated water storage method characterized in that the high specific gravity contaminated water is stored at the bottom of the underwater environment in a state of being confined by a confinement means.

The contaminated water storage method according to claim 1, wherein the confining means is disposed in a depression provided at a bottom of the underwater environment.

The contaminated water storage method according to claim 1, wherein the confinement means includes a flexible bag.

The method for storing contaminated water according to claim 3, wherein a gas vent pipe is connected to the bag, and the gas vent pipe has a specific gravity lower than that of the environmental water.

By transporting the contaminated water to a water surface on a storage place in the underwater environment with a liquid transport ship, and injecting the contaminated water from the liquid transport ship through a liquid feed pipe into the bag suspended on the water surface. The method for storing contaminated water according to claim 3 or 4, wherein the bag is allowed to settle.

The polluted water contains a radioactive pollutant, and the specific gravity difference between the high specific gravity polluted water and the environmental water is larger than the convergence value of the specific gravity decrease amount of the polluted water due to the decay heat of the radioactive pollutant. The contaminated water storage method according to any one of claims 1 to 5, wherein the dissolution is performed as described above.

A contaminated water storage system for storing contaminated water in an underwater environment,
A high specific gravity treatment unit for dissolving a solute in the contaminated water so that the contaminated water has a higher specific gravity than the environmental water of the underwater environment;
Confinement means disposed at the bottom of the underwater environment in a state where the high specific gravity contaminated water is confined;
A contaminated water storage system characterized by comprising: