JP2020020726A - Hydrogen gas vent for radioactive substance storage container and radioactive substance storage container using the same - Google Patents
Hydrogen gas vent for radioactive substance storage container and radioactive substance storage container using the same Download PDFInfo
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Abstract
Description
この発明は、放射性物質保管容器用水素ガスベント及びこれを用いた放射性物質保管容器に関する。 The present invention relates to a hydrogen gas vent for a radioactive substance storage container and a radioactive substance storage container using the same.
放射性物質を輸送、保管・貯蔵、埋設処分等において、放射性物質を容器に入れた場合に、容器内に含まれる水などが放射線分解して水素ガスや酸素ガスなどが発生することによる容器内の圧力上昇による容器の破損や変形、あるいは水素ガス爆発の危険がある。 When transporting, storing / storing, or disposing of radioactive materials, when radioactive materials are placed in containers, water and other substances contained in the containers are radiolyzed to generate hydrogen gas, oxygen gas, etc. There is a risk of damage or deformation of the container due to pressure increase, or explosion of hydrogen gas.
放射線を発する放射性物質を輸送、保管・貯蔵、処分等を行う場合、放射性物質を漏洩させず、外部からの雨水等の浸入を防ぎ、あるいは、放射線の遮蔽を目的として、通常は、何らかの密閉容器に入れ埋設され、あるいは、施設内で管理される。この時、水などが存在すると、水の放射線分解によってＨ２、Ｏ２、Ｎ２、ＣＯ２などのガスが生成する。これらガスの生成は、容器内の圧力を上昇させ、容器の破損や変形を生じる恐れがあり、破損では放射性物質が漏洩し、あるいは、変形することで容器を覆う様々な遮蔽体に影響を及ぼす可能性がある。 When transporting, storing, storing, or disposing of radioactive materials that emit radiation, some sealed containers are usually used for the purpose of preventing leakage of radioactive materials, preventing intrusion of rainwater, etc. from the outside, or shielding radiation. It is buried in the building or managed in the facility. At this time, if water or the like is present, gases such as H 2 , O 2 , N 2 , and CO 2 are generated by radiolysis of the water. The generation of these gases can increase the pressure inside the container and cause damage or deformation of the container, which can cause radioactive material to leak or deform, affecting various shields covering the container. there is a possibility.
放射性物質は、細かな粒状を呈するものや、焼却飛灰など粉状である場合、あるいは、液状である場合があり、万一の容器の破損や経年劣化等によって、これら放射性物質が外界へ漏出する危険性を回避する必要がある。これら放射性物質を安定させるためセメント系材料で固形化することが有効であるが、セメント系材料は水を含むものが多い。また、ガラス固化体での固化でも、容器内でセメント系材料を用いて固定化で水を含むことがあり、放射線によりガスの発生が課題となる。 Radioactive materials may be in the form of fine particles, in the form of powder such as incinerated fly ash, or in the form of liquid.They may leak to the outside world due to damage to containers or deterioration over time. You need to avoid the danger of doing so. To stabilize these radioactive substances, it is effective to solidify with a cement-based material, but many cement-based materials contain water. Further, even in the case of solidification with a vitrified body, water may be included in the fixation using a cement-based material in a container, and the generation of gas by radiation is a problem.
特に、水由来のＨ２（水素ガス）は、その濃度が爆発限界あるいは燃焼限界に達し、静電気によるスパークなどの発生で火炎伝播を生じる危険性があり、容器内のみならず、これらを貯蔵する施設においても適切に水素ガス等の濃度を限界値以下に管理することが求められる。 In particular, water-derived H 2 (hydrogen gas) has a concentration reaching the explosion limit or the combustion limit, and there is a risk of causing flame propagation due to generation of sparks or the like due to static electricity. It is necessary for facilities to properly control the concentration of hydrogen gas, etc., below the limit value.
特許文献１によると、多孔質基材の表面にセラミックス製の多孔質膜を形成し、さらにその上にフッ素原子を含む有機ケイ素化合物を付与し、水不透過性のセラミック分離膜で水素ガスを分離できる。しかし、この構造は複雑であり、製造工程では熱処理が必要で、安全保管を目的とし、ガス種類に応じた孔径のセラミックス製の多孔質膜を得ることが困難であった。また、水素ガスの透過率は低く、分離膜の耐久性、特に、機械的強度が不十分で放射性物質の遮蔽には不向きである。 According to Patent Document 1, a porous film made of ceramics is formed on the surface of a porous substrate, and an organosilicon compound containing a fluorine atom is further provided thereon. Hydrogen gas is passed through a water-impermeable ceramic separation membrane. Can be separated. However, this structure is complicated, heat treatment is required in the manufacturing process, and it is difficult to obtain a ceramic porous film having a pore size corresponding to the gas type for the purpose of safe storage. Further, the permeability of hydrogen gas is low, and the durability of the separation membrane, particularly, the mechanical strength is insufficient, so that it is not suitable for shielding radioactive substances.
また、密閉容器に発生ガスの圧力を感知して作動するリークバルブを設けたとしても、水素ガスの爆発限界は４体積％であって極めて低いため，爆発限界に達してもこの水素分圧に相当する低圧でリークバルブの作動は困難であり、リークバルブでは容器内の水素ガス爆発を防止出来ない。 Also, even if a leak valve is provided in the sealed container to operate by sensing the pressure of the generated gas, the explosion limit of hydrogen gas is extremely low at 4% by volume. It is difficult to operate the leak valve at a correspondingly low pressure, and the leak valve cannot prevent hydrogen gas explosion in the container.
そこで、放射性物質の輸送、保管、貯蔵、埋設等の処分において、放射線によって発生するガスが容器内の閉鎖空間に発生することによる圧力変形や水素ガスによる爆発などを防ぐとともに、放射性物質保管用容器内の閉鎖空間からの放射性物質の漏出や、外界からの雨水等の浸入を防ぎ、効率的に水素ガスおよび他の放射線分解生成ガスを逃がすガスベントを提供することを課題とした。 Therefore, in the disposal of radioactive materials, such as transport, storage, storage, and burial, the gas generated by radiation in the closed space inside the container prevents pressure deformation and explosion due to hydrogen gas, etc. It is an object of the present invention to provide a gas vent that prevents leakage of radioactive materials from a closed space in the inside and intrusion of rainwater or the like from the outside and efficiently releases hydrogen gas and other radiolysis generated gases.
本発明は上述のような課題に鑑みてなされたものであり、水素ガスベント及びこれを用いた放射性物質の容器、を提供するものである。本発明は、発生した水素ガスおよび酸素ガスを容器内から逐次放出するガスベントを提供するものである。 The present invention has been made in view of the above problems, and provides a hydrogen gas vent and a container for a radioactive substance using the same. The present invention provides a gas vent for sequentially releasing generated hydrogen gas and oxygen gas from the inside of a container.
前記課題を解決するため、本発明は、
［１］放射性物質を保管する容器に設置し、水の放射線分解によって発生するガスを、容器外へ排出させるガスベントであって、液体を透過しないが気体を透過することのできる気体透過性膜と、これを保持する透気性多孔質担持体を有する水素ガスベント、を提供する。
In order to solve the above problems, the present invention provides:
[1] A gas vent that is installed in a container for storing radioactive substances and discharges gas generated by radiolysis of water to the outside of the container, and is a gas-permeable membrane that does not transmit liquid but can transmit gas. And a hydrogen gas vent having a gas-permeable porous carrier holding the same.
［２］前記気体透過性膜はシリコーンゴムであることを特徴とする［１］の水素ガスベント、を提供する。 [2] The hydrogen gas vent according to [1], wherein the gas permeable membrane is a silicone rubber.
［３］前記透気性多孔質担持体は多孔質セラミックスまたは多孔質金属であり、前記気体透過性膜の厚さが０．１〜５ｍｍであることを特徴とする［１］〜［２］の水素ガスベント、を提供する。 [3] The method according to [1], wherein the gas-permeable porous carrier is a porous ceramic or a porous metal, and the thickness of the gas-permeable film is 0.1 to 5 mm. Provide a hydrogen gas vent.
［４］［１］〜［３］の水素ベントは、透気口および排気口を有するボックスに気体透過性膜と前記透気性多孔質担持体を保持させ、透気口は容器内に開放し、排気口はチューブを用いて容器外排気口に接続したことを特徴とする放射性物質保管容器、を提供する。 [4] The hydrogen vents of [1] to [3] allow the gas permeable membrane and the gas permeable porous carrier to be held in a box having a gas permeable port and an exhaust port, and the gas permeable port is opened into the container. And a radioactive substance storage container characterized in that the exhaust port is connected to the external exhaust port using a tube.
［５］［１］〜［３］の水素ベントは、前記気体透過性膜と前記透気性多孔質担持体を容器の外壁の一部とするように円筒状ボックス１５内に設置したことを特徴とする放射性物質保管容器、を提供する。 [5] The hydrogen vent of [1] to [3] is characterized in that the gas permeable membrane and the gas permeable porous carrier are installed in a cylindrical box 15 so as to be a part of an outer wall of a container. A radioactive material storage container.
図１に放射性物質の容器２０内における放射線によるガス発生とガスベント１０の機能の概念を示す。放射性物質３０は、固形化物４０とともに容器内に保管される。このとき放射線によって発生するガスが容器内の閉鎖空間に発生することによる圧力変形や水素ガス（図１のＨ２）による爆発などを防ぐとともに、放射性物質保管用容器内の閉鎖空間からの放射性物質３０の漏出や、外界からの雨水等の浸入を防ぎ、安全かつ効率的に水素ガスを逃がすガスベント１０を提供する。 FIG. 1 shows the concept of the function of the gas vent 10 and the generation of gas by the radiation in the container 20 of the radioactive substance. The radioactive substance 30 is stored in a container together with the solidified material 40. At this time, it is possible to prevent pressure deformation and explosion due to hydrogen gas (H 2 in FIG. 1) due to the gas generated by the radiation being generated in the closed space inside the container, and to prevent the radioactive material from the closed space inside the radioactive material storage container Provided is a gas vent 10 that prevents leakage of hydrogen gas from the outside and intrusion of rainwater or the like from the outside world and allows hydrogen gas to escape safely and efficiently.
液体を透過しないが気体を透過することのできる気体透過性膜
ガスベントに用いる気体透過性膜は、液状水を透過せず、ガスを透過する膜であり、製造における取扱い性、水やガスの透過性、耐熱性耐寒性などの耐久性、経済性、などの観点から、シリコーンゴムが好適である。ジメチル系、メチルビニル系、メチルフルオロアルキル系などのシリコーンゴムが好ましい。さらに、ＳｉＯ２のエアロジルや石英粉、珪藻土などをフィラー（混合材）として用いることで強度特性を改善した複合材とすることが好ましい。シリコーンゴムは水素ガスの透過性に優れるとともに、他のその他の放射線分解生成ガスの透過性にも優れるため、密閉容器の変形、破損を防止でき、好適である。
Gas permeable membrane that is impermeable to liquid but permeable to gas The gas permeable membrane used for gas vents is a gas permeable membrane that does not allow liquid water to pass through it. Silicone rubber is preferred from the viewpoints of heat resistance, heat resistance, durability such as cold resistance, economy, and the like. Preferred are silicone rubbers such as dimethyl, methylvinyl, and methylfluoroalkyl. Furthermore, it is preferable to use aerogel, quartz powder, diatomaceous earth or the like of SiO 2 as a filler (mixing material) to obtain a composite material having improved strength characteristics. Silicone rubber is excellent in permeability of hydrogen gas and also excellent in permeability of other gas generated by radiolysis, so that deformation and breakage of the sealed container can be prevented, which is preferable.
さらにまた、シリコーンゴムの分子構造中にフェニル基を３〜２０モル％含有すると放射線に対する耐久性が向上するだけでなく、容器を低温環境下で保管することもあることから耐寒性を付与することができる。フェニル基を有するメチルフェニルビニルシリコーンゴムが例示される。 Furthermore, when a phenyl group is contained in the molecular structure of the silicone rubber in an amount of 3 to 20 mol%, not only the durability against radiation is improved but also the container is stored in a low-temperature environment, so that cold resistance is imparted. Can be. Methylphenyl vinyl silicone rubber having a phenyl group is exemplified.
気体透過性膜は、剛性率を０．５〜１０ＭＰａとすることで、外界の温度変化に対して追従性が増し、液状水などの容器内容物が漏出することを防ぐ。また、気体透過性膜の水素ガス透過性は、０．１ｃｃ・ｃｍ／（ｃｍ２・ａｔｍ・ｄａｙ）以上が望ましい。 By setting the rigidity of the gas permeable membrane to 0.5 to 10 MPa, the followability to a temperature change in the outside world increases, and leakage of the contents of the container such as liquid water is prevented. Further, the hydrogen gas permeability of the gas permeable membrane is desirably 0.1 cc · cm / (cm 2 · atm · day) or more.
気体透過性膜を保持する透気性多孔質担持体
ガスベントに用いる透気性多孔質担持体は、ステンレスなどの金属の多孔体、Ａｌ２Ｏ３、ＳｉＯ２、ＺｒＯ２、ＭｇＯ、ＴｉＯ２、Ｙ２Ｏなどを主成分とする多孔質セラミックで１ｎｍ〜１ｍｍの細孔径を有するもの、セメント硬化体、あるいは石こう硬化体などを用いることができる。
The gas-permeable porous carrier used for the gas vent is a metal porous material such as stainless steel, Al 2 O 3 , SiO 2 , ZrO 2 , MgO, TiO 2 , and Y 2. A porous ceramic containing O or the like as a main component and having a pore diameter of 1 nm to 1 mm, a hardened cement material, a hardened gypsum material, or the like can be used.
これら透気性多孔質担持体のガス透過性は、１００ｃｃ・ｃｍ／（ｃｍ２ ・ａｔｍ・ｄａｙ以上が好ましい。これにより、気体透過性膜によるガス透過を妨げず、効果的にガスを容器内から排出できる。さらに、透気性多孔質担持体および気体透過性膜のガス透過量の比である、（透気性多孔質担持体のガス透過量）／（体透過性膜のガス透過量）は水素ガス透気性多孔質担持体の拡散性から１０以上が望ましい。この比の値は、水素ガスベントを設計する上でも重要であり、例えば、体透過性膜のガス透過量は必要とする水素ガスの透過性から設定し、さらに、ガス透過量は通気率と厚さで決まることから、この比である１０を用いることで、透気性多孔質担持体のガス透過量が算出でき、用いる透気性多孔質担持体のガス透過性の実測値やカタログ値などから、透気性多孔質担持体の厚さの上限を決めることができる。 The gas permeability of these air-permeable porous supports is preferably 100 cc · cm / (cm 2 · atm · day or more. Thereby, gas permeation by the gas permeable membrane is not hindered, and gas can be effectively transferred from inside the container. Further, the ratio of the gas permeation amount of the gas-permeable porous carrier and the gas-permeable membrane, (gas permeation amount of the gas-permeable porous carrier) / (gas permeation amount of the body-permeable membrane) is hydrogen. From the viewpoint of the diffusivity of the gas-permeable porous carrier, it is desirable that the value be not less than 10. The value of this ratio is also important in designing a hydrogen gas vent. Since the gas permeability is determined by the gas permeability and the thickness, the gas permeability of the gas-permeable porous carrier can be calculated by using this ratio of 10. Measured value of gas permeability of porous carrier The upper limit of the thickness of the gas-permeable porous carrier can be determined from the values of the gas and the catalog.
また、破壊強度は４点曲げ試験で５ＭＰａ〜２００ＭＰａであると、機械的な外力を受けても損傷せずに担持体としてのガス透過性能が保持される。望ましくは２０〜１００ＭＰａとすると容器内のガス圧が上昇にも耐え、加工が容易である。透気性多孔質担持体の厚さは、１ｍｍ〜２ｃｍであり、厚さ０．１〜５ｍｍの薄い坦持体を積層し透気性多孔質担持体としたり、あるいは、薄い坦持体を積層した間に気体透過性膜を設置したりしても良い。 Further, when the breaking strength is 5 MPa to 200 MPa in a four-point bending test, gas permeation performance as a carrier is maintained without being damaged even when subjected to a mechanical external force. Desirably, when the pressure is set to 20 to 100 MPa, the gas pressure in the container can withstand an increase, and processing is easy. The thickness of the permeable porous carrier is 1 mm to 2 cm, and a thin carrier having a thickness of 0.1 to 5 mm is laminated to form a permeable porous carrier, or a thin carrier is laminated. A gas permeable membrane may be provided between them.
ガスベントを用いた容器の構成
図２にガスベントの容器への設置の一例を示す。ガスベント１０は、前記気体透過性膜１１と前記透気性多孔質担持体１２を有し、これらを保持する構造を持つものである。保持する方法は特に制限されないが、透気口１３および排気口１４を有するボックス１５に前記気体透過性膜１１と前記透気性多孔質担持体１２を保持させ、透気口１３は容器内に開放し、また排気口１４はチューブ１６等を用いて容器２０に配した容器外排気口２１に接続する構成とする。ガスベント１０は、放射性物質が格納される容器２０に突起物とならないように容器内に設置し、また、液状水の外界からの浸入を防ぐため、容器外排気口の位置より上に設置することが望ましい。
Configuration of Container Using Gas Vent FIG. 2 shows an example of installation of a gas vent in a container. The gas vent 10 has the gas permeable membrane 11 and the gas permeable porous carrier 12, and has a structure for holding them. The method of holding is not particularly limited, but the gas permeable membrane 11 and the gas permeable porous carrier 12 are held in a box 15 having a gas permeable port 13 and an exhaust port 14, and the gas permeable port 13 is opened in the container. In addition, the exhaust port 14 is configured to be connected to an external exhaust port 21 arranged in the container 20 using a tube 16 or the like. The gas vent 10 should be installed in the container 20 in which the radioactive material is stored so as not to become a protrusion, and should be installed above the position of the exhaust port outside the container in order to prevent ingress of liquid water from the outside. Is desirable.
容器外排気口２１に設ける孔の大きさは特に制限されないが、ガス拡散が早いことから開口面積が大きい必要は無く、容器体積にも依存するが２ｍｍ２〜１００ｃｍ２の開口面積とすることが良い。容器外排気口２１には、外部からの機械的作用に対する抵抗性を増す目的や、ゴミなどの容器内への飛来を防ぐ目的で、ガスの透気性を阻害しない金属メッシュあるいはパンチングメタルや、空隙率が５〜５０％程度の金属多孔体や多孔質セラミック又は不織布等を用いたフィルター２２を設置すると良い。ガスベントの排気口１４は、容器外排気口２１に直接接する構造とすれば、接続チューブは不要となる。 The size of the hole provided in the outside vent 21 is not particularly limited. However, since the gas diffusion is fast, the opening area does not need to be large. Depending on the container volume, the opening area may be 2 mm 2 to 100 cm 2. good. For the purpose of increasing resistance to mechanical action from the outside and preventing dust and the like from flying into the container, a metal mesh or a punching metal that does not hinder gas permeability, a void, It is preferable to install a filter 22 using a metal porous body, a porous ceramic, a nonwoven fabric, or the like having a ratio of about 5 to 50%. If the exhaust port 14 of the gas vent is configured to directly contact the exhaust port 21 outside the container, a connection tube is not required.
気体透過性膜１１の透気性多孔質担持体１２への設置は、例えば、硬化したシリコーンゴムを支持体に機械的あるいは接着剤等を用いて設置する、熱硬化型、UV硬化型、湿気硬化型のシリコーンゴムを支持体に塗布し、それぞれの硬化方法で硬化させても良い。気体透過性膜１１は透気性多孔質担持体１２の片面、両面、あるいは透気性多孔質担持体内に積層された構造とすることができる。このとき透気性多孔質担持体１２の両面への設置が可能であり、容器内および容器外からの液状水などを効果的に遮断できる。また、水蒸気の結露水を抜くドレーン口１７を設けることが好ましい。
気体透過性膜１１の膜厚は、総計で０．１〜５ｍｍが好ましく、より好ましくは総計０．１〜２ｍｍであり、０．１ｍｍ以下であると熱膨張などの影響で膜が破断する虞があり、５ｍｍ以上であるとガス透過が阻害され虞がある。
The gas permeable membrane 11 is installed on the permeable porous carrier 12 by, for example, installing a cured silicone rubber on a support mechanically or using an adhesive, a thermosetting type, a UV curing type, a moisture curing type. A mold silicone rubber may be applied to the support and cured by each curing method. The gas permeable membrane 11 may have a structure in which one or both surfaces of the permeable porous carrier 12 or a layer laminated in the permeable porous carrier. At this time, the air-permeable porous carrier 12 can be installed on both sides, and liquid water and the like from inside and outside the container can be effectively shut off. Further, it is preferable to provide a drain port 17 for draining dew condensation water vapor.
The total thickness of the gas-permeable membrane 11 is preferably 0.1 to 5 mm in total, and more preferably 0.1 to 2 mm in total. If it is 0.1 mm or less, the membrane may be broken due to thermal expansion or the like. If it is 5 mm or more, gas permeation may be hindered.
ガスベントを用いた容器の構成
図３にガスベントの容器への設置の別の一例を示す。ガスベント１０は、前記気体透過性膜１１と前記透気性多孔質担持体１２を容器の外壁の一部とするように円筒状ボックス１５内に設置した構成とする。フィルター２２と網目キャップ２１を一体化して円筒状ボックス１５と外壁の一部に付着させた。
Configuration of Container Using Gas Vent FIG. 3 shows another example of installation of the gas vent in the container. The gas vent 10 has a configuration in which the gas permeable membrane 11 and the gas permeable porous carrier 12 are installed in a cylindrical box 15 so as to be a part of an outer wall of a container. The filter 22 and the mesh cap 21 were integrated and attached to the cylindrical box 15 and a part of the outer wall.
放射性物質保管用容器内の閉鎖空間からの放射性物質の漏出や、外界からの雨水等の浸入を防ぎ、効率的に水素ガスおよび他の放射線分解生成ガスを逃がすガスベントにより、発生した水素ガスおよび酸素ガス等を容器内から逐次放出し、放射性物質の輸送、保管、貯蔵、埋設等の処分において、放射線によって発生するガスが容器内の閉鎖空間に発生することによる圧力変形や水素ガスによる爆発などを防ぐことができる。 Hydrogen gas and oxygen generated by gas vents that prevent leakage of radioactive materials from the enclosed space inside the container for storing radioactive materials and infiltration of rainwater etc. from the outside and efficiently release hydrogen gas and other radiolysis generated gases Discharge gas, etc. sequentially from inside the container, and in the disposal of radioactive materials such as transport, storage, storage, burying, etc. Can be prevented.
１０：ガスベント
１１：気体透過性膜
１２：透気性多孔質担持体
１３：透気口
１４：排気口
１５：ボックス
１６：チューブ
１７：ドレーン口
２０：容器
２１：容器外排気口
２２：フィルター
10: Gas vent 11: Gas permeable membrane 12: Air permeable porous carrier 13: Air permeable port 14: Exhaust port 15: Box 16: Tube 17: Drain port 20: Container 21: Exhaust port 22 outside the container: Filter
透気性多孔質担持体として、曲げ強さ８０ＭＰａのアルミナムライト混合焼結体（１３００℃）を厚さ０．９８ｃｍとし、３．８２ｍｍ×３．８２ｍｍに加工した。前記坦持体の両面に非晶質シリカを５〜１０％含有する湿気硬化型メチルビニルシリコーンを厚さ０．４３ｍｍ／片面となるよう塗布し、室内で硬化させ気体透過性膜とした。これを金属製のボックスの上部に、透気性多孔質担持体の周囲をエポキシ樹脂で接着させ、水素ガスベントの片面を大気開放の状態とした。 As a gas-permeable porous carrier, a mixed sintered body of aluminum mullite (1300 ° C.) having a bending strength of 80 MPa was processed to a thickness of 0.98 cm to 3.82 mm × 3.82 mm. A moisture-curable methylvinylsilicone containing 5 to 10% of amorphous silica was applied on both surfaces of the support so as to have a thickness of 0.43 mm / one surface, and was cured in a room to form a gas-permeable film. This was bonded to the top of a metal box with an epoxy resin around the permeable porous carrier, and one side of the hydrogen gas vent was opened to the atmosphere.
金属ボックスの透気性多孔質担持体を除く内部容積は３６．７ｃｃであり、ボックス底部にはチューブ取付け口を配し、ガスベントとした。なお、ガスベントの大気開放面を水に浸したが、液状水透過による質量増加は認められず、また、透過膜は水をはじいた状態であり、深さ１ｍの位置に水没させても液状水は透過しないことを確認した。 The internal volume of the metal box excluding the permeable porous carrier was 36.7 cc, and a tube mounting port was provided at the bottom of the box to provide a gas vent. In addition, the air vent surface of the gas vent was immersed in water, but no increase in mass due to liquid water permeation was observed, and the permeable membrane was in a state where water was repelled. Did not pass through.
このガスベントの取付け口に、純度９９．９％以上の水素ガス３８４ｃｃを入れた水素ガス不透過性アルミラミネートサンプルバックを接続し、水素ガスのベント量をサンプルバック中の水素ガス体積の減少量として継時的に測定し、図４に示した。ガスベント量、シリコーン厚さ、担持体を介して大気と接する透過膜の面積、およびアルミバック中の水素と、空気が充満していた金属容器容積から求まる水素分圧差から、ガス透過率を算出した結果、水素ガス透過率は０．８９５ｃｍ３／ｃｍ２・ｄａｙ・ａｔｍ となった。 A hydrogen gas-impermeable aluminum laminate sample bag containing 384 cc of hydrogen gas having a purity of 99.9% or more is connected to the mounting port of the gas vent, and the vent amount of the hydrogen gas is used as a reduction amount of the hydrogen gas volume in the sample bag. Measured over time and shown in FIG. The gas permeability was calculated from the gas vent amount, the thickness of the silicone, the area of the permeable membrane in contact with the atmosphere via the carrier, and the hydrogen partial pressure difference obtained from the hydrogen in the aluminum bag and the volume of the metal container filled with air. As a result, the hydrogen gas permeability was 0.895 cm 3 / cm 2 · day · atm.
ここで、２００リットルの密閉容器に入ったＣｓ１３７を含む放射性物質（放射線強度１０１０Ｂｑ／ｋｇ、体積１８０リットル、含水率２０％、比重２．０）にこのガスベントを取り付けた場合、保存容器中の水素ガス発生量は以下のように見積もられる。 Here, when this gas vent is attached to a radioactive substance containing Cs137 (radiation intensity: 10 10 Bq / kg, volume: 180 liters, water content: 20%, specific gravity: 2.0) contained in a 200-liter closed container, Is estimated as follows.
水素ガスの発生Ｇ値（吸収エネルギー１００ｅＶあたりに発生する生成物の個数）をＧ＝０．４５とすると、標準状態での１日当たりの水素ガス発生量Ｖは、
Ｖ＝１０１０×（２４×６０×６０）×０．２×Ｇ×１０４×２２４００／（６．０２×１０２３）＝１０ｃｍ３となる。
Assuming that the generated G value of hydrogen gas (the number of products generated per 100 eV of absorbed energy) is G = 0.45, the hydrogen gas generation amount V per day under the standard condition is
V = 10 10 × (24 × 60 × 60) × 0.2 × G × 10 4 × 22400 / (6.02 × 10 23 ) = 10 cm 3 .
容器の体積が２００Ｌで試料充填率が９０％なので，容器空隙内での発生ガスの分圧は５×１０−４気圧となる。よって水素ガスベントが無いとすれば，水素ガス分圧は８０日間で引火点である４ｖｏｌ％＝０．０４気圧に達することとなる。 Since the container volume is 200 L and the sample filling rate is 90%, the partial pressure of the generated gas in the container gap is 5 × 10 −4 atm. Therefore, assuming that there is no hydrogen gas vent, the hydrogen gas partial pressure reaches the flash point of 4 vol% = 0.04 atm in 80 days.
分圧が引火点以下になるためには、分圧０．０４気圧における水素ガスベントからの水素ガス漏出量が標準状態で１日当たり１０ｃｍ３以上であればよい。使用した水素ガスベントの水素ガス透過率は０．８９５ｃｍ３／（ｃｍ２・ａｔｍ・ｄａｙ）であるから、水素ガス透過膜の面積Ｓは、Ｓ＝１０／（０．８９５×０．０４）＝２７９ｃｍ２となる。よって半径１０ｃｍの透過膜を有するガスベントを設置すれば，放射線強度１０１０Ｂｑ／ｋｇの放射線強度を有する、含水率２０重量％、比重２の放射性廃棄物（比重２はセメント固化した廃棄物の標準的物性）１８０リットルを２００リットルの密閉容器（標準的ドラム缶の体積）に封入し保管しても、水素ガス濃度は爆発限界以下となり、ガスベントとして有効に機能することが確認された。
In order for the partial pressure to be lower than the flash point, the amount of hydrogen gas leaked from the hydrogen gas vent at a partial pressure of 0.04 atm should be 10 cm 3 or more per day under standard conditions. Since the hydrogen gas permeability of the used hydrogen gas vent is 0.895 cm 3 / (cm 2 · atm · day), the area S of the hydrogen gas permeable membrane is S = 10 / (0.895 × 0.04) = 279 cm 2 . Therefore, if a gas vent having a permeable membrane with a radius of 10 cm is installed, a radioactive waste having a radiation intensity of 10 10 Bq / kg, a water content of 20% by weight, and a specific gravity of 2 (specific gravity 2 is the standard of cement-solidified waste) Even when 180 liters were sealed and stored in a 200-liter closed container (volume of a standard drum), the hydrogen gas concentration was below the explosion limit, and it was confirmed that the hydrogen gas effectively functions as a gas vent.
Claims (5)
The hydrogen vent according to any one of claims 1 to 3, wherein the gas permeable membrane and the gas permeable porous carrier are installed in a cylindrical box so as to be a part of an outer wall of a container. Characteristic radioactive material storage container.
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