JP6560379B1 - Method for producing reclaimed granulated crushed stone from soil containing residues containing naturally occurring radioactive materials including thorium or uranium - Google Patents
Method for producing reclaimed granulated crushed stone from soil containing residues containing naturally occurring radioactive materials including thorium or uranium Download PDFInfo
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Abstract
【課題】自然起源放射性物質を含有する残渣・土壌から再利用可能な造粒再生砕石を製造する方法を提供する。【解決手段】本発明は、（ａ）自然起源放射性物質を含有する残渣を含む土壌の所定量を均一に混ざるように混合して原料を製造する工程と、（ｂ）自然起源放射性物質の放射能濃度が２０００Ｂｑ／ｋｇ未満の原料と略同量の所定の添加材とを混合して、放射能濃度が１０００Ｂｑ／ｋｇ未満の造粒前混合原料を製造する工程と、（ｃ）造粒前混合原料に、セメント、水、及び不溶化材を加えて造粒処理して、５ｍｍ以上の粒径を有する造粒物を製造する工程と、（ｄ）７０〜９０重量％のリサイクル・コンクリート（ＲＣ）４０に、１０〜３０重量％の造粒物を混合させて、放射能濃度が１００Ｂｑ／ｋｇ以下の造粒再生砕石を製造する工程と、を含む。【選択図】図１The present invention provides a method for producing a regenerated granulated crushed stone that can be reused from a residue or soil containing a naturally occurring radioactive substance. The present invention includes (a) a step of producing a raw material by uniformly mixing a predetermined amount of soil containing a residue containing a naturally occurring radioactive substance, and (b) radiation of the naturally occurring radioactive substance. A step of mixing a raw material having an active concentration of less than 2000 Bq / kg and a predetermined additive of substantially the same amount to produce a pre-granulated mixed raw material having a radioactivity concentration of less than 1000 Bq / kg, and (c) before granulation Adding a cement, water and an insolubilizing material to the mixed raw material and granulating the mixture to produce a granulated product having a particle size of 5 mm or more; (d) 70 to 90% by weight of recycled concrete (RC And 40) mixing a granulated product of 10 to 30% by weight to produce a granulated regenerated crushed stone having a radioactivity concentration of 100 Bq / kg or less. [Selection] Figure 1
Description
本発明は、トリウムやウラン等の自然起源放射性物質を含有する残渣・土壌の処理方法、より具体的には、製造施設等で発生するトリウム含有残渣、またはこれら残渣を含む土壌等から再利用可能な造粒再生砕石を製造する方法に関する。 The present invention is a method for treating residues and soil containing radioactive materials of natural origin such as thorium and uranium, more specifically, thorium-containing residues generated at manufacturing facilities, etc., or reusable from soils containing these residues, etc. The present invention relates to a method for producing a granulated recycled crushed stone.
過去において、例えば精製したトリウムを添加した各種製品（一例としてガラス製品（レンズ等））が製造されていた。その製造の際に出るトリウム含有残渣、及び製造施設の解体等に伴い発生したトリウム含有残渣を含むコンクリート塊や土壌等は、回収され製造施設の屋内外で保管されている。トリウムやウランは放射線を放出する放射性物質であるので、トリウム又はウランを含む原材料、製品等の安全管理が求められる。具体的に、非特許文献１は、トリウムやウランを含む原材料、製品等の安全確保に関するガイドライン（法令による規制ではない）を定めている。
In the past, for example, various products added with purified thorium (for example, glass products (lenses, etc.)) have been manufactured. Thorium-containing residues produced during the production and concrete lumps and soils containing thorium-containing residues generated during the dismantling of the manufacturing facility are collected and stored indoors and outdoors in the manufacturing facility. Since thorium and uranium are radioactive substances that emit radiation, safety management of raw materials and products containing thorium or uranium is required. Specifically, Non-Patent
したがって、トリウム、ウラン等の自然起源放射性物質を含む残渣や土壌等を保有している事業者は、そうしたガイドラインに従って適切な管理等をする必要がある。一方で、2011年の東日本大震災のような大規模な自然災害を想定した場合、放射能汚染被害を最小限に抑えるためには、保管物の放射能濃度を適切に評価し、再資源化等により保管量をできるだけ少なくした上で長期的な管理が必要となるものについては適切に保管、管理していくことが望まれる。 Therefore, businesses that have residues or soil containing radioactive materials of natural origin such as thorium and uranium need to be properly managed according to such guidelines. On the other hand, in the event of a large-scale natural disaster such as the 2011 Great East Japan Earthquake, in order to minimize the damage caused by radioactive contamination, the radioactive concentration of stored items will be evaluated appropriately and recycled, etc. Therefore, it is desirable to appropriately store and manage items that require long-term management while reducing the storage amount as much as possible.
しかし、トリウム、ウラン等の自然起源放射性物質を含む残渣や土壌等の処理については、現状確立された処理や再資源化の手法が無く、保管物の放射能特性評価を行うこともなく、各事業所の倉庫棟内に一時的に保管されている状態にある。そのうち、トリウム含有残渣を含む土壌等については、特にその量が多いことから、ドラム缶等に入れて保管する場合、膨大な数のドラム缶等を用意し、かつ広い保管場所を確保しなければならない。したがって、トリウム含有残渣を含む土壌等について、放射能濃度がガイドラインで提示される濃度を超えるものを除いて、土木資材として再生利用（再資源化）することができれば全体の保有量を削減でき、より適切な保管管理を行う上での効果が大きく、かつ資源の有効活用の面からも望ましい。 However, with regard to the treatment of residues and soil containing natural radioactive materials such as thorium and uranium, there is no currently established treatment or recycling method, and the radioactivity characteristics of stored items are not evaluated. It is temporarily stored in the warehouse building of the office. Among them, the soil containing thorium-containing residue is particularly large in quantity, and therefore, when storing it in a drum can etc., it is necessary to prepare a huge number of drum cans and to secure a wide storage place. Therefore, if the soil containing thorium-containing residue, etc., whose radioactivity concentration exceeds the concentration indicated in the guidelines, if it can be recycled (recycled) as civil engineering materials, the total holding amount can be reduced, It is highly effective for more appropriate storage management and is desirable from the viewpoint of effective use of resources.
一方で、本出願の発明者は、特許文献１において、造粒工程を含む一連の工程によって放射性廃棄物から放射能を低減した造粒再生砕石を得ることができることを提案している。
On the other hand, the inventor of the present application proposes in
本発明は、自然起源放射性物質を含有する残渣・土壌から再利用可能な造粒再生砕石を製造する方法を提供することを目的とする。 An object of this invention is to provide the method of manufacturing the granulated regenerated crushed stone which can be reused from the residue and soil containing a natural origin radioactive substance.
本発明は、自然起源放射性物質を含有する残渣を含む土壌から再利用可能な造粒再生砕石を製造する方法を提供する。その製造方法は、（ａ）自然起源放射性物質を含有する残渣を含む土壌の所定量を均一に混ざるように混合して原料を製造する工程と、（ｂ）自然起源放射性物質の放射能濃度が２０００Ｂｑ／ｋｇ未満の原料と略同量の所定の添加材とを混合して、放射能濃度が１０００Ｂｑ／ｋｇ未満の造粒前混合原料を製造する工程と、（ｃ）造粒前混合原料に、セメント、水、及び不溶化材を加えて造粒処理して、５ｍｍ以上の粒径を有する造粒物を製造する工程と、（ｄ）７０〜９０重量％のリサイクル・コンクリート（ＲＣ）４０に、１０〜３０重量％の造粒物を混合させて、放射能濃度が１００Ｂｑ／ｋｇ以下の造粒再生砕石を製造する工程と、を含む。造粒再生砕石は、造粒物による自己遮蔽効果、及び造粒物とＲＣ４０との混合による遮蔽効果により放射能濃度を低減させたことを特徴とする。 The present invention provides a method for producing regenerated granulated crushed stone from soil containing residues containing naturally occurring radioactive materials. The production method includes (a) a step of producing a raw material by uniformly mixing a predetermined amount of soil containing a residue containing a naturally occurring radioactive substance, and (b) a radioactive concentration of the naturally occurring radioactive substance. Mixing a raw material of less than 2000 Bq / kg with a predetermined amount of a predetermined additive to produce a pre-granulated mixed raw material having a radioactivity concentration of less than 1000 Bq / kg; and (c) a pre-granulated mixed raw material. Adding a cement, water, and an insolubilizing material to produce a granulated product having a particle size of 5 mm or more, and (d) 70-90% by weight of recycled concrete (RC) 40 And a step of mixing 10 to 30% by weight of the granulated product to produce a granulated regenerated crushed stone having a radioactivity concentration of 100 Bq / kg or less. The granulated reclaimed crushed stone is characterized in that the radioactivity concentration is reduced by the self-shielding effect by the granulated material and the shielding effect by mixing the granulated material and RC40.
本発明の一態様では、添加材は、砂、リサイクル・コンクリート（ＲＣ）４０の細粒成分、廃石膏、及びセメントのいずれか一つまたは複数を含むことができる。不溶化材は、硫酸第一鉄とキレート剤のいずれか一方または両方を含むことができる。セメントは高炉セメントＢ種を含むことができる。造粒処理によって製造される造粒物を少なくとも４日以上養生させる工程をさらに含むことができる。自然起源放射性物質は、トリウムとウランのいずれか一方または両方を含むことができる。 In one aspect of the present invention, the additive may include any one or more of sand, recycled concrete (RC) 40 fine grain components, waste gypsum, and cement. The insolubilizing material can contain one or both of ferrous sulfate and a chelating agent. The cement may include blast furnace cement type B. It may further include a step of curing the granulated product produced by the granulation treatment for at least 4 days. Naturally occurring radioactive material can include either or both of thorium and uranium.
図面を参照しながら本発明の実施の形態を説明する。以下の説明では、自然起源放射性物質（核種）としてトリウムを例にとり説明するが、ウラン等の他の核種の場合でも基本的に同様に本発明の方法を適用することが可能である。図１は、本発明の一実施形態の自然起源放射性物質を含有する残渣を含む土壌から再利用可能な造粒再生砕石を製造する方法の工程を示す図である。なお、以下の説明で言うトリウム含有残渣を含む土壌は、トリウム含有原料取扱い施設の製造・加工の際に出る各種の残渣、及びこれら残渣を含むコンクリートや土壌等の総称の意味として用いている。トリウムは、２３２Ｔｈ（以下、Ｔｈ２３２とも記す）を意味する。造粒再生砕石は、造粒物とリサイクルコンクリート（ＲＣ）との混合物を意味する。土壌は土と同じ意味（同義）で用いている。 Embodiments of the present invention will be described with reference to the drawings. In the following explanation, thorium will be described as an example of a naturally occurring radioactive substance (nuclide), but the method of the present invention can be basically applied to other nuclides such as uranium as well. FIG. 1 is a diagram illustrating the steps of a method for producing a regenerated granulated crushed stone that can be reused from soil containing a residue containing a naturally occurring radioactive substance according to an embodiment of the present invention. In addition, the soil containing the thorium containing residue said by the following description is used as the general meaning of the various residues which appear in the case of manufacture and processing of a thorium containing raw material handling facility, and concrete, soil, etc. containing these residues. Thorium means 232 Th (hereinafter also referred to as Th232). Granulated recycled crushed stone means a mixture of granulated material and recycled concrete (RC). Soil is used in the same meaning (synonymous) with soil.
図１の工程Ｓ１において、自然起源放射性物質（トリウム）を含有する残渣を含む土壌の所定量を均一に混ざるように混合して原料を製造する。混合に用いるトリウム含有残渣を含む土壌（以下、単に「土壌」とも呼ぶ）は、事業所の倉庫内等にドラム缶等の容器に充填、一時保管されているものを含む。これら土壌は、容器から取り出し、移動コンテナ、あるいは台車に乗せられ移動可能なホッパーに入れられる。 In step S1 of FIG. 1, a raw material is produced by mixing a predetermined amount of soil containing a residue containing a naturally occurring radioactive substance (thorium) so as to be uniformly mixed. Soil containing thorium-containing residues used for mixing (hereinafter also simply referred to as “soil”) includes those that are filled and temporarily stored in a container such as a drum can in a warehouse of an office. These soils are taken out of the container and placed in a movable container or a hopper that can be placed on a carriage.
移動コンテナや移動可能なホッパー内の土壌は、台秤によってその重量が測定される。所定重量（例えば５００ｋｇ等）の土壌が選択されてベルトコンベアに乗せられて混合機に移される。所定重量は、混合機のサイズ（容積）に応じて決められる。混合機は、回転ドラムタイプあるいは内部に回転する攪拌羽根を有するタイプを用いることができる。混合機内で土壌はドラム／攪拌羽根の回転と共に混合されて、トリウム含有残渣を含む土壌が均一に混合されて原料が製造（調製）される。トリウム含有残渣を含む土壌の均一化を図るのは、次工程のトリウムの放射能濃度測定において、その測定精度を高める、すなわち原料となる土壌における測定値のバラツキを小さくするためである。 The weight of the soil in the movable container or the movable hopper is measured by a platform scale. A predetermined weight (for example, 500 kg) of soil is selected, placed on a belt conveyor, and transferred to a mixer. The predetermined weight is determined according to the size (volume) of the mixer. As the mixer, a rotating drum type or a type having a stirring blade rotating inside can be used. In the mixer, the soil is mixed with the rotation of the drum / stirring blade, and the soil containing the thorium-containing residue is uniformly mixed to produce (prepare) the raw material. The reason why the soil containing the thorium-containing residue is made uniform is to increase the measurement accuracy in the measurement of the radioactive concentration of thorium in the next step, that is, to reduce the variation in the measured value in the soil as the raw material.
工程Ｓ２において、均一化された原料（混合物）のトリウムの放射能濃度の測定を行う。その測定は、例えば、ＮａＩ放射能検出装置を用いてトリウム系列の永続平衡状態としての２０８Ｔｌから放出される２．６１５ＭeＶのガンマ線により定量する。測定は、例えばバックグラウンド及び各測定位置（領域）について一定間隔をおいて複数回（目安３回）測定し、各測定値及びその平均値を記録することにより行うことができる。 In step S2, the radioactive concentration of thorium in the homogenized raw material (mixture) is measured. The measurement is quantified, for example, by 2.615 MeV gamma rays emitted from 208 Tl as a thorium series permanent equilibrium using a NaI radioactivity detector. The measurement can be performed, for example, by measuring a plurality of times (standard three times) at regular intervals with respect to the background and each measurement position (area), and recording each measurement value and its average value.
工程Ｓ３において、自然起源放射性物質（トリウム）の放射能濃度が２０００Ｂｑ／ｋｇ未満の原料と略同量の所定の添加材とを混合して、放射能濃度が１０００Ｂｑ／ｋｇ未満の造粒前混合原料を製造する。所定の添加材を混合物とほぼ同量混合するのは、次工程の造粒処理による造粒物の強度を高めるためであるが、併せて混合によって原料中トリウム放射能濃度の低減効果も得られる。なお、同量以上の添加材を加えてもよい。混合は、工程Ｓ１で用いた混合機によって添加材が均一に混ざるように行う。この２回目の混合により混合原料（トリウム含有残渣を含む土壌）の均一性をさらに高めることができる。添加材は、砂、リサイクル・コンクリート（ＲＣ）４０の細粒成分、廃石膏、及びセメントのいずれか一つまたは複数を含むことができる。 In step S3, a raw material with a radioactive concentration of a naturally occurring radioactive substance (thorium) less than 2000 Bq / kg is mixed with a predetermined amount of a predetermined additive to mix before granulation with a radioactive concentration of less than 1000 Bq / kg. Produce raw materials. The reason why the predetermined amount of the additive is mixed in substantially the same amount as that of the mixture is to increase the strength of the granulated product by the granulation process in the next step. . In addition, you may add the additive more than the same quantity. The mixing is performed so that the additive is uniformly mixed by the mixer used in step S1. By this second mixing, the uniformity of the mixed raw material (soil containing thorium-containing residue) can be further improved. The additive may include any one or more of sand, recycled concrete (RC) 40 fine-grained components, waste gypsum, and cement.
所定の添加材混合後の造粒前混合原料は、一時保管するために所定の袋または容器に入れて事業所内で保管される。所定の袋または容器としては、例えば円筒型のポリエステル製のフレコンバックを用いることができる。袋詰めされた造粒前混合原料は、工程Ｓ２の場合と同様な方法によりトリウムの放射能濃度を測定し、その放射能濃度が１０００Ｂｑ／ｋｇ未満であることを確認する。トリウムの放射能濃度が１０００Ｂｑ／ｋｇ未満でない場合は、混合機でさらに追加の混合を行い、その際に必要に応じて希釈効果を高めるために添加材あるいは副原料を追加して混合する。 The pre-granulated mixed raw material after mixing with a predetermined additive is stored in the office in a predetermined bag or container for temporary storage. As the predetermined bag or container, for example, a cylindrical polyester flexible container bag can be used. The mixed raw material before granulation is measured for the radioactive concentration of thorium by the same method as in step S2, and it is confirmed that the radioactive concentration is less than 1000 Bq / kg. If the radioactivity concentration of thorium is not less than 1000 Bq / kg, additional mixing is further performed with a mixer, and at that time, an additive or auxiliary material is added and mixed as necessary in order to increase the dilution effect.
トリウムの放射能濃度が２０００Ｂｑ／ｋｇ以上である土壌については、所定容積（例えば２００Ｌ）の保管容器に入れて事業所内あるいは他の指定場所において保管される。保管容器は、例えば長期間の保管を考慮して樹脂ライナー付きの鋼製ドラム缶を用いることができる。保管に際して、土壌が入った保管容器の重量、容器表面の線量等を測定し記録しておく。保管容器は建屋内の平坦な床の上に置かれる。その際に、地震等による揺れを吸収し位置ずれ（滑り）を最小に抑えるために、床と保管容器の間に樹脂製パレットを配置することができる。 About the soil whose radioactive concentration of thorium is 2000 Bq / kg or more, it puts in the storage container of predetermined volume (for example, 200L), and is stored in an office or another designated place. As the storage container, for example, a steel drum with a resin liner can be used in consideration of long-term storage. During storage, measure and record the weight of the storage container containing the soil and the dose on the surface of the container. Storage containers are placed on a flat floor in the building. At that time, a resin pallet can be arranged between the floor and the storage container in order to absorb a shake caused by an earthquake or the like and to minimize a displacement (slip).
工程Ｓ４において、トリウムの放射能濃度が１０００Ｂｑ／ｋｇ未満の造粒前混合物原料にセメント、水、及び不溶化材を加えて造粒処理して造粒物を製造する。造粒に用いセメントは、固化材として六価クロムやホウ素のような有害物質が溶出されることを防ぐ効果があり、例えば高炉セメントＢ種を含むことができる。不溶化材は、硫酸第一鉄、キレート剤等の中から選択された少なくとも１つを含むことができる。硫酸第一鉄は、添加するセメントに由来する六価クロムの溶出を防ぐ効果がある。キレート剤は、ホウ素を不溶化する効果がある。各不溶化材は、造粒後の造粒物からの溶出量が環境基準（「土壌汚染対策法施行規則」（平成14年12月26日付環境省令第29号）で定める基準を示す、以下同様）を下回るように、所定の量（割合）で添加される。所定の量（割合）は、一例として、セメント５〜１５ｗｔ％に対して、硫酸第一鉄、キレート剤が、順番に０．５〜１．０ｗｔ％、０．２〜１．０ｗｔ％である。 In step S4, cement, water, and an insolubilizing material are added to the pre-granulation mixture raw material having a thorium radioactivity concentration of less than 1000 Bq / kg to produce a granulated product. The cement used for granulation has the effect of preventing the elution of harmful substances such as hexavalent chromium and boron as a solidifying material, and can include, for example, blast furnace cement B type. The insolubilizing material can include at least one selected from ferrous sulfate, a chelating agent, and the like. Ferrous sulfate has the effect of preventing elution of hexavalent chromium derived from the cement to be added. The chelating agent has an effect of insolubilizing boron. For each insolubilized material, the amount of elution from the granulated product after granulation indicates the standard specified by the Environmental Standards ("Enforcement Regulations of the Soil Contamination Countermeasures Law" (Ministry of the Environment Ordinance No. 29 dated December 26, 2002)) ) In a predetermined amount (ratio) so as to be less than. As an example, the predetermined amount (ratio) is 0.5 to 1.0 wt% and 0.2 to 1.0 wt% in order of ferrous sulfate and chelating agent with respect to 5 to 15 wt% of cement. .
造粒処理は、所定の造粒機で行う。造粒物の粒度は、造粒機の攪拌羽根の回転速度や回転時間等に応じて変化し、回転時間（すなわち造粒時間）を長くすることにより粒度の大きな造粒物の割合を増やすことができる。ここでは、トリウムの放射能を閉じ込めるため、あるいは再資源材としての利用を考慮して、例えば５ｍｍ以上の粒径を有する造粒物を生成することが望ましい。工程Ｓ４の造粒は、種々の原料の再資源化を行うために設置された施設内の造粒設備を用いて実施することができる。 The granulation process is performed with a predetermined granulator. The particle size of the granulated product varies depending on the rotation speed and rotation time of the agitation blade of the granulator, and the proportion of the granulated product having a large particle size is increased by increasing the rotation time (ie granulation time). Can do. Here, in order to confine the radioactivity of thorium, or considering use as a recycling material, it is desirable to generate a granulated product having a particle size of, for example, 5 mm or more. The granulation in step S4 can be performed using granulation equipment in a facility installed to recycle various raw materials.
工程Ｓ５において、造粒工程Ｓ４で得られた造粒物を養生する。養生は造粒物の強度を改善する上で重要であり、また、造粒物のトリウムの放射能濃度をさらに低減する意味でも重要である。なお、養生期間は少なくとも４日以上で必要に応じて期間を決めることができる。 In step S5, the granulated product obtained in granulation step S4 is cured. Curing is important for improving the strength of the granulated product, and also important for further reducing the radioactive concentration of thorium in the granulated product. The curing period is at least 4 days and can be determined as necessary.
工程Ｓ６において、工程Ｓ５の養生後の造粒物をリサイクル・コンクリート（ＲＣ）４０と混合して、トリウムの放射能濃度が１００Ｂｑ／ｋｇ以下の造粒再生砕石を製造する。その際、トリウムの放射能濃度の低減を考慮して、７０〜９０重量％のＲＣ４０に、１０〜３０重量％の造粒物を混合させて造粒再生砕石を製造することが望ましい。なお、造粒再生砕石のトリウムの放射能濃度を１００Ｂｑ／ｋｇ以下とするのは、放射性防護の規制の対象から除外できるいわゆるクリアランス・レベル同等とすることにより、造粒再生砕石を再利用可能な資材として何ら制限無く使用するためである。 In step S6, the granulated product after curing in step S5 is mixed with recycled concrete (RC) 40 to produce a granulated reclaimed crushed stone having a thorium radioactivity concentration of 100 Bq / kg or less. In that case, considering the reduction of the radioactive concentration of thorium, it is desirable to produce granulated recycled crushed stone by mixing 10 to 30% by weight of granulated material with 70 to 90% by weight of RC40. In addition, the radioactive concentration of thorium in the granulated reclaimed crushed stone is set to 100 Bq / kg or less so that the granulated reclaimed crushed stone can be reused by making it equivalent to the so-called clearance level that can be excluded from the regulation of radioactive protection. This is because the material can be used without any limitation.
このトリウムの放射能濃度を１００Ｂｑ／ｋｇ以下の造粒再生砕石は、最大で１０００Ｂｑ／ｋｇ近くまであった造粒前混合原料が、工程Ｓ４の造粒、工程Ｓ５の養生、及び工程Ｓ６の造粒物とＲＣ４０との混合の各工程における放射能濃度低減の相乗効果によって、最大で約十分の一程度までその濃度を低減させることができる結果として得られるものである。その放射能濃度の代表的な低減効果の内訳は、本発明者が実験等で得た知見によれば、工程Ｓ４の造粒で約３０％、工程Ｓ５の養生で約１０％、工程Ｓ６の造粒物とＲＣ４０との混合工程で約６０％程度とすることができることが分かっている。なお、この各工程でのトリウムの放射能濃度の低減効果（％）は、混合される添加材（特にセメント）の量（重量割合）、造粒物のサイズ（粒径）、養生期間、造粒物とＲＣ４０との混合割合に応じて変化するが、これらを調整・制御することによりトリウムの放射能濃度を１００Ｂｑ／ｋｇ以下にすることができる。 The granulated regenerated crushed stone with a radioactive concentration of thorium of 100 Bq / kg or less is a mixture raw material before granulation which has been close to 1000 Bq / kg at the maximum, granulation in step S4, curing in step S5, and granulation in step S6. The synergistic effect of reducing the radioactivity concentration in each step of mixing the granule and RC40 results in that the concentration can be reduced to about one tenth at most. According to the knowledge obtained by the present inventors through experiments and the like, the breakdown of the typical reduction effect of the radioactivity concentration is about 30% in the granulation in step S4, about 10% in the curing in step S5, and in step S6. It has been found that about 60% can be achieved in the mixing step of the granulated product and RC40. In addition, the reduction effect (%) of the radioactive concentration of thorium in each step is the amount (weight percentage) of the additive (particularly cement) to be mixed, the size (particle size) of the granulated product, the curing period, Although it changes according to the mixing ratio of the granules and RC40, the radioactivity concentration of thorium can be reduced to 100 Bq / kg or less by adjusting and controlling these.
造粒後の放射能低減効果は、造粒物による放射線（Ｔｈ２３２からのγ線等、以下同様）の自己遮蔽効果によるもので、造粒再生砕石中の放射能濃度の低減効果は、ＲＣ４０との混合によるＴｈ２３２含有濃度の低減、及びＲＣ４０による遮蔽効果によると考えられる。また、造粒においては、セメント添加による放射能濃度の低減効果があると考えられる。 The effect of reducing the radioactivity after granulation is due to the self-shielding effect of the radiation (γ rays from Th232, etc.), and the effect of reducing the radioactivity concentration in the granulated recycled crushed stone is RC40 and This is considered to be due to a reduction in the concentration of Th232 by mixing the two, and a shielding effect by RC40. In granulation, it is considered that there is an effect of reducing the radioactivity concentration by adding cement.
ここで、自己遮蔽効果は以下のように説明できる。すなわち、造粒により一次粒子を５ｍｍ以上の造粒物とした場合、造粒物内では一次粒子が固着しており、高密度の塊状物質となる。この高密度の塊状物質となることで、Ｔｈ２３２からのγ線の自己吸収率が改善し、その効果で外部から測定した際の放射能濃度（外部に放出する放射線量）が低下した数値となると考えられる。同様に造粒物とＲＣ４０を混合した場合、造粒物と比較して大量のＲＣ４０が造粒物を取り囲む効果が顕在化し、放射能濃度（外部に放出する放射線量）が低減すると考えられる。ただし、Ｔｈ２３２から放出されるγ線はＣｓ１３７等から放出されるγ線と比較するとエネルギーが高く自己遮蔽効果は低下する。 Here, the self-shielding effect can be explained as follows. That is, when the primary particles are made into a granulated product having a diameter of 5 mm or more by granulation, the primary particles are fixed in the granulated product, resulting in a high-density massive substance. By becoming this high-density massive substance, the self-absorption rate of γ rays from Th232 is improved, and the radioactivity concentration (the amount of radiation emitted to the outside) when measured from the outside is reduced due to the effect. Conceivable. Similarly, when the granulated product and RC40 are mixed, it is considered that the effect that a large amount of RC40 surrounds the granulated product becomes apparent as compared with the granulated product, and the radioactivity concentration (the amount of radiation emitted to the outside) is reduced. However, the gamma rays emitted from Th232 have higher energy and lower the self-shielding effect than the gamma rays emitted from Cs137 and the like.
工程Ｓ７において、造粒物、造粒再生砕石の品質管理を行う。品質管理は、造粒物、造粒再生砕石が用途に合った仕様を満たしているかを検査／確認する。 In step S7, quality control of the granulated product and granulated reclaimed crushed stone is performed. In quality control, it is inspected / confirmed whether the granulated product and granulated recycled crushed stone meet the specifications suitable for the application.
図２は、本発明の製造方法で得られた造粒再生砕石をアスファルト舗装用の路盤材として利用する場合の模式図である。アスファルト舗装用の路盤材は、アスファルト舗装における、アスファルトを含む表層／基層１０の下に配置される路盤材２０を意味し、特に路盤材の下層路盤の材料を意味する。図２に示されるように、造粒再生砕石は、路盤材２０として、ＲＣ４０（２２）の間を埋めるように混合された造粒物２４を含んでいる。造粒物２４は、例えば、７０〜９０重量％のＲＣ４０（２２）に対して１０〜３０重量％の割合で混合されている。
FIG. 2 is a schematic view when the granulated regenerated crushed stone obtained by the production method of the present invention is used as a roadbed material for asphalt pavement. The roadbed material for asphalt pavement means the
本発明の実施形態について、図を参照しながら説明をした。しかし、本発明はこれらの実施形態に限られるものではない。本発明はその趣旨を逸脱しない範囲で当業者の知識に基づき種々なる改良、修正、変形を加えた態様で実施できるものである。 Embodiments of the present invention have been described with reference to the drawings. However, the present invention is not limited to these embodiments. The present invention can be implemented in variously modified, modified, and modified embodiments based on the knowledge of those skilled in the art without departing from the spirit of the present invention.
１０ アスファルトを含む表層／基層
２０ 路盤材（下層路盤材）
２２ ＲＣ４０
２４ 造粒物
10 Surface layer / base
22 RC40
24 Granulated material
Claims (5)
前記自然起源放射性物質を含有する残渣を含む土壌の所定量を均一に混ざるように混合して原料を製造する工程と、
前記自然起源放射性物質の放射能濃度が２０００Ｂｑ／ｋｇ未満の前記原料と略同量の所定の添加材とを混合して、前記放射能濃度が１０００Ｂｑ／ｋｇ未満の造粒前混合原料を製造する工程と、
前記造粒前混合原料に、セメント、水、及び不溶化材を加えて造粒処理して、５ｍｍ以上の粒径を有する造粒物を製造する工程と、
７０〜９０重量％のリサイクル・コンクリート（ＲＣ）４０に、１０〜３０重量％の前記造粒物を混合させて、前記放射能濃度が１００Ｂｑ／ｋｇ以下の造粒再生砕石を製造する工程と、を含み、
前記造粒再生砕石は、前記造粒物による自己遮蔽効果、及び前記造粒物と前記ＲＣ４０との混合により前記放射能濃度を低減させたことを特徴とする、方法。 A method for producing regenerated granulated crushed stone that can be reused from soil containing residues containing naturally occurring radioactive materials including thorium or uranium ,
A step of manufacturing the raw material by mixing such uniformly mixed with a predetermined amount of soil containing a residue containing the natural origin radioactive substance,
The raw material having a radioactive concentration of the naturally occurring radioactive substance is less than 2000 Bq / kg and a predetermined amount of a predetermined additive are mixed to produce a pre-granulation mixed raw material having a radioactive concentration of less than 1000 Bq / kg. Process,
A step of producing a granulated product having a particle diameter of 5 mm or more by adding cement, water, and an insolubilizing material to the pre-granulated mixed raw material and granulating it;
70 to 90 wt% recycled concrete (RC) 40 is mixed with 10 to 30 wt% of the granulated product to produce a granulated recycled crushed stone having a radioactivity concentration of 100 Bq / kg or less; Including
The granulated reclaimed crushed stone is characterized in that the radioactive concentration is reduced by the self-shielding effect by the granulated product and the mixing of the granulated product and the RC40.
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