JP4621450B2 - Preparation method of dripping stock solution - Google Patents
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本発明は、滴下原液調製方法に関し、詳しくは、高温ガス炉用燃料核製造に使用される滴下原液調製方法に関する。 The present invention relates to a dripping stock solution preparation method, and more particularly to a dripping stock solution preparation method used for manufacturing a fuel core for a HTGR.
高温ガス炉は、高温ガス炉用燃料を投入する炉心構造を熱容量が大きく、高温健全性の良好な黒鉛で構成している。この高温ガス炉においては、冷却ガスとして高温下でも化学反応の起こらないヘリウムガス等の気体を用いることにより、安全性が高く、出口温度が高い場合でも冷却ガスを取り出すことが可能となっている。そのため、炉心において約９００℃くらいまで上昇しても、発電はもちろん水素製造や化学プラント等、幅広い分野での安全な熱利用を可能にしている。 In the high temperature gas reactor, the core structure into which the fuel for the high temperature gas reactor is charged is made of graphite having a large heat capacity and good high-temperature soundness. In this high-temperature gas furnace, by using a gas such as helium gas that does not cause a chemical reaction even at a high temperature as the cooling gas, the safety is high and the cooling gas can be taken out even when the outlet temperature is high. . For this reason, even if the temperature rises to about 900 ° C. in the core, it is possible to use heat safely in a wide range of fields such as hydrogen production and chemical plants as well as power generation.
一方、この高温ガス炉に投入される高温ガス炉用燃料は、一般的に、燃料核と、この燃料核の周囲に被覆された被覆層とを備えて成る。燃料核は、例えば、二酸化ウランをセラミックス状に焼結してなる直径約３５０〜６５０μｍの微小粒子である。 On the other hand, the fuel for a HTGR to be charged into the HTGR generally includes a fuel nucleus and a coating layer coated around the fuel nucleus. The fuel core is, for example, fine particles having a diameter of about 350 to 650 μm formed by sintering uranium dioxide into a ceramic form.
被覆層は、４層構造を有し、燃料核表面側より、第一層、第二層、第三層、および第四層とを備えて成る。被覆層を構成する被覆粒子の直径は、例えば、約５００〜１０００μｍである。 The coating layer has a four-layer structure, and includes a first layer, a second layer, a third layer, and a fourth layer from the fuel core surface side. The diameter of the coated particles constituting the coating layer is, for example, about 500 to 1000 μm.
第一層は、密度が約１ｇ/ｃｍ３の低密度熱分解炭素からなり、ガス状の核分裂生成物（以下、「ＦＰ」と略す場合がある。）のガス溜めとしての機能および燃料核のスウェリングを吸収するバッファとしての機能を有するものである。第二層は、密度が約１．８ｇ/ｃｍ３の高密度熱分解炭素からなり、ガス状ＦＰの保持する機能を有するものである。 The first layer is made of low-density pyrolytic carbon having a density of about 1 g / cm 3 , functions as a gas reservoir for gaseous fission products (hereinafter sometimes referred to as “FP”), and the fuel nucleus. It has a function as a buffer that absorbs swelling. The second layer is made of high-density pyrolytic carbon having a density of about 1.8 g / cm 3 and has a function of holding the gaseous FP.
第三層は、密度が約３．２ｇ/ｃｍ３の炭素珪素（以下、「SiC」と略す場合がある。）からなり、固体ＦＰの保持する機能を有するものであり、被覆層の主要な強度材である。第四層は、第二層と同様の密度が約１．８ｇ/ｃｍ３の高密度熱分解炭素からなり、ガス状ＦＰの保持する機能を有するとともに、第三層の保護層としての機能を有するものである。 The third layer is made of carbon silicon having a density of about 3.2 g / cm 3 (hereinafter sometimes abbreviated as “SiC”) and has a function to be held by the solid FP. It is a strength material. The fourth layer is made of high-density pyrolytic carbon having a density of about 1.8 g / cm 3 similar to that of the second layer, and has a function of holding the gaseous FP and also functions as a protective layer of the third layer. It is what you have.
以上のような高温ガス炉用燃料は、一般的に以下のような工程を経て製造される。まず、酸化ウランの粉末を硝酸に溶かし硝酸ウラニル原液とする。次に、この硝酸ウラニル原液に純水、増粘剤を添加し、攪拌して滴下原液とする。調製された滴下原液は、所定の温度に冷却され粘度を調製後、細径の滴下ノズルを用いてアンモニア水溶液に滴下される。 The HTGR fuel as described above is generally manufactured through the following steps. First, uranium oxide powder is dissolved in nitric acid to obtain a uranyl nitrate stock solution. Next, pure water and a thickener are added to this uranyl nitrate stock solution, and stirred to obtain a dropping stock solution. The prepared dripping stock solution is cooled to a predetermined temperature to adjust the viscosity, and then dropped into an aqueous ammonia solution using a small-diameter dropping nozzle.
このアンモニア水溶液に滴下された液滴は、アンモニア水溶液表面に達するまでの間に、アンモニアガスを吹きかけられる。このアンモニアガスによって、液滴表面をゲル化させるため、アンモニア水溶液表面到達時における変形を防止することができる。アンモニア水溶液中における硝酸ウラニルは、アンモニアと十分に反応し、重ウラン酸アンモニウム粒子（以下、「ADU粒子」と略す場合がある。）となる。 The droplets dropped on the aqueous ammonia solution are sprayed with ammonia gas before reaching the surface of the aqueous ammonia solution. Since the droplet surface is gelled by this ammonia gas, it is possible to prevent deformation when reaching the surface of the aqueous ammonia solution. Uranyl nitrate in the aqueous ammonia solution sufficiently reacts with ammonia to become ammonium heavy uranate particles (hereinafter sometimes abbreviated as “ADU particles”).
この重ウラン酸アンモニウム粒子は、乾燥された後、大気中で焙焼され、三酸化ウラン粒子となる。さらに、三酸化ウラン粒子は、還元・焼結されることにより、高密度のセラミック状の二酸化ウラン粒子となる。この二酸化ウラン粒子をふるい分け、すなわち分級して、所定の粒子径を有する燃料核粒子を得る。 The ammonium heavy uranate particles are dried and then baked in the air to form uranium trioxide particles. Further, the uranium trioxide particles are reduced and sintered to become high-density ceramic uranium dioxide particles. The uranium dioxide particles are screened, that is, classified to obtain fuel core particles having a predetermined particle size.
この燃料核粒子を流動床に装荷し、被覆層を形成するためのガスを熱分解して、燃料核粒子表面に被覆層を形成する。被覆層の第一層の低密度熱分解炭素の場合は、約１３００℃でアセチレンを熱分解する。また、被覆層の第二層、第四層の高密度熱分解炭素の場合は、約１４００℃でプロピレンを熱分解する。さらに、被覆層の第三層のSiCの場合は、約１５００℃でメチルトリクロロシランを熱分解する。 The fuel core particles are loaded onto the fluidized bed, and the gas for forming the coating layer is pyrolyzed to form the coating layer on the surface of the fuel core particles. In the case of the low-density pyrolytic carbon of the first layer of the coating layer, acetylene is pyrolyzed at about 1300 ° C. In the case of the high density pyrolytic carbon of the second layer and the fourth layer of the coating layer, propylene is pyrolyzed at about 1400 ° C. Further, in the case of SiC as the third layer of the coating layer, methyltrichlorosilane is thermally decomposed at about 1500 ° C.
被覆層が形成された後、高温ガス炉用燃料は、一般的な燃料コンパクトとして成型される。この燃料コンパクトは、高温ガス炉用燃料を黒鉛粉末、粘結剤等からなる黒鉛マトリックス材とともに、中空円筒形等にプレス成型またはモールド成型したのち、焼成して得られる(非特許文献１,２参照)。 After the coating layer is formed, the HTGR fuel is molded as a general fuel compact. This fuel compact is obtained by press-molding or molding a HTGR fuel into a hollow cylindrical shape together with a graphite matrix material made of graphite powder, a binder, etc., and then firing (Non-Patent Documents 1 and 2). reference).
しかしながら、前述の非特許文献１に記載の高温ガス炉用燃料の製造方法においては、硝酸ウラニル原液に純水、増粘剤を添加し、攪拌して重ウラン酸アンモニウム粒子するための滴下原液を得ているが、必要な詳細条件が全く記載されておらず、これのみでは、真球度が良好であり、内部組織も良好である重ウラン酸アンモニウム粒子を得ることができないという問題がある。 However, in the method for producing a HTGR fuel described in Non-Patent Document 1 above, a dripping stock solution for adding pure water and a thickener to a uranyl nitrate stock solution and stirring to form ammonium heavy uranate particles is used. Although necessary detailed conditions are not described at all, there is a problem in that it is impossible to obtain ammonium biuranate particles having good sphericity and good internal structure.
本発明は、このような従来の問題点を解消し、真球度が良好であり、内部組織も良好である重ウラン酸アンモニウム粒子を得ることができる滴下原液調製方法を提供することをその課題とする。 It is an object of the present invention to provide a dripping stock solution preparation method capable of solving such conventional problems and obtaining ammonium deuterated uranate particles having good sphericity and good internal structure. And
上記課題を解決するための手段として、
請求項１は、硝酸ウラニル溶液と水溶性環状エーテルとを混合して硝酸ウラニル含有溶液を調製し、水溶性ポリマーと水とを混合して水溶性ポリマー水溶液を調製し、前記水溶性ポリマー水溶液と水溶性環状エーテルとを混合して水溶性ポリマー溶液を調製し、前記硝酸ウラニル含有溶液と前記水溶性ポリマー溶液とを混合することを特徴とする滴下原液調製方法であり、
請求項２は、滴下原液全体中の前記水溶性ポリマー水溶液は、滴下原液全体の１５〜２０体積％であることを特徴とする前記請求項１記載の滴下原液調製方法であり、
請求項３は、滴下原液全体中の水溶性環状エーテルは、滴下原液全体の４０〜５０体積％であることを特徴とする前記請求項１または請求項２記載の滴下原液調製方法であり、
請求項４は、前記硝酸ウラニル含有溶液と前記水溶性ポリマー溶液とを攪拌しながら混合し、その後ガス抜き操作および純水添加操作をして体積調整を行うことを特徴とする前記請求項１〜請求項３のいずれか１項に記載の滴下原液調製方法であり、
請求項５は、前記水溶性ポリマー水溶液と前記水溶性環状エーテルとを混合して水溶性ポリマー溶液を調製する際には、それら混合物の温度を低くても５０℃になる前に、水溶性環状エーテルを添加することを特徴とする前記請求項１〜請求項４のいずれか１項に記載の滴下原液調製方法である。
As means for solving the above problems,
In claim 1, a uranyl nitrate solution and a water-soluble cyclic ether are mixed to prepare a uranyl nitrate-containing solution, and a water-soluble polymer and water are mixed to prepare a water-soluble polymer aqueous solution. A method for preparing a dripping stock solution characterized by mixing a water-soluble cyclic ether to prepare a water-soluble polymer solution, and mixing the uranyl nitrate-containing solution and the water-soluble polymer solution.
Claim 2 is the dropping stock solution preparation method according to claim 1, wherein the water-soluble polymer aqueous solution in the whole dropping stock solution is 15 to 20% by volume of the whole dropping stock solution,
Claim 3 is the dropping stock solution preparation method according to claim 1 or 2, wherein the water-soluble cyclic ether in the whole dropping stock solution is 40 to 50% by volume of the whole dropping stock solution.
Claim 4 is characterized in that the uranyl nitrate-containing solution and the water-soluble polymer solution are mixed while being stirred, and then the volume is adjusted by degassing operation and pure water addition operation. It is the dripping stock solution preparation method of any one of Claim 3,
According to claim 5, when preparing the water-soluble polymer solution by mixing the water-soluble polymer aqueous solution and the water-soluble cyclic ether, the water-soluble cyclic solution is used before the temperature of the mixture reaches 50 ° C. at the lowest. Ether is added, It is the dripping stock solution preparation method of any one of the said Claims 1-4 characterized by the above-mentioned.
本発明によると、硝酸ウラニル含有溶液、水溶性ポリマー水溶液、および水溶性ポリマー溶液を調製し、そして前記硝酸ウラニル含有溶液と前記水溶性ポリマー溶液とを混合することにより、滴下原液が不均一となることもないので、真球度が良好であり、内部組織も良好である重ウラン酸アンモニウム粒子を得ることができる。 According to the present invention, by preparing a uranyl nitrate-containing solution, a water-soluble polymer aqueous solution, and a water-soluble polymer solution, and mixing the uranyl nitrate-containing solution and the water-soluble polymer solution, the dropping stock solution becomes non-uniform. Therefore, ammonium biuranate particles having good sphericity and good internal structure can be obtained.
さらに、滴下原液全体中の前記水溶性ポリマー水溶液は、滴下原液全体の１５〜２０体積％であることにより、上記範囲内であると、水溶性ポリマー及び水溶性環状エーテルが均一に分散してなる滴下原液を調製することができる。 Furthermore, the water-soluble polymer aqueous solution in the whole dropping stock solution is 15 to 20% by volume of the whole dropping stock solution. A dripping stock solution can be prepared.
そして、滴下原液全体中の水溶性環状エーテルは、滴下原液全体の４０〜５０体積％であることにより、滴下原液から滴下される液滴中の硝酸ウラニルの含有量が過少にならず、かつ、適正な粘度を有する液滴が形成されて、最終的には真球度の高い燃料核を得るための液滴を調製することができる。 And the water-soluble cyclic ether in the whole dropping stock solution is 40-50% by volume of the whole dropping stock solution, so that the content of uranyl nitrate in the droplet dropped from the dropping stock solution is not too small, and A droplet having an appropriate viscosity is formed, and finally, a droplet for obtaining a highly spherical fuel nucleus can be prepared.
また、前記硝酸ウラニル含有溶液と前記水溶性ポリマー溶液とを攪拌しながら混合し、その後ガス抜き操作および純水添加操作をして体積調整を行うことにより、真球度が良好であり、内部組織も良好である重ウラン酸アンモニウム粒子を得ることができる。 Further, by mixing the uranyl nitrate-containing solution and the water-soluble polymer solution while stirring, and then adjusting the volume by degassing operation and pure water addition operation, the sphericity is good and the internal structure In addition, it is possible to obtain ammonium biuranate particles that are also excellent.
［滴下原液調製方法］
本発明の滴下原液調製方法は、図１に示されるように、硝酸ウラニル溶液と水溶性環状エーテルとを混合して硝酸ウラニル含有溶液を調製し、水溶性ポリマーと水とを混合して水溶性ポリマー水溶液を調製し、前記水溶性ポリマー水溶液と水溶性環状エーテルとを混合して水溶性ポリマー溶液を調製し、前記硝酸ウラニル含有溶液と前記水溶性ポリマー溶液とを混合することを基本とする。
[Drip stock solution preparation method]
As shown in FIG. 1, the dripping stock solution preparation method of the present invention prepares a uranyl nitrate-containing solution by mixing a uranyl nitrate solution and a water-soluble cyclic ether, and mixes a water-soluble polymer and water to form a water-soluble solution. Basically, a polymer aqueous solution is prepared, the water-soluble polymer aqueous solution and the water-soluble cyclic ether are mixed to prepare a water-soluble polymer solution, and the uranyl nitrate-containing solution and the water-soluble polymer solution are mixed.
［硝酸ウラニル含有溶液の調製］
まず、硝酸ウラニル溶液と水溶性環状エーテルとを混合して硝酸ウラニル含有溶液を調製する。
[Preparation of uranyl nitrate-containing solution]
First, a uranyl nitrate-containing solution is prepared by mixing a uranyl nitrate solution and a water-soluble cyclic ether.
［硝酸ウラニル溶液］
硝酸ウラニル溶液は、硝酸に酸化ウランを溶解することにより容易に形成することができる。前記硝酸は硝酸水溶液の形態で通常に使用される。硝酸水溶液の濃度としては、特に制限がなく、公知の濃度でよい。滴下原液におけるウラン含有量としては、通常、０．６〜０．９mol−Ｕ/Ｌであるのが好ましい。
[Uranyl nitrate solution]
A uranyl nitrate solution can be easily formed by dissolving uranium oxide in nitric acid. The nitric acid is usually used in the form of a nitric acid aqueous solution. There is no restriction | limiting in particular as a density | concentration of nitric acid aqueous solution, A well-known density | concentration may be sufficient. The uranium content in the dropping stock solution is usually preferably 0.6 to 0.9 mol-U / L.
ウラン含有量が前記範囲内にあると、水溶性環状エーテル及び水溶性ポリマーの共存とによって、真球度の高い重ウラン酸アンモニウム粒子を良好に再現性よく製造することができ、前記範囲を外れると、真球度の低い重ウラン酸アンモニウム粒子が生成することがある。 When the uranium content is within the above range, the coexistence of the water-soluble cyclic ether and the water-soluble polymer makes it possible to produce highly sphericity ammonium heavy uranate particles with good reproducibility. In this case, ammonium biuranate particles having low sphericity may be generated.
［水溶性環状エーテル］
前記水溶性環状エーテルとしては、テトラヒドロフルフリルアルコール、オキセタン、テトラヒドロフラン、及びジオキサン等の炭素数１〜４の水溶性環状エーテル、並びに２，５−テトラヒドロフランジメタノール等の、炭素数が１〜３のアルカノール基を前記環状エーテルに結合するアルカノール基含有水溶性環状エーテル等を挙げることができる。
[Water-soluble cyclic ether]
Examples of the water-soluble cyclic ether include C1-C4 water-soluble cyclic ethers such as tetrahydrofurfuryl alcohol, oxetane, tetrahydrofuran, and dioxane, and C1-C3 such as 2,5-tetrahydrofuran dimethanol. An alkanol group-containing water-soluble cyclic ether that binds an alkanol group to the cyclic ether can be exemplified.
これら各種の水溶性環状エーテルはその一種を単独で滴下原液中に含められていても、また、それらの二種以上が滴下原液中に含められていてもよい。この発明において好ましい環状エーテルとしては、テトラヒドロフラン、ジオキサン、テトラヒドロフルフリルアルコール及び２，５−テトラヒドロフランジメタノール等の水溶性環状エーテルを挙げることができる。 One of these various water-soluble cyclic ethers may be included alone in the dropping stock solution, or two or more thereof may be included in the dropping stock solution. Preferred cyclic ethers in this invention include water-soluble cyclic ethers such as tetrahydrofuran, dioxane, tetrahydrofurfuryl alcohol and 2,5-tetrahydrofuran dimethanol.
滴下原液全体中の水溶性環状エーテルは、通常、滴下原液全体の４０〜５０体積％であり、特に、４３〜４７体積％が好ましい。滴下原液全体中の水溶性環状エーテルが前記範囲内にあると、滴下原液から滴下される液滴中の硝酸ウラニルの含有量が過少にならず、かつ、適正な粘度を有する溶液が形成されて、最終的には真球度の高い燃料核を得るための液滴を調製することができる。 The water-soluble cyclic ether in the whole dropping stock solution is usually 40 to 50% by volume of the whole dropping stock solution, and particularly preferably 43 to 47% by volume. When the water-soluble cyclic ether in the entire dropping stock solution is within the above range, the content of uranyl nitrate in the droplets dropped from the dropping stock solution is not excessive, and a solution having an appropriate viscosity is formed. Finally, it is possible to prepare a droplet for obtaining a highly sphericity fuel nucleus.
前記硝酸ウラニル溶液と水溶性環状エーテルとの混合は、１５℃以下に冷却しながら行うことが好ましい。混合操作は、滴下原液を調製する貯留槽で行うのが好ましく、その貯留槽は、硝酸ウラニル溶液と水溶性環状エーテルとの攪拌を、約１５℃以下に保持しつつ実行可能な装置であればよい。そのため、次の滴下工程のため貯留槽は、１５℃以下に冷却可能な装置を備えることが好ましい。 The mixing of the uranyl nitrate solution and the water-soluble cyclic ether is preferably performed while cooling to 15 ° C. or lower. The mixing operation is preferably performed in a storage tank that prepares the dropping stock solution, and the storage tank is an apparatus that can perform the stirring of the uranyl nitrate solution and the water-soluble cyclic ether at about 15 ° C. or less. Good. Therefore, it is preferable that a storage tank is equipped with the apparatus which can be cooled to 15 degrees C or less for the next dripping process.
［水溶性ポリマー水溶液の調製］
次に、水溶性ポリマーと水とを混合して水溶性ポリマー水溶液を調製する。
[Preparation of water-soluble polymer aqueous solution]
Next, a water-soluble polymer and water are mixed to prepare a water-soluble polymer aqueous solution.
［水溶性ポリマー］
前記水溶性ポリマーとしては、ポリビニルアルコール、ポリアクリル酸ナトリウム及びポリエチレンオキシド等の合成ポリマー、カルボキシメチルセルロース、ヒドロキシエチルセルロース、メチルセルロース、及びエチルセルロース等のセルロース系ポリマー、可溶性でんぷん、及びカルボキシメチルでんぷん等のでんぷん系ポリマー、デキストリン、及びガラクタン等の水溶性天然高分子等を挙げることができる。
[Water-soluble polymer]
Examples of the water-soluble polymer include synthetic polymers such as polyvinyl alcohol, sodium polyacrylate and polyethylene oxide, cellulose polymers such as carboxymethyl cellulose, hydroxyethyl cellulose, methyl cellulose, and ethyl cellulose, starch-based polymers such as soluble starch, and carboxymethyl starch. And water-soluble natural polymers such as dextrin and galactan.
これら各種の水溶性ポリマーはその一種を単独で滴下原液中に含められていても、また、それらの二種以上が滴下原液中に含められていてもよい。これらの中でも、水溶性ポリマーとして前記合成ポリマーが好ましく、特にポリビニルアルコールが好ましい。 One of these various water-soluble polymers may be included alone in the dropping stock solution, or two or more of them may be included in the dropping stock solution. Among these, the synthetic polymer is preferable as the water-soluble polymer, and polyvinyl alcohol is particularly preferable.
前記水溶性ポリマーの滴下原液における含有量としては、通常、１０〜１５ｇ/Ｌが好ましい。前記水溶性ポリマーの滴下原液における含有量が前記範囲内にあると、滴下原液の粘度を良好に維持することができて真球度の高い重ウラン酸アンモニウム粒子を良好に再現性よく製造することができ、前記範囲を外れると、真球度の低い重ウラン酸アンモニウム粒子が生成することがある。 As content in the dripping stock solution of the said water-soluble polymer, 10-15 g / L is preferable normally. When the content of the water-soluble polymer in the dropping stock solution is within the above range, the viscosity of the dropping stock solution can be maintained satisfactorily and ammonium uranate particles having high sphericity can be produced with good reproducibility. If it is out of the range, ammonium deuterated uranate particles with low sphericity may be produced.
さらに、滴下原液全体中の前記水溶性ポリマー水溶液は、滴下原液全体の１５〜２０体積％であることが好ましい。滴下原液全体中の前記水溶性ポリマー水溶液が、上記範囲内であると、水溶性ポリマー及び水溶性環状エーテルが均一に分散してなる滴下原液を調製することができる。 Furthermore, it is preferable that the said water-soluble polymer aqueous solution in the whole dripping stock solution is 15-20 volume% of the whole dripping stock solution. When the water-soluble polymer aqueous solution in the entire dropping stock solution is within the above range, a dropping stock solution in which the water-soluble polymer and the water-soluble cyclic ether are uniformly dispersed can be prepared.
前記水溶性ポリマーの水溶性ポリマー水溶液における含有割合としては、通常、６〜９質量％が好ましく、特に、７〜８質量％が好ましい。前記水溶性ポリマーの水溶性ポリマー水溶液における含有割合が前記範囲内にあると、硝酸ウラニル含有滴下原液の粘度を、０．０４〜０．０６Ｐａ・ｓの範囲内に良好に維持することができ、さらに、水溶性ポリマー水溶液、例えば、ポリビニルアルコール水溶液（以下、ＰＶＡ水溶液と略する。）中にＰＶＡ等の水溶性ポリマーの溶解残渣が生じることがない。 As a content rate in the water-soluble polymer aqueous solution of the said water-soluble polymer, 6-9 mass% is preferable normally, and 7-8 mass% is especially preferable. When the content ratio of the water-soluble polymer in the water-soluble polymer aqueous solution is within the above range, the viscosity of the uranyl nitrate-containing dropping stock solution can be well maintained within the range of 0.04 to 0.06 Pa · s, Further, a water-soluble polymer aqueous solution, for example, a polyvinyl alcohol aqueous solution (hereinafter abbreviated as PVA aqueous solution) does not cause a residue of water-soluble polymer such as PVA.
前記水溶性ポリマーの水溶性ポリマー水溶液における含有割合が６質量％未満であると、最終的に得られる硝酸ウラニル含有滴下原液の粘度が小さくなり過ぎて硝酸ウラニル含有滴下原液の滴下に支障を来たし、９質量％を超えると水溶性ポリマー水溶液に水溶性ポリマーの溶解残渣を生じてしまう。 When the content ratio of the water-soluble polymer in the water-soluble polymer aqueous solution is less than 6% by mass, the viscosity of the finally obtained uranyl nitrate-containing dripping stock solution becomes too small, which hinders the dripping of the uranyl nitrate-containing dripping stock solution, When it exceeds 9 mass%, the melt | dissolution residue of a water-soluble polymer will be produced in water-soluble polymer aqueous solution.
前記混合に際しての加熱温度つまり水溶性ポリマーと水との混合物を加熱する温度は、低くとも７５℃つまり７５℃以上であるのが好ましい。前記加熱温度が７５℃以上であり、かつ上記の含有割合であれば、水溶性ポリマーの未溶解残渣がなく、均一な水溶性ポリマー水溶液を調製することができる。 The heating temperature at the time of mixing, that is, the temperature at which the mixture of the water-soluble polymer and water is heated is preferably at least 75 ° C., that is, 75 ° C. or higher. When the heating temperature is 75 ° C. or higher and the content is as described above, there is no undissolved residue of the water-soluble polymer, and a uniform water-soluble polymer aqueous solution can be prepared.
水溶性ポリマーと水との混合物は通常、攪拌される。攪拌時間は、通常、８０〜１００分であるのが好ましい。加熱しながら前記混合物を攪拌混合すると、水が蒸発して混合物中の水分の含有量が低下することがあるが、減少した水分量は、加熱されている混合物に適宜に水を添加することにより、補われる。 The mixture of water-soluble polymer and water is usually stirred. The stirring time is usually preferably 80 to 100 minutes. When the mixture is stirred and mixed while heating, water may evaporate and the water content in the mixture may decrease. The reduced water content can be reduced by adding water to the heated mixture as appropriate. To be compensated.
［水溶性ポリマー溶液の調製］
そして、前記水溶性ポリマー水溶液と水溶性環状エーテルとを混合して水溶性ポリマー溶液を調製する。
[Preparation of water-soluble polymer solution]
Then, the water-soluble polymer aqueous solution and the water-soluble cyclic ether are mixed to prepare a water-soluble polymer solution.
前記水溶性ポリマー水溶液と水溶性環状エーテルとの混合割合は、滴下原液を調製する際の前記水溶性ポリマー水溶液が滴下原液全体の１５〜２０体積％となる水溶性ポリマー水溶液の量に対し、前記水溶性環状エーテルの配合量が、滴下原液中の前記水溶性環状エーテルの全量に対して１〜５０体積％、特に３０〜４０体積％となるように、調整される。 The mixing ratio of the water-soluble polymer aqueous solution and the water-soluble cyclic ether is based on the amount of the water-soluble polymer aqueous solution in which the water-soluble polymer aqueous solution in preparing the dropping stock solution is 15 to 20% by volume of the whole dropping stock solution. The amount of the water-soluble cyclic ether is adjusted so as to be 1 to 50% by volume, particularly 30 to 40% by volume, based on the total amount of the water-soluble cyclic ether in the dropping stock solution.
前記水溶性環状エーテルの配合量が前記範囲内にあると、水溶性ポリマーが均一に分散した水溶性ポリマー溶液を得ることができる。 When the blending amount of the water-soluble cyclic ether is within the above range, a water-soluble polymer solution in which the water-soluble polymer is uniformly dispersed can be obtained.
また、前記水溶性環状エーテルと前記水溶性ポリマー水溶液とを混合する際には、それら混合物の温度を低くても５０℃、好ましくは、低くても６０℃になる前に、水溶性環状エーテルを添加するのが好ましい。 In addition, when the water-soluble cyclic ether and the aqueous water-soluble polymer solution are mixed, the water-soluble cyclic ether is added before the temperature of the mixture is at least 50 ° C., preferably at least 60 ° C. It is preferable to add.
前記水溶性ポリマー水溶液の温度が、５０℃未満になってから、水溶性環状エーテルを添加すると、水溶性ポリマー溶液中の水溶性ポリマーがゲル化してしまい、その結果、滴下原液を滴下するときに不都合を生じることがある。 When a water-soluble cyclic ether is added after the temperature of the water-soluble polymer aqueous solution becomes less than 50 ° C., the water-soluble polymer in the water-soluble polymer solution gels, and as a result, when the dropping stock solution is dropped. Inconvenience may occur.
［硝酸ウラニル含有溶液と水溶性ポリマー溶液との混合］
さらに、前記硝酸ウラニル含有溶液と前記水溶性ポリマー溶液とを混合する。
[Mixing of uranyl nitrate-containing solution and water-soluble polymer solution]
Further, the uranyl nitrate-containing solution and the water-soluble polymer solution are mixed.
また、前記硝酸ウラニル含有溶液と前記水溶性ポリマー溶液とを攪拌しながら混合し、その後ガス抜き操作および純水添加操作をして体積調整を行う。このようにすると、真球度が良好であり、内部組織も良好である重ウラン酸アンモニウム粒子を得ることができる。 Further, the uranyl nitrate-containing solution and the water-soluble polymer solution are mixed with stirring, and then the volume is adjusted by degassing operation and adding pure water. In this way, ammonium biuranate particles having good sphericity and good internal structure can be obtained.
なお、体積調製後の滴下原液のウラン濃度は、０．６〜０．９mol−Ｕ/Ｌであることが好ましい。 In addition, it is preferable that the uranium density | concentration of the dripping stock solution after volume preparation is 0.6-0.9 mol-U / L.
ここで、体積調整後の滴下原液のウラン濃度が、０．６mol/L未満であると、バッチ当たりのウラン量が少なくなる、または滴下時間が増大するという不利を生じることがある。 Here, when the uranium concentration of the dropping stock solution after volume adjustment is less than 0.6 mol / L, there may be a disadvantage that the amount of uranium per batch decreases or the dropping time increases.
体積調整後の滴下原液のウラン濃度が、０．９mol/Lを超えると、増粘剤等の添加量が相対的に少なくなり、真球度等の燃料核の品質に影響を与えるという不利を生じることがある。 If the uranium concentration in the dripping stock solution after volume adjustment exceeds 0.9 mol / L, the amount of thickener added will be relatively small, which will adversely affect the quality of the fuel core such as sphericity. May occur.
［重ウラン酸アンモニウム粒子の製造手順］
以上のような滴下原液調製方法で、調製された滴下原液は、所定の温度に冷却され粘度を調製後、細径の滴下ノズルを用いてアンモニア水溶液に滴下される。
[Procedure for producing ammonium heavy uranate particles]
The dripping stock solution prepared by the dripping stock solution preparation method as described above is cooled to a predetermined temperature and the viscosity is adjusted, and then dropped into an aqueous ammonia solution using a small-diameter dropping nozzle.
このアンモニア水溶液に滴下された液滴は、アンモニア水溶液表面に達するまでの間に、アンモニアガスを吹きかけられる。このアンモニアガスによって、液滴表面をゲル化させるため、アンモニア水溶液表面到達時における変形を防止することができる。アンモニア水溶液中における硝酸ウラニルは、アンモニアと十分に反応し、重ウラン酸アンモニウム粒子（ADU粒子）となる。 The droplets dropped on the aqueous ammonia solution are sprayed with ammonia gas before reaching the surface of the aqueous ammonia solution. Since the droplet surface is gelled by this ammonia gas, it is possible to prevent deformation when reaching the surface of the aqueous ammonia solution. Uranyl nitrate in the aqueous ammonia solution sufficiently reacts with ammonia to form ammonium heavy uranate particles (ADU particles).
［燃料核の製造手順］
この重ウラン酸アンモニウム粒子は、乾燥された後、大気中で焙焼され、三酸化ウラン粒子となる。さらに、三酸化ウラン粒子は、還元・焼結されることにより、高密度のセラミック状の二酸化ウラン粒子となる。この二酸化ウラン粒子をふるい分け、すなわち分級して、所定の粒子径を有する燃料核を得る。
[Procedure for fuel core production]
The ammonium heavy uranate particles are dried and then baked in the air to form uranium trioxide particles. Further, the uranium trioxide particles are reduced and sintered to become high-density ceramic uranium dioxide particles. The uranium dioxide particles are screened, that is, classified to obtain fuel nuclei having a predetermined particle size.
［高温ガス炉用燃料］
なお、この燃料核を使用してなる高温ガス炉用燃料は、以下のような構造を有している。高温ガス炉用燃料は、燃料核と、この燃料核の周囲に被覆された被覆層とを備えて成る。燃料核は、上記したようにして得られた二酸化ウラン粒子をセラミックス状に焼結してなる。
[Fuel for HTGR]
Note that the fuel for the HTGR using the fuel core has the following structure. The fuel for the HTGR comprises a fuel nucleus and a coating layer coated around the fuel nucleus. The fuel core is obtained by sintering the uranium dioxide particles obtained as described above into a ceramic form.
また、被覆層は、４層構造を有し、燃料核表面側より、第一層、第二層、第三層、および第四層とを備えて成る。被覆層を構成する被覆粒子の直径は、例えば、約５００〜１０００μｍである。 The coating layer has a four-layer structure, and includes a first layer, a second layer, a third layer, and a fourth layer from the fuel core surface side. The diameter of the coated particles constituting the coating layer is, for example, about 500 to 1000 μm.
第一層は、密度が約１ｇ/ｃｍ３の低密度熱分解炭素からなり、ガス状の核分裂生成物（以下、「ＦＰ」と略す場合がある。）のガス溜めとしての機能および燃料核のスウェリングを吸収するバッファとしての機能を有するものである。 The first layer is made of low-density pyrolytic carbon having a density of about 1 g / cm 3 , functions as a gas reservoir for gaseous fission products (hereinafter sometimes referred to as “FP”), and the fuel nucleus. It has a function as a buffer that absorbs swelling.
第二層は、密度が約１．８ｇ/ｃｍ３の高密度熱分解炭素からなり、ガス状ＦＰの保持する機能を有するものである。第三層は、密度が約３．２ｇ/ｃｍ３の炭素珪素からなり、固体ＦＰの保持する機能を有するものであり、被覆層の主要な強度材である。第四層は、第二層と同様の密度が約１．８ｇ/ｃｍ３の高密度熱分解炭素からなり、ガス状ＦＰの保持する機能を有するとともに、第三層の保護層としての機能を有するものである。 The second layer is made of high-density pyrolytic carbon having a density of about 1.8 g / cm 3 and has a function of holding the gaseous FP. The third layer is made of carbon silicon having a density of about 3.2 g / cm 3 , has a function to be held by the solid FP, and is a main strength material of the coating layer. The fourth layer is made of high-density pyrolytic carbon having a density of about 1.8 g / cm 3 similar to that of the second layer, and has a function of holding the gaseous FP and also functions as a protective layer of the third layer. It is what you have.
［高温ガス炉用燃料の製造手順］
高温ガス炉用燃料の製造手順は、以下のとおりである。まず、上記のようにして得られた二酸化ウラン粒子を流動床に装荷し、被覆層を形成するためのガスを熱分解して、高温ガス炉用燃料核微粒子としての二酸化ウラン粒子表面に被覆層を形成する。被覆層の第一層の低密度熱分解炭素の場合は、約１３００℃でアセチレンを熱分解する。
[Manufacturing procedure of fuel for HTGR]
The manufacturing procedure of the HTGR fuel is as follows. First, the uranium dioxide particles obtained as described above are loaded onto a fluidized bed, the gas for forming the coating layer is pyrolyzed, and the coating layer is formed on the surface of the uranium dioxide particles as fuel core fine particles for the high temperature gas reactor. Form. In the case of the low-density pyrolytic carbon of the first layer of the coating layer, acetylene is pyrolyzed at about 1300 ° C.
また、被覆層の第二層、第四層の高密度熱分解炭素の場合は、約１４００℃でプロピレンを熱分解する。さらに、被覆層の第三層の炭素珪素の場合は、約１５００〜１７００℃でメチルトリクロロシランを熱分解する。 In the case of the high density pyrolytic carbon of the second layer and the fourth layer of the coating layer, propylene is pyrolyzed at about 1400 ° C. Further, in the case of carbon silicon as the third layer of the coating layer, methyltrichlorosilane is thermally decomposed at about 1500 to 1700 ° C.
以上の被覆層が形成された後、高温ガス炉用燃料は、一般的な燃料コンパクトとして成型される。この燃料コンパクトは、高温ガス炉用燃料を黒鉛粉末、粘結剤等からなる黒鉛マトリックス材とともに、中空円筒形等にプレス成型またはモールド成型したのち、焼成して得られる。 After the above coating layer is formed, the HTGR fuel is molded as a general fuel compact. This fuel compact is obtained by press-molding or molding a fuel for a high-temperature gas reactor into a hollow cylinder or the like together with a graphite matrix material made of graphite powder, a binder, and the like, followed by firing.
以下、実施例および比較例を挙げて、本発明をより具体的に説明する。なお、本発明は実施例の内容に限定されるものではない。 Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. In addition, this invention is not limited to the content of the Example.
［実施例１］
前記実施形態において、以下の具体的条件で、滴下原液を調製した。
ＴＨＦＡの滴下原液全体の割合 ：４５体積％
ＰＶＡ溶液の滴下原液全体の割合 ：１８体積％
ＰＶＡ溶液中のポリビニルアルコール水溶液の濃度 ：７．３質量％
体積調製後の滴下原液のウラン濃度 ：０．７６mol/L
[Example 1]
In the said embodiment, the dripping stock solution was prepared on the following specific conditions.
Total ratio of THFA dropping stock solution: 45% by volume
Ratio of the whole undiluted solution of PVA solution: 18% by volume
Concentration of polyvinyl alcohol aqueous solution in PVA solution: 7.3 mass%
Uranium concentration in stock solution after volume adjustment: 0.76 mol / L
[評価方法および評価結果]
実施例で得られた滴下原液を使用して得られた重ウラン酸アンモニウム粒子（ADU粒子）の内部組織の評価を行った。
[Evaluation methods and results]
The internal structure of ammonium deuterated uranate particles (ADU particles) obtained using the dripping stock solution obtained in the examples was evaluated.
[ＡＤＵ粒子の内部組織の評価方法]
重ウラン酸アンモニウム粒子を研磨して、横断面を顕微鏡観察した。この観察にて、クラック等がなければ、内部組織が良好に形成されていると判断した。その裁断面を観察したところ、均一な内部組織が形成されていることを確認した（図２参照）。
[Method for evaluating internal structure of ADU particles]
The ammonium biuranate particles were polished and the cross section was observed with a microscope. In this observation, it was judged that the internal structure was well formed if there were no cracks or the like. When the cut surface was observed, it was confirmed that a uniform internal structure was formed (see FIG. 2).
また、得られた重ウラン酸アンモニウム粒子を、乾燥した後、大気中で焙焼し、三酸化ウラン粒子とした。さらに、三酸化ウラン粒子を、還元・焼結することにより、高密度のセラミック状の二酸化ウラン粒子とした。この二酸化ウラン粒子をふるい分け、すなわち分級して、所定の粒子径を有する燃料核（二酸化ウラン粒子）を得た。その後、得られた燃料核（二酸化ウラン粒子）を用いて、真球度の評価を行った。 The obtained ammonium heavy uranate particles were dried and then baked in the air to obtain uranium trioxide particles. Further, the uranium trioxide particles were reduced and sintered to obtain high density ceramic uranium dioxide particles. The uranium dioxide particles were screened, that is, classified to obtain fuel nuclei (uranium dioxide particles) having a predetermined particle size. Thereafter, the sphericity was evaluated using the obtained fuel nucleus (uranium dioxide particles).
[燃料核の真球度の評価方法]
ＰＳＡ法によって、燃料核（二酸化ウラン粒子）の真球度の評価を行った。ＰＳＡ法とは、図３に示されるように、フォトダイオード、スリット、光源を使用する方法である。光源から照射された光がスリットを通過し、フォトダイオードおよびスリットの間を動く燃料核（二酸化ウラン粒子）の陰影をフォトダイオードにより測定する。フォトダイオードにより測定された燃料核（二酸化ウラン粒子）の陰影により粒子の直径が求められる。以上の測定を多数回行うことにより、燃料核（二酸化ウラン粒子）のあらゆる方向の直径を測定し、燃料核（二酸化ウラン粒子）の真球度が求められる。
[Evaluation method of sphericity of fuel nucleus]
The sphericity of the fuel core (uranium dioxide particles) was evaluated by the PSA method. The PSA method is a method using a photodiode, a slit, and a light source as shown in FIG. The light emitted from the light source passes through the slit, and the shadow of the fuel nucleus (uranium dioxide particles) moving between the photodiode and the slit is measured by the photodiode. The particle diameter is determined by the shadow of the fuel core (uranium dioxide particles) measured by the photodiode. By performing the above measurement many times, the diameter of the fuel nucleus (uranium dioxide particles) in all directions is measured, and the sphericity of the fuel nucleus (uranium dioxide particles) is obtained.
以上のように、重ウラン酸アンモニウム粒子（ADU粒子）の内部組織の評価を行った結果、良好な重ウラン酸アンモニウム粒子（ADU粒子）が得られたことが分かった。また、燃料核の真球度の評価を行った結果、真球度が良好な燃料核が得られたことが分かった。 As described above, as a result of evaluating the internal structure of ammonium heavy uranate particles (ADU particles), it was found that good ammonium heavy uranate particles (ADU particles) were obtained. Moreover, as a result of evaluating the sphericity of the fuel nucleus, it was found that a fuel nucleus having a good sphericity was obtained.
Claims (5)
水溶性ポリマーと水とを混合して水溶性ポリマー水溶液を調製し、
前記水溶性ポリマー水溶液と水溶性環状エーテルとを混合して水溶性ポリマー溶液を調製し、
前記硝酸ウラニル含有溶液と前記水溶性ポリマー溶液とを混合する
ことを特徴とする滴下原液調製方法。 A uranyl nitrate-containing solution is prepared by mixing a uranyl nitrate solution and a water-soluble cyclic ether,
A water-soluble polymer aqueous solution is prepared by mixing a water-soluble polymer and water,
A water-soluble polymer solution is prepared by mixing the water-soluble polymer aqueous solution and the water-soluble cyclic ether,
A method for preparing a dropping stock solution, comprising mixing the uranyl nitrate-containing solution and the water-soluble polymer solution.
ことを特徴とする前記請求項１記載の滴下原液調製方法。 The method for preparing a dropping stock solution according to claim 1, wherein the water-soluble polymer aqueous solution in the whole dropping stock solution is 15 to 20% by volume of the whole dropping stock solution.
ことを特徴とする前記請求項１または請求項２記載の滴下原液調製方法。 The method for preparing a dropping stock solution according to claim 1 or 2, wherein the water-soluble cyclic ether in the whole dropping stock solution is 40 to 50% by volume of the whole dropping stock solution.
ことを特徴とする前記請求項１〜請求項３のいずれか１項に記載の滴下原液調製方法。 The said uranyl nitrate containing solution and the said water-soluble polymer solution are mixed while stirring, and then the volume is adjusted by degassing operation and pure water addition operation. The dripping stock solution preparation method of Claim 1.
ことを特徴とする前記請求項１〜請求項４のいずれか１項に記載の滴下原液調製方法。
When preparing a water-soluble polymer solution by mixing the water-soluble polymer aqueous solution and the water-soluble cyclic ether, the water-soluble cyclic ether should be added before the temperature of the mixture reaches 50 ° C. at the lowest. The dripping stock solution preparation method of any one of the said Claims 1-4 characterized by these.
Priority Applications (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2004230327A JP4621450B2 (en) | 2004-08-06 | 2004-08-06 | Preparation method of dripping stock solution |
| PCT/JP2004/019171 WO2005061387A1 (en) | 2003-12-24 | 2004-12-22 | Liquid stock for dropping, method for preparing liquid stock for dropping, method for preparing uranyl nitrate solution, and method for preparing polyvinyl alcohol solution |
| US10/583,906 US7628970B2 (en) | 2003-12-24 | 2004-12-22 | Method of preparing feedstock liquid, method of preparing uranyl nitrate solution, and method of preparing polyvinyl alcohol solution |
| EP04807528.7A EP1714943B1 (en) | 2003-12-24 | 2004-12-22 | Liquid stock for dropping, method for preparing liquid stock for dropping, method for preparing uranyl nitrate solution, and method for preparing polyvinyl alcohol solution |
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| JP2004230327A JP4621450B2 (en) | 2004-08-06 | 2004-08-06 | Preparation method of dripping stock solution |
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| JP2006045017A JP2006045017A (en) | 2006-02-16 |
| JP4621450B2 true JP4621450B2 (en) | 2011-01-26 |
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH05256973A (en) * | 1992-03-13 | 1993-10-08 | Nuclear Fuel Ind Ltd | Method and device for selecting solidified droplet |
| JPH05279043A (en) * | 1992-03-27 | 1993-10-26 | Nuclear Fuel Ind Ltd | Process and apparatus for production of ammonium diuranate particle |
| JPH0954187A (en) * | 1995-08-11 | 1997-02-25 | Nuclear Fuel Ind Ltd | Producing method for nuclear fuel pellet using uranium oxide particle as raw material |
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Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH05256973A (en) * | 1992-03-13 | 1993-10-08 | Nuclear Fuel Ind Ltd | Method and device for selecting solidified droplet |
| JPH05279043A (en) * | 1992-03-27 | 1993-10-26 | Nuclear Fuel Ind Ltd | Process and apparatus for production of ammonium diuranate particle |
| JPH0954187A (en) * | 1995-08-11 | 1997-02-25 | Nuclear Fuel Ind Ltd | Producing method for nuclear fuel pellet using uranium oxide particle as raw material |
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| JP2006045017A (en) | 2006-02-16 |
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