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山口 敏男*; 吉田 亨次*; 町田 真一*; 服部 高典
Journal of Molecular Liquids, 365, p.120181_1 - 120181_10, 2022/11
被引用回数：1 パーセンタイル：16.81(Chemistry, Physical)3mol/kg NaCl重水溶液を0.1MPa/298K, 1GPa/298K, 1GPa/523K, 4GPa/523Kの温度圧力条件において中性子散乱測定した。また、得られたデータにEmpirical potential structure refinement法を適用し、対相関関数,配位数分布,角度分布(配向相関),空間密度関数(3次元構造)を抽出した。それらの結果から、イオンの溶媒和と会合、溶媒水構造の圧力と温度依存性を議論した。
ssbauer spectroscopic study熊谷 友多; 日下 良二; 中田 正美; 渡邉 雅之; 桐島 陽*; 秋山 大輔*; 佐藤 修彰*; 佐々木 隆之*
no journal, ,
Fuel debris generated in the Fukushima Daiichi NPS accident remains in the damaged reactors and substantial time and effort will be required until the retrieval of the debris. The debris is most likely contacted with water since the accident. The contact with water has possibility to induce degradation of the debris. According to the researches of uranium oxides and spent fuels, the uranium oxide matrix of fuels is oxidized and gradually dissolved as a consequence of water radiolysis. This oxidative dissolution process must be associated with surface alteration. In order to examine these possible degradation processes, we have conducted leaching experiments using simulated fuel debris combined with surface analysis by Raman spectroscopy and 
Fe Mssbauer spectroscopy in backscatter geometry. The simulated fuel debris used in this study was prepared from powders of UO
and stainless steel (1 : 1 in atomic ratio of U : Fe + Cr + Ni) by heat treatments. The samples were immersed in pure water or aqueous HO solution for up to 30 days. Aqueous HO solution was used to simulate the water radiolysis. After certain periods of immersion, the samples were analyzed by Raman spectroscopy and Mssbauer spectroscopy as well as chemical analysis of leached elements. The analysis of leached elements showed a selective dissolution of U from the samples. The U dissolution was facilitated by the reaction of HO. The reaction of HO also resulted in formation of solid uranyl peroxides, UO
4HO and UO2HO. The formation of uranyl peroxides on the surface was clearly confirmed by the Raman spectroscopy. The Fe Mssbauer spectroscopy, in contrast, showed insignificant change between the spectra before and after the immersion. The result of Fe Mssbauer spectroscopy suggests that phases containing Fe are stable toward water and HO.
-SUS system prepared by irradiation or tracer doping method佐々木 隆之*; 頓名 龍太郎*; 小林 大志*; 秋山 大輔*; 桐島 陽*; 佐藤 修彰*; 熊谷 友多; 日下 良二; 渡邉 雅之
no journal, ,
Under the high-temperature conditions in the reactor cores of Fukushima Daiichi Nuclear Power Station (FDNPS) during the accident, UO, zircaloy, and structural materials such as stainless steel are thought to be reacted. Since it will take a long time to retrieve the fuel debris, it is essential to accumulate basic knowledge for anticipating the secular change of chemical properties. In this study, to examine the dissolution behavior to water, the simulated alloy-based debris samples were prepared by two methods, and the dissolution behavior was analyzed; 1) Irradiation method: the simulated debris was irradiated by thermal neutrons to introduce FP, 2) Doping method: non-radioactive elements (cold FPs) simulating FPs were doped to the sample. Based on the concentration 
of the nuclide M in the sample, the leaching ratio 
was evaluated from the relationship of 
/ 
. The leaching ratio 
which was normalized by 
was also discussed. In samples of U
O
, U
Zr
O
and UCr(Fe)O, Cs leached preferentially to U immediately after immersion (
) in both the irradiation and the doping methods, and then the value decreased with time, suggesting U dissolution would be a rate-limiting reaction thereafter. Divalent Ba (FP) and Sr (cold FP) also leached preferentially to U, while trivalent Nd (FP) and Eu (cold FP) showed a harmonious dissolution with U. The value was in the order of pure water (PW) and 0.1 M NaClO (Na) 
artificial seawater (SW), and the effect of complex formation with anions in the solution on the order was observed. The 
values depended on the valence of ions; PW and Na 
SW for and 
, while PW Na and SWfor 
. The leaching behavior will be discussed in relation to the existing state in the solid phase and the chemical state in the aqueous phase.
桐島 陽*; 秋山 大輔*; 佐藤 修彰*; 佐々木 隆之*; 熊谷 友多; 日下 良二; 渡邉 雅之
no journal, ,
On March 11, 2011, a loss of coolant accident occurred at the Fukushima Daiichi Nuclear Power Station in Japan. The fuel debris was generated by the reaction of nuclear fuel with zircaloy cladding, control rods, and other structural materials at high temperature. For the safe retrieval and long-term storage of the fuel debris, the understanding of the chemical property of it is critically important. The debris are, however, highly radioactive and release a lot of heat, which prevents direct access and sampling of them so far. Therefore, to provide supportive information, we have initiated a basic chemical research by synthesizing and analyzing several types of simulated fuel debris in laboratories. The type of debris can be categorized into slightly damaged fuels, fuel-cladding debris (U-Zr-O system), fuel-alloy debris (U-SUS-O system), and molten core-concrete interaction (MCCI) debris. We have synthesized the simulated debris of U-Zr-O and MCCI systems, and reported the crystal structures and the leaching behavior of the actinides and fission products (FPs) in the debris. In this study, therefore, we focus on fuel debris generated from structure materials and fuels. We synthesized the simulated debris of UO-SUS system by heat treatment at up to 1700 
C, and then analyzed their chemical property by XRD, SEM-EDX, and laser Raman spectroscopy. After that, the simulated debris were immersed in water to observe ageing effect on their chemical structure and the leaching behavior of contained actinides and FPs. The result indicates that stable solid solution having UO structure and composite oxides like UFeO are formed by the high temperature heat treatment, which were chemically stable for the aging treatment in water. Also, the actinide leaching from the debris was remarkably suppressed in comparison with that from non-heat treated UO.
紀室 辰伍; 鈴木 慎也*; 舘 幸男
no journal, ,
As components of dissolved organic materials in the groundwater, humic acid (HA) is of significant importance in the environmental behavior of metals, since their mobility is influenced by the complexation with HA. Experimental data detailing the interaction of the tetravalent cations with HA is currently limited, mainly due to the assumption that the low solubility and strong hydrolysis behavior of tetravalent cations preclude the formation of complex under aqueous environmental condition. However the data is of importance for the safety assessment of geological disposal. In this study, capillary electrophoresis, coupled with inductively coupled plasma mass spectrometry (CE-ICPMS) was applied to the interaction of HAs with Zr (IV) to determine the apparent complexation constants. HA was isolated from deep groundwater at 250m depth of Horonobe, Hokkaido, Japan. As a result, the characteristic complexation property of groundwater HA was revealed by the comparative study. Additionally, the validity of equilibrium constants of groundwater HA, which were determined by other experimental methods in previous study was discussed.
木本 裕子*; 米山 海*; 佐藤 勇*; 松浦 治明*; 鈴木 恵理子; 三輪 周平
no journal, ,
コンクリートへのSr浸透挙動解明に資する知見を取得するために、SrCl及びSr(OH)水溶液を用いたコンクリートへの浸透実験を行い、XRF及びEXAFS分析によりコンクリート中のSrの濃度及び局所構造を調査した。XRF分析の結果、それぞれの水溶液から有意量のSrが浸透するが、浸透速度はSrCl水溶液の方が大きい可能性があることが分かった。また、EXAFS分析の結果、SrCl水溶液から浸透したSrは、Sr-ClではなくSr-Oに近い構造であることが分かった。
青柳 登
no journal, ,
Liquid-liquid phase transition is a significant phenomenon common across soft matters such as living cells, liquid crystals, colloidal particles, and, surprisingly, simple water. It sometimes results in intrinsic ordered structures when experiencing the phase separations in those materials; moreover, the liquid contains the condensed phase of multi-component complex fluids. The circumstances often let the non-equilibrium process being with two different ratios: a near-equilibrium reaction and a far-from-equilibrium reaction. Here, we report the real-time observation of the crystal growth and simultaneous nanocrystal aggregation that proceeds from ceric ammonium nitrate (CAN) toward nanoparticles of cerium dioxide in liquid water. Being exposed to strong acid, they become two or three ranges of size, which are different. Utilizing small-angle X- ray scattering (SAXS) for the bulk solutions and peculiar images taken by transmissive electron microscopy (TEM) compares the in-situ nature of the condensed fluids. Our results verified the formation of the hierarchically-assembled structure in solutions as a quasi-ceria colloid-comprised of both of the primary core clusters with 1-3 nm size and the secondary 20-30 nm colloids, in which they are patterning spherical aggregates and flocculation-agglomeration. The dissipation structure and the corresponding fluctuation might play a vital role in controlling this aggregation in order. The present observation expounds on the geometrical ensemble of polyoxometalates in the liquid state. The more massive assembly structure in a complex fluid is of cardinal significance in exploring the potential development of the nanoceria architectures. Our model case using nanoparticle and complex fluid is only one instance of many, regulating two different reactions under the principle of live-and-let-live across non-equilibria.
永石 隆二; 桑野 涼*; 伊藤 辰也
no journal, ,
福島第一原子力発電所(1F)ALPS凝集沈殿系の炭酸塩スラリー廃棄物で起きた溢水事象は、低粘性である水等の流体と異なり、高粘性であるスラリーが放射線分解で生成した水素(H)を保持したことに起因する。しかし、その保持特性(メカニズム)及びその放射線効果は、安全に長期保管する上で重要であるにも関わらず、微視的によく分かっていない。そこで本研究では、模擬スラリーの放射線(EB, 
)照射前後の物性や粘度特性から、スラリーのH保持特性に及ぼす放射線効果を調べた。スラリーの高粘性は懸濁物(SS)粒子中の水酸化マグネシウムMg(OH)の親水性(Mg(OH)分子間の水分子の共有)によって発現しており、Mg(OH)分子には1分子以上の水分子が結合していることが評価された。そして、照射実験では、H保持を抑制するSS粒子の破壊・細分化や不可逆な粘性の低下が観測された。
伊部 淳哉*; 麻生 めぐみ*; 高畠 容子; 渡部 創; 渡部 雅之; 松浦 治明*
no journal, ,
乾式再処理により発生した試験廃塩は、ウランやプルトニウムを含むこと、空気中の水分を吸収しやすく、機器や配管を腐食させることから、安定して保管・処分するためには、適切な処理が必要である。本研究では、酸素供与体として酸化物を添加し、沈殿物として塩からウランを分離する。次に減圧蒸留により浴構成元素を蒸発分離させる2段階のプロセスを検討している。1段階目の沈殿分離プロセスについて、沈殿剤を酸化リチウム、ウランの代替物質としてセリウムを使用した。2段階目の蒸発分離プロセスについて第2段階の蒸発分離工程では、蒸留装置を組み立て、その動作を確認した。次に蒸留後のセリウムの有無の確認及び蒸発分離の最適な条件の探索を行った。酸化物の添加量が多いほど沈殿量は増加し、セリウムの回収率はオキシクロライドの浴塩への溶解度に依存することがわかった。沈殿物はオキシクロライドと似たEXAFS振動、X線回折パターンであるためオキシクロライドが生成されたと推察できる。
松浦 治明*; 麻生 大貴*; 豊崎 綾香*; 浅沼 徳子*; 高畠 容子; 星野 貴紀; 渡部 創; 渡部 雅之
no journal, ,
Recovery of uranium from the waste solution is one of the important treatments of them. Various kinds of zeolites were selected for the separation of uranium and zirconium, and influence of chemical form of uranium and zirconium in zeolite on adsorption behavior were evaluated to find out an optimal condition for the effective U/Zr separation. Zeolites and zirconium nitrate solutions were shaken. Local structure of zirconium and uranium in adsorbed zeolites were evaluated by extended X-ray absorption fine structure using K and L3 absorption edge at BL27B, PF, KEK, respectively. By the comparison between distribution coefficients of zirconium and uranium, Kd, onto 13X and LZY type zeolites. 13X must be decomposed by solution with larger pH condition. Difference between local structures of zirconium and uranium in 13X was wider than that in LZY, therefore, this fact also supported above discussion. Thus, selective uranium adsorption can be achieved at this condition using LZY zeolite.
渡辺 茂樹*; 近藤 浩夫*; 江夏 昌志*; 高井 俊秀; 大久保 成彰; 古川 智弘; 石岡 典子*
no journal, ,
線内用療法用の有望な線源のひとつとしてアスタチン211が期待されている。アスタチン211は
Bi(alpha, 2n)
At反応により生成される。複数の病院に提供可能なGBqオーダーの核種製造には、大電流照射が必要であるが、標的となるビスマスの融点が低く、低電流照射でも標的が溶融してしまうため、大電流化が困難であった。そこで、高電流化を達成する方策として、高速炉や核融合炉の液体金属利用技術を活用した液体標的システムを考案し、実現可能性を確認するため、試作機を製作して実照射試験を実施した。本照射試験により生成されたアスタチン211量は367MBqと推定されるが、これは同条件下で従来の固体標的で生成されるアスタチン量と同等であった。
奥村 雅彦; 小林 恵太; 中村 博樹; 山口 瑛子; 板倉 充洋; 町田 昌彦
no journal, ,
機械学習分子動力学法は、密度汎関数法等の量子力学計算の結果を人工ニューラルネットワーク等で学習し、低い計算コストで量子力学計算並みの高精度シミュレーションを実施することが可能な手法である。本手法は複雑な物質、具体的には、多原子種からなる物質や複雑な構造を持つ物質には適用が難しいとされていた。しかし、我々は、機械学習分子動力学法のハイパーパラメーターを適切に与えることによって、固液界面を含むセメントの模擬物質や複雑な構造を持つ粘土鉱物の機械学習シミュレーションに成功した。本発表では、得られた機械学習ポテンシャルの性能や、機械学習分子動力学法で初めて計算が可能になった高精度な長時間シミュレーションが必要な物理量など、シミュレーション結果の詳細を報告する。
