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首页> 外文期刊>Environmental Science & Technology >Uptake of Np(IV) by C-S-H Phases and Cement Paste:An EXAFS Study
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Uptake of Np(IV) by C-S-H Phases and Cement Paste:An EXAFS Study

机译：C-S-H相和水泥浆对Np（IV）的吸收：EXAFS研究

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摘要

Nuclear waste disposal concepts developed worldwide foresee the use of cementitious materials for the immobilization of long-lived intermediate level waste (ILW). This waste form may contain significant amounts of neptunium-237, which is expected to be present as Np(IV) under the reducing conditions encountered after the closure of the repository. Predicting the release of Np(IV) from the cementitious near field of an ILW repository requires a sufficiently detailed understanding of its interaction with the main sorbing components of hardened cement paste (HCP). In this study, the uptake of Np(IV) by calcium silicate hydrates (C-S-H) and HCP has been investigated using extended X-ray absorption fine structure (EXAFS) spectroscopy. The EXAFS studies on Np(IV)-doped C-S-H and HCP samples reveal that Np(IV) is predominantly incorporated in the structure of C-S-H phases having different Ca:Si ratios. The two main species identified correspond to Np(IV) in C-S-H with a Ca:Si mol ratio of 1.65 as in fresh cement and with a Ca:Si mol ratio of 0.75 as in highly degraded cement. The local structure of Np(IV) changes with the Ca:Si mol ratio and does not depend on pH. Furthermore, Np(IV) shows the same coordination environment in C-S-H and HCP samples. This study shows that C-S-H phases are responsible for the Np(IV) uptake by cementitious materials and further that incorporation in the interlayer of the C-S-H structure is the dominant uptake mechanism.
机译：世界范围内发展起来的核废料处理概念预见到将使用水泥材料来固定长寿命中级废料（ILW）。这种废物形式可能包含大量的-237，在储存库关闭后所遇到的还原条件下，预计会以Np（IV）的形式存在。预测Np（IV）从ILW储存库胶结性近场中的释放需要充分了解Np（IV）与硬化水泥浆（HCP）的主要吸附组分之间的相互作用。在这项研究中，已使用扩展X射线吸收精细结构（EXAFS）光谱研究了水合硅酸钙（C-S-H）和HCP对Np（IV）的吸收。对Np（IV）掺杂的C-S-H和HCP样品的EXAFS研究表明，Np（IV）主要掺入具有不同Ca：Si比的C-S-H相的结构中。所确定的两个主要种类对应于C-S-H中的Np（IV），如新鲜水泥中的Ca：Si摩尔比为1.65，而如高度降解的水泥中的Ca：Si摩尔比为0.75。 Np（IV）的局部结构随Ca：Si摩尔比而变化，并且不依赖于pH。此外，Np（IV）在C-S-H和HCP样品中显示出相同的配位环境。这项研究表明C-S-H相是胶结材料对Np（IV）吸收的原因，此外，掺入C-S-H结构的中间层是主要的吸收机理。

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  • 来源
    《Environmental Science & Technology》 |2011年第20期|p.8765-8771|共7页
  • 作者

    Xavier Gaona; Rainer Dahn; Jan Tits; Andreas C. Scheinost; Erich Wieland;

  • 作者单位

    Laboratory for Waste Management, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland Institut fiir Nukleare Entsorgung, Karlsruhe Institute of Technology, P.O. Box 3640, D-76021 Karlsruhe, Germany;

    Laboratory for Waste Management, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland;

    Laboratory for Waste Management, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland;

    Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiochemistry, D-01314 Dresden, Gennany Rossendorf Beamline (ROBL) at ESRF, F-38043 Grenoble, France;

    Laboratory for Waste Management, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);美国《生物学医学文摘》(MEDLINE);美国《化学文摘》(CA);
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