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Experimental investigation on buffer/backfill materials for radioactive waste repository downward facing sorption additivity of cesium, strontium and cobalt with different concentrations

Experimentelle Untersuchung von Verfüllungsmaterialien für ein Endlager für radioaktive Abfälle mit nach unten gerichteter Sorptionsadditivität von Cäsium, Strontium und Kobalt in unterschiedlichen Konzentrationen
C.-P. Lee, Y. Hu, Y. Sun, Y. Shi, N.-C. Tien, L.-Y. Chuang and W. Liu
From the journal Kerntechnik

Abstract

Buffer/backfill materials for radioactive waste disposal sites consist of pure bentonite or bentonite-rock mixtures. In this study, the batch test method was used to obtain the sorption characteristics of important radionuclides such as Cs, Sr and Co on buffer/backfill materials; i. e., mixing Wyoming MX-80 bentonite or local Taiwanese Zhi-Shin bentonite with possible host rock (argillite and granite) in different proportions (0∼100%). The distribution coefficients (Kd) for Cs, Sr and Co were obtained from the experiments. The distribution coefficient for the bentonite-rock mixtures were found, with more than 50% of mixing proportion of bentonite to argillite or granite, to have very similar values to that of pure bentonite. Furthermore, it was clearly found that the sorption of Cs, Sr and Co to bentonite-rock mixtures is decreased as ionic strength of the liquid phase is increased from 0.001M to 1M for NaCl solutions. According to the experimental results, in synthetic groundwater, it is quite convenient and helpful to assess the distribution coefficients (Kd) of Cs, Sr and Co for buffer/backfill materials using batch sorption experiments with bentonite-rock mixtures of fixed mixing proportions.

Abstract

Puffer-/Backfill-Materialien für Endlager für radioaktive Abfälle bestehen aus reinem Bentonit oder Bentonit-Gesteingemischen. In dieser Studie wurde die Batch-Test-Methode verwendet, um die Sorptionscharakteristik von wichtigen Radionukliden wie Cs, Sr und Co an Puffer-/Verfüllungsmaterialien zu bestimmen, d. h. das Mischen von Wyoming MX-80 Bentonit oder lokalem taiwanesischem Zhi-Shin Bentonit mit möglichem Wirtsgestein (Argillit und Granit) in verschiedenen Anteilen (0∼100%). Die Verteilungskoeffi-zienten (Kd) für Cs, Sr und Co wurden aus den Experimenten gewonnen. Es wurde festgestellt, dass die Verteilungskoeffizienten für die Bentonit-Gesteinsmischungen bei einem Mischungsverhältnis von mehr als 50% zwischen Bentonit und Argillit bzw. Granit sehr ähnliche Werte aufweisen wie die von reinem Bentonit. Darüber hinaus wurde festgestellt, dass die Sorption von Cs, Sr und Co an Bentonit-Gesteinsmischungen abnimmt, wenn die Ionenstärke der flüssigen Phase von 0,001 M auf 1 M für NaCl-Lösungen erhöht wird. In Übereinstimmung mit den experimentellen Ergebnissen ist es in synthetischem Grundwasser recht bequem und hilfreich, die Verteilungskoeffizienten (Kd) von Cs, Sr und Co für Puffer-/Verfüllungsmaterialien mit Hilfe von Batch-Sorptionsexperimenten mit Bentonit-Gesteinsmischungen fester Mischungsverhältnisse zu ermitteln.

Funding statement: This project was major supported by Doctor Initial Financial Project (No. 1410000434), East China University of Technology. The experimental and instrumental analysis of this study was supported by Department of Nuclear Environmental Science, China Institute for Radiation Protection (CIRP), Taiyuan, CHINA. The part financial the Ministry of Science and Technology (MOST, Taiwan R.O.C) and the Atomic Energy Council (AEC, Taiwan R.O.C) through a 2 years mutual fund program project under contract number 109-2623 -E-007 -006 -NU and 110-2623 -E-007 -004 -NU .

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Received: 2021-06-11
Published Online: 2021-10-23

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