Book/Report

FZJ-2016-05848

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Immobilization of MAW in Alkali-Activated Aluminosilicate Binders (Geopolymers)

Khalil, M. Y. ; Merz, E.FZJ*

1992
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag Jülich

Please use a persistent id in citations: http://hdl.handle.net/2128/12684

Report No.: Juel-2615

Abstract: Intermediate-level waste is immobilized in a monolithic solid of low dispersibility. Portland cement, bitumen, and organic polymers are used by many waste conditioning plants to achieve that purpose. However, each has some drawbacks that cause concern, and requires improvements or even the switch to a different better solidifying agent. Alkali-activated aluminosilicate binders, known as geopolymers, are investigated in this work for possible application in intermediate-level waste solidification. Samples were preparedfrom commercial geopolymer (TROLIT), loaded with 10 wt.% or 15 wt.%, dry simulated ILW. Quinary brine or water were used as leachants. Samples were soaked for more than six months and the fraction of Sr, Cs, and Mo leached was measured with time. Some samples were loaded with ILW plus NH$_{4}$TcO$_{4}$, ILW plus UO$_{2}$(NO$_{3}$)$_{2}$, or U$_{3}$O$_{8}$ for comparison. Control samples were made of high alumina cement with sodium-silicate hardener (cementglass). Results show that strontium is reasonably immobilized. Its concentrations in water were below detection limit. In Q-brine, 2-7 wt.% was leached in 6 months. Cesium was leached more rapidly than strontium. Leached fractions were 1-11 wt.% and 14-28 wt.% in water and Q-brine, respectively, depending on the composition. Retention of high valence ions, such as Mo$^{6+}$, Tc$^{7+}$, and U$^{6+}$, was poor. 20-40 wt.% of the Mo was leached in water, and 4-18 wt.% was leached in Q-brine. Technetium (starting as NH$_{4}$TcO$_{4}$) was almost all in the leachant (water or Q-brine) in about one month . From solidified UO$_{2}$(NO$_{3}$)$_{2}$ plus ILW, 36 wt.% was leached in water. The results for Sr, and Cs are better than those published for ordinarypPortland cement. However, the values obtained for technetium and uranium are unfavorable. Tolerance of solidified matrix to water was quite adequate. Samples maintained their shape, dimensions, and strength to the end of the experiments. On the contrary, tolerance of most compositions to Q-brine was poor. Samples were sometimes cracked between one and four weeks. Some compositions experienced no changes through the experimental duration. In comparison, cement-glass gave better results under the same conditions. Concentrations of Mo, and Sr were below detection levels in all cases. Cs was also not detectable in Q-brine. Only 4-6 wt.% of cesium was leached into water. In addition, tolerance to both water and Q-brine was quite good.

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Contributing Institute(s):

1. Publikationen vor 2000 (PRE-2000)

Research Program(s):

1. 899 - ohne Topic (POF3-899) (POF3-899)

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