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Solubility of Radionuclides in Fresh and Leached Cementitious Systems at 22°C and 50°C

Published online by Cambridge University Press:  10 February 2011

M. Ochs ,
D. Hager ,
S. Helfer  and
B. Lothenbach
M. Ochs
Affiliation:
BMG Engineering Ltd, Ifangstrasse 11, CH-8952 Zürich-Schlieren, Switzerland
D. Hager
Affiliation:
BMG Engineering Ltd, Ifangstrasse 11, CH-8952 Zürich-Schlieren, Switzerland
S. Helfer
Affiliation:
BMG Engineering Ltd, Ifangstrasse 11, CH-8952 Zürich-Schlieren, Switzerland
B. Lothenbach
Affiliation:
BMG Engineering Ltd, Ifangstrasse 11, CH-8952 Zürich-Schlieren, Switzerland
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Abstract

The solubility of Ni, Sn, Pb, Eu, and Sr was investigated at 22°C and 50°C in simulated cement porewaters corresponding to fresh cement (‘FPW’, pH 13.2) and cement leached of soluble alkalis, whose porewater chemistry is dominated by equilibrium with portlandite (‘APW’, pH 12.5). Solubility limits were approached from undersaturation, using Ni(OH)2(c), SnO2(c) (cassiterite), PbO(red), and Eu(OH)3(c) as solids. For Sr, no solubility experiments were carried out since the cement contains enough Sr to reach equilibrium with strontianite and celestite. Solubilities generally increase with increasing pH and temperature. The measured solubility of Pb ranges from about 4× 10−3 to 1×1O−2M and is within thermodynamically predicted values. The measured solubility of Ni is <O.5-1.3×10−7M in APW and about 3-4×10−7M in FPW, which is lower than predicted by most thermodynamic data. The measured solubility of Eu ranges from <6.6×10−10M in APW to 1.8-2.7×10−9M in FPW, which agrees well with thermodynamic calculations. The solubility of cassiterite is low, with dissolved Sn concentrations ranging from 3.5× 10−8M in APW to 3.3× 10−6M in FPW. Thermodynamic calculations predict much higher solubilities, presumably for less crystalline phases. However, oversaturation measurements in APW reproduced the solubility limits obtained by undersaturation within a factor of two. To our knowledge, no relevant thermodynamic data are available.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 506: Symposium – Scientific Basis for Nuclear Waste Management XXI , 1997 , 773
Copyright
Copyright © Materials Research Society 1998

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References

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