In order to get a better understanding for the spent fuel corrosion process, the variations of important intensive parameters such as pH and the redox potential (Eh) of the bulk solution have been continuously measured during long term sequential leaching experiments. These data may be used together with standard chemical analytical data for modeling spent fuel corrosion, especially in anoxic or reducing conditions. In order to overcome difficulties caused by the strong radiation field and the long experiment times, a method for in-situ measurements of pH and Eh using a computer controlled system was worked out. The stability of the measuring system over long time periods was then tested; pH values stable within 0.05 pH units/year in buffered systems were measured. The variations of these parameters in a variety of conditions and solution compositions were followed continuously during the spent fuel leaching process.
A discussion of the results of spent fuel leaching in anoxic conditions is presented, pointing out the difficulties to realize in laboratory near field conditions. An interesting case of calcite co-precipitation/co-dissolution is also presented. Dissolution experiments show that the calcite precipitated previously during spent fuel leaching experiments in synthetic groundwater contained considerable amounts of actinides and fission products.
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Spahiu, K., Werme, L., Low, J. et al. In Situ Long-Term Measurements of pH and Redox Potential During Spent Fuel Leaching Under Stationary Conditions-The Method and Some Preliminary Results. MRS Online Proceedings Library 608, 55 (1999). https://doi.org/10.1557/PROC-608-55