Leaching study of cesium from spent ion-exchange resins and Portland cement package

The leaching rate of ¹³⁴Cs in cement has been studied. The solidification matrix by a standard Portland cement mixed with the spent ion-exchange resins was previously developed. The leaching rates from cement matrices were measured in function of pH, the immersion and curing times, the resin amounts, and ¹³⁴Cs concentration. In all cases, the leaching rate was deduced from ¹³⁴Cs cumulative activity measured by gamma spectrometry. The study showed that only 11.8% of total ¹³⁴Cs has been leached. This fraction concentrated to the solid surface by silanols has been moved during 34 days through two mechanisms. The Langmuir and Freundlich isotherms attributed these two mechanisms at successive attacks, by water and multilayer and monolayer site formed at the interface package/water. The presence of the spent ion-exchange resins in the matrix, as waste, improves and increases ¹³⁴Cs retention power in the cemented package. In fact, the fraction of ¹³⁴Cs mobilized in the absence of resins (3.18 Bq/Kg) becomes negligible in the presence of 12% of resins.