Retention of strontium in high- & low-pH cementitious matrices – OPC vs. model systems

Matan Shiner , Ofra Klein-Bendavid (1, 2) , Emilie l'Hôpital (3) , Alexandre Dauzères (3) , Mejdi Neji (3) , Nadya Teutsch , Alva Peled , Gabriela Bar-Nes (1)

1 NRCN - Nuclear Research Center-Negev
2 BGU - Ben-Gurion University of the Negev
3 IRSN/PSE-ENV/SEDRE/LETIS - Laboratoire d'étude et de recherche sur les transferts et les interactions dans les sous-sols

Strontium can be found in low/intermediate level radioactive waste streams, often solidified by Ordinary Portland Cement (OPC) matrices. Amorphous silica is added to improve wasteform performance, leading to low-pH systems. Our aim is to identify the phases controlling strontium immobilization in OPC matrices. The novelty of this work resides in combination between two approaches: 1) Comparing OPC systems to model systems based on alite, yielding matrices containing only major phases, emphasizing the relative role of minor phases; 2) Comparing high- & low-pH pastes. Pastes were characterized using calorimetry, XRD, DTG, SEM/EDS and porosimetry. Leaching experiments were conducted to study Sr retention and diffusivity. Strontium diffusivities in low-pH pastes are lower with respect to high-pH equivalents, despite their higher porosities, due to preferred Sr sorption to low Ca/Si C-S-H. OPC pastes show better Sr retention relative to model systems, suggesting that minor phases (like ettringite and AFm) improve Sr retention.

Domaines: Chimie

Matan Shiner, Ofra Klein-Bendavid, Emilie l'Hôpital, Alexandre Dauzères, Mejdi Neji, et al.. Retention of strontium in high- & low-pH cementitious matrices – OPC vs. model systems. Cement and Concrete Research, 2022, 152, pp.106659. ⟨10.1016/j.cemconres.2021.106659⟩. ⟨hal-03784306⟩