Cement As a Waste Form for Nuclear Fission Products: The Case of (90)Sr and Its Daughters.

Lucile Dezerald, Jorge J Kohanoff, Alfredo A Correa, Alfredo Caro, Roland J-M Pellenq, Franz J Ulm, Andrés Saúl

Environmental science & technology 2015 Nov 17

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One of the main challenges faced by the nuclear industry is the long-term confinement of nuclear waste. Because it is inexpensive and easy to manufacture, cement is the material of choice to store large volumes of radioactive materials, in particular the low-level medium-lived fission products. It is therefore of utmost importance to assess the chemical and structural stability of cement containing radioactive species. Here, we use ab initio calculations based on density functional theory (DFT) to study the effects of (90)Sr insertion and decay in C-S-H (calcium-silicate-hydrate) in order to test the ability of cement to trap and hold this radioactive fission product and to investigate the consequences of its β-decay on the cement paste structure. We show that (90)Sr is stable when it substitutes the Ca(2+) ions in C-S-H, and so is its daughter nucleus (90)Y after β-decay. Interestingly, (90)Zr, daughter of (90)Y and final product in the decay sequence, is found to be unstable compared to the bulk phase of the element at zero K but stable when compared to the solvated ion in water. Therefore, cement appears as a suitable waste form for (90)Sr storage.

Citation

Lucile Dezerald, Jorge J Kohanoff, Alfredo A Correa, Alfredo Caro, Roland J-M Pellenq, Franz J Ulm, Andrés Saúl. Cement As a Waste Form for Nuclear Fission Products: The Case of (90)Sr and Its Daughters. Environmental science & technology. 2015 Nov 17;49(22):13676-83