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Environ Sci Technol. 2015 Nov 17;49(22):13676-83. doi: 10.1021/acs.est.5b02609. Epub 2015 Oct 29.

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

Author information

1
Department of Civil and Environmental Engineering, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States.
2
MultiScale Material Science for Energy and Environment, UMI 3466 CNRS-MIT, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States.
3
Atomistic Simulation Centre, Queen's University Belfast , Belfast BT7 1NN, United Kingdom.
4
Condensed Matter and Materials Division, Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory , Livermore, California 94550, United States.
5
Los Alamos National Laboratory , Los Alamos, New Mexico 87545, United States.
6
Aix-Marseille University, CINaM-CNRS UMR 7325 Campus de Luminy, 13288 Marseille cedex 9, France.

Abstract

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.

PMID:
26513644
DOI:
10.1021/acs.est.5b02609
[Indexed for MEDLINE]

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