Title: Understanding the Interaction between Low-Energy Electrons and DNA Nucleotides in Aqueous Solution
Author(s): McAllister M., Smyth, M., Gu B., Tribello G.A., Kohanoff J.,
Journal of Physical Chemistry Letters, 6, No. 15, pp. 3091-3097 (6 August 2015)
Reactions that can damage DNA have been simulated using a combination of molecular dynamics and density functional theory. In particular, the damage caused by the attachment of a low energy electron to the nucleobase. Simulations of anionic single nucleotides of DNA in an aqueous environment that was modeled explicitly have been performed. This has allowed us to examine the role played by the water molecules that surround the DNA in radiation damage mechanisms. Our simulations show that hydrogen bonding and protonation of the nucleotide by the water can have a significant effect on the barriers to strand breaking reactions. Furthermore, these effects are not the same for all four of the bases.
Title: Cement As a Waste Form for Nuclear Fission Products: The Case of 90Sr and Its Daughters
Author(s): Dezerald L., Kohanoff J., Correa A., Caro A., Pellenq R., Ulm F., Saúl A.
Environmental Science & Technology (2015)
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 90Sr 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 90Sr is stable when it substitutes the Ca2+ ions in C–S–H, and so is its daughter nucleus 90Y after β-decay. Interestingly, 90Zr, daughter of 90Y 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 ,90Sr storage.