A computational study of heavy ion irradiation of phosphate ceramics

The usage of monazite (monoclinic LnPO4) ceramics as potential waste forms for the immobilization of special nuclear waste streams, such as plutonium unsuitable for use in MOX fuels, has been under consideration already for some decades /1, 2/. One of the key issues for crystalline ceramic waste forms concerns potential property changes in response to radiation-induced phase transformations due to the alpha decay of the incorporated actinides. The radiation damage due to self-irradiation in ceramic waste forms is caused mainly by the recoiling nucleus and to a smaller extent by the emitted alpha-particles. Simulations of the radiation damage induced by irradiation with an Au-beam in the energy range 100 MeV to 200 MeV were performed with the software SRIM (http://www.srim.org) /3/ for several target compositions such as LaPO4 and SmPO4, using threshold displacement energies for the different atoms derived from atomistic simulations. Radiation damages were assessed, i.a. by the evaluation of atom displacements, generated vacancies and replacements, and compared to the results from corresponding experimental studies. Additional calculations using the code MARLOWE were employed for the comparison of the simulation results.References1. R.C. Ewing, L.M. Wang, Rev. Min. Geochem. 48 (2002) 673–6992. N. Dacheux, N. Clavier, R. Podor, Am. Min. 98 (2013) 833–8473. J.F. Ziegler, M.D. Ziegler, J.P. Biersack, Nucl. Instrum. Methods Phys. Res. B268, (2010), 1818–182