Radiation Tolerance of Hollandite Ceramics as Waste Forms for Cs and Transuranic Elements

Radiation effects of a series of Ba_{1.33-<i>x</i>}Cs<i>_x</i>Fe_{2.66-<i>x</i>}Ti_{5.34+<i>x</i>}O₁₆hollandite (<i>x</i> = 0, 0.1, 0.667, and 1.33) were evaluated for their potential application as waste forms for both fission products (e.g., Cs) and transuranic elements (e.g., Pu and Am).<br/><br/>200-300 keV electrons were used to simulate the effects of ionizing radiation by beta- and gamma-decay of Cs, and 1.2 MeV Kr ions were used to simulate the effects of displacement damage caused by alpha-decay of the transuranic elements. Atomic resolution transmission electron microscopy (TEM) with elemental mapping was used to characterize the material before irradiation. <i>In situ</i> TEM was conducted during both electron and ion beam irradiations. No amorphization was observed in any of the hollandite compositions under electron radiation with ionizing doses above 10¹² Gy. However, amorphization of both Ba- and Cs-end members of the hollandite series occurred after a fraction of a dpa (displacement per atom) under Kr ion irradiation at 200 degree C (due to beam heating). The critical amorphization dose of the Cs-end member is about 50% higher than that for the Ba-end member under Kr ion irradiation.<br/><br/>The results are analyzed and evaluated comparing to the radiation tolerance of other potential ceramic waste forms, and to the doses that might be received in the required service times of waste forms with various level of loadings of different radionuclides.