Structure determination of compounds for the immobilisation of Iodine-129 and Technetium-99

99Tc (half life 2.13 x 105 years) and 129I (half life 15.7 x 106 years) are abundant and long lived products of nuclear fission, with yields of 6% and 0.7% respectively for thermal fission of 235U. These radionuclides are of particular concern in closed nuclear fuel cycles, since the long half life and high production rate, combined with solubility and bioaccumulation. Future advanced nuclear fuel recycle strategies demand disposition of 99Tc and 129I in a robust wasteform, and isolation from the bio-sphere, in a deep geological disposal facility for 10E6 - 10E7 years. We have endeavoured to address this challenge, exploring the synthesis, structure and properties of ceramics for 129I and 99Tc disposition. Here, we propose to determine the structures of seven such ceramic compounds, within three families, using neutron powder diffraction, with natural isotopic abundance I and 99Tc.