Radiation damage studies in apatite, natural and artificial glasses

The problems of radiation damage arising by storing nuclear waste in a glass matrix for long term disposal have attracted increasing interest in recent years. As the apatite phase is a possible crystallization product of HLW-glasses (high level nuclear waste) under hydrothermal conditions, and apatite is also a possible candidate for long term storage, information about radiation damage and its influence on the properties of both, glass and apatite, is important. Radiation damage induced in natural fluorapatite (Ca10(PO4)6F2) and artificial sodium silica glass (Na2O x 2SiO2) by fission fragments, alpha decay (α decay of U in apatite and n, α reactions in the glass) and 2 MeV electron irradiation has been studied by optical absorption spectroscopy of the respective defect centers (H(II) centers in apatite and H+2 centers in glass) as a function of radiation dose. Annealing of radiation damage in natural fluorapatite has been studied with absorption spectroscopy for different sample orientation (parallel and perpendicular to the optical axis), sample thickness, annealing time and temperature, radiation source and radiation dose. Furthermore annealing of radiation damage in artificial sodium silica glass has been studied by absorption spectroscopy for different radiation sources as a function of annealing time and temperature. Activation energies and preexponential factors are given. Absorption spectroscopy of defects in natural apatite is proposed as a new method for age determination. (G.Q.)