Abstract

A new experimental method has been developed to measure the release of radionuclides from radiation-damaged materials using a combination of 500 keV H⁺ beam irradiation, electron microscopy, and electron microprobe analysis techniques. A good correlation between the radiation damage and changes in the release of radionuclides from irradiated zeolite-Y preloaded with Sr has been established. After irradiation with a 500 keV H⁺ beam to a dose of 3.6 × 10¹⁷ ions cm⁻², the release of Sr in 1 N NaCl, 1 N CaCl₂ and 10 mN AgNO₃ solutions was reduced by a factor of up to seven in the radiation-damaged material. A comparison of results obtained in 10 mN AgNO₃ solution with that of 1 N CaCl₂ solution showed that structural damage occurred not only to the supercages, but also to the small cages, i.e. sodalite cages and double 6-ring prisms. When the radiation dose was above 2.5 × 10¹⁰ Gy, the ion exchange of the large cations (Ca and Sr) was completely stopped, whereas the small cation-exchange (Ag and Na) could still proceed. A leach test in the deionized water showed that amorphization of zeolite-NaSrY can reduce the release of the adsorbed radionuclides, Sr, from 0.23 mg g⁻¹ for crystalline zeolite-NaSrY to 0.12 mg g⁻¹ after 234 h of leaching in 90 °C deionized water.