Résumé
In France, long-lived radioactive wastes are vitrified in a borosilicate glass matrix for disposal in a deep geological repository. After several thousand years, groundwater will interact with the glass, causing its degradation. Additionally, the self-irradiation of the glass due to the radionuclides affects its properties. To verify the safety of the repository, it is necessary to study the long-term behavior of nuclear glasses, considering alteration, self-irradiation, and their synergy.The effects of self-irradiation can be partly simulated using external irradiation beams on inactive samples, before alteration. However, it is also important to study the effects of irradiation on the alteration solution and the possible impact of its radiolysis on alteration kinetics. To this end, experiments were carried out at the Gammatec facility (STERIS, Marcoule), combining underwater alteration and gamma dose rate. Glass samples were first submitted to several external irradiations scenarios using electrons and/or Au3+ ions, and then altered under a gamma dose rate of about 1,200 Gy/hr generated by a 60Co source. The alteration kinetics were analyzed and the solids were characterized by ToF-SIMS and cryo-TEM. This study has therefore made possible to assess the impact of γ dose rate on glass alteration, and to identify a possible synergy with pre-irradiation, which simulates the effect of αβγ cumulative doses.