Résumé
The effect of external irradiation on $\beta$-thorium phosphate-diphosphate (tetravalent actini des bearing storage matrix) and the influence on its dissolution in aqueous media were studied. Highly energetic heavy ions were used to get the amorphization of the crystalline structure of the ceramic. The ex-situ dissolution expenments showed an increase of the dissolution versus amorphous fraction in several pH and temperature conditions. The in-situ dissolution experiments highlighted the primordial importance of radiolytic produced free radical species. From these results, the ceramic presents a good resistance to aqueous alteration even in amorphous state.