Process for packaging radioactive wastes in the form of synthetic rock

A method for packaging radioactive wastes, wherein the following successive steps are carried out:

• a/ radioactive wastes are treated for which the composition of the dry extract after calcination at 950° C., called starting composition hereafter, comprises at least 90% of compounds selected from CaO, Fe2O3, SiO2, Al2O3 and B2O3, and the composition of said wastes is supplemented so as to attain a target composition of said supplemented wastes after calcination, and
• b/ said supplemented radioactive wastes are melted and
• c/ said melt is cast in a container, so as to obtain after cooling, a monolith product comprising a synthetic either glassy or vitro-crystalline rock, having said target composition,
• wherein said starting composition and said target composition meet the following definitions, in a ternary (CaO, SiO2 and X2O3) system, wherein X2O3 is a trivalent oxide or a mixture of trivalent oxides selected from Al2O3, Fe2O3 et B2O3:
• for said starting composition:
• PC and PX are less than 90%, and
• PS is less than 75%, and
• for said target composition:
• PC is from 35 to 60%, and
• PS is from 10 to 45%,
• with, in both cases:
• PC+PS+PX=100%, and
• PX=PA+PH+PB, with
• PC=[MC/(MC+MS+MA+0.28MH+2MB)]×100%, and
• PS=[MS/(MC+MS+MA+0.28MH+2MB)]×100%, and
• PA=[MA/(MC+MS+MA+0.28MH+2MB)]×100%, and
• PH=[0.28MH/(MC+MS+MA+0.28MH+2MB)]×100%, and
• PB=[2MB/(MC+MS+MA+0.28MH+2MB)]×100%, and
• Pi and Mi, with i=C, S, A, H or B, are the mass percentages (Pi) and the masses (Mi) of CaO (i=C), SiO2 (i=S), Al2O3 (i=A), Fe2O3 (i=H) et B2O3 (i=B) respectively.