[en] In treating combustible radio-waste which may contain volatile radio nuclides, e.g. Ru, the waste is heated and agitated with concentrated sulphuric acid, and the resulting residue which comprises elemental carbon which retains the volatile radio-nuclides is separated from the acid. Compounds which form borosilicate glass may be added to the waste, and after removal of sulphate, the resulting residual mixture may be fused into a glass. If the sulphate is not removed from the borosilicate mix, the residual mixture produces a ceramic product on heating. (author)