CsAlSi5O12: a possible host for 137Cs immobilization

CsAlSi5O12 exhibits more acid resistance than pollucite (CsAlSi2O6). At pH values of 1.02 and 1.40, the extraction of Cs from CsAlSi5O12 at 250C was approximately proportional to the square root of leach time. The Cs extraction at 250C varied as [H+]sup(0.36) over the pH range of 1 to 6. Also, the Cs extraction in various brines at 3000C and 30 MPa was comparable with that for pollucite. CsAlSi5O12 can be crystallized at about 10000C from calcines if a small amount of CaO is present, but, in the absence of such sintering aids, crystallization temperatures of about 14000C are necessary. Compatibility data were also obtained with respect to several other phases with which CsAlSi5O12 might be expected to co-exist in tailored ceramics designed for high-level defence waste. (author)