Chemical durability of zircon

Zircon (ZrSiO4) exhibits a strong structural affinity for uranium and thori um together with a very high chemical durability. This makes it a potential crystalline host matrix to immobilize actinides issued from separation of nuclear wastes. Irradiation induces amorphization of the crystalline struct ure (the metamictization process) and thus may decrease the chemical durabi lity of the material. Leaching tests have been conducted on natural zircons from Brazil and Madagascar at 96 degreesC for a period of 1 month, using d eionized water. Leachates have been analysed by inductively coupled plasma mass spectrometry (ICP-MS) and UV-visible spectrophotometry. Zircon solid s urfaces have been investigated by coupling scanning electron microscopy and X-ray microanalysis (SEM-EDX) with nuclear microprobe analysis (mu PIXE, m u RBS and mu ERDA). From the mass balance between leachates and hydrated su rfaces, the probable mechanisms of zircon aqueous alteration are presented and discussed. (C) 2001 Elsevier Science B.V. All rights reserved.