Immobilization of actinides in stable mineral type and ceramic materials (high temperature synthesis)
Alternative vitrification technologies are being developed in the world for the immobilization of high radioactive waste in materials with improved thermodynamic stability, as well as improved chemical and thermal stability and stability to radiation. Oxides, synthesized in the form of analogs to rock-forming minerals and ceramics, are among those materials that have highly stable properties and are compatible with the environment. In choosing the appropriate material, we need to be guided by its geometric stability, the minimal number of cations in the structure of the material and the presence of structural elements in the mineral that are isomorphs of uranium and thorium, actinoids found in nature. Rare earth elements, yttrium, zirconium and calcium are therefore suitable. The minerals listed in the table (with the exception of the zircon) are pegatites by origin, i.e. they are formed towards the end of the magma crystallization of silicates form the residual melt, enriched with Ta, Nb, Ti, Zr, Ce, Y, U and Th. Uranium and thorium in the form of isomorphic admixtures form part of the lattice of the mineral. These minerals, which are rather simple in composition and structure and are formed under high temperatures, may be viewed as natural physio-chemical systems that are stable and long-lived in natural environments. The similarity of the properties of actinoids and lanthanoids plays an important role in the geochemistry of uranium and thorium; however, uranium (IV) is closer to the {open_quotes}heavy{close_quotes} group of lanthanoids (the yttrium group) while thorium (IV) is closer to the {open_quotes}light{close_quotes} group (the cerium group). That is why rare earth minerals contain uranium and thorium in the form of isomorphic admixtures.
- Research Organization:
- US Department of Energy (USDOE), Washington DC (United States)
- OSTI ID:
- 420656
- Report Number(s):
- CONF-951259-; ON: DE96011798; TRN: 97:002139
- Resource Relation:
- Conference: Plutonium stabilization and immobilization workshop, Washington, DC (United States), 12-14 Dec 1995; Other Information: PBD: May 1996; Related Information: Is Part Of US Department of Energy Plutonium Stabilization and Immobilization Workshop, December 12-14, 1995: Final proceedings; PB: 474 p.
- Country of Publication:
- United States
- Language:
- English
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