Uranium brannerite with Tb(III)/Dy(III) ions: Phase formation, structures, and crystallizations in glass

Abstract

Uranium brannerite phases with terbium(III) or dysprosium(III) ions have been investigated. The precursors with molar ratio of 0.5:0.5:2 (Ln: U: Ti with Ln = Tb or Dy) were prepared and calcined at 750°C in argon. Sintering the pelletized samples in argon at 1200°C led to the formation of pyrochlore phases with TiO2 rutile and U‐rich oxides while sintering in air led to the formation of brannerite phases with the nominal composition close to Ln0.5U0.5Ti2O6 together with trace amounts of TiO2 rutile and LnUO4. Incorporating an excess of TiO2 (20 wt%) and sintering at higher temperature (1300°C) resulted in no obvious change to the phase equilibrium. As designed, pentavalent uranium has been proven to be dominant in these brannerite phases with diffuse reflectance spectroscopy. The relationships between the cell parameters and the ionic radii of the A‐site cations have been explored and rationalized from the structure point of view for a range of titanate brannerite phases (ATi2O6). In addition, the crystallization of Ln0.5U0.5Ti2O6 brannerite in glass has been achieved via heat treatment at 1200°C and confirmed with X‐ray diffraction, scanning electron microscopy‐energy dispersive spectroscopy and transmission electron microscopy–selected area electron diffraction.

Synroc technology: Perspectives and current status (Review)

“…Research within ANSTO Synroc continues to pursue solutions for problematic nuclear waste streams, including solutions for the immobilization of Cs, 111 I, 112‐115 pyroprocessing wastes 116 and particularly Pu‐bearing wastes 99,100,117 . Research is also being undertaken at ANSTO for generation IV reactor wastes, and the Synroc process is relevant for graphite and fluoride molten salt wastes.…”

“…Research within ANSTO Synroc continues to pursue solutions for problematic nuclear waste streams, including solutions for the immobilization of Cs, 111 I, [112][113][114][115] pyroprocessing wastes 116 and particularly Pu-bearing wastes. 99,100,117 Research is also being undertaken at ANSTO for generation IV reactor wastes, and the Synroc process is relevant for graphite and fluoride molten salt wastes. With regard to the spent nuclear fuel from the current fleet of reactors, Dr Vance believed that a tailored Synroc wasteform would offer significant advantages over the current direct disposal method.…”

Ceramic Mineral Waste-Forms for Nuclear Waste Immobilization

“…While materials are mineral-like the principle ”from nature to nature” can be realized. Although many structures were included herewith, some could be missed, for example brannerite [15,99], which is currently considered for actinide immobilization [461]. Among most investigated structures one can note oxide ceramics.…”

Pyrochlore glass‐ceramics fabricated via both sintering and hot isostatic pressing for minor actinide immobilization

“…To overcome the disadvantages for either glass or ceramic waste forms, composite materials, for example glass‐ceramics (GCs), have been developed as potential waste forms for actinide waste management 16‐18 . The GC waste forms have the advantage of combining the simple processing and chemical flexibility of glasses (to accommodate processing chemicals) with the excellent chemical durability of ceramics (to host actinides) for the immobilization of actinide‐rich radioactive wastes containing impurities 17‐29 . So far, GCs based on stable titanate mineral phases, such as zirconolite, 17‐21 pyrochlore, 22‐26 and brannerite, 27‐29 have been primarily investigated as potential waste forms for actinide immobilization.…”

“…[16][17][18] The GC waste forms have the advantage of combining the simple processing and chemical flexibility of glasses (to accommodate processing chemicals) with the excellent chemical durability of ceramics (to host actinides) for the immobilization of actinide-rich radioactive wastes containing impurities. [17][18][19][20][21][22][23][24][25][26][27][28][29] So far, GCs based on stable titanate mineral phases, such as zirconolite, [17][18][19][20][21] pyrochlore, [22][23][24][25][26] and brannerite, [27][28][29] have been primarily investigated as potential waste forms for actinide immobilization.…”