Actinides immobilization in new matrices based on solid solutions: Th4−xMxIV(PO4)4P2O7, (MIV=238U,239Pu)

Synthesis and characterization of low-temperature precursors of thorium–uranium (IV) phosphate–diphosphate solid solutions

“…6(b)) versus temperature shows that this solid is stable up to 600°C. Above this temperature, it is transformed into a mixture of b-TUPD, a-Th 1Àz U z-P 2 O 7 and U 2Àw Th w O(PO 4 ) 2 instead of leading to pure b-TUPD solid solution which is consistent with literature [18,19,23].…”

“…Among the radionuclides to be stored, actinides must be considered carefully due to their long-term high radiotoxicity and to their long half-life period. Several phosphate-based materials such as apatites (Ca 10 (PO 4 ) 6 F 2 ) and associated britholites (Ca 9 Nd(PO 4 ) 5 (SiO 4 )F 2 ) [1,2], monazites (LnPO 4 ) and associated brabantites (M II M IV (PO 4 ) 2 ) [3][4][5][6][7][8][9], sodium dizirconium phosphate (NaZr 2 (PO 4 ) 3 , NZP) [10][11][12][13] or uranium and thorium phosphates [14][15][16][17][18][19][20][21] were studied as potential matrices to stabilize these radionuclides in solids (e.g. ceramics).…”

“…Actually, it was demonstrated that b-TPD can incorporate large amounts of tetravalent uranium (up to 47.6 wt%), neptunium (33.2 wt%) or plutonium (26.1 wt%) by substitution of thorium [17][18][19][20]23]. The synthesis of such solids was performed following several ways including either wet or dry chemistry routes.…”

Characterization of nanocrystalline (Th1−xCex)Oy powders synthesized by co-precipitation process

“…Some of these studies concerning different types of ceramic materials can be found in literature [1][2][3][4][5].…”

Improvement of the preparation of sintered pellets of thorium phosphate-diphosphate and associated solid solutions from crystallized precursors

“…Indeed, several natural phosphate ores such as brabantites ðCa 0:5 M IV 0:5 PO 4 Þ [1,2], monazites (M III PO 4 ) [3][4][5] or britholites ðCa 9 Nd 1Àx -M IV x ðPO 4 Þ 5Ày ðSiO 4 Þ 1þy F 2 Þ [6,7] can incorporate large amounts of uranium and/or thorium (up to 30 wt% in ThO 2 ) [3] and generally appear well-crystallized and resistant to aqueous alteration. In the last decade, several studies were also dedicated to the thorium phosphate-diphosphate (b-Th 4 (PO 4 ) 4 P 2 O 7 , b-TPD) [8][9][10][11][12][13] which appears as a promising material for the specific immobilization of tetravalent actinides since it allows the incorporation of uranium (up to 47.6 wt%), neptunium (33.2 wt%) and plutonium (26.1 wt%) by substitution of thorium in the crystal structure [11,12]. Moreover, the resulting solid solutions with actinides (b-An x Th 4Àx (PO 4 ) 4 -(P 2 O 7 ), b-TAnPD) exhibit good sintering properties [10,14] and present a strong resistance to aqueous corrosion [13].…”