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Safely probing the chemistry of Chernobyl nuclear fuel using micro-focus X-ray analysis

“…The upper bound of x reported here is slightly higher than that reported for chernobylite in real LFCM (x ¼ 0.05-0.10). 25,26 The abundance of U in Zr 1Àx U x SiO 4 has also been reported in simulant Fukushima molten core-concrete interaction (MCCI) products, at a higher value of x than chernobylite (x ¼ 0.19- 0.27). This discrepancy is likely a result of the slower cooling time for real LFCM, which allows for thermodynamic equilibration of U during Zr 1Àx U x SiO 4 formation.…”

Formation of plutonium(iv) silicate species in very alkaline reactive media

“…Measurements performed at pH ≤ 12 did not allow the identification of aqueous plutonium species. This observation could be explained by silicate ions protonation, considering HSiO 3 -/SiO The comparison with aqueous plutonium oxo-hydroxo colloids solution allowed to observe that the as-obtained plutonium species did not correspond to hydrolyzed plutonium (Figure 2) nor to the plutonium silicate complex, PuOSi(OH) 3 3+ , reported by Pazukhin et al 6 and Yusov et al 5 but might correspond to aqueous plutonium silicate species, such as Pu(SiO 3 ) n (4-2n)…”

“…Even if the formation of plutonium silicate complexes and solid plutonium silicate species (or that of other actinide or surrogate elements) has been reported, [5][6][7][8][9][10][11][12] plutonium (IV) chemistry in silicate environment remains poorly understood. Among them, Pu(OSi(OH) 3 ) 3+ was prepared between pH 0.3 and 1.4 in diluted aqueous plutonium and silicate solution and a log(β°) = 11.8 (1) value was evaluated according to equation (1).…”

“…Pazukhin et al 6 observed that the titration of Pu(IV) in nitric solution by a aqueous sodium metasilicate solution did not lead to the precipitation of plutonium hydroxide up to pH = 12 while its precipitation occurred at pH = 2 -4 for a titration performed with NaOH or NH 4 OH without metasilicate. They attributed these results to the formation of a plutonium silicate complex with a [Pu(IV)]:[Na 2 SiO 3 ] = 1:8 mole ratio.…”

The formation of PuSiO4under hydrothermal conditions

“…17 According to the literature, Pu(III) and Pu(VI) silicate species have been reported. [23][24][25][26][27][28] It is also the case for plutonium(IV) silicate aqueous species [29][30][31] , especially for Pu(OSi(OH) 3 ) 3+ .…”