Nuclear fuel cycle-oriented actinides separation in China

Abstract

In the last decades, the separation of actinides was widely and continuously studied in China. A few kinds of salt-free reductants to adjust Pu and Np valences have been investigated. , -dimethylhydroxylamine is a good reductant with high reduction rate constants for the co-reduction of Pu(IV) and Np(VI), and monomethylhydrazine is a simple compound for the individual reduction of Np(VI). Advanced PUREX based on Organic Reductants (APOR) was proposed. Trialkylphosphine oxide (TRPO) with a single functional group was found to possess strong affinity to tri-, tetra-and hexa-valent actinides. TRPO process has been first explored in China for actinides partitioning from high level waste and the good partitioning performance was demonstrated by the hot test. High extraction selectivity for trivalent actinides over lanthanides by dialkyldithiophosphinic acids was originally found in China. A separation process based on purified Cyanex 301 for the separation of Am from lanthanides was presented and successfully tested in a battery of miniature centrifugal contactors.

New insights into the uranium adsorption behavior of mesoporous SBA-15 silicas decorated with alkylphosphine oxide ligands

“…13 C CP-MAS spectra were measured at 75.5 MHz using a 7 mm rotor spinning at 6.5 kHz. And 29 Si MAS NMR spectra were measured at 59.6 MHz using 7 mm rotors spinning at 5 kHz. The chemical shis of 29 Si and 13 C are relative to tetramethylsilane (TMS), and that of 31 P is relative to phosphoric acid.…”

“…And 29 Si MAS NMR spectra were measured at 59.6 MHz using 7 mm rotors spinning at 5 kHz. The chemical shis of 29 Si and 13 C are relative to tetramethylsilane (TMS), and that of 31 P is relative to phosphoric acid. The N 2 adsorption/desorption isotherms were measured at 77 K using a Surface Area and Porosity Analyzer (Nava 3200e).…”

“…Trialkylphosphine oxides (TRPO, where R represents alkyl chain) is an neutral organophosphorus extracting agent, which plays a key role in the TRPO processes proposed by Chinese researchers for the removal of actinides from high-level liquid waste (HLLW). [29][30][31][32] The trialkylphosphine oxide groups possess good affinity to actinides in aqueous solutions, and high stability in strong acidic and radiation environment. In our previous communication, 33 we proposed a new protocol for developing uranium adsorption materials by covalently anchoring varieties of alkylphosphine oxide functionalities on the surface and inner channels of mesoporous silicas.…”

Involvement of 5f Orbitals in the Covalent Bonding between the Uranyl Ion and Trialkyl Phosphine Oxide: Unraveled by Oxygen K-Edge X-ray Absorption Spectroscopy and Density Functional Theory

“…6 In the TRPO process, the distribution ratio of UO 2 2+ far exceeds that for other metal ions. 6 The interactions of the phosphoryl group (OP) in 48 these ligands with UO 2 2+ are considered to be responsible to 49 the extraordinary extractability and selectivity and have been 50 investigated by crystallography and theoretical calculations 51 over the past several decades. 7−18 The crystal structures 52 suggest the coordination of the oxygen atoms in the phosphoryl group with UO 2 2+ .…”

Covalency between the uranyl ion and dithiophosphinate by sulfur K-edge X-ray absorption spectroscopy and density functional theory

“…Soft-donor ligands have demonstrated good performance in An III /Ln III separation, in which the dithiophosphinic acids (HS 2 PR 2 ) show great potential in the An III /Ln III separation process (Bessen et al, 2020). For example, bis(2,4,4-trimethylpentyl)dithiophosphinic acid (the purified Cyanex301) in kerosene can extract Am III from Eu III with a separation factor as high as 5000 (Chen et al, 1996(Chen et al, , 2014. Other dithiophosphinic acids with different substituents were also reported for the An III / Ln III separation studies (Peterman et al, 2009(Peterman et al, , 2010Xu et al, 2008;Wang, Jia, Pan et al, 2013;Pu et al, 2019Pu et al, , 2020Wang et ISSN 1600-5775 al., 2013.…”