A Study on Precipitation Behavior of Plutonium and Other Transuranium Elements with N-Cyclohexyl-2-pyrrolidone for Development of a Simple Reprocessing Process

Coordination Chemistry of Actinide Nitrates with Cyclic Amide Derivatives for the Development of the Nuclear Fuel Materials Selective Precipitation (NUMAP) Reprocessing Method

“…Indeed, PuO 2 (NO 3 ) 2 ( L1 ) 2 (Figure a) deposited from HNO 3 (aq.) as orange microcrystalline powder in 80–85 % yield ([PuO 2 2+ ] init = 42 m m , i.e., 6–8 m m soluble in 1.3 m HNO 3 and 0.35 m L1 ; 6.7 m m soluble in 3 m HNO 3 ) as shown in Figure b. Interestingly, its crystal structure (Figure b, monoclinic P 2 1 / c, a = 7.0236(5) Å, b = 18.431(1) Å, c = 10.5097(7) Å, β = 102.255(2)°) was fully different from that of UO 2 (NO 3 ) 2 ( L1 ) 2 (triclinic P 1, a = 8.6794(10) Å, b = 8.8490(10) Å, c = 9.7523(10) Å, α = 113.86(1)°, β = 93.31(1)°, γ = 109.06(1)°) despite the compositional analogy and was somewhat similar to that of UO 2 (NO 3 ) 2 ( L4 ) 2 (monoclinic P 2 1 , a = 7.089(2) Å, b = 18.117(5) Å, c = 8.849(2) Å, β = 101.95(3)°, Figure ).…”

“…Conditions: (a) [Pu 4+ ] = 42 m m , [HNO 3 ] = 1.3 m , [ L1 ]/[Pu] = 5; (b) [PuO 2 2+ ] = 42 m m , [HNO 3 ] = 1.3 m , [ L1 ]/[Pu] = 10. Reproduced from ref . (Copyright 2007) with permission from Taylor & Francis.…”

“…To solve this problem, Pu 4+ was oxidized to the hexavalent state, PuO 2 2+ . This reaction can be completed within several hours by simple heating of the HNO 3 solution with Pu 4+ . As actinides at the same oxidation state exhibit similar chemical behavior, we expected that PuO 2 2+ can be precipitated by addition of an appropriately selected NRP.…”

“…However, it is also necessary to consider how to avoid formation of the oily product (see Figure a) of Pu 4+ initially present in the dissolver solution of spent nuclear fuels or how to remove it from UO 2 (NO 3 ) 2 (NRP) 2 precipitate. Figure presents a process flow diagram proposed for a first‐generation precipitation‐based reprocessing process, in which only L1 is employed as a precipitant for UO 2 2+ and PuO 2 2+ , . The point is 70 % of UO 2 2+ is recovered in the first step, and both UO 2 2+ and PuO 2 2+ are subsequently retrieved in the second step.…”

“…Proposed process flow diagram of spent FBR fuel reprocessing in use of NCP ( L1 ) (1st generation) , . Reproduced from ref .…”