The Chemistry of Plutonium in Sol-Gel Processes

Abstract

Plutonium /Plutonium polymer/Colloids /Sols/Sol-gel process/ Nitrates /DenitrationSummary Studies of plutonium chemical behavior conducted in conjunction with plutonia sol-gel process development at ORNL are described. The colloidal solutions produced consist of "Pu(IV) polymer," and this is therefore the study of polymeric plutonium behavior. Spectrophotometric, electron diffraction, and electron microscopy studies, in addition to specific studies that were concerned with the colloidal behavior of Pu(IV) polymer, indicate several characteristics of polymer that are not generally recognized. The particle nature of Pu(IV) polymer indicated by electron microscopy, the amorphous-crystalline characteristics of primary polymer particles demonstrated by electron diffraction, and the reversible and irreversible aggregation of the primary particles shown by spectrophotometric techniques present a useful view of the nature of Pu(IV) polymer that has been helpful in solving orunderstanding various types of processing problems involving plutonium hydrolytic behavior. The colloidal characteristics of Pu (IV) polymer and crystallite growth of primary polymer particles by thermal denitration are also described.

New insights in the formation processes of Pu(IV) colloids

“…At pH c 1.8 (sample 8), this spectral pattern further increases and a clear shift towards λ = 620 nm is observed within five days. For sample 9 which was prepared the same as sample 8 but has aged for 2 years, a clear evolution of the spectrum towards the one of crystalline PuO 2 colloids published by Lloyd and Haire [41] is observed. Fig.…”

Surface chemistry of Pu oxides

“…Colloidal Pu(IV) hydroxide was prepared using the method reported by Lloyd and Haire [13] as follows: a Pu(IV) stock solution was prepared by dissolving weapons grade Pu (approximately 94% by weight 239 Pu and 6% 240 Pu) in 4 M HClO 4 and assayed for Pu(IV) using optical absorbance spectroscopy. A 0.52 mL aliquot of the resulting 0.76 M Pu stock solution was added to 3.0 mL of 4.0 M HNO 3 .…”

The Formation of Pu(IV)-Colloid by the Alpha-reduction of Pu(V) or Pu(VI) in Aqueous Solutions

“…These sols are almost certainly thermodynamically unstable with respect to large crystals of Pu0 2 , but are kinetically very stable. The exact nature of these sols is unknown but LLOYD and HAIRE [10] have precipitated Pu0 2 from alkaline solutions and prepared sols by peptization in dilute HN0 3 at temperatures up to 80°C. Electron diffraction measurements on dried sols showed either amorphous or crystalline primary particles with the cubic fluorite structure and the line-spacings for crystalline Pu0 2 [10].…”