Sol-Gel Processes for Nuclear Fuel Fabrication

Nagarajan, K.; Vaidya, V.N.

doi:10.1007/978-1-4614-1957-0_16

Cited by 3 publications

(1 citation statement)

References 35 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Sol–gel processes can be used to produce actinide oxide microspheres, e.g., UO 2 , PuO 2 , and ThO 2 , as well as mixed-oxide or composite microspheres, such as (U,Th)O 2 , (U,Pu)O 2 , and MA-bearing microspheres. − The approach to fabricate such mixed oxides is to mix the uranium feed broth with a solution containing the dopant and to process this “metal blend” solution in the same manner as the conventional feed broth. ,− The hydrolysis behavior of the individual metal ions during the gelation reaction affects the quality of the microspheres. An inhomogeneous mixing of the dopant element into the uranium matrix occurs if the precipitation pH of the individual ions diverges significantly, as is, e.g., the case for Ce 4+ and UO 2 2+ ions, and premature or incomplete gelation can take place.…”

Section: Introductionmentioning

confidence: 99%

Speciation and Ammonia-Induced Precipitation of Neptunium and Uranium Ions

et al. 2023

View full text Add to dashboard Cite

The pH evolution and corresponding changes in the UV−Vis−NIR absorption spectra of oxygenated neptunium (NpO 2 + and NpO 2 2+) and uranyl ions (UO 2 2+ ) in nitric acid are investigated during titration with an aqueous NH 3 solution. The speciation and precipitation regimes between acidic (pH 1.5) and alkaline (pH 10) conditions at room temperature are discussed to assess the suitability of Np(V) or Np(VI) in sol−gel conversion processes for fuel target fabrication. Under the applied experimental conditions, Np(V) hydrolyzes and precipitates into the insoluble hydroxide NpO 2 OH only above pH values 7.5 and an increase up to pH 10.0 is required to precipitate quantitatively. Np(VI) displays changes in the coordination environment of NpO 2 2+ ions in the pH interval 1.6− 4.0, similar to what is observed for U(VI). Precipitation into NpO 3 •H 2 O or other hydroxide compounds takes place between pH 4.0 and 5.9, which overlaps largely with precipitation of ammonium diuranate species from the U(VI) solution. The use of concentrated NH 3 aqueous solution, as commonly used in the external gelation process, will allow to quantitatively precipitate both Np(V) and Np(VI) species. Internal gelation process conditions, on the other hand, seem incompatible with the high pH required to precipitate Np(V) completely. For fabricating mixed-oxide (U,Np) targets using sol−gel conversion, a feed broth containing Np(VI) and U(VI) will be required to achieve homogeneous gelation.

show abstract