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Use of boiled hexamethylenetetramine and urea to increase the porosity of cerium dioxide microspheres formed in the internal gelation process

Journal Article · · Journal of Nuclear Materials
 [1];  [1];  [1]
  1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
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Cerium dioxide (CeO2) is a commonly used simulant for plutonium dioxide and for plutonium (Pu) in a mixed uranium (U) and Pu oxide [(U, Pu)O2] in nuclear fuel development. This effort developed CeO2 microspheres with different porosities and diameters for use in a crush-strength study. The internal gelation technique has produced CeO2 microspheres with limited initial porosity. When an equal molar solution of urea and hexamethylenetetramine (HMTA) is gently boiling for 1 hr and used in the gelation process, the crystallite size and porosity of mixed U and thorium oxide microspheres and the (U, Pu)O2 microspheres increased significantly. In this study with cerium, the combination of ammonium cerium nitrate and 1-h boiled HMTA-urea failed to produce a stable feed broth. However, when the 1-h heated HMTA-urea was combined with unheated HMTA-urea in 1 to 3 volume ratio or the boiling time of the HMTA-urea was reduced to 15-20 min, a stable solution of HMTA, urea, and Ce was formed at 273 K. This new Ce solution produced CeO2 microspheres with much higher initial porosities. Intermediate porosities were possible when the heated HMTA/urea was aged prior to use.
Research Organization:
Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
Sponsoring Organization:
USDOE
Grant/Contract Number:
AC05-00OR22725
OSTI ID:
1408648
Alternate ID(s):
OSTI ID: 1396929
Journal Information:
Journal of Nuclear Materials, Journal Name: Journal of Nuclear Materials Journal Issue: C Vol. 492; ISSN 0022-3115
Publisher:
ElsevierCopyright Statement
Country of Publication:
United States
Language:
English

References (6)

Fabrication of dense (Th,U)O2 pellets through microspheres impregnation technique journal November 2008
Treatment techniques to prevent cracking of amorphous microspheres made by the internal gelation process journal October 2010
Studies on preparation of (U0.47,Pu0.53)O2 microspheres by internal gelation process journal March 2013
Fabrication of size-controlled CeO 2 microparticles by a microfluidic sol–gel process as an analog preparation of ceramic nuclear fuel particles journal August 2013
The Basic Chemistry Involved in the Internal-Gelation Method of Precipitating Uranium as Determined by pH Measurements journal January 1987
Uranium kernel formation via internal gelation journal January 2004

Cited By (2)

Preparation of cerium dioxide microspheres by internal gelation with cerium citrate as precursor journal March 2019
Fabrication of CeO2–Nd2O3 microspheres by internal gelation process using M(OH)m and [MCit∙xH2O] (M=Ce3+, Ce4+, and Nd3+) as precursors journal July 2019

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Related Subjects

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS
Cerium oxide spheres
Internal gelation