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

Cerium dioxide (CeO 2) is a commonly used simulant for plutonium dioxide and for plutonium (Pu) in a mixed uranium (U) and Pu oxide [(U, Pu)O 2] in nuclear fuel development. This effort developed CeO 2 microspheres with different porosities and diameters for use in a crush-strength study. The internal gelation technique has produced CeO 2 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)O 2 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 CeO 2 microspheres with much higher initial porosities. Intermediate porosities were possible when the heated HMTA/urea was aged prior to use.
Authors:
 [1] ;  [1] ;  [1]
  1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Publication Date:
Grant/Contract Number:
AC05-00OR22725
Type:
Accepted Manuscript
Journal Name:
Journal of Nuclear Materials
Additional Journal Information:
Journal Volume: 492; Journal Issue: C; Journal ID: ISSN 0022-3115
Publisher:
Elsevier
Research Org:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS; Cerium oxide spheres; Internal gelation
OSTI Identifier:
1408648
Alternate Identifier(s):
OSTI ID: 1396929

Hunt, R. D., Collins, J. L., and Cowell, B. S.. Use of boiled hexamethylenetetramine and urea to increase the porosity of cerium dioxide microspheres formed in the internal gelation process. United States: N. p., Web. doi:10.1016/j.jnucmat.2017.04.061.
Hunt, R. D., Collins, J. L., & Cowell, B. S.. Use of boiled hexamethylenetetramine and urea to increase the porosity of cerium dioxide microspheres formed in the internal gelation process. United States. doi:10.1016/j.jnucmat.2017.04.061.
Hunt, R. D., Collins, J. L., and Cowell, B. S.. 2017. "Use of boiled hexamethylenetetramine and urea to increase the porosity of cerium dioxide microspheres formed in the internal gelation process". United States. doi:10.1016/j.jnucmat.2017.04.061. https://www.osti.gov/servlets/purl/1408648.
@article{osti_1408648,
title = {Use of boiled hexamethylenetetramine and urea to increase the porosity of cerium dioxide microspheres formed in the internal gelation process},
author = {Hunt, R. D. and Collins, J. L. and Cowell, B. S.},
abstractNote = {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.},
doi = {10.1016/j.jnucmat.2017.04.061},
journal = {Journal of Nuclear Materials},
number = C,
volume = 492,
place = {United States},
year = {2017},
month = {5}
}