Preliminary development of internal gelation flowsheets for preparing (Th,U)O/sub 2/ spheres
Internal gelation procedures were developed to prepare good, high-density (Th,U)O/sub 2/ spheres, 800- to 1200-..mu..m in diameter, as required for Sphere-Pac fabrication of nuclear fuels. Decomposition of hexamethylenetetramine (HMTA) dissolved in metal nitrate solution drops releases ammonia to solidify or gel the drops as hydrated metal oxides. The thorium-uranium nitrate feed solutions were made acid deficient by partial neutralization with NH/sub 4/OH or by solvent extraction of nitrate. For some feeds, gelation of drops was in trichloroethylene at 60 to 75/sup 0/C. Feeds with high concentrations of urea as a complexing agent for metals required higher temperatures and were gelled in perchloroethylene-mineral oil mixtures at 80 to 95/sup 0/C. Slow changes of concentration during washing with ammonia were important to prevent cracking of the 800- to 1200-..mu..m sintered spheres. The spheres were dried in steam atmospheres, calcined and then sintered in Ar-4% H/sub 2/ at 1450/sup 0/C to give (Th,U)O/sub 2/ spheres with nearly theoretical density (greater than or equal to 99%). The initial batches prepared with other washing and drying procedures showed severe cracking.
- Research Organization:
- Oak Ridge National Lab., TN (USA)
- OSTI ID:
- 6290142
- Report Number(s):
- ORNL/TM-7280; ON: DE81025663
- Country of Publication:
- United States
- Language:
- English
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