الفهرس 
AcknowledgmentOnly 14 pages are availabe for public view
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Abstract
Uranium dioxide (U02) in the form of spherical particles can be used in light water reactors (LWR), fast breeder reac¬tors (FBR), and high temperatlue Gas cooled reactors (HTGR).
UOJ-microspherrjs were prepared using hydrolysis process (H-process). The feed solution was prepared by issolving urea in a highly concentrated uranyl nitrate solution (about 500 g/l) and addition of hexamethylene-tetramine at tempera- ’
ture below 10°C. The gelled-microspheres were washed with car-
ban tetrachloride for 10 minutes (2 times) to remove the sili-
con oil (gelation medium)~ Afterwards, the microspheres were washed with either hot water (95°C) for 10 minutes and, or, 3% ammonia solution for 15 minutes ( 3 times). The washed micro-
spheres were dried at 70°C for 17 hours
The following treatments were undertaken The feed solution were aged for 1,2 and 3 hours. The obtained microspheres were washed by ammonia solution or hot water.
The gelled-microspheres were soaked in th0 gelation medium (silicon oil) for 1,2 and 3 hours. The obtained
microspheres were washed by ammonia sol u tion or hot water.
The gelled-microspheres were soaked in 3% ammonia solu- tion for 6, 12 and 24 hours before and af ter washing. The microspheres washed by ammonia solution
The washed microspheres wo,e dried at R.T. (20°0) for 36
hours, 140°0 for 10 hours, in a flowing steam for 1,2,3 and 4 hours, and dehydrated us1ng isopropyl, n-buty1, and ethyl alcohol. The dried microspheres have had the chemical formula of X NHJ• Y H20). The value of X and Y were determined thermal analysis. The values of X and Y were found to depend on the conditons of preparation, washing, and drying. lThe crystallite size was measured using X-ray diffraction. The crys talli te size waS found 110, 410 and 510 A for ammonia washed, hot water-washed and 1 hour steam dried microspheres, res¬The specific surface area WaS measured by using the single point differential nitroGen adsorption method. It WaS
and 2.8 m2/g for a.mmonia and hot water washed micro-
espectively. The dried UoJ-microspheres v/ere reduced in both h,ydrogen ammonia at a temperature ranging from 500 to 900°0 for 2 It waS found that reduction in an ammonia gas attained
a higher density than reauction in hydrogen for the ::ame mate¬ri~ls and similar conditions for reduction. When reduction was in a hydrogen gas at 600°0 for 2, 3, 4, 5 and 6 hours, th:t the reduced microspheres density increases increasing the reduction time up to 4 hours. The reduced micro spheres in hydroge~ or ammonia atmosphere at 60000 for 2 hours were sintered in an atmosphere of ammonia