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Internal gelation jUranylnitrate IHexamethylenetetramine/Urea / pH /PrecipitationAbstiact Studies were conducted to investigate the chemical reactions thought to be important during hydrolysis and gelatinous precipitation of acid-deficient uranyl nitrate (ADUN) in the internalgelation process for microsphere preparation. Investigations performed to determine pH profiles during urania gelation in conjunction with hexamethylenetetramine (HMTA) decomposition experiments were useful in defining important characteristics of four reactions and in determining process variables that affect reaction rates as well as pH regions in which ADUN precipitates. These variables are the nitrate-to-uranium and the HMTA-touranium mol ratios, the uranium concentration, and the gel formation temperature. The influenae of these process variables on the Solution pH and precipitation reactions is discussed.only limited supporting data were given.) Our study suggests that an increased understanding of these reactions and their kinetics should facüitate control of the product characteristics, which can vary widely with variations in process parameters. It is this inherent capability to produce metal oxide microspheres with precise properties that makes these processes uniquely useful for many applications.The major objectives of this study were to define and better understand the principal reactions that occur during hydrolysis and gelatinous precipitation of ADUN and to determine the effects of process variables on these reactions. A secondary objective was to determine the pH at which precipitation and gelation occur as a function of key process variables.

NTlS price codes-Printed Copy: A03 Microfiche A01 This report was prepared as an account of work sponsored by an agency of the United StatesGovernment Neither theU nited StatesGovernment nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy completeness, or usefulness of any information, apparatus product, or process disclosed, or represents that its use would not infringe privately owned rights Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise. does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United StatesGovernment or any agency thereof The views and opinions of authors expressed herein do not necessarily state or reflect those of theUnitedStatesGovernrnent or any agency thereof. ORNL/TM-9 5 6 5 DE85 015071 C h e m i c a l T e c h n o l o g y D i v i s i o n ALPHA RADIOLYSIS AND OTHER FACTORS AFFECTING HYDROLYSIS OF TRIBUTYL PHOSPHATE

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