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.

Plutonium /Plutonium polymer/Colloids /Sols/Sol-gel process/ Nitrates /DenitrationSummary Studies of plutonium chemical behavior conducted in conjunction with plutonia sol-gel process development at ORNL are described. The colloidal solutions produced consist of "Pu(IV) polymer," and this is therefore the study of polymeric plutonium behavior. Spectrophotometric, electron diffraction, and electron microscopy studies, in addition to specific studies that were concerned with the colloidal behavior of Pu(IV) polymer, indicate several characteristics of polymer that are not generally recognized. The particle nature of Pu(IV) polymer indicated by electron microscopy, the amorphous-crystalline characteristics of primary polymer particles demonstrated by electron diffraction, and the reversible and irreversible aggregation of the primary particles shown by spectrophotometric techniques present a useful view of the nature of Pu(IV) polymer that has been helpful in solving orunderstanding various types of processing problems involving plutonium hydrolytic behavior. The colloidal characteristics of Pu (IV) polymer and crystallite growth of primary polymer particles by thermal denitration are also described.

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A resin-bead loading and calcination technique developed at the Transuranium Processing Plant (TRU) of the Oak Ridge National Laboratory (ORNL) is used routinely for producing uniform particles of curium-americium oxide in the size range desired for the fabrication of targets for irradiation in the High Flux Isotope Reactor (HFIR). TRU is the storage, production, and distribution center for the heavy-element research program of the U. S. Department of Energy. Target rods are remotely fabricated at TRU, irradiated in the HFIR, and then processed chemically at TRU for the separation and purification of the heavy actinide elements. Berkelium, californium, einsteinium, and fermium are distributed to researchers. Unburned curium and americium that is recovered during the chemical processing is refabricated into targets for additional irradiation. About 200 g of curium-americium oxide is produced annually for use in fabricating HFIR targets. 50Start First Page Here. 35technique allows this criterion to be met easily even though remote operation is necessary for curium oxide production.In the following sections, a brief chronology of the development of this process is presented; the materials, equipment, and basic operations relating to the resin-bead loading and calcination method of producing sized curium-americium oxide microspheres at TRU are described; and typical production data are presented. Process DevelopmentDo Not Type Below This Line.During the mid-1960's, the feed material for the HFIR targets was 242p u . Plutonium oxide was prepared in glove box operations using hydroxide precipitation, calcination, andgrinding {]_)» When curium became available for use in HFIR targets, a sol-gel method for preparing curium oxide remotely was developed and was used from 1968 through 1970 (8).However, the sol-gel process was not well-suited for the small batch sizes that are involved in the TRU program. F.quipnient startup and shutdown were a major part of the operating time.The processing was plagued with erratic operation, poor yields, and production of oversize oxide particles that required undesirable grinding and screening operations. A simpler, more reliable oxide preparation method that was adaptable to remote operation was needed.The resin-bead loading and calcination process was deve- hich 150 g of curium oxide was successfully prepared and subequently used in HFIR targets. Two resins, which required lifferent process steps, were tested. The process using Dowex 0W resin, which contains sulfonic acid exchange groups, was elected for continued curium oxide production over a similar irocess using Amberlite IRC-50 resin, which contains carboxylic acid exchange groups. The Dowex 50W process (Fig. 1) requires ewer steps and is better suited for remote operation. In the )owex SOW process, pre-sized Dowex 50W-X8 resin beads are oaded to saturation from a dilute nitric acid solution of rurium-americium. The resin is rinsed with water and then the esin matrix is destroyed by calcination to form dense actinide 3xide micro...

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