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Title: STUDY OF DISPERSANT AGENTS FOR THORIUM OXIDE

Abstract

S>A preliminary study of dispersing agents for thorium oxide was completed and several of the dispersants have possible uses. Also many of the industrial dispersing agents tested are not usable with thorium oxide due to induced behavior causing balling and caking. The effects of nitric acid concentration were observed to also effect each dispersing agent. (auth)

Authors:
;
Publication Date:
Research Org.:
Oak Ridge National Lab., Tenn.
OSTI Identifier:
4109473
Report Number(s):
CF-59-8-43
NSA Number:
NSA-15-008584
Resource Type:
Technical Report
Resource Relation:
Other Information: Orig. Receipt Date: 31-DEC-61
Country of Publication:
United States
Language:
English
Subject:
CHEMISTRY; BEHAVIOR; COMPACTING; DISPERSIONS; GALLING; NITRIC ACID; THORIUM OXIDES

Citation Formats

Bate, L.C., and Leddicotte, G.W.. STUDY OF DISPERSANT AGENTS FOR THORIUM OXIDE. United States: N. p., 1959. Web. doi:10.2172/4109473.
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Bate, L.C., & Leddicotte, G.W.. STUDY OF DISPERSANT AGENTS FOR THORIUM OXIDE. United States. doi:10.2172/4109473.
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Bate, L.C., and Leddicotte, G.W.. Sat . "STUDY OF DISPERSANT AGENTS FOR THORIUM OXIDE". United States. doi:10.2172/4109473. https://www.osti.gov/servlets/purl/4109473.
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@article{osti_4109473,
title = {STUDY OF DISPERSANT AGENTS FOR THORIUM OXIDE},
author = {Bate, L.C. and Leddicotte, G.W.},
abstractNote = {S>A preliminary study of dispersing agents for thorium oxide was completed and several of the dispersants have possible uses. Also many of the industrial dispersing agents tested are not usable with thorium oxide due to induced behavior causing balling and caking. The effects of nitric acid concentration were observed to also effect each dispersing agent. (auth)},
doi = {10.2172/4109473},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Sat Aug 01 00:00:00 EDT 1959},
month = {Sat Aug 01 00:00:00 EDT 1959}
}
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Technical Report:
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DOI:  10.2172/4109473
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  • ; ;
    This investigation characterizes the double action compaction process through a study of the punch force and press motions involved in the operation of a Dorst model mechanical compacting press. Thorium oxide pellets were pressed with length-to-diameter ratios ranging from 0.25 to 1.95 and green densities of 55 to 64% theoretical density to identify controlling press parameters affecting crack type defects in the sintered high density pellet structure. Edge cracking was determined to be a compaction induced defect resulting from overpressing at the top of the pellet. Reduction in edge cracking without sacrificing geometric green density was achieved by control ofmore » the pellet axial density gradient.« less

  • < = B 9 8 9 = = ; < eposits formed on surfaces of the containing system during circulation of aqueous ThO/sub 2/ slurries at high temperature. Although entire surfaces of systems were coated with 1/4 to 1/8-in.- thick thoria deposits, cake formation was usually localized, forming preferentially in the pump impeller. Frequently, impeller deposits accelerated bearing failure. Cake formation was usually accompanied by formation of equal dense spherical aggregates 5 to 60 mu in diameter which remained suspended in the slurry. Caking and sphere forming phenomena, as investigated by tests of slurry properties in the laboratory and inmore » a 30-gpm slurry loop, are described, as are methods for preventing caking. Thoria cakes and spheres are believed to form by reagglomeration of small particles or fragments worn or chipped off the larger thoria particles composing the initial slurry. It is thought that small fragments are forced over each other by the shear stress into positions of minimum energy where they are held together by van der Waals' forces. Thoria solubility is not believed to be an appreciable factor in cske or sphere formation. The extent of chemical bonding in the deposits is not clear. Greatest cake-forming tendency was noted in thoria prepared by calcination of Th(C/sub 2/O/sub 4/)/sub 2/ at 800 deg C, though cakes did occur with other ThO/ sub 2/ preparations. Deposits formed from oxide batches that contained particles more resistant to degradation were softer, apparently because there were fewer fine fragments. A deposition preference between different metal surfaces as well as between differert velocity sections was noted. Cake formation by fresh batches of thoria, that is, slurry in which the initial oxide particles were not made finer by previous circulation, is prevented by any factor which reduces particle comminution. Cake formation is avoided if particles are too resistant to degradation or if they degrade rapidly to intermediate-size particles. Intermediate-size particles, 0.1 to 0.5 mu , apparently do not yield fine fragments readily because of the reduced shear forces which are acting on smaller particles. Improved particle integrity can be accomplished by the method of oxide preparation, for example, the use of high calcining temperature or long digestion time. Cake formation by fresh oxides is also prevented by the addition of small quantities of surface-active electrolytes to the slurry. Effective electrolytes tested included CrO/sub 3/, NsAlO/sub 2/, Na/sub 2/SiO/sub 3/, and MoO/sub 3/. The electrolytes are thought to be effective by means of reducing particle fragmentation. Prevention of cske formation by slurries already containing particles in the caking-size range (e.g., a slurry composed of spheres produced during circulation) is more difficult, because agglomeration of the fine particles must be prevented. Lithium sulfate tended to reduce cake formation but was not completely effective. Other electrolyte additives tested (CrO/sub 3/ and NsAlO/sub 2/) failed to hinder cake formation during ThC/sub 2/ sphere circulation. (These spheres were "loop produced" in a previous slurry circulation experiment.) However, after extended circulation during which partial dispersion of the spheres took place, cake formation was almost absent. It is postulated that the very fine particles wearing off the spheres gradually agglomerate into particles which are too large to form cskes but so small that fine particles or fragments are not worn off readily. Autoclaving of fresh thoria in water or dilute acids did not strengthen the particles sufficiently to prevent cake formation. Cake formation did not occur when the loop circulation temperature was reduced to 45 deg C. Extremely low thoria concentration did not deter cake formation. The integrity of loop-produced spheres was greatly improved by a combination of chemical and thermal treatment but was not improved sufficiently to prevent cake formation. Cake deposited in a ThO/sub 2/- circulation system is partially destroyed by thermal cycling and can be removed« less

  • The surface areas of several thorium oxide and thorium oxide--uranium oxide preparations were measured by the emanation method. The radioactive gas- counting system employed is described, and a discussion of the procedure for converting counting data to terms of emanating power and finally to surface area values is given. Surface area values by the emanation method were compared with BET values from like samples. The difference between values obtained by the two methods was attributed to the efficiency of the radioactive gas-detecting system and the porosity of the oxide samples. The contribution of Rn/sup 2//sup 2//sup 2/ from the oxidemore » samples containing uranium was found to be negligible and presented no problem. Samples fired at temperatures above 1500%DEC for one hour in air exhibited a marked increase in "room temperature" emanation rates. The predicted lattice-loosening temperature of metal oxides is approximately one-half their absolute melting point. Above this temperature, sufficient thermal agitation is induced to permit exchange and possibly permanent displacement of atoms in the crystal lattice. Therefore, firing these oxide preparations at temperatures above 1500 deg C would probably result in lattice defects throughout the crystal structure, with the surface defects contributing to an increase in surface area and a corresponding increase in the emanation rate. (auth)« less