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Title: Laboratory development of a process for recovering uranium from Rover fuel by combustion, liquid-phase chlorination with hexachloropropene, and aqueous extraction

Abstract

Declassified 24 Sep 1973. The purpose of this work was to develop a process for recovering the uranium from spent Rover fuels. Only one reactor is used, and the process involves a 4-hr combustion of the fuel in oxygen at about 800 deg C, a 4-hr chlorination of the U/sub 3/O/sub 8/-Nb/ sub 2/O/sub 5/ ash in refluxing hexachloropropene at 180 deg C, dissolution-extraction of the UCl/sub 4/ and NbCl/sub 5/ products at room temperature by dilute nitric acid, and extraction of the uranium from the resulting acid solution with 30% TBP in Amsco diluent. The results indicate that an extract containing 50 g of uranium per liter can be produced in seven or eight extraction stages, with total uranium losses of less than 0.02%. Corrosion rates of several possible construction materials during chlorination are less than 0.1 mil/month. Problems in the process involve handling about 10% of the niobium as a solid during the liquid- liquid separations, and handling solutions containing chloride. The results of this laboratory-scale work indicate that the liquid-phase chlorination and subsequent extraction operations are reducible to large-scale practice, since these operations resemble the liquid-phase operations typically performed in radiochemical separation plants. (auth)

Authors:
;
Publication Date:
Research Org.:
Oak Ridge National Lab., Tenn. (USA)
OSTI Identifier:
4392172
Report Number(s):
ORNL-3435
NSA Number:
NSA-29-004989
DOE Contract Number:
W-7405-ENG-26
Resource Type:
Technical Report
Resource Relation:
Other Information: Declassified 24 Sep 1973. Orig. Receipt Date: 30-JUN-74
Country of Publication:
United States
Language:
English
Subject:
N40450* -Chemistry-Radiochemistry & Nuclear Chemistry- Reactor Fuel Processing; *SPENT FUELS- REPROCESSING; *URANIUM- SEPARATION PROCESSES; AMSCO; CHLORINATED ALIPHATIC HYDROCARBONS; CHLORINATION; COMBUSTION; CORROSION; DISSOLUTION; NIOBIUM; NIOBIUM CHLORIDES; NIOBIUM OXIDES; NITRIC ACID; ORGANIC CHLORINE COMPOUNDS; OXYGEN; ROVER REACTORS; SOLVENT EXTRACTION; TBP; URANIUM CHLORIDES; URANIUM OXIDES U3O8; VERY HIGH TEMPERATURE; NESDPS Office of Nuclear Energy Space and Defense Power Systems

Citation Formats

Gens, T.A., and Borne, T.B. Laboratory development of a process for recovering uranium from Rover fuel by combustion, liquid-phase chlorination with hexachloropropene, and aqueous extraction. United States: N. p., 1963. Web. doi:10.2172/4392172.
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Gens, T.A., & Borne, T.B. Laboratory development of a process for recovering uranium from Rover fuel by combustion, liquid-phase chlorination with hexachloropropene, and aqueous extraction. United States. doi:10.2172/4392172.
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Gens, T.A., and Borne, T.B. Fri . "Laboratory development of a process for recovering uranium from Rover fuel by combustion, liquid-phase chlorination with hexachloropropene, and aqueous extraction". United States. doi:10.2172/4392172. https://www.osti.gov/servlets/purl/4392172.
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@article{osti_4392172,
title = {Laboratory development of a process for recovering uranium from Rover fuel by combustion, liquid-phase chlorination with hexachloropropene, and aqueous extraction},
author = {Gens, T.A. and Borne, T.B.},
abstractNote = {Declassified 24 Sep 1973. The purpose of this work was to develop a process for recovering the uranium from spent Rover fuels. Only one reactor is used, and the process involves a 4-hr combustion of the fuel in oxygen at about 800 deg C, a 4-hr chlorination of the U/sub 3/O/sub 8/-Nb/ sub 2/O/sub 5/ ash in refluxing hexachloropropene at 180 deg C, dissolution-extraction of the UCl/sub 4/ and NbCl/sub 5/ products at room temperature by dilute nitric acid, and extraction of the uranium from the resulting acid solution with 30% TBP in Amsco diluent. The results indicate that an extract containing 50 g of uranium per liter can be produced in seven or eight extraction stages, with total uranium losses of less than 0.02%. Corrosion rates of several possible construction materials during chlorination are less than 0.1 mil/month. Problems in the process involve handling about 10% of the niobium as a solid during the liquid- liquid separations, and handling solutions containing chloride. The results of this laboratory-scale work indicate that the liquid-phase chlorination and subsequent extraction operations are reducible to large-scale practice, since these operations resemble the liquid-phase operations typically performed in radiochemical separation plants. (auth)},
doi = {10.2172/4392172},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Fri Jun 28 00:00:00 EDT 1963},
month = {Fri Jun 28 00:00:00 EDT 1963}
}
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Technical Report:
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DOI:  10.2172/4392172
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  • Declassified 24 Sep 1973. Two chloride volatility processes for the recovery of uranium from the combustion ash from spent Rover fuel were studied in the laboratory. The fuel consists of graphite impregnated with uranium carbide. The cooling channels are of niobium carbide. In each method, the uranium is isolated as UCl/sub 4/ and it may be further processed by aqueous solvent extraction (Darex) or fluoride volatility methods. The combustion-- chlorination process involves burning the fuel elements in oxygen at 700 to 9O0 deg C and then chlorinating the uranium and niobium oxide products with 15 vol% CCl/sub 4/-85 vol% Cl/submore » 2/ at 500 deg C. The volatilized uranium and niobium chlorides are collected at room temperature and then separated by selective volatilization of niobium chloride by controlled heating to 400 deg C. Uranium recovery is quantitative, and less than 1% of the niobium remains with the uranium. Corrosion rates for nickel or high-nickel alloys are expected to average about 0.5 mil/month through the cycle. The combustion-chlorination process should be reducible to large-scale practice because the reactions proceed readily, and the corrosion problems are minor. In the direct chlorination process, rough-crushed Rover fuel is treated with chlorinating and mixed chlorinating-- oxidizing gases at 800 deg C. Uranium and niobium chlorides volatilize and are separated as in the combustion-- chlorination process. Uranium recoveries are greater than 99%. About 40% of the graphite burns. Corrosion rates are excessive, more than 1 in./ month for metal containers. Consequently, direct chlorination is not presently reducible to large-scale practice. (auth)« less

  • ;
    Declassified 24 Sep 1973. The development of aqueous methods for processing Rover fuel elements is summarized. The Rover fuel elements are dispersions of carbon-coated UC/sub 2/ particles in graphite matrices; hydrogen coolant channels in the elements are lined with NbC to retard corrosion. Since the coated particles are impervious toattack by aqueous reagents , burning of the fuel is necessary at one stage of the process. The two main processes under development are (1) the Deline-Burn-Dissolve (DBD) process, and (2) the BurnDissolve process. Both processes result in almost quantitative uranium recovery; however, based on the laboratory experiments, the DBD processmore » appears to have the best chance of success on an engineering scale. (auth)« less

  • Declassified 30 Aug 1973. Several aqueous methods for recovery of uranium from irradiated NbC-lined graphite-base Rover (nuclear rocket) fuels were evaluated on a laboratory scale. The burn-leach process, which is described in this report, is considered to be the simplest and best of the aqueous methods. ln the first step of this process, the fuel is burned at 700 to 750 deg C, preferably in a fluidized-bed of inert alumina. Volatilization of all fission products except ruthenium is expected to be low during combusion. The fluidized- bed product is transferred to a leacher and is leached first with hot 6more » to 10 M HNO/sub 3/ to recover 95 to 99% of the uranium; then, the residue is leached at 115 deg C with 10 M HNO/sub 3/-5 M HF (F/Nb mole ratio of about 10) to recover the remaining 1 to 5% of the uranium and practically all of the niobium. After leaching, the system is washed with water and all solutions are combined, along with the appropriate amount of aluminum nitrate solution, to produce a final solution having the composition 3 M HNO/sub 3/-- 1 M total F--0.06 M UO/sub 2/(NO/ sub 3/)/sub 2/--0.1 M Hsub 2/NbOF/sub 5/-0.2 M Al(NO/sub 3/)/sub 3/ . The uranium can be recovered from this solution and decontaminated by conventional tributyl phosphate solvent extraction procedures. Because the burnups of the Rover fuels are quite low (<0.04 at.%), plastic or plastic-lined vessels can be used for containing the highly corrosive HF--HNO/sub 3/ solutions in the leaching and feed adjustment steps. With aluminum nitrate present in the feed solution, rates of corrosion of types 309SCb and 347 stainless steels were <0.4 mil/month at room temperature, indicating that these alloys could be used as materials of construction for the solvent extraction system. Combustion of Rover fuel in a fixed-bed bunner at 700 to 800 deg C has also been studied. The U/sub 3/O/sub 8/- Nb/sub 2/O/sub 5/ combustion ash (even that produced at 1200 to 1300 deg C) can be dissolved in HF-HNO/sub 3/ (F/Nb mole ratio of about 10), using the two-stage leaching process. However, fixed-bed burning may not be as satisfactory as fluidized-bed burning because of engineering problems. Direct leaching of the ash (from either a fluidized-bed or fixed-bed burner) with 10 M HNO/sub 3/--5 M HF is an alternative to the two-stage leaching procedure but is not as practicable. Uranium and niobium recoveries are slightly lower in the direct leaching method; furthermore, uranyl fluoride will precipitate from the leach solution unless it is diluted with water while still hot. (auth)« less

  • Declassified 24 Sep 1973. Two detailed, conceptual process, equipment, and plant designs were prepared for facilities for recovering spent Rover fuel (highly enriched uranium-graphite) at the Idaho Chemical Processing Plart. The results of the study indicate that the fluoridevolatility process is preferred on both economic and technical grounds. Both processes employ a comnion fuel shipping, storage, and charging system and use continuous, fluidized-bed oxidation of the fuel as the first step of the head-end operation. Subsequent operations in the aqueous process include batch leaching the ash with 5 M HF--10 M HNO/sub 3/ in two parallel lines of Teflon-lined leachingmore » and feed-preparation equipment, followed by solvent extraction to decontaminate and recover the uranium as uranyl nitrate. Post-burning operations in the fluoride-volatiiity process include the continuous fluidized-bed and moving-bed fluorination of the ash followed by partial condensation to remove niobium pentafluoride and passage of the UF/sub 6/ through heated sodium fluoride pellets to completely decontaminate the uranium. The uranium is recovered as uranium hexafluoride. (auth)« less