Classifications

• • G—PHYSICS
  • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
  • G21C—NUCLEAR REACTORS
  • G21C3/00—Reactor fuel elements and their assemblies; Selection of substances for use as reactor fuel elements
  • G21C3/42—Selection of substances for use as reactor fuel
  • G21C3/58—Solid reactor fuel Pellets made of fissile material
  • G21C3/62—Ceramic fuel
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B32/00—Carbon; Compounds thereof
  • C01B32/90—Carbides
  • C01B32/914—Carbides of single elements
  • C01B32/928—Carbides of actinides
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2006/00—Physical properties of inorganic compounds
  • C01P2006/10—Solid density
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2006/00—Physical properties of inorganic compounds
  • C01P2006/80—Compositional purity
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E30/00—Energy generation of nuclear origin
  • Y02E30/30—Nuclear fission reactors
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S376/00—Induced nuclear reactions: processes, systems, and elements
  • Y10S376/90—Particular material or material shapes for fission reactors
  • Y10S376/901—Fuel

Definitions

• the present invention relates to fuels for nuclear reactors and has particular reference to fuels suitable for use in fast reactors.
• a process for producing a high density, enriched uranium carbide fuel material comprising the steps of providing an admixture of uranium and plutonium carbides, said admixture having a particle size substantially in the range 2 to 4 microns, a carbon content in the range 48 to 53 atomic percent and an oxygen content below 1 percent by weight, compacting said powder into pellets and sintering the pellets in an inert atmosphere of high purity inert gas.
• the difficulties experienced by previous workers in obtaining satisfactory sintered products were mainly due to the fact that excessive oxygen was introduced into the powders either before or during sintering and it appears that the. presence of large quantities of oxygen in the powder results in poor sintering.
• the oxygen content of the starting powder should be low and that the pellets obtained by compacting this powder should be sintered in an atmosphere which is inert and of high purity.
• the inert gas used for the sintering atmosphere is preferably argon having an oxygen content of less than 10 parts per million and a water vapour content of less than 10 parts per million. This atmosphere is conveniently obtained by passing high purity argon through a molecular sieve and over hot uranium.
• the very fine powders required as the starting material for the process of the present invention rapidly absorb oxygen and water vapour from the atmosphere and we have found that when the powders were prepared in an argon atmosphere containing less than parts per million of oxygen and 100 parts per million of water vapour, they showed a weight gain of approximately /2 percent per hour. Thus, even in an atmosphere containing quite small amounts of oxygen and water vapour, oxidation of the powders occurs at quite a fast rate. Therefore, if such an atmosphere is used in preparing the powders for use according to the present invention, it is necessary to effect all operations extremely rapidly in order to minimise the oxidation of the powder. a
• the mixed carbide material which is used in the present process may be prepared by any suitable known method, for example, are melting the metal with carbon, or reacting the oxide with carbon. In either case the carbides may be prepared together or separately and subsequently mixed together into the appropriate amounts.
• the oxygen content of the material must be maintained below the specified maximum permissible figure of 1% by weight. It will however be realised that although the handling conditions during the preparation of the fine powdered starting material of considerable importance in ensuring the purity of the starting material, this does not form part of the process of the present invention but is merely a preliminary step to the present process.
• the preferred degree of enrichment that is required for the fast reactors under study corresponds to 15 atomic percent of plutonium and with this proportion of plutonium, the proportion of carbon from 50 to 53 atomic percent lies in that portion of the phase diagram which corresponds, in the product, to a coherent matrix of uranium carbide, containing possibly a small proportion of plutonium carbide in solid solution and a disperse phase of plutonium sesquicarbide.
• the products having less than 50 atomic percent of carbon should show a disperse phase of uranium and plutonium metal but in point of fact we have not found such a disperse phase and we have deduced that a small percentage of oxygen is present in solution in the monocarbide.
• compositions are preferred containing approximately 52 atomic percent carbon so that the majority of the plutonium is present in the form of the sequicarbide and little is present in solid solution in the uranium monocarbide which therefore has its highest conductivity value.
• Example 1 In a preferred arrangement in accordance with the invention, a sample of mixed carbide which had been prepared by arc melting the metals with carbon in the requisite proportion was ground for a long period of time (about 20 hrs.) in a ball mill and the product thus obtained was sieved to retain the fraction smaller than 4 microns, this fraction being predominately larger than 2 microns.
• the are melting to form the mixed carbides was conducted in such a way that the amount of impurities were kept to a minimum and in particular graphite electrodes were used since with tungsten electrodes the small amount of tungsten introduced during the arc melting appears to prevent satisfactory sintering.
• the milling was eifected in such a way that the oxygen content of final powder was less than 1%.
• a 25 gm. portion of the mixed monocarbide powder thus prepared was then divided into five lots and each of these was formed into a pellet by being compacted under a pressure of 40 to 100 tons per square inch.
• Naphthalene in an amount of /2 to 1 percent by weight, could be used as a binder if desired, or alternatively, a die wall lubricant might be preferred.
• the compacts thus obtained had a green density of between 8 and 9 gms./cc. and were then sintered in an argon atmosphere of high purity at 15 C. for approximately four hours whilst being supported on molybdenum boats.
• the sintered product had a silvery appearance and a bulk density of 13.2 gms./ cc. Specific gravity measurements gave a value in the region of 13.2 gms/cc., thus showing that the open porosity of the product was very small. It should be noted that the theoretical density of the material was 13.6 gms/cc.
• a process for producing a high density enriched uranium carbide fuel body comprising the steps of providing a powder having a particle size distribution of essentially all particles in the range 2 to 4 microns, said powder comprising an admixture of uranium carbide and plutonium carbide having a carbon content of 48-53 atomic percent and containing less than 1% by weight of oxygen, compacting said powder into pellets and sintering said pellets in an inert atmosphere of high purity inert gas.
• plutonium carbide content corresponds to 15 atomic percent plutonium with respect to the total number of metal atoms.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Organic Chemistry (AREA)
• Ceramic Engineering (AREA)
• Plasma & Fusion (AREA)
• General Engineering & Computer Science (AREA)
• High Energy & Nuclear Physics (AREA)
• Inorganic Chemistry (AREA)
• Inorganic Compounds Of Heavy Metals (AREA)
• Carbon And Carbon Compounds (AREA)

Applications Claiming Priority (1)

Publications (1)

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ID=10008442

Family Applications (1)

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Citations (4)

Family Cites Families (1)

• 0
  • BE BE630429D patent/BE630429A/xx unknown
• 1962
  • 1962-04-02 GB GB12641/62A patent/GB954720A/en not_active Expired
• 1963
  • 1963-03-30 DE DEU9686A patent/DE1294573B/de active Pending
  • 1963-04-02 ES ES286687A patent/ES286687A1/es not_active Expired
• 1965
  • 1965-05-21 US US457835A patent/US3338989A/en not_active Expired - Lifetime

Patent Citations (4)

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