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
  • G21C3/60—Metallic fuel; Intermetallic dispersions
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C43/00—Alloys containing radioactive materials
• • 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

• This invention relates to uranium alloys. Particular alloys are herein described together with their heat treatments which have been developed by the inventors with the purpose of preventing in the fuel elements any preferential orientation, any coarse grains and any particular structure which during the research work proved to be undesirable; all these imperfections at the moment in which the fuel is employed in a nuclear reactor would result in dimensional modifications which are known under the name of growth under irradiation or would produce a rough surface of the element.
• Molybdenum added to uranium as an alloying element, is effective for producing ,a fine grains structure as a result of appropriate heat treatments; but, due to its large neutron absorbing cross section, it must be employed as an alloy component at the lowest possible percentage.
• the inventors have also found that structures of uranium alloys with zirconium are not sufficiently thermally stable.
• the alloys after casting in the form of unrefined bars show grains the size of which ranges from 100 to 175 a.
• a better refinement and more homogeneous grains can be obtained by heating again the alloy in the 7 phase (e.g. 900 C.) and subsequently cooling it at the rate of to 80 C. per minute. At a cooling rate lower than 5 C. per minute, rather coarse grains and lamellar structures are produced. At a cooling rate greater than 80 C. per minute, both a refinement of the grains and a finer lamellar structure are obtained; however the structures so produced are much less thermally stable (e.g. when subjected to a subsequent extended heating at 550 C.) than those obtained through a cooling rate ranging from 5 to 80 C. per minute.
• the heat treatments of ternary alloy bar conforming to the above specifications give a structure with or. grains the size of which ranges from 20 to 100 depending on the cooling rate.
• uranium alloys are prepared by melting a uranium ingot, together with a basic alloy, in a graphite crucible to which a lining of electro-melted magnesium oxide has been applied by centrifugal casting.
• the basic alloy is produced by melting uranium together with molybdenum and niobium or zirconium in 3,343,947 Patented Sept. 26, 1967 "ice an arc furnace and casting an ingot containing from 6 to 10% by weight of alloying elements.
• the furnace charge for producing the uranium alloys of this invention is melted by means of high frequency induction heating in vacuum.
• the product is kept in the melted state inside the crucible at 1,300'1,400 C. for 30 minutes and then is cast in a graphite chill to which a lining of electro-melted magnesium oxide has been applied by centrifugal casting and thereafter it is left to cool in the chill.
• uranium alloys bars are obtained the diameters of which range from 26 to 33 mm. and which are up to 1,000 mm. long.
• the size of the a grains ranged from to g.
• the size of the on grains in the unrefined cast bars can be modified within a fairly wide range, by means of a heat treatment consisting of heating the alloy up to a high temperature (e.g. 900 C.) and subsequently cooling it in a continuous way at the rate of 5 to 80 C. per minute.
• the treatment is carried out eiher in vacuum or in an inert atmosphere (as in argon) and, as already stated, it gives a structure of which the grain size ranges from 20 to 1001.1. depending on the cooling rate.
• a bar which has undergone the above heat treatment is free from the preferential orientations and the remarkable distortions which generally occur in the case of a very sharp cooling as for instance in a quenching.
• niobium (c) 0.3% by weight molybdenum and 2.0% by weight zirconium Heating in 7 phase (at 900 C.) during two hours in vacuum. Cooling at the rate of 60 C. per minute in vacuum. Average size of the a grains after heat treating:
• Uranium-molybdenum-niobium alloys having a fine grain structure after casting, said alloys having a molybdenum content from 0.1 to 0.3% by Weight and a niobium content from 0.6 to 0.8% by weight, the remainder of said alloy being substantially composed of uranium.
• a uranium-molybdenurn-niobium alloy having a fine grain structure after casting; said alloy having a molybdenum content of 0.5 by Weight and a niobium content of 0.5% by weight, the remainder of said alloy being substantially composed of uranium.
• Uranium-molybdenum-zirconium alloys having a fine grain structure after casting, said alloys having a molybdenum content from 0.2 to 0.4% by weight and a zirconium content from 1.5 to 2.2% by weight, the remainder of said alloys being substantially composed of uranium.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Dispersion Chemistry (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Mechanical Engineering (AREA)
• Materials Engineering (AREA)
• Plasma & Fusion (AREA)
• General Engineering & Computer Science (AREA)
• High Energy & Nuclear Physics (AREA)
• Manufacture And Refinement Of Metals (AREA)
• Monitoring And Testing Of Nuclear Reactors (AREA)
• Inorganic Compounds Of Heavy Metals (AREA)

Applications Claiming Priority (1)

Publications (1)

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Cited By (3)

Citations (6)

• 1965
  • 1965-05-21 FR FR17963A patent/FR1454421A/fr not_active Expired
  • 1965-05-21 DE DE19651483196 patent/DE1483196A1/de active Pending
  • 1965-05-28 GB GB22745/65A patent/GB1097904A/en not_active Expired
  • 1965-06-04 NL NL6507129A patent/NL6507129A/xx unknown
  • 1965-06-18 BE BE665642D patent/BE665642A/xx unknown
  • 1965-06-21 LU LU48886A patent/LU48886A1/xx unknown
  • 1965-06-24 US US466834A patent/US3343947A/en not_active Expired - Lifetime

Patent Citations (6)

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