Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C28/00—Alloys based on a metal not provided for in groups C22C5/00 - C22C27/00
• • G—PHYSICS
  • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
  • G21C—NUCLEAR REACTORS
  • G21C7/00—Control of nuclear reaction
  • G21C7/06—Control of nuclear reaction by application of neutron-absorbing material, i.e. material with absorption cross-section very much in excess of reflection cross-section
  • G21C7/24—Selection of substances for use as neutron-absorbing material
• • 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

Definitions

• Hafnium base alloys of improved tensile strength and suitable for nuclear reactor control rods consist of, by weight, 0.1% in total amount of one or more of the beta-stabilising elements niobium, chromium, molybdenum, nickel and iron, up to 0.5% silicon, up to 2% in total amount of at least one of the alpha stabilising elements tin and aluminum with the total alpha and beta stabilisers not exceeding 5%, balance hafnium and impurities.
• This invention relates to hafnium alloys.
• Hafnium is used for control rods in nuclear reactors because of its high neutron absorption coefficient. Its tensile strength is not great (about 25 tons/sq. in.) but it is very ductile and has good corrosion resistance.
• a hafnium-base alloy consists, by weight of 0.l-5% in total amount of one or more of the beta-stabilising elements niobium, chromium, molybdenum, nickel and iron, 0-0.5% silicon and optionally, 02% in total amount of one or both of the alpha stabilising elements, tin and aluminum, the total amount of alpha and beta stabilisers not exceeding 5%, balance hafnium and impurities.
• the impurities include zirconium in amounts up to about 4%, this unusually high impurity level being due to the common mineralogical source of hafnium and zirconium. Such a quantity of zirconium does not adversely affect the properties and hafnium having a high zirconium content is cheaper than purer grades.
• beta stabilising elements The effect of the beta stabilising elements is to strengthen hafnium; the alpha stabilising elements, whilst having little effect on strength when added alone, generally improve the properties of the beta stabilised alloy.
• beta stabilisers produces marked improvements in tensile strength and proof stress whilst good ductility is retained. There is a difference in the effectiveness of individual beta stabilisers in raising the tensile properties and molybdenum is particularly effective in this respect. Where more than one beta stabiliser is present, certain combinations are more effective than others, for example, chromium and silicon are more effective than niobium and molybdenum which, in turn, are better than chromium and molybdenum.
• alpha stabilisers on tensile properties is a further small increase in tensile strength and proof Patented June 2, 1970 stress with some loss of ductility.
• Certain groups of alpha and beta stabilisers are more effective than others as can be seen from the tables appended hereto and the more complexalloys, in general, have the greatest strength though the ductility and proof stress Vary with the combination of elements.
• the best alloys have twice the tensile strength and proof stress of hafnium with half the ductility.
• Sn Corrosion resistance depends upon the alloying elements added and the amount present. Chromium and nickel have least effect whilst molybdenum has a marked effect on the surface appearance. Certain of the more complex alloys have better corrosion resistance than certain binary alloy compositions, but the difference between pure hafnium and alloys having the least corrosion resistance to high temperature pressurised steam is one of small degree.
• the corrosion resistance of the alloys of the invention was determined by exposing cleaned bright samples to steam at a pressure of atmospheres and at a temperature of 400 C. for 72 hours.
• the corrosion behaviour of the alloys was compared by the appearance of the surface of the samples in accordance with the following classification.
• class (A) has the best corrosion resistance.
• the nuclear properties are not significantl affected.
• the tensile properties and corrosion resistance of a number of alloys in accordance with the invention are shown by way of example in Tables I and II in comparison with pure hafnium.
• the tensile tests were carried out on rod and in the tables the abbreviation 4 /A, used in connection with the elongation values, refers to the gauge length of test pieces, that is, a gauge length equal to four times the square root of the area of the cross-section of the test piece.
• the corrosion resistance was determined in accordance with the above classification.
• Table III are shown examples of the improvement in the strength of sheet produced from alloys in accordance with the invention compared with commercially pure 3 It will be observed that the alloy B(L), Hf-1.1Sn-O.6Cr is heat-treatable to produce marked increases in tensile TABLE III,,TENSILE PROPERTIES OF STRIP strength and proof stress Whilst the ductility remains at a 55 2 ⁇ 02% high level. Analysed spcci- I.S., U.T.S., tion on Alloy composltion men t.s.i. t.s.i. 1 in.
• a hafnium-base alloy according to claim 1 contain- .A. 3 25 ing 0.15-1.25% chromium. i 1 3 1 20 3. A hafnium-base alloy according to claim 1 contain- A 25 ing 0.1-0.40% molybdenum.
• a hafnium-base alloy according to claim 1 containing 0.52.0% niobium. 5. A hafnium-base alloy according to claim 1 containing 0.15%0.75% iron.
• a hafnium-base alloy according to claim 1 contain- TABLE II ing 0.l50.5% nickel.
• a hafmum base alloy accordmg to clam 1 contain more of the alpha stabilising elements, Sn, Al ing O.60.8% chromium and (18-12% SiliCOIl. Elonga 8.
• a hafnium-base alloy according to claim 1 contain- N min 1 Corro- 0 7 P U T S tion, per ing 0.6-0.8% chromium and 0.752.0% tin.
• a hafnium base alloy according to clalm 1 consist ing of 0.75% tin, 0.05% chromium, 0.06% iron and T10 231911-0251 6 gig g 40 0.02% nickel, balance hafnium apart from impurities.
• c 30.4 43.9 is g 36.1? i t l 5 References Cited ft 5%: UNITED STATES PATENTS n a detilfined 6 2,234,969 3/1941 Hensel et a1. 75134 0.75Mo-0.8Sn-0.2Si. 0 39.1 51.5 15 45 2,810,640 10/1957 Bolkcom et a1. 134

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• Engineering & Computer Science (AREA)
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• High Energy & Nuclear Physics (AREA)
• Plasma & Fusion (AREA)
• General Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Battery Electrode And Active Subsutance (AREA)
• Soft Magnetic Materials (AREA)
• Footwear And Its Accessory, Manufacturing Method And Apparatuses (AREA)

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Citations (2)

• 1965
  • 1965-12-02 GB GB51234/65A patent/GB1095807A/en not_active Expired
• 1966
  • 1966-11-28 US US597206A patent/US3515544A/en not_active Expired - Lifetime
  • 1966-12-02 BE BE690637D patent/BE690637A/xx unknown
  • 1966-12-02 FR FR86059A patent/FR1503206A/fr not_active Expired

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