US3308033A - Tubular fuel pencil having a thin flexible can for nuclear reactors - Google Patents

Tubular fuel pencil having a thin flexible can for nuclear reactors Download PDF

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Publication number
US3308033A
US3308033A US473420A US47342065A US3308033A US 3308033 A US3308033 A US 3308033A US 473420 A US473420 A US 473420A US 47342065 A US47342065 A US 47342065A US 3308033 A US3308033 A US 3308033A
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US
United States
Prior art keywords
pencil
folds
corrugations
sheaths
fuel
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Expired - Lifetime
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US473420A
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English (en)
Inventor
Alfille Lucien
Charrault Jean Claude
Lafontaine Francois
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European Atomic Energy Community Euratom
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European Atomic Energy Community Euratom
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    • 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
    • G21C3/02—Fuel elements
    • G21C3/04—Constructional details
    • 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

  • the invention relates to a tubular fuel pencil for nuclear reactors, including for example pressure fluid cooled power reactors, the pencil mainly comprising a cylindrical outer can and a cylindrical inner can which co-operate to receive in the annular space between the cans, .a tube or stack of rings of fissile material and two plugs for connecting and closing the ends of the said space.
  • Pencils of this form are desirable in the case of fuels of high specic power, the fuel being in an annular shape with the advantage that the outside and inside surfaces of the pencil may be cooled, the idea being to increase greatly the heat-exchange surfaces in Contact With the heat vehicle fluid for a given fuel cross-section. It is also known that, except for plastic or flexible cans which are engaged with the fuel by the action of the pressursed heat vehicle fluid, the fuel being metallic such as uranium or uranium-based alloys, the use of pencils of the kind described is in general very limited because of the dilculties in providing adequate thermomechanical stability of the inner can.
  • thermomechanical instability of the inner can is found with rigid cans not connected to the fuel, with cans connected to the fuel, for instance, by a diffusion barrier-in which case the connection first shears, whereafter folds or corrugations are formed-and with pencils having a rigid can not connected to the fuel and having a coeflicient of expansion less than the coefficient of expansion of the fuel.
  • the reason for the latter case is that when the fuel diseagages from the can because of expansion, the temperature of the inside surface of the tubular fuel rises, leading to further disengagement lof the fuel from the can and increased thermal and mechanical ⁇ stressing of the canning material and of the fuel.
  • the can which is too thin to be inherently rigid, can be produced in large diameters, stability being provided by deformation-permitting folds or corrugations whose convexity faces outwards and which are provided on that part of the can which is between the terminal closure-receiving zones (the folds or corrugations comprising longitudinal folds or corrugations per- 3,308,033 Patented Mar. 7, 1967 ice mitting radial deformation and, at at least one end of said part, peripheral or helical folds or corrugations which permit axial deformation and which are in extension of the longitudinal folds or corrugation), the folds and the clearance between the can and the fuel being filled by the material which is plastic when hot and which is preferably magnesium.
  • the can can withstand very high external pressures without suffering severe stressing by engaging with the hydrostatically stressed plastic cushion or the like, and the can can withstand forces caused by expansion of the fuel and of the plastic cushion and changes inthe dimensions of the fuel duringradiation, for all such changes, being transmitted to the corrugations by hydrostatic deformation, do not overstress the can material.
  • This invention relates to a tubular fuel pencil designed to have improved thermal and mechanical characteristics in order to reduce the thermomechanical instability associated with the inner can of the known constructions.
  • the invention provides a tubular fuel pencil for a nuclear reactor comprising tubular inner and outer cans defining between them an annular space containing a tube or a stack of rings of nuclear fuel and means for closing the ends of the annular space characterized in that the inner can has inwardly projecting longitudinal corrugations and that there is a rigid cylindrical member within the inner can against which the corrugations may bear to support the can.
  • the invention provides a fuel pencil of the kind described which comprises thin flexible cans separated from the fuel by a material which is plastic when hot and which serves to compensate for differences between the heat expansion of the fuel and the heat expansion of the inner can and to reduce the risk of local buckling or thermal instability, a central stiflening element being provided for improved transverse stiffness.
  • the pencil comprises thin (eg. 0,1 mm. or less in thickness) flexible cans which are preferably made of stainless steel and which have, in the part between the terminal plug-receiving zones, longitudinal folds or .corrugations permitting radial deformation and, at least one end of said part, peripheral or helical folds or corrugations permitting axial deformation, the cans having equidistant longitudinal folds or corrugations whose fold or co-rrugation height is greater than the fold or corrugation height of the corrugations or folds permitting axial deformation, the equidistant longitudinal folds or corrugations being internally strengthened by a strengthening or stiffening wire, the cans receiving between them the fuel with the interposition of a viscous layer of a material which is plastic at the working ternperatures of 4the pencil in the reactor, there being introduced into the hollow interior of the pencil a rigid. cylindrical member against whose surface the wire-strengthened longitudinal folds or corrugations of the
  • FIGURE 1 is a cross-section through one example of a tubular fuel pencil according to the invention.
  • FIGURE 2 is a section on the line A-A of the pencil shown in FIGURE 1, and
  • FIGURE 3 is a partial longitudinal-section of an alternative form of the pencil shown in FIGURES 1 and 2.
  • the drawin-gs show for each example, a pencil inner can 1 and outer can 2 (also called sheaths, clads, or jackets), fuel rings 3, which can be of metallic uranium or of a uranium-based allow or of ceramics, such as uranium carbide or uranium oxide, stacked one above another in the space between the inner can and the outer can; annular plugs 4 which connect and close the annular space between the cans, have raised edges 5 and 6 and annular projections 7 for supporting several pencils of a stack; and two refractory ceramic rings 8 placed between the fuel and the plugs to heat insulate the same from the fuel end faces.
  • fuel rings 3 can be of metallic uranium or of a uranium-based allow or of ceramics, such as uranium carbide or uranium oxide, stacked one above another in the space between the inner can and the outer can
  • annular plugs 4 which connect and close the annular space between the cans, have raised edges 5 and 6
  • the cans 1 and 2 are very thin i.e. have a thickness of 0.1 mm. or less-eg., from 0.05 to 0.06 mm., are preferably of stainless steel and have longitudinal folds or corrugations 9 in the part between the terminal plugreceiving zones. They also have, in the terminal zones of said part, peripheral or helical folds or corrugations 10 in extension of the longitudinal corrugations 9.
  • the cans are separated from the fuel by viscous layers 11 formed by a material, such as magnesium, which is plastic at the working temperatures of the pencil in the reactor.
  • the annular gaps between the can 1 and the inside surface of the rings 3 and between the outside surface of the rings 3 and the can 2 are completely filled by the material which is plastic when hot so that, since the tubular pencil experi-ences a hydrostatic pressure, for instance, from the cooling fluid, the viscous -layer or cushion 11 is compressed hydrostatically through the agency of the flexible cans.
  • the corrugations therefore have internal support from the triaxially stressed plastic metal and do not become fatigued because of geometric variations in the pencil elements due to different heat operating conditions in the reactor.
  • the inner can 1 experiencing the pressure of the cooling fluid is forced against the inside surface of the fuel 3 with the interposition of the plastic cushion 11, and the corrugations 9 and 10 reduce thermomechanical instability by compensating for ditferences between the expansion of the fuel and the expansion of the can by exing, thus reducing the risk of local buckling or of heat instability.
  • a rigid cylindrical member 12 is placed in the pencil coaxially thereof and is borne by the plug rings 7, and stilfening or strengthening wires 13 are placed in the longitudinal oorrugations 9.
  • the cylindrical member 12, which is preferably made of nuclear graphite, is rigidly connected to the cans by means, for instance, of spring steel wires 14 which are disposed in a cross and secured in apertures 15 in the rings 7.
  • One of the wires 14, which are placed one above another, is embedded in a diametric groove 16 in the member 12.
  • the channel 17 can be either an individual forcing or pressure tube of the kind disclosed by the applicants U.S. patent application Serial No. 385,194, led July 27, 1964, and now abandoned in favor of continuation application Serial No. 571,945 filed August 11, 1966 for Assembly of Fuel Elements for Nuclear Reactors, or the dismantleable structure for a bunch disclosed by the applicants U.S. patent application Serial 4 No. 263,351, filed March 6, 1963, entitled Nuclear fuel elements and nowV abandoned.
  • the longitudinal corrugations 9 are of a height which is greater than the height of the corrugations 10, to provide an adequate cooling fluid flow cross-section at the end zones of the pencil, and which is such as to ensure the effective cross-sections required for the cooling -uid veins 18 and 19 flowing between the surface of the can 1 and the member 12 and between the surface of the can 2 and the channel 17.
  • the lcorrugations 9 ⁇ are connected to the corrugations- 10, if the latter are helical, by corrugations ofprogressively-- sively varying height.
  • the same are formed, on those parts of their surfaces which are between the corrugations 9i permitting radial deformation, with small cooling folds or corrugations 20 which extend parallel with the corrugations 9 and whose length is not 'greater than the length of the corrugations 9.
  • the plugs 4 take the form of rings which are made of stainless steel or of the Isame material as is used for the cans, and the raised edges 5 and 6 of ther plugs are simultaneously respectively welded to the rings- 21 and 22 either by angon arc welding or by electron bombardment, to form a closure similar to the simple pencil closure disclosed by the applicants U.S. patent. application Serial No. 433,545, led February 15, 1965, ⁇ and now Patent 3,268,411 issued August 23, 1966, andy entitled Closure Method and Means for the Ends ofy Nuclear Fuel Rods Having a Very Thin Sheath.
  • the cans 1 and 2 can be: formed with longitudinal corrugations or folds permitting; radial distortion which are interleaved with corrugations- 9 strengthened by wires 13 and which are either of the: same height or of less height than the latter corrugations 9.
  • the ends thereof can be centered not by arms 24 of the spider 231 but by equidistant wings or the like on the ring 21.
  • a tubular fuel pencil for a nuclear reactor comprising tubular inner and outer sheath, said sheath defining; therebetween an annular space, a substantially cylindrical'A body of nuclear fuel, said nuclear fuel -being placed in said'V annular space, means for closing the ends of the said an nular space, inwardly projecting longitudinal corrugations'l on said inner sheath and a rigid cylindrical member' mounted within said inner sheath, said rigid cylindrical' member being rigidly secured to said end closing means, ⁇ said corrugations bearing against said cylindrical member to thereby support said inner sheath, and outwardly projecting longitudinal corrugations on said outer sheath.
  • a tubular fuel pencil as claimed in claim 1 in which longitudinal rods are fixed within said corrugations thereby strengthening said sheaths.
  • a tubular fuel pencil for a pressure fluid cooled power reactor comprising a cylindrical outer sheath, a cylindrical inner sheath, said sheaths being assembled to define an annular space therebetween, a substantially hollow cylindrical member of ssile material, two annular plugs for closing the end portions of said sheaths, said sheaths being constructed of a exible material preferably of stainless steel no greater than .1 mm. in thickness,
  • a tubular fuel pencil according to claim S in which the cylindrical member is connected to the pencil ends by means of a spider means having equidistant outwardly projecting radial arms.
  • a tubular fuel pencil according to claim 3 in which additional longitudinal folds are provided [between the longitudinal folds, said additional longitudinal folds being parallel to the longitudinal folds and being of a reduced fold height.
  • a tubular fuel pencil according to claim 3 wherein said folds for permitting axial deformation of said sheaths are helical folds.
  • a tubular fuel pencil according to claim 3 in which the peripheral folds are helical corrugations formed as a continuation of the longitudinal folds permitting radial deformation of said sheath.
  • a tubular fuel pencil according to claim 3 in which the surface of the sheath between the longitudinal folds permitting radial deformation and the equidistant internally supported longitudinal folds contains corrugations parallel to the aformentioned folds but of lesser height.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Plasma & Fusion (AREA)
  • General Engineering & Computer Science (AREA)
  • High Energy & Nuclear Physics (AREA)
  • Rigid Pipes And Flexible Pipes (AREA)
  • Monitoring And Testing Of Nuclear Reactors (AREA)
  • Solid Fuels And Fuel-Associated Substances (AREA)
  • Physical Or Chemical Processes And Apparatus (AREA)
US473420A 1964-08-14 1965-07-20 Tubular fuel pencil having a thin flexible can for nuclear reactors Expired - Lifetime US3308033A (en)

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Application Number Priority Date Filing Date Title
BE1852 1964-08-14

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US3308033A true US3308033A (en) 1967-03-07

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US (1) US3308033A (ko)
BE (1) BE651866A (ko)
DE (1) DE1489842A1 (ko)
ES (1) ES316247A1 (ko)
GB (1) GB1085384A (ko)
IL (1) IL24059A (ko)
LU (1) LU49312A1 (ko)
NL (1) NL6510553A (ko)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4853177A (en) * 1983-05-06 1989-08-01 The Babcock & Wilcox Company Void plug for annular fuel pellets
US8116423B2 (en) 2007-12-26 2012-02-14 Thorium Power, Inc. Nuclear reactor (alternatives), fuel assembly of seed-blanket subassemblies for nuclear reactor (alternatives), and fuel element for fuel assembly
US8654917B2 (en) 2007-12-26 2014-02-18 Thorium Power, Inc. Nuclear reactor (alternatives), fuel assembly of seed-blanket subassemblies for nuclear reactor (alternatives), and fuel element for fuel assembly
US9355747B2 (en) 2008-12-25 2016-05-31 Thorium Power, Inc. Light-water reactor fuel assembly (alternatives), a light-water reactor, and a fuel element of fuel assembly
US10037823B2 (en) 2010-05-11 2018-07-31 Thorium Power, Inc. Fuel assembly
US10170207B2 (en) 2013-05-10 2019-01-01 Thorium Power, Inc. Fuel assembly
US10192644B2 (en) 2010-05-11 2019-01-29 Lightbridge Corporation Fuel assembly

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2168192B (en) * 1984-12-07 1989-08-31 Atomic Energy Authority Uk Gas cooled nuclear reactors
DE19848581C1 (de) * 1998-10-21 2000-04-20 Siemens Ag Brennstab für ein Brennelement zum Einsatz in einem Kernreaktor

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB978737A (en) * 1962-06-20 1964-12-23 Euratom Improvements in fuel rods for nuclear reactors

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB978737A (en) * 1962-06-20 1964-12-23 Euratom Improvements in fuel rods for nuclear reactors

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4853177A (en) * 1983-05-06 1989-08-01 The Babcock & Wilcox Company Void plug for annular fuel pellets
US8116423B2 (en) 2007-12-26 2012-02-14 Thorium Power, Inc. Nuclear reactor (alternatives), fuel assembly of seed-blanket subassemblies for nuclear reactor (alternatives), and fuel element for fuel assembly
US8654917B2 (en) 2007-12-26 2014-02-18 Thorium Power, Inc. Nuclear reactor (alternatives), fuel assembly of seed-blanket subassemblies for nuclear reactor (alternatives), and fuel element for fuel assembly
US9355747B2 (en) 2008-12-25 2016-05-31 Thorium Power, Inc. Light-water reactor fuel assembly (alternatives), a light-water reactor, and a fuel element of fuel assembly
US10037823B2 (en) 2010-05-11 2018-07-31 Thorium Power, Inc. Fuel assembly
US10192644B2 (en) 2010-05-11 2019-01-29 Lightbridge Corporation Fuel assembly
US10991473B2 (en) 2010-05-11 2021-04-27 Thorium Power, Inc. Method of manufacturing a nuclear fuel assembly
US11195629B2 (en) 2010-05-11 2021-12-07 Thorium Power, Inc. Fuel assembly
US11837371B2 (en) 2010-05-11 2023-12-05 Thorium Power, Inc. Method of manufacturing a nuclear fuel assembly
US11862353B2 (en) 2010-05-11 2024-01-02 Thorium Power, Inc. Fuel assembly
US10170207B2 (en) 2013-05-10 2019-01-01 Thorium Power, Inc. Fuel assembly
US11211174B2 (en) 2013-05-10 2021-12-28 Thorium Power, Inc. Fuel assembly

Also Published As

Publication number Publication date
NL6510553A (ko) 1966-02-15
IL24059A (en) 1969-07-30
ES316247A1 (es) 1966-03-16
LU49312A1 (ko) 1967-02-13
GB1085384A (en) 1967-09-27
DE1489842A1 (de) 1969-06-26
BE651866A (ko) 1965-02-15

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