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
  • G21C3/02—Fuel elements
  • G21C3/04—Constructional details
  • G21C3/06—Casings; Jackets
  • G21C3/10—End closures ; Means for tight mounting therefor
• • 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 the field of a method for sealing a fuel rod by welding after the fuel rod has been pressurized with helium.
• tubes of usually a zirconium alloy, such as Zircaloy-2 or Zircaloy-4, are provided with an end closure whereupon the tube is filled with fuel pellets to the desired length.
• the rod is to be pressurized with helium before it is completely sealed.
• the rod is usually provided with plugs of a zirconium alloy which are designed such that part of the plug may make contact with the tube end of the rod and by welding around the joint between tube and plug, the rod is sealed.
• a number of different welding methods such as TIG welding, EB welding or resistance welding, are used in this connection.
• TIG welding TIG and resistance welding
• pressurization of the rod with helium can be carried out in connection with the plug being welded on.
• pressurization of the rod must be carried out separately. This is done by providing the plug with a fill hole through which helium may be supplied to the rod and which is thereafter sealed by means of TIG welding.
• Resistance welding as has been previously known, of the joint between the plug and the tube end of the rod entails problems in that the type of defects which may occur at the weld joint after resistance welding, such as, e.g., oxide streaks, cannot be controlled by some form of non ⁇ destructive testing. Since nuclear fuel rods operate at high pressures and contain substances, the spreading of which outside the rod is not desirable, it is of the utmost importance that sealing welds do not contain defects which may lead to continuous cracks in the weld.
• the circular weld between the plug and the rod may be carried out with a method such as, e.g., EB welding or TIG welding, which permit inspection by means of non-destructive testing and, after that, pressure reduction with helium may be carried out via the plug through a fill hole provided for the purpose.
• a body of a zirconium alloy of suitably the same type as that of which the plug consists is placed over the fill hole and formed such that the body has a volume which is larger than the volume of the upper part of the fill hole and the body makes contact with the edge of the fill hole along a border so that the contact surface is as small as possible.
• the rod is to be sealed, this can be done by resistance projection welding.
• the rod is thereby placed between two electrodes, one of which is placed over the body.
• a force is applied to one electrode and an electric current is passed through the body and the plug. Since the contact surface between body and plug is small, a high current concentration is obtained and the heating of the parts of the workpiece, which are in contact with each other, is good.
• material from the edge of the fill hole is welded together with material from the body and the body is pressed into the fill hole.
• the upper surface of the body is also deformed and may be pressed so that the upper surface of the body gets on a level with the surface of the plug.
• Figure 1 shows part of a fuel rod 1 with a plug 2.
• the plug is provided with a fill hole 3.
• the fuel rod 1 consists of a tube of a zirconium alloy, for example Zircaloy-2 or Zircaloy-4, or a zirconium-niobium alloy. Pellets of fuel, usually of uranium dioxide, are placed in the tube. The tube is sealed at both ends by means of welded-on plugs .
• the plugs are made of a zirconium alloy and may be of varying design.
• One of the plugs of the rod is provided with a fill hole for filling helium into the rod.
• Figure 2 shows a cross-section through a plug with a fill hole.
• a body 4 Above the fill hole is placed a body 4, the volume of which is larger than the upper part fo the fill hole and the surface of which is partially conical. Concentrically around the fill hole the plug is provided with a slot (not shown in the figure) .
• the resistance projection welding is carried out in a chamber and the rod 1 is placed in a V- shaped notch in an electrode block of copper or some copper alloy.
• the other electrode is placed over the body 4.
• the body is preheated by resistance heating with a lower current intensity than what is required for welding, so that the surface of the body becomes plastic. Thereafter, the current intensity and the press force on the body increase to effect welding. It is advantageous to use alternating current to impart sufficient heating to the body prior to welding.
• the method is useful for all types of fuel rods which are pressurized with helium both for BWR and PWR reactors and also for other reactor designs operating with pressurized fuel.

Landscapes

• Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• Plasma & Fusion (AREA)
• General Engineering & Computer Science (AREA)
• High Energy & Nuclear Physics (AREA)
• Butt Welding And Welding Of Specific Article (AREA)
• Monitoring And Testing Of Nuclear Reactors (AREA)
• Solid Fuels And Fuel-Associated Substances (AREA)
• Lining Or Joining Of Plastics Or The Like (AREA)

Priority Applications (2)

Applications Claiming Priority (2)

Publications (1)

Family

ID=20375886

Family Applications (1)

Country Status (7)

Cited By (2)

Families Citing this family (3)

Citations (5)

Family Cites Families (4)

• 1989
  • 1989-05-09 SE SE8901635A patent/SE465900B/sv not_active IP Right Cessation
• 1990
  • 1990-05-08 WO PCT/SE1990/000305 patent/WO1990013898A1/en active IP Right Grant
  • 1990-05-08 EP EP90908135A patent/EP0471770B1/en not_active Expired - Lifetime
  • 1990-05-08 DE DE69012114T patent/DE69012114T2/de not_active Expired - Fee Related
  • 1990-05-08 AT AT90908135T patent/ATE110877T1/de active
  • 1990-05-08 US US07/768,740 patent/US5251247A/en not_active Expired - Fee Related
  • 1990-05-08 JP JP2507646A patent/JP2931667B2/ja not_active Expired - Lifetime

Patent Citations (5)

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