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EP-4736194-A1 - END FITTING TREATMENT AND END FITTING

EP4736194A1EP 4736194 A1EP4736194 A1EP 4736194A1EP-4736194-A1

Abstract

An end fitting for a pressure tube in a nuclear reactor system includes an inboard end configured to surround and be joined to the end of the pressure tube in a fluid tight manner by a rolled joint. The rolled joint includes a grooved region having at least one annular groove. The end fitting also incudes a wettable inner surface that extends axially outboard from an outboard-most annular groove of the grooved region. The end fitting also incudes a corrosion barrier applied to form a coated portion of the wettable inner surface. The coated portion extends from a first position that is at or outboard of a coating reference position at the outside edge of the outboard-most annular groove, to a second position. An axial extent of the coated portion, measured axially from the coating reference position to the second position, is at least about 20 mm.

Inventors

  • SMITH, JARED
  • NORDIN, Heidi
  • TURNBULL, Joseph
  • HANLON, SEAN
  • MCCAUGHERTY, Kevin
  • WRIGHT, Michael David
  • READ, Scott
  • PRUDIL, Andrew

Assignees

  • Atomic Energy of Canada Limited/ Énergie Atomique du Canada Limitée

Dates

Publication Date
20260506
Application Date
20240816

Claims (20)

  1. 1. An end fitting for a pressure tube in a nuclear reactor system, the end fitting comprising: an inboard end configured to surround and be joined to the end of the pressure tube in a fluid tight manner by a rolled joint between an inner surface of the inboard end of the end fitting and an outer surface of the end of the pressure tube, wherein the rolled joint comprises a grooved region having at least one annular groove; a wettable inner surface that extends axially outboard from an outboard-most annular groove of the grooved region, the wettable inner surface comprising the portion of the end fitting that, during operation of the nuclear reactor system, is contacted by coolant water flowing through the pressure tube and the end fitting; and a corrosion barrier applied to form a coated portion of the wettable inner surface, the coated portion extending from a first position that is at or outboard of a coating reference position at the outside edge of the outboard-most annular groove of the grooved region, to a second position, wherein an axial extent of the coated portion, measured axially from the coating reference position to the second position, is at least about 20 mm.
  2. 2. The end fitting of claim 1 , wherein the axial extent of the coating is at least about 35 mm.
  3. 3. The end fitting of claim 2, wherein the axial extent of the coating is at least about 40 mm.
  4. 4. The end fitting of claim 3, wherein the axial extent of the coating is at least about 90 mm.
  5. 5. An end fitting for a pressure tube in a nuclear reactor system, the end fitting comprising: an inboard end configured to surround and be joined to the end of the pressure tube in a fluid tight manner by a rolled joint between an inner surface of the inboard end of the end fitting and an outer surface of the end of the pressure tube, wherein the rolled joint comprises a grooved region having at least one annular groove; a wettable inner surface that extends axially outboard from an outboard-most annular groove of the grooved region, the wettable inner surface comprising the portion of the end fitting that, during operation of the nuclear reactor system, is contacted by coolant water flowing through the pressure tube and the end fitting; and a corrosion barrier applied to form a coated portion of the wettable inner surface, the coated portion extending along the wettable inner surface from a first position that is at or outboard of a coating reference position at the outside edge of the outboard-most annular groove of the grooved region, to a second position, wherein a path length of the coated portion, measured along the wettable inner surface from the coating reference position to the second position, is at least about 20 mm.
  6. 6. The end fitting of claim 5, wherein the path length of the coated portion is at least about 45 mm.
  7. 7. The end fitting of claim 6, wherein the path length of the coated portion is at least about 100 mm.
  8. 8. The end fitting of any one of claims 1 to 7, wherein the first position is within 5 mm of the coating reference position.
  9. 9. The end fitting of claim 8, wherein the first position is within 2.5 mm of the coating reference position.
  10. 10. The end fitting of any one of claims 1 to 9, wherein the coated portion extends axially outboard substantially continuously from the first position to the second position.
  11. 11 . The end fitting of any one of claims 1 to 10, wherein the grooved region has three axially spaced apart annular grooves.
  12. 12. The end fitting of any one of claims 1 to 11 , wherein the grooved region is uncoated.
  13. 13. The end fitting of any one of claims 1 to 12, wherein the end fitting is made from ANSI 403 stainless steel.
  14. 14. The end fitting of any one of claims 1 to 13, wherein the corrosion barrier comprises at least one of: chromium, zirconium, zirconium oxide, gold, titanium, titanium oxide, and FeCrAI.
  15. 15. The end fitting of any one of claims 1 to 14, wherein the corrosion barrier has a thickness of between 5 and 20 pm.
  16. 16. The end fitting of any one of claims 1 to 15, further comprising a diffusion barrier applied to the inner surface of the inboard end of the end fitting at the grooved region or portions thereof.
  17. 17. An end fitting for a pressure tube in a nuclear reactor system, the end fitting comprising: a generally tubular inboard end configured to surround and be joined to the end of the pressure tube in a fluid tight manner by a rolled joint between an inner surface of the inboard end of the end fitting and an outer surface of the end of the pressure tube, the inboard end of the end fitting having an average radial thickness across the rolled joint; and a corrosion barrier that extends axially outboard along an axial length of an inner surface of the end fitting located outboard of the rolled joint, wherein the axial length is at least three times the average radial thickness.
  18. 18. The end fitting of claim 17, wherein the axial length is at least four times the average radial thickness.
  19. 19. The end fitting of claim 18, wherein the axial length is at least five times the average radial thickness.
  20. 20. The end fitting of claim 19, wherein the axial length is at least ten times the average radial thickness.

Description

END FITTING TREATMENT AND END FITTING CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This disclosure is related to and claims the benefit of priority to United States Provisional Patent Application No. 63/520,127, filed on August 17, 2023 and entitled END FITTING TREATMENT AND RELATED END FITTING, and United States Provisional Patent Application No. 63/571 ,294, filed on March 28, 2024 and entitled END FITTING TREATMENT AND RELATED END FITTING, the entirety of which are incorporated herein by reference. TECHNICAL FIELD [0002] This disclosure relates generally to a method for inhibiting or preventing the ingress of hydrogen into metallic materials, and more specifically to a method for inhibiting or preventing the corrosion of a stainless-steel component adjacent a zirconium alloy component in a nuclear reactor, thereby reducing the ingress rate of hydrogen into the stainless-steel component and reducing the inventory of hydrogen able to diffuse through the stainless-steel component to the adjacent zirconium alloy component. BACKGROUND [0003] During service, pressurized components in the fuel channel of a CANadian Deuterium Uranium (hereinafter CANDU™) reactor, including the pressure tubes and their end fittings, are exposed to heavy water at high temperature and pressure. Corrosion is known to occur on the inner diameter surfaces of CANDU™ fuel channel components that are wetted by heavy water. [0004] The pressure tubes are typically made from zirconium alloys, in part due to their relatively low neutron-capture cross section. The end fittings are typically made from stainless steel, and more specifically AISI type 403 stainless steel alloy. The alloy is used at least in part due to its strength, corrosion resistance, and impact resistance. [0005] To provide a diffusion barrier to hydrogen ingress from the end fitting to the pressure tube through a rolled joint connection, White et al. investigated the use of chromium plating in the rolled joint between the stainless steel end fitting and zirconium alloy pressure tube in a CANDll™ reactor. See “Plated end fittings to reduce hydrogen ingress at rolled joints in CANDll reactors” presented by A. J. White et al. at the International Conference on Expanded and Rolled Joint Technology, Toronto, Ontario, 1993. SUMMARY [0006] The following introduction is provided to introduce the reader to the more detailed discussion to follow. The introduction is not intended to limit or define any claimed or as yet unclaimed invention. One or more inventions may reside in any combination or sub combination of the elements or process steps disclosed in any part of this document including its claims and figures. [0007] In accordance with one broad aspect, there is provided an end fitting for a pressure tube in a nuclear reactor system, the end fitting comprising: an inboard end configured to surround and be joined to the end of the pressure tube in a fluid tight manner by a rolled joint between an inner surface of the inboard end of the end fitting and an outer surface of the end of the pressure tube, wherein the rolled joint comprises a grooved region having at least one annular groove; a wettable inner surface that extends axially outboard from an outboard-most annular groove of the grooved region, the wettable inner surface comprising the portion of the end fitting that, during operation of the nuclear reactor system, is contacted by coolant water flowing through the pressure tube and the end fitting; and a corrosion barrier applied to form a coated portion of the wettable inner surface, the coated portion extending from a first position that is at or outboard of a coating reference position at the outside edge of the outboard-most annular groove of the grooved region, to a second position, wherein an axial extent of the coated portion, measured axially from the coating reference position to the second position, is at least about 20 mm. [0008] In some embodiments, the axial extent of the coating is at least about 35 mm. [0009] In some embodiments, the axial extent of the coating is at least about 40 mm. [0010] In some embodiments, the axial extent of the coating is at least about 90 mm. [0011] In accordance with another broad aspect, there is provided an end fitting for a pressure tube in a nuclear reactor system, the end fitting comprising: an inboard end configured to surround and be joined to the end of the pressure tube in a fluid tight manner by a rolled joint between an inner surface of the inboard end of the end fitting and an outer surface of the end of the pressure tube, wherein the rolled joint comprises a grooved region having at least one annular groove; a wettable inner surface that extends axially outboard from an outboard-most annular groove of the grooved region, the wettable inner surface comprising the portion of the end fitting that, during operation of the nuclear reactor system, is contacted by coolant water flowing through the pressure tube and the en