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Comprehensive Core Shroud Repairs

Circumferential Weld Repairs / Tie Rod Repairs

AREVA has installed tie rods in two US plants that have operated flawlessly since 1996.  AREVA teamed with MPR Associates to provide a tie rod design to structurally replace the circumferential welds. Teams quickly took action and installed four tie rods in only six days.

Tie rod repairs provide structural support for all circumferential stainless steel welds in the core shroud (welds H1 through H8). The repair limits the vertical and lateral displacement of a failed shroud assembly to acceptable criteria under seismic and accident loads. The displacement limits ensure shroud function and proper control rod insertion. The tie rod assemblies can be pre-loaded to a value which prevents vertical separation of failed circumferential welds under normal operating conditions (even if welds H2 and H3, as well as H5 and H6, should subsequently fail after initial preloading).

Features & Benefits

  • Successfully installed at two U.S. plants
  • Meets the pertinent criteria for horizontal weld repairs
    — BWRVIP-02
        – Ensure core bypass leakage is limited to acceptable levels
        – Limits deflection and deformation for control rod insertion
        – Designed for all normal, upset, emergency and faulted conditions
    — Corrosion- Resistant Proven Materials and Fabrication
  • Accommodates cold feedwater injection
  • Can be installed without unloading fuel
  • Minimizes future ISI (In-Service Inspection)
  • Addresses circumferential welds (H1-H8)
  • Rugged and simple design; no loose parts

Vertical Weld Repair

Internal components are susceptible to intergranular stress corrosion cracking (IGSCC), which follows the heat-affected zone of welds on the core shroud. AREVA is the only vendor who has successfully repaired a vertical weld.  AREVA employs an innovative repair design that utilizes eccentric features that allow compression across the vertical weld.  Electrical-Discharge Machining (EDM) is used to facilitate installation of the repair. Our repair structurally replaces the flawed weld to allow continued safe operation.  In addition, it eliminates the UT inspection of the repaired vertical weld.

Features & Benefits

  • Meets the pertinent criteria for vertical weld repairs
    — BWRVIP-02
        – Maintains cylindrical configuration of shroud
        – Minimizes leakage
        – Designed for all normal, upset, emergency and faulted conditions
        – Analyzed for leakage within the limits of the Emergency Core Cooling System
    — Corrosion-Resistant; Proven Materials and Fabrication
  • No requirement to maintain clamp pre-load
  • Accommodates cold feedwater injection
  • No requirements for other design-reliant welds
  • Can be installed without unloading fuel
  • Minimizes future In-Service Inspection (ISI)
  • No interference with top guide, core plate wedges, or tie rods
  • Addresses any vertical welds, including welds behind core spray pipes

     

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Contact Us

Lisa Hawkins
Business Development Manager, CR&R
Tel: 434.832.2858