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Manufacture and Testing of a Large Zirconium Clad Vessel. David Clift , P.Eng. Production Manager Ellett Industries September 14, 2005. Abstract. Serviceability depends upon the quality of the clad corrosion liner

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Manufacture and Testing of a Large Zirconium Clad Vessel

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manufacture and testing of a large zirconium clad vessel

Manufacture and Testing of a Large Zirconium Clad Vessel

David Clift, P.Eng.

Production Manager

Ellett Industries

September 14, 2005

  • Serviceability depends upon the quality of the clad corrosion liner
  • Careful application of design details, skilled trades & systematic application of manufacturing controls and non-destructive examination.

Zirconium Clad Steel Reactor

3.6m diameter x 6.5m length (11’ 10” x 21’ 2

Shells are 22mm (7/8”) thick SA516-70 with 3mm (0.12”) nominal, 2.28mm (0.090”) minimum, thickness Zirconium 702 explosion clad liner. The hot pressed heads are of 37mm (1.5”) SA516-70 with a 4.7mm (3/16”) nominal thickness of clad liner

design details
Design Details

Separation of Longitudinal & Circumferential Welds


  • Containment of possible breaches
  • Efficient gas purging
  • Simplified helium testing
material procurement
Material Procurement
  • Base Metal N.D.E.
    • ASME SA 578 Level C
      • grid pattern or continuously scanned - grid pattern is standard
      • three inspection levels
        • A- least , B - moderate, C - most demanding; allows a discontinuity smaller than can be contained within a 25mm circle
  • Cladding N.D.E.
    • full compliance with ASME Section VIII & IX
      • production bend tests, PT examination and 100% RT before bonding
      • PT after bonding and, in the case of the heads, after forming. All clad surfaces were visually examined
ultrasonic examination of bonding
Ultrasonic Examination of Bonding

ASTM B 898 Acceptance Criteria

  • Class C is the standard Inspection Class of B 898
  • Class B was specified for this project
explosive cladding
Explosive Cladding
  • Current Practice
    • an interlayer of titanium when zirconium cladding exceeds 6.4 mm (1/4”) nominal thickness
    • Explosion detonation (booster) locations
      • corner, side or center of plates
      • an area of ultrasonic non-bond is typically located under the detonation point
      • non-bond related to the size of charge
vessel plate manufacture
Vessel Plate Manufacture
  • Central explosion detonation points for both shell and head plates on this unit
    • thin cladding, thick backing plates
    • ASTM B 898 Inspection Class B ultrasonic inspection (75mm maximum indication size)
  • Results
    • non-bond areas in shell plate were acceptable
    • head plate detonation points were removed as cut-outs for centrally located nozzles
plate surface defects
Plate Surface Defects
  • Damaged areas of clustered gouges were noted on three of the six shell plates
    • Gouge depth ranged from 1.2mm (0.047”) to 2.4mm ( 0.094”) deep
    • Gouge size varied –less than 13 cm2 (2 in2) in area
  • Root cause - “rock fall” that occurred during underground explosive blasting
repair plan
Repair Plan
  • Weld repair
    • shallow gouges (<1.2mm deep) were weld repaired in conformance with ASTM B 898.
    • Controls
      • customer approval
      • carbide burr removal
      • qualified weld overlay repair
      • PT inspect
      • fully documented
repair plan cont d
Repair Plan - cont’d
  • Deep gouges
  • Individually ported batten style covers
vessel seam weld test sequence
Vessel Seam Weld & Test Sequence
  • Carbon steel welds are applied and specified NDE performed prior to batten strap attachment
  • UT the cladding bond adjacent to the end of the longitudinal seam filler strips to find potential leak paths
  • Fit & weld longitudinal batten strips, silver braze to isolate and helium bubble test @ 1 bar pressure
  • Circumferential welds performed in a similar manner
  • Confirming PT of all ZR welds per ASME
fabrication cleanliness
Fabrication - Cleanliness
  • Tool surfaces to be of alloy, plated or hardened steel
  • Rolls & brake forming surfaces - confirmed free of all surface defects & contamination
  • Weld joint design should minimize carbon steel welding & grinding on process surfaces
  • Zirconium weld zones are mechanically and chemically cleaned prior to welding
final cleaning
Final Cleaning
  • Contaminated areas abrasively ground
  • Acid wash with HF/HNO3
  • Ferroxyl test per ASTM A 380
    • spray application of the potassium ferricyanide test solution on suspect areas
    • reacts with free iron to form a blue indication
helium and hydro testing
Helium and Hydro Testing
  • Helium Mass Spectrometer testing per ASME Section V, Article 10, Appendix IV was performed before and after hydro testing
  • Purging batten strip cavities
    • helium from bubble testing conducted up to a month earlier had to be purged with clean & dry air to eliminate false indications
  • Test conditions
    • 25% of the vessel’s maximum allowable working pressure (50 psig)
    • approx 20% helium concentration
test results
Test Results
  • Results
    • All purge vents located behind nozzle liners, seams and internal batten style patches were vacuum sniffed
    • All readings remained at a background or atmospheric helium concentration - equivalent to a leak of 5 x 10-6 atm cc/sec
additional research
Additional Research
  • Preparation and analysis of a zirconium weld overlaid coupon to assess built-up metal quality
  • CS - TI - ZR construction

After welding and step machining

Prepared block – ready to weld overlay

  • ZR overlay welding on both the titanium interlayer and the zirconium cladding, min thickness .76mm
  • Test results confirm a composition containing titanium and zirconium
  • No detectable iron was present in any of the test samples
  • 100% Zr when a 0.76mm thick layer was applied over a combined thickness of Ti and ZR of 3.05mm. The actual thickness of the ZR alone in this case was 1.3mm