Sept 12 Zirconium Clad Vessel Presentation
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Transcript of Sept 12 Zirconium Clad Vessel Presentation
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Manufacture and Testing of aLarge Zirconium Clad Vessel
David Clift, P.Eng.
Production Manager
Ellett Industries
September 14, 2005
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Abstract
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.
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3.6m diameter x 6.5m length
(11 10 x 21 2
Shells are 22mm (7/8) thick SA516-70with 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
Zirconium Clad Steel Reactor
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Design Details
Separation of Longitudinal & Circumferential Welds
Containment of possible breaches
Efficient gas purging
Simplified helium testing
Advantages
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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
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Ultrasonic Examination of Bonding
Inspection
Class
Inspection Single Indication
Allowable Size
Minimum Area of
Sound Bond
A 100%
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Explosive Cladding
Current Practice
an interlayer of titanium when zirconium claddingexceeds 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
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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)
Resultsnon-bond areas in shell plate were acceptable
head plate detonation points were removed as
cut-outs for centrally located nozzles
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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 variedless than 13 cm2 (2 in2) in
area Root cause - rock fall that occurred
during underground explosive blasting
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Repair Plan
Weld repair
shallow gouges (
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Repair Plan - contd
Deep gouges
Individually
ported batten
style covers
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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 thelongitudinal 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
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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
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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
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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 vessels maximum allowable working pressure
(50 psig)
approx 20% helium concentration
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Test Results
Results
All purge vents located behind nozzle liners,
seams and internal batten style patches werevacuum sniffed
All readings remained at a background or
atmospheric helium concentration - equivalent
to a leak of 5 x 10-6 atm cc/sec
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Additional Research
Preparation and analysis of a zirconium weld overlaid
coupon to assess built-up metal quality
CS - TI - ZR construction
Prepared blockready to weld overlay After welding and step machining
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Results
ZR overlay welding on both the titanium interlayer
and the zirconium cladding, min thickness .76mm
Test results confirm a composition containingtitanium 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
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Questions