sept 12 zirconium clad vessel presentation

7/28/2019 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

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