QUALITY ASSURANCE DIVISION ENGINEERING SERVICES GROUP IGCAR KALPAKKAM

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Quality Assurance Aspects of Reactor Assembly and
Weld Joint Components
B.Venkatraman and Baldev Raj
Quality Assurance Division Indira Gandhi Centre
for Atomic Research Kalpakkam
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Structure of the Talk

• Role of QA
• QA as part of
• Technology development phase of PFBR
• Manufacturing technologies PFBR
• Case Studies
• Role of NDE Status
• International status of NDE of ITER components
• Issues and Directions

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Quality assurance covers all activities from
design, development, production, installation,
servicing and documentation. ? It is the
essential link between the designer and the
user ensuring that the requirements of
design are met and ensuring that the user
gets a component or product that would serve
reliably and safely for the life time it is
intended for. ? Create the necessary and
accurate documentation which is a essential
especially when plants and components are
expected to have a life time of more than
20/40 years
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Quality Assurance Division A Profile

• Formed initially as Quality Assurance and testing
  Section to cater to the QA/QC needs of FBTR
  during construction in 1970s.
• Rigorous QA practices adopted testimony to the
  successful operation of FBTR with sodium water
  systems for the last 23 years without any major
  incidence.
• Extensive experience gained because of FBTR in
  piping, fabrication of SS components, NDE of
  complex welds
• Expertise fruitfully utilised during construction
  of KAMINI reactor/ A major challenging job was
  alignment of 11.2 m neutron radiography rig.
• Development of QA and NDE requirements for PFBR
  technology development
• Expertise to solve field problems PFBR

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Stage II Fast Breeder Test Reactor (FBTR)
Sodium technology (Pumps, Liquid Na) Reactor
Safety demonstrated
80 indigenous component
Cradle for development of HRD
Criticality Oct. 1985
40 MWt/ 13.2 MWe
Successful operation for 23 years
Unique (U,Pu)C fuel first time in world 157
GWd/tonne burnup without single fuel pin
failure in entire core
Robust design Good Manufacturing
prac Robust QA and NDT inspection methods Good
documentation
FBTR Success story-IGCAR embarks on a 500 MW(e)
FBR
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Material, Fabrication and Inspection issues in
FBRs
PITTING, CREVICE IGC, SCC, MIC
HE
Tube/tubesheet joint
prior to reactor operation
HE
Dissimilarjoint
Type IV cracking
MIC, GALVANIC PITTING, CREVICE
EROSION CORROSION SCC, HE, CF, PITTING
during interim wet storage

• Distortion
• Hot cracking
• Self-welding
• Creep Fatigue
• Remote repair

CAUSTIC, PITTING CREVICE, GENERAL IGC, IGSCC
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Design Requirements

• Operating temperatures 800-820 K with Sodium as
  Coolant
• Thin walled structures requiring manufacture to
  very close tolerances. Under Nuclear clean
  conditions.
• Acceptance criteria stringent than ASME Section
  III.
• Material of construction Austenitic Stainless
  Steels ( except Steam Generator and Top shields)
  with controlled chemistry and with additional
  tests and requirements as compared to ASTM
  Standards.
• Sensitisation of Stainless Steel materials to be
  kept low to avoid IGC, Pitting, Stress Corrosion
  cracking.
• Minimum distortion
• Maintain dimensional stability
• Minimum heat input to be used during welding
• Delta ferrite to be controlled

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Interacting Elements of Quality system
Knowledge Management
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WELDING PROCEDURE QUALIFICATION
Comparison of tests required for welding
procedure qualification
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FORMING AND BENDING PROCESS QUALIFICATION

• ALL HOT OR COLD FORMING PROCEDURE TO BE QUALIFIED
• QUALIFICATION TO BE CARRIED ON MATERIALS OF SAME
  SPECIFICATION, GRADE AND HEAT TREATMENT AS FOR
  THE COMPONENT MATERIAL
• FOR COMPLEX SHAPES STRAIN TO BE MEASURED USING
  A GRID PATTERN ON THE TEST SAMPLE
• AREA OF VALIDITY OF QUALIFICATION
• SAME WORK SHOP AND SAME TYPE OF MACHINE
• HIGHER VALUES OF DEFORMATION QUALIFY LOWER VALUES
• QUALIFIES BETWEEN 0.75 t TO 1.25 t 3MM
• QUALIFICATION VALID FOR SAME FORMING TECHNIQUE
  AND GIVEN TYPE OF MACHINE

contd...
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• ALL TESTS DONE ON ORIGINAL MATERIAL TO BE
  REPEATED ON THE TEST COUPON TAKEN OUT FROM FORMED
  PART USED FOR QUALIFICATION
• VISUAL
• LPE ON COMPLETE AREA BEFORE AFTER FORMING
• MECHANICAL TEST
• INTERQRANULAR CORROSION TEST
• MICROGRAPHIC EXAMINATION ( MICRO STRUCTURE
  GRAIN SIZE)
• CHEMICAL ANALYSIS FOR HOT FORMED SS PARTS OR
  THOSE HEAT TREATED AFTER FORMING
• IF TEST RESULTS DO NOT MEET MINIMUM SPECIFIED
  VALUES - SUITABLE HEAT TREATMENT TO BE GIVEN TO
  RESTORE DESIRED PROPERTIES
• IF STRAIN EXCEEDS SPECIFIED VALUE THEN SOLUTION
  ANNEALING IS MANDATORY FOR COMPONENTS WORKING
  ABOVE 700 K

contd...
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HEAT TREATMENT

• IN INERT OR SLIGHTLY OXIDISING ATMOSPHERE (1/2 TO
  2 OXYGEN) WITH LOW SULPHUR FUEL OR ELECTRIC OR
  GAS FIRED. MAXIMUM SULPHUR IN FURANCE ATMOSPHERE
  3 g/m3
• TEMPERATURE GRADIENT NOT TO EXCEED 33 K/m ON ANY
  POINT ON THE COMPONENT.
• LOADING TEMPERATURE NOT TO EXCEED 400C
• HEATING AND COOLING RATES DEPENDING UPON
  EQUIPMENT

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• Pool type reactor
• 500 MW ele.
• Main Vessel
• 13.0 m ?, 25 40 thk, 15 m Ht
• Safety Vessel
• 14.3 m ?, 25 thk, 15 m Ht
• CSRDM / DSRDM
• 120 ?, 12 m Lg
• Transfer Arm
• 200 ?,14 m Lg
• Steam Generator

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Diameter-ID 14.5 moverall height-15.0mMaterial-3
04LNWeight 150 t
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MANUFACTURING REQUIREMENTS FOR SAFETY VESSEL /
MAIN VESSEL / INNER VESSEL / THERMAL BAFFLES

• MANUFACTURE INVOLVES BOTH SHOP AND SITE
  FABRICATION
• DEVELOPMENT, DESIGN AND MANUFACTURE OF DIES AND
  PUNCHES FOR FORMING PETALS
• FORMING QUALIFICATION OF PETALS
• COLD PRESSING OF LARGE SIZED PETALS AND ROLLING
  OF SHELL/CONICAL SEGMENTS TO CLOSE TOLERANCES
• WELDING WITH CONTROLLED PARAMETERS, SEQUENCES ETC
  TO CONTROL DISTORTION
• NDE LIKE LPE AND RE (UE WHERE SATISFACTORY RE CAN
  NOT BE DONE)
• DIMENSIONAL INSPECTION BY CONVENTIONAL METHODS
  AND FINAL INSPECTION BY ELECTRONIC CO-ORDINATE
  DETERMINATE SYSTEM ( ECDS)
• HELIUM LEAK TEST (JACKET METHOD) OF 100 OF WELD
  LENGTH
• SURFACE TREATMENT

contd...
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Dished End

• Local deviations
• 1. Roundness of the dished end at any cross
  section perpendicular to the reference axis.
  Maximum deviation when checked with a template of
  chord length shall be
• 2. Contour of the inner surface of the dished
  end along the meridional direction maximum
  deviation when checked with a template of chord
  length
• 3. The circumference of the petal courses at
  their ends controlled within 3mm (value of
  p3.1415926)

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Dished End petal pressing with Punch Die
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Basket gauge for checking Petal profile
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Swing Arm Gauge for dished end inspection
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• Fit up of petals-tier wise without closing petal
• Welding of petals (long-seams)
• Cooling by water jacket (continuous flow) for
  controlling distortion
• Trimming Weld edge preparation of last petal
• Welding of last petal and cir-seam between
  consecutive tiers.

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Dished End assembly with Swing Arm Gauge
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Rolling of shell segment
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Rolling, Handling, Inspection and Welding of
Shell segment
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Safety Vessel shells and dished end
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Vertical axis of Safety Vessel Bottom Flange of
Support Assembly

• Optical techniques for dimensional measurement
  and alignment of the cylindrical shells
• Vertical axis of SV is arrived with best fit of
  centres of planes at 6 elevations of radius
  reading (36 orientations each at 6 elevations)
• Welding of 288 nos. stiffeners with bottom
  flange. Type of welding imp and inspectability

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INSPECTION and NDE REQUIREMENTS

• Visual and LPE
• 100 Radiography - High sensitive. Filmless and
  digital image processing for quantitative
  interpretation
• Ultrasonic examination wherever interpretation of
  RE is difficult. PE technique and recently in
  the shop floor advanced imaging techniques like
  TOFD and Phased array
• Helium Leak Test for all seams by jacket method
• Final dimensions by conventional and Electronic
  Coordinate Determinate Systems (ECDS)

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Robust NDE for Fast Reactor Technology in the
Context of Manufacturing based on technology
Development
Grid Plate NDE Challenge Uniformity and
adhesion of colomony overlay UT during process
and after completion Lock in thermography
Main Vessel of FBR 500 NDE Challenge thick
walled weld qualification UT, TOFD, dimensional
measurement optical techniques laser based ECDS
Thermal Insulation Panels
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ACCEPTANCE CRITERIA FOR NDE OF WELDS
contd...
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Steam generator Workhorse of a Power
Plant Critical Component
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Innovations Design and NDE
Case Study Steam Generator of Fast Reactor
Workhorse IGCAR Kalpakkam
Sodium flows on shell side and water in tube
side. Any leak would result in sodium water
reaction which is undesirable. Conventional
configurations (A), (B), (C) are fillet weld.
Not amenable to NDT. Most failures reported in
these configuration of welds. Innovation
Modification of design Configuration amenable to
microfocal radiography Challenges during
inspection - Innovation in Experimental Technique
? Special Mu Metal Probe ? Methodologies for
high sensitivity radiography
and evaluation
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Methodology successfully validated in shop floor.
More than 700 TTS joints examined (LT and
BHEL) Pores as small as 30 microns could be
detected. Sensitivity 1.6 of wt. Replica
(indigenous hardware) 20?m Method for
quantitative estimation of concavity by
radiography established.
Crater Crack detected by Radiography and weld
replica (bottom). Weld ripples can Be seen
clearly.
Density vs concavity. Concavity could be
mesaured with errors less than 10 .
Procedure given to industry
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QA PFBR Components For Testing in Na

• FABRICATION QA

TRANSFER ARM
PFBR FUEL SUB ASSEMBLY
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DC saturation Method Neural Network for On-line
Eddy Current Testing of Cladding Tube (0.4 mm
wall thickness) (NDED, IGCAR)
Schematic of a feed-forward error-back
propagation ANN
Typical ECT signals from clad tube having 0.2,
0.4, 0.8, 1.0 mm diameter holes

• Disturbing variables
• Thickness variation
• Probe wobble

Maximum deviation in sizing 25 ?m
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END CAP WELD INSPECTIONConventionally
Radiography with shape correction blockPhased
array and TOFD techniques are being tried for
defects such as lack of penetration
Endcap welds critical especially when long term
burnups of more than 150 GWD/t are considered
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ULTRASONIC ALTERNATIVE (AFFF)
Advantage Sensitivity to Planar defects
Challenges SS material - Low Thickness
examination 400 microns (wt) Anisotropic -
Scattering
Conventional Ultrasonic signal.
ITOFD of 50 micron ID notch - IGCAR
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NDE techniques at IGCAR Vision of Dr Baldev Raj
Micro to Macro
ECT Sensor by NDED for NPCIL
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NDE as applied for ITER components

• Pulse Echo Ultrasonic High frequency for weld
  inspection
• Immersion techniques for thin walled weldments
• Radiography and microtomography for welds and
  assemblies
• Thermography for brazed joints conventional and
  lock in
• Techniques modified for ITER requirements

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Issues and Directions

• Good QA Plan for each component with micro
  detailing and fixing responsibilities consciously
• Identify inspection tehniques
• Evolve procedures and quantify limits od
  detectability and establish the same through
  calibration blocks/defects and round robin tests
  (performance Demonstration and validation)
  Systematic R D required
• Evolve documentation procedures and practices

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THANK YOU