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Indian Presentation Outline
• Operating Experience with fuel channels inp g pIndia– By Ms Dipti Bhachawat, Nuclear Powery p ,
Corporation of India Limited, India• R&D strength and Modelling axialg g
elongation and diametral expansion ofpressure tube due to in-reactor creep andp pgrowth– By S.K. Sinha, Bhabha Atomic ResearchBy S.K. Sinha, Bhabha Atomic Research
Centre, India
OPERATING EXPERIENCE WITH FUEL CHANNELS IN INDIA
DIPTI BHACHAWAT
NUCLEAR POWER CORPORATION OF INDIA LIMITED
IAEA WORKSHOP ON PREDICTION OF AXIAL AND RADIAL CREEP IN HWR PRESSURE TUBESPRESSURE TUBES
16-18 NOVEMBER 2011
NUCLEAR POWER PLANTS IN INDIA
Narora, U.P.2X220 MWRawatbhata Raj. .
100+200+4X220 MW
2X700 MW
Kakrapar, GujaratKakrapar, Gujarat2X220 MW2X700 MW
Tarapur, Maharashtra2X160+2X540 MW
Kaiga, Karnataka4X 220 MW
Kalpakkam, T.N.2X220 MW 1X500 MW
Kudankulam, T.N .2X1000 MW
IN OPERATIONUNDER CONSTRUCTIONPROJECTS LAUNCHED
PROPOSED EXPANSION PLANFatehabad ,Haryana
4 X 700 MW PHWR SiteLWR Site Existing Site
Jabalpur, MP
2 X 700 MW
New Site
Haripur WBMithi Virdi, Gujarat
6 X 1000 MW Kovvada, AP
Haripur , WB
6 X 1000 MW
Kudankulam T N
Jaitapur, Maharashtra
6 X 1650 MW
Kovvada, AP
6 X 1000 MW
Kudankulam, T.N .
4 X 1000 MW
PHWRS IN INDIAPHWRS IN INDIA
• TOTAL 18 PHWRs UNDER• TOTAL 18 PHWRs UNDEROPERATION16 OF 220 MWe CAPACITY16 OF 220 MWe CAPACITY2 OF 540 MWe CAPACITY.
• 4 PHWRs OF 700 MWe UNDERCONSTRUCTION.
TYPICAL PHWR FUEL CHANNEL
PRESSURE TUBES OF INDIAN PHWRs
REACTOR PT MATERIAL GARTER SPRINGS REMARKSRAPS-1 ZR-2 2 NOS LOOSE FIT
RAPS-2 ZR-2.5%NB 4 NOS TIGHT FIT EMCCR DONERAPS 3&4 ZR-2.5%NB 4 NOS TIGHT FIT
RAPS 5&6 ZR-2.5%NB 4 NOS TIGHT FIT
MAPS 1&2 ZR-2.5%NB 4 NOS TIGHT FIT EMCCR DONENAPS 1&2 ZR-2.5%NB 4 NOS TIGHT FIT EMCCR DONEKAPS-1 ZR-2.5%NB 4 NOS TIGHT FIT EMCCR DONEKAPS-2 ZR-2.5%NB 4 NOS TIGHT FIT
KAIGA 1&2 ZR-2.5%NB 4 NOS TIGHT FIT
KAIGA 3&4 ZR-2.5%NB 4 NOS TIGHT FITKAIGA 3&4 ZR 2.5%NB 4 NOS TIGHT FIT
TAPS 3&4 ZR-2.5%NB 4 NOS TIGHT FIT
Zr-2.5%Nb PRESSURE TUBES PHWRs OPERATING HISTORY
Reactor FPY REMARKS
KAPS 2LEAD REACTOR
KAPS-2 12OLD SPECIFICATION
RAPS-2 8 5LEAD REACTOR
LATEST8.5 LATEST SPECIFICATION
RAPS-3 88
OLD SPECIFICATIONRAPS-4 7.5 OLD SPECIFICATION
KGS 1 7 OLD SPECIFICATIONKGS-1 7 OLD SPECIFICATION
RAPS-4 6 OLD SPECIFICATIONOTHER UNITS HAVE SEEN EVEN LESSER OPERATION ANDOTHER UNITS HAVE SEEN EVEN LESSER OPERATION AND PRESSURE TUBES MADE WITH LATEST SPECIFICATION
DIMENSIONS OF PRESSURE TUBES
Type of reactor220 MWe 540 & 700 Mwe
Length (mm) 5334 6330
Min. inside diameter (mm) 82.55 103.4
4.03(Zircaloy-2)
Mi ll thi k ( )Min. wall thickness (mm)3.32 4.3
(Zr 2.5 wt% Nb)( )
OPERATING ENVIORNMENTOPERATING ENVIORNMENT
• High temperature (~300 °C)• High pressure ~ 10 MPa• High pressure ~ 10 MPa• High flow (~10 kg/sec)• High neutron flux(~3 e13 n/cm²/sec)
DIMENSIONAL DEFORMATIONS O O O
• INCREASE IN DIAMETER –DIMETRAL CREEP & GROWTH• AXIAL ELONGATION-AXIAL CREEP AND AXIAL GROWTH• SAG (BENDING CREEP )• REDUCTION IN WALL THICKNESSREDUCTION IN WALL THICKNESS
AXIAL ELONGATION
• AXIAL ELONGATION IS MEASURED IN EACH BSD
• THE AXIAL LENGTH OF CHANNELS FROM ‘E’ FACE TO ‘E’THE AXIAL LENGTH OF CHANNELS FROM E FACE TO EFACE WAS MEASURED BY OPTICAL METHODS IN THEEARLY DAYS OF PHWRs. THIS WAS LABORIOUS AND MAN-REM INTENSIVE.
• CHANNEL LENGTH MEASURED IN ALL PHWRs USING THETMAC TOOL (POTENTIOMETER TECHNIQUE DEVELOPEDTMAC TOOL (POTENTIOMETER TECHNIQUE, DEVELOPEDBY RTD, BARC).
• NOW A NEW NON CONTACT METHOD USING ULTRASONICSENSOR BASED CHANNEL LENGTH MEASUREMENT HASBEEN DEVELOPED BY RTD, BARC AND BEING USED IN ALLPHWRS FOR MEASUREMENT OF AXIAL ELONGATION OFPHWRS FOR MEASUREMENT OF AXIAL ELONGATION OFCHANNELS.
CONCEPT OF CREEP MEASUREMENT
RFT E-face ref plane
LRRN Rs
RFTchannelN
F/MS
F/M
R t h l'Z' back plane
Lc
ΔCN
CN'Z' back plane(South)Cs
Reactor channelZ back plane(North)
channel E-face at the time of start of reactor
ΔCs
Channel E-face planemeasured at the time of Creep measurement
AXIAL ELONGATION DATA REVIEWAXIAL ELONGATION DATA REVIEW
• AXIAL ELONGATION RATE OF CHANNELS
• END FITTING JOURNAL RING POSITION IN BEARINGSLEEVES DURING SUBSEQUENT OPERATION TILL NEXT BSD
DIFFERENTIAL ELONGATION BETWEEN CHANNELS OF• DIFFERENTIAL ELONGATION BETWEEN CHANNELS OFSAME FEEDER BANK TO LOOK FOR POSSIBLE FEEDER-FEEDER OR FEEDER TO GRAYLOC HARDWAREINTERFERENCE LEADING TO CREEP/GROWTH RESTRAINTINTERFERENCE LEADING TO CREEP/GROWTH RESTRAINTOR POSSIBLE INTERFERENCE IN FM CLAMPING DUE TOHIGHER DIFFERENTIAL ELONGATION BETWEEN ADJECENTCHANNELSCHANNELS
• CREEP GAP MARGIN AVAILABLE AND ASSESSMENT OFCHANNEL NEEDING STUD-YOKE ASSEMBLY HARDWAREADJUSTMENTADJUSTMENT
Zr-2 5%Nb-Axial Elongation in Indian PHWRs
MAPS-2-AvRAPS-4-AvKGS 1 AvZr 2.5%Nb Axial Elongation in Indian PHWRs
30
35KGS-1-AvRAPS-3-AvKGS-2-AvRAPS-2-AvKAPS-2-Av
KAPS-2
25
m
M2-2sM2+2sR4-2sR4+2sR3 2KGS 1
15
20
long
atio
n, m
m R3-2sR3+2sKGS2-2sKGS2+2sK2-2s
RAPS-4,KGS-1 RAPS-3
KGS-2RAPS 2
KGS-1, KAPS-2
MAPS-2,
1.6 mm/FPY
5
10
Axi
al E
K2-2sK2+2sR2-2sR2+2sKGS-2sMAPS-2
RAPS-2 MAPS 2, RAPS-2
1 mm/FPY
0
5
0 500 1000 1500 2000 2500 3000 3500 4000
KGS1+2s
-5
FPD
OBSERVATION ON AXIAL ELONGATION
AXIAL ELONGATION OF PRESSURE TUBE IS 3-4MM/YEAR. SUFFICIENT DESIGN PROVISION ISAVAILABLE TO ACCOMMODATE AXIAL ELONGATIONTILL DESIGN LIFEIN SOME REACTORS PRESSURE TUBES WERE MADEUSING INDIGENEOUS INGOTS AS WELL ASOUTSORCED INGOTS WHILE PROCESS ROUTEADOPTED FOR MAKING PRESSURE TUBE WAS SAMEADOPTED FOR MAKING PRESSURE TUBE WAS SAMETUBES MADE USING INDIGEOUS INGOTS HASSHOWN LESSER CREEP RATE AS COMPARED TOOUTSORCED INGOTOUTSORCED INGOTDIFFERENTIAL ELONGATION BEHAVIOUR MAY POSEOPERATIONAL DIFFICULTY IN SOME OF THECHANNELSCHANNELS
KAPS 2: 3340 FPD High Flux Channels Axial Elongation NFC OutsourcedKAPS-2: 3340 FPD High Flux Channels Axial Elongation
30
35
NFC Outsourced
25
30
m
15
20
Elon
gatio
n m
10
15
Axi
al E
5
00 500 1000 1500 2000 2500 3000 3500 4000
FPD
KAPS-2: 3340 FPD-High Flux (90-100%) Channels-Axial Elongation
30
35NFC-16 Outsourced-34
25
30
mm
15
20
Elon
gatio
n, m
10
Axi
al
0
5
N J J J K M M M L L H J K M O O J K L L L L L M N N N N H M M K L NN-12
J-11
J-07
J-10
K-09
M-11
M-13
M-07
L-08
L-13
H-10
J-14
K-10
M-08
O-10
O-11
J-13
K-12
L-06
L-07
L-12
L-14
L-15
M-09
N-10
N-13
N-08
N-11
H-08
M-14
M-10
K-11
L-10
N-09
Channel ID
KAPS-2: Select Channels- Fe content v/s elongation rate35
Outsourced Material
25
30
PD
y = -0.0188x + 29.672R2 = 0.8298
20
, mm
, 334
0 FP
10
15
Elon
gatio
n,
NFC Material
5
00 200 400 600 800 1000 1200 1400 1600
Fe
KAPS 2: Select Channels Cr content v/s Axial ElongationKAPS-2: Select Channels - Cr content v/s Axial Elongation
30
35
Outsourced M t i l
25
FPD
y = -0.1215x + 28.857R2 = 0.7678
15
20
on, m
m, 3
340
10
15
Elon
gatio NFC Material
5
00 50 100 150 200 250
Cr content, ppm
MANAGEMENT STRATEGY FOR DIFFERENTIAL AXIAL ELONGATION IN EXISTING REACTORSAXIAL ELONGATION IN EXISTING REACTORS
THE ISSUE OF DIFFERENTIAL ELONGATION BETWEENADJECENT CHANNELS IS LIMITED TO FEW REACTORS
DIFFERENTIAL CREEP MANAGEMENT STARTEGYC G S GREPOSITION THE CHANNELWET QUARANTINE THE HIGH CREEPING CHANNEL TOREDUCE THE CREEP RATEREDUCE THE CREEP RATEREORIENT THE FEEDER CLAMP TO CREATE GAPREMOVE THE CHANNEL AND REPLACE THE CHANNELIN THE NEXT AVAILABLE OPPORTUNITYIN THE NEXT AVAILABLE OPPORTUNITY
KAPS-2: Gap between Grayloc Hardware and feeder before channel adjustment
KAPS-2: Gap between Grayloc Hardware and feeder after channel adjustment
DIAMETRAL EXPANSIONTHIS PARAMETER HAS BEEN RECOGNIZED AS ONE HAVING POTENTIAL TO LIMIT THE LIFE OF COOLANT CHANNEL.
LIMITED DATA BASE IS AVAILABLE ON ID MEAUSREMENTS TOESTABLISH THE TREND.
ONLY FIRST SET OF MEASUREMENTS HAVE BEEN CARRIEDOUT IN SOME OF THE UNITS.
FIVE TECHNIQUES ON ID MEASUREMENT HAVE BEENFIVE TECHNIQUES ON ID MEASUREMENT HAVE BEENDEVELOPED
• THREE POINT MICROMETER• THREE POINT MICROMETER• HYDRAULIC REMOTELY OPERATED INSIDE DIAMETER
MEASURING (HYRIM) TOOL• ULTRASONIC METHOD INTEGRATED WITH BARCIS• IDMT TOOL DEPLOYED USING FUELLING MACHINE• ID MEASUREMENT USING LVDT
INSERVICE INSPECTION OF PRESSURE TUBE
PRESSURE TUBES INSPECTED DURING SERVICE BY SPECIALCHANNEL INSPECTION SYSTEM BARCISCHANNEL INSPECTION SYSTEM BARCIS
ULTRASONIC TECHNIQUE FOR ID MEASUREMENTULTRASONIC TECHNIQUE FOR WALL THICKNESSMEASUREMENTEDDY CURRENT ESTIMATION OF GAP BETWEEN PRESSURETUBE AND CALANDRIA TUBEEDDY CURRENT DETECTION OF GARTER SPRINGSULTRASONIC AND EDDY CURRENT DETECTION OF FLAWS INCIRCUMFERENTIAL AND LONGITUDINAL DIRECTIONINCLINOMETER BASED SAG MEASUREMENT OF PRESSUREINCLINOMETER BASED SAG MEASUREMENT OF PRESSURETUBES
HYDROGEN/DEUTERIUM CONTENT IS MONITORED BY TAKINGHYDROGEN/DEUTERIUM CONTENT IS MONITORED BY TAKINGSAMPLES FROM PRESSURE TUBE INSIDE SURFACE BY SLIVERSAMPLE TOOL
H
ID MEASUREMENT BY UT TECHNIQUE
Calandria Tube
Heavy water moderator
Pressure Tube
Inspection head
Heavy water coolant
UT Probe 1 UT Probe‐2UT Probe‐1 UT Probe‐2
UT Probe‐3
(for calibration)
Step Target (Fixed)Step Target (Fixed)
ID MEASUREMENT BY UT TECHNIQUE
• TWO DIMETRICALLY OPPOSITE PROBE FOR IDMEASUREMENT AND ONE PROBE KEPT NORMALTO THIS AT A FIXED DISTANCE FROM AREFERENCE PLATE
• MEASURED ID = D2O PATH MEASURED BY PROBE 1+ D2O PATH MEASURED BY PROBE 2 + PROBE TOPROBE FACE DISTANCE ( FIXED VALUE)( )
• REFERENCE STEPPED REFLECTOR USED FORMEASURING ULTRASONIC VELOCITY IN H2O/ D2O2DURING CALIBRATION & IN-SITU CALIBRATION IND2O DURING ACTUAL MEASUREMENT INPRESSURE TUBE USING PROBE 3.PRESSURE TUBE USING PROBE 3.
ID MEASUREMENT USING IDMT TOOL
SALIENT FEATURES• THE FM OPERATED PRESSURE TUBE ID MEASUREMENT
TOOL(IDMT)• THE TOOL CONSISTS OF CASING REAR END ATTACHED
WITH BALL HOLDER WHICH HAS PROVISION TO ATTACH 3NOS. OF BALLS.
• THE BALLS ARE RADIALLY PUSHED BY A BALL ACTUATOR USING RAM FORCE AND TOUCHED THE PRESSURE TUBE.
• LINEAR MOVEMENT OF BALL ACTUATOR IS CALIBRATED INTERMS OF PRESSURE TUBE ID.
• QUCIKER MEASUREMNT• LESS MAN RAM CONSUMPTION• SIMPLE MECHANICAL TOOL WITH LOW MAINTENANCES C C OO O C
KAPS-2: ISI-2010 MEASURED ID at 11.215 FPY
84 4
84.6
84.8
83.8
84.0
84.2
84.4
m
83.2
83.4
83.6
83.8
BAR
CIS-
ID, m
82.6
82.8
83.0
B
82.2
82.4
1800 2800 3800 4800 5800 6800 7800
Di t f N th I l tDistance from North-Inlet, mmISI-2010-AVG ID RJ-North-Location RJ-South-Location GS1GS2 GS3 GS4 6-12 O'Clock2-8 O'Clock 4-10 O'Clock
KAPS-2: BARCIS-ID at 11.215 FPYBARCIS-2010RJ North Location
84 2
84.4
84.6RJ-North-LocationRJ-South-Location
83.8
84.0
84.2
m
83.4
83.6
BARC
IS-ID
, mm
82.8
83.0
83.2B
82.4
82.6
82.8
1800 2800 3800 4800 5800 6800 78001800 2800 3800 4800 5800 6800 7800
Distance from North-Inlet, mm
KAPS-2: 11.215 FPY Diametral Creep Rate Frequency Analysis
8
9
6
7
8
4
5
6
f Cha
nnel
s
2
3
4
No
of
0
1
2
0.08-0.10 0.10-0.12 0.12-0.14 0.14-0.16 0.16-0.18 0.18-0.20 0.20-0.22 0.22-0.24 0.24-0.25Diametral Creep rate Range, %/FPY
KAPS-2: Axial Creep Vs Diametrical CreepKAPS 2: Axial Creep Vs Diametrical Creep
0 25
0.30
0.20
0.25
%/F
PY
nt by
0.15
Cre
ep R
ate,
0.10
Dia
met
rical
C
0.05
0.000 10 20 30 40 50 60
Axial Elongation, mm
RAPS-2: 7.75 HOYs Effect of Fe on diametrical creep y = 7E-05x + 1.3703R2 = 0.00082.5
2
, %
1
1.5
met
rical
cre
ep,
0.5
1
Dia
m
00 100 200 300 400 500 600 7000 100 200 300 400 500 600 700
Iron Impurity content, ppm
CONCERNS DUE TO HIGHER DIMETRAL CREEPDIMETRAL CREEP
INCREASED DIAMETRAL DEFORMATION OF PRESSURE TUBES RESULTS IN
• INCREASED COOLANT BYPASS OF THE FUEL BUNDLESBUNDLES
• INCREASE IN STRESSES IN CHANNEL COMPONENTSCOMPONENTS
• ANALYZED UPTO 4% DIMETRAL EXPANSION FOR220 MWE AND 540 MWe REACTORS. ASSESSMENTFOR 700 MWE BEING DONEFOR 700 MWE BEING DONE.
AS INSTALLED CONDITION
AFTER DIMETRAL CREEP
MANAGEMENT OF DIMETRAL CREEP
• FOR OLD REACTORS IN LONG RUN REDUCTION OF THE CHANNELPOWER MAY BE REQUIRED IN SELECT CHANNELS TO ENSURE THATTHE CRITICAL HEAT FLUX (CHF) IN THE BUNDLES IS NOT EXCEEDED
• ACTION TAKEN FOR NEW REACORSCARRIED OUT DETAILED EVALUATION OF OFFCUTS ANDSURVELLIENCE TUBE
BASED ON INTERNATIONAL EXPERIENCE NEW SPECIFICATION FORPRESSURE TUBE EVOLVED WITH AN AIM TO REALISE LIFE OFPRESSURE TUBE TO ABOUT 25 YEARS
MANUFACTURING TRIALS TAKEN UP TO STUDY ROLE OF VARIOUSPROCESSING PARAMETERS ON PROPERTIES OF PRESSURE TUBE
THE MANUFACTURING PROCESS ROUTE FOR PRODUCTION OFPROTOTYPE TUBES FINALISED BASED ON DETAILD INVESTIGATIONAND EVALUATION OF VARIOUS PROPERTIES
PROTOTYPE TUBES ARE UNDER PRODUCTION
NEW PROCESS ROUTE
MAJOR PROCESS CHANGE• INGOT SIZE• CHEMISTRY• BREAKING OF CAST STRUCTURE BY TWO STAGE FORGING• HIGHER EXTRUSION RATIO• SINGLE PASS PILGERING
OBSERVATIONS• UNIFORM MICROSTRUCTURE• COARSER MICROSTRUCTURE• BETTER GRAIN ASPECT RATIO• LESS VARIABILITY FROM LEADING END TO TRAILING END• PRESENCE OF CONTINUOUS BETA PHASE• HIGHER Ft AND Ft-Fr VALUES
PRESSURE TUBE SAGCONCERNS-• PRESSURE TUBE - CALANDRIA TUBE CONTACT
EXCESSIVE SAG MAY CAUSE DIFFICULTY IN REFUELLING• EXCESSIVE SAG MAY CAUSE DIFFICULTY IN REFUELLING• DUE TO EXCESSIVE SAG CALANDRIA TUBE MAY CONTACT
WITH HORIZONTAL REACTIVITY DEVICES
EXPERIENCE -• SAG MEASUREMENT OF ZR-2 PRESSURE TUBE AND
CALANDRIA TUBE (DURING EMCCR) DONE TO VALIDATE THECALANDRIA TUBE (DURING EMCCR) DONE TO VALIDATE THECREEP SAG ESTIMATION CODES. LIMITED MEASUREMENTDONE FOR ZR-2.5%Nb PRESSURE TUBES ALSO.
• WITH FOUR NUMBERS OF TIGHT FIT GARTER SPRINGSUNIFORM GAP BETWEEN PRESSURE TUBE AND CALANDRIATUBE IS MAINTAINED
• IN 220 MWe REACTORS NO HORIZONTAL REACTIVITYDEVICES.
ISI09- Sag Profile at 10.425 FPYs for Channel K-11
6
21-18-15-12-9-6-3036
2052 2302 2552 2802 3052 3302 3552 3802 4052 4302 4552 4802 5052 5302 5552 5802 6052 6302 6552 6802 7052 7302 7552inm
m
-33-30-27-24-2118
Distance from E-face in mm
Sag
Distance from E face in mm
Measured Sag Calculated sag
PRESSURE TUBE SAG
VARIOUS OPTIONS ARE BEING CONSIDERED TO DEVELOP THE TOOL TO MEASURE GAP BETWEEN PRESSURE TUBE AND HORIZONTAL REACTIVITY DEVICES FOR 540 MWe AND 700 MWe REACTORS.
POST IRRADIATION EXAMINATION
ONE TUBE REMOVED FROM LEAD REACTOR
EXAMINATION DONE ON PRESSURE TUBE INCLUDE• VISUAL EXAMINATION• HYDROGEN/DEUTERIUM CONTENT MEASUREMENT ALONG
THE LENGTH• MICROSTRUCTURE AND TEXTURE EXAMINATION LONG THE
LENGTH• TENSILE STRENGTH AND FRACTURE TOUGHNESS• OXIDE THICKNESS MEASUREMENT• ID AND SAG MEASUREMENT• EDDY CURRENT AND ULTRASONIC EXAMINATION FOR FLAW• NEUTRON RADIOGRAPHY
CONCLUSION
• WELL PLACED INSPECTION PROGRAMME ANDINSPECTION SYSTEMS TO MONITORINSPECTION SYSTEMS TO MONITORDEFORMATIONS
• SUFFICIENT DESIGN PROVISIONS AVAILABLE FORAXIAL ELONGATION
• DIMETRAL CREEP COULD BECOME A LIFELIMITING PARAMETERLIMITING PARAMETER
• DEVELOPMENT OF MANUFACTURING ROUTETAKEN UP TO PRODUCE MORE CREEP RESISTANTTUBE FOR FUTURE REACTORS
IAEA Workshop on prediction of axial and radial creep of HWR pressure tubes; Nov. 16-18, 20111
About myself
• SK Sinha• Scientific officer – G• Work place: Reactor Engineering Division, Bhabha Atomic
Research Centre, Mumbai, India• Job experience 22 Years• Area of specialisation:
– Life Management of Coolant Channel– Corrosion and Hydride related degradation studies by modelling
and experimentation– Irradiation enhanced deformation modelling
IAEA Workshop on prediction of axial and radial creep of HWR pressure tubes; Nov. 16-18, 2011
Modelling In-Reactor DiametralExpansion and Axial Elongation in IndianZr-2.5%Nb Pressure tubes
S.K. Sinha and Dr. R.K. SinhaReactor Design & Development Group,Bhabha Atomic Research Centre, Mumbai, India
IAEA Workshop on prediction of axial and radial creep of HWR pressure tubes; Nov. 16-18, 2011
Scope
• R&D strengths in Bhabha Atomic Research Centre• R&D activities planned for the pressure tubes of Indian
PHWRs• Introduction about coolant channel of Indian PHWRs• Operational safety issues related to axial elongation and
diametral expansion• Safety of coolant channel components in the event of high
diametral expansion• Modelling approach• Comparison with ISI results
3
IAEA Workshop on prediction of axial and radial creep of HWR pressure tubes; Nov. 16-18, 2011
Pressure tube R & D strength (Out of Pile)
• Strong multi-disciplinary team supporting R&D activities on pressure tube – alloy development, process route development, micro-structure
and texture studies, corrosion studies, mechanical and fracturebehaviour characterisation
– New design with emphasis on easy replacement and inspection– degradation modelling and simulation– inspection, diagnostic and rehabilitation tools development– accident analysis and assessment
IAEA Workshop on prediction of axial and radial creep of HWR pressure tubes; Nov. 16-18, 2011
Pressure tube R & D strength (PIE)
• Post irradiation examination facility includes – a large hot cell to accommodate full length active pressure tube– CNC machines for preparing specimens for evaluation of mechanical
and fracture properties– Facilities for guaging the channel for ID, surface examination, visual
examination and flaw detection; metallurgical studies– Facilities for estimation of hydrogen concentration in zirconium alloy
samples– Burst test facility for evaluating burst strength and fracture toughness
estimation using slit burst test
IAEA Workshop on prediction of axial and radial creep of HWR pressure tubes; Nov. 16-18, 2011
Investigations carried out
• Texture and microstructure evaluation of offcuts and pressure removed for survellience purpose
• Fracture toughness and tensile strength for Zr-2 and Zr-2.5% Nb pressure tubes
• DHC velocity measurement• In past efforts taken up for irradiation creep tests on micro
pressure tubes at PFBR
IAEA Workshop on prediction of axial and radial creep of HWR pressure tubes; Nov. 16-18, 2011
Activities planned (1/2)
• Texture and micro-structure measurement– off-cuts of pressure tubes operating in different units
• Data generation on – Thermal expansion coeff. , Thermal conductivity and contact
conductance between pressure tube and calandria tube (accident analysis)
• Thermal creep tests– un-irradiated pressure tube specimens
IAEA Workshop on prediction of axial and radial creep of HWR pressure tubes; Nov. 16-18, 2011
Activities planned (2/2)
• Irradiation studies– irradiation of pressure tube samples in carrier bundles
• dimensional change, mechanical and fracture properties, DHC velocity– Irradiation of pressure tube / calandria tube specimens using
charged particle• dimensional changes, mechanical and fracture properties
• Test studies planned on irradiated pressure tubes removed from power reactor– Mechanical & fracture properties evaluation, DHC velocity
measurement and burst testing
IAEA Workshop on prediction of axial and radial creep of HWR pressure tubes; Nov. 16-18, 20119
Pressure tube in a coolant channel assembly of Indian PHWRsacts as a primary boundary against the high pressure and high temperature coolant and the nuclear radiation.
220 MWe PHWR: 306 Channels, typically 5.2 m PT Length & 83 mm PT ID
540 MWe PHWR: 392 Channels, typically 6.2 m PT Length & 104 mm PT ID
•(Zr-2/Zr-Nb) •(Zr-2)
•(Zr+2.5Nb+0.5Cu)
•(SS 403)
•[573 K]•[350 K]
Pressure = 10 MPa; Temperature = 250 C – 300 C, Neutron flux = 3E13 n/m2-sec
IAEA Workshop on prediction of axial and radial creep of HWR pressure tubes; Nov. 16-18, 201110
Materials of pressure tubes in Indian PHWRs have been changed progressively matching with the development sequence.
Cold drawn
Cold Pilgered
Zr-Nb
KAPS-2KGS-1&2RAPS-3&4
Zircaloy-2
MAPS-1&2NAPS-1&2KAPS-1
Zr-Nb with controlled chemistry
RAPS-5&6TAPS-3&4KGS-3&4
KA
PS-1
*N
APS
-1&
2*
MA
PS-1
&2*
RAPS-1&2
RAPS-2*Zircaloy-21
2
3
‘*’ Retubed Units
1 2 3
Alloy Development Sequence
Cold drawnZircaloy-2
Pilgered Zircaloy-2
Pilgered Zr-2.5%Nb
Pilgered Zr-2.5%Nb with controlled chemistry
RAPS-2 & MAPS –1&2 have open annulus design of coolant channel assembly.
IAEA Workshop on prediction of axial and radial creep of HWR pressure tubes; Nov. 16-18, 201111
The pressure tube operates under severe environment and undergoes degradation by
Mechanisms PT (Zr-2/ Zr-2.5Nb) CT (Zr-2/Zr-4)
GS (Zr-2.5Nb-0.5Cu)
EF (SS-403)
Fast neutron Irradiation Enhanced Creep & Growth
Elongation, DiametralexpansionBending across supports
Sag, Axial force on End Shield (?)
Relaxation of tight-fit (?)
In-service Corrosion &Hydriding
Delayed hydride cracking (DHC),Hydride reorientation,Embrittlement, Hydride blisters
(?) Hydride Reorientation, Hydride blisters,DHC (?)
(Hydrogen migration to PT ends)
Fast neutron Irradiation EnhancedEmbrittlement
Yes Yes Yes Yes
IAEA Workshop on prediction of axial and radial creep of HWR pressure tubes; Nov. 16-18, 201112
Consequences of unexpectedly large axial elongation and diametralexpansion are many like…
• Axial Elongation– End fitting coming out of bearing support much early in the
design life– Feeder to feeder and Grayloc hardware to feeder interactions if
differential axial elongation also exists• Diametral Expansion
– Coolant bypassing the fuel– Interaction amongst the components of coolant channel like girdle
wire, garter spring coil, PT and CT• Failure of girdle wire• Squeezing of garter spring between PT and CT• Loading of CT and its subsequent failure
IAEA Workshop on prediction of axial and radial creep of HWR pressure tubes; Nov. 16-18, 201113
Pressure tube
Fuel bundle
Fuel bundle in a Normal pressure tube
Fuel bundle in an Expanded pressure tube
Large annulus gap between the fuel bundle and the PT inside diameter existing at the top provides less resistance flow path for coolant as compared to flow paths between the fuel pins and thus leading to coolant bypass
Lower MCHFR in the expanded pressure tube(s) has financial implication in the form of derated capacity of the plant.
IAEA Workshop on prediction of axial and radial creep of HWR pressure tubes; Nov. 16-18, 2011
In a typical channel inside diameter variation profile along thelength of a pressure tube, peak occurs at garter spring location.
82.5
83.0
83.5
84.0
84.5
85.0
85.5
1500 2000 2500 3000 3500 4000 4500 5000 5500 6000 6500 7000 7500 8000 8500
Diatance from Inlet (South to North), mm
Mea
sure
d D
iam
eter
, mm
Peak location where radial gap between garter spring outertorus and CT ID is the minimum.
Courtesy: PIED
IAEA Workshop on prediction of axial and radial creep of HWR pressure tubes; Nov. 16-18, 2011
Structural integrity of the components in the event of interference has been analytically studied for 220 MWePHWR coolant channel.
• PT of maximum possible outer diameter, CT of minimum inside diameter (ID) and PT diametral expansion of 0.3%per year was selected for the analysis to account for the worst case scenario.
15
FE -Model
IAEA Workshop on prediction of axial and radial creep of HWR pressure tubes; Nov. 16-18, 2011
Different stages of deformation of coolant channel assembly observed during study
STAGE 4
STAGE 3STAGE -1
STAGE 2
STAGE 5
Stage-1: Girdle wire loading (12) ; stage-2: GS wire yielding (14.8); stage-3: CT loading (14.2), stage-4: CT yielding begin (15); stage-5: Through section yielding of CT (15.2)
Yielding of CT
IAEA Workshop on prediction of axial and radial creep of HWR pressure tubes; Nov. 16-18, 2011
Study of the worst case scenario reveals thatCalandria tube is the most vulnerable component amongst all in the event of interaction between the components as a result of high diametral expansion due to creep and growth .
17
IAEA Workshop on prediction of axial and radial creep of HWR pressure tubes; Nov. 16-18, 201118
The present modelling exercise is more of mathematical in nature. The kinetics of deformations published in open literature have been tuned to the results of inspection of Indian pressure tubes.
Effort has been made to relate variability in the deformationbehaviour of the pressure tubes to some of the pressure tube specific manufacturing inspection data like room temperature UTS and Fe content.
About Pressure tube Deformation Modelling Approach
IAEA Workshop on prediction of axial and radial creep of HWR pressure tubes; Nov. 16-18, 201119
Indian In-service Inspection (ISI) programme of coolant channel assembly is dedicated mainly to the pressure tube. It calls for…
• Axial elongation measurement every biennial shutdown• Inside diameter measurement every four years for normal
trending– frequency and quantum of inspection can be increased based on
feed back from inspection results.
IAEA Workshop on prediction of axial and radial creep of HWR pressure tubes; Nov. 16-18, 201120
In-service Inspection (ISI) programme of coolant channel assembly is dedicated mainly to the pressure tube. It calls for…
• Axial elongation measurement every biennial shutdown• Inside diameter measurement every four years for normal
trending– frequency and quantum of inspection can be increased based on
feed back from inspection results.
IAEA Workshop on prediction of axial and radial creep of HWR pressure tubes; Nov. 16-18, 201121
Recent observations made during the inspection of coolant channels
• Further investigation revealed that – raw materials of the pressure tubes in these five PHWR units have have
been sourced from two different places – CEZUS, France and NFC, India.
– CEZUS material has iron content (< 500 ppm) much less than the maximum specified (1500 ppm) where as NFC material has iron close to the maximum value.
• Axial elongation measurement in the five units KAPS-2, KGS – 1&2, RAPS - 3&4 indicated substantially large variation (min to max. ratio is 1:2.5) in elongation rates of pressure tubes.
– Investigation revealed that pressure tubes elongating at higher rates have consistently low iron content.
• Inside diameter measurement in these units and the other units indicated variability in the diametral expansion rate.
IAEA Workshop on prediction of axial and radial creep of HWR pressure tubes; Nov. 16-18, 201122
Axial Elongation variation with Fe Content in KGS -1
0.00
5.00
10.00
15.00
20.00
25.00
30.00
100.0 200.0 300.0 400.0 500.0 600.0 700.0 800.0 900.0 1000.0 1100.0 1200.0 1300.0 1400.0 1500.0
Fe Content (ppm)
Elon
gatio
n (m
m)
1.7 Years
4.2 Years
5.2 Years
7.5 Years
Pressure tube with low Fe content have high elongation rates
IAEA Workshop on prediction of axial and radial creep of HWR pressure tubes; Nov. 16-18, 201123
Nearly 70% of channels inspected belong to high flux regionStatistical distribution w.r. to chan Avg. flux
Statistical distribution of pressure tubes inspected for inside diameter with respect to neutron flux; observed diametralexpansion rates
0.00 0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00 2.25 2.500.010.10.51
25
10203040506070809095989999.5
99.90.00 0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00 2.25 2.50
0.00 0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00 2.25 2.5002468
1012141618202224
High flux pressure tubes
Num
ber o
f Cha
nnel
s
Channel Avg. Neutron Flux (x 1.0E13) n/m2-s
% o
f tot
al p
ress
ure
tube
s
Diametral expansion rate observed
0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 5500 60000.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
% D
iam
etra
l Exp
ansi
on R
ate
(/yea
r)
Location (mm) from Pressure tube Inlet End
Measured Diametral Expansion Rate
IAEA Workshop on prediction of axial and radial creep of HWR pressure tubes; Nov. 16-18, 201124
Statistics of diametral expansion rates observed in the peak regions of the inspected pressure tubes
0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.400.01
0.10.51
25
10203040506070809095989999.5
99.90.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40
0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.400
10
20
30
40
50
60
Num
ber o
f Loc
atio
ns
% Diametral Expansion Rate (/year)
% o
f tot
al lo
catio
ns
5.00E+016 1.00E+017 1.50E+017 2.00E+017 2.50E+017 3.00E+0170.05
0.10
0.15
0.20
0.25
0.30
0.35
% D
iam
etra
l Exp
ansi
on R
ate
Neutron Flux (n/m2-s)
Maximum diametral expansion observed in the inspected tubes
% Expansion rates at nearly 70% of the locations are <= 0.2% /year.
Need to focus on 30% of locations for the observed higher expansion rate.
IAEA Workshop on prediction of axial and radial creep of HWR pressure tubes; Nov. 16-18, 201125
Scope for modelling has been looked into to..
• help identification of vulnerable pressure tubes andprioritise them in order of their vulnerability
• get insight about importance of the metallurgical and or operating parameters affecting the deformation rate
IAEA Workshop on prediction of axial and radial creep of HWR pressure tubes; Nov. 16-18, 201126
Inspection data available for modelling
Axial Elongation Inside DiameterRAPS-2 KAPS-2 RAPS-4 KGS-1
7.75 HOYs 12.3 HOYs 7.3 HOYs 6.3 HOYs
16 15 15 15
KGS-1 1.7 – 7.5 Years
KGS-2 1.0 – 6.3 Years
IAEA Workshop on prediction of axial and radial creep of HWR pressure tubes; Nov. 16-18, 201127
Internationally published works have been the guiding references. Some of them are…
1) Holt, R. A., Causey, A. R., and Fidleris, Y. in Proceedings of the British Nuclear society, London,1983, p. 175.
2) Causey, A. R., Fidleris, V., MacEwen, S. R., and Schulte, C. W . in Influence of Radiation on Material Properties: Thirteenth International Symposium, ASTM STP 956, American Society for Testing and Materials, West Conshohocken, PA, 1988, p. 54.
3) Nichols, F. A.,Joumal of Nuclear Materials, Vol. 30, 1969, p. 249.4) Christodoulou, N., Causey, A. R., Holt, R. A., Tom, C. N., Badie, N., Klassen, R. J.,
Sauve, R., and Woo, C. H., Zirconium in the Nuclear Industry: Eleventh IntemationalSymposium, ASTM STP 1295, p.518
5) Christodoulou, N., Causey, A. R., Woo, C. H., Tome, C. N., Klassen, R. J., and Holt, R. A. Effect of Radiation on Materials: 16th International Symposium, ASTM STP 1175, p.1111
6) Dureja A.K. , Sinha S.K., Srivastava Ankit, Sinha R.K., Chakravarty J.K., Seshu P. ,Pawaskar D.N, “Flow Behaviour of Autoclaved, 20% Cold Worked, Zr-2.5Nb Alloy Pressure Tube Material in the Temperature Range of Room Temperature to 800°C”, Accepted for publication in Journal of Nuclear Materials.
7) R.A. Holt, Journal of Nuclear Materials Vol. 372 ,2008, p.182
IAEA Workshop on prediction of axial and radial creep of HWR pressure tubes; Nov. 16-18, 201128
Equations proposed by Ibrahim, Holt, Christodolou and others have been based on the basic assumptions of additive nature of three different modes of deformation.
Where
: Effective stresses thermal creep
:Effective stresses for irradiation creep
• Eth
= Kth C σth Exp(-Qth/T) • E
cr = Kcr (?) σcr φ Exp(-Qcr/T) + C1
• Egr
= Kgr (?) φ Exp(-Qgr/T)
Ed = Eth + Ecr + Egr
The coefficients used in the equations are termed compliances.
Effective stresses are related to radial, axial and transverse stresses by means ofHILL’s anisotropy factors.
IAEA Workshop on prediction of axial and radial creep of HWR pressure tubes; Nov. 16-18, 201129
Some of the constants used in equations have been obtained from references and others evaluated from the inspection data
Parameter Transverse creep and growth
Axial creep and growth
Values References Values ReferencesConstants for thermal creep (Kth)
5.66E-12* [4]
Anisotropic constants for thermal creep
121.25* [4]
Activation energy for thermal creep
1000 [4]
Contribution of thermal creep strain has not been considered in themodelling.
Activation energy for irradiation creep
9900 [4]
Activation energy for irradiation growth
-3000 [4]
Creep and growth compliances
Evaluated from the inspection data
Evaluated from the inspection data
* Evaluated from the test data of NRU pressure tube
IAEA Workshop on prediction of axial and radial creep of HWR pressure tubes; Nov. 16-18, 201130
We need to know about contributions of Creep & Growth in the total deformation [2,5]
Both the references suggest that25 – 30% of total longitudinal strain rate is growth strain rate while the remaining is creep.-33% of total transverse strain rate is growth strain rate while the remaining 133% is creep strain rate.
IAEA Workshop on prediction of axial and radial creep of HWR pressure tubes; Nov. 16-18, 201131
EVALUATION OF COMPLIANCES
Compliances for transverse creep and growth have been evaluated at each of the measured locations.
Average compliances and activation energy for axial creep and growth have been evaluated for each pressure tube.
IAEA Workshop on prediction of axial and radial creep of HWR pressure tubes; Nov. 16-18, 201132
Diametral expansion: Evaluation of compliances (1/4)
Pressure tubes in Indian units are installed with their numbered ends in one vault only (generally south vault). These ends are alternately cold and hot. Typical variation of creep/growth compliances with room temperature UTS along
the length of pressure tube for the cases when the numbered end is hot and when it is cold is shown.
Linear variation of the compliance data along the length of a pressure tube with respect to room temperature UTS variation along the length has been formulated in the form of equations.
Hot Cold
IAEA Workshop on prediction of axial and radial creep of HWR pressure tubes; Nov. 16-18, 201133
Creep compliances relationship with UTS when their numbered end is cold or hot. (2/4)
Creep compliance = C1*{1.0 - (UTS_x - Numbered_End _UTS)/(Un-numbered_End_UTS - Numbered_End_ UTS)}
= C1 + (UTS_x - Numbered End UTS)/ (Un-numbered_End_UTS– Numbered_End_UTS)*1.5
The constant C1 varies from tube to tube. It’s variation with Fe has been investigated and found to be revealing.
IAEA Workshop on prediction of axial and radial creep of HWR pressure tubes; Nov. 16-18, 201134
Variation of C1 with Fe content in pressure tubes (3/4)
Variation of C1 with Fe content indicates • sharp variation for the Fe content in the lower range (<500 ppm) –numbered end being hot or cold• gentle variation (500 < Fe<1500) for the pressure tubes having numbered end hot• Flattish trend (500 < Fe<1500) for pressure tubes having numbered end cold
Hot Cold
IAEA Workshop on prediction of axial and radial creep of HWR pressure tubes; Nov. 16-18, 201135
Diametral expansion: Growth compliance has been evaluated from its linear relationship with the creep compliance (4/4)
IAEA Workshop on prediction of axial and radial creep of HWR pressure tubes; Nov. 16-18, 201136
Axial elongation: evaluation of compliance and activation energy (1/4)
Observation:Pressure tubes whose ingots have beenanalysed to have Fe content >600 ppm (high Fe) have shown tendency to elongate at lower rate compared to those whose ingots have been analysed to have Fe content < 600ppm (low Fe).
Dependence of axial elongation on Fe was investigated by finding out relationship if any, between the creep-growth compliances & activation energy and Fe content.
IAEA Workshop on prediction of axial and radial creep of HWR pressure tubes; Nov. 16-18, 201137
Axial elongation: evaluation of compliance and activation energy (2/4)
• Methodology adopted– Entire range of iron content
has been divided into seven bands (0 -300, 300 – 500, 500 – 700, 700 – 900, 900 –1100, 1100 – 1300, 1300 –1500)
– pressure tubes have been grouped with respect to the iron content in them.
– Creep and growth compliances and activation energy have been evaluated for each band using the methodology described here.
IAEA Workshop on prediction of axial and radial creep of HWR pressure tubes; Nov. 16-18, 201138
Axial elongation: evaluation of compliance and activation energy (3/4)
Logarithmic fit of C1+C2*ln(Fe) nature has been used for Activation Energy (Q), Creep Compliance (Kcr) and Growth Compliance (Kgr) with appropriate values for constants C1 and C2.
Dependence of Activation Energy and Creep & Growth compliance with Fe
IAEA Workshop on prediction of axial and radial creep of HWR pressure tubes; Nov. 16-18, 201139
Axial elongation: evaluation of compliance and activation energy (4/4)
• Same activation energy for both the creep and growth respectively
• The variations of creep/growth compliance and the activation energy with Fe content in pressure tube are– very sharp up to 500 ppm of Fe content – asymptotic beyond it
• Activation energy – positive for Fe content < 500 ppm– negative for Fe content > 500 ppm
IAEA Workshop on prediction of axial and radial creep of HWR pressure tubes; Nov. 16-18, 201140
Computer code IDEAELP (In-reactor DiametralExpansion and Axial ELongation in Pressure tube)
• Correlations developed for axial elongation and diametralexpansion have been used in the computer code IDEAELP for estimating axial elongation and diametralexpansion
• IDEAELP can estimate the dimensional changes in length and inside diameter of pressure tube– under simulated reactor operating history– for channel specific inputs of dimensions, time varying coolant
temperature, pressure & neutron fast flux, and other material & metallurgical variables
IAEA Workshop on prediction of axial and radial creep of HWR pressure tubes; Nov. 16-18, 201141
Comparison of estimated dimensional changes with the measurement
IAEA Workshop on prediction of axial and radial creep of HWR pressure tubes; Nov. 16-18, 201142
Comparison between estimated and measured inside diameter of pressure tube (1/2)
IAEA Workshop on prediction of axial and radial creep of HWR pressure tubes; Nov. 16-18, 201143
Comparison between estimated and measured inside diameter of pressure tube (2/2)
Diametral expansion trend along the length has been correctly simulated and is reasonably conservative w.r. to the measured numbers
IAEA Workshop on prediction of axial and radial creep of HWR pressure tubes; Nov. 16-18, 201144
Comparison between estimated and measured axial elongation of pressure tubes
Prediction has been found to be • conservative in 50% - 60% cases for the measurement carried out in the initial period of
operation. • conservative in 90% of cases for the measurement belonging to later period of reactor
operation
IAEA Workshop on prediction of axial and radial creep of HWR pressure tubes; Nov. 16-18, 201145
Conclusions
• In-service inspection data for diametral expansion and axial elongation in Indian pressure tubes has been used to develop correlations for irradiation enhanced creep and growth strain rates.
• Variability in transverse creep and growth compliance along the length and also from pressure tube to pressure tube has been found to be related to room temperature ultimate tensile strength and Fe content.
• Pressure tube to pressure tube variability in the axial creep and growth compliance and the activation energy has been found to be related to Fe content.
• Computer code IDEAELP has been developed to predict diametral expansion and axial elongation using the developed correlations.
• Prediction of IDEAELP for diametral expansion is reasonably conservative with respect to the measured data.
• Axial elongation computed using IDEAELP is conservative in 90% of cases. Effect of Fe on the axial elongation has been captured in the correlation.
IAEA Workshop on prediction of axial and radial creep of HWR pressure tubes; Nov. 16-18, 201146
Scope for further work
• The predicting capability of these correlations will be further improved based on information being generated on variation in texture parameters, grain size, dislocation density etc.
• Carrier bundle is being designed to carry out experiment for generating growth data irradiating specimens in the power reactor. Such information would help in improving the accounting of contributions of creep and growth in the total deformation
IAEA Workshop on prediction of axial and radial creep of HWR pressure tubes; Nov. 16-18, 201147
Acknowledgements
• Authors sincerely thanks their colleagues in Division of Remote Handling and Robotics (DRHR) and Refuelling Technology Division (RTD), BARC and NPCIL for their efforts in carrying outin-service inspection of the coolant channels.
• Authors would like to thank Shri S. Vijayakumar, NPCIL for his help in providing ISI data, reactor operating history and manufacturing inspection data
• Authors would also like to thank all their colleagues in the Reactor Engineering Division, BARC who have directly or indirectly helped in preparing this presentation.
IAEA Workshop on prediction of axial and radial creep of HWR pressure tubes; Nov. 16-18, 201148
Thanks for the Kind Attention