indian presentation outline - international atomic … presentation outline ... mm/year. sufficient...

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


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


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


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


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


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


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


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


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


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.


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


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


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.


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


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


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


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


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


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.


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.


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.


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


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


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.


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


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


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


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.


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


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.


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.


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


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.


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


Diametral expansion: Growth compliance has been evaluated from its linear relationship with the creep compliance (4/4)


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.



• 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.



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



• 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


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


Comparison of estimated dimensional changes with the measurement


Comparison between estimated and measured inside diameter of pressure tube (1/2)


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


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


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.


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


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.


Thanks for the Kind Attention

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