Indian Presentation Outline

Transcription

1 Indian Presentation Outline Operating Experience with fuel channels in India By Ms Dipti Bhachawat, Nuclear Power Corporation of India Limited, India R&D strength and Modelling axial elongation and diametral expansion of pressure tube due to in-reactor creep and growth By S.K. Sinha, Bhabha Atomic Research By S.K. Sinha, Bhabha Atomic Research Centre, India

2 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 TUBES NOVEMBER 2011

3 NUCLEAR POWER PLANTS IN INDIA Rawatbhata Raj X220 MW Narora, U.P. 2X220 MW 2X700 MW Tarapur, Maharashtra 2X160+2X540 MW Kakrapar, Gujarat 2X220 MW 2X700 MW Kaiga, Karnataka 4X 220 MW Kalpakkam, T.N. 2X220 MW 1X500 MW Kudankulam, T.N. 2X1000 MW IN OPERATION UNDER CONSTRUCTION PROJECTS LAUNCHED

4 PROPOSED EXPANSION PLAN Fatehabad,Haryana 4 X 700 MW Jabalpur, MP 2 X 700 MW PHWR Site LWR Site Existing Site New Site Mithi Virdi, Gujarat 6 X 1000 MW Jaitapur, Maharashtra 6 X 1650 MW Kovvada, AP 6 X 1000 MW Kudankulam, TN T.N. 4 X 1000 MW Haripur, WB 6 X 1000 MW

5 PHWRS IN INDIA TOTAL 18 PHWRs UNDER OPERATION 16 OF 220 MWe CAPACITY 2 OF 540 MWe CAPACITY. 4 PHWRs OF 700 MWe UNDER CONSTRUCTION.

6 TYPICAL PHWR FUEL CHANNEL

7 PRESSURE TUBES OF INDIAN PHWRs REACTOR PT MATERIAL GARTER SPRINGS REMARKS RAPS-1 ZR-2 2 NOS LOOSE FIT RAPS-2 ZR-2.5%NB 4 NOS TIGHT FIT EMCCR DONE RAPS 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 DONE NAPS 1&2 ZR-2.5%NB 4 NOS TIGHT FIT EMCCR DONE KAPS-1 ZR-2.5%NB 4 NOS TIGHT FIT EMCCR DONE KAPS-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 FIT TAPS 3&4 ZR-2.5%NB 4 NOS TIGHT FIT

8 Zr-2.5%Nb PRESSURE TUBES PHWRs OPERATING HISTORY Reactor FPY REMARKS LEAD REACTOR KAPS-2 12 OLD SPECIFICATION LEAD REACTOR RAPS LATEST SPECIFICATION RAPS-3 8 OLD SPECIFICATION RAPS OLD SPECIFICATION KGS-1 7 OLD SPECIFICATION RAPS-4 6 OLD SPECIFICATION OTHER UNITS HAVE SEEN EVEN LESSER OPERATION AND OTHER UNITS HAVE SEEN EVEN LESSER OPERATION AND PRESSURE TUBES MADE WITH LATEST SPECIFICATION

9 DIMENSIONS OF PRESSURE TUBES Type of reactor 220 MWe 540 & 700 Mwe Length (mm) Min. inside diameter (mm) Min. wall thickness (mm) 4.03 (Zircaloy-2) (Zr 2.5 wt% Nb)

10 OPERATING ENVIORNMENT High temperature (~300 C) High pressure ~ 10 MPa High flow (~10 kg/sec) High neutron flux(~3 e13 n/cm²/sec)

11 DIMENSIONAL SO DEFORMATION O INCREASE IN DIAMETER DIMETRAL CREEP & GROWTH AXIAL ELONGATION-AXIAL CREEP AND AXIAL GROWTH SAG (BENDING CREEP ) REDUCTION IN WALL THICKNESS

12 AXIAL ELONGATION AXIAL ELONGATION IS MEASURED IN EACH BSD THE AXIAL LENGTH OF CHANNELS FROM E FACE TO E FACE WAS MEASURED BY OPTICAL METHODS IN THE EARLY DAYS OF PHWRs. THIS WAS LABORIOUS AND MAN- REM INTENSIVE. CHANNEL LENGTH MEASURED IN ALL PHWRs USING THE TMAC TOOL (POTENTIOMETER TECHNIQUE, DEVELOPED BY RTD, BARC). NOW A NEW NON CONTACT METHOD USING ULTRASONIC SENSOR BASED CHANNEL LENGTH MEASUREMENT HAS BEEN DEVELOPED BY RTD, BARC AND BEING USED IN ALL PHWRS FOR MEASUREMENT OF AXIAL ELONGATION OF CHANNELS.

13 CONCEPT OF CREEP MEASUREMENT RFT E-face ref plane RN LR Rs F/M N RFTchannel F/M S 'Z' back plane (North) CN Reactor channel Lc Cs 'Z' back plane (South) ΔCN ΔCs channel E-face at the time of start of reactor Channel E-face plane measured at the time of Creep measurement

14 AXIAL ELONGATION DATA REVIEW AXIAL ELONGATION RATE OF CHANNELS END FITTING JOURNAL RING POSITION IN BEARING SLEEVES DURING SUBSEQUENT OPERATION TILL NEXT BSD DIFFERENTIAL ELONGATION BETWEEN CHANNELS OF SAME FEEDER BANK TO LOOK FOR POSSIBLE FEEDER- FEEDER OR FEEDER TO GRAYLOC HARDWARE INTERFERENCE LEADING TO CREEP/GROWTH RESTRAINT OR POSSIBLE INTERFERENCE IN FM CLAMPING DUE TO HIGHER DIFFERENTIAL ELONGATION BETWEEN ADJECENT CHANNELS CREEP GAP MARGIN AVAILABLE AND ASSESSMENT OF CHANNEL NEEDING STUD-YOKE ASSEMBLY HARDWARE ADJUSTMENT

15 A xial E longation, mm m Zr-2 2.5%Nb-Axial Elongation in Indian PHWRs MAPS-2 RAPS-4, KGS-1 RAPS-3 KGS-2 RAPS mm/fpy KAPS-2 KGS-1, KAPS-2 MAPS-2, RAPS-2 1 mm/fpy MAPS-2-Av RAPS-4-Av KGS-1-Av RAPS-3-Av KGS-2-Av RAPS-2-Av KAPS-2-Av M2-2s M2+2s R4-2s R4+2s R3-2s R3+2s KGS2-2s KGS2+2s K2-2s K2+2s R2-2s R2+2s KGS-2s KGS1+2s FPD

16 OBSERVATION ON AXIAL ELONGATION AXIAL ELONGATION OF PRESSURE TUBE IS 3-4 MM/YEAR. SUFFICIENT DESIGN PROVISION IS AVAILABLE TO ACCOMMODATE AXIAL ELONGATION TILL DESIGN LIFE IN SOME REACTORS PRESSURE TUBES WERE MADE USING INDIGENEOUS INGOTS AS WELL AS OUTSORCED INGOTS WHILE PROCESS ROUTE ADOPTED FOR MAKING PRESSURE TUBE WAS SAME TUBES MADE USING INDIGEOUS INGOTS HAS SHOWN LESSER CREEP RATE AS COMPARED TO OUTSORCED INGOT DIFFERENTIAL ELONGATION BEHAVIOUR MAY POSE OPERATIONAL DIFFICULTY IN SOME OF THE CHANNELS

17 35 KAPS-2: 3340 FPD High Flux Channels Axial Elongation NFC Outsourced m A xial E longation m FPD

18 35 KAPS-2: 3340 FPD-High Flux (90-100%) Channels-Axial Elongation NFC-16 Outsourced Elongation, m m Axial 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- N Channel ID

19 35 KAPS-2: Select Channels- Fe content v/s elongation rate Outsourced Material 30 Elongation, mm, 3340 FP PD y = x R 2 = NFC Material Fe

20 35 KAPS-2: Select Channels - Cr content v/s Axial Elongation 30 Outsourced M t i l FPD Elongatio on, mm, y = x R 2 = NFC M aterial Cr content, ppm

21 MANAGEMENT STRATEGY FOR DIFFERENTIAL AXIAL ELONGATION IN EXISTING REACTORS THE ISSUE OF DIFFERENTIAL ELONGATION BETWEEN ADJECENT CHANNELS IS LIMITED TO FEW REACTORS DIFFERENTIAL CREEP MANAGEMENT STARTEGY REPOSITION THE CHANNEL WET QUARANTINE THE HIGH CREEPING CHANNEL TO REDUCE THE CREEP RATE REORIENT THE FEEDER CLAMP TO CREATE GAP REMOVE THE CHANNEL AND REPLACE THE CHANNEL IN THE NEXT AVAILABLE OPPORTUNITY

22 KAPS-2: Gap between Grayloc Hardware and feeder before channel adjustment

23 KAPS-2: Gap between Grayloc Hardware and feeder after channel adjustment

24 DIAMETRAL EXPANSION THIS PARAMETER HAS BEEN RECOGNIZED AS ONE HAVING POTENTIAL TO LIMIT THE LIFE OF COOLANT CHANNEL. LIMITED DATA BASE IS AVAILABLE ON ID MEAUSREMENTS TO ESTABLISH THE TREND. ONLY FIRST SET OF MEASUREMENTS HAVE BEEN CARRIED OUT IN SOME OF THE UNITS. FIVE TECHNIQUES ON ID MEASUREMENT HAVE BEEN DEVELOPED 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

25 INSERVICE INSPECTION OF PRESSURE TUBE PRESSURE TUBES INSPECTED DURING SERVICE BY SPECIAL CHANNEL INSPECTION SYSTEM BARCIS ULTRASONIC TECHNIQUE FOR ID MEASUREMENT ULTRASONIC TECHNIQUE FOR WALL THICKNESS MEASUREMENT EDDY CURRENT ESTIMATION OF GAP BETWEEN PRESSURE TUBE AND CALANDRIA TUBE EDDY CURRENT DETECTION OF GARTER SPRINGS ULTRASONIC AND EDDY CURRENT DETECTION OF FLAWS IN CIRCUMFERENTIAL AND LONGITUDINAL DIRECTION INCLINOMETER BASED SAG MEASUREMENT OF PRESSURE TUBES HYDROGEN/DEUTERIUM CONTENT IS MONITORED BY TAKING HYDROGEN/DEUTERIUM CONTENT IS MONITORED BY TAKING SAMPLES FROM PRESSURE TUBE INSIDE SURFACE BY SLIVER SAMPLE TOOL

26

27 ID MEASUREMENT BY UT TECHNIQUE Heavy water moderator Calandria Tube Heavy water coolant Pressure Tube Inspection head UT Probe 1 UT Probe 2 UT Probe 3 (for calibration) StepTarget (Fixed)

28 ID MEASUREMENT BY UT TECHNIQUE TWO DIMETRICALLY OPPOSITE PROBE FOR ID MEASUREMENT AND ONE PROBE KEPT NORMAL TO THIS AT A FIXED DISTANCE FROM A REFERENCE PLATE MEASURED ID = D 2 O PATH MEASURED BY PROBE 1 +D 2 O PATH MEASURED BY PROBE 2 + PROBE TO PROBE FACE DISTANCE ( FIXED VALUE) REFERENCE STEPPED REFLECTOR USED FOR MEASURING ULTRASONIC VELOCITY IN H 2O/ D2O DURING CALIBRATION & IN-SITU CALIBRATION IN D 2 O DURING ACTUAL MEASUREMENT IN PRESSURE TUBE USING PROBE 3.

29 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 3 NOS. 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 IN TERMS OF PRESSURE TUBE ID. QUCIKER MEASUREMNT LESS MAN RAM CONSUMPTION SIMPLE MECHANICAL C TOOL WITH LOW MAINTENANCE

30 KAPS-2: ISI-2010 MEASURED ID at FPY m BARCIS-ID, m Distance from North-Inlet, t mm ISI-2010-AVG ID RJ-North-Location RJ-South-Location GS1 GS2 GS3 GS O'Clock 2-8 O'Clock 4-10 O'Clock

31 KAPS-2: BARCIS-ID at FPY BARCIS-2010 RJ-North-Location RJ-South-Location BARCIS-ID, mm m Distance from North-Inlet, mm

32 KAPS-2: FPY Diametral Creep Rate Frequency Analysis Channels6 No of Diametral Creep rate Range, %/FPY

33 0.30 KAPS-2: Axial Creep Vs Diametrical Creep %/FPY 0.20 Diametrical C reep Rate, nt by Axial Elongation, mm

34 2.5 RAPS-2: 7.75 HOYs Effect of Fe on diametrical creep y = 7E-05x R 2 = , % Diam metrical creep, Iron Impurity content, ppm

35 CONCERNS DUE TO HIGHER DIMETRAL CREEP INCREASED DIAMETRAL DEFORMATION OF PRESSURE TUBES RESULTS IN INCREASED COOLANT BYPASS OF THE FUEL BUNDLES INCREASE IN STRESSES IN CHANNEL COMPONENTS ANALYZED UPTO 4% DIMETRAL EXPANSION FOR 220 MWE AND 540 MWe REACTORS. ASSESSMENT FOR 700 MWE BEING DONE.

36 AS INSTALLED CONDITION

37 AFTER DIMETRAL CREEP

38 MANAGEMENT OF DIMETRAL CREEP FOR OLD REACTORS IN LONG RUN REDUCTION OF THE CHANNEL POWER MAY BE REQUIRED IN SELECT CHANNELS TO ENSURE THAT THE CRITICAL HEAT FLUX (CHF) IN THE BUNDLES IS NOT EXCEEDED ACTION TAKEN FOR NEW REACORS CARRIED OUT DETAILED EVALUATION OF OFFCUTS AND SURVELLIENCE TUBE BASED ON INTERNATIONAL EXPERIENCE NEW SPECIFICATION FOR PRESSURE TUBE EVOLVED WITH AN AIM TO REALISE LIFE OF PRESSURE TUBE TO ABOUT 25 YEARS MANUFACTURING TRIALS TAKEN UP TO STUDY ROLE OF VARIOUS PROCESSING PARAMETERS ON PROPERTIES OF PRESSURE TUBE THE MANUFACTURING PROCESS ROUTE FOR PRODUCTION OF PROTOTYPE TUBES FINALISED BASED ON DETAILD INVESTIGATION AND EVALUATION OF VARIOUS PROPERTIES PROTOTYPE TUBES ARE UNDER PRODUCTION

39 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

40 PRESSURE TUBE SAG CONCERNS- PRESSURE TUBE - CALANDRIA TUBE CONTACT 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 THE CREEP SAG ESTIMATION CODES. LIMITED MEASUREMENT DONE FOR ZR-2.5%Nb PRESSURE TUBES ALSO. WITH FOUR NUMBERS OF TIGHT FIT GARTER SPRINGS UNIFORM GAP BETWEEN PRESSURE TUBE AND CALANDRIA TUBE IS MAINTAINED IN 220 MWe REACTORS NO HORIZONTAL REACTIVITY DEVICES.

41 ISI09- Sag Profile at FPYs for Channel K-11 in m m S a g Distance from E-face Eface in mm Measured Sag Calculated sag

42 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.

43 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

44 CONCLUSION WELL PLACED INSPECTION PROGRAMME AND INSPECTION SYSTEMS TO MONITOR DEFORMATIONS SUFFICIENT DESIGN PROVISIONS AVAILABLE FOR AXIAL ELONGATION DIMETRAL CREEP COULD BECOME A LIFE LIMITING PARAMETER DEVELOPMENT OF MANUFACTURING ROUTE TAKEN UP TO PRODUCE MORE CREEP RESISTANT TUBE FOR FUTURE REACTORS

45 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 1

46 Modelling In-Reactor Diametral Expansion and Axial Elongation in Indian Zr-2.5%Nb Pressure tubes S.K. Sinha and Dr. R.K. Sinha Reactor Design & Development Group, Bhabha Atomic Research Centre, Mumbai, India

47 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

48 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 fracture behaviour characterisation New design with emphasis on easy replacement and inspection degradation modelling and simulation inspection, diagnostic and rehabilitation tools development accident analysis and assessment

49 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

50 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

51 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

52 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

53 Pressure tube in a coolant channel assembly of Indian PHWRs acts as a primary boundary against the high pressure and high temperature coolant and the nuclear radiation. Pressure = 10 MPa; Temperature = 250 C 300 C, Neutron flux = 3E13 n/m 2 -sec (Zr-2/Zr-Nb) (Zr+2.5Nb +0.5Cu) (Zr-2) [350 K] [573 K] (SS 403) 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 9

54 Materials of pressure tubes in Indian PHWRs have been changed progressively matching with the development sequence. 2 Zircaloy-2 MAPS-1&2 NAPS-1&2 KAPS-1 1 Cold drawn KAPS-1* NAPS-1&2* MAPS-1&2* Zircaloy-2 RAPS-1&2 Cold Pilgered Zr-Nb with controlled chemistry RAPS-5&6 TAPS-3&4 KGS-3&4 RAPS-2* Zr-Nb KAPS-2 KGS-1&2 RAPS-3&4 3 * Retubed Units Cold drawn Zircaloy Pilgered Zircaloy-2 Alloy Development Sequence 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. 10

55 The pressure tube operates under severe environment and undergoes degradation by Mechanisms PT (Zr-2/ Zr-2.5Nb) CT (Zr-2/ Zr-4) Fast neutron Irradiation Enhanced Creep & Growth In-service Corrosion & Hydriding Elongation, Diametral expansion Bending across supports Delayed hydride cracking (DHC), Hydride reorientation, Embrittlement, Hydride blisters Sag, Axial force on End Shield (?) GS (Zr-2.5Nb- 0.5Cu) Relaxation of tight-fit (?) (?) Hydride Reorientation, Hydride blisters, DHC (?) EF (SS-403) (Hydrogen migration to PT ends) Fast neutron Irradiation Enhanced Embrittlement Yes Yes Yes Yes 11

56 Consequences of unexpectedly large axial elongation and diametral expansion 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 12

57 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 Pressure tube Fuel bundle Fuel bundle in a Normal pressure tube Fuel bundle in an Expanded pressure tube Lower MCHFR in the expanded pressure tube(s) has financial implication in the form of derated capacity of the plant. 13

58 In a typical channel inside diameter variation profile along the length of a pressure tube, peak occurs at garter spring location. Peak location where radial gap between garter spring outer torus and CT ID is the minimum. Courtesy: PIED 85.5 Measured Diameter, mm Diatance from Inlet (South to North), mm

59 Structural integrity of the components in the event of interference has been analytically studied for 220 MWe PHWR 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. FE -Model 15

60 Different stages of deformation of coolant channel assembly observed during study 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) STAGE 2 STAGE 5 STAGE 4 STAGE -1 STAGE 3 Yielding of CT

61 Study of the worst case scenario reveals that Calandria 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

62 About Pressure tube Deformation Modelling Approach 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 deformation behaviour of the pressure tubes to some of the pressure tube specific manufacturing inspection data like room temperature UTS and Fe content. 18

63 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. 19

64 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. 20

65 Recent observations made during the inspection of coolant channels 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. 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. 21

66 Axial Elongation variation with Fe Content in KGS Elongation (mm) Years 4.2 Years 5.2 Years 7.5 Years Fe Content (ppm) Pressure tube with low Fe content have high elongation rates 22

67 Statistical distribution of pressure tubes inspected for inside diameter with respect to neutron flux; observed diametral expansion rates % of total pressure tubes Number of Channels High flux pressure tubes Channel Avg. Neutron Flux (x 1.0E13) n/m 2 -s Statistical distribution w.r. to chan Avg. flux % Diametral Expansion Rate (/year) Nearly 70% of channels inspected belong to high flux region Measured Diametral Expansion Rate Location (mm) from Pressure tube Inlet End Diametral expansion rate observed 23

68 Statistics of diametral expansion rates observed in the peak regions of the inspected pressure tubes % Diametral Expansion Rate Maximum diametral expansion observed in the inspected tubes % of total locations E E E E E E+017 Neutron Flux (n/m 2 -s) % 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 Number of Locations % Diametral Expansion Rate (/year) 24

69 Scope for modelling has been looked into to.. help identification of vulnerable pressure tubes and prioritise them in order of their vulnerability get insight about importance of the metallurgical and or operating parameters affecting the deformation rate 25

70 Inspection data available for modelling Axial Elongation KGS Years Inside Diameter RAPS-2 KAPS-2 RAPS-4 KGS-1 KGS Years 7.75 HOYs 12.3 HOYs 7.3 HOYs 6.3 HOYs

71 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 ) 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 ) Nichols, F. A.,Joumal of Nuclear Materials, Vol. 30, 1969, p ) 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 Intemational Symposium, 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: 16 th International Symposium, ASTM STP 1175, p ) 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

72 Equations proposed by Ibrahim, Holt, Christodolou and others have been based on the basic assumptions of additive nature of three different modes of deformation. E d = E th +E cr +E gr E th = K th C σ th Exp(-Q th /T) E cr = K cr (?) σ cr φ Exp(-Q cr /T) + C 1 E gr = K gr (?) φ Exp(-Q gr /T) The coefficients used in the equations are termed compliances. Where : Effective stresses thermal creep :Effective stresses for irradiation creep Effective stresses are related to radial, axial and transverse stresses by means of HILL s anisotropy factors. 28

73 Some of the constants used in equations have been obtained from references and others evaluated from the inspection data Parameter Transverse creep and Axial creep and growth growth Values References Values References Constants for thermal 5.66E-12* [4] Contribution of thermal creep strain creep (K th ) has not been considered in the Anisotropic constants * [4] modelling. for thermal creep Activation energy for thermal creep Activation energy for irradiation creep 1000 [4] 9900 [4] Evaluated from the inspection data Activation energy for irradiation growth [4] Creep and growth Evaluated from the compliances inspection data * Evaluated from the test data of NRU pressure tube 29

74 We need to know about contributions of Creep & Growth in the total deformation [2,5] Both the references suggest that 25 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. 30

75 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. 31

76 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. Hot Cold 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. 32

77 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. 33

78 Variation of C1 with Fe content in pressure tubes (3/4) Hot Cold 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 34

79 Diametral expansion: Growth compliance has been evaluated from its linear relationship with the creep compliance (4/4) 35

80 Axial elongation: evaluation of compliance and activation energy (1/4) Observation: Pressure tubes whose ingots have been analysed 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 < 600 ppm (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. 36

81 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, , , , , , ) 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. 37

82 Axial elongation: evaluation of compliance and activation energy (3/4) Dependence of Activation Energy and Creep & Growth compliance with Fe Logarithmic fit of C1+C2*ln(Fe) nature has been used for Activation Energy (Q), Creep Compliance (K cr ) and Growth Compliance (K gr ) with appropriate values for constants C1 and C2. 38

83 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 39

84 Computer code IDEAELP (In-reactor Diametral Expansion and Axial ELongation in Pressure tube) Correlations developed for axial elongation and diametral expansion have been used in the computer code IDEAELP for estimating axial elongation and diametral expansion 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 40

85 Comparison of estimated dimensional changes with the measurement 41

86 Comparison between estimated and measured inside diameter of pressure tube (1/2) 42

87 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 43

88 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 44

89 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. 45

90 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 46

91 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 out in-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. 47

92 Thanks for the Kind Attention 48