ML20205T120

Steam Generator Tube Insp Rept for 1986 Refueling Outage

ML20205T120
Person / Time
Site:	Haddam Neck File:Connecticut Yankee Atomic Power Co icon.png
Issue date:	05/19/1986
From:	CONNECTICUT YANKEE ATOMIC POWER CO.
To:
Shared Package
ML20205T117	List: CY-85-062, Rev 2 to Steam Generator Tube Sleeving & Plugging CY-86-031, Rev 1 to 4.10.1(D) Inservice Insp of Steam Generator Tubes (Acceptance Criteria) ML20205T113 ML20205T120 ML20205T123 ML20205T153
References
NUDOCS 8606130058
Download: ML20205T120 (17)

Text

W Steam Generator Tube Inspection Report For 1986 Refueling Outage Haddam Neck Plant Connecticut Yankee Atomic Power Company Originator Date Reviewed by Date Approved by Date st o' $~ lb ~ h N '

i B606130058 860516 PDR ADOCK 05000213 G PDR w

i Steam Generator Tube Inspection Report Contents 1.0 Summary 2.0 Number and Extent of Tubes Inspected 3.0 Location and Percent Degradation For Each Flaw 4.0 Identification of Tubes Plugged 5.1 Safety Significance of Plugged Tubes 6.0 Total Tubes Plugged To Date Tables 1.0 Table 2.1 - Summary of 1986 ECT Inspection Attachments 1.0 Attachment 1 - Listing of All Tube Flaws - S.G.#1 2.0 Attachment 2 - Listing of All Tube Flaws - S.G.#2 l

3.0 Attachment 3 - Listing of All Tube Flaws - S.G.#3 4.0 Attachment 4 - Listing of All Tube Flaws - S.G.#4 Appendices 1.0 Appendix "A" - Safety Evaluations for Not Plugging Tube R37-C73 2.0 Appendix "B" - Safety Evaluations Justifying l Plugging Steam Generator Tubes l

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r7 Steam Generator Tube Inspection Report 1.0 Summary 1.1 An eddy current examination of steam generator tubing was performed between January 19, 1986 and February 26, 1986.

All tubes (except 4 tubes in row one of steam generator number four) were examined in each of four steam generators.

The eddy current examination was performed in accordance with USNRC Regulatory Guide 1.83 and Eaddam Neck Plant Technical Specification requirements.

1.2 The eddy current exauination was performed using the multifrequency testing technique. A 340 kilo-Hertz /100 kilo-Hertz differential frequency mix was used for general defect finding and interference elimination. A 100 kilo-Hertz absolute frequency was used for sludge depth detection. A 10 kilo-Hertz differential frequency was used for detecting tube support plate cracking. State of the art equipment was used.

Tubes were plugged for wall thinning if the degradation was 50 percent or greater. Tubes were plugged for denting if they restricted passage of a 0.460 inch eddy current probe.

Two tubes in steam generator #3 were plugged due to tube removal attempts. One tube section cut just below the 2nd support plate was removed successfully from the cold leg side. The second tube, also cut just below the 2nd support plate, was partially removed before becoming lodged in the tubesheet or lat support plate.

1.3 During a review of the steam generator plugging lists it was identified that tube R37-C33 was inadvertantly plugged in steam generator #2. It had a less than 20% through wall indication. The tube which should have been plugged, R37-C73 had a 55% through wall indication. The incorrect tube was plugged as a result of (1) an error in transposing the computer generated data to a plugging list and (2) an inadequate review of the plugging list.

Justification for not plugging R37-C73 can be found in the attached Appendix "A" to this report.

Page 1 of 5

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2.0 Number and Extent of Tubes Inspected The attached Table 2.1 shows for each steam generator the total number of tubes tested, the number of flaws per side (hot leg and cold lug), the number of tubes with flaws, the total number of flaws, the number of flaws at each location and the number of flaws greater than 50% through wall at each location.

3.0 Location and Percent Degradation For Each Flaw 3.1 The location and percent degradation of all flaws are shown in the following attachments (Attachment 1 for S.G. #1, Attachment 2 for S.G. #2, Attachment 3 for S.G. #3, and Attachment 4 for S.G. #4).

3.2 The flaw heights shown are the heights above the flaw location given.

3.3 The defect voltage shown, along with flaw size, helps to categorize the type of defect indicated. A large flaw size with a small defect voltage could indicate a pitting type flaw. A small flaw with a large defect voltage could indicate a wastage type flaw. The majority of the indications found were pitting type flaws just above the tubesheet on the cold leg side of the steam generator.

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4.0 Identification of Tubes Plugged Tubes Plugged In Steam Generator #1 Row Column Reason 5 81 66%

6 53 52%

9 75 71%

13 76 56%

18 46 70%

27 23 93%

29 17 54%

39 54 $1%

41 33 56%

43 45 78%

2 4 .460 Restriction - Hot Leg 3 5 .460 Restriction - Hot Leg 12 tubes plugged total Tubes Plugged In Steam Generator #2

. Row Column Reason 5 39 81%

8 18 52%

8 71 79%

10 66 52%

10 87 56%

12 84 59%

13 42 53%

13 44 95%

17 47 94%

17 51 71%

18 17 51%

18 43 94%

18 45 52%

18 46 96%

29 70 71%

31 84 52%

34 68 52%

36 33 52%

37 33 <20% (see 1.3) 31 89 .460 Restriction - Hot Leg 15 10 .460 Restriction - Hot Leg 2 5 Incomplete Test (.460 U-Bend Restriction) 22 tubes plugged total.

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Tubes Plugged in Steam Generator #3 Row Column Reason 6 29 54%.

32 30 52%

32 31 59%

33 31 69%

36 39 55%

11 50 53%

11 52 95%

14 55 53%

42 65 53%-

33 67 93%

32 88 66%

, 1 93 .460 Restriction - Hot Leg 26 34 Cold Leg Tube Pull 27 49 Cold Leg Tube Pull 14 tubes plugged total Tubes Plugged in Steam Generator #4, Row Column Reason S 74' 78%

15 41 86%

15 43 60%

15 45 58%

15 53 84%

16 61 52%

16 85 52%

17 56 58%

17 57 64%

17 85 92%

19 45 58%

20 66 74%

25 67 55%

13 tubes plugged total 4

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r 5.0 Safety Significance of Plugged Tubes The plugging of 61 tubes (total of 420 tubes plugged in all four steam generators to date) has no safety significance to the operation of the plant. The attached safety evaluations provide justification for plugging (and sleeving) up to 500 tubes per steam generator.

6.0 Total Tubes Plugged To Date Total Tubes Plugged To Date Steam Generator #1 140 Steam Generator #2 204 Steam Generator #3 38 Steam Generator #4 38 Total Tubes Plugged: 420 1,

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Table 2.1 Summary of 1986 ECT Inspection ,

i SE SCalPTION 1 S/G si l S/G a2 i S/G e 3 l S/G e4 1 7016L i

! H l C l hec i H l C l hec l H l C l hec l H l C l M*C l N l C l H+C 1

......................................l.....l.....l.....l.....l.....l.....l.....l.....l.....l.....l.....J ...l.....l.....l......I l los INSPECilmes I l l l l l l 1 1 1 ( l l I l l ND. il2Eh IESTED FULL LENGTH l l l 35991 l l 36091 l l % 701 l 1 36691 1 184547 i NO. TUBES TESTED TOTAL l l l 36661 l l % I21 l l 37101 l 1 3765l 1 184413 1

......................................l.....l.....l.....l.....l.....l.....l.....l.....l.....l.....l.....l.....l.....l.....l......t f.e ND. HAX. FLAWS PER 510E l l l l l l l l l l l l l l l l flaws *ex 1 4541 9281 1 4231 16491 1 2091 13781 1 2431 7651 1 13291 47111 1 ELAus >=20X l tell test i 1671 8651 1 541 5051 i eel alal I 4ast 17368 i FLAWS 4e-49x i 241 31 1 231 431 1 51 278 1 121 121 1 648 e51 I tLawS >=50x l 91 Il i 141 51 1 31 al 1 91 41 1 358 let i

......................................l.....l.....l.....l.....l.....l.....l.....l.....l.....l.....l ...l.....l.....l.....l..... 1

( 3.e NO. TUBE 5 WITH FLAWS l l l l l l l 1 l l 1 l i l i I i flAus >ex i 1 1 12701 1 1 18871 1 I 14991 I l 9568 I l Selt i Flaws >= tex i i 1 3251 1 8 9721 1 1 5451 l i 2968 I I El3s l Flaws 48 49x  ! l i 274 l l 661 1 1 328 l I 241 l t 149 i PLAus zesex l I I nel l l 191 1 1 Ill i 1 131 I l 53 I

......................................l.....l.....l.....l.....l.....l.....l.....l.....l.....l.....l.....l.....l.....l.....l.... l o.e No. ToiAL Flaws 1 1 1 I I I I I i 1 1 I I I I I plaws Sex 1 5651 9971 15621 4971 24098 29048 2671 17891 19661 3261 46el 18861 34551 59461 7644 i flaws >=ter rLaws os.49x i 1991 leal 3471 leal 9731 18551 251 601 5411 6031 tell atel 3311 S44l 14921 8436 i 1 31 tal 241 451 691 el 271 351 148 121 861 781 478 454 8 ftaws >= sex i 101 11 Ill 141 si 191 31 121 151 101 41 141 378 tal 59 l

......................................l.....l.....l.....l.....l.....l.....l.....l.....l.....l.....l.....l.. .l.....l.....l......l s.e NO. FLAWS AT fACH LOCA110N 1 l l l l l l t i I i l i l l i AT THE TumESHEET l 701 5461 6161 1041 2961 4001 171 2671 2841 451 3621 4078 2361 14711 1707 I A60vt THE iljBE SHE E T 931 4471 5401 1691 21001 22691 l 731 14461 85191 761 4961 5721 4tli 44498 4990'l AT On ABOVE THE TUBE 5HEET I 1631 9931 11561 2731 23961 26691 901 17131 18031 1211 4581 9791 6471 59608 6687 I AT OR ABOVE A IUBE SUPPORT PLATE I 2071 41 2811 1201 131 1338 ll 61 71 61 21 al 334l 251 359 8 AI AN Antt.vlaaAfloH 4AR I 1951 01 1951 104l Of 1041 1761 01 1761 1991 01 1991 6741 el 674 l TOTAL PLAWS I 5651 9971 15621 4971 24091 2906l 2671 17891 19461 3261 8601 1846l 16551 59451 764e 8

......................................l.....l.....l.....l.....l.....l.....l.....l.....l.....l.....l.....l.....l.....l.....l......I o.e NO. FLAWS *s50x AT EACH LOCATION l l l l l l l l l l l l l l l l AT IHE T UBE 5HE E T l 21 Il 38 21 31 51 Il 91 101 31 31 68 di 16l 24 i ADOVL THE TUBLSHEET I 18 01 Il 61 21 al el 31 51 71 Il el 141 el te i AT ON AbOVL THE TUBE 5 HEE T l 31 11 41 81 51 131 11 121 131 101 41 141 22l 221 44 i AT OR Anovt A Tunt SUPPORT PLATE 1 71 01 71 61 01 61 01 01 01 01 of el til el 13 1 As An Aust vseeATION SAR l Of 01 01 Of 01 Ol 21 01 21 01 el el di el 2l 10f AL F LAWS >a5ex 1 101 11 Ill 141 SI 191 31 121 151 lol Al 141 371 221 59 i

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Page 1 of 1

- - _ - . _ _ _ _ _ _ _ . ____________2

l Appendix A 1). Technical Specification Change Request CY - Steam Generator 2 (Tube R37/C73)

(8-pages) 2). Steam Generator Tube With 55% Through Wall Defect Safety Evaluation for Structural Integrity, (5-pages) 3). Integrated Safety Evaluation ISE/CY-86-031 (Rev. 01), (3-pages) 4 l

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Appendix A Technical Specification Change.Esquest CY 8t_eam Generato_r 2 (Tube 137/C73)

Introduction The proposed Haddam Neck Technical Specification Change Raquest addresses steam generator heat transfer tube integrity in that one tube (137/C73) La steam generator (SG) 2, containing a sas11 diameter 55 percent throughve11 pit, was not plugged. This evaluation is performed in accordance with REO Procedure 4.02.

, Discussion

The following discussion addresses the safety related questions relative to tube 137/C73 remaining in service for the upcoming cycle with a 55 percent throughwall pit. Specifically, the areas addressed ares e Pit Confirmation e Comparison of Actual Versus ECT Estimated Pit Depths (Laboratory Standards) s Comparison of Actual Versus ECT Estimated Pit Depths (Pulled Tube) e ECT Accuracy e Pit Progression Rates e Projected Pit Growth Eates e Primary to $scondary laak Detection on May 6, 1986, during preparation of the Connecticut Yankee (CT) SG eddy i current test (ICT) report, a tube in SC2 was identified as containing a repairable defect. The repair limit is greater than or egual to 50 percent of the nominal. Cube wall thickness. This defect. located on hbe 137/C73, was

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identified by ECT as being 8.5 inches above the third support piste hot leg.

. 'The defect depth identified by C0WAN, and verified by Combustion Engineering (CB) Table 1. Esference (1), is 55 percent throughes11. The amplitude of the

" defect signal is approximately 1.3 volts. Historical ECT data for Tube 137/C73 can be found in Table 2. Despite height discrepancias between inspection periode, we are comparing earlier RCT data with the 8.5 ineh.

55 percent throughwall defect identified during the 1966 BCT Inspection.

6 i Too other indications of 45 percent and 24 peroest througbwall were also

.< identified by BCT at 7.3 inches and 10 5 inches, respectively, above the third

- .q support plate. All three defects are judged to be pits based upon their

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~~i.7jatgnal 'Yvoacharacteristics. location and prior destructive esamination reesite two Set het leg tubes previonely removed during the 1984 Esfooling M.gOutage,Esfarense(2).

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i A transcription error during the evaluation of ECT data for Tube 137/C73 (55 percent throughwall pit) resulted in Tube 137/C33 being plugged by i mistake. All other tubes listed as plugged were then checked and verified l against both primary and secondary analysis lists by both CT ISI and ENC personnel (3). No further discrepancies were fotynd.

Comparison of Actual to ECT Estimated Pit Depths in IAboratory Test Standards As part of a probe qualification program, Rafarence (4), CE produced and tested flawed tube standards. Flaws representative of CY pits, in both diameter and depth (based on prior destructive examination), were machined into representative CY SG cubing. ECT of the tube standards was performed in the laboratory. A comparison of the actual to the ECT-estimated flaw depth. _. .

showed a good correlation.

For 30 flaws of various sizes (35 percent through 100 percent throughws11),

the average error in the estimated flaw depth was -3.1 percent with a standard deviation of 5.8 percent. The ECT error band was demonstratW by this test to be from an 8.9 percent throughwall undercall to a 2.7 percent throughwall overcall of the actual flaw depths, with a confidence limit of one standard deviation. The greatest difference between an actual and ECT-estimated flaw depth was a 15 percent throughwall undercall (80 percent .040 inch diameter actual versus 65 percent throughwall call) on one of the 30 tube flaw depths.

Comparison of Actual to ECT-Estimated Pit Depths in a CY Pulled Tube _

one tube (R.31/C64) of two which were removed from CT SC2 hot leg during the 1984 Refueling Outage was tested twice by ECT before removal, Reference (5).

Tha pits in the removed tube were located above the second tube support plate.

These pits showed similar ECT characteristics to the flaws located above the third support plate hot leg or Tube R37/C73. Two pitted regions were identified in the pulled tube, Table 3. The maximum pit depths.in each region, as measured by destructive examination (40 percent and 23 percent i throughwall, respectively), were less than the maximum estimated ECT measured pit depths in two separate field tests (overage depthe 46 percent and 37 percent throughwall respectively). This demonstrates that the maximan estimated depths of pitted field tubes were conservatively overestimated by

, BCT, in this casa.

ECT Accuracy in Measuring pit locations __

Many variables effect the accuracy of asasuring flaw locations by BCT (e,ge, probe speed, accuracy of SG design acasurssents, etc). Some estimated accuracy values for ECT flaw 1ccation measurements are

1. The accuracy in esasuring the height of a pit above a tube support plate, using the MIZ-18 data acquisition system. is approximately 11/2 inch. If, for example, the location calibration is not consistent from one analyst

- to another, a +1 inch accuracy any be espected. In comparing heights from

_ . earlier inspections (prior to. MIE-18), a much greater inaccuracy eaa he

(; attributed to variations [ in probe pulled -epeed.e these ,varia + . , . ,

- result in height inaccurscios. in sacese of ese tech.Q .a;. .gf,tioas,*s.as , .n.

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2. The accuracy in measuring the distance between pits which are within a

2-inch band is approximately +1/8 inch.

3. Using the A560SF probe, signals from pite spaced at least 0.10 inch apart can can be resolved, Reference (6).

Progression Rates

?rogression rates for those above tube support plate flaws (of prime consideration) and above tubesheet flaws (for comparative purposes) have been determined. Only those flave greater than 20 percent throughwall during each of 1984 and 1986 ECT inspections were utilised because of the higher degree of confidence associated with this data.

Only SGI and 2 had greater than 20 percent throughwall above tube support plate fiswo during both 1984 and 1986. As previously reported, Reference (7),

the calculated average progression rate for these flaws is -2 percent 29.

I A similar average progression rate of -2 peresnt 18 was calculated for the above tubasheet flaws. In this situation, data was available for all four 80s.

Pro (ected Plav Growth Rates During Cycle 14 Little or no increase in the indicated above tube support plate and above tubesheet flaw progression rates are anticipated during the upcoming cycle of operation. Overall secondary system chemistry control is expected to be, as a minimum, comparable to that experience during the November 1984 through January 1986 Cycle 13 operations, Reference (8). In fact, an apparent reduction in the rate of pitting corrosion from that predicted prior to the end of Cycle 13 may be a direct result of earlier plant improvements such as partial condenser recubing and significant removal of copper alloyed components from the feedtrain, Reference (9). Implementation of additional secondary water chemistry improvements, Reference (10), could further reduce

the rate of corrosion.

Conelusion The defect in Tube 137/C73 has been determined to be pitting corrosion sad to be accurately sised at 35 percent throughwell. Furthermore, the average progression rate for this type flaw has hen determined to be less than 10 percent throughwall per cycle and is espected to be comparable or lower over the next cycle. Therefore, t.he defect is not espected to progress throughve11 during Cycle 14. However, should this happen, the condition would be readily detectable through on-line monitoring of primary to secondary leakage and would be limited to less than 150 syd in accordance with technical

, +pecification limits. See Reference (11) for e similar analysis for Millstone 2. For these reasons, continued operation with Tube R37/C73 in service for the duration of Cycle 14 does not represent a safaty concern and is not an unreviewed safety question since it does met

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1. Increase the probability of occurrence or the consequences of an accident or malf unction of equipment important to safety previously evaluated in the safety analysis report.

2. Create the possibility for an accident or malfunction of a different type

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than any evaluated previously, or

3. Reduce the margin of safety in the basis for any technical specifiestion.

/2 -

L .' . Taskowski, Engineer s+/x Datt '

N ear Materials and Chemistry Section

/ .. AAbr 0 J. f.' Klisiedica, Supervibt Date Nuclear Materials & Chemistry Section l

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TABLE 1 SG#2 Tube Bow 37. Colush 73

_(CE ECT Data Esanalysis)(a)

ECT Flaw Flaw Depth Flaw Signal Amplitude Frequency Height (Inches) (Percent W) (Volta) 340 KHZ 7.4" ATSP #3 45 3 1.53V 340 KEZ 8.5" ATSP #3 54 % 1.24V 340 KHZ 10.7" ATSP f3 24 % 1.30V (a) Data f rom combuetion Engineering Reanalysis Flaw Signal Printouts, dated May 6, 1986 e

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. l TABLE 2 Historical SG ECT Data .

(For SGf2 Tube Row 37 Column 73)

FIELD DATA ECT Flaw Flaw Depth Flaw Signal Amplitude Inspection Year Height _(Inches) (Percent TW) _ __

(Vo1ts) 1981 (b)* 5" ATSP #3 (HL) 49 % -

1983 (c)* 6" ATSP #3 (HL) 47 1 --

1984 (d)* 6.7" ATSP #3 (HL) 49 2 1.8 7.5" ATSP #3 (NL) 45 I 1.65 1986 (e)** 8.5" ATSP #3 (HL) 55 % 1.34 10.5" ATSP f3 (HL) 24 2 1.29 (b) J. M. Fackelmann to R. H. Graves, Letter JMF-83-1. Table 7 dated January 18, 1983 (c) J. M. Fackelmann to R. H. Graves, letter JMF-84-32 Appendix 1 dated August 3, 1964 (d) J. M. Fackelmann to H. H. Graves, letter JMF-84-48, dated October 16, 1984 (a) L. J. laskowski to R. H. Graves, letter HMC-85-187, to be issued.

• Sased on field data analysis. Vendor was instructed to identify maximum depth flaw at and above each support location.

• • Based on detailed data analysis. Yondor was instructed to identify all fiswe,

1. m . - - - ~. -~ _ _ . . . - - .. 1 TASLE 3 4

Comparison of Field ICT Fit Depths to"hetual Pit Depths (For SGJ1 Tube Row 31 Column 64-Ramoved During 1984 outage)

Flaw Sising Flaw Height - . flaw Depth biswSignalAmplitude Method (Inche.) >

17ercent TV)

(Volts)

Field Ecr 3.3" ATSP #2 46 I -

1.1 Results* 2.0" ATSP #2 37 I l 0.7 Destructive -- 40 g y/A Examination --

23 % N/A 9

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REFERENCES (1) Combustion Engineering, Data Review, dated May 6,1986. CRISP #1800212 (2) D. E. Powell (CE), " Destructive Examination of Steam Generator Tubes from Connecticut Yankee", CENPDS-298, March 1985 (3) L. J. Laskowski and M. Ranieri, Telephone Conversation, May 6,1986 (4) 1. C. Jacques (CE) to J. M. Denson, "Pinal Raport, Connecticut Yankee.

Pitted Steam Generator Tube Test Proj ect" , MP2-86-051, dated Pebruary 21, 1986 (5) CE Report (CE NPSD-298), " Destructive Examinations of Steam GeLorator Tubes from CT", dated March 1985 (6) CE Report (MP2-83-222) " Probe Selection and Copper Elimination Tests for the Examination of Pitting at Millstone Point 2", dated June 29, 1983 (7) J. W. K11siewict to M. H. Ahern, " Connecticut Yankaa Steam Generator 2, Tube 137/C73 Information", JWK-86-12, dated May 7,1986 (8) J. M. Fackelmann/K. Eber to J. H. Perguson/G. H. Bouchard, " Summary at Connecticut Yankee Cycle 13 Secondary Chemistry, November 1984 through January 1986", NMC-86-98, dated February 28, 1986 (9) K. Eber to L. J. Nadeau, " Connecticut Yankee Botwell Sampling System",

NMC-086-97, dated March 25, 1986 (10) K. E5e r/J. M. Fackelmann to M. D. Quinn, " Changes to Connecticut Yankee Chemistry Procedures for Cycle 14", NMC-86-127, dated March 26, 1986 (11) J. M. Fackelmann to J. J. Eelley, " Assessment of Potential for Tube Rupture Due to Degradation at Millstone 2 Staan Generators". EMC-85-152 dated June 27, 1985 l

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