ML20151R875

Rev 2 to Evaluation of 1984 Required Tech Spec Exam for TMI-1 Once-Through Steam Generator

ML20151R875
Person / Time
Site:	Three Mile Island
Issue date:	11/22/1985
From:	Barley R, Tira Patterson, Torborg M GENERAL PUBLIC UTILITIES CORP.
To:
Shared Package
ML20151R847	List: ML20151R842 ML20151R850 ML20151R854 ML20151R862 ML20151R869 ML20151R875 ML20151R882 ML20151R886
References
TDR-652, TDR-652-R02, TDR-652-R2, NUDOCS 8602060294
Download: ML20151R875 (95)

Text

APPEAIDIXC W

I Toh NG. REVISION NO. 2 g

ACTIVITY NO. 123125 PAGE 1 OF  %

TECHNICAL DATA REPORT Ouality ^88urance/Special PROJECT. DEPARTMENTISECTION Processes & Prostrams THI Unit i OTSG Eddy Current Program RELEASE DATE REVISION D ATE DOCUMENT TITLE: Evaluation of the 1984 Required Technical Specification Examination for the TMI-1 OTSG ORIGINATOR SIGNATI'RE DATE APPROVALISI SIGNATURE DATE

- n D G. E. Rhedrick See Rev. O i R. O. Barley Q tt% %g M. T. Torborg h //Z"Z-6d T. J. Patterson g]M[ Agf22fE D. L. Langan See Rev. 0 / i q . Kazapas 4( { 4g MOfAL FOh EXTERNAL DISbl8UTIONl DATE ML W Does this TDR include recommendation (si? Oyes E No if yes. TFWR/TR #

• DISTRIBUTION ' ASSTRACT: Statement of Problem The results of the 1984 eddy current examination performed on B. E. Ballard the TMI-1 steam generator tubing had identified 328 tubes with R. O. Barley confir=ed indications of > 40% through wall penetration. These G. R. Capodanno indications were not identified in previous eddy current examin-J. J. Colitz ations performed prior to mechanical thermal and hydraulic load-B. D. Elam ing evolutions which took place in the steam generators.

I. R. Finfrock Technical Approach F. S. Giacobbe Knowing the locations of the 1984 confirmed indications, a re-H. D. Hukill view of the 1983 and 1982 examinations has confirmed the earlier J. S. Jandovitz presence for a majority of these indications. A characteriza-N. C. Kazanas tion o *he 1984 indications by defect location, signal ampli-S. Kovkabany tude, percent through wall and circumferential extent was per-D. In I.an gan formed and compared to the 1982 examination results. A growth R. Im Long sample study on a random selection of tubes was performed after R. L. Miller the detection of the 1984 indications in order to determine if R. Ostrowski evidence of an active mechanism was occurring.

T. J. Patterson Findings G. E. Rhedrick It was observed that the 1984 indications we.e located in the M. T. Torborg same affected axial and radial areas previously identified dur-R. F. Wilson ing the 1982 examination. The 1984 indications were predominately shorter in circumferential extent. The review of 1984, 1983 I and 1982 examination results revealed that the percent through DRF 029572 vall determination showed no trend of continued through wall growth. 90% of the new indications were of size at or near the threshold of GPUN standard differential technique sensitivit' of detection. The results of the growth sample study showed no evidence of an active mechanism occurring during the period of observation.

Conclusion The 1984 examination identified indications that were already present in the tubes in 1982 but because of their weak signal amplitude were masked by background noise. The mechanical, thermal and hydraulic loads imposed on the OTSG since 1982 examination may have enhanced the eddy currrent detection of small indications by increasing the signal amplitude but with-out evidence of increase to percent through wall.

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DOCUMENT NO Mr TnR-652 eage ti TITLE Evaluation of the 1984 Required Technical Specification Examination for the TMI-1 OTSG REV APPROVAL DATE

SUMMARY

OF CHANGE 2 Page 1: Replaced Revision 0 cover page to permit signatures ofdifferent originators and approvers )l-22g for Revision 2.

Page 1: Changed wording in abstract to reflect conclusions of Section VI. # O II'

.d Page 2: Revised Table of Contents to incorporate new Section VI. Oft 1.kT.S Page 4: Revised conclusion number two (2).

g%s a hthf Pages 6, 10, 12, 13, 18, 19: Revised numbers (

of tubes to reflect final disposition of tuber.

Page 11: Added reference to Section VI.

Page 14: Added Note to Table 1.

Page 29: Added reference to Section VI.

Pages 34, 35: corrected typos 20-40.

Page 35: Clarified first sentence.

Page 37: Added statement on accuracy of ECT at broached support locations.

Page 39: Added reference to Section VI.

2 Page 43: Added note to Table 5.

E Page 43: Corrected typo 28-31, 5

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annnnnsa 12 33

DOCUMENT NO.

ME TDR 652 Page IB TITLE Evaluation of the 1984 Required Technical Specification Examination for the TMI-1 OTSG REV

SUMMARY

OF CHANGE APPROVAL DATE 2 Pages 44-63: Added Section VI. Evaluation of Changes In The Eddy Current Signals From 1982 fl 22-65 to 1984.

Page 64: Renumbered Section. I g.t2*kf T%

Page 66: Renumbered Section.

- 4 1.L\%

Page 68: Added reference 6.

Page 68: Renumbered Section. I Page 77: Corrected typo 3-coils.

Figures: Added Figure 7.

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I' annnnata 12 33

• • "*'~"a Nuclear TDR-652

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TITLA Evaluation of the 1984 Retuired Tecnnical Specification Exa-19ation for tne TMI-1 0753 agy -

SUMMARY

OF CHANeg APMt0 VAL OA?!

i 1 I The nurcer cf confirmed indications 2401 thru f' g ,

I wall in " A" Once inreagn Stear: Generater has j CH.nger. to 798 tilhet frne ?97 Nihet Tne tntsi l

e m w s t- ve 6vov:, wit 9 inoications 3 *L/n f or Detr.

aAa 1 d3a mas fases.s J r,y e.se L. 3CO.

3;3 fg i

l 7;.12 add subtitle " Status of ISI Tubes."

Revises Table 1, 5 T.W. & Yolts 1983 & 1984 p;C(3lM!I"

Revised Table 2, quantity of tubes in " A" OTSG l

witn indicatice.s 3 40% to 22 fror 20 and to 298  ! ,

-  : fro. 297. Revised Table 3, add column t: report

- j l 1 ' 15' tabes that were preventively plugged. i Revised Table 4. revised Quantity of tabes examine: ar.c to es NR I t be in agreseest with

, revision made to Tacle 3.

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Revised Table 5, 1 T.W. & Volts - 1983 & 1934 ,

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DOCUMENT NO roR-es2 ENuclear TITLE Evaluation of the 1984 Required Technical Specification Exanination for the T'i!-1 075G APMtOVAL DATE ngy _ _

SUMMARY

OF CHANGE The number of confirmed indicationsz 40% thru 3.E. Rhedrici/s/ 3'613 1

wall in " A" Once Througn Steam Generator has changed to 293 tubes from 297 tubes. The total R .O. Earles's! 3':5 !! I number of tubes witn indicationsz 40% for both V.C. Kazanas's/ 3': 53 "A" & "B" has increased by one to 328.

Pg. 12 add subtitle " Status of 15: Tubes."

Revised Table 1, % T.W. & Volts 1983 & 1934 i

Revised Table 2, quantity of tubes in " A" OTSG j ',

with indications.3 40 to 22 fron 20 and to 29S fron 297. Revised Ta 1e 3, add column to recer i IS: tubes tnat were preventively plugged.

Revised Table 4, revised quantity of tebes exanined and tubes NR : to ce in agreement with i revision nade to Table 3.

Revised Table 5, % T..i. & Volts - 1933 & 1954 l

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TDR 652 Rev. 2 Page 2 of 80 TABLE OF CONTENTS Pace SUMMARE 3 I. INTRODUCTION 6 II. METHOD OF EXAMINATION 7 III. SCOPE OF EXAMINATION 8 IV. RESULTS OF 1984 EXAMINATIONS 10 A. INDICATIONS REPORT 10 B. ISI TESTS 10 C. CHARACTERIZATION OF INDICATIONS 15

1. RADIAL DISTRIBUTION 16

2. AXIAL DISTRIBUTION 17

3. SIGNAL AMPLITUDE 18

4. PERCENT THROUGH HALL 18 .

5. CIRCUMrERENTIAL EXTENT 20 D.

SUMMARY

OF INDICATION CHARACTERIZATION 21 V. REVIEW PRE-KINE'IC.

T POST KINETIC AND POST HOT FUNCTIONAL EXAMINATION DATA 25 VI. EVALUATION OF CHANGES IN ECT SIGNALS FRCH 1982-1984 44 VII. GRCHTH PROGRAM 64 VIII. CONCLUSION 66 1X. REFERENCES 68 FIGURES la-e, 2a-b, 3a-b, 4a-b, Sa-b, 6, 7 APPENDIX A ABSTRACTION ON THE DUAL INSPECTION DEVELOPMENT AND PERCENT THROUGH WALL CCHVERSION CURVE B 1982-1984 EDDY CURRENT STATISTICS

ICR 552 R2v. 2 I

Pega 3 of 80

SUMMARY

During tne 1984 Technical Specification required eddy current examination, performed on the once through steam generator tuning at TMI Unit 1. a numcer of new relevant indications were detected in the "A" and "B" steam generater tubes. These new indications were not detected back in November 1982 hen a full length eddy current examination was conducted on all the inservice ~'a" and "B" steam generator tutes. During botn inspection perieds the same eccy current examination technicue was employed.

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Since the 1982 eday current examination ectn steam genera:crs nac uncergone mechanical loading cue to kinetic encansion tuce repair and thermal /hycraulic loading due to two not functicnal tests.

GPUN first cetermined that a new corrosion mecnanism was not active. This was ceterminec througn ret-it eudy current examinatiens On a centro 11ec grcuc cf tuces in 1984 after initial detection of :ne new inci:atices. Inis revealec that no grcwth cr change in given eccy current signals occurred for tre time period s:uciec.

The 1984 Indications were cnaracterized as to si:e, loca:icn, deo:n anc :nen comcared to the 1982 examtnation results. GPUN concluced tra: the 1984 inci-cations are a smaller additional sucset of : nose dete:ted in 1982 examira-tion. Tne cercent :nrougn aal! and circumferential estent fer 9G% of tne t'

TDR 652 Ree. 2 Page 4 of 80 1984 Indications are of a size that approximates the threshold of detection for the measured sensitivity curve using the GPUN quallfled standard dif-forential eddy current examination process.

Detailed analysis of the new 1984 indications reveal, that by knowing the specific location of the indication, the majority can be found in the 1982 eddy current tapes. The indications that could be measured in the 1982 taces including the in service inspection tubes reveal that:

(1) No new indications were detected in the ISI subset (one exception explained)

(2) The percent tnrough wall assignments, as determined by phase angle measurement, did not show continued through wall degradation from 1982 to 1984.

(3) For incications not previously. identified in 1982, the amolituce of the eddy current signal has substantially increased in the 1984 taoes which would result from some increase in the discontinuity volume.

Presumably the latter is a reflection of the mechanical / thermal working of the tubing.

(4) For indications not previously ident4 fled in 1982 the increase in tne amplitude of the indications in 1984 contributed to our ability to detect the small indications which now revealed tnemselves above tne surrounding oackground noise. The latter combined with the low amplitudes associatec with tne.11gnals from the incications preventec earlier detection.

r

TDR 652 Rev. 2 ,

. Page 5 of 80  !

Implicit within this fact 15 that the earlier undetected indications were in fact very small. This is substantiated by the characterization Stuales for the 1984 Indications wnich show them.to be smaller percent througn wall and circumf'erential extent than the 1982 indications. Additionally, the 1984 in-dications are located in areas which identify closely to intergranular stress assisted corrosion cracking revealed earlier in the 1981-1982 examina:1:ns.

TOR 652 Rev. 2 Dage 6 of 80 I. INTRODUCTION In Nov'mber e of 1984, eccy current examination was performed on the TMI -

Unit 1, once througn steam generator (OTSG) tueing in accordance witn Technical Specification, 4.19. The examination ultimately included 14,615 tubes in the "A* OTSG and a: proximately 6,500 tubes,in .the "B" OTSG. This examination was concluded with a total count of 328 tuces with confirmed indications having tube wall degradation measuring 40 percent througn wall or greater. This is a criterion that requires engineering disposition.

There were another 309 tubes tnat hac confirmed indications with a measured through wall degracation less than 40 percent. Those tuces =l:h-20 40% tnrougn wall incication are classified "cegraced" tubes and a e required to be monitored for cnange at future examinations. In acci:lon.

tnose tubes which contain indications of 40% through wall or greater cut do not meet the accroved plugging criteria will also be monitorec.

Since :ne last com:lete ecay current examination (1982 caseline) performec n :ne OTSG in 1982 :ne OTSG t;:es nave een su:jectec :o mecnanical loacing cue to Kinetic expansion recairs and thermal and hydraulic loacings cue to the two hot functional tests. The eccy current esamina-tions performed subsequent to these loadings have resulted in the detec-tion of indications not seen previously.

l

TOR 652 Rev. 2 Page 7 of 80 The analysis performee herein has the following purposes:

1. To characterize and report the indications identifiec during the 1984 examination and compare these characteristics with indications re-ported during the 1982 baseline examination. The purcose of tnis comparison is to evaluati the cattern of cefect cistribution and to determine if the affected areas corresconc to the previously affected areas.

2. Determine the correlation of the kitietic encansion and sucsecuent not functional test to the detecticn of indications not cetectec crice to tnese loacing events. And, evaluate the imcact from a checnolcgical cerspective.

3. Review tne cata from tne 1984 Growtn Program anc evaluate tne results te cetermine if evidence Of centinuec tuce cegracation entstec.

II. METHOD OF ExaMINATICN The ecay current examinations performed in Novemoer of 1984 utiliced coth standard cifferential and absolute ecdy current examination techniques.

inis dual examinaticn method was ceveloped oy GPUN to scecifically cetect and confirm small volume but predominately circumferentially crientec inner clameter cefects. (See Accencis A). .

TDR 652 Rev. 2 Page 8 of 80 The dual examination method involved first examining the tu0ing witn a high gain standard differential technique using a .540" clameter ecay current proce. If no indications are detected the examination is com-plete and the tube is considered acceptable. Tubes fcund to have standard differential indicaticns were examinec a second time using tne absolute Sul technique wnich used a probe *. sing 8 incependent coils.

The acsolute 8x1 examinaticn determines tie circumferential extent of tre defect and also determines if the indications are relevant or non-rele-vant. A relevant indication is a flaw that has cean confirmec cy absc-lute Sul evamination.

This cual examination metnce is the same method GPUN cualifiec anc usec for tne 1982 baseline eday current examination of the THI-1 OTSG tuoing (Ref. 1)

III. SCCDE Cr ExAMINATICN Tne initial set of tuces fcr the 1984 eccy :urrent enaminaticns nas a 3*.

samole selectec in accorcance with :ne recairements of Tecnnical Specifi-cation 4.19. As reauirec by 4.19, this set includec all tuces remaining in service whicn were classified "degraced tubes. These tuces nac crev-tously reported indications of 20 40% througn wall and are referred to as the ISI tubes. Approximately 50% of tne 3% samole was from the nign :e-fect area (outer periphery) with the remaining 50% ceing located ran::mly througnout tne generators.

iO4 ti; ReU. 3 Page 9 cf 80 The examination of the initial sample identified some discontinuities which exceeded the 40% through wall technical specification limit. As a result of these discontinuttles, the examination scope was increased to include 100% of the tubes in the affected area of both OTSGs. This in-creased scope included 100% of the tubes in OTSG "A" and 100% of the tubes in the cuter ceriphery of OTSG "B". This outer cericnery is ce-fined as the area cutside the outer tie rod circle anc includes approst-mately 5500 tubes.

The November 1984 examination was not continued into the center cf the "B" generator because no ccnfirmed indications la0% througn wall ere found in this area curing ne random examination. The indicaticns re-ported in tne "B" generator were at a significantly Icwer frecuency inan recorted in tne "A" generator. And their distribution declinea snarcly witn distance from tne cuter cerimeter anc was tcunced cy tne cuter tie roc circle.

As cart of tne expanded scoce, a selected 100 tube samcle, cestgnated tne "A" Growtn Program, was monitored in creer to cetermine tf inere was an active mechanism initiating the 1984 eddy current incications. This .

1 samcle was also ccmcaratively evaluated against the ecay current taces from the 1982 examination.

O

TOR 652 Rev. 2 Page 10 of 80 Examinations discussed witnin this reccrt included the full length of the.

unespanded region of the tubes. Espanced ortions of the tuces cannot ce effectively examined and evaluated with the standard differential tech-nique and are therefore not included in the tubing evaminations.

IV. RESULTS OF 1984 EXAMINATIONS A. INDICATIONS REPORT As a result of encanding tne scope of the examinations. 14.615 tutes in OTSG "A" and accroilmately 6500 tubes in OTSG "B" were examned.

Of these tubes, 298 in OTSG "A" and 30 in OTSG B were identiftec as having relevant indications 40% througn wall or greater. In acci-tion, 265 tuces in OTSG "A" and 44 tubes in OTSG "B' were teen:iftec as having confirmed indications from 20 40% througn wall and are classified as " degraded tutes". These tuces and any tuces with ccnfirmed Indications 40% througn wall or greater nich do not meet the accroved clugging :riteria =ill ce monitore: during future examinations as "ISI tu es".

B. ISI TUEES The sucset of ISI tubes included 28 tubes in OTSG A and 56 tubes in OTSG B which had indications of 20 40% througn wall.cenetration identtfied and recorded curing ;revious examinations.

These ISI tubes were examined as a suose; and an in depth evaluatior and comaarison of tne 1984 data to the crevious data was cerformec.

Ne :urcose of tais eva'uation sec ::mcarts:n aas t: cetermine

'f :ne

e,'ns'y tsentif*e: ta:':at*:rs ac 'gr: n-

TCR 652 Rev. 2 Page 11 of 80 The criteria used to establish growth acdressed significant cnanges e

in cercent tnrougn wall determinations, changes in signal voltage er changes in arc length of the monitored incication. When performing evaluations of this type, i t must be noted that changes of acout 10%

through wall can be causec by a change of only .3 degrees in the chase angle measurement of the standard differential resconse signal. When addressing small voltage signals, measurement errors of this tyce can be expected. For the aD50 lute 8x1, the orientation of the coils :

the defect may change tne numcer of coils an indication accears on cy 1 additional coil during receat esaminations. The evaluations mus

nerefere factor in these limitations on receatacility.

An incectn analysis of tne cnase angles of the indications from 1982, 1983 anc 1984 was ce formec anc is accressec in section VI cf tnis TDR.

!S! Tuces in tne "A" Generator From the "A" generator 28 of the 23 ISI tubes snowed no evicence Of growth for any of tne creviously identified incications.

Two taces A-2-9 anc A-SS-128. nad incications crevicusly identified as ceing <4'0% thr0ugn wall wnten were subsecuently recorted as ;4C' througn wall in 1984 Inese indications were compared by tne data w

a-ICE fil Rev. 2.

Page II Of 80 analyst On a one-tC-ene basis to the previ,Cus cata and it =45 eter-mined tnat tre change in the cercent thrcugh wall determinations were caused by variaticns in tne repeatacility of the overall e::y currect process and cct by the Onysical changes in the tube. (See tatte 1.'.

ISI Tutes in t*e "E" Ge era:Or In OTSG "B" there was no indi:ation of *grc=:n" for 56 of tre 56 tutes. One tute E-95-5 ci nase an indi:atien recorte: as greater tnan 47, inreugn = ail an: <e:;i e: fur:ner evaluation. Tne : eta +1:

for this tute are sn =r i- Ta:1e 1. .

Tne 1984 an: cresicus ca a fce : tis tute was re-evaluate: Oy the.0att analyst to ccmcare the e::/ current signal's snace. The analyst de-term +ne: the varia:ler in :ne :eece9: ter:cg* =all determinati rs =a!

attribute: t0 cistcr!!Cn Cf e::y Carrent sigeais cause: ty multiple indicatiens and =as not a result of physical changes in the tube.

Status _cf I5I Tubes l

A numbe' cf tubes prestously pla:e: in the ISI category during tre 1982 baseline esamination were determined to nave non-releva9t in:'

catiens as a result cf tne 1984 absolute 8 1 examination.

TOR 652 Rev. 2 Dage 13 of 80 These tubes had non-relevant Indications as determinto by acsolute 8:1 in 1982 but were claced on the ISI list for monitoring purposes in order to verify the crecision of the absolute 8 1 confirmation esams during future dual examination exercises. With tne completion of.the 1984 examination and the consistency of recorting the same standard differential indication as'non-relevant, these tuces .ere removed from the ISI list.

The numcer of ISI tubes (Degraded Tuces) has increased as 254 tuces in OTSG A and 20 tubes in OTSG B had confirmec indications from 20 40% through wall in 1984 which nere not previously icentifiec.

This outs ne present copulation of ISI tuces between 20 40*, tnrcugn wall at 255 tuces in "A" anc 44 tuces in "B".

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TDR 652 i Rev. 2 Page 14 of 80 t

Table 1 4

ISI Confirmed Indications Greater Than 40% Througn Wall in 1954 April hov.

Incication 1953 Post KE Data 1954 Post nFT Cata Gen Row Tube Elevation Origin  % T.W. Voi r.s  % volts A 2-9 US+06* ID 40% 1.7 45% 1.E

- 55 - 125 12+05 10 < 20% 0.9 31w 1.4  !

1 13-u9 10 < 2 0'. 0.6 < iv. 0.5 i c5-11 IS 23% 1.9 41% 2.5

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5 95 - 5 C5-07* !s 47% 2.3 4h 4.0 us+01 10 '20% 1.9 <2C% i.0 US+04 ID < 2 0'. 2.3 21% 3.5

• imre:iately celow ex:ance; area Note: These tubes were removed from service in 1985.

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724 652 Rev.3 Page 15 of 80 C. CHARACTERIZATION OF INDICATIONS The indications detected curing the 1984 examinatiens were character-tzed by the location and extent of cegracation cased on the eccy cur-rent response signal. Details, listing the data in succort of this section are included in Accendix B.

The characterization is further defined by comparing ine 1984 indica-tions with those recerted in 1982. For tnis ccmcarison GPUN usec Ne 1984 cata descricea crevicusly and the 1982 stancara differential nign gain cata case. The 1982 cata case incluced all tuces e=aminec using :ne GPUN ual examinatien methcc crior to 1984. This cata case was crevicusly usec to disposition the OTSG tuces for :ne (inetic excansion crocess anc sucsecuent tuce clogging. This data case con-tains tne 1982 caseline results which are summarized in TCR 442.

(See Ref. 2).

Sc:n 09e stancarc cifferen:tal anc acsolute :ecnnicues are usec :o furnish these characterizaticn as described below.

Stancarc differential rescense signal offers :ne following:

a. Amplitude (this relates to tne defects geometry and solume. anc is recorted as a voltage reaci9;).

c. Percent tnrougn wall (this relates to the rescense signal's : ase angle and is mecturec in degrees).

70R 652 Rev. 2 Page 16 of 80

c. Asial Iccations are reportec by distance from the tube support plates'tnat are spaced at known elevations in the generators.

Absolute Sul signal offers the following:

a. Numter cf coils (tnis relates .to the defect's circumferential eutent). The maximum'circumferential extent is 8 coils and re: resents a defe:t circumferential arc length that could be as much as 360 cegrees.

NOTE: Anclituce. pnase anc asial location are also recorced on the absolute 8 1 results; however, these results are used only to confirm tne standard differential indica-tions.

1. RAOIAL CISTRIBUTICN ine indications cetecte: curing tne 1984 examination were locatec in essentially the same areas of the OTSGs as those discovered in 1952. The indications were located predominately towards the outer periphery of botn OTSG A and B. In addition to the indica-tions ic:ated in the pertonery there was also a smaller numcer of incications present in the center of OTSG A. No indications greater than or ecual to 40*- through wall were reportec in the center cf OTSG E. (See Figures la and it).

TOR 652 Rev. 3 Page 17 of 80

2. AXIAL DISTRIBUTION The axial locatten of the 1984 incications can ce cnaracterized as being towards the top of the OTSGs. For OTSG A, 79 percent of the indications during the 1984 examination are located in or above the 15th span with 57 percent of tne incications in OTSG B Iccated in this region. This corresponds alth 82 percent in "A" generator and 74 percent in "B" generator for tne 1982 examina-tien.

In order to compare the 1982 and 1984 axial distributions, it must ce noted that the majority of the indications detectec cur-ing 1982 ere witnin the uccer tute sneet area and were caotured y the kinetic encansion c'r0 cess. As a result of the ex ansion crecess anc the coining cf tne tute wall against the tuce sneet an esamination of the coinec area was not cessiele ustrg the standar: :ifferentia' Orece. Only the area of the tuce celew tne encansion :ene c:uld :+ evamicea us'n; :ne stan:ar: siffe ear'ai tecnnicue.

With the exception of tne upper tube snect region, tne overall distribution of tne incications in 1984 closely resemoles the 1982 districuticn. inis cistricution snows the incications a e concentrated towarcs the uppermost regions of tne OTSGs anc - e frequency of occurrence decreases snaroiy at tne Ic.er regtens.

(See Figures 2a ana 20).

TCR 652 Rev. 2 Page 18 of 80

3. SIGNAL AMPLITUDE The majority of the discontinuities detected in 1984 were small volume as indicated by the amelitube of the standarc cifferential signal. In OTSG A, 93 percent of the 1984 indications detectec were 2 volts or less in amplitude, while in OTSG B 74 percent of the indications were in this category.

This voltage distribution corresponds to approximately 93 percent of the 1982 indications in OTSG A and 78 percent of tne iccica-tions in OTSG B as being 2 volts or less. (See Figures 3a anc 3b).

To estaclisn a reference volume for the discontinuities in tnis range a cemoarison can ce mace to the resconses from the cali-bration stancarc. This stancara has a 100% through wall 0.052" clameter crillec nole wnten crocuces a 15 volt rescense signal for calicratt0n eurocses. Inis indicates tnat tne cisccettru-ittes cresent in the OTSGs are of a significantly smaller volume tnan tne calibration stancara.

4. PERCENT THROUGH WALL The 1984 edcy current examination results have snown tnat a c:n-siderable numcer of tne recortec indications measurec less t in 40% through wall penetration. The 1984 examination recortec 563

TDR 652 Rev. 3 Page 19 of 80 tubes in "A" and 74 tubes in "B" with confirmed indications. In the "A" generator the indications in 47% of the 563 tuces were less than 40% through wall and in the "B" generator tne indica-tions in 59% of the 74 tubes were less than 40% through wall.

For the 1982 examination, the results indicated higher percent through wall degradation. In the "A" generator, 50% of the indt-cations recorted were 90% tnrough wall cenetration or greater while 3% of the repc-ted indications were less than 40% thrcugh wall. In the "B" generator, 16% of.the indications recorted were 90% tnrougn wall penetration or greater and 40% of the recorted indications were less tnan 40% througn wall. (See figures da ans 4b).

The Contrast cetween the 1982 and 1984 examination results for cercent tnr0ugn wall ccmcarison must consider tnat most of tre tucing witnin tne up;er t.:esneet regten c:uld n:t te esaminec in 1984 This regi:n accounted for 63% in "4" and 61% in "S" of tne recorted ind1(ations in tne 1982 eramination. Tnis ccecarts:r serves as an arcrortmation enly, since an tmoroved inner diameter conversion cuive was used for the Novemcer 1984 examinations (Ref. 3).

TCR 652 Rev. 2 Page 20 of 80

5. CIRCUMFERENTIAL EXTENT To confirm the relevancy of the reported standard differential indication an absolute 8xl examination is performed. *ife numcer of coils that respond to a relevant Indication provides an esti-

~

mate of tne indication's circumferential extent. Tne 1984 exam-Ination results showed that the confirmed Indications ranged ' rem 1 to 3 coils. The circumferential extent for a one coil indica.

tion is from the threshold of detection to 0.194". A two coil indication is from 0.024" to 0.413" whereas a three coil indi:a-tion is from 0.219" to 0.632". (Ref. 4). For the "A" generat:r approximately 90% of tne confirmed indications were I cott, ac-proximately 10% were 2 coils, and only 2 indications were 3 cetts of wnten one was outer clameter. For tne "B generator 79% o' the conftreed tecications were I coll. 20% were 2 coils, ar: :nly

, one was 3 cotis.

For the 1982 examination tne results snowed tnat tne c:nfirmed indications ranged from 1 to 8 coils. For tne 'a" geeerat:r 66%

of the confirmed indications were i coti and for t,e "S* gener-ator 50% of the confirmed indications were 1 cotl. a greater number of 2 coil and greater indications were confirmed by aese-lute 8xl during the 1982 examination than in tne 1934 eiamina-tion. (See figures 5a and Sb).

s

TCR 652 Ree. 2 Page 21 of 80

0.

SUMMARY

OF INDICATION CHARACTERIZATION The eddy current examinations performed in 1982 and 1984 Dotn util-ized the GPUN quallfled examination program using a comCination of standard differential high gain .540" probe and absolute 8 1 orcee.

This cual examination method was develoced to detect intergranular stress assisted cracking, credominately circumferentially orientec and initiated on tne tute's inner diameter wall.

4 The 1982 eddy current examinations prior to the kinetic escanston recair were full lengtn examinations cerformed on all in service tuces in bo:n "A" and 3" generat:rs. The 1984 examination were also full lengtn newever the kinetic escanded area could not be examined.

Some tu:es c:uld not be esamined with t9e 5.0. 540" rece celow tre center of the lower tubesheet due to ligament distor: ton from a:ja-cent enclostve clugs.

The c m arison of the 1982 to 1984 data sn =ed 00:9 similarities and differences in the cnaracterizatico of tne incications recorted. the enaracterization of the antal and racial districution snowed tne in-dications occurred in the same regions of tne OTSGs in coth 1982 and 1984 The amelitudes of the indications also accears t: ce simitar in 1982 and 1984. The differences eetween :ne two sets of dati a:-

Dear in the cercent tnrough walls,

which are signiflCantly lower in 1984 than in 1982 and in the circumferential entent wnten is also smaller in 1984 tnan in 1982.

TC4 652 Rev. 2 Page 23 of 80 This characterization and comparison would suggest the 1984 Indica-tions are a smaller additional subset of those detected during the 1982 examination.

To determine how the size of the new 1984 Indications reflect on the given sensitivity curve estaclished in TOR 401 and 423, the mailmtm size of the new incications detected was estabitshed and compared to the above. It was determined that approstmately 90% of the indica-tions are a maximum of one coil. (Note: a one coil indicatten if not Dreferentially oriented could give a two coil resconse). Adat-ttcnally, ac;rcsimately 90% of the new indications .ere ceterminec to De between 20-60% tnrcugn wall. Using this data against tne senst-tivity curve shown in TOR 423, the new indications accear to credem-inately reveal themselves at or near the tnreshold of detectlen of the given sensitivity curves.

!! was retermined tnat a :rcuimately 10% =as ' rem a c:ulaticn :nat nas 16 0% through wall cetermination. For indications 160% througn wall all were 1 er 2 cells with tne esce0tien of one indicaticn in tube B-97-5. The Indication (76% through wall, 3 cotis) was located at the upper tube sneet lower face regien. It is encetted that tne sensitivity fcr detection is suporessed during the eddy current crece cassage into and out of (0.5" distance) :nis regten. (Ref. 1).

TOR 652 Rev. a Page 23 of so The t.wo other 3 coil indications in tubes A-84-131 and A-79-1 had

, <20% and 52% througn wall determinations respectively.

The three, 3 coll circumferential extent indications, and the 160%

through wall indications are of dimension below those analyzed to withstand the main steam line brake loadings (See Figu?e 6).

The following is the breakdown of the 1982 and 1984 characterization:

1982 1984

1. Radial Distributien Prajominately in tne outer Precominately in the peripnery of both "A" & outer pertonery of boti "B" (significantly fewer *A" & "B* (significantly in "B") fewer in "B*)

2. Axial Districution precominately in the UTS Most in UTS Region :50%.

Region :63% anc Some in 16th scan :19; 16tn scan 214%

3. amplitude 76". Iets than 2 volts in 75". Tess traq 2 volts in (Voltage) "A" and 51% less tnan ' A" anc 47% less tnan 2 volts in "B" 2 volts In "B

4 Percent 50% greater tnan 90% T.W. 2% greater t9an 9C% i.W.

Througn Wall and 96% greater tnan 40% and 40% greater t9an 40%

T.W. in "A". 16% greater i.W. In "A" 1% greater tnan 90% T.W. and 60% than 90% T.W. and 27%

greater than 40% T.W. In greater than 40% T.W. In g .. g

• 0R'652 Ree.2 Page 24 of 80 1992 1984

5. Circumferential The indications ranged The indications rangee Extent from 1 to 8 cotis in botn from 1 to 3 cotis in coth "A" and "B". For "A" "A" and "B". For "A" 90%

more than 90% of the in- of the indications were 1 dications were 1 and 2 coll. For "B" more than coils (66% - I coil and 90% of the indicattens 30% - 2 cotis). For "B" were I and 2 cotts (79% -

more than 90% of the in- I coli and 20% - 2 coils).

dictations were 1, 2. 3 There was a total of 3 cotts (50% -1, 34% -2 indications with 3 cotts coils ana 8% - 3 cotis) 2 were inner clameter ano I was outer diameter

!3R 552 Rev.2 Page 25 o9 80

v. REVIEW OF PRE KINETIC, POST KINETIC & POST HOT FUNCTIONAL EXAMINATION DATA A. OVERVIEW GPUN performed a 100% Examination of the OTSG tubes in 1982. This examination is referred to as the 1982 baseline.

Since performing this examination GPUN nas reenamined a select number of tne OTSG tubes to monitor the effects of the kinetic expansion recair (KE) and the subsecuent hot functional testing (HFT).

These examinations revealed tne presence of indications wnicn were not creviously identified curing tne 1982 baseline examinations. 70 more fully uncerstanc the accearance of these indications GPUN cer-formec detailed evaluations of tne availacle eddy current data to cetermine if the indications had been cresent but C0uld not ce ce-tected on crevious esaminations or if the indications were 11 crevi-cusly unaffe:tec areas of' tubing.

Includec in these evaluations were data sets of-1982 In Drocess Examinattens for Kinetic Eveansion (Octocer. 1952)

Purpose:

Cetermine tne effects of (inetically escancing tre OT5G tuces.

e .

TDR 652 Rev. 2 Page 26 of 80 This data set ccnststed of examining 437. tubes in OTSG A anc B after the tuOes were espanded. The data was then compared to the 1982 baseline.

1983 Post KE Examinations (Acril, 1983)

Purc0se: Determine the effects of the complete kinetic expansion crocess on tne OTSG tubes.

Tnts cata set censisted of examining 477 tuces in OTSG A & B after tne kinetic encansion recair was completed. The data was then ccm-pared te the 1982 caseline. This cata set includes the ISI tubes.

1984 Post H~T Examinations (Nevemcer. 1984)

Purpose:

Cetermine tne cu.mulative effects of the kinetic espan-sien repair and subsecuert HFT on the condition of tne OTSG tubes.

A data set of 375 tubes was taentified from the November 1984 popula.

tion which remained in service for which GPUN had 1983 post kinetic espansion cata. Tnis. data set includes the ISI tubes. This data .as then C0mpared to the 1983 cost kinetic expansion and the 1982 base-line data.

~ , - ,

TOR 652 Rev.a Page 27 of 80 Also included in the review were 45 tubes with indications icentified as >407. through wall, during the 1984 examinations. These tubes were selected from tubes included in the 1984 flaw growth program. Since no 1983 post KE data was available, the evaluation results were com-pared to the 1982 baseline.

B. METH00 0F EVALUATION During the evaluations, the cata analyst reviewed the magnetic taces of the previous eddy current data for tutes witn newly detectec indi-cations. This review was accomolished by isolating the scecific area of interest anc performing a cetailed review of the ecdy current sig-nals. By isolating the kncwn area of interest, the cata analyst was able to perform an intense analysis of the eddy current signals at a higher level of sensitivity than allowed cy Droduction analysis tecn-niques. This intense focus permitted tne cata analyst to identify tne cossiele cresence of Icw levei eccj c;rren: signals .nien may te masKec by cacKground noise curing crocuction analjsts.

Once the signal was identified and isolatec. tne analyst then measured and recorded the signals amolituce, anicn indicates the vol-ume of the discontinuity, and the Dhase angle, whicn indicates tne death of the ciscontinuity.

TDR 552 Rev. 3 Page 28 of 80 The amplitudes and chase angles of the signals were then character-ized to determine the relative size of the discontinuities. The evaluations from the successive examinations were then compared to establish when the signals were first detectable by eddy current.

This also characterized any enanges which made the signal detectacle by production eddy current tecnniques.

C. RESULTS CF EVALUATICNS As a result of the evaluations cerformed on these data sets GPUN con-cluded that:

1. Knewing the exact location of a reported indication, most Of the indications could te identified in previous examination data.

This indicated the disccntinuities nere creviously present Out not detectacle due to tnetr low amc11tude.

2. As a result c' tre (tnetic excansion and tre act functional test-ing the amclitude of cre"iously unidentified signals increased making tne signal resconse more detectable. This was tycically a 100-200% increase in amc11tude =nicn brought tne signals acove the thresnold of detection. This can ce attributed to an in-crease in :ne volume of tne discontinuity.

Examcle: 198a data snows 1.5 voit signal in 0.5 voit noise, re-review of 1982 data shows 0.5 volt signal in 0.5

/olt noise at tne same location.

e- - - , - - * - -

70R 652 Rev. 2 Dage 29 of 80

3. Althougn the amplitude of the signals increased, the onase angle of the signals did not snow a correscending increase for the indications first detected in 1984. This would indicate that, although the volume of the discontinuity changed, the cercent through wall penetration remained constant. This is ciscussec in greater detail in Section VI of this TDR.

4 The new (1984) indications whicn were reviewec are 1ccated at the upper elevations of the OTSGs. This correscones to the previously affected are&s of the OTSGs identifiec curing :ne 1982 examinations.

D. OETAILS OF EVALUATIONS PERFORMED ine following is a brief descriction of the evaluations cerformed anc the cetails of the data sets utilized. Tne data sets are cresented in enronological orcer to demens: rate :ne cumulative effects Of :ne varicus OT5G activities ucon :ne :accs since tne 1982 caseitne. Tnis enronology is also contained in Table 2.

1982 In Process Examinations for Kinetic Espansion (October, 1982)

Purcose: Determine tne effects of (inetically exoancing tne OtSG tuces.

l TDR 652 Ree. 2 1 Page 30 cf so In order to monitor the effects of the kinetic espansions GPUN ex-amined 437 tubes. The tubes selected for these examinations were the

~

first tubes to be expanded, located in rows 1-8. In coth OTSGs.

This examination identified discontinuities wnich were not previously recorded in 15 Of th'e 437 tubes examined (3.5%). An evaluation was cerformed at tnat time to determine why the indicaticns were not identified Dreviously.

This evaluation is documented in TOR 401 (Ref. 4) anc TR-008 (c. 44-45) (Ref. 5) and ccnclucea :nat:

1. The incications ere not initiated by the kinetic encansien crc-

ess nce was t9ere any evidence of cetectable arcoagaticn cf existing 19 Citations.

2. The cefects aere smail (t9ee3nc10) ty:e 'n:icatiers trat 9a:

either teen masked y the hign cackgrounc noise levels in tre uceer tube sheet regions or were sufficiently tignt that signifi-cant metal removal was not present to permit detection. <inett:

expansion may nave altered these areas to make tnem more :etect-acle.

TOR 652 Rev. 2 I Page 31 of 80 1983 Post Kinetic Exoansion Examinations (Acril. 1983)

Purpose:

Determine the effects of the Kinetic Expansion Repair and associated Tube Plugging Activities GPUN examined a samcle of 477 tubes in OTSGs A and B using tne cual examination methed. This samcle was selected to determine if the kinetic evDansion crecess had significantly altered the ccncitien cf the OTSG tubes.

The samole was casec cn the requirements of GPUN scecificatten 57 1101-22-014 ahich is summarizec in TR-008 Accencis A (p. 109 113). The samole recuirements are summarized below:

(a) All tubes with <4G*. tnrcugn wall inc! cations wnten retainec in-service. (ISI Tuces)

(c) All tuces adjacent to 10 telectec sincly cluggec tuces 'tn defects in tne 15th. ICtn anc ist scans. (10 tuces eacn OTSG).

(c) All tutes adjacent to 10 selected simoly clugged tuces. '-

tne cerinnery of eacn OTSG.

(d) 50 tuces in nign ol'ugging censity areas in eacn OTSG.

i

.-. __- -_ - . - - . ._L

7OR 552 Ree. 3 Page 32 of 80 (e) All tubes adjacent to 5 plugged tuees in each OTSG with >3 volt signals in the lower part of the OTSGs.

(f) In' addition to (a) through (e) above, all tubes identifled as leaking during the post repair drip and or bubble tests were included. -

The examination of the above sample of tuces provided an evaluation of the " worst case" areas of the OTSGs'. The examination resulted in the identification of indications 140% through wall whicn mere not previously re:orded in 35 tuces (7.5%). In addition, 1 of tne indi-cations oreviously identified as ceing (40% througn wall in OT5G A acceared as 140% and recuired further dispositioning. Tne ccmcarison of the tube status prior to and after the (inetic encansion crc:ess is summarized in Table 3 and in TR-008. Accendt A(c.109-113$.

i In its 1983 evaluat'on 3 PUN reviewed tre 1952 aseline to esta:16 sn the cause of the newly detected indications. This review c ncluded that:

1. The majority Of the indications could De detected during detailed reviews Of SDecific areas of the 1982 baseline data. These re-views showed tne indications had typically ceen present at 10 amplitudes and signal to noise ratios of 1 to 1 or less.

j

~

70R 652 Rev.3 Page 33 of 80

2. The kinetic expansion process accarently caused the amplitude and corresponding signal to noise ratio of the indications to in-crease thereby making them acre detectable.

3. The indications were located near the too of the OTSG. Twenty eight (28) of the 35 (80%) of the indications 240% througn wall which had not previously been detected were located within the uceer tube sheet. This would be the area most affected cy the kinetic expansion process.

. 4 The onase angles of the indications recorted in 1983 cid not snow a relevant increase in the percent through wall when comcared to

. the 1982 taseline data.

GPUN also reviewed the 1982 caseline and 1983 cost (E data to cr-termine if the indication (ISI tuce in 1982) creviously identifies as ceing <40% througn wall in 1982, and tnen reported as greater tnan 40% tnrough wall in 1983, indicated a enange in tne status of the tuce. A detailed review of tnis tuce and crior associated 'ndica-tions revealed that they were outside diameter originated and are therefore not part of this evaluation for primary side attack. Its disDosition was covered Dy the TMI Unit I tecnnical sce:1ficatices reduirements and ne tube was removed from service.

TOR 652 Rev. 2 Page 34 of 80 192d Post Hot Functional Testing Enaminations (November, 1984)

Purpose:

Determine the cumulative effects of the kinetic espan-sien repair and subsequent hot functional testing on tne condition of the OTSG tubes.

Following the net functional testing (HFT) performed a'ter the kin-etic e Dansion repairs (KE) GPUN perfcrmed the 1984 examinations of t,e TMI OT5Gs. These examinations provided a basis for determining the cumulative effects cf tne kinetic expansion repair and subsequent not functicnal testing of the OTSG tubes. Tnese examinations identi-fled indications not recorded in previous esaminations. To charac-terize the newly recorded indicati0ns anc determine when they could first be detected, GPUN Cerformed entensive reviews of the historical '

Cata fo" 2 data sets. These data sets are discussed in (A) and (6) telC=.

(A) Tne first cata set selected for evaluatiCn from the November, 1984 data set was 375 tubes for which post kinetic espansion cata was available. This data set included:

(1) All tubes remaining in service in OTSG A which were previe.!-

ly esamined curing the 1983 post KE esamination. This con-sisted of 163 tubes with no previously retorded indications

'and 28 tutet cre.tously identified as ha<ing 20-40% teroug-wall indicaticns (!S Tutei).

TOR 652 Ree. 2 Page 35 of SO (2) All tubes in the outer periphery of OTSG 8 which had been examined in 1983 and remained in service following the.1983 post KE examinations. This consisted of 128 tubes with no previous indications and 56 tubes previously identified as having 20-40% througn wall indications (ISI Tubes).

As a result of these examinations, 14 of the 291 (5%) tubes with no prevleus indications were identifled as hating indications 240% through wall. Of the 84 previous ISI tubes 3 tubes had indications reported in 1984 which had not been previously identified in 1983. These la tubes with no previous indications and the 3 ISI tubes are discussed separately below. The results of the examinations are summarized in Tables 4 and 5.

Tubes With No previous Indications For tne 14 tubes witn indications 140% tnrougn wall which .ere not previously recorded, a complete evaluation of the historical data was performed. The review characterized the indications and determined if they had been present during the previous esaminations. This evaluation concluded that:

1. During the review of the 1983 post (E data, 14 of the ;4 Indications were detectable but were low amplitude signals within the noise. During the review of the 1982 baseline

70R 652 Rev. 2 Page 36 of 80 data 9 of the la indications could ce 6dentified. This would suggest that both the kinette encanston and not func-tional testing increased the detectaellity of the indications.

2. The amplitude of tne indications increased from the 1983 post (E esamination to the 1984 post HFT esaminations making them more cetectacle frem the surrouncing noise.

3. The indications recerced during the 1984 Post HFT esamina-tiens have a small circumferential estent as sncan ey the 8 1 acsolute pecce. Of the la indications naving 240% tnrcugn wall cenetrations. 13 accear as I coil and I accears as a 2 cott indication. A 360' Indication would accear as an a cetl tecication.

ISI Tuces For tne tnree crevtcus ISI tuces anten nave incications 140%

thecugh wall, anten were not creviously identl*ted anc recerted in 1983, the evaluattens are as fo11cas:

One tube A-120 106 snewed an additional Indication anlen was identtfted as eetrg 95% tnreugn wall and 4.0 volts and nas 'c-cated at the edge of the IStn succort clate.

g 4-

TCR 652 Ree. 2 Page 37 of 90 Upon a re-review of the 1983 Post <inetic Escansion Data it was determined that the indication was present at accrontmately 55%

througn wall and 2.1 volts but the ilgnal was masked by the signal from the tube support plate. The effects of the support plate signal also distorts the pnase angle of the eddy current. Signal making an accurate cercent through wall determination impractical.

Thi$ particular tube succort is a drilled succort and cannot be

• mlued out* using tne multifrecuency eddy current tecnnicues used to esamine the broached succoets located tnrougnout the rema'inder of the OT5Gs. ints creates a zone of reduced sensitivity (accrontmatet/ .5"

& cove and calow the edges of the sucport plate) at the drilles succort locations. The 1983 signal at 2.1 volts is celow the 3.3 volt thresnold of detection for the drilled succort Dia'te as establisned in TDR 423 ints :ene of re:uce3 sensitivity acc les to tre e3;es of coth the uccer and lower tubesneets an: tne drilled hole in the 15tn succort

, clate. The drilled noles are located only in the entreme outer certenery of the 15th support clate. Tne remainder of the 15tn support plate and the otner la succort 014tes are tne

• broach" design and althougn they reduce tne accuracy for si:ing indica!!cns in t*.'!

area, they do not have this 20ne of reduced sensitivity for detect'en 3f indtCattons.

TOR 652 Rev. 2 l Page 38 cf 80 '

l The other two tutes. A-3-31 and A-149-14. had indications greater l

than 40% througn wall recorted in 1984 wnten had not :een crevl.

ously identified. In the re-review of the 1983 data at the scoc-Ifled location, the indications were identified and comparec to the 1984 data. Inis comcartson snowed tne indications were low

.. asolltuce signals masked by noise in the 1983 data. (See Table l

l 5). -

l 1

(8) The second data set selected for evaluatten from the govemcer 1984 data set was 46 tuces altn Indications first identtftec car.

ing tne 1984 esaminations. ints cata set included:

1 (1) 12 tutes attn incicattens less t an 40% tnrougn wall anc 34 tutes itn lect:sti:ns greater 9an 40*. tne:ugn all. Tre tuces selected for tnit evaluatien were crevicusly incluces in t9e 1984 Greatn 8r: gram. The twees .ere 10cate: 19 tne cuter cerinnery cf tne GTSG A.

l 'ne Indications were cnaractert:ec anc ::mcares to tae 1982 casettee data. The results of the evaluation Conclude t94t:

I

1. (nCwing the enact IccatiCn Cf tPe 1984 inctCattens, tne corres.

DCnding Indicaticns c uld te identifie3 curing a review of t*e 1982 casellne data for 32 (70*) of the tuces, ints Culd ledt-cate the areas nac caen affected prior to tne 1982 castline etim-Inations.

i 1

4 724 652 Rev. 2 Page 39 cf so i

2. A comcarlsen of the 1982 to 1984 cata snows the average l amelitude increased from 0.6 volts in 1982 to 1.5 volts in 1984. This demonstrates the amclituce of the in icatient J

l Increased during this time period maAlng them more detectable.

t 2 ,

I i

3. Tne comcartson of the 1982 to 1984 cercent througn wall ceterminations snowed a slight downward trend of accros.

imately 11 cercent tnrcugn wall (ecu1 valent to 3* cnase angle change). Bases on this Dnate angle evaluation, no

$1;ntftcant tren: cf tnrcugn wa!! growtn can ce estac.

11sne3. This trend is further discussed in Sectico V! Of nts 70R.

~

I b

I r

b 4 ,

i, l

I i

TCR 652 Rev. 2 Page 40 of so Table 2 Chronology of Steam Generator Evolutions and Corresponding Eddy Current Examination Steam Generator Eddy Current Examination Even: Duratten Data Sets Results > a0% T.w.

A 8 Start-up & Test -

. 131 tubes leak Oct-Nov 1981 July-Sept 1982 885 273 (1982 baseline)

Kinette Escanston Repair Oct-Dec 1982 Oct-hov 1982 9 6 (in process)

Aortl-May 1983 22 la (Post)

Not Func: tonal Aug-Oct 1983 - .

Tes: M4y 1984 Leak its: June 1984 July 1984 0 1 Dry Lay u: June-Nov 1984 - -

Tech Scec a.19 Nov-Cec 1984 rec < - J a a 1984 298 30 4,

TOR 652 Rev. 2 Page 41 of so Table 3 Results of 1983 Post Kinetic Expansion Examinations Status Prior to Kinetic Expansion (1982 Baseline) 151 Tw:

Tuoes Tuoes Tubes Tubes Prevent 0T53 Examinec N41 < 40s (151 Tubes) #40% Plue <

A 215 200 14 0 1 6 263 212 51 0 C TOTA 5 478 412 65 0 1 Status After Kinetic Expansion (1983 Examinations) 15! Tu To es TuSes TuDes TuDes Prevent CTS 3 E x a?.i n e: NRI <4C% (ISI Tutes) 1 40% Plugg A 214 163 25 (12 previous ISI) 22 (1* previous 15!) 1 (16 previous NRI) (21 previous NR!)

E 263 193 56 (51 Previcus ISI)

~~ --

14 (0 previous !$1) --

( 5 Previous NRI) (14 Previous hRI) 70T4.5 477 356 84 36 1 hRI . No Relevant Indications NOTES:

• In 1 tubes, indications reportec as <4C% tnrougn wall in 1932 were reportec as 240% througn wall in 1983. Tnese indicati:ns are outsice cia eter initiatec and are not constoerea relevant t:

tne present evaluations.

• • inese !$1 tu:es were preventively plugge: in accordance attn engineering dispositioning basec on location (axial and/or racial) of *425 tnru aall indications,

TOR 652 l Rev. 2 Page 42 Cf 60 Tacle 4 Results of post Not Functional Testina Examinations Status of Tubes Prior to H.F.T.

-Tutes Tuces . Tubes Tutes OT5G bastned NRI <40% (ISI Tubes) 240%

A 191 163 28 0 5 184 128 56 0 TC!al N [fI 3 7 Status Cf Tutes After H.F.T.

Tuces Tuces Tuees Tuees 075G E4 mined NRI <40% (ISI Tutes) 140%

a 191 133 39 (23 orevious 151) 19 ( 5 previous 151)

,16 previous NRI)

( (14 previous NRI) 5 184 127 56 (55 crevious ISI) J( 1( 0orevious ISI)

( 1 crevious NRI) previcus NRI)

TCtal 375 260 95 20 NRI . No Relevant Inditati;ns e e M

l TOR 652

, Rev. 2 j Page 43 of so l

Table 5 ISI Confirmed Indications l Greater Than 40% Through Wall in 1984 April hov.

l Incication 1983 Post KE Data 1984 Post HFT Data

! Gen Row Tute Elevation Origin 1 T.W. Volts  % volts A 3 - 31 13+C ID 33%* 1.1 33% 1.5 13+04 ID 27%" 0.8 <20% 1.3 13+05 10 33% 1.3 36% 3.3 13+08 10 40%" 0.6 45% 1.5 13+15 10 30%" 0.3 28-31% 0.8 A 149 - 14 14-06 10 S6%" 0.4 76% 0.6 15-16 10 80%" 0.5 69% 0.7 US+04 13 20% 1.0 Not Detected 120 - 106 12+C9 10 40%** 0.5 41% 1.4 13-C8/15-08 10 50%" O.4 48% 0.7 15+0 10 55% 2.1 95% 4.0 05+02 10 20% 1.1 ,

20% 1.2

• Reoresents re-evaluation of 1983 cata, j " Incications not previously identified curing production examinations, inci-cations first icentified curing 1984 review of 1983 cata.

Note: These tubes were removed from service in 1985.

6 L

TDR 652 Rev. 2 Page 44 of 80 VI. EVALUATION OF CHANGES IN THE E00Y CURRENT $1GNALS FROM 1982 to 1984 A. CVERVIEW GPUN's evaluation of the historical data (1982, 1983) for indications first detected in 1984 revealed changes in the eddy current signals from 1982 to 1984. These changes are characterized as an increase in the amplitude (voltage) of the signal with a corresponding decrease in the phase angle of the eddy current signal. This phase angle change has resulted in an apparent decrease in the depths of the indications observed from 1982 to 1984. This phenomenon was first identified in 1984 during a review of the historical data for the tubes included in the OTSG A growth program discussed in Section VII of this report. To better uncerstand the cause and impact of these changes in the ECT signals, GPUN evaluated additional sets of avall-able data considered most amplicable. These data sets included tubes creviously identified as ISI tutes (Degraded Tubes), tubes previously removed from the'OTSGs, tuces sucjected to Long Term Corrosion Testing (LTCT) and tubes with synthetic defects (EDM Notches) previously used as cualification standards for the GPUN examination techniques.

The purpose of these evaluations was to:

1) Investigate the cause of the changes in the ECT signals

2) Determine the impact of the changes in the ECT signals on the GPUN ECT program.

3) Quantify tne degree of change in terms of cercent througn wall.

. #9

. = _ - - _ . ._. -.

VDR 652 Ree. 2 Page 45 of 80

4) Identify the areas in the OTSGs in which the ECT signals were affected.

i 5) Determine the effect of the changes on future ECT examinations.

The evaluations performed by GPUN to address these areas are dis-cussed in the body of this section.

)

8. CONCLUSIONS '

I i

Through the evaluations of the available eddy current data from 1982,  !

1983 and 1984, GPUN was able to characterlZe and further define the

" phase shift" (decrease in phase angle) previously identified in Revision 0 of this TDR. These evaluations have demonstrated that the present GPUN ECT techniques, used to disposition the 1984 examination I

data, are acceptable as presently cuallfled and are not affected by the 00$erved enanges in the ECT signals. Althougn GPUN .as unable to I

determine the root cause of the " chase shift the following conclusions can be drawn from the technical evaluation of the available data.

• The review of the ECT process variables shows tne reported l

! " phase shift" is noi a result of changes in the ECT technicues.

• The metallurgical data indicates the GPUN ECT program is acce::-

able for dispositioning ECT signals which have been affected oy i L the observed changes, i

[

_ . . _ _ _ . _ _ . . _ - _ __._.,f__.__._._..___-.___._,,__.~-.___,_____._____._____.__.I__..____._._,__

TOR 652 Rev. 2 Page 46 of 80 The " phase snift" initially identified as -11% through wall included both changes in the ECT signals and variablitty in the ECT data evaluation process. This phase shift was redefined as -6.9% throuch a reevaluation of the data.

The " phase shift" which was initially identified in the OTSG "A" Growth Sample from 1982 to 1984 has also been identified in the OTSG "A" 151 tube samples from 1982 to 1983.

The shift in pnase angles appears to have occurred at all axial and radial locations in tne OTSG wnere inner diameter indications were observed.

ine OTSG A ISI Tubes (Cegracec Tubes) cetonstrate that once the discontinuities become detectable durino production esaminations, the pnase angle of the ECT signal remains constant (within enDected repeata0111ty) during subsequent examinations.

• The percent through wall penetrations of ECT indications of one (1) volt or greater are shown to be accurately evaluated using the Qualified GPUN ECT Program. Indications of less than one (1) volt have been shon e to result in the assignfrent of overly conservative percent throuch wall values. At a minimum these indications will be evaluated and monitored during successive inspections.

70R 652 Ree. 2 Page 47 of 80 C. ECT PROCESS REVIEW Prior to evaluating the changes in the ECT signals, GPUN reviewed the variables involved in the overall ECT process to verify the validity of the data sets. The variables reviewed included both the ECT cata collection process and the subsequent data evaluation process. The review of the data collection process included the ECT eculement.

probes, calibration standards and calibration techniques used during the 1982, 1983 and 1984 examinations. The data evaluation technicues were also reviewed to determine if changes in the method of analysts from 1982 to 1984 or variations tetween tne data analysts could ce Identifled.

d The review of'tne process variables was performed using certified data analysts from two separate NDE contractors. This review concluded that tne ECT tecnnicues used in 1982. 1983 and 1984 ere Consistent anc the enanges teentified in the ECT signals were not tne result of changes in tre process variables. The results of this review are dccumented separately.

During the review of the evaluation techniques, GPUN and their ECT centractors determined the Innerent vartantitty of the ECT evaluat':r process was introducing additional data scatter into tne data eva*.a.

tion process and blated the Initial comparisons of the 1982 and 1984 data. After identifying this variability GPUN was able to account for this bias in subsequent evaluations.

4 g M%

70R 652 Reu. 2 Pace 43 of 80

0. DISCUSSION OF SIGNAL, CHANGES To further define the esta9t of the identified phase angle changes GPUN character 12ed both the signal to noise ratios ($/N Ratlos) of the ECT signals and the sh40es of the ECT signals. This character-12ation was performed for both the 1982 and 1984 ECT signals and showed a definite change in the signals during this time period.

This charactertration snowed the 1982 signals were predominantly very tight locDed. Straight signals, with very poor signal to notte ratios (typteally less than 1 to I). By contrast, the 1984 signals en-hielted ercader loops with complet signal formations. The signal to noise ratto of the 1984 signals was also' greatly improved over the 1982 signals. Typical changes in the signals from 1982 to 1984 are shown in Figure 7.

E. *Ef*CD Cr qEviEW 70 address the Questions raised by the change in the ECT stqnals from 1982 to 1984 GPUN performed evaluations of various sets of data.

This section detatis the methods of evaluation and the data sets utt112ed to resolve these questions.

6

TOR 652 Rev. 3 Page 49 of 80

1) Investlaate the Cause of the Channes in the ECT Slanals I

The review of the EDM notch standards showed the characteristic shape of the ECT signal from the inner diameter notches enanged I

in relationship to the signal amplitude. The characteristic shape of the signals from the notches was stellar to the signals observed in the OTSGs in that the low amplitude signals from tne smaller volume EDM notches have the same easic shape as the small amplitude 1982 signals. The htgner amolitude signals from the larger volume notches have the same easic shape as the 1984 ECT signals.

As the shape and the amplitudes of the ECT signals changed from l 1982 to 1984, the phase angle of the signals also changed, this change in the chase angle (cercent through wall) can ce associated with changes in the volume of the discontinutties.

Researen perforted in the Industry (Reference 6) has shown a strong decencence of the enase angle of tne ECT signal on tne size of the discontinuity, where the geceetric snace and tne depth of the discontinuity remained constant while the volume was varied. For this reason it is important that the methods used for evaluating the chase angles of the ECT signals ce cased on geometries and volumes representative of the discontlnutties 8ased on the acove information the changes in the shape and chase angle of the ECT signals 400 ears to be a function of changes in the volume of the inner diameter defects, inese factors have teen addressed in the quellflCatton of sne 08'JN E U techniques.

t =

70R 652 Reu. 2 Page 50 of so

2) Determice the Imoact of tne Chances in the ECT Stanats on tne CPUN ECT Program

! To cetermine the locact of the signal changes on the previously quellfled GPUN ECT technlaues. GPUN evaluated data resulting

. from the ECT esaminations of synthetic defects (ECM Notenes) and the results of metallurgical esaminations performed on tubes remo<ed from the TMI OfSGs in 1981 and 1982.

l The ECT cata from the EDM Notches was reanalyzed to verify that tne metnod of interpretation of the notch death was consistent witn tne metneds used for Interpretation of tne insitu E07 cata. Other analysts techntoues such as measuring the steecest angle of the ECT signal ano analyzing tne auititary frecuencies (i.e. 20CKH g 80CKW,) were also evaluateo, these evalua-tiens showed the present method of analysis to te Consistent

=ttn tnote usea to cualify tne tecnntoues and the most acetic-acle for the fM! 07535.

To further define the iroact of the octerved changes on the accuracy of the CPUN ECT technioues, additional correlations of the esisting metallurgical cata were performed. The data set used for tnis samcle incluced all taentified cart through we

IGSAC. This cata set includes 6 dita cotnts which were previously used to the metallurgical correlations in TCR 642.

• ne data set 4's3 Includes 2 addit l0nal cati coints previously esclucec fr:m *04 642 tocause Of c0or st;nal t: nette rattos.

70R 653 Rev. 3 Page 51 of 80 These data points are included in this set because they are representative of the signal to noise ratios of the indications {

observed during the review of the 1982 data. The ECT data for these examinations consists of both .510 S.D. ana .5a0 H.G.S.0.

which was performed using the insitu ECT procedures and is considered representative of the insitu data.

The data set of 8 points for whl'cn metallurgical data was availasle was statistically evaluated both as a complete set and as 2 additional subsets. These subsets were the 4 Indications with signal amplitudes of I volt or greater which are typical of the 1984 Indications and the 4 Indications with less than 1 volt signals which are typical of the indications identified during the review of the 1982 data. The statistical evaluations are as follows:

Sh

- ~

TOR 652 Rev. 2 Page 52 of 80 Statistical Evaluation of Part-Through Wall IGSAC Data Set: All available part-through wall IGSAC. Includes 6 data points from TOR 642 and 2 additional data points.

Indications  % T.W. 1 T.W. 1 Otff.

In Sample Stat. Met E.C.T. Met /E.C.T 8 I 45.9 63.4 + 17.5 e 21.8 27.7 25.9 Data Set: Data cotnts from above set with signal amplitudes less than I volt. (Typical of Indications identifled during review of 1982 data.)

' Indications 1 T.W. 1 T.W. 1 Otff.

In Sample Stat. Met E.C.T. Met /E.C.T 4 i 46.3 77.5 + 31.3 e 25.4 25.4 31.9 Data Set: Data cotnts from above set with signal amcIltudes I volt or greater. (Typical of indications identified during the 1984 examinations.)

Indications  % T.W. 1 T.W.  % Otff.

In Sample Stat. Met E.C.T. Met /E.C.T 4 I 45.5 49.3 + 3.8 0 21.4 24.7 6.2 I Mean Value e 1 Standard Deviation (Samole)

TDR 652 Rev. 2 Page 53 of 80 The statistical evaluation of this sample can be used to show a general trend in the accuracy of the percent through wall calls. When all 8 data points are included the mean overcall is 17.5%. When only the 4 signals.of one volt or less are consid-ered the mean overcall is 31.3%. By contrast the 4 signals with amplitudes of I volt or greater showed a mean overcall of 3.8%.

This data set is limited and the indications included have not experienced the mechanical and thermal stresses applied to the insitu tubes and therefore cannot be used to define exact margins of overcall for part through wall IGSAC. However, the data indicates a consistent trend of overcalling the percent through wa'l of the small, poor signal to noise ratto indica-tions typical of those Identified during the review of the 1982 data. The data from the larger, 1 volt or greater, signals typical of the 1984 data, implies a degree of accuracy more consistent with tne GPUN Qualified techniques (Reference 3) than observed for the lower amplitude signals.

Since the 1984 ECT signals may be the result of IGA, IGSAC, or both, GPUN reviewed available data to determine the accuracy of sizing IGA with IGSAC protruding from the bottom. The data available was limited to only one data point. This data cote:

had a 35% tnrough wall IGA pit with an IGSA crack extending m

TOR 652 Rev. 2 Page 54 of 80 completely through wall. The data reviewed for this defect was

.510 S.0. insitu data which showed the indication to be greater than 100% through wall (recorded as 95%). The indication did not appear to be affected by the IGA and would have been properly dispositiened. l

3) Quantify the Degree of Change in Terms of Percent Through Wall GPUN evaluated data from 3 data sets to quantify the degree of changes in the ECT signals in terms of percent through wall.

These various data sets include the OTSG A Growth Program and the OTSG A&S Degraded Tutes (ISI Tubes). The review of a 4tn i cata set. the LTCT data from examinations performed by Westing-I hou:e indicated the ECT process was not consistent with the TMI }

ECT program and therefore the data was not included.

~

OTSG A Growth Program (100 Tubes)

The primary cata set used to cuantify the changes in the ECT signals was the 39 indications identified in the OT5G A Growth Program. This data set did ng include any indications pre-viously identified during the 1982 examinations and was further limited to those indications 20% through wall or greater.

Prior to performing a statistical evaluation of the 1982 and 1984 data, the data was re-evaluated oy a single data analyst.

The re-evaluation was performed to account for the variability previously identified during the review of the ECT process.

TOR 652 Ree. 3 Page 55 of 80 This variability applied primarily to the larger amplitude 1984 ECT signals and therefore biased the initial 1982 to 1984 data comparisons. This re-evaluation does not impact the previous disposition of the 1984 data as the majority of the tubes which were included in this sample were removed from service based on the original 1984 evaluations. For the tubes which remain inservice, the percent through wall values assigned during the re-evaluation process did not exceed 46%. Inherent in the plugging criteria (40% T.W.) is a tolerance ( 10% based on industry standards) for ECT accuracy. None of the indications remaining in service exceed this tolerance (50% T.W.). The statistical evaluations performed herein are considered to core accurately reflect the changes in the ECT signals and supercede previously reported values.

The statistical evaluation of the data was performed using tne complete data set of 39 points and a sucset of 16 points. The subset of 16 points included indications which had signal amplitudes of .6 volts or greater in both 1982 and 1984 This subset represents a 2:1 neminal signal to noise ratio for the indications. The results of these evaluations are as follows.

e

TOR 652 Rev. 2 Page 56 of 80 Statistical Eva!vation of OTSG "A" Growth Program Data Set: All indications 1 20% T.W. (I.O.) which were confirmed by 8x1. Includes only tubes 1 20% T.W. In both 1982 and 1984.

Indications 1982 1984 1982-1984 In Sample Stat. V 1- V at av 39 i 55.3 .6 48.4 1.6 -6.9 +1.0 0 18.9 4 17.4 1.2 10.7 1.0 Data Set: All indications 1 20% T.W. (I.O.) whten were confirmed by 8 x 1. Includes only tubes 1 20% and 1 6V in 82 and 84 Indications 1982 1984 1982-1984 In Sample Stat. I V  % V a% av 16 i 50.3 .9 46.0 2.1 4.3 +1.2 0 18.9 .5 19.5 1.8 7.6 1.3 I - Mean Value 0 - 1 Standard Deviation (Sample)

TOR 652 Ree. 2 Page 57 of 80 The statistical evaluation of this population showed a trend of increased signal voltage and a decrease in the reported percent through wall from 1982 to 1984. The mean decrease in reported percent through wall for the initial data set (39 Pts) was -6.9%

^

while the mean decrease for the second data set (16 Pts) was

-4.3%. The evaluations of the signal amplitudes also showed a consistent trend for both data sets with the initial data set

i. rowing a mean increase in voltage.from .6 volts to 1.6 volts for a mean increase of 167%. The same trend was observed in the second data set as the mean voltage increased from .9 volts to 2.1 volts for a mean increase cf 144% from 1982 to 1984.

Although these data sets showed similar trends in the changes to the ECT signals. the difference in the magnituce of the phase shift (-6.9% versus -4.3%) indicates the noise associated with the 1922 data may be a factor.

OTSG A&B Degraded Tuces (ISI Tuces)

The evaluation of the 100 tube growth program reeresented indications which were below the threshold of detectability in 1982 and became detectable in 1984. By contrast the OTSG A and B Degraded Tubes (ISI Tubes) provide a population of tubes whic1 were detectable in both 1982 and 1984 These populations represent better signal to noise ratio indications in 1982 and 1983 and are typical of the indications to remain inservice as degraded tuces.

TDR 652 Rev. 2 Page 58 of 80 The total population of ISI tubes with inner diameter indications was 15 tubes in OTSG A and 14 tubes in OTSG 8.

(Indications at support plates which are considered areas of reduced accuracy are excluded from this evaluation.)

(Reference 1)

The data sets were statistically evaluated, by OTSG, as a total population for 1982, 1983 and 1984 and as a subset of indica-tions for OTSG A. For the statistical evaluation of the total population the indications identified as 20% T.W. or less were all treated as 20% T.W. For the evaluation of the OTSG A subset, all indications less than 20% T.W. In 1982. 1983 or 1984 were excluded. The results of these evaluations are as shown on Table 6.

The statistical evaluation of these copulations shcws sig-nificant differences between OTSG A & B. Because of tnese differences the data sets will be discussed se;arately by OTSG.

The statistical evaluation of the OTSG A 2 20% subset from 1982 to 1983 showed a mean increase in the signal amplitude of .5 volts (83%) witn a mean decrease in the reported percent thrcu;n wall of -16.6%. From 1983 to 1984 the mean voltage increasec oy

.9 volts (82%) however, the percent through wall remained more constant with a 2.9% increase. This same trend was also observed in the data set containing all inoications. n e e 4

TDR 652 Rev. 2 Page 59 cf 80 By contrast the evaluation of the OTSG B data set showed no significant changes from either 1982 to 1983 or from 1983 to 1984. In OTSG 8 the limited number of data points (2) with

> 20% T.N. evaluations in 1982, 1983 and 1984 prevented using this criteria for subset. The evaluations were therefore performed using the complete data set in which the mean percent through wall for 1982 was 22.8% while 1983 was 22.0% and 1984 was 22.0%. The signal amplitudes for the examinations also remained constant with a mean voltage of 1.6 volts in both 1982 and 1983 and 1.5 volts in 1984 GPUN further evaluated the ISI data sets from OTSGS A & B to determine,the cause of the significant differences in the statistical results. This evaluation included a subjective review of the signals by a t.evel III data analyst and determined the OTSG B indications may not be indict.tions of IGA or IGSAC but may be caused by other surface ancmalies, i

i The review of the above data sets would indicate the change in the phase angles of the ECT signals has occurred at various times in the OTSGs and is not associated with a specific thermal or mechanical cycle. The changes identified in the OTSG A ISI tubes from 1982 to 1983 were similar to those identified in the OTSG A Growth Program from 1983 to 1984 L

TCR 652 Rev. 2 Page 63 of 80 Tbe data from the OTSG A Growth Prcgram was evaluated using stricter controls than the procuction data sets and therefore represents the best available data for additional analysis.

4) Characterize the Lo:ations in the OTSGs where Changes in the ECT l

Signals Occurrec The previously descriced data sets were reviewed to characteri:e the axial anc radial locations of the OTSGs in whien changes in the ECT signals occurred. The available data indicates tne changes in the signals occurred at all locations wnere inner clameter 'ncications were present. This includes auial loca-tions from tne 5tn T.S.P. to tne k.inetically espanced area. The radial locatiens of the indications was limited to tne outer cericnery of the OTSG, in this cerictery all locations accea ec

~

to be affected ecually.

l

5) Determine the E'fect of the Ceservec Changes in tre ECT Sigrals i

en F"ture Evaminations The changes identified in the snace anc cnase angles of tne ECT signals have been identified in cata from examinations-ce-formed at various times since the 1982 baseline. The change in the ECT signals can first ce icentifiec .nen ccmearirg the 1982 casei' e cata to the 1983 cost repair ECT. The enanges observec cur + ;

this time certoc are very similar to the changes ceserved tetween :ne 1982 anc tne 1984 cata. '

w w- , - + - - ~ - , = _ ,_

TOR 652 Rev. 2 Page 61 of 80 During the 1982 examinations the strict plugging criteria applied to the OTSGs required most of the tubes with indications to be removed from service. The only available data base of indications detected during 2 or more production examinations is therefore the comparison of 1983 and 1984 Degraded Tubes (ISI tubes). This data set includes 7 indications'in OTSG A and 2 indications in OTSG B which were greater than or equal to 20%

T.d. and can De used for analysis. The remainder of the data sets discussed in this section therefore represent the comparison of indications which were below the threshold of detection on the first esam- Ination and have increased in amplitude to cecome detectacle during the second examination.

The comparison of these two types of data (previously detected and not previously detected) snows significant differences in

~

the repeatability of the enamination results. A review of the statistical data in Table 6 snc s that when an indication is first detectable during production evaluations and then compared to the previous examinations, a definite shift in the phase angles o' the indications can be observed. This shift occurs as the signal amplitude and the signal to noise ratio change to make the indicati0n detectacle. In the OTSG A Growth Pr: gram, which represents this type of data, the mean change in sign 11 amplitudes was +1.0 volts from 1982 to 1984 while tne reported percent througn wall decreased cy a mean of -6.9%.

e e .

VDR 652 Ree. 2 Page 62 of 80 By contrast, where indications were of sufficient amplitude to be detected during the 1983 production examinations, phase shifts of this magnitude have not been observed in the 1984 data. The comparison of. the 1983 to 1984 data for this population of tubes (OTSG A Degraded Tube) shows a mean increase in the amolitude of the indications of .9 volts while the mean crange in percent through wall was +2.9%.

Based on this ECT data the phase angles of indications which have become detectable in 1984 and have experienced the phase shift since 1982'would be expected to stabilize during future examinations. For indications which increase in amplitude and are first detected during future outages, phase shifts similar to those observed from 1982 to 1994 would be expected.

The results of tne metallurgical correlations show the low amplitude indications of less than I volt are not being accurately evaluated and result in an overly conservative disposition of the tubes. To minimize the impact of the tracturacles ass 0 cited with these small amplitude signals, GPUN can implement guidelines to provide a voltage threshold for evaluating indications. The evaluation of the OTSG A Growth Program and tne Degraded Tubes (ISI Tubes) indicate a 1 volt threshold for evaluating indications would improve accuracy -

determining the percent through wall penetration of discontinuities. Tubes with indications below this threshold can be furtner evaluated using additional data such as 3 = 1 acsolute to cetermine if the tube should ce removed from se stce or mcnitored during future examinattens.

s e 4

• 4 TADtt 6 SupetAav 8t SIAll5IICAL tvattmTION Of 1982, 1981 AND 1984 (CI DAIA 1983 1984 82-83 83-84 87-84 1982 1 V 1 V  % V k k k OW k k s Pts. Stat.

1994. Growth -

54.3 .9 46.0 2.1 -4.3 1.2 All Inds. }292 16 x F.6 1.3 8: 18.9 .5 19.5 3.8 2 6V in 1982 Subset: _

48.4 1.6 -6.9 1.0 sample - All 39 I: 55.3 .6 10.2 1.0 8: 18.9 4 17.4 l.2 Inds. 220%

Ol5G.A.151 _

18.8 .F (23 25.8 1.2 123 27.3 1.F -13.0 +.5 +1.5 +.5 -11.5 1.8 All in h. Varies X = (29 .5 .5 .F er vr. 8 Pts) 16.5 .6 Pts) 7.3 .F Pts! 9.3 .8 Subset: 35.6 2.9 -16.6 +.5 +2.9 .9 -11.7 1.3 Inds. F/9% _Mz 49.2 .6 32.7 8.3 F

7.7 .6 10.7 .7 18.5 .4 8.5 .6 29.6 .6 8 16.3 .5 Ol%_S .151 -

3.0 22.0 3.1 .8 e.) 0 .8 +.3 .8 All lads. Varies X (24 22.8 2.8 (25 22.0 (25 F.4 1.6 Pts) 6.4 1.6 Pts) 6.5 1.5 .8 .F l.1 Sy Yr. 8: Pts) 4 Subset: 2.6 .5 e.5 +.8 0 +.8 ind. 2281 2 _E: 43.0 1.8 42.5 3.8 43.0 0 8 9.9 0 F.8 .F F.I 2.8 17.1 .F I4.8 f.3 2.8 2.1 I = plean Valve , ,o y g se < :o 8 = I 5tandard Deviatlea (Samplel e &

LJ PJ O

M On O

tCR 552 Rev. 2 Page 64 of 80 VII . GROWTH PROGRAM GPUN initiated a growth program curing the examinations in Novemcer 1984 7

to determine if a growth mechanism was active curing the current f

(July-Nov 1984) period of extenced dry layup of the TMI-1 OTSGs. This sample included a occulatto.1 of 100 tubes in 'A' and 50 tubes in 'B'.

The~ tubes for both generators were selected from nign cefect areas of the generators and were examined full length using the GPUN cual examinaticn method.

l OTSG A GROWTH PROGRAM The growtn cr: gram in tne 'A' CtSG consistec of esamining a copulati:n cf 100 tuces 3 times at accreatmately 2 eet intervals. Initially. tnese tuces were esaminec as cart of tse crecuctten eddy current program in Mid-Novercer 1984. The tubes were sucsecuently esamined a seconc time 'n B

late Novemcer 1984 and a thtre time in Mid-Cecemcer 1984 Results of the 3 esaminattens of eacn tuce ere then ccmcare: for tnanges in tne numcer I of inc1catt0ns anc fer cnanges in signal resc0nse voltage or cer:ent tnrougn wall ceterminations.

The 100 tuces in the 'A' Grcwtn program incluced 55 tuces witn c nfirmec incications anc 45 witn no relevant indications. Tne :cmcarisons of tne receat evaminations .ere ;erf:rmec cy evatuating tne stgral amolituces

(

and cercent tnrougn wall ceterminations. These evaluaticns revealec 4!-

sentia11y no enange in tne voltage or cercent tnrougn all cetermina-i tions. These results indicate tnat tnere was no :entinued cegracati n 0 curing the three esaminations fr0m Nove90er !O CeCemce*, ig84 1

l 1

t e4 .

. , . _ _ _ . . _ _ _ _ - _ , . _ . _ _ _ _ _ . . _ _ , _ . . . . . . .,,._,.,..,-___._.-__.,_-.___m. _ _ . . _ . _ _ . . - , _ _ . , . . . - _ _ _ _ _ ~

70R 652 Rev. 3 Page 65 of 80 OTSG B GROWTH PROGRAM The Growth Program in 'B' consisted of a Mid-Novemoer 1984 esaminatten cf 50 tubes which were prevleusly examined in July 1984. These 50 tuces were selected from the high defect area for full length examination in July 1984 during a limited sccoe examination performed when crimary to l

secondary leakage was detected.

The July anc Novem0er 1984 Eddy Current results were then ecmcarea anc no previously undetectec indications were found to entst in the Novemcer 1984 res'ults. There was no evidence cf continueo degracation in these tuces cetneen July anc Novemcer 1984.

CROWTH PROGRAM CCNCLUSIONS Tne Growth Drogram evaivations tecicate - ere .as ,o significant enarge in tne concition of tne tu:es from July to Novemcer 1984 in tne 'B' OTSG or frcm Mid-N0vem er t Mtc. ecemcer '9 1984 'Or t9e 'A' OTSG. Inis tr-formation :ces not indicate any correta: ten met een entences :ry lay-u:

and identification cf previously undetectec incications.

4 l

70R 652 l Rev. 2 Page 66 of 80 l

l VIII . CONCLUSICNS Based on the characterlZation of the 1984 Indications, a review of the 1982, 1983 and the growth program data. GPUN was able to draw the follcw-ing conclusions for tne 1984 examination results.

1. The characterizatten cf the 1984 Indications by axial and radial 10-cations, and their correlation to the incteations recortec in tre 1982 baseline suggest that the 1984 indications are an adattienal sucset of tne 1982 incications.

2. the re-evaluation of crevicus cata suggests that the indica icns icentifiec in 1984 ere alreacy cresent curing the 1982 esaminatten cut nere itnin t9e cac(grounc noise.

~ne kinet'c e<cantien recair are not functional testing may nave in-creasec tne amclituce Of tnese crevicusly e<tsting incications anc mate trem cetectacle curing creduction evaminations. tnere was no trene of througn wall grcwth assectatec witn this amolituce increase.

3. Based en the evaluation Of tne Growth Program, tnere is no evidence of centinuing tuce cegracation since the OT5Gs were claces in :ry layuo in July 1984.

TOR 652 Rev.2 Page 67 of 80

4. The characterizatien.cf the 1984 indications shows that approximately 90% of the ' indications are 20-60 percent through wall and 1 coll.

These indications are at er near the threshold of detection for the previously establishec sensitivity curve.

5. Accroximately 10% cf the Indications are higher percent through wall (260%) with a circumferential extent of 1 or 2 coils. There is a total of three 3- coli circumferential extent indications. All of these indications are between the threshold for detection and the most conservative curse for critical crack size. (Main Steam Line Break).

4 m

TOR 652 Rev. 3 Page 68 of SO I). REFERENCES

1. GPUN TOR 423 Rev. 1 R. Barley, J. Jantszewski, G. Rhedrick,

'M. Torborg, "Three Mlle Island - Unit 1 OTSG Tubing Eddy Current Program Qualification," 3/15/84 ,

2. GPUN TDR 442 Rev. O G Rhedrick, " Eddy Current Examination Results of Three Mlle Island Unit 1 OTSG," 8/29/83.

3. GPUN TDR 642 Rev. O M. Torborg, G. Rhedrick, "Cualificat'lon of Conversion Curve for Inner Diameter Olscentinuities," 1/29/85.

4. GPUN TDR 401, Rev. O, G. Rhedrick, " Report on Eddy Currect Indications Found Subsecuent to Kinetic Expansion of TMI-1 Steam Generator Tubes," April 1983.

5. GPUN Topical Report 008. Rev. 3. T.H. Moran, " Assessment of TMI-1 Plant Safety for Return to Service After Steam Generator Repatr",

August 19, 1983.

6. Sagar, Amrit, "Multifrequency Eddy Current Method and the Separation of Test System Variables," Eddy Current Characterization of Materials and Structures, ASTM STP 722 George Birnbaum and George Free Eds..

American Society for Testing and Materials, 1981, pp. 269-297.

6

TDR 652 Rev. 2 Page 69 of 80 APPENDIX A ABSTRACT CN THE DEVELOPMENT OF THE DUAL INSPECTICN TECHNICUE AND PERCENT THROUGH WALL CALIBRATICN CURVE P

e Q

um ::.

Rev. 2 Page 70 of 80 Prior to the 1982 OTSG tueing inspection, GPU Nuclear had always performed its OTSG tubing examinations with the standard differential eddy current technicue for detecting indications that normally originated on the outer diameter of the tube wall. The eddy current inspection system was operated at normal gain and the probes used for these inspections measured 0.510" diameter. These parameters traditicnally were censicered acceDtable for inscetting the OTSG tubing which nas a nominal inner diameter of 0.557.

After 131 tubes leaked uocn start-uc and test in Novemcer 1981, eddy current examinatiens were immediately performed with the standard cifferential (5.D.)

.510" technique and scme of tne teaming incteations were not detectec, a sue-secuent examinaticn was performed with a muitt-coil absolute eddy current tecnnicue and indicattens were identified in the roll transition of tne leak-ing tubes. In additten, Other indications wnich nad not been detectec Oy the previous 5.0. 510* examination were identified. The cefects discoverec in

ne OTSG tubing ere me:allurgically evaluated as innte clameter initiatec.

very tignt. and crientated arounc tre circumference of :ne tuces. It was tre, reccgnizec that tne 5.0. 510" tecnnique was not sensitive enougn for cetect-ing all cf :1e new inner diameter discontinuities.

GPU Nuclear modified and improvec tne sensitivity of its standard differential tecnnicue by increasing tne probe's clameter to 0.540", and increasing tne operating gain. ,

This modificatien tecrovec :ne stancare cifferential's se it-tivity for cetection of crecominately circumferential, :.3. Initiatec In:ica-tions by approximately 175% over tne older tecnnicue. The cisaavantage of using tne high gain anc imcrovec fill factor is tnat the standard cifferential examigattenbecomeseverlysensitisetosurfaceancmalies.

I

'l l

l

TDR 652 Rev.2 Page 71 of 80 The absolute technicue usec to confirm the standard differential inspection results was also modified and improvec. The develcoment of the SX1 Aesolute probe with eight pancate shape co115 placed arounc the probe body provided 360 degrees coverage on the circumference of the tube wall. This design cermitted a single cass of the orcee in the tuce during an examination as compared to multiple passes anen fewer coils are used. The eight :olls also providec a fair estimate of the arc length of an Indication because the rescense signal from each cott represents its prcximity to the indicaticn.

Usfng the Imorovec S.D. 540" high gain and absolute 8:1 tecnnicues. GPU Nuclear develcced a cual metnce eccy current insoection tecnnicue. Tne ini-tial examination .as cerformec ey the 5.0. 540" nigh gain technicue. ;f the examinatten my 5.0. 540" snewec no evidence of a defect, its esaminatten ce-

ame :ne final i nscec: ten of re: crc.

If the 5.0. 5 0" enaminatien re:cr ec an 'ncicati:n. i se::rc e<amina:':n .as

erformec using :ne aosolute 8xl tecnnicue. The acsolate 8 1 e=amina:1cn ce-terminec if the reecrtec indicatien was relevan: :r non-relevant. F:- :rcse indications cetermined to ce relevant, the absolute 841 result .as usec to estimate the are lengtn and also confirm : e origin (I.D.-/0.0.) anc antal ic-cation of the indication.

During a stancard differen lal eccy current examination :ne cer:ent inr:u;-

dall penetration of a flaw is cetermined by measuring the rescense signal's onase angle and converting that measurement to tne aer:ent tnrougn wall. A l

y - .--- - - - -

TDI652 Rev. a Page 72 of 80 calibration for this conversion is established by setting uc the stancard dif-forential eculpment and testing a known stancara. The onase angle fer the eddy current response signal is acjusted to a scecified measurement =hicn gen-erally is 40 degrees for a 100 cercent through wall by .052" diameter nole standard. This calibration is cone in accordance with the ASME Secticn XI code. The traditional conversicn curve for phase angle measurement to inner diameter initiated cercent through wall is cetermined by the values that are extracolated frem the 40 degree phase angle-100 percent througn wall (given cy the .052" diameter hole stancarc) to zero cegree pnase angle--zero cercent through wall.

The estimated cercent :nrough wall :nat is extracolated fecm :ne conversten curve tencs to cvercall One actual cercent through wall of a small volume flaw. This over calling is censicerec conservative eccy current evaluation and was instituted in tne 1982 cual inspection tecnnicue.

nac always ceen ac(newlecgec tha: :nis tract tenal curse overcallec small volume inner ciameter discentinuities. The presence of smaller inner clameter initiated cracks in tne THI-1 CTSG's nac recuirec GPUN to cevelec a mere ac-curate means of assigning tne percent through wall cene: ration. Therefore, the traditional inner diameter conversion curve was ennantec by using succle-mental data frcm ECM with varicus (newn cecths. ints ca:a as asec : ceve'cc

~

a conversion curve unien more accurately represented small volume, inre c -

ameter initiated cl5 continuities anc this accuracy was serified through metal-lurgical correlations using actual intergranular s:*ess assistec crack samcles.

70R 652 Rev. 2 Page 73 of 80 APPENDIX S 1952. 1984 EC0Y CURRENT STAT!5 TICS O

1

TOR 652 Rev. 2 Page 14 of 80 TMI STEAM GENERATOR A A(IAL LOCATIONS OF CONFIRMED INDICATIONS 0-1001 THROUGH WALL PERCENT VS SPAN 1982 VS 1984 1982 . 1984

. Support Fra:Iuency  % Frequency 1 LP-1 6 .19 1 .090 1-2 23 .717 2 .181 2-3 8 .249 8 .726 34 8 .249 19 1.725 4-5 17 .53 .7 .635 5 58 1.808 19 1.725 6-7 34 1.714 26 2.361 7-8 55 1.060 5 .458 8-9 34 1.714 12 . 1.'1 9-10 11 .343 4 .367 10-11 24 .748 8 .726 11-12 54 1.683 13 1.181 12 13 53 1.964 54 4.920 13-14 146 4.551 57 5.177 14-15 97 3 024 78 7.084 15-US 530 16.521 217 19.70 US-UP 2040 63.591 571 51.861 TOTAL 3208 1101 Note: (1) 1984 data incluces the lengtn of tubing celow tre ninetically e.-

Danced 2006. (ADDroximately US.7 and below).

(2) 1982 cata incluces the length of tubing from US.15 and below.

(3) Data taten frcm 1982 anc 1984 cata bases as of 2/15/85.

CR 652 Rev. 2 page 75 of 80 1 TMI STEAM GENERATOR S AXIAL LOCATION OF CONFIRMED INDICATIONS 0-100% THROUGH WALL PERCENT VS SPAN 1982 VS 1984 1982 1984 Support Frequency  : Frequency  %

LS 6 468 6 3.109 1.036 1-2 3 .234 2 2-3 4 .312 1 .518 l 3-4 20 1.561 3 1.554 -

4-5 9 .7C3 6 3.109 5-6 9 .703 4 2.072 6-7 24 1.874 8 4.145 7-8 12 937 7 3.627 8-9 19 1.483 4 2.072  !

9-10 20 1.561 9 4.663 i

10 11 15 1.171 2 1.036 11 12 34 2.654 12 6.218 12-13 34 2.654 12 6.218 13-14 106 8.275 7 3.627 14-15 81 6.323 7 3.627 15-US 98 7.650 25 12.953 US 787 61.144 78 .40.414 ,

TOTAL 1281 193 e

Note: (1) 1984 data in:1ades the length Cf tuting Celow tPe Ainett: ally e'-

. candec :ene. (acercutmately US.7 anc celow).

(2) 1982 data incluces the length of tubing fecm US.15 and tel ..

(3) Data taken from 1982 and 1984 data cases as of 2/15/85

i

TCR 652 Rev. 2 Page 76 of 80 THI STEAM GENERATOR A VOLTAGE DISTRIBUTION FOR CCNFIRMEO INDICATIONS 0-1007. THROUGH WALL PERCENT VS VOLTS 1982 VS 198a 1982 1984 Volts Percent Volts Percent 0 31.807 0 34.968 1 44.653 1 35.15 2 16.595 2 23.615 3 4.702 3 4.814 4 1.537 4 .636 5 .338 5 .363 6 '84 6 .091 7 .061 7 182 8 .092 8 .182 9 0 9 0 10 .331 10 0 Note: (1) 1954 data includes the lengtn of tubin9 Delow tne kinetically ei-panded zone. (Aporoximately US.7 and melow).

(2) 1982 data inclu:es tre lengt'i of tubin9 ' rem U515 ano celcw.

(3) Data taken frem 1982 and 1984 data cases as of 2/15/85.

.s e32 I Rev. 2 Page 77 of 80 l TMI STEAM GENERATOR S VOLTAGE DISTRIBUTION FOR CONFIRMED INDICATIONS 0-100% THROUGH WALL PERCENT VS VOLTS 1982 VS 1984 1982 1984 Volts Percent Volts Percent 1 0 23.878 0 26.425 1 28.897 1 20.207 2 25.019 2 27.979 3 9.810 3 11.917 4 6.844 4 5.699 5 1.901 5 3.109 6 1.597 6 1.036 7 508 7 1.554 8 1.217 8 1.554 9 .

0 9 0 10 376 10 .518 11 . 52 11 3 Note: (1) 1984 data includes the len9th of tubing DelCw the kinetically es-panded zone. (Approximately US.7 and celev).

(2) 1982 data includes the lengtn of tuotng from US.15 and celca.

(3) Data taken from 1982 ano 1984 data cases as of 2/15/85.

. 704 i32 Rev. 2 Page 78 of 80 TMI STEAM GENERATOR A CONFIRMED PERCENT THROUGH WALL DISTRIBUTION FOR CONFIRMED IN0! CATIONS 0-100% THROUGH WALL PERCENT VS PERCENT THROUGH WALL 1982 VS 1984 1982 1984

% Thru-Wall  %  % Thru-Wall 1 0-19 .281 0-19 0 20-29 1.434 20-29 39.055 30-39 1.309 30-39 21.163 40 49 6.827 40 49 17.802 50-59 13.585 50-59 7.629 60-69 9.757 60-69 5.904 70-79 7.512 -

70-79 2.186 80-89 8.635 30-89 1.907 90-100 50.561 90-100 3.724 Note: (1) 1984 data includes the length cf tubing celcw the Kineticaily ev-cancee zone. (Accronimately US.7 anc celow).

(2) 1982 cata incluces the lengtn Of tucing from 05,15 and celcw.

(3) Data taken from 1982 anc 1984 cata bases as of 2/15/85.

..s ..-

Rev. 2

- Page 79 of 80 TMI STE.aM GENERATOR S CONFIRMED PERCENT THROUGH WALL OISTRIBUTION FOR CONFIRMED INDICATIONS 0-100% THROUGH WALL PERCENT VS PERCENT THROUGH WALL 1982 V! 1984 1982 1984

% Thru-Wall  %  % Thru-Wall  %

0-19 11.788 0-19 0 20-29 11.866 20-29 63.212 30-39 16.472 30-39 13.99 40 49 10.617 40 49 11.917 50-59 13.349 50-59 4.663 60-69 8.041 60-69 3.109 70-79 6.401 70-79 2.073 ,

80-89 5.699 80-89 0 90 100 15.769 90-100 1.036 Note: (1) 1984 data includes the lengtn of tubing below tne kinetically en-canceo zone. (Accro=Imately US.7 and celow).

(2) 1982 cata includes the length of tubing from US+15 and teicw.

(3) Data taken from 1982 and 1984 data bases as of 2/15/85.

m

TCR 652 Ree. 3 Page 80 of 80 CIRCUMFERENTIAL EXTENT FOR CONFIRMED INDICATIONS GENERATOR A 1982 1984 Coils Frequency 1 Coils Frequency  %

0 270 (N/A) 0 321 (N/A) 1 655 66.973 1 1111 89.959 2 301 30.777 2 122 9.878 3 18 1.840 3 2 0.162 4 1 0.102 4 0 0 5 1 0.102 5 0 0 6 0 0 6 0 0 7 1 0.102' 7 0 0 8 1 0.102 8 0 0 TOTAL 978 1235

~

GENERATOR B 1982 1984 Coils Frecuency . Coils Frequency  ;

0 361 (N/A) 0 321 (N/A) 1 147 50.000 1 102 79.069 2 102 34.694 2 26 20.155 3 26 8.843 3 1 .775 4 7 2.351 4 0 0 5 4 1.360 5 0 0 6 0 0 7 0 0 7 0 0 8 0 0 8 8 2.721 9 0 0 TOTAL 294 129 Note: (1) 1984 data includes the length of tubing celow the Kinetically en-panded zone. (Approximately US+7 and belcw).

(2) 1982 data includes the length of tubing from US.15 and celcw.

(3) Data taken from 1982 and 1984 data bases as of 2/15/85.

e

i 1

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