ML20087C947

Nonproprietary Responses to NRC Questions on SG Operating Cycle Evaluation for North Anna,Unit 1

ML20087C947
Person / Time
Site:	North Anna
Issue date:	12/31/1991
From:	Wootten M WESTINGHOUSE ELECTRIC COMPANY, DIV OF CBS CORP.
To:
Shared Package
ML20087C941	List: ML20087C936 ML20087C943 ML20087C947
References
WCAP-13121, NUDOCS 9201150070
Download: ML20087C947 (193)

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WESTNGHOUSE CLASS 3 WCAP 13121 f

RESPONSES TO NRC QUESTIONS ON THE STEAM GENERATOR OPERATING CYCLE EVALUATION FOR NORTH ANNA UNIT 1 December 1991 i

%k Approved by:

MQ.Wootten,Mana r Steahqenerator Tech ology & Engineering

.?

C 1991 Westinghouse Electric Corporation All Rights Reserved

TABLE OF CONTENTS FECTr>4 IIILE PKiE

1.0 INTRODUCTION

11 2.0 RESPONSESTOGENERALCOfAAhTS 21 3.0 RESPONSES TO SECTON 2.0 QUESTOl49 31 4.0 RESPONSESTOSECTION 3.0 OUESTONS 41 5.0 RESPONSESTO SECTION4.0QUESTONS 51 6.0 RESPONSESTO SECTION S.O OUESTONS 61 7.0 RESPONSESTO SECTION 6.0OUESTONS 71 8.0 RESPONSESTOSECTION 7.0QUESTONS 81 9.0 RESPONSESTOSECTION 8.0QUESTONS 91 10.0 RESPONSESTO SECTION 9.0 QUESTONS 10-1 11,0 REFERENCES 11 1 APPENDIX A REQUEST FOR ADDITIONALINFORMATON A1 APPENDIX B EDDY CURRENT ANALYSIS GUIDEUNES B1 i

l 1.0 NmODUCTION This report provides responses to the NRC Request for Additional Information (Reference

1) relative to Westinghouse report NSD TAP 1093/SG 9107 043 (Reference 2).

NSD TAP 1093 provided analysis and discussion of the acceptable operating duration for North Anna Unit 1. and was subsequently also issued as WCAP.13034 (Reference 3) in a proprietary version, and as WCAP 13035 in a non-proprietary _ version.

The responses contained in this report are organized sim!!arly to the Reference i quest;ons. Each quettion was numbered (Questions #1 through #66) and repeated in the text, and each is followed by a response. Section 2.0 addresses the

• General Comments

• and Sections 3.0 through 10.0 address the questions on specirc sections of WCAP 13034. The original questions have also been provided in Appendix A, while the 1990/91 eddy current inspection Guidelines have been provided in Appendix B. Section 11.0 provides a list of references.

l l

0 F

9 11

2.0 RESPONSESTOGENERALCOA.MS l

This section provides responses to the general comments of Reference 1.

\\

Ouest6n #1 (GeneralComments. Ref. L a 1)

The argument forleak-before-break (LBB)is suspect for Vorth Anna. The tube ptIIed In t991 had a large angle of circumferentialcraaking yet leaked at a very bw rate compamd to the rate predicted by Westinghouse (less than 16 gaVday versus 460 gaVday). Thus the concept of defense in depth as providedby LBB cannot be made for circumferentialcracks.

The concept of defense in depth as applied for the North Anna 1 operating cycle evaluation includes leak-before break (LBB) as only one element of the hierarchy for defense in depth. The overall defense in depth includes:

Extensive inspection and tube plugging at the last outage to establish tube integrity.

For circumferential cracking, this inspection includer' the first 100% RPC inspection of the hot leg WEXTEX transition and 100% 8x1 Inspection at least to the 4th TSP in all steam generators, in SG A and SG C 20%. and in SG-B 100% were inspected to the 7th hot leg TSP. For axial cracks, a 100%, full length bobbin coli inspection was performed.

The bounding tube integrity analyses of WCAP 13034 were performed to demonstrate that indications potentia!!y left in service can operate a full 18 month operating cycle while meeting the criteria of RG 1.121.

A conservatively low operating leak limit of 50 opd has been ertablished. Operat.ng led. age for the last 4 years, with less extensive outage inspections, has been less than 15 gpd.

Aedundant and state-of the-art N 16 leak tinic leakage monitoring capability in the control room is available. This provides real time data to plant operators.

21

Conservative action levels to respond to operating leakage have been established.

These action levels are basad on leakage trending, and response to sudden leakage increases and rapidty increasing leak rates with controlled shutdown in r. period of between 30 minutes and 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />, depending on tho rate of leakage increase.

l The leak before break (LBB) criterla of RG 1.121 have been applied to establish a high probabl!!ty of leak before break. Leak rate limits have been conservatively set to 50 opd based on segmented crack models rather than uniform throughwall cracks to further enhance the likelihood of LBB, However,it is recognized that LBB cannot be abse!utely assured. The WCAP 13034 analyses were performed to assure adequate margins such that high rollance on LBB is not necessary. The concept of leak before break has been applied for circumferential cracks in the S&me context that it can be made for any morphology of stress corrosion cracking especially those kcated near structures such as tube support plates and tubesheets. Whether axial or circumferentialin orientation, several factors influence the leak rate, such as constraint of the adjacent structure, the presence of unbroken ligaments, be!ng located within sludge, and/or crud bulldup at the f

crack location (Ref. EPRI NP 6864 L. Dec.1990), in addition,it is not unusual for i

short length SCC to result in little or no leakage during normal operation even when i

through wall. These results may in fact be beneficialin that the short length cracks, either single or in segmented cracks, do not challenge structuralintegrity raargins. hi j

our judgement, the principal causes of low leakage in service are associated with I

constraint of adjacont support structures or with ligaments, in this case the reason for low leakage also contributes to structural burst capability, and as has been shown with the segmented crack model for circurt.forential cracking, the strength - )ntribution more than compensates for the reduced leakage from a leak before break point of view.

The 1991 pulled tube, R11014, had negligible leakage although a throughwall crack of about 70* and riearly throughwall over 90' was present. The nominal leakage for a fatigue crack of this size woulcl be about [

)b c lthough the totalleakage in SG B a

the prior operating cycle was about 3 4 opd. As noted in the response to Question #54, the morphology of the ODSCC crack face for this indication showed a highly irregular or interlocking crack face. While low leakage Or this morphology can be expected for small crack angles, the crack opening area lncreases with crack length and would be expected to leak at > 50 gpd before reaching a crack angle of [

}b4 for a 3aP

.O.

N 22 m.us._._a am.-

l t

burst capability. In response to Questien #ES, it is shown that skpificant leakage occurrences at North Anna 1 in 1984 and 1985 are reasonably predicted by the segmented leakage model for PWSCO. While the analysis results are not unique answers without known crack features, the leakage events themselves demonstrate that cracks develop In time to well beyond current leakage limits requiring the plant's shutdown, in first time RPC inspectim of WEXTEX transitions at a number of plants, RPC measured crack angles oxceeding 225' have been found with no measurable operating teakage. In these cases, ligaments, as confhmed by UT inspections (See Section 1.5.3 of WCAP 13034), minimize leakage and increase burst capability. For segmented PWSCO, cracks (at WEXTEX transitions and dented TSPs) la ge enough to challenge tube integrity during postulated accidents, a marginal condition would be signaled by the high r

pabability that loss of ligaments will resul'. In dotectable changes in leak rates. The North Anna 1 leak rate monitoring v.ould detect that loss of ligat it.t.4 and track leakage trends below the 50 gpd shutdown limit as described below.

Overall the operating leakage limit of 50 gpd would, to a high probability, be exceeded for throughwall cre41ng or as loss of ligaments progressing to the point of challenging tube burst capabiht, vtolated accident conditions. An additional 1.BB consideration is that associated with t.

ntial for crack propagation due to turbulence induced o

vibration and, at larger crack anglec, due to fluidelastic vibrstion. As noted in Section 7.6 of WCAP 13034, ligaments typical of the segmented crack model or wall thicknes:

ligart.ents on the order of 10% remaining wall would not result in crack propagation due to turbulence or fluidelastic vibration. If, however, vibration is assumed to initiato (l;mited to peripheral tube region at W IXTEX or 1st TSP), the initial vibration would begin to break ligaments and tend to flatten irregularities at the crack faces. Leak rates

]b,c t - 70* crack, for example) and be would approach that of fatigue cracks ([

a detected by the N-16 leakage monitors as step changes in leakage. (See section 7.8 of WCAP 13034 for more detailed discussion.) Significant sten changes in lekkage (on the order of 10 to 20 gpd leakage above prior levels) lead to trending of the leak rate by the plant operators. Leak rates which increase in nn exponential manner result in plant shutdown; for a 100 gpd or higher increase in the leak rate during a 30 minute period a plant trip is initiated. For slower rates of increase in leakage, depending on the leakrate, shutdown is required within two hours. Under tube vibration conditions, detectable leakage is essentially assured and plant shutdown wc91d be achieved well before a tube rupture.

2-3

Overall, LBB can be expected to a high probability for corrosion cracks approaching accident condition tube burst limits and is essentialy ausured unoer tube s Nation conditions. The North Anna 1 N 16 toakage monitoring system and implementing ac' ion steps including the censervative 50 gpd shutdown limit would lead to plant shutdowri in response to increasing leak rate trends well before tube rupture.

Duestion e2 (GenemlComments. Ref.1.. D.1)

The number of pulled tubes at North Anna l' ave been few in number. Selected tubes appear to be those with strong ETIndicalions. As such the selected tubes provide a weak basis for validating field ETreliability with destruative examinations. Destructive examination of t..c.a pulled tubes coukt greatly enhance confidence in field ET inspectbns. The sample of tubes shouldinclude locations with no ETindications, but where the potential for cracking is believed to be high.

The following pages identify tubes pulled from North Anna Unit 1 between 1985 and 1991:

I e

2-4

CONSOLIDATED TUBE PULL INFORMATION -- NORTl

..NNA UNIT 1 TUBE EXAMINATION HISTORY (EXCLUDES 1987 TUBE RUPi.TRE EXAMINATION) 1995 TUBE REMOVAI, ErroRT fMG-c)

FIELD ECT LAB ECT B C ET.EVATION OBEERVATIONM OBfERVAT10NM METAttoGRAPHY/ REM 3 41 WEXTEX NDD NDD NO ATTACK 3 41 IST TSP DISTORTED Axial Indic'n OD and ID Axial SCC DENT TSP, 9/16 inch Contained in TSP 40-100% Deep Max. depth:

0.D. 25%i I.D. 50%.

3 41 2ND TSP 94% Ind.

5 Axial Ind.

2 Axial crack networks, at 3 orient.

ID initiated Cracks 0.8 All ID in, above to 0.2 below.

Max 90% deep.

Max. depth 100%.

3 41 3RD TSP DISTORTED DENT Single axial Chemically examined, ind, at TSP edge No metallography.

ID w/ max >90%.

9 58 WEXTEX NDD NDD Minor OD attack (5-10%).

9 58 IST TSP DISTORTED IND Axial ind, w/in OD and ID attack in TSP TSP ar.d o.15 in, and up to 0.3 in above above TSP CD, 40% top of TSP..ID max, depth above TSP.

Max, depth and length:

OD: 40%

0.2.in.

ID: 85%

- 0. 6 in.

OD: 3-10% above TSP.

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iss? Tunr tvAutumTrow rsa-At 1

FIELD ECT LAB ECT g c EtrVATION OBSERVATIONS PREERVA? IONS METAtt& GRAPHY /SEM 17 31 WEXTEX 150 degree 150 degree cire.

10.7K psi burst cire, ind.

w/possible ext.

. press. w/176 degree around tube, rp to 90% thru wall penetration.

)

17 31 1ST TSP NDD

.NDD

-CD IGC from bottom edge TSP to top-edge. Cire.

i oriented, short microcracks.

I below to7 edge of TSP up to-28% in about 80' band.

ID-SCC at one zone up to 22%..

18 36-WEXTEX

-120 degree 120 degree Corrosion tested w/

circ.ind.

circ.;ind.

.5 1/hr leak, burst' at-

[

9250 pai, 128 degree

(

ID SCC, with 53-degree thru wall.-

18 36 Above TSH NDD NDD No attack

(

1991 Tunt FYAMTNATrow t.cG-ni' j

FIELD ECT

' LAB ECT I

ac rtrvAtinn nmeruvATTOMM -. OBRERVATTONS METAttOGRAPHY/SEM 11 14 WEXTEX NDD NDD IGSCC up to;21%, but avg 6-8%.

Il 14 IST TSP

- 2 coil ex1 160 and 140 deg.

IGSCC.up to 1004 Up. Edge 150 degree & ind. on' opposite tthru wall on.oppos.

I axial or cir sides of tube sides of tube.

on oppos.

360 degree macro-

-- s

[

sides of tube.

~ crack._Two deep l

regions being 124 I

and:113 degrees'long 11 14 1ST TSP Not called

• 3' circ. ind.-

IGSCC up to 98% thru ~

Low edge.

around tube with wall,.but generally l

longest of 80 deg. 40-80% thru wall.

two areas-onLoppos.

t l

sides of tube.

L l

• Indication not recorded in the field as for 8x1,.the TSP was, identified for l

PIC due to the upper TSP.

On RPC, the rules did not require adjusting the.

L l span width to analyze the~ top and. bottom edges of the plate, so the bottom signal was overwhelmed by the size of-the. top TSP edge signal.

However,' based upon review of' aimilar signals,' it was cencluf.ed that the bottom edge of the l

TSP would have -been detected with 8x1' and tonfirmed by RPC if the indication, had existed alone on the tube.

2-6 s

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A

As can be seen from the above, a series of tube removal and examination efforts have been performed at North Anna 1 over the last six years. A total of six TSP locations and five WEXTEX areas have been exainined, representing a rather extensfve tube pud data base when compared to the tube pull information from most other plants. Both NDD areas and degraded areas have been examined. Each tube removal effort has focused on

• differcnt degradation mechanism and has permitted optimum focus on both eddy current and structural integrity issues. This allowed for proper adjustments to eddy current Inspection guidelines or establishment of lower leakage limits to provide additional compliance to leak before break.

For example, intersections such as the first support plate area of R9C58 were classified as distorted indications and were plugged during the 1985 outage. The tube examination efforts provided confirmation that such plugging should be performed. Additionally, a review of the eddy current data was conducted that later led to identifcation of other indications that were potentially pluggable. The structural and eddy current significance of these indications was addressed in WCAP 11310," North Anna Unit 1 Steam Generator Tube Integrity Safety Evaluation", dated October 1986. Eddy current rules were revised for the next outage (April 1987) and tubes plugged accordingly.

Similarly, the 1987 and 1991 tube examination efforts have been used in the development of both the detection threshold and the models used in WCAP-13034 to assess the significanoe of the observed and projected degradation.

With regard to future tube removals, recent evaluations performed by Virginia Power resulted in the advancement of the planned steam generator replacement from 1995 to l

early 1993. Therefore, while a tube pull may be determined to be necessary during the upcoming outage, none is currently planned.

Question #3 (GeneralComments Ref.1.. n 1)

Projections for end-of-cycle crack angles assumes only single cracks at a given tube cross-section. The tube pulledin 1991 had two cracks that togethergave a inuch greater crack angle than shown in any of the crack size distnbutions presentedin the report. The assurnption of one crack willlead to unconservative calculations for probabilities of tube rupture.

2-7 l-

This response also addresses the following questions:

Question 7, Effect of Assuming Two cracks at TSP Versus One Question 12, Basis for MCI Below Top of Tubesheet Ouestion 20, Modeling of ODSCC and MCls Questbn 24, Measurement of Ligaments Question 36, Consideration of MCis Ouestion 42 Total Crack Angles for MCis The basis for utilizing only single circumferential indications (SCis) rather than MCis in the crack angle projections and structural analyses is addressed in WCAP 13034, Sections 4.2.3,4.5.3 and 5.0. The WCAP information is further detailed below.

Eddy Current Guideline Definition of an MCI For the RPC data analysis guidelines in place at North Anna 1, an MCI call requires that the signal ampGtude complete a full retum to the null amplitude level between identified indications. The null amplitude is the background level away from the indication. RPC amplitudes which show a drop that does not return to the null level are called SCis even though the presence of a ligament is anticipated. Test results for EDM slots separated by a ligament (Figure 4 2 of WCAP 13034) show that a 30' ligament between slots is required for the RPC amplitude to retum to the null point. Thus the ligament between MCis is expected to be a minimum of 30* and approximately the RPC measured ligaments plus 30*. RPC measured ligaments for WEXTEX indications ranged from 7' to 96*

(Figure 4-1 of WCAP 13034) such that the minimum ligament between circumferential cracks is about 37*. The minimum sum of measured ligaments in WEXTEX transitions was 83* which would be expected to be 110*-140* after corrections for RPC resolution. As discussed later, these ligaments are sufficient to consider the MCis as structurally separated SCis for tube burst and vibration considerations.

The presence of large ligaments in an RPC SCI call (without retum to null amplitude) has also been confirmed by UT measurements. Figures 4 36 to 4-38 of WCAP-13034 show RPC and UT results for an RPC SCI call of 322* crack angle. The RPC amplitude shows a dip that does not retum to the null point. The UT results gated to emphasize OD 28 l

{

l

crack discrimination show a large 20-30' ligament between the two significant cracks and overall smaller crack angle. The UT results also demonstrate the strongly segmented crack morphology found in pulled tubes and used to formulate the segmented crack model for PWSCC.

In addition. the WEXTEX MCis are often separated by axial ligaments (See Table 4-2 of WCAP 13034). These ligaments range from 10 to 50 mil axial separation behveen cracks, The three largest single crack angles (only indications >190') of the MCis are associat ' Vith axially and azimutha!!y separated cracks.

Overall, the above results show that RPC MCI ca!!s can be evaluated as cracks separated by >3/ ligaments and that SCI calls showing amplitude dips above tha null point are likely to also have structurally significant ligaments. Thus MCl calls should be structurally evaluated as two separate circumferential cracks and not as the sum of the two crack angles.

Axial Eleva' ion of WEXTEM MCis The WEXTEX circumferential cracks tend to be located just above (0.12* average) the bottom of the WEXTEX transition (la:;t contact point unhe tubesheet). The bottom of the WEXTEX transitions are below the TTS an average distance of 0.19" (See Figure 412 of WCAP-13034). The circumferential crack elevations averago 0.07" below the TTS with only a few indications above the TTS (See Figure 412). As noted above, the largest crack angles of the MCis have axialligaments r4 well as azimuthal ligaments between cracks. Thus tube burst is prevented by the tubest"et constraint for most, but not all, of the WEXTEX circumferential cracks. Conservatively, no benefits have been taken for tubesheet constraint either in the deterministic or probabilistic analyses.

MCfs at TSPs Only 9 MCis out of a total of 110 circumferential indications were identified at TSPs,

- The largest SCI was 212* compared to the largest single crack in an MCI of 166*. The minimum RPC measured ligament size was 32* for which the actualligament would be up to about 30' larger due to probe resolution limitations. The minimum sum of measured ligaments at TSPs was 98* which would correspond to 130' to 160' after 2-5

correcting for RPC resolution. Thus the structural strength of ligaments between MCis at TSPs is even greater than for the WEXTEX region.

$ttuctural Sionificance of MCis and Uanments The MCis with significant [

]b,c ligaments between cracks behave structurally more like the largest single crack angle than the sum of the crack angles.

)

With an adequate ligament between MCis, tube burst capability is dominated by the largest single crack. Similarly, crack propagation due to tube vibration is more sensitive to the largest single angle than the sum of the crack angles. Analyses were performed to assess minimum ligaments between cracks rotative to tube burst capability and tube stiffness for tube vibration considerations.

For tube burst, two ligaments with individual minimum are segments of [

]b, care sufficient to provide burst capability of 3AP

.O. as long as the largest throughwall crack N

angle is no greater than the [

]b,c I mit for a single crack. As noted previously, the minimum sum of ligaments found in the WEXTEX region was 83' 143' and at TSPs was 98* to 158', The noted range covers as measured to up to 60* increases for RPC resolution effects. This analysis is based on the axial separation or pull mode for tensile burst which is conservative for dented tube conditions. Thus tube burst capabl!!ty is limited by the largest single circumferential crack which has been found to occur in SCis.

For tube vibration, two [

]b,c ligaments and an average crack depth -90%

throughwall in one crack (or a third ligamen9 and throughwallin the other crack of an MCI are sufficient to limit the minimum crack angle for initiating turbulence induced crack propagction to [

]b.c as found for a single crack. Two [

]b,c separate cracks in an MCI would provide 116' of totalligaments. This esse envelopes the pulLxf L

tube R11C14 MCI mnrphology which had 70'-90* throughwall in a 124' (>40% depth) crack angle argi an average depth of 90% for the second 113* (: 40% depth) crack angle.

For WEXTEX indications, one segmented crack is equivalent to the 90% average depth such that the second crack, like an SCl, would have to have a throughwall crack angle of

[ ]b.c to initiate crack propagation by turbulence. As long as ligaments in one crack keep the crack from opening under vibration conditions, the second assumed 2 10

i throughwall crack behaves like an SCl. In each case, the largest single crack angle is limiting for initiating crack propagation due to vibrat'on.

If only two ligarrionts are present between uniformly throughwall cracks, the minimum ligament size would have to be about [ )b,c to limit crack propagation by vibration to single crack limits. As noted above, the minimum sum or ligaments, as corrected for RPC resolution, found in 1991 was >140'. Uniform throughwall cracking over the remaining 220' total crack angle is extremely unlikely. As noted elsewhere in these question responses, throughwall crack angles >60% of the RPC measured angle have not been found in tube pulls for ODSCC. For WEXTEX, segmented cracks have been found in tube pulls. Thus it is considered to be unrealistic to postulate two uniformly throughwall cracks approaching tha RPC measured angles in an MCI. It is considered conservative to evaluate all circumferential Indications as SCis which increases the number and angles of the limiting large angles (fer a given numbar of indications) as compareo to including the individual, smaller angles of each crack in an MCI in the population.

The above vibration conclusions are based on [

}a,c. It is judged that the results are conservative for this application of estimating ligament she requirements.

Modelina of MCis The above assessments show that MCis have >[ jb,c ligaments between cracks and that the structural integrity of the tube la dominated by the largest single circumferential c ack. Based on these results, the crack angle projections to the EOC and the detailed structural and vibration analyses were performed for single circumferential cracks.

9 Ouestion #4 (Geners!Commen*1 Ref.1.. n 11 A 100% probability of detection (POD) has been assumedby Westinghause for deep (50% of wall) andlong (greater than 75c) circumferential cracks. Thus, it is assumed that there is zero probability of any existing thmugh-wall craci50% Depth Ouestion 31 Reliability for Detecting Cire. Cracks The EOC projections in WCAP 13034 are based upon detectabi!!ty of about 100% for throughwall crack angles of 50' for an RPC probe and 75' for an 8x1 probe. For ODSCC at TSPs, the report model assumes that depths >50% are included in the sum of threshold throughwall crack angle + growth + NDE uncertainty (See Figure 5-5 of WCAP-13034). It is important to distinguish this summation for crack angles >50%

depth from assuming depths >50% are detected with 100% probability. The detection threshold + NDE uncertainty accounts for about 60% (45% detectability,15%

uncertainty) of the projected EOC crack angle while growth (based on measured angles) accounts for only about 40% of the projected EOC crack angle (See Table 5.4). Clearly, with 60% of the projected angles accounting for NDE lim!tations, no assumption is made that all cracks >50% deep are detected with 100% probability. The conservative assumption is made that the average depth for 360* outside the RPC angles is 50% depti,.

The following acproach is used to develop the detection probabilities:

Estimate the RPC detection threshold for throughwall and depth in roll transitions from pulled tubes and laboratory corrosion specimens.

Conservatively assume same detection threshold for the generally more smooths varying diametral changes at dents than for roll transitions.

/

2-12

,.._r.w.-

---

,-N Compare 8x1 vs RPC detectabHity ba%o upon:

Probe Design Considerations North Anna 18x1 vs RPC detection experience at TSPs EOC Crack Angle SensitMty to Detectability flPC DetectaNIity for Circumferentist Cracks Ne th Anna 1, Westinghouse and EPRI collected dature avaHable to assess RPC detectability of circumferentialcracks. The North Anna 1 data are pulled tubes for WEXTEX and TSP Indications. The Westinghouse data includes pulled tube and laboratory generated corrosion specimen. The latter were prepared to evaluate detectability and destructively examined to map tha degradation Separate macrocracks from the lab specimens provide individual data points. The EPRI data, which includes French pulled tube results, is available only as detectability versus RPC angle and maximum depth.

Thus these data could not be independently evaluated. The data base is dominantly for hard rou transitions with the exception of the North Anna 1 data. Since hard rou transitions have greater rates of diametral changes versus length than WEXTEX or dented TSP intorsections, the clata tend to provide conservative detectability information for the current applications.

Table 21 in this Section provides the RPC circumferential crack detection data. The data are given for are length by destructive exam versus depth in 10% increments on throughwan depth. The table provides an outline of detectability cut off for 30' angles and 50% depth For smaller than 30* crack angles and for <SO% depth, the probabHity of detection (P.O.D.) is 24% For longer and deeper cracks, the P.O.D is 91%. The three pulled tube indications not detected at greater than 30' crack angle and maximum depths of 64% 62% and 100% are for mixed mode or combined axial and circumferentiat cracks in European units. The mixed mode degradation significantly increases the difficulty of detecting circumferential cracks within the axialindications, if the three mixed mode indications are deleted, the P.O.D, hereases to 95% Detailed tube examination and EC results are not avallable to directly assess the specific influence of mixed mode cracklag on detection of the circumferentialindications. Mixed mode cracking has not been lound in WEXTEX transitions where circumferential cracking is more common than axial cracking, in contrast, axial cracking dominates the ind' ations -

c found in roll transitions. Thus it is reasonable to exclude the mixed mode data points of 2 13

Table 2.1 in evaluating the RPC P.O.D. for North Anna 1, Overall, the data support RPC P.O.D. >95% for North Anna 1 crack angles >30' with depths >50%. The RPC P.O.D. applied in WCAP 13034 was 50% at 23' to 100% at 50'. The 23' value represents EPRI evaluation for WEXTEX Westinghouse Owner's Subgroup of RPC detectability for uniform throughwall indications of - 4 mm length.

The data of Table 2.1 support the 100% P.O.D. at 50' for very deep or throughwall cracking which is the intent of WCAP 13034.

Comoarison of RPC and Br1 Detecta5flity Experience has shown that RPC detectability in expansion transitions is greater than that for 8x1 probes. This difference is attributable to greater lift off of the larger 8x1 coils (0.3" for 8x1 vs 0.1" for RPC) over the short axial lengths of the transitions and to the 45' coil spacing of 8x1 probes. For dented TSPs, the diametral changes are generally more slowly varying than for expansion transitions such that lift off is not expected to be a significant concem at dented intersections. The coli spacing of 8x1

~

probes compared to con rotation for RPC probes is judged to permit missing of very i hort circumferential cracks that might be detocted by a RPC (See Figure 4 35 of WCAP 13034). For this reason, the 50' detectability threshold for a RPC was increased to 75* for the 8x1. The coli designs are similar for the two probes such that detectability for cracks traversed by the coils should be simliar. Thus it is expected that 8x1 and RPC POD's at TSPs should be similar with the possibility of the 8x1 not detecting snpil (25-75') cracks found by the RPC.

There is very little tube pull data with 8x1 inspection data to directly assess 8x1 detectability for circumferential indications. For North Anna 1 tube R11C14, the 3 of 4 ci cumferential indications detected by ths IPC were also detected by the 8x1. At the bottom edge of the tube support plate on this tube, the three coil response exhibited voltages ranging from 1.6 to nearly 4 volts. while the five coil response from the upper edge of the plate ranged from approximately 18 volts. As can be seen from Figure 21, these voltages are indicative of other voltages called with the 8x1 and confirmed during the 1991 inspection. Similarly, the two pulled WEXTEX indications were detected by-bc. Jie RPC and 8x1 probes.

2-14

l Additionally, the noise contribution from the 8x1 probe was discussed during the December 2 meeting. While there is a horizontal noise component from the 8x1, this noise component lies in the same phase angle range of ID-initiated flaws. From examination of the R11C14 tube, the circumferential degradation was determined to be OD in nature. As the signal component for these OD flaws does not lie in the same plane as the noise component, the 8x1 probe noise will have a small effect on signal analysis.

To further assess ex1 detectability at TSP intersections, relative comparisons of 8x1 and RPC detectability are given below.

1991 inipaction Results for APC and 8x1 DetectabiHtv A total of 110 8x1 indications at TSPs were confirmed by RPC as exhibiting circumferential!y oriented indications. An additional 433 TSP intersections were inspected by RPC that were primarily bobbin coil potentialindications subject to RPC confirmation. None of these 433 intersections were found to have circumferential indications by RPC. This significantly large sample supports comparable detectabi!!!y between the RPC and 8x1 probes at TSPs.

Sensitivity of PrNected 1991 Indientions to 8x1 Detect %n Threshold An indirect mathod of assessing the adequacy of the 75' threshold assigned to the 8x1 probe is to compare predicted 1991 liidications at TSPs with the inspection results using both 75* and 05' thresholds. Based on tefinement of the ax1 data analysis guidelines based on the RPC inspection results, a reevaluation of 1G89 8x1 data indicated (Table 5.3 of WCAP-13034) that about C5 of the 101 SCIindications found in 1991 were present in 1989. By adding allowances for growth and NDE uncertainties to t

the 65 indications left in service in 1989 and to the detectability threshoid angles for the 36 new indications, projections were made cf the 1991 indications as described in Section G.5 of WCAP.13034. Figure 2-2 (at the end of t!ns section) compares the projection 1991 Indications for both the 75* and 95' 8x1 threshold angles with the 1991 actual distribution. From this figure,it is seen that increasing the threshold for a

100% detectability from 75* to 95* does not affect the mcximum projected crack angle of 2'.5'. Both threshold angles show projected distributions rounded to integer numbers of indications that are the same above 160* crack angles. Batween 120' and 160', the 95' threshold increases the projected number of indications compared 1175' while even 2-1 5 l

the 75'

• 1shold projections exceed the actual distribution. Below 120' crack angles, Le 75' threshold projections exceed the 95' projections with the 75* threshold results showing modest improvement in agreement with the actual values.

Overall, the 75' 8x1 threshold shows improved agreement of projections with 1991 actuals compared to the 95* threshold. This resuh provides indirect support for the adequacy of the 75' threshold for projecting circumferential crack angles at TSPs in combination with growth rates and NDE uncertainty developed from the 8x1 and RPC data.

Conclusions The following conclusions on detectability can be made based on the above results:

RPC detectability for circumferential cracks is about 95% for crack angles >

30* and depths > 50% It is reasonable to bound detectability at about 100%

for crack angles > 50' and depths essentially throughwall or segmented cracks as assumed in WCAP 13034.

The[

Ja.c crack model applied for ODSCC at TSPs does not assume 100% detectability > 50% depth. Conservative allowances ute included

(

for detection thresholds and NDE uncertainties in projecting 1992 crack angles I

> 50% depth. The 50% crack depth is conservatively applied to the total tube circumference greater than the RPC crack angle.

The 75* 8x1 detectability threshold for deep cracks potentially left in service i

provides adequate conservatism for 1992 crack angle projections based upon:

1 Expected differences between RPC and 8x1 probes and their influence on detectability at dented TSP intersections RPC inspection of 433 TSP intersections found no circumferential indications missed by 8x1 in this sample. A!! RPC circumferential indications found at TSPs were also found by the 8x1.

2 16

Comparisons of projected and actual 1991 circumferentialindications at TSPs shows overprediction of crack angles > 120* with the 75' threshold.

Further increases in the threshold add unnecessary conservatism.

Quedion #5 tGeneral Comments Ref.1.. n.1)

The Westinghouse report discusses flow induced fatigue of tubes with bng shrough-wall cracks, but does not discuss the fatigue crack prowth data (6Kthreshokf usedto calculate critical crack sizes. Effects of fbw induced vibrations muld be sensitive to assumod values ofsK reshokt n contrast the report has extended discussions of other th i

factors such as damping factors.

Existin0 crack propagation threshold data were used to determine a reasonable value of AK f

threshold or inconel 600 tubing. Figure 2-3 contains a plot of AK reshold vs. R th (Min Kl/ Max KI) for various nicket based alloys. Data contained in this plot were obtained from a variety of sources but a significant portion was obtained from Reference

4. Note that the filled-in-triangles are data polnik obtained using 1600. Figure 2 4 contains an additional plot of the information with two curves superimposed on the data.

Since it can be argued that the crack propagation threshold for nickel based alloys would be somewhat similar,it may be reasonable to treat all the data as a single group. A regression curve frt of all the data was generhied and plotted in the figure. This appears as the upper line in the plot and could be taken as a mean representation of the data.

However, this line was not used Ir *he evaluation to define AK reshold. The curve that th was used in the cvaluation was generated using only the 1600 data. As can be observed in the figure, this curve envelopes nearly all the data. The curve also follows the trend of increased crack propagation potential with increased values of R that is exhibited by all alckel alloy data. Note that the data contained in the curve was generated in room temperature air. AK scales with Young's Modulus and is typically increased rather than decreased in aqueous environments. The curve used in the evaluation was modified to account for temperature differences, but was not modified to account for the increase in threshold due to the aqueous environment.

2-17

l Since the circumferential cracks are not fatigue induced, but are a result of SCC, the l

morphology of the crack is such that various small erack branches extend along ths grain boundaries. A single crack face, typical of fatigue induced crack propagation, would not be present since SCC is the crack initiator. However, since the crack propagation due to i

FIV is fatigue induced, rather than SCC induced, a change in the type of crack must occur before fatigue induced crack propagation muld occur. As a result of this change, an increase in the crack tip stress intensity is required to provide the necessary driving

{

force for crack propagation. Figure 2 5 contains a plot of the ratio of K ranched unbranched vs. angle between cracks. This curve indicates that a high valus b

M

(-0.7) of K ranched unbranched would mnservatively envelope a sub.stantial number b

/K of microbranch variations. Since the reciprocalof K i

K d

branched unbranched escribes a multiplier to convert multi-branch cracks to fatigue cracks, use of a large value of K

/K branched unbranched would be conservative. Therefore, a multiplier of [

l

]b,c was applied to the curve contained in Figure 2-4 to account for mul'l~ branch effects.

j j

i I

l l

l l

2-18 4

Table 21 North Anna Unit 18x1 Call Analysis Percent Through Wall A clength' 0 10 11 20 21 30 31 40 41 50 51 60 61 70 71 80 81 90 91 100 15 llll lo o

++

lo o

30 llllll l

l

+l

+lll+

l++o

+o

'o

+++

+

==

45 l

+

1. ff 60 lll l

l 0 (*)

+#

75 ll

+

f 90 l

f f

105 o

+

++

+

1. ffo(*)

120 o

+f

<dif 135

+

o (*)

150 165 13 Hits 4 Misses 40 Misses 40 Hits 180 24% P.O.D.

9'% P.O.D.

f f

195 1 Miss 39 Hits 210 95% P.O.D.

without mixed see 225 alssed indication f

240 f

f 255 f

270 f

l 285 s

300 315 310 345 360 o

p RPC Circumferentini Crack Detection

(*) Mixed mode axial and circumferential cracks in European plants which makes detection of circumferential cracks more difficult.

l.o No Detection from (l) Lab $ ample or (o) Pulled 'iube

+,f Detection free (+) Lab Saarle or (f) Pulled Tube 2 19

L i

t NORTH ANNA UNIT 1 8X1 CALL ANALYSIS 4

)

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i

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1 I

Figure 2-2 TSP Circumferential Cracks:

i 1991 Actual vs. Projected Crack Distributions I

with 75* and 95* Detection Thresholds L

30 I

l3_

[

f 5

25'

. O ~ A::tual Distribution

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95' Threshold

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& 15* 25* 35' 45' 55' 65* 75' 8E' 95* 10S*11S*125*135*145*155*165*175*186*195%6*215' c

RPC.. Crack Angle (Degrees) 12/5/91-3 2

- j i

4

.r

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Rgure 2 3 AKThreshold alues for Nickel-Based Alloys V

>0 V

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o O

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2-23

J a,c 3

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l Angle Between Cracks,' e.

.., j Figure 2-5 Ratio of Stress Intensity Factors for Branched versus Unbranched Cracks of the Same Total Length 2-24

3.0 RESPONSESTOSECTION 2.0 QUESTIONS Question #6 (Pace 2-1. Ref. 2 1st Bullet n 2. Ref.1)

The bottom line conclusion of this report is that a mid-cycle inspection is not needed, because no cracks wiH be so large that any tubes wia rupture due to operating pressure, accidents including steam line breaks, or vibrational fatigue from flow induced sources.

Pl case compile a list of the majorassumptions made in the evaluallon, and estimate the sensitMty of the evaluation to changes in these assumptions. For example, What is the effect ofincreasing the threshokt of crack detection (e.0, 60% versus 50%

through-walldepth)?

Increasing the crack detection from 50% through-wall to 60% through wall would result in a decrease in the threshold of FlV induced crack propagation. For the condition where the crack is located just below TSP 1, the threshold angle for the most limiting tube would decrease 17*, from [

]b,c, While increasing the threshold of detection from 50% to 60% affects the FIV (turbulence) threshold, it would also affect the Probabilistic Assessments contained in Table 2.3 of WCAP 13034 for ODSCC at the tube support plate edges. (It has no effect on the WEXTEX PWSCC probabilities). By scaling back the threshold angle for FIV,it roughly doubles the population of tubes that could be susceptible to turbulence-induced vibration, and therefore approximately doubles the probability from ~1% to -2% that one tube in the three SGs could have crack propagation initiated by turbulence-induced vibration. As noted in WCAP 13034, turbulence-induced vibration leads to slow crack propagation rates which provide ample time for leak detection and plant shutdown prior to a tube rupture.

With respect to tube burst, tho critical angles for 3AP and steamline break will be b

J,c, respectively. Since the largest projected crack angle reduced to [

for an 18 month cycle is 185', the reduction in tube burst for 60% depth does not impact the tube integrity conclusions. While revised support plate circumferential crack distributions have no! been perfomled for the shorter (13 month) operating interval, both the increase in probability and reduction in burst margin for the 60%

3-1 l

case would be at least partially, if not fully, offset by the shortened operating interval.

However, as noted in the respense to Question #4, the 50% depth for ODSCC represents the average depth of degradation over 360' outside the projected EOC crack angle. The EOC crack angles include allowances for undetected erseks and NDE uncertainties. Please refer to Question #4 for further discussion of the ODSCC model.

Ouestion 17 (Paoe 2-1. Ref. 2:2nd Bullet. a 2. Ref.1)

What is the etlect of assuming two cracks at TSP Intersections versus only one crack?

~ 9 geometries are postulated whereby two cracks exist at the TSP locations. For the fitt<t case, two circumferential cracks exist on the same side of the TSP but are separated by a ligament. Since inis geometry is a crack with a ligament, and cracks with L ligaments have been addressed previously (in the response to Question #3), this -

configuration does not need to be considered again in this response. The second crack -

geometry is the case where a circumferential crack occurs on both sides of the TSP. In this case, the FIV response of the tube for each crack is considered separately, The i

j evaluation is performed in this manner since the modal responses of each section of tube (above the TSP and below the TSP) are not coupled due to the fixity of the tube at the TPS. Since the tubes are fixed in p'. ace due to denting at the TSP, and force and moment --

loadings are not transferred across the fixed location, it is not necessary to consider coLpling of two cracks under this configuration.

Question 18 (Pane 2-1. Ref. 2: 3rd Bullet. o. 2. Ref: 1)

[

What is the effect of decreasing the assumed upperbound on probability of detection (for j

long and deep cracks) from 100% to say 9S% ?

Use of the model detection thresholds is discussed in detailin the Question #4 response.

It is not unreasonable to assume that at some point for long and deep cracks a 100%

probability of detection occurs. For purpose of this evaluation, this was assumed to occur at a throughwall angle of 75*. With the addition o' f the 8x1 probe measurement uncertainties, this results in an effective 100% POD at a throughwall angle of approximately 100*. Pieaso refer to Question #4 for further discussion.

3-2

Ouestion #9 (Pace 2-1. Re! 2:4th BuUet. n 2. Ref.1)

Whatis the eilect on tube vibrationalfailure ofincreasing M reshold y a factorof th b

2.07 Increasing the threshold for crack propagation willincrease the angle at which turbulence will propagate circumferential cracks in the WEXTEX zone. Figure 31 (at the end of this section) contains a plot of threshold values vs. R for a variety of assumed curves. The curve with the empty squares is the curve used in the evaluation, while the top curve (plotted using +) is the cune where a factor of 2.01s applied. When the factor of 2.0 curve is used, crack propagation via turbulence does not occur as the turbulence induced stresses are not large enough to result in crack tip stress intensities that exceed the threshold. All crack propagation wM result as a function of fluidelastic excitation, as the threshold angle will increase from the turbulence calculated

[ ]b,c to the fluidelastic calculated [

]b,c, in addition, if a factor of 1/2 is used to decrease the threshold for crack propagation, the threshold angle will also decrease. The lower curve in Figure 3-1 contains the tnreshold values where a factor of 1/2 was applied, if the lower curve is used, the threshold angle for turbulence induced crack propagation in WEXTEX transitions decreases from the original [

]b,c, to approximately [

)b,c ith the 1/2 factor w

applied. At[

]b,c, only two tubes are affected. As the assumed WEXTEX crack angle increases, the number of tubes exceeding the threshold for crack propagations increases.

Figure 3 2 contains a ph.,t of the number of tubes effected for a [135']a,c assumed crack.. As can be observed in the figure, approximately 1046 peripheral tubes are affected. However, with an assumed decrease in the threshold angle of turbulence induced c.ack propagation, the time required for FlV induced crack propagation hereases. With an essumed reduction in the threshold of crack propagetM it has been determined that the amount of time required for turbulence to grow a crack from [ -

]b,o (the original threshold) is approximately 390 days, it is expected that this -

would result in observable leakage well in advance of reaching the original [

]b,c -

threshold for crack propagation due to the increased leak rate for fatigue cracks compared to stress corrosion cracks.

3-3 i

i Question #10 (Pace 2-1. Ref. P. 5th Bullet n 2. Ref.1)

Whatis the effect ofincreasing the assumedlength of the indMdualsegments of the WEXTEXcradcs by a factorof 2.0?

The evaluation considered the case where the limiting tube would have a series of [

]b,c cracks, separated by [

]b,c ligaments. The evaluation determined that turbulence induced stresses would be insufficient to result in crad propagation. An evaluation has recently been performed to determine the effect of doubling the size of the crack segment while not changing the ligament size. The result would be a network composed of[

]b,c separated by [

]b.c ligaments. It has been determined that if the segment size is increased to this,'alue, the crack tip stresses would also increase and exceed the crad propagation threshold stress by approximately 3% However, the evaluation conservatively used the largest value of FIV induced bending stress in the calculation. This bending stress was calculated using the limiting crack stiffness. It would be expected that the actual stiffness of the cracked tube vould approach that of an uncracked tube due to the presents of the ligaments. Therefore, the bending stress used in the crack propagation evaluation would be conservative.

The segmented crack model for burst capability for burst capability of 0.25 inch cracks separated by 0 020 inch ligaments was also re-evaluated assuming 0.5 inch cracks with 0.020 Inch ligaments. The result is shown in Fi ure 3-3, which indicated a critical 0

l macrocrack angle of[

]b,c for 3AP.O. burst capability. This e.y19 is well above N

the maximum angle expected at the end of the projected 18 month cycle 245*. With regard to leakage, doubling the crack angle results in a potential factor of [ ]b,c on leak rate, providing earlier indication of a potentia!!y large crack.

I 1

Ovestion #11 (Pace 2-1. Ref. 2)

If a mid-cycle inspection is not necessary, then what would be the maximum period of time between inspections that would give acceptable risk?

c Based upon the evaluations contained in WCAP 13034, full cycle operation is acceptable. The current 13-month cycle for North Anna 1 provides further margin.

3-4

Ouestion #12 (Pace 2-10. Ref. 2)

What is the basis for expechg th91allMCI willoccur below the tubesheet? In this regard, the thirdparagraph of this page was difficult to interpret. Please clarify the wrding of this paragraph.

MCis are discussed in detailin the cesponse to Question #3. As discussed in the December 2 meeting, the presence of ligaments is the important parameter related to the structural integrity of the tube, not the fact that the MCis are located below the top of the tubesheet. Tubesheet constraint is not relied upon as a part of this evaluation.

Ouustion #13 (Pace 211. Ref. 2)

The possibility of mixed mode cracking (cracks with both axial and circumferential components)is dismissed The argument is made that axialandcircumferentialcracks willbe offset by 90* (minor axis versus major ax!s of ovatized tube). Since circumferentialc:acks can exceed an angle of 90* (as evidenced by the pulled tube R t !Ct4), please omlain why mixed mcde cracking cannot occur? Since ID cracking and OD circumferentialacking are known to occur at the same axiallocations in the emansion transitions at McGuire, what is the basis for assuming a similar scenario cannot occurat North Anna?

Both the areas at the tubes support plates and at the WEXTEX transition were assessed for the potential of r'11xed mode cracking. The bulk of this assessment relles upon reviews of the inspection data from the recent inspection, results reported from prior inspections, and observations from tube pulls. For the tube support plate area, no occurrences of intersecting axial or circumferential cracks were :ound on the 5 intersections identified as containing both types of indications. Specific tube examination efforts performed at North Anna in 1985 (Row 9, Column 58) and 1991 (Row 11, Column 14) revealed that the PWSCC axial cracks were confined to the minor diameter of the ovalized tubes, while the ODSCC circumferential cracks were centered approximately 180* apart on the major diameter of the ovalized tubes. Profilometry data and tube pull data indicates that the separated axial and circumferential cracks occur at dented and ovalized intersections. Thus, physicai data supports that separatior, is expected to ba maintained both between two potential sets of circumferential cracks 3-5

l l

and between potential circumferential and axial a ccks as determined from the tuba examination results and the RPC inspection results.

In order for the circumferential and axial cracks to intersect with the observed 90*

separation, a circumferential crack of approximately 180' would be required. Using a 95% cumulative probability, the maximum crack angle predicted for 18 months of operation is 165'. With the planned operating intenal of 13 months, this angular extent would be reduced by approximately 20' down to 146', Therefore, the presence of a 180' circumferential crack at a tube support plate is considered highly unlikely.

For the WEXTEX area, the observed Indications are dominantly circumferential in natute. From the recent inspection, there were no occurrences of both circumferential i

and axial cracking on the saine tube in the WEXTEX area. Therefore, as there have been l

4 no occurrences of mixed mode degradetion in the transition area to date at North Anna, no mixed mode cracking is expected in the future. Additionally, the predicted WEXTEX crack angles at EOC are also smaller than those encountered in prior inspections, even considering the relatively large and conservative NDE uncertainty (49 ) applied for the WEXTEX projections. A further reduction in the estimated crack angles is ermected for the reduced operating interval of 13 months.

With respect to the[

]Q comparison, the [

}Q tubesheet expansion was hardrolled, while the North Anna transition was explosively expanded. The stresses are different between these two types of transitions and accounts for the differences in crack orientation. Hardroll expansion experience has revealed cracking that is predominantly axial in orientation, with multiple axial cracks being observed in a single transition.

Few circumferential cracks have been detected. However, as the ohserved cracking has consisted of numerous axial cracks, if a circumferential crack were to occur, it would have a higher potential for intersecting an axlal crack. Overall, a hardroll transition '

would be expected to have a higher potential for mixed mode cracking than a WEXTEX transition should circumferential cracking occur.

3-6

Figure 31 Ranges of Ki Threshold Versus R M

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4.0 RESPONSES TOSECTION30QUESDONS Qe abn #14 (Pace 31. Ref. 2) hhlle tubes at Nonh Anna have been pulled from the steam generators for examination, these tubes have been fewin number. Also these tubes appear to be those with sitong ET indications. Please explain why such a telection of tubes provides anything other than a weak basis for the crack models described on page 2.4 and for validLting field ET reliability with destructive examinations. Do future plans for tube removals Indude tubes without indications, but from a zone where cracking is know to occur?

Both industry and North Anna specific data were used to support the validity of feld eddy current. Other transition zone incidences of circumferential cracks have been verified in Plant B and Plant C (explosive expansion) and in Plant D (mechanical expansion) in the U.S.: four plants in Spain have also detected and verl%d circumferential cracks via tubo pulls. Plants in France, Sweden and Japan have also characterized crack lengths witn tubts pulls. The correlation of all thic availablo data has shown that the lengths derived from the RPC data have predict 0d the actual crack lengths found in metatiographic examinations with acceptable accuracy.

The differences between the expansion methods are rGgarded as minor relative to influence on the performance of the RPC in detection of circumferentialcracks. Removal of tubes without detected cracks does not affect the correlation of measured to ac!ual cracks; rather it provides information relative to probab!!lty of detection of cracks with varying lengths and depths of penetration. The available data provide confidence that cracks greater than 50' and 50% throughwall are detected, with detection at 100%

penetration achieved with length as short as 23' azimuthal extent.

l The programmatic tube removals and subsequent destructive examinations at North Anna i have allowed site specific guidelines to be generated and revised accottung to the examination resuhs. These guidelines account for the known conditions of the steam generator tubing and allow for disposition of suspect tubing based on the tube pull data.

For further information, see the responses to Questions #2 and #4.

41 u

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Quggtlen #15 (Pace 3-1. Ref. 2)

Only one tube was pulled after the !$9t inspection. Wtwt was the basis forselecting the particular tube (RIIC14)? Were there any %vist case

• features for this tube (such as largest RPC angle) evident from the field ETinspection ?

1. 4 in 1991, three tubes were select 4d as candidates for tube pull based on unquantifiable (in terms of a known damage mechanism) TSP Indications. The three tubes were ranked in priority based upon the strength of the RPC E/C signals at TSPs. R1 lC14 exhibited both ID and OD oriented phase angle signals within the TSP reghn. As such, it was the highest priority tube pull car didate.

Other selection considerations were related to radiation exposure and induded such field technical issues as proximity to peripheral areas of the S/G (such tubes lequire additional cutting due to limited clearance between the tubeaheat and channelhead and therefore consume more radiation exposure), avoidance of tubes requiring greater than one TSP interstetion to be removed due to potential difficuttles with circumferential indications at the TSP resulting in tube breakege, and removal of tubes from one steam generator to minimize exposure associated with equipment set-up and teardown.

Difficulties were encountered in the removal of the two other candidate tabes in 1991 and the removal effort on these tubes was aborted.

Dusstion #16 (Pace 3-7. Ref. 2)

A number of assumptions regarding crack characteristics are made such as Ilgament dimensions for WEXTEX craaks and the 60% throughwall ettent of TSP RPC crack angles.

These assumptions are based on exam] nations of pulled tubes. How many data point,e and from whatplants support these assumptions ? Please cite au relevant data used to s

support these assumptions.

1 j

Evaluation of RPC contour plots (see Figure 41) has been porformed for a number of circumferential crack indications. The behavior of the scan line with the largest amplitude response was examined to assess the fraction of the indication total are length over which the amplitude exceeded 50% of the maximum amplitude observed. This approach assigns 'o the maximum amplitude, and all points for which amplitude exceeds 42

50% of the maximum amplitude, a 100% throughwall penetration. When this evaluation was performed on 95 tubes, a consistent set of data was obtained whbh Indicated that on the average less than 60% of the crack length determined from RPC testing had an amplitude which execeded 50% of the maximum amplitude. Additionally, the pulled tube data ([

]Q and North Anna) discussed in the response to Question

1. 17 were used to substantiato use of the [

la c. There are no known cases of pulled tubes with rJgnificant circumferential cracks having [

la,c, Ouestion #17 (Pace 3-7. Ref 21 It is stated that the destructive examination results on tube R11014 support modeling of the RPC angles, whereas there apoears to be no mention of evaluations to support th!s conclusion? Whatis the basis for this conclusion? Is the[

fe,c factoractually usedin any of the Section 50 crack distribution estimates?

Page 3 7 of WCAP 13034 describes la detail how the de,tructive exmination ressults were used to support the ODSCC crack model. Unlike the PWSCC nedel, the ODSCO model assumes the presence of a throughwall crack section without ligaments. The upper support plate crack from tube R11014 was used to establish the difference between the measured RPC crack angle and the percentage of that angle that h truly throughwall.

From the larger crack at the top edge of the support plate, the actual extent of the crack that is throughwall from destructive examination is approximately 90 degrees. This represents less than [

ja,c. From the destructive examination of a tube with ODSCO in the roll transition removed from

[

jG, a similar comparison of actual throughwall versus the measured RPC angle la,c f the measured RPC Engle being actually throughws!!.

results in less than [

o Therefore, data from these two tube pulls are used to support the [ la.c factor, a

This 60% ractor for the RPC is NOT used in SecGon 5.0 of the report. Section 5.0 c

reflects projected total RPC angles. This [ ja.c factor is used only in determining the potential for tube vibration and for estimating potential leakage during a steam line break event.

4-3 l

Duestion #18 (Pace 310. Ref. 2)

Rgure 3 1 shons the circumferential cracking seen by destructive examination at the TSP of pulled tube R11C14. Compare in detall the field ET estimates of flaw lengths and depths with the results of destructive examinations. Provide ETdata displays (as in Figure 416) for this TSPlocation.

The flaw lengths derked from the RPC contour plots are summarized in Table 2.1 of I

WCAP 13034 with the corresponding metallographic iengths. Flaw depths for circumferential cracks are not provided, since crack like Indications are all regarded as through wall with respect to tube repair dispositbn. The RPC contour dispiay is shown in Figure 41 of this report. Only 22' of the opposing crack at the lower edge exceed 50% dopth according to the metallography; this was not detected clearly in the re analysis.

Quest!On #19 (face 3-10. Ref. El The cracking of Figwe 31 and the ETperformance as indicatedin Table 21 sould support a detection thrssholdno better than 60% through walldepth. Whatis the basis for assuming a 50% detection threshold?

The eddy current detection threshold basis is discussed in deta3 in the response to Question #4. The bottoin support plate destructive examination findings were used to devotop this two-part ODSCC model. First, the smaller crack located at the bottom edge of the suppon plate was used to derive the 50% crack depth. This is based upon the average depth of the undetected crad being 51% throughwall, even though this crad is locally in excess et 60% deep in extremely short areas. Average depth rather thar: local depth is the important parameter when assessing tube 8alegrity and vibration.

Also, a study performed in 1999 for a Spanish utility compared the performance of RPC,

, i bobbin, and 8x1 eddy current probes and ultrasonio testing with metallurgical

]

evaluation of circumferential ODSCC induced in the laboratory mockups of roll transitions. This data shows that RPC detectability for isolated circumferential cracks greater than 50% depth and 30* is approximately 95% Similar depth detectability is expected for the 8x1 probe.

44

.. _ _ _ _ _ _ _.. ~ _ _ _. _ _ _ _. _

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While depth is an important consideration, there is another part to the ODSCC model which forms its basis. The other aspect deals with the assumed throughwall portion of the erack. The model assumes that up to 75' oould be throughwall and remain undetected. When the eddy current uncertainty is added to the the jetection threshold, I

this yleids 1.' effective 100* throughwall crack that could be potentially left in servlos.

Even with this wnservatism, tube structural integrity can be maintained with high l

margin for a full cycle of operation. With the substantially shortened cycle, additional f

margin b provided with respect to the structurallimits, l

Question g20 (Paae 310. Raf. 21 Figure 315 hows part through circumferentialoracking 100% around the tube with superimposed through wallcracking. How does the ideblized modelof 00S00 basedon RPC angles compare wkh the actualcraaking observedItom examination of the pulled i

tube? The pulled tube shows two symmetrically opposed oracks, wherens the idealized i

model assumss a single crack on one side of the tube. How to the burst strengths endleak rate predictions cornpate for these two differentpattems of cracking?

The basis for modeling MCis as SCis for the structural evaluation is ghton in the -

response to Questbn #3. As noted therein, the burst stro..gth is limited by the largest crack which occurs,as SCl rather than an MCI. Similarly, leakage increases by orack 16ngth to the third power so that the largest SCis dominate the leak rate. Assuming all 1992 projected indications are SCis leads to a distribution of larger angles than if separate MCl crack angles were included in the distribution. Combining both MCl crack

- angles as a sum to represent a single crack angle would be excessively conservative for-burst, vibcation, and leakage considerations.

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5.0 REPONSESTOSECTICN 4.0 OUESTIONS Ouestbn 121 (Pace 4 1. Ref. 2)

What differences existedbetween the 1989 and 19J1 Inspecibn methods and data bletivotations ? Give speclRc reasons why circumferentlaf defects were not detectedin 1989, but were later an 1991 found to exist afterlookhg again at the 1989 Inspectbn data.

In order to estimate growth rates, the prior inspection data for 8x1 testing in 1989 were re. evaluated using a more conservative approach. All behavior suggestive of flaws was reported at 8x1 coil hits, r:ausing reports of indications where the original htorpretation hgd not identified their presence in 1989.

The analysis guidelines for 1992 have not yet been finallred. IAodification of the guidolines is not performed until 30-60 days prior to the inspection so that appropriate ladustry knowleoge and site specific experience can be incorporated. However, such modification is now uncarway. The principal difference between the 1992 and 1991 guidelines revolve about the question of frequency correlation between 2 or more channels for the 8x1 probe. Correlation will not be required in the 1992 8x1 guidelines. Other issues such as voltage threshold were addressed in the guidelines used in 1991. These revised guidelines will be provided upon resolution of the issues raised by recent pulled tube experience.

Doestbn #22 (Pane 41. He!. 2)

How wer* the data analysis gukielines modined to account for the lessons leamed from the 1991 ISI? Please provide a copy of the current data analysis gul?elines.

The new guidelines for 8x1 probe data evaluation (1) require separate evaluation of upper and lower edgcs of the dented TSPs by reducing the observation window in order to evaluate only small sections of the tube at a time,(2) require evaluation of the mix channel data for flawlike behavior and (3) delete requirements for phase angle correlatinn from single frequency channels, No confirmation from single frequency channels is required for positive evidence of f;uws. A similar procedure is used for RPC 5 1-l

data evaluation with one exception only the primary test frequency data is used for RPC data evaluation. Also, the support plate windows wl!I be expanded to permit coparate evalut. tion of indications at the upper and lower edges of the TSPs. A copy of the guidelines usod in 1091 is included in Appendix D.

Question #23 (Pace 41. Ref. 2)

In reference to Table 4 1, can it be assumed that alltubes with WEXTEX degradstion were plugged, r fthout regard M the measuredIcngth or depth of the degradation? What specifU criteria are being used to set an ET signal threshold for classifying a WEXTEX transillon degraded?

All tubes identitled during the 100% TTS RPC inspection for WEXTEX dagracation were plugged regardless of the measuredlength of thein6 cation. Phase angie depth of RPC

{

signals are influenced by the geometry change associated with WEXTEX expansions.

Therefore, all Indications in this region are characterized based on their axially or circumferentially oriented pattoms. (sal, mal, SCl, MCl) 1 Any transition exhibiting verticalllawlike excursion in the RPC data ls evaluated for degradation using the guidelines given above. There is no minimum voltage, depth or length criteria for signal threshold.

Question #24 (Pace 4-4. Ref. 2)

In the measurement ofligament lengths between regions of circumferential cracking, what specific criteria were used to decide that the orop in signal was suffelent to conclude that the ligament was uncracked? Have ISIdata andconclusbns regarding ligament lengths for MCI been validated with pulled tubes ? How nould the conclusions from the assessments of tube Integrity (Sectbns 5 and 6) change 11a small traction of the tubes (say 5 to 10%) of the tubes were to give falso evidence of uncrackedligaments between regions of circumferential cracking ?

The guidelines call for an RPC measurement to be performed by evaluating where the signal departs from and retums to a " null

• condition of tubing. By reviewing / scrolling through the data, the analyst can determine " good" or " null

• tubing and then measure -

52 mm_

signal departure from the "known" tube condition. There has been testing performed on known EDM notch samples that are i,cparated by certain distances. The RPC terrain plots can depict a retum to 'nult condition when the slots are approximately 0.25" apart in this particular example. The field practice for evaluation was to report the whole angular extent of a signal unless a retum to 'nu!r was observed and the analyst could clearly define ligaments between indications.

MCis were not present in the 1987 WEXTEX tube examinations. However, they were present in the 1991 tube examination. At the upper edge of the plate, the RPC also indicated the presence of these ligaments. UT measurements (Section 4.5.3) show that -

large (20' 30') ligaments can be associated with valleys in the RPC amptitudes that do not return to the 'nulf condillon. It would be excesskely conservative to assume that RPC amp!!tudes that retum to the

• null" condition are false avYeo:o of an uncracked ligament, and thurefore falf.e evidence of uncracked ligamonts has not been considered.

The response to Question #3 also has a detailed discussion on the presence of ligaments.

Questbn #25 iPsagf& Ref. M The bobbin coilInspection is reported to be insufficiently effective to ensure detection of axialcracks conhned wl!hin the TSP. How effective is the 8x1 probe in detecting such axialcracking within the TSP? How does the 8x1 probe compare to the bobbin calland RPC probe in detecting axial cracks both within and outside the TSP?

Metallographic evidence from the 1985 tube pulls and subsequent RPC data characterizing bobbin probe indications have shown that some PWSCC identified at support plates have components both within and outside of the dented tube section Tubes identified with PWSCO totally within the support plata/ dented tube section were plugged, notwithstanding the likelihood that these posed no threat to tube integrity. Review of the 1991 EC inspection data shows that the bobbin coil performs well in identifying axial PWSCC outside the dented support region, 8x1 probes doloy an array of surface-riding pancake coils which are quite sensitive to circumferential cracking; all the known cracks of this nature at TSPs were identified as Pts (possible indications) by this probe, its sensitivity for axial cracking (PWSCC) is good in principle, but the geometric coverage of the 8 colls leaves short arc iongths S-3 l

covered by weak eddy current fields; approximately 25% of the axial cracks were fourd by the 8x1 as opposed to 95% found by tne bobbin probe.

All the axial and circumferential cracks identified at North Anna 1 TSPs were corroborated by the RPC probe. This prote effectively overcomes the limitations of the bobbin and the 8x1 probes, at the cost of lengthy extensione of InspectiorJ me. The single coil RPC probe examines a 6* length of tubing, e.g., a support plate lotorsection, in 36 seconds at 200 rpm with a 0.050' pitch; this compares with 0.25 seconds for the bobbin probe at 24*/second and 1.0 seconds for the 8x1 probe at 6*/second. There are 54.208 Intersectbns which are rcutinely artalyzed with the bobbin probe in each steam generator. For this reason, the RPC probe is used inalnly for characterization or to-examination of degradation.

!n semmary, the bobbin probe can detoct axial cracks within the support plate intersections with low level dents (10 volts). It is inacequate for detecting flaws wi^iin the intersections if the dont signals are large, but X is effectNe in detecting axial cracks extending outside the TSPs even in the presence of large cent signals,11 is not a good probe for detecting c!rcumferential cracks in general. The 8x1 probe detects axial cracks with reduced effectiveness due to geometric coveiace, but it is r ot as strongly affected by denting. RPC probes provide fu:1 coverage and insensitivity to dents.

Question #26 (Pace 4-6. Ref. 21 Please clarity the following point. Was cracking outside the TSP usually or always associated with cracking within the TSP? Were there some cases where cracking occurred outside the TSP without associated crtis within the TSP? What has l'een the plugging practice at North Anna regarding cracks tl.at are entirely within the TSP? Are such cracks pluggod only ll the Indicated depth exceeds 40% of the wall thickness ?

From the 1985 tube examination and from RPC inspations performed since 1937, cracking outside the tube support plates is usually asscciated with cracking inside the support plate region. There have been some occasions wnere axial cracks have been l:

detected by the bobbin probes and had no detectable cracks with!n the support plate.

Indications identified as cracking, even though contained entirely within the support plate, are plugged without iegard to indicated depth.

54

Ducrtion s27 (Pace 4 8. Ref. 2)

It is sta.'ed that an additbnal 433 TSP Intersecibns were inspected with the 11PC probe.

Were these Intersections in addition to those descnbed on page 4 t ? What was the basis for selecting these 433 intersections? Was It a random sample? Or was it a criteria such as the extent of denting at the intersectbns ?

The additional intersections examined by RPC are included in those described on page 41 of Reference 2, i.e., all indications reported to be greater than or equal to 40%

throughwall depth by bobbin coil as well as those characterized as dis (distorted indic.tions). Tho sample was not random, nor did it relate to the extent of donting at the intersection.

Question #28 [ Pace 4-8. Ref.2)

No circumicrantialcracks were reportedin the 433 tubes inspected by the 11PC probe, but were any axlat IndUstions found? Ilso, how were these Indicatbns d!spositbned?

Yes, these were additional tests beyond the original plan, based on bobbin throughwall

• percent

• values or Dl's. (Refer to pg. 41, Sec. 3,3rd line.) The 'aoditional* that is referenced are those tubes which exhib!!ed reportable bobbin and 8xt Indications, and were subjected to RPC testing. The possible indications identified during the 8x1 inspection included all the indications (-110) which were volumetric or circumferentialin.iature; the balance of the toisi of -540 additional tubes examined with the RPC were derived from the bobbin TSP indications rather than from a random sample. Axial cracks were found on approximately 321 intersections, mainly from bobbin calls, some from dual 8x1 and bobbin calls; all were plugged if cracklike signals were observed.

Ouestion #29 (Pace 4-9. Ref. 2)

Whatis the reason for detecting more cracks at the top versus bottom of the TSP 7 Are

-l the corrosion conditions different at the top versus bottom bcation? Is the inspecibn more effectivelsensitive v1 detecting cracks at the top of the TSP?

55

The sensitivity of crack detection by any of ther.e probes is the rame at the top or bottom edge of the TSPs. The appearance of more cra&6 at the im of TSPs irnplies a more aggresshte conditions in this region. A conceptual possibility for the cause is potential sludge deposits at the top of the TSPs.

Question #30 (Pace 412. Ref.f)

The structuralIntegrity assessment assumes that 'long' dstects that are greater than S0% of the wallin depth wl" be detected with 100% probability. What evidence is there from performance demonstrations or other sources to support this 100% value and'or other very high level for the probability of detectbn ? Are there any data from performance demonstralbns to suppott specific values of high (say greater than 90%)

detectbn probabillry? How would the conclusions of the structuralIntegrity and reliability evaluatbns change if the upper bound on detection probability were less than 100% (say 95%)?

This question is essentially the samo as Questuns #4, #3 and #19. Please see the responses to those questions.

Question #31 (Paco 412. Ref. 2)

It is stated that all tubes with circumferentialIndications are plugged. What is the estimated reliability of detecting circumferential cracks, and what evidence is available to support this reliability estimate? What os the estimatedreliability ofclas*llying Indicatbns as circumferential cracks, and what evidence is available to support this estimate?

Please see the responses to Questions #4 and #19 for info.mation on detectability of circumferential cracks. The reliability of classifying indcations as circumferential cracks is very high for significant indications such as greater than about 45*. There is -

no nend to distinguish smalier cracks betwean circumferential and axial cracks, since all indications are plugged.

56

Question #32 (Table 41. Ref. 2)

What is meant by *ateve the tubesheet*? Does this refer to degradation in the sludge pile rogbn of the generator?

Yes. 'Above the tubenheet* Impiles sludge pile region if sludge is present in the region.

Quesrion #33 fTable 4-4. Ref. 2)

Were there any TSP locations where axlalIndicatbns were detected within the TSP (by ths Bx t probe) and where these inJicatbns also extended (detected by bobbin coll inspection ) beyond the TSP 7 llso, how are such bcations reportedin Table 4 47 Do tha bobNn call findings have hierarchy over the 8x! probe l'ndings la the rspotting scheme of TaNo 4 47 Yes. Some cracks outside the TSPs detected by bobbin were found to extend within the TSPs and were observed by the 8x1 proba. The extension of tne axial cracks is not reported in the Jx1 data: rather, such information is obtained from the bobbin inspection and also from the RPC data if needed.

Any indication observed by 8x1 or bobbin is plugged, unless the confirmatory RPC data suggests other than crack-Ike origin. The use of RPC probes for indication confirmation has been used at North Anna since 1987. Thus, RPC findings are given hierarchical prefernnco over the other probes because of the characterization that can be obtained from tile RPC data. The 8x1 and bobbin results in T.1ble 4 4 are mutually exclusive as is explained in Sections 4.3.1 and 4.3.2 of WCAP 13034 Question #3A (Table 4-4. flof. 2)

What is meant by

• percent depth calls by RPC'? Were all the tubes with TSP Indications as reportedin Table 4 4 plugged?

The " percent" calls by RPC were based on the putts versus depth curves generated from an EDM notch standard at the prime test frequency. All but a few very shallow RPC depth calls in 3 tubes are plugged. These tubes were not considered to have any erack Ike 57 l

r

tube degradatic*i, but were noted as a 1% Indication to aid trading within the data base and for comparison at the next inspection.

Duestbn #35 (Table 4-4. Ref. 2)

It wlumetrk signals are found at support plates, to what type of degradation were these signals attributod? Were these sknals interpreted as evidence ofIntergranular attack ?

I Initially, all 8x1 indications woro called Pls (possible indication). Those were then sorted out as circumferential, single axial, or rnultiple axialindications using the RPC data. There is no evidence of signircaat InterDranular attad in North Anna 1 tube pulls. All crack like signa!S were attributed to PWSCC (ID origin) or ODSCC (secondary side origin). Those not crack like in appearance wore given a depth based on phase angles observed ir the RPC traces. All the

• percent

• calls were CD in character and not immediately given Oribution; the tube pull data supports ODSCO as the probable mechanism. Closely spaced, small ODSCC axial cracks can appear to be

• volumetric

• due to the limited RPC resolution capability to resolve individual cracks.

S8

i 6.0 RESPCt4SESTOSECTO45.0QUESTO4S t

QLggtlan 138 (Pace 5-5. fh This report makes assumptions about details of crack morphology based on data from examinations of pulled tubes. Examinatlors of pulled tube R11C14 would support the assumption of two drcumferentialcracks at TSP locatbns. Why was only one crack of t

depth greater than the 50% thresl.old assumed, rather than two cracks as suggested by the data from the pulledtubes?

As stated in the response to Question #3, the structural and vibration response of the tubo is governed by the larger of the two cracks provided the cracks are Oeparated by a ligament ofl jb,c or more. With the pulled tube, the crack centers are approximatNy 180' apart and are separated by structurally significant ligaments.

Therefore, the structural performance wl!! be governed by the larger of the two cracks.

This is entirely consistent with the ODSCO model.

,QygstMn 137 (Pace !.6. Ref. 2)

Please clarity the statement *basedon assessing the sensitMtyof these projectbns'. To witat are these projections sensitive ?

This section refers to the tube plugging projections at the next inspection. Such tube plugging projections are performed using a log normal distribution based upon the prior history of the indications. Upper bound and lower bound projections of tube plugging were performed based upon the specific tube plugging history at North Anna and reviews of oddy current data. These projections are sensitive to which year tube plugging is attributed and to changes in the eddy current inspection techniques or the ruler / guidelines employed in some cases, eddy current data is reviewed from a prior inspection and tubes actually plugged in a later inspection will be attrbuted to an eartier (usually the prior) Inspection. For the upper bound projections, the 1992 tube plugging was projected by attributing tube plugging in the inspection period in which it was performed. This results in a higher estimate than what would have been developed by attributing a portion of the plugging to the 1989 inspection.

61

=

puestion #38 (Pace 5 6. Ref. 21 1he ET uncertainties in the 8x t data are basedon comparisons with *true' crack for>gths taken from RPC data. Do the limited metallographic data frompulled tubos support those ostimates of ETuncertaintios?

Evaluation of the field generated 8x1 data using the improved interpretation guidelines was performed to provide correlations with the pulled tube metatlography. Table 61 at i

the end of Mis section describes this correlation, which is reasonably consistent with the metallographic results. The number of 8x1 coll hits correlated with the actual fractography of the 1987 pulled tube suggests reasonable consistency with degradation exceeding 50% for both the support plate and the WEXTEX cracks. The 1991 WEXTEX and 1987 support plate cracks were too shallow to be detected.

Duestion #39 (Paae 515. Ref.2)

Table 52 suggests that in some cases the observed 1989 to 1991 growth was < 0 *hlts',

meaning that some indsations appeared to decrease in size. How many of such

• negative growth

• Indications were obse'ved and what were the magnitudes of such *negallve growth *?

The heading in Table 5.2 was intended to indicate *less than or equal to' zero 8x1 hit changes. The distribution of '918x1 hits remaining the same (*=0*) as the number of

'89 or less than the number of '89 hits (*- 1*, *-.2") for Single COls are as follows:

Tube Sonnen Plato Indientiont 33 r.2 m:1 m:2 m3 A

5 0

0 0

B 1

2 0

0 0

10 2

D A

Totals 16 4

0 0

l 62

WEXTEX Indkations El nD a:1 m:.2 m.:3 A

9 6

0 0

B 5

1 0

C H

A 2

0 Totals 32 17 3

0 Cynttlen e40 (Proe S 22. Ref. 21 Table 5.9(Pptheta column) Implies that during the current operating cycle there is a 1% probability that a Ist span willfalldue to vbrallon of a tubs with a WEXTEX crack.

Is this a coTect interpretation of this table? Is this probab!!ity of one tube rupture per 100 teactar operating years consistent with requirements for safe operation ?

For Pptheta < 1, Pptheta can be interpreted as the probability that one tube in the three steam generators at North Anna Unit I will experience a circumferential crack that exceeds the through wall crack length threshold angle for crack propagation. However, it does not represent the probabEy of a single tube rupture event. For fluidelastic driven crack propagation for VTXTEX cracks, it is calculated that it takes approximately seventy hours to proceed to tube separation. Since North Anna Unit 1 prKdes continuous leakage monitoring and shutdown capability within two hours of exceeding the 50 opd administrative leak rate limit, fluidelastic driven crack propagation would also be detected and the plant shutdown prior to tube ruptur9. For circumferential cracks at tube support plate edges, no cases have been found that would be calculated to result in flouelastic instability (largest angle of [ ]b,c),

Based on a review of NUREG-0844, *NRC Integrated Program for the Resolution of Unresolved Safety issues A-3. A 4, and A-5 Regarding Steam Generator Tube Integrity",

the staff assumed that a steam generator tube rupture, as an initiating event, has a frequency of occurrence of 1.5 x 10-2/RY. The NRC staff concluded with this frequency of occurrence that the core-melt probability from all SGTR related causes is acceptably low, i.e.,3.9 X 10-6/RY. The 1.0 X 10 2 RY frequency of occurrence identified in Table

/

5.9, although not representative of the frequency of occurrence of a steam generator tube rupture event, compares favorably with the 1.5 X 10-2/RYinput value utilized by 63 l

the NRC in the analysis referenced in NUREG 0844.

Ouestion #41 (Pace 5 29. Ref. 2)

The lettering of the bwer scale is missing on Figure 5 7pbt of cumulative ET uncertainty What are the labels and numerical values for this scale?

The label for the horizontal axis should be 'EC Uncertainty *, The values range frota 60' at the left hand side, and increase in 20' increments to 60' on the right hand side.

,Ouestion #42 (Pace 5 30. Ref. 2)

Please fustify the conservatism of the projected 1992 distribution of RPC angles given in figure 514. Compare these TSP dicumferentialcracks with the measured 1991 RPC angles of Figure 5 12. Why is the maximum projected angle for 1992 (185*) less than the maximum angle (2fS*) measuredin 19917 According to Table 2.1 the measured angle for pulled tube R11C14 had a totalangle c1232* (two cracks of 158*

and 74*). This angle is notincludedin the distributbn of Figure 512. Since tube rupture is a function of totalcrack angle, why are not total crack angles used as the basis forcrack angle distrbution?

The maximum projected angle of 185' in 1992 is less than the 1991 measured angle of 215' due to the extensive tube plugging for circumferential indications at TSPs in 1991 The 1992 projection starts at 800 with crack angles at the detection threshold.

l The EC data review based on revised 8x1 analysis methods shows t' tat many of the circumferentialindicationc found in 1991 were present in 1989. Theses indications l

left in service (no tube plugging for circumferential Indications in 1989) were larger in size than the current detection threshold such that larger indications should be expected for 1991 than 1992.

Tube rupture is not a function of total crack angles for cracks separated by significant

([ ]b,c) ijgaments. Thus, total crack angles for MCis are not used in the -

distribution of Figure 512 or the structural evaluations, as also discussed in the response to Question #3.

64

_ = - _

P TABLE 61 8x1 Uncertaintles vs. Pullod Tube Metallography S'Q h

Metsfloornehv Br1 Hits A

R17C31 (1987)

TTSWEXTEX 176' with 12 ligaments, max depth 3 coils 90%, average depth 70 80%

1H Upper Axlal PWSCO s 22%;

O colls Circumferential ODSCC s 28%

1H L.ower No detectable degradation 0 colls A

R18C36 (1987)

TTS 128* mth 5 ligaments 2 coils 53' throughwall B

R11014 (1991)

TTS Max 21%, average 6-8%

0 ooils 1H Upper Two 120' cracks centered 180' apart 5 co'is (1) 100% thruwall for 70' 90' (2) loca!!y 100%,75% avg. depth H Lower 2 opposite macrocrad.s 3 coils (1) 150', average ~70% dep!h with very short section near 100%

(2) 120', average -51% depth 22' > 50%

t 6-5

7.0 RESPONSESTOSECTUJ6.0 QUES 110NS DJ2ffian #43 (Pace 6 2. Ref 2)

Descrbe test specimen configuration, test setup, test temperature, and other relevant details of the burst tests. Is there another document (s) that can be provided that gives additionaldetalls of burst test results and experimental techniques? Were the tests discussed on page 6 2 performed specifically forpurposes of the North Anna evaluation?

The test set up, test temperature and other relevant details of the burst tests are adequately describod in Sections 6.1 and 6.2 of WCAP.13034. With respect to the test specimen configuration, it is pertinent to point out that lateral restraint was provided by a simualtod tube support plate with prototyplo spacing and prototypic gap. In one series of tests, denting was simulated by clamping at the TSP location. This condition is referred to as lateral plus axla! restraint. The burst test for tubes w)*h circumferential cracks were tested for Nodh Anne and for the Westinghouse Owner's Group WEXTEX subgroup.

Question #4_4 (Pace 6-5 Ret 2)

Does the ledage model with flashing liquid have relevance to leakage at operating conditions, or only to the steamline break acckknt?

Flashing of liquid occurs when the pressure is dropped below the saturatlon prstsure corresponding to the fluid temperature, in the current leakage model the pressure loss due to the phase change is always calculated. But if the leakage fbw is not choked at the crack exit, as generally at the normal oporating conditions, the code only accounts for the Irrocoverable losses such as the entrance, single phase friction and exit loss. The pressure losses due to area and phase changes are conaldered to be recovered at the crack exit (

Reference:

EPRI Report NP 3395,' Calculation of Leak Rates Through Cracks in Pipes and Tubes *). If the leak flow is choked, as at the steamline break conditions, the pressure losses due to area and phase changes are taken into account in the overall pressure drop calculations. In other words, the liquid flashing has relevance only when the leak flow is choked, which depends on the crack geometry and exit pressure.

71 i

i

\\

Questlen 045 (Pace 610. Ref. 21

!$ there a document that gives further Information on details of the CRACKFLO 00mputer codo ? Is this a pudic domain code, or 12 It a code developed andis !!isoprietary to Westinghouse?

There are Westinghouse intemal reports and Calculation Noter documenting the dwelopment of the CRACKFLO code. The code was develo;ed and proprietary to Westinghouse. It is therefore not a pubtle domain oode.

Question ffB. (Pnce 610. Ret. 2)

References in the text to Figures 6 7 and 6-8 should M corrected to isfor to Figures 6 5 and 6 6.

The figure reference should be corrected to Figures 6 S and 0 6.

Overtion e47 (Pace B 10. Ref 2)

Please describe the types of cracks usedin the leak test specimens of Figures 6 5 and 6-6 Provide a reference for the leak rate data of Figures 6-5 and 6 6, Were these tests performed on steam generator tubes or on larger diameterpping specimens ?

What t> pes of craaks were in the specimens (i.e. machined defects, stress cottosbn craaks. etc.)? Were the detects of the leak tests representative of the craak morphology forcracks in North Anna tubes?

Both fatigue and SCC cracking types are present in the steam generator tube $amples tested and included in the comparisons of predicted versus measured leak raios. (Sou Figures 71 and 7 2.) The data from fatigue crack samples are Westhighouse data and have been presented in several publications. The SCC roll transition (RT) crack data are from an EP91 program performed by Westinghouse The (

}0 pulled tube data were obtahadby B&W for[

JO, who has presented the data i.' e NRC.

The roterences are the same as the ' crack data base' references 10 in the response to Ouost'00 #48. The Plant A pulled tube data in Rouros 6 5 and 6 6 are pulled tube results developed in a roll transition program for [

l1, still in progress,

)

1 72 l

, Question etB (Pace 611. Ref 21 Please provide references for the leah rate data referred to as the

• crack date base *.

The

• Crack Data Base

• Includes tne following:

,a,c.g QJestion #49 (Pace 6-12. Ref. 2)

Are the burst data in the WCAP 12522 report for dentedIntersections only, or is the case with a crevict gap also addressed?

The reference to WCAP 12522 on page 612 is for the flow stress value only. There are burst data in WCAP 12522 but not for dented tubes. Burst capability for tubes with axial cracking at TSP interrsections is referred to on page 612 also The reference given is WCAP 12349. WCAP 12349 presents data with TSP support including TSP / tubs nominal gap clearance, (See Figure 7 3.)

Question HBO (Pace B-13, Ref 2)

The equaticns on pages 6 13 and 614 are diffeult to follow. The parameter S is not defined, is X the totalang'e of the circumferen%slcrack? lbes this angle include the t

73

lengths of the small unbroken Egaments? Please provide a reference for these equations. Is the equation on Lhe bottom ofpage 6 13 correct, since It is noted that Arcsin(sin (TH2)).TH2?

S is tube stress. X is the 12141 angle of the circumferential unck in degrees including the unbroken ligaments. The equation for stress 'without tigament* has a typographical error. The term 'Arcsin (sin (TK2))* should be 'Arcsin ((sin (TH))/2)* or 8

Arcsin 1

2 4

The equation utilized is from NtJREG/CR 3464.

Duantion 151 rPson B-f t Ref 2) 11 is stated that for angles greater than [ )b,c the mode of failure changes from bending so sxtal'pullseparation. Does this apply only for a single unsegml.ntedcraok, or also for segmentedcracks?

in general, s)veral modes 01 plastic collapse are possible. The mode with the lowest collapse pressure will determine the structural performance. When the not cross sectional area of a tube becomes very small, the limiting pressure is typically determined by an axial pull separation mode in this case, plastic collapse and fracture occur when the average nel section axial stress is equal to the ultimate strength of the material. This criterion can be Wied to either single or segmented cracks. For a single crack the axial separation mode becomes limiting at [ - }b,c as nnled above.

The segmented crack ang'e would be just above [ ]b,c(Figure 611 of WCAP 13034). With 50% wall thickness ligaments, the angle is less ([

}b,c, see Figure 614 of WCAP 13034.)

Question #52 (Page 8-15. Rof 2)

Please comment on the North Anna experience with leakage rates. Given the sizes of measured defects in the tubes, were the observed leak rates at North Anna during the last operating cycle consistent with predictive models forleakage? Has the increase in 74

i leakage before the 1991 Inspection been attributed to one or tnote of the particular tubos that were plugged during the outage? Worso any in situ leaks on individual tubos performed during the outage 10 identity the tube (s) that were the probable source of the leakage? Ilso, what were the sizes of the measureddolects in those tubos?

The North Anna 1 operating loakago experience over the last seven y3ars is suminarlzod in Table 71 in this Section. Operating leakage las been low since 1'985. Axial PWSCC at the TSPs was the cause ni he higher leak rates in 1984 to 1985. Tube pulls in 1985 aldod correlation of the eddy current inspection to the axlal cracks which facilitated identification by inspection of the tubo degradation and removal of the tubos with PWSCC beyond the TSP odge from service, erior to the 1991 refueling outage, the most slgnifice.ntly leeing SG observed was steam generator A (SG.A). The maximum leak 390 from the N 16 monitors was approximately 10 GPD. Prior to performing the eddy curront, inspection a lonk test at approximate!y 450 pl was performed. From this, five tubes in this steam generator (SO-A) were reporM wet or dripping. Tubes from other steam generr.tcrs were also observed leaking. Thase tubos, areas of degradation, and characterization are given in Table 7 2 of this Soction.

The low leakage associated with these indications shows the presence of part throughwall degradatk n of extensive ligaments which can be associated with high burst pressures.

The leakage from these tubes is less than would tio predicted for the associated crack longths due to the expected remaining ligaments. The pretance of ligament in the PWSCO axlal and circumferential cracks is supported by the North Anna pulled tube examinations (WCAP 13034, Section 3) and by WEXTEX UT inspections such as describod in Section 4.5.3 nf the WCAP See the rrsponse to Question #1 for additional discoulon on leakage aM the leak before break considerations.

Questior' #53 (Pace 617. Ref. 2)

How weis the crack opening areas calculated for use In the leak rate predictions tabulatedonpage 6177 The tabulated leak ratos on page 617 in Section 6.5.2 are for circumferential eracks.

The circumferential crack leakage model description was inadvertently.omitted from Section 6.3 The description of the circumferentialleakage model follows:

75

The equation used for calculation of leak rates through circumferential cracks is essentially empirical.11is given by 8,c v

Questbn #54 (Pace & f 7. Ref. 2)

The tabulated leak rate predictions for circumferentialcracks imply that a 100* crack shouldleak at a rate greater than 400 gpd for normaloperation. These predictions imply that the pulled tube R11C14 (through wallangle of 90*) should havs kaked at a rate much greater than the observed rate (no more than 15 gpd). Based on this unfavorable evkience, what argument can be made for LBB of circumferentially cracked tubes?

The throughwall crack angle of tube R11014 was approximately 70' as given la Table 3.1 of WCAP 13034. An additional 20' was nearly throughwall. No large, uncorroded ligaments were present in the 70* throughw.:3 Sector although the tube exam did not attempt to search for very small ligaments. The crack was initiated by closely spaced parallel and nearly aligned microcracks. The corrosion procesh led to lirNog of the microcracks to form a highly irregular, interlocking crack face.

76

Lea %. through the crack tace would have to folow very tutuous path and would be 2xpected to be lower than obtained for circumferential fatigue crac4J v'9d as the primary basis for the circumferential leak rate Inodel. For the R11014 crack face morphology, it Is expected that the leak rate at a given angle would be less than the fatigue analysis modei, which would yield about [

jb,c for a 70' throughwal crack. However, as the crack iongth increases, the crack opening increases such that the leakage path through the crack face becomes less important. The North Anna 1 operating r

leak limit of 50 gpd has been SPt based on low leakage, segraented crack models for PWSCC cracks. The 3 gpd lim t for an ODSCC crack can be expected to ba reached before the 3AP

.O. throughwall crack angle of [ )b,c is reached and certainly before N

a [ ]b,c thrwghwall crack angle is reauhed. See the response to Question #1 for the influence of fatigue on leakage and P.dditional inforamtion on leak before break.

Raistion #SS (Pace 6-17. Ref. 2)

It appears that LF5.~tguments may not apply for ss;mented axialcracks. Tts LBB argument for segmented axial cracks unccaserv atively assumes mean leak rate correlations. In the evaluats.r,:c 'er unsegmented axlalcracks on page 616 a bwer bound or error factor of 0.1' +. wa.<. pt'ed to average leak rates in the LBB evaluatbn.

What is the basis for not alw wq

..s uma error factor for segmented axial cracks?

This lactor can be used to adjust the leak rate curve of Figure 6-16. When this adjustment is made on Figure 6-16, a leak rate of 50 gpd requires a segmented crack abouf 4.0 inches bny. Table 2.4 Indicates that a 4.0 inch bng segmentedcrack would cause tube burst at the SLB pressure, since the criticallength for segmented arial cracks is given as 2.0 incia. Thus LBB criteric are not met.

The segmentt.d crtick model was developed to help reconcile the fact that in service stress corrosion cracks leak at a lower rate thard sharp fatigue cracks of the same total length. Mary of the eat '^ak rate measurements were peric.med on tubes with laboratory-produced fatigue cracks. Part of the reason stress corrosion cracks leak less than fatigue crac,ks is that stress corrosion cracks are often a network of celinear crack segments, hence the physical bas!r of the segmented crack model. Figure 6-17 of WCAP 13034 demonstrates the conservatism in expected leakrates for the segmented model used to establish LBB for Nona Anna 1 as compared to the exoected leakage from l

l 77 1-4

l l

j

\\

l fatigue cracks. The segmented model yleLs leak rates about two decades lower than for l

throughwall, circumferential cracks.The segmented crack model has the advantage of reasonable predictions of leak rates coupled with good strength predictions. The leak befon,-break argument is a defense in depth position and it is not absolute. It is recognized that, wii,1 a range of possble crack morphologies, there may exist cases where the leakap 4. less than that calculated from any given model. It is recognized throughout tN rulear industry that tha occurrence of sogmented stress corrosion cracle in steam generator tubes may or may not result 1,11eak before break in all postulated cases.

'5 wever, for segmented axial cracks, actual plant leakage (leakage detected from leaking

• v os) has been correlated to the measured eddy current crack length. These -

ro Darisons were presented in the July 1989 restart meeting for North Anna 1 and also da Jrsed at the December 2,1991, meeting. The segmented modelleakage prediction is cv ustent with the actual leakage experienced h the plant attributed to axial cracks.

,pplication of the los ir bound error factor results in a gross underestimation of the leakagc. This is demonstrated in Table 7 3 in this Section.

WCAP 13034 rLiles upon a test and analysis 6 sis for demonstrating burst capability and lee' go of tubes with axial and circumferential cracks which meet RG 1.121 criter

• e and of cycle (EOC) crack length distributions projected for 1992 show for i

(

,egmented axial and circumferential cracks that, with the exception of j

sr mm.; axial cracks at the TSP elevations, projected crack lengths are such that, with a tror certainty,3 times normaloperating pressure differential (of 4300 psi)is expected to bo maintained. For segmented axial cracks extending above and below the tube support plate edges at North Anna Unit 1, the maximum projected crack length of 0.82 inches slightly exceeds the crack length that would provide 3 times normal operating pressure differential burst capability [

-]b,c but is well below the 2.0 inch steam line break burst capability length. Pertaining to leak before break considerations, for a typical S/1 aspect ratio crack, on a mean predicted leak rate basis, l-the 50 gpd limit corresponds to a macrocrack containing three microcracks with a total length of(

]b,c. Lengths of cracking extending in excess of 2 inches beyond the edges of the tube support plates are not anticipated during Cycw 9 operation of North Anna Unit 1, and have not been seen in prior inspections.

78

Ouestion #56 (Pace 618. Ref. 2 Pleese discuss the conservatisms usedin the predictions of the ;oatage for SLB pressure.

Estimate the sensitMties ofpredictedleak rates to the assumptions usedin the predictbns. The predictions havr.wumed meen leak rate correlations, and have predicteda SLB leakage of 9.5 gpm. Bounding type wrrelations on page 6 17 suggest a factor of 3.7 on leak rates to conservatively account for uncertainties in leak rate wrrelations. Also, the SLB leakagepredictions have assumed that TSP circumferential through-wallcracks are( )b,c f the measured RPC angles, andhave assumed that o

all WEXTEX and axialcracks are segmented. We have estimated a factor of about S between leakage from segmented versus unsegmented cracks. Thus a bounding leak rate for the SLB could be estimated at 9.5 x 3.7 x S = ;'7S gpm.

The estimated steamline break leakago was established flom the predicted leakage from a single axlal crack leaking at the established 50 GPD limit. This condition was considered most limiting as the SLB leakage is expected to be targest from axial cracks. In the event that more than one axial crack were leaking, (for instance two cracks each leaking at 25 GPD) each crack would be shorter. As the SLB leakage varies with the third power of the crack length, the estimated leakage at SLB conditions in a two crack scenario would be less than that for a single creck scenario.

The mean leak rate from a 0.5 inch single crack (from a 95% curve) leaking at 50 GPD durin] no nal operation (leakage evaluated at lower 95% confidence at normal

]b,c t SLB conditions. Factortra a operation to maximize crack length) is [

a b

]b,c ields a leakage of[

]b,c tgreater l,c by the suggested [

mean of[

y a

than 95% mnfidence. Thus, the [

}b,cvalue contained in our estimate includes the [ ]b.c factor discussed in the question.

With respect to circumferential cracks, the SLB [

}b,c leakrate corresponds io a 180* crack from the segmented crack model usinn a minimum aspect ratio of 4 to 1.

The estimate assumes that this crack is leaking at 50 GPD during normal operation and

]b,c t SLB conditions. The increases to the single crack value of [

a conservatisms of the error in single crack leakage and the effect of segmented cracks are i

not applied redundantly to this estimated leakage.

1 l

l 7-9

WCAP 13034 also describes an extremely conservative methodology to establish an upper bound on SLB leakage. A 49 GPM leakrate from a postulated steam line break event is derived from this extremely conservative methodology, e

l o

7-10

Table 71 North Anna Unit 1 Steam Generator Tube Leakage History 1 Maximum Primary to Outaae Date Reason for..Oldaos Saaondarv Lanknoe January 1984 Forced SG Tube Leak 396 GPD May 1984 Refueling 90 GPD August 1985 Forced SG Tube Leak 213 GPD November 1985

- Refueling -

90 GPD -

April 1987 Refueling 14 GPD February 1989 Forced-Plug Top Release 15 GPD2 Event February 199t Refueling 15 GPD 1 Excludes tube ruptere event due to fatigue, 2 Reflects hig!c,st observed isakage prior to reactor trip and plug top release events, 9

A 7 11 4

_m.

Table 7-2 indications Contributing to 1991 Operatino Leakage of ~10 GPD Steam Generator A r

82E Jotumn _ Elevation Characterization 17 9

1. Hot Large bobbin signal also seen with 8x1.

A single axial crack, approx. 0.36" long'

_i 24 52 WEXTEX 135 degree circumferential crack 8

53 5-Hot Larce bobbin signal,2 axial crackst '

11 66 WEXTEX 189 degree circoinferential crack -

11 71 WEXTEX 125 degree circurnferentialcrack

• Denotes exposed crack length outside the TSP.

t For the R8053 Location, the cracks extended both above and below the TSP and were -

~

reported as b.92* above and 0.65' below (exposed length),

Steam Generator B -

17 9

1. Hot Large bobbin signal also seen with 8x1.

Maltiple axlal crack.

2 86

1. Hot Large bobbin signal Multiple' axial crack.

Steam Generator C 26 60 YEXTEX 204' circumferential crack 7.

- ~

l Table 7 3 Comparison of Predicted and Actual Leak Rates Predicted Leakage Indication Length

-0.25' Segments Scn Column Locafton Bevond TSP Edce (in3 Nominal 95% Conf.

b,C

'~

Steam Generater *B' January 1984 13 34 1 HL 0.59 1 HL 0.77 13 35 1 HL 0.59 1 HL 0.77 13 40 1 HL 0.49 1 HL 0.87 Steam Generator "C" - January 1984 3

10 1 HL 0.69 1 HL 0.57 2 HL 1.09 2 HL 0.97 3

39 4 HL 0.19 4 HL 0.57 5-HL 0.19 5 HL 0.57 Actual Leakage - 396 GPD (1/04)

Steam Generator *A" August 1984 5

40 1 HL 0.54 1 HL 0.77 3

84 5-HL 0.00 4

69 1 HL 0 57 1 HL 0.69 Actual Leakage = 213 GPD (8/85) 7-13

_ COMPARISON BETWEEN PREDICTED G MEASURED LEAK RATES b,c m

5 Q~

T

=

n_

LD 5

~

tu

=

k c

x sk Y

EO J

O

$e w

r4 o

-B e

m G-3 E*

MEASURED LEAK flATE (GPM)-

g

_COMPARISONBETWEENPREDICTEDSMEASUREDLEAKRATESy Ia E

T r

0-Ia N

Y 5

g 35 v

w J

is

=. k en G

b s

k g

O

?

G-E O

Oa E

E HEASURED LEAK RATE (GPN)

,:]

l Figure 7 3 I

Dented Tubo Burst Strength l

l' l

,bd

-l i

EXPOSED CRRCK LENGTH, IN t

7-1 6

Figure 7 4 Leak Rate Versus Circumferential Crack Length 2

b,o Eo CC ew CRRCK LENGTH. INCH

~

4 7 17

. _. _ _ ~

~. ~. -..

. ~. -

8.0 RESPONSESTOSECTION7.0 QUESTIONS Dunstian #57 (Pane 7-2. Ref 2)

In calculating tube eigenvalues and eigenvectors of the tube segments, were the bibwing effects conskiered?.

• addedmass ettectof theprimary water

• effectsof axialtubestress The added mass effects of the primary water are included in the vbration assessments. -

Axial tube stress effects on eigenvalues and eigenvectors have previously been shown to be of second order and therefore will not change the results within Wicable accuracy.

Questian #58 (Psae 72. Ref 2)

Fluid flowing in a non-straight tube causes transverse loading. The tubes may have slight deviations in straightness or be slightly bent due to flowinduced krces. ' For steam generator tubes is this load significant?

- Steam generator tube devlh on in straightness (as well as other straight leg geometrio

_ parameters) and resultant fluid effects are extremely small, These would also lead to -

second or higher order effects in terms of forces on the tubes. Therefore, the numerloal results of the vibration evaluations would not be materially changed if these effects were:

in::luded.=

Ouestiorr #59 (Pace 7-8. Ref. 2) -

^

~

l.

l'

' Does the code FASTVIB consider only stabili,y of a single tube, oris tube 10 tube l..

Interaction treated? If not, where are the arguments supporting the neglect of tube to tubeinteraction?

The FASTVlB code considers [

ja.c -

8;1

Ouestion 980 (Pace 710. Ref. 2)

Does intemalibw in the tubes influence damping? If so, where is it treated?

For vibration assessments it is conservative to neglect any damping due to fluid flow internal to the tube.

Question #B1 (Ptoe 7-13. Ref. 2)

Two methods were apparently used to get tube damping properties, the pluck test method, and the shaker test bandwidth method. Do the two methods yield equivalent dampingproperties?

For lir,,ar systems the two methods should yield the sarne value of Zeta, the percent critic si damping, for damping less than [ ]b,c. For Zeta greater than [ ]b,c, the legarithmic decrement, Delta, as determined by the pluck test, deviates for the approximately linear relationship with Zeta as given on page 714. The exact relationshipis Delta = [

ja,b,c Since the damping of steam generator tubes is in the order of a few percent or less, the deviation above Zeta equal [ ]b,c is not a significant factor in the present application, in nonlinear systems, such as a tube with a throughwall crack, the damping can be vibration amplitude dependent, Therefore, the shaker test method gives [

ja,C 82

Ouestion #82 (P.sae 7-45. Ref. 2)

There is no discussion of the da'dN versus AKcurves used to predict crack gran1h due to ibw induced vibration. Recognizing that the conditions for stress corrosion cracking do exist, how are effects of environmentally enhanced fatigue crack gron1h addressed?

The methodology used to determine the rate of crack gruwth due to turbulence is conservative. Turbulence excitation producos a response that is random in both magnitude and direction. The crack growth method used in the evaluation has productd a crack growth rate that is based upon [

ja,c The da/dN versus AK curves for some materials are available in the ASME curve.

Properties for carbon steel and low alloy materials are available in Section XI of the ASME code, but properties for inconel 600 are not currently available. However, tests have bee 1 performed (Reference 5 and 6) in both hot (600* F) air and hot water.

Figure 81 contains the curve used in the evaluation.

The curve in Figure 8-1 envelopes all data points in the plot. Stress intensity ranges are determined from the far field tube stress and AK solutions. For through walf.

circumferential cracks, the AK solution is provided in Reference 7. These expressions yield AK as a function of the nominal tube stress and crack size.

Note that the fatigue crack growth rate data on which the curve is based were obtained in primary water environments for both pressurized and boiling water reactors. [ ~

ja.c Therefore, enhanced fatigue crack growth due to the existing SCC conditions would not be expected to occur.

8-3 1

Ouestion #B3 (Pace 7-58. Ref. 2)

How were the allowable stress values for flowinduced vibrations established? Were they based on estimated values forsK reshold or fatigue crack growth? What th f

support;ng data were used for estimating AK reshold?

th The maximum turbulence induced FlV stress that would not result in crack propagation was determined [

Ja.c Existing crack propagation threshold data was used to determine [

l l

W ja,e 1

l 84

I ja,c, Since initlation of the circumferential cracks are not fatigue induced but are a result of SCO, the morphology of the crack is such that various small crack Oranches extend along the grain bouncarles. A single crack face, typical of fatigue induced crack propagation, would not be present since SCC is the crack inillator, However, sirce the crack propagation due to FIV is fatigue induced rather then SCC induced, a change in the type of -

crack must occur before fatigue induced crack propagation could occur. As a result of this change, an increase in the crack tip stress intensity is required to provide the necessary drMng force for crack propagation. [

ja,e e

8-5 l

1 I

....._,.7.

m_

i 1

- Figure 81 '

Upper Bound Curve for Crack Growth Used in the Analysis I

_ 'l 3

Curve Used in Analysis -

(Upperbound of Data)- 1 Slope = 3.68 -

t, t

1 t

[~

l l'

t..

I..

r L

--l Reference Fatigue Crack Growth 1.aw for Inconel 600::

~

in a Water Environment at 600F.

8 -

9.0 RESPONSESTO SECTON 8.0 OUEST10NS

_ Question #M (Pace 8-7. Ref. 2)

Given that tubes are fixed at the TSPs due to denting, was the loading on the tubes due to pressure differentials across the tubeshee! under accident conditions included in the analysis?

Figure 9-1 shows the primary, secondary, and differential pressure histories during a typical SLB event. Although this figure is not specific to North Anna, the response histories for th6 steam generators is typical Vibration of the tubes due to secondary flow velocities during a SLB event occur in less than one second from SLB initiation (see pages 8-3 and 8-4, Section 8.1.1, of WCAP 13034). It is readily seen from Figure 9-1 that the change in the difference in pressure across the tubeshest at the beginning of the SLB ovent (time duration from 0.0 to 1.0 secondr) is quite small. Hence the effects of this pressure diffe;ence change on tube vibrations which occur during this time period are negligble.

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Figure 91 Steam Une Break Primary and Secondary Pressures f

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10.0 RESPONSESTO SECTO49.0OUESTICNS Question #65 (Pace 9-1. Ref. 21 For the SSE analysis, a response spectrum (referred to as an

• umbrella

• response spectrum) was used. Presumably, this adds some conservatism to the SSE results.

Please comm3nt on the level of conservatism in the assumed ' umbrella

• response spectrum, and estimate the sensitivity of the evaluations to attemative assumptions.

The umbrella spectrum used in the analysis was developed from plant specific spectra for a number of plants with 51 Series steam generators. The degree of conservatism in the umbrella spectrum varies from plant to plant. There would be less conservatism in the spectra for plants whose spectra comprise part of the boundary of the envelope than for those plants whose spectra lie well below the envelope boundary. A comparison of the umbrella spectra used in the analysis with the North Anna spectra used in developing the umbrella is shown in Figure 10-1. It shows the North Anna spectra to coincide vAth the boundary of the umbrella in the four to five hertz range.

In regards to the sensitivity of the analysis results to using a different (lower) spectra, a method has been developed for approximating seismic loads / stresses from existing time history solutions. The method involves calculating the energy content of the several spectra in question, and then developing scale factors based o't a ratio of the energy content of the spectra. Tio accuracy of the approximation is directly related to the l-similarity in the frequency content of the spectra. If one set of spectra is shifted l

relative to the other in the frequency domain, then the accuracy of the approximat6n drops off. Calculating the energy content of the umbre!!a and North Anna spec. ras and ratioing the results shows the umbrella spectra to be higher than the Nonh Anna spectra by 1.477. Thus. if the North Anna spectra alone were used, the resulting stresses / TSP Icads would be expected to be reduced by as much as one-third (1.0 - 1.0/1.477).

Question #86 (Pace 9-2. Ref. 21 The method used to assess tube failure (during an SSE) in the vicinity of a circumferentialcrack seems to be invalid. In the vicinity of a circumferentialcrack, a i

very short beam of very smallmoment ofinertia is incorporatedinto the model. For a 10-1

l Very long through-wall crack, this would be equivahnt to placing a hinge at the crack location. For SSE bading, the bending moments at the crack location were shown to be less than those of an unilawed tube. It was subsequently concluded, that the flawed tube could easit' 'urvive the postulated SSE. ll this logic is correct, then flaws will(the bigger, the better) enhance tube survivalin an SSE. Please clarify this situation which is ditficult to understand.

Due to the dynamic nature of the SSE loading, the response of the tube is a function of the frequency content of the tube versus the fraquency content of loading, as well as the source of the loading. The dynarnic lesponse of the unflawed tube and the corresponding bending stresses are primarily a function of the overall bundle response, rather than the response of an individual tube. The presence of the circumferential crack, which approaches a hinged joint for cracks heving a high circumferential extont, tends to isolate the flawed tube from the overall bundle response, and the response is based on the mass and stiffness properties of the flawed tubo relative to the SSE excitation. The results of this analysis show the single tube response to be less than the overall bundle response.

Regarding the issue of "the bigger, the better" in terms of crack size, that is not necessarily the case. First, as stated above, the response of the tube is a function of the frequency content of the loading as well as the froquency of the tube. As the crach size changes, so too does the frequency content of the tube. Although a larger crack may result in reduced response (bending moments), the stress necessary to propagate the crack also reduces with increased crack size. Thus, although the bending stress mcy be l

lower, the corresponding crack propagation may be higher. In performing the analysis, the maximum observed crack size was selected for the analysis on ihe basis that this formed a bounding case. Selection of a smaller crack size might have resulted in higher projected crack growth, but as the crack size approached the larger value, the tube response would converge to that calculated for the larger crack angle.

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r APPENDIX A REQUEST FOR ADDITIONALINFORMATION 9

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UNITED STATES NUCLEAR REGULATORY COMMISSION 2

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WASHINGTON, D. C. 20E5 November 7, 1991 Docket No. 50-338

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Mr. W. L. Stowart

. Senior Vice President - Nuclear Virginia Electric and Power Company Rec'd. NOV 2 51991 S000 Dominion Blvd.

Glen Allen, Virginia 23060 Nuclear Operations near Mr. Stewart:

IlCenSing Supervisor RE0llEST FOR ADDITICHAL INFORMATION, STEAM GENERATdR$ -(SGs)

SUBJECT:

NORTH ANNA POWER 51 ATION, UNIT NO.1 (NA-1) (TAC NO. 8070?

By letter dated August 6,1991, you submitted an analysis supportino full-tenn operation of the NA-1 SGs for the current operating cycle. Your submittal included a Westinghouse report (WCAP-13034) providing a detailed justification for full-cycle operation.

The NRC staff and its consultant, Battelle-Pacific Northwest Laboratory (PNL),

have reviewed your submittal and have identified a number of questions concerning the Westinghouse report which must be resolved before the staff and PNL can complete their review. The request for additional information is provided in the enclosure to this letter.

We request t'nat you expeditiously address the request for additional information and give us your schedule for providing your responses to the NRC. Please notify us of your schedule _ as quickly as possible.

Please note that the enclosure contains proprietary information to be withheld from public disclosure pursuant to 10 CFR 2.790.

l This requirement afftets fewer than.10 respondents-and, therefore, is not subject to Office of Management and Budget review under P.L.96-511.

Sincerely,

]9 H-Leon B. Engl Pr jec Manager Project Direc ra e 11-2

' Division of Rea r Projects - 1/II Office of Nuclear Reactor Regulation

Enclosure:

Request for Additional Information (Proprietary) cc w/o enclosure:

See next page l

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-l Mr. W. L. Stewart North Anna Power Station Virginia Electric & Power Coir.pany Units 1 and 2 CC:

Mr. W1111ain C. Porter, Jr.

C. M. G. Buttery, M.D., M.P.H.

l County Administrator State Health Comissioner Louisa County Office of the Comissioner P.O. Box 160 Virginia Department of Health Louisa, Virginia 23093 P.O. Box 2448

)

Richmond, Virginia 23218

" Michael W. Maupin Esq.

1 Hunton and Williams Regional Administrator, Regior !!

P. 0.' Box 1535 U.S. Nuclear Regulatory Comission Richmond, Virginia 23212 101 Marietta Street, N.W., Suite 2900 Atlanta, Georgia 30323 l

Dr. W. T. Lough Virginia Stath Corporation Commission Mr. G. E. Kane, Manager Division of Energy Regulation North Anna Power Station P. O. Box 1197 P.O. Box 402 l

Richmond, Virginia-23209 Mineral, Virginia 23117-Old Dominion Electrh coorerative Mr. J. P. O'Hanlon 4201 Dominion Givd.

Vice President - Nuclear Services Glen A11.n, Virginia 23060

. Virginia Electric and Power Company' 5000 Dominion Blvd.,

Mr. E. Wayne Harrell Glen Allen,-Virginia 23060 l

Vice President - Nuclear Operations Virginia Electric and Power Co.

Mr. Martin Bowling-5000 Dominion Blvd.

Manager - Nuclear Licensing Glen Allen, Virginia 23060 Virginia Electric and Power Company 5000 Dominion Blvd.

Mr. Patrick A. 0' Hare Glen Allen, Virginia 23060 Office of the Attorney Genert i Supreme Court Building-101 North 8th Street F :5mond, Virginia 23219 Senior Resident Inspector North Anna Power'Statie, i

U.S. Nuclear Regulatory Comission i

Route 2, Box 78 Mineral, Virginia 23117 1

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5 ENCLOSURE 1 REQUEST FOR ADDITIONAL INFORMATION ON It0RTH AWNA UNIT 1 STEAM GENERATOR OPERATING CYCLE EVAlb.STION Note:.The foilowing. questions.and com ants apply to Westinghouse report NSD-TAP-1093/SG 91-07-043

.(Proprietary) which was submitted by letter dated

- August 6,1991 by Virgfraa Electric Power Company.

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GENERAL COMMENT

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The argument for leak before break (LBB) is suspect for North Anna. The e

tube pulled in 1991 had a large angle of circumferential cracking, yet leaked at a very low rate compared to the rate predicted by Westinghouse (less than 15 gal / day versus 460 gal / day). Thus the concept of defense in depth as provided by LBB cannot be made for circumferential cracks.

The number of pulled tubes at North Anna have been few in number.

Selected tubes appear to be those with strong ET indications.

As such the selected tubes provide a weak basis for validating field ET-reliability with destructive examinations. Destructive examination of more pulled tubes could greatly enhance confidence in field ET inspections. The semple of tubes should include locations with no' ET indications, but where the potential for cracking is believed to be-high.

Projections for end-of cycle crack angles assumes only single cracks at a given-tube cross-section. The-tube pulled-in 1991 had two cracks that together gave a much greater crack angle than shown in any of the crr k.

size distributions presented in'the report.. The assumption of one en.ck will lead to.unconservative calculations for probabilities of tube rupture.

A 100% probability of detection-(P00) has-been. assumed by Westinghouse for c'eep (50% of wall) and long (greater than 75*) circumferential cracks. Thus, it is assumed that there is zero probability of any cxisting through wall cracks greater than 73* at the beginning of the

~

operating cycle. No basis is given for assigning a 100% POD for these long cracks.

It is likely that some long cre.cks will be difficult to detect (due to noise, surface conditions, denting, etc.). - Recognizing that long cracks have occurred-at North Anna, we suggest that Westinghouse estimate the probability that some long cracks remained unplugged after the 1991 inspection.

It'is recommended that structural integrity evaluations address the prababilistic implications of such cracks.- This seems particularly icporte tldue to the LBB situation.

The Westinghouse report discusses flow induced fatigue of. tubes with

-long through-wall cracks, but does not discuss'the fatigue crack growth used-to ca'c.ulate critical crack sizes.

Effects of data (AK flow indggsh9da)tions coulo be sensitive to assumed-values of-l.

In contrast the report has extended discussions of other AKfaggghguNhasdampingfactors.

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iECTION 2.0

SUMMARY

N'O CONCLUSIONS Page 2.)

The bottom.line conclusion of this report is that a mid cycle inspection is not needed, beccuse no cracks will be so large that any tubes will rupture due to operating pressure, accidents ir.cluding steam line breaks, or vib.*ational fatigue from flow induced sources. Please compile a list the major assumptions made in the evaluation, and estimate the sensitivity of the evaluation to changes 1: these assumptions.

For example.

What is the effect of increasing the threshold of crack i

f detection (e.g. 60% versus 50% through wall depth)?

What is tho effect of assuming two cracks at TSP e

intersections versus only one crack?

What is the effect of decreasing the assumed upper bound on proh bility of detection (for long and deep cracks) from 100% to say 95%?

What is the effect on tube vibrational f ailure of increasing threshold by a factor of 2.07 AK Wiiat is the effect of increasing the aswmed length of the 4ncividual segeents of the WEXTIX cracks by a factor of 2.07 Page 2 1 If a mid. cycle inspection is not necessary, then what would be the maximura period of time between inspections that woulo Live acceptable risk?

Page 2 10 What is the basis for expecting that all MCI will occur below the tube sheet?

Ir this regard, the third paragraph of this page was difficult to interpret, Please clarify the wording of this paragraph.

Page 2-11 The possibility of mixed mode cracking (cracks with both axial and circumferential components) is dismissed. The argument is made that Axial and circumferential cracks will be offset by 90* (minor axis versus major axis of ovalized tube).

Since circumferential cracks can exceed an angle of 90* (as evidenced from the pulled tube R11C14), please explain why mixed mode cracking cannot occur?

Since 10 axial cracking and 00 circumferential cracking are known to occur at the same axial locations in the expansion transitions at McGuire, what is the basis for assuming a similar scenario-cannot occur at North Anna?

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SECTION 3.0 PUI. LED TUBE EXAMINATIONS 4

Page 3 1 While tubes at North Anna have been pulled from the steam generators for examination, these tubes have been few in number.

Also these tubes appear to be those with strong ET indications.

Please explain why such a selection of tubes provides anything other than a weak basis for the crack models described on page 2.4 and for validating field ET reliability with destructive examinations. Do future plans for tube removals include tubes without indications, but from a zone where cracking is Lacwn to occur?

Page 3 1 Only one tube was pulled after the 1991 inspection. What was the basis for selecting the particular tube (RllCl4)? Were there any

' worst case' features for this tube (such as largest RPC angle) evident from the field ET inspection?

Page 3 7 A number of assumptions regardin0 cracl. characteristics are made such as ligament dimensions for WEXTEX cracks and the 60% through-wall extent of TSP RPC crack angles. These assumptions are based on examinations of pulled tubes. How many data points and from what plants support these assumptions? Please cite all relevant data used to support these assumptions.

Page 3 7 It is stated that the destructive examination results on tube R11C14 support modeling of the RPC angles, whereas there appears to be no mention of evaluations to support thigeonclusion? What is the basis for this conclusion? Is the(

Tractor actually used in eny of the Section 5.0 crack distribution estimates?

Page 3 10 Figure 31 shows the e lecumferential cracking seen by destructive examination at the TSP c. pulled tube R11Cl4. Compare in detail the field El estimates of flaw lengths and depths with the results of destructive examinations. Provide ET data displays (as in l

Figure 4 16) for this TSP location.

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Page 3 10 The cracking of Figure 3-1 and the ET performance as indicated in Table 2-1 would suppo t a detection threshold no better than 60%

through wall depth. What is the basis for assuming a 50%

detection threshold?

l Page 3 10 Figure 3 1 shows part through circumferential cracking 100% around the tube with superimposed through+ wall cracking. Hov does the idealized model of ODSCC based on RPC angles compare with the actual cracking observed from examination of the pulled tube? The I

oulled tube shows two symmetrically opposed cra.ks, whereas the l

idealized model assumes a single crack on one side of the tube.

How do the burst strengths and leak rate predictions compare for l

these two different patterns of cracking?

I 3

SECTION 4.0 EDDY CURRENT DATA REVIEN Page 4 1 What differences existed between the 1999 and 1991 inspection methods and data interpretations? Give specific reasons why circumferential defects were not detected in 1989, but were later in 1991 found to exist after looking again at the 1989 inspection data.

Ptge 4 1 How were the data analysis guidelines modified to account for the lessons learned from the 1991 IS!? Please provide a copy of the current data analysis guidelines.

Page 4 1 In reference to Table 4 1, can it be assumed that all tubes with WEXTEX degradation were plugged, without regard to the measured length or depth of the degradation? What specific criteria are being used to set an ET signal threshold for classifying a WEXTEX i

transition degraded?

Page 4 4 In the measurement of ligament lengtns between regions of circumferential cracking, what specific criteria were used to decide that the dros in signal was sufficient to conclude that the ligament was uncracted? Have ISI data and conclusions regarding ligament lengths for MCI been validated with pulled tubes? How would the conclusions from the. assessments of tube integrity o

(Sections 5 and 6) change if a small f action of the tubes (say 5

)

to 10%) of the tubes were to give false evidence of uncracked ligaments between regions of circumferential cracking?

Page 4 6 The bobbin coil inspection is reported to be insufficiently effective to ensure detection of axial cracks confined within the TSP. How effective is the 8xl probe in detecting such axial cracking within the TSP 7 How does the 8xl probe compare to the bobbin coil and RPC probe in detecting axial cracks both within and outside the TSP 7 Page 4 6 Please clarify the following point. Was cracking outside'the TSP usually or always associated with cracking within the TSP? Were there some cases where cracking occurred outside the TSP without associated cracks within the TSP 7 What has been the olugging practice at North Anna regarding cracks that are entiraly within the TSP? Are such cracks plugged only if the indicated depth erceeds 40% of the wall thickness?

l' Page 4 8 it is stated that an additional 433 TSP intersections were.

inspected with the RPC probe. Were these inspections.in addition l /

to those described on page 4 17 What was the basis-for selecting these 433 intersections? Was it a random sample? Or was it a criteria such as the extent of denting at the-intersections?

Page 4 8 No circumferential' cracks were reported in the 433 tubes inspected by the RPC probe, but were any axial indications found?

If so, how were these indicAttons dispositioned?

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Page 4 9 What is the reason for detecting more cracks at the top versus bottom of the TSP? Are the corrosion conditions different at the tap *tersus bottom location? Is the inspection more effective / sensitive in detecting cracks at the top of the TSP 7 Page 4 12 1h6 structural integrity assessment assumes that "long" defects ti.at are greater than 50% of the wall in depth will be detected with IQM probability. What evidence is there from performance demonstrations or other sources to support this 100% value and/or other very high level for the probability of detection? Are there any data from performance demonstrations to support specific values of high (say greater than 90%) detection probability? How would the conclasions of the structural integrity and reliability i

evaluations change if the upper boured on detection probability were less than 100% (say 95%)?

t Page 4 12 It il stated that all tubes with circumferential indications are pluged. What is the estimated reliability of detecting circuniferential cracks, and what evidence is available to suppnrt this reliability estimate? What is the estimated reliability of classifying indications as circumferential cracks, and what evidence is available to support this estimate?

Table 4 1 What is meant by "above tube sheet"? Does this refer to degradation in the sludge pile region of the generator?

Table 4 4 Were there any TSP locations where axial indications were detected within the TSP (by the 8x1 probe) and where these indications also extended (detected by bobbin coil inspection) beyond the TSP 7 If so, how are such locations reported in Table 4 47 Do the bobbin coil findings have hierarchy over the 8x1 probe findings in the reporting scheme of Table 4 47 Table 4-4 What is meant by " percent depth calls by RPC'? Were all the tubes with TSP indications as reported in Table 4 4 plugged?

Table 4 4 If volumetric signals are found at support plates, to what type of degradation were these signals attributed? Were these signals interpreted as evidence of intergranular attack?

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SECTION 5.0 PROJECTED E0C CIRCUNFERENTIAL CRACK DISTRIBUTIONS Page 5 5 This report makes assumptions about details of crack morphology based on data from examinations of pulled tubes. Examination of pulled tube R11C14 would support the assumption of two circumferential cracks at TSP locations. Why was only one crack of depth greater than the 50% threshold assumed, rather than two cracks as suggested by the data from pulled tubes?

. Page 5 6 Please clarify the statement ' based on assessin the sensitivity of these projections". To what are the project ons sensitive?

Page 5 6 The ET uncertainties in the 8x1 data are based on comparisons with

)

• true' crack lengths taken from RPC data. Do the limited metallographic data from pulled tubes support these estimates of ET uncertainties?

Page 5 15 Table 5.2 suggests that in some cases the observed 1989 to 1991 growth was < 0 "htts', meaning that some indications appeared to decrease in size. How many of such

• negative growth' indications were observed and what were the niagnitudes of such

• negative growth *?

Table 5.9 (P implies that during the current operating cycle there N column) bability that a 1st span will fail due to Page 5 22 a 1% pro vibration of a tube with a WEXTEX crack.

Is this a correct interpretation of this table? Is this probability of one tube rupture per 100 reactor operating years ccdsistent with requirements for safi operation?

Page 5 29 The lettering of the lower scale is missing on Figure 5 7 plot of cumulative ET uncertainty, What are the labels and numerical-values for this scale?

Page 5 38 Please justify the conservatism of the projected 1992 distribution of RPC angles given in Figure 5 14. Compare these TSP circumferential cracks with the measured 1991 RPC angles of Figure 5 12. Why is the maximum projected angle for 1992 (185*) less than the maximum angle (215*) measured in 19917 According to Table 2.1 the measured angle for pulled tube R11C14 had a total angle of 232' (two cracks of 158' and 74*).

This-angle is not included in.the distribution of Figure 5 12. Since tube rupture is a function of total crack angle, why are not total crack angles used as the basis for crack angle distributions?

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Page 6 2 Describe test specimen configuration, test setup, test temperature and other relevant de\\ ails of the burst tests.

is there another document (s) that Nr. % provided that gives additional detatis of burst test result; 43d *perime tal techniques? Were the tests i

discussed on pagt TQ penme specifically for purposes of the North Anna evalu m rq

. Page 6 5 Does the leakage model wi.n flashing liquid have r-levance to i

leakage at opsrating corJitions, or only to the steamline break accident?

Page 6 10 is there a document that gives further information on details of the CRACKFL0 computer code? Is this a public domain code, or is it a code developed and proprietary to Westinghouse?.

j Page 6 10 References in the text to' Figures 6 7 and 6 8 should be corrected i

to refer to figures 6 6 and 6 6.

Page 6 10 Please describe the types of cracks used in the leak-test specimens of Figures 6 5 and 6 6.

Provide a reference for the leak rate data of Figures 6 5 and 6 6.

Were these tests performed on steam generator tubes or on larger diameter piping specimens?

.t What types of cracks were in the specimens (i.e. machined defects stress. corrosion cracks, etc.)? Were the defects of the leak-tests representative of the crack morphology for cracks in North Anna tubes?

Page 6 11 Please provide. references-for the leak rate data referred to as the ' crack data base'.

Page 6 12 Are the burst data in the WCAP 12522 report for dented-intersections only, or is the case with a crevice gap also addressed?

Page 6 13 The: equations on pages 6 13 and 6 14 are difficult'to follow. The parameter S is not defined..- Is X the total angle of the

-circumferential crack?- Does-this angle include the lengths of the small unbroken ligaments? Please provide a reference for these equations.

Is the equation on the bottom of page 6 13 correct, since it is noted that Arcsin (sin (TH/2)) = TH/27

]6.c Page 6 14-It is stated that for angles greater than the mode of failure changes from bending to. axial pull separa on..:Does this apply only for a single unsegmented crack,:or also for segmented cracks?

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Page 6 15 Please coment on the North Anna experience with leakage rates.

Given the sizes of measured defects in the tubes, were the observed leak rates at North Anna during the last operating cycle consistent with predictive models for leakage? Has the increase in leakage before the 1991 inspection been attributed to one or more of the particular tubes t1st were plugged during the outage?

Were any in situ leak tests on individual tubes performed during the outage to identify the tube (s) that were the probable source of leakage? If so, what were the sizes of the measured defects in these tubes?

Page 6 17 How were the crack opening areas calculated for use in the leak rato predictions tabulated on page 6 177 i

Page 6 17 The tabulated leak rate predictions for circumferential cracks imply that a 100* crack should leak at a rate greater than 400 gpd for normal operation. These predictions imply that the pulled tube RllCl4 (through wall angle of 90') should have leaked at a rate much greater than the observed rate (no more than 15 gpd).

Based on this unfavorable evidence, what argument can be made for LBB of circumferentially cracked tubes?

Page 6 17 It a) pears that LBB argt..nents may not apply for segmented axial cracts.

The LBB argument for segmented axial cracks unconservatively assumes mean leak rate correlations.

In the evaluations for unsegmented axial cracks on page 6 16 a lower bound or error factor of 0.1653 was applied to average leak rates in the LDB evaluation. What is the basis for not also using this same error factor for segmented axial cracks? This factor can be used to adjust the leak rate curve of Figure 6 16. When this adjustment is made on Figure 6-16, a leak rate of 50 gpd requires a segmented crack about 4.0 inches long. 'iable 2.4 indicates that a 4.0 inch long segmented crack would cause tube burst at the SLB pressure, since the critical length for segmented axial cracks is given as 2.0 inch. Thus LBB criteria are not met, i

Page 6-18 Please discuss the conservatisms used in predictions of the leakage for SLB pressure.

Estimate the sensitivities of predicted leak rates to the assumptions used in the predictions. The predictions have assumed mean leak rate correlations, and have predicted a SLB leakage of 9.5 gpm. Bounding type correlations on page 6-17 suggest a factor of 3.7 on leak rates to conservatively account for uncertainties in leak rate correlations. Also, the l

SLB leakage predictions have issumed that TSP circumferential through wall cracks are[ d axial cracks are segmented.]bfthem assumed that all WEXTEX an We have estimated a factor of about 5 between leakage from segmented t

versus unsegmented cracks'. Thus a bounding leak rate for the SLB could be estimated as 9.5 x 3.7 x 5 175 gpm.

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$ECT10N 7.0 Tutt V!BRATION A55E5$MDITS 0

4 Page 7 2 in calculating tube eigenvalues and eigenvectors of the tube egments, were the following effects censidered?

added mass effect of the primary water e

effects of axial tube stress Page 7 2 Fluid flowing in a non straight tube causes transverse 'sading.

The tubes may have slight deviations in straightness or oe j

slightly bent due to flow induced forces.

For steam generator tubes is this load significant?

s Page 7 6 Does the code FASTV!B consider only stability of a single tube, or is tube to tube interaction treated? If not, where are the arguments supporting the neglect of tube to tube interaction?

page 7 10 Does internal flow in the tube influence damping?

If;so, where is it treated?

page 7 13 Two methods were esparently used to get tube damping pro>erties.

the p'iuck test motiod, and the shaker test bandwidth met 1od. Do the two methods yield equivalent damping properties?

Page 7 45 There is no discussion of the da/dN versus AK curves used to predict crack growth due to flow induced vibration.

Recognizing that the conditions for stress corrosion cracking do exist, how are effects of environmentally enhanced fatigue crack growth-addressed?

Page 7 56 How were the allowable stress values for flow induced vibrations established?

Were they based on estimated values for AK for fatigue crack growth? Whatsupportingdatawereusebhf8fhold estimating AKthresholdi e

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SECTION 8.0 EVALUATIM OF POTENTIAL CRACK PROPASAT!M UNDER SLB FL W CON 0!f!MS Page 8 7 Given that tubes are fixed at the TSPs due to denting, was the loading on the tubes due to pressure differentials across the tube sheet under accident conditions included in the analysis?

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Page 9 1 For the SSE analysis, a response spectrum (referred to as an

' umbrella' response spectrum) was used.

Presumably, this adds some conservatism to the SSE results. Please coment on the level of conservatism in the assumed "umbre114' response spectrum, and estimate the sensitivity of the evaluations to alternative assumptions.

Page 9 2 The method used to assess tube failure (during an SSE)d.

in the vicinity of a circumferential crack seems to be invali In the i

vicinity of a circumferential crack, a very short beam of very e

small moment of inertia is incorporated into the model.

For a very long through wall crack, this would be equivalent to placing a hinge at the crack location. For SSE loading, the bending momenta at the crack location were-shown-to be less than those of i

an unflawed tube.

It was subsequently concluded, that the flawed tube could easily survive the )ostulated SSE.

If this logic is correct then flaws will (the )igger, the better) enhence tube survival-inanSSE.

Please clarify this situation which is difficult to understand.

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1 APPENDIX B INSPECTION GUIDELINES t

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VIRGINIA POWER CORPORATION NORTH ANNA UNITS 1 & 2 STEAM GENERATOR ED0Y CURRENT I

DATA ANALYSIS PROGRAM JUNE, 1990 REVISION 1 Prepared By:

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,I 7~/I'D Level !!!, Westinghouse Approved By:

k 3-2. L - 90 Level 111. Virginia Power SNOC Approval:

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TABLE OF CONTENTS NORTH ANNA UNITS 1 & 2 STEAM GENERATOR EDDY CURRENT DATA ANALYSi$ PROGRAM SCOPE OF PROGRAN i

ATTACHMENTS Eddy Current Data Analyst Qualification Prograa Protocol of Data Evaluation Analysis Rules Bobbin Coil

!!!.1 Glossary of Terms

!!!.2 Initial Step and Glossary of Terms

!!!.3 Frequencies 111.4 Analysis Criterta~

1

!!!.S Classification Criteria at TSP's and TTS'S 1

Figure 1 Indication Reporting Parameters

!!!.6 Length Measurement Rules Figure 2 Schematic of E/C Distance Measurements l

!!!.7 Pluggables for Length, Selection Criteria.

111.8 Primary / Secondary Analyst's Responsibilities i

III.g Primary /, Secondary Resolutions

!!!.10 Bobbin Coil Calibration

!!!.21 Graphics.

Bobbin Coil with MRPC Support l

IV.

Analysis Rules 8x1 Coils V.

Analysis Rules - RPC VI.

Analysis Guidelines ZETEC Computer Data screening Vll.

8.Co11 Profilometry VI!!.

Tube Support Plate Heat Treat Analysis Appendix A WESTINGHOUSE GENERIC DATA ANALYS!$ GUIDELINES,.REV. 4 f

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SGPM5018:2 I

REY. 1 NORTH ANNA UNITS 1 & 2 STEAM GENERATOR ED0Y CURRENT DATA ANALYSIS PROGRAM (EDAP)

SCOPE OF PROGRAM The analysis guidelines originally developed for the May 1987 North Anna Unit 1 inspection and expanded / clarified during the July 1987 outage at North Anna 1 are the basis for this combined Analysis Guideline document for the North Anna site. The October 1987 inspection of North Anna Unit 2 showed evidence of indications similar to those in North Anna 18 thus, the same guidelines were deemed applicable to Unit 2 ss well.

This revision expands the guidelines to define rules for monitoring of ODSCC confirmed to be present in other steam generators of similar design as those installed at North Anna.

To ensure that the evaluation of eddy current data from North Anna steam generators is of the highest quality and remains consistent with previous inspections, a program with the following five elaments is being continued from previous North Anna outages:

1.

Each data analyst will be required to demonstrate their ability to interpret the data correctly.

2.

Data evaluation will be performed by two analysts working totally independent of each other.

3.

A resolution book containing discrepancies between primary and secondary. analysts, subsequent resolutions,.and associated graphics will be prepared for review by the Virginia Power Level !!!

representative.

SGPMS018:3

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REY. 1 4.

_A document, ' Analysis Rules.' has been written which provides instructions on how to interpret signals specific to, and those that may be present in North A r t steam generators. These rules are based on facts learned from pra oms examinations and tube pulls.

Complex indications classified as Ol's, PI's, and TI's shall be considered relevant until demonstrated to be nonrelevant by RPC data.

The dotatis of these elements are contained in the following eight attachments:

1.

'E00Y CURRENT DATA ANALYST QUAllFICATION PROGRAM'

!!. ' PROTOCOL 0F DATA EVALUATION" Ill. 'ANALY$l$ ROLE $1 BOSSIN C0!L' IV. 'ANALYS!$ RULES Sal COIL $'

V.

'ANALYS!$ RULES RPC'-

VI. 'ANALY$l$ GUIDELINES ZETEC COMPUTER DATA SCREENING Vll. 'ANALY$l$ RULES 8 C0ll ?R0FILONETRY VI!!. 'ANALY$15 GUIDELINES TUSE $UPPORT PLATE HEAT TREAT J

k Future inspections of North Anna Unit I any also require the analysis of data aftertheheattreatmentoftubesupport-plates (TSP's). The guidelines for the analysis-of TSP heat treat data are being incorporated herein for information and employment during any outage in which TSP heat treatment has-been performed.

SGPMS018:4

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t ATTACHMENT !

REY. 1 NORTH ANNA UNITS 1 & 2 EDAP I. EDDY CURRENT DATA ANALYST QUALIFICATION PROGRAM The evaluation of eddy current data from North Anna Steen Generators for evidence of tube degradation will consist of data from three rtifferent eddy i

current probe types standard bobbin, 8x1, and rotating pancake coil (RPC).

This program requires each analyst to demonstrate the ability to interpret, for degradation, the data generated by specific probe types before being allowed to evaluate current data. An analyst is not required to qualify in all three methods,butmayonlyinterpretdatagatheredbytheprobetype(s)forwhich they have been qualified.

An analyst is ' qualified' when a practical test derived'from previous inspection data has been taken and passed. An analyst who fatis initial testing may be retested one time.

If the analyst again fatis, evaluation of eddy current data taken with that specific probe type will not be allowed. The analyst will be expected to follow the ' Analysis Rules' during the testing process. This document is the basis of data interpretation used by the data analyst.

Its directions are based upon data obtained from previous examinations and tube pulls. A Virginia Power Level !!! (Eddy Current) will either develop or approve all tests.

An analyst fails to qualify primarily by not identifying two or more of the pluggable tubes contained within the test, or by not identifying an excessive amount of indications below the plugging limit, Points will not be deducted for administrative errors; however it is advised that~close attention be paid to test extents, locations, and proper classification of-indications both' while.

taking the performance demonstration and analysis of actual inspection data.

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.ATTACRMENT !

REY. 1 A written record will be established of an analyst's test rssults which will serve as evidence of qualification. This recoro will be considered the same as a nondestructive examination qualification documents and therefore, is a quality assurance record.

Computer assisted analysis tools may be used in the data evaluation process, provided the tools are subjected to qualification. Qualification will be l

demonstrated by the tool's ability to pass a perfomance demonstration similar in nature to the manual operation.

For example, if the tool's purpose is to eliminate nonrelevant signals for evaluation by an analyst, then the tool must present all relevant indications on the test to the analyst. Similarly, the qualification of a tool must be documented and the documentation will be considered a quality assurance record.

Additional data analysis, such as 8 coil profilometry, tube support plate heat treatment, dent sizing, etc. may also be an integral part of an outages programs however, testing of data analysts will not be required for any analysis that is not related to tube degradation. Analysts who perform any of these analyses must be familiar with the analysis techniques prior to commencing analysis, i

The specific analysis rules for bobbin, 8x1, and RPC are contained in subsequent attachments. Should a situation arise that is not covered by the l

specific rules, then the guidelines of Appendix A (Westinghouse Generic Data Analysis Guidelines) shall be used for analysis disposition, reporting, resolution, and data management functions.

l SGPH5018:6

ATTACHMENT !!

REV. 1 L

NORTH ANNA UNITS 1 & 2 EDAP PROTOCOL 0F DATA EVALUATION 1.

All degradation data will be evaluated by two different data analysts who have been qualified in accordance with the " Eddy Current Data Analyst i

Qualification Program."

2.

The evaluation by the two data analysts will be totally independent of each other. Each analyst will reach a decision and document the results on the respective final reports. Consultation with another analyst is allowed, but not with the analyst making the independent evaluation.

3.

~.onflicts in interpretation shall be resolved by a shift lead analyst reviewing the signal in question.

If the shift lead analyst considers that the sigal may present a relevant indication, the _ signal will be classified as required by the " Analysis Rules.' If the shift lead analyst decides the signal does nel represent a relevant indication, agreement of an additional analyst is required before the signal can be classified as nonrelevant.

Failure of shift lead and another analyst to agree will result in the signal going to the overall lead analyst for final resolution.

4.

All signals going to the overall lead analyst for final resolution will be presented to a Virginia Power Level !!! for concurrence.

In addition, a resolution book previously described will be prepared for review by the Virginia Power Level !!!.

5.

If a signal is-classified as a distorted indication (D1), possible indication (PI) or a tube sheet indication (TI), it may only be evaluated as nonrelevant based upon data obtained from a rotating pancake coil (RPC).

6.

Analysis of nondegradation data may be limited to a single anal) sis upon agreement by the Virginia Power Level !!!.

SGPMS018:7

ATTACHMENT !!!

REY. 1 I

NORTH ANNA UNITS 1 8 2 EDAP

!!! ANALYSIS RULES 80881N C0!L

!!!.1 GLOSSARY OF TERMS A.

RELEVANT Any indication that is associated with In Service tube wall degradation. Examples _ PWSCC cracking at dented TSP's or at TTS transitions: 00$CC cracking at non dented TSP's or TTS transitions.

J 2

Pitting, Thinning, Wastage, AVB wear.

8.

NON RELEVANT - Any_ indication that is associated with the manufacturing process or related to secondary side chemisty/ deposits.

Examplis: M8M's, M8's Sludge and Copper _ deposits. Dents, Permeability, l

C.

SPECIFIC LOCATION TECHNIQUES - Specific Analysis, Techniques;(described

]

herein) are required at' the following locations:-

7 1.

Any indication thatLis located within +/ 2. inches of the TSP center 1tne.

2.

Any' indication that is located within.+3/ 2 inches of the TTS-l signal'.

l ALLOTHERLOCATIONS?ny;indicationthatliprimarily_locatwthway-D.

A from the above-defined specific locations.' This is also generally-i

_known as-a MlBlBLtype indication.

Examples are defined below, E.

005CC Stress Corrosi.on Cracking associated with non dented or~

i slightly dented intersections. 00initiatepadusuallycontained within,: but may extend beyond the TSP region. May be found at hot-legi TSP's. and possibly the upper supports of the cold leg., 00$CC has -

~

also been observv at the TTS region.

' SGPMS018:8

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ATTACHMENT !!!

REV. 1 F.

PWtCC Stress Corrosion Cracking associated with deformed intersections at the Wextex expansion at the TTS, dented TSP's, and low row U bend transition areas. Nonsally 10 oriented and not easily detected until the signal overrides or extends beyond these deformed regions. Can be found at hot leg TTS, hot leg TSP's, and low row U Bends.

May also be found at upper cold leg TSP's if dents exist.

G.

NORMAL - Any indication not associated with SCC: 1.e., Pitting.

Thinning, Wastage, or AVB wear. Pitting may be found at the cold leg TTS in the midst of a copper or sludge deposit, or at.the hot leg TTS awayfromthehighstressregion(westexexpansiontransition):

whereas wastage is generally associated with phosphate chemistry corrosion. Thinning is norwally found at the lower two cold leg support plates of the periphery, and AVB wear is found in the higher-row U Bend regions.

!!!.2 INITIAL SETUP A.

Measurement of indications shall be in 1/100th of an inch (with a nominal 50.50 inch TSP to TSP dimension) instead of the normal 1/10th inch.

B.

Active absolute coil verification - The need to verify which coil is active is essential because of the' 0.060 inch disp).coment (6tita coil on Figure 1) and itr, uffect on length nantrements.

1.

Perform by observing 400K DIFF and 400K ABS horizontal channels :

and Aerolling thru a flaw or dent on the standard.

a.

if the signals track at the.same time, then the lead coil (BottomorB)isactive.

b.

If the ABS signal lags the DIFF signal, then the trailing cotl (Top or A) is active.

SGPMS018:9

ATTACHMENT 111 REY. I 2.

Record At:ive &c.) in final Report at normal probe description' location 9 A feport using following:

Utu e f trit letter of probe type E for Echoram normal bobbin, a.

I hr /r;ric bobbin, or S for Echoram special probe (related to TSV hinst Trent).

b.

the 9 fu lend or Bottom coil c.

Us.e A f$r Trailing or Top coil d.

The probe diameter will be unchanged e.

Etampin:

1) EE.720 Lead or Bottom coil active on Echoram 720 diam >ater Bobbin Probe.

2) 7M00. Trailing or Top coil active on Zetec 700 diameter Bobbin Probe.

3) SS.M0 lead or bobbon coil active on Echoram 700 diameter special ; robe.

D.

All Analysts - Watch for probe changes in middle of reel.

!!!.3 FREQUENCMS l

A.

400, 200, 100, 10 Khz ABS and DIFF B.

Earlier i.'.ini studies had indicated that a 400/100 ABS mix provided slightly better detection than a 400/200 ABS mix, which was the original basis six setup for the May 1987 inspection at North Anna 1.

If additional laboratory testing (EPRI Alternative Plugging Criteria Prograns, etc) shows no major differences, then 200 Khz may be substituted for 100 Khz.

I S

1.

As necessary in this documer.L. where differences between a 400/100 and 400/200 mix are important, e.g., length measurement calculations (INCH 2), those differences will be noted.

l SGPM5018:10 i

ATTACHMENT !!!

REY. 1 l

C.

An alternate of 600 Khz may be substituted during the inspection process as an aid to further quantify TSP indications.

The 600 Kht frequency is important for detection of PWSCC and may provide a screening method for 00$CC.

The basis for using 600 Khz is in an effort to predict the need for RPC testing based on an amplitude ratto between 600 Kht and the Dif mix. As RPC results become known, the amplitude ratios will be reviewed to determine if in fact such a ratio can be establised to limit future RPC inspections.

!!!.4 ANALYSIS CRITERIA A.

NORMAL INDICATION LOCATIONS - Those indications that are not 'AT*

i TSP's and TTS, and will be addressed by normal percentage (%) calls.

[

1.

Minimum reportable percentage is 105 and greater for all indications that may be present throughout the tube.

2.

At TSP's, any indication greater than +/

2" from the TSP centerline is to be treated as a normal indication.

l 3.

At TTS, any indication greater than + 3' from TTS is to be treated as a normal indication.

B.

SPECIFIC LOCATION INDICAT10NS Those indications that are 'AT* TSP'S or TTS as defined below:

1.

Ali TSP indications within +/

2' of TSP centerline will be categorized by the following criteria:

i a.

Indications at Dented TSP's

.b.

Indications at non Dented TSP's i

l 2.

All TTS indications within + 3/ 2' of TTS will be categorized as _a Tubesheet Indication (TI), unless.otherwise considered to be a normal indication.

j SGPMS018:ll 1

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REY. !

3.

All indications not contained within the TSP (the departurn from null is located outside the support plate region), will have length measureunts and are to be reported using the absolute mix.

Indications that are contained within the TSP region will be reported with respect to the centerline of the ISP and are to be reported using the differential mix.

Those indications at the tubesheet region will be reported with respect to the TTS using either the absolute (preferred) or differential mix. NOTE:

l.ength measurements may be dropped at a later date upon notification by the lead analyst or Virginia Power representative.

4.

400/100 ABS MIX will be the prime analysis channel at dented TSP's where'the indication extends beyond (above c. below) the confines of the TSP. 400/100 DIF HlX will be the prime analysis channel for those indications centained within the TSP. An addittor.al t

mix: 200/100 DIF, may also be used as an aid in detecting indications which are contained within ?1ightly deformed TSP regions. Confirmation and subsequent classificatior, r;!*s of critical indications will be addressed in Section !!!.5.

5.

For TTS indications, experience has shown that the ABS MIX may prove more reliable and should be used as the initial screening channel. However, the OlF Mix can also be used to assist in-detection. The channel used to detect the indication shall be used as the calling channel.

C.

If it should be deemed necessary to revise these rules, additional justification will be developed and incorporated into this rule base through revision. A determination of the need to reanalyze previous data (prior to the revision) will be made by Westinghouse and the concurrence of Virginia-Power will be obtained' prior to executing any-reanalysis.

SGPMS018: 12-

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ATTACHMENT 111 REV. 1 l

i 111.5 CLA$$1FICAT!0N CRITERIA AT TSP's AND TTS j

A.

DitTDattD INDicAT10N1 AT DENTED T1P'1. To be used only for those indications where the departure free null is located outside the TSP i

region. Recorded as 'DI' in '!ND' column of report, reported from the..

Abs MIX, and defined as follows:

a s

1.

This signal must have a distinct vertical excursion in the Ats mix. These excursions are generally AT (OR NEAR) the beginning e.-

j end (top or bottom of TSP-respectively) of the dont signal. On i

the Ina signals, only the entrance angle of the Att signal _may be present(thedontoverridestheexitsignal). On the hoitas i

signal, only the exit of the Als signal may be present.- again because of the dent..

i 1

2.

Theverticalexcursion(measuredasinA.1above)lEIhavea phase angle between 108 and 110' (for entrance angles) or 190'and290(for~exitangles)(SeeFigure1) t C E:

Probe motion phase angle away from the signal must be i

considered when it is compared to the signal.

In general, l

if the signal is _not + 10 degrees -from the probe motion, l

be suspicious that it say. net be real.

I 1

3.

To be classified as a O!, one of the-following _three ' criteria must be mett-1 1

a.-

An A85 MIX response supported by one or more Att raw frequency

, :)

phase angles, and no differential als response. ~$ee fig.:A..

OR

..l b.

A O!F MIX response supported by one or more DIF raw frequency j

phase angles._and no absolute six response.

See Fig. B..

SGPMS018:13

ATTACHMENT !!!

REY. 1 OR Any response that is identified in the DIF and A W mixes with c.

no support from the raw frequencies. See Fig, t.

d.

All of the above responses are subject to RPC for further evaluation.

4.

The above criteria is broken down into detail in an effort to fully describe previot 11y identified indication responses found at North Anna.

5.

Length measurements are required.

4 6.

THERE !$ NO MINIMUM OR MAXIMUM VOLTAGE REQUIREMENT.

B.

PERCENT INDICATIONS AT DENTED TSP'S To be used for indications where the departure froni null is located outside the TSP region.

Recorded as the actual measured % thru. wall value in the '!ND' column, reported from the ABS MIX. Further definition as follows:

1.

The signals will have very distinct vertical excursions and could have amplitudes that begin to override the dent.

2.

The vertical excursion (measured per A.1) 15l11 have a phase angle between 10' and 1100(forentrancesignals)or190'and 2900(forexitsignals).

-3.

To be classified as a % indication, rather than a DJ, the following must be true:-

l a.

An ABS MIX response with good phase angle support from the raw absolute frequencies and a differential mix response.

See Fig. D.

l.

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REY. I b.

A DIF MIX response with good phase angle support from the raw differential frequencies and an absolute mix response.

See Fig. D.

4.

Any % indication that has an amplitude >3.0 Volts may n.qi ruquire subsequent RPC testing at the discretion of the lead analyst or Virginia 0 wer representative.

0 s

5.

Any % indication that has an amplitude <l.0 Volts, regardless of the % thru wall value, will require RPC for further evaluation and disposition.

6.

THERE IS NO MINIMUM OR MAXIMUM VOLTAGE REQUIREMENT.

7.

Length measurements are required.

C.

PERCENT INDICATIONS AT NON.0ENTED TSP's To be used for those indications that are contained totally within the confines of the TSP. Recorded as the actual measured % thru wall value in the *!ND

column, reported from the O!F MIX.

Further definition as follows:

1 1.

Any flaw like signal which shows a response in two (2) mixes. O!F and ABS is to be called a % thru wall, reported from the OlF HlX.

2.

It is not necessar/ to expect or find substantial raw frequency i

phase angle correlations therefore, for any indication contained I

within a non dented TSP region, no correlation is required.

j 3.

Length measurements are not required.

l 4.

Location of the indication determined with respect to the centerline of that TSP, l

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REY 1 3

5.

RPC of the indication will be required for further evaluation.

6.

THERE IS NO MINIMUM OR MAXIMUM VOLTAGE REQUIREMENT.

D.

DIST0RTED INDICATIONS AT TTS - Ret.orded as 'TI' in 'IND* column of Report and is defined as follows:

1.

This signai must have a distinct vertical excursion in ABS mix.

g This excursion will be at or near the. transition signal (bulge signal - which means the transition signal will go to the left in ABSmode).

2.

Phase angles will generally be 00 rather than 10 as at TSP's.

3.

THERE IS NO MINIMUM OR MAXIMUM VOLTAGE REQUIREMENT.

4.

Phase angle correlation should exist betwen 400/100 ABS mix and 400/100 DIFF MIX. Raw frequency phase angle support may or may not exist due-to the effects of the transitic. signal; however, should a flaw-like response be exhibited it must be called a TI and will be RPC'd.

E.

RULES F29 PHASE ANGLE MEASUREMENU AND V0LTAGE MEASUREMENT OF DI'$ AND

% INDICATIONS AT TSP'S AND TI'5 AT TTS 1.

Even though sosie sigt als in ABS mode may appear to 'be one large signal at-the beginning and end of the dent, they may be two

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separate signals. This can true for those signals whose amplitudes have not yet overcome the effects of the dent.

SGPMS018:16 bA r

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f' 4eMENT: 111-

- REV. I-2.

The larger amplitude signals _ will basically overconc TP dent-nnd-provide a reasonably normal transition on which to esasure phase angle and voltage.

3.

Each dented TSP may have up to two calls, one classified as above

-TSP centeritne (if it exists) and one classified as below the TSP centerline (if it-exists).

a a) Heasure voltage and phase angle of each signal above and/or below the TSP (at or near the beginning, or at or near the end ofthe: signal)..

b) Detenmine classification (D! or %).of the indication as defined in section !!!.5.4 or !!!.5.8 as applicable and,-

c) Record each. classification in the IND column, and report measured lengths as required in'section i11.6.

4.

For non-dented TSP's,-there will probably be only one (1) call at the intersection and should be contained within the confines of!

the TSP..

a)- Measure voltage and phsse _ angle of the signal:as defined:in section III.5.C and record its location as defined in Section

- !!I.6.

5.. At expansion transition regions at;TTS, there orobably will be

?

only one signal, and thisisignal will :robobly not overcome the TTS transition signal.

a) For signals at TTS regions indications are reported as 'TI' only..

SGPMS018:17 a

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ABSOLUTE CHANNELS HAVE A RPC HA8 AXIAL INDICATIONS DIFFERENTIAL CHANNELS SIGNAL (NOISE LIKE) IN IN THE CENTER OF THE TUBE HAVE A SMALL KTCK ABSOLUTE CHANNELS SHOW THE FLAN PIANE SU PPO'...

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REY. 1 PHASE ANGLE / VOLTAGE RELATIONSHIPS - TSP'S e

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DI'S at TSP.

%'S at TSP TI'S at TTS q

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NO MAXIMUM VOLTAGE DI's at TSP 4

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e SW NOTE: PHASE ANGLE ON TTS WILL GENERALLY BE OD IN NATURE RATHER-THAN ID AS SHOWN ABOVE. SAME BASIC RELATIONSHIPS APPLY.-

J Ill01 CATION REPORTING PARAMETERS

. FIGURE 1 SGPM5018: 18

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ATTACHMENT !!!

REV. I b) All measurements will be TTS +3/ 2 inches.

!!!.6 LENGTH MEASUREMENT RULES A.

LENGTH MEASUREMENTS - TSP'S 1.

The scale will be established between two TSP centerlines with 10 Khz differential.

2.

Length measurements will be determined utilizing a ' departure from

~J11' method on those indications that initiate outside the confines of the TSP. Normally these are associated with dented intersections.

a.

' Departure from Null" measures the signal response as it departs from the ' null' condition of the tube utilizing the vertical channel of the ASS MIX as it is displayed on the expanded strip chart, b.

Measureatnts will be + (from TSP centerline) for signals above etnterline of the TSP and - (from TSP centerline) for signals that are below centerline of the TSP.

3.

As measured signal lengths will' be _ transmitted to Supertubin where correction factors for delta coil and eddy current error will be applied as depicted in Figure 2.

The as measured length will be -

recorded in the Supertubin final report under the ' INCH l' column.

4.

The corrected length will then be calculated in Supertubin and reported in _the " INCH 2" column of _the final report. The_IN2A or IN2B values on_ Figure 2 represent these values.

SGPHS011:19 i

I w.

e

+ - - - -

~ ATTACHMENT 111 REY. 1 S.

For those indications within the confines of the TSP (normally associated with non dented TSP's and ODSCC), the location will be identified with respect to the certerline of the TSP as measured on the DIFF mix after setting scale. Supertubin translation of lengths will net be performed as long as the location is within

+/- 0.375 inches from the center of the TSP; i.e., INCH 2 will be set to 0.0.

B.

LENGTH MEASUREMENTS - TTS 1.

Measure. length from " departure from null" in the ABS mode to the TTS.

(Same technique as described above utilizing the TTS signal in lieu of the TSP centerline.) NOTE:

If DIFF mix is used to detect, and no ABS signal is present, then measurement is made from the DIFF mix signal to the'" center" of that signal.

2.

Normal indication locations to be reported with respect to the TTS signal.

3.

Set scale between TTS and #1 TSP or TTS and TEH.

C.

NOMENCLATURE USED ON FIGURE 2

+a; -b - as measured departure of ABS E/c signal from " Null" condition. The designation, +a, is above TSP centerline and -b is-below TSP centerline.

Delta coil = 0.060" from centerline of Differential coils to centerline of one coil used for absolute. This is normally the _ lead

/

coil. Equations are based on lead coil being activated. Analysts will verify coil attivated.

y.-

SGPMS018:20 I

4 F10VRE 2

• ATTACHMD(T !!!-

SCEMATI OF t/C DISTANCE NEASUREMDff3 IIY* 1

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1 SGMtS018:21 j

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---w

l ATTACHMENT III REY. 1 Xoc This value is addy current error. The-original value of 0.095*

was developed by comparing actual crack lengths on pulled tubes to the attentive eddy current signals using a 400/200 Khz ABS mix.

A-correlation of measured lengths using-a 400/100 Khz A85 mix indicates that Xoc would change to 0.096".

Due to the as measured lengths being-in 1/100th of an inch and normal rounding techniques, it is considered that there is no need to char.ge the 0.095' value and either six can be used interchangeably without affecting the final exposed crack lengtn value.

Delta T in the figure has been determined to be not applicable lfor North Anna Unit 1._ A study of relative location of Dent centerlines with respect to TSP centerlines of North Anna 1 data indicates that TSP's are locked to the tubes because of the dents andltherefore both move together. Should it be decided to 'SAVE' tubes based on crack lengths in North Anna 2, then-it will be necessary to perform the-Dent / TSP relative centerline position study to detemine if tubes are

' locked' in Unit-2.

III.7 PLUGGABLES FOR LENGTH, SELECTION CRITERIA The following criteria were initially established' for use during the May 1987 North Anna'fl inspection at TSP's. :The original-intent was L

to leave some DI's ~ in service based on a *1ength of' crack' not

~

exceeding an adjusted critical =. crack length.- The-ultimate decision-in

- May 1987 was to-plug all'0!'s: at North Anna fl. This-information is D

retained herein to maintain consistency with the previous inspections for length seasurements. Crack length measurements were also

' performed during the October-1987 inspection of North Anna ft. All Dl's will be inspected by RPC and pluggables will be determined by-L these results and/or as-directed byl Virginia Power.

l SGPMS018:22.

l l

l

~+

e wr:

= ATTACHMENT-!!!-

REY.--: 1

\\

For the July 1987. Inspection'of North Anna 1 and!the October:1987 inspection of North Anna 2, a TI' Category at TTS was added.- This

category is retained and all-TI's at TTS will be RPC tested and final f

plugging will be based on RPC results and/or as directed by Virginia _

Power.:

Should a pluggi_ng linit' based _ on length be implemented, then this.

" Plugging Limit length Value" will be compared to ABS value of IN2A or

.IN2B of. Figure 2 and if IN2A or IN28 are greater than' plugging limit,-

then tube is "QH' plugging list.

l With respect tof00 SCC % thru wall indications:(those' indications which are contained totally within the TSP region), and as more information is_learne'd following the EPRI-sponsored ' Alternative-Plugging Criteria Program, dispositon and/or plugging requirements ~ willi be determined :

at that time.

III.8. PRIMARY / SECONDARY ANALYST'S RESPONSIBILITIES' A.

PRIMARY - may be automated or manual analysis as defined at-the time

-of inspection.

u B.

BOTH PRIMARY AND SECONDARY will report all: indications as-defined in this document.

E C.-

All PREVIOUS-HISTORY will-be reported as follows:.

1.

Report all previous-history with-the; actual %Lthrough-wall value -

that'the bobbin test'indic'ates during'the present inspection..

'4 h

There will.be no.INR's reported.at'this time.

p:

SGPMS018:23 I

l=

L

+

__ _. ~.__- _ _ _

ATTACHMENT Ill REV..

2.

If the present indication can not be found within </- 0.5" of_ the-original call, the recorded call is INF at the history location.

Accordingly, tf idication that may.bo.found away from the i

previous lc~ e wJ ' ther be recorded-at its proper location.

3.

Dents, disto i>

anomalies will not be called by either p;imary -

they 6re to be called at any

~

^

time, they will h ary analyst or,as: directed by the-N lead analyst.

D.

Graphics are required for all % IND's, DI's, and TI's:-

1.

Manual or Automated for TSP's (DI's and %) and TTS-(T!'s) - show a 4 or 8 lissajous' pattern displaying the-raw - frequencies and 2 mixes-as applicable,to. pictorially represent the f1aw properly.-

i All traces-are to be displayed with full. window and spans such that indication And. vector points are clear.

If at all possible, the center cursor of the expanded: strip-chart shall be set' at the measured departure from Null.-

2.

For "Nomal" calls,-such as AVB's, show a (f or Blissajous pattern utilizing the frequencies whichisupport the call' being made;- i.e.,

AVB wear, show the AYS mix.on the graphics,-- and any-other -

supporting information as applicable.-

E.

Primary and secondary analysis will be carried out'with total 1 - jopendence of the analysts involved in the= analysis-of. any given; tube.-

'I

~

SGPMS018:24

[

't 1--'

T T'-

T' T'1r us v

'r1y w ' NY y

v id' e ' --

v' W

w-d *

(--

tr

• 4

ATTACHMENT !!!

REY. 1 1.

Shift turnovers will be performed with all analysts together.

2.. Analysts are.to review graphics data-books from the current-inspection periodically to ensure each is current on real flaws and those that are not real to minimize continua

• ton of overcalls.

F.

With respect to length measureatnts, the following precautions must be taken:

1.

Analysts utilizing manual equipment must ensure the center cursor on the expanded strip chart is positioned at " departure.from null' to obtain the accurate location. -

2.

Analysts utflizing automated equipment, (if applicable), must -

ensure to pick the departure from null-(if not properly located by the computer) and measure to the TSP centerline display on the expanded window.

G.

If " Normal' degradation is found that must-be referenced:to a TSP (or greater than 3' above TTS), add a special comment that signifies "These are not crack length neasurements so Supertubin will not _ apply _

variables to call" as follows:

1.

On a manual system this is designated by putting an N in the last space of the location column.

2.

On-automated systems, an applicable or alternata designation _will be determined if necessary.

1' L

SGPMS018:25 e

op-

,,v+-e r

ATTACHMENT III REY. 1 III.9 PRIMARY / SECONDARY RESOLUTIONS A.

For all degradation El at TSP's,(greater than +/- 2* of TSP centerline) or at TTS (giaater than + 3" of TTS), resolution is required if % indication variatc,ns by more than +/-10% on depth (except over/under plugging limit where any % difference must be resolved) and if locations vary by more than +/-0.5' on location.

B.

For DI's at TSP's and TI's at TTS - Location of departure from null requires resolution if primary and secondary vary by more than +/ 0.10 inch.

C.

For % indications within +/-2" of TSP centerline, - Location of departure from null requires resolution if variation is more than

+/-0.10".

Percentage differences shall. be within +/-10%.

D.

All resolutions are to be recorded on the manual analysis sysytes crimary data disk as per Westinghouse guidelines, DAT-GYD-001, REV 4.

Appendix B.

Enter all correct values in the appropriate column.

NOTE: IF optical discs are used, this data may also be recorded on the opticial disc.

III.10 BOBBIN COIL OETUP NOTE: ANY SECTIONS IDENTIFIED DURING THE' SETUP TECHNIQUE ARE TO BE REFERENCED TO WESTINGHOUSE DATA ANALYSIS GUIDELINES, REV. 4.

A.

Calibratiert NOTE:

Verify frequencies are per job data sheet or plant specifics.

Ensure screening is disabled before continuing.

SGPMS018:26 l

1:

ATTACHMENT 111 REV. 1 1.

Phase angle and voltage measurements shall be performed as -

follows:

Phase angle measurements shall be made utilizing volts a.

peak to peak or max rate for differential curves, and. volts peak-to-peak for absolute curves.

Selection:of volts-peak to-peak versus max rate shall be based on whichever

' technique-assigns an angle along the signal transition--line more accurately.

b..

Voltage measurements for AVB's shall be performed utilizing-vertical max for both calibration _and sizing. Measurements-shall be on the most conservative leg of the signal if an ABS:

technique is used_or vertical; max on the entire signal if DIF

-is used.

s 2.

Scans and Rotations Adjust the rotation on differential-degradation channels a.

(normally 1,- 3,.and 5) so that phase angle from the 1007, through wall hole is-40Ldegreest(+/- 1-degree) with the-initial excursion down and to the right.---

a.1 Adjust the' rotation on a111 remaining channels and mixes--

so that, probe motion is horizontal. -Initial excursions from flaw signal' shall be1DOWN on differentia 1' channels' s

and UP on absolute channels. When probe motion is not evident the dont signal;can be adjusted to horizontal as an option.

SGPM5018:27

_E-

-ATTACHMENT !!!

REY. I a.2 Low frequency.(10 Xhz) differential channel shall be rotated-such that the initial excursion of the support plate signal is to the left and down with the transition line vertical.

Low frequency absolute channel shall be rotated such that the init4a1 excursion of_ the support plate signal is down and to the right, and the peak to peak measurement points lie horizontal.

a b.

Adjust the span on prime frequency channel (normally channel

1) and mix #1 so that the signal lfrom the 20% through wall-hole is at least four screen divisions peak-to-peak. Verify.

that--the signal from the 100% through wall hole is at least 50% of full screen height. Adjust if necessary, b.1 On other frequencies, adjust spans such that _ flaw transition signals are clearly discernible for adequate placement of'-

measurement points.

3.

Establish Mixes a.

Mix 1:

400/100 DIF. -Prime frequency degradation differential mix; set up by eliminating TSP; use max rate for establishing curve;;. Degree vs. Percent curve.

[b. Mix 2:

400/100 DIF. AV8 Mix-Setup Same as' Mix-1;-use vert max for establishing' curve; Differential. or Absolute; Volts (Amplitudi) _ vs.' Percent curve.

c.

Mix 3:

.400/100 ABS

Prime frequency degradation ABSOLUTE-mix;; set up by eliminating TSP;' set.' dent horizo'tal;-

n use volt peak-to-peak on entrance angle for establishing curve; Degree vs.f Percent curve.

SGPMS018:28-

_a__-________

ATTACHMENT 111 REV. I d.

Mix 4:

200/100 DIF. Setup by eliminating the TSPt use max rate for establishing curve Degree vs. Percent curve.

To be utilized at slightly dented or otherwise deformed TSP's as an aid in detecting ODSCC.

e.

Perform mix.

s 4.

Set Volts, Set voltage on 20% flaw to equal 4.0 volts peak-to peak on a,

prime frequency (Normally CH #1).

a.1 Save, store to all other channels and mixes.

a.2 For Mix 2 set the 40% Wear indication at 5.0 volts utilizing vert max. Save~and store to this channel.

If the standard does not have a 40% indication, the 50% wear flaw shall be substituted.

5.

Set curves Calibration curves should be established using normalized a.

values; 'as-built' dimensions may be utilized if requested by the utility. Normalized curves are generated utilizing phase angles whick_{prtased on nominal wall thickness and a Standard Depthf Penetration of 0.37.

b.

All ASME STD tube wall degradation curves shall use the-

~

~

L normalized, "as built"_ dimensions for these ' nominal values:

l Set Point - 1 100%

Set Point - 2 60%

Set Point - 3' 20%

.SGPM5018:29

' ATTACHMENT Ill REV. I c.

All AVB wear scar six curves shall typically use:

Set Point 1 - 0% at 0.0 volts Set Point 2 - Approx. 20% (Depending on actual std.)

Set Point 3 - Approx. 40%-(Depending on actual std.)

d.

Store above set-up variables to data disc to avoid potential loss during subsequent steps.

6.

Permanent Storace of Succested Variables to Disc a.

Recossended strip chart displays a.1 Left Chart - Vertical channel of Hix 1.

a.2 Right Chart - Vertical channel of lowest absolute degradation frequency, b.

Recossended Chart lengths:

Full Length 90 U-Bend-50 1st TSP 20 I

l c.

Set extent such that it. describes the expected begin and end-test: F/L test from inlet has extent as TEC TEH.

[.*

d.

Store final set up of variables to data' disc, and enable screening.

l l

SGPMS018:30 l

ATTACHMENT III REY. I 7.

Storaae of E/C Standards to Disc a.

Store the following signals from standards to E/C Data on the data dise:

(See Fig. 1).

a.1 ASME: TSP - Prime Frequency 100% through 2D5 - Prime Frequency 1

Dents - Mix 1 a.2 AVB: All wear scars - Mix 2 a.3 CUD /SLG; CUD and SLG Signals (if required)

_ Prime Frequency 8.

Documentation of Summarv Section (See Fio. 2) a.

On plant line, place 3 letter utility code followed by Data Disc - Tape f. (DD-f, and type cf analysis - Primary or Secondary).

EXAMPLE-- Tape #8 DD-8P or D0-85.

b.

Verify (or enter) tape number on tape reel line.

c.

In comment 'section enter analyst's name, certification level and date evaluated, d.

Update summary and enter to disc.

1 9.

Documentation of Final ReDort (See Fio.1) a.

Line 1 - In % column - enter "PR0"

- In location.section - enter " Probe size and. type" (Refer ~to Paragraph III.2.B.1 for-active coil)

- In extent section - enter " PROBE" SGPM5018:31

ATTACHMENT !!!-

REV.- !

Line 2 - In location-section - anter ' START TAPE l' and *DD f" In extent section enter 'PRI' or "SEC' Line 3 - In volts column - enter (INT). - analysts' initials

- In channel column enter 3 letter utility, code

- In location section entar name, certification level, and date

- In extent section enter ' time"_(1215 llAS).

NOTE:

When utilizing the Westinghouse utilities' disc and entering PW-(probe size), TW-(start tape and data disc), and NW (name) sequentially,-the above tasks-can be accomplished by entering the correct information in the spaces provided.-

b.

shift Turnover Entries - Same as Line 3 of g.a.

Entry.

required for analyst signing off and analyst signing on.-

c.

End of Renort Line 1 -- In location section - entor 'End tape' andDD #"

.In extent col, enter "PRI' or 'SEC' Line 2 - Same as Line of 9.a.-

B.

In]1Rien Theevalu$ tion-shallconsistofreviewinglissajous-andstrip

-1.

chart displays to the extent that all= tube wall degradation and-anomalies defined.by this document:are detected;-' sized, and.

recorded in accordance with this document-or site specific guidelines.

SGPMS018:32

ATTACHMENT 111 REY. 1 2.

All data recorded shall be evaluated regardless of _ the extent tested.

l 3.

Restrictions shall be analyzed to point of restriction and subsequent reanalysis with a smaller diameter probe from point of_

restriction and beyond.

4.

Probe speed shall be vertfled at least once per tape, not to exceed approved Job Data Sheet requirements, l

!!!.11 GRAPHIC EXAMPLES BOBBIN C0!L WITH RPC SUPPORT Basic bobbin coil graphic examples for TSP and TTS indication are attached.

The bobbin cuil. graphics depicted herein are supported, when available, with I

RPC graphics to show the geometries of the flaws reported by bobbin coll.

Additional graphics will be added as necessary to depict a change in philosophy or an increased understanding of the nature of the indications.

l I

SGPMS018:33

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ATTACHMENT IV REY. 1 l

NORTH ANNA UNITS 1 & 2 EDAP 1

IV. ANALYSIS RULES 8xl COILS DEGRADATION A.

FREQUENCIES: 400 AND 200 KHZ WITH A 400/200 MIX B.

REJECTABLE DATA: WHEN ONE OR MORE C0!LS EXHIBli BAD DATA (MECHANICALLY OR ELECTRICALLY INDUCED DISTORTION AT A TSP OR TTS INTERSECTION) OR NO DATA.

C.

SETUP

1) PERFORM SETUP WITH FILTERS OFF.

2) REVIEW SUPPORT RING ON STANDARD, PERFORM OR TOUCH UP MIX AS REQUIRED.

3) SET VOLTS ON THE 20s CIRCUMFERENTIAL GROOVE TO 3 VOLTS (BASELINE TO PEAK) FOR THE 400 KHZ RESPONSE, FIX, SAVE, STORE, STORE.TO THE ASSOCIATED 200 KHZ AND MIX. REPEAT FOR ALL C0ILS.

4) REVIEWFIRSTTUBEENTRY(ORSUBSEQUENTTUBESIFNECESSARY) SET THE ROLL TRANSITION $1GNAL HORIZONTAL ON ALL CHANNELS.

5) REVIEW CAllBRATION STANDARD, ENSURE THE RESPONSE FROM THE 1005 FLAW IS UP AND 10 THE LEFT (APPROXIMATELY 15 - 25 DEGREES).IF,

NOT, RELOAD FIRST TUBE ENTRY AND REVIEW EXPANSION TRANSITION OR ROLL TRANSITION FOR PROPER SET UP.

-SGPMi018:34

. =.

ATTACHNENT-IV REV 1

6) ADD 10 E/C DATA THE TSP, 100, 80, 60, 40, 20 GROOVES FRON ONE -

00ll DN THE TOP $ET OF C0ILS AND ONE FROM THE BOTTON SET OF r0!LS.

7) NORMALLY, DATA WILL, BE ANALYZED WITHOUT BAND PA$$ FILTERING. WHEN 11 l$ NECES$ARY TO U$E BAND Pass FILTERING TO REVIEW CERTAIN TUSES Ok PORTIONS OF TUBES, SUSPECT $1GNALS DETECTED VILL ALSO BE EVALUATED WITHOUT FILTER!M..

D.

ANALYS15;

!) _WHEN THE INSPECTION !$ TH!!00GH THE TOP (7) TSP AND THE COMPUTER !$-

NOT EQUIPPED WITH TW0 NEGA8YTES OF MEMORY, LOAD THE FIR $T FOUR-TSP (7,6,$,4)-$1GNALS. REVIEW THE RESPONSE ON ALL MIX CHMNELS, MONITORING FOR FLAW LIKE EXCUR$10NS (TYPICALLY RAP!0 EXCUR$10NS UP AND TO THE LEFT).

NOTE:

IF THE COMPUTER HAS ADEQUATE MEMORY, THE ENTIRE Tutt CAN BE LOADED AT THis TIME.

2) REPORT ALL INDICATIONS As PI (P0$$1BLE INDICATION) IN THE 5 -

COLUM.

5) GRAPHICS SHALL BE THE ASSOCIATED MIX CHANNEL, A2 THE SUPPORTING' 200KHZOR400KNZ-(WHICHEVERBEST$UPPORTSTHEMIX).

4) NOTE THE TOTAL NUNBER OF LOIL RESPONSES IN THE LAST SPACE IN THE LOCATION COLUM.

$) LOAD THE LAST PORT!'ON 0F THE TUSE ENTRY AND RESUME ANALYS15, As APPLICABLE.

6) FOLLOW ALL ESTABL15HED CRITERIA FOR P/5 RESOLUTIONS.

H SGPM1018:!$

$~

ATTACHMENT IV REY. 1

7) THE REQUIRED EXTENT OF 811 EXANS 15 EITHER THROUGH THE FIRST TSP OR THE TOP T$P THROUGH THE TUSE END. TO MININIZE RETESTS, AN ACCEPTABLE TEST !$ FROM THE FIRST (0R TOP) TSP THROUGH THE TURE SHEET EXPANSION AT THE TTs.

THl$ EXCEPTION TO NORMAL TEST EX1ENT$

!$ BASED ON THE CRITICAL AREAS BEING THE TOP TSP AND THE TRANSITION AT THE TOP 0F TuttsHEET.

e E '.

GRAPHICS EXAMPLES.

BASIC GRAPHIC EXAMPLES ARE ATTACHED. THESE ARE.

BASED ON PREVIOUS 8xl RESULTS THAT HAVE BEEN VERIFIED BY RPC.

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- - _ _ - - - - - - - - " - - - - - - ~ - - - - - - - - - - - -

ATTACHMENT V REV. !

NORTH ANNA UNITS 1 & 2 EDAP V.

ANALYSIS RULES R K A.

GENERAL INFORM TION AND HISTORY r

RPC HAS BEEN PERF0MED AT NORTH ANNA $1NCE THE MAY 1967 0UTAGE AS A MEANS TO FURTHER D!5 POSITION AND CLA$$1FY B0881N D! AND E CALLS AT TSP INTER $tCTIONS, AND T!'$ AT TT$ INTER $ECTIONS. FOR THOSE I W ICATIONS AT T5P INTERSECTIONS, RK HA5 SHOW TO BE AN EFFECTIVE NETHOD TO A!D IN CONFIRMING INDICATIONS THAT MAY NOT BE CLEARLY DEFINED BY tott!N Coll. FOR TI CALLS AT TTS INTER $ECTIONS, RK WA5 PERF0MED TO FURTHER DEFINE THE FLAW CHARACHTER15 TICS (AXIAL OR CIRCUNFERENTIAL) F00i40 AT THE TT5 AND ALLOW FOR PROPER RECOMENDATION OF PLUGGING OR STABILIZING TECHNIQUES.

RK WILL AGAIN BE PERF0NED ON ALL Dl's AE l's AT TSP INTER $ECTIONS DURING THE FALL NORTH ANNA UNIT t OUTAGE TO ASSESS IF A MININUM tott!N Coll DETECTION V0LTAGE CAN DE DETEMINED FRON INDICATIONS THAT ARE-SUPPORTED BY RK RESULT $.

IN ADDITION, A 1005 RK TTS HOT LES INSPECTION OF ALL 5/4'5:!$ PUNTED FOR THE FALL 1990 NORTH ANNA t OUTAGE WHICH WILL BOTH D15Po$1 TION THE TI'$ FOUND DURING THE INITIAL 00881N COIL INSPECTION, AND REPLACE AN SXI COIL INSPECTION FOR DETECTION OF CIRCWFERENTIAL= IWICATIONS SHOW T0 SE PRESENT AT THE WEXTEX EXPAND TRAN$!TIONS.

THE RESULTS OF THE RK TESTING NaY DETEMINE THE NEED FOR FUTf:RE 1005 TTS HOT LES INSPECTIONS SY RK.

R.-

FREQUENCIE$t 400,300,150,and10KHZ(TRIGGER)

P SGPNS018:37

ATTACHNENT V REY. 1 C.

REJECTABLE DATA:

WHEN DATA EXHISITS NECHANICALLY Ok ELECTRICALLY IN00CEO 0!$TORTION, DROP 00T OR N0 DATA AT A TSP OR TTS INTER $ECTION.

D.

SETUP

1) REVIEW $TANDARD FROM TAPE. PERFORM A MIX ON TH( TSP $1GNAL OR s

TOUCH WP MIX FRON PREVIOUS TAPE. MIXING !$ CON $10ERED As AN OPTION FOR THE ANALYST.

t) $ET ROTATION BY PLACING PROSE MOTION HORIZONTAL ON ALL ANALYS15 CHANNELS. THE RESPON$E FROM 1HE 1005 EDM NOTCH SHOULD BE APPR0XIMATELY 15 TO 22 DEGREES ON ALL CHANNELS.

A. THE k[$P0NSE FROM THE TRIGGER SHALL #E SET VERTICAL AND THE

$ PAN SET JUST BELOW SATURATION.

3) SET VOLTS ON THE 1005 EDM NOTCH 70 20.00 VOLTS ON THE PRIME FREQUENCY. FIX, SAVE, A m STORE, TO PRIME FREQUENCY AND ALL OTHER CHANNELS.

4) SET CURVES WITH THE 1005. 80s, Am 405 FLAWS, IF P0$$1BLE.

$US$T!TUTE THE 605 FLAW IF NECESSARY.

$) STORE THE 1005, 405, 605, AND 405 EDM NOTCHES TO E/C DATA.-

SGPMS018:38

_____w_w

ATTACHMENT V REV. 1 E.

EVALUATION 1)

IT !$ RECOMENDED TMT WHILE THE Tutt !$ LOADING, NONITOR CMNNEL 1 (400 KHZ) OR THE MIX IN THE X/Y Ll55MOU$ D15 PLAY, CHANNEL 1 VERTICAL ON THE LEFT $1 RIP CHART DISPLAY AND CHANNEL 3 (150 KHZ)

VERTICAL ON THr. RIGHT STRIP CHART DISPLAY. THE CHANNEL 3 VERTICAL COMPONENT !$ $UGGESTED A5 IT M Y St HELPFUL IN SEGREGATING-e INDICATIONS FROM DEPOSITS.

IT IS NOTED TMT IT !$ THE ANALYST'S DISCRET!0N AS TO WHICH CHANNELS SHALL BE MONITORED OR DISPLAYED.

A) VERIFY THE COMPLETE INTER $ECTION HAS BEEN RECORDED.

2) SCROLL EACH INTER $ECTION WITH ALL FREQUENCIES, !NCLUDING NIX, A5 NECESSARY TO CONFIRN INDICATION AND 10 LOCATE As BEST-As POs$1BLE, THE LARGEST AND DEEPEST $1GML.

f) D15 PLAY AN ISOMETRIC PLOT 0F THE MD$T SUITABLE FREQUENCY OR MIX THAT ALLOWS THE ANALYST To fl$Pos! TION THE CONDITION AT THE LOCATION BEING TESTED.

4) REPORTING 0F RPC CALLS THAT APPEAR TO BE CRACKS SELL BE BASED ON THE ACTUAL PICTORIAL REPRESENTATION OF THE-THREE DIMEN$10NAL PLOT OF THE RPC $1GNAL AND SHALL-BE REPORTED AS FOLLOW $.

A)

IF THE !$0 METRIC GRAPHICS DEPICT A CIRCUNFERENTIALLY ORIENTED ~

INDICATION (NORMALLY BLTT NOT ALWAY $, Ass 0CIATED WITH ROLL OR EXPAND TRANSITIONS,' WHERE THE-AX1AL EXTENT 15 LESS THAN THE-CIRCUNFERENTIAL EXTENT, THEN ENTER 'MCl* OR 'SC1", A5 APPROPRIATE, FOR MULTIPLE OR 5!NGLE CIRCUMFERENTIAL INDICATION.-

1 SGPMS018:39

ATTACHMENT V REY. I B)

IF THE RPC ISOMETRIC CRAPHICS DEPICT ONE OR HOR.* INDICATIONS THAT ARE LONGER AXIALLY TRAN THEY kdE CIRCUHFERENTIALLY, ENTER EITHER ' sal' OR ' mal', AS APPROPRIATE, FOR MULTIFLE OR 51NGLE AXIAL INDICATION.

C)

IF THE RPC SHOWS GENERAL WASTAGE (OR PITTINC) WHICH CAN BE QUANTIFIED, WITH NO EYlDENCE OF AX1AL OR CIRCUHFERENTIAL INDICATIONS THEN RECORD THE FLAW DEPTH, VOLTS, PHASE ANGLE, ETC. INTO THE FINAL REPORT, WITH AN 'N' (FOR NORMAL INDICATION) INSERTED AT THE FAR RIGHT OF THE LOCATION COLUMN.

D) IF THE RPC DATA SHOW! NO EVIDENCE OF DEGkADATION, ENTER NDO IN THE REPORT.

E)

IN ALL CASES, ENTER THE INTERSECTION DESIGNATOR BEING TESTED IN THE EXTENT COLUMN E.G., TSH TSH, TSH TRH,1C IC, ETC.

F) FOR DEFINITIONS OF HCI, SCI, MA1, AND sal, REFERENCE WESTINGHOUSE DAT GYD 001 REV 4.

5.

GRAPHICS PLOTS ARE REQUIRED AND THALL SONTAIN AN ISOMETRIC PLOT OF THE FREQUENCY UPON WHICH THE DECISION WAS MADE AND A SUPPORTING PLOT 0F AN X/Y LISSMOUS DISPLAY. ANOTHER ISOMETRIC PLOT MAY BE SUBSTITUTED FOR THE X/Y LIS$MOUS IF IT MORE CLEARLY PRESENTS THE SUPPORTING INFORMATION.

THE LISS M OUS MAY BE DISPLAYED IN THE LOWER LEFT CORNER Of THE ISOMETRIC PLOT $0 THAT THE LOCATION WILL ALSO BE SHOWN.

6.

FOLLOW ALL ESTABLISHED RU ES FOR P/S RESOLUTIONS.

e SGPMS018:40

=_- - - __ - - - -

ATTACHMENT V REY. 1 F.

IINGTH MEASURENENTS FOR TUBES WITH CIRCUMFERENTIAL INDICATIONS 1.

SET THE SCALE FOR THE CIRCUMFERENTIAL LENGTH OF THE TUBE BY USING THE TRIGGER SIGNALS. EACH TRIGGER $1GNAL REPRESENTS ONE PROBE REVOLUTION. SET TiiE DISTANCE FROM ONE TRIGGER $1GNAL TO THE NEXT EQUAL TO 3.60. THIS LENGTH MEASUREMENT SETTING $1GNIFIES 360 DEGREES.

(SEEFIGURE1) 2.

UTILIZING THE VERTICAL COMP 0NENT OF THE EXPANDED STRIPCHART, FIND THE LONGEST ED0Y CURRENT TRACE. TH15 15 GENERALLY WHERE THE PANCAKE COIL PASSES DIRECTLY OVER THE CIRCUMFERENTIAL CRACK.

IT

!$ REC 0m ENDED THAT THE PRIMARY FREQUENCY BE USED.

3.

MEASURE THE LENGTH OF THE I MICATION. SET THE SCALE TO ZERO WHERE THE ED0Y CURRENT TRAlt ORIGINALLY DEPARTS FROM NULL. SCR0LL THROUGH THE $1GNAL TO WHERE IT RETURNS TO NULL. LENGTH MEASudEMENT !$ IN D;GREES. TO 08TAINE THE ACTUAL MEASUREMENT, MUL11 PLY THl$ NUM8ER BY 100.

(SEEFIGURES2&3) 4.

IN THE CASE OF MULTIPLE CIRCUMFERENTIAL INDICATIONS, LENGTH MEASUREMENTS FROM EACH $1GNAL WITHIN ONE REV0LUTION WILL BE RECORDED.,JHOULD THE CRITERJ0N FOR STABILIZATION INCLUDE THE NEED FOR THE SHORTEST ANGULAR SPAN BETWEEN THE MC1'S, THIS MEASUREMENT WILL ALSO BE RECORCED ON A SEPARATE LINE ENTRY.

5.

CURRENT PLANS' CALL FOR EDITING hlE DEGREE COLUM AND ENTERING THE DEGREES MEASURED IN 3 OR 4 AB0VE THEREIN. THl$ WILL BECOME-THE L.'

PERMANENTRECORDFORTHEIN0!CATIONLENGTH(S)FORANY CIRCUMFERENTIALLY IRIENTED INDICATIONS. SHOULD A VARIATION TO THE RECORDING METHOD GC EADL, ALL ANALYSTS WILL BE ADVISED OF THE CHANGES AT THE TIME.

i l

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ATTACHM 4T VI REY. I HORTH ANNA UNITS 1 & 2 EDAP VI. ANALYSIS GUIDELINES - ZETEC COMPUTER DATA SCREENING A.

SET,UP PROCEDURE FOR ZETEC COMPtTTER DATA SCREENING

1. Load Tape and set-up as per Bobbin Coil Calibration guidelines (Para. I!!.g) (Spans / Rotations Voltage Values, Curves, etc.).

2. Set-up long strip charts to monitor MIX 1 on the left and MIX 2 on the right. Set spans for both of those channels to 20.

3. After setting the appropriate spans, rotations, and voltage values for all channels, update the summary section of data disk.

4. Store set-up variables to data disk.

5. ' ENABLE' the screening function.

(Foundin'DATEVAL' menu).

6. In the ' AUTO EVAL' mode, press ' SET SORTS' followed by' ' SET SORT l' softkeys.

(Primary Sort Screen should appearti)

7. Press ' SPAN & ROT +' (SHIFTED). This action will update the CDS Sort Channels with the proper calibration parameters..e.g., Spans and Rotation values.

IMPORTAN1 NOTE: Step 7 must be done whenever the set-up spans and rotations are changed so the sort channels will screen the data correctly. Example: start of tape, probe changes, extension change, etc.

SGPMS018:42

ATTACHMENT VI-REY. 1.

8.

Enter first tube to be evaluated into RAM. Observe MIX 3 as the 1

tube enters.. Determine the phase _ rotation correction needed for.

primary sort channel fit,- (MIX 1). To accomplish this proceed as follows:

1 Scroll the cursor so that some ID signals in the tubesheet' region are displayed in the window. Go into the ' SPAN / ROT' Mode. Press softkey ' SET _ ROT' then 'GET_ CURVE'. (Before rotating remember original ' rotation value). Rotate with the rotating knob until-these signals are horizontal. Remember this rotation value. Rotate back to original setting, then -

press ' SET CURVE' (restores curve to original set.up).

3 9.

Go back into the primary sort screen using steps described above. With the cursor and the knob change the rotation.value of sort channel #12.to the value determined in Step 8.

At this point, calibration has been completed.

A.

ANALYSIS 1.

Return to 'INPT DATA' mode, refresh long strip charts, then back to ' ANALYZE' mode and load first tube.

2.

Go to ' AUTO EVAL' mode. ' Press softkey 'D0 THIS'... (Support.

structures will be located and screening will commence.).

3.

Periodically the program will pause and the phrase ' WAITING-F0R RESOLUTION' will appear. At this time the keyboard is free to-evaluate the signal-as desired (cursor knob, Volts P_P, window

+/-ETC...).

If the indication is not reportable, pressing the

'SPACEBAR' will continue the program. If the signal is reportable, _ evaluate per the North Aana Analysis Rules.=

EDIT' SGPMS018:43 e

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ATTACHMENT VI REY. I in the appropriate indication code, as required. Dump Graphics, as required. Enter the evaluation on the final report by pressing softkey marked ' INS LN' (Insert Line). The words

' ENTERED INTO RESULTS' will not be written en the disk. Press

'SPACEBAR' to continue screening. After screening is complets for a tube, all of the evaluations will be automatically written to disk.

NOTE:

Editing of the final report can still be accomplished as usual. Results can be written to disk prior to the completion of screening by first pressing the

' RESULT' key to allow one line editing as it appears-at the bottom of the screen, then to enter it onto diskbypressing' RESULT'(Shifted).

When dumping graphics, do not type in the printer code 'PFF" as it will start the CDS program and the command will not be carried out.

(Manually form feed whennecessary.)

4.

If the spacebar is pressed without the ' WAITING FOR RESOLUTION' message present, the program will abort (Pac Man tunt will be heard), restart by pressing 'D0 THIS'.

5.

After the tube has been screened and all desired entries are recorded, press softkey 'DO.NEXT' to input the next tube and-start the screening process once again.

NOTE:

While the next tube enters, the analyst should observe MIX 1 to detect any existing indications which CDS may not screen.

SGPMS018:44

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REY. 1 CDS is being used interactively, therefore, it is not programmed to taake -

evaluation decisions for the analyst and it may not stop on every indication which is defined as reportable by the analysis rules. The analyst-is-ultimately responsible for the evaluation of any given tube-and should be looking at the entire tube not just the areas in which the' screening program stops. The screening is merely being used as an aid to the efficiency of the analysis process.

SGPMS018:45-

ATTACHMENT VII REY. 1 NORTH ANNA UNITS 1 & 2 EDAP VII. TYPICAL TUBESHEET PROFILE SET-UP ANALYSIS RULES A.

8-Coil Profilometry

/

1.

Set-Un a.

Install a 'DDA-4 MIZ-18 Data Analysis' module and an '8 Co11 Profilometry" module on the DOA 4 computer.

b.

Boot up the DDA-4 using " System Disc, 200/300 Series, Edition 18.6 Revision 5' software followed by the '8-coil Profilometry Rev. 3 Supplement to System Disc Edition 16.6 Rev. 5' binary software.

c.

Load Westinghouse utilities disc utilizing 272 load. Enter S/G as applicable, d.

Load the special profilometry macros from the utility disk by typing "485 Load" followed by enter, e.

Initialize data disks to be used if not previously done and return to the main screen.

2.

Calibration a.

Load the data tape into the recorder and read index.

b.

Set "Ch 1-Vert" and "Ch 9 Vert" as the left and right strip chart displays.

SGPM5018:46

ATTACHMENT VII REY.~l c.

Load the first tube tested (not the cal std) into the DDA-4'.

d.

If the strip chart displays are off scale to the left or right, move the cursor to approximately half way down the display and press ' Analyse',. ' Data Eval", ' Null', and

" Refresh'. This should balance both displays and bring them to center scale.

e Adjust strip chart lengths so that the entire length of the tube is_ displayed, f.

In the ' Analyze" mode, toggle ' Strain' until " Meas Max' is displayed on the soft key functions and " Measured Maxima" is displayed in the upper left corner of the screen.

g.

Press ' Data Eval", " Calibrate", and ' Set Step". Using the thumb wheel to adjust the Cal Std Step ID' until it reads the

-appropriate value as defined by the cal std drawings.

h Similarly adjust " Set Noa',-' Sat Probe", and ' floc Chan" as appropriate for the site specifics -

1.

Press ' Data Eval' and' ' Refresh".:

j.. Move the cursor to a nominal section of the tube above the 1

tubesheet and away from the supports, k.

Press " Null'. -- The display will: indicate the appropriate -

nominal' ID of the std as set above.

1.

Hove the cursor to a location approximately;in the center of-the tubesheet.-

SGPMS018:47 1

e

---

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ATTACMENT VII REV.

1--

m.

Press = shifted " Auto. cal' and wait for " Auto Calibration Complete

• to appear in the conter of the screen. Pressing

' Analyze', !!nput*, and ' Refresh' will display the ' strip charts as currently calibrated.

j i

n.

Load the calibration standard-into the DDA 4.

e a

o.

Press ' Analyze", " Data Eval",' ' Calibrate", and ' Set Step'..

Use the thumb-wheel to re-adjust the ' Cal-Step:ID' to a reading equivalent to the step detailed on th6 standard drawings.

p.

Press " Data' Eval, " Screen!", and " Refresh'.-

t q.

Nove tue cursorito a location in the calibration standard where thel' Avg Dias' as displayed at the top of.the screen is

-within tolerance of the calibration std Id.

r.

Press-' Null'.

s.

Nove the cursor to another location in the enlibrat' ion standard where the ' Avg Diasis within the tolerance of the -

cal std ID-step.-

t.

Press. shifted -" Auto Cal" and wait forL' Auto Calibration Complete" to appear in the center of the scrun. PressingL

' Analyze', " Input Data", and ' Refresh'i will display the strip :

i charts in the final calibration configuration.

' l

/

u.

This completes the profilometry calibration.

SGPMS018:48

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4TTACIMENT VII-REY. 1 4

3.

Data Analvtis a.

Set up the data disc utilizing the standard header fonnation identified in Section 4.9.

b.

Store the nominal and step dimensions to E/C data.

- l Update-the Summary as' defined in Section 4.8 realizing it will-c.

be necessary to utilize multiple data discs as only 13 tubes o

are capable of belwa analyzed per disc.

d.

Load the first tube to be analyzed into the 004 4.

- i H

e.

Enter the appropriate extent _ tested. While in-thel' Input-

- l Data" mode, press shifted ' Set Zero'. This enters the Code -

into the' extent column of the final report, f.

Move the cursor until it is in the center of the first support plate. Adjust the window of_the exapoded strip _ charts so_that it is-opened just slightly more than the length of the support plate.

g. _ Move the cursor to the top of the tubesheet or approximately in the center of the expansion transition.

h.

Toggle the "Next/Last Loc" keys until "TSH* appears as the :

location,

i. From the keyboard, type _"NAH' and press

• ENTER". This-l measures the nominal tube diameter above the tubesheet and measures the maximum and minimum tube diameters at the.

tubesheet location and enters Lthem into..the; final report.

SGPMS018:49-I

- a

l ATTACHMENT VII REY. 1

j. Hove the cursor to the center of the second support plate.

k.

Prest " Recall" which brings back 'NBH" to the screen and press

' ENTER".

1.

Repeat steps j and k. for the remainder of the support locations in the tube.

Load the next tube to be analyzed into the DDA-4 and repeat m.

steps g. through 1. for each successive tube, n.

When the data disc is full, enter the standard end header on the disc and proceed to the next data disc until all tubes on the tape have been analyzed. Ed't the summary as applicable for each data disc and update in the usual manner.

It is not necessary to store the standard to disc on successive data discs as long as the information has been previously stored.

l SGPMS018:50 l

l l

l ATTACHMENT VI!!

f REY. 1 NORTH ANNA UNITS 1 & 2 EDAP VIII. TUBE SUPPORT PLATE HEAT TREAT ANALYSIS RULES VIII.1 INTRODUCTION r

THIS ATTACHMENT IS TO BE UTILIZED FOR THE INPROCESS AND SUBSEQUENT BASELINE INSPECTION OF HEAT TREATED SUPPORT PLATE INTERSECTIONS.

MODIFICATION OF SETUP AND ANALYSIS TECHNIQltES ADDRESSED IN THIS ATTACHMENT MAY OCCUR ONLY WHEN SUPPORTED BY ALTERNATE TEST NETH005, I.E., 8 COIL PROFILE AND/OR RPC, AND SUBMITTED TO A VIRGINIA POWER LEVEL III FOR CONCURRENCE.

VIII.2 INITIAL SETUP A.

FREQUENCIES: 400 KHZ, 200 KHZ,100 KHZ ABS AND DIFF AN ALTEMATE OF 600 KHZ MAY BE USED IN LIEU OF 100 KHZ.

B.

ABSOLUTE CDIL VERIFICATION SHALL BE DONE IN ACCORDANCE WITH III.1 a, I.E., EllCH COIL IS ACTIVE A or. B.

C.

BOBBIN COIL SETUP WILL BE PERFORMED IN ACCORDANCE WITH III.9.

VIII.3 ANALYSIS CRITERIA A.

MIX-3(400/200 ABS) SHALL BE THE PRIMARY ANALYSIS CHANNEL FOR THIS INSPECTION. OTHER FREQUENCIES SHOULD BE UTILIZED TO AID THE ANALYST IN DETERMINING ACTUAL ELEVATIONS OF THE HAZ, (HEAT AFFECTED ZONE) AND ANY DISTORTIONS, I.E., BULGES AND/OR DENTS WITHIN THIS REGION.

SGPM5018:51

ATTACHMENT VIII REY. I B.

THE'ANALYSISRULESFORTUBEWALLDEGRADATION(Ol' SAND % CALLS)AT SUPPORT PLATES SHALL FOLLOW SECTION !!! 0F THIS GUIDELINE.

C.

SCALE SHALL BE SET UTILIZING 10 KHZ DIFF BETWEEN SUPPORT PLATES.

D.

HAZ(HEATAFFECTEDZONE) 1.

THE HAZ LENGTH AND AXIAL POSITION SHALL BE REPORTED UTILIZING MIX-3 WITH REFERENCE TO '.E CENTERLINE OF THE SUPPORT PLATE. A SINGLE LINE ENTRY INTO THE FINAL REPORT SHAll. RECORD R0W, COLUMN, VOLTS, ANGLE, HAZ, CHANNEL, LOCATION FROM -T0+, AND EXTENT.OF TEST., I.E.,

I I 2 1 3.44 1 90 i HAZ l M-3 1 3-HL -2,1 TO +2.1 1 03H 02H SEE FIGURE VII #1 AND #2 2.

GRAPHIC PLOT REQUIRED ONLY WHEN THE HAZ IS NOT DETECTED OR THE HAZ APPEARS TO BE OFF CENTER MORE THAN ONE INCH.

E.

BULGE 1.

DISTORTIONS WHICH INDICATE AN AVERAGE INCREASE IN LIAMETER DUE TO-THE HEAT TREAT PROCESS THAT ARE IN EXCESS OF 25.00 V0LTS SHALL BE REPORTED UTILIZING MIX-3. A SINGLE LINE ENTRY INTO THE FINAL REPORT SHALL RECORD R0W, COLutet, VOLTS, ANGLE, B (BULGE), CHMINEL~,

LOCATION, AND EXTENT OF TEST, I.E.,

I I 2 1 26.00 ! 3 i B 1 M-3 1 3-HL +0.7! l 03H 02H SGPMS018:52

1 ATTACMENT VI!!

REV. 1 2.

GRAPHIC PLOT REQUIRED WHEN THE BULGE IS IN EXCESS OF 100 VOLTS.

SEE FIGURES VII #3 AND #4.

VIII.4 SUPPLEMENTARY TESTING A.

8 COIL PROFILONETRY 1.

8 COIL PROFILONETRY MAY BE UTILIZED TO FURTHER CLASSIFY AND QUANTIFY DIAMETER DISTORTIONS REPOR1ED BY THE BOBBIN EXAM.

2.

THIS DATA WILL BE COLLECTED BOTH BEFORE AND AFTER THE HEAT TREAT PROCESS ON A SELECT NUM8ER OF TUBES.

\\

B.

ROTATING PEUT C0IL (RPC) 1.

RPC MAY BE UTILIZED AS A TEST METH00 FOR DEGRADATION DETECTION IN THE CASE WHERE THE BULGE SIGNAL HINDERS THE BOEBiN RESULTS.

2.

THIS DATA WILL BE COLLECTED BOTH BEFORE AND AFTEV TH5 HEAT TREAT PROCESS ON A SELECT i; UMBER OF TUBES.

BOTH THE ABOVE MENTIONED TESTS WILL BE LITILIIED IF THE NEED SHOULD ARISS TO M00!FY THESE GUIDELINES.

f l

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GRADING CRITERIA NORTH ANNA UNITS I & 2 EDDY CURRENT DATA ANALYSTS TEST PROGRfM I.

PASSING CRITERIA - A minimum score of 80 is required to. pass each of the bobbin, 8x1, or RPC tests.

2.

BOBBIN COIL TEST POINT DEDUCTIONS For the purposes of the test, both the top and bottom of each TSP is to be treated as an intersection. Points will >e deducted as follows for each MISS, except that for the case where a tube has an indication above and below a given TSP, a miss of one of the two indications will result in one-half the penalty imposed for a miss at a TSP where only one indication exists. This variation is based on the logic that with two calls in the S/G, only one is required to trigger additional RPC testing. Based on this clarification, the following Grading Criteria applies:

A.~

MISS with only one indication at a TSP: -10 noints B.

HISS with two indications at a TSP:

-5 ooints far each miss C.

Overcalls >10 overcalls:

-1 noint for each after 10 D.

NORMAL INDICATIONS: 8 05: -10 ooints each 395:

-1 ooint.gigh E.

Administrative Errors - Improper identification of information such as wrong extent of test, DI vs. %, TI vs. %, ete: Satisfactory or unsatisfactory only F.

Setup improper per guidelines: Satisfactory or Unsatisfactory only 3.

8xl TEST POINT DEDUCTIONS A.

MISS of a call at an intersection: -10 noints B.

! of coils not identified:

-1 noint C.

Extent of test or location of indication: Satisfactory or Unsatisfactory on1v D.

Setup improper per guidelines: Satisfactory or U'nsatisfacterv oniv 4.

RPC TEST POINT DEDUCTIONS A.

Miss of indication: -10 coints J

B.

Improper classification of IND:.-5 noints C.

Improper extent of test: Satisfactory or Unsati;{1112fv en1v D.

Setup improper per guidelines: Satisfactory or Unsatisfactory oniv SGPMS018:54

Student's Name:

GRADE SHEET NORTH ANNA UNITS 1 & 2 EDDY CURRENT DATA ANALYSTS TEST PROGRAM 1.

Bobbin Coil - Test #

Category:

A.

TSP w/one Ind:

Points B.

TSP w/two Ind's:

Points C.

Overcallsj>s:0):

1 Points D.

Normal Ind Points E.

Admin errors:*

-f-Instances Instances ((S)or(U)

F.

Misclassification -f S) or (U G.

Setup errors:

Satisfactory (S),

Unsatisfactory (U) t TOTAL (-) POINTS:

Points 1

FINAL SCORE:

100 -

_ _ _ =

Grader /Date 2.

8xl Coils

. Test f Category:

A.

Niss:

' Points B.

f Coils:

Points C.

Ext. or Loc.:*

Instances'(S) or (U)

D.

Setup:

Satisfactory (S), Unsatis (U)

TOTAL (-) PolNTS Points FINAL SCORE:

100.-

'rader/Date 3.

RPC - Test #

Category:

A.

Miss of Ind:

Points B.

Improper Class:

Points C.

Extent:*

i Instances (S) or (U)

O.

Setup:-

Points [ Satisfactory (S),

Unsatisfactory (U)]-

TOTAL (-) POINTS Points FINAL SCORE:

100 -

=

Grader /Date SGPMS018:55

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