Text

C17 Voltage-Based ARC 90-Day Report
	ML11266A158
Person / Time
Site:	Sequoyah
Issue date:	09/16/2011
From:	; Tennessee Valley Authority
To:	; Office of Nuclear Reactor Regulation
References
	86-9166911-000
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ENCLOSUREI TENNESSEE VALLEY AUTHORITY SEQUOYAH NUCLEAR PLANT, UNIT 2 SEQUOYAH 2C17 VOLTAGE-BASED ARC 90-DAY REPORT Document No. 86-9166911-000

0402-01-F01 (Rev. 016, 03/31/2011)

A CALCULATION

SUMMARY

SHEET (CSS)

AREVA Document No.

86 9166911 000 Safety Related: 0 Yes

] No Title Sequoyah 2C17 Voltage-Based ARC 90-Day Report PURPOSE AND

SUMMARY

OF RESULTS:

Purpose:

This report summarizes the results of the Sequoyah-2 2C17 inspection results relative to the voltage-based alternate repair criterion as specified in NRC Generic Letter 95-05 [1]. This document provides the "as-found" and projected probability of burst and leak rate calculations for submittal to the NRC. This report provides a non-proprietary summary of the results. The supporting proprietary calculations and code verifications are contained in Reference [2].

Summary: The calculated as-found probability of burst and leak rate for the bounding steam generator (SG24) meet all requirements of Generic Letter 95-05. In addition, the probability of burst and leak rate for the projected conditions at EOC-18 also meet the requirements of Generic Letter 95-05..

THE DOCUMENT CONTAINS ASSUMPTIONS THAT SHALL BE THE FOLLOWING COMPUTER CODES HAVE BEEN USED IN THIS DOCUMENT:

VERIFIED PRIOR TO USE CODENERSION/REV CODENVERSION/REV F

Y L 7 rYES LKR97VB r30.F90 / Rev3 POB97VB R20.F90 / Rev2

[*

NO Page 1 of 56

A AREVA 0402-01-FOI (Rev. 016, 03/31/2011)

Document No. 86-9166911-000 Sequoyah 2C1 7 Voltage-Based ARC 90-Day Report Review Method: M Design Review (Detailed Check)

D 1Alternate Calculation Signature Block Name and Title PIR/A (printed or and Pages/Sections typed)

Signature LP/LR Date Prepared/Reviewed/Approved Alan M Brown P

0 All Principal Engineer

/7 Victor F Newman R

All Principal Engineer Jeffrey M Fleck A

All Manager

~

/a{

l Clayton B Webber

/

/j l,

Customer All TVA Approval Note: P/R/A designates Prcparcr (P), Reviewer (R), Approver (A);

LP/LR designates Lead Preparer (LP), Lead Reviewer (LR)

Project Manager Approval of Customer References (N/A if not applicable)

Name Title (printed or typed)

(printed or typed)

Signature Date NA Mentoring Information (not required per 0402-01)

Name Title Mentor to:

(printed or typed)

(PIR)

Signature Date NA Page 2

A AR EVA 0402-01 -FOl (Rev. 016, 03/31/2011)

Document No. 86-9166911 -000 Sequoyah 2C1I7 Voltage-Based ARC 90-Day Report Record of Revision Revision PageslSectio nslParag rap hs No.

Changed Brief Description / Change Authorization 000 All Original Release I

t i

i Page 3

A AR EVA Document No. 86-9166911-000 Sequoyah 2C17 Voltage-Based ARC 90-Day Report Table of Contents Page SIGNATURE BLOCK.............................................................................................................................

2 RECORD OF REVISION.......................................................................................................................

3 LIST OF TABLES..................................................................................................................................

5 LIST OF FIGURES................................................................................................................................

6

1.0 INTRODUCTION

7 2.0

SUMMARY

8 3.0 ASSUMPTIONS.........................................................................................................................

8 4.0 2C17 INSPECTION RESULTS AND VOLTAGE GROWTH RATES......................................

9 4.1 In spe ctio n R e su lts.............................................................................................................................

9 4.2 Voltage Growth Rates....................................................................................................................

11 4.3

+Point TM to Bobbin Voltage Correlation....................................................................................

12 4.4 Probe W ear Monitoring..................................................................................................................

12 4.5 Upper Voltage Repair Limit.......................................................................................................

14 4.6 Evaluation of Negative Growth Rates........................................................................................

14 5.0 DATABASES APPLIED FOR LEAK AND BURST CORRELATIONS.................................. 42 5.1 Burst Pressure Correlation.........................................................................................................

42 5.2 Probability of Leak and Conditional Leak Rate........................................................................

43 6.0 OTHER MISCELLANEOUS INPUTS...................................................................................

44 6.1 Tube Material Properties............................................................................................................

44 6.2 Probability of Detection..................................................................................................................

45 6.3 C ycle Le ng th s.................................................................................................................................

4 5 6.4 NDE Uncertainties..........................................................................................................................

45 7.0 2C17 CONDITION MONITORING.......................................................................................

48 8.0 OPERA TIONAL ASSESSMENT...........................................................................................

50

9.0 REFERENCES

56 Page 4

A AREVA Document No. 86-9166911-000 Sequoyah 2C17 Voltage-Based ARC 90-Day Report List of Tables Page Table 4-1: 2C 17 D S Is >2 V olts.........................................................................................................

16 Table 4-2: 2C17 AONDB Indications................................................................................................

16 Table 4-3: Summary of Inspection Results for SG21.....................................................................

17 Table 4-4: Summary of Inspection Results for SG22......................................................................

18 Table 4-5: Summary of Inspection Results for SG23......................................................................

19 Table 4-6: Summary of Inspection Results for SG24......................................................................

20 Table 4-7: Cycle 17 Voltage Growth Rates....................................................................................

21 Table 4-8: Cycle 17 vs. Cycle 16 Growth Comparison (Cumulative Distributions)...........................

22 Table 4-9: Cycle 17 vs. Cycle 16 Average Growth Comparison......................................................

23 Table 4-10: Retested DSIs that Were on Cal Groups that Failed the Probe Wear Check................ 24 Table 4-11: New DSIs with 2C16 and 2C17 Probe Wear Results....................................................

26 Table 4-12: Summary of Probe Wear Results from 2C16 Inspection...............................................

28 Table 4-13: Summary of New DSIs for Probe Wear Comparison....................................................

28 Table 4-14: Growth in Quantity and Voltage of Bobbin Indications..................................................

29 Table 5-1: Burst Pressure vs. Bobbin Amplitude Correlation...........................................................

42 Table 5-2: Probability of Leak Correlation......................................................................................

43 Table 5-3: Leak Rate vs. Bobbin Amplitude Correlation (2405 psi).................................................

44 Table 6-1: NDE Uncertainty Distributions.........................................................................................

46 Table 7-1: 2C17 Condition Monitoring Leak Rate and POB Results................................................

48 Table 7-2: As-Found EOC-17 vs. Projected EOC-17 Conditions....................................................

49 Table 8-1: Operational Assessment Projections for EOC-18 Conditions........................................

50 Table 8-2: Projected EOC-18 Voltage Distributions (0.6 POD).........................................................

51 Page 5

A AREVA Document No. 86-9166911-000 Sequoyah 2C17 Voltage-Based ARC 90-Day Report List of Figures Page Figure 4-1: 2C17 As-Found Voltage Distributions for SG21 and SG22..........................................

30 Figure 4-2: 2C17 As-Found Voltage Distributions for SG23 and SG24..........................................

30 Figure 4-3: Plugged Voltage Distributions for SG21 and SG22......................................................

31 Figure 4-4: Plugged Voltage Distributions for SG23 and SG24......................................................

31 Figure 4-5: RTS and Confirmed or Not Inspected w/ +PointTM (SG21 & SG22)..............................

32 Figure 4-6: RTS and Confirmed or Not Inspected w/ +Point TM (SG23 & SG24)..............................

32 Figure 4-7: All Indications Returned to Service for SG21 and SG22...............................................

33 Figure 4-8: All Indications Returned to Service for SG23 and SG24...............................................

33 Figure 4-9: Cycle 17 Growth Distribution for SG21 and SG22.........................................................

34 Figure 4-10: Cycle 17 Growth Distribution for SG23 and SG24......................................................

34 Figure 4-11: Cycle 17 vs. Cycle 16 Growth Comparison.................................................................

35 Figure 4-12: Voltage Change vs. BOC Voltage for SG21...............................................................

36 Figure 4-13: Voltage Change vs. BOC Voltage for SG22...............................................................

36 Figure 4-14: Voltage Change vs. BOC Voltage for SG23...............................................................

37 Figure 4-15: Voltage Change vs. BOC Voltage for SG24...............................................................

37 Figure 4-16: Voltage Change vs. BOC Voltage for All SGs.............................................................

38 Figure 4-17: Bobbin Volts vs. +Point TM Volts for 2C17....................................................................

39 Figure 4-18: 2C17 Probe Wear Voltage Comparison......................................................................

40 Figure 6-1: NDE Uncertainty Distributions.......................................................................................

47 Figure 8-1: Projected EOC-18 Voltage Distribution for SG21..........................................................

52 Figure 8-2: Projected EOC-1 8 Voltage Distribution for SG22...........................................................

53 Figure 8-3: Projected EOC-18 Voltage Distribution for SG23...........................................................

54 Figure 8-4: Projected EOC-18 Voltage Distribution for SG24...........................................................

55 Page 6

A AR EVA Document No. 86-9166911-000 Sequoyah 2C17 Voltage-Based ARC 90-Day Report

1.0 INTRODUCTION

Sequoyah Unit 2 (SQN2) completed the seventeenth cycle of operation in May 2011. The unit employs four Westinghouse-designed Model 51 SGs with %-inch OD mill annealed alloy 600 tubing and 3/4/4-inch carbon steel drilled-hole tube support plates (TSPs). The 2C17 scope of the eddy current inspections at Sequoyah (SQN) included a bobbin coil inspection of the straight legs of all in-service tubes in all four steam generators. The inspections were performed in accordance with the requirements of NRC Generic Letter (GL) 95-05, "Voltage-Based Repair Criteria for Westinghouse Steam Generator Tubes Affected by Outside Diameter Stress Corrosion Cracking" [1]. This is the last scheduled in-service inspection for the SQN2 steam generators. Steam generator replacement is scheduled for the 2C 18 outage in 2012.

In accordance with Generic Letter 95-05, ARC (Alternate Repair Criteria) implementation requires a pre-startup assessment [3] and a 90-day post-startup tube integrity assessment. NRC Generic Letter 95-05 outlines ARC requirements for allowing tubes containing ODSCC (Outside Diameter Stress Corrosion Cracking) indications to remain in service if the indications are contained within the TSP structure and the measured bobbin voltage is

<2.0 volts. A complete list of criteria for excluding TSP intersections from ARC application is provided in section L.b of Reference [1].

The steam generator TSP inspection results and the postulated MSLB leak rate and tube burst probabilities are summarized in this report. AREVA uses Monte Carlo codes, as described in References [4] and [5], to provide the burst and leak rate analysis simulations. Although the voltage-dependent POPCD (Probability of Prior Cycle Detection) has been approved for use at SQN2 [6], the results documented herein use the more conservative POD (Probability of Detection) of 0.6 from GL 95-05.

These evaluations are based on the methods in Reference [7] (for burst) and the slope sampling method for calculating the leak rate as discussed in Reference [13].

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A AR EVA Document No. 86-9166911-000 Sequoyah 2C17 Voltage-Based ARC 90-Day Report 2.0

SUMMARY

During the 2C17 inspection, a total of 3711 bobbin DSIs (Distorted Support Indications) were reported. There were an additional four axial ODSCC indications detected with +PointTM that did not have a corresponding bobbin OD signal. For the four indications not detected with bobbin, a bobbin voltage was inferred based on the

+PointTM voltage. Therefore, a total of 3715 indications were included in the condition monitoring assessment documented herein.

The condition monitoring assessment is an assessment of the as-found conditions. The results of the condition monitoring assessment show that the as-found leak rate and probability of burst (POB) were well below the acceptance criteria of 3.7 gpm for leakage and 1.OE-02 for P013. In addition, the as-found leak rate, POB, and number and voltages of the indications were well below the values projected during the previous operational assessment prepared after the 2C 16 outage [9].

This report also documents the projected conditions at the end of Cycle 18 (EOC-18) conditions. As required by GL 95-05, the limiting growth rate from the last two operating cycles should be used in the operational assessment. A comparison of the growth rates from Cycles 16 and 17 showed that the Cycle 16 growth rates were clearly bounding. Hence, the Cycle 16 growth rates were used in the operational assessment. The EOC-18 projections for leak rate and POB were well below the acceptance criteria.

Implementation of the voltage-based ARC requires that SQN2 participate in a tube pull program approved by the NRC. The industry developed a tube pull program which was approved by the NRC in 2000. The NRC-approved tube pull requirements are provided in the latest EPRI update of the ARC database [13]. Normally, a tube pull (minimum of two intersections) is required after three cycles of operation since the last tube pull. Since the last tube pull at SQN2 occurred during the 2C14 outage, a tube pull would normally have been required during the 2C17 outage. However, the NRC also approved an exemption for plants planning to replace steam generators.

This exemption waives the tube pull requirement if the above requirements coincide with the plant's last scheduled outage before steam generator replacement.

Since SQN2 is scheduled to replace steam generators during the next outage (2C 18), no tube pull was required nor performed during the 2C 17 outage.

3.0 ASSUMPTIONS No assumptions were used in the calculations summarized in this document.

Page 8

A AR EVA Document No. 86-9166911-000 Sequoyah 2C17 Voltage-Based ARC 90-Day Report 4.0 2C17 INSPECTION RESULTS AND VOLTAGE GROWTH RATES The SQN 2C 17 bobbin coil inspection consisted of a full-length bobbin coil examination of all in-service tubes in all four steam generators except for the u-bends of Rows I through 10 which were inspected with either +PointTM or array coils. All in-service TSP intersections on both the hot leg and cold leg sides of the tube bundle were inspected with 0.720" diameter bobbin probes.

Special interest +PointTM examinations were conducted in support of the voltage-based ARC, and in accordance with the Degradation Assessment [8] as follows:

100% of bobbin DSIs >l.0v 100% of intersections with dents >2.0v from HO1 through C06 100% of new DSIs in cold leg thinning region 100% of mixed residual indications (MRI) 100% of copper signals 4.1 Inspection Results Based on the bobbin inspections, a total of 3711 indications were identified. Four additional TSP intersections had axial ODSCC indications confirmed with +PointTM, but had no bobbin indication reported. Therefore, a total of 3715 intersections were included in the analyses documented in this report. The results of the inspection are summarized as follows:

1. Ten DSIs were greater than the lower repair limit of 2.0 volts. All of these indications were confirmed as axial ODSCC and were removed from service by plugging the affected tubes. All of these indications were located in SG24 as shown in Table 4-1.

2.

No indications were identified that exceeded the upper repair limit of 5.91 volts. The largest bobbin indication had a bobbin voltage of 3.08 volts. This same location in SG24 also had the largest +PointTM voltage detected (2.15v).

3. As mentioned above, four intersections were identified as containing AONDB (axial ODSCC not detected by bobbin) indications. These are +PointTM indications of axial ODSCC that have no signal present in the bobbin data. All four of these indications were small voltage +PointTM indications at dented intersections.

As discussed in Section 4.3, a correlation was developed to infer a bobbin voltage from the +PointTM voltage. All of the inferred voltages were relatively small (less than 1.2 equivalent bobbin volts). All four of these intersections were removed from service by plugging the affected tubes. These locations are shown in Table 4-2.

4. A total of 72 DSI/AONDB indications were removed from service during the 2C 17 outage (11 in SG21, 6 in SG22, 13 in SG23, and 42 in SG24). Some of these were removed from service due to axial ODSCC at TSPs, but others were removed from service due to other indications in the affected tube.

5. All DSI indications that were confirmed as axial ODSCC were at hot leg TSP intersections. No axial ODSCC indications were confirmed at cold leg TSP intersections.

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A AR EVA Document No. 86-9166911-000 Sequoyah 2C17 Voltage-Based ARC 90-Day Report

6.

A total of 518 intersections with DSIs were inspected with +PointTM. Of these intersections, 445 were confirmed as containing axial ODSCC indications for an overall confirmation rate of 86%. Excluding the cold leg intersections, of which none were confirmed, the confirmation rate increases to 88%.

7.

Of the confirmed axial ODSCC at TSPs, none extended outside of the TSP.

8. No indications of copper deposits were detected.

9.

Four Mixed Residual Indications (MRIs) were reported with the bobbin coil. All four intersections were inspected with +PointTM as required by GL 95-05. Three of the four indications were reported as NDF (No Defect Found) from the +PointTM examination. One intersection was confirmed as containing an axial PWSCC indication. This location, however, was also accompanied by a dent and a DDI (Distorted Dent with Indication) from the bobbin coil inspection (i.e., this indication was detected with bobbin).

Since the alternate repair criteria don't apply to PWSCC indications, this tube was removed from service.

Table 4-3 through Table 4-6 show the as-found voltage distributions for SG21 through SG24, respectively. These tables also show the 2C 17 voltage distributions based on +PointTM inspection results and plugging status for the affected tubes. As required by GL 95-05, these results are also shown graphically in Figure 4-1 through Figure 4-8.

As mentioned above, the largest bobbin voltage was 3.08v. This is considerably smaller than the largest bobbin voltage (6.55v) measured during the previous (2C16) inspection. In addition, as discussed in Section 7.0, the as-found voltages were considerably smaller than what was projected in the previous operational assessment [9].

The maximum 2C 17 voltage is more consistent with the inspection results from the 2C 15 outage during which the maximum bobbin voltage was 2.77v.

GL 95-05 requires that all indications greater than the lower repair limit (>2.0v) be inspected with a technique capable of flaw characterization (such as +PointTM).

During the last several outages at SQN2, additional inspections have been performed of indications less than 2.0v. These inspections are performed as a proactive measure to help identify indications that may be vulnerable to large voltage growth rates during the upcoming cycle as happened at Diablo Canyon Unit 2. During the 2C17 outage, all bobbin indications >1.0v were inspected with +PointTM.

Based on these supplemental inspections, an additional 6 tubes were preventatively plugged utilizing the +PointTM results and lessons learned from operating experiences.

The largest bobbin indication returned to service for Cycle 18 was a 1.91v indication in SG23. This indication was confirmed as a 0.12v axial ODSCC indication with +PointTM.

The largest +PointTM flaw returned to service for Cycle 18 was a 0.96v axial ODSCC indication in SG24. The bobbin voltage associated with this TSP intersection was 1.24v.

Page 10

A AR EVA Document No. 86-9166911-000 Sequoyah 2C17 Voltage-Based ARC 90-Day Report 4.2 Voltage Growth Rates For projection of leak rates and tube burst probabilities at EOC-18, voltage growth rates were developed from the 2C16 and 2C17 inspection data. Cycle 17 was 523.0 EFPD (Effective Full Power Days) in length [10]. This equates to 1.432 EFPY (Effective Full Power Years; 523/365.25). For indications reported as DSI in both the 2C16 and 2C17 inspections, growth rates were determined based on comparison of the voltages reported in both inspections. For indications not reported during 2C16, but reported during 2C17 (i.e., new at 2C17), the 2C16 bobbin coil data were reviewed for presence of an OD signal. In all cases, bobbin signals were present in the 2C16 data based on the lookup reviews. The 2C16 voltages from these lookups were then used to calculate bobbin voltage growth rates for all of the newly-reported indications.

The 2C17 voltage growth rate distributions are shown in Table 4-7.

These distributions are also shown graphically in Figure 4-9 and Figure 4-10. Table 4-8 and Figure 4-11 provide the growth rate distributions in cumulative probability format. This table and figure also provide a comparison of the Cycle 17 growth rates to the Cycle 16 growth rates. The Cycle 16 growth rate was taken from Reference [9] and is a bounding growth rate considering growth rate distributions from each individual steam generator. As shown in Table 4-8, the Cycle 16 bounding growth distribution clearly bounds the Cycle 17 growth rates.

Table 4-9 provides a comparison of average growth rates from Cycles 16 and 17. As shown in the table, the average change in voltage during Cycle 17 was slightly negative and less than the average voltage change in Cycle 16.

This phenomenon of negative growth during Cycle 17 was noticed early during the bobbin coil inspection.

Possible causes of the negative growth rates and the potential impact on both the condition monitoring and operational assessments are discussed in Section 4.6.

GL 95-05 requires that the limiting growth rate distribution from the last two cycles be used for the operational assessment. As discussed in Section 4.6, the negative bias in the Cycle 17 growth rates is believed to be due to a change in probe design. Since the Cycle 17 growth rates are not necessarily reflective of real flaw growth, a review of the Cycle 15 growth rates was also performed to determine if Cycle 15 growth rates should be considered for use in the operational assessment. As documented in Reference [9], the Cycle 16 growth rates bound the Cycle 15 growth rates. Therefore, since the growth rates from Cycle 16 bound those from both Cycle 15 and Cycle 17, the Cycle 16 growth rates were used in the operational assessment documented in this report.

Additional discussion is provided in Section 4.6.

Figure 4-12 through Figure 4-16 show the Cycle 17 growth rates plotted against the BOC-17 voltages for all four steam generators individually and one chart with all steam generators combined. The intent of these charts is to determine if there's any tendency for the larger indications to grow at a higher rate than the smaller indications.

This phenomenon (referred to as voltage-dependent growth) has been observed at some other similar plants and can have a non-conservative effect on the operational assessment projections. As shown in the figures, the slope is negative in all cases, thus indicating that the larger indications grow at a lower rate on average compared to the smaller indications. This is similar to the pattern observed during Cycle 16 at SQN2 as documented in Reference

[9].

Therefore, voltage-dependent growth is not expected to have a detrimental effect on the operational assessment and will, therefore, not be considered in the OA projections documented herein.

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A AR EVA Document No. 86-9166911-000 Sequoyah 2C17 Voltage-Based ARC 90-Day Report 4.3

+Point TM to Bobbin Voltage Correlation As mentioned previously, four TSP intersections had axial ODSCC indications reported by +PointTM that weren't reported with bobbin. These indications are referred to as AONDB (Axial ODSCC Not Detected with Bobbin) and are typically smaller voltage ODSCC indications (by +PointTM) that may be accompanied by a dent that masks the bobbin voltage. In all four of these cases, there was only one axial ODSCC indication present. These four indications are listed in Table 4-2.

In order to include these indications in the condition monitoring and operational assessments, a bobbin voltage must be inferred from the +PointTM voltage. This was accomplished by first plotting the 2C 17 bobbin voltages against the corresponding +PointTM voltages for all bobbin indications at non-dented intersections that were inspected and confirmed as containing axial ODSCC. This plot is shown in Figure 4-17.

An upper 95%

confidence bound on the linear regression was then determined and a second order polynomial curve was fit to the upper 95th curve. The equation for the polynomial fit is:

VBobbin95UCL = 0.0054

V+PT 2 + 0.8 17

V+PT + 0.963 This equation was used to infer a bobbin voltage for each of the four +PointTM indications shown in Table 4-2.

4.4 Probe Wear Monitoring In order to maintain consistent detection and sizing capabilities throughout the inspection, probe wear is monitored by following the requirements of Reference [11], which is documented in Reference [12]. The first NRC requirement regarding probe wear is to minimize the potential for tubes to be inspected with a probe that has failed the probe wear check.

This was accomplished by implementing the bobbin Examination Technique Specification Sheet (ETSS), which.required the probe be discarded when failing the probe wear check. Review of the probe wear log sheets and the eddy current test results indicate that no tubes were inspected with a probe that had previously failed the probe wear check.

If the DSI voltage is at or above the retest threshold (1.5 volts or higher) and the calibration group is designated as "ARC Out" on the cal board, the indication code is changed from DSI to RPW (Retest due to Probe Wear) indicating that a retest is required with a good probe. No new indications were detected in the tubes when retested with the good probe.

The 2C 17 eddy current inspection resulted in 21 bobbin indications in excess of 1.5 volts that were inspected with a worn probe. Table 4-10 shows these RPW indications, plus any indications less than 1.5 volts in the same tubes. This table also shows the DSI voltages after retest with a good probe. Figure 4-18 shows a comparison of the worn probe and good probe voltages. The average change in voltage from the worn probe to the good probe was slightly negative at -0.03v (i.e., on average, the voltage with the good probe was about 0.03v less than the voltage with the worn probe). As shown in Table 4-10 and Figure 4-18, there were five cases where the worn probe voltage was less than the lower repair limit of 2.Ov but greater than the lower repair limit with the good probe. However, there were no indications that went from <1.5v with a worn probe to >2.Ov with a good probe.

Therefore, the 1.5v criterion for retesting DSIs is reasonable and justified. In the event that an indication <1.5v Page 12

A AR EVA Document No. 86-9166911-000 Sequoyah 2C17 Voltage-Based ARC 90-Day Report was undersized due to probe wear, there are multiple conservatisms in both the inspection and analyses processes to offset such a condition. Among these conservatisms are 1) the fact that TVA proactively inspects all bobbin indications >1.0v with +PointTM, 2) TVA preventatively plugs some bobbin indications <2.Ov based on the

+PointTM results, and 3) TVA applies a probability of detection of 0.6 for the operational assessment.

The next requirement involves monitoring tubes that contain new DSIs that were inspected with probes that failed the wear check in the previous outage. This evaluation is intended to look for "new" large indications or a non-proportionately large percentage of "new" indications in tubes that failed the check in the previous outage. Table 4-11 shows the new 2C17 DSI indications along with the probe wear results from both the 2C16 and 2C17 inspections. As shown in Table 4-11, the largest new indication in a tube inspected with a worn probe in 2C16 was a 1.02v indication in SG21. The 2C16 lookup voltage for this indication was 0.8 lv. In addition, there were ten other new indications >1.0v in tubes that were inspected with good probes in 2C16. The facts that 1) all newly-reported indications were detectable on a lookup review of the 2C16 data, and 2) the largest new indications were inspected with good probes in 2C16, show that the new indications are more related to the probability of detection and not probe wear.

To determine if there is a non-proportionately large percentage of new indications in tubes inspected with probes that failed the probe wear check in the previous outage, one must first look at the overall percentage of inspections performed with worn probes in the previous outage. This information is provided in Table 4-12. As shown in the table, 5402 inspections were performed with worn probes, compared to 12825 inspections that were performed with good probes. Therefore, 29.6% of the inspections in the previous outage were performed with worn probes.

Table 4-13 summarizes new DSI indications for probe wear comparisons. Overall, there were 3711 DSIs detected during the 2C 17 inspection. 68 of these DSIs were newly-reported indications. Of the 68 total new indications, 20 were in tubes inspected with a worn probe in 2C 16 for a ratio of 29.4%. Additionally, the number of new large indications (>0.5v) was determined to be 56. Out of these 56 indications, 17 were in tubes that were inspected with a worn probe in 2C17 for a ratio of 30.4%. Since these ratios for new indications (29.4%) and new large indications (30.4%) are comparable to the ratio for all 2C16 inspections (29.6%), the new indications are not biased toward tubes inspected with worn probes in 2C16.

In summary, the NRC analysis requirements regarding probe wear monitoring were met during the 2C17 bobbin coil inspection and a more stringent wear tolerance is not required at SQN2.

Page 13

A AR EVA Document No. 86-9166911-000 Sequoyah 2C17 Voltage-Based ARC 90-Day Report 4.5 Upper Voltage Repair Limit Per GL 95-05, the upper repair limit must be calculated prior to each outage. The more conservative of the plant-specific average growth rate per EFPY or 30 percent per EFPY should be used as the anticipated growth rate input for this calculation.

Since the average growth rate for Cycle 16 was 6.8%/EFPY (Table 4-9), the required 30%/EFPY was used for the upper repair limit calculation. The structural limit of 9.40v used for this calculation is based on the Addendum 7 database at an accident pressure differential of 2405 psid. The expected cycle length for the upcoming cycle (Cycle 18) is 1.30 EFPY (Effective Full Power Years) [10]. Based on these inputs and the following formula, the upper repair limit was calculated to be 5.91 v.

V URLVSL

% VNDE

% VCG 1+-

+

100 100 where:

VURL = upper voltage repair limit, VNDE = NDE voltage measurement uncertainty = 20%,

VCG = voltage growth anticipated between inspections = 30%/EFPY x 1.30 EFPY = 39.0%,

VSL = voltage structural limit from the burst pressure - Bobbin voltage correlation, where the limit of 9.40 volts was used based on Reference 8.

4.6 Evaluation of Negative Growth Rates As discussed previously, it was noted during the inspection that an unusually large number of DSIs were decreasing in bobbin voltage compared to what was reported during the. 2C16 inspection.

The primary differences between the two inspections were the facts that a different frequency generator was used and a different probe manufacturer was used. The 2C16 inspection was performed by Westinghouse which used a Corestar frequency generator and Westinghouse designed probes (built.by Corestar or Zetec) while the 2C17 inspection was performed by AREVA which used a Zetec frequency generator and Zetec probes (not built to the Westinghouse design).

When this was first noticed early during the bobbin coil inspection, the lead analyst reviewed the bobbin data for several indications that showed a decrease in bobbin voltage. This review (of both the 2C16 and 2C17 results) showed that the indications were correctly reported in both outages.

After the outage, additional reviews were done to determine the cause of this downward bias in the 2C17 bobbin voltages. This review covered calibration standards, voltage normalization, and probe design.

The calibration standards were the same in both outages. The voltage normalization processes were also the same in both outages and in accordance with the requirements of GL 95-05. In addition, the voltage normalization process used by AREVA during the 2C17 inspection at SQN2 is the same process used by AREVA during previous outages at Diablo Canyon (which also applied the voltage-based ARC prior to steam generator replacement).

A review of the probe design, however, showed that the design of the bobbin probe was slightly different between the two inspections. The probes used by AREVA in the 2C 17 outage were standard bobbin coil probes designed and built by Zetec. The probes used during the 2C16 were built by either Zetec or Corestar, but were built to a Westinghouse design.

Page 14

A AR EVA Document No. 86-9166911-000 Sequoyah 2C1 7 Voltage-Based ARC 90-Day Report A review of probes used in outages prior to 2C16 showed that the change from the Zetec design to the Westinghouse design was made during the 2C14 outage. The 2C14 inspection showed an abnormally high growth rate and an abnormally large number of new indications. The high growth rate and large number of new indications observed during 2C14 is believed to be associated with the change in probe design. Based on the increase in growth and number of indications seen during 2C14, a similar decrease would be expected when going back to the Zetec designed probe as occurred during 2C 17.

Table 4-14 and Figure 4-19 show the indication counts for the 2Cl 1 through the 2C17 inspections as well as the growth in percent growth per EFPY for Cycles 11 through 17. It should be noted that the number of indications shown in the table were taken from the previous 90-Day Reports. Since the number of AONDB indications has been relatively small, no attempt was made to remove these from the indication counts. The small number of AONDB indications seen at SQN2 would not affect the conclusions drawn from this study.

As shown in the table, the number of indications reported typically increases by about 500 indications in each cycle provided there is no change in probe design. From 2C13 to 2C14, however, the population of detected indications increased by 900 indications. Likewise, the growth increased from previous values of about 10% per EFPY to nearly 18% per EFPY.

When going from the Westinghouse probe design (2C16) back to the Zetec design (2C17), the number of indications remained relatively flat (3747 indications in 2C16 to 3715 indications in 2C17). The growth rate also decreased from a rate of 6.8% per EFPY in Cycle 16 to -7.4% per EFPY in Cycle 17. These decreases seen at 2C17 are similar in magnitude to the increases seen at 2C14.

Therefore, the apparent inspection transient observed during the 2C 17 inspection is believed to be reflective of the change in probe design.

Since the Cycle 17 growth rate had a negative bias that was not necessarily reflective of a decrease in flaw growth, the Cycle 15 growth rate was also reviewed. This was done because GL 95-05 requires that the limiting growth distribution from the last two cycles be used for the operational assessment. Since the Cycle 17 growth rates are not necessarily indicative of real flaw growth, a comparison of growth rates from the two cycles prior to Cycle 17 was performed. This comparison, as documented in Reference [9], showed that the Cycle 16 growth rates bound those from Cycle 15. Therefore, the Cycle 16 growth was used in the operational assessment.

In conclusion, the probes, eddy current techniques, calibration standards, and voltage normalization practices used during the 2C17 inspection were all in accordance with the requirements of GL 95-05. A review of probes used in previous inspections relative to growth of indications showed that there was an upward bias on growth rates when going from the Zetec design to the Westinghouse design. The decrease in growth rates when going back to the Zetec design was similar in magnitude to the above-mentioned increase in growth rates. Therefore, the 2C17 results are believed to be consistent with the results from inspections prior to 2C14 relative to bobbin voltage response for a given axial ODSCC flaw.

In addition, since the Cycle 17 growth rates were affected by the change in probe design, the most limiting growth distribution from the last three cycles (Cycles 15, 16, and 17) was used for the OA. The comparison of Cycle 16 to Cycle 17 growth rates is provided in Section 4.2. The comparison of Cycle 16 to Cycle 15 growth rates is provided in Reference [9]. These comparisons showed that the Cycle 16 growth rates bounded those from both Cycle 15 and Cycle 17.

Therefore, the Cycle 16 growth rates were used for the operational assessment documented in this report.

Page 15

A AR EVA Document No. 86-9166911-000 Sequoyah 2C17 Voltage-Based ARC 90-Day Report Table 4-1: 2C17 DSls >2 Volts SG Row Cal Id Iev Volts SG24 17 26 DSI H02 2.42 SG24 18 18 DSI H01 2.21 SG24 18 33 DSI H01 2.01 SG24 20 30 DSI H02 2.65 SG24 20 39 DSI H05 2.64 SG24 20 48 DSI H05 2.25 SG24 20 49 DSI H04 2.2 SG24 20 59 DSI H04 3.08 SG24 29 26 DSI H02 2.02 SG24 34 50 DSI H03 2.03 Table 4-2: 2C17 AONDB Indications Inferred

+PointTM Dent Ifre SG Row Col Elev Ind Vonts Dent Bobbin Volts Volts Vot Volts SG22 6

13 H02 SAI 0.14 1.19 1.077 SG22 36 24 H01 SAI 0.18 4.08 1.110 SG24 12 2

H02 SAI 0.24 1.13 1.159 SG24 36 75 H01 SAI 0.21 1.25 1.135 Page 16

A AR EVA Document No. 86-9166911-000 Sequoyah 2C17 Voltage-Based ARC 90-Day Report Table 4-3: Summary of Inspection Results for SG21

+PointTM Inspection Results DSI's Returned to Service Volage 2C17 As-Confirmed Inspected but Bin As-Confirmed Not Confirmed Not Plugged Confirmed or Found as Axial Not Inspected Total ODSCC as Axial Inspected w/ +PointT m

ODSCC 0.1 1

0 0

1 0

1 1

0.2 45 0

0 45 0

45 45 0.3 68 0

0 68 1

67 67 0.4 73 2

0 71 2

71 71 0.5 103 0

0 103 3

100 100 0.6 91 1

2 88 0

91 89 0.7 84 1

1 82 3

81 80 0.8 47 1

0 46 0

47 47 0.9 38 0

0 38 0

38 38 1

37 1

1 35 1

36 35 1.1 21 19 2

0 1

20 18 1.2 11 11 0

0 0

11 11 1.3 9

9 0

0 0

9 9

1.4 6

5 1

0 0

6 5

1.5 3

3 0

0 0

3 3

1.6 4

2 2

0 0

4 2

1.7 0

0 0

1.8 1

1 0

0 0

1 1

1.9 1

1 0

0 0

1 1

2 0

0 0

2.1 0

0 0

2.2 0

0 0

2.3 0

0 0

2.4 0

0 0

2.5 0

0 0

2.6 0

0 0

2.7 0

0 0

2.8 0

0 0

2.9 0

0 0

3 0

0 0

3.1 0

0 0

3.2 0

0 0

3.3 0

0 0

3.4 0

0 0

3.5 0

0 0

>3.5 0

0 0

Total 643 57 9

577 11 632 623

>1V 56 51 5

0 1

55 50

>2V 0

0 0

Page 17

A AR EVA Document No. 86-9166911-000 Sequoyah 2C17 Voltage-Based ARC 90-Day Report Table 4-4: Summary of Inspection Results for SG22

+PointTM Inspection Results DSI's Returned to Service Volage 2C17 As-Confirmed Inspected but Bin Fon asnAage Not Confirmed Not Plugged Confirmed or Found as Axial Not Inspected Total ODSCC as Axial Inspected w/ +Point TM ODSCC 0.1 4

0 0

4 0

4 4

0.2 32 0

0 32 0

32 32 0.3 73 1

2 70 2

71 69 0.4 120 1

1 118 0

120 119 0.5 105 1

0 104 0

105 105 0.6 102 0

1 101 0

102 101 0.7 86 2

0 84 0

86 86 0.8 57 4

0 53 0

57 57 0.9 37 1

1 35 0

37 36 1

33 3

0 30 0

33 33 1.1 21 18 3

0 1

20 17 1.2 12 10 2

0 2

10 8

1.3 17 15 2

0 0

17 15 1.4 9

8 1

0 0

9 8

1.5 5

4 1

0 0

5 4

1.6 1

1 0

0 0

1 1

1.7 1

1 0

0 0

1 1

1.8 0

0 0

1.9 1

1 0

0 1

0 0

2 0

0 0

2.1 0

0 0

2.2 0

0 0

2.3 0

0 0

2.4 0

0 0

2.5 0

0 0

2.6 0

0 0

2.7 0

0 0

2.8 0

0 0

2.9 0

0 0

3 0

0 0

3.1 0

0 0

3.2 0

0 0

3.3 0

0 0

3.4 0

0 0

3.5 0

0 0

>3.5 0

0 0

Total 716 71 14 631 6

710 696

>1V 67 58 9

0 4

63 54

>2V 0

0 0

Page 18

A AREVA Document No. 86-9166911-000 Sequoyah 2C17 Voltage-Based ARC 90-Day Report Table 4-5: Summary of Inspection Results for SG23

+PointTM Inspection Results DSI's Returned to Service Voltage 2C17 CInspected but Bin As-Confirmed Not Confirmed Not Plugged Confirmed or Foundas Axial Inspected Not Inspected Total ODSCC ODSCC w/ +PointTM 0.1 9

0 0

9 0

9 9

0.2 22 0

0 22 0

22 22 0.3 75 0

0 75 0

75 75 0.4 107 1

1 105 2

105 104 0.5 108 1

2 105 0

108 106 0.6 113 1

1 111 3

110 109 0.7 110 0

4 106 3

107 103 0.8 86 3

3 80 0

86 83 0.9 57 1

1 55 1

56 55 1

51 2

3 46 0

51 48 1.1 39 31 8

0 2

37 30 1.2 33 28 5

0 0

33 28 1.3 28 24 4

0 1

27 23 1.4 20 15 5

0 1

19 14 1.5 4

4 0

0 0

4 4

1.6 8

8 0

0 0

8 8

1.7 5

5 0

0 0

5 5

1.8 0

0 0

1.9 2

2 0

0 0

2 2

2 1

1 0

0 0

1 1

2.1 0

0 0

2.2 0

0 0

2.3 0

0 0

2.4 0

0 0

2.5 0

0 0

2.6 0

0 0

2.7 0

0 0

2.8 0

0 0

2.9 0

0 0

3 0

0 0

3.1 0

0 0

3.2 0

0 0

3.3 0

0 0

3.4 0

0 0

3.5 0

0 0

>3.5 0

0 0

Total 878 127 37 714 13 865 829

>1V 140 118 22 0

4 136 115

>2V 0

0 0

Page 19

A AREVA Document No. 86-9166911-000 Sequoyah 2C17 Voltage-Based ARC 90-Day Report Table 4-6: Summary of Inspection Results for SG24

+Point TM Inspection Results DSI's Returned to Service Voltage 2C17 Confirmed Inspected but Bin Fon asnAial Not Confirmed Not Plugged Confirmed or Found as Axial Not Inspected Total ODSCC as Axial Inspected w/ +Point TM ODSCC 0.1 4

0 0

4 0

4 4

0.2 45 0

0 45 0

45 45 0.3 162 0

0 162 1

161 161 0.4 207 1

2 204 10 197 195 0.5 210 1

2 207 2

208 206 0.6 208 1

1 206 2

206 205 0.7 165 1

2 162 4

161 159 0.8 118 1

1 116 0

118 117 0.9 105 1

0 104 0

105 105 1

74 13 0

61 1

73 73 1.1 49 47 2

0 2

47 45 1.2 50 48 2

0 6

44 42 1.3 15 15 0

0 1

14 14 1.4 16 15 1

0 0

16 15 1.5 11 11 0

0 0

11 11 1.6 11 11 0

0 0

11 11 1.7 6

6 0

0 0

6 6

1.8 6

6 0

0 2

4 4

1.9 5

5 0

0 0

5 5

2 1

1 0

0 1

0 0

2.1 3

3 0

0 3

0 0

2.2 1

1 0

0 1

.0 0

2.3 2

2 0

0 2

0 0

2.4 0

0 0

2.5 1

1 0

0 1

0 0

2.6 0

0 0

2.7 2

2 0

0 2

0 0

2.8 0

0 0

2.9 0

0 0

3 0

0 0

3.1 1

1 0

0 1

0 0

3.2 0

0 0

3.3 0

0 0

3.4 0

0 0

3.5 0

0 0

>3.5 0

0 0

Total 1478 194 13 1271 42 1436 1423

>1V 180 175 5

0 22 158 153

>2V 10 10 0

0 10 0

0 Page 20

A AR EVA Document No. 86-9166911-000 Sequoyah 2C17 Voltage-Based ARC 90-Day Report Table 4-7: Cycle 17 Voltage Growth Rates Voltage Growth per SG21 SG22 SG23 SG24 All SGs EFPY

<0 462 511 626 1048 2647 0.1 125 146 156 297 724 0.2 41 42 57 89 229 0.3 13 13 26 17 69 0.4 2

2 8

10 22 0.5 0

0 4

4 8

0.6 0

0 1

3 4

0.7 0

0 0

4 4

0.8 0

0 0

2 2

0.9 0

0 0

1 1

1 0

0 0

1 1

1.1 0

0 0

1.2 0

0 0

1.3 0

0 0

1.4 0

0 0

1.5 0

0 0

1.6 0

0 0

1.7 0

0 0

1.8 0

0 0

1.9 0

0 0

2 0

0 0

>2 0

0 0

Total 643 714 878 1476 3711 Page 21

A AR EVA Document No. 86-9166911-000 Sequoyah 2C1 7 Voltage-Based ARC 90-Day Report Table 4-8: Cycle 17 vs. Cycle 16 Growth Comparison (Cumulative Distributions)

Cycle 17 Growth Cycle 16 Growth Voltage Growth per EFPY SG21 SG22 SG23 SG24 All SGs Bounding Composite 0

0.7185 0.7157 0.7130 0.7100 0.7133 0.3442 0.1 0.9129 0.9202 0.8907 0.9112 0.9084 0.7455 0.2 0.9767 0.9790 0.9556 0.9715 0.9701 0.9010 0.3 0.9969 0.9972 0.9852 0.9831 0.9887 0.9568 0.4 1.0000 1.0000 0.9943 0.9898 0.9946 0.9802 0.5 1.0000 1.0000 0.9989 0.9925 0.9968 0.9887 0.6 1.0000 1.0000 1.0000 0.9946 0.9978 0.9915 0.7 1.0000 1.0000 1.0000 0.9973 0.9989 0.9947 0.8 1.0000 1.0000 1.0000 0.9986 0.9995 0.9954 0.9 1.0000 1.0000 1.0000 0.9993 0.9997 0.9969 1

1.0000 1.0000 1.0000 1.0000 1.0000 0.9969 1.1 1.0000 1.0000 1.0000 1.0000 1.0000 0.9985 1.2 1.0000 1.0000 1.0000 1.0000 1.0000 0.9985 1.3 1.0000 1.0000 1.0000 1.0000 1.0000 0.9985 1.4 1.0000 1.0000 1.0000 1.0000 1.0000 0.9985 1.5 1.0000 1.0000 1.0000 1.0000 1.0000 0.9989 1.6 1.0000 1.0000 1.0000 1.0000 1.0000 0.9989 2.2 1.0000 1.0000 1.0000 1.0000 1.0000 0.9989 2.3 1.0000 1.0000 1.0000 1.0000 1.0000 0.9993 4.6 1.0000 1.0000 1.0000 1.0000 1.0000 0.9993 4.7 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000

>4.7 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 Page 22

A AR EVA Document No. 86-9166911-000 Sequoyah 2C1 7 Voltage-Based ARC 90-Day Report Table 4-9: Cycle 17 vs. Cycle 16 Average Growth Comparison SG21 SG22 SG23 SG24 All SGs Average BOC Volts 0.671 0.663 0.756 0.707 0.704 Cycle Average Growth per EFPY 0.057 0.033 0.037 0.057 0.048 16 Average Percent Growth per EFPY 8.5%

5.0%

4.9%

8.0%

6.8%

Average BOC Volts 0.666 0.650 0.749 0.688 0.691 Cycle Average Growth per EFPY

-0.059

-0.051

-0.060

-0.042

-0.051 17 Average Percent Growth per EFPY

-8.9%

-7.8%

-8.0%

-6.1%

-7.4%

Page 23

A AREVA Document No. 86-9166911-000 Sequoyah 2C17 Voltage-Based ARC 90-Day Report Table 4-10: Retested DSIs that Were on Cal Groups that Failed the Probe Wear Check Worn Probe Good Probe SG Row Col Elev

% Diff Ind Volts Leg-Cal Ind Volts Leg-Cal SG23 20 86 H01 RPW 1.68 Cold-24 DSI 1.13 Cold-35

-32.7%

SG23 24 12 H01 RPW 1.82 Cold-13 DSI 1.62 Cold-48

-11.0%

SG23 24 12 H02 RPW 1.01 Cold-13 DSI 0.7 Cold-48

-30.7%

SG23 24 16 H01 RPW 1.74 Cold-13 DSI 1.61 Cold-48

-7.5%

SG23 24 16 H02 RPW 0.59 Cold-13 DSI 1.03 Cold-48 74.6%

SG23 26 11 H03 RPW 1.11 Cold-13 DSI 0.83 Cold-48

-25.2%

SG23 26 12 H01 RPW 0.73 Cold-13 DSI 0.69 Cold-48

-5.5%

SG23 26 12 H03 RPW 1.59 Cold-13 DSI 0.9 Cold-48

-43.4%

SG23 26 28 H01 RPW 1.85 Cold-13 DSI 1.23 Cold-48

-33.5%

SG23 26 28 H03 RPW 1.09 Cold-13 DSI 0.79 Cold-48

-27.5%

SG23 34 25 H01 RPW 2.22 Cold-13 DSI 1.62 Cold-48

-27.0%

SG23 34 25 H02 RPW 1

Cold-13 DSI 0.84 Cold-48

-16.0%

SG23 34 25 H03 RPW 0.81 Cold-13 DSI 0.54 Cold-48

-33.3%

SG23 34 25 H04 RPW 0.77 Cold-13 DSI 0.58 Cold-48

-24.7%

SG23 35 58 H02 RPW 1.66 Cold-23 DSI 1.6 Cold-48

-3.6%

SG23 35 58 H04 RPW 0.28 Cold-23 DSI 0.27 Cold-48

-3.6%

SG23 35 58 H05 RPW 0.44 Cold-23 DSI 0.39 Cold-48

-11.4%

SG24 17 27 H01 RPW 1.62 Cold-14 DSI 1.55 Cold-34

-4.3%

SG24 17 27 H03 RPW 0.39 Cold-14 DSI 0.38 Cold-34

-2.6%

SG24 18 18 H01 RPW 2.3 Cold-14 DSI 2.21 Cold-34

-3.9%

SG24 20 25 H01 RPW 1.8 Cold-14 DSI 1.76 Cold-34

-2.2%

SG24 20 25 H02 RPW 0.93 Cold-14 DSI 0.96 Cold-34 3.2%

SG24 20 25 H04 RPW 1.16 Cold-14 DSI 1.14 Cold-34

-1.7%

SG24 20 25 H06 RPW 0.61 Cold-14 DSI 0.5 Cold-34

-18.0%

SG24 20 25 H07 RPW 0.29 Cold-14 DSI 0.31 Cold-34 6.9%

SG24 20 29 H02 RPW 1.86 Cold-14 DSI 1.94 Cold-34 4.3%

SG24 20 29 H04 RPW 0.5 Cold-14 DSI 0.61 Cold-34 22.0%

SG24 20 30 H02 RPW 1.74 Cold-14 DSI 2.65 Cold-34 52.3%

SG24 20 30 H04 RPW 0.32 Cold-14 DSI 0.34 Cold-34 6.3%

SG24 20 48 H01 RPW 1.18 Cold-19 DSI 1.21 Cold-45 2.5%

SG24 20 48 H02 RPW 0.86 Cold-19 DSI 1.14 Cold-45 32.6%

SG24 20 48 H05 RPW 1.55 Cold-19 DSI 2.25 Cold-45 45.2%

SG24 20 49 H01 RPW 0.34 Cold-19 DSI 0.32 Cold-45

-5.9%

SG24 20 49 H02 RPW 0.44 Cold-19 DSI 0.41 Cold-45

-6.8%

Page 24

A AR EVA Document No. 86-9166911-000 Sequoyah 2C17 Voltage-Based ARC 90-Day Report Table 4-10: Retested DSIs that Were on Cal Groups that Failed the Probe Wear Check Worn Probe Good Probe SG Row Col Elev

% Duff Ind Volts Leg-Cal Ind Volts Leg-Cal SG24 20 49 H03 RPW 1.17 Cold-19 DSI 1.2 Cold-45 2.6%

SG24 20 49 H04 RPW 1.88 Cold-19 DSI 2.2 Cold-45 17.0%

SG24 20 59 H01 RPW 1

Hot-20 DSI 1.05 Cold-45 5.0%

SG24 20 59 H04 RPW 3.02 Hot-20 DSI 3.08 Cold-45 2.0%

SG24 20 59 H05 RPW 0.32 Hot-20 DSI 0.4 Cold-45 25.0%

SG24 21 51 H01 RPW 1.58 Cold-19 DSI 1.71 Cold-45 8.2%

SG24 21 51 H02 RPW 0.45 Cold-19 DSI 0.44 Cold-45

-2.2%

SG24 25 60 H01 RPW 1.72 Hot-21 DSI 1.63 Cold-45

-5.2%

SG24 25 60 H02 RPW 1.3 Hot-21 DSI 1.28 Cold-45

-1.5%

SG24 25 60 H04 RPW 0.43 Hot-21 Not Reported NA SG24 27 27 H02 RPW 1.73 Cold-14 DSI 1.59 Cold-34

-8.1%

SG24 29 26 H02 RPW 1.83 Cold-14 DSI 2.02 Cold-34 10.4%

SG24 31 58 H02 RPW 1.13 Hot-21 DSI 1.12 Cold-45

-0.9%

SG24 31 58 H03 RPW 1.53 Hot-21 DSI 1.37 Cold-45

-10.5%

SG24 34 50 H03 RPW 1.89 Cold-19 DSI 2.03 Cold-45 7.4%

SG24 34 50 H04 RPW 0.28 Cold-19 DSI 0.37 Cold-45 32.1%

Page 25

A AR EVA Document No. 86-9166911-000 Sequoyah 2C1 7 Voltage-Based ARC 90-Day Report

Table 4-11: New DSIs with 2C16 and 2C17 Probe Wear Results 2C17 2C16 SG Row Col Ind Elev ARC ARC Cal Ou*

Volts Cal Ou*

Volts**

Out*

SG21 10 15 DSI H01 Hot-1 0.6 Cold-18 0.84 SG21 10 41 DSI H01 Hot-43 0.99 Cold-24 1.45 SG21 32 71 DSI H02 Hot-24 Out 1.02 Cold-30 Out 0.81 SG21 44 54 DSI C01 Hot-21 0.57 Cold-26 Out 0.28 SG21 44 59 DSI H04 Hot-22 0.62 Cold-27 0.56 SG22 2

85 DSI H05 Hot-63 0.56 Hot-5 0.52 SG22 8

6 DSI H03 Hot-3 0.36 Hot-1 0.19 SG22 8

93 DSI H02 Hot-57 0.6 Hot-5 0.45 SG22 10 13 DSI H03 Hot-3 0.29 Cold-15 0.37 SG22 10 72 DSI H02 Hot-7 Out 0.83 Cold-31 1

SG22 10 91 DSI H02 Hot-63 0.78 Cold-30 0.99 SG22 12 37 DSI H01 Cold-14 0.92 Cold-39 1

SG22 15 40 DSI H01 Cold-21 Out 0.92 Cold-22 0.7 SG22 15 62 DSI H02 Hot-35 0.62 Cold-27 Out 0.7 SG22 20 55 DSI H01 Hot-33 Out 0.58 Cold-25 Out 0.51 SG22 24 26 DSI H02 Cold-18 0.82 Cold-18 0.45 SG22 25 32 DSI H02 Cold-19 0.7 Cold-20 Out 0.3 SG22 28 45 DSI H01 Cold-22 0.44 Cold-22 0.45 SG22 30 12 DSI C01 Cold-16 0.27 Cold-16 0.24 SG22 31 37 DSI H01 Cold-21 Out 1.31 Cold-19 1.05 SG22 33 18 DSI H05 Cold-17 Out 1.01 Cold-16 1.09 SG22 35 62 DSI H03 Hot-35 0.84 Cold-23 0.76 SG22 38 29 DSI H02 Cold-18 0.97 Cold-17 Out 0.8 SG22 41 43 DSI H01 Cold-21 Out 0.47 Cold-40 0.52 SG22 43 64 DSI H01 Hot-35 0.67 Cold-23 0.76 SG22 44 39 DSI C01 Cold-20 0.52 Cold-39 0.58 SG23 2

31 DSI H06 Hot-61 1

Hot-3 1.05 SG23 2

39 DSI H05 Hot-62 Out 0.75 Hot-3 0.92 SG23 2

88 DSI C03 Cold-9 0.68 Cold-5 Out 0.73 SG23 8

18 DSI H01 Hot-2 1.14 Hot-3 1.26 SG23 9

42 DSI H01 Hot-62 Out 0.69 Hot-3 0.72 SG23 11 11 DSI H05 Cold-6 0.6 Cold-13 0.66 SG23 16 15 DSI H01 Cold-13 Out 1.05 Cold-13 0.72 SG23 19 45 DSI H02 Cold-18 0.63 Cold-46 0.5 SG23 23 84 DSI H03 Cold-21 0.76 Cold-23 0.82 Page 26

A AR EVA Document No. 86-9166911-000 Sequoyah 2C1 7 Voltage-Based ARC 90-Day Report Table 4-11: New DSIs with 2C16 and 2C17 Probe Wear Results 2C17 2C16 SG Row Col Ind Elev ARC ARC Cal Ou*

Volts Cal Ou*

Volts**

Out*

SG23 26 10 DSI H02 Cold-13 Out 0.88 Cold-14 0.73 SG23 26 13 DSI H01 Cold-13 Out 1.16 Cold-13 1.15 SG23 26 16 DSI H01 Cold-13 Out 0.6 Cold-14 0.45 SG23 31 13 DSI H01 Cold-13 Out 0.87 Cold-14 0.36 SG23 31 35 DSI H02 Cold-16 0.62 Cold-16 Out 0.76 SG23 35 26 DSI H02 Cold-14 0.82 Cold-10 Out 0.98 SG23 36 35 DSI H03 Cold-15 0.8 Cold-10 Out 0.9 SG23 38 26 DSI H01 Cold-13 Out 1

Cold-10 Out 0.68 SG23 38 40 DSI H02 Cold-18 0.81 Cold-11 Out 0.48 SG23 39 36 DSI H02 Cold-15 0.87 Cold-10 Out 0.96 SG23 42 33 DS1 C02 Cold-16 0.38 Cold-10 Out 0.57 SG23 44 44 DS!

C01 Cold-18 0.48 Cold-16 Out 0.82 SG24 3

20 DSI H03 Hot-2 0.51 Hot-1 0.44 SG24 7

26 DSI H02 Hot-1 0.65 Hot-3 Out 0.59 SG24 8

28 DSI H02 Hot-1 0.86 Hot-4 Out 0.82 SG24 8

30 DS1 H02 Hot-1 0.68 Hot-4 Out 0.55 SG24 8

88 DSI H07 Hot-5 0.31 Hot-3 Out 0.13 SG24 9

20 DSI H03 Hot-2 0.56 Hot-1 0.65 SG24 15 39 DSI H02 Cold-13 0.76 Cold-16 0.91 SG24 19 48 DSI H02 Cold-18 1.9 Cold-15 1.82 SG24 20 26 DS1 H01 Cold-15 0.57 Cold-9 0.69 SG24 20 26 DS1 H04 Cold-15 0.69 Cold-9 0.76 SG24 20 48 DS1 H05 Cold-45 2.25 Cold-15 1.52 SG24 23 74 DS1 H03 Hot-24 0.24 Cold-19 0.31 SG24 27 23 DS1 H03 Cold-14 Out 0.91 Cold-10 0.88 SG24 29 24 DS0 H01 Cold-15 0.7 Cold-9 0.81 SG24 29 58 DSI H05 Hot-21 Out 0.32 Hot-31 0.3 SG24 34 16 DS1 C01 Cold-16 0.63 Cold-7 0.47 SG24 34 18 DS1 C01 Cold-16 0.49 Cold-9 0.47 SG24 35 18 DS1 C01 Cold-17 0.67 Cold-9 0.48 SG24 39 57 DSI C05 Hot-21 Out 0.44 Cold-18 0.51 SG24 43 63 DS!

C03 Hot-22 1.09 Hot-31 1.22 SG24 44 34 DSI C01 Cold-12 0.53 Cold-11 Out 0.51

"Out" indicates that the probe on the specified calibration group failed the probe wear check.

- 2C16 voltages for newly-reported indications were obtained from lookups of the 2C16 raw bobbin data.

Page 27

A AR EVA Document No. 86-9166911-000 Sequoyah 2C17 Voltage-Based ARC 90-Day Report Table 4-12: Summary of Probe Wear Results from 2C16 Inspection Number of Number of Percent of Total Number SG Inspections Inspections of Inspections Inspections with Good with Worn with Worn Probe (2C16)

Probe (2C16)

(2016)

Probe (2C16)

SG21 3092 1473 4565 32.3%

SG22 3199 1187 4386 27.1%

SG23 3116 1530 4646 32.9%

SG24 3418 1212 4630 26.2%

Total 12825 5402 18227 29.6%

Table 4-13: Summary of New DSIs for Probe Wear Comparison New Insp Percent of New >=0.5v Percent of Ne np New Inds New >=0.5v Nw>05 SG All 2C17 New w/ Worn Insp w/

New Insp w/Worn New/>=.5 DSIs Inds Probe in

>=0.5v Probe in Insp w/Worn 2C16 Worn Probe 20 Probe in in 2C16 2C16 SG21 643 5

2 40.0%

5 2

40.0%

SG22 714 21 4

19.0%

16 4

25.0%

SG23 878 21 9

42.9%

19 7

36.8%

SG24 1476 21 5

23.8%

16 4

25.0%

Total]I 3711

[68

[

20 129.4%

56 17 1

30.4%

Page 28

A AREVA.

Document No. 86-9166911-000 Sequoyah 2C17 Voltage-Based ARC 90-Day Report Table 4-14: Growth in Quantity and Voltage of Bobbin Indications Operating Cycle Probe Design Number of Indications Percent Growth per EFPY Cycle 11 Zetec 1045 7.5%

Cycle 12 Zetec 1545 10.3%

Cycle 13 Zetec 1847 10.6%

Cycle 14 Westinghouse 2747 17.8%

Cycle 15 Westinghouse 3223

-0.7%

Cycle 16 Westinghouse 3747 6.8%

Cycle 17 Zetec 3715

-7.4%

Page 29

A AREVA Document No. 86-9166911-000 Sequoyah 2C1 7 Voltage-Based ARC 90-Day Report Figure 4-1: 2C17 As-Found Voltage Distributions for SG21 and SG22

A C0 160 0

z 250 200 150 100 50 03SG21

SG22 iii

~EIFIr 0

ýjr.1 m -;

in D r-00

)

-1

-1 r,4 M -Z in LD tI 00 M r-4 -4 C-4 MY L n to r

CO M~ M r-I 4 rN

(

66 6

6 6

r-r-I' _mmm4 41

ý

ý"

ýn Bobbin VoltsA Figure 4-2: 2C17 As-Found Voltage Distributions for SG23 and SG24 250 200 inC 150 0

L.

CU 1500 50 0

I I

0. 0 0 00..0 r

q.-4

-1. (N m. r.

In*

-c 1

m. *.

4 r4 N N

m M M

(

A Bobbin Volts Page 30

A AREVA Document No. 86-9166911-000 Sequoyah 2C17 Voltage-Based ARC 90-Day Report Figure 4-3: Plugged Voltage Distributions for SG21 and SG22 12 1 0 F

S G 21

SG22 I-0 8

,l U

6 0

E 4

2 0

,-I n iq Lp I**

Io aI

t Iq Iq r,

oq cý 1qr q

0J m

C3 C~D 0~

CD CD

-0

-4

-4 mý 1-1-1

-o C14 r'

N mq r4 LA (D Cq Oq m

r-n (n

A Bobbin Volts Figure 4-4: Plugged Voltage Distributions for SG23 and SG24 12 10 C nSG2

.2 8

6 0

03 z

2 0

I4 (N

i

Lq w r-. wO Qý ~-1

~

Nc Ln

q. Ir-Co o' Ný 4

m ujL w r-wO m m (N

N a 0 0 C6 0 0o o o o

r-I I r-I

ýA r 1-4.-A 1-(N(N(

(Nj (j (4

N N

(

M M e A

Bobbin Volts Page 31

A ARE VA Document No. 86-9166911-000 Sequoyah 2C17 Voltage-Based ARC 90-Day Report Figure 4-5: RTS and Confirmed or Not Inspected w/ +Point TM (SG21 & SG22)

/-U 4A M

0 6.2

.0 E

z 200 1 cfl E2SG21

SG22 1500 500 50

-4 "N

't Ln W

F*

0 Oq rI 14 (N

,I m-q LP r- 00 M

(N r4 e i

Lf

! ri 0 Oq ( M r-4 (N (N A

Bobbin Volts Figure 4-6: RTS and Confirmed or Not Inspected w/ +Point TM (SG23 & SG24) 250 200 150 100 50 0

II

-1 "N In Id Ui 00 r-C17

-i "N In 14 i

IR "I W~ M(N

.i "N In 1*

LA rý "0 Cý M ~-1 "N "

600 0

D00000 0

-4 1-4 1-4 1-4 1-4 1-4 '-1 1-4 r14 NN (Nr r

1 r.J e.J mm m

A Bobbin Volts Page 32

A AR EVA Document No. 86-9166911-000 Sequoyah 2C17 Voltage-Based ARC 90-Day Report Figure 4-7: All Indications Returned to Service for SG21 and SG22 0

E z

250 200 150 100 50 FE SG 21 ESG22 0

~-i "N mý -ý n

W r co 0i

- ~-1 IN m mr Ln t

r-. oo a)

IN

-1 IN4 m in

z. r, 00 0)I M

.-14 IN I

A Bobbin Volts Figure 4-8: All Indications Returned to Service for SG23 and SG24 C

0

.0 E

z 250 200 150 100 50 4

U-I1 0 SG23 U SG 24 II IIiu 0

66 00 000 Cq M

'-4

-4 IN e q

i B

ob iIn N

Vo lt0 ts 0 W M M-4 66 rj-

-1 4 1

.NINININ menf Bobbin Volts I4 enA Page 33

A AR EVA Document No. 86-9166911-000 Sequoyah 2C17 Voltage-Based ARC 90-Day Report Figure 4-9: Cycle 17 Growth Distribution for SG21 and SG22 1200 1000 IA

.2 800 U

C 600 0

I-0)E0 400 E

200 0

oý 14 MN

-:t n

LO r,-

00 C) r-

-I EN M

-T Ln LA 6 6 6

6 6

4r r

4r 4

A Delta Volts per EFPY Figure 4-10: Cycle 17 Growth Distribution for SG23 and SG24 1200 1000

.2 800 U

C 600

.4,-

0

.0E 400 2

200 0

0

-I N

M I-T LA k

r, CO o)

.-I

-I-EN M

m

ý r Ln LA 6

6 6

6 65 6

6 A

Delta Volts per EFPY Page 34

A AR EVA Document No. 86-9166911-000 Sequoyah 2C17 Voltage-Based ARC 90-Day Report Figure 4-11: Cycle 17 vs. Cycle 16 Growth Comparison 1.0 X

0.8 ix_"

S.6--

Bounding Cycle 17

~(-x-Bounding Cycle 16 0a-(D0.4 E

= 0.2 0.0 0

0.5 1

1.5 2

2.5 3

3.5 4

4.5 5

Delta Volts per EFPY Page 35

A AREVA Document No. 86-9166911-000 Sequoyah 2C17 Voltage-Based ARC 90-Day Report Figure 4-12: Voltage Change vs. BOC Voltage for SG21 U-wL IA 1.0 0.8 0.6 0.4 0.2 0.0

-0.2

-0.4

-0.6

-0.8

-1.0 0.0 0.5 1.0 1.5 2.0 2.5 BOC-17 Bobbin Volts Figure 4-13: Voltage Change vs. BOC Voltage for SG22 1.0 0.8 0.6 0.4 a-L 0.2 C. 0.0

-0.2 "1 -0.4

-0.6

-0.8

-1.0 0.0 0.5 1.0 1.5 2.0 2.5 BOC-17 Bobbin Volts Page 36

A AREVA Document No. 86-9166911-000 Sequoyah 2C17 Voltage-Based ARC 90-Day Report Figure 4-14: Voltage Change vs. BOC Voltage for SG23 1.0 0.8 0.6 0.4 LL 0.2 I-

0. 0.0 IA 4.w o -0.2

-0.4

-0.6

-0.8

-1.0 0.0 0.5 1.0 1.5 2.0 2.5 BOC-17 Bobbin Volts Figure 4-15: Voltage Change vs. BOC Voltage for SG24 1.0 0.8 0.6 0.4 a,.

u 0.2 L.

0. 0.0 4A o -0.2

-0.4

-0.6

-0.8

+

++-

+

÷+

+

I- +

++

+

+-0.081x+0.014

++#+

+ + +.

+.,.

+

-1.0 0.0 0.5 1.0 1.5 BOC-17 Bobbin Volts 2.0 2.5 Page 37

A AR EVA Document No. 86-9166911-000 Sequoyah 2C17 Voltage-Based ARC 90-Day Report Figure 4-16: Voltage Change vs. BOC Voltage for All SGs LL U-wL 1.0 0.8 0.6 0.4 0.2 0.0

-0.2

-0.4

-0.6

-0.8

-1.0 0.0 0.5 1.0 1.5 2.0 BOC-17 Bobbin Volts 2.5 Page 38

A AR EVA Document No. 86-9166911-000 Sequoyah 2C17 Voltage-Based ARC 90-Day Report Figure 4-17: Bobbin Volts vs. +Point TM Volts for 2C17 4

3.5 3

& 2.5 3

0 1.5 1

0.5 0

0 0.5 1

1.5 2

2.5 3

3.5

+PointTM Volts 4

Page 39

A AREVA Document No. 86-9166911-000 Sequoyah 2C17 Voltage-Based ARC 90-Day Report Figure 4-18: 2C17 Probe Wear Voltage Comparison G.0 0

a-to a.

M 0

CO 3.5 3

2.5 2

1.5 1

0.5 0

0 0.5 1

1.5 2

2.5 3

3.5 Bobbin Voltage (Good Probe)

Page 40

A AR EVA Document No. 86-9166911-000 Sequoyah 2C1 7 Voltage-Based ARC 90-Day Report Figure 4-19: Bobbin Indication Growth History 4000 30%

Number of Inds Reported 3500 0 Percent Growth per EFPY 25%

3000 20%

Probe Change (2C16 to 2C17)

Westinghouse to Zetec 2500 15%

0.u W

2000 10%

,M0

.U E* *

Probe Change (2C13 to 2C14) 1000 Zetec to Westinghouse 0%

500

-5%

o 0....-10%

2C11 2C12 2C13 2C14 2C15 2C16 2C17 Outage Designation Page 41

A AR EVA Document No. 86-9166911-000 Sequoyah 2C17 Voltage-Based ARC 90-Day Report 5.0 DATABASES APPLIED FOR LEAK AND BURST CORRELATIONS Per GL 95-05, the databases used to perform the tube integrity evaluations should be the latest NRC approved industry database.

The latest approved correlations are those contained in Addendum 7 of the EPRI ARC Database [13]. The parameters for these correlations are provided in this section.

5.1 Burst Pressure Correlation For the case of the burst pressure versus voltage correlation, the Addendum 7 database contained in Reference

[13], meets all GL 95-05 requirements and was used in the as-found EOC-17 calculations and the EOC-18 projections. The correlation parameters were taken from Reference [13] and are shown in Table 5-1.

Table 5-1: Burst Pressure vs. Bobbin Amplitude Correlation P, = ao + a, log(Volts)

Parameter Addendum 6 Intercept, a0 7.4801 Slope, a1

-2.4002 2

79.67%

Std. Dev., a Error 0.8802 Mean Log(V) 0.3111 SS of Log(V) 51.6595 N (data pairs) 100 Structural Limit (2560 psi)(l) 7.51V Structural Limit (2405 psi)"')

9.40V p Value for a1 (2) 5.60.10-36 Reference af 68.78 ksi (3)

Notes: The number of significant figures reported simply corresponds to the output from the calculation code and does not represent true engineering significance.

(1) Values reported correspond to applying a safety factor of 1.4 on the differential pressure associated with a postulated SLB event.

(2)

Numerical values are reported only to compare the calculated result to a criterion value of 0.05. For such small values the relative change is statistically meaningless.

(3)

This is the flow stress value to which all data was normalized prior to performing the regression analysis.

Page 42

A AR EVA Document No. 86-9166911-000 Sequoyah 2C17 Voltage-Based ARC 90-Day Report 5.2 Probability of Leak and Conditional Leak Rate Reference [13] presents the results of the regression analysis for the leak rate correlation using the Addendum 7 leak rate database for 7/8" tubes. It should be noted that, for the 2405 psi delta pressure, the one-sided p-value for the slope parameter in the voltage dependent leak rate correlation is 0.5%, which meets the 5% threshold for an acceptable correlation specified in Generic Letter 95-05.

AREVA computer simulations include the slope sampling method for the leak rate correlation that is presented in Reference [13].

The methodology used in the calculation of these parameters is consistent with NRC criteria in GL 95-05. The probability of leak and leak rate correlation parameters used in the CM and OA were taken from Reference [13]

and are shown in Table 5-2 and Table 5-3, respectively.

Table 5-2: Probability of Leak Correlation 1

Pr(Leak) =

1 + e-[b, +b2 log(Volt,)]

Parameter I

Addendum 6 Intercept, b,

-5.0407 Slope, b2 7.5434 Vi 1 (1) 1.3311 V 1 2

-1.7606 V2 2 2.7744 DoF(2 )

118 Deviance 32.37 Pearson SD 0.611 MSE 0.279 Notes:

1) Parameters V1j are elements of the covariance matrix of the coefficients, bi of the regression equation.

2) Degrees of freedom.

Page 43

A AR EVA Document No. 86-9166911-000 Sequoyah 2C17 Voltage-Based ARC 90-Day Report Table 5-3: Leak Rate vs. Bobbin Amplitude Correlation (2405 psi)

Q = 1 0 [b3+b4 1og(Volts )]

Parameter Addendum 6 Intercept, b3

-0.8039 Slope, b4 1.2077 Index of Deter., r2 20.0%

Std. Error 0.7774 Mean of Log(Q) 0.5090 Std. Dev. of Log(Q) 22.6667 p Value for b4 0.5%

Data Pairs, N 32 Mean of Log(V) 1.0871 SS of Log(V) 3.1116 Note: The number of significant figures reported simply corresponds to the output from the calculation code and does not represent true engineering significance.

6.0 OTHER MISCELLANEOUS INPUTS This section provides other miscellaneous inputs necessary for the tube integrity evaluations documented in this report.

6.1 Tube Material Properties Since the burst pressure for a given flaw varies with the material properties of the tube, the material properties of the tubes must be included as an input into the POB program. This data was obtained from Reference [7]. The values used for the both the condition monitoring and operational assessment calculations were taken directly from Reference [7] and were a mean flow stress of 68.78 ksi and a standard deviation of the flow stress of 3.1725 ksi.

Page 44

A AR EVA Document No. 86-9166911-000 Sequoyah 2C17 Voltage-Based ARC 90-Day Report 6.2 Probability of Detection The condition monitoring assessment in Section 7.0 provides an evaluation of the "as-found" conditions and, therefore uses a probability of detection (POD) of 1.

For the operational assessment, a POD must be applied to account for those indications that may have been present but not reported and, hence, returned to service for Cycle 18. Although the use of a voltage-dependent POD has been approved for use at SQN2, the analyses presented in this report use the standard and more conservative POD of 0.6 from GL 95-05.

6.3 Cycle Lengths The actual cycle length from Cycle 17 and the projected length for the upcoming cycle were both taken from Reference [10].

The actual operating length of Cycle 17 was used to calculate the growth of indications in terms of change in voltage per EFPY (Effective Full Power Year). Per Reference [10], the operating length of Cycle 17 was 523.0 EFPD (Effective Full Power Days). Converting this value to EFPY using a calendar year of 365.25 days gives a cycle length of 1.432 EFPY (523 / 365.25).

The expected operating length of the current operating cycle (Cycle 18) is needed to project conditions at the end of Cycle 18. This value was provided in Reference [10] as 473.0 EFPD. Converting this value to EFPY gives a cycle length of 1.295 EFPY for Cycle 18. For the operational assessment (Section 8.0), this value was rounded up to 1.30 EFPY.

6.4 NDE Uncertainties NDE (Non-Destructive Examination) uncertainties must be considered in both the condition monitoring and operational assessments documented in this report. The NDE uncertainties used in the calculations documented herein are provided in Reference [7]. The acquisition uncertainty was sampled from a normal distribution with a mean of zero, a standard deviation of 7%, and a cutoff limit of 15% based on the implementation of the probe wear criteria discussed in Section 4.4. The analyst uncertainty was sampled from a normal distribution with a mean of zero, a standard deviation of 10.3%, and no cutoff limit. These uncertainty distributions are provided in both tabular and graphical format in Table 6-1 and Figure 6-1.

Page 45

A AREVA Document No. 86-9166911-000 Sequoyah 2C17 Voltage-Based ARC 90-Day Report Table 6-1: NDE Uncertainty Distributions Analyst Uncertainty Acquisition Uncertainty Percent Cumulative Variation Probability

-40.0%

0.00005

-38.0%

0.00011

-36.0%

0.00024

-34.0%

0.00048

-32.0%

0.00095

-30.0%

0.00179

-28.0%

0.00328

-26.0%

0.00580

-24.0%

0.00990

-22.0%

0.01634

-20.0%

0.02608

-18.0%

0.04027

-16.0%

0.06016

-14.0%

0.08704

-12.0%

0.12200

-10.0%

0.16581

-8.0%

0.21867

-6.0%

0.28011

-4.0%

0.34888

-2.0%

0.42302 0.0%

0.50000 2.0%

0.57698 4.0%

0.65112 6.0%

0.71989 8.0%

0.78133 10.0%

0.83419 12.0%

0.87800 14.0%

0.91296 16.0%

0.93984 18.0%

0.95973 20.0%

0.97392 22.0%

0.98366 24.0%

0.99010 26.0%

0.99420 28.0%

0.99672 30.0%

0.99821 32.0%

0.99905 34.0%

0.99952 36.0%

0.99976 38.0%

0.99989 40.0%

0.99995 Percent Cumulative Variation Probability

<-15.0%

0.00000

-15.0%

0.01606

-14.0%

0.02275

-13.0%

0.03165

-12.0%

0.04324

-11.0%

0.05804

-10.0%

0.07656

-9.0%

0.09927

-8.0%

0.12655

-7.0%

0.15866

-6.0%

0.19568

-5.0%

0.23753

-4.0%

0.28385

-3.0%

0.33412

-2.0%

0.38755

-1.0%

0.44320 0.0%

0.50000 1.0%

0.55680 2.0%

0.61245 3.0%

0.66588 4.0%

0.71615 5.0%

0.76247 6.0%

0.80432 7.0%

0.84134 8.0%

0.87345 9.0%

0.90073 10.0%

0.92344 11.0%

0.94196 12.0%

0.95676 13.0%

0.96835 14.0%

0.97725 15.0%

0.98394

>15.0%

1.00000 Std Deviation = 7.0%

Mean =0.0%

Cutoff= +/- 15.0%

Std Deviation = 10.3%

Mean =0.0%

No Cutoff Page 46

A AREVA Document No. 86-9166911-000 Sequoyah 2C17 Voltage-Based ARC 90-Day Report Figure 6-1: NDE Uncertainty Distributions (U

0.

2 E-E 1.0 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0.0

-40%

-30%

-20%

-10%

0%

10%

20%

30%

Percent Variation in Voltage 40%

Page 47

A AREVA Document No. 86-9166911-000 Sequoyah 2C1 7 Voltage-Based ARC 90-Day Report 7.0 2C17 CONDITION MONITORING This section provides the 2C17 condition monitoring results as well as a comparison to the projections from the previous operational assessment prepared after the 2C16 outage [9]. The condition monitoring assessments were performed using AREVA monte carlo codes [4] [5].

All of the calculations performed for the condition monitoring assessment were based on 500000 monte carlo simulations.

The condition monitoring assessment is an evaluation of the as-found conditions. The condition monitoring assessment, therefore, uses a POD of 1.0 and includes no growth component. Material property and NDE uncertainties, however, are included as discussed in Sections 6.1 and 6.4.

The leak rate and probability of burst (POB) results are provided in Table 7-1.

This table also provides a comparison to the projected leak rate and POB from the previous operational assessment. As shown in the table, the as-found leak rate, POB, and number of indications were all significantly under the values projected from the previous operational assessment. The as-found leak rate and POB are also well below the acceptance criteria of 3.7 gpm for leak rate and 1.OE-02 for POB.

Table 7-2 provides a comparison of the as-found voltages to the projected voltages from the previous operational assessment. As shown in this table, the numbers of indications detected during the 2C 17 inspection as well as the voltages of the indications were well bounded by the previous operational assessment.

Table 7-1: 2C17 Condition Monitoring Leak Rate and POB Results Summary of GL 95-05 ARC Calculations EOC-17 (As-found) vs. Projections SG21 SG22 SG23 SG24 Number of As-Found 643 716 878 1478 DSI Plus AONDB Projected (1) 1082 1172 1445 2455 Leak Rate23 As-Found 0.108 0.118 0.227 0.427 (gpm)

Projected 0.654 0.694 1.07 1.67 As-Found 4.62 x 10.5 6.05 x 10-9.05 x 10s 1.42 x 10.'

POBW1)

Projected 6.53 x 10-4 7.25 x 10"4 1.01 x 10-3 1.80 x 10-3 Acceptance Criteria 1.0 x 10.2 (POB) 3.7 gpm Notes: (1) The 95% Upper Confidence Limit (UCL) is based on the number of trials with one or more failures.

(2) Equivalent volumetric rate at room temperature.

(3) The calculated total leak rate reflects the upper 95% quantile value at an upper 95% confidence bound.

Page 48

A AREVA Document No. 86-9166911-000 Sequoyah 2C17 Voltage-Based ARC 90-Day Report Table 7-2: As-Found EOC-17 vs. Projected EOC-17 Conditions Voltage SG21 SG22 SG23 SG24 Bin As-Found Projected As-Found Projected As-Found Projected As-Found Projected 0.1 1

1.07 4

1.27 9

0.25 4

0.72 0.2 45 12.99 32 15.98 22 6.76 45 17.79 0.3 68 40.69 73 41.6 75 30.04 162 66.72 0.4 73 72.74 120 79.6 107 69.08 207 144.53 0.5 103 101.48 105 118.23 108 108.63 210 221.71 0.6 91 120.37 102 139.43 113 137.15 208 271.89 0.7 84 124.9 86 139.53 110 151.99 165 285.56 0.8 47 118 57 126.92 86 154.15 118 270.1 0.9 38 103.95 37 109.01 57 144.91 105 240.17 1

37 87.19 33 90.23 51 128.06 74 204.72 1.1 21 70.54 21 73.02 39 109.25 49 168.23 1.2 11 55.87 12 57.96 33 91.99 50 134.08 1.3 9

43.75 17 44.96 28 76.46 15 104.83 1.4 6

33.77 9

34.19 20 61.9 16 81.05 1.5 3

25.62 5

25.61 4

48.36 11 62.18 1.6 4

19.07 1

19.1 8

36.27 11 47.42 1.7 0

13.95 1

14.41 5

26.31 6

35.82 1.8 1

10.12 0

10.9 0

18.61 6

26.77 1.9 1

7.25 1

8.24 2

13.06 5

19.72 2

0 5.17 0

6.14 1

9.11 1

14.21 2.1 0

3.63 0

4.42 0

6.37 3

10.03 2.2 0

2.52 0

3.08 0

4.43 1

7 2.3 0

1.73 0

2.11 0

3.08 2

4.86 2.4 0

1.18 0

1.43 0

2.12 0

3.42 2.5 0

0.8 0

0.98 0

1.45 1

2.43 2.6 0

0.55 0

0.68 0

0.98 0

1.72 2.7 0

0.39 0

0.47 0

0.66 2

1.22 2.8 0

0.29 0

0.33 0

0.45 0

0.87 2.9 0

0.22 0

0.24 0

0.3 0

0.62 3

0 0.17 0

0.18 0

0.2 0

0.45 4

0 0.69 0

0.75 0

0.94 0

1.79 5

0 0

0 0.61 0

0.28

>5 0

1 0

1.09 0

2.39 Total 643 1081.66 716 1172 878 1445.02 1477 2455.3

<=1 587 783.38 649 861.8 738 931.02 1298 1723.91

>1 56 298.28 67 310.2 140 514 179 731.39

>2 0

13.17 0

15.67 0

22.68 9

37.08

>3 0

1.69 0

1.75 0

2.64 0

4.46

>4 0

1.69 0

1.75 0

2.64 0

4.46 POB 4.62E-05 6.53E-04 6.05E-05 7.25E-04 9.05E-05 1.01 E-03 1.42E-04 1.80E-03 Leak Rate 0.11 0.65 0.12 0.69 0.23 1.07 0.43 1.67 Page 49

A AR EVA Document No. 86-9166911-000 Sequoyah 2C1 7 Voltage-Based ARC 90-Day Report 8.0 OPERATIONAL ASSESSMENT This section provides the results of the EOC-18 POB and leak rate projections. The operational assessment calculations were performed using AREVA monte carlo codes [4] [5].. All of the calculations performed for the operational assessment were based on 500000 monte carlo simulations.

The AREVA monte carlo simulation codes develop the BOC-18 voltage distributions based on the as-found EOC-18 voltage distributions (Table 4-3 through Table 4-6) adjusted for both POD (Section 6.2) and the tubes removed from service (Table 4-3 through Table 4-6). As discussed previously, the operational assessment documented herein uses a conservative probability of detection (POD) of 0.6 from GL 95-05.

The operational assessment also includes NDE sizing uncertainties (Section 6.4), material property uncertainties (Section 6.1), and growth of indications (Section 4.2). As discussed in Section 4.2, the Cycle 16 growth rates bounded the Cycle 17 growth rates and were, therefore, used in the EOC-18 projections. The bounding Cycle 16 growth distribution is provided in Table 4-8. The Cycle 18 operating interval used in the operational assessment was 1.30 EFPY (Section 6.3).

Table 8-1 provides the leak rate and POB operational assessment results. As shown in the table, the projected leak rate and POB are well below the acceptance criteria of 3.7 gpm for leak rate and 1.OE-02 for POB.

The projected EOC-18 voltage distributions are provided in Table 8-2.

These results are also provided graphically in Figure 8-1 through Figure 8-4 for SG21 through SG24, respectively.

Table 8-1: Operational Assessment Projections for EOC-18 Conditions Summary of GL 95-05 ARC Calculations Operational Assessment for EOC-18 Projections SG21 SG22 SG23 SG24 Leak Rate (gpm) 0.45 0.49 0.80 1.24 POB 4.26 x 10-4 4.12 x 10-4 7.04 x 10-4 1.10 x 10-3 Acceptance Criteria 1.0 x 10-2 (POB) 3.7 gpm Page 50

A AR EVA Document No. 86-9166911-000 Sequoyah 2C17 Voltage-Based ARC 90-Day Report Table 8-2: Projected EOC-18 Voltage Distributions (0.6 POD)

Voltage Bin SG21 SG22 SG23 SG24

<=0.1 1.80 3.07 5.53 3.43 0.2 26.30 21.66 19.41 33.01 0.3 59.28 59.40 55.95 112.31 0.4 89.47 108.13 102.17 203.20 0.5 116.51 143.49 138.53 269.22 0.6 133.91 156.52 160.10 300.39 0.7 133.31 150.64 166.33 294.46 0.8 118.04 131.08 157.27 262.65 0.9 96.85 105.66 137.23 220.85 1

76.65 81.32 113.95 178.95 1.1 59.14 61.41 92.88 140.37 1.2 43.95 46.02 75.35 106.77 1.3 31.58 34.58 60.33 78.89 1.4 22.38 25.84 46.97 57.24 1.5 15.67 18.90 35.29 41.43 1.6 10.97 13.30 25.57 30.23 1.7 7.63 8.97 18.06 22.50 1.8 5.25 5.87 12.51 16.85 1.9 3.60 3.73 8.52 12.53 2

2.43 2.32 5.71 9.19 2.1 1.63 1.44 3.80 6.63 2.2 1.07 0.90 2.51 4.74 2.3 0.70 0.59 1.64 3.39 2.4 0.46 0.39 1.07 2.42 2.5 0.31 0.26 0.70 1.75 2.6 0.20 0.18 0.46 1.27 2.7 0.13 0.12 0.30 0.94 2.8 0.08 0.08 0.20 0.71 2.9 0.05 0.05 0.13 0.54 3

0.04 0.03 0.08 0.42 3.1 0.03 0.03 0.06 0.33 3.2 0.05 0.04 0.06 0.30 3.3 0.06 0.07 0.09 0.32 3.4 0.07 0.09 0.10 0.31 3.5 0.08 0.09 0.10 0.27 3.6 0.07 0.08 0.09 0.23 3.7 0.06 0.06 0.08 0.18 3.8 0.04 0.05 0.07 0.14 3.9 0.03 0.03 0.05 0.11 4

0.02 0.02 0.04 0.08 5

0.05 0.06 0.11 0.18 6

0.00 0.00 0.00 0.01 7

0.59 0.66 0.74 1.30 8

0.11 0.12 0.22 0.28

>8 0.00 0.00 0.00 0.01 Total J

1060.67 1187.33 1450.33 1 2421.33 Page 51

A AR EVA Document No. 86-9166911-000 Sequoyah 2C17 Voltage-Based ARC 90-Day Report Figure 8-1: Projected EOC-18 Voltage Distribution for SG21 350 300 250 fn 0

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A AR EVA Document No. 86-9166911-000 Sequoyah 2C 17 Voltage-Based ARC 90-Day Report Figure 8-2: Projected EOC-18 Voltage Distribution for SG22 350 300 250 0

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A AREVA Document No. 86-9166911-000 Sequoyah 2C1I 7 Voltage-Based ARC 90-Day Report Figure 8-3: Projected EOC-18 Voltage Distribution for SG23 350 300 250 0

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A ARE VA Document No. 86-9166911-000 Sequoyah 2C17 Voltage-Based ARC 90-Day Report Figure 8-4: Projected EOC-18 Voltage Distribution for SG24 350 300 250 200 150

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A AR EVA Document No. 86-9166911-000 Sequoyah 2C1 7 Voltage-Based ARC 90-Day Report

9.0 REFERENCES

1.

NRC Generic Letter 95-05, "Voltage-Based Repair Criteria for Westinghouse Steam Generator Tubes Affected by Outside Diameter Stress Corrosion Cracking", August 1995.

2.

AREVA Document 32-9163252-000, "Sequoyah-2 2C17 Voltage-Based ARC Startup Calculations".

3.

AREVA Document 86-9162789-000, "Sequoyah-2 2C17 Voltage-Based ARC Startup Report".

4.

AREVA Document 51-5001160-02, "Steam Generator POB Simulation Code POB97VBR20.F90".

5.

AREVA Document 51-5001151-02, "Steam Generator Leak Rate Simulation Code LKR97VB_r30.F90".

6.

Letter from Ronald Hernan (NRC) to Oliver Kingsley, Jr. (TVA), "Issuance of Technical Specification Amendments for the Sequoyah Nuclear Plant, Units 1 and 2 (TAC Nos. M96998 and M96999) (TS 96-05", NRC ADAMS Accession Number ML013320497, April 1997.

7.

Westinghouse Report WCAP 14277, "SLB Leak Rate and Tube Burst Probability Analysis Methods for ODSCC at TSP Intersections", Revision 1, December 1996.

8.

AREVA Document 51-9161601-000, "Steam Generator Degradation Assessment for Sequoyah 2C 17 Inspection".

9.

Westinghouse Report SG-SGMP-10-2, "Condition Monitoring and Operational Assessment: GL-95-05 Alternate Repair Criterion End of Cycle 16 90 Day Report Sequoyah Unit 2", NRC ADAMS Accession Number ML100550773, January 2010.

10.

AREVA Document 38-9166901-000, "Sequoyah Nuclear Plant - U2C 17 Steam Generator Tube Integrity Inpection".

11.

Letter from Brian Sheron (NRC) to Alex Marion (NEI), "Probe Wear Criteria", February 1996.

12.

AREVA Document 51-9162787-000, "Sequoyah-2 2C17 ARC Probe Wear Report".

13.

EPRI Report 1018047, "Steam Generator Tubing Outside Diameter Stress Corrosion Cracking at Tube Support Plates Database for Alternate Repair Limits: Addendum 7", September 2008.

Page 56

ENCLOSURE2 TENNESSEE VALLEY AUTHORITY SEQUOYAH NUCLEAR PLANT, UNIT 2 SEQUOYAH 2C17 W-STAR 90-DAY REPORT Document No. 51-9168622-000

ML11266A158

Text

SUMMARY

SUMMARY

Purpose:

1.0 INTRODUCTION

SUMMARY

9.0 REFERENCES

1.0 INTRODUCTION

SUMMARY

9.0 REFERENCES

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