ML20199J257
| ML20199J257 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 01/31/1998 |
| From: | WESTINGHOUSE ELECTRIC COMPANY, DIV OF CBS CORP. |
| To: | |
| Shared Package | |
| ML20199J227 | List: |
| References | |
| SG-98-01-002, SG-98-1-2, NUDOCS 9802050271 | |
| Download: ML20199J257 (52) | |
Text
. _ -. -. _. -.. - _.
= -. - - - -. -
j I
ATTACllMENT 1 i
i 4
SG 98 01002 I
l l
l SEQUOYAH UNIT 2 1
CYCLE 9 VOLTAGE BASED REPAIR CRITERIA 90 DAY REPORT 1
l January 1998 i
)
1 l
O Westinghouse Electric Company I
Energy Systems Business Unit Nuclear Services Division P.O. Box 158 Madison, Pennsylvania 15663 0158 l
i N
9802050271 980129 PDR ADOCK 05000328 P
- _ ~.
1 SG 98 01002 SEQUOYAH UNIT 2 CYCLE 9 VOLTAGE BASED REPAIR CRITERIA 90-DAY REPORT January 1998
Table of Contente i
Page No.
1.0 Intreducticn 11 2.0 Summary and Conclusions 21 3.0 EOC 8 Inspection Results and Voltage Growth Rates 31 3.1 EOC-8 Inspection Results 31 3.2 Voltage Growth Rates 32 3.3 NDE Uncertainties 33 3.4 Probability of Prior Cycle Detection (POPCD) 34 3.5 Assessment of RPC Confirmation Rates 36 3.6 Probe Wear crite-ia 3-6 4.0 Database Applied for Leak and Burst Correlation
- 41 5.0 SLB Analysis Methods 51 6.0 Bobbin Voltage Distributions 6-1 6.1 Calculation of Voltage Distributions 61
+
6.2 Probability Of Detection (POD) 62 6.3 Limiting Growth Rate Distribution 62 6.4 Cycle Operating Period 62 6.5 Projected EOC 9 Voltage Distributions 63 6.6 Comparison of Actual and Projected EOC 8 Voltage Distributions 6-3 7.0 SLB Leak Rate and Tube Burst Probability Analyses 71 7.1 Leak Rate and Tube Burst Probability for EOC 9 71 7.2 Leak Rate and Tube Burst Probability for EOC 8 72 83 References 81 S:\\ ape \\ ten 97\\ EOC8.90d doc i
Sequoyah Unit 2 Cycle 9 Voltage Based Repair Criteria 90 Day Report 1.0 Introduction This report provides a summary of the Sequoyah Unit 2 steam generator (SG) bobbin and rotating pancake coil (RPC) probe inspections at tube support plate (TSP) intersections together with postulated Steam Line Break (SLB) leak rate and tube burst probability analysis results.
These results support continued implementation of the 2.0 volt voltage based repair criteria for Cycle 9 as outlined in the NRC Generic Letter 95 05 (Reference 81). Information required by the Generic Letter is provided in this report including SLB leak rates and tube burst probabilities calculated using end of cycle (EOC) conditions for the recently completed cycle (Cycle 8) and projection of bobbin voltage distributions, leak rates and burst probabilities for the ongoing cycle (Cycle 9).
Analyses for Cycle 8 were carried out using actual bobbin voltage distributions measured during the EOC 8 outage and the results compared with corresponding values from projections performed based on the last (EOC-7) bobbin voltage data (presented in Reference 8 2). These evaluations utilized the Westinghouse generic Monte Carlo methodology presented in Reference 8 3.
Analyses were also performed to project leak rates and tube burst probabilities for postulated SLB conditions at the end of the ongoing cycle (Cycle 9) based on the 2.0 volt repair criteria. These analyses utilized bobbin voltage distributions measured during the recent (EOC 8) inspection and a limiting growth rate distribution from the last two inspections (EOC 7 and EOC 8 inspections).
Tubes were pulled from Sequoyah Unit 2 during the May 1996 inspection, and per the Generic Letter 95 05 requirement no additional tube pulling is required until the outage after March 1999 (34 months after the last tube pull). Therefore, no tubes were pulled during the October 1997 outage.
S:\\apcuen97\\EOC8.90d doc 1-1
2.0 Summary and Concluelons A total of 480 axial outside diameter stress corrosion cracking (ODSCC) indications were found at TSP intersections during tbt EOC 8 inspection in all four steam i
generators combined, of which 20 indications had a voltage above one volt and none above two volts. Steam generator 4 had the largest number of indications (282), of which 15 were above 1.0 volt. SG-3 had the largest indication detected in this inspection (1.70 volts). Thirty seven indications were inspected with a RPC probe and 35 were confirmed as flaws.
No ID indications at dented TSP intersections or circumferential indientions at the TSP intersections or indications extending outside the TSP were found in this inspection.
SLB leak rate and tube burst probability ans. lyses were performed for the actual EOC 8 bobbin voltage distributions as well as the projected EOC.9 bobbin voltage distributions. EOC-8 actual measured bobbin voltages are all lower than the corresponding projections performed using the EOC 7 outage bobbin voltage data for both constant probability of detection (POD) of 0.0 as well as the voltage-dependent POD distribution used (probability of prior cycle detection, POPCD).
Except for SG 4, the actual number of indicatioris detected during the EOC 8 inspection for all SGs are 30% to 50% below their corresponding projections. For SG-4, the number ofindications predicted with POD =0.6 is in agreement with the measurement, but the voltage dependent POPCD predicts a larger number of EOC-8 indications because at low BOC-8 voltages (below -0.6 volt) POPCD value is less than 0.6. The SLB leak rate and tube burst probability values based on the actual measured voltages show large margins relative to their projected values; however, the absolute macnitudes of these quantities are small.
Leale rate and tube burst probability projections at EOC conditions for the current cycle (Cycle 9) are also well within their acceptable limits. The limiting SLB leak rate projected for the EOC 9 conditions using the NRC SER endorsed probability of detection of 0.6 is 1.22 gpm (room temperature). This value is projected for SG-4 which has the largest number of indications, and it is less than one half of the allowable EOC 9 leakage limit of 2.7 gpm (room temperature). This leak rate estimate is obtained conservatively assuming that leak rate is independent of bobbin voltage because the 7/8" tube leak rate data do not pass the test for a correlation. However, in a recent NRC/ industry meeting it was agreed that the p-value for the slope of the leak rate correlation determined on a one sided basi 3 (as opposed to a two-sided basis used until now) can be used to test for significance of correlation.
The slope parameter p-value for the 7/8" tube leak rate data determined on a one-sided basie meets the 5% limit specified in the Generic Letter 95-05. Therefore, EOC 9 leak rate projection for the limiting SG (SG-4) was repeated using a voltage dependent leak rate correlation developed using the latest database for 7/8" tubes. The limiting EOC 9 leak rate thus predicted (014 gpm) is Shpe\\ ten 97\\ EoC8.93d doc 3-1
~.. -
en;y 1,'9* of that obtained using a constant leak rate; thus, the margin in the EOC-9 SLS leak rate is significantly higher than that implied by projections presented here. The highest tube burst probability,5.3x106,is also predicted for SG 4 which has 4 of the 6 'r.rgest ind!caticas found in the EOC 8 inspection, and this predicted EOC 9 burst probability is 3 decades below the NRC reporting guideline of10 2 Probahnity of detection (POPCD) for EOC 7 inspection was assessed using EOC 7 and EOC 8 inspection data. N results support a detection probability greater than the NRC mandated vah_te of 0.6, but POPCD values could not be established reliab}y abovo 0,8 volt since the data is sparse. Only one EOC 7 RPC NDD indication was lef in agrwre dudng Cyclo 8 and it was not RPC tested during EOC 8 inspection. Therew, RPC confirmation rate for prior evele NDDs could not be determined for this inepection. All RPC NDD indicatfort are included in the EOC 9 projections presented in thu. report.
i S:\\apeuen97\\EOC8.90d doc 22
3.0 EOC 8 Inspection Results nnd Voltage Growth Rates 3.1 EOC 8 Inspection Results According to the guidance provided by the NRC Generic Letter 95 05, the EOC 8 inspection of the Sequoyah Unit 4 SGs consisted of a complete,100% eddy current (EC) bobbin probe full length cr.ainination of the tube bundles % all four SGs. A 0.720 inch diameter probe was used for all hot and cold leg TSPs where voltage baseu repair criteria was applied. Subsequently, RPC examination was perfonned on 37 indications and 35 of them were confirmed as flaws. However, since none of the indications exceeded the 2 volt repair limit, no tubes were repaired because of ODSCC at TSPs. The largest hot leg indication was 1.70 volts, and the largest cold leg indication was 0.75 volt.
No unexpected eddy current results were found in this inspection. There were no RPC circumferential indications at TSPs, no indications extending outside TSPs, and no RPC indications with potential ID phase angles at dented intersections.
Nc flaws were identified in the mixed residual artifact signals.
Four intersections had signal interference from copper deposits; they were all RPC tested and found NDD.
A summary of the EC indications for all four SGs is shown on Table 31, which tabulates the number of field bobbin indications, the number of those indications that were RPC inspected,-the number of RPC confirmed indications, and the number ofindications removed from service due to tube repairs. The indications that remain active for Cycle 9 operation is the difference between the observed and the ones removed from service.
Overall, the combined data for all four SGs of Sequoyah Unit 2 show the following:
Out of a total of 480 TSP indications identified during the inspection, a total of 37 were RPC inspected.
Of the 37 RPC inspected,35 were RPC confirmed.
None of the indications exceeded the 2 volt repair limit; therefore, no tubes were repaired because of TSP ODSCC related cauws.
A total of 478 indications were returned to service for Cycle 9 operation.
A review of Table 31 indicates that more indications (a quantity of 282 indications, with 15 above 1.0 volt) were returned to service in SG-4 than the other SGs; thercPy, it potentially will be the limiting SG at EOC 9 from the standpoint of SLB 8:\\ ape \\ ten 97\\EoC8.90d doc 31 1
leak rate and tube burst.
t Figure 31 shows the actual bobbin voltage distribution determined from the EOC.
8 EC inspection; Figure 3 2 shows the population distribution of those EOC 8 indications removed from service due to tube repairs; Figure 3 3_ shows the distribution for indications returned to service for Cycle 8. Only 2 indications are in tubes repaired during the ou' age, and they were repaired for degradation mechanisms other than ODSCC at TSPs.
The distribution of EOC 8 indications as a function of support plate location is summarized in Table 3 2 and plotted in Figure 3-4.
The data show a strong predisposition of ODSCC to occur in the first few hot leg TSPs (403 out or 480 indications occurred at hot leg intersections in the first three TSPs), although the mechanism extended to highor TSPs. Only 21 indications were detected on the cold leg side. This distribution indicates the predomh. ant temperature dependence of ODSCC at Sequoyah Unit 2, s:milar to that observed at other plants.
All dented intersections over 5 volts in the EOC 7 EC database of all 4 SGs were tested in the current inspection with a + Point RPC probe. Also,100% of dents below 5 volts (in the EOC 7 database) at TSPs 1,2 and 3 and 20% at TSP 4 were RPC tested. No degradation was found at those locations.
3.2 -
Voltage Growth Hates For projection of leak rates and tube burst probabilities at the end of Cycle 9 operation, voltage growth rates were developed from EOC-8 (October 1997) inspection data and a reevaluation of the EOC-7 (May 1996) inspection EC eignals for the same indications. Table 3 3 shows the cumulative probability distribution for growth rate in each Sequoyah Unit 2 steam generator during Cycle 8 (July '96 -
September '97) on an EFPY basis, along with the corresponding Cycle 7 growth rate distributions. Cycle 8 growth data are also plotted in Figure 3 5, The curve labelled ' cumulative' in Figure 3 5 represents averaged composite growth data from all four SGs.
Average growth rates for each SG during Cycle 8 are summarized in Table 3-4. It is evident that the absolute magnitude of average growth in all SGs are relatively small (s 0.1 volt). Among the four steam generators, SG-4 has the largest average absolute growth while SG 1 has the largest percentage growth for Cycle 8. The average growth rates over the entire voltage range vary between 10.4% and 22.0%
(of the BOC voltage) per EFPY, between SGs, with ~an overall average of 18.9% per EFPY The small average BOC voltage (about 0.41 volt) leads to a relatively large 5:\\npchen97\\EoC8.90d doc 3-2
percentage growth even though the average growth (about 0.077 volt per EFPY)is very small. The average growth for indications less than 0.75 volt is 20.8% per EFPY while it is only 8.8% per EFPY for indications greater than or equal to 0.75 volt; however, the absolute magnitude of average growth in indications over 0.75 volt is higher. Among the 4 SGs, SG 4 has a slightly higher average voltage at BOC 8 as well as a larger average voltage growth during Cycle 8. Steam generator 4 has the top 5 growth values for Cycle 8.
Figure 3 6 is a plot of voltage growth during Cycle 8 vs. BOC 8 voltage. Itis evident from Figure 3 6 that growth during Cycle 8 does not increase with the BOC 8 voltage. The tall of the growth distribution defined by BOC voltages above 0.8 volt includes only one out of the top 30 growth values for Cycle 8, which does not suggest growth dependency on BOC voltage. For the maximum BOC voltage of about 1.5 volt, voltage dependent growth would not be expected as available data show that voltage dependent growth occurs at higher BOC voltages.
Averaged composite voltage growth data from all four steam generators for the last two operating periods (Cycle 7 and 8) are summarized in Table 3 5 Figure 3 7 shows the cumulative probability distributicn for composite growth rate data from all SGs during Cycles 7 and 8. It is evident that the composite growth rates during Cycle 7 are slightly higher than those during Cycle 8. Therefore, Cycle 7 provides the more limiting cumulative probability distribution for growth for the last two cycles. The guidelines in Generic Letter 95 05 require the use of more conservative growth rato distributions from the past two inspections for projecting EOC distributions for the next operating cycle. Ilence, Cycle 7 growth rates were used to develop EOC 9 predictions. Cycle 7 growth rates for S12 are slightly higher than the composite growth distribution and, per the methodology presented in Reference 8 3, SG-specific growth rates are to be used for SG-2 while the composite growth rates should be applied for the other three SGs.
Table 3 6 lists the top 30 indications on the basis of Cycle 8 growth rates in descending order. Five of those indications were RPC confirmed and the remaining 25 were not inspected (since they are all significantly below the 2 volt repair limit).
Twenty of the 30 indications shown are new indications, and EOC-7 voltages used to estimate growth rates for them were obtained by revaluating the last inspection data; they are all small indications with an average BOC voltage of only about 0.3 i
volt.
3.3 NDE Uncertainties The NDE uncertainties applied for the Cycle 8 voltage distributions in the Monte Carlo analyses for leak rate and burst probabilities are the same as those S \\ ape \\ ten 97\\EOC8.90d doc r
l l
33
I previously reported in the Sequoyah Unit 2 voltage based repair criteria report of
^
Reference 8 2 and NRC Generic Letter 95 05 (Reference 81). They are presented in Table 3 7 as well as graphically illustrated in Figure 3 8.
The probe wear uncertainty has a standard deviation of 7.0 % about a mean of zero and haa a cutoff at 15 % based on implementation of the probe wear standard.
The analyst variability uncertainty has a standard deviation of 10.3% about a mean of zero with no cutoff. These NDE uncertair$. Satributions are included in the Monte Carlo analyses for SLB leak rates and
. burst probabilities based on the EOC-8 actual voltage distributions as well as fw the EOC 9 projections.
3.4 Probability of Prior Cycle Detection (POPCP)
The inspection results at EOC 8 permit an evaluation of the probability of detection (POD) at the prior EOC 7 inspection. For voltage based repair criteria applications, the important indications are those that could significantly contribute to EOC leakage or burst probability. These significant indications can be expected to be detected by bobbin and confirmed by RPC inspection. Thus, the population of interest for voltage based repair criteria POD assesuments is the EOC RPC confirmed indications that were detected or not detected at the, cior inspection.
The probability of prior cycle detection (POPCD) far the EOC-7 hnpection can then be defined as follows.
EOC 7 cycle reported
+ Indications confirmed indications confirmed by and repaired in EOC 7 RPC in EOC 7 inspection inspection POPCD =
(EOC-7)
( Numerator)
+
New indications RPC l
confirmed in EOC-8 inspection POPCD is evaluated at the 1996 EOC-7 voltage values (from 1997 reevaluation for growth rate) since it is an EOC 7 POPCD assessment. The indications detected at EOC 7 that were RPC confirmed and plugged are included as it can be expected i
that these indications would also have been detected and confirmed at EOC 8. It is also appropriate to include the plu6Eed tubes for voltage-based repair criteria applications since POD adjustments to define the BOC distribution are applied prior to reduction of the EOC indication distribution for plugged tubes.
It should be noted that the above POPCD definition includes all new EOC-8 i
S;\\apcup97\\ EOC8.90d. doc 34
\\
~ _ _,.. -.,,,,,,, _ _ _ _ _
indications not reported in the EOC 7 inspection. The new indications include EOC 7 indications present at detectable levels but not reported, indications present at EOC 7 below detectable levels and indications that initiated 'uring Cycle 8.
Thus, this definition, by including newly initiated indications, differs from the traditional POD definition. Since the newly initiated indications are appropriate for voltage based repair criteria applications, POPCD is an acceptable definition and eliminates the need to adjust the traditional POD for new indications.
The above definition for POPCD would be entirely appropriate if all EOC 8 indications were RPC inspected. Since only a fraction of bobbin indications are generally RPC inspected, POPCD could be distorted by using only the RPC inspected indications. Thus, a more appropriate POPCD estimate can be made by assuming that all bobbin indications not RPC inspected would have been RPC confirmed. This definition is applied only for the 1997 EOC 8 indications not RPC inspected since inclusion for the EOC 7 inspection could increase POPCD by including indications on a tube plugged for non ODSCC causes which could be RPC NDD indications. In addition, the objective of using RPC confirmation for POPCD is to distinguish detection ofindication at EOCo. that could contribute to burst at EOCn so that the emphasis is on EOCn RPC confirmation. This POPCD can be obtained by replacing the EOC-8 RPC confirmed by RPC confirmed plus not RPC inspected in the above definition of POPCD.
For this report, both POPCD definitions are evaluated for Sequoyah Unit 2.
The POPCD evaluation for the 1996 EOC-7 inspection data is summarized in Table 3-8 and illustrated in Figure 3 9. As seen from Table 3 8, there are only 10 RPC confirmed indications called during both EOC 7 and EOC-8 inspections, which is insufiicient to define a POPCD distribution for EOC 7 inspections based on RPC confirmed indications only.
Therefore, only results based on RPC confirmed plus not RPC inspected indications are shown in Figure 3 9. A generic POPCD distribution developed by analyses of 15 inspections in 8 plants, presented
~
in Table 7 4 of Reference 8-4, is also shown in Figu o 3-9. It is seen from Figure 3-9 that the POPCD values for Sequoyah Unit 2 compare well with the generic POPCD for voltages up to 0.8 volt. Between 0.8 to 1.5 volts, EOC 7 POPCD values are slightly below the generic values, but equal to or higher t.han the NRC mandated value of 0.6. There are only 16 indications in the voltage range 0.8 to 1.5 volte in the EOC 7 inspection which is insuflicient to provide a reliable POPCD distribution above 0.8 volt.
In summary, the Sequoyah Unit-2 EOC-7 POPCD supports a POD higher than the S:\\apcuen97\\ EOC8_90d doc
_ _3 5
NRC mandated POD value of 0.6 above 0.4 volt. However, POPCD values could not established reliably above 0.8 volt since the data is sparse.
3.5 Assessment of HPC Confirmation Hates This section tracks the 1996 EOC 7 indications that were left in service at BOC 8 relative to RPC inspection results in 1997 at EOC 8. The composite results for all SGs are given in Table 3 9.
For 1996 bobbin indications left in service, the indications are tracked relative to 1997 RPC confirmed,1997 RPC NDD,1997 bobbin indications not RPC inspected, and 1996 bobbin indications with no indication found in 1997. Also included are new 1997 indications. The table shows, for each category of indications, the number ofindications RPC inspected and RPC confirmed in 1997, as well as the percentage of RPC confirmed indications.
Only one EOC 7 RPC NDD indication was in service at BOC 8, and it was not RPC tested during the EOC 8 inspection. Therefore, the RPC wnfirmation rate for prior RPC NDD indications could not be established.
3.6 Probe Wear Criteria An alternate probe wear criteria approved by the NRC (Reference 8 5) was applied during the EOC 8 inspection. When a probe does not pass the 15% wear limit, this alternate criteria requires that only tubes with indications above 75% of the repair limit inspected since the last successful probe wear check be reinspected with a good probe. As the repair limit for Sequoyah Unit 2 is 2 volts, all tubes containing indications for which worn probe voltage was above 1.5 volts are to be inspected with a new probe. Only two indications with a bobbin voltage above 1.5 volts were found during the entire inspection, and neither of them was inspected with a failed probe. Therefore, no tubes had to be retested because of probe wear.
8:\\npe\\ ten 97\\EOC8.90d. doc 36 l
Table 3-1 4,A Unit 2 October 97 Outage Samunary of liespectine and Repair For Tubes im Service Durina Cyde 8 Seease Generseer I Seemse Generseer 2 C
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Table 3-2 Sequoyah Unit 2 October 1997 TSP ODSCC Indication Distributions for Tubes in Service During Cycle 3 Steam Generator I Steam Generator 2 Co nposite of A!! SGs Tm Number af Stasimew A urage Lartest A wrnee Number d Stasimum Average Larrest Aversee Number es Statemen Average Larygt A wrage ledications Vettare vettage Growth Growth Indiestiam Vestage Vettare Growth Grw th Imrication.
Vestsee v.atsee Gew-th Growth
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.p.82 al2 1102 20 0.35 OAS 0.57 0.16 21 1.27 0.59 024 0.05 129 1.27 OA9 0.77 UD9 1103 4
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0.75 036 020 0.03 Total 51 50 480 Steam Generator 3 Steam Generator 4 Tm S*PPort Plate Number er Alasimum Average Largest Averace Numbe-er masanem Average Imrgest Avsnee Indications Vettage Veitage Growth Growth Indicatseng Yeltmee Voltage Growth Crowth 1101 55 1.70 0.65 03I 0.14 153 1.51 0.57 0.82 0.12 1I02 17 0.75 0.42 0.26 0.04 71 1.15 030 0.77 029
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_C04
_0
_.3 __. _ _ 0A0 031
_ ROI
-0 0*
C03 1
0.27 027
-0.09
-0.09 0
.__I 0.24
_ OJ4_
_-0._03.
_ -0 03_
2_
_033__.
_030
_ 0.00__
_-0.02 COI 3
034 030 0.03 022 3
0.75 0.52 020 0.07 Total g 97 282 3-8
Table 3-3 Sequoyah UDit 2 October 97 Signal Growth Statistics For Cycle 8 on an EFPY Basis Steam Generator 1 Steam Generator 2 Steam Generator 3 Steam Generator 4 Cumulative Delta Cycle 7 Cycle 8 Cycle 7 Cycle 3 Cycle 7 Cycle 8 Cycle 7 Cycle 3 Cycle 7 Cycle #
Volts CPDF CPDF CPDF CPDF CPDF CPDF CPDF CPDF CPDF CFDF
-0.2 0.0 0
0.0 0.0 2_
0.04
_ 0.0 0
_00_
0.0_ _1_
0.004 0.0 _
3 0.006 O_ I_ $$
5 0.098_
0.017 3
_0_. I _
0.022_. _ 2_ _
0_021,
. _0.006. _ 9_. _0.035 _
0.016_
_I 9_
0.046 0
0.333 12___
0.333 0.172
_ 11 0.32
.,0.183_ _2_6_
0.289_
0.082_ _53__
0.223_
0.153_
102_
,0 258_
. 0.l_
0.511_
l_8__
0.686 0.466 21 0.74_ _
0.452_._39 _ _ 0.691
_ 0.4
_128
_0.677 OA37
_ 2_06_ _ 0.688
_ 0.2_
0822_ __ 8 _ _0.843_
0.845
_ 11
_0.96_ _
_0.785
_ l_6
_0.856 0.8
_.._5 6__.
0.87_6_
0.4 %
_91_
0.877
_0.3 0.956 4
0.922 0.931 1
_0 98_
0.892 12
__0.9_79 _ 0.947_
19 0.943,_
C.932 36_
_0.952 OA
.,_1.0__ _
3 0.98 0.966
_., 1
_, 1.0._
0.989
_I _ _ _ 0.99_
0.988 9
_0.975_
_0.986_ _ 14._
OSSI 0.5 1.0 1
1.0 0.983 0
1.0 1.0 1
1.0 0.994 4
0.989 095 6
0.994 0.6 1.0 0
1.0 0.983 0
1.0 1.0 0
1.0 1.0 0
0.989 OS97 0
0.'N4 0.7 1.0 0
1.0 1.0 0
1.0 1.0 0
1.0 1.0 3
1.0 1.0 J
1.0 Total 51 50 97 282 480 m.* cua i2r22;97 3 3,m 3-9
=
Table 3-4 Sequoyah Unit 2 - October 1997 Outage Average Voltage Growth During Cple 8 Voltage Number of
- Average Voltage Range Indications BOC Entire Cycle Per EFPY '
Entire Cycle Por EFPY
- Composite of All Stearn Generator Data Entire Voltage _ Range __
480 0.41 0.094 0.078
_233%__
193 %
V soc <.75 Volts 447 036 0.094 0.078 25.7 %
213 %
2.75 Volts 33 0.%
0.108 0.086 10.9 %
9.0%
Steam Generator 1 Entire Voltage Range
_ SI 033 0.089 _
0.074 27.0 %
22.5% _
50 032 0.087 0.073 27.5 %
_ 22.8%
. V soc <.75 Volts l
2.75 Volts I
0.82 0.150 0.125 18 't%
15.2 %
1 Steam Generator 2 Entire Voltage _ Range 50 0.46 0.060 0.049 12.9 %
10.7 %
_ _s.oc <.75 Volts 46 0.41 0.058 0.048 14.0 %
I I.6%
V 2.75 Volts 4
1.03 0.030 0.066 7.8 %
6.4 %
Steam Generator 3 Entire Voltage Range 97 0.43 0.091 0.075 213 %
17.7 %
V soc <.75 Volts 90 038 0.089 0.074 23 3 %
193 %
i 2.75 Volts 7
1.03 0.121 0.101 11.7 %
9.7%
Steam Generater4 Entire Voltage Range 282-0.40' O.103 0.085
_.25.6% _, _ _21.2% _
V soc <.75 Volts 261 036 0.103 0.085 28.6%
23.7 %
2.75 Volts 21 0.92 0.100 0.083 10.9%
9.0%
GrootWTaNeM1MMW) 30 mt 3-10
' ~ ~ ~ ' ' ' ' ' '
~
._3----.
' ~ " ' ' ' ' - '
Table 3-5 Sequoyah Unit 2 October 1997 Average Voltage Giuwth Statistics Composite of All Steam Generator Data Bohhin Voltage Number of Average Voltage Average Voltage Growth Average Percentage Growth Range Indications BOC Entire Cycle Per EFPY Entire Cycle Per EFPY Cycle 8 Uuly 1996 - October 1997) - 450 EFPD Entire Voltage Range 480 0.41 0.094 0.077 233 %
18.9 %
V noc <.75 Volts 447 036 0.094 0.076 25.7 %
20.8 %
2.75 Volts 33 0.%
0.104 0.084 10.9%
8.8%
Cycle 7 (1995 - 1996) - 481 EFPD Entire Voltage Range 366 0.27 0.161 0.122 59.6%
453 %
V noc <.75 Volts 364 0.26 0.161 0.122 60.8 %
46.2%
2.75 Volts 2
1.01 0.155 0.118 153 %
11.7 %
o Cwomth!TaNe411/4M81L f 9 FM 3-11
Table 3-6 Sequoyah Unit 2 October 1997 Summary of Largest Voltage Growth Rates for BOC-8 to EOC 8 Steam Generator Bobbin Voltage RPC New SG Row Col Elevation EOC BOC Growth Confirmed ?
Indication ?
4_
17 87 OlH 134
_ 0.52 0.82 Nf
_ _.- N _. _
4 3
71 OlH 1.04 0.25 0.79 NT Y
4 22 47
_ 02H _ __ l.04 0.27 0.77 NT
____Y____
., 4_ _ _ _2_5_
_53 OlH 0.83
_0.21_
0.62 NT Y__
.._ 4 _ _8_.
._.8 3_.__ Ol H 1.1 _ _ 0.52 0.58 NT Y
~
l 36 39 02H 0.85 0.28 0.57 Y
E ~~'
4 27 70 OlH 1.32 0.76 0.56 NT
~
~
N 3
5 19 OlH 1.12 0.61 0.51 NT N
_ 4_ __I 2_. 72 _ __ Ol H
_l.51 1
0.51 NT N
4 3
72 OlH 0.69 0.21 0.48 NT N
1 44 42 02H 0.59 0.13 0.46 NT Y
_.l_
37
_ 61_
02H 0.69 0.24 0.45 NT Y
4 13 47 OlH 0.62 0.17 0.45 NT Y
_4_
8 89 OlH 1.04 0.6 0.44 NT Y
4 22 25 03H 0.62 0.18 0.44 NT Y
4 13 29 02H 0.58 0.15 0.43 NT Y --
_ _2_
15 89 OlH
_. l.02
_ 0.6 _
0.42 NT N
4 _.
_ 25_
_ 83 OlH 0.57 0.17 0.4 Y
Y 3
30 23 OlH 0.95 0.56 0.39 NT N
4 27 82 03H 0.7 0.31 039 NT Y
I
_ 20
_65 __
02H 0.54
_ 0.16 0.38 NT Y [_]
4 13 38 OlH 0.8 0.42 0.38 NT N
4 26 68 OlH 1.15 0.77 038 NT Y
~
._ 4__ _ 27 69
_0 l H__
0.79 0.42 0.37 NT Y
_l_ _ 3 _ __10__ _ 0 l H___
0.75
_039 036 Y
_. __ Y _._
_4_
23 87 OlH
_0.75 039 036 NT Y
4 2
76 OlH.
0.68 033 0.35 NT N_
4 29 48 OlH 0.52 0.17 035 NT Y
3 6
10 OlH 0.65 031 034 Y
Y 4
8 37 OlH 1.44 1.1 034 Y
N p
Footnotes
- NT = Not tested com raies ines it iuu 3-12 1
t Tcble 3 7 Probe Wear and Analyst Variability Tabulated Values Analyst Variability Probe Wear Variability Std. Dev = 10.3% Mean = 0.0%
Std. Dev = 7.0%
Mean = 0.0%
No Cutoff Cutoff at +/ 15%
Value Cumul. Prob.
Value Cumul. Prob.
-40.0%
0.00005 _
__i-15.'.)%
_0.000W._
-38.0% _. _ _
OiX)011
-15.0%
0.01606
._ __ 6p%__
0.00024
_ -14.0%__ _ 0.02275_ _
3
-34.0%
0.(XX)48
- 13.0%
0.03165
-32.0%
01X)095
-12.0%
0.04324
__ 3Qp%._
0
_ 00179
-11.0%
_ J.28.0% _.
-_l0.0%
_ 0.05804
_ _ -24S1_ _..._
_3W58p_
-9.0 %__
_ 0.07656,
0.00328
_:26.0%
gj9927 0.00990
-8.0%
0.12655 22.0 %
_ 0.01634 _
-7.0%
0.15866.__
_ _ 20.0%
0.
_ 02608 _
___ _-6.0%
_ Z.6.0 % _
_ 3 04927 _
_ _-5.0*__
__ 0.19568_ _
_ -18.0%
023753 _
I
-4.0%
_ _-I48%
_0.06_016 _
0.28385 _
_ _ -l_2.0%__
-3.0%
0.08704
___12200
_ 0.33412 0.
__ DSS
- _._
0.16581 _
_ -2.0%
0.38755
- 1.0%
0.44320_
-8.0%
0.21867 0.0%
0.50000
-6.0%
0.28011 1.0%
0.55680
._d8%__
_ _ _ 9:34888___
0.61245 2.0
-2.0%
0.42302 3.0%
0.66588__
0.0%
0.50000 4.0%
0.71615 2.0%
0.57698 5.0%
0.7624f ~
4.0%
0.65112 6.0%
0.80432 6.0%
0.71989 7.0%
0.84134 8.09c 0.78133 8.0%
0.87345 10.0%
0.83419 9.0%
0.90073 l 8.0%
0.95973 13.0 %
0.96835 20.0 %
0.97392 14.0 %
0.97725 22.0 %
0.98366 15.0 %
0.98394 24.0 %
0.99010
> 15.0%
l.00000 26.0 %
0.99420 28.0 %
0.99672 30.0 %
0.9982 I 40.0%
0.99995 NDEunecrt Table 1712/22/97 3 44 PM 3 13 j
I l
l Table 3-8 Sequoyah Unit 21997 EOC-8 Evaluation for Probability of Prior Cycle Detection Composite of All Steam Generator Data New Indications insp ction POPCD C
96 i
Bobbin 1997 1997 RPC Inspection inspection RPC Confirmed 1997 RPC 1997 RPG 1996 Confirmed Plus Not Voltage inspection Confirmed inspection Confirmed Inspection Bin RPC plus not RPC plus not Confirmed inspected Confirmed Inspected Confirmed inspected and Pluggeo' Frac.
Count Frac.
Count I
> 0 - 0.2 5
75 0
13 O
0.0 0/5 0.148 13/88 0.2 - 0.4 9
123 3
87 0
0.250 3/12 0.414 87/210 1
0.4 - 0.6 6
39 3
74 0
0.333 3/9 0.655 74 /113 0.6 -0.8 0
13 2
30' O
1.030 2 '2 0.698 30/43 0.8 - 1.0 1
5 0
9 0
0.000 0/1 0.643 9/14 1.0 - 1.5 4
4 2
5 1
9.429 3/7 0.600 6/10 1.5 - 2 0
0 0
1 0
0/0 1.000 1/1 TOTAL 25 259 10 219 1
> 1V 4
4 2
6 1
Pnpcd Tamer 1/3N8 'O 12 AM 3-M
Tabla 3-9 Sequoyah Unit 2 Analysis of RPC Data from 1936 and 1997 Inspections Combined Data from All Steam Generators Tetal Total Total Total Percent 1996 1997 1997 1997 1997 Group of Indications inspection Inspection Inspection Inspection Inspection Bobbin Bobbin RPC RPC RPC Indication Indication inspected Confirmed Confirmed Less than or Equal to 1.0 Volt isi 1997 Inspection 1996 Inspection Bobbin Left in Service _
349 207 10 8
80.0
- 1996 Inspection RFC Confirmed 1
1 0
0
- 1996 !n_spection RPC NDD 1
1 0
0 19_96 Inspection RPC_ N_ot in_spected
_ _ 205 205 10 8
80.0 No 1997 Inspection _ Bobbin
- _
__247_
20__ __
_ _ 20_.
_100,0 _
142
_ Newl997 In_spection Indicati_on
_ 349 454 30 28 93.3 Sum of All 1997 Inspection Indication Greater than 1.0 Volt in 1997 Inspection 1996 Inspection Bobbin Left in Service 15 14 2
2 100.0
- 1996 Inspection RPC Confirmed 0
0 0
O_ _
0 0
0 0_
- 1996 Inspection RPC NDD 14 14 2
2 100.0
- 1996 Inspection RPC Not inspected
- No 1997 Inspection Bobbin
- 1 New 1997 Inspection Indication 12 5 _._ _
5_
_ 100.0 t
l Sum of All 1997 Inspection Indication 15
_ 26 7
_ 7 100.0 _
All Voltages in 1997 Inspection
__ _1996 Inspe_ction Bobbin Left in Service
_ _364
__ _221 _ _
12 _
_ ___ 10 _ _ _
83.3 _
1_996. Inspection RPC _ Confirmed 1
_._1_ _
_0_
_ _0 _
1 1
0 0
_ _ _._1996 Inspection RPC NDD
- 1996 Inspection RP_C Not inspected
_ 219 _..
_ 219_ _
_ 12_ _
10__
83.3 _.
No 1997_ Inspection Bobbin
- _
259
- 25....
_ _25_
94.6 143 New 1997 Inspection Indication 100.0 Sum of All 1997 Inspection Indication 364 480 37 35
- Indicahons spht is based on 1996 Inspectum bobbet voltage Poped TaNe2 t/W98 l&l2 AM 3-15
__.i.....
m -- - - - - - - - - - ' :_.-.-.--.-,-----........-- ' " - "'
" ' " ' ' ' ' ' " ' " ' ' ' ' ' " ' ' ^ ' ' ' ' '
=
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t h
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m m
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9 r g
9 u a
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1 t l
e 3 rR o
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e n
8 o e i
1 et b 9 b c
r u
0 b 3
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g2 r B
iFt o ifn s 8
Un F
0 o
hi at u y
I ob 7
i u r 0
qt s ei SD eg 6
a 0
t loV n
5 i
0 bb oH 1
0 3
0 2
0 0
0 0
,o 0
0 5
4 3
1
's E o. j jy n,,
.an i
l
Figure 3-4 Sequoyah Unit 2 - October 1997 ODSCC Axial Distributions for Tubes in Senice During Cycle 8 l
160 140 ESG-1 120 O SG-2 100 B SG-3
.w 80 E SG-4 C
60 z
e 5
40 5
5 5
20 N
~
O 1101 1102 1103 1I04 1105 1106 1107 C07 C06 C05 C04 C03 CO2 COI Tube Support Plate 3-19
/
~.
Figure 3-5 Sequoyah Unit 2 Cycle 8 ( July.1996 to October 1997 )
Cumulative Probability Distributions for Voltage Growth on an EFPY Basis x
I
._O
. _ w._..- -
W..
ig= -= ~
- f,_
o,9
--) e, 0.8 r
,o
}0.7
~~~
c---------
0 SG-1 o
/
g 0.6
---------- ----------- ------- SG-2
/
_5
.c
.7/
~
0.5
-- ------- ---- j//--------------------------------------------
- - * - - SG-3
~~~
Q
.//
} 0.4
f,'l-----------------------------------------------
_,_ _ gg_4
.//
es
~5
'//
/
5 03
------ ---______.Y/
--x-Cumulative mU
. X.
0.2
- - - - - - - - - - - - - - - - - - f ;/ d
/-----------------------------------------------------------------------
f/
/, '
,-d'
- --- -- ------------------------------------------ - - -----^--------- -
O.]
f
//
..? W:W 0
-0.2
-0.1 0
0.1 0.2 03 0.4 0.5 0.7 Voltage Growth 3-20
n Figure 3-6 Sequoyah Unit -2 October 1997 Outage Voltage Growth During Cycle 8 vs BOC-8 Voltage - All SG Data l
)
8 l
l l
j l
l o SG-1 l
X*
f i
0.75 l
0 SG-2 t
I I
I i
X I
X !
i i
e i
0 j
X i
A SG-3 o
4
~
"U 0.5 f
h f
O x&l:
0 xl p[.
y x
a x sG-4 AX X
j C
A I
Yh x 1 xp A x2
- A f
$ 0.25
- 'i
=
a x
l g
x:
x u
A N*>X X hX *M A
0 x
V g
o*# lXhu
- l l
a
- U x
o ox l
I X
j i
-0.25 x
n a
i f
i
-0.5 0
0.2 0.4 0.6 0.8 1
1.2 1.4 1.6 BOC-8 Voltage Cnomthfig3-61/4/98 7 08 PM 3-21
Figure 3-7 Sequoyah Unit 2 - October 1997 Bobbin Signal Growth History - Cumulative Probability Distributions on an EFPY Basis Composite of All Steam Generators 1.0 -
e-1'
'~
0.9 D'
0.8 y 0.7
g------------------------------------------------------------------
C c
a I0.6
~
o
'D
=
c
=
.c 5 0.5 F.
---*-Cycle 7 4 0.4
/----- --------------------------------------------
4 5
6 03
- - O --Cycle 8 0.2 0.1
f'---------------------------------------------------------------------------------------
0.0 U ' ' ' '..... -tf l
-0.2
-0.1 0
0.1 0.2 03 0.4 0.5 0.6 0.7 Voltage Growth 3-22
04
!!I l!'
- i i
- 8
,t1!
0 3
il-lit [l
'f!
1' l'
i!'
02
)
}'
!!I!
,fi li lI!
t!
%(
0 eg 1
a s
t n
o l
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i t
l u
a b
ng ir 1
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i l'i
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-3 n
e y o
i t
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ui i
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- ii
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t 1
c
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ec U
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i r r a a V e 0
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W tsy e la b n o r
AP t
0 0
0 %
r 0 0 3 0
00 0
0 M
0
- f 0
4 0 %
4 3
- 0
/
7 9
4 9
8 7
6 5
4 3
7 1
0 -
f 1
22 0
0 0
0 0
0 0
0 0
2 1
i xG5sjI>=
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ua
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i n
)
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n a
m 0
m 0
9 8
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1 0
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0 0
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.C 5'3 y5e.aiub aepor 1\\'
l,
4.0 Database Applied for Leak and Burst Correlations The leak and burst correlations utilized in the analyses presented in this report -
are based an updated version of the database presented in Reference 8-4. The database protocol submitted to the NRC in the Fall of 1997 indicates that the database should be updated if "...the inclusion of new data results in a non -
conservative shift in the correlation predictions..." Inclusion of recent pulled -
tube data from Plant A-1 and A 2 makes the leak and burst correlations less conservative. So, as an interim update of the database, Plant A-1 and A 2 detn were added to the Reference 8-4 database and leak and burst correlaticas were reevaluated. The parameters of the updated leak and burst correlations are presented in Reference 8-6. As required by the NRC, Model Boiler specimen 542-4 and Plant J 1 pulled tube R8C74, TSP 1 be included in the database applied.
The updated leak rate database does not satisfy the statistical test applied until now for acceptability of a voltage dependent leak rate correlation. Thus, SLB -
leak rates reported here were estimated without utilizing a leak rate correlation, However, in a recent meeting (Reference 8-7) the NRC agreed to the use of a p-value for leak rate correlation slope parameter determined on a one-sided (rather than a two-sided p-value used until now) for evaluating the significance of regression. Reference 8-8 presents results of a regression analysis for voltage dependent leak rate correlation using the updated leak rate database for-7/8" tubes mentioned above. It is shown that the one-sided p-value for the slope parameter in the voltage dependent leak rate correlation is 3.8% which is below the 5% threshold for an acceptable correlation specified in the Generic Letter 95-
- 05. Thus, leak rate database for 7/8" tubes now-satisfies statistical test for a-correlation.
The following leak rate correlation is developed in Reference 8-8 for 7/8" tubes based an updated database that includes the recent Plant A 1 and A-2 data.
~
f N
Leak Rate (l/hr) 10
=
The above leak rate correlation was used to perform a second set of EOC-9 SLB leak rate projection for thMimiting SG.
1 S:\\ ape \\ ten 97\\EOC8_90d, doc 4-1
I 5.0 SLB Analysis Methods Monte Carlo analyses are used to calculate tb.> SLB' leak rates and tube burst probabilities for both actual EOC-8 and projected EOC-9 voltage distributions. The Monte Carlo analyses account for parameter uncertainty.
The analysis methodology is described in the Westinghouse generic methods report of Reference 8 3, and the same methodology was applied to leak and burst analyses performed during the EOC-7 outage.
In general, the methodology involves application of correlations for burst pressure, probability ofleakage and leak rate to a measured or calculated EOC distribution to estimate the likelihood of tube burst and primary to-secondary leakage during a postulated SLB event. NDE uncertainties and uncertainties associated with burst pressure, leak rate probability and leak rate correlations are explicitly included by considering many thousands of voltage distributions through a Monte Carlo sampling process. The voltage distributions used in the projection analyses for the next operating cycle are obtained by applying growth data to the BOC distribution.
The BOC voltage distributions include an adjustment for detection uncertainty and occurrence of new indications, in addition to the acijustments for NDE uncertainties. Comparisons of projected EOC voltage distributions with actual distributions after a cycle of operation have shown that the Monte Carlo analysis technique yields conservativo estimates for EOC voltage distributions and as well as leak and burst results based on those distributions. Equation 3.5 in Reference 8-3 was used to determine the true BOC voltage.
s:\\apc\\ ten 97\\EoC8.90d. doc 5-1
8.0 Bobbin Voltage Distributions This section describes the salient input data used to calculate EOC bobbin voltage distributions and presents results of calculations to project EOC-9 voltage distributions. Also, EOC-8 voltage projections performed during the last outage based on EOC-7 inspection bobbin voltage data are compared with the actual bobbin distributions from the current inspection.
6.1 Calculation of Voltage Distributions The analysis for EOC voltage distribution starts with a cycle initial voltage distribution which is projected to the end of cycle conditions based on the growth rate and the anticipated cycle operating period.
The number of indications assumed in the analysis to project EOC voltage distributions, SLB leak rates and tube burst probabilities is obtained by adjusth g the number of reported indications to account for detection uncertainty and birth of new indications over the projection period. This is accomplished by using a POD factor, which is defined as the ratio of the actual number ofindications detected to total number ofindications present. A conservative value is assigned to POD based on historic data, and the value used herein is discussed in Section 6.2. The calculation of projected bobbin voltage frequency distribution is based on a net total number of indications returned to service, defined as follows.
NTot aTs = Ni/ POD - Nwpatma + Nd,piogg.a
- where, NTot ars =
Number of bobbin indications being returned to service for the next cycle, Ni Number of bobbin indications (in tubes-in service)
=
identified after the previous cycle, POD Probability of detection,
=
Nrepair.d Number of Ni which are repaired (plugged) after the last
=
- Cycle, Ndeptuerea Number ofiadications in tubes deplugged after the last
=
cycle and returned to service in accordance with voltage-based repair criteria.
There are no deplugged tubes returned to service at BOC-9; therefore, Ndepiugg.a = 0.
The methodology used in the projection of bobbin voltage frequency predictions is S:\\apc\\ ten 97\\EoC8_90d. doc 6-1
deceribed in Reference 8 3, and it is same as that used ha performing EOC-8 predictions during the last (EOC-7) outage (Reference 8@
Salient input data used for projecting EOC 8 bobbin voltage frequency are further discussed below.
6.2 Probability of Detection (POD)
The Generic Letter 95-05 (Reference 8-1) requires the application of a constant POD value of 0.6 to define the BOC distribution for EOC voltage projections, unless an alternate POD is approved by the NRC. A POD value of 1.0 represents the ideal situation where all indications are detected. A voltage-dependent POD provides a more accurate prediction of voltage distributions consistent with voltage-based repair criteria experience.
In this report both NRC mandated constant POD of 0.6 as well as a voltage-dependent POD developed for EPRI (POPCD) are used. The EPRI POPCD is developed by analyses of15 inspections in 8 plants and is presented in Table 7-4 of Reference 8-4. The POPCD values applied -
represent lower 95% confidence bound, and they are reproduced here in Table 6-1 as well as graphically illustrated in Figure 6-1, 6.3 Limiting Growth Rate Distribution As discussed in Section 3.2, the NRC guidelines in Generic Letter 95-05 stipulate that the more conservative growth rate distributions from the past two inspections should be utilized for projecting EOC distributions for the next cycle. It is evident from Figure 3-7 that growth rates for Cycle.7 on an EFPY basis are higher than those of Cycle 8; therefore, Cycle 7 growth rate distribution is used to develop EOC-9 predictions. Cycle 7 growth rates for SG-2 are slightly higher than the all SG composite growth distribution and, per the methodology described in Reference 8-3, SG-specific growth rates are to be used for SG-2 while the composite growth rates should be applied for the other three SGs.
6.4 Cycle Operating Period The operating periods used in the growth rate /EFPY calculations and voltage projections are as follows.
Cycle 8
- BOC-8 to EOC-8 440 EFPD or 1.20 EFPY(actual)
Cycle 9
- BOC-9 to EOC 512 EFPD or 1.40 EFPY(fuellimit)
S:\\apc\\ ten 97\\EoC8_90d. doc 6-2 l
6.5 Projected EOC 9 VoRage Distribution Calculations for EOC-9 bobbin voltage projections were performed for all four SGs based on the EOC-8 distributions shown in Table 6-2. The BOC ditributions were adjusted to account for probability of detection as described above, and the adjusted number ofindications at BOC-9 are also shown in Table 6-2 Calculations were performed using a constant POD of 0.6 as well as the EPRI POPCD distribution (presented in Table 6-1). The total number of EOC-9 indications predicted with the EPRI POPCD are slightly higher than those based on the POD value of 0.6, and the reason being that a majority of the indications at EOC-8 are below 0.5 volt and the EPRI POPCD value for such indications is less than 0.6.
The larger growth rates for the last two cycles of operation, which are the EOC-7 growth rates shown in Table 3-3, were applied. The EOC 9 voltage distributions thus projected for all four SGs are summarized on Table 6 3. These results are also shown graphically on Figures 6-2 to 6 5. In general, results based on a constant POD of 0.6 are slightly more conservative (0.1 volt larger maximum EOC voltage) than those using the voltage-dependent EPRI POPCD, although the EPRI POPCD yields a slightly larger number ofindications.
6.6 Comparison of Actual and Projected EOC-8 Voltage Distributians Table 6-4, and Figures 6-6 and 6-7 provide a comparison of the EOC-8 actual measured bobbin voltage distributions vith the corresponding projections performed using the last (EOC-7) inspection bobbin voltage data and presented in Reference 8 2 Both EOC 8 projections based on a constant POD of 0.6 as well as EPRI POPCD are shown. As predicted in Reference 8-2, SG-4 has the largest number ofindications. While SG-2 was predicted to have the largest indication, the largest actual bobbin voltage was found in SG-3; however, the peak voltage predicted for SG-2 is only 0.2 volt above that predicted for SG-3. The actual peak voltages measured for all SGs are equal to or less than their projected value.
A comparison of the actual and projected voltage distributions in Figures 6-6 and 6-7 show that in general the indication population above 0.5 volt is substantially overestimated in the projections based on a constant POD of 0.6. This POD value is conservative for voltages above about 0.5 volt but non-conservative below 0.5 volt as seen in Figure 6-1. The projections using POPCD show better agreement with the actual voltages, while remaining a conservative projection, over the entire voltage range than found for POD =0.6 S \\ ape \\ ten 97\\EoC8.90d. doc 6-3
Table 61 EPRI POPCD Distribution Based on Data from 15 Inspections in 8 Plants Voltage EPRIPOPCD' Bin
-_.0.1 0.24 0.2 0.34 0.3 0.44 0.4 0.53 0.5 _ _
0.6 0.62 0.67 0.7 0.73 0.8 0.77 0.9 0.81 1
0.83 1.2 0.88
]_
~
~
1.6 0.92 1.8 0.93 2
'~
3 0.04 0.98 3.5 1.0 I
- Data from Table 7-4 in-Reference 8-4.
6-4 epnpopcc Tabe 611/5/98 2:53 PM
Tchle 6 2 Segmyth Unit 2 Oct:ber 1997 EOC-8 Robbin and Assumed HOC 9 Bobbin Distributions in SLH Leak Rate and Tube Hurst Analyses Steam Generator 1 Steam Generator 2 i
Voltage EOC*8 llOC*9 EOC.8 BOC.9 field Bobbin Indkattens M)D Held Bobbia indkainons M)D g3pg gg,p Indkations Repaired 0.6 Indkations kepaired 0.6 0.2 6
0 10.00 17.65 3
0 5.00 8.82 0.3 10 0
16.67 22.73 4
0
_6.67.. _
9.09 0.4 13 0
21.67 24.53 10 0
16.67 18.87 I
0.5 8
0 13.33 12.00 9
0 15.00 14.52 0.6 6
0 10.00
__8.96 11
_0
_18.33 _.
_ 16.42 0.7 2
0 3.33 2.74 6
0 10.00 8.22
__0=8_ _
_ _ _. _2
_,_ _. O _ _3.3 3_._2.60 _
_2__
0
_ 3.33 2.60 0.9 3
0 5.00 3.70 1
0
_l.67 _
_ l.23 _
1 1
0
_l.67_ _l.20_
0
,_0_
_ 0.00 _
__0.00
_l 1 _._ __0,,_._,.
O_
_ _0.00 _
0.00
_1 0_
_l.67..
1.17 1.2 0
0 0.00 0.00 1
0 1.67 1.14 1.3 0
0 0.00 0.00 2
0 3.33 2.23 1.4 0
0 0.00 0.00 0
0 0.00 0.00 1.5 0
0 0.00 0.00 0
0 0.00 0.00 1.6 0
0 0.00 0.00 0
0 0.00 0.00 1.7 0
0 0.00 0.00 0
0
')00 0.00 Total
$1 0
85.00 97.01 50 0
83.33 84.31
> IV 0
0 0.00
)
0.00 4
0 6.67 4.54 Steam Generator 3 Steam Generator 4 Voltage EOC.8 BOC.9 EOC.8 BOC.9 Field Bobb6n Indkaunns M)D HektBobbia Indkations POD Indkations Repaired 0.6 Indications Repaire!
0.6 D
0.2 9
0 15.00 26.47 21 0
35.00 61.76 0.3 16 1
25.67 35.36 38 0
63.33 86.36 0.4 18 0
30.00 33.96 56 0
93.33 105.66
_01_ _14 __ _ _ _ _ L_. _ 22:33 _
_ 21. 58 _ _ _ 50 0
_ 83.33 _ _ 80.65_
0.6 7
0 11.67 10.45 39 0
_ 65.00 _
$_8 21 0.7 8
0 13.33 10.96 27 0
45.00 36.99 0.8 9
0 15.00 11.69 22 0
36.67 28.57 0.9 6
0 10.00 7.41 8
0 13.33 9.88 1..
3 0
5.00
_. 3.61._
6 0
10.00 7.23
. I.. L. ____3__,
_ 0. ___. ___5.00_
3.51 7
0 11.67 8.19 1.2 3
0 5.00 3.41 4
0 6.67 4.55 1.3 0
0_
0.00 0.00 0
0 0.00 0.00 1.4 0
0 0.00 0.00 2
0 3.33 2.20 1.5 0
0 0.00 0.00 1
0 1.67 1.09 1.6 _ _
__0__
O
_0.00_
0.00 1
0 1.67 1.09 1.7 1
0 1.67 1.08 0
0 0.00 0.00 Total 97 2
159.67 169.49 282 0
470.00 492.42
> lV 7
0 11.67 8.00 15 0
25.00 17.11 6-5
-e
Table 6-3 Sequoyah Unit 2 October 1997 Predicted Voltage Distributions for EOC-9 Steam Generator 1 l
Steam Generator 2 l
Steam Geis::ter 3 l
Steam Generator 4 yg Projected Number ofIndications at EOC-9 Bin POD EPRI POD EP8M POD EPRI POD EPRI 0.6 POPCD 0.6 POPCD 0.6 POPCD 0.6 POPCD
_ _ _0.1_ _ _0.07
_ _ 0.13,
_ 02.
1.6 6 _.._
_2.64___
0._04 _ _ _ __ _ 0.07
__ 0.1 1 _ _ _ _.__020
_ _026._
_ _0.46___
0.85
___1.4 5 ___ _ _2.34_.._
3.99 __
.._ __ 5.52 _.. _
.. 9.36 _. _.
_ _ _ _14.31 12.92- _ _ - -. -. _ _(--
g 0.7 12.87 13.13 20.04 21.95 67.65 71.81 O.8 10.26 10.67 11.92 11.34 17.54 17.62 61.63 60.80 0.9 7.61 7.39 9.60 8.75 14.82 13.69 50.61 46.81 1.0 5.46 4.95 6.46 5.69 12.57 10.73 38.55 33.67
_ 11 __
3.85 _ _ _ 3.28___
4.03 _ __ 3.44
__ 1022___ _ 826 _ _ _27.51__ _ 22.84 1.2_ _
. _2.60 _ _ __2.14 2.66_ ___
2 2 4__ _ _
_ _ _.7.90_ _ _ _ _ 6.15__ __ _18.92 1.3 1.61 1.30 2.04 1.64 5.91 4.46 12.98..
._ 1_S.1_0. _
9.99 1.4 0.75 0.37 1.77 1.38 423 3.12 8.88 6.64 1.5 0.00 0.70 1.51 1.12 2.82 2.04 5.99 4.34
___ 1.6 _
0.7_0
_0.30 117 0.86 1._77 126__
__ _3 99,,,
_ _ _2.82_ _
_ _1.7 _ _ 040 0.00
_, 0.77 026
__ 1.09___
0._77_
_ 2.63_ _
__1.83_
1.8 0.00 0.00 0.01 0.00 0.70 0.49 1.69
_1._16 1.9 0.00 0.00 0.70 0.70 0.48 0.08 1.06.,
20 0.00 0.00 0.00 0.30 0.14 0.00 0.39
, _ 0.64 0.00 2.1 0.00 0.00 0.30 0.00 0.00 0.70 0.00 0.70 2.2_. _ _. 0.00. _
0.00 0.00 0.00 0.70 0.00
_0.70
_0.30 2.3 0.00 0.00 0.00 0.00 0.00 0.30_
0.30
. 0.00_
2.4 0.00 0.00 0.00 0.00 0.30 0.00 0.00 0.00
}
TOTAL 85.00 9725 83.34 84.49 159.66 169.56 470.00 492.50 i
>1V 9.81 8.09 14.96 11.94 36.26 27.63 85.04 66.36
[
>2V 0.00 0.00 0.30 0.00 1.00 1.00 1.00 1.00 f
. %- i. "
6-6 r
Table 6-4 Sequoyah Unit 2 October 1997 Comparison of Predicted and Actual EOC-8 Voltage Distributions Steam Generator 1 Steam Generator 2 Steem Generator 3 Steem Generator 4 Number of Indications EOC G Prediction EOC-8 EOC-8 Prediction EOC-8 EOC-8 Prediction EO C-8 EOC-8 Pr.h EOC8 Voltage Bin EPRI Actual EPRf Actual EPM Actuel EPRI Actuel POD = 0.6 POPCD POPCD POPCD POPCD 02 0.69 1.23 6
0.87 1.53 3
1.21 2.14 9
2.08 3.67 21
~ ~d.5~
_ 5.40.-
'__ E I~U8 1I[d5._
~~ It
~
E85 19.8E' 38
~
6.
16 8.17 10 4.19 g7
,,,Lgg
- j7,g-8 ii68
~i85 ~ ~ 's -
21.67 27.30 14 4e 98 5A15
~
~
~ ~
~
~~
50 06 14.95 17.99 6
17.46 19.16 11 25.15 28.02 7
51.39 5.91 55 0
9.76 10.92 2
16.35 16.60 24.17 2436 6
44.15 45.78 27
_._.7_
.~.._ 6__
8 2
1928 9
32.59 22 5 67 6p2_
1230 _ _3.85_ _2_
_ 20.41 _
3{65 _
a8
_ 329_
_ 20.50 _
8_ _
1 6
2225 14.69 a9
_ 337
_ 34 _ _3_
7 72 7.19 1_
1.0 2.14 2 09 1
4.46 4.06 0
9.45 8.27 3
15.11 13.35 6
1.1 1.45 1.40 0
2.63 236 1
5.77 4.95 3
10.21 8.78 7
1.2 0.78 0.62 0
1.68 1.45 _
1 339 2.83 3_
_ 5.56_
6.62 4
_.._._..1 0_ _
3.9 3.22
__.5_4_
1.
0 0.93 _
2_
1.94 1.3 0.00 0.00 0
1.11 0.70 _
0.56 _ _ _0 _
1.14 0.87
_0_
_ 2.09_
2_
14 0.70 0.70 0
1.68 1.5 0.30 030 0
0.43 0.33 0
0.70 0.52 0
1.00 0.55 1
1.6 0
0 0
0.31 022 0
0.49 031 0
0.00 0.00 1
0.
0 0.40 030 1
0.70 0.70 0
1.7 _
0
_0 0
029
_ 05_
1.8 0
0 0
030 0.00 0
0.07 0 70 0
0.30 0.30 0
1.9 0
0 0
0.01 0.70 0
0.00 0.00 0
0 0
0 2.0 0
0 0
0.00 0.00 0
0.70 0.00 0
0 0
0 2.1 0
0 0
0.70 0.00 0
0.30 030 0
0 0
0 2.3 0
0 0
0 30 0
0 0
0.00 0
0 0
0 TOTAL (
75.00 9228 51.00 95.66 104.88 50.00 154.00 167.16 97.00 283.33 314.35 282.00
>1V 3.23 3.02 0.00 8.45 6.90 4.00 14.90 12.03 7.00 24.82 20.79 15.00
> 2V I O
O O
1.00 0.30 0
0.30 0.30 0
0 0
0 Predcomp Pmkxvnp 1/4.98 7:10 PM 6-7
ljl 5
3 s
l 3
tna lP 8
n i
sno 5
i 2
tcd epn s u n o I B 5 e 1 c 1 nn 2
e
-6 o e l
d d
di u
e ef t
i r s n lp u ao iBC m
g A
Fn%
8 n
o5 6
i i9 b
t b
ur b e 5
oB l
1 iw r
t o sL i
D DCP O
l 1
P IRPE 5
l 0
ura2 2
/
n i
ma 0
2 0
9 8
7 6
5 4
3 2
1 0
s_n 1
0 O
0 0
0 0
0 0
0 0
nw
-v.
E.g 34 E=jc2*
c
.e llll
Figure 6 2 Sequoyah Unit 2 -
SG 1 Predicted Bobbin Voltare Distribution for Cycle 9 l
POD = 0.6 25 20 O B OC-9 i
A Predicted EOC 9 3
in l
E
!. E 01 0.2 0.3 04 05 0.6 0.7 00 0.9 1.0 1.1 1.2 13 1.4 1.6 1.7 Bobbin Voltage POD = EPRI POPCD 20 0 BOC-9 15 A Predicted EOC-9 i
1 io._. _
Z 5
Illi..._
0 01 0,2 0.3 04 0.5 0.6 0.7 0.6 0.9 1.0 1.1 1.2 1.3 1.4 1.5 16 Bobbin Voltage m........,=~
6-9
I Figure G-3 Sequoyah Unit 2. SG 2 Predicted Bobbin Voltage Distribution for Cycle 9 P O 9 = 0.6 te 16 O BOC-9 14 -
W Predicted E0C-9 10 e-6 4
_J s-II IlIIa oi o.2 0.3 04 o,s os o.7 o.s os to 1.
1.2 1.3 14 1.s 1s 1.7 i.e 19 2.1 POD = EPRI POPCD 20 18 16 14 -
12 E Predicted EOC-9 10 1
6 4
2 0
0.1 0.2 0.3 0.4 05 0.6 0.7 08 0.9 1.0 1.1 1.2 1.3 14 1.5 1.6 1.7 19 20 Bobbin Voltage mwg 3 in2v 12 30 ew 6-10
Figure 6 4 Sequoyah Unit 2 SG 3 l'redicted Hobbin Voltage Ulstribution for Cycle 9 POD = 0.6 30 i
26 -
~
0800-9 l
l
- 0
~
~
~ ~
~
s predicted toc.9 is.
E in.
s E
- O h _ m _m. _
m.
- : : : : : : : : 3 2,,,2 POD = EPlil POPCD 40 35 g
O BOC-9
~_
35 4 Predicted EOC-9 go
._[
is.
to,
- z
~
~
~
~
91 1 t.._ _
=
=
Bobbin Voltage PmtWg 419w t? t 23 Pw
Figure 6 5 Sequoyah Unit 2 SG 4 Predicted Ilobbin Voltage Distributton for Cycle 9 Combined Data for Ilot and Cold leg Indications
~~
POD = 0.6 tw l
t; y.
l 60 080C9 to.
~
g4 I
. Predicted E OC-9 so 3o.
20 -
io J _.f__
I.
FI rl,[ J m o
- : : : : : : : : : : : : : : : : : : : : a B bbin ven.9e p_ ____
POD = EPRI POPCD 120 1N' O BOC-9 3-
.,*eteooC.9 i.
to -
0 EE - " " -
EI f'
Bobbin Voltage
~~vanns om g.3g I
Figure 6 6 Sequoyah Unit 2 October 1997 Bobbin Voltage Distributions for Cycle 8 Steam Generator 1 l
25 4
to 51*redleted l'0D = 0.6
.! 15 3
BPredicted EPitt POPCD T
j iO E
5 0
~
~:
0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
1.1 1.2 1.4 1.5 llobbin Voltage Steam Generator 2 25 OActual E Predicted POD =0.6
.! 15 I
BPredicted EPill POD T
j 10 i
Z 5
0 0.2 03 0.4 0.5 0.6 0.7 08 0.9 1
1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.1 2.22.3 Ilobb Voltage Predcomp Fg.612h2/97 3 59 PM
-_A
d Figure 6 7 Sequoyah Unit 2 October 1997 Ilobbin Voltage Distributions for Cycle 8 I
~}
Steam Generator 3 0
l 25 DActual E Predicted POD = 0.0 20
.]g M Predicted EPill POD 4
g 10 -
x 0
E*N 0.2 0.3 0.4 0.5 0.6 0.7 0.0 0.9 1
1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 2
2.1 Bobbin Voltage l
Steam Generator 4 70 60 DActual e
~~
~
E Predicted POD =0.6 j 40 l
C j
2 Predicted EPiti POD 30 --
20 a
i 10 l
l 0
0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
1.1 11 1.3 1.4 1.5 1.6 1.7 1.8 Bobbin Voltage Prodcomp Fq.7 IT22/97 4 09 PM
7.0 SLB Leak Rate and Tube Burst Probability Analyses This section presents results of analyses carried out to predict leak rates and tube burst probabilities for postulated SLB conditions using the actual voltage distributions from the EOC 8 inspection as well as for the projected EOC 9 voltage distributions. The methodology used in these analyses is described in Section 5.0.
SG 4 with the largest total number ofindications as well as indications over 1 volt is expected to yield the limiting SLB leak rate and burst probability for Cycle D.
7.1 Leak Rate and Tube Burst Probability for EOC 8 Analyses to calculate EOC-8 SLB leak rates and tube burst probabilities were perfonned using the actual bobbin voltage distributions presented in Table 6 2.
Results of Monte Carlo calculations are summarized on Table 71. A comparison of the EOC 8 actuals in Table 71 with the corresponding predictions performed during the EOC 7 inspection, presented in Reference 8 2, indicates the following, a)
Total number ofindications found in the EOC-8 inspection for all SGs are well below their projection using both POD =0.6 and POPCD. The peak measured voltage for all SGs are bounded by their projected values.
b)
Leak rate and tube burst probability results for the projected EOC-8 indication population distribution, based on the EOC-7 inspection data, are conservative compared to the corresponding values calculated using EOC 8 actual measured bobbin measurements for all SGs. The leak rates are conservatively predicted using both POD =0.6 and POPCD.
c)
SG-4 was predicted to be the limiting steam generator at EOC-8 based on the SLB leak rate projection performed during the EOC-7 outage, and both SGs 3 and 4 were predicted to have the highest tube burst probability value predicted. SG-4 was confirmed to have the highest tube leak rate based on actual EC bobbin measurements for EOC-8. The highest burst probability
~
calculated using the actual voltages agrees with that projected for SGs 3 and 4.
d)
Leak rate and tube burst probability predictions for all four SGs based upon EOC-8 actual bobbin measurements are well within their allowable limits.
In summary, actual measured EOC-8 bobbin voltage distributions for all SGs are below the corresponding projections obtained using the NRC mandated probability of detection of 0.6. Limiting values for SLB leak rate (0.25 gpm) and tube burst s \\npc\\ ten 97\\EOC8.90d doc 71
_. ~
i probability (1.9 x 10 8) obtained using the actual measured voltages are more than an order of magnitude below the allowable Cycle 8 SLB leakage limit of 2.7 gpm (room temperature) and the NRC reporting guideline of 102 for the tube burst probability.
7.2 Leak Rate and Tube Burst Probability for EOC 9 Calculations to predict SLB leak rate and tube burst probability for the limiting steam generator in Sequoyah_ Unit 2 at the EOC 9 condition were carried out using two values for POD: 1) NRC required constant value of 0.6,2) voltage dependent EPRI POPCD distribution. The methodology used for these predictions is the same as previously described for analysis based on EOC 8 actual voltages. Projected results for EOC 9 conditions are summarized on Table 7 2 With a constant POD of 0.6, the limiting EOC 9 SLB leak rate projected is 1.22 gpm (room temperature),
and it is predicted for SG 4 which has the largeet number ofindications returned to service for Cycle 9 operation. This limiting leak rate value is less than one half of the allowable SLB leakage limit for Cycle 8 of 2.7 gpm (room temperature). The limiting tube burst probability,5.3x10-5, is also predicted for SG-4 which had 4 of the 5 largest indications found in the EOC 8 inspection;it is more than 2 orders of magnitude below the NRC reporting guideline of10-2 The above limiting leak rate (1.22 gpm) is obtained conservatively assuming that leak rate is independent of bobbin voltage because requirements for a voltage-dependent correlation is not met. However, as mentioned in Section 4.0, the NRC recently accepted the use of p value for leak rate correlation slope parameter determined on a one-sided basis (as opposed to a two sided p value used until now) to test for significance of correlation. The 7/8" tube leak rate data do meet the requirement for a correlation specified in the Generic Letter 95 05 based on p-value determined on a one sided basis. Therefore, EOC 9 leak rate projection for the limiting SG (SG-4) was repeated using a voltage dependent leak rate correlation developed using the latest data for 7/8" tubes (shown in Section 4.0),
and the these results are also shown in Table 7 2. The EOC 9 leak rate predicted applying the correlation (0.14 gpm)is only 1/9th of that obtained using a constant leak rate. Thus, there is significantly more margin in the EOC 9 SLB leak rate than indicated by the projection based on a constant leak rate. The tube burst probability value for SG-4 shown with the leak rate based on a correlation is different from the one in the base case because it is obtained using a database that includes 1996 Sequoyah Unit 2 pulled tube data in addition to the recent Plant A 1 1
and A 2 data. Inclusion of1996 Sequoyah Unit 2 data increases structurallimit by 0.1 volt and slightly decreases tube burst probability predicted.
S:\\apcuen97\\EOC8.90d doc 72
l i
t With the EPRI POPCD, the total number ofindleations predicted are higher than i
those for POD =0.6. The reason for this is that below about 0.5 volt, the detection probability calculated from EC inspection data could be significantly below 0.6 as shown by the EPRI POPCD distribution in Table 61 and Figure 61. About 50% of the indicatio:2 returned to service for Cycle 8 operations are below 0.5 volt.
Because oflarger number of EOC 9 indications predicted with EPRI POPCD, SLB burst probability for SGs 1 and 3 based on EPRI POPCD are slightly higher than those with POD =0.6.
In summary, SLB leak rates and tube burst probabilities predicted for EOC 9 are substantially smaller than their respective allowable and burst probability limits.
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Table 71 Sequoyah Unit. 2 October 1997 Outage Summary of SLB Tube Leak Rate and Burst Probability Based on EOC.8 Actual Measured Voltage Distributions Steam No of Burst Probability SLBLeak Oenerator POD Indic.
Max. Volts Rate ations 1 Tube 21 Tube (gpm)*
EOC 8 Predicted (Based on the Current NRC Approved Database) 0.6 75 1.5'
< 1.9 x 104
< 1.9 x 104 0,03 1
POPCD 92 1.6'
< 1.9 x 104
< 1.9 x 104 0.03 0.6 96 2.38
< 1.9 x 104
< 1.9 x 104 0.10 2
POPCD 105 2.2*
< 1.9 x 104
< 1.9 x 104 0.09 l
0.6 154 2.18 1.9 x 104 1.9 x 104 0.19 3
POPCD 167 2.18
< 1.9 x 104
< 1.9 x 104 0.17 0.6 283 1.88 1.9 x 104 1.9 x 104 0.35 4
POPCD 314 1.88
< 1.9 x 104
< 1.9 x 104 0.34 i
EOC.8 Actuals (Based on a Database that includes '96 Plant A 1 and '97 Plant A 2 Data) 1 1
51 1,0
< 1.9 x 104
< 1.9 x 104
< 0.01 2
1 50 1.3
< 1.9 x 104
< 1.9 x 104 0.01 3
1 96 1.7 1.9 x 104 1.9 x 104 0.07 4
1 282 1.5
< 1.9 x 104
< 1.9 x 104 0.25
' Voltages include NDE uncertainties from Monte Carlo analyses.
- Equivalent volumetric rate at room temperature.
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Table 7 2 Sequoyah Unit.1 October 1997 Outage Summary of Projected Tube Leak Rate and Burst Probability for EOC.9 250k Simulations SLB Steam No. of Max.
Leak Burst Probability Generator POD Indle.
Voltsm Rate ationsm 1 Tube 1 or More (gpm)(8)
Tubes EOC 0 PROJECTIONS (Leak Rate Assumed Independent of Voltage) 1 0.6 85 1.7
< 1.2x104
<1.2x104 0.09 2
0.0 83.3 2.1 3.1x104 3.1x104 0.15 3
0.6 159.7 2.4
<1.2x104
<1.2x104 0.39 4
0.6 470.0 2.3 5.3x104 5.3x104 1.22 1
POPCD 97.2 1.6 1.2x104 1.2x104 0.09 2
POPCD 84.5 2.0 1.9x104 1.9x104 0.13 3
POPCD 169.6 2.3 3.7x104 3.7x104 0.33 4
POPCD 492.5 2.2 4.3x104 4.3x104 1.10 EOC 9 PROJECTIONS (Voltage Dependent Leak Rate Correlation Applied) 0.6 470.0 2.3 3.1x104 (4) 3.1x104 (4) 0.14
- 4 POPCD 492.5 2.2 3,7x104 (4) 3.7x104 (4) 0.12*
Hnka (1) Number ofindications adjusted for POD.
(2) Voltages include NDE uncertainties from Monte Carlo analyses.
(3) Equivalent volumetric rate at room temperature.
(4) Database of burst probability correlations includes 1996 Sequoyah Unit 2 data (in addition to the recent Plant A 1 and A-2 data, Reference 8-8).
(5) A leak rate correlation for 7/8" tubes developad in Reference 8-8 applied.
S \\ ape \\ ten 97\\EOC8,.90d doc 75
8.0 References 81 NRC Generic Letter 95 05, " Voltage Based Rgair Criteria for the Repair of Westinghouse Steam Generator Tubes Affected by Outside Diameter Stress Corrosion Cracidng," USNRC Office of Nuclear Reactor Regulation, August 3,1995.
82 SG 96 08 010,"Sequoyah Unit 2 Cycle 8 Alternate Repair Criteria 90 Day Report," Westinghouse Electric Corporation, August 1996.
83 WCAP 14277, Revision 1, "SLB Leak Rate and Tube Burst-Probability Analysis Methods for ODSCC at TSP Intersections", Westinghouse Nuclear Services Division, December 1996.
84 EPRI Report NP 7480 L, Addendum 1, " Steam Generator Tubing Outside Diameter Stress Corrosion Cracking at Tube Support Plates Database for Alternate repair Limits," Electric Power 'Research Institute, November i
1996.
85 Letter from B. W. Sheron, Nuclear Regulatory Commission, to A. Marion, Nuclear Energy Institute, dated February 9,1996, 86 SG 97 08 004, "Farley Unit 1 1997 Alternate Repair Criteria 90 Day Report," Westinghouse Electric Corporation, August 1997.
87 Public meeting between industry and NRC Staff representatives on the subject of statistical methods for the regression analysis of ARC data, December 3,1997.
88 Letter from C. A. Stock, Westinghouse Electric Company, to R. Thomas, Electric Power Research Institute," Updated ODSCC ARC Correlations for 7/8" Diameter Tubes," NSD EPRI 1175, dated January 9,1998.
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