ML20212A150
| ML20212A150 | |
| Person / Time | |
|---|---|
| Site: | Braidwood  |
| Issue date: | 10/15/1997 |
| From: | Tulon T COMMONWEALTH EDISON CO. |
| To: | Johnson I COMMONWEALTH EDISON CO. |
| References | |
| NUDOCS 9710230171 | |
| Download: ML20212A150 (48) | |
Text
.- - . _ . . .
Memorandum Date: October if,1997 To: Irene Johnson, Acting Regulatory Sersices Manager
Subject:
Braidwood Staion's Review of Comed Response to NRC RAI Regarding the Steam Generator Interim Plugging Criteria 90 Day Report for the Braidwood Unit 1 Sixth Refuel Outage (AlR06).
We have reviewed the attached response for the NRC Request for Additional Information regarding the Steam Generator Interim Plugging Criteria 90 Day Report for the Braidwood Unit I sixth refuel outage (AIR 06). T he Braidwood Station concurt sith the -
enclosed esponse as proposed for Comed. Please forward our response to die NRC stafT, accordingly.
If there are any questions or comments concerning this letter, please contact T. W.
Simpkin, Regulatory Assurance at extension 2980.
Respectfully, A
V o T' .ot iy J. Tulon ite Vice President 1 i Braidwood Nuclear Generating Station fb ,
Enclosure 01..nre 97120mt doc AD 0 0 6 ,hf
Response to NRC Staff RAls on IIraidwood 90 Day Report t o
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BYRON /BRAIDWOOD All predicted SLB leak rate values provided in response to questions in this RAl are equivalent volumetric rates at room temperature (i.e., leak rate at SLB conditions condensed and measured at room tempernture).
. 1. - Requested Irtformation
"" For the ' redictions p of the EOC conditions at Braidwood-1, Comed used a lower voltage value of 1.1 volts for the highest bin. Since the behavior of voltages between 1.1 and 1.5 appears to be different than the behavior of voltages above 1.5 volts (ref. Fig. 5-3 of 8/14 submittal), discuss the appropnateness of the lower voltage value of 1.1 volt other than that the 1.1 limit provides 200+ indications as mentioned in GL95-05. Assess the chang in the calculated EOC conditions (i.e.,
voltage distributions and MSLB leakage) for 3raidwood-1 as the lower voltage value of the highest voltage bin changes from 1.1 volts to higher voltages, such 1.45 and
+
2.0 volts, using NRC approved methodology (i.e., POD = 0.6).
l Response 4
Anoropriateness of Lower Voltage Values for Growth Bins
, As discussed in the Braidwood-190-day report, the cycle 6 growth data show an increased frequency of larger growth indications with increasing voltage but that 2
the magnitude (AV) of the growth values is not strongly voltage dependent. The voltage dependent growth methodology was then developed to vary tl c frequency (probability) of the larger growth rates as a function of voltage. Ideally, the number of indications used to develop a growth distribution over a given voltage range -
should be the same as the number of BOC indications over the same voltage range for which the growth distribution is applied. Then, the resulting number of large growth occurrences in the projections would be the same as for the population used to develop the growth rates. However, the number of BOC indications in the higher voltage ranges increases due to growth of the indications and the n
M (f)' application dependent growthof a isPOD rates to applytothe deilne the larger growth BOC rates to largerdistribution.
BOC indication T hb voltages than would occur with a voltage independent growth distribution.
The largest influence of the voltage dependent growth rates occurs from the upper one or two voltage growth bins. Therefore, the methodology has an inherent consen*atism in that the number of indications in the upper growth bin ranges is higher in the BOC distribution used for the projection analysis than in the prior cycle distribution used to develop the growth rates. This results from growth of the indications over at least one cycle and application of a POD to define the BOC distribution. This difference in the number ofindications between that used for the growth ' dis,tribution and that for the projected BOC distribution becomes -
significantly magnified when a POD of 0.6 is applied as this increases the BOC population by about a 1.7 factor. Thus, this POD has the effect of nearly doubling mu-o.memn%e% 1 iono m o m
Response to NRC. Staff RAls on Braidwood 90 Day Report
, the. large growth-indic2tions compared L to the population used to develop the ,
growth rates. Increasing the voltage boundary for the upper voltage growth bin '
increases conservatism in the projections by applying the larger growths to larger BOC 1 indications. When the ccuservatism of higher voltage growth _- bins is combined with a POD of 0.6, the methodology becomes excessively conservative as shown by the analysis results given in later sections of this RAI response.
]
The selection of the voltage ranges for growth bins must be tied to the number of ,
indications in the growth values within the growth bins, it is also necessary to have fixe'd guidelines for defining the voltage bins, particularly the highest voltage ;
- bin, so that the analyses are repeatable without iterations on the voltage bin size.
A population of about 200 indications for a single growth distribution (bin) provides
~
a high confidence that the distribution is well defined. A lower bound of about 25 '
indications -is necessary to have any reasonable confidence that the growth distribution is acceptably characterized. A minimum of 50 indications in the upper voltage bin may be more appropriate even for a voltage dependent POD so that a variability of a few indications-in the growth values do not overly influence the '
growth distribution. For application with a POD of 0.6, which adds conservatism on the number of indications, the upper growth bin population of 'about 200 indications was selected and shown to produce conservative projected EOC leak rates (See also re.sponse to RAI-Question 3). Further reductions in the number of indications with an increase in the lower voltage boundary of the upper growth bin results in excess ve conservatism in the projected leak rates as shown in the second half of t'2e response to this question. When POD, is increased, it is appropriate to. increase the upper bin voltage boundary such that a boundary
, corresponding to about the highest 25 to 50 indication voltages is recommended for
- use with a voltage dependent POD such as POPCD. !
i L The influence of a POD of 0.6 on the difference in the populations used to develop .
the growth-distribution and the number of BOC indications is shown in Table la '
for Braidwood-1. For the recommended Braidwood-1, upper voltage growth bin cutoff of .1.1 volt, it is seen that 210 indications are included in the. growth
= distribution but that this growth distribution is applied -to almost 5 times (955 indications) as many indications at BOC-7 for a POD of 0.6._ As a consequence, the occurrence of large growth values above 1.1 volt will be almost 5 times as large as
- found for cycle-6 which was used to develop the growth rates. The benchmarking s of the methodology was performed for cycle-6, which had the number ofindications only 1.5 ' times the number used to develop the growth rates. Thus, the benchmarking for cycle-6 is considerably less conservative than the . cycle 7
. application. Similar differences in the number of indications in the growth and
! BOC-7 distributions are found for the upper voltage bin thresholds of 1.45 and 1.6 volts. For these higher thresholds, the number of indications in the . BOC-7 distribution for a POD of 0.6 is more than a factor of 10 higher than in the cycle 6 distribution used to develop the growth rates and excessive conservatism in the 1 projected EOC conditions can be expected. In th_e latter cases, the larger growths are applied to larger BOC indications with further increases in analysis _
conservatism. This conservatism will not be apparent in comparisons of projected w ,m e o wc w n % oi m 2 ionom u m
Response to NRC Staff RAls on Braidwood 90 Day Report and cctual distributions et EOC-6 since the BOC-6 population is less than twice the number ofindications used to develop the growth distributions.
Chance in Calculated EOC Conditions for Varied Growth Bin Voltaces Development of Growth Distributions with Vaned Bin Voltages During Cycle 6, SG-C had more indications experiencing large growth than the other three SGs, and it had the largest growth observed for the cycle. Figure 1
~~ shows th'e variation of growth with Woc for SG-C. SG-D had the second largest number of large growths, and its growth vs Woc data is shown in Figure 2. A-comparison of Figures 1 and 2 confirms that SG-C had the limiting growth during Cycle 6. SG-C also had the largest number ofindications found among the 4 SGs at EOC-6. Therefore, sensitivity analysis to examine the effect of vaging voltage growth bins on the calculated EOC conditions was carried out using the SG-C data. The niethodology presented in the Braidwood-1, Cycle 7 90-day report to select v. .q,e dependent growth requires a hybrid growth distribution that includes top three growth values from all SGs. SG-C had the top two growths for Cycle 6 and SG-A had the third largest growth. Therefore, a hybrid growth distribution consisting of all SG-C data and the largest growth in SG-A (to include the three largest growth values in all SGs) was used. -
The hybrid growth rate data for Cycle 6 were grouped into several bins using the guidelines established in the Braidwood-1 Cycle 7 90-day report and cumulative probability distributions were calculated separately for each bin To obtain growth distributions appropriate for use with a constant POD =0.6 using the recommended guidelines, the hybrid growth data was split into three bins. The width of the highest voltage bin was selected to include at least 200 indications (per discussion above); it contains top three growth values for Cycle 6. Figure 3 shows cumulative probability distributions for the three bins selected to represent growth data for POD =0.6. It is evident that the distribution representing the highest voltage bin in Figure 3 shows a much higher frequency oflarge growth occurrence than the other two distributions representing the growth data.
In response to this RAI, two other groupings of growth distributions were also applied with a constant POD of 0.6, and they are illustrated in Figures 4 and 5. ,
Figure 4 shows cumulative probability distributions for the case with the lower boundag for the highest voltage bin moved up to just behind the third largest growth value in the hybrid data (1.45 volts) and total number of bins increased to four. This choice of highest voltage bin reduces the indication population for that bin to less than one quarter of that in the recommended distribution for POD =0.6, which significantly increases the frequency of occurrence of large growths in that bin Figure 5 shows growth distributions for a third case where the population in the highest voltage bin boundary is further reduced by about 50% by moving the lower boundary of the highest voltage bin to 1.6 volts. A comparison of cumulative probability distributions for the highest voltage bins in Figures 4 and 5 with that in ..
Figure 3 shows that the frequency of occurrences of large growths increased substantially by moving the lower boundary of the highest voltage bin from 1.1 to mwamwwn,.o u, .a 3 sonow n m
Response to NRC Staff RAlgn Braidwood 90 Dry Report
. 1.45 and 1.6 volts. As note cbove, growth of the indications and application or a POD substantially increase the population of tubes for which the upper bin growth distribution is applied. The resulting population is much higher than used to develop the upper bin growth distribution and results in projections of more high voltage indications, increasing the upper growth bin boundary results in less reliable growth distributions due to the small population of indications while resulting in more conservative projections of voltage distributions. EOC-6 voltage distributions and SLB leak rate estimates based on the growth distributions shown in Figures 3 to 5 (with POD =0.6) are discussed in the following paragraphs.
- Change in EOC SLB Leak Rates with Varied Growth Rate Bin Voltages The SLB leak rate analysis results using the alternate higher voltage growth bin thresholds are given in Table 2. Cumulative probability distributions for the >
different growth distributions used in this evaluation are shown in Figures 3 to 5.
The Table 2 results for SO C include the SLB leak rates for the actual EOC-6 distribution, projections of EOC-6 leak rates using each of the voltage growth distributions evaluated and projections of the EOC-7 leak rate for each growth distribution. The best estimate for the leak rate from the actual EOC 6 voltage distribution is oft'ained for a 5% NDE uncertainty since the leak rate is dominated by high voltare indientinm for which a 10% NDE uncertainty is excessively c_onservative. Jor SO C, the limiting SG for cycles 6 and 7, all EOC-6 projections of SLB leak rates applying the voltage dependent growth projection (Cases 2 to 4 in Table 2) exceed the actual distribution leak rate at EOC-6. The EOC-6 leak rate for s the actual distribution of 9.8 gpm is underestimated by 2 gpm when growth 5 l independent of voltage is applied. Application of the larger voltage threshold for the l
highest bin, as shown for Cases 3 and 4, result in increased conservatism in predicting the leak rate for the actual distribution. The recommended growth bins of Case 2 already overestimate the actual leak rate by over 3 gpm (9.8 actual vs.
13.1 projected). Since the recommended upper voltage growth bin threshold of 1.1 volt for a POD of 0.6 results in the predicted EOC-6 leakage significantly exceeding that calculated from the actual distribution, further increases in the voltage threshold result in unnecessary conservatism. As shown for Case 4a, the higher voltage growth bin threshold of 1.6 volts is appropriate for application with a voltage dependent POD since the number of BOC-6 indications in the upper voltage range is not increased by the 1.7 factor obtained for a POD of 0.6. Case 4a shows .,
that applying the best estimate of POD with the higher upper bin voltage threshold for growth results in excellent agreement with the leak rate for the actual EOC-6 distribution (9.9 vs. 9.8 gpm).
Although the larger voltage growth thresholds requested for evaluation in this RAI are not necessary for adequate methodology conservatism, EOC-7 projections of SLB leak rates were performed as summarized in Table 2. The EOC-7 SLB leak rate with IRBs included is 27.2 gpm with voltage independent growth and 57.1 gpm with the recommended voltage growth bins (Cases 5 and 6 of Table 2). Application of the voltage dependent, EPRI POD with the upper voltage bin threshold of 1.6 ,
volts (Case 8a) results in a leak rate of 54.9 gpm.
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i Response to NRC Staff RAls on Braidwood 90 Day Report i , -i
- When the alternate growth bins (increased upper voltage thresholds) are applied with a POD of 0.6, the SLB leak rates increase to 100.0 gpm for alternate 1 with a 1.45 volt threshold and 98.0 gpm for alternate 2 with a 1.6 volt threshold (Cases 7 and 8 of Table 3). Thic is the expected result based on the discussion given above relative to the large number ofindications in the upper voltage bins when a POD of 0.6 is applied. As shown in Table la, the upper bin voltage distribution is deveh; ped from about 46 indications for a 1.45 volt threshold and about 25 indications for a 1.6 volt threshold. The BOC-7 distribution for a POD of 0.6 has 504 and 329 indications, respectively, in these upper voltage bins. Application of
~ -- the voltage dependent growth with these factor of >10 increases in the number of Indications results in the excessive conservatism in EOC-7 leak rates fot.nd for Cases 7 and 8.
I'n summary, it is shown from the results of Case 2 in Table 2 that the i
recommended voltage dependent growth bins provide conservative predictions in comparison with that obtained from the actual Braidwood-1 EOC 6 voltage distribution. Further increases in the voltage growth thresholds are not warranted for application with a POD of 0.6. This is further supported by the Byron-1 analyses discussed in the response to RAI question 2 given below.
- 2. Requested Information For the predictions of the EOC conditions at Byron 1, Comed used a lower voltage value of 0.9 volts for the highest bin. Since the behavior of voltages between 0.9 and 1.5 appears to be different than the behavior of voltages above 1.5 volts (ref.
Fig. A-4 of 8/14 submittal), discuss the appropriateness of the lower voltage value of 0.9 volt other than that the 0.9 limit provides 200+ indications as mentioned in GL95-05. Assess the change in the calculated EOC conditions (i.e., voltage distributions and MSLB leakage) for Byron 1 as the lower voltage value of the highest voltage bin changes from 0.9 volts to higher voltages, such 1.45 and 2.0 volts, using NRC approved methodology (i.e., pod =0.6).
Response
Annropriateness of Lower Voltate Values for Growth Bins ,
As noted in the respon_e to RAI Question 1 for Braidwood-1, the effect of the voltage dependent growth rates is to apply the larger growth rates to larger BOC voltages than obtained with voltage independent growth. The discussion of this i
topic given in RAI Question 1 is also applicable to Byron-1. Table Ib provides a comparison of the number of indications in the growth bins used to develop the growth rates with the number of BOC indications. For the largest voltage growth I bin, the number of indications in the BOC distributions is about a factor of 2.5 l higher (654 vs. 264 indications) for the largest recommended bin with a POD of 0.6. For the alternate growth distributione, the ratio of BOC to growth bin
~
indications increases to about a factor of 3. These ratios are smaller than described above for Braidwood-1 although still significantly mereasing nume-mu on. 5 iononm. . ~
~
Response to NRC Staff RAls on Braidwood 90 Day Report conservatism for the higher voltage cutoffs. As shown below and in the response to RAI Question 3, the increase in the upper voltage bin cutoffs above the recommended procedure add increased and unnecessary conservatism to the analysis methodology.
Chance in Calculated EOC Conditions for Varied Growth Rate Bin Voltanes Development of Growth Distdbutions with Vaded Bin Voltages Steam generators B and C had a comparable growth during Cycle 78, and their growth rates were significantly higher than those of the other two SGs. Figures 6 and 7 show the variation of growth with Vooc for SGs B and C. The two plots look very similar; however, above a Vaoc of about 1.45 volts, SG-B shows several relatively high growths and SG C has three indications with growth 1.5 volts or higher between 0.6 and 1.2 volts for which there are no comparable values in the other SG. The methodology presented in the Braidwood-1, Cycle 7 90 day report to select voltage dependent growth requires a hybrid growth distribution that includes top three growth values from all SGs. With this requirement, the differences between the hybrid growth distributions based on the SG B and SG C data would be small. The hybrid growth distribution based on the SG B data includes a few more growths on the high voltage end and, therefore, appears to be more limiting than that obtained with SG C data. Hence, SG B growth data was applied to SG C in assessing the effect of voltage dependent growth. However, the results would not be significantly different if SG C's own growth rates were used as shown in the analysis results given below.
To account for growth dependency on BOC voltage, growth rate data were split into several bins using the guidelines established it; the Brasdwood-1 Cycle 7 90-day report and cumulative probability distributions were established separately for each bin. A hybrid growth distribution that included all SG B data and the largest growth in SG C (la include the three largest growth values in all SGs) was used.
The distributions obtained for use with a constant POD =0.6 are shown in Figure 8.
The width of the highest voltage bin was selected to include at least 200 indications (per discussion in response to RAI Question 1) and it contains two of the three largest growth values. Figure 8 also includes the cumulative probability .'
distribution for the case wherein growth is assumed independent of Veoc. It is evident that the distribution representing the highest voltage bin in Figure 8 shows a much higher frequency oflarge growth occurrence than the distribution based on growth independent of BOC volts.
In response to this RAI, two other groupings of growth distributions were also applied with a constant POD of 0.6, and they arc illustrated in Figures 9 and 10.
Figure 9 shows cumulative probability distributions for the case with the lower boundary for the highest voltage bin raised to 1.1 volts, which reduces the indication population for that bin by about 50% (in comparison to the distribution ~
recommended for POD =0.6). Figure 10 shows growth distributions for a third case
"+ere 'he population in the highest voltage bin boundary is further reduced by gip an< m n =w 6 ,onow u n M
~
Response t3 NRC Staff RAls on Brakiwood 90 Day Report about 50% by moving the highest voltage bin boundary to 1.4 volts. A comparison of cumulative probability distributions for the highest voltage bins in Figures 8 and 10 show that the frequency of occurrences of large growths increased substantially by moving the highest voltage bin boundary from 0.9 to 1.4 volts. The effects of applying the growth distributions shown in Figures 8 to 10 (with POD =0.6) on the estimated SLB leak rate are discussed in the following paragraphs.
Change in EOC SLB Leak Rates with Van'ed Growth Rate Bin Voltages
- The SLB' leak rate analysis results using the alternate higher voltage growth bin thresholds are given in Table 3. Figures 8 to 11 show the cumulative probability distributions for the growth distributions used in these evaluations. Data in Figures 8 to 10 are based on the SG-B growth data, and Figure 11 shows growth based on the SG-C data. The Table 3 results for SG C include the SLB leak rates for the actual EOC-7B distribution, projections of EOC-7B leak rates using each of the voltage growth distributions evaluated and projections of the EOC-8 leak rate for each growth distribution. Based on the similarity of growth rates for SGs B and C, the growth distributions for SG B were also used for SG C analyses. This is supported by the results of Cases 2 and 2a in Table 3 which show the same leak rates for separate analyses for the SG B and C growtb distributions. For SG C, the limiting SG for cycle 8, all EOC-7B projections of SuB leak rates including the voltage independent growth projection (Cases 1 to 4 in Table 3) exceed the actual distribution leak rate at EOC-7B. This indicates that growth rates in this SG are not strongly BOC voltage dependent and all analysis methods are conservative. It is shown in the response to RAI Question 3 that voltage dependent growth is desirable to improve agreement with the actual EOC-7B leak rate for SG B. The recommended upper voltage growth bin threshold of 0.9 volt results in the predicted EOC-7B leakage exceeding that calculated from the actual distribution and further increraes in the voltage threshold result in unnecessary conservatism. .
Although the larger voltage growth thresholds requested for evaluation in this RAI are not necessary for adequate methodology conservatism, EOC-8 projections of SLB leak rates were performed as summarized in Table 3. The EOC-8 SLB leak
, rate with IRBs included is 19.0 gpm with voltage independent growth and 22.8 gpm with the recommended growth bins (Cases 5 and 6 of Table 3). When the alternate growth bins with increasing upper voltage threshold are applied, the SLB leak rates .
increase to 26.2 gpm for alternate 1 with a 1.1 volt threshold and 27.0 gpm for alternate 2 with a 1.4 volt threshold (Cases 7 and 8 of Table 3). This is the expected result based on the discussion noted above relative to the large number of indications in the upper voltage bins when a POD of 0.6 is applied. The increases in leak rate for alternate growth bins 1 and 2 for Byron-1 are significantly less than found for Braidwood-1 in Table 2. This results as the number ofindications in the BOC-8 distribu, tion for the large voltage bins (Table Ib) are a factor of about 3 higher than used to develop the growth dist6utions compared to the factor of 10 increase found for Braidwood-1.
~
In summary, it is shown from the results of Cases 1 and 2 in Table 3 that the recommended voltage dependent growth bins provide conservative predictions in m m m e m oe w n w oi 7 ionom. n -
Respor.se ta NRC Staff RAls en Braidwood 90 Dry Report g a comparison with th:t cbtained from the actual- Byron-1 EOC-7B voltage.
distribution. Further increases in the voltage growth thresholds are not warranted for application with a- POD of 0.6. This result is consistent with that found- for Braidwood-1 in the response to RAI question 1.
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Retponse to NRC Staff RAls on Braidwood 90 Day Report 3, Requested DV:rmattn i
Discuss why an independent as essment of the voltage dependent methodology is not needed. What is the _.us s for Comed's conclusion that benchmarking the methodology using the scan: data used to develop the methodology provides an adequate demonstration of the ability of the voltage dependent methodology to conservatively predict the EOC conditions at Braidwood-1 and Byron-1.
Response
. The intent of the benchmarking analyses in the Braidwood-190 day report was to demonstrate the adequacy of the methodology for the most limiting SG C. SG C is the limiting SG with regard to leakage for the actual EOC-6 distribution (4 gpm larger leakage than SG D) and for the projected EOC-7 distribution.
Demonstration of the adequacy of the voltage dependent methodology for SG C was expected to be conservative for the other Braidwood-1 and . Byron-1 SGs. To confirm this expectation and to respond to the RAI concern for additional benchmarking analyses, comparisons of SLB leak rates for projected and actual EOC distribtitions were made for all 4-Braidwood-1 SGs and for the .3yron-1 SGs B and C. The actual EOC-7B leak rates for Byron-1 SGs A and D were too small (<
0.1 gpm) to warrant consideration for methodology comparisons..
f The results of the additional benchmarking analyses are given in Table 4.
Comparisons of SLB leak rates from predicted and actual distributions are made for EOC-6 at Braidwood-1 and EOC-7B at Byron-1. The projections for each SG in Table 4 use the SG specific growth distribution rather than any use of composite of
'nultiple SG growth data or bounding growth distributions. The SG specific values tre used to better assess the methodology without additional conservatism from other bounding growth distributions.
The SLB leak rates for each Braidwood-1 SG are given in Table 4 as calculated from the actual and projected EOC-6 voltage distributions. The results for SG C were also discussed in the response to RAI Question 1 based on Table 2. For SGs A and D,-the projections based upon the recommended procedure for developing voltage dependent growth distributions are 3 to 4 gpm higher than that obtained from the actual distributions even with a 10% NDE uncertainty applied for the actual ..
distributions. This conservatism in addition to the 1.6 gpm margin found for SG C projections is -partly due to the hybrid methodology of including the largest 3 growth values from all SGs in the growth distribution. For SGs C, A, D and B, respectively, the hybrid methodology adds 1,2,3 and 3 large growth indications to the SG specific distribution. The. impact of the hybrid methodology is particularly conservative for SG B for which the leak rate is overestimated by > 7 gpm for the projections. The,se results tend to indicate that the hybrid methodology should be modified to include only 1 of the largest indications from other SGs in the SG specific growth distribution. This topic is further addressed in the response to RAI Question 8. Overall, it is concluded that the recommended voltage dependent _
growth methodology is conservative with large margins for all four Braidwood-1 SGs.
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Response to NRC Staff RAls en Braidwood 90 Dry Report For Byron-1, the SLB leak rates based on the actual EOC-78 voltage distributions are 0.27 and 0.13 gpm for SGs B and C, respectively. For the recommended voltage dependent growth rate bins, the corresponding predicted leak rates are 0.30 and 0.26 gpm which exceed that found from the actual distributions. This confirms the adequacy of the recommended methodology for the Byron SGs.
The results of Table 4 increase the number of SGs for benchmarking the voltage dependent growth methodology from 1 to 6 SGs. The recommended methodology provides ' conservatively projected SLB leak rates for all 6 SGs evaluated and the methods are adequate for analyses of the Braidwood-1 and Byron-1 SGs. Any changes to the recommended methodology should be directed at decreasing the conservatisms rather than an increase in conservatism.
BRAIDWOOD 1
- 4. Requested Information in the 8/14/97 submittal, Table 6-2 and Fig. 6-5 presented a comparison of predicted and actual bobbin voltage distributions for S/G C,- EOC 6, using the voltage dependent cycle 6 growth and a pod of 0.6. The Staff is interested in how well the voltage dependent methodology works for each S/G and at all voltage levels (i.e., both above and below 3 volts). ,
A) Provide similar tables and figures for all 4 S/Gs for all voltage levels.
B) Discuss how well the voltage dependent growth rates conservatively predict the actual voltages for all S/Gs and for all voltage ranges. Discuss how well the voltage dependent growth rates conservatively predict EOC 6 MSLB leakage for each S/G.
Response
A) Predicted and Actual EOC-6 voltage distributions for All 4 SGs are shown in Figures 12 through 15. These distributions correspond to the voltage dependent, .
EOC-6 projection results given in Table 4 for each SG. The predicted EOC-6 voltage distributions shown in these figures were obtained applying voltage dependent growth distributions established using the guidelines presented in the Braidwood-1, Cycle 7 90-day report and a constant POD of 0.6, For clarity, high voltage end of the distributions (over 3 volts) are presented separately. The predicted peak voltages are compared with the actual peak voltages in Table 4 (which corresponds to Table 6-2 of 8/14/97 submittal). Further comparisons of the predicted and actual EOC-6 voltage distributions are included in the response to item (B) below.
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Response to NRC Staff RAls on Braidwood 90 Day Report B) Discussion of Actual EOC Voltage and Associated SLB Leak Rate Predictions Comparisons of the predictions of the EOC-6 SLB leak rates with those calculated for the actual distributions are discussed in the response to RAI Question 3 given above. The comparisons of the predicted an'd actual voltage distributions based on the figures o response item (A) above are discussed herein.
For S -A, total number of EOC-6 indications is underpredicted because of
- ~~ under stimation of the indication population below 0.7 volt. This is at least in part, to the fact that the POD is <0.6 below about 0.5 volt. However, above 0.7 volt /)
the predictions substantially exceed the actuals as evident in Figure 12. For z@
i,ndication population exceeding 1 volt, 2 volts and 3 volts, the predictions exceed the actuals by about 51%, 66% and 55%, respectively. Therefore, the predicted voltage distribution is significantly more conservative than the actual distribution.
This is reflected in the predicted EOC-6 leak rate for SG-A which exceeds that based on the actual distribution by about 50% (see Table 4).
An examination 'of Figure 13 clearly shows that the predicted EOC-6 distribution for SG-B is substantially more conservative that the actual distribution. Total EOC-6 predicted population for SG-B exceeds the actual total, and for indication population above 1 volt, above 2 volts and above 3 volts, the predictions exceed the actuals by about 94%,149% and 63%, respeciively. The predicted EOC-6 leak rate is also very conservative as it exceeds that based on the actual distribution by about a factor of 20 (see Table 4). The primary reason for such large overestimation of EOC-6 voltages and leak rate is inclusion of 3 largest growth values from all SGs which are substantially higher than the largest growth observed in SG-B. SG-B did not have any of the largest 25 growth values for Cycle
- 6. This is further elaborated in the response to RAI Question 5.
Figure 14 provides a comparison of the predicted versus actual EOC-6 voltage distributions for SG-C, and again the predicted distribuuon is substantially more conservative that the actual distribution except for the largest 'ndication found in the inspection. Total EOC-6 predicted population exceeds the actual total, and for indication population above 1 volt,2 volts and 3 volts, the predictions exceed the actuals by about 63%,68% and 67%, respectively. The predicted SOC-6 leak rate .'
for SG-C exceeds that '_,ased on the actual voltages by about 14% to 34%
depending on the NDE uncertainty assumed (see Table 4).
As with SG A, although the total number ofindications at EOC-6 is underpredicted for SG-D because of underestimation of indication population below 0.7 volt, the voltage distribution is more conservative overall (see Figure 15). For indication population exce.eding 1 volt,2 volts and 3 volts, the predictions exceed the actuals by about 51%, 73% and 54%, respectively. Also, the predicted SLB leak rate exceeds that based on the actual measured distribution by about 60%.
Overall, EOC-6 voltage distributions for all SGs predicted using a constant POD =0.6 and a voltage dependent growth distribution following the guidelines ummmen.wewn%o% 11 ione m oe a
Response to NRC Staff RAls on Braidwood 90 DQy Report presentednin Lthef Braidwood-1, ' Cycle - 7 90-day report are conservative in comparison to the f actual; measured voltage- distribution. Consequently, the:
predicted EOC-6 leak rates are also conservative..
- 5. iRequested Jrportnation Fig 5 3 of the 8/97 L submittal. depicts the voltage growth' during Cycle 6:as a function of BOC 6 voltage. Provide similar figures for the remainirc S/Gs as well
- as a composite figure. Discuss the voltage dependency of growth for each S/G
. based on the data in the figures.
-Response Figures 16 and 17 show the variation of voltage growth during Cycie 6 versus the BOC voltage for SGs A and, B, respectively, and similar data for SG-D are presented
-in Figure 2. (Figure 5-3 of the 8/97 submittalis reproduced bere as Figure 1. Each of these plots also includes top three growth values from 4 3Gs during Cycle 6. A composite plot cohtaining i.imilar data from all four SGs is presented as Figure -18.
Cumulative probability distributions representing growth data for SGs A, B, C and D obtained by applying the growth binning guidelines presented in the Braidwood-1, Cycle 7 90-day report are shown in Figures'19,20,3 and 21, respectively.
SG-A-had the third largest growth indication during Cycle 6 among all SGs. An
- examination of Figure 16 indicates that Cycle
- 6 growth for SG-A shows'a small dependency on Vsoc. For Vooc over about i volt, the relative frequency of larger
! growths (above 1 volt) increases with Vsoc. Figure 17 shows Cycle 6 growth versus l Vsoc data for SG-B. It is evident that the largest growth observed in SG-B is
[ . substantially smaller than the three . largest growths in all SGs. Without the-largest
[ indication with about 4 volts growth,- SG-B . growth data does notL exhibit .any dependency on Vooc. Therefore, it_is concluded that the SG-B growth data is not
- - _ dependent on Vsoc. SG-D had the fourth largest growth during Cycle 6. It is evident L' from the growth versus Veoc data in Figure 18 that SG-D growth shows dependency-on Vsoc.
t j In . summary, Cycle 6 growth data for SGs A, C and D show a dependency on Vsoc. .~
f however, SG-B does not show such a trend.
- '6. Requested Irgermation Discuss other characteristics that could possibly explain the apparent dependency of growth rates, on initial bobbin coil voltage. What. other factors has Comed j; evaluated in an effort to understand the high growth behavior of these indications?
] Include as a minimum in the response: 1.) location of the indications, and,11) the
! age of the indications. ,
j l
LimouAnc\swo4ocinAnnm.oire doc 12 ionom. n o w i
Response to NRC Staff RAls on Braidwood 90 Day Report
Response
As discussed in EPRI reports and GL 95-05, the ARC was developed with the need for a continuing review of whether or not growth rates are dependent upon the BOC voltage. The need for this review was~ based on the independence of voltage found for domestic data while European data at higher voltages indicated growth dependence on BOC voltage. Prior to data obtained in late '96 to '97, these reviews supported the continued use of growth rates independent of BOC voltage for low
~~ voltage (less than about 1.5 volt) indications.
The general trend for a higher frequency of large change.s in voltage growth for larger volt indications can be expected based on the dependence of voltage on crack
, depth. Bobbin voltage increases exponentially with depth, particularly as near through wall indications are obtained. Thus a small change in depth for a deep indication will have a much larger increase in voltage than from the same change in depth for a shallower indication. On the average, it is expected that growth in depth over an operating cycle is approximately independent of the initial depth. As the BOC voltages' increase, the depths of the BOC indications can be expected to be larger and it should be expected that the frequency of larger voltage growth values would increase for the same increase in depth as for lower BOC voltages. The lower'BOC voltages require a larger depth increase to obtain the same voltage growth as the higher voltage indications. Based on leakage data and the i
probability of leakage correlation for %" tubing, throughwall indications begin to occur at around 2 volts. Thus, it would be expected that the change to voltage dependent growth would also occur around this voltage level as found in the Braidwood-1 data. It is important that voltage growth trends not be assumed to indicate a corresponding percentage change in depth. Voltage analyses become increasingly conservative as the indication depth increases. ,
To respond to the RAI request, assessments of the Braidwoo voltage data were performed to assess location and age of indication effect . Figure 22 provides a plot of the locations of larger growth rates on each o lower support plates. In this figure, the different symbols correspond to th ' V growth values for Cycle 6 normalized using time at RCS temperature > 500aF (413 days)'(DVCY6) over 1 volt intervals. The results show that the larger growth values are not dependent upon .,
TSP tube location but occer principally at the lower TSP which has the higher temperatures. The lower TSPs have consistently shown the largest number of indications and the associated uequency of larger growth values should also be expected.
Figure 23 shows the EOC-6 signal amplitude versus the age (time since first detected by bobbin inspection) of the indication in terms of operating cycles (cycle 1 is EOC-5, etc.). More of the larger voltage indications were initially found two cycles ago at EOC-4. The ARC repair limit at Braidwood-1 was increased from 1 to 3 volts at EOC-5. Thus, more of the EOC-4 indications with higher growth rates could be left in service at EOC-5 than for indications found at EOC-3 which were repaired at 1.0 volt at EOC-4. !! 4 %5d Whe change in repair limits at m o.w.me m ocwn%.oa. e 13 / ionom. o m a
, Rcsponse to NRC Staff RAls on Braidwood 90 D;y Report EOC 5 is more influential on the trends of Figurc 23 than the age of the indicatio:.s.
- 7. Requested Information Provide a comparison between the projected EOC leakage obtained following the approved methodology using the Cycle 6 hybrid growth distribution and the proposed voltage dependent growth rate methodology discussed in the 8/14 submittal. Discuss how the difference between the 2 values justilles the
- --- application of a vsltage dependent growth rate methodology.
Response
it is assumed for this response that the requested approved methodology using the cycle 6 ' hybrid' growth distribution is a voltage independent growth that includes the three largest indications found in all sos as used for the voltage dependent growth. In this manner, identical data is used to compare voltage dependent and voltage independent analyses. Analysis results using the approved methods of WCAp-14277 that rio not include the three largest indications from all sos are given in Table 4. The analyses for Braidwood-1 SG C and Byron-1 SO B result in underestimates of the leak rates obtained for the actual EOC voltage distributions.
The projection for Byron-1 SG C overestimates the leak rate from the actual ribution.
. A. tysis results for all four Braidwood-1 sos using the cycle 6
- hybrid" voltage independent and voltage dependent growth rates are given in Table 5 for the projected EOC-6 distributions. The results for the actual and voltage dependent growth distributions are repeated from the Table 4 data to facilitate comparisons with the voltage independent results. The voltage dependent growth rate projections for all 4 sos result in the projected leak rates exceeding the leak rates obtained from the actual distributions. With the voltage independent " hybrid" growth, the projected leak rates exceed that from the actual distributions for sos A and B but are less than that for the actual distributions for sos C and D. SG C is the limiting SO for leakage and thus the most important SO for assessing the adequacy of the projections.
It is clear from the results of Tables 4 and 5 that the combination of voltage dependent growth rates with the hybrid of the three largest indications from all sos is unnecessarily consen'ative. The use of the hybrid including the three largest indications with voltage independent growth rates provides an improvement over the NRC approved WCAP-14277 methodology by adding the conservatism of the hybrid to compensate for the lack of voltage dependence. However, the voltage independent hybrid growth methodology underestimates the limiting SO C leak rate for Braidwood-1 at EOC 6.
Y L \tOMU.Mfwb EOC\RAl\ Rm,0lre dec 14 10/10/R 11 M AM
Response to NRC Staff RAls on Braidwood 90 Day Report
- 8. Requested Information ,
Discuss the bases for limiting the hybrid growth distribution to include the largest 3 growth values found in any of the S/Os. Ascess the effect of including the top 5 or 10 growth values on your projected EOC leakage.
Response
The SLB leak and burst analyses are strongly influenced by the largest indications l'n the distribution. There is ne assurance that the largest indications will occur in the same SO between successive cycles. Therefore, the hybrid concept ofincluding the largest growth values in the growth diatribu.fon for individual sos was applied to recognize the potential shift of the largest growth between sos. .' .ssuming ^
equivalent corrosion potsntial between sos, the probability that the largest growth will occur in a specific SO is about % for a 4 loop plant. The probability that the largest two growth values will occur in the same SO is about 1/16. Inclusion of the 1
l two largest growth values in one SO thus establishes about a 9.5% probability that I
the largest growth values are included in the projection analyses. However, the methodology was intended to also cover 3 loop plants which would require the largest 3 indications to obtain about 95% probability of including the largest growth values. Therefore, the methods were defined to include'the 3 largest growth indications in each SO growth distribution. For the 4 loop Braidwood-1 and Byron-1 units, this is added consen'etism since there is only about a 2%
probability of the three largest growths occurring in the same SG.
As noted in the response to RAI Question 7, the inclusion of the 3 largest indications in the hybrid distribution appears to be unnecessarily conservative when combined with voltage dependent growth rates. The fact that the projections overestimate the leak rates obtained from the actual voltage distributions implies the methodology should be made less consen'ative Thus, it would be more appropriate to reduce the number of largest growth values in the hybrid distribution to 1 or 2 indications than to consider increasing the number in the ,
hybrid distribution. Nevertheless, to be responsive to the RAI request, leak rate calculations were performtd with the 5 and the 10 largest growth indications included in the distribution. The probability of the 5 largest indications occurring in the same SO is less than about 0.1%. Figures 24 and 25 show cumulative probability distributions for growth bins which include the 5 and the 10 largest growth values.
The leak rate a'nalysis res.ults for hybrid distributions including the 3, 5 and 10 largest indications are given in Table 6 for SG C. As expected, the use of the 5 or 10 largest indications results in increased and unnecessary consen'atism in the leak rate projections. The leak rates from the actual EOC 6 distribution are '
overestimated for the recommended hybrid distribution, and the overestimates n a m o m u oe m na. .i,.
- 15 uom no.u I
m J
. Response to NRC Staff RAls en Braidwood 90 D y Report bec me larg:r cs the number cf largest indic2ti:ns in the hybrid distribution is I increased. This effect is smaller for SG C than would be obtained for the other SGs since SG C already includes 3 of the largest 5 growth values and 6 of the largest 10 i values. '
It is concluded that any modifications made'to the hybrid distribution should be to reduce the number of the largest growth values included in the growth analysis to less than the 3 indications currently applied.- Larger- numbers should not be considered due to the unnecessary, increased conservatism that results in the leak ,
-* rate analyses, i I
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, Response to 14RC Staff RAls on Braidwood 90 Day Report Table la Braldwood 1.SG C Number ofIndications in Growth Illn and BOC Distrinutions Growth Rad Growth Bin No. Ind. No. Indications in BOC 6 No. Indications in BOC 7 Bin Option Voltage in Growth Distribution Distribution Range Bin Actual POD = 0.6 Actual POD = 0.6 Recommended s 0.7 1230 676 1133 796 1342
' "~
0.7 to 1. I 665 593 993 664 1114
> 1.1 210 191 320 551 955 Alternate i s 0.5 734 319 534 374 631 0.5 to 1.0 1059 843 1414 976 1641 1.0 to 1.4 266 240 401 377 635 ,
> 1.4 46 58 97 2;'4 504 Alternato 2 s0.5 734 319 f$'d 374 631 0.5 to 1.0 1059 843 1414 976 1641 1.0 to 1.6 287 273 456 480 810
> 1.6 25 25 42 181 329 Table Ib Byron 1, SG B Number of1ndications in Growth Bins and BOC Distributions Growth Rate Growth Bin No. Ind. No. Indications In BOC- No. Indications in BOC 8 Bin Option Voltage In Growth 7B Distribution Distribution Range Bin Actual POD = 0.6 Actual POD = 0.6 Recommended s0.5 826 483 824 615 1042 0.5 to 0.9 657 680 1165 690 1170
> 0.9 264 284 523 375 654 Alternate I s 0.5 825 483 824 615 1042 0.5 to 0.8 551 562 965 584 991 0.8 to 1.1 249 269 462 267 456
> 1.1 122 133 261 214 377 Alternate 2 s 0.5 825 483 824 615 1042 O.5 to 0.9 658 680 1166 690 1170 0.9 to 1.4 212 228 413 290 499
> 1.4 52 56 110 85 155 O'
n o m w o.tx w nnm.oi... 17 ionem u n au
. Reliiponse to NRC Staff RAls on Braidwood 90 D y Report Tcble 2 Braidwood l Summary of EOC 6 ar.d EOC-7 SLB Leak Rate Projections SG - C HL Indications Only SLB Leak Rate Case Cycle 6 Growth Voltage Bin Widths No. of Mu. (gpm)*
No. POD Ind.N Volts * ***'""
~~ ' With Free IRBs Span Actual EOC-6 "Best Estimate" for Comparison with Projection Methods Ref. N. A. I 2098 11.3 9.8 8.0 5% NDE unc.
{
Ref. N. A. I 2098 11.9 11.5 9.3 10.3% NDE une.
Per GL 95 05 Projected EOC 6 for Comparison with Actual EOC 6 Dependence on Voltage Range for Voltage Dependent Growth a WCAP 14277 Voltage Indep. Growth 0.6 2382 9.7 7.8 2 Recommended Growth Bins 0.6 2382 10.3 13.1 , 10.6 Fig. 3 growth Os.7, 0.7 1.1, > 1.1 3 Altemate 1 Growth Bins 0.6 2382 10.8 14.2 11.8 Fig -4 growth Os.5, 0.5 1,1 1.45, > l .45 4 Alternate 2 Growth Bins 0.6 2382 11.1 14.2 11.8 Fig. 5 growth 0s.5, 0.5 1,1 1.6, > 1.6 4A Same as Case 4 EPRI 1973 10.9 9.9 8.0 Projected EOC 7 Dependence on Voltage Range for Voltage Dependent Growin <
5 WCAP 14277 Voltage Indep. Growth 0.6 3411 12.8 27.2 24.2 6 Recommended Growth Bins 0.6 3411 14.5 57.1 52.2 Fig. 3 growth Os.7, 0.7 1.1, > l .1 7 Alternate I Growth Bms 0.6 3411 17.0 100.0 92.3 Fig. 4 growth Os.5, 0.5 1,1 1.45, > 1.45 8 Altemate 2 Growth Dins 0.6 3411 17.1 98.0 90.4 Fig. 5 growth -
05.5, 0.5 1,1 1.6, > 1.6 8a Same as Case 8 EPRI 2722 12.8 54.9 Notes:
(1) Number ofindications adjusted for POD.
(2) Voltages include NDE uncertainties from Monte Carlo analyses and exceed measured voltages.
(3) Equivalent volumetric rate at room temrerature.
e naamcwmoewn a.i.oi.. .- 18 ionom. n v w
%Q#dMWTVKFJMDfl@&ls on BraidwooT96~ Day Report Tchte 3 l Ilyron 1 Summary of EOC-7B and EOC 8 SLB Leak Rate Projections SG - C IIL Indications Only Cycle 7B Growth Data SLB Leak Rate Case Cycle 7B, Growth Bin Width Voltage No. of Mu. (gpm)*
No. Range POD Ind.* Volt:(, Comments
~ .. With Free IRBs Span Actual EOC 7B l "Best Estimate" for Comparison with Projection Methods Ref. N. A. I 2035 15 0.13 l
0.13 10.3% NDE unc.
Per GL 95 05 Projected EOC 7B for Comparison with Actual 20C 7B j
Dependence on Voltage Range for Voltage Dependent Growth I WCAP 14277 Voltage Indep. Growth 0.6 2606 3.6 0.17 0.17 2 Recommended Growth Bins 0.6 2606 3.8 0.26 0.26 Fig 8 growth.
O s 0.5,0.5-0.9, > 0.9 SG B growth.
2a Same as Case 2 with SG C growth 0.6 2606 3.9 0.26 0.26 Fig. lI growth.
distribution SG C growth.
3 Alternate 1 Growth Bins 0.6 2606 4.0 0.29 0.29 Fig. 9 growth 0 s 0.5,0.5 1,1 1.1, > 1.1 l 4 Alternate 2 Growth Bins 0.6 2606 4.2 0.31 0.3 i Fig.10 growth 0 s .5,0.5 1,1 1.4, >l.4 Projected EOC 8 i
. Dependence on Voltage Range for Voltage Dependent Growth 5 WCAP14277 Voltage Indep. Growth 0.6 3317 11.5 19.0 16.0 6 Recommended Growth Bins 0.6 3317 11.0 22.8 19.6 Fig 8 growth 0 s 0.5,0.5 0,9, > 0.9 7 Alternate I Growth Bins 0.6 3317 11.3 26.2 22.8 Fig 9 growth 0 s 0.5, 0.5 0.8, 0.8 1.1, > 1.1 8 Alternate 2 Growth Bms 0.6 3317 11.7 27.0 23.7 Fig 10 growth -
0 $ .5, 0.5 0.9, 0.9 1.4, > l .4 Notes:
(1) Number ofindications adjusted for POD.
(2) Voltages ir.clude NDE uncertainties from Monte Carlo analyses and exceed measured voltages.
(3) Equivalent volumetrie rate at room temperature -
M L WAtANG\DWMOC\RAl\kai,0lte det 19 10/10/9*.llJ7AM
. Response to NRC Staff RAls on Braidwood 90 Dry Report Tr.ble 4 Braidwood Unit-1 EOC-6 and Byron 1 EOC 7B Comparison of SLB Leak Rate Results Based on Actual and Projected Voltage Distributions l
SLB No. of Mat Leak Rate Comments SG Growth Voltage Bin Widths POD Indications (" Volts * (gpm)*
Braidwood l EOC 6 ACTUALS A N. A. I 1754 10.2 6.39 10.3% NDE unc.
B N. A. I 801 5.8 0.36 10.3% NDE unc.
C N. A. I 2098 11.9 11.5 10.3% NDE une.
C N. A. I 2098 11.3 ' 9. 8 5% NDE unc.
D N. A. 1 2099 9.7 6.99 10.3% NDE unc.
EOC- 6 PROJECTIONS A SG A data: O s 0.5,0.5 1.0, > 1.0 0.6 1679 10.2 9.4 Fig.15 growth B SO B data: O s 0.5,0.5-0.8, > 0.8 0.6 916 10.0 7.5 Fig 16 growth C SO C data: 0 s 0.7,0.71,1, > 1.1 0.6 2382 10.3 13.1 Fig 3 growth WCAP 14277 Voltage Indep. Growth 0.6 2382 9.7 7.8 D SG D data: 0 s 0.5,0.5 1.0, >l.0 0.6 1769 10.2 11.2 Fig.17 growth Byron-1 EOC-7B ACTUALS B N. A. I 1779 4.5 0.27 10.3% NDE unc.
C N. A. I 2035 3.5 0.13 10.3% NDE unc.
EOC-7B PROJECTIONS B SG B data: O s 0.5, 0.5-0.9, > 0.9 0.6 2513 4.1 0.30 Fig 8 growth WCAP-14277 Voltage Indep. Growth 0.6 2513 3.8 0.21 C SG C data: O s 0.5, 0.5-0.9, > 0.9 0.6 2606 3.9 0.26 Fig. lI growth .
WCAP-14277 Voltage Indep. Growth 0.6 2606 3.6 0.17 Notes:
(1) Number ofindications adjusted for POD.
(2) Voltages include NDE uncertainties from Monte Carlo analyses and exceed measured voltages.
(3) Equivalent volumetric rate at room temperature.
e u m w a m stoe m na.._on... 20 ionom. n n w
Response to NRC Staff RAls on Braidwood 90 Day Report Tcble 5 Braidwood Unit-1 EOC-6 Projections i
Comparison of SLB Leak Rate Results for Voltage Dependent and Voltage Independent Growth SLB N'o. of Max. Leak Rate Comments SG Growth Voltage Bin Widths POD Indications
- Volts * (gpm)*
Braidwood-l EOC 6 ACTUALS A N. A. I 1754 10.2 6.39 10.3% NDE unc.
B N. A. I 801 5.8 0.36 10.3% NDE unc.
^
l C N. A. 1 2098 11.9 11.5 10.3% NDE une.
C N. A. I 2098 11.3 ' 9.8 5% NDE une.
j D N. A. I 2099 9.7 6.99 10.3% NDE unc.
EOC- 6 PROJECTIONS A 0 s 0.5,0.5 1.0, > 1.0 0.6 1679 10.2 9.4 Fig 15 growth Voltage Independent Hybrid Growth 0.6 1679 9.6 '6.5 B $0.5, 0.5-0.8, >0.8 0.6 916 10.0 7.5 Fig.16 growth Voltage Independent Hybrid Growth 0.6 916 9.6 6.1 C 0 s .7, 0.7 1.1, > l.1 0.6 2382 10.3 13.I Fig. 3 growth Voltage Independent Hybrid Growth 0.6 2382 9.7 8.7 D 0 s 0.5, 0.5 1.0, >l .0 0.6 1769 10.2 11.2 Fig -17 growth Voltage Independent Hybrid Growth 0.6 1769 9.5 6.7 .
Notes:
(1) Number ofindications adjusted for POD.
(2) Voltages include NDE uncertainties from Monte Carlo analyses and exceed measured voltages.
(3) Equivalent volumetric rate at room temperature.
i 9 !
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namewo toeswsu.on. 21 ionom. n a o J
~
. Re:ponse to NRC Staff RAls on Braidwoo'd 90'Dy Report "
4 Table 6 Braidwood 1 Comparison of EOC-6 and EOC-7 Projections for Varying Hybrid Growth Distributions SG - C HL Indications Only SLB Leak Rate Case Cycle 6, Growtl, Voltage Bin Widths No. of mal (gpm)("
POD Ind.(" Volts * ***"'
With Free IRBs Span ,
~~
Actual EOC-6 "Best Estimate" for Comparison with Projection Methods Ref. N. A. I 2098 11.3 9.8 8.0 5% NDE unc.
Ref. N. A. I 2098 11.9 11.5 9.3 10.3% NDE unc.
Per GL 95 05 Projected EOC-6 for Comparison with Actual EOC-6 -
Dependence on Number of Hybrid Growth Values for Voltage Dependent Growth 1 Recommended ifybrid Growth 0.6 2382 10.3 13.1 10.6 Fig. 3 growth Hybrid = 3 largest powth values Bins = Os.7,0.71,1, >1.1 2 Altemate 1 Hyb.id Growth 0.6 2382 10.3 14.4 11.8 Fig l8 growth Hybrid = 5 largest g.owth values (*)
Bins = Os.7,0.7 i.1, >l.1 3 Altemate 2 Hybrid Growth 0.6 2382 10.3 15.4 12.9 Fig.19 growth Hybrid = 10 largest growth values Bins = Os.7,0.7 1.1, >l.1 Projected EOC 7 Dependence on Voltage Range for Voltage Dependent Growth .
4 Recommended Hybrid Growth 0.6 3411 14.5 57.1 52.2 Fig. 3 growth Hybrid = 3 largest growth values Bins = Os.7,0.71.1, >l.1 5 Altemate i Hybrid Growth 0.6 3411 14.7 62.5 57.1 Fig 18 growth Hybrid = 5 largest growth values (')
Bins = Os 7,0.71.1, >l.1 6 Altemate 2 Hybrid Growth 0.6 34Ii 14.9 67.7 61.9 Fig.19 growth Hybrid = 10 largest growth values Bins = Os 7,0.7 1.1, >l.1 Notes:
(1) Number ofindications adjusted for POD.
(2) Voltages include NDE uncertainties from Monte Carlo analyses and exceed measured voltages.
(3) Equivalent volumetric rate at room temperature.
(4)lncluding 5* largest growth is the same as including 4* largest growth as the 5* to 7* largest growth values occur in SG C L \ROMANG\BO LOC \RAl\Ratoire dar 22 ionom. n e au
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,T 4 <hq
%- 'E. .,- --
P O 8'O hp 'W h ..
- k 'N 90 3 I
- k. -
N '$ . . , M -
VO h **y . ,,
.g 0
%Q"%.it -
-0 4 t-o- !
Q %
. W+
M 1 o o h 9 n
-b vo-o o v. 9 d o o N : A e
o o o ,
uopaung uopaqpas50 upegnam3 ,',
. As.
. ~.l Figuru 6 *
( {
Byrom Unit-1 Ocseiner1996 Outage 4 Vokage Growth During Cycle 7B vs BOC-78 vokage - AM SG-B + Largest .
7 NeransHaed Using Dee at RCS Tengerature > SOFF (102 days)
A t
64 -
.: l xsG s esIndicssons)
X -
5 a 4 .sGC(Largee Growsh) -
0 E4 I e 4
i M*
2
& x lx x l --
\ l 4
o ,
,% - -, xl M x
$ [ X X
- i *
- l ;
& 2- x v* k I x x x x '-
x= x 5 x a I, gM X X ~g , X XX X
~
i f
yt wE _
Y _m v," b ** x x 2; n,g f . , u j, .. m. ...; . xx w I n : x x
_ C L mj f J.f ..q .0 '.
l o.
- fxWx xx
! -r y I
. gan i x l .
- -2 ' '
i l
i ;
0 0.5 g
j 23 2 2.5 j 3 5 soc.7s v.a.se .
WWsuseena aPne 0 .- _ _ __ - _ - - - __--- ________ __ __.
Figure 7
- i Byrna Unit-1 Ocseber19!NiOutage {
e Voltage Growth During Cycle 7B vs BOC-78 voltage - AE SG-C+ 2 Largest in SG B -
7 i Nornesiired Using Thee at RCS Temperature > 50FF(102 day's) l } - '
l 0 ; i 1
' l ,
I
- I
- o SG4(AN%) ~
o o 5 l l
.2i g thisee l o 1 1 l
24 *
? '
i I I
>* 3- , , h i
a i s
R g l o g o, o o, I o o h2 '
- c o! I p
g w a og , . g h
% o oeo .oo ooc o
c o
d ohog gE.
g --
co gg I g*'
o o e oo o
o S 800 o o
~I I
o o
,P
~ 80 _o e n a o"
l o 'o ,
o \
-2 g ]
0 0.5 !
I 1.5 :
2 2.5 3 BOC-75 Voltage s w,wwwsum 8 ._ .. _
ii , l' ;' l < !;! >'
I .a*
- )
s
_e k .;"
o v
F . ' .'
C 5g
-=
- O .n~
B
> _ u. f ;~
g, o a
!e em r
h g
. h-t
- z n
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5) w e
s
= ._ 2 8
(
8 5
6
(
4 6
2
( 4 I
- n
.n MUw _3 -4 k
v o i t
o v
k s
o ht w ::
RT c- v o 5
0 9
9 G r :n f_ t o
0 t
o 0-r
(
B ja p e
-A U 5
0 v
O G
- a
- S u a_
1~
- C C 8 1~
8 g
_g.p e
- l 5' be e
r # 5- w u 5- k i
g # 4 F
4 P* 4- ge a
- e. o, k- ko E= r-e k- V
,- s g 5
< -# P b b
fP
- /
b b
- 8. d d $
h* -
g* !n a $
b
+ l-B -
fd i
.:' p.! .
g .
.f r .
!.I .
r dr f .#*
g 5
~ ' .
0 E
I b .
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0 6 5 - :
1 0 0 4 3 2 _
0 0 0 0 1
0 -
t 0 0 0 eoE3haEa5g2u2"$U -
I p
l t
Figure 9 '
Byron Unit -1 Cycle 7B Hybrid Growth -NorniaHaed Usieg Tkne et RCS Temperature >See 1.0 - AH SG-B + Largest in SG-C - Variation 1 of Recesammendesi ILL "
"*w for POD =0.6 y~ ,5 4 4 & D- e- r "
0.9 -
__22- G g.Y rs- n s n-c-Q*D'c.a-a-c y -
g 0.8 --
_ a.
7
, ,er a-i
- # a a 0.7 -
f #
i
$v Y g a e
/ p Ia< 0.6 - "
8 -
u' -
T J
2 3
s d
f ,a
/ \
. E 00
- a 1 /
f /
- P E d d .
y y 0.4 - ,'
p e
3 I, i .
--o--Up to 05 vok (825) e 8
a d -
v 03 - d' 'I -
e l
- c- 0.5 to 0.8 vok (551)
,1 g # -
/ / - -c- 0.8 sol.1 vehs (249) 0.2- D, /
f j
- c-- Over 1.1 C (122)
D.1 -
p1/P o' '
/ -- m --SG-B (Growth Independear ofBOC vohs) k'$-G ,
n/.
0.0 C : : :
444,'94o : : : : : *;;
9 6 a: , , , . --
o o o d d 6 ,--,,",,,:
o ------,,,-
an, .
n, - - - -
" ^
- d 3 , . ,
e4 ed e4 e a a a * ,w- a- d e, d -
Vo4sge Growth
. ,. e f
~
]
Mgerre le .
Byren Unit -1 Cycle 7B Hybrid Growth - Nors:alized Using Tinse at Tenspersenre>
1.0 AU SG-B + Largest in SG-C- Variation 2 of Reconnanded Distribestions for POD =0 .
$4F - - - - ,;. ;; .E e- a -a -L ; ;
- j. 5 "
0.9 ,y X 5.a -
A a_ a.o"n u-D #
13-D 0 -0 A-o e -o y W" *a
.D-D*G~D 0.8 -
'p .tr.tr i a -
m 0.7 &
~
9' P"G-G o -
g 'I
.d .u. u E i tr
.T E==
0.6 - (1, : cf a
r, ,
ps t .5 n .o
- T: 0.5 - .D. d '
'I g
p- -o-Up to 0.5 vok (825)
,. ,o .
- D
$ CA -
~3 p' ,i ! -c- 0.5 to 0.9 vok (658) 8 S 1 d -
u 0.3- #ji i
- p-d -- 0 --0.9 to 1.4 voit (212) 3
.I - .
I I
g i -
0.2'
}3 - Over 1.4 volts (52)
.- 6
/ l [
r d ., . -e- SG-B Only(All Volu) ~
0.1- -t1 1 , \
P,u
~
D-G-G" 0.0 4 ; "
- a .
a: s a: s: s. :aa:2 ,,',:
e-e Voltage Growth ana! saran:22-- " l wwm ... '
I Myn 11 . I Byrom Unit -1 Cyde 7B Hybrid Growth -Norsusilmed Using Thee at RCS Tensperature > SOS F 1.0 All SG-C + 2 Largest la SG-B - Cum =Imerve F. 2_1Z!y Distributions Ter Use with N6
-: ___y a+ m pp__
-m- K " " * " -
M M*E~~~~~ &
0.9 -
wB .m m' >=
7 /
g_g _
}E Y f p' 87 0 -
s -*.
a P P J i
- = 0.6 f (
f _
5
- a 1 /
0.5 -
p
! : Up too.5 voit(955)
/
jo.4- DE .
)
g j
3 -c- 0.5 k) 0.9 voi: (840)
D
/ /
u 03 - f /
b;F - *-- Over0.9 volts (230) 0.2-
. --* --SGC Only(Ali volts)
,*g*
0.1 .
{ 0.0 2 :
$ 5 2 3 3 3 0 2 2 3 3 S 2 O 3 3
% 2 2 ; ; 2 Veitage Growth
h Figune 12 Braidwood Unit 4 - Steaua Generator A Comparbon of Prodjeted and Antunt Bobbin Voltage Distributions f Voltage Dependent Growth Eates Applied. POD =0.6 .
, Stenan Generator A . Up to a volta
~~
O ActualRoc 4(Up to 3 voks)
~
~~
4Pm#eted EoC4 (up to a veh.) _
in --
. . cye e Growin
'i te - - - - _
ins _ _a_
g -- - - . .
too --- - . . . . E
- n -
- ,l _
60 - - . . . , ,
H i# .
"j [ . ,- - , ,,.. , s ,. s o s e11r :2I I 1 II rl1 1,,ar ,,. L a.m von 23.a,,,,.,,,3 e- Steam Generator A Over 3 volts s-0 ActuelEoC4(over 3 vons)
Wgp POD e oa(over voete)
~
r 3
l E s- - -
- t. .. _ ,
i
" l illlii..allll
.3-
" l
= .3 : : : ;3 3 : ; ; 3 .- "
Bobbin vohege e
Pigure is Braidwood Unit.1 - Steam Generator B Comparison of Prodloted and Actual Bobbin Voltage or SGB, EOC. 6 Distribu Voltase Dependcat Growth Rates Applied. POD =0.6 no -
Sta=m Generato~r B . Up to 3 volta n
_E-
~* ,o _.
0Amaluoc.s(up to a vens)
_ u - II ,
% .ao -
lg
- w. = _ _ . . - II 1 ,, _ _ _ . til 11:
,, 1 _ _ . -
. 1.
so -
,o
_ _ _ _ = =
. Jim -
, 1 i Ea_
I_ Il aaas :aa :: asa:ILIAtlAa a n.,m ...._
monen voneos aaaasnaanna 8 team Generator B . Over 3 volts OActueltoc-a(overa vons) mPrometed,Poo.o.s(owwa vone) t croie a onowei i f y
- A._L 5
'i i
hi....
- . ::::::::::... II llii l t...
potMn voneg, :::::::::::::iI::::::3 .. ,
m in , . . an e
- e L
_ _ _ _ . _ - _ - - - -_ - .. - - ..__ - .. - . . -.= _- - - _- - - -- - - ..
Figure 14 Braidwood Unit 1 - Stensa Generator C Comeparison of Predicted and Actual Bobbin Voltage Ulstrib Voltare Dependent Growth Rates Apolled. POD =0.8s or SG sno Steam Generator C. Up to 3 volta O Actualsoc4(up to a voit )
300 -
r - >
3; iso
- - 7-l-l WPredo.ned 0,. m .. EOC-4 (up to 3 volts)-
+ . . . 1Ii
.f
= = LIIi l too
_. .. _ =
IIi 76 so -
+ - = =
- 11i
- - - - = - - - IIi - - -
as L
su, 3
23333333:
I 11IIl1I.1Mi a- u m,,4 DD32305533QD2232223 ocaninv.n Steam Generator C Over3 volts _ _ .,
\
s q QAatual EOC4 (Over 3 volts) 9 M i
5N Cyete'A POD e U.S (Over 3 volte) 8 Growth
- anguemmens g.
I t
't l I
' " l i,
I
}
=: :
- : : : : : : : : : :,o::::::::l::
il 1 h ...__ l li . . ...IH t a: : : : : : : : : _l: ;l i,1 nebbin vennes equussaIn s t trop tt 98 Aas h
9
Figure 15 Braidwood Unit Steam GeneratorD Comparison of Predicted and Actual Bobbin Voltage Distri Voltare Dependent Growth Rates Apptled, POD-0.6 , 8 4 ano 7 Steam Generatof.D . Up to 3 volta __
i guo '
j peo DActual EOC 4 (Up to 3 voits) sao -
~ ~
r ..
,,, - - - 8 P
" cv P'"a *****d
- 8 0 0 (U 8 #*)
soo _ _ _'
- ,, _ _ _ Ie _.
,. _ L I-sno - _
'I I Ils ~
~
lla ~_
oo - _ .. _
. )R 4e
.kI e '
il s.
2.
o I Irlil J. raw.,.2._
a a a : : : a s s e :: ena aaa n sa a ea a sa .ma}s notmin venmee an Steam Genty mr D . Over 3 volta QActualEOC 4(Over a vous) a -
mPrased, Pon = as(over: vann) cyose e om,th
.. h 1
l l i
2: 1: : 3 : 11lll13...._,ill 'i .I l 3
233:sotsinvoneye
- 33322221 23 : : : : 3: :
ww wiimme
. x.
~ .
1 Figure 16 t i l BraMwood Unk-1 AprH IM Outage ' ;
Voltage Growth During Cycle 6 vs BOC-6 Vokage - HybrW of AM SG A + 2 Largest in SG C 8 Growth NorniaMzed Using Time at RCS Tensperature > 50FF (413 days) o SG-A (A!!Indcaricts) ',
7 mTwo Largest Growthin SG-C '
~
O
- 6 -
I t5 e
o I4 y O O O
}3 ;
/
O
}I O O -
,o O Z2 0 0 00 O g O 8 % 9 03 3 33 I
25 3 BOC4 Vehage m.rmneerns eu l
E_ t -- - -
. ~.'
o .
O I Figure 17 Braidweed Unit-1 Aydi1997Ontage - '
Voltage Growth During Cyde 6 vs BOC4 Vettage - Hybeht oferSGs All SG B + 3 Larg Growth I
Nw *:d Uslag *nsee at RCS Temeyerstave>5e#F(413 days) o SG-B(MInications) l I.
7 --
e
+
a largest Growth in SG-A (3rd Largest in M SGs)
I
~
a !
.2 ta.gutin sec t we a as so.)
l 5-E C
, w 4
' t C
~
l3 i 3
- V E o -
Z2 i,
80 O
O O O4 0 g O O O O g O g
) C _,5) n n O
-I i 0 !
0.5 1
f.5 l 2
2.5 soc.6 ven.se
- e. c m 1 = m i
o .-
~
~_- i
- - I
, c> ,
i
- 5 .
FIgore 18 Braidwood Unit-1 AprilIFIOntage ~
i Voltage Growth During Cycle 6 vs BOC 6 Voltage - Cesuposite of All JG Data ,
8 !
Growth Norusalised Using llame at RCS Tesaperature > SOFF (413 days)
\ !
A SG-A '
7 0 g I
- . . SG-B I a A !
i 6 ----
i D
DSG-C l D D X D X SG-D
- O '
X w 4 _
b n o a a XX D 4 U D X D
~ s D i
l
.: 3 D kX DD X A ,
4 a n x g a i I b XA a D -
i S2 *A A N
^
- I va D a x, x_ i
+ '
u BOC 6 Voltage ,
I e5*P N attSF222PM t l
.. ! i< t i L iiii i!t ( t' !.' ,:.l iill x- !
.6 I
- x. . ,. d g :
.e F a- )
s 6
0 0) )
e l
t
- 4 56 r. 4 8
1 2 )
l v o
>0 -# (
G U e= ,4e i :
t
- rD - ~[
~
i o h G A
( : ..
l ~t toO = 7~
- - 5 v e v
t y .e aP W l
n r
ei s =- E- 0 a O
- 4 e
pi s o o l aw t A
wG t : 4 s
e e m. p 5 - e U 0 .e TsU S *x . -
O -
S
- 4 Cr o - x. :
c - :4 Rf -
m
- e t s ano .= -
- - : a4e .
r ei .a . - 4e _
mt s u - _
I -
Tibr .e -
u- i gt r i
nis . y 1 x- :;
sD .
Uy .
eg
- .4 .
di lt ,
ei .
s ,
- n4 9ib l a ht
- 1 ab .
e r mor m, ,~ : ,.- w r ,
o r
uoP gN e
. x.1-X,
- y.
G i
F - v .
- x.. sae ht le i
t 4 .
- x. e
- r. .,..ie -
wia v on " :
n-GC r a r r dr - . ri i
K.
bCy -
5 r~
HG S -- -
x od 6 n ei dt
. f,c ~.
. 6 ye s . :
.d Crg a
- I *
.d j_.
1 L t 2 .# :
mo i
n+ r j: .
UA - i#
'Y , g -
5o d 2 oG 1,f ,I :
no oS wl yyIII .:~~
- i kA a
r l
f i
- - 2 :
no B i *./ : .d .
o
~
- - ( .
- r. N 4
3 W
- ,\
0 9 8 -
9 1
0 7 6 5 4
! ,y t f t 0 0 0 3 2 ^-
0 0 0 1
0 g 0 0 O a $ E j *=aa*5 b e Is=a $ U j , -
y
4
}
@ re 20 ,
t
. Braidwood Unit-1 Cycle 6 Hybru Growth -Norinallaed Using'11me at RCS Temperatuse > 50 1.0-AllSG-B+ 3 Largest in All SGs - Cumulative Probabilky Distributions for Use with POD 4.6
^
<gs-j d. =.6, -e- *~'*"* * '[_ . . '.:.'."::X. - Y- E - * * "* "
0.9
- **.,....x--- -
g $*
0.8-
// ..-
- * . .x * * .x t ,X a 0.7-
- X O !
g E
A 0.6-g"/
f /
~
g i R '
f: Up to 0.7 volt (338) -
.a 1-0.5 ; ,,'
- c- 0.7 to 1.1 volts (284) -
P aa'$ 0.4
--m--Over 1.1 voits (189) __
5 U 03 -
_._ - SG-B Only (All volts) i 0.2-0.1- I
.- i J.*. '
0.0 ' d ' . . r 4 3 a : : -
2 Q Q 3 3 3 , - : : -
E 3 a
~
2 2 3 3 S S S "
2 3 Z Voltage Growth wieseramm e ,
i
- l Flyn 21 i
- Braidwood Unit -1 Cycle 6 Hybrid Growth - Normelised Using Time at RCS Tesspratare > 500 F All SG-D + 3 Largest in All SGs-- Cumulative Probability Distribadons for Use with POD =0.6 1.0
_ : ;. ,_ o r g g g y g _ ,_ g, w ; ,_;; ,, , , ;; ;
___g,g,g,,..a 09 p
m x *-"**** ~
R
/ .r- 4' x. 4- E ,, .
' 0.8 d
m
,..x*
Fp
. x ' ,x. *.
-4 x m 0.7 - .
O
- l 3a
- s :
E 0.6= I g J g'
.a . -+-Up to 0.5 voit (953)
.8 <
l g 0.5 - 3 y is l l
-c- 0.5 to i vok (940) -
e ( -
E .ji
.5 0.4 - l a t y -- * --Over 1.1 volts (212)- _
3 ,,
l ---- so.o oa rca ,.u,>
0.2 - .
0.1- . '
+
~
O.0 ! P . .: :
2a2$2$EE$'~~232333'3"2N2UUU"2M22U$7770202 VeHage Growth
-a.=
t 1 o .-
Figure 22 Braidwood Unit-1 - t-Location of Large Growths During Cycle 8 at TSP Elevations Combined Data from.All Steam Generators r a . .
q-r',,,C t i=
! .= -
i
!i N ,% !!.t !
i 9
a .
/ ! =i i=i '
. --- .i--- 1 i i
.! Mi$l Nj! Note: Elevationis mapped i
I :
l=
! ge-. el M.-
=
l'S jy,!l to sqpport plates as:
/- ; : . A;i {
fif* i
- g
.'- ,,; a i a=s ; a j i
- . - '._!j!
--:5! 1 = 03H Y
i r -- ! E!:: ,! 2 = 05H
= =! N iJ a=om
- ,/ ! f ! =-1
- == i
! !!!i;Il
$l! 4 = 08H
/ i = > 4 =9 i
! +'h!!!i 5=09H E::2 5;-
~
!" + i h,!!II i tE
- A c , _ _ " . I, k' i !! it:
p,a* gA 3 ,.
l 3 gg, j ia my {,fj ;
}i, i r,r w
jt q..,. "g , n l
,- ' ij o : - ==:: :
d i A i M;:8 : :
l m i!. 3; -
s'a i i, m a i
- mA :** : o . N.:: si9!
3 ;; . g
" i ,g ti- .i gu..--r--- -q.am-w *Ae.&.Aj'"a.3Qil! p.o .
$jl =
DVCY6>=2 and DVCY6<3
!~
i.
i i i.!:! =
DVCY6>=3 AND DVCY6<4 i _ .i . _ i i 1,i
- DVOY6>=4 AND DVCY6<5 j- !- i i i j! =
f-DVCY6>=5 AND DVCY6<6
! i i i i .
'i + DVCY8>=6 Plate outline l
g . . _ ..
L .. - - . . . . . ... . -
J 5 Figum 23 .
' t'
, Braidwood Unit-1 Distribution of EOC-8 Voltages as a Function ofIndicatioh Combined Data fron. All Steam Generah ;
, 1 e
10
- 4 1
+
t Ea ,
1 s %
. +
- f
_ e t i
E -
y %
- r. i :
. e -'
11 o + : .
S 4o -
e i ;
i ,
}
l o
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. s e u v G Td n = .
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- :2 Cs c
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