ML060540467
| ML060540467 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 02/22/2006 |
| From: | Pace P L Tennessee Valley Authority |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| TAC MC8118 | |
| Download: ML060540467 (19) | |
Text
February 22, 2006
U.S. Nuclear Regulatory Commission
ATTN: Document Control Desk
Washington, D.C. 20555
Gentlemen:
In the Matter of ) Docket No. 50-328 Tennessee Valley Authority )
SEQUOYAH NUCLEAR PLANT (SQN) - RESPONSE TO REQUEST FOR
ADDITIONAL INFORMATION REGARDING UNIT 2 STEAM GENERATOR (SG)
REPORTS FROM CYCLE 13 REFUELING OUTAGE (TAC NO. MC8118)
Reference:
NRC letter to TVA dated January 13, 2006, "Sequoyah Nuclear Plant, Unit 2 - Request for
Additional Information Regarding the 15-Day and
90-Day Steam Generator Tube Inservice Inspection
Reports for the End-of-Cycle 13 Refueling Outage
in 2005 (TAC No. MC8118)"
The enclosure to this letter provides additional information
requested by the referenced letter. The additional
information supports the basis for certain conclusions and
statements in the SQN Unit 2 SG reports and results from
detailed review of the SG tube inspection data from the SQN
Unit 2 Cycles 12 and 13 refueling outages.
Please direct questions concerning this issue to me at
(423) 843-7170 or J. D. Smith at (423) 843-6672.
Sincerely, Original signed by James D. Smith for:
P. L. Pace
Manager, Site Licensing and
Industry Affairs
Enclosure
cc: See page 2 U.S. Nuclear Regulatory Commission Page 2 February 22, 2006
cc (Enclosure):
Mr. Douglas V. Pickett, Senior Project Manager
U.S. Nuclear Regulatory Commission
Mail Stop O8G-9a
One White Flint North
11555 Rockville Pike
Rockville, Maryland 20852-2739 NRC Resident Inspector
Sequoyah Nuclear Plant
2600 Igou Ferry Road
Soddy-Daisy, Tennessee 37379-3624
Regional Administrator
U.S. Nuclear Regulatory Commission
Region II
61 Forsythe St., SW, Suite 23T85
Atlanta, Georgia 30303-3415
E1-1 ENCLOSURE TENNESSEE VALLEY AUTHORITY (TVA)
SEQUOYAH NUCLEAR PLANT (SQN)
UNIT 2 RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION REGARDING
STEAM GENERATOR REPORTS FROM CYCLE 13 REFUELING OUTAGE NRC Question 1 On Page 4-6 (of Westinghouse Report SG-SGDA-05-29, Rev.0), it was stated that only one indication was 2-volts or greater out of the
302 (sizing sample) indications at the end-of-cycle (EOC) 13 that
were tested with a worn probe during the EOC 12 inspection. With
this information, you concluded that probe wear has no
significant effect on the population of indications. In
addition, it was stated that out of 365 (population sample)
indications at the EOC 13 only 81 were inspected with a worn
probe during the EOC 12 inspection. You further concluded that
this information indicates that tubes inspected with worn probes
do not contain a larger number of new indications. The basis for
these statements is not clear to the staff, therefore, please
provide justification for these statements.
This justification should include a comparison of the percentage
of new indications at the EOC 13 that were inspected with a worn
probe during the EOC 12 inspection to the percentage of new
indications that were inspected with a good probe during the EOC
12 inspection. In addition, please compare the percentage of new
indications greater than or equal to 0.5-volts at the EOC 13 that
were inspected with a worn probe during the EOC 12 inspection to
the percentage of new indications greater than or equal to 0.5-
volts at EOC 13 that were inspected with a good probe during the
EOC 12 inspection. If there are significant differences, please
provide an assessment of the adequacy of the probe wear criteria
and its impact on your operational assessment for EOC 14. A
value of 0.5-volts was chosen to be consistent with the NRC
staff's approval of the alternate probe wear criterion (refer to
NRC letter to the Nuclear Energy Institute dated February 9, 1996). TVA Response.
In response to this question, the NDE data was reviewed in
detail. The study reported here includes all tubes in all
calibration groups that were reported out of calibration.
E1-2 The indication data reported in the EOC-13 90 Day Report (Westinghouse Report SG-SGDA-05-29, Rev.0) and the EOC-12 90 Day
Report (Westinghouse Report SG-SGDA-03-55, Rev.0), were compared
to identify the new indications. From the EOC-12 NDE data, all
tubes which were in calibration groups that were reported out of
calibration are identified by comparing the NDE data list with
the list of calibration groups that were reported out of
calibration. Then, both new and previously existing indications
can be identified as having been tested with a worn probe at EOC-
12 or not, and the total number of tubes which were tested with a
worn probe can also be determined. The results of this data
sorting procedure are given in the Tables below.
Sequoyah Unit 2 Tube Status Prior to 2005 Inspection (EOC 13)
SG Original Tubes Number plugged at EOC 13 Number of open tubes at EOC 13 1 3388 71 3317 2 3388 158 3230 3 3388 114 3274 4 3388 111 3277 Results of NDE Data Review Steam Generator 1 Number of new indications in EOC-13 56 Worn Probe in EOC-12 Number of new indications tested with worn probe in EOC-12 21 Number of these equal to or greater than 0.5 V in EOC-13 5 Number of tubes tested with worn probe 1578 Good Probe in EOC-12 Number of new indications tested with good probe in EOC-12 35 Number of these equal to or greater than 0.5 V in EOC-13 16 Number of tubes tested with good probe 1739 Ratio of new indications in tubes tested with worn probe to number of tubes tested with a worn probe 21/1578 = 0.0133 Ratio of new indications in tubes tested with good probe to number of tubes tested with a good probe 35/1739 = 0.0201 Percentage of new indications equal to or greater than 0.5 V in tubes tested with worn probe 5/21 = 24%
Percentage of new indications equal to or greater than 0.5 V in tubes tested with good probe 16/35 = 46%
Steam Generator 1 Number of previous indications in EOC-13 238 Worn Probe in EOC-12 Number of prev indications tested with worn probe in EOC-12 89 Number of these exceeding 2.0 V in EOC-13 0 Highest voltage indication of these in EOC-13 1.16 V E1-3 Steam Generator 2 Number of new indications in EOC-13 65 Worn Probe in EOC-12 Number of new indications tested with worn probe in EOC-12 16 Number of these equal to or greater than 0.5 V in EOC-13 5 Number of tubes tested with worn probe 1290 Good Probe in EOC-12 Number of new indications tested with good probe in EOC-12 49 Number of these equal to or greater than 0.5 V in EOC-13 14 Number of tubes tested with good probe 1940 Ratio of new indications in tubes tested with worn probe to number of tubes tested with a worn probe 16/1290 = 0.0124 Ratio of new indications in tubes tested with good probe to number of tubes tested with a good probe 49/1940 = 0.0253 Percentage of new indications equal to or greater than 0.5 V in tubes tested with worn probe 5/16 = 31%
Percentage of new indications equal to or greater than 0.5 V in tubes tested with good probe 14/49 = 29%
Steam Generator 2 Number of previous indications in EOC-13 240 Worn Probe in EOC-12 Number of prev indications tested with worn probe in EOC-12 90 Number of these exceeding 2.0 V in EOC-13 0 Highest voltage indication of these in EOC-13 1.97V
E1-4 Steam Generator 3 Number of new indications in EOC-13 119 Worn Probe in EOC-12 Number of new indications tested with worn probe in EOC-12 59 Number of these equal to or greater than 0.5 V in EOC-13 35 Number of tubes tested with worn probe 1583 Good Probe in EOC-12 Number of new indications tested with good probe in EOC-12 60 Number of these equal to or greater than 0.5 V in EOC-13 32 Number of tubes tested with good probe 1691 Ratio of new indications in tubes tested with worn probe to number of tubes tested with a worn probe 59/1583 = 0.0373 Ratio of new indications in tubes tested with good probe to number of tubes tested with a good probe 60/1691 = 0.0355 Percentage of new indications equal to or greater than 0.5 V in tubes tested with worn probe 35/59 = 59%
Percentage of new indications equal to or greater than 0.5 V in tubes tested with good probe 32/60 = 53%
Steam Generator 3 Number of previous indications in EOC-13 293 Worn Probe in EOC-12 Number of prev indications tested with worn probe in EOC-12 125 Number of these exceeding 2.0 V in EOC-13 1 Highest voltage indication of these in EOC-13 2.36V
E1-5 Steam Generator 4 Number of new indications in EOC-13 125 Worn Probe in EOC-12 Number of new indications tested with worn probe in EOC-12 81 Number of these equal to or greater than 0.5 V in EOC-13 31 Number of tubes tested with worn probe 1992 Good Probe in EOC-12 Number of new indications tested with good probe in EOC-12 44 Number of these equal to or greater than 0.5 V in EOC-13 16 Number of tubes tested with good probe 1285 Ratio of new indications in tubes tested with worn probe to number of tubes tested with a worn probe 81/1992 = 0.0407 Ratio of new indications in tubes tested with good probe to number of tubes tested with a good probe 44/1285 = 0.0342 Percentage of new indications equal to or greater than 0.5 V in tubes tested with worn probe 31/81 = 38%
Percentage of new indications equal to or greater than 0.5 V in tubes tested with good probe 16/44 = 36%
Steam Generator 4 Number of previous indications in EOC-13 711 Worn Probe in EOC-12 Number of prev indications tested with worn probe in EOC-12 428 Number of these exceeding 2.0 V in EOC-13 0 Highest voltage indication of these in EOC-13 1.74V
E1-6 All Steam Generators Combined Number of new indications in EOC-13 365 Worn Probe in EOC-12 Number of new indications tested with worn probe in EOC-12 177 Number of these equal to or greater than 0.5 V in EOC-13 76 Number of tubes tested with worn probe 6443 Good Probe in EOC-12 Number of new indications tested with good probe in EOC-12 188 Number of these equal to or greater than 0.5 V in EOC-13 78 Number of tubes tested with good probe 6655 Ratio of new indications in tubes tested with worn probe to number of tubes tested with a worn probe 177/6443 = 0.0275 Ratio of new indications in tubes tested with good probe to number of tubes tested with a good probe 188/6655 = 0.0282 Percentage of new indications equal to or greater than 0.5 V in tubes tested with worn probe 76/177 = 42.9%
Percentage of new indications equal to or greater than 0.5 V in tubes tested with good probe 78/188 = 41.5%
All Steam Generators Combined Number of previous indications in EOC-13 1482 Worn Probe in EOC-12 Number of prev indications tested with worn probe in EOC-12 732 Number of these exceeding 2.0 V in EOC-13 1 Highest voltage indication of these in EOC-13 2.36V The indications found in the current inspection that were tested with a worn probe in the previous (EOC-12) inspection were
identified as seen in the tables above. Of the 732 indications
found in the current inspection that were tested with a worn
probe in the previous inspection, only one was 2 volts or
greater. Of the 750 indications found in the current inspection
that were tested with a good probe in the previous inspection, two were 2 volts or greater. Therefore, there is no significant
difference in the number of repairable indications for tubes
previously tested with a worn probe.
As required by the NRC letter to the Nuclear Energy Institute
dated February 9, 1996, the number of new indications detected in
the present inspection in tubes that were inspected with a worn
probe in the last inspection was also determined. Out of a total
of 365 new indications reported in the current inspection, 177 E1-7 were in tubes inspected with a worn probe during the last inspection. Steam Generator 4 has the highest number of
indications and the highest ratio of new indications that were
identified in tubes tested with a worn probe in EOC-12 to the
number of tubes tested with a worn probe in EOC-12 of 0.0407.
The ratio of new indications that were identified in tubes tested
with a good probe in EOC-12 to the number of tubes tested with a
good probe in EOC-12 for Steam Generator 4 is 0.0342. The
percentage of new indications equal to or greater than 0.5 V in
tubes tested with a worn probe in SG 4 is 38%, and the percentage
of new indications equal to or greater than 0.5 V in tubes tested
with good probe in SG 4 is 36%. The similarity of these ratios
and percentages indicate that there is no significant difference
in the rate of occurrence or magnitude of new indications found
in the EOC-13 inspection due to testing with a worn probe in the
EOC-12 inspection. Thus, the requirements specified for applying
the alternate probe wear criteria are met.
NRC Question 2 In Section 6.4 of Enclosure 1 to your August 15, 2005, letter, it was indicated that the EOC 14 voltage distribution (using both
the Cycle 12 and Cycle 13 growth rates) are shown in Table 6-2
and in Figures 6-1 through Figure 6-4. In reviewing the table
and figures only one voltage distribution was provided for each
Please clarify whether the tables and graphs provided were
determined using the Cycle 12 or Cycle 13 voltage growth rate
distribution.
In addition, Section 6.4 indicates that the voltage distributions
predicted using both growth rates are similar, however, the
predictions using the Cycle 13 growth rates were populated with
somewhat greater frequency in the lower voltages and with higher
tail-end voltages. Since the most limiting voltage growth rate
distribution is the one that results in the highest projected
probability of burst and leakage, discuss how it was determined
that the Cycle 12 growth rate distribution was the most limiting.
The staff notes that sometimes the higher tail end voltages can
result in more limiting probability of burst or leakage estimates (i.e., the largest voltage indication may have a significant
effect on the leakage and burst calculations depending on the
distribution of indications).
TVA Response The Cycle 12 growth rate clearly has a longer upper tail due to the inclusion of the one large voltage indication found at EOC-
- 12. Only the results using the Cycle 12 growth rate were included
in the EOC-13 90 Day Report (Westinghouse Report SG-SGDA-05-29, Rev.0) since this did produce the more conservative results.
The Table 6-2 and Figures 6-1 to 6-4 and Table 6-3 all are
results using the Cycle 12 growth rate.
E1-8 The reference to using both growth rates is an editorial error.
The statement "voltage distributions predicted using both growth
rates are similar, however, the predictions using the Cycle 13
growth rates were populated with somewhat greater frequency in
the lower voltages and with higher tail-end voltages" is also an
editorial error.
In order to demonstrate that the Cycle 12 growth rate results in the more conservative predictions the predictive results of using
both the Cycle 12 and Cycle 13 growth rates are presented here.
The analyses clearly indicate that the Cycle 12 growth rate
results are more conservative. Therefore, the results in the
report are correct.
E1-9 Operational Assessment: Tube Leak Rate and Burst Probabilities at EOC-14 1. Analysis Approach The BOC-14 voltage distributions are developed, within the Cyclesim3.1 program, from the measured EOC-13 distribution by
considering the probability of detection (POD) and the indications
that are removed from service. The EOC-14 voltage distribution is
developed considering the NDE uncertainties and voltage growth
during the cycle. Both the bounding Cycle 12 growth rate and the
bounding Cycle 13 growth rate were used in these projections in
order to assure the more conservative results. The latest burst
and leakage correlations, are used for the EOC-14 predictions. The
burst probabilities and leak rates are computed using the computed
EOC-14 voltage predictions to address the acceptance criteria at
the end of the cycle.
The beginning of Cycle 14 (BOC-14) voltage distributions are
shown in Table 1.
Table 1: BOC-14 Voltage Distributions Volts SG 1 SG 2 SG 3 SG 4 0.1 0 0 0 0 0.2 13.33 21.67 15 33.33 0.3 68.33 53.33 59 137.33 0.4 83.33 89 68.33 212.33 0.5 70 95.67 97.33 224 0.6 60 51.67 76.67 193.33 0.7 59 61.67 91.67 158.33 0.8 45 49 72.33 119 0.9 35 25.67 40 110 1 18.33 19 38.33 72.33 1.1 16.67 10.67 31.67 43.33 1.2 11.67 8.33 28.33 30 1.3 3.33 10 21.67 18.33 1.4 0 1.67 13.33 11.67 1.5 1.67 0 10 8.33 1.6 0 3.33 7.33 8.33 1.7 1.67 0 1.67 7.33 1.8 0 0 5 0 1.9 0 0 0 0 2 1.67 0.67 0 0 2.1 0 0 1.33 0 2.2 0 0 0 0 2.3 0 0 0 0 2.4 0 0 0.67 0 2.5 0 0 0 0 Total 489 501.3 679.7 1387.3 E1-10 3. Voltage Growth Rates for Cycle 14 The Cycle 12 and Cycle 13 bounding voltage growth rates, shown in Figure 3-15 and Figure 3-16 of EOC-13 90 Day Report (Westinghouse
Report SG-SGDA-05-29, Rev.0), indicate that the Cycle 12 growth
rate is the more conservative. To assure the more conservative
results, both growth rates were used in these projections.
- 4. Prediction of Voltage Distributions at EOC-14 The prediction of the EOC-14 voltage distributions is based on the BOC-14 indications and the composite growth rate. The length
of Cycle 14 is established at 545 effective full power days (EFPD). The EOC-14 predicted voltage distributions (using both
the Cycle 12 and Cycle 13 growth rates) are shown in Table 2 and
in Figure 1 through Figure 4. The voltage distributions
predicted using both growth rates are similar, with the
predictions using the Cycle 13 growth rates populated with
somewhat greater frequency in the lower voltages and with higher
tail-end voltages as seen in Table 2.
Table 2 EOC -14 Voltage Distributions Cycle 12 Growth Rate Cycle 13 Growth Rate EOC-14 Voltage Distributions EOC-14 Voltage Distributions Volts SG1 SG2 SG3 SG4 SG1 SG2 SG3 SG4 0.1 0.17 0.28 0.19 0.43 0.17 0.27 0.18 0.41 0.2 4.79 6.29 4.92 11.11 4.62 6.07 4.75 10.71 0.3 19.98 19.06 17.92 43.4 19.04 18.03 17.02 41.3 0.4 37.39 37.83 34.19 88.81 34.67 35.21 31.73 82.73 0.5 51.95 55.37 52.3 134.58 47.96 51.52 48.7 124.85 0.6 59.57 63.96 66.57 163.78 56.74 60.4 63.05 154.57 0.7 59.13 63.33 72.95 168.95 58.31 62.11 70.58 164.27 0.8 55.24 57.8 73.45 158.74 55.8 58.5 72.57 159.08 0.9 48.52 49.26 67.56 140.03 49.53 50.83 67.84 143.2 1 40.03 39.34 58.17 117.28 41.68 41.31 59.91 121.97 1.1 31.33 29.77 48.53 93.56 33.72 32.27 51.05 99.54 1.2 23.37 21.72 39.88 71.2 25.92 24.59 42.73 77.96 1.3 16.71 15.58 32.53 52.24 19.02 17.94 35.06 58.9 1.4 11.59 11.16 26.18 37.78 13.44 12.88 28.41 43.27 1.5 7.91 8.02 20.73 27.46 9.1 9.15 22.54 31.14 1.6 5.23 5.7 15.94 19.99 5.98 6.29 17.34 22.16 1.7 3.5 4.02 12.08 14.53 3.85 4.23 13 15.61 1.8 2.53 2.85 9 10.64 2.53 2.86 9.54 10.91 1.9 1.88 2.12 6.56 7.7 1.81 1.99 6.92 7.71 2 1.4 1.5 4.69 5.45 1.38 1.46 4.96 5.51 2.1 1.07 1.06 3.31 3.8 1.04 1.09 3.54 3.87 2.2 0.95 0.83 2.45 2.79 0.77 0.75 2.5 2.63 2.3 0.83 0.73 1.82 2.2 0.59 0.52 1.77 1.75 2.4 0.65 0.61 1.39 1.73 0.33 0.06 1.24 1.15 2.5 0.48 0.44 1.06 1.3 0 0.7 0.84 0.77 2.6 0.36 0.32 0.83 0.96 0.7 0 0.58 0.33 E1-11 Table 2 EOC -14 Voltage Distributions Cycle 12 Growth Rate Cycle 13 Growth Rate EOC-14 Voltage Distributions EOC-14 Voltage Distributions Volts SG1 SG2 SG3 SG4 SG1 SG2 SG3 SG4 2.7 0.27 0.24 0.63 0.7 0 0.3 0.31 0 2.8 0.19 0.17 0.45 0.52 0.3 0 0 0.7 2.9 0.13 0.11 0.32 0.37 0 0 0.7 0 3 0.08 0.07 0.24 0.25 0 0 0 0.3 3.1 0.06 0.05 0.17 0.17 0 0 0.3 0 3.2 0.03 0.03 0.13 0.11 0 0 0 0 3.3 0.02 0.02 0.09 0.07 489 501.35 679.66 1387.3 3.4 0.01 0.01 0.06 0.05 3.5 0.01 0.01 0.04 0.03 3.6 0 0.01 0.03 0.02 3.7 0 0 0.02 0.01 3.8 0 0 0.01 0.01 3.9 0 0 0.01 0 4 0 0 0 0 4.1 0 0 0 0 4.2 0 0 0 0 4.3 0 0 0 0 4.4 0 0 0 0 4.5 0 0 0 0 4.6 0 0 0 0 4.7 0 0 0 0 4.8 0 0 0 0 4.9 0 0 0 0 5 0 0 0 0 5.1 0 0 0 0 5.2 0 0 0 0 5.3 0 0 0 0 5.4 0 0 0 0 5.5 0 0 0 0 5.6 0 0 0 0 5.7 0 0 0 0 5.8 0 0 0 0 5.9 0 0 0 0 6 0 0 0 0 6.1 0 0 0 0 6.2 0 0 0 0 6.3 0 0 0 0 6.4 0 0 0 0 6.5 0 0 0 0 6.6 0 0 0 0 6.7 0 0 0 0 6.8 0 0 0 0 6.9 0 0 0 0 7 0 0 0 0 7.1 0 0 0 0 7.2 0 0 0 0 7.3 0 0 0 0 7.4 0 0 0 0 7.5 0 0 0 0 E1-12 Table 2 EOC -14 Voltage Distributions Cycle 12 Growth Rate Cycle 13 Growth Rate EOC-14 Voltage Distributions EOC-14 Voltage Distributions Volts SG1 SG2 SG3 SG4 SG1 SG2 SG3 SG4 7.6 0 0 0 0 7.7 0 0 0 0 7.8 0 0 0 0 7.9 0 0 0 0 8 0 0 0 0 8.1 0 0 0 0 8.2 0 0 0 0 8.3 0 0 0 0 8.4 0 0 0 0 8.5 0 0 0 0 8.6 0 0 0 0 8.7 0.05 0.07 0.06 0.13 8.8 0.21 0.18 0.18 0.44 8.9 0.26 0.28 0.24 0.67 9 0.09 0.13 0.29 0.71 9.1 0 0 0.28 0.63 9.2 0.7 0.7 0.2 0.52 9.3 0 0 0 0.41 9.4 0 0 0 0.07 9.5 0.3 0.3 0.7 0 9.6 0 0 0 0.7 9.7 0 0 0 0 9.8 0 0 0.3 0.3 9.9 0 0 0 0 489.00 501.35 679.66 1387.30 E1-13 0 10 20 30 40 50 60 70 800.10.30.50.70.91.11.31.51.71.9 2.12.32.52.72.93.13.33.53.73.98.78.99.19.39.59.79.9VoltsNumber of Indications .Using Cycle 12 Growth RateUsing Cycle 13 Growth Rate Figure 1: Predicted EOC-14 Voltage Distribution, SG1
E1-14 0 10 20 30 40 50 60 70 800.10.30.50.7 0.91.11.3 1.51.7 1.9 2.1 2.3 2.5 2.7 2.9 3.1 3.3 3.5 3.7 3.9 8.7 8.9 9.1 9.3 9.5 9.7 9.9VoltsNumber of Indications Using Cycle 12 Growth RateUsing Cycle 13 Growth Rate Figure 2: Predicted EOC-14 Voltage Distribution, SG2 E1-15 0 10 20 30 40 50 60 70 800.10.30.50.70.91.11.31.51.7 1.9 2.1 2.3 2.5 2.7 2.9 3.1 3.3 3.5 3.7 3.9 8.7 8.9 9.1 9.3 9.5 9.7 9.9VoltsNumber of Indications Using Cycle 12 Growth RateUsing Cycle 13 Growth Rate Figure 3: Predicted EOC-14 Vo ltage Distribution, SG 3 E1-16 0 20 40 60 80100 120140160180 0.1 0.30.50.70.9 1.1 1.31.51.7 1.92.12.3 2.52.72.9 3.1 3.3 3.5 3.7 3.9 8.7 8.9 9.1 9.3 9.5 9.7 9.9VoltsNumber of Indications Using Cycle 12 Growth RateUsing Cycle 13 Growth Rate Figure 4: Predicted EOC-14 Vo ltage Distribution, SG 4 E1-17 5. Prediction of Tube Leak Rates and Burst Probabilities at EOC-14 The Monte Carlo analysis results for predicted EOC-14 voltage distributions are shown in Tables 3A and 3B. One-quarter-million
Monte Carlo trials were performed for each steam generator in
this operational assessment. The leakage rate is the 95 th percentile evaluated at 95% confidence. The burst probability is
95% confidence based on the number of trials.
The predictions using the Cycle 12 growth rate distribution, Table 3A, results in significantly larger values for both the
burst probability and the bounding leak rate as would be expected
due to the longer tail of the voltage growth curve.
Table 3A: EOC-14 Predicted Results Using Cycle 12 Growth Rate SG Number of Monte Carlo
Trials Number of Indications Maximum Volts* Burst Probability 95% Confidence 95/95 SLB Leak Rate (gpm) 1 250,000 489.0 9.5 2.20 X 10
-3 0.519 2 250,000 501.3 9.5 2.47 X 10
-3 0.530 3 250,000 679.7 9.8 3.41 X 10
-3 0.874 4 250,000 1387.3 9.8 6.51 X 10
-3 1.47
- Voltage where tail is accumulated to 0.3 indications Table 3B: EOC-14 Predicted Results Using Cycle 13 Growth Rate SG Number of Monte Carlo
Trials Number of Indications Maximum Volts* Burst Probability 95% Confidence 95/95 SLB Leak Rate (gpm) 1 250,000 489.0 2.8 6.79 X 10
-5 0.184 2 250,000 501.3 2.7 9.24 X 10
-5 0.182 3 250,000 679.7 3.1 1.90 X 10
-4 0.413 4 250,000 1387.3 3.0 1.86 X 10
-4 0.628
- Voltage where tail is accumulated to 0.3 indications
- 6. Comparison with Acceptance Criteria All steam generators are below the burst acceptance criterion of 1.0 x 10-2 , and the Sequoyah Unit 2 leakage criterion of 3.7 gpm.