ML13043A178
| ML13043A178 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 02/08/2013 |
| From: | Burdick S Morgan, Morgan, Lewis & Bockius, LLP, Southern California Edison Co |
| To: | Gary Arnold, Anthony Baratta, Hawkens E Atomic Safety and Licensing Board Panel |
| SECY RAS | |
| References | |
| RAS 24111, 50-361-CAL, 50-362-CAL, ASLBP 13-924-01-CAL-BD01 | |
| Download: ML13043A178 (85) | |
Text
Stephen J. Burdick 202.739.5059 sburdick@morganlewis.com Morgan, Lewis & Bockius LLP 1111 Pennsylvania Avenue, NW Washington, DC 20004 Tel. 202.739.3000 Fax: 202.739.3001 www.morganlewis.com February 8, 2013 E. Roy Hawkens, Chair Dr. Anthony J. Baratta Dr. Gary S. Arnold Atomic Safety and Licensing Board U.S. Nuclear Regulatory Commission Washington, DC 20555-0001 Docket:
Southern California Edison Company, San Onofre Nuclear Generating Station, Units 2 and 3, Docket Nos. 50-361-CAL & 50-362-CAL Re:
Second Notification of Responses to RAIs
Dear Licensing Board Members:
On December 26, 2012, the Nuclear Regulatory Commission (NRC) issued Requests for Additional Information (RAIs) to Southern California Edison Company (SCE) regarding SCEs October 3, 2012 response to the March 27, 2012 Confirmatory Action Letter for San Onofre Nuclear Generating Station Units 2 and 3.
The purpose of this letter is to provide notification to the Licensing Board of additional SCE responses to these RAIs. The enclosed letters provide SCEs responses to RAIs 6, 8, 14, 20, 21, 22, 23, 24, 25, 26, 29, and 31. SCE submitted proprietary and non-proprietary versions of the responses to the NRC in the letters for RAIs 20, 21, 22, 23, 24, 25, 26, 29, and 31. Only the non-proprietary versions are enclosed. Please let us know if you would like us to send the Licensing Board copies of the proprietary versions pursuant to the Protective Order.
Atomic Safety and Licensing Board February 8, 2013 Page 2 Respectfully submitted, Signed (electronically) by Stephen J. Burdick Stephen J. Burdick Counsel for Southern California Edison Company Enclosures
DB1/ 73025731.1 UNITED STATES OF AMERICA NUCLEAR REGULATORY COMMISSION BEFORE THE ATOMIC SAFETY AND LICENSING BOARD
)
In the Matter of
)
) Docket Nos. 50-361-CAL & 50-362-CAL SOUTHERN CALIFORNIA EDISON COMPANY )
)
(San Onofre Nuclear Generating Station,
) February 8, 2013 Units 2 and 3)
)
)
CERTIFICATE OF SERVICE I hereby certify that, on this date, a copy of the Second Notification of Responses to RAIs was filed through the E-Filing system.
Signed (electronically) by Stephen J. Burdick Stephen J. Burdick Morgan, Lewis & Bockius LLP 1111 Pennsylvania Avenue, N.W.
Washington, D.C. 20004 Phone: 202-739-5059 Fax: 202-739-3001 E-mail: sburdick@morganlewis.com Counsel for Southern California Edison Company
BOARD NOTIFICATION ENCLOSURE 1
BOARD NOTIFICATION ENCLOSURE 2
BOARD NOTIFICATION ENCLOSURE 3
BOARD NOTIFICATION ENCLOSURE 4
Page 6 of 12 Reference 3, Figure 6-2: Zones Used to Develop Characteristic Distributions of Contact Forces for Each AVB in the Zone
BOARD NOTIFICATION ENCLOSURE 5
ENCLOSURE 1 Notarized Affidavit
Page 1 ENCLOSURE 3 SOUTHERN CALIFORNIA EDISON RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION REGARDING RESPONSE TO CONFIRMATORY ACTION LETTER DOCKET NO. 50-361 TAC NO. ME 9727 Response to RAI 25 (NON-PROPRIETARY)
Page 2
RAI 25
Reference 3, page 59 of 129 -There is a statement in the last paragraph that reads, "Patterns of dents and associated high contact forces are in good agreement with the final quarter model calculations." Provide or show this comparison.
RESPONSE
Note: RAI Reference 3 is the SONGS U2C17 Steam Generator Operational Assessment for Tube-to-Tube Wear, AREVA Document No. 51-9187230-000, Revision 0, October 2012.
The evidence supporting the statement in RAI Reference 3 that Patterns of dents and associated high contact forces are in good agreement with final quarter model calculations is provided below.
Classic dents/dings at Anti Vibration Bar (AVB) to tube intersections were observed in both Pre-Service Inspection (PSI) and In-Service Inspection (ISI) surveys of the steam generators at SONGS. The ding data from the PSI inspections was used by MHI to guide and benchmark finite element analysis (FEA) calculations of contact forces. Laboratory experiments provided plots of ding voltage versus load for an AVB in contact with a tube. Ding voltage was obtained under load and then again after a load was applied and released. Under a load of [ ] a ding voltage of 0.5 volts is observed. This value increases to about 2.2 volts for a load of [ ].
Figures 1 and 2 (corresponding to Figure 6-19 and 6-20 in RAI Reference 3) show tubesheet maps of dings equal to or greater than 0.5 volts at the PSI inspections of SG 2E-089 and SG 3E-089 respectively. These dings are associated with contact forces of [ ] and higher.
There are more dings in SG 2E-089 compared to SG 3E-089 by a factor of about 13. Figures 1 and 2 show that dings occur primarily in rows. These rows correspond to the noses of AVB pairs. See Figure 3 which is the same as Figure 3-1 of RAI Reference 3. There are sporadic dings in high rows near the periphery. The row pattern is much more distinct in SG 2E-089 simply because there are many more dings in SG 2E-089.
Figures 4 and 5 plot tube sheet maps of calculated contact forces equal to or greater than [ ]
in the cold condition corresponding to the PSI results. A comparison of Figures 1 and 2 with Figures 4 and 5 shows that observed ding locations compare very well with FEA calculations of where dings should be observed.
Since ding voltage is correlated with contact force it is instructive to plot ding voltage versus row number and compare these plots with plots of calculated contact force versus row number.
Figures 6 and 7 show plots of ding voltage versus row number and Figures 8 and 9 show plots of calculated contact force versus row number. Ding voltages are equal to or greater than 0.5 volts and therefore calculated forces are equal to or greater than [ ]. The comparison between Figure 6 and Figure 8 for SG 2E-089 is excellent. Not only do the peak locations coincide but the relative numbers of points at various peak locations are in agreement.
Furthermore the peak heights are in agreement. Consider the largest peak near row 30, the maximum ding voltage is about 2.2 volts which agrees with a maximum contact force of about
[ ].
Since there are relatively few dings in SG 3E-089 a few spurious dings near row 42 in Figure 7 distorts the peak comparison to some degree. However the calculated contact forces in Figure 9 match the observation of numerous dings near row 30 and agree with SG 2E-089
Page 3 calculations in terms of the region near row 30 being a dominant region of high contact forces.
Perhaps more importantly ding voltages near row 30 lead to an expectation of a relatively small spread of contact forces compared to SG 2E-089. This expectation is met. Near row 30 the maximum calculated contact force is about [ ] which agrees with a maximum observed ding voltage of about 0.8 volts.
Figures 10 and 11 provide a comparison of histograms of numbers of dings and numbers of calculated high contact force locations. Row numbers are binned with a bin width of 6 rows.
The percentage of total data points is plotted versus mid bin row number. Figure 10 shows an excellent match of relative number of dings and calculated high contact forces versus row number for SG 2E-089. Figure 11 shows a good match for SG 3E-089 but is influenced to some degree by the relatively low number of dings and the presence of some spurious dings.
The statement that Patterns of dents and associated high contact forces are in good agreement with final quarter model calculations, is well supported.
While classic dents/dings observed in the PSI inspections was used by MHI to guide and benchmark FEA calculations of contact forces a further check of the reasonableness of the FEA results is provided by the non-classical contact signals described in RAI Reference 3. Three dimensional plots of these contact signals are provided in Figures 6-22 through 6-25 of RAI Reference 3. Most of these contact signals are low amplitude signals extending down to a threshold of 0.25 volts. This has the advantage of reflecting lower contact forces than the larger amplitude classic dent/ding signals. Hence contact forces throughout the bundle are reflected.
The patterns of contact signals are consistent with expected regions of higher stiffness in the bundle such as AVB noses and support structures in the periphery.
The substantial difference between contact forces in Units 2 and 3 is demonstrated by the relatively high amplitude classic dent/ding signals. This substantial difference is also reflected by the more numerous, lower amplitude contact signals. Table 1 lists the numbers of contact signals at ISI inspections.
Table 1 Contact Signal Threshold 0.25 Volts Steam Generator Number of Contact Signals Unit 2, SG 88 5602 Unit 2, SG 89 6316 Unit 3, SG 88 2284 Unit 3, SG 89 1814 Contact force calculations are appropriately reliable to demonstrate maintenance of adequate margins relative to the onset in plane fluid-elastic instability at 70% power. The key point is the capture of the essential features of the patterns and magnitudes of contact forces and gaps such that the observed instability behavior of Units 2 and 3 can be benchmarked and extended to provide a reliable evaluation of the margins present at 70% power. This has been accomplished.
Page 4 Figure 1. Tubesheet Map of Dings => 0.5 volts, SG 2E-089, PSI Inspection 0
10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 0
20 40 60 80 100 120 140 160 180 Row Column Unit 2, SG 89, PSI 0.5 to 1.5 volts Larger Symbol Size is Larger Voltage
Page 5 Figure 2. Tubesheet Map of Dings => 0.5 volts, SG 3E-089, PSI Inspection 0
10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 0
20 40 60 80 100 120 140 160 180 Row Column Unit 3, SG 89, PSI 0.5 to 1.5 volts Larger Symbol Size is Larger Voltage
Page 6 Figure 3. Arrangement of Tube Supports
Page 7
Page 8
Page 9 Figure 6. Ding Voltage => 0.5 volts versus Row Number, SG 2E-089, PSI Inspection Ding Voltage SG 2-89 PSI Inspection 0
0.5 1
1.5 2
2.5 0
20 40 60 80 100 120 140 Row Number Ding Voltage, volts
Page 10 Figure 7. Ding Voltage => 0.5 volts versus Row Number, SG 3E-089, PSI Inspection Ding Voltage SG 3-89 PSI Inspection 0
0.5 1
1.5 2
2.5 0
20 40 60 80 100 120 140 Row Number Ding Voltage, volts
Page 11
Page 12
Page 13
Page 14
BOARD NOTIFICATION ENCLOSURE 6
Page 1 ENCLOSURE 3 SOUTHERN CALIFORNIA EDISON RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION REGARDING RESPONSE TO CONFIRMATORY ACTION LETTER DOCKET NO. 50-361 TAC NO. ME 9727 Response to RAI 29 (NON-PROPRIETARY)
RAI 29
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