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
Morgan, Lewis & Bockius LLP 1111 Pennsylvania Avenue, NW Washington, DC 20004 Tel. 202.739.3000 Fax: 202.739.3001 www.morganlewis.com Stephen J. Burdick 202.739.5059 sburdick@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
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 DB1/ 73025731.1
BOARD NOTIFICATION ENCLOSURE 1
BOARD NOTIFICATION ENCLOSURE 2
BOARD NOTIFICATION ENCLOSURE 3
BOARD NOTIFICATION ENCLOSURE 4
Reference 3, Figure 6-2: Zones Used to Develop Characteristic Distributions of Contact Forces for Each AVB in the Zone Page 6 of 12
BOARD NOTIFICATION ENCLOSURE 5
ENCLOSURE 1 Notarized Affidavit
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 1
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 2
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 3
Unit 2, SG 89, PSI 150 140 130 120 110 Larger Symbol Size is 0.5 to 1.5 Larger Voltage volts 100 90 80 Row 70 60 50 40 30 20 10 0
0 20 40 60 80 100 120 140 160 180 Column Figure 1. Tubesheet Map of Dings => 0.5 volts, SG 2E-089, PSI Inspection Page 4
Unit 3, SG 89, PSI 150 140 130 120 Larger Symbol Size is Larger Voltage 110 100 90 0.5 to 1.5 volts 80 Row 70 60 50 40 30 20 10 0
0 20 40 60 80 100 120 140 160 180 Column Figure 2. Tubesheet Map of Dings => 0.5 volts, SG 3E-089, PSI Inspection Page 5
Figure 3. Arrangement of Tube Supports Page 6
Page 7 Page 8 Ding Voltage SG 2-89 PSI Inspection 2.5 2
1.5 Ding Voltage, volts 1 0.5 0
0 20 40 60 80 100 120 140 Row Number Figure 6. Ding Voltage => 0.5 volts versus Row Number, SG 2E-089, PSI Inspection Page 9
Ding Voltage SG 3-89 PSI Inspection 2.5 2
1.5 1
Ding Voltage, volts 0.5 0
0 20 40 60 80 100 120 140 Row Number Figure 7. Ding Voltage => 0.5 volts versus Row Number, SG 3E-089, PSI Inspection Page 10
Page 11 Page 12 Page 13 Page 14 BOARD NOTIFICATION ENCLOSURE 6
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)
Page 1
RAI 29
Reference 5, Figurres 2-12 and d 2 Prrovide simillar figures ffor Case 78 8 (all AVBs missing)).
RESPONSE
Note: Re eference 5 is the Westinghouse Operationa O l Assessme ent, SG-SG GMP-12-10,,
Revision n 3. Figures 2-12 and 2-13 of this s report resspectively ccontain the out-of-plan ne excitatioon ratio and d in-plane sttability ratio o maps for C Case 60 (seven ineffe ective AVB supports s) at 70% power.
p The requ uested out--of-plane ex xcitation rattio and in-pplane stabiliity ratio maps for Westing ghouse Cas se 78 at 70% % power arre attached , representting the extrreme condition where all twelve an nti-vibration bar (AVB) supports a are ineffective. No Unit 2 steam generato or tubes ha ave this suppport condition; hence,, there are no tubes w with excitatioon or stability ratios as inndicated in these t figure es. A comp parison of in-plane sta ability ratioss calculate ed by Westtinghouse and a MHI shows that W Westinghousse in-plane stability rattios are highher for the hypothetica h l support coondition reppresented b by Case 78. Howeverr, over thee range of actual a AVB support con nditions preesent in Un nit 2 steam g generators, in-plane stability ratios calcula ated by Wes stinghouse agree with h those calcculated by M MHI.
No Tube es in Unit 2 Have Tw welve Ineffe ective AVB B Supports Westing ghouse dete ermined tha at there are no tubes in n the Unit 2 steam gen nerators with twelve inneffective AVB A supporrts from theeir review off the eddy ccurrent data a for SG 2E-0 088 and SG G 2E-089. TheT review included a approximate ely 600 tube es in SG 2E-0 088 and approximately y 800 tubes s in SG 2E--089 with in ndications oof tube-to-A AVB wear. Westinghou W se used the e eddy currrent data to o identify ap ppropriate AAVB supporrt cases fo or use in the eir flow-indu uced vibration (FIV) an nalysis. De efining inefffective AVB B support locations as a locations s with AVB wear, w Westtinghouse d determined the FIV analysis s case appliicable to ea ach tube ac ccording to tthe number of conseccutive ineffectivve AVB sup pport locatioons.
The Westinghouse finding tha at there are no tubes in n Unit 2 ste eam genera ators with twelve inneffective AVB A supporrts was inde ependently corroboratted by ARE EVAs analyysis of proba ability of instability. Fo or this analy ysis, AREVA A performe ed Monte Carlo simulatio ons of Unit 2 steam ge enerators considering the variability of AVB support effectiveeness at ind dividual tube-to-AVB in ntersectionss in the steam generator. AREVA A determin ned AVB su upport effec ctiveness frrom probab bilistic distrib butions of ttube-to-AVB B Paage 2
contact forces f acco ounting for tube-to-AVB wear. Th he Monte CCarlo simula ations typically included d 10,000 triaals. Each trial t individu ually modeled all tubess susceptib ble to in-plane fluid-elastic instabillity at 100%
% power (the e model inccluded approximately 1/5 of the bundle) and probab bilistically sampled s the e number off effective AAVB suppo orts at a giveen operatinng time. To o envelop co onditions foor the next UUnit 2 operrating intervval, separatte Monte Carlo C simula ations were e performed d at the begginning of cyycle and att 6 months a after the beginning of cy ycle. AREV VA has revie ewed these e simulationns and dete ermined tha at there we ere no instaances of a tube t with tw welve ineffeective AVB ssupports in n any of the 20,000 trials t contaiined in thesse two simu ulations. AR REVAs ressults demon nstrate thatt there is no significaant likelihoood of Unit 2 steam gen nerators havving any tubes with the extreme e AVB support conditio on represen nted by Casse 78 at anyy time durin ng the next operatinng interval.
Comparrison betw ween Westinghouse and a MHI In-Plane Sta ability Ratio o Results Westing ghouse com mpared the input param meters and methodolo ogy of their in-plane FIV V analysiss to the corrresponding elements of o MHIs FIV V. Differen nces betwee en the meth hods include:
- 1) Differences D in thermal-hydraulic calculation m methods: W Westinghou use uses proprietary ATHOS A pre e-processorrs and post--processorss. MHI use es the EPRI-standa E ard version of ATHOS.
- 2) Differences D in Connors s coefficient:
- 3) Differences D on of effecttive velocityy: Westinghouses approach in calculatio conservative ely maximiz zes the ene ergy added to the tube e by conside ering the re esultant vellocity norma al to the tubbe axis while minimizing the enerrgy re emoved by considering the veloc city compon direction of tube nent in the d displacemen nt. MHIs method m culates ene rgy added tto the tube using calc th he compone ent velocityy in the direection of tub be displacement and considers en nergy remo oved both axial and no ormal to the e tube axis o over the fu ull length off the tube.
- 4) Differences D in damping g ratio:
Paage 3
Figure 1 shows the e overall efffect of thesee difference es in input pparameterss and methodo ology by co omparing 10 00% powerr in-plane sttability ratio os calculate ed by MHI a and Westingghouse for nine n representative tub be locationss, considerring the num mber of ineffectiv ve AVB sup pports to bee the study parameter . With fewe er than ten ineffective AVB sup pports, the two method ds show rea asonable a agreement, both in the e values of in-plane stability ratio and in thhe rate of change c in in n-plane stab bility ratio w with increassing number of ineffectiv ve AVB sup pports. MH HI results arre consisten ntly conservvative compare ed to Westinghouse re esults in thiss range. H However, for twelve ine effective AV VB supportss, Westingh house in-pla ane stabilityy ratios for tubes abovve Row 100 0 are higherr than MHHI in-plane stability s ratiios.
Figure 2 compares MHI and Westinghou W use in-plane e stability ra atios at 70% % power. W With fewer than eight ine effective AVVB supports s, the two m methods co ontinue to a agree. The same div vergence ata higher nu umbers of in neffective A AVB supporrts observed at 100%
power iss also preseent at 70% power, affe ecting the in n-plane stability ratios with greate er than eight ineffectivve AVB sup pports.
Paage 4
Pa age 5
The folloowing table compares the Westin nghouse an nd MHI in-plane stabilitty ratios forr the
[ ] tu ubes in Unitt 2 with this support coondition. Th he MHI in-p plane stability ratios foor these su upport condditions are higher h than the Westin nghouse in--plane stab bility ratios.
Figures 1 and 2 demonstrate that in-plan ne stability rratios for alll remaining g Unit 2 tubes, which ha ave fewer than eight in neffective AVB A supporrts, follow a similar patttern.
Over the e range of actual a AVB support co onditions pre esent in Un nit 2 steam generatorss, in-plane stability ratios calculaated by Wes stinghouse agree with h those calcculated by M MHI.
Number of o Tube T Ineffective In- plane Stability Ratio a at 70% Pow wer Location SG AVB A Suppo orts Weestinghouse e MHI Paage 6
Pa age 7
Pa age 8