Letter Sequence Draft RAI |
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Initiation
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MONTHYEARML12285A2652012-10-0101 October 2012 Attachment 4 - MHI Document L5-04GA564 - Tube Wear of Unit-3 RSG, Technical Evaluation Report Project stage: Request ML12285A2672012-10-0101 October 2012 Attachment 4: SG Tube Wear Analysis for Unit-2/3 Project stage: Request ML12285A2662012-10-0101 October 2012 Attachment 4: Appendix-2 Attachment-1, Tube-to-TSP Wear Depth Diagram for Unit-2/3 Project stage: Request ML12285A2642012-10-0101 October 2012 Attachment 3 - Areva Document 51-9180143-001 - SONGS Unit 3 February 2012 Leaker Outage Steam Generator Condition Monitoring Report Project stage: Request ML12285A2682012-10-0202 October 2012 Attachment 6 - Appendix B: SONGS U2C17 - Steam Generator Operational Assessment for Tube-to-Tube Wear Project stage: Request ML12285A2692012-10-0202 October 2012 Attachment 6: Appendix a: Estimates of FEI-Induced Ttw Rates Project stage: Request ML12285A2632012-10-0303 October 2012 Confirmatory Action Letter - Actions to Address Steam Generator Tube Degradation Project stage: Request ML12338A1102012-11-30030 November 2012 Email, Request for Additional Information Southern California Edison'S Response to Nrc'S Confirmatory Action Letter (CAL) 4-12-001 Dated March 27, 2012 Project stage: RAI ML12341A1122012-12-0707 December 2012 Notice of Meeting with Southern California Edison to Discuss Its Response to Nrc'S Confirmatory Action Letter and Return to Service Report for San Onofre Nuclear Generating Station, Unit 2 Project stage: Meeting ML12347A0662012-12-0707 December 2012 Revised Notice of 12/18/12 Meeting with Southern California Edison to Discuss Its Response to Nrc'S Confirmatory Action Letter and Return to Service Report for San Onofre Nuclear Generating Station, Unit 2 Project stage: Meeting ML12345A4272012-12-10010 December 2012 Revised Email, Request for Additional Information Review of Southern California Edison'S Response to Nrc'S 3/27/2012 Confirmatory Action Letter (CAL) 4-12-001 and Return to Service Report Project stage: RAI ML12353A0972012-12-13013 December 2012 LTR-12-0795 - E-mail Don Leichtling Concerns Media Alert - Nuclear News - NRR Forthcoming Meeting with Southern California Edison Company Project stage: Meeting ML12352A3852012-12-18018 December 2012 Licensee Slides for 12/18/12 Public Meeting Project stage: Meeting ML12352A4112012-12-18018 December 2012 NRC Slides for 12/18/12 Meeting with Southern California Edison Project stage: Meeting ML12356A1982012-12-20020 December 2012 Email, Request for Additional Information, Round 3, Review of Southern California Edison'S Response to Nrc'S 3/27/2012 Confirmatory Action Letter (CAL) 4-12-001 and Return to Service Report Project stage: RAI ML13009A3492013-01-0808 January 2013 Response to Request for Additional Information Regarding Confirmatory Action Letter Response Project stage: Response to RAI ML13014A2512013-01-0909 January 2013 Response to Request for Additional Information (RAI 30) Regarding Confirmatory Action Letter Response Project stage: Response to RAI ML13014A2492013-01-0909 January 2013 Response to Request for Additional Information (RAI 15) Regarding Confirmatory Action Letter Response Project stage: Response to RAI ML13015A0042013-01-10010 January 2013 Response to Request for Additional Information (RAI 16), Regarding Confirmatory Action Letter Response (TAC No. Me 9727) Project stage: Response to RAI ML13022A0882013-01-16016 January 2013 Response to Request for Additional Information (RAI 19) Regarding Confirmatory Action Letter Response (TAC No. Me 9727) Project stage: Response to RAI ML13022A4132013-01-17017 January 2013 Response to Request for Additional Information (RAIs 10 and 17) Regarding Confirmatory Action Letter Response Project stage: Response to RAI ML13022A4812013-01-18018 January 2013 Response to Request for Additional Information (RAI 13), Regarding Confirmatory Action Letter Response Project stage: Response to RAI ML13022A4082013-01-18018 January 2013 Response to Request for Additional Information (RAI 12), Regarding Confirmatory Action Letter Response (TAC No. Me 9727) Project stage: Response to RAI ML13022A4112013-01-21021 January 2013 Response to Request for Additional Information (RAI 11) Regarding Confirmatory Action Letter Response (TAC Me 9727) Project stage: Response to RAI ML13022A4052013-01-21021 January 2013 Response to Request for Additional Information (RAI 28), Regarding Confirmatory Action Letter Response (TAC No. Me 9727) Project stage: Response to RAI ML13028A0982013-01-24024 January 2013 Response to Request for Additional Information (RAI 18) Regarding Confirmatory Action Letter Response Project stage: Response to RAI ML13028A4752013-01-25025 January 2013 Response to Request for Additional Information (RAI 27) Regarding Confirmatory Action Letter Project stage: Response to RAI ML13028A4742013-01-25025 January 2013 Response to Request for Additional Information (RAIs 5, 7, and 9) Regarding Confirmatory Action Letter Response Project stage: Response to RAI ML13032A0092013-01-29029 January 2013 Response to Request for Additional Information (RAI 14) Regarding Confirmatory Action Letter Response (TAC No. Me 9727) Project stage: Response to RAI ML13037A1122013-01-31031 January 2013 Response to Request for Additional Information (RAI 29) Regarding Confirmatory Action Letter Response Project stage: Response to RAI ML13053A3672013-02-0101 February 2013 E-mail, Draft Request for Additional Information Southern California Edison'S Response to Nrc'S Confirmatory Action Letter Project stage: Draft RAI ML13038A0102013-02-0404 February 2013 Response to Request for Additional Information (RAI 8) Regarding Confirmatory Action Letter Response Project stage: Response to RAI ML13038A0092013-02-0404 February 2013 Response to Request for Additional Information (RAI 6) Regarding Confirmatory Action Letter Response Project stage: Response to RAI ML13039A2782013-02-0606 February 2013 Response to Request for Additional Information (RAIs 20, 21, 22, 23, 24, 26 & 31), Confirmatory Action Letter Project stage: Response to RAI ML13039A3172013-02-0707 February 2013 Response to Request for Additional Information (RAI 25) Regarding Confirmatory Action Letter Response Project stage: Response to RAI ML13050A1892013-02-14014 February 2013 Supplemental Document Submittal Regarding Confirmatory Action Letter Response, Concerning Steam Generator Tubes Project stage: Supplement ML13051A1972013-02-15015 February 2013 Enclosure 6, LTR-SGDA-12-36, Rev. 3, Flow-Induced Vibration and Tube Wear Analysis of the San Onofre Nuclear Generating Station Unit 2 Replacement Steam Generators Supporting Restart. Cover Through Page 227 of 415 Project stage: Other ML13051A1992013-02-15015 February 2013 Enclosure 6, LTR-SGDA-12-36, Rev. 3, Flow-Induced Vibration and Tube Wear Analysis of the San Onofre Nuclear Generating Station Unit 2 Replacement Steam Generators Supporting Restart. Page 228 of 415 Through End Project stage: Other ML13046A1232013-02-15015 February 2013 2/27/2013 Notice of Forthcoming Meeting with Southern California Edison Company to Discuss Confirmation Action Letter Project stage: Meeting ML13051A1932013-02-18018 February 2013 Enclosure 5, L5-04GA585, Rev. 2, Analytical Evaluations for Operational Assessment Project stage: Other ML13051A1922013-02-18018 February 2013 Enclosure 4, L5-04GA567, Rev. 6, Evaluation of Stability Ratio for Return to Service Project stage: Other ML13051A1902013-02-18018 February 2013 Supplemental Document Submittal Regarding Confirmatory Action Letter Response to Address Steam Generator Tube Degradation Project stage: Supplement ML13056A0922013-02-20020 February 2013 Email, Draft Request for Additional Information Nos. 38-52, Southern California Edison'S Response to Nrc'S Confirmatory Action Letter Project stage: Draft RAI ML13053A1732013-02-21021 February 2013 Email, Draft Request for Additional Information, Nos. 53-67, Southern California Edison'S Response to Nrc'S Confirmatory Action Letter Project stage: Draft RAI ML13053A1842013-02-21021 February 2013 Draft Request for Additional Information, Nos. 53-67, Southern California Edison'S Response to Nrc'S Confirmatory Action Letter Project stage: Draft RAI ML13058A0262013-02-25025 February 2013 Response to Request for Additional Information (Rals 2, 3, and 4) Regarding Confirmatory Action Letter Response (TAC No. Me 9727) Project stage: Response to RAI ML13056A6012013-02-25025 February 2013 Response to Request for Additional Information (RAI 32) Regarding Confirmatory Action Letter Response Project stage: Response to RAI ML13059A1572013-02-27027 February 2013 Licensee Slides from 2/27/13 Meeting Regarding a Request for Additional Information Project stage: Meeting ML13059A1522013-02-27027 February 2013 NRC Meeting Slides from 2/27/13 Public RAI Meeting Project stage: RAI ML13074A7932013-03-14014 March 2013 Operational Assessment for 100% Power Case Regarding Confirmatory Action Letter Response Project stage: Other 2013-01-25
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Category:Request for Additional Information (RAI)
MONTHYEARML21117A3492021-03-30030 March 2021 March 30, 2021, Email from Public Watchdogs on Providing New Information to Its October 13, 2020, 2.206 Petition ML21068A2722021-03-0909 March 2021 SONGS Endangered Species Act Additional Information Request ML20343A1292020-12-0808 December 2020 NRR E-mail Capture - Request for Additional Information ML18193A2002018-07-19019 July 2018 SONGS ISFSI Only Dqap RAI ML15083A4552015-03-27027 March 2015 and Independent Spent Fuel Storage Installation - Request for Additional Information Decommissioning Quality Assurance Program Review ML15071A1842015-03-19019 March 2015 Independent Spent Fuel Storage Installation - Request for Additional Information Regarding the 10 CFR 50.54(p) Changes to the Security Plans ML15042A3942015-01-23023 January 2015 NRR E-mail Capture - SONGS - Draft RAI Permanently Defueled Technical Specifications License Amendment Request ML15033A0522014-12-11011 December 2014 NRR E-mail Capture - SONGS - Draft RAI Permanently Defueled Technical Specifications License Amendment Request ML14248A5902014-09-18018 September 2014 Independent Spent Fuel Storage Installation - Request for Additional Information, Amendment Request to Revise Emergency Plan to Support Permanently Defueled Condition ML14248A5602014-09-18018 September 2014 Independent Spent Fuel Storage Installation - Request for Additional Information, Amendment Request to Revise Emergency Action Level Scheme to Support Permanently Defueled Condition ML14258A0172014-09-11011 September 2014 NRR E-mail Capture - SONGS - Revised Draft RAI Concerning TS Section 5 Administrative Controls License Amendment Request (TACs MF2954 and MF2955) ML14209A0052014-08-27027 August 2014 Request for Additional Information, Exemption Request from 10 CFR 50.47 and 10 CFR Part 50 Appendix E, Discontinue Offsite Emergency Planning Activities and Reduce Scope of Onsite Emergency Planning (TAC MF3835-MF3837) ML14139A4782014-06-0505 June 2014 Request for Additional Information, License Amendment Request to Revise Technical Specifications 5.1, 5.2, and 5.3 to Reflect Reduced Staffing/Training in Permanently Shutdown and Defueled Condition ML14093A6772014-05-0101 May 2014 SONGS - Request for Additional Information Concerning Pre-Emption Authority ML13352A0912013-12-30030 December 2013 Decommissioning Funding Status Report - Request for Additional Information ML13191A8372013-09-12012 September 2013 Request for Additional Information, Review of Decommissioning Funding Status Report ML13154A4312013-06-0404 June 2013 Rai'S Following Ifib Analysis of Edison'S 2013 Decommissioning Funding Status Report for San Onofre Units 2 and 3 ML13113A2562013-05-10010 May 2013 Request for Additional Information No. 73 Regarding Response to Confirmatory Action Letter ML13072A0542013-03-18018 March 2013 Redacted, Request for Additional Information, Nos. 33-67, Southern California Edison'S Response to Nrc'S Confirmatory Action Letter ML13074A6872013-03-15015 March 2013 Email, Draft Request for Additional Information, Nos. 68-72, Southern California Edison'S Response to Nrc'S Confirmatory Action Letter ML13053A1842013-02-21021 February 2013 Draft Request for Additional Information, Nos. 53-67, Southern California Edison'S Response to Nrc'S Confirmatory Action Letter ML13056A0922013-02-20020 February 2013 Email, Draft Request for Additional Information Nos. 38-52, Southern California Edison'S Response to Nrc'S Confirmatory Action Letter ML13053A3672013-02-0101 February 2013 E-mail, Draft Request for Additional Information Southern California Edison'S Response to Nrc'S Confirmatory Action Letter ML12356A1982012-12-20020 December 2012 Email, Request for Additional Information, Round 3, Review of Southern California Edison'S Response to Nrc'S 3/27/2012 Confirmatory Action Letter (CAL) 4-12-001 and Return to Service Report ML12345A4272012-12-10010 December 2012 Revised Email, Request for Additional Information Review of Southern California Edison'S Response to Nrc'S 3/27/2012 Confirmatory Action Letter (CAL) 4-12-001 and Return to Service Report ML12338A1102012-11-30030 November 2012 Email, Request for Additional Information Southern California Edison'S Response to Nrc'S Confirmatory Action Letter (CAL) 4-12-001 Dated March 27, 2012 ML12313A4752012-11-0808 November 2012 Request for Additional Information Email, Relief Request IST-4-P-2, ASME OM Code Requirements for Testing CSS and LPSI Pumps, Fourth 10-Year Inservice Inspection Interval ML12297A3972012-10-23023 October 2012 Request for Additional Information Email, Relief Request ISI-3-36, Reactor Coolant Pressure Boundary Testing, Third 10-Year Inservice Inspection Interval ML12283A2302012-10-0909 October 2012 Request for Additional Information Email, Round 3 W/Corrected Due Date, Request to Revise Technical Specification (TS) 2.1.1.2, TS 4.2.1, and TS 5.7.1.5, to Support Unrestricted Use of Areva Fuel ML12283A2252012-10-0909 October 2012 Request for Additional Information Email, Round 3, Request to Revise Technical Specification (TS) 2.1.1.2, TS 4.2.1, and TS 5.7.1.5, to Support Unrestricted Use of Areva Fuel ML12220A0492012-08-0707 August 2012 Request for Additional Information Email, Round 2, License Amendment Request to Revise Technical Specification (TS) 2.1.1.2, TS 4.2.1, and TS 5.7.1.5, to Support Unrestricted Use of Areva Fuel ML12207A2612012-08-0101 August 2012 Redacted, Request for Additional Information, License Amendment Request to Revise Technical Specification (TS) 2.1.1.2, TS 4.2.1, and TS 5.7.1.5, to Support Unrestricted Use of Areva Fuel ML12201A1552012-07-19019 July 2012 R. Onge Ltr Request for Additional Information Decommissioning Funding ML12056A0502012-03-12012 March 2012 Enclosure 4 - Recommendation 2.3: Flooding ML12056A0512012-03-12012 March 2012 Enclosure 5 - Recommendation 9.3: Emergency Preparedness ML12056A0482012-03-12012 March 2012 Enclosure 2 - Recommendation 2.1: Flooding ML12056A0472012-03-12012 March 2012 Enclosure 1 - Recommendation 2.1: Seismic ML12056A0492012-03-12012 March 2012 Enclosure 3 - Recommendation 2.3: Seismic ML1200603242012-01-19019 January 2012 Fleet, RAI, Proposed Alternative to Use American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code Case N-789 (N-789) ML1126604602011-10-14014 October 2011 Request for Additional Information Regarding Use of American Concrete Institute Reports for Restoration of Unit 3 Containment ML11182C0322011-06-30030 June 2011 Notification of Inspection (Inspection Report 05000361; 05000362/2011004) and Request for Information ML1113003952011-05-10010 May 2011 Email, Draft Request for Additional Information, Review of Biennial Decommissioning Funding Status Report ML1113004002011-05-10010 May 2011 Draft Request for Additional Information, Review of Biennial Decommissioning Funding Status Report ML1112307842011-05-0303 May 2011 Draft Request for Additional Information, Relief Requests ISI-3-32 Through ISI-3-34, Alternative to Requirements for Examinations of Welds and Core Support Structure Surfaces, Third 10-Year Inservice Inspection ML1106006612011-03-0101 March 2011 Draft Generic Request for Additional Information, License Amendment Request to Revise License Condition and Approve Cyber Security Plan ML1024301262010-08-31031 August 2010 Request for Additional Information Relief Request ISI-3-31 ML1022404532010-08-11011 August 2010 Draft Request for Additional Information LAR on Fuel Assembly Movement ML0933601212009-12-0202 December 2009 Request for Additional Information Relief Request ISI-3-30 ML0831705532008-12-0808 December 2008 Request for Additional Information, License Amendment Request to Support Replacement Steam Generators ML0831901202008-11-26026 November 2008 Request for Additional Information Test Protocol Used in the Testing at Vuez 2021-03-09
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OFFICE OF NUCLEAR REACTOR REGULATION REQUEST FOR ADDITIONAL INFORMATION SOUTHERN CALIFORNIA EDISON SAN ONOFRE NUCLEAR GENERATING STATION, UNIT 2 RESPONSE TO MARCH 27, 2012, NRC CONFIRMATORY ACTION LETTER DOCKET NO. 50-361 TAC NO. ME9727 On March 27, 2012, the NRC issued a Confirmatory Action Letter (Agencywide Documents Access and Management System (ADAMS) Accession No. ML12087A323) to Southern California Edison (SCE) for the San Onofre Nuclear Generating Station (SONGS), Units 2 and
- 3. The Confirmatory Action Letter (CAL) confirmed the commitments made in SCE's March 23, 2012, letter entitled, "Steam Generator Return-to-Service Action Plan" (RTS Action Plan; ADAMS Accession No. ML12086A182). Commitment 2 of the RTS Action Plan states in part that SCE will determine the cause(s) of the tube-to-tube interactions that resulted in steam generator (SG) tube wear in Unit 3, and will implement actions to prevent loss of integrity due to these causes in the Unit 2 steam generator tubes. Commitment 3 of the RTS Action Plan states in part that, prior to entry of Unit 2 into Mode 2, SCE will provide to the NRC the results of SCE's assessment of Unit 2 steam generators, and the basis for SCE 's conclusion that there is reasonable assurance, as required by NRC regulations, that Unit 2 will operate safely.
By letter dated October 3, 2012 (ADAMS Accession No. ML122850320), SCE submitted its response to the NRC Confirmatory Action Letter (CAL), for SONGS Unit 2. By letter dated November 28, 2012 (ADAMS Accession No. ML12348A287), SCE submitted proprietary versions of several reports enclosed with the October 3, 2012 CAL response, along with affidavits supporting SCEs request for withholding the proprietary information under 10 CFR 2.390.
Steam generator tubes are an integral part of the reactor coolant pressure boundary and are relied on to maintain primary system pressure and inventory. The operating licenses for SONGS Units 2 and 3 require SCE to conduct a Steam Generator Program (Technical Specification (TS) 5.5.2.11), to ensure that steam generator tube integrity is maintained. TS 5.5.2.11 specifies performance criteria for maintaining SG tube integrity. The processes used to meet the SG performance criteria are defined by NEI 97-06, "Steam Generator Program Guidelines." These processes include performing detailed technical evaluations, called operational assessments, to demonstrate that tube structural integrity will be maintained under normal and accident conditions for the proposed operating cycle.
The NRC staff is continuing its detailed review of the information provided by SCE in support of SCEs conclusion that SG tube integrity will be maintained, and that there is reasonable assurance, as required by NRC regulations, that Unit 2 will operate safely. To complete this review, the staff has determined that additional information is needed regarding the operational assessments discussed in your CAL response.
The staffs latest request for additional information (RAI) is attached. Please note that although the NRC staff has determined that the attached questions are not proprietary, many of the questions refer to information that SCE has requested be withheld in its letter dated November 28, 2012. If the responses to these questions include proprietary information, SCE should provide additional requests for withholding under 10 CFR 2.390, as necessary. (Note: The NRC staff previously provided an RAI regarding the CAL response to SCE in the form of 32 initial questions, which were sent by letter dated December 26, 2012 (ADAMS Accession No. ML12361A065). The staff also transmitted two additional RAIs containing proprietary information via electronic mail to SCE on February 1, 2013 (5 questions), and February 20, 2013 (15 questions). For continuity, the numbering scheme for the additional questions below begins where the NRCs previous RAI questions ended.)
- 53. In Reference 1, Section 4.6.2, [Tube-to-Tube (TTW)] Growth Model, was the regression fit slope and intercept uncertainty modeled (e.g., as was done for the burst pressure versus voltage model in NRC Generic Letter 95-05)? If not, why is this conservative? Was the data scatter about the regression fit modeled as normally distributed? If so, provide justification for the adequacy of this assumption (i.e., normal distribution) to fully capture the upper tail of the distribution as shown in Figure 4-12 on page 4-25.
- 54. In Reference 1, Figures 4-11 and 4-13, the maximum depths in Figure 4-11 have been divided by the Unit 3 cycle length of 0.926 years to yield the growth rates in Figure 4-13.
The staff understands that Figure 4-13 should be simply a scaled version of Figure 4-11.
Please explain why some of the data in Figure 4-11 are not shown in Figure 4-13; for example, the three flaws shown in Figure 4-11 with maximum depths ranging from 89 to 100% (AREVA resized).
- 55. In Reference 2, page 107 of 129, second to last paragraph, did total gap also include wear of the anti-vibration bars (AVBs) themselves? If not, explain why the approach is conservative. If so, how was wear of the AVBs determined? (This question is a follow-up on RAI No. 26 from the NRCs December 26, 2012, letter).
- 56. For Reference 2, Figure 8-3, provide an assessment of the robustness of the Figure 8-3 predictions of the probability of instability versus time in terms of how well it accommodates uncertainty in these predictions for purposes of ensuring acceptable tube integrity margins during the planned 5-month inspection interval for Unit 2. Robustness refers in part to accommodating increases or decreases in the rate at which instability increases with time and the calculated value of the probability of instability at the beginning of cycle (BOC) 16 for Units 2 and 3 and BOC 17 for Unit 2. Robustness also considers the time interval between onset of instability and the loss of acceptable tube integrity margins.
- 57. In Reference 3, Appendix 9, Table 6.2-1, why is tube support plate (TSP) hole mis-location not included in the table headings? If not accounted for in the analysis, explain
why the approach is conservative. If used in the analysis, provide an updated table that includes the TSP hole mis-location parameter.
- 58. In Reference 3, Appendix 9, Table 6.2-1, which parameters are sampled randomly at each tube/AVB intersection? Why is this appropriate in lieu of assuming a functional relationship for each given parameter from tube to tube in a given column of tubes? For parameters (e.g., AVB twist) assumed to follow a functional relationship from tube to tube in the same column, provide the basis for the assumed relationship. For AVB twist, how does the assumed relationship relate to Figure 6.2-2?
- 59. In Reference 3, Appendix 9, Attachment 9-1; define the statistical distributions which were actually sampled for Unit 2 and Unit 3. What is the technical justification for the assumed distributions compared to the actual distribution of the data?
- 60. In Reference 3, Appendix 9, Figures 7.2-3 and 7.2-5 apply to Unit 3. Please provide similar figures for Unit 2.
- 61. Reference 3, Appendix 9, Attachment 9-3, Figure 4.1.2-3. Discuss the pedigree of the data in this figure and how it differs from Reference 2, Figure 6-19 and 6-20. Please explain the differences between the Reference 3 versus the Reference 2 figures for dings exceeding 0.5 volts?
- 62. In Reference 2, Figure 8-3, the staff understands that the stability ratio (SR) in the context of Figure 8-3 is a 95% upper bound estimate, both for the last operating period for both Units 2 and 3 and for the next operating period for Unit 2. Why wasnt a best estimate SR used for benchmarking the probability of SR>1 at the conclusion of the last operating period for both Units 2 and 3? (Benchmarking refers to selecting a contact force criterion for effective AVB support such as to produce probabilities of SR>1 at the end of the last operating period consistent with what was actually observed.) How would a best estimate SR have affected the curves presented for the last operating period?
Discuss whether the use of a 95% upper bound estimate for benchmarking purposes essentially negates the conservatism of using 95% upper bound SR estimates for future operation of Unit 2?
- 63. In Reference 3, Page 66, the last sentence on this page states, Therefore, the difference of the contact forces between Unit-2 and Unit-3 is caused by the difference of the manufacturing dimensional tolerances other than the outer-most tube-to-AVB gaps.
Explain the basis for this conclusion in light of the omission of the measured tube-to-AVB gaps at the outer tubes as a boundary condition in the contact force model described in Appendix 9 of Reference 3.
- 64. In Reference 3, Appendix 9, page 9-6 (355 of 474), it is stated, Especially for AVB twist, AVB twist factor in consideration of torsion stiffness is defined as a decrease function of distance from AVB bending peak, because the more contact points leave from AVB nose, the less AVB torsion stiffness is. Please clarify the meaning of this
sentence by answering the following questions: What is the AVB twist factor? What is meant by AVB twist factor in consideration of torsion stiffness? What parameter is decreasing as a function of distance from the AVB nose, AVB twist or AVB torsional stiffness? Why does torsional stiffness vary as function of distance from the AVB nose?
Describe the specific variation of torsional stiffness with distance from nose function that was used in the analysis. How was this variation determined?
- 65. In Reference 3, Appendix 9, Figure 6.2.2 shows AVB twist factor as a function of distance from AVB nose tip. Is this the function that was used in the contact force analysis? For all AVBs? If not, what twist factor functions were used for the other AVBs? How were these twist factor functions determined? Explain the relationship between twist factors shown in this figure versus those shown in Table 6.2-1.
- 66. In Reference 3, Appendix 9, page 9-6 (355 of 474) it is also stated, In AVB nose area, the factor is always 1, because increased twist from nose tip and decreased stiffness from nose tip cancel each other. Please provide a detailed clarification of this sentence.
The staff further notes that twist and stiffness have different units. How can they cancel each other out?
- 67. Reference 3, Appendix 9, Attachment 9-3; describe in detail any tuning of the contact force model that was performed to replicate the ding signals observed during pre-service inspection.
REFERENCES
- 1. Letter from Peter T. Dietrich, SCE, to Elmo E. Collins, USNRC, Docket No. 50-361, Confirmatory Action Letter - Actions to Address Steam Generator Tube Degradation, San Onofre Nuclear Generating Station, Unit 2, October 3, 2012; Enclosure 2, San Onofre Nuclear Generating Station Unit 2 Return to Service Report, Revision 0.
Attachment 6, SONGS U2C17 Steam Generator Operational Assessment, Appendix C, Operational Assessment for SONGS Unit 2 Steam Generators for Upper Bundle Tube-to-Tube Wear Degradation at End of Cycle 16, prepared by Intertek APTECH for Areva, Report No. AES 12068150-2Q-1, Revision 0, September 2012.
(ADAMS Accession No. ML12285A269)
- 2. Letter from Richard J. St. Onge, SCE, to Document Control Desk, USNRC, Docket No.
50-361, Confirmatory Action Letter Response - Proprietary Documents, San Onofre Nuclear Generating Station, Unit 2, November 28, 2012. (ADAMS Accession No. ML12348A287); Enclosure 6, SONGS U2C17 Steam Generator Operational Assessment for Tube-to-Tube Wear, prepared by Areva NP Inc. Document No. 51-9187230-000, Revision 0), October 2012. [Proprietary] [Note: a non-proprietary version of this report was provided as Enclosure 2, Attachment 6, Appendix B, to SCEs letter dated October 3, 2012. See ADAMS Accession Nos. ML12285A267, ML12285A268, and ML12285A269]
- 3. Letter from Richard J. St. Onge, SCE, to Document Control Desk, USNRC, Docket No.
50-361, Confirmatory Action Letter Response - Proprietary Documents, San Onofre Nuclear Generating Station, Unit 2, November 28, 2012. (ADAMS Accession No. ML12348A287); Enclosure 3, MHI Document L5-04GA564 Rev. 9, Tube Wear of Unit-3 RSG - Technical Evaluation Report. [Proprietary] [Note: a non-proprietary version of this report was provided as Enclosure 2, Attachment 4, to SCEs letter dated October 3, 2012. See ADAMS Accession Nos. ML12285A265, ML12285A266, andML12285A267]