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| {{#Wiki_filter:U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555 Re: St. Lucie Unit 2 Docket No. 50-389 AUG 2 1 2019 Refueling Outage SL2-24 Steam Generator Tube Inspection Report RAI Response | | {{#Wiki_filter:AUG 2 1 2019 L-2019-166 10 CFR 50.55a 10 CFR 50.36 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555 Re: St. Lucie Unit 2 Docket No. 50-389 Refueling Outage SL2-24 Steam Generator Tube Inspection Report RAI Response |
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| ==References:== | | ==References:== |
| | : 1. FPL Letter L-2019-064 dated March 22, 2019, "Refueling Outage SL2-24 Steam Generator Tube Inspection Report." Adams Accession No. ML19081A146 |
| | : 2. NRR E-mail Capture dated July 11, 2019, "Request for Additional Information - St. Lucie Plant, Unit No. 2, Fall 2018 Refueling Outage Steam Generator Tube Inspection Report (EPID L-2019-LR0-0023) ." Adams Accession No. ML19192A137 In reference 1 above, Florida Power & Light Company (FPL) submitted the St. Lucie Unit 2 Technical Specification 6.9.1.12 steam generator tube inspection report for the fall 2018 refueling outage (SL2-24). |
| | During the NRC Staff review of the submittal, they determined that additional information was required in order to complete their review. This request for additional information (RAI) was made in reference 2 above. |
| | FPL's response to the RAI request is contained in the attachment to this correspondence. |
| | Please contact Ken Frehafer at (772) 467-77 48 should you have any questions regarding this submittal. |
| | Sincerely, Wyatt Gades Licensing Manager St. Lucie Plant. |
| | MJS/KWF Attachment cc: USNRC Regional Administrator, Region II USNRC Senior Resident Inspector, St. Lucie Nuclear Plant Florida Power & Light Company 6501 S. Ocean Drive, Jensen Beach, FL 34957 |
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| L-2019-166 10 CFR 50.55a 10 CFR 50.36 1. FPL Letter L-2019-064 dated March 22, 2019, "Refueling Outage SL2-24 Steam Generator Tube Inspection Report." Adams Accession No. ML19081A146
| | L-2019-166 Attachment Page 1 of 3 |
| : 2. NRR E-mail Capture dated July 11, 2019, "Request for Additional Information
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| -St. Lucie Plant, Unit No. 2, Fall 2018 Refueling Outage Steam Generator Tube Inspection Report (EPID L-2019-LR0-0023)." Adams Accession No. ML19192A137 In reference 1 above, Florida Power & Light Company (FPL) submitted the St. Lucie Unit 2 Technical Specification 6.9.1.12 steam generator tube inspection report for the fa ll 2018 refueling outage (SL2-24).
| | ==Background:== |
| During the NRC Staff review of the submittal, they determined that additional information was required in order to complete their review. This request for additional information (RAI) was made in reference 2 above. FPL's response to the RAI request is contained in the attachment to this correspondence.
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| Please contact Ken Frehafer at (772) 467-77 48 should you have any questions regarding this submittal.
| | The U.S. Nuclear Regulatory Commission (NRC) staff previously reviewed the licensees spring 2014 SG tube inspection report and provided a summary to the licensee in a letter dated August 19, 2015 (ADAMS Accession No. ML15209A646). The spring 2014 inspections were performed during RFO |
| Sincerely, Wyatt Gades Licensing Manager St. Lucie P l ant. MJS/KWF Attachment cc: USNRC Regional Administrator, Region II USNRC Senior Res i dent Inspector, St. Lucie Nuclear Plant Florida Power & Light Company 650 1 S. Ocean Drive, Jensen Beach, FL 34957 L-2019-166 Attachment Page 1 of 3 Background
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| The U.S. Nuclear Regulatory Commission (NRC) staff previously reviewed the licensee's spring 2014 SG tube inspection report and provided a summary to the licensee in a letter dated August 19, 2015 (ADAMS Accession No. ML15209A646). The spring 2014 inspections were performed during RFO | |
| : 21. In the summary, the NRC staff noted that the four feedring inspection port covers (two per SG) were found to be loose during the secondary side inspections. The loose covers allowed the feedrings to drain, which created steam voids in the feedrings and resulted in a water hammer event that damaged the feedring supports for both SGs. The feedring supports were repaired during RFO 21 and all four inspection port covers were replaced with welded end caps to prevent loosening. | | : 21. In the summary, the NRC staff noted that the four feedring inspection port covers (two per SG) were found to be loose during the secondary side inspections. The loose covers allowed the feedrings to drain, which created steam voids in the feedrings and resulted in a water hammer event that damaged the feedring supports for both SGs. The feedring supports were repaired during RFO 21 and all four inspection port covers were replaced with welded end caps to prevent loosening. |
| | | The licensees fall 2015 SG tube inspection report, dated April 15, 2016 (ADAMS Accession No. |
| The licensee's fall 2015 SG tube inspection report, dated April 15, 2016 (ADAMS Accession No. | |
| ML16111B235), noted that during inspection of the SG 2B feedring, the inner support brackets were found to be slightly deformed. The new brackets had been installed during RFO 21 and appeared to have been displaced by a pressure transient in the feedring during the subsequent operating cycle. The licensee noted during the inspection that the welds remained intact. The condition was documented in the corrective action program, and the brackets were repaired with support braces/stiffeners. No deficiency was observed with the SG 2A feedring and supports. These inspections and repairs were performed during RFO 22. | | ML16111B235), noted that during inspection of the SG 2B feedring, the inner support brackets were found to be slightly deformed. The new brackets had been installed during RFO 21 and appeared to have been displaced by a pressure transient in the feedring during the subsequent operating cycle. The licensee noted during the inspection that the welds remained intact. The condition was documented in the corrective action program, and the brackets were repaired with support braces/stiffeners. No deficiency was observed with the SG 2A feedring and supports. These inspections and repairs were performed during RFO 22. |
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| In the fall 2018 SG tube inspection report, the licensee stated that the secondary side inspection activities were mainly comprised of a visual inspection of the feedwater ring support system in each SG. The inner support brackets of the SG 2A feedring were found to be slightly deformed from a pressure transient in the feedring during the previous operating cycle. The licensee also stated that this condition was expected for SG 2A, based on monitoring criteria established for this phenomenon, and does not jeopardize SG tube integrity. All welds of the feedring support system were noted to be intact. The as-found condition was documented in the corrective action program, and the brackets were repaired by attaching support braces/stiffeners to them. No deficiency was observed with the SG 2B feedring supports. | | In the fall 2018 SG tube inspection report, the licensee stated that the secondary side inspection activities were mainly comprised of a visual inspection of the feedwater ring support system in each SG. The inner support brackets of the SG 2A feedring were found to be slightly deformed from a pressure transient in the feedring during the previous operating cycle. The licensee also stated that this condition was expected for SG 2A, based on monitoring criteria established for this phenomenon, and does not jeopardize SG tube integrity. All welds of the feedring support system were noted to be intact. The as-found condition was documented in the corrective action program, and the brackets were repaired by attaching support braces/stiffeners to them. No deficiency was observed with the SG 2B feedring supports. |
| Issue: | | Issue: |
| The cause of the water hammer event that initially damaged the feedring supports for both SGs, was attributed to the loose inspection port covers, which allowed the feedrings to drain. Although repairs were made in RFO 21, additional repairs were required in RFO 22 and RFO 24, due to pressure transients in the SG feedrings. | | The cause of the water hammer event that initially damaged the feedring supports for both SGs, was attributed to the loose inspection port covers, which allowed the feedrings to drain. Although repairs were made in RFO 21, additional repairs were required in RFO 22 and RFO 24, due to pressure transients in the SG feedrings. |
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| Request: | | Request: |
| : 1. The fall 2018 SG tube inspection report stated, "-this condition was expected for SG 2A, based on monitoring criteria established for this phenomenon and does not jeopardize SG tube integrity." Does this statement mean that the feedwater ring support system is designed to deform during pressure transients? Discuss why this does not pose a loose part threat to tube integrity. | | : 1. The fall 2018 SG tube inspection report stated, this condition was expected for SG 2A, based on monitoring criteria established for this phenomenon and does not jeopardize SG tube integrity. |
| | Does this statement mean that the feedwater ring support system is designed to deform during pressure transients? Discuss why this does not pose a loose part threat to tube integrity. |
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| L-2019-166 Attachment Page 2 of 3 Response to Request #1 | | L-2019-166 Attachment Page 2 of 3 Response to Request #1: |
| : | | The feedwater ring support system was designed such that the inner supports (c-brackets) would plastically deform and absorb some of the loading if the loading is above a specified amount, and still maintain the allowable stress limits of the materials including the welds. In the event a loose part is developed due to a pressure transient, the SG is equipped with a fine-mesh, loose-part trapping (debris) screen, designed to preclude loose parts from entering the tube bundle. The screen is designed such that only very small objects such as small wires or small pieces of deposits can pass through. No loose parts from internal components of the SG have ever been identified within the tube bundle (i.e., downstream of the debris screens) during SG secondary-side inspections. For the above reasons, the recent pressure transients were considered to not pose a loose part threat to SG tube integrity. |
| The feedwater ring support system was designed such that the inner support s (c-brackets) would plastically deform and absorb some of the loading if the loading is above a specified amount, and still maintain the allowable stress limits of the materials including the welds. In the event a loose part is developed due to a pressure transient, the SG is equipped with a fine | |
| -mesh, loose | |
| -part trapping (debris) screen | |
| , designed to preclude loose parts from entering the tube bundle. The screen is designed such that only very small objects such as small wires or small pieces of deposits can pass through. No loose parts from internal components of the SG have ever been identified within the tube bundle (i.e., downstream of the debris screens) during SG secondary | |
| -side inspection s. For the above reasons, the recent pressure transients were considered to not pose a loose part threat to SG tube integrity. | |
| : 2. Have feedring inspection port cover inspections confirmed the weld repairs to the end caps remain adequate and functioning as designed? | | : 2. Have feedring inspection port cover inspections confirmed the weld repairs to the end caps remain adequate and functioning as designed? |
| | Response to Request #2: |
| | As stated in the NRC summary for the SL2-21 SG Tube Inspection Report (Ref. 1), the SG feedring supports were repaired during RFO 21 and all four inspection port covers were replaced with welded end caps to prevent loosening. No damage or degradation has been identified during each subsequent inspection of the feedwater ring end caps. Inspections have confirmed that the original weld repairs on the end caps remain adequate and functioning as designed, without leakage. |
| | : 3. Has a root cause analysis been performed on the initial water hammer event and the subsequent pressure transients? Is it possible for multiple transients or a larger magnitude transient to cause greater damage than has been experienced, generating loose parts that could challenge tube integrity? |
| | Response to Request #3: |
| | A root cause analysis has been performed on the initial water hammer events which led to repairs in RFO 21 and the subsequent pressure transient in Cycle 21 which led to repairs in RFO 22. The pressure transient in Cycle 23 which led to repairs in RFO 24 was also evaluated in the corrective action program. As noted in previous NRC Integrated Inspection Reports for the St. Lucie Plant (Ref. 2, 3 and 4), the condition report and root cause analysis were reviewed by the NRC inspection team. The inspectors reviewed the evaluations and circumstances associated with the condition evaluated, and verified that corrective actions were planned and/or implemented that are commensurate with the significance of the identified issue. |
| | The largest magnitude transient possible is from an automatic initiation of the auxiliary feedwater actuation system (AFAS) when SG level is below the discharge point of the j-tubes. This type of transient was experienced during the water hammer events of Cycles 21 and 23, and no loose parts |
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| Response to Request #2
| | L-2019-166 Attachment Page 3 of 3 were generated from these events based on secondary-side visual inspections in RFO 22 and RFO 24, respectively. If more than one pressure transient is experienced in the SG feedwater ring of St. |
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| | Lucie Unit 2 during a cycle, a visual inspection of the feedwater ring and supports (of the affected SG) is required by procedure prior to unit startup to assess potential damage. No loose parts have ever been generated in the current feedwater ring support design. The restrictions placed on unit operation with multiple transients, and the presence of the debris screens provide reasonable assurance that the integrity of the SG tubes is maintained. |
| As stated in the NRC summary for the SL2-21 SG Tube Inspection Report (Ref. 1), the SG feedring supports were repaired during RFO 21 and all four inspection port covers were replaced with welded end caps to prevent loosening. No damage or degradation has been identified during each subsequent inspection of the feedwater ring end caps. Inspections have confirmed that the original weld repairs on the end caps remain adequate and functioning as designed
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| , without leakage.
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| : 3. Has a root cause analysis been performed on the initial water hammer event and the subsequent pressure transients? Is it possible for multiple transients or a larger magnitude transient to cause greater damage than has been experienced, generating loose parts that could challenge tube integrity?
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| Response to Request #3
| | ==References:== |
| : | |
| A root cause analysis has been performed on the initial water hammer events which led to repairs in RFO 21 and the subsequent pressure transient in Cycle 21 which led to repairs in RFO 22. The pressure transient in Cycle 23 which led to repairs in RFO 24 was also evaluated in the corrective action program. As noted in previous NRC Integrated Inspection Reports for the St. Lucie Plant (Ref. 2, 3 and 4), the condition report and root cause analysis were reviewed by the NRC inspection team. The inspectors reviewed the evaluations and circumstances associated with the condition evaluated, and verified that corrective actions were planned and/or implemented that are commensurate with the significance of the identified issue
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| The largest magnitude transient possible is from an automatic initiation of the auxiliary feedwater actuation system (AFAS) when SG level is below the discharge point of the j-tubes. This type of transient was experienced during the water hammer events of Cycles 21 and 23, and no loose parts L-2019-166 Attachment Page 3 of 3 were generated from these events based on secondary
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| -side visual inspections in RFO 22 and RFO 24, respectively. If more than one pressure transient is experienced in the SG feedwater ring of St. Lucie Unit 2 during a cycle, a visual inspection of the feedwater ring and supports (of the affected SG) is required by procedure prior to unit startup to assess potential damage. No loose parts have ever been generated in the current feedwater ring support design. The restrictions placed on unit operation with multiple transients, and the presence of the debris screens provide reasonable assurance that the integrity of the SG tubes is maintained
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| References
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| : 1. Review of the Spring 2014 Steam Generator Tube Inservice Inspection Report for Refueling Outage 21 (Accession No. ML15209A646). | | : 1. Review of the Spring 2014 Steam Generator Tube Inservice Inspection Report for Refueling Outage 21 (Accession No. ML15209A646). |
| : 2. St. Lucie Plant | | : 2. St. Lucie Plant - NRC Integrated Inspection Report 05000389/2015001 (Accession No. |
| - NRC Integrated Inspection Report 05000389/2015001 (Accession No. ML15126A323) | | ML15126A323) |
| : 3. St. Lucie Plant | | : 3. St. Lucie Plant - NRC Integrated Inspection Report 05000389/2015002 (Accession No. |
| - NRC Integrated Inspection Report 05000389/2015002 (Accession No. ML15216A565) | | ML15216A565) |
| : 4. St. Lucie Plant | | : 4. St. Lucie Plant - NRC Integrated Inspection Report 05000389/2017001 (Accession No. |
| - NRC Integrated Inspection Report 05000389/2017001 (Accession No. ML17129A510)}} | | ML17129A510)}} |
Letter Sequence Request |
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EPID:L-2019-LRO-0023, Refueling Outage SL2-24 Steam Generator Tube Inspection Report (Approved, Closed) |
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Category:Letter type:L
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Aging Management Request for Additional Information (RAI) 4.3.1-1a(second Round) - Class 1 Fatigue Response2022-10-26026 October 2022 Subsequent License Renewal Application - Aging Management Request for Additional Information (RAI) 4.3.1-1a(second Round) - Class 1 Fatigue Response L-2022-160, Station,, Point Beach Units 1 and 2, License Amendment Request for Common Emergency Plan Consistent with NUREG-0654, Revision 22022-10-0404 October 2022 Station,, Point Beach Units 1 and 2, License Amendment Request for Common Emergency Plan Consistent with NUREG-0654, Revision 2 2024-01-08
[Table view] Category:Response to Request for Additional Information (RAI)
MONTHYEARL-2023-155, Supplement to Response to Request for Additional Information, Revised NextEra Common Emergency Plan, and Revised Site-Specific Emergency Plan Annexes Regarding License Amendment Request for Common Emergency Plan Consistent with NUREG-06542023-11-28028 November 2023 Supplement to Response to Request for Additional Information, Revised NextEra Common Emergency Plan, and Revised Site-Specific Emergency Plan Annexes Regarding License Amendment Request for Common Emergency Plan Consistent with NUREG-0654, L-2023-162, Response to 50.69 2nd Round of Rals2023-11-21021 November 2023 Response to 50.69 2nd Round of Rals L-2023-118, Response to Request for Additional Information Regarding License Amendment Request to Adopt 10 CFR 50.69, Risk-Informed Categorization and Treatment of Structures, Systems and Components for Nuclear Power Reactors2023-09-11011 September 2023 Response to Request for Additional Information Regarding License Amendment Request to Adopt 10 CFR 50.69, Risk-Informed Categorization and Treatment of Structures, Systems and Components for Nuclear Power Reactors L-2023-098, and Point Beach Units 1 and 2 - Response to Request for Additional Information Regarding License Amendment Request for Common Emergency Plan Consistent with NUREG-0654, Revision 22023-08-0707 August 2023 and Point Beach Units 1 and 2 - Response to Request for Additional Information Regarding License Amendment Request for Common Emergency Plan Consistent with NUREG-0654, Revision 2 L-2023-059, Subsequent License Renewal Application - Aging Management Requests for Additional Information (RAI) Set 4 Supplemental Response2023-04-21021 April 2023 Subsequent License Renewal Application - Aging Management Requests for Additional Information (RAI) Set 4 Supplemental Response L-2023-026, Subsequent License Renewal Application - Aging Management Requests for Additional Information Set 42023-03-27027 March 2023 Subsequent License Renewal Application - Aging Management Requests for Additional Information Set 4 ML23013A2032023-01-13013 January 2023 RAI Set 4 Draft Response L-2022-165, Subsequent License Renewal Application - Aging Management Request for Additional Information (RAI) 4.3.1-1a(second Round) - Class 1 Fatigue Response2022-10-26026 October 2022 Subsequent License Renewal Application - Aging Management Request for Additional Information (RAI) 4.3.1-1a(second Round) - Class 1 Fatigue Response L-2022-156, Correction to Subsequent License Renewal Application - Aging Management Requests for Additional Information (RAI) Set 1a Response2022-09-19019 September 2022 Correction to Subsequent License Renewal Application - Aging Management Requests for Additional Information (RAI) Set 1a Response L-2022-143, Subsequent License Renewal Application - Aging Management Requests for Additional Information Set 1A Response2022-09-0808 September 2022 Subsequent License Renewal Application - Aging Management Requests for Additional Information Set 1A Response L-2022-115, Subsequent License Renewal Application - Aging Management Requests for Additional Information (RAI) Set 3 Response and Submittal of Superseded Response for One Set 2 RAI and One Supplement 1 Attachment2022-08-0909 August 2022 Subsequent License Renewal Application - Aging Management Requests for Additional Information (RAI) Set 3 Response and Submittal of Superseded Response for One Set 2 RAI and One Supplement 1 Attachment L-2022-108, Subsequent License Renewal Application - Aging Management Requests for Additional Information (RAI) Set 2 Response2022-07-11011 July 2022 Subsequent License Renewal Application - Aging Management Requests for Additional Information (RAI) Set 2 Response L-2022-075, Subsequent License Renewal Application-Aging Management Requests for Additional Information (RAI) Set 1A Response and Request for Confirmation of Information (RCI) Set 1 Response2022-06-13013 June 2022 Subsequent License Renewal Application-Aging Management Requests for Additional Information (RAI) Set 1A Response and Request for Confirmation of Information (RCI) Set 1 Response L-2022-000, License Amendment Request for the Technical Specifications Conversion to NUREG- 1432 Revision 5 - Request for Supplemental Information (Rsi) Response2022-01-19019 January 2022 License Amendment Request for the Technical Specifications Conversion to NUREG- 1432 Revision 5 - Request for Supplemental Information (Rsi) Response L-2021-105, Response to Request for Additional Information for St. Lucie License Amendment Request to Allow Risk Informed Completion Times (RICT) for the 120-Volt AC Instrument Bus Requirements2021-05-12012 May 2021 Response to Request for Additional Information for St. Lucie License Amendment Request to Allow Risk Informed Completion Times (RICT) for the 120-Volt AC Instrument Bus Requirements L-2021-065, Response to Request for Additional Information. Relief Request Number RR 15, Extension of St. Lucie Unit 2 RPV Welds from 10 to 20 Years2021-04-0101 April 2021 Response to Request for Additional Information. Relief Request Number RR 15, Extension of St. Lucie Unit 2 RPV Welds from 10 to 20 Years L-2020-165, Supplement to Updated Final Response to NRC Generic Letter 2004-022020-12-0404 December 2020 Supplement to Updated Final Response to NRC Generic Letter 2004-02 L-2020-094, Supplemental Response to Request for Additional Information Regarding License Amendment Request to Modify the Reactor Coolant Pump (RCP) Flywheel Inspection Program Requirements2020-06-26026 June 2020 Supplemental Response to Request for Additional Information Regarding License Amendment Request to Modify the Reactor Coolant Pump (RCP) Flywheel Inspection Program Requirements L-2020-061, Response to Request for Additional Information Regarding License Amendment Request to Modify the Reactor Coolant Pump (RCP) Flywheel Inspection Program Requirements2020-04-30030 April 2020 Response to Request for Additional Information Regarding License Amendment Request to Modify the Reactor Coolant Pump (RCP) Flywheel Inspection Program Requirements ML20015A0282020-01-14014 January 2020 NMFS to NRC, Concurrence with Interim Response to Requests for Additional Information for St. Lucie Endangered Species Act Section 7 Consultation L-2019-164, Response to Request for Additional Information Regarding License Amendment Request to Relocate the MOV Thermal Overload Protection Bypass Devices Requirements to Licensee Control2019-09-11011 September 2019 Response to Request for Additional Information Regarding License Amendment Request to Relocate the MOV Thermal Overload Protection Bypass Devices Requirements to Licensee Control L-2019-166, Refueling Outage SL2-24 Steam Generator Tube Inspection Report RAI Response2019-08-21021 August 2019 Refueling Outage SL2-24 Steam Generator Tube Inspection Report RAI Response L-2019-153, Exigent Technical Specification Amendment Request Supplemental RAI Reply One-Time Allowed Outage Time Extension for Inoperable EDG2019-07-25025 July 2019 Exigent Technical Specification Amendment Request Supplemental RAI Reply One-Time Allowed Outage Time Extension for Inoperable EDG L-2019-149, Exigent Technical Specification Amendment Request RAI Reply One-Time Allowed Outage Time Extension for Inoperable EDG2019-07-24024 July 2019 Exigent Technical Specification Amendment Request RAI Reply One-Time Allowed Outage Time Extension for Inoperable EDG L-2019-118, Response to Request for Additional Information Regarding License Amendment Request to Allow Performance of Selected Emergency Diesel Generator (EDG) Surveillance Requirements (Srs) During Power Operation2019-06-28028 June 2019 Response to Request for Additional Information Regarding License Amendment Request to Allow Performance of Selected Emergency Diesel Generator (EDG) Surveillance Requirements (Srs) During Power Operation L-2019-107, License Amendment Request - Iodine Removal System Elimination2019-05-17017 May 2019 License Amendment Request - Iodine Removal System Elimination L-2019-056, Inservice Inspection Plan RAI Reply, Fifth Ten-Year Interval Unit 1 Relief Request2019-03-0707 March 2019 Inservice Inspection Plan RAI Reply, Fifth Ten-Year Interval Unit 1 Relief Request L-2018-205, Response to Request for Additional Information Regarding License Amendment Request to Reduce the Number of Control Element Assemblies2018-11-15015 November 2018 Response to Request for Additional Information Regarding License Amendment Request to Reduce the Number of Control Element Assemblies L-2018-153, Supplemental Information for License Amendment Request to Reduce the Number of Control Element Assemblies2018-08-17017 August 2018 Supplemental Information for License Amendment Request to Reduce the Number of Control Element Assemblies L-16-001, Units. 3 and 4, Response to Request for Supplemental Information Generic Letter 2016-01, Monitoring of Neutron-Absorbing Materials in Spent Fuel Pools.2018-05-24024 May 2018 Units. 3 and 4, Response to Request for Supplemental Information Generic Letter 2016-01, Monitoring of Neutron-Absorbing Materials in Spent Fuel Pools. L-2018-068, Florida Power and Light Co. - Response to Request for Additional Information Re Decommissioning Funding Plan Updates for Independent Spent Fuel Storage Installations2018-04-0303 April 2018 Florida Power and Light Co. - Response to Request for Additional Information Re Decommissioning Funding Plan Updates for Independent Spent Fuel Storage Installations L-77-291, Attachment a to L-77-291 Response to NRC Questions of May 24, 19772018-03-29029 March 2018 Attachment a to L-77-291 Response to NRC Questions of May 24, 1977 L-2018-040, Response to Request for Additional Information Regarding License Amendment Request to Add New Required Actions for an Inoperable Auxiliary Feedwater Pump Steam Supply2018-02-14014 February 2018 Response to Request for Additional Information Regarding License Amendment Request to Add New Required Actions for an Inoperable Auxiliary Feedwater Pump Steam Supply L-2018-006, Third Response to Request for Additional Information Regarding License Amendment Request to Adopt Risk Informed Completion Times TSTF-505, Revision 1, Provide Risk-Risk Informed Extended Completion Times - RITSTF Initiative 4b2018-02-0101 February 2018 Third Response to Request for Additional Information Regarding License Amendment Request to Adopt Risk Informed Completion Times TSTF-505, Revision 1, Provide Risk-Risk Informed Extended Completion Times - RITSTF Initiative 4b L-2017-210, Updated Final Response to NRC Generic Letter 2004-022017-12-20020 December 2017 Updated Final Response to NRC Generic Letter 2004-02 L-2017-216, License Renewal Commitments: Reactor Vessel Internals Aging Management Plan, Clarification of Responses to RAI 1 and RAI 62017-12-19019 December 2017 License Renewal Commitments: Reactor Vessel Internals Aging Management Plan, Clarification of Responses to RAI 1 and RAI 6 L-2017-209, Response to Request for Additional Information Regarding Fifth 10-Year Inservice Testing (IST) Program Interval Relief Request PR-012017-11-30030 November 2017 Response to Request for Additional Information Regarding Fifth 10-Year Inservice Testing (IST) Program Interval Relief Request PR-01 L-2017-159, Response to Request for Additional Information Regarding Inservice Inspection Plan, Fifth Ten-Year Interval Unit 1 Relief Request No. 3, Revision 02017-09-13013 September 2017 Response to Request for Additional Information Regarding Inservice Inspection Plan, Fifth Ten-Year Interval Unit 1 Relief Request No. 3, Revision 0 L-2017-116, Response to Request for Additional Information Regarding License Amendment Request to Revise the Technical Specifications (TS) for the Reactor Protection System (RPS) Power Rate-of-Change Instrumentation and Add New TS 3.0.52017-07-0303 July 2017 Response to Request for Additional Information Regarding License Amendment Request to Revise the Technical Specifications (TS) for the Reactor Protection System (RPS) Power Rate-of-Change Instrumentation and Add New TS 3.0.5 L-2016-220, License Amendment Request EDG Day Tank Fuel Volume Change2016-12-0505 December 2016 License Amendment Request EDG Day Tank Fuel Volume Change L-2016-188, Response to Generic Letter 2016-01, Monitoring of Neutron Absorbing Materials in Spent Fuel Pools, Response to NRC Request for Information Pursuant to Title 10 of the Code of Federal Regulations 50.54(f)2016-11-0303 November 2016 Response to Generic Letter 2016-01, Monitoring of Neutron Absorbing Materials in Spent Fuel Pools, Response to NRC Request for Information Pursuant to Title 10 of the Code of Federal Regulations 50.54(f) L-2016-153, Response to Request for Additional Information Regarding License Amendment Request for Biological Opinion License Changes2016-08-11011 August 2016 Response to Request for Additional Information Regarding License Amendment Request for Biological Opinion License Changes L-2016-135, Second Response to Request for Additional Information Regarding License Amendment Request to Adopt TSTF-505, Provide Risk-Informed Extended Completion Times - RITSTF Initiative 4B2016-07-22022 July 2016 Second Response to Request for Additional Information Regarding License Amendment Request to Adopt TSTF-505, Provide Risk-Informed Extended Completion Times - RITSTF Initiative 4B L-2016-143, Response to Request for Additional Information for the Proposed Technical Specification Change to Remove the 10 Year Sediment Cleaning of the Fuel Oil Storage Tank and Relocate to Licensee-Controlled Documents2016-07-15015 July 2016 Response to Request for Additional Information for the Proposed Technical Specification Change to Remove the 10 Year Sediment Cleaning of the Fuel Oil Storage Tank and Relocate to Licensee-Controlled Documents L-2016-114, Response to Request for Additional Information Regarding License Amendment Request to Adopt TSTF-505, Provide Risk-Informed Extended Completion Times - RITSTF Initiative 48.2016-07-0808 July 2016 Response to Request for Additional Information Regarding License Amendment Request to Adopt TSTF-505, Provide Risk-Informed Extended Completion Times - RITSTF Initiative 48. L-2016-102, RAI Reply - License Amendment Request, Containment Vacuum Gothic Analyses and Conforming Changes2016-05-0606 May 2016 RAI Reply - License Amendment Request, Containment Vacuum Gothic Analyses and Conforming Changes L-2016-104, RAI Reply - Application for Technical Specification Change Regarding Moderator Temperature Coefficient (Mtc) Surveillance Test Elimination at the End of Cycle2016-05-0606 May 2016 RAI Reply - Application for Technical Specification Change Regarding Moderator Temperature Coefficient (Mtc) Surveillance Test Elimination at the End of Cycle L-2016-096, Inservice Inspection Plan, RAI Reply for Fourth Ten-Year Interval Relief Request No. 10, Revision 02016-04-21021 April 2016 Inservice Inspection Plan, RAI Reply for Fourth Ten-Year Interval Relief Request No. 10, Revision 0 L-2016-084, Response to Request for Additional Information Regarding License Amendment Request for Adoption of Technical Specifications Task Force (TSTF) Traveler TSTF-422, Revision 2, Change in Technical Specifications End States.2016-04-20020 April 2016 Response to Request for Additional Information Regarding License Amendment Request for Adoption of Technical Specifications Task Force (TSTF) Traveler TSTF-422, Revision 2, Change in Technical Specifications End States. L-2016-040, License Renewal Commitments, Reactor Vessel Internals Aging Management Plan, Response to Request for Additional Information2016-02-26026 February 2016 License Renewal Commitments, Reactor Vessel Internals Aging Management Plan, Response to Request for Additional Information 2023-09-11
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Text
AUG 2 1 2019 L-2019-166 10 CFR 50.55a 10 CFR 50.36 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555 Re: St. Lucie Unit 2 Docket No. 50-389 Refueling Outage SL2-24 Steam Generator Tube Inspection Report RAI Response
References:
- 1. FPL Letter L-2019-064 dated March 22, 2019, "Refueling Outage SL2-24 Steam Generator Tube Inspection Report." Adams Accession No. ML19081A146
- 2. NRR E-mail Capture dated July 11, 2019, "Request for Additional Information - St. Lucie Plant, Unit No. 2, Fall 2018 Refueling Outage Steam Generator Tube Inspection Report (EPID L-2019-LR0-0023) ." Adams Accession No. ML19192A137 In reference 1 above, Florida Power & Light Company (FPL) submitted the St. Lucie Unit 2 Technical Specification 6.9.1.12 steam generator tube inspection report for the fall 2018 refueling outage (SL2-24).
During the NRC Staff review of the submittal, they determined that additional information was required in order to complete their review. This request for additional information (RAI) was made in reference 2 above.
FPL's response to the RAI request is contained in the attachment to this correspondence.
Please contact Ken Frehafer at (772) 467-77 48 should you have any questions regarding this submittal.
Sincerely, Wyatt Gades Licensing Manager St. Lucie Plant.
MJS/KWF Attachment cc: USNRC Regional Administrator, Region II USNRC Senior Resident Inspector, St. Lucie Nuclear Plant Florida Power & Light Company 6501 S. Ocean Drive, Jensen Beach, FL 34957
L-2019-166 Attachment Page 1 of 3
Background:
The U.S. Nuclear Regulatory Commission (NRC) staff previously reviewed the licensees spring 2014 SG tube inspection report and provided a summary to the licensee in a letter dated August 19, 2015 (ADAMS Accession No. ML15209A646). The spring 2014 inspections were performed during RFO
- 21. In the summary, the NRC staff noted that the four feedring inspection port covers (two per SG) were found to be loose during the secondary side inspections. The loose covers allowed the feedrings to drain, which created steam voids in the feedrings and resulted in a water hammer event that damaged the feedring supports for both SGs. The feedring supports were repaired during RFO 21 and all four inspection port covers were replaced with welded end caps to prevent loosening.
The licensees fall 2015 SG tube inspection report, dated April 15, 2016 (ADAMS Accession No.
ML16111B235), noted that during inspection of the SG 2B feedring, the inner support brackets were found to be slightly deformed. The new brackets had been installed during RFO 21 and appeared to have been displaced by a pressure transient in the feedring during the subsequent operating cycle. The licensee noted during the inspection that the welds remained intact. The condition was documented in the corrective action program, and the brackets were repaired with support braces/stiffeners. No deficiency was observed with the SG 2A feedring and supports. These inspections and repairs were performed during RFO 22.
In the fall 2018 SG tube inspection report, the licensee stated that the secondary side inspection activities were mainly comprised of a visual inspection of the feedwater ring support system in each SG. The inner support brackets of the SG 2A feedring were found to be slightly deformed from a pressure transient in the feedring during the previous operating cycle. The licensee also stated that this condition was expected for SG 2A, based on monitoring criteria established for this phenomenon, and does not jeopardize SG tube integrity. All welds of the feedring support system were noted to be intact. The as-found condition was documented in the corrective action program, and the brackets were repaired by attaching support braces/stiffeners to them. No deficiency was observed with the SG 2B feedring supports.
Issue:
The cause of the water hammer event that initially damaged the feedring supports for both SGs, was attributed to the loose inspection port covers, which allowed the feedrings to drain. Although repairs were made in RFO 21, additional repairs were required in RFO 22 and RFO 24, due to pressure transients in the SG feedrings.
Request:
- 1. The fall 2018 SG tube inspection report stated, this condition was expected for SG 2A, based on monitoring criteria established for this phenomenon and does not jeopardize SG tube integrity.
Does this statement mean that the feedwater ring support system is designed to deform during pressure transients? Discuss why this does not pose a loose part threat to tube integrity.
L-2019-166 Attachment Page 2 of 3 Response to Request #1:
The feedwater ring support system was designed such that the inner supports (c-brackets) would plastically deform and absorb some of the loading if the loading is above a specified amount, and still maintain the allowable stress limits of the materials including the welds. In the event a loose part is developed due to a pressure transient, the SG is equipped with a fine-mesh, loose-part trapping (debris) screen, designed to preclude loose parts from entering the tube bundle. The screen is designed such that only very small objects such as small wires or small pieces of deposits can pass through. No loose parts from internal components of the SG have ever been identified within the tube bundle (i.e., downstream of the debris screens) during SG secondary-side inspections. For the above reasons, the recent pressure transients were considered to not pose a loose part threat to SG tube integrity.
- 2. Have feedring inspection port cover inspections confirmed the weld repairs to the end caps remain adequate and functioning as designed?
Response to Request #2:
As stated in the NRC summary for the SL2-21 SG Tube Inspection Report (Ref. 1), the SG feedring supports were repaired during RFO 21 and all four inspection port covers were replaced with welded end caps to prevent loosening. No damage or degradation has been identified during each subsequent inspection of the feedwater ring end caps. Inspections have confirmed that the original weld repairs on the end caps remain adequate and functioning as designed, without leakage.
- 3. Has a root cause analysis been performed on the initial water hammer event and the subsequent pressure transients? Is it possible for multiple transients or a larger magnitude transient to cause greater damage than has been experienced, generating loose parts that could challenge tube integrity?
Response to Request #3:
A root cause analysis has been performed on the initial water hammer events which led to repairs in RFO 21 and the subsequent pressure transient in Cycle 21 which led to repairs in RFO 22. The pressure transient in Cycle 23 which led to repairs in RFO 24 was also evaluated in the corrective action program. As noted in previous NRC Integrated Inspection Reports for the St. Lucie Plant (Ref. 2, 3 and 4), the condition report and root cause analysis were reviewed by the NRC inspection team. The inspectors reviewed the evaluations and circumstances associated with the condition evaluated, and verified that corrective actions were planned and/or implemented that are commensurate with the significance of the identified issue.
The largest magnitude transient possible is from an automatic initiation of the auxiliary feedwater actuation system (AFAS) when SG level is below the discharge point of the j-tubes. This type of transient was experienced during the water hammer events of Cycles 21 and 23, and no loose parts
L-2019-166 Attachment Page 3 of 3 were generated from these events based on secondary-side visual inspections in RFO 22 and RFO 24, respectively. If more than one pressure transient is experienced in the SG feedwater ring of St.
Lucie Unit 2 during a cycle, a visual inspection of the feedwater ring and supports (of the affected SG) is required by procedure prior to unit startup to assess potential damage. No loose parts have ever been generated in the current feedwater ring support design. The restrictions placed on unit operation with multiple transients, and the presence of the debris screens provide reasonable assurance that the integrity of the SG tubes is maintained.
References:
- 1. Review of the Spring 2014 Steam Generator Tube Inservice Inspection Report for Refueling Outage 21 (Accession No. ML15209A646).
- 2. St. Lucie Plant - NRC Integrated Inspection Report 05000389/2015001 (Accession No.
ML15126A323)
- 3. St. Lucie Plant - NRC Integrated Inspection Report 05000389/2015002 (Accession No.
ML15216A565)
- 4. St. Lucie Plant - NRC Integrated Inspection Report 05000389/2017001 (Accession No.
ML17129A510)