RA-20-0177, Supplement to H.B. Robinson Steam Electric Plant, Unit No. 2, Seismic Probabilistic Risk Assessment (SPRA) Submittal - Site Actions
| ML20171A761 | |
| Person / Time | |
|---|---|
| Site: | Robinson  |
| Issue date: | 06/19/2020 |
| From: | Kapopoulos E Duke Energy Progress |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| RA-20-0177 | |
| Download: ML20171A761 (13) | |
Text
Ernest J. Kapopoulos, Jr.
H. B. Robinson Steam Electric Plant Unit 2 Site Vice President Duke Energy 3581 West Entrance Road Hartsville, SC 29550 o: 843.951.1701 f: 843.951.1319 Emie.Kapopoulos@duke-energy.com Serial: RA-20-0177 June 19, 2020 10 CFR 50.4 10 CFR 50.54(f)
U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 H. B. Robinson Steam Electric Plant, Unit No. 2 Docket Number 50-261 Renewed Facility Operating License No. DPR-23
Subject:
Supplement to H.B. Robinson Steam Electric Plant, Unit No. 2, Seismic Probabilistic Risk Assessment (SPRA) Submittal - Site Actions
Reference:
Duke Energy Letter, H.B. Robinson Steam Electric Plant, Unit No. 2 - Seismic Probabilistic Risk Assessment (SPRA), Response to March 12, 2012, Request for Information Regarding Recommendation 2.1: Seismic, of the Near-Term Task Force Related to the Fukushima Dai-ichi Nuclear Power Plant Accident, dated December 12, 2019 Ladies and Gentlemen:
In a letter dated December 12, 2019 (i.e., Reference), Duke Energy Progress, LLC (Duke Energy), provided the seismic probabilistic risk assessment (SPRA) associated with the seismic hazard reevaluation for H. B. Robinson Steam Electric Plant, Unit No. 2 (HBRSEP). The submittal included a discussion of a planned plant modification to provide additional protection from re-evaluated seismic hazards.
The purpose of this submittal is to provide supplemental information associated with the planned modification and describe other actions, completed or planned, to reduce seismic risk.
The supplemental information, provided in Enclosure 1 to this letter, addresses mitigating strategies, training, procedure changes, interim measures, and plant modifications. The permanent plant modifications PM1 and PM4 in Enclosure 1 implement the planned action described in Table 6-1 in the referenced letter. Enclosure 2 contains the actions from Enclosure 1 to which HBRSEP has committed. HBRSEP will ensure that operator actions associated with the permanent plant modifications are validated in accordance with NEI 12-06, Appendix E, Revision 2, Diverse and Flexible Coping Strategies (FLEX) Implementation Guide.
Please address any comments or questions regarding this matter to Mr. Art Zaremba, Director - Nuclear Fleet Licensing, at (980) 373-2062.
U.S. Nuclear Regulatory Commission Page 2 of 2 I declare, under penalty of perjury, that the foregoing is true and correct.
Executed on iCf Svt N , 2020.
Sincerely, Ernest J. Kapopoulos, Jr.
Site Vice President LJG/ljg
Enclosures:
- 1. H. B. Robinson SPRA Supplement, Site Actions
- 2. H. B. Robinson Steam Electric Plant (HBRSEP), Unit No. 2, Seismic Probabilistic Risk Assessment - Regulatory Commitments cc: Ms. L. Dudes, USNRC Regional Administrator, Region II Mr. M. Fannon, USNRC Sr. Resident Inspector - HBRSEP Ms. T. Hood, USNRC NRA Project Manager - HBRSEP
Enclosure 1 H. B. Robinson Steam Electric Plant (HBRSEP), Unit No. 2 H. B. Robinson SPRA Supplement Site Actions
RA-20-0177 Enclosure 1 Page 1 of 7 H. B. Robinson SPRA Supplement Site Actions Action Description Scheduled Risk Benefit in Completion SCDF/SLERF Date (Approximate)
Mitigating Strategies
[Note: MS1 through MS10 are Pre-Existing Strategies]
MS1: Mitigating Strategy - S/G Feedwater High benefit action, Complete with adequate water Extreme Damage Mitigation Guideline EDMG-004, sources supplied within Steam Generators (S/G), provides guidance to the one hour (approx.)
inject alternate water supply into one or more time line. Sensitivity depressurized S/G for core cooling. Alternate water provides approximately supply is provided by EDMG-010, Emergency Diesel 3.7E-5 and 6.1E-6 Make-Up Pump (EDMP) Setup and Operation.
reductions for seismic core damage frequency (SCDF) and seismic large early release frequency (SLERF), respectively.
MS2: Mitigating Strategy - Flooding Containment Less than 5% SLERF Complete reduction expected as Extreme Damage Mitigation Guideline EDMG-005, the chance of Containment Vessel (CV), provides guidance to scrubbing increases for inject alternate water supply into the CV. Alternate non-bypass water supply is provided by EDMG-010, Emergency sequences.
Diesel Make-Up Pump (EDMP) Setup and Operation.
MS3: Mitigating Strategy - Alternate Water Supply Facilitates post-event Complete operator and Extreme Damage Mitigation Guideline EDMG-010, emergency response Emergency Diesel Make-Up Pump (EDMP) Setup organization (ERO) and Operation, provides guidance for accessing responses.
alternate makeup or spray water from the Refueling Water Storage Tank (RWST), Firewater System, FLEX Tanks, Lake Robinson, or the Discharge Canal, if available.
RA-20-0177 Enclosure 1 Page 2 of 7 Action Description Scheduled Risk Benefit in Completion SCDF/SLERF Date (Approximate)
MS4: Mitigating Strategy - RCS Makeup Defense in depth and a Complete small risk reduction for Extreme Damage Mitigation Guideline EDMG-012, slow progression Core Cooling Using Alternate Water Source, accident sequences provides guidance to inject alternate water supply that require RCS into the depressurized Reactor Coolant System makeup such as very (RCS) for core cooling. Alternate water supply is small loss-of-coolant provided by EDMG-010, Emergency Diesel Make-accident (VSLOCA).
Up Pump (EDMP) Setup and Operation.
Less than 1% SCDF and SLERF reductions are expected.
MS5: Mitigating Strategy - RCS Boration Defense in depth for Complete slow progression Extreme Damage Mitigation Guideline EDMG-014, accident sequences Alternate RCS Boration, provides guidance to inject that require RCS borated alternate water supply to the depressurized makeup such as RCS. Alternate water supply is provided by the FLEX VSLOCA. Less than Fire Pump or EDMG-010, Emergency Diesel Make-1% SCDF and SLERF Up Pump (EDMP) Setup and Operation.
reductions are expected.
MS6: Mitigating Strategy - RCS Makeup Defense in depth for Complete slow progression Flex Support Guideline FSG-001, Long Term RCS accident sequences Inventory Control, provides guidance to restore RCS that require RCS inventory using a primary or alternate makeup water makeup such as source. Alternate makeup sources include the VSLOCA. Less than RWST, Spent Fuel Pool (SFP), Lake Robinson, or 1% SCDF and SLERF the Discharge Canal.
reductions are expected.
MS7: Mitigating Strategy - S/G Feedwater High risk benefit action Complete assuming the action Flex Support Guideline FSG-003, Alternate can be implemented Feedwater, provides guidance to inject alternate within one hour and water supply into one or more S/G (pressurized or there is a reliable water depressurized) for core cooling. Alternate water source. Sensitivity sources include the Condensate Storage Tank provides approximately (CST), FLEX Tanks, Condensate Inlet Waterbox, 3.7E-5 and 6.1E-6 Deepwell Pump D, Lake Robinson, or the Discharge reductions for SCDF Canal, if available.
and SLERF, respectively.
RA-20-0177 Enclosure 1 Page 3 of 7 Action Description Scheduled Risk Benefit in Completion SCDF/SLERF Date (Approximate)
MS8: Mitigating Strategy - Initial Assessment This action is for the Complete use of alternate water Flex Support Guideline FSG-005, Initial Assessment supplies to support and FLEX Equipment Staging, provides guidance for MS1 and MS2 actions the initial assessment of plant equipment and system and the associated risk status. The assessment of available water sources benefit.
includes the RWST, CST, SFP, Service Water System, FLEX Tanks, Condensate Inlet Waterbox, Deepwell Pump D, Lake Robinson, and the Discharge Canal.
MS9: Mitigating Strategy - RCS Boration Defense in depth for Complete slow progression FLEX Support Guideline FSG-008, Alternate RCS accident sequences Boration, provides guidance to inject borated water that require RCS into the RCS. Alternate makeup sources include the makeup such as RWST, Lake Robinson, or the Discharge Canal.
VSLOCA. Less than 1% SCDF and SLERF reductions are expected.
MS10: Mitigating Strategy - Cooling Containment Defense in depth to Complete reduce containment FLEX Support Guideline FSG-012, Alternate pressure for non-Containment Cooling, provides guidance for cooling bypass accident the CV using external water spray, internal water sequences. Less than spray, or recirculating fan cooling. Alternate water 5% SLERF reduction sources include fire tankers from the local fire expected.
department, and fire water per EDMG-005.
Procedures and Training P1: Procedures - Mitigating Strategy Review Improves success of August 13, 2020 operator and ERO Select Operations and ERO personnel to conduct a responses.
strategy review meeting (e.g., table top exercise) of relevant EDMG and FSG procedures, to identify additional enhancements for extreme seismic events.
P2: Procedures - Revisions Improves success of October 29, 2020 operator and ERO Following strategy review meeting detailed in action responses.
P1 above, update relevant EDMG and/or FSG procedures to provide additional guidance for potential loss of capability due to extreme seismic events.
RA-20-0177 Enclosure 1 Page 4 of 7 Action Description Scheduled Risk Benefit in Completion SCDF/SLERF Date (Approximate)
T1: Training Improves success of Complete operator response.
Provide training to Operations personnel on seismic probabilistic risk assessment (SPRA) results and plant impacts.
T2: Training Improves success of Complete mitigation strategies.
Provide training to ERO personnel on SPRA results and plant impacts.
Plant Modifications PM/I1: Plant Modification - Interim Measure Defense in depth June 26, 2020 action and could be Hose will be pre-staged to connect Deepwell Pumps significant depending A, B and C to the suction of the existing FLEX upon sequences of Auxiliary Feedwater (AFW) pumps, or for use with events with other other mitigation strategies.
systems and buildings This interim measure will address the liquefaction which impact timing.
failure mode of supply from Deepwell Pumps, A, B Sensitivity provides and C. This interim measure also provides alternate approximately 3.7E-5 sources of cooling water to mitigate a postulated loss and 6.1E-6 reductions of the Ultimate Heat Sink (UHS). for SCDF and SLERF, respectively.
This interim measure will remain in place until implementation of the permanent plant modification to install sections of piping or hose is complete (i.e.,
permanent plant modification PM3).
PM/I2: Plant Modification - Interim Measure Defense in depth with August 27, 2020 an immediate water Structural supports will be added to the existing tanks source for the more which supply cooling water to the FLEX AFW pumps.
frequent low to medium This interim measure will add structural supports to seismic events. Less reduce the failure probability due to seismic uplift and than 5% SCDF and overturning of the tanks. SLERF reductions are expected.
This interim measure will remain in place until installation of new Deepwell Pump E is complete (i.e.,
permanent plant modification PM4).
RA-20-0177 Enclosure 1 Page 5 of 7 Action Description Scheduled Risk Benefit in Completion SCDF/SLERF Date (Approximate)
PM/I3: Plant Modification - Interim Measure High SCDF and September 30, SLERF impact, when The existing pre-staged discharge hose from the 2020 combined with PM2, FLEX AFW pumps will be reconfigured to include a PM3, and PM4 branch which routes to the existing FLEX AFW (Deepwell Pump E) or connection (AFW-165) located inside the Motor-if the existing deepwell Driven AFW Pump Room. The current configuration pumps can be aligned connects to the FLEX AFW connection near the with the FLEX AFW Steam-Driven AFW Pump (AFW-166). The new pump as an initial configuration will feature isolation of the two branches cooling water source.
such that the branch which connects to AFW-165 will A sensitivity for the not be vulnerable to a potential failure of the Turbine combined case of PM1 Building Class III structure. Hose sections will be pre-through PM4 provides staged near AFW-165 assembly post-event.
approximately 5.6E-5 This interim measure will remain in place until and 7.2E-6 reductions implementation of Plant Modification PM1 is for SCDF and SLERF, complete. respectively.
PM1: Plant Modification - Permanent High SCDF and July 30, 2021 SLERF impact, when The existing pre-staged discharge hose from the combined with PM2, FLEX AFW pumps will be reconfigured to include a PM3, and PM4 branch which routes to the existing FLEX AFW (Deepwell Pump E) or connection (AFW-165) located inside the Motor-if the existing deepwell Driven AFW Pump Room. The current configuration pumps can be aligned connects to the FLEX AFW connection near the with the FLEX AFW Steam-Driven AFW Pump (AFW-166). The new pump as an initial configuration will feature isolation of the two branches cooling water source.
such that the branch which connects to AFW-165 will A sensitivity for the not be vulnerable to a potential failure of the Turbine combined case of PM1 Building Class III structure.
through PM4 provides This modification provides an AFW flow path that is approximately 5.6E-5 not vulnerable to seismic failure of the Turbine and 7.2E-6 reductions Building Class III structure, and adds redundancy to for SCDF and SLERF, the current pre-staged FLEX AFW strategy. respectively.
RA-20-0177 Enclosure 1 Page 6 of 7 Action Description Scheduled Risk Benefit in Completion SCDF/SLERF Date (Approximate)
PM2: Plant Modification - Permanent Defense in depth as an May 29, 2021 alternate long-term For the existing Deepwell Pumps A, B and C, cooling water source.
isolation valves, hose connections and pipe will be A sensitivity for the installed to protect the above ground portion of the combined case of PM1 piping from the seismic event.
through PM4 provides This modification will address the liquefaction failure approximately 5.6E-5 mode of supply from Deepwell Pumps, A, B and C. and 7.2E-6 reductions This modification also provides alternate sources of for SCDF and SLERF, cooling water to mitigate a postulated loss of the respectively.
PM3: Plant Modification - Permanent Defense in depth as an June 30, 2021 alternate long-term For the existing Deepwell Pumps A, B and C, hose cooling water source.
and/or pipe will be routed from each pump to the A sensitivity for the suction header for the existing FLEX AFW pumps.
combined case of PM1 The shortest and most seismically preferable routes through PM4 provides will be utilized, as best possible. For high traffic approximately 5.6E-5 areas, hose will be permanently staged in lieu of and 7.2E-6 reductions permanent installation. To mitigate probable damage, for SCDF and SLERF, the routes will include sections to allow for easy respectively.
disassembly and connection of new sections.
This modification supplements permanent plant modification PM2 above, to provide alternate sources of cooling water to mitigate a postulated loss of UHS.
RA-20-0177 Enclosure 1 Page 7 of 7 Action Description Scheduled Risk Benefit in Completion SCDF/SLERF Date (Approximate)
PM4: Plant Modification - Permanent High SCDF and December 31, SLERF improvement, Install a new Deepwell Pump E to provide suction 2021 when combined with directly to the existing FLEX AFW pumps. The PM1, PM2, and PM3.
construction of the new deepwell pump will include A sensitivity for the similar seismically rugged features as existing combined case of PM1 Deepwell Pump D. The new Deepwell Pump E and through PM4 provides appurtenances will be located, or otherwise approximately 5.6E-5 protected, to prevent adverse seismic impact from and 7.2E-6 reductions other structures or equipment. The new deepwell for SCDF and SLERF, pump will be located and configured to support time respectively.
sensitive operator actions per the guidance of NEI 12-06, Revision 2, Diverse and Flexible Coping Strategies (FLEX) Implementation Guide. Power for the new deepwell pump will be provided by normal AC power, and a new diesel generator, similar to existing Deepwell Pumps A, B and C.
This modification will address the high failure probability of the existing tanks which provide suction to the FLEX AFW pumps. This modification also provides an alternate source of cooling water to mitigate a postulated loss of UHS.
Enclosure 2 H. B. Robinson Steam Electric Plant (HBRSEP), Unit No. 2 Seismic Probabilistic Risk Assessment Regulatory Commitments
RA-20-0177 Enclosure 2 Page 1 of 2 List of Regulatory Commitments The following table identifies the actions from Enclosure 1 to which the H. B. Robinson Steam Electric Plant, Unit No. 2 (HBRSEP), has committed. Other site actions in this submittal, with the exception of those listed in the table below, are provided for information purposes and are not considered commitments. Please direct any questions regarding these commitments to Mr. Art Zaremba, Director - Nuclear Fleet Licensing, at (980) 373-2062.
Commitment Description Scheduled Completion Date PM1: Plant Modification - Permanent July 30, 2021 The existing pre-staged discharge hose from the FLEX AFW pumps will be reconfigured to include a branch which routes to the existing FLEX AFW connection (AFW-165) located inside the Motor-Driven AFW Pump Room. The current configuration connects to the FLEX AFW connection near the Steam-Driven AFW Pump (AFW-166). The new configuration will feature isolation of the two branches such that the branch which connects to AFW-165 will not be vulnerable to a potential failure of the Turbine Building Class III structure.
PM2: Plant Modification - Permanent May 29, 2021 For the existing Deepwell Pumps A, B and C, isolation valves, hose connections and pipe will be installed to protect the above ground portion of the piping from the seismic event.
PM3: Plant Modification - Permanent June 30, 2021 For the existing Deepwell Pumps A, B and C, hose and/or pipe will be routed from each pump to the suction header for the existing FLEX AFW pumps. The shortest and most seismically preferable routes will be utilized, as best possible. For high traffic areas, hose will be permanently staged in lieu of permanent installation. To mitigate probable damage, the routes will include sections to allow for easy disassembly and connection of new sections.
PM4: Plant Modification - Permanent December 31, 2021 Install a new Deepwell Pump E to provide suction directly to the existing FLEX AFW pumps. The construction of the new deepwell pump will include similar seismically rugged features as existing Deepwell Pump D.
The new Deepwell Pump E and appurtenances will be located, or otherwise protected, to prevent adverse seismic impact from other structures or equipment. The new deepwell pump will be located and configured to support time sensitive operator actions per the guidance of NEI 12-06, Revision 2, Diverse and Flexible Coping Strategies (FLEX)
Implementation Guide. Power for the new deepwell pump will be provided by normal AC power, and a new diesel generator, similar to existing Deepwell Pumps A, B and C.
RA-20-0177 Enclosure 2 Page 2 of 2 Commitment Description Scheduled Completion Date Submit a letter to the U.S. Nuclear Regulatory Commission (NRC) January 31, 2022 providing notification that implementation of the four permanent plant modifications (i.e., PM1, PM2, PM3, and PM4) have been completed.