ML15286A076

Duke Energy Presentation in Support of October 13, 2015, Public Meeting with NRC Staff Pre-Application Meeting for LAR to Support Khu Stator Replacement. (Revised)

ML15286A076
Person / Time
Site:	Oconee
Issue date:	10/13/2015
From:	Duke Energy Carolinas
To:	Division of Operating Reactor Licensing
Whited J
References
Download: ML15286A076 (26)

Text

Oconee Nuclear Station Pre-Application Meeting - October 13, 2015 LAR to Support Keowee Stator Replacement

Duke Participants Doug Phelps, Critical Systems Engineering Director, Oconee Nuclear Station Chris Wasik, Regulatory Affairs Manager, Oconee Nuclear Station Darla King, Keowee Electrical System Lead Engineer, Oconee Nuclear Station Boyd Shingleton, Licensing Lead Engineer for Stator LAR, Oconee Nuclear Station For Information Only 2

Agenda Introduction/Background Chris Wasik Proposed Technical Specification Change Chris Wasik Keowee Outage Timeline Doug Phelps Diverse Backup Power for Emergency Power System Doug Phelps Risk Reduction Measures Doug Phelps For Information Only 3

Introduction Chris Wasik Regulatory Affairs Manager, Oconee Nuclear Station For Information Only 4

Keowee Generator Stator Project Keowee Hydro Station commissioned in 1971 2008 - 2009 preventative maintenance inspections identified aging mechanisms in rotor pole assemblies 2009 Duke Energy started planning efforts to refurbish/overhaul both Keowee generators First phase refurbished/replaced all 56 generator field poles on each KHU

• KHU-2 performed January 2014

• KHU-1 performed July 2014 Second phase is to replace stator for each KHU

• KHU-1 scheduled January 2018

• KHU-2 scheduled January 2019 For Information Only 5

Keowee Generator Stator Project For Information Only 6

Keowee Generator Stator Project Licensing Background NRC approved LAR for one-time extended TS Completion Time to allow KHU rotor pole rewind work on January 8, 2014 ONS plans to request a one-time extended TS Completion Time to allow stator on each KHU to be replaced Similar justification will be provided for stator LAR For Information Only 7

Proposed Technical Specification Change Current TS 3.8.1 C - KHU aligned to the overhead path inoperable

• Cumulative 45 day Completion Time to restore inoperable KHU over a 3 year period The License Amendment Request (LAR) will request a one-time 55 day Completion Time for each KHU to allow stator replacement For Information Only 8

Keowee Generator Stator Project Doug Phelps Critical Systems Engineering Director Oconee Nuclear Station For Information Only 9

Keowee Generator Stator Project Implementation Strategy Original strategy was a standard rewind, estimated to require a 100-120 day Technical Specification (TS) Allowed Outage Time (AOT)

Alternate strategy was developed based on benchmark trip Benchmark plant strategy was to pre-build stator remote to unit Feasibility study was conducted to determine if a pre-build strategy was viable for Keowee Study concluded pre-build stator strategy was feasible and reduces the required TS AOT by ~50%

ONS selected option to pre-build the stator in an assembly building to minimize required TS AOT As a result, the scope of the project expanded to include:

• New Frames

• Stator Assembly Building

• Powerhouse Modifications

• Heavy hauling from the assembly facility to the powerhouse and haul path evaluation For Information Only 10

Keowee Generator Stator Outage Timeline 55 Days - Total Work Window 2 days - Dewater 2 days - Dewater Dual KHU Outage Start Dual KHU Outage Finish 25 days physical work with contingency 24 days physical work, generator restoration & testing with contingency 2 days - Generator Isolation & Prep for Rotor/Stator Lifts For Information Only 11

ONS Electrical Distribution System ELECTRICAL 1 2 ASBURY

( NORTH GREENVILLE)

( CENTRAL) ( CENTRAL) DISTRIBUTION NEWPORT OCONEE CALHOUN KATOMA SOUTH HALL DACUS B W B W B W 230 KV 7C Lee KEOWEE OVERHEAD 525 KV CT RED BUS RED BUS 34 Switchyard 8C 100KV CT AUTO KEOWEE 4 7 10 13 16 19 22 28 31 TRANSFORMER 54 57 60 HYDRO 11 12 2 1 13 9 10 8 11 14 17 20 23 26 55 58 61 OCB 11 12 22. 6 Miles 41 40 Central 4 3 White 4T 5T Central CS Switchyard Gen 2 Gen 1 9 12 15 18 21 24 27 30 33 56 59 90 100 KV OCB YELLOW BUS YELLOW BUS 8. 5 Miles 35 AUXILIARY AUXILIARY Fant W B POWER SYSTEM POWER SYSTEM Black JOCASSEE to B3T to B4T

13. 8 KV UNDERGROUND FEEDER Main Transformer Main Transformer Main Transformer 1T CT1 2T CT2 3T CT3 A B D C Aux Transformer Startup Transformer Aux Transformer Startup Transformer Aux Transformer Startup Transformer 6900 6900 4160 6900 4160 6900 4160 6900 6900 4160 B6T/B7T Main Generator Main Generator Main Generator PSW Unit #1 Unit #2 Unit #3 4160 EMERGENCY STARTUP BUS OCB 101 6900 STARTUP BUS CT4 NORMAL CT5 SOURCE 1TA 1TB 4160 4160 1A1 1B1 1A2 1B2 RCP RCP RCP RCP 2TA 2TB 3TA 3TB STARTUP SOURCE NORMAL SOURCE 2A1 2B1 2A2 2B2 3A1 3B1 3A2 3B2 RCP RCP RCP RCP RCP RCP RCP RCP STARTUP SOURCE SK1 SK2 SL1 SL2 NORMAL SOURCE STARTUP SOURCE STANDBY BUS #1 STANDBY BUS #2 N1 N2 E1 E2 S1 S2 N1 N2 E1 E2 S1 S2 N1 N2 E1 E2 S1 S2 MFB #1 MFB #1 MFB #1 MFB #2 MFB #2 MFB #2 1TC 1TD 1TE B A 2TC 2TD 2TE SSF 3TC 3TD 3TE PSWP OTS1 HPSWP For Information Only 12

ONS Transmission Lines Oconee Nuclear Oconee NuclearStation Station For Information Only 13

Backup Power for Emergency Power System Proposed LAR will credit the following backup power sources:

• Underground Keowee Hydro Unit

• Dedicated Lee Combustion Turbine energizing both Standby Buses during extended completion time

• Remaining LCT available and capable of energizing the Standby Buses within one hour

• Required offsite power sources available

• SSF capable of mitigating SBO for at least 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />

• Two dedicated Jocassee Hydro Units available either of which has capacity of powering ONS shutdown loads in approximately one hour

• Temporary diesel generator at Keowee capable of restoring unwatered Underground KHU within 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />

• PSW power system capable of powering SSF For Information Only 14

Alternate Methods of Maintaining Safe Shutdown The following systems/equipment can be used to maintain all three Oconee units in a safe shutdown condition:

• SSF operable and capable of providing alternate shutdown capability

• PSW System operable and capable of providing alternate shutdown capability

• Turbine Driven Emergency Feedwater Pump capable of feeding steam generators

• FLEX equipment available One or more of the following power sources can be used to place all three Oconee units in cold shutdown:

• One LCT energizing ONS standby buses prior to outage start

• Underground KHU

• A second LCT can be started and aligned to the standby buses within one hour

• Two Jocassee Hydro Units available, either of which can be aligned to the Oconee 230kV Yellow Bus in approximately one hour

• Any of multiple offsite power sources For Information Only 15

Lee Combustion Turbines Two LCTs (7C, 8C) available to power Oconee standby buses Dedicated line electrically separated from the system grid and offsite loads Capacity to supply ONS shutdown loads Routinely operated/tested, demonstrating reliability Black start capable, tested annually Included in the ONS Normal and Emergency Operating Procedures Verified available each shift Staffed continuously For Information Only 16

Lee Combustion Turbines For Information Only 17

Jocassee Hydro Station Two of the four Jocassee Hydro Units can be separated from the grid and dedicated to ONS in approximately one hour Each Jocassee Hydro Station unit is rated at 195 MVA Two transmission lines, north of ONS, directly connect the Jocassee 230 kV switchyard to the Oconee 230 kV switchyard Capacity to supply ONS shutdown loads Routinely operated/tested, demonstrating reliability Black start capable, tested annually Included in the ONS Emergency Operating Procedures Verified available each shift Staffed continuously For Information Only 18

Jocassee Hydro Station For Information Only 19

Temporary DG located at Keowee for restoring U/G KHU Onsite DG supplies backup power to KHS during dual KHU outage when unwatered Adequate capacity to restore the underground KHU Allows for rapid restoration of the underground KHU during loss of all power ( 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />)

Black start capable Use approved Keowee operating procedures Operated and tested prior to outage Verified available each shift Keowee Hydro Station continuously staffed For Information Only 20

Standby Shutdown Facility and Protected Service Water System Standby Shutdown Facility Provides an alternate means to achieve and maintain the ONS units in safe shutdown conditions Provides additional defense in depth protection by serving as a backup to existing safety systems Includes a dedicated power system including a diesel generator Credited to mitigate Station Blackout, and other non design basis events Mission time is 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> Staffed continuously during dual KHU outages when unwatered Protected Service Water Provides an alternate means to achieve and maintain the ONS units in safe shutdown conditions Provides additional defense in depth protection by serving as a backup to existing safety systems Alternate power path to connect the SSF switchgear, with sufficient capacity to operate SSF equipment in the event of a failure of the SSF diesel generator For Information Only 21

Defense-in-Depth - Multiple Diverse Backup Power Sources Keowee Outage Timeline 55 Days - Total Work Window 2 days - Generator Isolation & Prep for Rotor/Stator Lifts Start 2 days - Dewater Finish Dual KHU Outage 2 days - Dewater Dual KHU Outage 25 days physical work 24 days physical work, generator restoration & testing 9 offsite power sources available Underground (U/G) KHU 1 Lee CT running and energizing Standby Buses nd 2 Lee CT in Standby available within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> SSF Operable (including SSF DG)

Two Jocassee Hydro Units available within ~ 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> Temporary Diesel Generator at Keowee for restoring KHU associated U/G Path PSW Power System available* and capable of providing power to the SSF FLEX equipment available

• commercial power feed during dual KHU outage, Keowee or commercial power feed during single KHU outage existing additional For Information Only 22

Risk Reduction Measures - Regulatory Commitments Duke Energy will commit to the following:

ONS will not start the extended single KHU outage or a dual KHU outage if severe weather conditions are forecast within the next two days.

ONS will contact the system load dispatcher once per day to ensure no significant grid perturbations (high grid loading not able to withstand a single contingency of line or generation outage) are expected during extended TS completion time.

ONS will avoid component testing or maintenance of safety systems and important non safety equipment in the offsite power systems that can increase the likelihood of a plant transient (unit trip) or LOOP. In addition, no discretionary switchyard maintenance will be performed.

ONS will verify that TS required systems, subsystems, trains, components, and devices that depend on the remaining power sources are operable and preclude subsequent nondiscretionary testing or maintenance activities on these systems, subsystems, trains, components, and devices during the extended TS completion time.

ONS will control the steam-driven emergency feedwater pump(s) as protected equipment during the extended TS completion time.

ONS will continuously staff the SSF during the dual KHU outages in which the intake is de-watered.

For Information Only 23

Other Risk Reduction Measures Critical Activity Plan, approved by the Plant Operations Review Committee prior to implementation, used for risk management. Plan will include the following risk reduction measures:

LCT and Central Switchyard protected 2nd LCT protected and available within one hour Two Jocassee Hydro Units available either of which can be aligned to the Oconee 230kV Yellow Bus in approximately one hour Temporary DG located at Keowee Hydro Station with capability to restore available KHU unit to operable status within 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> from dual KHU outage Reduced RCS Inventory not permitted during dual KHU outage PSW available to backup SSF FLEX equipment available For Information Only 24

Summary Stator replacement is needed and will improve equipment reliability for emergency power system

• Stator replacement outages scheduled for January 2018 and January 2019 Additional diverse backup power sources result in electrical system defense-in-depth that provides level of protection equivalent with Branch Technical Position guidelines Additional risk reduction measures will be implemented and managed by critical activity plan Staff approval of LAR is essential to allow Duke Energy to implement KHU reliability improvements For Information Only 25

26