Oconee Nuclear Station - Nuclear Regulatory Commission · Jocassee Hydro Station Two of the four Jocassee Hydro Units can be separated from the grid and dedicated to ONS in approximately

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


Introduction

Chris Wasik

Regulatory Affairs Manager, Oconee Nuclear Station


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

5 For Information Only




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


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



Doug Phelps

Critical Systems Engineering Director Oconee Nuclear Station




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

Keowee Generator Stator Outage Timeline


Start Finish

55 Days – Total Work Window

2 days - Dewater Dual KHU Outage

24 days physical work, generator restoration & testing with contingency 25 days physical work with contingency


2 days - Generator Isolation & Prep for Rotor/Stator Lifts

ONS Electrical Distribution System


2 1

4 3

4 7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

26

27

28 31

33

54

55

56

57

58

59

60

61

4T

KEOWEEHYDRO

Gen 2 Gen 1

40

AUXILIARY POWER SYSTEM

to B4T

1T CT1

6900

Main Generator Unit #1

6900 4160

NORMAL SOURCE

STARTUP SOURCE

2TA 2TB

2T CT2

6900 4160


6900 4160

NORMAL SOURCE

STARTUP SOURCE

3TA 3TB

3TC 3TD 3TE

3T CT3

6900


6900 4160

NORMALSOURCE

STARTUP SOURCE

N1 N2 E1 E2 S1 S2

AUXILIARY POWER SYSTEM

to B3T

MFB #1MFB #2

MFB #1MFB #2

CT4

4160

CS 90

CT5

4160

22. 6 MilesCentral White

SK1 SK2

AUTOTRANSFORMER

5T

STANDBY BUS #1STANDBY BUS #2

KEOWEE OVERHEAD

KATOMA

ASBURY NEWPORT

SOUTH HALL

525 KVRED BUS

YELLOW BUS

RED BUS

YELLOW BUS

230 KV

(NORTHGREENVILLE)

DACUS

( CENTRAL)OCONEE

( CENTRAL)CALHOUN

JOCASSEE

13. 8 KV UNDERGROUND FEEDER

4160 EMERGENCY STARTUP BUS

6900 STARTUP BUS

ELECTRICAL DISTRIBUTION

B W WB WB

W B

Aux Transformer Aux Transformer Aux Transformer

Main Transformer Main Transformer Main Transformer

Startup Transformer Startup Transformer Startup Transformer

1TC 1TD 1TE

N1 N2 E1 E2 S1 S2

2TC 2TD 2TE

N1 N2 E1 E2 S1 S2

MFB #1MFB #2

AHP

SWP

BPS

WP

SSFOTS1

30

1TA 1TB

1A1RCP

1B1RCP

1A2RCP

1B2RCP

2A1RCP

2B1RCP

2A2RCP

2B2RCP

3A1RCP

3B2RCP

3A2RCP

3B1RCP

OCB 41

OCB 101

Central Switchyard

100 KV

1

11

7CCT

8CCT

2

12

34

13

Lee Switchyard

100KV

8. 5 MilesFant

Black

OCB 35

SL1 SL2

A B D C

9 10

11 12

B6T/B7T

PSW

ONS Transmission Lines


Oconee Nuclear Station Oconee

Nuclear Station

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 hours • 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

hours • PSW power system capable of powering SSF


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


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


Lee Combustion Turbines


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


Jocassee Hydro Station


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

hours) Black start capable Use approved Keowee operating procedures Operated and tested prior to outage Verified available each shift Keowee Hydro Station continuously staffed


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 hours 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


Defense-in-Depth – Multiple Diverse Backup Power Sources


Start Finish

Keowee Outage Timeline

55 Days – Total Work Window


FLEX equipment available

SSF Operable (including SSF DG)

1 Lee CT running and energizing Standby Buses

2nd Lee CT in Standby available within 1 hour

9 offsite power sources available

Two Jocassee Hydro Units available within ~ 1 hour

25 days physical work


Underground (U/G) KHU

existing additional

2 days - Generator Isolation & Prep for Rotor/Stator Lifts

24 days physical work, generator restoration & testing

Temporary Diesel Generator at Keowee for restoring KHU associated U/G Path

PSW Power System available* and capable of providing power to the SSF

*commercial power feed during dual KHU outage, Keowee or commercial power feed during single KHU outage

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.


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 hours from dual KHU outage Reduced RCS Inventory not permitted during dual KHU outage PSW available to backup SSF FLEX equipment available


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


26

Documents

Oconee Nuclear Station - Nuclear Regulatory Commission · Jocassee Hydro Station Two of the four Jocassee Hydro Units can be separated from the grid and dedicated to ONS in approximately