ML17032A347
| ML17032A347 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 01/30/2017 |
| From: | Teresa Ray Duke Energy Carolinas |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| Download: ML17032A347 (15) | |
Text
~~DUKE
~ ENERGY Thomas D. Ray Vice President Ocon13e Nuclear Station Duke Energy ON01VP I 7800 Rochester Hwy Seneca, SC 29672 o: 864.873.3274 ONS-2017-007 10 CFR 50.90 f. 864.873.4208 Tom.Ray@duke-energy:com January 30, 2017 ATTN: Document Control Desk U. S. Nuclear Regulatory Commission 11555 Rockville Pike
- Rockville, Maryland 20852
Subject:
Duke Energy Carolinas, LLC Oconee Nuclear Station (ONS)
Docket Numbers 50-269, 50-270, and 50-287 Additional Information Regarding License Amendment Request for Temporary Completion Time for One Keowee Hydro Unit Inoperable for Generator Stator Replacement License Amendment Request No. 2015-08, Supplement 1 On February 26, 2016, Duke Energy Carolinas, LLC (Duke Energy) submitted a License Amendment Request (LAR) requesting the Nuclear Regulatory Commission (NRC) approve a Technical Specification (TS) change that adds a temporary Completion Time to TS 3.8.1 Required Action C.2.2.5 to allow time to perform major maintenance on each Keowee Hydro Unit (KHU). By email dated December 21, 2016, the NRC requested Duke Energy submit additional information associated with the LAR. The enclosure provides the requested information.
Inquiries on this proposed amendment request should be directed to Boyd Shingleton, ONS Regulatory Affairs Group, at (864) 873-4716.
I declare under penalty of perjury that the foregoing is true and correct. Executed on January 30, 2017.
Sincerely, .
6'1c!it Vice President Oconee Nuclear Station
Enclosure:
Duke Energy Response to NRC Request for Additional Information**
License Amendment Request No. 2015-08 Page2 Supplement 1 January 30, 2017 cc w/enclosure:
Ms. Catherine Haney, Administrator, Region II U.S. Nuclear Regulatory Commission Marquis One Tower 245 Peachtree Center Ave., NE, Suite 1200 Atlanta, GA 30303-1257 Mr. James R. Hall, Senior Project Manager (by electronic mail only)
Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Mail Stop 0-8G9A 11555 Rockville Pike Rockville, Maryland 20852 Mr. Eddy Crowe NRC Senior Resident Inspector*
Oconee Nuclear Station Ms. Susan E. Jenkins, Manager, (by electronic mail only: jenkinse@dhec.sc.gov)
Infectious and Radioactive Waste Management, Bureau of Land and Waste Management Department of Health & Environmental Control 2600 Bull Street
- Columbia, SC 29201
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ENCLOSURE Duke Energy Response to NRC Request for Additional Information (RAI)
Enclosure - Duke Energy Response to NRC RAI Page 1 License Amendment Request No. 2015-08, Supplement 1 January 30, 2017
RAI 1
An off-site power system (preferred power) and an onsite power system (KHUs) are provided for each ONS unit to supply power to the unit auxiliaries during normal operation, and to the Reactor Protective System and Engineered Safeguards (ES) Protective System during abnormal and accident conditions. Each ONS unit has multiple available sources of electrical power to the ES Protective System. These include each unit's Main Generator to Auxiliary Transformer (designated as 1T, 2T, and 3T, for Units 1, 2, and 3, respectively), multiple offsite sources to the 230kV Switchyard yellow bus to each unit's Startup Transformer (designated as CT1, CT2, and CT3, for Units 1, 2, and 3, respectively), the Keowee Overhead Power Path to the 230kV Switchyard yellow bus, and the Keowee Underground Power Path through transformer CT-4 to the redundant standby power buses.
In light of the March 6, 2016, main transformer MT1 failure, which lead to the unavailability of the Keowee overhead emergency power path, please provide the following information in order for the staff to better understand the reliability of the ONS power transformers and alternate sources:
A. Confirm and explain how all power transformers, including overhead lines and connections, used for onsite and offsite power systems will be inspected and tested prior (i.e., 3-6 months) to the planned KHU outages in accordance with applicable industry standards.
- 8. Provide a brief summary of the most recent test results, including preventive maintenance and condition monitoring actions, and surveillances performed to demonstrate that the power sources are reliable and operable.
Response to RAI 1 Power Transformers Oconee performs routine inspections on all of its large power transformers to ensure proper continuous operation. These tasks are performed in accordance with the Duke Energy nuclear fleet preventative maintenance (PM) guidelines. These tasks include:
- Manual oil sampling for dissolved gas analysis every 3 months,
- Thermographic scans every 6 months (with the exception of *cTS performed every 2 years), *
- Electrical (Doble) testing every 2-4 years,
- Oil pump vibration testing every 2 years, and
- PM inspections every 2 years to include (overall visual inspection, bushing inspections, and ancillary device inspections).
Table 1-1 below outlines the last date these PMs were performed on each transformer and the next scheduled date for the PM. **
- Overhead Lines and Connections .
Overhead lines and connections to Oconee's large power transformers are inspected at routine intervals to ensure integrity. T~e task includes the inspection of overhead buslines from the
Enclosure - Duke Energy Response to NRC RAI Page2 License Amendment Request No. 2015-08, Supplement 1 January 30, 2017 switchyard to the transformer yard. This inspection has historically been performed on a 6-year frequency. Due to the CT3 open-phase event that occurred in December of 2015 (Reference Oconee Licensee Event Report (LER) 287/2015-002 dated February 5, 2016, ADAMS Accession Number ML16041A170), detailed inspections were performed on the startup transformers, Keowee main step-up transformer, and Lee Steam Station power path transformer CT5 in the first quarter of 2016 to ensure no other issues were present.
As a result of the Oconee open phase event, the visual inspection frequency of the startup transformer buslines is being increased from 6 years to 2 years (inspections every outage).
Duke Energy plans to complete these inspections prior to the first Keowee stator outage with the main transformer buslines and startup transformer buslines inspections being performed in the upcoming outages for each Oconee unit. This means that the overhead lines for each of the startup and main transformers will have a detailed visual inspection during their respective outages prior to the first Keowee Stator outage. Performing the inspections during outages allows additional views of the buslines and connections because the lines are de-energized.
Additionally, the connections at the transformer (CT5) for the Lee Steam Station power path will be inspected during a scheduled PM of the transformer in 2018.
In addition to the detailed visual inspections, the following maintenance and monitoring actions are routinely performed:
- 1) Thermography scans are performed on a 6-month frequency in the transformer yard and the 230/525kV switchyards.
- 2)
- Operator rounds are performed daily in the transformer yard and the 230/525kV switchyards. The rounds procedure instructs the operator to verify that there are no failed connections or insulators.
- 3) Maintenance performs monthly switchyard/transformer rounds. This walkdown of the transformer yards and switchyards includes general equipment inspections where signs of degradation are noted and addressed.
The latest PM results and next scheduled date can be found in Table 1-2.
Enclosure - Duke Energy Response to NRG RAI Page 3 License Amendment Request No. 2015-08, Supplement 1 January 30, 2017 Table 1-1: Transformer PM Summary Latest Completion Transformer PM Activity Results Summary Next Scheduled Date Date Thermography Scan 11/30/2016 All results satisfactory December 2018 Oil Testing 12/7/2016 Newly identified Ethane gas level December 2018 Vibration Testing 9/26/2016 All results satisfactory 9/27/2018 Unit 1_Main HV Bushings-Fall 2018 Doble Testing 11/07/2016 All results satisfactory Transformer - Fall 2020 2 broken standoff lightning arrester insulators Routine Transformer 11/07/2016 replaced. All fans replaced and minor oil Fall 2018 PM leaks repaired.
Thermography Scan 11/30/2016 All results satisfactory December 2018 Oil Testing 12/7/2016 All results satisfactory December 2018 1TAux Doble Testing 3/06/2016 All results satisfactory N/A- Next Scheduled_ Fall 2020 Routine Transformer Swapover circuit timing out of sequence. Timing 11/6/2016 Fall 2018 PM corrected. All other results satisfactory.
Thermography Scan 11/30/2016 All results satisfactory December 2018 Oil Testing 12/7/2016 All results satisfactory December 2018 CT1 Startup HV Bushings-Fall 2018 Doble Testing 3/18/2016 All results satisfactory Transformer - Fall 2020 Routine Transformer Chips on lightning arrester sealed to prevent moisture 3/18/2016 Fall 2018 PM ingress. All other results satisfactory.
Enclosure - Duke Energy Response to NRC RAI Page 4 License Amendment Request No. 2015-08, Supplement 1 January 30, 2017 Latest Completion Transformer PM Activity Results Summary Next Scheduled Date Date Thermography Scan 11/30/2016 All results satisfactory ' December 2018 Oil Testing 12/7/2016 All results satisfactory December 2018 Vibration Testing 9/17/2015 All results satisfactory 9/17/2017 Unit 2 Main HV Bushings-Fall 2018 Doble Testing 10/28/2015 All results satisfactory Transformer - Fall 2020 Routine Transformer 10/28/2015 New transformer installed. All results satisfactory. Fall 2017 PM Hot spot found on 4kV bus coming off of transformer 2T, December 2018 Thermography Scan 11/30/2016 repaired 1/11/2017 Oil Testing 12/7/2016 All results satisfactory December 2018 2TAux Doble Testing 10/16/2015 All results satisfactory N/A- Next Scheduled Fall 2019 Routine Transformer 10/16/2015 All results satisfactory Fall 2017 PM Thermography Scan 11/30/2016 All results satisfactory December 2018 Oil Testing 12/7/2016 All results satisfactory December 2018 CT2 Startup Doble Testing 10/22/2013 All results satisfactory Fall 2017 Routine Transformer 10/22/2015 Chips on lightning arrester sealed to prevent moisture Fall 2017 PM ingress. All other results satisfactory.
Enclosure - Duke Energy Response to NRC RAI Page 5 License Amendment Request No. 2015-08, Supplement 1 January 30, 2017 Latest Completion Transformer PM Activity Results Summary Next Scheduled Date Date Thermography Scan 11/30/2016 All results satisfactory December 2018 Oil Testing 12/7/2016 All results satisfactory December 2018 Unit 3X Vibration Testing 3/14/2016 All results satisfactory 3/15/2018 Main HV Bushings-Spring 2018 Doble Testing 4/29/2016 All results satisfactory Transformer - Spring 2020 Routine Transformer 4/29/2016 All fan motors changed Spring 2018 PM Thermography Scan 11/30/2016 All results satisfactory December 2018 Oil Testing 12/7/2016 All results satisfactory December 2018 Unit 3V Vibration Testing 3/14/2016 All results satisfactory 3/15/2018 Main HV Bushings-Spring 2018 Doble Testing 4/25/2016 All results satisfactory Transformer- Spring 2020 Routine Transformer 4/25/2016 Minor oil leak identified and repaired. Spring 2018 PM Thermography Scan 11/30/2016 All results satisfactory December 2018 Oil Testing 12/7/2016 All results satisfactory December 2018 Unit 3Z Vibration Testing 3/14/2016 All results satisfactory 3/15/2018 Main HV Bushings-Spring 2018 Doble Testing 4/25/2016 All results satisfactory Transformer - Spring 2020 Routine Transformer 4/25/2016 Minor oil leak identified and repaired. Spring 2018 PM
Enclosure - Duke Energy Response to NRG RAI Page 6 License Amendment Request No. 2015-08, Supplement 1 January 30, 2017 Latest Completion Transformer PM Activity Results Summary Next Scheduled Date Date Thermography Scan 11/30/2016 All results satisfactory December 2018 Oil Testing 12/7/2016 All results satisfactory December 2018 N/A- Spare Transformer not Unit 3S Vibration Testing 3/14/2016 All results satisfactory energized Main HV Bushings-Spring 2018 Doble Testing 4/25/2016 All results satisfactory Transformer - Spring 2020 Routine Transformer 4/25/2016 Minor oil leak identified and repaired. Spring 201S PM Thermography Scan 11/30/2016 December 2018 All results satisfactory Oil Testing 12/7/2016 All results satisfactory December 2018 3TAux Doble Testing 4/24/2016 All results satisfactory Spring 2020 Routine Transformer 4/24/2016 All results satisfactory Spring 2018 PM Thermography Scan 11/30/2016 All results satisfactory December 2018 Oil Testing 12/7/2016 All results satisfactory December 2018 CT3 Startup Doble Testing 4/21/2014 All results satisfactory Spring 2018 Routine Transformer 4/27/2016 Chips on lightning arrester sealed to prevent moisture Spring 2018 PM ingress. All other results satisfactory.
Enclosure - Duke Energy Response to NRC RAI Page 7 License Amendment Request No. 2015-08, Supplement 1 January 30, 2017 Latest Completion Transformer PM Activity Results Summary Next Scheduled Date Date Thermography Scan 9/26/2016 All results satisfactory December 2018 Oil Testing 12/7/2016 All results satisfactory December 2018 CT4 Doble Testing 8/9/2016 All results satisfactory 1/12/2018 Routine Transformer 1/13/2015 Minor oil leak identified and repaired. 1/12/2018.
PM Thermography Scan 10/31/2015 All results satisfactory Fall 2017 .
Oil Testing 12/7/2016 All results satisfactory December 2018 CT5 Doble Testing 1/22/2015 All results satisfactory 1/21/2018 Routine Transformer 9/8/2016 All results satisfactory 1/21/2018 PM
Enclosure - Duke Energy Response to NRC RAI Page.a License Ame'ndment Request No. 2015-08, Supplement 1 January 30, 2017 Table 1-2: Transformer Bus Line Inspection PM Summary Latest Completion Transformer PM Activity Results Summary Next Scheduled Date Date Overhead Line Unit 1 MSU 11/24/2014 All results satisfactory Fall 2018 Inspection Overhead Line en startup Inspection 11/10/2016 Found and replaced damaged cotter pin Fall 2018 Overhead Line Unit 2 MSU 11/9/2013 All results satisfactory Fall 2017 Inspection Overhead Line CT2 Startup* 10/23/2015 All results satisfactory Fall 2017 Inspection Overhead Line Unit 3X MSU 4/28/2014 Found and replaced 3 damaged cotter pins Spring 2018 Inspection Overhead ~ine Unit 3Y MSU 4/28/2014 All results satisfactory Spring 2018 Inspection Overhead Line Unit 3Z MSU 4/28/2014 All results satisfactory Spring 2018 Inspection Overhead Line Unit 3S MSU 4/28/2014 All results satisfactory Spring 2018 Inspection Overhead Line CT3 Startup 4/25/2012 All results satisfactory Spring 2018 Inspection Overhead Line
. CT5 Startup 12/21/2015. All results satisfactory 2018 Inspection
Enclosure - Duke Energy Response to NRC RAI Page 9 License Amendment Request No. 2015-08, Supplement 1 January 30, 2017 Periodic testing is performed to ensure the following:
- _Surveillance Requirements (SRs) specified in the station's Technical Specifications (TSs) and Updated Final Safety Analysis Report (UFSAR) are satisfied,
- Testing commitments made in accordance with regulatory requirements (e.g. NRC Generic Letters, Significant Operating Experience Reports, and Information Notices) are met,
- Testing commitments to satisfy insurance requirements are met, and
- Testing requirements to satisfy manufacturer's recommendations are satisfied.
Electrical System Weekly Surveillance This test is used to:
- Verify proper breaker alignments, component voltages and frequency to ensure the electrical system meets Surveillance Requirements of TS 3.8 for required electrical equipment common to all Units or shared by two Units.
- Test satisfies TS SR 3.8.1.1 SR 3.8.1.1 "Verify correct breaker alignment and indicated power availability for each required offsite source."
This SR ensures proper circuit continuity for the offsite AC electrical power supply to the onsite distribution network and availability of offsite AC electrical power. The breaker alignment verifies that each breaker is in its correct position to ensure that distribution buses and loads are connected to their power source, and that appropriate separation of offsite sources is maintained.
Keowee Operation Test (31-day frequency)
This test is used to:
- Periodically test operation of each Keowee Hydro Unit's (KHU) ability to automatically start and energize the Overhead and Underground Power Paths.
- Test the Keowee Overhead or Underground Power Path(s) as required by performing operability verification of a KHU or Power Path.
- Test satisfies TS SR 3.8.1.3 and 3.8.1.4.
SR 3.8.1.3 "Verify the KHU associated with the underground emergency power path starts automatically and energizes the underground emergency power path. Manually close the SK breaker to each de-energized standby bus."
This SR verifies the availability of the KHU associated with the underground emergency power path to start automatically and energize the underground power path. Utilization of either the auto-start or emergency start sequence assures the control function OPERABILITY by verifying proper speed control and voltage. Power path verification is included to demonstrate breaker OPERABILITY from the KHU onto the standby buses. This is accomplished by closing the Keowee Feeder Breakers (SK) to energize each deenergized standby bus.
Enclosure - Duke Energy Response to NRC RAI . Page 10 License Amendment Request No. 2015-08, Supplement 1 January 30, 2017 SR 3.8.1.4 "Verify the KHU associated with the overhead emergency power path starts automatically and automatically or manually synchronize it to the Yellow bus in 230 kV switchyard.
Energize the underground emergency power path after removing the KHU from the overhead emergency power path."
This surveillance verifies the availability of the KHU associated with the overhead emergency power path. Utilization of either the auto-start or emergency start sequence assures the control function OPERABILITY by verifying proper speed control and voltage.
The ability to supply the overhead emergency power path is satisfied by demonstrating the ability to synchronize (automatically or manually) the KHU with the grid system. If an automatic start of the KHU is performed and a manual synchronization is desired, the KHU will need to be shutdown and restarted in manual to allow a manual synchronization of the KHU. The SR also requires that the underground power path be energized after removing the KHU from the overhead emergency power path. This surveillance can be satisfied by first demonstrating the ability of the KHU associated with the underground emergency path to energize the underground path then synchronizing the KHU to the overhead emergency power path.
Keowee Emergency Start Test (12-month frequency)
This test is used to:
Demonstrate operability of each KHU emergency start channel on actual or simulated emergency actuation signal from each Control Room and Cable Room.
Demonstrate that each KHU achieves frequency;:: 57 Hz and s 63 Hz and voltage ;:: 13.5kV
- and s 14.49kV in s 23 seconds of emergency start initiation Verify actuation times for time-delay relays for close permissive to ACB-1, ACB-2, ACB-3 and ACB-4.
Verify KHU Air Circuit Breakers (ACBs) close automatically to the underground path Verify each KHU supplies the equivalent of one Unit's maximum safeguard loads plus two Units' hot shutdown loads when synchronized to system grid and loaded at maximum practical rate.
Keowee Over Frequency Protection Functional Test (18-month.frequency)
This test is used to:
Verify upon emergency start signal when generating to the grid, each KHU's overhead and undergreund generator breakers trip and realign to the correct position from an initial condition of commercial operation.
Verify upon emergency start signal when generating to the grid, each KHU's frequency reaches s 66 Hz in s 23 seconds from an initial condition of commercial power generation.
Auxiliary Power Transfer Surveillance (18"'.'ITionth frequency)
This test is used to:
Demonstrate the ability of KHU*1 or KHU-2 600V Auxiliary Load Center 1X or 2X to close its' alternate feeder breaker after time delay (30 seconds) from its' normal feeder breaker opening whether aligned as the underground or overhead power path unit.
Enclosure - Duke Energy Response to NRC HAI Page 11 License Amendment Request No. 2015-08, Supplement 1 January 30, 2017 Demonstrate the ability of KHU-1 or KHU-2 600V Auxiliary Load Center 1X or 2X to close its' normal feeder breaker after its' alternate feeder breaker opens whether aligned as the underground or overhead power path unit.
Keowee Out of Tolerance Test (18-month frequency)
This test is used to:
Demonstrate the ability of the Out of Tolerance (OOT) logic to operate properly. The OOT logic provides voltage and frequency protection for the two Oconee emergency power paths. This protection monitors each Keowee Unit and isolates either unit from its designated power path if an OOT voltage or frequency is detected.
Emergency Power Switching Logic Functional Test (24- month frequency)
This test is used to:
Verify Emergency Power Switching Logic (EPSL) functions to maintain Main Feeder Susses (MFBs) energized by the most reliable source without operator actions.
Degraded Grid and Switchyard Isolation Test (18-month frequency)
This test is used to:
Functionally verify Keowee ACB-1, ACB-2, ACB-3, ACB-4 and Switchyard PCB operation during Switchyard Isolation and Keowee Emergency Start.
Demonstrate operability of Degraded Grid Voltage Protection (DGVP) System.
Demonstrate ability of Keowee to energize 230KV Yellow Bus, all three Startup Transformers (CT-1, CT-2 and CT-3) and Underground Path (CT-4) after a load rejection.
Power Supply from Lee Steam Station (24-month frequency)
This test shall be included in the Lee Combustion Turbine (LCT) Testing program to verify a LCT can provide equivalent of one Unit's maximum safeguard loads within one hour through 100 KV line electrically separated from system grid and offsite loads.
RAl2 The staff understands that ONS has implemented interim corrective actions to manually detect open phase conditions (OPC) until plant modifications are completed by December 2018. Please confirm that OPC modifications will be implemented prior to this scheduled KHU
- stator replacement maintenance of the onsite power systems.
Response to RAI 2 Duke Energy' plans to complete necessary OPC modifications by December 31, 2018. The first
'Keowee stator replacement maintenance is currently sched.uled to begin in mid-January 2019.
Enclosure - Duke Energy Response to NRC RAI Page 12 License Amendment Request No. 2015-08, Supplement 1 January 30, 2017 RAl3 Section 2.4 of the LAR, "Keowee Stator Replacement Schedule," under "Schedule Contingency," states that a one-day contingency has been included prior to the start of each dual KHU outage to account for schedule delays caused by delayed entry into each dual KHU outage for severe weather. Three days of contingency have been added to account for schedule delays caused by severe weather (icing, high humidity, rain). Duke Energy has committed to not enter an extended single KHU outage or a dual KHU outage if severe weather is forecast to occur withi.n 2 days.
A. Assuming all the prerequisite planned actions have been completed in readiness for the KHU outage, please explain why a one day contingency prior to each KHU dual outage is needed.
B. Please confirm that, prior to scheduling the maintenance outage, plant staff will review operating experience and historical weather patterns in order to minimize risk to plant power sources due to severe weather.
Response to RAI 3A As committed in the February 26, 2016, License Amendment Request (LAR) (ADAMS Accession Number ML16064A020), Duke Energy will check the weather forecast prior to entry into the single KHU outage, which starts the Keowee stator maintenance outage and again prior to entry into each dual KHU outage. The first dual KHU outage is planned approximately two days after the* start of the overall maintenance outage. While a delay into entry into the start of the overall stator maintenance outage due to severe weather does not impact schedule, once in this outage subsequent severe weather delays for starting a dual KHU outage will effectively extend the overall schedule by the wait time for the severe weather to pass. One day has been allotted for contingency for each of the two planned dual KHU outages. While it is not likely that weather delays would be incurred for both KHU outages (and less likely that a delay would be incurred for the _first dual KHU outage due to its closeness to the start of the overall outage), one day contingency for each dual KHU outage is considered appropriate since the delay in entry into a dual KHU outage would likely exceed one day.
The three days of weather contingency is not to accommodate potential delays in entry into the dual KHU outages. This contingency is to account for potential delays in transporting the replacement stator to the Keowee Hydroelectric Station from its temporary location due to severe weather (icing, high humidity, rain).
Response to RAI 38 Oconee procedures require plant staff to review operating experience and historical weather patterns during the development of critical activity plans for maintenance outages to manage risk during work a.ctivities. Prior to the release of work for execution, Operations personnel must consider the effects of severe weather and grid instabilities on plant operations. This qualitative evaluation is an inherent aspect of the duties of the Work Control Center Senior Reactor Operator (WCC SRO). Responses to actual plant risk due to severe weather or grid instabilities are programmatically incorporated into applicabl.e plant emergency or response procedures.