IR 05000220/2019014
| ML19344C980 | |
| Person / Time | |
|---|---|
| Site: | Nine Mile Point  |
| Issue date: | 12/09/2019 |
| From: | Glenn Dentel NRC Region 1 |
| To: | Bryan Hanson Exelon Generation Co |
| References | |
| IR 2019014 | |
| Download: ML19344C980 (9) | |
Text
December 9, 2019
SUBJECT:
NINE MILE POINT NUCLEAR STATION, UNITS 1 AND 2 - TEMPORARY INSTRUCTION REPORT 05000220/2019014 AND 05000410/2019014
Dear Mr. Hanson:
On November 20, 2019, the U.S. Nuclear Regulatory Commission (NRC) completed an inspection at Nine Mile Point Nuclear Station, Units 1 and 2 and discussed the results of this inspection with Mr. Todd Tierney, Plant Manager and other members of your staff. The results of this inspection are documented in the enclosed report.
No findings or violations of more than minor significance were identified during this inspection.
This letter, its enclosure, and your response (if any) will be made available for public inspection and copying at http://www.nrc.gov/reading-rm/adams.html and at the NRC Public Document Room in accordance with Title 10 of the Code of Federal Regulations 2.390, Public Inspections, Exemptions, Requests for Withholding.
Sincerely,
/RA/
Glenn T. Dentel, Chief Engineering Branch 2 Division of Reactor Safety
Docket Nos. 05000220 and 05000410 License Nos. DPR-63 and NPF-69
Enclosure:
As stated
cc w/ encl: Distribution via LISTSERV
SUMMARY
The U.S. Nuclear Regulatory Commission (NRC) continued monitoring the licensees performance by conducting a Temporary Instruction at Nine Mile Point Nuclear Station, Units 1 and 2, in accordance with the Reactor Oversight Process. The Reactor Oversight Process is the NRCs program for overseeing the safe operation of commercial nuclear power reactors.
Refer to https://www.nrc.gov/reactors/operating/oversight.html for more information.
List of Findings and Violations
No findings or violations of more than minor significance were identified.
Additional Tracking Items
None.
INSPECTION SCOPES
Inspections were conducted using the appropriate portions of the inspection procedures (IPs) in effect at the beginning of the inspection unless otherwise noted. Currently approved IPs with their attached revision histories are located on the public website at http://www.nrc.gov/reading-rm/doc-collections/insp-manual/inspection-procedure/index.html. Samples were declared complete when the IP requirements most appropriate to the inspection activity were met consistent with Inspection Manual Chapter (IMC) 2515, Light-Water Reactor Inspection Program - Operations Phase. The inspectors reviewed selected procedures and records, observed activities, and interviewed personnel to assess licensee performance and compliance with Commission rules and regulations, license conditions, site procedures, and standards.
OTHER ACTIVITIES
- TEMPORARY INSTRUCTIONS, INFREQUENT AND ABNORMAL
2515/194 - Inspection of the Licensees Implementation of Industry Initiative Associated with the Open Phase Condition Design Vulnerabilities In Electric Power Systems (NRC Bulletin 2012-01)
The inspectors reviewed the licensees implementation of the Nuclear Energy Institute Voluntary Industry Initiative, (ADAMS Accession No. ML15075A454) dated March 16, 2015. This included reviewing how the licensee updated their licensing basis to reflect the need to protect against open phase conditions.
Inspection of the Licensees Implementation of Industry Initiative Associated with the Open Phase Condition Design Vulnerabilities In Electric Power Systems (NRC Bulletin 2012-01) (1 Sample)
- (1) Exelon selected the open phase detection system designed and manufactured by Schweitzer Engineering Laboratories (SEL) as the design vendor for the open phase condition system at Nine Mile Point Nuclear Station. The open phase protection system is designed to protect the offsite power sources from a loss of phase condition.
Nine Mile Point Nuclear Station Unit 1 has two 115kV independent offsite power sources (Lines 1 and 4), which provide power to the station through breakers R10 and R40, and through Reserve Transformer 101N and Reserve Transformer 101S. Unit 2 has two 115kV independent offsite power sources (Lines 5 and 6),which provide power to the station through Reserve Transformer A, Reserve Transformer B, and the Auxiliary Boiler Transformer. SEL relays were installed to monitor, alarm, and provide a trip function on each of the 5 offsite power transformers, and for breakers R10 and R40. The relays are wired to provide annunciation and are configured to trip the associated power sources if a loss of phase condition is detected. The loss of phase detection relays include main control room annunciation and plant process computer alarms for relay trips, relay malfunction, and, in some cases, minimum loading conditions.
At the end of the inspection, the SEL system was in the alarm only mode of operation. The relay trip signals were isolated from the lockout relays by leaving test switches open. Exelon plans to pursue an alternate implementation method (i.e. risk based with manual actions) for Unit 1 and Unit 2 to comply with the open phase detection initiative.
INSPECTION RESULTS
Temporary Instruction 2515/194-03.01 - Voluntary Industry Initiative 2515/194 Based on discussions with Exelon staff, review of design and testing documentation, and walkdowns of installed equipment, the inspectors had reasonable assurance that the Exelon is appropriately implementing, with noted exceptions discussed below, the voluntary industry initiative at Nine Mile Point Nuclear Station. The inspectors determined that:
Detection, Alarms and General Criteria
1. The open phase condition design and protective schemes minimize misoperation or
spurious action in the range of voltage unbalance normally expected in the transmission system that could cause separation from an operable off-site power source. Additionally, Exelon has demonstrated that the actuation circuit design does not result in lower overall plant operation reliability. 03.01(a)(3)
2. No Class 1E circuits were being replaced with non-Class 1E circuits in this design.
03.01(a)(4)
Protective Actions Criteria
1. The identified offsite power sources are susceptible to an open phase condition and
the licensee was implementing design changes to mitigate the effects. 03.01(b)(1)
2. With an open phase condition present and no accident condition signal, Technical
Specification Limiting Conditions for Operation would be maintained, important-to-safety equipment would not be damaged by the open phase condition, and shutdown safety would not be compromised. Exelon's open phase condition design solution added a set of additional tripping inputs in parallel with existing power isolation devices. These additional devices added a new tripping condition (open phase) to the previously analyzed electrical faults which result in isolation of the transformers. The credited plant response was unaffected and would be the same regardless of the conditions that generated the isolation of the transformers. 03.01(b)(2)
No findings were identified.
Detection, Alarms and General Criteria Exceptions 2515/194 03.01(a)(1) In general, open phase condition detection and alarming was adequately implemented at Nine Mile Point Nuclear Station. Inspectors noted one exception to this criteria.
During a system walkdown on November 18, 2019, inspectors identified that a test switch associated with the SEL relay for the 101N transformer was tagged in the open position. The test switch was opened on May 20, 2019, in response to nuisance alarms in the main control room associated with a minimum loading condition on the 101N transformer. Operators opened the test switch, believing that the plant process computer would still produce an alarm in the main control room. However, inspectors determined that with the test switch opened, no alarms would be received for any detected open phase condition for transformer 101N and that additional compensatory measures to monitor for these conditions should be in place. Inspectors did not identify any additional compensatory measures in place while the open phase condition alarm was bypassed for the 101N transformer. However, operators monitor transformer bus voltages every four hours and would have likely recognized an open phase condition. At the end of the inspection, additional compensatory measures were established, including taking additional transformer voltage and current readings at least once per shift. This issue was documented in their corrective action program as issue report 04298487.
03.01(a)(2) For cases in which automatic detection was not possible in very low or no loading conditions when the offsite power transformers are in a standby mode, inspectors determined that automatic detection would occur as soon as loads were transferred to the standby source. However, Exelon determined that additional shiftly surveillances were needed to adequately monitor and detect an open phase condition while in a very low or no loading condition. This was identified during an Exelon self-assessment performed prior to the inspection and documented in issue report 04296560.
03.01(a)(5) Exelon had neither updated the Nine Mile Point Unit 1 Updated Final Safety Analysis Report (UFSAR) nor the Unit 2 Updated Safety Analysis Report (USAR) to discuss the design features and analyses related to the effects of, and protection for, any open phase condition design vulnerability. The Unit 2 USAR did include a listing of the added open phase condition relays, without further system or analysis description. This was identified during an Exelon self-assessment performed prior to the inspection and documented in issue report 04296560.
Protective Actions Exceptions 2515/194 03.01(b)(3) Inspectors determined that with an open phase condition and an accident condition signal present, the open phase detection system would not adversely affect the function of the load shedding and sequencing system to provide a means of disconnecting and sequencing of loads on the safety-related buses. Automatic detection of an open phase condition has been installed, but the automatic actuation of the system has been bypassed. Exelons operating procedures, once detection has occurred, would allow operators to diagnose the condition and transfer the required loads to the non-affected offsite source, or the onsite emergency power source. A loss of voltage caused by isolation of offsite sources due to an open phase condition does not have an adverse effect on the availability of the non-affected offsite sources, or to the onsite emergency power sources. The bypass of the automatic isolation was identified during an Exelon self-assessment performed prior to the inspection and documented in issue report 04296567.
03.01(b)(4) Relay setpoints associated with the open phase detection scheme were verified and validated as part of acceptance factory testing, and as part of the system monitoring period. Preventative maintenance testing and periodic calibrations were developed for some aspects of the open phase detection system for Unit 1 systems, but none had been developed for Unit 2 systems. This was identified during an Exelon self-assessment performed prior to the inspection and documented in issue report
EXIT MEETINGS AND DEBRIEFS
The inspectors verified no proprietary information was retained or documented in this report.
- On November 20, 2019, the inspectors presented the Temporary Instruction results to Mr. Todd Tierney, Plant Manager and other members of the licensee staff.
DOCUMENTS REVIEWED
Inspection
Procedure
Type
Designation
Description or Title
Revision or
Date
2515/194
Calculations
115kV-
OPENPHASE-
STUDY
NMP1 Open Phase EMTP Analysis
Revision
0000
115kV-
OPENPHASELOCA-
STUDY
Revision
0000
115KV-
OPENPHASEXFMR-
Unit 1 XF-101N and XF-101S Relay Settings for Open
Phase
Revision
0000
NMP2 Open Phase EMTP Analysis
Revision
0000
NMP2 Open Phase LOCA Analysis
Revision
0000
Unit 2 SEL-487E Relay Settings
Revision
0000
NMP2 Open Phase Alternate Offsite Source Analysis
Revision
0000
Corrective Action
Documents
04015088
296556
250274
296554
250274
296560
292365
Corrective Action
Documents
Resulting from
Inspection
298477
Door C288-1 Failed to Latch on First Closure
298484
Discrepancies Noted with Unit 1 and Unit 2 Open Phase
Relay (clocks)
298487
N1-OP-033A Procedure Discrepancy Identified
298493
Scriba Yard Relay Data Historian UPS in Alarm
Engineering
Changes
ECP-14-000340
Unit 1 Open Phase Relaying for Transformers XF-101S
and XF-101N
Revision
0001
ECP-14-000922
NMP2 Open Phase Detection System Implementation
Revision
Inspection
Procedure
Type
Designation
Description or Title
Revision or
Date
(Scriba Transformers)
0002
ECP-15-000297
Open Phase Detection System Implementation (NMP2
Transformers)
Revision
0002
ECP-16-000021
Unit 1 Open Phase Detection Implementation (115 kV Line
- 1 (BKR-R10) and 115 kV Line #4 (BKR-R40))
Revision
0001
ECP-17-000507
NMP Unit 1 & 2 - Open Phase Algorithm and OPD Relay
Setting Change Modification
Revision
0000
ECP-17-000507
NMP Unit 1 & 2 - Open Phase Algorithm and OPD Relay
Setting Change Modification
Revision
0001
Miscellaneous
NRC Open Phase Inspection TI 2515/194 Self-
Assessment
10/22/2019
N1-PM-S1
NMP1 Control Room Parameter Monitoring
(Compensatory Measures) for OPC 101N
11/19/2019
NMP1 LER 05-004
Operation Prohibited by Technical Specification due to
Unrevealed Inoperability of One Off-site Power Source
2/17/2006
PCRS-18-01100
Update to N1-OP-033A
05/28/2018
Tag ACPS NMP-U1
19-055
ACPS to Maintain Configuration of Open Phase Mod Knife
Switch (P&ID C34857C, Sht 2)
11/18/2019
Procedures
N1-ARP-A8
Control Room Panel A8
Revision
01500
N1-OP-033A
115kV System
Revision
03300
N2-ARP-852600
2CEC*PNL852 Series 600 Alarm Response Procedures
Revision
01100