ML19336C483
| ML19336C483 | |
| Person / Time | |
|---|---|
| Site: | LaSalle  |
| Issue date: | 12/02/2019 |
| From: | Robert Daley Division of Reactor Safety III |
| To: | Bryan Hanson Exelon Generation Co, Exelon Nuclear |
| Shared Package | |
| ML19336C545 | List: |
| References | |
| BL-12-001 IR 2019013 | |
| Download: ML19336C483 (10) | |
Text
December 2, 2019 Mr. Bryan C. Hanson Senior VP, Exelon Generation Company, LLC President and CNO, Exelon Nuclear 4300 Winfield Road Warrenville, IL 60555
SUBJECT:
REISSUE - LASALLE COUNTY STATION, UNITS 1 AND 2 - NRC INSPECTION OF TEMPORARY INSTRUCTION 2515/194, INSPECTION OF THE LICENSEE'S IMPLEMENTATION OF INDUSTRY INITIATIVE ASSOCIATED WITH THE OPEN PHASE CONDITION DESIGN VULNERABILITIES IN ELECTRIC POWER SYSTEMS (NRC BULLETIN 2012-
- 01) REPORT 05000373/2019013 AND 05000374/2019013
Dear Mr. Hanson:
The U.S. Nuclear Regulatory Commission (NRC) identified an administrative error in the NRC Inspection Report 05000374/2019013 (ML19325D947) dated November 21, 2019, the report is being reissued in its entirety to include the missing inspection scope section.
On October 4, 2019, the U.S. Nuclear Regulatory Commission (NRC) completed an inspection at LaSalle County Station, Units 1 and 2 and discussed the results of this inspection with Mr. Phil Hansett 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/
Robert C. Daley, Chief Engineering Branch 3 Division of Reactor Safety Docket Nos. 05000373 and 05000374 License Nos. NPF-11 and NPF-18
Enclosure:
As stated cc w/ encl: Distribution via LISTSERV
ML19336C483 x Non-Sensitive x Publicly Available x SUNSI Review Sensitive Non-Publicly Available OFFICE RIII RIII NAME IHafeez:bw RDaley DATE 11/29/2019 12/2/2019 U.S. NUCLEAR REGULATORY COMMISSION Inspection Report Docket Numbers: 05000373 and 05000374 License Numbers: NPF-11 and NPF-18 Report Numbers: 05000373/2019013 and 05000374/2019013 Enterprise Identifier: I-2019-013-0014 Licensee: Exelon Generation Company, LLC Facility: LaSalle County Station, Units 1 and 2 Location: Marseilles, IL Inspection Dates: September 30, 2019 to October 4, 2019 Inspectors: I. Hafeez, Reactor Inspector Approved By: Robert C. Daley, Chief Engineering Branch 3 Division of Reactor Safety Enclosure
SUMMARY
The U.S. Nuclear Regulatory Commission (NRC) continued monitoring the licensees performance by conducting a NRC Inspection of Temporary Instruction 2515/194, Inspection of the Licensee's Implementation of Industry Initiative Associated with the Open Phase Condition Design Vulnerabilities in Electric Power Systems (NRC Bulletin 2012-01) at LaSalle County 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.
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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) 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 objective of Temporary Instruction 2515/194 is to verify that licensees have appropriately implemented the Nuclear Energy Institute voluntary industry initiative (ADAMS Accession No. ML15075A454), dated March 16, 2015, including updating their licensing basis to reflect the need to protect against open phase conditions (OPCs). The inspectors discussed the impacts of OPCs on the licensees electrical system design, the ability to detect and alarm OPCs on station transformers, and ongoing implementation of training and updates to operating procedures with plant staff. The inspector reviewed licensee and vendor documentation and performed system walkdowns to verify that the installed equipment was supported by the design documentation. The inspector verified that the licensee had completed the installation and testing of equipment (with the exception of the tripping functions), installed and tested alarming circuits both locally and in the control room, and analyzed potential impacts associated with the design implementation on the current licensing basis. The inspectors also reviewed licensee analysis and calculations and performed distribution system and switchyard equipment walkdowns.
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) Temporary Instruction 2515/194-03.01 - Voluntary Industry Initiative (Part 1)
Lasalle County Station has Installed Schweitzer Engineering Laboratories 451-5 microprocessor based relays for the OPC Relays which are located on the high voltage side (345kV) of System Auxiliary Transformers (SATs) 142 & 242. The relay schemes monitor and compare the positive, negative and zero sequence current input from existing Current Transformers. The OPC relays monitors/detect an open phase condition, which is defined as one or two phases, with or without a ground for the OPC or low load conditions. The relay algorithm/scheme and associated setpoint calculations were developed by the licensee to detect the loss of phase on the preferred offsite source for the engineered safety feature buses and initiate actions to separate that source from the onsite distribution system. The relay schemes also 3
used a time delay to ride out a short duration transient but allow sufficient time to detect a valid phase failure condition. The licensee completed the monitoring mode of operation of open phase system and enabled the tripping function for full implementation in October 4, 2017.
INSPECTION RESULTS Observation: Detection, Alarms, and General Criteria 2515/194 (1) OPCs that are detected will be alarmed in the Main Control Room (MCR) common annunciator panel.
(2) See item 2 in table titled Detection, Alarms, and General Criteria Exceptions for inspector identified exceptions.
(3) The licensees design document, test results and analysis showed that the short time delay (a time delay of 0.65 seconds was selected for the OPC relays to coordinate with the fault clearing time of 345kV switchyard primary and zone 2 relays) used in the open phase condition design/protective scheme is expected to minimize misoperation or spurious trips in the range of voltage unbalances normally expected in the transmission system. The analysis also showed that the time delay may properly coordinated with switchyard fault assumptions. Based on this, the inspector had reasonable assurance that the actuation circuit design would not result in lower overall plant operation reliability.
Additionally, the open phase condition scheme was activated or placed in-service in October of 2017. Since that time, there have not been any inadvertent actuations of this system that resulted in a trip signal or spurious actions.
(4) No Class-1E circuits were being replaced with non-Class 1E circuits in the design.
(5) The licensee revised Lasalle Updated Final Safety Analysis Report, Section 8.3.1.1.2.
Offsite Power Sources (SATs), and added the loss of phase protection to Table 8.3-2.
The change was incorporated into the Updated Final Safety Analysis Report.
See item 5 in table titled Detection, Alarms, and General Criteria Exceptions for inspector identified exceptions.
Observation: Protective Actions Criteria 2515/194 (1) LaSalle County Station has determined that OPCs are credible events and have implemented design changes to mitigate the effects. EC 387695 and EC 387696 have installed an open phase relay scheme to detect, alarm and protect from open phase conditions.
(2) The inspectors determined that with an open phase condition present and no accident condition signal, the OPC protection relay system would not adversely affect the function of important-to-safety systems, structures and components when the trip function is active.
As per the design description, the OPC relays will trip the System Auxiliary Transformer (SAT) lockout relays after a 0.65 second time delay. The SAT lockout relays would isolate the SAT by opening both primary and secondary side breakers. After the SAT isolates, an automatic fast transfer connects the safety-related buses fed by the SAT to 4
the Unit Auxiliary Transformer (UAT). The licensees analysis verified that the OPC relays can detect and isolate an OPC prior to any motor damage. The algorithm time delay limits the motors exposure to negative sequence current which helps prevent excessive motor heating.
The Lasalle UFSAR states that during a power loss to the M-G set, the high-inertia flywheel is designed to maintain generator output within 5 percent of rated values for at least one second to keep the Reactor Protection System (RPS) bus energized. The fast bus transfer from the SAT to UAT recovers the bus voltage allowing RPS operation to be sustained throughout the transient. Analyses completed by the licensee support the ability of this arrangement to be completed within associated time constraints.
See item 2 in table titled Protective Actions Criteria Exceptions for inspector identified exceptions.
(3) See item 3 in table titled Protective Actions Criteria Exceptions for inspector identified exceptions.
(4) No surveillance requirements for the SEL 451-5 were added to the plant Technical Specifications.
See item 4 in table titled Protective Actions Criteria Exceptions for inspector identified exceptions.
Observation: Detection, Alarms, and General Criteria Exceptions 2515/194 (2) Based on review of the licensees calculation for the relay settings used in the Open Phase Condition (OPC) algorithms, the inspectors determined that the OPC relay detection does not function under all loading conditions. The design is sensitive enough to identify an OPC when SAT transformer loading is above the MINLOAD threshold. To insure detection of an OPC, the design/implementation of OPC detection at LaSalle has a minimum loading requirement for the SAT transformers. Specifically, an OPC will be detected as long as the primary positive sequence current in the SAT is greater than the MINLOAD (low load) alarm setting (approximately 3.6MVA (L-003786, Rev. 0)). During normal operations, the SATs are routinely loaded above the MINLOAD threshold.
(5) While the change was incorporated into UFSAR table as a trip to the SAT lockout relays, the revision did not reference any design analysis, discuss design features, discuss theory of operation for the OPC system, or list major components associated with the open phase condition equipment in detail. However, the licensee maintained that the level of detail provided in the UFSAR for the open phase condition protection was consistent with the level of detail provided for other non-safety conditions that provide an input to the associated transformer lockout relay trips.
Observation: Protective Actions Criteria Exceptions 2515/194 (2) During low loading of the SAT or open phase detection (OPD) relay trouble alarms, manual actions may be required to address the existence of an OPC condition. The inspectors discussed the potential need for manual actions with the licensee and the licensee agreed that the current procedures did not specifically address implementation of protective actions if manual actions were required. The lack of guidance for system 5
response when manual actions are needed, and weaknesses identified in alarm response procedures was captured in IR 04284977, NRC IDD Procedure Enhancement.
(3) The following information was aggregated from engineering analyses, training materials and conversations with licensee staff as a detailed description of the system operation and performance was not located within the UFSAR.
The inspectors noted that, for the case where an OPC occurs and an accident condition (LOCA) signal are present simultaneously, safety-related equipment would receive a start request and would attempt to start while the OPC exists on the safety-related buses. This first start attempt occurs due to the time delay associated with 1) OPC coordination with other protective features and 2) the time delay associated with detection and actuation of the OPC equipment.
Once the SAT lockout relays isolate the SAT by opening both primary and secondary side breakers, the analysis showed the safety-related undervoltage relaying scheme would automatically separate the engineered safety feature (ESF) busses from the SAT.
Subsequently, the Emergency Diesel Generator (EDG) associated with each ESF bus would automatically connect to the ESF bus and allow the ESF loads to be powered from the EDG.
(4) At the time of this inspection, the licensee had established a functional test schedule which includes testing the relay metering function and verifying relay settings against calculated values. The licensee had not established a periodic setpoint calibration testing schedule to verify relay performance is within the tolerances assumed within the supporting analyses. The licensees relay testing procedure for microprocessor-based relays does not require calibration or setpoint verification.
EXIT MEETINGS AND DEBRIEFS The inspectors verified no proprietary information was retained or documented in this report.
- On October 4, 2019, the inspectors presented the NRC Inspection of Temporary Instruction 2515/194, Inspection of the Licensee's Implementation of Industry Initiative Associated with the Open Phase Condition Design Vulnerabilities in Electric Power Systems (NRC Bulletin 2012-01) results to Mr. P. Hansett and other members of the licensee staff.
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DOCUMENTS REVIEWED Inspection Type Designation Description or Title Revision or Procedure Date 2515/194 Calculations L-003750 LaSalle Offsite Power System Open Phase EMPT Evaluation 001 L-003786 Unit 1 and Unit 2 Loss of Phase Detection Relay Settings 003 L-003885 Open Phase Detection LOCA Analysis 1 Corrective Action 04284977 NRC IDD Procedure Enhancement 10/04/2019 Documents Resulting from Inspection Drawings 1E-1-4000FC Key Diagram Essential Div. 2 125V DC Distribution Panel P 112X (1DC12E) and Panel 112Y (1DC13E) 1E-1-4004AG Schematic Diagram Main Power System MP Part 7 K 1E-1-4005DQ Schematic Diagram Auxiliary Power System AP Part 87 M 1E-2-4000A Single Line Diagram Generator, Transformers & 6900V V Buses Part 1 1E-2-4000NF Relaying & Metering Diagram System Auxiliary G Transforme242 (2AP91E)
Engineering 387695 Single Phase Fault Mitigation 000 Changes Procedures LOA-AP-101 Unit 1, AC Power System Abnormal 59 LOR-1PM01J- Sat 142(242) System 1 Prot Relay Trip 3 A117 LOR-1PM01J- Sat 142 Low Load 3 A405 LOR-242 Loss of Sat 242 Loss of Phase Relay Trouble 4 Phase Relay Trouble LOR-2PM01J- SAT 242 System 2 Prot Relay Trip 3 A217 LST-2013-040 Single Phase Fault Mitigation Relay (EC 387695) 0 LST-2015-009 Open Phase Condition Concurrent with a LOCA Bus Transfer 0 Logic Change (EC 400355)
MA-LA-773-231 Unit 1, System Aux Transformer Relay and Meter 8 Calibrations By OAD 7
Inspection Type Designation Description or Title Revision or Procedure Date Work Orders 01513170 OAD Perform Bench Testing of Relay SEL-451 Per 12 EC387696 8