ML19178A247
| ML19178A247 | |
| Person / Time | |
|---|---|
| Site: | Quad Cities  |
| Issue date: | 06/26/2019 |
| From: | Robert Daley NRC/RGN-III |
| To: | Bryan Hanson Exelon Generation Co, Exelon Nuclear |
| References | |
| IR 2019012 | |
| Download: ML19178A247 (11) | |
Text
June 26, 2019 Mr. Bryan C. Hanson Senior VP, Exelon Generation Company, LLC President and CNO, Exelon Nuclear 4300 Winfield Road Warrenville, IL 60555
SUBJECT:
QUAD CITIES NUCLEAR POWER STATION, UNITS 1 AND 2NRC INSPECTION OF TEMPORARY INSTRUCTION 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); INSPECTION REPORT 05000254/2019012 AND 05000265/2019012
Dear Mr. Hanson:
On May 17, 2019, the U.S. Nuclear Regulatory Commission (NRC) completed an inspection at your Quad Cities Nuclear Power Station, Units 1 and 2, and discussed the results of this inspection with Mr. Ken Ohr, Site Vice President, and other members of your staff. The results of this inspection are documented in the enclosed report.
The NRC inspectors did not identify any finding or violation of more than minor significance.
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, Part 2.390, Public Inspections, Exemptions, Requests for Withholding.
Sincerely,
/RA/
Robert C. Daley, Chief Engineering Branch 3 Docket Nos.: 05000254 and 05000265 License Nos.: DPR-29 and DPR-30
Enclosure:
IR 05000254/2019012 and 05000265/2019012 cc: Distribution via LISTSERV
ML19178A247 x Non-Sensitive x Publicly Available x SUNSI Review Sensitive Non-Publicly Available OFFICE RIII RIII IHafeez via NAME RDaley email:cl DATE 06/26/19 06/26/19
U.S. NUCLEAR REGULATORY COMMISSION Inspection Report Docket Numbers: 05000254 and 05000265 License Numbers: DPR-29 and DPR-30 Report Numbers: 05000254/2019012 and 05000265/2019012 Enterprise Identifier: I-2019-012-0021 Licensee: Exelon Generation Company, LLC Facility: Quad Cities Nuclear Power Station, Units 1 and 2 Location: Cordova, IL Inspection Dates: May 13, 2019, to May 17, 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 Licensees Implementation of Industry Initiative Associated with the Open Phase Condition Design Vulnerabilities in Electric Power Systems (NRC Bulletin 2012-01) at Quad Cities Nuclear Power 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. Findings and violations being considered in the NRCs assessment are summarized in the table below.
List of Findings and Violations No findings or violations 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)
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 local 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)
Temporary Instruction 2515/194-03.01 - Voluntary Industry Initiative (Part 1)
Quad Cities Nuclear 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 Reserve Auxiliary Transformers (RAT) T-12 & T-22. 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 used a time delay to ride out a short duration transient but allow sufficient time to detect a valid phase failure condition. The licensee is still in monitoring mode of operation of OPC.
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INSPECTION RESULTS Observation: Detection, Alarms, and General Criteria 2515/194 (1) OPCs that are detected will be alarmed in the Main Control Room common annunciator panel.
(2) See item 2 in table titled, Detection, Alarms, and General Criteria Exceptions, for inspector identified exceptions (3) The licensees design was operating in the monitoring mode with established setpoints during the inspection. The licensee is currently gathering data to ensure that the OPC design and protective schemes minimize misoperation, or spurious actuations in the range of voltage unbalance normally expected in the transmission system. Because actual demonstration of this criterion required the system to be in operation with final trip setpoints established, the inspector was not able to fully verify this criterion.
After discussions with licensee staff, reviews of design document and test results, the licensees analysis showed that the short time delay (a time delay of 0.7 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 OPC 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.
(4) No Class-1E circuits were being replaced with non-Class 1E circuits in the design.
(5) See item 5 in table titled, Detection, Alarms, and General Criteria Exceptions, for inspector identified exceptions Observation: Protective Actions Criteria 2515/194 (1) Quad Cities Station has determined that OPCs are credible events and have implemented design changes to mitigate the effects. Engineering Change 389172 and Engineering Change 389173 have installed an open phase relay scheme to detect, alarm and protect from OPCs.
(2) 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) See item 4 in table titled, Protective Actions Criteria Exceptions, for inspector identified exceptions 4
Observation: Detection, Alarms, and General Criteria Exceptions 2515/194 (2) Based on review of the licensees calculation for the relay setting limits used in the OPC algorithms, the inspectors determined that the OPC relay detection circuits are sensitive enough to identify an OPC. Specifically, an OPC is detected as long as the primary positive sequence current in the RAT is greater than the MINLOAD (low load) (alarm setting Load approximately 0.38MVA based on relay sensitivity). The RATs are normally loaded above the MINLOAD threshold.
(5) The licensee revised Quad Cities Updated Final Safety Analysis Report (UFSAR),
Section 8.3.1.2, Offsite Power Sources (RATs), and added, The RATs have protective relaying that includes phase and neutral overcurrent, current differential, sudden pressure, and open phase detection (alarm only). The revision added the phrase, open phase detection (alarm only), description to the pre-existing list of protective relaying associated with the RAT. The licensee concluded that the level of detail provided for the OPC was consistent with the level of detail provided for the other conditions that could trip the RAT feed breakers to the engineered safety feature buses. Although the licensee acknowledged that OPCs are credible events, within design documents, the UFSAR revision does not provide a detailed description of the OPC as an event.
Observation: Protective Actions Criteria Exceptions 2515/194 (2.) As per the design description, the OPC relays will trip the RAT lockout relays after a 0.7 second time delay. The RAT lockout relays would isolate the RAT by opening both primary and secondary side breakers. After the RAT isolates, an automatic fast transfer connects the safety-related buses fed by the RAT to the unit auxiliary transformer. 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 inspectors determined that with an OPC 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.
Since the OPC scheme is in monitoring mode, no protective actions will be automatically initiated.
The Quad Cities 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 RAT to unit auxiliary transformer 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.
Manual actions would be required to address the existence of an OPC condition while in monitoring mode. The inspector noted that expected delays associated with use of manual actions were not evaluated or supported by analyses and concluded that RPS actuation may occur. The inspectors discussed this potential outcome with the licensee and the licensee agreed that the current design analysis did not specifically address implementation of protective actions when manual actions were used. The lack of analysis for system response while in monitoring mode was captured in Issue Report 04249628, NRC Open Phase Inspection Calculation Delta Review.
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Additionally, the licensee initiated Issue Report 04249549, NRC Open Phase Procedure Enhancements, to address weaknesses identified in alarm response procedures. The inspector noted that various alarm response procedures did not provide Operations personnel instructions for the cases where the OPC condition might exist in conjunction with low loading of the RAT or open phase detection relay trouble alarms.
Due to the lack of analyses for the cases where manual actions are used (monitoring mode), the inspector was not able to conclude that an OPC condition does not adversely affect the function of important-to-safety structures, systems, and components.
(3.) When the trip function is active, the inspectors determined that with an OPC present and an accident condition signal present, the OPC protection relay system would result in tripping the RAT lockout relays after a 0.7 second time delay. The RAT lockout relays would isolate the RAT by opening both primary and secondary side breakers resulting in de-energizing of the safety-related busses. After the RAT isolates, with an accident signal present, the respective Emergency Diesel Generators would automatically start and re-energize the safety-related buses. The licensee evaluated the case of an OPC with an accident signal present and concluded that the safety-related loads will transfer from the RAT directly to the emergency diesel generators.
While in monitoring mode, the inspectors determined that with an OPC present and an accident condition signal present, the emergency diesel generators would start based on the presence of the accident signal. Depending on which phase(s) were involved, the automatic loading sequence may not occur due to the safety-related busses having some power from off-site sources. In time, control room staff will use manual actions to separate from off-site power. Once a loss of all power to the safety-related buses is detected, the diesels will be connected to their respective buses, restoring power to safety-related buses.
Additionally, the inspectors determined that with the OPC system in monitoring mode, the automatic isolation of the RAT would not occur. If an OPC condition were detected, the signal to isolate the RAT would not occur because the isolation signal is generated as a result of the OPC trip function.
Due to the lack of analyses for the cases where manual actions are used (monitoring mode), the inspector was not able to conclude that the licensee has shown that all design basis accident acceptance criteria are met with the OPC, given other design features.
(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 calibrations testing schedule to verify relay performance is within tolerances assumed within supporting analyses. The licensee entered this issue into their Corrective Action Program as IR 04249635, NRC Open Phase Inspection PM Review, to evaluate the need to perform additional preventative maintenance testing.
To date, no technical specification surveillances have been created as a result of changes associated with OPC modifications.
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EXIT MEETINGS AND DEBRIEFS The inspectors verified no proprietary information was retained or documented in this report.
- On May 17, 2019, the inspector presented the NRC Inspection of Temporary Instruction 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) results to Mr. Ken Ohr, Site Vice President, 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 QDC-6200-E- Current Transformer(s) Performance Calculation 001B 0993 QDC-6200-E- CT Burden Calculation 00A 1516 QDC-6700-E- Unit 1 and Unit 2 Open Phase Detection Relay Settings 001 2035 QDC-6700-E- Quad Cities Unit 1 and Unit 2 Offsite Power System Open 001 2036 Phase EMTP Evaluation QDC-6700-E- Quad Cities Open Phase Detection LOCA Analysis 000 2119 QDC-6700-E- Quad Cities Backfeed Open Phase EMTP Evaluation 000 2252 Corrective Action 04249549 NRC Open Phase Procedure Enhancements 05/16/2019 Documents 04249628 NRC Open Phase Inspection Calculation Delta Review 05/16/2019 Resulting from 04249635 NRC Open Phase Inspection PM Review 05/16/2019 Inspection Drawings 4E-1301 Single Line Diagram AR 4E-1333 Relaying & Metering Diagram Reserve Auxiliary Z Transformers 12-1 and 4160V Switchgears 13 and 14 4E-1334 Relaying & Metering Diagram 4160V Switchgears 13-1 and AJ 14-1 4E-1339 Schematic Diagram Reserve Auxiliary Transformer 12 T Tripping Relays 4E-1377J Schematic Diagram Reserve Auxiliary Transformer 12 A 4E-1575BG Schematic Diagram Main Control Room Annunciator Panel U 901-8 Part 2 of 6 4E-1575BH Schematic Diagram Main Control Room Annunciator Panel O 901-8 Part 3 of 6 4E-1583 Window Engraving Main Control Room Annunciator Panels CK 901-7, 901-8, and 912-5 4E-1608A Nameplate Reserve Auxiliary Transformer 12 B 4E-1609C Wiring Diagram Reserve Auxiliary Transformer 12 Part 3 F 8
Inspection Type Designation Description or Title Revision or Procedure Date 4E-1689 Front Elevations and Assembly Details Panel 901-29 V 4E-1690B Wiring Diagram Transformers Relay and Meter Panel 901-29 AG 4E-1690F Wiring Diagram Relay and Meter Panel 901-29 Section E D 4E-1815AH Wiring Diagram Annunciator Input Cabinet 901-34 Rack 5R Z 4E-1815AP Wiring Diagram Annunciator Input Panel 901-34 Chassis 11- L 20, TB11-TB20 Engineering 0000624926 Open Phase Detection - Monitoring Report Changes Procedures QCAN 901-8-E2 Reserve Auxiliary Transformer 12 Trip 1 QCAN 901-8-H4 Reserve Auxiliary Transformer 12 Open Phase Detection 0 Low Load/Trouble QCAN 902-8-E2 Reserve Auxiliary Transformer 22 Trip 1 QCAN 902-8-F4 Reserve Auxiliary Transformer 22 Open Phase Detection 2 Low Load/Trouble QOA 6100-01 Loss Of Reserve Auxiliary Transformer 12(22) During Power 34 Operation QOA 6100-13 Reserve Auxiliary Transformer 12 Trouble 22 9