ML17072A001

From kanterella
Jump to navigation Jump to search
NRR E-mail Capture - Draft RAI for QC LAR Re Loss of Voltage Relay Setting Change
ML17072A001
Person / Time
Site: Quad Cities  Constellation icon.png
Issue date: 02/09/2017
From: Kimberly Green
Plant Licensing Branch III
To: Nicely K
Exelon Generation Co
Green K
References
Download: ML17072A001 (5)
v • d • e


Text

NRR-PMDAPEm Resource From: Green, Kimberly Sent: Thursday, February 09, 2017 10:55 AM To: Nicely, Ken M.:(GenCo-Nuc)

Subject:

Draft RAI for QC LAR re Loss of Voltage Relay Setting Change Attachments: Quad Cities LOV draft RAI Sent to EGC.docx

Dear Mr. Nicely:

By letter dated September 12, 2016, as supplemented by letter dated November 21, 2016, Exelon Generation Company, LLC (EGC), submitted an amendment request for Quad Cities Nuclear Power Station, Units 1 and 2 (Agencywide Documents Access and Management System Accession No. ML16258A149). The proposed amendment would modify the allowable value for Function 1, 4160 V Essential Service System Bus Undervoltage (Loss of Voltage), in Technical Specification Table 3.3.8.1-1, Loss of Power Instrumentation.

The U.S Nuclear Regulatory Commission (NRC) staff is reviewing your submittal and has identified areas where additional information is needed to complete its review. Attached, please find a draft request for additional information (RAI).

The draft RAI is being sent to ensure that the questions are understandable and the regulatory basis for the questions is clear. This email and the attachment do not convey or represent an NRC staff position regarding EGC's request.

Please let me know if you need a call to clarify the staffs request.

Sincerely, Kimberly Green, Sr. Project Manager Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation (301) 415-1627 kimberly.green@nrc.gov 1

Hearing Identifier: NRR_PMDA Email Number: 3394 Mail Envelope Properties (Kimberly.Green@nrc.gov20170209105500)

Subject:

Draft RAI for QC LAR re Loss of Voltage Relay Setting Change Sent Date: 2/9/2017 10:55:12 AM Received Date: 2/9/2017 10:55:00 AM From: Green, Kimberly Created By: Kimberly.Green@nrc.gov Recipients:

"Nicely, Ken M.:(GenCo-Nuc)" <ken.nicely@exeloncorp.com>

Tracking Status: None Post Office:

Files Size Date & Time MESSAGE 1291 2/9/2017 10:55:00 AM Quad Cities LOV draft RAI Sent to EGC.docx 38261 Options Priority: Standard Return Notification: No Reply Requested: No Sensitivity: Normal Expiration Date:

Recipients Received:

DRAFT REQUEST FOR ADDITIONAL INFORMATION EXELON GENERATION COMPANY, LLC QUAD CITIES NUCLEAR POWER STATION, UNITS 1 AND 2 DOCKET NOS. 50-254 and 50-265 By letter dated September 12, 2016, Exelon Generation Company, LLC (Exelon, EGC, or licensee), submitted a license amendment request (Agencywide Documents Access and Management System (ADAMS) Accession No. ML16258A149). The proposed amendment would revise the loss of voltage (LOV) relay settings in Technical Specification (TS) Table 3.3.8.1-1, Loss of Power Instrumentation. The additional information below is needed to support the NRC staffs continued technical review of the license amendment request (LAR).

1. On page 2 of Attachment 1 of the LAR, ECG has provided a summary of the problem statement and states, [t]he concern was that, if the voltage at the 4.16 kV safety related buses dropped to slightly above 75 percent of the nominal voltage, the operating motors would experience approximately a 28 percent increase in current. Exelon has further stated that, [t]his voltage drop, complicated by potential motor starts, including the potential start of the motor-driven auxiliary feedwater pump if a plant trip occurred, could result in adverse consequences that had not been evaluated. The LAR does not discuss the impact of large motor starting during degraded voltage conditions and how the proposed setpoint of the LOV relays will preclude complications during plant shutdown.
a. Please provide details, including assumptions used, on the Quad Cities voltage drop evaluation that was performed to demonstrate the adequacy of the proposed LOV setpoint in combination with the existing setpoints (voltage and time) of the degraded voltage relay (DVR) for protecting safety related equipment following a plant trip and large motor (e.g., feedwater pump, drywell coolers, service water pumps) starts.
b. Please confirm if this voltage drop evaluation enveloped any process-related demand for a large motor start that can occur during the required design basis operational modes such as normal plant operation, controlled shutdown, anticipated operational occurrences or post-accident conditions with a unit trip and a fast bus transfer to the reserve auxiliary transformer. If the evaluation did not consider these, please explain why the proposed LOV relay settings are adequate. The staff notes that UFSAR Table 8.3-2 identifies that the CRD pump and service water pump are manually started after 10 minutes.
2. The staff reviewed LAR Attachment 3, Design Analysis QDC-6700-E-2173, Evaluation of Degraded Voltage 5 Minute Timer on Normally Running Safety-Related Loads, Revision 000, and made the following observations:

motors that may be running during normal operation. The staff notes that loads such as drywell coolers, service water pump, and control room air handling units (AHU) or heating, ventilation and air conditioning (HVAC) systems are not included in the list.

  • Page 8 of 18 states that the analysis will evaluate the safety-related motors that may be running during normal conditions during a severely degraded voltage condition that lasts for an extended period of time.
  • Page 9 of 18 states that there are no normally running, safety-related 480 V switchgear motors or 4.16 kV switchgear motors.

The staff notes that grid-related degraded voltage conditions can occur at any time during normal plant operation, controlled shutdown, anticipated operational occurrences or post-accident conditions and impact redundant trains of equipment. The evaluation included in the LAR considered only the ECCS-related AHU loads. The staff notes that there are other motors that are connected to switchgear buses and may be running during normal plant operation but were not evaluated for degraded voltage conditions in the analyses provided. Please confirm the following:

a. The ECCS room coolers are single packaged units containing fans, coils, filters, dampers air conditioning compressors, etc., and external chillers or compressors are not required for room cooling and are therefore not considered in the DVR and LOV relay setpoint analyses.
b. If any control room related HVAC systems are normally operating and any compressors or chillers are required during normal operation and plant shutdown for postulated events.
c. Degraded voltage conditions resulting from grid related events can occur on redundant safety buses and can adversely impact redundant equipment. Please explain if pumps and motors associated with cooling water systems such as station service water, reactor building closed cooling water, drywell coolers, etc.,

have been evaluated for low voltage conditions similar to the AHUs discussed in the LAR. If the loss of motors associated with cooling water systems have not been evaluated, then please confirm if loss of redundant trains of cooling water systems for an extended duration can adversely impact the plant systems during normal operation or during controlled shutdown with no accident signal postulated and station buses connected to offsite power.

3. Section 3.3.1 of Attachment 3 to the LAR states, The results of the transient EDG voltage dip analyses from diesel loading calculations 9390-02-19-1, 9390-02-19-2, and 9390-02-19-3 are used in this calculation. The Unit 1, Unit 2, and 1/2 diesel loading calculations are not maintained (emphasis added) and have been superseded by ETAP calculation QOC-6700-E-1503 Furthermore, an exact value for the transient voltage dip is not needed as the results are used to show that margin exists between LOV relay setpoint and the transient voltage dips. The staff understands that raising the LOV relay setpoint can potentially impact emergency diesel generator (EDG) operation.
a. Please explain the use of unmaintained diesel loading calculations for input into calculations maintained by a 10 CFR Appendix B Design Control program.
b. Please provide details on the margin between LOV relay setpoint and the largest voltage transient observed during motor starting.
c. Quad Cities Technical Specification Surveillance Requirements such as 3.8.1.2 and 3.8.1.8 require that a minimum EDG steady state voltage of 3952 V be verified. Please confirm that the EDG voltage transient dips were evaluated based on a starting voltage of 3952 V and unlike the DVR setpoint analyses, an infinite bus is not connected to each of 4.16 kV essential service system buses in order to model a specific operating voltage.
4. In response to the request for supplemental information, EGC sent a letter dated November 21, 2016 (ML16326A200). Exelons response addressed clarifications regarding assumptions and provided a drift analysis. The NRC staff observed that the drift analysis did not identify how as-found values which are outside the allowed tolerances are addressed. Provide additional information to clarify how out of tolerance values are addressed. This information is requested to confirm compliance with 10 CFR 50.36(c)(ii)(A) and the guidance of Regulatory Guide 1.105, Revision 3.
Retrieved from "https://kanterella.com/w/index.php?title=ML17072A001&oldid=2229156"