RBG-47232, Response to Request for Additional Information on License Amendment Request 2011-05
| ML12108A004 | |
| Person / Time | |
|---|---|
| Site: | River Bend  |
| Issue date: | 04/11/2012 |
| From: | Roberts J Entergy Operations |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| RBG-47232, RBF1-12-0052 | |
| Download: ML12108A004 (6) | |
Text
Entergy Operations, Inc.
River Bend Station 5485 U.S. Highway 61 N St. Francisville, LA 70775 SEntergy Tel 225 381 4149 Fax 225 635 5068 jrober3@entergy.com Jerry C. Roberts Director, Nuclear Safety Assurance RBG-47232 April 11,2012 U. S. Nuclear Regulatory Commission Attn.: Document Control Desk Washington, DC 20555-0001
SUBJECT:
Response to Request for Additional Information on License Amendment Request 2011-05 River Bend Station - Unit 1 Docket No. 50-458 License No. NPF-47
REFERENCES:
- 1. Entergy letter to NRC, dated December 8, 2011, License Amendment Request 2011-05, Degraded Voltage Surveillance Frequency Extension and Allowable Value Changes (Letter No.
RBG-47193)
- 2. NRC letter to Entergy (via email), dated March 12, 2012, Request for Additional Information RBF1-12-0052
Dear Sir or Madam:
On December 8, 2011, Entergy Operations, Inc. (Entergy) submitted a request to extend the frequency of a surveillance requirement and revise the allowable value for degraded voltage relays (Reference 1). During their review, the NRC staff determined that additional information is needed to complete the processing and approval of Entergy's request. The request for that information was transmitted to Entergy per Reference 2.
The attachment to this letter contains the requested information.
This letter contains no commitments. If you have any questions on this matter, please contact Joey Clark, Manager - Licensing, at 225-381-4177.
I declare under penalty of perjury that the foregoing is true and correct. Executed on April 11,2012.
Sincerely, obr- erS Director - Nuclear Safety Assurance
RBG-47232 April 11,2012 Page 2 of 2
Attachment:
Response to Request for Additional Information cc: Regional Administrator U. S. Nuclear Regulatory Commission Region IV 1600 E. Lamar Blvd.
Arlington, TX 76011-4511 NRC Senior Resident Inspector River Bend Station U. S. Nuclear Regulatory Commission Attn: Mr. Alan Wang MS 8-G14 One White Flint North 11555 Rockville Pike Rockville, MD 20852 Department of Environmental Quality Office of Environmental Compliance Radiological Emergency Planning and Response Section JiYoung Wiley P.O. Box 4312 Baton Rouge, LA 70821-4312 Ms. Tracie Lowery Public Utility Commission of Texas 1701 N. Congress Ave.
Austin, TX 78711-3326
Attachment RBG-47232 Response to Request for Additional Information
Attachment RBG-47232 April 11,2012 Page 1 of 3 REQUEST (a)
Provide a brief summary of the evaluation that demonstrates that all Class 1 E motors have adequate starting and running voltages based on the setpoint values specified in TS Table 3.3.8.1 rather than higher voltage shown on the grid stability study. Verify that protective devices such as relays, thermal overloads, fuses and contactors will not actuate during the start sequence.
RESPONSE
Calculation G13.18.3.6*016, Degraded Voltage Calculation for Class 1E Buses and 480 V Motor Operated Valves (MOVs), contains the evaluation that demonstrates all Class 1E motors have adequate starting and running voltages based on the proposed setpoint values specified in TS Table 3.3.8.1. Analysis in the calculation is performed using a dynamic model at the respective Lower Analytical Limit. The evaluation in the calculation was performed using ETAP Version 7.1.ON.
Loss of Voltage Relay Analysis The Lower Analytical Limit calculated in G13.18.3.6*016 for the Division I and II Loss of Voltage Relays is 2950 VAC and 2935 VAC for Division I1l. These values bound the allowable values in TS Table 3.3.8.1-1. The analytical limit for the relays is selected by calculating the 4160 VAC bus voltage such that the worst case motor has greater than 70% terminal voltage. No motors were found to have less than 70% steady state terminal voltage at the Loss of Voltage Relay Lower Analytical Limit.
Degraded Voltage Transient Analysis at Lower Analytical Limit The degraded voltage relay protection analysis at the Lower Analytical Limit is performed to show that if the relay drop out is set at the Lower Analytical Limit, which bounds the allowable values in TS Table 3.3.8.1-1, motors and MOVs will have adequate voltage to perform their safety function should the grid degrade substantially below 97.5%. Analysis in G13.18.3.6*016 shows that during a Loss of Coolant Accident (LOCA) with the grid below 97.5%, voltage on the bus recovers to reset the relay and all of the motors and MOVs will have adequate voltage.
Degraded Voltage No-LOCA Time Delay The upper analytical limit calculated in G13.18.3.6*016 for the Division 1,11, and III Degraded Voltage Relay No-LOCA Time Delay is 60 seconds.
Protective Devices Review of calculation E-200, Overcurrent Device Setpoints, shows that the safety related motors will be able to carry load at 70% terminal voltage for 60 seconds without tripping the supply breaker. This ensures that motors will not trip on overload at the Lower
Attachment RBG-47232 April 11,2012 Page 2 of 3 Analytical Limit provided they are operated at this value for less than the Degraded Voltage No-LOCA Time Delay.
Per calculation E-200, the motor feeder time overcurrent elements are set as follows:
- 4160 VAC Motor Feeders:
- 1. Time-overcurrent (TOC) is set at a minimum of 1.15 x Motor Full Load Current to alarm for moderate overloads.
- 2. High-dropout instantaneous is set at a minimum of 1.65 x Motor Full Load Current to trip in conjunction with TOC element for excessive overloads.
- 3. Standard instantaneous is set at a minimum of 1.73 x Locked Rotor Current to trip for motor feeder faults.
- 480 VAC Motor Feeders:
- 1. Long time pick up is set at a minimum of 1.65 x Motor Full Load Current for overloads.
- 2. Instantaneous pick up is set at a minimum of 1.73 x Locked Rotor Current for motor feeder faults.
- 3. Instantaneous overcurrent relay with a build-in-timer connected across a CT is set at a minimum of 1.15 x Motor Full Load Current to alarm for moderate overloads after allowing 15 seconds for motor acceleration time.
At 70% terminal voltage, the current is expected to increase by 100/70 % (= 1.43%).
This increase is lower than the long time pickup setting criteria of 1.65 x Motor Full Load Current for overloads and therefore, will not cause the breaker to trip.
Calculation E-210, Cable Loop Length Criteria for Voltage Drop AC Circuits, evaluates 120 VAC control circuits to determine if adequate voltage is available for relays and contactors. The conclusion of this analysis is that there is sufficient voltage available for these devices to operate using the minimum available Motor Control Center (MCC) voltages as calculated in G13.18.3.6*016.
REQUEST (b)
Provide details on how the grid voltage is maintained at or above 97.5%. If grid operator actions are required, then validate that MOVs will remain functional and perform their intended safety functions with the safety bus voltages at the degraded voltage relay set point as specified in TS Table 3.3.8.1.
RESPONSE
Grid voltage is maintained above 97.5% in accordance with the current revision of procedure DC-1 99, Off-Site Power Supply Design Requirements. DC-199 requires that grid voltage be maintained greater than 224.25 kV (97.5%), with the unit on or offline.
Attachment RBG-47232 April 11, 2012 Page 3 of 3 Grid operators maintain voltage above 97.5% using capacitor banks and control of multiple plants. Grid operators can direct the control room to adjust reactive load or voltage.
MOVs are analyzed with a dynamic model at the Lower Analytical Limit. The degraded voltage relay protection analysis at the Lower Analytical Limit is performed to show that if the relay drop out is set at the Lower Analytical Limit, which is below the TS Table 3.3.8.1 value, motors and MOVs will have adequate voltage to perform their safety function should the grid degrade substantially below 97.5%. Analysis in G13.18.3.6*016 shows that during a Loss of Coolant Accident (LOCA) with the grid below 97.5%, voltage on the bus recovers to reset the relay and all of the motors and MOVs will have adequate voltage.
REQUEST (c)
Verify that plant modifications and replacement equipment installed since the original plant construction have maintained 70 or 80 percent minimum voltage operating requirements.
RESPONSE
Calculation G13.18.3.6*016 uses a dynamic model for analysis at the Lower Analytical Limit. Plant modifications have been verified to have been included in the model. The calculation shows that all equipment has sufficient voltage to meet operating requirements.