1CAN032001, Supplemental Information Related to License Amendment Request to Revise Loss of Voltage Relay Allowable Values
| ML20079K973 | |
| Person / Time | |
|---|---|
| Site: | Arkansas Nuclear  |
| Issue date: | 03/19/2020 |
| From: | Gaston R Entergy Operations |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| 1CAN032001 | |
| Download: ML20079K973 (10) | |
Text
10 CFR 50.90 1CAN032001 March 19, 2020 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555
Subject:
Supplemental Information Related to License Amendment Request to Revise Loss of Voltage Relay Allowable Values Arkansas Nuclear One, Unit 1 NRC Docket No. 50-313 Renewed Facility Operating License No. DPR-51 By letter dated January 24, 2020 (Reference 1), Entergy Operations, Inc. (Entergy), requested NRC approval of a proposed change to the Arkansas Nuclear One, Unit 1 (ANO-1) Technical Specifications (TSs) that would revise the 4160 volt switchgear Loss of Voltage relay setpoints.
During the course of review, the NRC determined supplemental information was required to complete the acceptance review process.
The NRC issued a request for supplemental information on March 6, 2020 (Reference 2), with a required response date of March 23, 2020). The requested supplemental information is included in the attached enclosure. This information does not impact the no significant hazards consideration provided in the original amendment request (Reference 1).
No new regulatory commitments are included in this submittal.
In accordance with 10 CFR 50.91, Entergy is notifying the State of Arkansas of Entergy's supplemental information by transmitting a copy of this letter and enclosure to the designated State Official.
If there are any questions or if additional information is needed, please contact Riley Keele, Manager, Regulatory Assurance, Arkansas Nuclear One, at 479-858-7826.
Entergy Operations, Inc.
1340 Echelon Parkway Jackson, MS 39213 Tel 601-368-5138 Ron Gaston Director, Nuclear Licensing
1CAN032001 Page 2 of 2 I declare under penalty of perjury that the foregoing is true and correct.
Executed on March 19, 2020.
Respectfully, ORIGINAL SIGNED BY RON GASTON Ron Gaston RWG/dbb
Enclosure:
Supplemental Information Related to Revising the Loss of Voltage Relay Allowable Values
References:
- 1.
Entergy Operations, Inc. (Entergy) letter to U. S. Nuclear Regulatory Commission (NRC), License Amendment Request to Revise Loss of Voltage Relay Allowable Values, Arkansas Nuclear One, Unit 1 (1CAN012002) (ML20024E639), dated January 24, 2020.
- 2.
NRC letter to Entergy, Arkansas Nuclear One, Unit 1 - Supplemental Information Needed for Acceptance of Requested Licensing Action Re:
License Amendment Request to Revise Loss of Voltage Relay Allowable Values (EPID L-2020-LLA-0013), (1CNA032001) (ML20065H799), dated March 6, 2020.
cc:
NRC Region IV Regional Administrator NRC Senior Resident Inspector - Arkansas Nuclear One NRC Project Manager - Arkansas Nuclear One Designated Arkansas State Official
Enclosure 1CAN032001 Supplemental Information Related to Revising the Loss of Voltage Relay Allowable Values
1CAN032001 Enclosure Page 1 of 7 SUPPLEMENTAL INFORMATION RELATED TO REVISING THE LOSS OF VOLTAGE RELAY ALLOWABLE VALUES By letter dated January 24, 2020 (Reference 1), Entergy Operations, Inc. (Entergy), requested NRC approval of a proposed change to the Arkansas Nuclear One, Unit 1 (ANO-1) Technical Specifications (TSs) that would revise the 4160 volt (V) switchgear Loss of Voltage (LOV) relay setpoints. The NRC issued a request for supplemental information on March 6, 2020 (Reference 2), with a required response due March 23, 2020. The requested supplemental information is included below.
Supplemental Information Request 1 Provide a summary of the ANO-1 LOV Relay setpoint uncertainty calculation to support the proposed Allowable Value in SR 3.3.8.2.b. The summary should include the relay setting design basis, such as the nominal setpoint to be used during calibration surveillances, the uncertainties associated with these settings (inclusive of the Potential Transformer ratio and the Institute of Electrical and Electronics Engineers (IEEE) Standard C57.13 Accuracy Class), the expected relay drift between surveillances, measurement and test equipment uncertainties, and the as-found and as-left tolerance acceptance values to be applied during technical specification surveillances. Alternatively, the full setpoint uncertainty calculation may be provided for convenience, but is not necessary.
Entergy Response The function of the LOV relay is to detect the loss of offsite power (LOOP) to the plant auxiliary loads and shed safety motors when fast transfer to a standby offsite power source is not successful. This relay also initiates a timer to allow closure of the Emergency Diesel Generator (EDG) output breaker (once the EDG has reached rated speed/voltage) and trip the tie breaker between the respective safety-related 4160 V switchgear and the non-safety related 4160 V switchgear in 2.5 seconds after the relay has dropped out. CALC-18-E-0015-01 includes verification that protective devices for loads are adequate to prevent tripping prior to the LOV time delay plus acceleration time of loads on the onsite power source.
The LOV relay dropout setting limits the exposure of motors to voltages that may cause the stalling of running Class 1E motors. To prevent stalling of 4160 V and 480 V running motors, the setting must achieve 75% voltage (based on the ANO large motor specification) on the motor buses. To account for voltage drop and margin, a value of 81.3% is used as the minimum acceptable dropout for the LOV relay. Calc-18-E-0015-01 includes verification that this value is adequate to ensure that Class 1E motors will not stall. CALC-18-E-0015-01 also verifies that the LOV relay is set to ensure that the Class 1E motors have adequate voltage to start when the 4160 V switchgear bus voltage is at the minimum LOV relay TS Surveillance Requirement (SR) allowable limit. The relay pickup (or reset) setting is not critical for LOV function; however, the nominal pickup setting calculation is included for completeness.
The safety related 4160 V switchgears A3 and A4 LOV relays are the same model of 27N relays used on the safety related 480 V load centers B5 and B6. Therefore, the relay uncertainty and drift values calculated in CALC-95-E-0001-01 for the B5 and B6 relays are used to determine the A3 and A4 LOV relay dropout and pickup settings.
1CAN032001 Enclosure Page 2 of 7 The relay drift is calculated based on the performance of a statistical analysis of the as-left and as-found data (32 data points over a 6-year period). Based on this statistical analysis, the relay dropout voltage drift is documented as 0.816%.
The relay channel uncertainty or "total loop uncertainties," including the 0.3 class potential transformer (PT), is determined as follows:
CU = +/- (PM)2 + ( ((RA)2 + (TE)2 + (VE)2 + (MTE)2) )2 Where:
CU
= Channel Uncertainty PM
= Process Measurement = 0.003 (PT accuracy)
= Module Reference Accuracy = 0.001 (Relay Accuracy)
= Temperature Effect = 0.004 VE
= Voltage Effect = 0.001 MTE = Measurement and Test Equipment (MT&E) Effect = 0.002 CU = +/- (0.003)2 + ( ((0.001)2 + (0.004)2 + (0.001)2 + (0.002)2) )2 CU = +/- 0.0056 The desired dropout setting or "nominal trip setpoint" is determined as follows:
VDRD = [(VMA)(4000 V)(1/PTR)] / (1 - RD)(1 - CU)
Where:
VDRD = Desired Relay Dropout Voltage VMA
= Minimum Acceptable Dropout = 81.3%
RD
= Relay Drift = 0.816%
CU
= Channel Uncertainty = 0.56%
PTR
= PT Ratio = 4200/120 VDRD = [(0.813)(4000 V)(120/4200)] / [(1 0.00816)(1 0.0056)]
VDRD = 94.2 V (+ 0.1 V for added margin)
Therefore, the relay dropout setting = 94.3 V or 82.5% of Motor Base (3300.5 V).
To obtain the nominal pickup voltage and 0.5% band (Dropout/Pickup = 0.995) the pickup is set at 94.8 V (94.3 V / 0.995 = 94.8 V) or 83.0% of Motor Base (3318.0 V).
1CAN032001 Enclosure Page 3 of 7 The as-left limits are determined as follows:
Dropout Calibration Upper Limit = 94.3 V + 0.1 V (calibration tolerance) = 94.4 V (3304.0 V)
Dropout Calibration Lower Limit = 94.3 V - 0.1 V (calibration tolerance) = 94.2 V (3297.0 V)
The as-found limits for voltage are determined by taking the square root of the sum of the squares of the reference accuracy of the relay, and the M&TE accuracy plus the relay drift, to determine the as-found tolerance. Once the as-found tolerance is determined, the as-found limits can be determined by adding or subtracting the as-found tolerance from the nominal setpoint.
The as-found limits for the voltage are calculated as follows:
Where:
Reference accuracy of relay = 0.001 M&TE accuracy = 0.002 Relay dropout voltage drift = 0.00816 As-found Tolerance = (0.0012 + 0.0022) + 0.00816 = 0.010396 Dropout Maximum As-Found Limit = 94.3 V x (1 + 0.010396) = 95.28 V (3334.8 V)
Dropout Minimum As-Found Limit = 94.3 V x (1 - 0.010396) = 93.32 V (3266.2 V)
The TS allowable limits are adjusted for channel uncertainties, relay drift, and margin and are determined as follows:
Dropout Upper Setting Adjusted for CU = 94.3 V x (1 + 0.0056) = 94.8 V (3318.0 V)
Dropout Lower Setting Adjusted for CU = 94.3 V x (1 - 0.0056) = 93.8 V (3283.0 V)
Maximum TS Allowable = 94.8 V x (1 + 0.00816) + *0.1 V = 95.7 V (3349.5 V)
- the 0.1 V is added for margin Minimum TS Allowable = (0.813) x (4000 V) x (120 V / 4200 V) = 92.9 V (3251.5 V)
LOV Time Delay Because the LOV relay is not intended to actuate on a normal fast transfer to another offsite power source, a delay is established to allow time for the feeder breaker LOV relays to actuate, the currently closed bus feeder breakers to trip open, and the alternate source breakers to close (actually the breaker trip and close are simultaneous; however, for conservatism no overlap is
1CAN032001 Enclosure Page 4 of 7 assumed), and to account for potential overtravel of the relay. Since the new time delay is longer than the existing time delay, the requirements above are maintained with the new time delay. Adjustments for Calibration Tolerance, Channel Uncertainty, and Relay Drift are accounted for in the time delay settings. The relay dropout setting is confirmed to be able to ride through system transients since the voltage recovers to above the pickup setting within the TS Allowable lower limit of 2.0 seconds.
Because the A3 and A4 switchgear LOV relays are the same model of 27N relays used on the B5 and B6 load centers, the relay timer uncertainty and drift values calculated in CALC-95-E-0001-01 for the B5 and B6 relays were used to validate the A3 and A4 LOV relay time delay setting of 2.3 seconds. A time delay of 2.3 seconds is established based on motor stall times for the affected buses, given the maximum voltage drop experienced by these buses when starting large motors. CALC-18-E-0015-01 verifies the acceptability of this setpoint selection.
The relay timer drift is calculated based on the performance of a statistical analysis of the as-left and as-found data (32 data points over a 6-year period). The relay timer drift is documented as 0.45%.
The relay timer channel uncertainty or "total loop uncertainties" is determined as follows:
CU
= Channel Uncertainty PM
= Process Measurement = 0 RA
= Module Reference Accuracy = 0.10 (Relay Accuracy)
= Temperature Effect = 0.01*
VE
= Voltage Effect = 0*
MTE = MT&E Effect = 0.02
- When the effect of voltage variation and temperature variation on the relays is not available from the manufacturer, the total effect is assumed to be 1%.
CU = +/- (0)2 + ( ((0.10)2 + (0.01)2 + (0)2 + (0.02)2) )2 CU = +/- 0.102 The TS upper and lower limits are determined as follows:
TUB = (TD)(1 + CU)(1 + RD)
TLB = (TD)(1 - CU)(1 - RD)
1CAN032001 Enclosure Page 5 of 7 Where:
CU
= Channel Uncertainty = 0.102 RD
= Relay Drift = 0.0045 TD
= Desired Relay Time Delay = 2.3 Seconds TUB = Time Delay Upper Band TLB = Time Delay Lower Band TUB = (2.3 s)(1 + 0.102)(1 + 0.0045)
TUB = 2.55 s (using 2.6 seconds for margin)
TLB = (2.3 s)(1 - 0.102)(1 - 0.0045)
TLB = 2.06 s (using 2.0 seconds for margin)
The as-left limits are determined as follows:
Calibration Upper Limit = 2.3 s + 0.1 s (relay calibration tolerance) = 2.4 s Calibration Lower Limit = 2.3 s - 0.1 s (relay calibration tolerance) = 2.2 s The as-found limits for time delay are determined by taking the square root sum of the squares of the reference accuracy of the relay and the M&TE accuracy plus the relay drift to determine the as-found tolerance. Once the as-found tolerance is determined, the as-found limits can be determined by adding or subtracting the as-found tolerance from the nominal setpoint.
The as-found limits for the voltage are calculated as follows:
Reference accuracy of relay = 0.10 M&TE accuracy = 0.02 Relay dropout timer drift = 0.0045 As-found tolerance = (0.102 + 0.022) + 0.0045 = 0.10648 Maximum As-Found Limit = (2.3 s)(1 + 0.10648) = 2.54 s Minimum As-Found Limit = (2.3 s)(1 - 0.10648) = 2.06 s With respect to the PT ratio, the maximum input range for the LOV relay is 110 V. Using the PT ratio of 4200/120, 110 V (100% of the input voltage range) at the LOV relay equates to 3850 V on the associated switchgear bus (110*(4200/120)). Likewise, 120 V at the LOV relay represents 4200 V on the switchgear bus (120*(4200/120)).
1CAN032001 Enclosure Page 6 of 7 The following depiction is provided as a high-level summary of the various calibration components.
Note: Percent voltages are calculated on the motor base voltage.
Supplemental Information Request 2 Provide the full ABB catalog number, including options of the new definite time LOV relay, ABB Single Phase Voltage Relays Type 27N, which will provide the applicable pickup and dropout voltages, performance tolerances, and the range of time delays of this proposed device.
Indicate whether a harmonic filter will be used, which could affect the repeatability versus temperature range uncertainty.
Entergy Response The ABB catalog number is Model 411T5175-HF-L. This model includes a harmonic filter as indicated by the "HF" in the model number.
Supplemental Information Request 3 Provide the actual time delay setting range selected for use in the LOV relay application.
Entergy Response Per the ABB vendor manual for Type 27N undervoltage relays, the Model 411T5xxx has a time delay setting range of 2 to 20 seconds.
3349.5 V (83.7%) - TS Allowable Limit 3334.8 V (83.4%) - As-Found Limit 3318.0 V (83%)
3283.0 V (82.1%)
3266.2 V (81.7%) - As-Found Limit 3251.5 V (81.3%) - TS Allowable Limit Allowance for Relay Drift & Margin Allowance for Relay Drift & Margin Channel Uncertainty Channel Uncertainty Maximum Circuit Voltage Drop Calibration Tolerance 3300.5 V (82.5%) - Desired Setting 3304.0 V 3297.0 V 3000 V (75%) - Minimum Equipment Acceptable Voltage
1CAN032001 Enclosure Page 7 of 7 REFERENCES
- 1.
Entergy Operations, Inc. (Entergy) letter to U. S. Nuclear Regulatory Commission (NRC), License Amendment Request to Revise Loss of Voltage Relay Allowable Values, Arkansas Nuclear One, Unit 1 (1CAN012002) (ML20024E639), dated January 24, 2020.
- 2.
NRC letter to Entergy, Arkansas Nuclear One, Unit 1 - Supplemental Information Needed for Acceptance of Requested Licensing Action Re: License Amendment Request to Revise Loss of Voltage Relay Allowable Values (EPID L-2020-LLA-0013),
(1CNA032001) (ML20065H799), dated March 6, 2020.