Cheryl A. Gayheart Regulatory Affairs Director

Docket Nos.: 50-424 NL-21-0444

50-425

U. S. Nuclear Regulatory Commission

ATTN: Document Control Desk

Washington, D. C. 20555-0001

Southern Nuclear Operating Company

Vogtle Electric Generating Plant – Units 1 and 2

Supplement to License Amendment Request to Revise

Technical Specification 3.3.5.2 Allowable Values

Ladies and Gentlemen:

On March 30, 2021 (ML21089A388), pursuant to the provisions Section 50.90 of Title 10 Code

of Federal Regulations (CFR), Southern Nuclear Operating Company (SNC) requested a

license amendment to Vogtle Electric Generating Plant (VEGP) Unit 1 renewed operating

license NFP-68 and Unit 2 renewed operating license NFP-81. The proposed amendment

revises Technical Specification (TS) 3.3.5, “Loss of Power (LOP) Instrumentation”, Surveillance

Requirement (SR) 3.3.5.2 Allowable Values.

On April 19, 2021 (ML21095A087), the U.S. Nuclear Regulatory Commission (NRC) staff

provided the results of their acceptance review and concluded that technical information was not

provided in sufficient detail to enable the NRC staff to complete its detailed review. In order to

make the application complete, the NRC staff requested that SNC supplement the application

by May 6, 2021.

SNC’s response is provided in the Enclosure.

SNC requests the same approval and implementation schedule as requested in its original

application.

The conclusions of the No Significant Hazards Consideration Determination Analysis and

Environmental Consideration contained in the original application have been reviewed and are

unaffected by this supplement.

This letter contains no NRC commitments. If you have any questions, please contact Jamie

Coleman at 205.992.6611

SNC Response to NRC Request for Supplemental Information

E-1

NRC Request to Supplement

The NRC staff identified that the following information is needed, within 13

working days from the date of this letter, to begin its detailed technical review:

 The as-found tolerance (AFT) and as-left tolerance (ALT) values of the

nominal trip setpoint (NTS) calibrations.

 The potential transformer ratio (for voltage conversion from the

transformer’s primary winding to secondary winding).

 Verification of (a) the current Analytical Limits (ALs) of the 4.16 kV

Engineered Safety Features (ESF) Bus LOP Instrumentation are 2912 V

(Loss of Voltage) and 3683 V (Degraded Voltage), and (b) these ALs are

not changed in the calculation.

The NRC staff identified the following information as a request of additional

information (RAI) which should be provided with the supplemental information

requested for acceptance. If this information cannot be provided, please provide

a date when it will be available:

 The full model numbers and the vendor (ABB) datasheets of the affected

relays, including the relays’ applicable pickup and dropout voltages and

performance tolerances. Also, discuss whether a harmonic filter will be

used, which could affect the repeatability versus temperature range

uncertainty.

 The full model numbers and the vendor datasheets of the voltage-tocurrent

module and the analog-to-digital module, including the uncertainty

values of these devices.

The NRC staff needs the above information to begin its detailed technical review

and perform an independent verification of the allowable values for the LOV and

DV relays’ trip setpoints.

SNC Response to NRC Request for Supplemental Information

E-2

of the sensing transformer. Using the sensing transformer ratio of 35:1, the

AFT and ALT Values on the 4160 Volt side of the sensing transformer is

equal to +/- 0.30 Volts x 35. The Loss of Voltage AFT and ALT Values are

+/- 10.5 Volts about the NTS of 2975 Volts.

 The winding ratio of the sensing potential transformer is 35:1.

 The Analytical Limit (AL) for Degraded Voltage is 3683V and for LOP is

2912V. The ALs have not changed in the calculation.

 There are not any physical bistable relays. They are modeled in software.

The pickup and dropout voltages are the ‘Setpoint’ and ‘Reset’ values. The

values and tolerances on the 120 Volt side of the sensing transformer for

degraded voltage and loss of voltage are listed below. A harmonic filter is not

needed because there aren’t any physical relay contacts opening and closing

and generating harmonics when doing so. There is an analog low pass

prefilter and a digital low pass filter built into the analog-to-digital module

(ABB AI620).

Degraded Voltage:

Setpoint (pickup) = 107.03V Hi Limit = 107.33V Low Limit = 106.73V

Reset (dropout) = 108.53V Hi Limit = 108.83V Low Limit = 108.23V

Loss of Voltage:

Setpoint (pickup) = 85.00V Hi Limit = 85.30V Low Limit = 84.70V

Reset (dropout) = 86.50V Hi Limit = 86.80V Low Limit = 86.20V

 The Dataforth voltage-to-current module part number supplied by

Westinghouse is DSCA33-1566. The accuracy data for this Westinghouse

part number is the same as the non-proprietary accuracy data for Dataforth

part number DSCA33-04C. The non-proprietary data sheet for Dataforth part

number DCCA33-04C is provided as Attachment 1 to this Enclosure. The

ABB analog-to-digital module part number is Al620. The non-proprietary data

sheet for the ABB part number AI620 is provided as Attachment 2 to this

Enclosure.

Features

• Interfaces RMS Voltage (0 – 300V) or