ML17179A179
| ML17179A179 | |
| Person / Time | |
|---|---|
| Site: | Vogtle  |
| Issue date: | 07/07/2017 |
| From: | Michael Orenak Plant Licensing Branch II |
| To: | Hutto J Southern Nuclear Operating Co |
| Orenak, M D, NRR/DORL/LPLII-1, 415-3229 | |
| References | |
| CAC MF9745, CAC MF9746 | |
| Download: ML17179A179 (4) | |
Text
UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 Mr. James J. Hutto Regulatory Affairs Director Southern Nuclear Operating Co., Inc.
P.O. Box 1295, Bin 038 Birmingham, AL 35201-1295 July 7, 2017
SUBJECT:
VOGTLE ELECTRIC GENERATING PLANT, UNITS 1 AND 2 - REQUEST FOR ADDITIONAL INFORMATION (CAC NOS. MF9745 AND MF9746)
Dear Mr. Hutto:
By application dated March 24, 2017, Southern Nuclear Operating Company, Inc. submitted a license amendment request to revise the Vogtle Electric Generating Plant, Units 1 and 2, Surveillance Requirement 3.3.1.3 to change the thermal power at which the surveillance may be performed.
The U.S. Nuclear Regulatory Commission staff has reviewed the submittal and has determined that additional information is needed to complete its review. On July 5, 2017, Mr. Joyce of your staff agreed to provide a response to these questions within 45 days of the date of this letter.
Docket Nos. 50-424 and 50-425
Enclosure:
Request for Additional Information Sincerely, Michael Orenak, Project Manager Plant Licensing Branch, 11-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation
UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 REQUEST FOR ADDITIONAL INFORMATION REGARDING CHANGES TO SURVEILLANCE REQUIREMENT 3.3.1.3, SOUTHERN NUCLEAR OPERATING COMPANY, INC.
VOGTLE ELECTRIC GENERATING PLANT, UNITS 1 AND 2 SOUTHERN NUCLEAR OPERATING COMPANY DOCKET NOS. 50-424 AND 50-425 By application dated May 24, 2017 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML17144A408), Southern Nuclear Operating Company, Inc.
(SNC, the licensee) submitted a license amendment request to revise Vogtle Electric Generating Plant (VEGP), Units 1 and 2, Technical Specifications (TS) Surveillance Requirement (SR) 3.3.1.3 to change the thermal power at which the surveillance may be performed.
The U.S. Nuclear Regulatory Commission staff reviewed the submittal and determined that the enclosed additional information is needed to complete its review.
At VEGP, Units 1 and 2, four excore detectors (external to the core) are used to measure axial flux difference (AFD), which is defined as the difference in normalized flux signals between the top and bottom halves of a two-section excore neutron detector. AFD is an input to the Overtemperature Delta-T (OT.LiT) reactor trip function. Note 1 of TS Table 3.3.1-1 on TS page 3.3.1-20 lists the equation for calculating the OT.LiT setpoint. The term in the equation, f1(AFD),
would reduce the OT Li T setpoint when the AFD exceeds the values specified in Note 1 of TS Table 3.3.1-1. Specially, the f1(AFD) requires the OT.LiT setpoint be reduced by 3.3 percent rated thermal power (RTP) for each AFD that is below -23 percent, and the setpoint be reduced by 1.95 percent RTP for each percent AFD that is above +10 percent.
The SR 3.3.1.3 requires a comparison of the incore AFD to the indicated excore AFD and adjustment of the instrument channel if the acceptance criterion is not met. The surveillance is performed to verify the f1(AFD) input to the OT.LiT trip function. The current NOTE to SR 3.3.1.3 specifies that following a refueling outage, the first performance of this SR is not required until 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> after the thermal power reaches 15 percent RTP. To increase the flexibility of the SR performance, the licensee proposed to increase the threshold power level in the NOTE from 15 percent RTP to 50 percent RTP. The licensee states that the AFD input to the OT.LiT trip function is initially calibrated with projected full-power detector currents until plant conditions allow for more accurate measurement of detector currents and incore AFD. In support of its SR changes, the licensee states on page E 1-6, in part, that:
Enclosure The initial calibration of the AFD input to the OT ti T trip function is sufficient to meet the requirements of the safety analyses until SR 3.3.1.3 is performed.
- 1)
Please identify the Condition 11, 111, and IV events from Chapter 15 of the updated final safety analysis report (UFSAR) (ADAMS Accession Nos. ML16330A433 and ML17032A143), that have analyses crediting the OTtiT trip function with initial power levels ranging from 0 percent RTP to 50 percent RTP.
- 2)
For the limiting events from (a), please provide additional information on why using the initial calibration of the AFD input to the OTtiT trip function is sufficient to meet the requirements of the safety analyses until SR 3.3.1.3 is performed at 50 percent RTP.
- 3)
Please discuss the impact of not including the effect of the f 1 (AFD) input to the OT ti T trip function on the applicable UFSAR Chapter 15 analyses for power levels below 50 percent RTP.
ML17179A179 OFFICE DORL/LPL2-1 /PM DORL/LPL2-1/LA NAME MOrenak KGoldstein DATE 06/29/17 06/29/17 DSS/SRXB/BC*
EOesterle 06/27/17