ML25224A234
| ML25224A234 | |
| Person / Time | |
|---|---|
| Site: | Vogtle  (NFP-091, NPF-092) |
| Issue date: | 08/15/2025 |
| From: | John Lamb NRC/NRR/DORL/LPL2-1 |
| To: | |
| Shared Package | |
| ML25224A237 | List: |
| References | |
| EPID L-2025-LRM-0109 | |
| Download: ML25224A234 (1) | |
Text
August 15, 2025 LICENSEE:
Southern Nuclear Operating Company, Inc.
FACILITY:
Vogtle Electric Generating Plant, Unit 4
SUBJECT:
SUMMARY
OF AUGUST 11, 2025, OBSERVATION PRE-SUBMITTAL MEETING HELD WITH SOUTHERN NUCLEAR OPERATING COMPANY, INC.,
REGARDING A PROPOSED EMERGENCY LICENSE AMENDMENT REQUEST TO CHANGE TECHNICAL SPECIFICATION 3.5.2, CORE MAKEUP TANKS (CMTs) - OPERATING, FOR VOGTLE ELECTRIC GENERATING PLANT, UNIT 4 (EPID L-2025-LRM-0109)
On August 11, 2025, an Observation meeting was held between the U.S. Nuclear Regulatory Commission (NRC) and representatives of Southern Nuclear Operating Company, Inc. (SNC, the licensee). The purpose of the meeting was for SNC to describe its plan to submit a proposed emergency license amendment request (LAR) for Vogtle Electric Generating Plant (Vogtle), Unit 4.
SNC is proposing to add a note to Technical Specification (TS) 3.5.2, Core Makeup Tanks (CMTs) - Operating, and a note to Surveillance Requirement (SR) 3.5.2.4 regarding boron concentration at Vogtle, Unit 4.
A list of attendees is provided as an Enclosure.
On August 11, 2025 (Agencywide Documents and Access Management System (ADAMS)
Accession No. ML25223A053), the meeting was noticed on the NRC public web page.
The NRC staff opened the meeting with introductory remarks and a rollcall of the attendees.
The SNC representative presented the final slides contained in ML25223A299 and the draft slides are located in ML25224A170.
SNC representatives discussed the following topics: (1) background, (2) TS SR 3.5.2.4 planned changes, (3) technical evaluation, (4) schedule, and (5) discussion.
=
Background===
The Passive Core Cooling System (PXS) primary function is to provide emergency core cooling following postulated design basis events. The PXS includes two redundant CMTs connected to the direct vessel injection lines. The two CMTs contain borated water at >3400 ppm to assure reactivity control. The CMTs inject into the reactor coolant system (RCS) on loss of inventory.
The CMTs provide emergency boration and core makeup when the chemical volume system is unavailable and to mitigate consequences of any design basis accident (DBA) requiring safety injection of borated water.
TS 3.5.2, Condition B and SR 3.5.2.4 Technical Specification (TS) 3.5.2, Core Makeup Tanks (CMTs) - Operating, Condition B states:
CONDITION REQUIRED ACTION COMPLETION TIME B. One CMT inoperable due to water temperature or boron concentration not within limits.
B.1 Restore water temperature and boron concentration to within limits.
72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> TS 3.5.2, SR 3.5.2.4 states:
SURVEILLANCE FREQUENCY SR 3.5.2.4 Verify the boron concentration in each CMT is 3400 ppm and 4500 ppm.
31 days SNC stated that the outlet valve leakage dilutes CMT at lower RCS boron concentrations.
SNC said that it proposes to add two Notes to SR 3.5.2.4. The Notes would state the following:
For Unit 4 until 4R01 in MODE 4 with RCS being cooled by RNS, CMT A minimum boron concentration is 3100 parts per million (ppm) provided average of CMT A and CMT B boron concentration is >3400 ppm.
Not required to be performed for Unit 4 until startup from 4R01.
Technical Evaluation SNC said that there is no adverse impact on the Loss of Normal Feedwater event and no adverse impact on shutdown margin for Small Break Loss of Coolant Accidents. The CMT boration is not credited in the Steam Generator Tube Rupture event. For the Large Break Loss of Coolant Accidents, the CMT injects with 3100 ppm boron concentration.
For the Anticipated Transient Without a SCRAM (ATWS), the minimum allowable average boron concentration of 3400 ppm is offset by conservatisms. Conservatisms in the ATWS and safe shutdown (SSD) analyses would more than offset the 100ppm reduction (3500 ppm -
3400 ppm) in combined CMT boron concentration.
SNC stated that the margins in these analyses are sufficient to bound the impacts of a CMT A boron concentration as low as 3100 ppm provided the boron concentration from CMT A and B combined are 3400 ppm.
SNC said that utilizing the most recent sample result of 3479 ppm on August 9, 2025, at 1:57 pm and the calculated leakage of 46.9 gallons per day (gpd) into the CMT, CMT A will remain 3400 ppm for a period of 8.8 days, from the time of the sample. To ensure margin, SNC calculated the change in boron concentration at a leakage rate of 66 gallons per day and determined that CMT A boron concentration would be 3403 ppm at the end of 6 days and 3138.5 ppm at the end of 28 days.
SNC stated that using the volume of Bleed and Feed to change concentration, the CMT A will be 3403 ppm in 6 days and 3140.5 ppm in 28 days.
SNC said that RCS monitoring will be ongoing to confirm the concentration in CMT A remains above the TS limit of 3100 ppm until the Vogtle, Unit 4, refueling outage, scheduled for fall 2025.
Schedule SNC representative stated that the proposed emergency LAR is expected to be submitted to the NRC on August 11, 2025, with a request for the NRC staff approval by August 16, 2025.
Discussion The NRC staff asked the following questions:
What are the emergency circumstances?
Can SNC describe which valve is leaking?
Can SNC describe when the valve was first discovered leaking?
Did SNC have a planned maintenance outage since the valve was discovered leaking?
Why wasnt the valve repaired during the planned maintenance outage in spring 2025?
Did SNC consider placing a Note in the limiting condition for operation instead of SR 3.5.2.4?
What is the boron concentration in CMT B?
Why doesnt SNC want to perform SR 3.5.2.4 for CMT B?
How did SNC come up with the lower boron concentration limit of 3100 ppm?
Will SNC provide its calculations in the LAR?
What is the result of a DBA with a single failure of the CMT B?
One of the slides mentions conservatisms; will those conservatisms be explained in detail in the LAR?
How does SNC plan to monitor the boron concentrations?
What action plans will SNC have in place?
Closing Remarks There were no members of the public in attendance.
The NRC staff did not make any regulatory decisions during the meeting. Once received, the NRC staff will perform a thorough review of the proposed LAR. The NRC staff will make any regulatory decisions in writing in a timely manner. Public Meeting Feedback forms were available, but no comments were received.
The meeting adjourned at 11:20 am eastern time (ET).
Please direct any inquiries to me at John.Lamb@nrc.gov or 301-415-3100.
/RA/
John G. Lamb, Senior Project Manager Plant Licensing Branch, II-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No.52-026
Enclosure:
List of Attendees cc: Listserv
Enclosure LIST OF ATTENDEES AUGUST 11, 2025, PRE-SUBMITTAL MEETING WITH SOUTHERN NUCLEAR COMPANY REGARDING A PROPOSED EMERGENCY LICENSE AMENDMENT REQUEST TO CHANGE TS 3.5.2 FOR VOGTLE ELECTRIC GENERATING PLANT, UNIT 4 ATTENDEE REPRESENTING John G. Lamb U.S. Nuclear Regulatory Commission (NRC)
Mike Markley NRC Summer Sun NRC Fred Forsaty NRC Steve Smith NRC Theo Fanelli NRC Alan Blamey NRC Hanry Wagage NRC Evan Davidson NRC Vic Cusumano NRC John Budzynski NRC Jay Robinson NRC Ahsan Sallman NRC Milton Valentin NRC Amini Noushin NRC Ken Lowery Southern Nuclear Operating Company (SNC)
Ryan Joyce SNC Jamie Coleman SNC Adam Quarles SNC Michael Coker SNC Jeremiah Gilbreath SNC Dan Williamson SNC Jordan Rice SNC Will Garrett SNC Rebecca Willmott SNC Robert Uhurchuk SNC Bradley Balltrip SNC Ben Rothschadl SNC James Wyble Westinghouse Daniel Wise Westinghouse Jennifer Meneely Westinghouse Kevin May Westinghouse Allison Fisher Westinghouse Doug Hake Westinghouse
PKG: ML25224A237 Meeting Notice: ML25223A053 SNC FINAL Slides: ML25223A299 SNC Draft Slides: ML25224A170 Meeting Summary: ML25224A234 OFFICE DORL/LPL2-1/PM DORL/LPL2-1/LA DSS/SNSB/BC DORL/LPL2-1/BC DORL/LPL2-1/PM NAME JLamb KZeleznock NDifrancesco (ASallman for)
MMarkley JLamb DATE 08/12/2025 08/15/2025 08/15/2025 08/15/2025 08/15/2025