ML25083A109
| ML25083A109 | |
| Person / Time | |
|---|---|
| Site: | Braidwood  |
| Issue date: | 04/16/2025 |
| From: | Scott Wall NRC/NRR/DORL/LPL3 |
| To: | Rhoades D Constellation Energy Generation |
| Wall, S | |
| References | |
| EPID L-2024-LLA-0172 | |
| Download: ML25083A109 (1) | |
Text
April 16, 2025 David P. Rhoades Senior Vice President Constellation Energy Generation, LLC President and Chief Nuclear Officer Constellation Nuclear 4300 Winfield Road Warrenville, IL 60555
SUBJECT:
BRAIDWOOD STATION, UNITS 1 AND 2 - REGULATORY AUDIT IN SUPPORT OF REVIEW OF THE APPLICATION TO INCORPORATE A DIURNAL CURVE TO BRAIDWOOD STATION TECHNICAL SPECIFICATIONS 3.7.9 FOR THE ULTIMATE HEAT SINK (EPID L-2024-LLA-0172)
Dear David Rhoades:
By \
letter dated December 20, 2024 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML24355A058), Constellation Energy Generation, LLC (the licensee) submitted a license amendment request (LAR) for Braidwood Station, Units 1 and 2 (Braidwood). The proposed LAR would modify the Braidwoods Technical Specifications (TSs) to change TS Surveillance Requirement (SR) 3.7.9.2 to support an Ultimate Heat Sink (UHS)
TS temperature limit that would reflect the diurnal effect that weather conditions have upon the UHS.
The U.S. Nuclear Regulatory Commission (NRC) staff has found the need for a regulatory audit to examine the licensees non-docketed information with the intent to gain understanding, to verify information, or to identify information that requires docketing to support the basis of the licensing or regulatory decision.
The NRC staff will conduct the audit virtually via Teams using a licensee-established electronic portal available to NRC staff from approximately May 1, 2025, through September 1, 2025, with formal audit meetings to be scheduled during this period as needed. The detailed audit plan is enclosed with this letter.
D. Rhoades If you have any questions, please contact me at (301) 415-2855 or by e-mail at Scott.Wall@nrc.gov.
Sincerely,
/RA/
Scott Wall, Senior Project Manager Plant Licensing Branch III Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. STN 50-454 and STN 50-455
Enclosure:
Audit Plan cc: Listserv
Enclosure REGULATORY AUDIT PLAN BY THE OFFICE OF NUCLEAR REACTOR REGULATION TO INCORPORATE A DIURNAL CURVE TO BRAIDWOOD STATION TECHNICAL SPECIFICATIONS 3.7.9 FOR THE ULTIMATE HEAT SINK CONSTELLATION ENERGY GENERATION, LLC BRAIDWOOD STATION, UNITS 1 AND 2 DOCKET NOS. STN 50-456 AND STN 50-457
1.0 BACKGROUND
By \
letter dated December 20, 2024 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML24355A058), Constellation Energy Generation, LLC (the licensee) submitted a license amendment request (LAR) for Braidwood Station, Units 1 and 2 (Braidwood). The proposed LAR would modify the Braidwoods Technical Specifications (TSs) to change TS Surveillance Requirement (SR) 3.7.9.2 to support an Ultimate Heat Sink (UHS)
TS temperature limit that would reflect the diurnal effect that weather conditions have upon the UHS.
The staff from the Nuclear Regulatory Commissions (NRC), Office of Nuclear Reactor Regulation (NRR) has initiated its review of the LAR in accordance with NRR Office Instruction LIC-101, License Amendment Review Procedures (ML19248C539).
2.0 REGULATORY AUDIT BASIS A regulatory audit is a planned license-or regulation-related activity that includes the examination and evaluation of primarily non-docketed information associated with the LAR. An audit is conducted to gain understanding, to verify information, and to identify information that will require docketing to support the basis of a licensing or regulatory decision. An audit will assist the NRC staff in efficiently conducting its review and gaining insights to the licensees processes and procedures. Information that the NRC staff relies upon to make the safety determination must be submitted on the docket. This audit will be conducted in accordance with NRR Office Instruction LIC-111, Regulatory Audits Revision 1, dated October 2019 (ML19226A274), with exceptions noted within this audit plan.
The NRC staff performs the audit to support its evaluation of whether the licensees LAR can be approved per Title 10 of the Code of Federal Regulations (10 CFR), Section 50.90, Application for amendment of license, construction permit, or early site permit. An audit was determined to be the most efficient approach toward a timely resolution of questions associated with this LAR review because the NRC staff will have an opportunity to minimize the potential for requests for additional information and ensure no unnecessary burden will be imposed by requiring the licensee to address issues that are no longer necessary to make a safety determination. The NRC staff is requesting an initial set of internal licensee information to be audited by the staff using an online reference portal. Upon completion of this audit, the NRC staff is expected to achieve the following.
- 1.
Confirm internal licensee information that supports statements made in the LAR.
- 2.
Determine whether the information included in the documents is necessary to be submitted to support a safety conclusion.
The audit information the NRC staff determines to be necessary to support the development of the NRC staffs safety evaluation will be requested to be submitted on the docket.
3.0 REGULATORY AUDIT SCOPE AND METHODOLOGY The purpose of the remote audit is to gain a more detailed understanding of the information supporting the licensees request to revise TSs to reflect the diurnal effect that weather conditions have upon the UHS at Braidwood.
4.0 INFORMATION AND OTHER MATERIAL NECESSARY FOR THE AUDIT The NRC staff requests information and audit meeting(s) throughout the audit period. The NRC staff uses an audit items list to identify the information (e.g., methodology, process information, and calculations) to be audited. The NRC staff provides the final audit items list as an enclosure to the audit summary report, which will be publicly available. The attachment to this audit plan includes the initial audit items list. Throughout the audit period, the NRC staff provides the licensee with audit questions and audit-related requests so that the licensee can better prepare for audit discussions with NRC staff. Any information accessed through the licensees portal is not held or retained in any way by NRC staff. The NRC staff requests the licensee to have the requested audit information listed in the audit items list to be readily available and accessible for the NRC staffs review via a Web-based portal.
5.0 TEAM ASSIGNMENTS The audit team will consist of the following NRC staff from NRR and contractors.
Scott Wall, Plant Licensing Branch III (LPL3)
Joshua Wilson, Technical Specifications Branch (STSB)
David Nold, Containment and Plant Systems Branch (SCPB)
Gordon Curran, SCPB Samir Darbali, Instrumentation and Controls Branch B (EICB)
Youssef Rokes, EICB Robert Beaton, Nuclear Systems Performance Branch (SNSB)
Thomas Scarbrough, Mechanical Engineering and Inservice Testing Branch (EMIB)
Roberto Torres Davis, EMIB Kamishan Martin, Operator Licensing and Human Factors Branch (IOLB)
To be determined, contractor(s)
The NRC staff may request access for additional staff as the audit progresses.
6.0 LOGISTICS To support the review schedule communicated to the licensee when the NRC staff accepted the LAR for technical review, audit activities will be performed remotely and virtually using Microsoft Teams, teleconference, and a Web-based portal or other virtual meeting space created by the licensee. NRC information requests and communications with licensee staff is coordinated through the NRCs licensing project manager.
A desktop audit will take place between May 1, 2025, through September 1, 2025. The NRCs licensing project manager informs the licensee of the entrance and exit meeting dates when they are established. The NRC intends to set up audit meeting(s) (e.g., a single, multi-day audit meeting; periodic audit meetings throughout the audit period) on mutually agreeable dates and times (to be determined) to discuss information needs and questions arising from the NRCs review of the audited items. The NRC staff may change and/or add audit dates and times when deemed necessary. Audit meeting agenda and questions will be sent in advance of the audit meeting.
The NRC staff requests the licensee to have the information referenced in Section 4.0 of this audit plan available and accessible for the NRC staffs review via an internet-based portal within 2 weeks of the date of this audit plan. The NRC staff requests that any supplemental information requested be available and accessible for the NRC staffs review within 1 week of the date of the NRCs notification to the licensee of the new requests. The NRCs licensing project manager informs the licensee via routine communications when the NRC staff no longer needs access to the portal. The NRC staff requests the licensee to notify the NRC licensing project manager when an audit item is added to its portal by sending an e-mail to the NRC licensing project manager.
7.0 SPECIAL REQUESTS The NRC requests access to requested documents and information through a Web-based portal that allows the NRC staff and contractors to access documents over the Internet. The following conditions associated with the online portal must be maintained while the NRC staff and contractors have access to the online portal:
The online portal will be password protected. A separate password will be assigned to each member of the NRC staff and NRC contractors taking part in the audit.
The online portal will prevent the NRC participants from printing, saving, downloading, or collecting any information directly from the online portal.
Conditions of use of the online portal will be displayed on the login screen and will require acknowledgment by each user.
Username and password and/or other Web-based portal access information should be provided directly to members of the NRC staff and contractors as needed. The NRC licensing project manager will provide the licensee with names and contact information of the NRC staff and contractors participating in the audit. All other communications should be coordinated through the NRC project manager.
8.0 DELIVERABLES The NRC staff will develop any RAIs, as needed, via NRR Office Instruction LIC-115 and issue such RAIs separately from audit-related correspondence. The NRC staff will issue an audit summary report prior to completing its review of the LAR.
Initial Audit Items List Item #
Audit Item 1
Licensee application dated December 20, 2024 (ML24355A058) references NRC \
letter dated July 26, 2016, BRAIDWOOD STATION, UNITS 1 AND 2 - ISSUANCE OF AMENDMENTS RE: ULTIMATE HEAT SINK TEMPERATURE INCREASE (CAC NOS. MF4671 AND MF4672) (ML16133A438), which approved the license amendment request in \
letter dated August 19, 2014 (ML14231A902). As part of the staffs review of the August 19, 2014 LAR the NRC staff reviewed calculations and procedures during an audit (ML15232A589) to validate instrument uncertainty relationship to the UHS water temperature change.
In support of the current licensee application dated December 20, 2024 (ML24355A058), provide:
Methodology to calculate the overall precision instrument uncertainty.
Procedures for monitoring the UHS temperature using the precision instrument.
Calculation for each value of the UHS Diurnal curve temperature in Figure 3.7.9-1 which takes into account the precision instrument uncertainty. In the summary of the calculation, please indicate how the as-left and as-found surveillance test acceptance criteria were determined.
2 Engineering Change 641059, Revision 1, Support Analyses for the License Amendment Request to Raise the Maximum Temperature for the UHS in TS LCO 3.7.9 Utilizing a Diurnal Temperature Profile 3
Documentation/analysis used to derive the Figure 3 of LAR, which includes assumptions and inputs.
AUDIT QUESTIONS REGARDING LICENSE ADMENTMENT REQUEST TO INCORPORATE A DIURNAL CURVE TO BRAIDWOOD STATION TECHNICAL SPECIFICATIONS 3.7.9 FOR THE ULTIMATE HEAT SINK CONSTELLATION ENERGY GENERATION, LLC BRAIDWOOD STATION, UNITS 1 AND 2 DOCKET NOS. STN 50-456 AND STN 50-457
1.0 BACKGROUND
By \
letter dated December 20, 2024 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML24355A058), Constellation Energy Generation, LLC (the licensee) submitted a license amendment request (LAR) for Braidwood Station, Units 1 and 2 (Braidwood). The proposed LAR would modify the Braidwoods Technical Specifications (TSs) to change TS Surveillance Requirement (SR) 3.7.9.2 to support an Ultimate Heat Sink (UHS)
TS temperature limit that would reflect the diurnal effect that weather conditions have upon the UHS.
The U.S. Nuclear Regulatory Commission (NRC) staff has identified the need for a regulatory audit to examine the licensees non-docketed information with the intent to gain understanding, to verify information, or to identify information that will require docketing to support the basis of the licensing or regulatory decision. The staff is providing the questions below to aid discussion during the audit.
2.0 AUDIT QUESTIONS 2.1 Nuclear Systems Performance Branch (SNSB) Audit Question 1 In Section 3.1, UHS Structure and Evaluation, of the LAR, the licensee states, in part:
Figure 2 shows the UHS temperature response to a DBA LOCA for each of the start times, every 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> in a 24-hour period, for the 33 days period post-accident, and Figure 3 shows an expanded view of the same response for initial 3 day period.
Figure 3, Maximum UHS temperature - 3 SX Pumps - 3 Days, does not appear to show three days for all the cases. For example, it only provides two days and three hours for the case that starts at 9 PM.
Confirm that the peak temperatures during the initial three-day period are shown on the Figure for all cases.
2.2 SNSB Audit Question 2 In Section 3.5, Accident Analyses, sub-section RCFC [Reactor Containment Fan Coolers]
Performance Margin, of the LAR, the licensee states, in part:
The RCFC heat removal performance curve used in the accident analyses is based on 10% tube plugging level while the maximum actual tube plugging level range is 0.83% to 3%.
What controls are in place to assure tube plugging remains below 10 percent in the future?
2.3 SNSB Audit Question 3 In Section 3.5, sub-section, Non-LOCA Transient Analyses, of the LAR, the licensee states, in part:
The proposed change to the UHS temperature limit supports a maximum UHS temperature of 104°F for non-LOCA transients.
a) What non-LOCA events would result in an increase to the UHS temperature?
b) Confirm that the maximum temperature would not exceed 104°F for these cases.
ML25083A109 OFFICE NRR/DORL/LPL3/PM NRR/DORL/LPL3/LA NRR/DSS/SCPB/BC NRR/DSS/SNSB/BC NAME SWall SRohrer MValentin DMurdock DATE 03/24/2025 03/25/2025 04/09/2025 04/07/2025 OFFICE NRR/DSS/STSB/BC NRR/DEX/EICB/BC NRR/DEX/EMIB/BC NRR/DORL/LPL3/BC(A)
NAME SMehta FSacko SBailey IBerrios DATE 03/25/2025 04/07/2025 04/10/2025 04/15/2025 OFFICE NRR/DORL/LPL3/PM NAME SWall DATE 04/16/2025