ML21295A412

Closeout of Bulletin 2012-01, Design Vulnerability in Electric Power System

ML21295A412
Person / Time
Site:	Millstone
Issue date:	11/15/2021
From:	Richard Guzman NRC/NRR/DORL/LPL1
To:	Stoddard D Dominion Energy Nuclear Connecticut
Guzman R
References
BL-12-001, EPID L-2017-CRS-0063
Download: ML21295A412 (4)

Text

November 15, 2021 Mr. Daniel G. Stoddard Senior Vice President and Chief Nuclear Officer Dominion Energy Nuclear Connecticut, Inc.

Millstone Power Station Innsbrook Technical Center 5000 Dominion Boulevard Glen Allen, VA 23060-6711

SUBJECT:

MILLSTONE POWER STATION, UNITS 2 AND 3 - CLOSEOUT OF NRC BULLETIN 2012-01, DESIGN VULNERABILITY IN ELECTRIC POWER SYSTEM (EPID L 2017-CRS-0063)

Dear Mr. Stoddard:

The purpose of this letter is to inform you that the U.S. Nuclear Regulatory Commission (NRC) staff has verified that Dominion Energy Nuclear Connecticut, Inc. (the licensee) has provided the necessary information requested in NRCs Bulletin (BL) 2012-01, Design Vulnerability in Electric Power System, dated July 27, 2012 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML12074A115), for Millstone Power Station, Units 2 and 3 (Millstone). The NRC staff has completed its review of this information and has closed out BL 2012-01 for this facility.

The NRC issued BL 2012-01 on July 27, 2012, to all holders of operating licenses and combined licenses for nuclear power reactors, except those who have permanently ceased operation and have certified that fuel has been removed from the reactor vessel. The Bulletin requested information about each facilitys electric power system designs that would allow the NRC staff to verify the systems capability to address open phase conditions. Specifically, the NRC requested licensees to provide the following information:

A description of how the protection scheme for engineered safety features buses (Class 1E for current operating plants or non-Class 1E for passive plants) is designed to detect and automatically respond to a single-phase open circuit condition or high impedance ground fault condition on offsite power circuits or another power source; and A description of the operating configuration of engineered safety features buses (Class 1E for current operating plants or non-Class 1E for passive plants) at power (i.e., normal operating condition).

By letter dated October 24, 2012 (ADAMS Accession No. ML12305A017), the licensee provided its response to BL 2012-01 for Millstone. By letter dated February 3, 2014 (ADAMS Accession No. ML14035A458), the licensee provided supplemental information for this facility in response to an NRC staff request for additional information issued on December 20, 2013 (ADAMS Accession No. ML13351A314).

D. Stoddard By letters dated October 9, 2013, and March 16, 2015 (ADAMS Accession Nos. ML13333A147 and ML15075A454, respectively), the Nuclear Energy Institute (NEI) submitted a voluntary industry initiative to address open phase conditions at nuclear power plants. The NEI letter dated March 16, 2015, stated, in part: The initiative is a formal commitment by the companies that operate nuclear power plants to follow a specific policy or plan of action. The initiative calls for a proactive plan and schedule for addressing potential design vulnerabilities to the open phase condition.

To evaluate the adequacy of the open phase isolation systems designs, the NRC staff issued Temporary Instruction (TI) 2515/194, Inspection of the Licensees Implementation of Industry Initiative Associated with the Open Phase Condition Design Vulnerabilities in Electric Power Systems (NRC Bulletin 2012-01), dated October 31, 2017 (ADAMS Accession No. ML17137A416), which provided temporary inspection instructions for the purpose of verifying that licensees appropriately implemented the NEI voluntary industry initiative dated March 16, 2015. The NRC staff piloted the use of TI 2515/194 by inspecting four nuclear power plants with four distinct open phase isolation system designs. A summary of the NRC staffs preliminary observations and issues needing additional clarity were discussed with industry representatives in two public meetings conducted on September 19, 2018, and October 17, 2018. The meeting summaries can be found in ADAMS under Package Accession Nos. ML18268A342 and ML18309A226, respectively.

By letter dated June 6, 2019 (ADAMS Accession No. ML19163A176), NEI submitted Revision 3 of the voluntary industry initiative to include an option for plants to perform a risk evaluation under certain boundary conditions to support manual response to an open phase condition. NEI also submitted NEI 19-02, Guidance for Assessing Open Phase Condition Implementation Using Risk Insights on June 20, 2019 (ADAMS Accession No. ML19172A086). On August 18, 2020, the NRC staff issued Revision 2 of TI 2515/194 (ADAMS Accession No. ML20230A328),

which provided temporary inspection instructions for the purpose of verifying that licensees appropriately implemented Revision 3 of the NEI voluntary industry initiative. The revision accounted for changes reflected in Revision 3 of the NEI voluntary initiative.

In March 2021, the NRC staff performed inspections at Millstone using TI 2515/194 Revision 2.

This inspection at Millstone was performed to verify the licensees implementation of the voluntary industry initiative at this facility. To address the open phase condition design vulnerability issue at this facility, the licensee implemented open phase isolation system plant modifications, which provide detection and alarm in the control room, and necessary plant procedures that allow operators to diagnose and take manual action to mitigate an open phase condition. The NRC inspection report listed below documents the results of the TI 2515/194 inspection.

Millstone Power Station, Units 2 and 3 - Temporary Instruction 2515/194 Inspection Report 05000336/2021012 and 05000423/2021012, dated March 17, 2021 (ADAMS Accession No. ML21076A411)

The NRC staff reviewed the information submitted by the licensee and the results of the TI 2515/194 inspection for Millstone. In the inspection report, an exception is identified regarding the inconsistency between the licensees risk analysis and the guidance and methodology described in NEI 19-02. However, as noted in the inspection report, the licensees risk analysis results are low and bounded by the ceiling criteria for the core damage frequency.

Therefore, the NRC staff finds the exception acceptable. Based on this review, the NRC staff concludes that the licensee provided the necessary information requested in BL 2012-01 and

D. Stoddard has completed the implementation of its open phase isolation system. Therefore, the NRC staff closes BL 2012-01 for Millstone.

If you have any questions, please contact me at 301-415-1030 or via e-mail at Richard.Guzman@nrc.gov.

Sincerely,

/RA/

Richard V. Guzman, Senior Project Manager Plant Licensing Branch I Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. 50-336 and 50-423 cc: Listserv

ML21295A412 OFFICE NRR/DORL/LPL1/PM NRR/DORL/LPL1/LA NRR/DEX/EEEB/BC NAME RGuzman KEntz WMorton DATE 10/22/2021 10/27/2021 10/05/2021 OFFICE NRR/DRA/APOB/BC NRR/DRO/IOEB/BC NRR/DORL/LPL1/BC NAME AZoulis LRegner JDanna DATE 10/22/2021 10/27/2021 11/15/2021 OFFICE NRR/DORL/LPL2-1/PM NAME RGuzman DATE 11/15/2021