RA-24-0097, Response to Request for Supplemental Information Supporting the Request for Exemption from Certain Requirements in 10 CFR 50.55a(h)(2) Using Risk-Informed Process for Evaluations

Response to Request for Supplemental Information Supporting the Request for Exemption from Certain Requirements in 10 CFR 50.55a(h)(2) Using Risk-Informed Process for Evaluations

ML24094A105
Person / Time
Site:	Harris
Issue date:	04/03/2024
From:	Kidd C Duke Energy Progress
To:	Office of Nuclear Reactor Regulation, Document Control Desk
References
RA-24-0097
Download: ML24094A105 (1)

Text

Chad Kidd e.__f_~ DUKE General Manager

• Nuclear Engineering Harris Nuclear Plant

? ENERGY 5413 Shearon Harris Rd New Hill, NC 27562-9300

984.229.3140

10 CFR 50.12 April 3, 2024 Serial: RA-24-0097

ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555-0001

Shearon Harris Nuclear Power Plant, Unit 1 Docket No. 50-400 Renewed License No. NPF-63

Subject:

Response to Request for Supplemental Information Supporting the Request for Exemption from Certain Requirements in 10 CFR 50.55a(h)(2) using Risk-Informed Process for Evaluations

Ladies and Gentlemen :

By letter dated February 6, 2024 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML24037A284), Duke Energy Progress, LLC (Duke Energy) submitted a request under the Risk-Informed Process for Evaluations (RIPE) for an exemption from the requirements of 1 0 CFR 50.55a(h)(2), Protection systems, requiring protection systems meet the requirements of IEEE 279-1971, "Criteria for Protection Systems for Nuclear Power Generating Stations," for the Shearon Harris Nuclear Power Plant, Unit 1 (HNP). Specifically,

the exemption request would remove the requirement for the Reactor Protection System (RPS) cables that terminate within the Turbine Control System (TCS) Cabinet G (1TCS-CAB-G) meet the IEEE 279-1971 Section 4.6, Channel Independence, requirement that the cables be independent and physically separated.

The U.S. Nuclear Regulatory Commission (NRG) staff reviewed the application and determined that supplemental information is needed to complete their independent assessment regarding the acceptability of the proposed exemption in terms of using RIPE. Duke Energy received the request for supplemental information from the NRC by letter dated March 18, 2024 (ADAMS Accession No. ML24058A246).

The enclosure to this letter provides the requested supplemental information to the application.

There are no new regulatory commitments contained within this letter.

Please refer any questions regarding this submittal to Ryan Treadway, Director - Nuclear Fleet Licensing, at 980-373-5873.

Sincerely,, /.:/.

~J ~_:w Chad Kidd General Manager - Nuclear Engineering U.S. Nuclear Regulatory Commission Page 2 of 2 Serial: RA-24-0097

Enclosure:

Response to Request for Supplemental Information

cc: P. Boguszewski, Senior NRC Resident Inspector, HNP L. Brayboy, Radioactive Materials Branch Manager, NC DHHS M. Mahoney, NRC Project Manager, HNP L. Dudes, NRC Regional Administrator, Region II U.S. Nuclear Regulatory Commission Serial: RA-24-0097 Enclosure

ENCLOSURE

RESPONSE TO REQUEST FOR SUPPLEMENTAL INFORMATION

2 PAGES PLUS THE COVER

U.S. Nuclear Regulatory Commission Page 1 of 2 Serial: RA-24-0097 Enclosure

INTRODUCTION

By letter dated February 6, 2024 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML24037A284), Duke Energy Progress, LLC (Duke Energy) submitted a request under the Risk-Informed Process for Ev aluations (RIPE) for an exemption from the requirements of 10 CFR 50.55a(h)(2), Protection systems, requiring protection systems meet the requirements of IEEE 279-1971, Criteria for Protection Systems for Nuclear Power Generating Stations, for the Shearon Harris Nuclear Power Plant, Unit 1 (HNP). Specifically, the exemption request would remove the requirem ent for the Reactor Protection System (RPS) cables that terminate within the Turbine Contro l System (TCS) Cabinet G (1TCS-CAB-G) meet the IEEE 279-1971 Section 4.6, Channel Independence, requirement that the cables be independent and physically separated.

The U.S. Nuclear Regulatory Commission (NRC) staff reviewed the application and determined that supplemental information is needed to complete their independent assessment regarding the acceptability of the proposed exemption in terms of using RIPE. Duke Energy received the request for supplemental information from the NRC by letter dated March 18, 2024 (ADAMS Accession No. ML24058A246).

REQUEST FOR SUPPLEMENTAL INFORMATION

The NRC staff has identified information insuffic iencies related to how the request addresses the following screening questions from the NRCs Guidelines for Characterizing the Safety Impact of Issues, Revision 2, May 2022 (ADAMS Accession No. ML22088A135), Section 4.1, Screening for No Impact, regarding any adverse impact on safety:

Question 2: Does the issue result in an adverse impact on the availability, reliability, or capability of SSCs [systems, structures, and components] or personnel relied upon to mitigate a transient, accident, or natural hazard?

Question 5: Does the issue result in an adv erse impact on defense-in-depth capability or impact in safety margin?

NRCs Nuclear Reactor Regulation Temporary Staff Guidance, Risk-Informed Process for Evaluations, TSG-DORL-2021-01, Revision 3 (ADAMS Accession No. ML23122A014), states, in part:

Changes made under RIPE are reviewed by staff in a manner consistent with the principles of risk-informed decision-making (RIDM) outlined in Regulatory Guide (RG) 1.174, An Approach for Using Probabilistic Risk Assessment in Risk-Informed Decision on Plant-Specific Changed to the Licensing Basis, which included ensuring that the proposed change meets current regulations (unless an exemption is requested), is consistent with defense-in-depth (DID) philosophy, maintains sufficient safety margins (SM), is consistent with the Commissions Safety Goal Policy Statement, and included performance monitoring strategies.

Based on the staffs review and the information addressed above, the staff has identified that in the unlikely event of a fire in the Turbine Control System (TCS) Cabinet G (1TCS-CAB-G), the lack of separation between class and non-class 1E components could have adverse impacts on U.S. Nuclear Regulatory Commission Page 2 of 2 Serial: RA-24-0097 Enclosure

the Reactor Protection System (RPS) cables, whic h terminate in that cabinet. While the licensee has determined that this event is not credible, RG 1.174 provides guidance that licensees demonstrate that defense-in-depth and safety margins are maintained to ensure those adverse impacts are minimal.

The staff requests that the licensee provides evaluations as supplemental responses to questions 2 and 5 in Section 4.4 of the exemption request that adequately evaluate the potential adverse impacts to defense-in-depth and safety margins to enable the NRC staff to process the exemption request under RIPE.

RESPONSE

The original exemption request submittal provided the results of a qualitative engineering evaluation that focused on design features and the potential for an electrical anomaly to occur at a common point within the TCS cabinet G and cause both trains of the Solid-State Protection System (SSPS) to become inoperable. This evaluation established that no credible events would impact both trains of safety-related equipment (i.e., SSPS) from fulfilling the design basis functions.

The submittal also provided the results of the Probabilistic Risk Assessment (PRA) evaluation of the condition described in the HNP violation. It did not take into consideration the results of the qualitative evaluation. This quantitative evaluation focused on considering the impacts identified in the violation and how that impact could be re flected in the HNP PRA model. The quantitative risk impact of the deficiency described in t he HNP violation for the failure to ensure independence between TCS circuits and RPS circuits was found to constitute a minimal safety impact.

In addition to the qualitative and quantitative evaluations mentioned above, defense-in-depth was further analyzed to supplement the responses to questions 2 and 5 in Section 4.4 of the original exemption request. The issue being addressed by the exemption request does not result in an adverse impact on the availability, reliability, or capability for manual initiation of the RPS and Engineered Safety Features Actuation System (ESFAS) signals. Emergency Operating Procedures (EOPs), including EOP-E-0 R eactor Trip or Safety Injection, require operators to manually actuate a reactor trip if an RPS setpoint is exceeded and an automatic reactor trip does not occur. Additionally, if an RPS setpoint is being approached and time allows, operators are expected to preempt the automatic actuation through manual actuation of a reactor trip. If an ESFAS setpoint is exceeded and the function does not actuate or actuates incompletely, operators are expected to manua lly actuate the function. If SSPS did not automatically align the components, the operator s would manually align per station procedures.

Defense-in-depth is preserved against potentia l common cause failures of the redundant SSPS that was postulated in the violation.