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Constellation Project Highlights
	ML25071A218
Person / Time
Site:	Calvert Cliffs, Dresden, Peach Bottom, Nine Mile Point, Byron, Braidwood, Limerick, Ginna, Clinton, Quad Cities, FitzPatrick, LaSalle
Issue date:	03/12/2025
From:	Rickey A; Constellation Energy Generation
To:	Scott Wall; Constellation Energy Generation, Office of Nuclear Reactor Regulation
References
	ISG-06
	Download: ML25071A218 (1)
	v • d • e

ISG-06 Lessons Learned Workshop March 2025 Ashley Rickey Licensing Engineer Mark Samselski Engineering Manager

Began Operation:

Unit 1: February 1, 1986 Unit 2: January 8, 1990 Reactor Type: BWR 4 Plant Builder: Bechtel Power Corp Plant Design: General Electric Limerick Generating Station - Units 1 & 2 License Extension:

Unit 1: 2044 Unit 2: 2049 Licensed 100% Reactor Thermal Power: 3,515 MWth/Unit Gross electrical output:

Unit 1: 1,220 Mwe Unit 2: 1,220 Mwe 1

Limerick Generating Station - Units 1 & 2 724 Employees Power > 2 Million Homes Carbon-free Electricity Offset > 17 M tons of CO2 Potential for a License Extension of an additional 20 years 2

Three LARs have been proposed to support the project:

Modification Principal LAR - Submitted on 09/26/22 - SER is pending Conducted 12 Pre-submittal Meetings (Started June 2021)

Incorporated the removal of the automatic Main Steam High-Temperature isolation Discontinues the Redundant Reactivity Control System (RRCS) feedwater runback Changed RRCS classification to non-safety Addressed Common Cause Failure Installation Support LAR - SER has been issued Aids in the pre-outage demolition of RRCS (both channels) to allow for the installation of the new PPS system within the designated outage timeframe Incorporates additional industry TSTF installation facilitators Risk Informed Completion Time (RICT) LAR - Preparation is nearing completion Expected to be finalized by March 2025 LAR submission must occur after the modification SER is issued to prevent linked LARs Aims to restore instrument-related RICTs following the LGS 1 refueling outage in 2026 Limerick Project Licensing Actions 3

The Licensing Action Request (LAR) was developed in accordance with DI&C-ISG-6, Revision 2, to streamline the licensing process and implement the Alternate Review Process (ARP)

The industry sees the ARP as a crucial component for efficiency of safety-related digital upgrades The Limerick LAR is among the first to use the ARP for a significant large-scale protection system replacement

There was extensive utilization of pre-submittal meetings aimed at reducing risks associated with first-of-a-kind technical, regulatory, and NRC licensing review processes Technical Specifications related to the new design Replacement of discrete indicators with integrated flat panel displays in the Main Control Room (MCR)

Adoption of touch screen displays for safety functions in operations Diversity and Defense-in-Depth Consolidation of sensors

Key documents were submitted early to enhance the pre-submittal process and foster a better understanding of the system design Limerick Project Licensing Methodology 4

Limerick Lessons Learned for ISG-06 Alternate Review Process 5

Risk Insights Human Factors Technical Specifications

The ISG-06 ARP does not thoroughly address all aspects related to large-scale digital upgrades of protection systems NRC staff participated in pre-submittal meetings to gain insight for the scope to use of Alternate Review Process (ARP)

Limerick Digital Modernization is not a 100 % ARP licensing action; considered a 'hybrid LAR The aspects were addressed through the pre-submittal process, including considerations for human factors in Main Control Room (MCR) changes, the integration of Risk Informed Completion Times (RICT) and changes to Technical Specifications.

Limerick Lessons Learned for ISG-06 Alternate Review Process Scope 6

Pre-submittal meetings have been proven valuable in refining License Amendment Request (LAR) submissions and their supplements to satisfy NRC requirements Many digital retrofit initiatives being contemplated by utilities, particularly in safety-related systems, involve significant complexity and are predominantly First-of-a-Kind at this stage It is advantageous to mitigate project and regulatory risks while aligning on the necessary level of detail for a 'complete' application NRC staff were well-prepared with participation from various NRC branches The prompt distribution of meeting minutes (and/or reports) is critical to ensure that all topics are fully understood, that no further clarification is needed, and to identify subjects for future meetings Include the NRC region in pre-submittal meetings to support planning for Vendor Oversight Activities Best practice - meetings should be conducted early and frequently, and do not always need to follow formal face-to-face protocols; remote meetings are acceptable Best practice - list of discussion topics for upcoming meetings should be established well in advance, such as Equipment Qualification (EQ), D3 Common Cause Failure (CCF), and Licensing Technical Specification changes, with staff feedback being essential Best Practice - examples or materials should be provided to enhance the NRC's understanding of the proposed new systems, ideally through PowerPoint presentations or other support documentation Pre-submittal Meetings 7

A clear set of objective criteria is needed for licensees to show compliance

Vendor Oversight Scope Discussions:

Defining what needs to be addressed, the timing, and the objectives for observation

Regular and proactive communication occur among the Licensee, NRC HQ, and the regional inspectors involved in the project

This approach supports organizational adjustments in capacity, capability, and technical authority

Coordination of schedules and priorities for inspections

Clarification of anticipated communication regarding scheduling among all stakeholders (including Regional representatives)

Consider including inspection guidance or review criteria reference (e.g., IP 52003)

Vendor Oversight 8

Licensees perceive this process as beneficial for improving the understanding of submissions

Offers the licensee a chance to clarify any questions that staff might have

Helps to minimize Requests for Additional Information (RAIs)

Fosters an environment conducive to providing clarity Alleviates the administrative load associated with RAIs Increases the licensee's administrative and technical responsibilities to address Open Items promptly but observed as a benefit vs RAI Necessitates an effort between the licensee and NRC staff to ensure responses are thorough, thereby reducing the number of questions on a single issue

Ensure that questions within the Open Items Process are coupled to regulatory and/or safety conclusions

Best Practice - Create a centralized SharePoint (or similar portal) site for all involved stakeholders Open Item Audit 9

The Equipment Qualification aspect is insufficiently considered Detailed design may introduce new components that require qualification after the LAR submission

The Human Factors Engineering elements of the upgrade must either comply with existing licensing commitments or formally propose any changes within the LAR Approaches based on NUREG-0711 can lead to inefficiencies Fulfill current HFE licensing obligations while utilizing any relevant standards or guidance The route taken by the licensee to meet existing HFE licensing obligations is at their discretion, allowing them to use any available standards or guidance (such as NUREG, IEEE, or others) or develop their own methodology to meet licensing requirements

Technical Specifications Additional submissions may be needed, as the detailed design could include new components that require further surveillance

The use of precedent should be addressed during pre-submission meetings It is essential to guide licensees on how NRC reviewers might integrate risk considerations into their applications.

Submissions should strictly adhere to the requirements outlined in the ISG-06 to promote efficiency The ARP is based on established requirements The implementation of detailed design is subject to audit or inspection Areas for Improvement 10 l Constellation Energy Generation, LLC © 2025

ARP - Alternate Review Process

CCF - Common Cause Failure

D3 - Diversity & Defense-in-Depth

EQ - Equipment Qualification

HFE - Human Factors Engineering

HQ - Headquarters

IEEE - Institute of Electrical and Electronic Engineers

LAR - License Amendment Request

MCR - Main Control Room

NUREG - Reports or brochures on regulatory decisions, results of research, results of incident investigations, and other technical and administrative information

RAI - Request for Additional Information

RICT - Risk Informed Completion Time

RRCS - Redundant Reactivity Control System

SER - Safety Evaluation Report

TSTF - Technical Specification Task Force Traveler

ML25071A218

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