ML19282B718

Revised Response to Request for Additional Information Regarding the Application to Adopt 10 CFR 50.69, Risk-informed Categorization and Treatment of Structures, Systems, and Components for Nuclear Power Reactors

ML19282B718
Person / Time
Site:	Calvert Cliffs
Issue date:	10/09/2019
From:	David Gudger Exelon Generation Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
Download: ML19282B718 (3)

Text

Exelon Generation © 200 Exelon Way Kennett Square, PA 19348 www.exeloncorp.com 10 CFR 50.90 10 CFR 50.69 October 9, 2019 U.S. Nuclear Regulatory Commission ATIN: Document Control Desk Washington, DC 20555-0001 Calvert Cliffs Nuclear Power Plant, Units 1 and 2 Renewed Facility Operating License Nos. DPR-53 and DPR-69 Docket Nos. 50-317 and 50-318

Subject:

Revised Response to Request for Additional Information Regarding the Application to Adopt 10 CFR 50.69, "Risk-informed categorization and treatment of structures, systems, and components for nuclear power reactors"

References:

1) Response to Request for Additional Information Regarding the Application to Adopt 10 CFR 50.69, "Risk-informed categorization and treatment of structures, systems, and components for nuclear power reactors," dated July 1, 2019.

2) E-mail from Michael Marshall, U.S. Nuclear Regulatory Commission, to Enrique Villar, Exelon, titled "[External] Calvert Cliffs Nuclear Power Plant, Units 1 and 2 - Request for Additional Information Regarding Request to Adopt 10 CFR 50.69 Risk Informed Categorization and Treatment of Systems, Structures, and Components (EPID L-2018-LIA-0482)," dated June 4, 2019. (ML19155A127).

By letter dated November July 1, 2019 (Agencywide Documents Access and Management System (ADAMS) Package Accession No. ML 19183AO 12) Exelon Generation Company, LLC (Exelon) submitted its 30-day response to Request for Additional Information 4, 5, 6, and 8 as requested in Reference 2.

Exelon hereby revises its response to RAI #6 as documented in Attachment 1 of this letter.

There are no regulatory commitments contained in this letter.

I declare under penalty of perjury that the foregoing is true and correct. Executed on the 9th day of October 2019.

Revised Response to RAI #6 Application to Adopt 10 CFR 50.69 October 9, 2019 Page 2 If you should have any questions regarding this submittal, please contact Enrique Villar at 61 0-765-5736.

Respectfully, I /) * ,_ / J tlf CA.- cl I. ~ yv-David T. Gudger Acting Director - Licensing Exelon Generation Company, LLC

Attachment:

1) Response to Request for Additional Information to License Amendment Request to Adopt 10 CFR 50.69 cc: Regional Administrator, NRC Region I NRC Senior Resident Inspector NRC Project Manager D. A. Tancabel, State of Maryland

Attachment 1 Revised Response to Request for Additional Information #6 in Support to License Amendment Request to Adopt 10 CFR 50.69 Page 1 of 1 REVISED RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION (RAil #6 "Exelon will perform the categorization of any functions/SSCs that serve as an interface between two or more systems in accordance with its categorization procedures.

If an interface component is found to be HSS for the system being categorized, then it will be categorized RISC-1 or RISC-2 (and will not receive alternative treatments) even if it supports other systems.

In most cases, interface components that support uncategorized interfacing systems (and are LSS for the system being categorized) will be uncategorized and will not receive alternative treatment prior to completing the categorization of all systems that they support.

One of the initial steps in the Exelon's system categorization procedure is to develop a list of system functions. If the system includes components that support functions of other systems, then support functions are created to identify the supported systems (e.g., provide support for system xx) as needed.

Support functions are not categorized. These functions identify system components that cannot be fully categorized until the categorization of other systems is completed. Additional support functions are added as required during the component mapping process, where the focus is on individual component functions. Interface components that support other system functions will be identified by this process.

In some cases, impacts that an interfacing component could have on an interfacing system can be fully determined and the interface component can be categorized (and alternative treatment implemented) without categorizing the entire interfacing system.

In this event, an assessment of interface component risk associated with uncategorized systems will be limited to:

1. cases where an interface component failure cannot prevent performance of interface system functions, and

2. the risk is limited to passive failures assessed as low safety-significant following the passive categorization process for the applicable pressure boundary segments.

The interface component can be assessed without performing a full interface system categorization because adequate interface system function knowledge is available to perform the functional assessment and passive risk assessment. Categorizing the entire interfacing system would produce the same functional assessment and passive risk significance for the component. Therefore, Exelon considers this approach to be consistent with the intent of 10 CFR 50.69(c)(1 )(v) and NEI 00-04 guidance."