ML19217A337

Response to RAI #6 Regarding the Application to Adopt 10 CFR 50.69

ML19217A337
Person / Time
Site:	Calvert Cliffs
Issue date:	08/06/2019
From:	Marshall M Plant Licensing Branch 1
To:
Marshall M, NRR/DORL/LPLI, 415-2871
References
EPID L-2018-LLA-0482
Download: ML19217A337 (2)

Text

Talking Points August 6, 2019 Public Telephone Conference Calvert Cliffs Nuclear Power Plant, Units 1 &2 - Response to RAI #6 Regarding the Application to Adopt 10 CFR 50.69 (ML19183A012)

Paragraph 50.69 (c) requires that the categorization process:

(i) Consider results and insights from the plant-specific PRA. This PRA must at a minimum model severe accident scenarios resulting from internal initiating events occurring at full power operation.

(ii) Determine SSC functional importance using an integrated, systematic process for addressing initiating events (internal and external), SSCs, and plant operating modes, including those not modeled in the plant-specific PRA.

(iii) Maintain defense-in-depth (iv) Include evaluations that provide reasonable confidence that for SSCs categorized as RISC-3, sufficient safety margins are maintained The response to RAI 6 states that interfacing components that support uncategorized interfacing systems may be categorized, in some cases by:

[], an assessment of interface component risk associated with uncategorized systems will be limited to:

1. cases where an interfacing component failure cannot prevent performance of interface systems functions, or

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 above assessment that will be used in some cases is a deviation from the NEI 00-04 guidance. To support the NRC staff review of the licensees proposal, a step-by-step description of the process to implement the above assessment for categorizing interface components should be provided. This would include a description of the scope, a methodology to assess the impact to interfacing system functions, and examples including those that would result in categorizing the interfacing component as LSS.

a. It is unclear how the determination that the interfacing component failure cannot prevent performance of interface systems functions is accomplished, and how that meets the requirement for an integrated, systematic categorization process that maintains defense-in-depth and sufficient safety margins. The categorization process in NEI 00-04 includes several deterministic steps for the evaluation of systems functions to satisfy all the rule requirements. Please clarify if and how all the applicable steps in the categorization process are applied to the interface system functions supported by the interfacing component or explain how the process otherwise satisfies all the requirements in 50.69(c).

b. Clarify why only 1 of the 2 criteria listed in the RAI response needs to be met. (if the or after 1 should be an and). Explain why if only one of the criteria is successfully applied, why the other criterion is no longer important.

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c. Provide specific examples of applying the two proposed criteria to categorization of interface components, including examples that would result in categorizing the interfacing component as LSS.

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