ML22013A301

TRP60 St. Lucie SLRA - Breakout Questions Fatigue Monitoring

ML22013A301
Person / Time
Site:	Saint Lucie
Issue date:	12/21/2021
From:	Office of Nuclear Reactor Regulation
To:
Rodriguez-Luccioni H
References
EPID L-2021-SLR-0002, L-2021-SLR-0002
Download: ML22013A301 (5)

Text

Page 1 of 5 St. Lucie SLRA: Breakout Questions SLRA Section B.2.2.1, Fatigue Monitoring TRP: 60 Note: Breakout Questions are provided to the applicant and will be incorporated into the publicly-available audit report.

Technical Reviewer Seung Min 12/9/2021 Technical Branch Chief Matt Mitchell 12/21/2021 Breakout Session Date/Time To be filled in by PM Applicant Staff NRC staff To be filled out by PM during breakout Question Number SLRA Section SLRA Page Background / Issue (As applicable/needed)

Discussion Question / Request Outcome of Discussion 1

B.2.2.1 B-24 SLRA Section B.2.2.1 indicates that a new limit of 500 cycles will be specified for the loss of letdown flow transient for 80 years of operation, as listed in SLRA Tables 4.3.1-5 and 4.3.1-6. This new cycle limit is significantly greater than the existing cycle limit of 50 that is listed in SLRA Table 4.3.1-1. In relation to this discussion, Enhancement 3 of the Fatigue Monitoring program addresses the update to the plant procedure to monitor and track the loss of letdown flow transient for the subsequent period of extended operation (SPEO).

1. Explain the acceptability of increasing the cycle limit for the loss of letdown flow transient from 50 to 500.

As part of the discussion, clarify whether the increase in the cycle limit can cause the projected 80-year environmental cumulative usage factors to exceed the design limit of 1.0. If so, describe how the aging effect of EAF will be managed.

Page 2 of 5 Question Number SLRA Section SLRA Page Background / Issue (As applicable/needed)

Discussion Question / Request Outcome of Discussion However, the SLRA does not clearly explain the acceptability of increasing the cycle limit for the loss of letdown flow transient from 50 to 500 in terms of environmentally assisted fatigue (EAF) analysis.

2 B.2.2.1 B-25 Enhancement 1 of the Fatigue Monitoring program is to update the program governing procedure in order to monitor the chemistry parameters that provide inputs to environmental fatigue correction factors (Fen) used in environmental cumulative usage factor (CUFen) calculations. The applicant also explained that the chemistry parameters include dissolved oxygen and sulfate and are controlled and tracked in accordance with the Water Chemistry program (SLRA Section B.2.3.2).

The staff noted that the applicant relies on the guidance in NUREG/CR-6909, Revision 1 for calculating Fen and CUFen values. However, the guidance does not identify sulfate concentration as an input parameter for Fen and CUFen calculations.

Therefore, the staff found a need to clarify whether the sulfate concentration of reactor coolant is used as an input parameter for the applicants calculations of Fen and CUFen values.

1. Clarify whether the sulfate concentration of reactor coolant is used as an input parameter for the applicants calculations of Fen and CUFen values. If so, explain why the use of the sulfate concentration is consistent with the guidance in NUREG/CR-6909, Revision 1.

Page 3 of 5 Question Number SLRA Section SLRA Page Background / Issue (As applicable/needed)

Discussion Question / Request Outcome of Discussion 3

B.2.2.1 B-25 Enhancement 2 of the Fatigue Monitoring program is to update the program governing procedure in order to identify and require monitoring of the 80-year plant design cycles, or projected cycles that are utilized as inputs to CUFen (environmental cumulative usage factor) calculations, as applicable.

Tables 3-1 and 3-2 of Westinghouse LTR-SDA-II-20-31-NP, Revision 2 provide the leading environmentally-assisted fatigue (EAF) locations for the equipment components and piping components, respectively. Tables 3-1 and 3-2 indicate that, for some equipment and piping components, reduced cycles of designed transients are used for the EAF analysis, compared to the design transient cycles described in SLRA Section 4.3.1.

The staff noted that Enhancement 2 addresses the fatigue monitoring for the reduced cycles used in the EAF analysis.

However, some of the transients, which involve the reduced cycles in the EAF analysis, are not monitored in the Fatigue Monitoring program as discussed in SLRA Tables 4.3.1-1 and 4.3.1-2.

Specifically, the applicant proposed not to monitor the reduced cycles of the following transients used in the EAF analysis: (1) plant unloading transient (for Unit 1 control element driving mechanism motor housing, and Unit 1 and

1. Clarify whether Enhancement 2 includes the monitoring of the transients associated with the reduced cycles (i.e.,

plant loading, plant unloading, purification and boric acid dilution transients) used in the EAF analysis. If not, provide the basis for excluding these transients from fatigue monitoring given that the reduced cycles of these transients are used in the EAF analysis.

Page 4 of 5 Question Number SLRA Section SLRA Page Background / Issue (As applicable/needed)

Discussion Question / Request Outcome of Discussion 2 charging system); (2) plant loading transient (for Unit 1 and 2 charging system); and (3) purification and boric acid dilution transients (for Unit 1 and 2 charging system).

The staff found a need to clarify whether Enhancement 2 includes the monitoring of these transients associated with the reduced cycles (i.e., plant loading, plant unloading, purification and boric acid dilution transients). If not, the staff needs to confirm the adequacy of the basis for excluding these transients from fatigue monitoring given that the reduced cycles of these transients are used in the EAF analysis.

4 B.2.2.1 B-25 Enhancement 5 of the Fatigue Monitoring program is to update the program governing procedure to add an additional acceptance criterion associated with high-energy line break (HELB) CUF criteria.

This enhancement is applied only to St.

Lucie Unit 2 and is related to the HELB analyses addressed in SLRA Section 4.3.4.

The staff noted that the enhancement does not clearly define the additional acceptance criterion associated with the HELB CUF criteria. In addition, the enhancement does not clearly address any additional corrective actions that may

1. Clarify (1) what the additional acceptance criterion associated with HELB CUF criteria is and (2) why the criterion is needed (e.g., criterion is needed to determine HELB locations).

2. Describe any additional corrective actions that may need to be performed beyond the actions specified in the corrective actions program element if

Page 5 of 5 Question Number SLRA Section SLRA Page Background / Issue (As applicable/needed)

Discussion Question / Request Outcome of Discussion need to be performed beyond the actions specified in the corrective actions program element if the additional criterion associated with the HELB CUF criteria is not met.

the additional criterion is not met (e.g., additional HELB analysis for newly identified break locations and their effects).

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