ML25076A730
| ML25076A730 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 03/17/2025 |
| From: | Mark Yoo NRC/NRR/DNRL |
| To: | |
| Shared Package | |
| ML25076A728 | List: |
| References | |
| Download: ML25076A730 (1) | |
Text
REQUEST FOR ADDITIONAL INFORMATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION DRESDEN, UNITS 2 AND 3, SUBSEQUENT LICENSE RENEWAL REVIEW - SAFETY CONSTELLATION ENERGY GENERATION, LLC DRESDEN, UNITS 2, 3 DOCKET NO. 05000237, 05000249 ISSUE DATE: 3/17/2025 Set # 1 RAI 4.3.1-1 Regulatory Basis Pursuant to 10 CFR 54.21(c), the SLRA must include an evaluation of time-limited aging analyses (TLAAs). The applicant must demonstrate that (i) the analyses remain valid for the subsequent period of extended operation, (ii) the analyses have been projected to the end of the subsequent period of extended operation, or (iii) the effects of aging on the intended function(s) will be adequately managed for the subsequent period of extended operation.
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Background===
SLRA Tables 4.3.1-1 and 4.3.1-2 indicate the Unit 2 turbine roll and increase to rated power and the Units 2 and 3 main steam fill during flood-up transient are projected to exceed the design transient cycles before 80 years (i.e., 160 and 20 cycles, respectively). The transient cycle is also called the transient occurrence.
The applicant dispositioned the fatigue TLAAs for the isolation condensers and the Unit 2 replacement core spray piping in accordance with 10 CFR54.21(c)(1)(i), as discussed in SLRA Sections 4.3.7 and 4.7.5, respectively.
Issue Given the TLAA dispositions for the components discussed above in accordance with 10 CFR 54.21(c)(1)(i) (i.e., not using cycle projections or Fatigue Monitoring AMP), the staff needs clarification on whether the 80-year projected cycles of the Unit 2 turbine roll and increase to rated power transient and the Units 2 and 3 main steam fill during flood-up transient, which exceed the design cycles, may affect the validity of the TLAA dispositions (e.g., resulting in the 80-year CUF values greater than 1.0).
Request Given the TLAA dispositions for the components discussed above in accordance with 10 CFR 54.21(c)(1)(i), clarify whether the 80-year projected cycles of the Unit 2 turbine roll and increase to rated power transient and the Units 2 and 3 main steam fill during flood-up transient, which exceed the design cycles, may affect the validity of the TLAA dispositions. If the validity of the TLAA dispositions is affected, explain why the applicants TLAA evaluations are acceptable.
RAI 4.3.3-1 Regulatory Basis Pursuant to 10 CFR 54.21(c), the SLRA must include an evaluation of time-limited aging analyses (TLAAs). The applicant must demonstrate that (i) the analyses remain valid for the subsequent period of extended operation, (ii) the analyses have been projected to the end of
the subsequent period of extended operation, or (iii) the effects of aging on the intended function(s) will be adequately managed for the subsequent period of extended operation.
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Background===
SLRA Section 4.3.3 addresses the screening EAF evaluation to determine the plant-specific EAF locations that may be more limiting than the NUREG/CR-6260 locations. The SLRA section explains that the screening evaluation uses bounding environmental fatigue correction factor (Fen) and environmentally adjusted cumulative usage factor (CUFen) values.
Issue The SLRA does not clearly discuss how the bounding Fen and CUFen values are calculated.
Specially, the following items are not clear to the staff: (1) how the bounding temperature is calculated for each location (e.g., use of the maximum temperature of the thermal zone for the component location or the component-specific maximum temperature); (2) how the bounding strain rate is calculated; and (3) how bounding sulfur content is calculated for the components fabricated with carbon or low alloy steel.
In addition, the SLRA indicated that the detailed EAF evaluation was performed to refine the CUFen values to reduce the excessive conservatism associated with the screening CUFen values. However, the SLRA does not clearly discuss how the applicant refined the CUFen values for the limiting locations.
Request
- 1. Discuss the following items related to the applicants approach to calculate the bounding Fen and CUFen values in the screening evaluation: (1) how the bounding temperature is calculated for each location (e.g., use of the maximum temperature of the thermal zone for the component location or the component-specific maximum temperature); (2) how the bounding strain rate is calculated; and (3) how bounding sulfur content is calculated for the components fabricated with carbon or low alloy steel.
- 2. Discuss how the detailed EAF evaluation refined the CUFen values by reducing the excessive conservatism associated with the screening CUFen As part of the discussion, clarify the applicants approach used in the detailed EAF evaluation in terms of determining the transient temperature, strain rate and evaluated cycles, as compared to the approach used in the screening evaluation.
RAI 4.3.3-2 Regulatory Basis Pursuant to 10 CFR 54.21(c), the SLRA must include an evaluation of time-limited aging analyses (TLAAs). The applicant must demonstrate that (i) the analyses remain valid for the subsequent period of extended operation, (ii) the analyses have been projected to the end of the subsequent period of extended operation, or (iii) the effects of aging on the intended function(s) will be adequately managed for the subsequent period of extended operation.
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Background===
SLRA Table 4.3.1-3 describes the limiting EAF locations and their CUF en values.
Issue SLRA Table 4.3.1-3 does not clearly describe the thermal zones evaluated in the EAF analysis and specific materials of fabrication associated with the limiting EAF locations. In addition, the
SLRA does not clearly discuss whether a thermal zone may be bounded by another thermal zone in the EAF analysis so that a limiting location may not be identified for a thermal zone.
Request
- 1. Clarify the thermal zones and materials of fabrication associated with the limiting EAF locations described in SLRA Table 4.3.1-3.
- 2. Clarify whether a thermal zone is bounded by another thermal zone in the EAF analysis so that a limiting location may not be identified for a thermal zone. If so, describe how the applicant determined that a thermal zone is bounded by another thermal zone.
RAI 4.3.4-1 Regulatory Basis Pursuant to 10 CFR 54.21(c), the SLRA must include an evaluation of time-limited aging analyses (TLAAs). The applicant must demonstrate that (i) the analyses remain valid for the subsequent period of extended operation, (ii) the analyses have been projected to the end of the subsequent period of extended operation, or (iii) the effects of aging on the intended function(s) will be adequately managed for the subsequent period of extended operation.
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Background===
SLRA Section 4.3.4 addresses the fatigue waiver TLAAs for ASME Code Section III, Class 1 components (e.g., reactor pressure vessel steam outlet nozzle and vent nozzle). Specifically, SLRA Table 4.3.4-2 discussed the number of transient cycles evaluated in the fatigue waiver reanalysis for 80 years of operation for each of the ASME Code Section III, N-415.1 criteria for fatigue waiver (i.e., N-415.1(a) through (f)).
Issue SLRA Table 4.3.4-2 does not clearly describe the 80-year projected cycles in comparison with the cycles evaluated in the 80-year fatigue waiver reanalysis.
In addition, SLRA Table 4.3.4-2 does not describe the following information on the N-415.1(f) criterion regarding significant mechanical load fluctuations: (1) transients evaluated in the fatigue waiver reanalysis, (2) transient cycles evaluated in the existing fatigue waiver analysis, (3) transient cycles evaluated in the fatigue waiver reanalysis, (4) 80-year projected cycles of the transients and (5) whether the fatigue waiver criterion is met in the fatigue waiver reanalysis.
Request
- 1. Describe the 80-year projected cycles in comparison with the cycles evaluated in the 80-year fatigue waiver reanalysis to confirm that the transient cycles evaluated in the fatigue waiver reanalysis are bounding for the 80-year projected cycles.
- 2. Describe the following information on the N-415.1(f) criterion regarding significant mechanical load fluctuations: (1) transients evaluated in the fatigue waiver reanalysis, (2) transient cycles evaluated in the existing fatigue waiver analysis, (3) transient cycles evaluated in the fatigue waiver reanalysis, (4) the 80-year projected cycles of the transients to confirm that the transient cycles evaluated in the fatigue waiver reanalysis are bounding for the 80-year projected cycles and (5) whether the fatigue waiver criterion is met in the fatigue waiver reanalysis.
RAI 4.3.5-1 Regulatory Basis Pursuant to 10 CFR 54.21(c), the SLRA must include an evaluation of time-limited aging analyses (TLAAs). The applicant must demonstrate that (i) the analyses remain valid for the subsequent period of extended operation, (ii) the analyses have been projected to the end of the subsequent period of extended operation, or (iii) the effects of aging on the intended function(s) will be adequately managed for the subsequent period of extended operation.
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Background===
SLRA Section 4.3.5 addresses the fatigue TLAAs for the non-Class 1 piping systems (i.e.,
ASME Section III Class 2 and 3 and ANSI B31.1 piping systems). The TLAAs are also related to the allowable stress and high energy line break (HELB) analyses for the piping systems. The TLAAs regarding allowable stress analyses rely on the implicit fatigue analysis provisions in the ASME Code Section III and ANSI B31.1 code. These provisions allow no reduction in the allowable stress range for thermal expansion stresses below 1.0, if the number of equivalent full temperature cycles does not exceed 7000 cycles.
Issue SLRA Table 4.3.5-2 describes the conservative 80-year projected cycles for the non-Class 1 piping systems that are affected by the transients other than the reactor coolant system (RCS) transients in SLRA Tables 4.3.1-1 and 4.3.1-2. However, SLRA Section 4.3.5 does not clearly describe how the 80-year projected cycles were determined (e.g., based on piping system design information, plant operation procedures, test requirements, UFSAR information and specific system-level knowledge).
Request Discuss how the applicant determined the 80-year projected cycles listed in SLRA Table 4.3.5-2 (e.g., based on piping system design information, plant operation procedures, test requirements, UFSAR information and specific system-level knowledge).