ML25010A352
| ML25010A352 | |
| Person / Time | |
|---|---|
| Site: | Clinton  |
| Issue date: | 01/10/2025 |
| From: | Tyree C NRC/NRR/DNRL/NLRP |
| To: | Wilson C Constellation Energy Generation |
| Shared Package | |
| ML25010A350 | List: |
| References | |
| Download: ML25010A352 (1) | |
Text
1 REQUEST FOR ADDITIONAL INFORMATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION CLINTON LRA SAFETY REVIEW CONSTELLATION ENERGY GENERATION, LLC CLINTON, UNIT 1 DOCKET NO. 05000461 ISSUE DATE: 01/10/2025 Set 1 RAI B.2.1.42-1 Regulatory Basis 10 CFR 54.21(a)(3) requires an applicant to demonstrate that the effects of aging for structures and components will be adequately managed so that the intended function(s) will be maintained consistent with the current licensing basis for the period of extended operation. One of the findings that the staff must make to issue a renewed license (10 CFR 54.29(a)) is that actions have been identified and have been or will be taken with respect to managing the effects of aging during the period of extended operation on the functionality of structures and components that have been identified to require review under 10 CFR 54.21, such that there is reasonable assurance that the activities authorized by the renewed license will continue to be conducted in accordance with the current licensing basis. In order to complete its review and enable making a finding under 10 CFR 54.29(a), the staff requires additional information in regard to the matters described below.
Background
GALL-LR Report AMP XI.M42, Internal Coatings/Linings for In-Scope Piping, Piping Components, Heat Exchangers, and Tanks, as added by LR-ISG-2013-01, Aging Management of Loss of Coating or Lining Integrity for Internal Coatings/Linings on In-Scope Piping, Piping Components, Heat Exchangers, and Tanks, recommends conducting baseline inspections in the 10-year period prior to the period of extended operation in order to establish the condition of coatings/lining prior to entering the period of extended operation. In addition, these baseline inspections provide input to the interval of subsequent inspections.
LRA Section B.2.1.42, Internal Coatings/Linings for In-Scope Piping, Piping Components, Heat Exchangers, and Tanks Program, describes operating experience from the Division 2 diesel generator fuel oil storage tank cleaning in 2015 in which fourteen separate indications related to the integrity of the tank internal coatings system were documented. LRA Section B.2.1.42 also states that an evaluation was performed which determined that because the affected areas were very small, the remaining coated surface was in good condition, and no loose coating was identified that could affect downstream components, the tank could be returned to service until the next scheduled inspection. The next tank cleaning will be performed in 2025 with any coating repairs taking place during this time.
Issue It is unclear to the staff if the next scheduled inspection of the Division 2 diesel generator fuel oil storage tank, described in LRA Section B.2.1.42 under the operating experience description, will be in 2025 when the tank is next scheduled to be cleaned.
2 It is also unclear to the staff if the next scheduled inspection of this tank will be considered as part of the baseline inspections recommended by GALL-LR Report AMP XI.M42.
It is unclear to the staff if all fourteen indications in the Division 2 diesel generator fuel oil storage tank internal coating/lining, documented during a 2015 inspection, will be repaired during the tank cleaning proposed to be performed in 2025. If not all fourteen indications in the Division 2 diesel generator fuel oil storage tank internal coating/lining will be repaired during the tank cleaning proposed to be performed in 2025, it is unclear to the staff what acceptance criteria and corrective actions will be applied to the indications to assure acceptability of the internal coating/lining as the tank enters the period of extended operation.
Request
- 1. Confirm the year of the next scheduled inspection of the Division 2 diesel generator fuel oil storage tank.
- 2. Clarify if the next scheduled inspection of the Division 2 diesel generator fuel oil storage tank will be considered as part of the baseline inspections recommended by GALL-LR Report AMP XI.M42.
- 3. Clarify if all fourteen indications in the Division 2 diesel generator fuel oil storage tank internal coating/lining, documented during a 2015 inspection, will be repaired during the tank cleaning proposed to be performed in 2025. If not all fourteen indications will be repaired, clarify what acceptance criteria and corrective actions will be applied to the indications to assure acceptability of the internal coating/lining as the tank enters the period of extended operation.
RAI 3.1.2.2.1 -1 Regulatory Basis Pursuant to 10 CFR 54.21(c), the LRA must include an evaluation of time-limited aging analyses (TLAAs). The applicant must demonstrate that (i) the analyses remain valid for the period of extended operation, (ii) the analyses have been projected to the end of the period of extended operation, or (iii) the effects of aging on the intended function(s) will be adequately managed for the period of extended operation.
Background
LRA Table 3.1.2-3 addresses the aging management review (AMR) results for the jet pump assembly holddown beam in relation to AMR item 3.1.1-3 (LRA page 3.1-69). LRA Table 3.1.2-3 also addresses the AMR results for the jet pump assembly inlet riser, brace and sleeve, elbow, wedge, diffuser, and holddown beam bolts in relation to AMR item 3.1.1-3 (LRA page 3.1-70).
The LRA table indicates that these jet pump components are subject to a fatigue TLAA.
Issue LRA Section 4.3.7.1 addresses the fatigue TLAA for the jet pump riser brace. However, the LRA does not clearly describe the fatigue TLAA evaluations and dispositions for the other jet pump components discussed in the background section above (i.e., jet pump assembly holddown beam, inlet riser, sleeve, elbow, wedge, diffuser, and holddown beam bolts).
Therefore, the staff needs to clarify the following items: (1) which specific jet pump components discussed in the background section are subject to a fatigue TLAA; (2) specific LRA sections
3 that describe the fatigue TLAA evaluations and dispositions for the jet pump components subject to a fatigue TLAA; and (3) whether the jet pump riser brace is bounding for the other jet pump components in terms of fatigue analysis (e.g., in terms of cumulative usage factor (CUF) analysis).
Request
- 1. Describe which specific jet pump components discussed in the background section are subject to a fatigue TLAA.
- 2. Clarify the specific LRA sections that describe the fatigue TLAA evaluations and dispositions for the jet pump components subject to a fatigue TLAA.
- 3. Clarify whether the jet pump riser brace is bounding for the other jet pump components in terms of fatigue analysis (e.g., in terms of CUF analysis). If so, discuss how the applicant determined the bounding nature of the jet pump riser brace.
- 4. Revise the LRA as needed to provide the fatigue TLAA evaluations and dispositions for the jet pump components, consistent with the discussion above.
RAI 4.3.2-1 Regulatory Basis Pursuant to 10 CFR 54.21(c), the LRA must include an evaluation of time-limited aging analyses (TLAAs). The applicant must demonstrate that (i) the analyses remain valid for the period of extended operation, (ii) the analyses have been projected to the end of the period of extended operation, or (iii) the effects of aging on the intended function(s) will be adequately managed for the period of extended operation.
Background
LRA Section 4.3.2 indicates that the screening values of environmental fatigue correction factor (F en ) are based on the component material, maximum operating temperature, and bounding dissolved oxygen. The LRA also indicates that sulfur content is also an input for the screening F en values of carbon and low alloy steel components.
Issue LRA Section 4.3.2 does not clearly discuss how the applicant determined conservative sulfur content (for carbon and low alloy steels) and strain rates in the screening evaluation for EAF.
The staff also noted that the applicant reduced the conservatism associated with the screening environmentally adjusted cumulative usage factor (CUF en ) values in the detailed EAF evaluation after the screening evaluation. Therefore, the staff needs clarification on how the applicant reduced the conservatism associated with the screening CUF en values in the detailed EAF evaluation.
Request
- 1. Describe how the applicant determined conservative sulfur content (for carbon and low alloy steels) and strain rates in the screening EAF evaluation.
- 2. Describe how the applicant reduced the conservatism associated with the screening CUF en values in the detailed EAF evaluation after the screening EAF evaluation.
4 RAI 4.3.2-2 Regulatory Basis Pursuant to 10 CFR 54.21(c), the LRA must include an evaluation of time-limited aging analyses (TLAAs). The applicant must demonstrate that (i) the analyses remain valid for the period of extended operation, (ii) the analyses have been projected to the end of the period of extended operation, or (iii) the effects of aging on the intended function(s) will be adequately managed for the period of extended operation.
Background
LRA Section 4.3.2 addresses the EAF TLAA for Class 1 piping systems. The 60-year projected CUF en values for the limiting (bounding) EAF locations are described in LRA Table 4.3.1-2.
Issue LRA Table 4.3.1-2 does not describe the materials of the limiting locations. The staff also needs clarification on whether the applicant eliminated certain EAF locations based on the more limiting EAF locations fabricated with a different material in the screening evaluation to determine the limiting EAF locations (e.g., a low alloy steel location was eliminated in consideration of the more limiting stainless steel location in the screening evaluation for EAF).
In addition, LRA Table 4.3.1-2 does not describe the specific piping systems or components (e.g., reactor vessel) of the limiting EAF locations.
Request
- 2. Clarify whether the applicant eliminated certain EAF locations based on the more limiting EAF locations fabricated with a different material in the screening evaluation to determine the limiting EAF locations. If so, describe the eliminated EAF locations and discuss how the applicant determined the more limiting nature of the EAF locations fabricated with a different material (e.g., comparisons of F en and CUF en values).
- 3. Describe the specific piping systems or components (e.g., reactor vessel) of the limiting EAF locations in LRA Table 4.3.1-2.
RAI 4.3.5-1 Regulatory Basis Pursuant to 10 CFR 54.21(c), the LRA must include an evaluation of time-limited aging analyses (TLAAs). The applicant must demonstrate that (i) the analyses remain valid for the period of extended operation, (ii) the analyses have been projected to the end of the period of extended operation, or (iii) the effects of aging on the intended function(s) will be adequately managed for the period of extended operation.
Background
LRA Section 4.3.5 addresses the allowable stress and related high-energy line break (HELB)
TLAAs for the piping systems designed in accordance with ASME Code Section III, Class 2, Class 3, and ANSI B31.1 design rules. LRA Table 4.3.5-2 describes the number of 60-year projected cycles for each non-Class 1 piping system to confirm that the 60-year projected cycles do not exceed 7000 cycles in the implicit fatigue analysis.
5 Issue However, LRA Section 4.3.5 does not clearly describe how the 60-year cycles were determined (e.g., based on piping system design information, plant operation procedures, test requirements, USAR information and specific system-level knowledge).
Request Clarify how the applicant estimated the 60-year cycles for the non-Class 1 piping systems (e.g.,
based on piping system design information, plant operation procedures, test requirements, USAR information and specific system-level knowledge).
RAI 4.3.1-1 Regulatory Basis Pursuant to 10 CFR 54.21(c), the LRA must include an evaluation of time-limited aging analyses (TLAAs). The applicant must demonstrate that (i) the analyses remain valid for the period of extended operation, (ii) the analyses have been projected to the end of the period of extended operation, or (iii) the effects of aging on the intended function(s) will be adequately managed for the period of extended operation.
Background
LRA Table 4.3.1-1 indicates that the number of the 60-year projected occurrences (cycles) of the design hydrostatic test transient is 44, which is greater than the design transient cycles of 40.
Similarly, LRA Table 4.3.1-1 indicates that, for the turbine roll transient and HOTZERO - Hot Zero Power Scram transient, the number of 60-year projected cycles exceed the number of design transient cycles.
Issue In comparison, the applicant dispositioned the fatigue TLAAs for the following components in accordance with 10 CFR54.21(c)(1)(i): (1) main steam isolation valves; (2) safety/relief valves; (3) recirculation system flow control valves; (4) recirculation system gate valves; (5) recirculation system pumps; (6) control rod drives; and (7) core plate stiffener to skirt weld and top guide/grid reactor vessel internal components.
Given the TLAA disposition for the components discussed above in accordance with 10 CFR54.21(c)(1)(i) (i.e., not using cycle projections or the Fatigue Monitoring AMP), the staff needs clarification on whether the 60-year projected cycles of the design hydrostatic test transient, turbine roll transient and HOTZERO - hot zero power scram transient, which are greater than the design cycles, may affect the validity of the fatigue TLAA disposition (e.g.,
resulting in the 60-year CUF values of these components exceeding the design limit).
Request Given the TLAA disposition for the components discussed in the issue section in accordance with 10 CFR54.21(c)(1)(i) (i.e., not using cycle projections or the Fatigue Monitoring AMP),
clarify whether the 60-year projected cycles of the design hydrostatic test transient, turbine roll transient and HOTZERO - hot zero power scram transient, which are greater than the design cycles, may affect the validity of the fatigue TLAA disposition (e.g., resulting in the 60-year CUF values of these components exceeding the design limit).
6 RAI 4.7.5-1 Regulatory Basis Pursuant to 10 CFR 54.21(c), the LRA must include an evaluation of time-limited aging analyses (TLAAs). The applicant must demonstrate that (i) the analyses remain valid for the period of extended operation, (ii) the analyses have been projected to the end of the period of extended operation, or (iii) the effects of aging on the intended function(s) will be adequately managed for the period of extended operation.
Background
LRA Section 4.7.5 addresses the fatigue TLAA for hydraulic control units (HCUs). The LRA also explains that the USAR Section 3.9.1.1.3, Hydraulic Control Unit Transients, documents the transients and transient occurrences that were considered in the design of the HCUs.
Issue The staff noted that USAR Section 3.9.1.1.3 indicates that the following design cycles related to scrams were evaluated in the existing fatigue analysis for the HCUs: (1) 140 cycles of the scram test transient; (2) 160 cycles of startup scram transient; and (3) 300 cycles of operational scram transient. However, LRA Section 4.7.5 does not clearly describe the 60-year projected cycles for these scram transients compared to the transient cycles evaluated in the existing fatigue analysis.
In addition, LRA Section 4.7.5 indicates that USAR Section 3.9.2.2.1.6.4 Hydraulic Control Unit (HCU), documents that the HCUs were analyzed for faulted conditions including the effects of seismic and hydrodynamic loads. The LRA explains that this design adequacy was determined by testing and analysis and that the qualification testing included vibration testing equivalent to 1800 safety relief valve (SRV) actuations, one operational basis earthquake (OBE), and one safety shutdown earthquake (SSE). However, LRA Section 4.7.5 does not clearly describe the 60-year projected cycles (occurrences) of the SRV actuations.
Request
- 1. Describe the 60-year projected cycles of the following scram-related transients to confirm that the 60-year projected cycles are bounded by (less than) the cycles evaluated in the existing fatigue analysis for the HCUs: (1) scram test transient; (2) startup scram transient; and (3) operational scram transient. As part of the discussion, explain the basis of these cycle projections.
- 2. Describe the 60-year projected cycles of the SRV actuations to confirm that the projected cycles are bounded by (less than) the SRV actuation cycles (i.e., 1800 cycles) evaluated in the fatigue analysis for the effect of seismic and hydrodynamic loads on the hydraulic control units. As part of the discussion, explain the basis of the cycle projection.
RAI 4.3.7-1 Regulatory Basis Pursuant to 10 CFR 54.21(c), the LRA must include an evaluation of time-limited aging analyses (TLAAs). The applicant must demonstrate that (i) the analyses remain valid for the period of extended operation, (ii) the analyses have been projected to the end of the period of extended
7 operation, or (iii) the effects of aging on the intended function(s) will be adequately managed for the period of extended operation.
Background
The LRA explains that the 40-year CUF for the core shroud support plate, which is the limiting location for the core shroud support structure and core shroud stabilizer assembly, is 0.426. The LRA indicates that the CUF value is based on safety relief valve (SRV) actuation transient cycles, which are greater than 12000 cycles in the 40-yearfatigue analysis. The LRA also explains that the SRV actuation transient is the most significant contributor to the fatigue in the core shroud support plate.
Issue In contrast, the following General Electric report indicates that the most significant contribution to the 40-year CUF of the core shroud support plate is due to thermal cycles (i.e., contribution of 0.406 due to certain thermal cycles) (
Reference:
GE-NE-26A-6217, Shroud and Shroud Support Structure, Section 6.2.5.2, March 9, 2005). The reference also indicates that the calculation of the CUF contribution (0.406) is based on the maximum usage factor in the shroud support plate for a similar standard BWR/6 plant.
The reference further explains that the 40-year CUF contribution of the SRV actuation cycles to the core shroud support plate is approximately 0.013 and that the 40-year CUF contribution of other thermal transients is less than 0.01.
However, the LRA does not clearly discuss the following items related to the maximum CUF contribution (0.406) due to certain thermal cycles: (1) specific thermal transients and their cycles evaluated in the CUF calculation for a standard BWR/6 plant; (2) whether the transient cycles evaluated for the standard plant reasonably represent the 40-year transient cycles of the Clinton Power Station.
Request
- 1. Given the maximum CUF contribution due to thermal cycles (non-SRV-actuation cycles) for the core shroud support plate discussed in the reference in the issue section, clarify whether the SRV actuation transient is the most significant contributor to the 40-year CUF of the core shroud support plate. If not, describe the following information: (1) the transients and their 40-year cycles that make the most significant contribution to the CUF and (2) the most significant contribution of these transients to the CUF (i.e., the partial CUF due to these transient cycles).
- 2. Clarify whether the transient cycles, which make the most significant CUF contribution to the core shroud support plate, reasonably represent the 40-year cycles of the Clinton Power Station in terms of the fatigue analysis for the core shroud support plate.
- 3. Revise the LRA as needed based on the discussion above.
RAI 4.3.2-3 Regulatory Basis Pursuant to 10 CFR 54.21(c), the LRA must include an evaluation of time-limited aging analyses (TLAAs). The applicant must demonstrate that (i) the analyses remain valid for the period of extended operation, (ii) the analyses have been projected to the end of the period of extended
8 operation, or (iii) the effects of aging on the intended function(s) will be adequately managed for the period of extended operation.
Background
LRA Section 4.3.2.2 addresses the environmentally assisted fatigue analysis (EAF). Specifically, the following report describes the EAF analysis for limiting locations (
Reference:
Structural Integrity Associates (SIA) 1701003.305, Environmentally Assisted Fatigue Calculations for Sentinel Locations at Clinton, March 17, 2023). The report indicates that the calculation of the environmental fatigue correction factor (F en ) uses the average temperature of a transient.
Issue NUREG/CR-6909, Revision 1, Section 4.1.4 and related discussions explain that the average temperature of a transient may be used in the F en calculation for a simple, linear transient.
NUREG/CR-6909, Revision 1 also indicates that, if a transient is complex, justification is needed to use an average temperature rather than the maximum temperature. However, the LRA does not clearly discuss the basis for the use of the average temperature approach.
Request Clarify whether the applicants use of an average temperature is only for simple, linear transients. If not, provide the following information: (1) justification for the average temperature approach and (2) plant-specific demonstration that the conservatism of the applicants approach is comparable to that of the modified rate approach described in NUREG/CR-6909, Revision 1, Section 4.4 in terms of calculating the Fen and environmentally adjusted cumulative usage factor (CUFen ).
RAI 4.6.1-1 Regulatory Basis 10 CFR 54.21(a)(3) requires an applicant to demonstrate that the effects of aging for structures and components will be adequately managed so that the intended function(s) will be maintained consistent with the current licensing basis for the period of extended operation. As described in the SRP-LR, an applicant may demonstrate compliance with 10 CFR 54.21(a)(3) by referencing the GALL-LR Report when evaluation of the matter in the GALL-LR Report applies to the plant.
Background
LRA Section 4.6.1 provides TLAA evaluations for two types of transients: monitored transients and unmonitored transients, claiming consistency with 10 CFR 54.21(c)(1)(i). However, it is not clear whether this is consistent with SRP-LR Section 4.6.3.1.1.1. Per SRP-LR Section 4.6.3.1.1.1, the number of assumed transients in the existing analysis needs to be compared with the extrapolation to 60 years of operation of the number of operating transients experienced to date. It is not clear how monitored and unmonitored transients are related to operating transients experienced to date and whether unmonitored transients have never happened to the plant.
Request
- 1. Clarify how unmonitored transients are related to transients the plant has experienced to date.
9
- 2. Confirm that the calculations tallied in the fourth column of LRA Table 4.6.1-1 considered both monitored and unmonitored transients that were applicable to each penetration calculation. Or confirm that the monitored transients listed in LRA Table 4.6.1-1 are only applicable transients in calculations considered in the fourth column of LRA Table 4.6.1-1 for the sake of cumulative fatigue analysis.
- 3. The third column of LRA Table 4.6.1-2 provides the type and number of assumed unmonitored transients applicable to each group of penetrations listed in the first column of LRA Table 4.6.1-2. Confirm that there are no other monitored transients that may be applicable to each group of penetrations.
RCI B.2.1.22-1 Regulatory Basis Title 10 of the Code of Federal Regulations Section 54.21(a)(3) requires the applicant to demonstrate that the effects of aging for structures and components will be adequately managed so that the intended function will be maintained consistent with the current licensing basis (CLB) for the period of extended operation. As described in the SRP-LR, an applicant may demonstrate compliance with 10 CFR 54.21(a)(3) by referencing the GALL-LR Report when evaluation of the matter in the GALL-LR Report applies to the plant.
Background
Procedure CL-AMPBD-SLI, Selective Leaching Inspection Sample Basis Document, Revision 0, discussed performing metallurgical analysis of components in place of visual examinations and that the sample size could be reduced by a factor of three (i.e., 6.7 percent or a maximum of 9 components) if the entire material and environment population is evaluated using metallurgical analysis in lieu of visual examinations. During the audit, this procedure was revised to remove the discussion related to reducing sample size if metallurgical analyses are performed.
Request Confirm that Revision 1 of procedure CL-AMPBD-SLI removed the discussion related to reducing sample size if metallurgical analyses are performed and that the sample sizes at Clinton Power Station will be consistent with GALL LR Report AMP XI.M33, Selective Leaching.