ML25328A242
| ML25328A242 | |
| Person / Time | |
|---|---|
| Site: | Hatch  |
| Issue date: | 11/24/2025 |
| From: | Harris B NRC/NRR/DNRL/NLRP |
| To: | |
| Shared Package | |
| ML25328A240 | List: |
| References | |
| Download: ML25328A242 (0) | |
Text
REQUEST FOR ADDITIONAL INFORMATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION EDWIN I. HATCH, UNITS 1 AND 2, SUBSEQUENT LICENSE RENEWAL REVIEW - SAFETY SOUTHERN NUCLEAR OPERATING COMPANY HATCH, UNITS 1, 2 DOCKET NO. 05000321, 05000366 ISSUE DATE: 11/24/2025 Set # 1 RAI B.2.3.27-1 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-SLR Report AMP XI.M41, Buried and Underground Piping and Tanks, Table XI.M41-1, Preventive Actions for Buried and Underground Piping and Tanks, recommends that cathodic protection is provided for buried carbon steel piping; however, it does not recommend that cathodic protection is provided for buried stainless steel piping. In addition, GALL-SLR Report AMP XI.M41 states the following:
[f]ailure to provide cathodic protection in accordance with Table XI.M41-1 may be acceptable if justified in the SLRA. The justification addresses soil sample locations, soil sample results, the methodology and results of how the overall soil corrosivity was determined, pipe to soil potential measurements and other relevant parameters. If cathodic protection is not provided for any reason, the applicant reviews the most recent 10 years of plant-specific operating experience (OE) to determine if degraded conditions that would not have met the acceptance criteria of this AMP have occurred. This search includes components that are not in-scope for license renewal if, when compared to in-scope piping, they are similar materials and coating systems and are buried in a similar soil environment. The results of this expanded plant-specific OE search are included in the SLRA.
[a]dditional inspections, beyond those in Table XI.M41-2 [Inspection of Buried and Underground Piping and Tanks] may be appropriate if exceptions are taken to program element 2, preventive actions, or in response to plant-specific OE.
SLRA Section B.2.3.27, Buried and Underground Piping and Tanks, states the following:
Exception 1[:][c]athodic protection is not installed at HNP [Hatch Nuclear Plant] as recommended in NUREG-2191, Table XI.M41-1.
HNP is proactively replacing portions of buried carbon steel piping with stainless steel as part of corrective actions driven by the existing program.
[the Buried and Underground Piping and Tanks program is] continuing to evaluate installation of cathodic protection in targeted locations and installation of targeted cathodic protection in additional locations if determined it would significantly improve plant safety.
[HNP will] install cathodic protection on the diesel fuel oil storage tanks prior to the SPEO [subsequent period of extended operation].
The plant specific OE discussion in SLRA Section B.2.3.27 notes external corrosion and leaks in buried piping due to coatings failure. In addition, in relation to previous inspections and OE for buried carbon steel plant service water piping, SLRA Section B.2.3.27 notes [s]everal unsatisfactory results due to both internal and external degradation.
During its audit, the staff reviewed a report which noted that (a) site testing suggests that implementing targeted cathodic protection at HNP may be feasible but presents challenges and more testing is needed to fully evaluate the practicality of cathodic protection; (b) installing semi-deep anode groundbeds is potentially feasible at the site; and (c) buried piping systems at HNP are experiencing varying degrees of corrosion, with particular concern for those systems composed of carbon steel.
Issue:
- 1. The staff seeks additional information with respect to (a) how much in-scope buried carbon steel piping has been replaced with stainless steel piping to date; (b) why the SLRA does not include commitments to replace in-scope buried carbon steel piping with stainless steel piping since the site is proactively doing piping replacements; and (c) the amount of in-scope carbon steel piping that would be remaining during the SPEO once these replacements have occurred. This information is relevant to the staffs review of Exception No. 1 since cathodic protection is a recommended preventive action for carbon steel but not for stainless steel.
- 2. The staff seeks additional information with respect to why installation of cathodic protection is limited to the diesel fuel oil storage tanks and does not include any in-scope buried carbon steel piping. Based on the staffs observations noted in the Background section above, it appears that providing cathodic protection for in-scope carbon steel piping is potentially feasible.
- 3. Based on plant-specific OE and other observations noted in the Background section above (related to the condition of external coatings and ongoing external corrosion), the staff seeks additional information with respect to why cathodic protection will not be provided for in-scope carbon steel piping during the SPEO. It appears that external coatings and quality backfill cannot be relied upon as the only barriers to prevent external corrosion moving into the SPEO.
Request:
- 1. Provide additional information with respect to (a) how much in-scope buried carbon steel piping has been replaced with stainless steel piping to date; (b) why the SLRA does not include commitments to replace in-scope buried carbon steel piping with stainless steel piping since the site is proactively doing piping replacements; and (c) the amount of in-scope carbon steel piping that would be remaining during the SPEO once these replacements have occurred.
- 2. Provide additional information with respect to why installation of cathodic protection is limited to the diesel fuel oil storage tanks and does not include any in-scope buried carbon steel piping.
- 3. Provide additional information with respect to why external coatings and quality backfill can be relied upon as the only preventive actions for in-scope buried carbon steel piping during the SPEO.
RAI 4.3.7-1 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 4.3.7 indicates that after the screening evaluation for environmentally assisted fatigue (EAF) to determine the limiting locations, the applicant performed a detailed evaluation to reduce excessive conservatisms associated with the screening environmentally adjusted cumulative usage factor (CUFen) values.
In addition, NUREG/CR-6909, Revision 1, Section 4.1.4 indicates that the average temperature approach for the calculation of the environmental fatigue correction factor (Fen) can be used for a simple, linear transient in consideration of the threshold temperature for Fen (i.e., the average temperature calculation uses the threshold temperature in place of the minimum transient temperature when the minimum transient temperature is less than the threshold temperature). A more conservative approach than the average temperature approach is the Fen calculation with the maximum temperature of each transient.
Issue SLRA Section 4.3.7 does not clearly describe how the detailed evaluation reduces the excessive conservatism associated with the screening CUFen values that are based on conservative temperature, strain rate, and sulfur content in steels.
In addition, SLRA Section 4.3.7 does not clearly discuss the following: (1) whether the average temperature approach is used for the Fen calculation in the detailed evaluation after the screening evaluation; (2) if so, whether the average temperature approach is used only for a simple, linear transient and whether the Fen threshold temperature for each material type is used per NUREG/CR-6909, Revision 1; and (3) if the average temperature approach is used for a complex transient, why the conservatism of the applicants approach is comparable to or greater than that of the modified rate approach described in NUREG/CR-6909, Revision 1, Section 4.4 (i.e., plant-specific demonstration of the adequacy of the applicants approach).
Request
- 1. Explain how the detailed evaluation reduced the excessive conservatism associated with the screening CUFen values that are based on conservative temperature, strain rate, and sulfur content in steels. As part of the response, clarify how the detailed evaluation determines the temperature, strain rate, and sulfur content in steels in the calculation Fen calculation.
- 2. Clarify the following: (1) whether the average temperature approach is used for the Fen calculation in the detailed EAF evaluation; and (2) if so, whether the average temperature approach is used only for a simple, linear transient and whether the Fen threshold temperature for each material type is used per NUREG/CR-6909, Revision 1 (e.g., 150 ºC for carbon and low alloy steels).
- 3. If the average temperature approach is used for complex transients in the detailed EAF evaluation, describe the following: (1) the complex transients; (2) the components for which the complex transients are evaluated; and (3) why the conservatism of the applicant's average temperature approach is comparable to or greater than that of the modified rate approach described in NUREG/CR-6909, Revision 1, Section 4.4 (i.e., plant-specific demonstration of the adequacy of the applicant's approach by comparing the Fen and CUFen values between the average temperature approach and the modified rate approach).