ML24255A582
| ML24255A582 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 09/10/2024 |
| From: | Hammock J NRC/NRR/DNRL/NLRP |
| To: | Tennessee Valley Authority |
| References | |
| Download: ML24255A582 (1) | |
Text
1 REQUEST FOR ADDITIONAL INFORMATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION BROWNS FERRY SLRA SAFETY REVIEW TENNESSEE VALLEY AUTHORITY BROWNS FERRY, UNITS 1, 2, 3 DOCKET NO. 05000259, 05000260, 05000296 ISSUE DATE: 09/10/2024 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.
RAI B.2.1.271
Background:
GALL-SLR Report AMP XI.M41, Buried and Underground Piping and Tanks, Table XI.M411, Preventive Actions for Buried and Underground Piping and Tanks, recommends that cathodic protection is provided for buried 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 plantspecific 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 inscope for license renewal if, when compared to inscope piping, they are [of] similar materials and coating systems and are buried in a similar soil environment. The results of this expanded plantspecific OE search are included in the SLRA.
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[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.
Exception No. 1 to SLRA Section B.2.1.27, Buried and Underground Piping and Tanks, documents the basis for why the installation of a cathodic protection system to protect buried steel piping is impractical at Browns Ferry Nuclear Plant (BFN). In addition, based on its review of SLRA Section B.2.1.27, the staff noted six inspections of buried steel piping will be conducted in each 10year interval, consistent with Preventive Action Category E defined in GALLSLR Report Table XI.M412 (adjusted for a threeunit site). Furthermore, SLRA Section B.2.1.27 states the following:
based on review of BFN-specific operating experience, no leaks in the subject buried piping due to external corrosion have been observed and no significant buried piping coating degradation has been observed.
[f]rom the 2009 soil sample APEC [Area Potential Earth Current] survey there were 6 recommended inspection locations that could possibly reflect localized areas of potential coating damage and active corrosion. It was recommended that these locations be excavated and directly inspected. There were also 6 locations recommended for excavation and direct examination based on the 8 soil samples from 2023 combined with the 48 total native potential measurements recorded as CIS [Close Interval Survey].
During its audit, the staff noted several instances of buried piping leaks and an instance of buried piping not being coated in accordance with design specifications. The first three examples below are related to buried service air piping (not inscope based on the systems listed in SLRA Section B.2.1.27 (page B119)) and the 4 th and 5 th examples are related to buried fire protection piping (inscope based on the systems listed in SLRA Section B.2.1.27 (page B119)).
- 1. The staff reviewed CR 793555 and noted the suspected cause of the leak was corrosion similar to that seen in two service air piping leaks earlier in 2013.
- 2. The staff reviewed CR 1120048 and noted the source of the leak was determined to be service air and not fire protection.
- 3. The staff reviewed CR 898407 and noted (a) a section of service air piping had no visible exterior tape coating or polyethylene coating as required by design drawings; and (b) the uncoated section of piping had multiple thru wall holes.
- 4. The staff reviewed CR 828934 and noted it was indeterminate whether the leak was coming from a slipjoint between sections of pipe or a hole in the pipe wall.
- 5. The staff reviewed CR 1102016 and noted that a contributing cause of a break in buried fire protection piping was outer diameter graphitic corrosion. The staff noted that although managing loss of material due to graphitic corrosion is not within the scope of the Buried and Underground Piping and Tanks program, it does provide evidence that inscope buried steel piping is potentially exposed to an aggressive environment.
3 During its audit, the staff reviewed SL016653, Evaluation of Cathodic Protection for Buried Piping, which noted that a sitewide impressed current cathodic protection (ICCP) system is not likely to be successful; however, it also notes that protecting a small scope of buried piping that is highrisk due to the pipe construction, process fluid, or the soil conditions in the area is likely achievable. The staff also reviewed BP2023002703TR, Browns Ferry License Renewal Buried Piping Cathodic Protection Review, which provides a similar discussion.
Issue:
During its audit, the staff noted several instances of leaks and an instance of buried piping not being coated in accordance with design specifications. It is the staffs understanding that the OE described in the CRs above did not involve inscope buried steel piping; however, the staff seeks additional information with respect to why the condition of piping documented in theses CRs is not representative of the condition of inscope buried steel piping.
The staff recognizes that installation of a sitewide ICCP system is likely impractical at BFN.
However, based on its review of SL016653 and BP2023002703TR, it appears that protecting a limited scope of highrisk inscope buried steel piping may be practical. The staff seeks additional information with respect to why providing cathodic protection for a limited scope of highrisk inscope buried steel piping is considered impractical.
The 2009 and 2023 soil surveys referenced above recommended six inspection locations that could possibly reflect localized areas of potential coating damage and active corrosion. The staff noted that this also corresponds to the recommended number of inspections for Preventive Action Category E in GALLSLR Report Table XI.M412 (adjusted for a threeunit site). Since coatings are the only barriers to aging at BFN, and coatings will continue to degrade over time, the staff seeks additional information with respect to why increased inspection quantities (beyond those prescribed in GALLSLR Report Table XI.M412) are not necessary to provide reasonable assurance that loss of material on the external surfaces of inscope buried steel piping will be adequately managed during the subsequent period of extended operation.
Request:
Provide additional information documenting the basis for why the condition of piping documented in the CRs above is not representative of the condition of inscope buried steel piping. Include a discussion of the following as a minimum:
- 1. Similarities or differences in materials of construction for (a) inscope buried steel piping; (b) buried service air piping referenced in the CRs above; and (c) buried fire protection piping referenced in the CRs above.
- 2. Similarities or differences in external coating types used for (a) inscope buried steel piping; (b) buried service air piping referenced in the CRs above; and (c) buried fire protection piping referenced in the CRs above.
- 3. Similarities or differences in soil corrosivity in the vicinity of (a) inscope buried steel piping; (b) buried service air piping referenced in the CRs above; and (c) buried fire protection piping referenced in the CRs above.
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- 4. Detailed results of inspections of inscope buried steel piping, including whether the piping was externally coated in accordance with design specifications.
Provide additional information documenting the basis for why providing cathodic protection for a limited scope of highrisk inscope buried steel piping is considered impractical.
Based on plantspecific OE and the absence of cathodic protection, state the basis for why increased inspection quantities (beyond those prescribed in GALLSLR Report Table XI.M412) are not necessary to provide reasonable assurance that loss of material on the external surfaces of inscope buried steel piping will be adequately managed during the subsequent period of extended operation.
OFFICE NRR/DNRL/NLRP/PM NRR/DNRL/NLRP/BC NRR/DNRL/NCSG/BC NAME JHammock LGibson SBloom DATE 08/07/2024 08/06/2024 07/29/2024