ML24171A015

Update to Subsequent License Renewal Application (SLRA) Response to NRC Request for Additional Information Set 2 Safety Review

ML24171A015
Person / Time
Site:	Summer
Issue date:	06/17/2024
From:	James Holloway Dominion Energy South Carolina
To:	Office of Nuclear Reactor Regulation, Document Control Desk
References
24-222
Download: ML24171A015 (1)

Text

Serial No.: 24-222 Docket No.: 50-395

Enclosure 1

RESPONSE TO VCS SLRA REQUEST FOR ADDITIONAL INFORMATION SET 2 SAFETY REVIEW

Dominion Energy South Carolina, Inc.

(Dominion Energy South Carolina, or DESC)

Virgil C. Summer Nuclear Station Unit 1 Serial No.: 24-222 Docket No.: 50-395 Enclosure 1, Page 2 of 6

By letter dated August 17, 2023 [Agencywide Documents Access and Management System (ADAMS) Package Accession No. ML23233A179], Dominion Energy South Carolina, Inc.

(Dominion, Dominion Energy South Carolina, or DESC) submitted an application for the subsequent license renewal of Renewed Facility Operating License No. NPF-12 for Virgil C. Summer Nuclear Station (VCSNS) Unit 1.

The NRC staff has identified areas where additional information is needed to complete their review. In an email from Marieliz Johnson (NRC) to Eric S. Carr (DESC), dated May 6, 2024 (ADAMS Accession No. ML24127A110), the NRC staff transmitted Set 1 of their requests for additional information (RAIs) to support completion of the Safety Review. DESC responded to RAI Set 1 by letter dated May 30, 2024 (ADAMS Package No. ML24155A146).

In an email from Marieliz Johnson (NRC) to Eric S. Carr (DESC), dated June 3, 2024 (ADAMS Accession No. ML24156A001), the NRC staff transmitted Set 2 of their RAIs for Safety Review. DESC agreed to respond within 30 days of receipt of RAI Set 2.

The NRCs RAIs and DESCs RAI responses for Set 2 (Safety Review) are provided in this enclosure.

RAI 3.3.2.2.7-1 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.

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Background===

NUREG-2192 provides a standard review plan for subsequent license renewal applications (SRP-SLR). Section 3.3.2.2 of the SRP-SLR provides aging management review results for which further evaluation is recommended. SRP-SLR, Section 3.3.2.2.7 provides recommendations for the further evaluation of recurring internal corrosion. Included in these recommendations are that the applicant state:

(a) why the programs examination methods will be sufficient to detect the recurring aging effect before affecting the ability of a component to perform its intended function,

Serial No.: 24-222 Docket No.: 50-395 Enclosure 1, Page 3 of 6

(b) the basis for the adequacy of augmented or lack of augmented inspections, (c) what parameters will be trended as well as the decision points where increased inspections would be implemented (e.g., the extent of degradation at individual corrosion sites, the rate of degradation change),

(d) how inspections of components that are not easily accessed (i.e., buried, underground) will be conducted, and

(e) how leaks in any involved buried or underground components will be identified.

Issue

1. SLRA section 3.3.2.2.7, Loss of Material Due to Recurring Internal Corrosion, subsection B, Fire Water System (B2.1.16) program, states in part that the applicant will meet SRP-SLR criterion (a) by using the Low Frequency Electromagnetic Technique (LFET) or similar technique for screening piping during each refueling cycle, and that thinned areas found during this scan are followed up with wall thickness examinations. SLRA section 3.3.2.2.7, subsection B, does not discuss LFET in its writeup on inspection of components that are not easily accessed (SRP-SLR criterion (d)). The context of SLRA section 3.3.2.2.7 suggests that LFET will not be used for inspection of components that are not easily accessed.

2. SLRA section 3.3.2.2.7, subsection B, describes in its discussion of SRP-SLR criterion (d) a condition assessment requiring the sectioning of pipe that was performed in 2022.

The SLRA refers to the 2022 condition assessment of the pipe sections as inspections and then follows with a discussion of future inspections. It is not clear to the NRC staff if this discussion indicates that the applicant plans to inspect components not easily accessed during the period of extended operation by performing similar pipe sectioning.

Request

1. Clarify whether or not the LFET or similar technique for screening piping, as discussed in SLRA section 3.3.2.2.7, subsection B, will be used in areas that are not easily accessed (i.e. buried or underground).

2. Clarify the discussion of SRP-SLR criterion (d) in SLRA section 3.3.2.2.7, subsection B.

Does the applicant intend to inspect components not easily accessed during the period of extended operation by performing similar pipe sectioning?

DESC Response to RAI 3.3.2.2.7-1

1. Recurring Internal Corrosion (RIC) has been identified in unlined/uncoated steel fire service piping within the scope of the Fire Water System (B2.1.16) program.

Accordingly, LFET or a similar technique will be used to screen fire service piping subject to RIC. The fire service piping that is not easily accessed (i.e., buried piping)

Serial No.: 24-222 Docket No.: 50-395 Enclosure 1, Page 4 of 6

is cement-lined and is not subject to RIC. Therefore, screening of the cement-lined fire service piping for wall thinning due to RIC will not be performed.

2. The fire service piping that is not easily accessed (i.e., buried piping) is cement-lined and is not subject to RIC. The inspections performed in July 2022 are identified in B2.1.28, Buried and Underground Piping and Tanks (Operating Experience #7) and B2.1.21, Selective Leaching (Operating Experience #3). These inspections were primarily focused on identifying the extent of exterior-initiated selective leaching of the buried piping. The pipe was sectioned at locations with the deepest exterior loss of material to get a more accurate measurement of corrosion depth. During the inspection, it was noted that the inside of the ductile iron pipe was in excellent condition and the mortar lining on the inside surface was in good to excellent condition.

Aging Management Program B2.1.29, Internal Coatings/Linings for In-Scope Piping, Piping Components, Heat Exchangers, and Tanks permits opportunistic inspections of the lining of buried internally coated/lined fire water system piping, in lieu of periodic inspections. Three conditions related to flow testing, monitoring system pressure, and operating experience must be fulfilled to use the opportunistic inspection provision. These conditions are being met for the buried fire service piping at VCSNS. Opportunistic inspections of internal coating/lining do not require sectioning of pipe.

RAI B2.1.15-1 Regulatory Basis

Section 54.21(a)(3) of Title 10 of the Code of Federal Regulations (10 CFR) 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 U.S. Nuclear Regulatory Commission (NRC) 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 in the requests for information.

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Background===

The Monitoring and Trending program element in Aging Management Program (AMP)

XI.M26, Fire Protection, in Volume 2 of NUREG-2191, Generic Aging Lessons Learned Serial No.: 24-222 Docket No.: 50-395 Enclosure 1, Page 5 of 6

for Subsequent License Renewal (GALL-SLR) Report (Agencywide Documents Access and Management System (ADAMS) Accession No. ML17187A204), states the following:

• The results of inspections of the aging effects of cracking and loss of material on fire barrier penetration seals, fire barriers, fire damper assemblies, and fire doors are trended to provide for timely detection of aging effects so that the appropriate corrective actions can be taken. [NOTE: Draft Revision 1 of the GALL-SLR, Volume 2, proposes to clarify the Monitoring and Trending program element in AMP XI.M26 to indicate inspection results of all aging effects be trended (ML23180A188).]

• The performance of the halon/CO2 fire suppression system is monitored during the periodic test to detect any degradation in the system. These periodic tests provide data necessary for trending.

Issue

Subsequent License Renewal Application (SLRA) Supplement 2 dated May 6, 2024 (ML24129A200), revised and renumbered the enhancement to the Monitoring and Trending program element (renumbered from enhancement 2 to enhancement 3). The revised enhancement in SLRA Table A4.0-1 and SLRA Section B2.1.15 states, in part, Procedure(s) will be revised to specify that inspection results of materials susceptible to delamination, change in material properties, separation, increased hardness, shrinkage, or loss of strength will be trended. However, it is unclear to the NRC staff why the revised enhancement does not include loss of material and cracking, which are applicable aging effects for fire barriers as indicated in the SLRA (e.g., SLRA Table 3.5.2-14).

SLRA Supplement 2 dated May 6, 2024 (ML24129A200), added a new enhancement to the Monitoring and Trending Program element (new enhancement 4). The new enhancement in SLRA Table A4.0-1 and SLRA Section B2.1.15 states, in part, Procedure(s) will be revised to specify that inspections will be performed to identify cracking and loss of material for CO2 fire protection system components, and that those results are trended and appropriate corrective actions identified, if necessary. The added enhancement appears to address trending of the visual inspection results of the CO2 fire protection system but does not address trending the results of the periodic tests of the CO2 fire protection system.

Therefore, it is unclear whether the results of the periodic tests of the CO2 fire protection system will be trended during the subsequent period of extended operation.

Request:

1. Please discuss why revised and renumbered enhancement 3 does not include loss of material and cracking since they are applicable aging effects for fire barriers as indicated in the SLRA.

2. Consistent with the Monitoring and Trending program element in GALL-SLR Report AMP XI.M26, please discuss whether trending of the CO2 fire suppression system periodic test results will be performed during the subsequent period of extended operation, including any changes needed to new enhancement 4.

Serial No.: 24-222 Docket No.: 50-395 Enclosure 1, Page 6 of 6

DESC Response to RAI B2.1.15-1

1. Enhancement 3 of the Fire Protection Program has been revised to include the aging effects of loss of material and cracking. The updated enhancement is provided in the Enclosure 2 markups.

2. Enhancement 4 of the Fire Protection Program has been revised to state that the results of the periodic tests of the CO2 fire protection system will be trended during the subsequent period of extended operation The updated enhancement is provided in the Enclosure 2 markups.

Serial No.: 24-222 Docket No.: 50-395

Enclosure 2

SLRA MARK-UPS REQUEST FOR ADDITIONAL INFORMATION SET 2 SAFETY REVIEW

Dominion Energy South Carolina, Inc.

(Dominion Energy South Carolina, or DESC)

Virgil C. Summer Nuclear Station Unit 1

Enclosure 2 Serial No.: 24-222 Page 3 of 4 Virgil C. Summer Nuclear Station Application for Subseq uent License Renewal RAI Set 2 Appendix B - Aging Management Programs

The Fire Protection program is a risk-informed, performance-based program built upon National Fire Protection Association (NFPA) 805, Performance-Based Standard for Fire Protection for Light Water Reactor Electric Generating Plants, 2001 Edition. Adoption of NFPA 805 in accordance with Title 10 of the Code of Federal Regulations (1 0 CFR) 50.48(c) serves as the method of satisfying 10 CFR 50.48(a) and General Design Criterion 3.

NUREG-2191 Consistency The Fire Protection program is an existing program that, following enhancement, will be consistent with NUREG-2191,Section XI.M26, Fire Protection, as modified by SLR-ISG-2021-02-MECHANICAL, "Updated Aging Management Criteria for Mechanical Portions of the Subsequent License Renewal Guidance."

Exception Summary None Enhancements Prior to the subsequent period of extended operation, the following enhancements will be implemented in the following program elements:

Scope of Program (Element 1), Parameters Monitored / Inspected (Element 3); Detection of Aging Effects (Element 4); and Acceptance Criteria (Element 6)

1. Procedure(s) will be revised to provide guidance for detection of loss of material, cracking, holes, and gaps during the visual inspections of fire dampers to ensure that any deficiencies are noted on a condition report, and to determine the acceptability of the findings. (Revised -

Supplement 2)

2. Procedure(s) will be revised to require that inspections of fire barrier elastomeric penetration seals and seismic gap filler identify shrinkage, loss of strength, and hardening, or any other sign of degradation. (Added - Supplement 2)

Monitoring and Trending (Element 5)

3. Procedure(s) will be revised to specify that inspection results of materials susceptible to loss of material, cracking, delamination, change in material properties , separation, increased hardness, shrinkage, or loss of strength will be trended. Where practical, identified degradation will be projected until the next scheduled inspection. Resu lts will be evaluated against acceptance criteria to confirm that the timing of subsequent inspections will maintain the components intended functions throughout the subsequent period of extended operation based on the projected rate of degradation. (Renumbered and Revised - Supplement 2 ,

Revised - RAI Set 2)

Page B-86 Enclosure 2 Serial No.: 24-222 Page 4 of 4 Virgil C. Summer Nuclear Station Application for Subseq uent License Renewal RAI Set 2 Appendix B - Aging Management Programs

4. Procedure(s) will be revised to specify that inspections will be performed to identify cracking and loss of material for CO 2 fire protection system components, and that those results are trended and appropriate corre ctive actions identifie d, if necessary. Wher e practical, identified degradation will be projected until the next scheduled inspection. Re sults will be evaluated against acceptance criteria to confirm that the timing of subsequent inspections will maintain the components intended functions throughout the subsequent period of extended operation based on the projected rate of degradation. Trending of the results of the CO2 fire suppression system periodic tests will also be performed. (Added - Supplement 2, Revised - RAI Set 2)

Corrective Actions (Element 7)

5. Procedure(s) will be revised to specify that for inspection results that will fail to meet acceptance criteria prior to the next sched uled inspection, inspection frequencies will be adjusted as determined by the Corrective Action Program. (Renumbered and Revised -

Supplement 2)

Operating Experience Summary The following examples of operating experience provide objective evidence that the Fire Protection program has been, and will be, effective in managing the aging effects for SSCs within the scope of the program so that the intended functions will be maintained consistent with the current licensing basis during the subsequent period of extended operation.

1. In July 2014, a 1-inch diameter hole was identified on a gypsum fire barrier wall in the switchgear room. The hole penetrated the gypsum (fire barrier) but not the corrugated steel on the opposite side (pressure boun dary). The pressure boundary was intact, but the fire barrier was degraded. The hole in the gypsum board was patched with joint compound to correct the condition and restore the function of the gypsum wall as a fire barrier.

2. In February 2015, during a plant walkdown, a fire barrier penetration seal was found to contain a void. The penetration was supposed to contain 10 inches of foam seal material. The degradation was 3-2/3 inches deep within th e 10-inch foam, and was approximately 6 inches high. It appeared to be due to shrinkage rather than any external damage. The void in the penetration seal was filled with the required amount of additional foam sealant to correct the condition, and to restore the penetration seal as a fire barrier.

3. In March 2016, during scheduled inspections of fire barriers in the Control Building, it was identified that the Kaowool fire barrier for one of the penetrations was degraded due to a gap between the Kaowool triple wrap and the adjace nt drywall. The gap was closed using RTV fire-resistant foam to reconnect the Kaowool triple wrap to the drywall, thus correcting the condition and restoring the fire barrier function.

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