ML20013G730

Safety Evaluation for Vogtle Electric Generating Plant Unit 4 (LAR 19-016)

ML20013G730
Person / Time
Site:	Vogtle
Issue date:	02/03/2020
From:	Jennivine Rankin NRC/NRR/VPOB
To:	City of Dalton, GA, Georgia Power Co, MEAG Power, Oglethorpe Power Corp, Southern Nuclear Operating Co
References
EPID L-2019-LLA-0181, LAR-19-016
Download: ML20013G730 (11)

Text

SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 173 TO THE COMBINED LICENSE NO. NPF-92 SOUTHERN NUCLEAR OPERATING COMPANY, INC.

GEORGIA POWER COMPANY OGLETHORPE POWER CORPORATION MEAG POWER SPVM, LLC MEAG POWER SPVJ, LLC MEAG POWER SPVP, LLC CITY OF DALTON, GEORGIA VOGTLE ELECTRIC GENERATING PLANT UNIT 4 DOCKET NO.52-026

1.0 INTRODUCTION

By letter dated August 22, 2019, as revised by letter dated October 25, 2019 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML19234A327 and ML19298D420, respectively), Southern Nuclear Operating Company (SNC) requested that the U.S. Nuclear Regulatory Commission (NRC or Commission) amend Vogtle Electric Generating Plant (VEGP) Unit 4, Combined License (COL) Number NPF-92. Revised license amendment request (LAR) 19-016R1 replaced LAR 19-016, dated August 22, 2019, in its entirety. LAR 19-016R1 requested changes to the Updated Final Safety Analysis Report (UFSAR) in the form of departures from the incorporated plant-specific Design Control Document (DCD) Tier 2* information.

In LAR-19-016R1, SNC seeks approval to revise the provided area of horizontal and vertical steel reinforcement for VEGP Unit 4 Wall L from elevation 117'-6" to 135'-3"; and revise the provided area of horizontal steel reinforcement for VEGP Unit 4 Wall 7.3 from elevation 117'-6" to 135'-3". The proposed changes impact UFSAR Tier 2* information in UFSAR Tables 3H.5-5, Interior Wall on Column Line 7.3 Details of Wall Reinforcement and 3H.5-7, Interior Wall on Column Line L Details of Wall Reinforcement, and Figures 3H.5-4, Typical Reinforcement in Wall 7.3 and 3H.5-12, Typical Reinforcement in Wall L.

On September 24, 2019, the NRC staff published a proposed no significant hazards consideration (NSHC) determination in the Federal Register (84 FR 50082) for the proposed amendment. Subsequently, by letter dated October 25, 2019, SNC provided additional information that expanded the scope of the amendment request as originally noticed in the Federal Register. Accordingly, the NRC published a second proposed NSHC determination in the Federal Register on November 19, 2019 (84 FR 63900), which superseded the original notice in its entirety.

2.0 REGULATORY EVALUATION

The staff considered the following regulatory requirements in reviewing the LAR.

Title 10 of the Code of Federal Regulation (10 CFR) Part 52, Appendix D,Section VIII.B.5.a allows an applicant or licensee who references this appendix to depart from Tier 2 information, without prior NRC approval, unless the proposed departure involves a change to or departure from Tier 1 information, Tier 2* information, or the Technical Specifications (TS), or requires a license amendment under paragraphs B.5.b or B.5.c of the section.

The specific NRC technical requirements applicable to LAR 19-016R1 are the general design criteria (GDC) in Appendix A, General Design Criteria for Nuclear Power Plants, to 10 CFR Part 50, Domestic Licensing of Production and Utilization Facilities. In particular, these technical requirements include the following GDC:

10 CFR Part 50, Appendix A, GDC 2, Design Bases for Protection Against Natural Phenomena, provides, in part, that structures, systems, and components important to safety shall be designed to withstand the effects of natural phenomena such as earthquakes, tornadoes, hurricanes, floods, tsunami, and seiches without loss of capability to perform their safety functions.

10 CFR Part 50, Appendix A, GDC 4, Environmental and Dynamic Effects Design Basis, provides, in part, that structures, systems, and components important to safety shall be designed to accommodate the effects of and to be compatible with the environmental conditions associated with normal operation, maintenance, testing, and postulated accidents, including loss-of-cooling accidents.

3.1 TECHNICAL EVALUATION

OF THE REQUESTED CHANGES The design of the AP1000 auxiliary building is a reinforced concrete structure with three floors above plant grade1 and two floors below plant grade. The auxiliary building is part of the nuclear island (NI) and its C-shape structure wraps around approximately 50 percent of the circumference of the shield building. The auxiliary building wall at column line 7.3 is a reinforced concrete wall and is discussed in the UFSAR Subsection 3H.5.1.2, Wall at Column Line 7.3. The column line 7.3 extends from the basemat to the top of the roof. This wall runs in the east-west direction of the NI and connects the reinforced concrete portion of the shield building wall with the reinforced concrete wall on column line I.

During construction at VEGP Unit 4, SNC identified three independent nonconformities at two separate locations (Wall L and Wall 7.3). At Wall L, the as-built amount of horizontal and vertical reinforcement provided does not meet the specified minimum provided reinforcement in 1

In the plant-specific DCD, plant grade is defined as elevation 100'-0".

the UFSAR. At Wall 7.3, the as-built amount of horizontal reinforcement provided does not meet the specified minimum provided reinforcement in the UFSAR.

LAR 19-016R1 seeks to revise the provided area of horizontal and vertical steel reinforcement for VEGP Unit 4 Wall L from elevation 117'-6" to 135'-3"; and revise the provided area of horizontal steel reinforcement for VEGP Unit 4 Wall 7.3 from elevation 117'-6" to 135'-3". The proposed changes impact UFSAR Tier 2* information in UFSAR Tables 3H.5-5 and 3H.5-7, and Figures 3H.5-4 and 3H.5-12.

To perform the technical evaluation, the NRC staff considered Vogtle UFSAR Section 3.8, Design of Category I Structures. The staff also examined the portions of NUREG-1793, Supplement 2, Final Safety Evaluation Report Related to Certification of the AP1000 Standard Plant Design (ADAMS Accession No. ML112061231), and Final Safety Evaluation Report for the Vogtle Electric Generating Plant Units 3 & 4 Combined License Application (ADAMS Accession No. ML110450302) documenting the staffs technical evaluation of those aspects of the AP1000 DCD and VEGP COL application, respectively.

The NRC staff performed an audit as part of its review of LAR 19-016R1. The audit, in part, confirmed SNCs evaluation of the as-built reinforcement areas as compared to the design requirements. A summary of the audit is provided in audit reports dated October 11, 2019, and December 16, 2019 (ADAMS Accession Nos. ML19280D872 and ML19336A376, respectively).

3.1.1 Wall L Horizontal Evaluation As described in UFSAR Subsection 3H.5.1.3, Wall at Column Line L, the wall at column line L (Wall L) is a shear wall on the west side of the Main Control Room (MCR) and extends from the top of the basemat at elevation 66'-6" to the top of the roof. The wall is two feet thick. The segment of the wall that is a part of the MCR boundary is from elevation 117'-6" to elevation 135'-3". In addition to the dead, live, and seismic loads, the wall is designed to withstand a 6.5 pounds per square inch pressure load due to a pipe break in the main steam isolation valve room even though it is a break exclusion area. UFSAR Table 3H.5-6, Interior Wall at Column Line L Forces and Moments in Critical Locations, shows the governing load combination and associated design loads that are due to the postulated pipe rupture. Table 3H.5-7 and Figure 3H.5-12 present the details of the wall reinforcement.

The design of Wall L requires horizontal reinforcement bar (rebar) consisting of #11@6" Each Face (EF)2 + #10@12" EF in two layers from elevation 117'-6" to elevation 135'-3", and vertical rebar consisting of #11@6" EF + #10@6" EF in two layers, with the #11 bars on the outside and

1. 10 bars on the inside layer, from elevation 117'-6" to elevation 135'-3" as shown in UFSAR Figure 3H.5-12.

According to SNC, the changes proposed in LAR 19-016R1 specifies that a portion of one horizontal rebar, #11@6" EF, located directly above elevation 117'-6" is to be omitted from the VEGP Unit 4 Wall L (elevation 117'-6" to elevation 135'-3"). Since this rebar is not fully developed for the entire width of the wall, the bar is not considered to be credited as a portion of the provided steel area for Wall L.

The Shield Building wall (i.e., the south boundary of Wall L) has 35 #11 hook bar dowel outs EF from elevation 117'-6" to 135"-3" while Wall 11 (i.e., the north boundary of Wall L) has 36 #11 2

This nomenclature refers to #11 sized rebar at 6 spacing.

hook bar dowel outs. Therefore, one hook or dowel bar is missing on the Shield Building wall to splice horizontal reinforcement bar #11 on EF. At VEGP Unit 4, one horizontal bar cannot be installed because it cannot be spliced to the hooks of Wall 11 and Wall L. SNC requested a change to omit the horizontal #11 bar located directly above elevation 117'-6". All other horizontal rebars remain unchanged and are installed as required by the design, including one row directly above the omitted row consisting of both a #11 and #10 bar EF.

To justify the omission of the bar, SNC used Finite Element Analysis (FEA) to calculate the reinforcement necessary to satisfy American Concrete Institute (ACI) 349-01 (Reference 8) requirements using the applicable load combinations and design criteria, in accordance with UFSAR Table 3.8.4-2, Load Combinations and Load Factors for Seismic Category I Concrete Structures, and ACI 349-01. As shown in UFSAR Table 3H.5-7, the horizontal demand in Wall L between elevations 117'-6" to 135'-3" (1.36 in2/ft) remains less than the revised capacity of this wall segment (4.36 in2/ft).

SNC stated that the elements impacted by the proposed change (displayed in green) are not located near the critical element (displayed in red) in Figure 5 of LAR 19-016R1. Therefore, SNC stated the proposed change does not reduce the design margin for Wall L.

In addition, SNC provides the following analysis in LAR 19-016R1, Enclosure 3, pages 11 and 12 to support the change to the horizontal reinforcement of Wall L:

Considering the subject reduction in area of provided horizontal reinforcement presented in this LAR, the maximum calculated interaction ratio [IR] of the local impacted elements is IRLocal=0.26. Since the IR remains less than 1.0, the proposed change is acceptable and continues to satisfy the acceptance criteria of ACI 349-01 and applicable design criteria. Furthermore, the IRLocal is less than the documented critical element interaction ratio.

The CJ [construction joint] between Wall L and the Shield Building is impacted by the proposed change. The amount of provided rebar, considered transverse to the CJ, in the design analysis is 8.78 in2/ft. This is equivalent to #11@6" +

1. 10@12" (EF). Since the horizontal #11 bar (EF) is not installed directly above

[elevation] 117'-6" transverse to this CJ, the reduction to the provided horizontal reinforcement for the impact portion of the CJ results in an area of 8.39 in2/ft.

The nominal shear strength of the CJ is controlled by concrete strength and geometry in accordance with ACI 349-01, Section 11.7.5. Therefore, the calculated IR of 0.735 remains unchanged. Since the IR remain less than 1.0, the proposed change is acceptable and continues to satisfy the acceptance criteria of ACI 349-01 and applicable design criteria.

The proposed change regarding horizontal reinforcement does not impact the vertical reinforcement or the ability to install shear reinforcement.

The proposed change has no impact to adjacent walls and slabs. Adjacent walls and slabs remain in conformance with ACI 349-01 requirements.

The staff reviewed UFSAR Subsection 3H.5.1.3 and applicable ACI 349-01 code provisions pertaining to concrete, critical sections, and loads. The staff also performed an audit as part of its review of this LAR and reviewed the AP1000 Nonconformance and Disposition Report SV4-CR01-GNR-000583, U4 Walls 7.3 & L (EL 117'-6" to 135'-3") Reinfo. w/o a Splice (ESR 50026080 & 50026091), to confirm SNCs evaluation of the as-built reinforcement areas as compared to the design requirements. During the audit, the staff reviewed Nonconformance &

Disposition Reports for Wall L, which included drawings, calculations, photographs and justifications. Considering the applicable loading scenarios and acceptance criteria required by the current licensing basis, the demands in Wall L remain below their respective capacities.

The staff noted there would be a small stiffness change for Wall L. Therefore, the staff found that the design margin may change, however the change would be acceptable because the stiffness change would be minimal. In addition, the staff confirmed that the minimum provided reinforcement is 4.36 in2/ft, and found this acceptable because it is greater than the required reinforcement of 1.36 in2/ft. Additionally, staff found that the proposed changes will not have significant impacts on the seismic analysis of the NI because it does not significantly affect the mass or stiffness of the seismic model. Furthermore, the location of the reduction of the reinforcement in the elements are not near the critical elements of the wall. Lastly, the staff confirmed that the IR remains below 1.0 and confirmed the applicable acceptance criteria of ACI 349-01 is met. As such, the staff concluded that the change to the horizontal reinforcement between elevation 117'-6" to elevation 135'-3" will have an insignificant impact on the design margin for Wall L and is in accordance with and continues to satisfy the acceptance criteria of ACI 349-01.

3.1.2 Wall L Vertical Evaluation The licensee installed the vertical rebar such that the spacing of the bars resulted in an overall reduction of the number of bars in the wall. The spacing of the rebar is generally uniform throughout the length of the wall. Since the total number of vertical bars has been reduced, the provided area of steel has been reduced.

The licensee used FEA to calculate the reinforcement necessary to satisfy ACI 349-01 requirements using the applicable load combinations and design criteria, in accordance with UFSAR Table 3.8.4-2 and ACI 349-01.

SNC provided the following analysis in LAR 19-016R1, Enclosure 3, pages 12 and 13 to support the change to the vertical reinforcement of Wall L:

As shown in UFSAR Table 3H.5-7, the required vertical reinforcement in Wall L between elevations 117'-6" to 135'-3" (2.02 in2/ft) remains less than the revised provided reinforcement of this wall segment (5.55 in2/ft).

The proposed change results in a reduction to the provided reinforcement located throughout the entire wall segment of Wall L from [elevation] 117'-6" to 135'-3". Therefore, all individual elements of the [FEA] are impacted by this proposed change. The design ratio and margin for the entire wall segment is determined based on the demand of the most critical element [of the wall].

The qualification of Wall L shows that the maximum design ratio for the vertical reinforcement in Wall L between [elevation] 117'-6" to 135'-3" is 0.418 (the required steel = 2.365 in2/ft in the most critical element and the provided steel =

5.660 in2/ft each face). The design required area of steel of 2.365 in2/ft, which considers all applicable loads including combined [safe shutdown earthquake]

and thermal loads, is higher than the required value of 2.02 in2/ft as specified as specified in UFSAR Table 3H.5-7 and, therefore, is more conservative. While the proposed change has vertical bars omitted in each of the four layers (East/West, inside/outside), at worst only a single bar in each layer is missing over an effective width of 2 times the thickness. This is a conservative interpretation of the ACI limit as defined in ACI 349-01, Section 14.2.4. The average provided reinforcement in a distance of two times the wall thickness of 2 feet is reduced to 4.95 in2/ft each face. The design ratio becomes 0.478, which is less than 1.0.

Therefore, the subject wall (Wall L, Section 4) is still qualified with a design margin of 52.2%.

SNC also noted that the proposed change does not impact the shear reinforcement and has no impact to adjacent walls and slabs. Adjacent walls and slabs remain in conformance with ACI 349-01 requirements.

The staff reviewed UFSAR Subsection 3H.5.1.3 and applicable ACI 349-01 code provisions pertaining to concrete, critical sections and loads. The staff also performed an audit as part of its review of this LAR and reviewed the AP1000 Nonconformance and Disposition Report SV4-CR01-GNR-000583 and SV4-CR01-GNR-000610, Wall L Vertical Dowels Missing at EL 117-6 to 135-3 (ESR 50030817), to confirm SNCs evaluation of the as-built reinforcement areas as compared to the design requirements. During the audit, the staff reviewed Nonconformance

& Disposition Reports for Wall L, which included drawings, calculations, photographs and justifications. Considering the applicable loading scenarios and acceptance criteria required by the current licensing basis, the demands in Wall L remain below their respective capacities.

The staff noted there would be a small stiffness change for Wall L. Therefore, the staff found that the design margin may change, however the change would be acceptable because the stiffness change would be minimal. In addition, the staff confirmed that the minimum provided reinforcement is 5.55 in2/ft, and found this acceptable because it is greater than the required reinforcement of 2.02 in2/ft. The NRC staff found that the proposed changes will not have significant impact on the seismic analysis of the NI because it does not significantly affect the mass or stiffness of the seismic model. Furthermore, SNC demonstrated there is sufficient margin considering the reduction in area of provided reinforcement. Lastly, the staff confirmed the IR remains below 1.0 and confirmed the applicable acceptance criteria of ACI 349-01 is met.

As such, the staff concluded that the change to the vertical reinforcement between elevation 117'-6" to elevation 135'-3" does not reduce the design margin for Wall L and is in accordance with and continues to satisfy the acceptance criteria of ACI 349-01.

3.1.3 Wall 7.3 Horizontal Evaluation SNC provides the following description of Auxiliary Building Wall 7.3 in LAR 19-016R1, , pages 4 and 5:

As described in UFSAR Subsection 3H.5.1.2, the wall at column line 7.3 (Wall 7.3) is a shear wall that connects the shield building and the [NI] exterior wall at column line I. It extends from the top of the basemat at elevation 66'-6" to the top of the roof.

The auxiliary building design loads are described in UFSAR Subsection 3H.3.3,

[Loads,] and the wall is designed for the applicable loads. For various segments of this wall, the corresponding governing load combination and associated design loads are shown in UFSAR Table 3H.5-4, [Interior Wall at Column Line 7.3 Forces and Moments in Critical Locations.] UFSAR Table 3H.5-5 and Figure 3H.5-4 present the details of the wall reinforcement. The sections where the required reinforcement is calculated are shown in UFSAR Figure 3H.5-2 (Sheet 2).

SNC provided the following analysis in LAR 19-016R1, Enclosure 3, page 8 to support the change to the horizontal reinforcement of Wall 7.3:

In accordance with UFSAR Figure 3H.5-4, the design of the Auxiliary Building Wall 7.3 from [elevation] 117-6 to [elevation] 135-3 requires horizontal [rebar]

consisting of #10@12" EF + #10@12" EF in one layer (note that this is equivalent to #10@6 EF). As specified on design drawings, straight bar is utilized to span a majority of the width of the wall. At the boundaries of the wall, this straight bar is spliced to [rebar] (referred to as dowels) developed within the bounding walls. The vertical construction joint at the face of the Shield Building represents the west boundary for Wall 7.3. At VEGP Unit 4, the Shield Building wall has 35 #10 hook bar dowel outs EF from [elevation] 117'-6" to [elevation]

135'-3". The vertical construction joint at the face of Wall I represents the east boundary for Wall 7.3. At VEGP Unit 4, Wall I has 36 #10 hook bar (or U-bar) dowel outs EF from [elevation] 117'-6" to [elevation] 135'-3". This means that for one #10 bar EF there is not a Shield Building wall dowel (35 dowel out EF) to splice to that matches the configuration of Wall I (36 dowel out EF).

One horizontal reinforcement bar #10 (EF) located directly below [elevation] 135'-

3" is to be spliced to standard hook bar (EF) in Wall I and extend to 2'-0" from the Shield Building. The associated #10 (EF) dowel developed into the Shield Building is not installed.

A simplified sketch of the typical #10 rebar configuration is shown in Figure 3. A simplified sketch of the proposed change for one horizontal reinforcement bar

1. 10 (EF) located directly below EL. 135'-3" is shown in Figure 4.

Figure 3 and Figure 4 from the LAR are shown below.

Figure 3: Typical #10 Rebar Configuration for Wall 7.3 Figure 4: Proposed Rebar Configuration directly below EL. 135'-3" for Wall 7.3 As clarified by Figure 4, the single #10 (EF) is not developed for the entire width of Wall 7.3. Therefore, this bar is unable to be credited as provided reinforcement. This results in the as-built provided amount of horizontal reinforcement area being less than the existing UFSAR Table 3H.5-5 Wall Section 3 (Elevation 117-6 to 135-3) provided minimum value of 2.54 in2/ft.

The actual provided value is 2.50 in2/ft for this segment of Wall 7.3. This condition results in the provided reinforcement area and reinforcement configuration not in compliance with the Tier 2* information contained in UFSAR Table 3H.5-5 and Figure 3H.5-4. The impacted area is a subsection of Wall 7.3 Section 3 as shown in UFSAR Figure 3H.5-2 (Sheet 2). All other sections shown on UFSAR Figure 3H.5-2 (Sheet 2) remain unaffected by this activity.

SNC proposed to add a note that explains the configuration change for VEGP Unit 4 in UFSAR Table 3H.5-5. Changes are also proposed to UFSAR Figure 3H.5-4, because the figure shows #10@6" horizontal rebar with the full development length between elevation 117'-6" and 135'-3". Because a single #10 (EF) is not developed for the entire width of Wall 7.3, a note is added to UFSAR Figure 3H.5-4 to explain the configuration change for VEGP Unit 4.

SNC used FEA to calculate the reinforcement necessary to satisfy ACI 349-01 requirements using the applicable load combinations and design criteria, in accordance with UFSAR Table 3.8.4-2 and ACI 349-01. As shown in UFSAR Table 3H.5-5, the horizontal demand in Wall 7.3 between elevation 117'-6" and 135'-3" (2.03 in2/ft) remains less than the revised provided reinforcement of this wall segment (2.50 in2/ft).

Additionally, SNC provided the following evaluation to support the change to the horizontal reinforcement of Wall 7.3:

The documented design margin for Wall 7.3 ([elevation] 117'-6" to [elevation]

135'-3") is 17.2% based on the critical element. The elements impacted by the proposed change are not located near the critical elements as shown in Figure 6 and have a margin of 17.86% considering the subject reduction in area of provided reinforcement presented in this LAR. Therefore, the proposed change does not reduce the design margin for Wall 7.3. [The NRC staff notes that Figure 6 of the LAR shows that the elements impacted by the proposed change (displayed in green) are not located near the critical element (displayed in red).]

Considering the subject reduction in area of provided horizontal reinforcement presented in this LAR, the calculated interaction ratio of the local impacted elements is IRLocal=0.82. Since the IR remains less than 1.0, the proposed change is acceptable and continues to satisfy the acceptance criteria of ACI 349-01 and applicable design criteria.

The CJ between Wall 7.3 and the Shield Building is impacted by the proposed change. The amount of provided rebar, considered transverse to the CJ, in the design analysis is 5.08 in2/ft, and this is equivalent to #10@6" (EF). Since the horizontal #10 bar (EF) is not installed directly below [elevation] 135'-3" into the Shield Building, this results in a reduction to the horizontal provided rebar considered transverse to the CJ. The provided reinforcement for the impacted portion of the CJ is 4.76 in2/ft. The nominal shear strength of the CJ is controlled by concrete strength and geometry in accordance with ACI 349-01, Section 11.7.5. Therefore, the calculated IR of 0.847 remains unchanged. Since the IR remains less than 1.0, the proposed change is acceptable and continues to satisfy the acceptance criteria of ACI 349-01 and applicable design criteria.

SNC also noted that the proposed change has no impact on the design of the wall opening in Wall 7.3 and has no impact to adjacent walls and slabs. Adjacent walls and slabs remain in conformance with ACI 349-01 requirements.

The staff reviewed UFSAR Subsection 3H.5.1.3 and applicable ACI 349-01 code provisions pertaining to concrete, critical sections and loads. The staff also performed an audit as part of its review of this LAR and reviewed the AP1000 Nonconformance and Disposition Report SV4-CR01-GNR-000583 to confirm SNCs evaluation of the as-built reinforcement areas as compared to the design requirements. During the audit, the staff reviewed Nonconformance &

Disposition Reports for Walls 7.3, which included drawings, calculations, photographs and justifications. Considering the applicable loading scenarios and acceptance criteria required by the current licensing basis, the demands in Wall 7.3 remain below their respective capacities.

The staff noted there would be a small stiffness change for Wall 7.3. Therefore, the staff found the design margin may change, however the change would be acceptable because the stiffness change would be minimal. In addition, the staff confirmed that the minimum provided reinforcement is 2.50 in2/ft, and found this acceptable because it is greater than the required reinforcement of 2.03 in2/ft. The NRC staff found that the proposed changes will not have significant impact on the seismic analysis of the NI because it does not significantly affect the mass or stiffness of the seismic model. Furthermore, the location of the reduction of the reinforcement in the elements are away from the critical element of the wall and SNC demonstrated there is sufficient margin considering the reduction in area of provided reinforcement. Lastly, the staff confirmed the IR remains below 1.0 and confirmed the applicable acceptance criteria of ACI 349-01 is met.

Based on the above, the staff concluded that the change to the horizontal reinforcement between elevation 117'-6" to elevation 135'-3" will remain within the design margin for Wall 7.3 and is in accordance with and continues to satisfy the acceptance criteria of ACI 349-01.

3.2 Evaluation Summary The NRC staff reviewed the SNCs analysis provided in the LAR. Based on its review, the NRC staff concludes that the changes to the reinforcement do not reduce the design margins significantly for Walls L and 7.3, and are in accordance with and continue to satisfy the acceptance criteria of ACI 349-01. The staff also concludes that the proposed changes do not significantly affect the seismic response or response to dynamic effects in the design bases because the mass or stiffness of the seismic model is not affected. Therefore, there is reasonable assurance that the requirements of GDC 2, and GDC 4 of 10 CFR Part 50 Appendix A and Appendix D (Design Certification Rule for the AP1000 Design) to 10 CFR Part 52, Licenses, Certifications, and Approvals for Nuclear Power Plants, will continue to be met. The NRC staff finds that the proposed amendment meets relevant code provisions. Therefore, the NRC staff finds SNCs request in LAR 19-016R1 to change current licensing basis documents UFSAR Tables 3H.5-5 and 3H.5-7, and Figures 3H.5-4 and 3H.5-12 to be acceptable.

4.0 STATE CONSULTATION

In accordance with the Commission's regulations, the Georgia State official was notified of the proposed issuance of the amendment on January 8, 2020. The State official had no comments.

5.0 ENVIRONMENTAL CONSIDERATION

The amendment changes a requirement with respect to installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20. The staff has determined that the amendment involves no significant increase in the amounts, and no significant change in the types, of any effluents that may be released offsite, and that there is no significant increase in individual or cumulative occupational radiation exposure. The Commission has previously issued a proposed finding that the amendment involves no significant hazards consideration, and there has been no public comment on such finding November 19, 2019 (84 FR 63900). Accordingly, the amendment meets the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9). Pursuant to 10 CFR 51.22(b), no environmental impact statement or environmental assessment need be prepared in connection with the issuance of the amendment.

6.0 CONCLUSION

The staff has concluded, based on the considerations discussed in Section 3.1 that there is reasonable assurance that: (1) the health and safety of the public will not be endangered by operation in the proposed manner, (2) there is reasonable assurance that such activities will be conducted in compliance with the Commissions regulations, and (3) the issuance of the amendment will not be inimical to the common defense and security or to the health and safety of the public. Therefore, the staff finds the changes proposed in LAR 19-016R1 acceptable.

7.0 REFERENCES

1. Southern Nuclear Operating Company, Vogtle Electric Generating Plant Unit 4, Request for License Amendment: Reinforcement Changes for Wall L and Wall 7.3 (LAR-19-016),

August 22, 2019 (ADAMS Accession No. ML19234A327).

2. Southern Nuclear Operating Company, Vogtle Electric Generating Plant Unit 4, Request for License Amendment: Reinforcement Changes for Wall L and Wall 7.3 (LAR-19-016R1),

October 25, 2019 (ADAMS Accession No. ML19298D420).

3. Audit Report for Vogtle Electric Generating Plant Unit 4, Request for License Amendment:

Reinforcement Changes for Wall L and Wall 7.3 (LAR-19-016), October 11, 2019 (ADAMS Accession No. ML19280D872).

4. Audit Report for Vogtle Electric Generating Plant Unit 4, Request for License Amendment:

Reinforcement Changes for Wall L and Wall 7.3 (LAR-19-016R1), December 16, 2019 (ADAMS Accession No. ML19336A376).

5. Vogtle Electric Generating Plant Units 3 and 4, Updated Final Safety Analysis Report Revision 8, Chapter 3, Design of Structures, Components, Equipment and Systems, Appendix 3H, Auxiliary and Shield Building Critical Sections (ADAMS Accession No. ML19171A061).

6. Combined License NPF-92 for Vogtle Electric Generating Plant Unit 4, Southern Nuclear Operating Company (ADAMS Accession No. ML14100A135).

7. AP1000 Design Control Document, Revision 19, dated June 13, 2012 (ADAMS Accession No. ML11171A087)

8. American Concrete Institute (ACI), ACI-349-01. Building Code Requirements for Nuclear Safety-Related Concrete Structures.

9. NUREG-1793, Supplement 2, Final Safety Evaluation Report Related to Certification of the AP1000 Standard Plant Design (ADAMS Accession No. ML112061231),

10. Final Safety Evaluation Report for the Vogtle Electric Generating Plant Units 3 & 4 Combined License Application (ADAMS Accession No. ML110450302)