ND-18-1057, Request for License Amendment and Exemption: Passive Core Cooling System (Pxs) Gutter Drain Line Vents (LAR-18-022)

Request for License Amendment and Exemption: Passive Core Cooling System (Pxs) Gutter Drain Line Vents (LAR-18-022)

ML18239A375
Person / Time
Site:	Vogtle
Issue date:	08/27/2018
From:	Whitley B Southern Nuclear Operating Co
To:	Document Control Desk, Office of New Reactors
References
LAR-18-022, ND-18-1057
Download: ML18239A375 (25)

Text

B. H. Whitley Southern Nuclear Director Operating Company, Inc.

Regulatory Affairs 3535 Colonnade Parkway Birmingham, AL 35243 Tel 205.992.7079 Fax 205.992.5296 August 27, 2018 Docket Nos.: 52-025 ND-18-1057 52-026 10 CFR 50.90 10 CFR 52.63 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Southern Nuclear Operating Company Vogtle Electric Generating Plant Units 3 and 4 Request for License Amendment and Exemption:

Passive Core Cooling System (PXS) Gutter Drain Line Vents (LAR-18-022)

Ladies and Gentlemen:

Pursuant to 10 CFR 52.98(c) and in accordance with 10 CFR 50.90, Southern Nuclear Operating Company (SNC) requests an amendment to the combined licenses (COLs) for Vogtle Electric Generating Plant (VEGP) Units 3 and 4 (License Numbers NPF-91 and NPF-92, respectively). The requested amendment proposes to depart from information in the Updated Final Safety Analysis Report (UFSAR) (which includes the plant-specific Design Control Document (DCD) Tier 2 information) and involves related changes to plant-specific Tier 1 information, with corresponding changes to the associated COL Appendix C information.

Pursuant to the provisions of 10 CFR 52.63(b)(1), an exemption from elements of the design as certified in the 10 CFR Part 52, Appendix D, design certification rule is also requested for the plant-specific DCD Tier 1 material departures.

The requested amendment proposes changes to add vent lines to the passive core cooling system (PXS) lines which drain the containment gutters to the in-containment refueling water storage tank (IRWST). provides the description, technical evaluation, regulatory evaluation (including the Significant Hazards Consideration Determination) and environmental considerations for the proposed changes. provides the background and supporting basis for the requested exemption. identifies the requested changes and provides markups depicting the requested changes to the VEGP Units 3 and 4 licensing basis documents.

This letter contains no regulatory commitments. This letter has been reviewed and determined not to contain security related information.

U.S. Nuclear Regulatory Commission ND-18-1057 Page 2 of 4 SNC requests NRC staff review and approval of this license amendment request (LAR) no later than February 24, 2019. Approval by this date will allow sufficient time to implement licensing basis changes necessary to support closure of an Inspections, Tests, Analyses, and Acceptance Criteria (ITAAC) item. SNC expects to implement the proposed amendment within thirty days of approval of the LAR.

SNC also expects to submit a Preliminary Amendment Request (PAR) along with this LAR submittal to support more near-term related construction activities. This PAR is expected to request a "no objection" finding from the NRC Staff by mid-October 2018.

In accordance with 10 CFR 50.91, SNC is notifying the State of Georgia by transmitting a copy of this letter and its enclosures to the designated State Official.

Should you have any questions, please contact Ms. Amy Chamberlain at (205) 992-6361.

I declare under penalty of perjury that the foregoing is true and correct. Executed on the 271h of August 2018.

Respectfully submitted, Brian H. Whitley Director, Regulatory Affairs Southern Nuclear Operating Company Enclosures 1) Vogtle Electric Generating Plant (VEGP) Units 3 and 4 - Request for License Amendment Regarding Passive Core Cooling System (PXS) Gutter Drain Line Vents (LAR-18-022)

2) Vogtle Electric Generating Plant (VEGP) Units 3 and 4 - Exemption Request:

Passive Core Cooling System (PXS) Gutter Drain Line Vents (LAR-18-022)

3) Vogtle Electric Generating Plant (VEGP) Units 3 and 4 - Proposed Changes to Licensing Basis Documents (LAR-18-022)

U.S. Nuclear Regulatory Commission ND-18-1057 Page 3 of 4 cc:

Southern Nuclear Operating Company / Georgia Power Company Mr. S. E. Kuczynski (w/o enclosures)

Mr. D. G. Bost (w/o enclosures)

Mr. M. D. Meier (w/o enclosures)

Mr. D. H. Jones (w/o enclosures)

Mr. J. B. Klecha Mr. G. Chick Mr. D. L. McKinney (w/o enclosures)

Mr. T. W. Yelverton (w/o enclosures)

Mr. B. H. Whitley Ms. C. A. Gayheart Mr. C. R. Pierce Ms. A. G. Aughtman Mr. D. L. Fulton Mr. M. J. Yox Mr. E. W. Rasmussen Mr. J. Tupik Mr. W. A. Sparkman Ms. A. C. Chamberlain Ms. A. L. Pugh Ms. P. Reister Document Services RTYPE: VND.LI.L00 File AR.01.02.06 Nuclear Regulatory Commission Mr. W. Jones (w/o enclosures)

Ms. J. Dixon-Herrity Mr. C. Patel Ms. J. M. Heisserer Mr. B. Kemker Mr. G. Khouri Ms. S. Temple Mr. F. Brown Mr. T.E. Chandler Ms. P. Braxton Mr. T. Brimfield Mr. C. J. Even Mr. A. Lerch State of Georgia Mr. R. Dunn

U.S. Nuclear Regulatory Commission ND-18-1057 Page 4 of 4 Oglethorpe Power Corporation Mr. M. W. Price Ms. A. Whaley Municipal Electric Authority of Georgia Mr. J. E. Fuller Mr. S. M. Jackson Dalton Utilities Mr. T. Bundros Westinghouse Electric Company, LLC Mr. L. Oriani (w/o enclosures)

Mr. C. Churchman (w/o enclosures)

Mr. M. Corletti Mr. M. L. Clyde Ms. L. Iller Mr. D. Hawkins Mr. J. Coward Other Mr. S. W. Kline, Bechtel Power Corporation Ms. L. A. Matis, Tetra Tech NUS, Inc.

Dr. W. R. Jacobs, Jr., Ph.D., GDS Associates, Inc.

Mr. S. Roetger, Georgia Public Service Commission Ms. S. W. Kernizan, Georgia Public Service Commission Mr. K. C. Greene, Troutman Sanders Mr. S. Blanton, Balch Bingham Mr. R. Grumbir, APOG NDDocumentinBox@duke-energy.com, Duke Energy Mr. S. Franzone, Florida Power & Light

Southern Nuclear Operating Company ND-18-1057 Enclosure 1 Vogtle Electric Generating Plant (VEGP) Units 3 and 4 Request for License Amendment Regarding Passive Core Cooling System (PXS) Gutter Drain Line Vents LAR-18-022 (This Enclosure consists of 10 pages, including this cover page)

ND-18-1057 Request for License Amendment Regarding Passive Core Cooling System (PXS) Gutter Drain Line Vents (LAR-18-022)

Table of Contents

1.

SUMMARY

DESCRIPTION

2. DETAILED DESCRIPTION and TECHNICAL EVALUATION

3. TECHNICAL EVALUATION (Incorporated into Section 2, above)

4. REGULATORY EVALUATION 4.1. Applicable Regulatory Requirements/Criteria 4.2. Precedent 4.3. Significant Hazards Consideration 4.4. Conclusions

5. ENVIRONMENTAL CONSIDERATIONS

6. REFERENCES Page 2 of 10

ND-18-1057 Request for License Amendment Regarding Passive Core Cooling System (PXS) Gutter Drain Line Vents (LAR-18-022)

Pursuant to 10 CFR 52.98(c) and in accordance with 10 CFR 50.90, Southern Nuclear Operating Company (SNC) hereby requests an amendment to Combined License (COL) Nos.

NPF-91 and NPF-92 for Vogtle Electric Generating Plant (VEGP) Units 3 and 4, respectively.

1.

SUMMARY

DESCRIPTION The proposed changes would revise the COL and licensing basis documents to add vent lines to the piping between the passive core cooling system (PXS) collection boxes and in-containment refueling water storage tank (IRWST) to remove entrained air and improve the drain line flow rates. Updated Final Safety Analysis Report (UFSAR) Figure 6.3-1 Sheet 2 is modified to add the vents to the figure. The proposed change involves the plant-specific Tier 1 information and the corresponding COL Appendix C, Inspections, Tests, Analyses, and Acceptance Criteria (ITAAC) Information to revise Table 2.2.3-2 to add the vent lines to the listed IRWST gutter drain lines. No structure, system, or component (SSC) design function or analysis as described in the UFSAR is adversely affected.

This enclosure requests approval of the license amendment necessary to implement these changes.

2. DETAILED DESCRIPTION and TECHNICAL EVALUATION As described in UFSAR Section 6.3, the passive core cooling system provides emergency core cooling following postulated design basis events. In order to accomplish this primary function, the passive core cooling system is designed to perform the following functions: emergency core decay heat removal, reactor coolant system emergency makeup and boration, safety injection, and containment pH control. The system is designed to operate without the use of active equipment such as pumps and ac power sources. The passive core cooling system depends on reliable passive components and processes such as gravity injection and expansion of compressed gases.

UFSAR Subsection 6.3.2.1.1 describes the process by which emergency core decay heat removal at high temperature and pressure conditions occurs. The passive residual heat removal heat exchanger (PRHR HX) is used to maintain an acceptable, stable reactor coolant system (RCS) condition. It transfers decay heat and sensible heat from the RCS to the IRWST, the containment atmosphere, the containment vessel, and finally to the ultimate heat sink - the atmosphere outside of containment. This does not occur until after the IRWST saturation is reached and steaming to containment initiates.

Once steaming from the IRWST has initiated (due to the IRWST reaching its saturation temperature), containment pressure increases as steam is released. As containment temperature increases, condensation begins to form on the subcooled metal and concrete surfaces inside containment. Condensation on these surfaces transfers energy to the bulk metal and concrete until they come to equilibrium with the containment atmosphere. Most of the condensate formed on the containment vessel wall is collected in a safety-related gutter Page 3 of 10

ND-18-1057 Request for License Amendment Regarding Passive Core Cooling System (PXS) Gutter Drain Line Vents (LAR-18-022) arrangement. A gutter is located near the operating deck elevation, and a downspout piping system is connected at the polar crane girder and internal stiffener, to collect steam condensate inside the containment during PXS operation and return it to the IRWST. This arrangement allows the inventory that is steaming into the containment to be returned to the IRWST to provide continued core cooling.

The PXS is tested prior to operation to confirm that the operation of the system meets the design requirements. A gutter flow capacity test is performed to demonstrate proper return flow to the IRWST from the collection boxes. The gutter isolation valves are closed and flow is directed to the collection boxes at each end of the IRWST, then finally draining from the boxes into the IRWST. (The layout of the IRWST and drain piping from the collection boxes is shown in UFSAR Figure 6.3-1 Sheet 2.) The test demonstrates that sufficient condensate return flows make it to the IRWST.

During testing at another AP1000 site, the PXS downspout and gutter flow capacity test was performed. The condensate returned to the IRWST during the test met the minimum requirements as specified by the safety analysis. However, the test did not achieve the flow rates that were expected based on the design of the system. It was determined that there were increased head losses in the drain piping between the PXS collection boxes to the IRWST due to air in the gutter piping. In order to improve the flow rates, vents were added to the two redundant drain lines to allow air to escape. After the vents were added, the flow testing was re-performed and demonstrated marked improvement in flow to the IRWST. Therefore, it is proposed to add these vents to the Vogtle Units 3 and 4 design in order to improve the condensate return flow rate.

The original design, without the vents, was sufficient to meet the safety analysis requirements for condensate return. The proposed change to add vents does not change the safety analysis, or impact previous conclusions by the US NRC (as documented in Reference 1) that the PXS design is safe and meets the regulatory requirements. The addition of the vents to the gutter piping adds additional margin to the condensate return analysis by improving demonstrated return flow rates while also preventing additional condensate losses. The PXS will continue to perform its functions as specified in UFSAR Section 6.3.

Additional Impact Evaluation The proposed changes do not adversely affect or require any change to the AP1000 probabilistic risk assessment (PRA) presented in UFSAR Chapter 19, including the Fire PRA, results and insights (e.g., core damage frequency and large release frequency). The proposed changes do not result in any changes to the existing failures of the PXS included in the PRA model, and no new postulated failures of the PXS are required in the PRA model. Therefore, there are no changes required to initiating event frequencies and system logic models of the PRA. The existing PRA risk significance investment protection determination for the PXS is not affected.

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ND-18-1057 Request for License Amendment Regarding Passive Core Cooling System (PXS) Gutter Drain Line Vents (LAR-18-022)

The proposed changes do not adversely affect a structure, system or component (SSC),

function or feature used for the prevention or mitigation of accidents or their safety / design analyses. The changes do not affect any SSC accident initiator or initiating sequence of events, or adversely affect any safetyrelated SSC or function used to mitigate an accident.

The proposed changes do not involve a change to a fission product barrier. The changes cannot result in a new failure mode, malfunction or sequence of events that could affect safety.

The changes would not allow for a new fission product release path, result in a new fission product barrier failure mode, or create a new sequence of events that would result in significant fuel cladding failures.

The proposed changes do not adversely affect any safetyrelated equipment, design code limit, safety-related function, safetyrelated design analysis, safety analysis input or result, or design or safety margin. No safety analysis or design basis acceptance limit or criterion would be challenged or exceeded. The proposed changes do not revise any aspects of the plant that could have an adverse effect on safety and security, including the site emergency plan.

There are no fire area changes required because of these proposed changes. The physical design and operation of the system, as described in the UFSAR, is not changed, and thus there are no changes required to the fire protection analysis described in UFSAR Appendix 9A.

There are no radiation zone changes or radiological access control changes required because of these proposed changes. The physical design and operation of the system, as described in the UFSAR, is not changed, and thus there are no changes required to the radiation protection design features described in UFSAR Section 12.3.

The proposed changes do not affect the containment, control, channeling, monitoring, processing or releasing of radioactive and nonradioactive materials. The proposed changes do not adversely affect the containment and control of radioactive and nonradioactive materials inside containment, and do not adversely affect the containment boundary.

The proposed changes do not adversely affect the design functions of any SSC to prevent the unmonitored release of airborne radioactivity to the atmosphere or adjacent plant areas.

Therefore, no effluent release path is affected by these changes. In addition, the types and quantities of expected effluents are not changed by the proposed changes. Therefore, radioactive or nonradioactive material effluents are not affected by these changes.

Licensing Basis Changes:

UFSAR Figure 6.3-1, Sheet 2:

• Add six vent lines to the simplified diagram of the passive core cooling system.

Note that while 1.5 and smaller vent lines are not typically included on simplified UFSAR figures (refer to note on Figure), the vents added by this change are 4 lines and therefore are shown on the Figure.

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ND-18-1057 Request for License Amendment Regarding Passive Core Cooling System (PXS) Gutter Drain Line Vents (LAR-18-022)

COL Appendix C and plant-specific Tier 1 Table 2.2.3-2, IRWST gutter drain line:

• Add ASME Code Section III lines as line numbers: PXS-L183A, PXS-L183B, PXS-L184A, PXS-L184B, PXS-L185A, PXS-L185B.

3. TECHNICAL EVALUATION (Incorporated into Section 2 above)

4. REGULATORY EVALUATION 4.1 Applicable Regulatory Requirements/Criteria 10 CFR 52.98(f) requires NRC approval for any modification to, addition to, or deletion from the terms and conditions of a Combined License (COL). This activity involves a departure from COL Appendix C information and corresponding plant-specific Tier 1 Information; therefore, this activity requires a proposed amendment to the COL.

Accordingly, NRC approval is required prior to making the plant-specific changes in this license amendment request.

10 CFR 52, Appendix D, Section VII.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, or requires a license amendment under paragraphs B.5.b or B.5.c of this section. The proposed change involves a change to COL Appendix C (and plant-specific Tier 1) ITAAC information.

Therefore, NRC Approval is required prior to making the change to Tier 2 information.

10 CFR 50, Appendix A, General Design Criterion (GDC) 34, Residual heat removal requires the plant be designed with a residual heat removal system to transfer fission product decay heat and other residual heat from the reactor core at a rate such that specified acceptable fuel design limits and the design conditions of the reactor coolant pressure boundary are not exceeded. The passive residual heat removal heat exchanger (PRHR HX) is capable of cooling the RCS in accordance with the provisions of SECY-94-084. The changes proposed provide an improved return fraction of condensate returned to the in-containment refueling water storage tank (IRWST) over time that is in addition to the return fraction necessary to ensure adequate PRHR HX performance. The proposed changes improve the condensate return fraction, the requirement for the IRWST and PRHR HX to remove residual heat is not changed, the passive core cooling system (PXS) and components continue to comply with GDC 34.

10 CFR 50, Appendix A, GDC 35, Emergency Core Cooling, requires the PXS be able to provide an abundance of core cooling to transfer heat from the core at a rate so fuel and clad damage will not interfere with continued effective core cooling. The functionality of the components of the PXS providing direct injection to the reactor coolant system (RCS) for emergency core cooling is not affected by the proposed changes. The Page 6 of 10

ND-18-1057 Request for License Amendment Regarding Passive Core Cooling System (PXS) Gutter Drain Line Vents (LAR-18-022) changes described herein provide an improved return fraction of condensate required to the IRWST ensure the PRHR HX can provide adequate core cooling during non-LOCA events, in conjunction with core makeup tank and accumulator operation. Therefore, the PXS continues to satisfy GDC 35.

4.2 Precedent None.

4.3 Significant Hazards Consideration Southern Nuclear Operating Company (SNC) is requesting an amendment to Combined License (COL) Nos. NPF-91 and NPF-92 for Vogtle Electric Generating Plant (VEGP)

Units 3 and 4, respectively. The proposed changes revise the Updated Final Safety Analysis Report (UFSAR) Tier 2 information to add the vents to UFSAR Figure 6.3-1, and involve a change to the corresponding Combined Licenses (COLs) in regard to COL Appendix C, Inspections, Tests, Analyses, and Acceptance Criteria (ITAAC) information to modify the passive core cooling system ITAAC Table 2.2.3-2 to add the vent lines to the piping between the PXS collection boxes and in-containment refueling water storage tank (IRWST) to remove entrained air and improve drain line flow rates.

An evaluation to determine whether or not a significant hazards consideration is involved with the proposed amendment was completed by focusing on the three standards set forth in 10 CFR 50.92(c), Issuance of Amendment, as discussed below.

4.3.1 Does the proposed amendment involve a significant increase in the probability or consequences of an accident previously evaluated?

Response: No.

The proposed changes modify the PXS drain lines to add vent lines to the piping between the PXS collection boxes and IRWST to remove entrained air and improve drain line flow rates, the corresponding ITAAC is modified to reflect this design change. The proposed changes do not have any adverse effects on the design functions of the PXS. The probabilities of accidents evaluated in the UFSAR are not affected.

The changes do not adversely impact the support, design, or operation of mechanical and fluid systems. The changes do not impact the support, design, or operation of any safety-related structures. There is no adverse change to the plant systems or response of the systems to postulated accident conditions.

There is no change to the predicted radioactive releases due to normal operation or postulated accident conditions. The plant response to previously evaluated accidents or external events is not adversely affected, nor do the proposed changes create any new accident precursors.

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ND-18-1057 Request for License Amendment Regarding Passive Core Cooling System (PXS) Gutter Drain Line Vents (LAR-18-022)

Therefore, the proposed amendment does not involve a significant increase in the probability or consequences of an accident previously evaluated.

4.3.2 Does the proposed amendment create the possibility of a new or different kind of accident from any accident previously evaluated?

Response: No.

The proposed changes modify the PXS drain lines to add vent lines to the piping between the PXS collection boxes and IRWST to remove entrained air and improve drain line flow rates, the corresponding ITAAC is modified to reflect this design change. The proposed changes do not have any adverse effects on the design functions of the PXS, the structures or systems in which the PXS is used, or any other systems, structures, and components (SSCs) design functions or methods of operation that result in a new failure mode, malfunction, or sequence of events that affect safety-related or non-safely related equipment. This activity does not allow for a new fission product release path, result in a new fission product barrier mode, or create a new sequence of events that result in a significant fuel cladding failure.

Therefore, the proposed amendment does not create the possibility of a new or different kind of accident from any accident previously evaluated.

4.3.3 Does the proposed amendment involve a significant reduction in a margin of safety?

Response: No.

The proposed changes modify the PXS drain lines to add vent lines to the piping between the PXS collection boxes and IRWST to remove entrained air and improve drain line flow rates, the corresponding ITAAC is modified to reflect this design change. The proposed changes do not have any adverse effects on the design functions of the PXS.

No safety analysis or design basis acceptance limit/criterion is challenged or exceeded by these changes. Therefore, the proposed changes do not involve a significant reduction in the margin of safety.

Based on the above, it is concluded that the proposed amendment does not involve a significant hazards consideration under the standards set forth in 10 CFR 50.92(c), and, accordingly, a finding of no significant hazards consideration is justified.

4.4 Conclusions Based on the considerations discussed above, (1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, (2) such activities will be conducted in compliance with the Commissions Page 8 of 10

ND-18-1057 Request for License Amendment Regarding Passive Core Cooling System (PXS) Gutter Drain Line Vents (LAR-18-022) regulations, and (3) the issuance of amendment will not be inimical to the common defense and security or to the health and safety of the public. Therefore, it is concluded that the requested amendment does not involve a significant hazards consideration under the standards set forth in 10 CFR 50.92(c), and, accordingly, a finding of no significant hazards consideration is justified.

5. ENVIRONMENTAL CONSIDERATIONS This review supports a request to amend the Updated Final Safety Analysis Report (UFSAR) and the involved Combined License (COL) and plant-specific Tier 1 information to allow departure from an element of Inspections, Tests, Analyses, and Acceptance Criteria (ITAAC) certification information. The proposed amendment specifies the information required to modify the licensing requirements for the passive core cooling system.

Sections 2 and 3 of this license amendment request provide the details of the proposed changes.

A review has determined that the proposed changes require an amendment to the COL.

However, a review of the anticipated construction and operational effects of the requested amendment has determined that the requested amendment meets the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9), in that:

(i) There is no significant hazards consideration.

As documented in Section 4.3, Significant Hazards Consideration, of this license amendment request, an evaluation was completed to determine whether or not a significant hazards consideration is involved by focusing on the three standards set forth in 10 CFR 50.92, Issuance of amendment. The Significant Hazards Consideration determined that (1) the proposed amendment does not involve a significant increase in the probability or consequences of an accident previously evaluated; (2) the proposed amendment does not create the possibility of a new or different kind of accident from any accident previously evaluated; and (3) the proposed amendment does not involve a significant reduction in a margin of safety. Therefore, it is concluded that the proposed amendment does not involve a significant hazards consideration under the standards set forth in 10 CFR 50.92(c), and accordingly, a finding of no significant hazards consideration is justified.

(ii) There is no significant change in the types or significant increase in the amounts of any effluents that may be released offsite.

The proposed changes are unrelated to any aspect of plant construction or operation that would introduce any change to effluent types (e.g., effluents containing chemicals or biocides, sanitary system effluents, and other effluents) or affect any plant radiological or non-radiological effluent release quantities. Furthermore, the proposed changed do not Page 9 of 10

ND-18-1057 Request for License Amendment Regarding Passive Core Cooling System (PXS) Gutter Drain Line Vents (LAR-18-022) affect any effluent release path or diminish the functionality of any design or operational features that are credited with controlling release of effluents during plant operation.

Therefore, it is concluded that the proposed amendment does not involve a significant change in the types or a significant increase in the amounts of any effluents that may be released offsite.

(iii) There is no significant increase in individual or cumulative occupational radiation exposure.

The proposed change in the requested amendment to the PXS ITAAC does not affect or alter any walls, floors, or other structures that provide shielding. Plant radiation zones and controls under 10 CFR 20 preclude a significant increase in occupational radiation exposure. Therefore, the proposed amendment does not involve a significant increase in individual or cumulative occupational radiation exposure.

Based on the above review of the proposed amendment, it has been determined that anticipated construction and operational effects of the proposed amendment does not involve (i) a significant hazards consideration, (ii) a significant change in the types or significant increase in the amounts of any effluents that may be released offsite, or (iii) a significant increase in the individual or cumulative occupational radiation exposure. Accordingly, the proposed amendment meets the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9). Therefore, pursuant to 10 CFR 51.22(b), no environmental impact statement or environmental assessment need be prepared in connection with the proposed amendment and proposed exemption.

6. REFERENCES

1. NRC Issuance of Amendment and associated Safety Evaluation Report, ADAMS Accession Nos. ML17024A317 and ML17024A307, Safety Evaluation by the Office of New Reactors Related to Amendment Nos 72 and 71 to the Combined License Nos NPF-91 and NPF-92, Respectively, February 2017.

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Southern Nuclear Operating Company ND-18-1057 Enclosure 2 Vogtle Electric Generating Plant Units 3 and 4 Exemption Request:

Passive Core Cooling System (PXS) Gutter Drain Line Vents (LAR-18-022)

(This Enclosure consists of 8 pages, including this cover page)

ND-18-1057 Exemption Request: Passive Core Cooling System (PXS) Gutter Drain Line Vents (LAR-18-022) 1.0 Purpose Southern Nuclear Operating Company (the Licensee) requests a permanent exemption from the provisions of 10 CFR 52, Appendix D, Section III.B, Design Certification Rule for the AP1000 Design, Scope and Contents, to allow a departure from elements of the certification information in Tier 1 of the generic AP1000 Design Control Document (DCD). The regulation, 10 CFR 52, Appendix D, Section III.B, requires an applicant or licensee referencing Appendix D to 10 CFR Part 52 to incorporate by reference and comply with the requirements of Appendix D, including certified information in DCD Tier 1. The Tier 1 information for which a plant-specific departure and exemption is being requested includes changes to reflect revisions to the piping between the passive core cooling system (PXS) collection boxes and the in-containment refueling water storage tank (IRWST) to add vents to remove entrained air and improve drain line flow rates.

This request for exemption provides the technical and regulatory basis to demonstrate that 10 CFR 52.63, §52.7, and §50.12 requirements are met and will apply the requirements of 10 CFR 52, Appendix D, Section VIII.A.4 to allow departures from generic Tier 1 information due to proposed clarifications to Inspections, Tests, Analyses, and Acceptance Criteria (ITAAC) related Table 2.2.3-2 to reflect the added piping.

2.0 Background The Licensee is the holder of Combined License (COL) Nos. NPF-91 and NPF-92, which authorize construction and operation of two Westinghouse Electric Company AP1000 nuclear plants, named Vogtle Electric Generating Plant (VEGP) Units 3 and 4, respectively.

As described in Updated Final Safety Analysis Report (UFSAR) Section 6.3, the PXS provides emergency core cooling following postulated design basis events. In order to accomplish this primary function, the passive core cooling system is designed to perform the following functions: emergency core decay heat removal, reactor coolant system emergency makeup and boration, safety injection, and containment pH control. The system is designed to operate without the use of active equipment such as pumps and ac power sources. The passive core cooling system depends on reliable passive components and processes such as gravity injection and expansion of compressed gases.

UFSAR Subsection 6.3.2.1.1 describes the process by which emergency core decay heat removal at high temperature and pressure conditions occurs. The passive residual heat removal heat exchanger (PRHR HX) is used to maintain an acceptable, stable reactor coolant system (RCS) condition. It transfers decay heat and sensible heat from the RCS to the IRWST, the containment atmosphere, the containment vessel, and finally Page 2 of 8

ND-18-1057 Exemption Request: Passive Core Cooling System (PXS) Gutter Drain Line Vents (LAR-18-022) to the ultimate heat sink - the atmosphere outside of containment. This does not occur until after the IRWST saturation is reached and steaming to containment initiates.

Once steaming from the IRWST has initiated (due to the IRWST reaching its saturation temperature), containment pressure increases as steam is released. As containment temperature increases, condensation begins to form on the subcooled metal and concrete surfaces inside containment. Condensation on these surfaces transfers energy to the bulk metal and concrete until they come to equilibrium with the containment atmosphere. Most of the condensate formed on the containment vessel wall is collected in a safety-related gutter arrangement. A gutter is located near the operating deck elevation, and a downspout piping system is connected at the polar crane girder and internal stiffener, to collect steam condensate inside the containment during PXS operation and return it to the IRWST. This arrangement allows the inventory that is steaming into the containment to be returned to the IRWST to provide continued core cooling.

The PXS is tested prior to operation to confirm that the operation of the system meets the design requirements. The gutter flow capacity test is performed to demonstrate proper return flow to the IRWST from the collection boxes. The gutter isolation valves are closed and flow is directed to the collection boxes at each end of the IRWST, then finally draining from the boxes into the IRWST. (The layout of the IRWST and drain piping from the collection boxes is shown in UFSAR Figure 6.3-1 Sheet 2.) The test demonstrates that sufficient condensate return flows make it to the IRWST.

The proposed change is to add the new ASME Code Section III vent lines to the listing of IRWST gutter drain lines in plant-specific Tier 1 Table 2.2.3-2.

Plant-specific Tier 1 Table 2.2.3-4 specifies the ITAAC related to the PXS. The inspections and acceptance criteria of plant-specific Tier 1 Table 2.2.3-4, Item 2.a, verify that design reports exist for the ASME Code Section III piping within the PXS as listed in Table 2.2.3-2.

3.0 Technical Justification of Acceptability During testing at another AP1000 site, the PXS downspout and gutter flow capacity test was performed. The condensate returned to the IRWST during the test met the minimum requirements as specified by the safety analysis. However, the test did not achieve the flow rates that were expected based on the design of the system. It was determined that there were increased head losses in the drain piping between the PXS collection boxes to the IRWST. In order to improve the flow rates, vents were added to the two redundant drain lines to allow air to escape. After the vents were added, the flow testing was re-performed and demonstrated marked improvement in flow to the IRWST due to air in the gutter piping. Therefore, it is proposed to add these vents to the Vogtle Units 3 and 4 design in order to improve the condensate return flow rate.

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ND-18-1057 Exemption Request: Passive Core Cooling System (PXS) Gutter Drain Line Vents (LAR-18-022)

The original design, without the vents, was sufficient to meet the safety analysis requirements for condensate return. The proposed change to add vents does not change the safety analysis, or impact previous conclusions by the US NRC (as documented in Reference 1) that the PXS design is safe and meets the regulatory requirements. The addition of the vents to the gutter piping adds additional margin to the condensate return analysis by improving demonstrated return flow rates while also preventing additional condensate losses. The PXS will continue to perform its functions as specified in UFSAR Section 6.3.

Additional details and technical justification supporting this request for exemption is provided in Sections 2 and 3 of the associated License Amendment Request in Enclosure 1 of this letter.

4.0 Justification of Exemption 10 CFR Part 52, Appendix D, Section VIII.A.4 and 10 CFR 52.63(b)(1) govern the issuance of exemptions from elements of the certified design information for AP1000 nuclear power plants. Since SNC has identified changes to the Tier 1 information as discussed in Enclosure 1 of the accompanying License Amendment Request, an exemption from the certified design information in Tier 1 is needed.

10 CFR Part 52, Appendix D, and 10 CFR 50.12, §52.7, and §52.63 state that the NRC may grant exemptions from the requirements of the regulations provided six conditions are met: 1) the exemption is authorized by law [§50.12(a)(1)]; 2) the exemption will not present an undue risk to the health and safety of the public [§50.12(a)(1)]; 3) the exemption is consistent with the common defense and security [§50.12(a)(1)]; 4) special circumstances are present [§50.12(a)(2)]; 5) the special circumstances outweigh any decrease in safety that may result from the reduction in standardization caused by the exemption [§52.63(b)(1)]; and 6) the design change will not result in a significant decrease in the level of safety [Part 52, App. D, VIII.A.4].

The requested exemption satisfies the criteria for granting specific exemptions, as described below.

1. This exemption is authorized by law The NRC has authority under 10 CFR 52.63, §52.7, and §50.12 to grant exemptions from the requirements of NRC regulations. Specifically, 10 CFR 50.12 and §52.7 state that the NRC may grant exemptions from the requirements of 10 CFR Part 52 upon a proper showing. No law exists that would preclude the changes covered by this exemption request. Additionally, granting of the proposed exemption does not result in a violation of the Atomic Energy Act of 1954, as amended, or the Commissions regulations.

Accordingly, this requested exemption is authorized by law, as required by 10 CFR 50.12(a)(1).

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ND-18-1057 Exemption Request: Passive Core Cooling System (PXS) Gutter Drain Line Vents (LAR-18-022)

2. This exemption will not present an undue risk to the health and safety of the public The proposed exemption from the requirements of 10 CFR 52, Appendix D, Section III.B would allow changes to elements of the plant-specific Tier 1 DCD to depart from the AP1000 certified (Tier 1) design information. The plant-specific DCD Tier 1 will continue to reflect the approved licensing basis for VEGP Units 3 and 4, and will maintain a consistent level of detail with that which is currently provided elsewhere in Tier 1 of the DCD. Therefore, the affected plant-specific DCD Tier 1 ITAAC will continue to serve its required purpose.

The added vents are included to remove entrained air and improve the drain flow and as such do not represent any adverse impact to the design function of the PXS which will continue to protect the health and safety of the public in the same manner. The added vents are ASME Code Section III lines which do not introduce any new industrial, chemical, or radiological hazards that would represent a public health or safety risk, nor do they modify or remove any design, operational controls or safeguards intended to mitigate any existing on-site hazards. Furthermore, the proposed change would not allow for a new fission product release path, result in a new fission product barrier failure mode, or create a new sequence of events that would result in fuel cladding failures.

Accordingly, this change does not present an undue risk from any existing or proposed equipment or systems.

Therefore, the requested exemption from 10 CFR 52, Appendix D, Section III.B would not present an undue risk to the health and safety of the public.

3. The exemption is consistent with the common defense and security The requested exemption from the requirements of 10 CFR 52, Appendix D, Section III.B would allow the licensee to depart from elements of the plant specific DCD Tier 1 design information. The proposed exemption does not adversely alter the design, function, or operation of any structures or plant equipment that is necessary to maintain a safe and secure status of the plant. The proposed exemption has no impact on plant security or safeguards procedures.

Therefore, the requested exemption is consistent with the common defense and security.

4. Special circumstances are present 10 CFR 50.12(a)(2) lists six special circumstances for which an exemption may be granted. Pursuant to the regulation, it is necessary for one of these special circumstances to be present in order for the NRC to consider granting an exemption request. The requested exemption meets the special circumstances of 10 CFR 50.12(a)(2)(ii). That subsection defines special circumstances as when Application of the regulation in the particular circumstances would not serve the Page 5 of 8

ND-18-1057 Exemption Request: Passive Core Cooling System (PXS) Gutter Drain Line Vents (LAR-18-022) underlying purpose of the rule or is not necessary to achieve the underlying purpose of the rule.

The rule under consideration in this request for exemption is 10 CFR 52, Appendix D, Section III.B, which requires that a licensee referencing the AP1000 Design Certification Rule (10 CFR Part 52, Appendix D) shall incorporate by reference and comply with the requirements of Appendix D, including Tier 1 information. The VEGP Units 3 and 4 COLs reference the AP1000 Design Certification Rule and incorporate by reference the requirements of 10 CFR Part 52, Appendix D, including Tier 1 information. The underlying purpose of Appendix D,Section III.B is to describe and define the scope and contents of the AP1000 design certification, and to require compliance with the design certification information in Appendix D.

The proposed change is to add new ASME Code Section III vent lines to the IRWST gutter drain lines identified in plant-specific Tier 1 Table 2.2.3-2.

The added vents are included to remove entrained air and improve the drain flow from the gutters to the IRWST. The proposed changes do not adversely affect any function or feature used for the prevention and mitigation of accidents or their safety analyses. The proposed changes do not involve nor interface with any SSC accident initiator or initiating sequence of events related to the accidents evaluated and therefore do not have an adverse effect on any SSCs design function. Accordingly, this exemption from the certification information will enable the Licensee to safely construct and operate the AP1000 facility consistent with the design certified by the NRC in 10 CFR 52, Appendix D.

Therefore, special circumstances are present, because application of the current generic certified design information in Tier 1 as required by 10 CFR Part 52, Appendix D, Section III.B, in the particular circumstances discussed in this request is not necessary to achieve the underlying purpose of the rule.

5. The special circumstances outweigh any decrease in safety that may result from the reduction in standardization caused by the exemption.

Based on the nature of the changes to the plant-specific Tier 1 information and the understanding that these changes have been determined to not adversely impact the design function of the SSCs within the rooms, it is expected that this exemption may be requested by other AP1000 licensees and applicants. However, a review of the reduction in standardization resulting from the departure from the standard DCD determined that even if other AP1000 licensees and applicants do not request this same departure, the special circumstances will continue to outweigh any decrease in safety from the reduction in standardization because the key design functions of the structures associated with this request will continue to be maintained. Furthermore, the justification provided in the license amendment request and this exemption request and the associated mark-ups demonstrate that there is a limited change from the standard Page 6 of 8

ND-18-1057 Exemption Request: Passive Core Cooling System (PXS) Gutter Drain Line Vents (LAR-18-022) information provided in the generic AP1000 DCD, which is offset by the special circumstances identified above.

Therefore, the special circumstances associated with the requested exemption outweigh any decrease in safety that may result from the reduction in standardization caused by the exemption.

6. The design change will not result in a significant decrease in the level of safety.

The exemption revises the plant-specific DCD Tier 1 information by including vent lines to improve the drain flow to the IRWST as discussed in Section 2.0. The improved drain flow meets the analyzed flow for return to the IRWST, and thus does not impact the design requirements of the PXS and IRWST. Because the SSC functions continue to be met, there is no reduction in the level of safety.

5.0 Risk Assessment A risk assessment was not determined to be applicable to address the acceptability of this proposal.

6.0 Precedent Exemptions None.

7.0 Environmental Consideration The Licensee requests a departure from elements of the certified information in Tier 1 of the generic AP1000 DCD. The Licensee has determined that the proposed departure would require a permanent exemption from the requirements of 10 CFR 52, Appendix D, Section III.B, Design Certification Rule for the AP1000 Design, Scope and Contents, with respect to installation or use of facility components located within the restricted area, as defined in 10 CFR Part 20, or which changes an inspection or a surveillance requirement; however, the Licensee evaluation of the proposed exemption has determined that the proposed exemption meets the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9).

Based on the above review of the proposed exemption, the Licensee has determined that the proposed activity does not involve (i) a significant hazards consideration, (ii) a significant change in the types or significant increase in the amounts of any effluents that may be released offsite, or (iii) a significant increase in the individual or cumulative occupational radiation exposure. Accordingly, the proposed exemption meets the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9). Therefore, pursuant to 10 CFR 51.22(b), an environmental impact statement or environmental assessment of the proposed exemption is not required.

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ND-18-1057 Exemption Request: Passive Core Cooling System (PXS) Gutter Drain Line Vents (LAR-18-022)

Specific details of the environmental considerations supporting this request for exemption are provided in Section 5 of the associated License Amendment Request provided in Enclosure 1 of this letter.

8.0 Conclusion The proposed changes to Tier 1 are necessary to add vent lines to the ASME Code Section III lines in the PXS to remove entrained air and improve the drain line flow rates.

The exemption request meets the requirements of 10 CFR 52.63, Finality of design certifications, 10 CFR 52.7, Specific exemptions, 10 CFR 50.12, Specific exemptions, and 10 CFR 52 Appendix D, Design Certification Rule for the AP1000. Specifically, the exemption request meets the criteria of 10 CFR 50.12(a)(1) in that the request is authorized by law, presents no undue risk to public health and safety, and is consistent with the common defense and security. Furthermore, approval of this request does not result in a significant decrease in the level of safety, satisfies the underlying purpose of the AP1000 Design Certification Rule, and does not present a significant decrease in safety as a result of a reduction in standardization.

9.0 References

1. NRC Issuance of Amendment and associated Safety Evaluation Report, ADAMS Accession Nos. ML17024A317 and ML17024A307, Safety Evaluation by the Office of New Reactors Related to Amendment Nos 72 and 71 to the Combined License Nos NPF-91 and NPF-92, Respectively, February 2017.

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Southern Nuclear Operating Company ND-18-1057 Enclosure 3 Vogtle Electric Generating Plant Units 3 and 4 Proposed Changes to Licensing Basis Documents (LAR-18-022)

Insertions Denoted by Blue Underline and Deletions by Red Strikethrough Omitted text is identified by three asterisks ( * * * )

(This Enclosure consists of 3 pages, including this cover page)

ND-18-1057 Proposed Changes to Licensing Basis Documents - (LAR-18-022)

Revise COL Appendix C Table 2.2.3-2, and corresponding plant-specific Tier 1 Table 2.2.3-2, as shown below.

Table 2.2.3-2 ASME Leak Functional Code Before Capability Line Name Line Number Section III Break Required PXS-L142A, PXS-L142B, PXS-L183A, PXS-L183B, PXS-L184A, PXS-L184B, Yes No Yes IRWST gutter drain line PXS-L185A, PXS-L185B PXS-L141A, PXS-L141B Yes No No Page 2 of 3

ND-18-1057 Proposed Changes to Licensing Basis Documents - (LAR-18-022)

Revise UFSAR Figure 6.3-1, Sheet 2 of 3, Simplified Passive Core Cooling System Piping and Instrumentation Diagram (REF) PXS 002, as shown below.

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