NL-25-0317, Emergency License Amendment Request: One-Time Change to Technical Specification 3.5.2, Core Makeup Tanks (Cmts) - Operating

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Emergency License Amendment Request: One-Time Change to Technical Specification 3.5.2, Core Makeup Tanks (Cmts) - Operating
ML25223A334
Person / Time
Site: Vogtle 
Issue date: 08/11/2025
From: Coleman J
Southern Nuclear Operating Co
To:
Office of Nuclear Reactor Regulation, Document Control Desk
References
NL-25-0317
Download: ML25223A334 (1)
v • d • e


Text

Regulatory Affairs 3535 Colonnade Parkway Birmingham, AL 35243 205 992 5000 August 11, 2025 NL-25-0317 10 CFR 50.90 10 CFR 50.91(a)(5)

Docket No.52-026 ATTN: Document Control Desk U. S. Nuclear Regulatory Commission Washington, D. C. 20555-0001 Southern Nuclear Operating Company Vogtle Electric Generating Plant - Unit 4 Emergency License Amendment Request: One-Time Change to Technical Specification 3.5.2, Core Makeup Tanks (CMTs) - Operating Pursuant to the provisions of 10 CFR 50.90 and 10 CFR 50.91(a)(5), Southern Nuclear Operating Company (SNC) hereby requests an emergency license amendment to the Technical Specifications (TS) for Vogtle Electric Generating Plant (VEGP) Unit 4 facility operating license NPF-92. The requested amendment would temporarily revise the operating license, Appendix A, TS 3.5.2, Core Makeup Tanks (CMTs) - Operating to reduce the minimum allowable CMT A boron concentration and to not require performance of SR 3.5.2.4 until startup from the first VEGP Unit 4 refueling outage. The requested amendment would be effective until startup from the first VEGP Unit 4 refueling outage.

SNC requests approval of the proposed license amendment in accordance with the provisions of 10 CFR 50.91(a)(5). A discussion of the emergency situation is provided in the enclosure to this letter.

The enclosure to this letter provides the description, technical evaluation, regulatory evaluation (including the Significant Hazards Consideration Determination) and environmental considerations for the proposed changes.

Attachments 1 and 2 to the Enclosure provide the marked-up TS pages and clean revised TS pages, respectively, depicting the requested changes.

Approval of the proposed amendment is requested by August 16, 2025, to avoid potentially shutting down VEGP Unit 4. This request is for a one-time temporary change. If approved, this license amendment will be effective as of the date of its issuance and will be implemented upon issuance.

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

U. S. Nuclear Regulatory Commission NL-25-0317 Page 2 In accordance with 10 CFR 50.91, SNC is notifying the State of Georgia of this license amendment request by transmitting a copy of this letter, enclosure, and attachments to the designated State Official.

If you have any questions, please contact Ryan Joyce at 205-992-6468.

I declare under penalty of perjury that the foregoing is true and correct.

Executed on the 11th day of August 2025.

Respectfully submitted, Jamie M. Coleman Director, Regulatory Affairs Southern Nuclear Operating Company

Enclosure:

Evaluation of the Proposed Change cc:

NRC Regional Administrator, Region ll NRR Project Manager - Vogtle 3 & 4 Senior Resident Inspector - Vogtle 3 & 4 Director, Environmental Protection Division - State of Georgia RType: VND.LI.L00 Digitally signed by JAMIEMCO Date: 2025.08.11 20:23:20

-05'00'

ENCLOSURE to NL-25-0317 Evaluation of the Proposed Change

Subject:

Emergency License Amendment Request: One-Time Change to Technical Specification 3.5.2, Core Makeup Tanks (CMTs) - Operating

1.

SUMMARY

DESCRIPTION

2. DETAILED DESCRIPTION 2.1 System Design and Operation 2.2 Current Technical Specifications Requirements 2.3 Description of the Proposed Change 2.4 Reason for the Proposed Change 2.5 Basis for Emergency Processing
3. TECHNICAL EVALUATION 3.1 Deterministic Evaluation 3.2 Implementation and Compensatory Measures
4. REGULATORY EVALUATION 4.1 Applicable Regulatory Requirements/Criteria 4.2 Precedent 4.3 No Significant Hazards Consideration Determination 4.4 Conclusions
5. ENVIRONMENTAL CONSIDERATION
6. REFERENCES ATTACHMENTS:
1. Proposed Technical Specification Changes (Mark-ups)
2. Clean Revised Technical Specification Pages

Enclosure to NL-25-0317 Evaluation of the Proposed Change E-2

1.

SUMMARY

DESCRIPTION Pursuant to the provisions of 10 CFR 50.90 and 10 CFR 50.91(a)(5), Southern Nuclear Operating Company (SNC) hereby requests an emergency license amendment to the Technical Specifications (TS) for Vogtle Electric Generating Plant (VEGP), Unit 4. The requested amendment would temporarily revise the combined license, Appendix A, TS 3.5.2, Core Makeup Tanks (CMTs) - Operating to add a Note to the Limiting Condition for Operation (LCO) to reduce the minimum allowable CMT A boron concentration and to add a Note to Surveillance Requirement (SR) 3.5.2.4 to defer performance of SR 3.5.2.4 until entry into TS 3.5.3 Applicability during startup from the first VEGP Unit 4 refueling outage (4R01).

2.

DETAILED DESCRIPTION 2.1 System Design and Operation As described in UFSAR Section 6.3, the Passive Core Cooling System (PXS) performs the primary function to provide emergency core cooling following postulated design basis events.

PXS is a seismic Category I, safety-related system and consists of two CMTs, two accumulators, the in-containment refueling water storage tank (IRWST), the passive residual heat removal heat exchanger, pH adjustment baskets, and associated piping, valves, instrumentation, and other related equipment. The automatic depressurization system valves and spargers, which are part of the reactor coolant system (RCS), also provide important passive core cooling functions. The two redundant CMTs provide sufficient borated water to assure Reactor Coolant System (RCS) reactivity and inventory control for all design basis accidents (DBAs), including both loss of coolant accident (LOCA) events and non-LOCA events.

The CMTs are cylindrical tanks with hemispherical upper and lower heads. They are made of carbon steel and clad on the internal surfaces with stainless steel. They are located in containment at an elevation slightly above the reactor coolant loops. Each tank is full of borated water. During normal operation, the CMTs are maintained at RCS pressure through a normally open pressure balance line from the cold leg.

The outlet line from each CMT is connected to one of two direct vessel injection lines, which provides an injection path for the water supplied by the CMT. The outlet line from each CMT is isolated by parallel, normally closed, fail open valves. Upon receipt of a safeguards actuation signal, these four valves open to align the CMTs to the RCS.

The CMTs will inject to the RCS as inventory is lost and steam or reactor coolant is supplied to the CMT to displace the water that is injected. Steam or reactor coolant is provided to the CMT through the cold leg balance line, depending upon the specific event that has occurred. The inlet line from the cold leg is sized for LOCA events, where the cold legs become voided and higher CMT injection flows are required.

The CMT size and injection capability are selected to provide adequate RCS boration and safety injection for the limiting DBA. One CMT is adequate for this function during a small break LOCA where one CMT completely spills via the pipe break. The CMTs also provide reactor coolant system makeup and boration during events not involving loss of coolant when the normal makeup system is unavailable or insufficient. The boration capability of these tanks provides adequate core shutdown margin following a steam line break.

The pressure balance line from the cold leg is normally open to maintain the CMTs at RCS pressure, which prevents water hammer upon initiation of CMT injection.

Enclosure to NL-25-0317 Evaluation of the Proposed Change E-3 The cold leg pressure balance line is connected to the top of the cold leg and is routed continuously upward to the high point near the CMT inlet. The normal water temperature in this line will be hotter than the discharge line.

During water recirculation, hot water from the cold leg enters the CMTs, and the cold water in the tank is discharged to the reactor coolant system. This results in reactor coolant system boration and a net increase in reactor coolant system mass.

The operating process for the CMTs depends on conditions in the reactor coolant system, primarily voiding in the cold leg. When the cold leg is full of water, the cold leg pressure balance line remains full of water and the injection occurs via water recirculation. If reactor coolant system inventory decreases sufficiently to cause cold leg voiding, then steam flows through the cold leg balance lines to the CMTs.

Following an event such as steam-line break, the reactor coolant system experiences a decrease in temperature and pressure due to an increase of energy removed by the secondary system as a consequence of the break. The cooldown results in a reduction of the core shutdown margin due to the negative moderator temperature coefficient. There is a potential return to power, assuming the most reactive rod cluster control assembly is stuck in its fully withdrawn position. The actuation of the CMTs following this event provides injection of borated water via water recirculation to mitigate the reactivity transient and provide the required shutdown margin.

In case of a steam generator tube rupture, CMT injection together with the steam generator overfill prevention logic terminates the reactor coolant system leak into the steam generator.

This occurs without actuation of the automatic depressurization system and without operator action. In a steam generator tube rupture, the CMTs operate in the water recirculation mode to provide borated water to compensate for reactor coolant system inventory losses and to borate the reactor coolant system. In case of a leak rate of 10 gallons per minute, the passive core cooling system can delay the automatic depressurization system actuation for at least 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> while providing makeup water to the reactor coolant system. After the actuation of the automatic depressurization system, the passive core cooling system provides sufficient borated water to compensate for reactor coolant system shrinkage and to provide the reactor coolant system boration.

Each Unit 4 CMT is provided with two sample lines, one in the upper head and the other in the lower head. Samples from the CMTs are taken periodically in accordance with TS 3.5.2 Surveillance requirements to check boron concentration of the solution in the CMT. Prior to the collection of liquid samples either in the laboratory or in the grab sampling unit, the lines are purged with source liquid to provide representative samples. The purging flow returns to the effluent holdup tank of the liquid radwaste system. Because the CMT is in open communication with the RCS via the balance line, whenever the surveillance is performed, the volume removed is replaced by water via the balance line. The RCS water is typically at a lower boron concentration; therefore, each sample dilutes the CMT.

A fill connection is provided for CMT make up water from the chemical and volume control system. Connections are provided for remotely adjusting the boron concentration of the borated water in each CMT during normal plant operation, as required. Makeup water for the CMT is provided by the Chemical and Volume Control System (CVS).

2.2 Current Technical Specifications Requirements TS LCO 3.5.2 requires both CMTs to be operable when in Modes 1, 2 and 3 and Mode 4 with the Reactor Coolant System (RCS) not being cooled by the Normal Residual Heat Removal

Enclosure to NL-25-0317 Evaluation of the Proposed Change E-4 System (RNS). If one CMT is inoperable due to water temperature or boron concentration not within limits, the plant is allowed to continue operation for up to 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. If the water temperature and boron concentration are not restored to within limits within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, the plant must be in Mode 3 within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and Mode 5 within 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />. TS SR 3.5.2.4 requires verifying that the boron concentration in each CMT is 3400 ppm and 4500 ppm at a frequency of every 31 days.

2.3 Description of the Proposed Change The TS 3.5.2 Limiting Condition for Operation (LCO) is revised to include a Note stating:

For Unit 4 until entry into TS 3.5.3 Applicability during shutdown for 4R01, CMT A may be considered OPERABLE with boron concentration < 3400 ppm provided:

a.

CMT A boron concentration 3100 ppm and

b.

Average of CMT A and CMT B boron concentration is 3400 ppm.

The TS SR 3.5.2.4 to verify the boron concentration in each CMT is 3400 ppm and 4500 ppm is revised to include a Note stating:

Not required to be performed for Unit 4 until entry into TS 3.5.3 Applicability during startup from 4R01.

Markups showing the TS change are provided in Attachment 1.

2.4 Reason for the Proposed Change Due to the arrangement of the CMTs (see UFSAR Figure 6.3-1 Sheet 1), when borated water leaves a CMT, inventory is drawn from the RCS cold leg into the CMT through the balance line.

This is referred to as in-leakage from the RCS to the CMT and occurs as a result of sampling the CMT. CMT in-leakage can also occur as result CMT outlet valve leak-by. Because the RCS is typically at a lower boron concentration, the in-leakage reduces the boron concentration in the CMT. In addition to in-leakage, the large concentration gradient between the RCS and the borated water in the CMT results in some diffusion from the CMT through the normally open balance line and reduces the boron concentration in the CMT.

The Vogtle Unit 4 CMT A has been experiencing CMT in-leakage both from sampling activities and due to leak-by of the CMT discharge isolation valves (PXS-V014A/V015A). Work orders to correct the CMT A outlet valves leak-by are planned for the 4R01 outage scope.

Vogtle Unit 4 is at the end of cycle with approximately one month remaining before entering a refueling outage. At this time in the cycle the RCS boron concentration is at its lowest concentration. This creates a large concentration gradient between the RCS and the CMTs which are connected to the RCS. This dynamic has created challenges in maintaining CMT boron concentration. Based on the end of cycle and identified valve leakage, the site implemented a strategy of more frequent CMT borations to maintain the TS boron concentration through the remainder of the cycle. Based on sample trending, the boration frequency was raised in June 2025.

Revising the CMT A lower boron concentration limit and adding a provision for a CMT A and CMT B combined average provides flexibility for maintaining CMT A operable while continuing to provide the assumed accident analysis boration. Without this change, CMT A boron concentration is estimated to decrease below the current 3400 ppm required limit on August 17, 2025.

Enclosure to NL-25-0317 Evaluation of the Proposed Change E-5 While CMT A will not require another SR 3.5.2.4 periodic sample until after 4R01, CMT B sampling will be required to be performed prior to the upcoming Unit 4 refueling outage (4R01) and will inherently result in lowering its boron concentration. Deferring further SR 3.5.2.4 sampling will eliminate one cause for decreased CMT boron concentration.

There is no indication of similar leakage past the Unit 4 CMT B outlet valves, and the most recent boron concentration sample from CMT B identified boron concentration to be greater than 4000 ppm. Therefore, this leakage is indicative of a stand-alone condition with no indication of common cause failure.

2.5 Basis for Emergency Processing In 10 CFR 50.91(a)(5), the NRC refers to emergency situations as those in which failure to act in a timely way would result in derating or shutdown of a nuclear power plant, or in prevention of either resumption of operation or of increase in power output up to the plants licensed power level. Under such a situation, the Commission may issue a license amendment involving no significant hazards consideration without prior notice and opportunity for a hearing or public comment.

It is estimated that CMT A boron concentration will decrease to below the current 3400 ppm lower limit on August 17, 2025. Without approval of this proposed change, a shutdown of Unit 4 would be required until such time that the CMT boron concentration is restored to within limits or Mode 4 (Safe Shutdown) with RCS being cooled by RNS is reached. Failure to meet the boron concentration limit would place the unit in a 72-hour Action Statement, which would not allow sufficient time for processing a licensing request.

Repair of the Unit 4 CMT A outlet valves are planned for the upcoming Unit 4 refueling outage.

Repair of the outlet valves cannot be completed online and must be completed during an outage. Repair of the valves was not previously completed during a planned maintenance outage because the valves had been planned for repair during the refueling outage and the site had a strategy based on plant conditions at that point in time for maintaining CMT A boron levels in TS limits. Supporting the approach was operating experience from Unit 3 end of cycle during which similar outlet valve leakage was observed and the CMT boron concentration was able to be maintained within the TS limits.

Based on the challenges with being at the end of cycle and valve leak-by conditions, the site could not reasonably foresee challenges to maintaining TS limits and steady-state operation over the final few weeks of the Unit 4 cycle.

The 31-day surveillance of the CMT B boron concentration is required by SR 3.5.2.4 to be performed by August 25, 2025. Taking into account the 25% surveillance interval grace period allowed by SR 3.0.2, this surveillance must be completed no later than September 2, 2025.

In conclusion, the proposed changes meet the criteria for an emergency situation to avoid an unnecessary shutdown of Unit 4 prior to the upcoming refueling outage.

3. TECHNICAL EVALUATION 3.1 Deterministic Evaluation Evaluation of Minimum Allowable Boron Concentration An engineering evaluation was performed to confirm that CMT A meets its defined safety functions and will continue to satisfy these safety functions throughout the duration of the

Enclosure to NL-25-0317 Evaluation of the Proposed Change E-6 operating cycle. Given the observed leakage resulting in a gradual, but constant, dilution of CMT A, a deterministic approach was followed to evaluate the boron concentration for the remainder of the operating cycle to support reasonable assurance that safety functions are maintained. The evaluation also established the appropriate compensatory measures to support maintaining reasonable assurance of CMT A operability while the requested license amendment is in effect.

Utilizing the most recent boron concentration sample result of 3479 ppm taken on August 9, 2025 and the current calculated leakage rate of 46.9 gallons per day (gpd), the boron concentration in CMT A will remain greater than 3400 ppm for a period of 8.8 days, from the time of the sample. Furthermore, also assuming the current calculated leakage rate of 46.9 gpd, the CMT A boron concentration will remain above the requested limit of 3100 ppm through the end of this operating cycle.

If the CMT A leakage increases to 66 gpd, the final concentration at the end of 6 days will be 3403 ppm and at 28 days will be 3138.5 ppm using infinite dilution equation. Using the Volume of Bleed and Feed to Change Concentration, the CMT A will be 3403 ppm in 6 days and 3140.5 ppm in 28 days.

RCS monitoring is ongoing to confirm the concentration in CMT A remains above TS limit of 3100 ppm until entry into 4R01.

This analysis of known leakage from CMT A bounds any leakage from CMT B with a boron concentration of greater than 3700 ppm (i.e., the CMT B contribution to the 3400 ppm combined average concentration limit, assuming the CMT A concentration is 3100 ppm). CMT B does not show indications of RCS in-leakage via outlet valve leak-by. The boron concentration of the last sample on July 25, 2025, was 4052 ppm. Currently, the only dilution mechanisms in CMT B are via taking samples and diffusion due to the concentration gradient between the CMT and the RCS. To support an average of 3400 ppm, assuming CMT A is at the proposed minimum limit of 3100 ppm, CMT B must remain greater than 3700 ppm. If CMT B started to leak it would also cause an increase in boron in the RCS and would be detected in the RCS samples being taken to monitor CMT A leakage. Therefore, there is reasonable assurance that CMT B will remain greater than 3700 ppm until the LCO 3.5.2 applicability is exited in 4R01 and this value is bounding. Historical trends show the maximum dilution to be less than 200 ppm.

Based on the above, there is adequate assurance that CMT A remains above minimum boron concentration of 3100 ppm until Mode 5 is reached during entry into 4R01 after September 7, 2025 and that CMT A and CMT B meets all design safety functions to maintain shutdown margin.

Design Basis Event Evaluation The following non-LOCA events credit boration from CMT actuation:

Steamline and Feedline Break (SLB/FLB) Mass and Energy (M&E) Release Hot Zero Power Steamline Break (HZP SLB): Core Response Increase in Reactor Coolant Inventory (Inadvertent CMT Actuation and Chemical and Volume Control (CVS) Malfunction)

Loss of Normal Feedwater (LONF), Loss of ac Power (LOAC), and FLB (non-M&E)

Safe Shutdown Duration (SSD) and Safe Shutdown Temperature (SST) non-Design Basis Accident (DBA) events Anticipated Transient Without SCRAM (ATWS) non-DBA events

Enclosure to NL-25-0317 Evaluation of the Proposed Change E-7 Some non-LOCA events, including SLB M&E, HZP SLB, and increase in reactor coolant inventory, credit CMT injection with a minimum boron concentration of 3400 ppm in both CMTs.

Since there is no credible single failure that would prevent a CMT from actuating based on having CMT outlet valves in parallel, as long as the average boron concentration from both CMTs is 3400 ppm, these non-LOCA events as analyzed in Chapters 6 and 15 of the UFSAR would not be impacted.

Other non-LOCA events model the CMTs at a maximum boron concentration of 4500 ppm. For the LONF, LOAC, and FLB events, a higher boron concentration was found to be bounding. As such, this change would not adversely impact the LONF, LOAC, and FLB non-M&E events.

The non-DBA ATWS scenario discussed in UFSAR Section 15.8 associated with demonstrating compliance to 10 CFR 50.62 (ATWS Rule) and the non-DBA SSD/SST analyses are performed with better estimate conditions, including the assumption that both CMTs inject at a boron concentration of 3500 ppm. The minimum average boron concentration of 3400 ppm allowed by this change is offset by conservatisms in these evaluations, namely:

For both ATWS and SSD/SST, maintaining the Unit 4 CMT A and B average boron concentration at or above 3400 ppm is sufficient to bound the impacts of a CMT A boron concentration as low as 3100 ppm. This will ensure that the nominal boron concentration assumption remains valid for these analyses.

For the ATWS analysis, the end of life/cycle (EOL) moderator temperature coefficient (MTC) is more negative than the beginning of cycle and the ability of the EOL MTC to mitigate an ATWS event is increased significantly. Use of the EOL MTC would also more than offset the 100 ppm difference in CMT boron concentration for the ATWS events.

For the SSD/SST analysis, the steam generator trip masses modeled in the evaluation, which are based on the UFSAR Chapter 15 LONF safety analysis, are conservatively low.

For the SSD/SST analysis, additional conservatisms associated with RCS and PRHR HX heat transfer that would significantly impact the analyses are provided in NF-GP 082 and are considered Westinghouse Proprietary Class 2.

It is concluded that the conservatisms in the ATWS and SSD analyses would more than offset the 100 ppm reduction (3500 ppm - 3400 ppm) in combined CMT boron concentration associated with this change.

In the case of a steam generator tube rupture (SGTR), CMT injection provides borated water to compensate for RCS leakage; however, CMT boration is not credited in the SGTR event as control and shutdown rods are assumed to trip and provide adequate shutdown margin.

For Small Break Loss of Coolant Accidents (SBLOCAs) control and shutdown rods are assumed to insert and provide adequate shutdown margin. Therefore, there is no adverse impact on shutdown margin for SBLOCA events as a result of this change.

For Large Break Loss of Coolant Accidents (LBLOCAs) including Long Term Core Cooling (LTCC) analyses, boration from emergency core cooling system (ECCS) injection sources are credited. Of the LOCA events the double-ended direct vessel injection (DEDVI) line break is limiting for boration considerations. Due to the break location for this event, one train of ECCS (1-CMT, 1-Accumulator) is assumed to not inject into the reactor vessel. This limiting scenario was evaluated assuming the lower boron concentration CMT was the injection source. The results of this evaluation showed that if the injected CMT was at a boron concentration of 3100 ppm there would be > 800 ppm of shutdown margin available.

Enclosure to NL-25-0317 Evaluation of the Proposed Change E-8 SNC has evaluated the impact of allowing the Unit 4 CMT A boron concentration to be less than the required limit on the capability of the passive core cooling system to perform its design function as discussed in UFSAR Chapters 6 and 15. The margins in these analyses are sufficient to bound the impacts of CMT A boron concentration as low as 3100 ppm provided the combined boron concentration from CMT A and B is 3400 ppm.

3.2 Implementation and Compensatory Measures During the period(s) of operation with the proposed TS effective, an Adverse Condition Monitoring Plan (ACMP) will be implemented as a defense-in-depth effort. The ACMP will be built around the daily RCS boron samples with the following features:

Utilize changes in boron concentration with the Operability Determination Support Basis (ODSB) methodology for calculating CMT leak-by and projected boron concentration.

Periodically recalculate the projected time at which the CMT A boron concentration will fall below the requested 3100 ppm minimum limit or the current 3400 ppm minimum limit.

Apply trigger points based on rising CMT leakage and projected times for going below 3100 ppm boron or 3400 ppm boron, including actions to:

o Re-evaluate station plans, including potentially de-rating the unit to support a CMT boration.

o Evaluate the need and timing of confirmatory CMT samples.

4.

REGULATORY EVALUATION 4.1 Applicable Regulatory Requirements/Criteria This activity involves changes to the operating license Appendix A, Technical Specifications; therefore, in accordance with 10 CFR 50.90 and 10 CFR 50.91(a)(5), this activity requires an amendment. As such, NRC approval is required prior to making the proposed changes in this license amendment request.

10 CFR 50, Appendix A, General Design Criterion (GDC) 26 requires, in part, that [t]wo independent reactivity control systems of different design principles shall be provided. The second reactivity control system is chemical shim (boric acid). The proposed temporary change to reduce the Unit 4 CMT A lower boron concentration limit and to not require performance of SR 3.5.2.4 until startup from the startup from the first Unit 4 refueling outage as conservative analyses have shown that sufficient boron concentration will be available from either or both CMTs to perform the design basis function of the CMTs. Therefore, the proposed changes comply with the requirement of GDC 26.

10 CFR Part 50, Appendix A GDC 27, Combined reactivity control systems capability, requires that [t]he reactivity control systems be designed to have a combined capability, in conjunction with poison addition by the emergency core cooling system, of reliably controlling reactivity changes to assure that under postulated accident conditions and with appropriate margin for stuck rods the capability to cool the core is maintained. The proposed changes do not affect the means of making and holding the core subcritical under anticipated conditions and with appropriate margin for contingencies. Shutdown margin is not affected. Therefore, the proposed changes comply with the requirement of GDC 27.

Enclosure to NL-25-0317 Evaluation of the Proposed Change E-9 10 CFR Part 50, Appendix A GDC 35, Emergency core cooling, requires a system to provide abundant emergency core cooling whose safety function is to transfer heat from the reactor core following any loss of reactor coolant at a rate such that fuel and clad damage that could interfere with continued effective core cooling is prevented and clad metal-water reaction is limited to negligible amounts. The proposed changes to the SR 3.5.2.4 do not change the design of the system to perform these functions with abundant emergency core cooling. Therefore, the proposed changes comply with the requirement of GDC 35.

10 CFR Part 50, Appendix A GDC 37 requires, in part, that the emergency core cooling system be designed to permit appropriate periodic functional testing to assure the operability of the system. The testing of the CMT boron concentration at the proposed frequency is sufficient to assure the operability of the system.

10 CFR 50.36(c)(2) requires that TSs include Limiting Conditions for Operation (LCOs). Per 10 CFR 50.36(c)(2)(i), LCOs are the lowest functional capability or performance levels of equipment required for safe operation of the facility. The regulation also requires that when an LCO of a nuclear reactor is not met, the licensee shall shut down the reactor or follow any remedial action permitted by the TS until the condition can be met. The proposed temporary change to SR 3.5.2.4to reduce the minimum allowable boron concentration of Unit 4 CMT A and to not require performance of SR 3.5.2.4 until startup from the first Unit 4 refueling outage continues to reflect the lowest functional capability required for safe operation and continues to provide appropriate remedial actions including a required plant shutdown if they are not met.

4.2 Precedent None.

4.3 No Significant Hazards Consideration Determination Pursuant to 10 CFR 50.90 and 10 CFR 50.91(a)(5), Southern Nuclear Operating Company (SNC) requests an amendment to Vogtle Electric Generating Plant (VEGP), Unit 4 combined license NPF-92. The requested amendment would temporarily revise the operating license, Appendix A, Technical Specification (TS) 3.5.2, Core Makeup Tanks (CMTs) - Operating, Surveillance Requirement (SR) 3.5.2.4 to reduce the minimum allowable CMT A boron concentration and to not require performance of SR 3.5.2.4 until startup from the first VEGP Unit 4 refueling outage.

SNC has evaluated whether a significant hazards consideration is involved with the proposed amendment(s) by focusing on the three standards set forth in 10 CFR 50.92, "Issuance of amendment," as discussed below:

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

Response: No.

The proposed changes do not adversely affect the operation of any structures, systems, or components (SSCs) associated with an accident initiator or initiating sequence of events. The proposed changes do not affect the design of the passive core cooling system.

The proposed amendment does not affect accident initiators or precursors nor adversely alter the design assumptions, conditions, or configuration of the facility. The proposed amendment does not alter any plant equipment or operating practices with respect to such initiators or precursors in a manner that the probability of an accident is increased. The proposed amendment to temporarily reduce the minimum allowable Unit 4 CMT A boron concentration

Enclosure to NL-25-0317 Evaluation of the Proposed Change E-10 and to not require Unit 4 core makeup tank (CMT) boron concentration to be verified again until startup from the first Unit 4 refueling outage does not adversely affect the operation of the assumed mitigation systems or the containment fission product barrier assumptions. As demonstrated in the SNC request, the temporary reduction in minimum allowable Unit 4 CMT A boron concentration is more than offset by existing margins in the safety analyses. As such, the proposed change will not alter assumptions relative to the mitigation of an accident or transient event. The proposed amendment does not increase the likelihood of the malfunction of an SSC or adversely impact analyzed accidents.

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

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 do not change the design function of the CMTs. These proposed changes do not introduce any new equipment or components that would result in a new failure mode, malfunction or sequence of events that could adversely affect safety-related or non-safety-related equipment. This activity will 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.

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

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

Response: No.

The margin of safety is related to the ability of the CMTs to provide adequate shutdown margin throughout the duration of the temporary change. Evaluation of the impact of allowing the Unit 4 CMT A boron concentration to be less than the required limit on the capability of the passive core cooling system to perform its design function has confirmed that margins in these analyses are sufficient to bound the impacts of a CMT A boron concentration as low as the proposed lower limit provided the average boron concentration from both CMTs is greater than the proposed combined average limit. The change to the frequency of boron concentration surveillance doesnt change the validation of the CMTs to support safety analysis initial conditions. No safety analysis or design basis acceptance limit/criterion is challenged or exceeded by the requested change, thus no margin of safety is reduced.

Therefore, the proposed change does not involve a significant reduction in a margin of safety.

Based on the above, SNC concludes 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 In conclusion, 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 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.

Enclosure to NL-25-0317 Evaluation of the Proposed Change E-11

5.

ENVIRONMENTAL CONSIDERATION The proposed changes to the Technical Specifications (TS) are described in Section 2 of this Enclosure, which require a license amendment. SNC has evaluated this license amendment request against the criteria for identification of licensing and regulatory actions requiring environmental assessment in accordance with 10 CFR 51.21.

The requested amendment meets the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9), in that the amendment would 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 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

6.

REFERENCES None.

to the Enclosure of NL-25-0317 Proposed Technical Specification Changes (Mark-ups)

Insertions Denoted by Blue text.

Technical Specifications CMTs - Operating 3.5.2 VEGP Units 3 and 4 3.5.2 - 1 Amendment No.

13___ (Unit 3)

Amendment No.

13___ (Unit 4) 3.5 PASSIVE CORE COOLING SYSTEM (PXS) 3.5.2 Core Makeup Tanks (CMTs) - Operating LCO 3.5.2 Both CMTs shall be OPERABLE.

- NOTE -

For Unit 4 until entry into TS 3.5.3 Applicability during shutdown for 4R01, CMT A may be considered OPERABLE with boron concentration

< 3400 ppm provided:

a.

CMT A boron concentration is 3100 ppm and

b.

Average of CMT A and CMT B boron concentration is 3400 ppm.

APPLICABILITY:

MODES 1, 2, and 3.

MODE 4 with the Reactor Coolant System (RCS) not being cooled by the Normal Residual Heat Removal System (RNS).

ACTIONS CONDITION REQUIRED ACTION COMPLETION TIME A.

One CMT inoperable due to one CMT outlet isolation valve inoperable.

A.1 Restore outlet isolation valve to OPERABLE status.

72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> B.

One CMT inoperable due to water temperature or boron concentration not within limits.

B.1 Restore water temperature and boron concentration to within limits.

72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> C.

Two CMTs inoperable due to water temperature or boron concentration not within limits.

C.1 Restore water temperature and boron concentration to within limits for one CMT.

1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> from discovery of LCO 3.5.2 Condition C entry concurrent with LCO 3.5.1 Condition B entry AND 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />

Technical Specifications CMTs - Operating 3.5.2 VEGP Units 3 and 4 3.5.2 - 2 Amendment No. 185___ (Unit 3)

Amendment No. 183___ (Unit 4)

ACTIONS (continued)

CONDITION REQUIRED ACTION COMPLETION TIME D.

One CMT inlet line with noncondensible gas volume not within limit.

D.1 Restore CMT inlet line noncondensible gas volume to within limit.

24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> E.

One CMT inoperable for reasons other than Condition A, B, or D.

E.1 Restore CMT to OPERABLE status.

1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> from discovery of LCO 3.5.2 Condition E entry concurrent with LCO 3.5.1 Condition B entry AND 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> F.

Required Action and associated Completion Time of Condition A, B, C, D, or E not met.

OR Two CMTs inoperable for reasons other than Condition C.

F.1 AND F.2 Be in MODE 3.

Be in MODE 5.

6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> 36 hours SURVEILLANCE REQUIREMENTS SURVEILLANCE FREQUENCY SR 3.5.2.1 Verify the temperature of the borated water in each CMT is < 120°F.

24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> SR 3.5.2.2 Verify each CMT inlet isolation valve is fully open.

12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> SR 3.5.2.3 Verify the volume of noncondensible gases in each CMT inlet line has not caused the high-point water level to drop below the sensor.

24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />

Technical Specifications CMTs - Operating 3.5.2 VEGP Units 3 and 4 3.5.2 - 3 Amendment No. 185___ (Unit 3)

Amendment No. 183___ (Unit 4)

SURVEILLANCE REQUIREMENTS (continued)

SURVEILLANCE FREQUENCY SR 3.5.2.4

- NOTE -

Not required to be performed for Unit 4 until entry into TS 3.5.3 Applicability during startup from 4R01.

Verify the boron concentration in each CMT is 3400 ppm and 4500 ppm.

31 days SR 3.5.2.5 Verify each CMT outlet isolation valve strokes open.

In accordance with the Inservice Testing Program SR 3.5.2.6 Verify each CMT outlet isolation valve actuates to the open position on an actual or simulated actuation signal.

24 months SR 3.5.2.7 Verify system flow performance of each CMT in accordance with the System Level OPERABILITY Testing Program.

10 years

to the Enclosure of NL-25-0317 Clean Revised Technical Specification Pages

Technical Specifications CMTs - Operating 3.5.2 VEGP Units 3 and 4 3.5.2 - 1 Amendment No.

___ (Unit 3)

Amendment No.

___ (Unit 4) 3.5 PASSIVE CORE COOLING SYSTEM (PXS) 3.5.2 Core Makeup Tanks (CMTs) - Operating LCO 3.5.2 Both CMTs shall be OPERABLE.

- NOTE -

For Unit 4 until entry into TS 3.5.3 Applicability during shutdown for 4R01, CMT A may be considered OPERABLE with boron concentration

< 3400 ppm provided:

a.

CMT A boron concentration is 3100 ppm and

b.

Average of CMT A and CMT B boron concentration is 3400 ppm.

APPLICABILITY:

MODES 1, 2, and 3.

MODE 4 with the Reactor Coolant System (RCS) not being cooled by the Normal Residual Heat Removal System (RNS).

ACTIONS CONDITION REQUIRED ACTION COMPLETION TIME A.

One CMT inoperable due to one CMT outlet isolation valve inoperable.

A.1 Restore outlet isolation valve to OPERABLE status.

72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> B.

One CMT inoperable due to water temperature or boron concentration not within limits.

B.1 Restore water temperature and boron concentration to within limits.

72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> C.

Two CMTs inoperable due to water temperature or boron concentration not within limits.

C.1 Restore water temperature and boron concentration to within limits for one CMT.

1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> from discovery of LCO 3.5.2 Condition C entry concurrent with LCO 3.5.1 Condition B entry AND 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />

Technical Specifications CMTs - Operating 3.5.2 VEGP Units 3 and 4 3.5.2 - 2 Amendment No.

___ (Unit 3)

Amendment No.

___ (Unit 4)

ACTIONS (continued)

CONDITION REQUIRED ACTION COMPLETION TIME D.

One CMT inlet line with noncondensible gas volume not within limit.

D.1 Restore CMT inlet line noncondensible gas volume to within limit.

24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> E.

One CMT inoperable for reasons other than Condition A, B, or D.

E.1 Restore CMT to OPERABLE status.

1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> from discovery of LCO 3.5.2 Condition E entry concurrent with LCO 3.5.1 Condition B entry AND 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> F.

Required Action and associated Completion Time of Condition A, B, C, D, or E not met.

OR Two CMTs inoperable for reasons other than Condition C.

F.1 AND F.2 Be in MODE 3.

Be in MODE 5.

6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> 36 hours SURVEILLANCE REQUIREMENTS SURVEILLANCE FREQUENCY SR 3.5.2.1 Verify the temperature of the borated water in each CMT is < 120°F.

24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> SR 3.5.2.2 Verify each CMT inlet isolation valve is fully open.

12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> SR 3.5.2.3 Verify the volume of noncondensible gases in each CMT inlet line has not caused the high-point water level to drop below the sensor.

24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />

Technical Specifications CMTs - Operating 3.5.2 VEGP Units 3 and 4 3.5.2 - 3 Amendment No.

___ (Unit 3)

Amendment No.

___ (Unit 4)

SURVEILLANCE REQUIREMENTS (continued)

SURVEILLANCE FREQUENCY SR 3.5.2.4

- NOTE -

Not required to be performed for Unit 4 until entry into TS 3.5.3 Applicability during startup from 4R01.

Verify the boron concentration in each CMT is 3400 ppm and 4500 ppm.

31 days SR 3.5.2.5 Verify each CMT outlet isolation valve strokes open.

In accordance with the Inservice Testing Program SR 3.5.2.6 Verify each CMT outlet isolation valve actuates to the open position on an actual or simulated actuation signal.

24 months SR 3.5.2.7 Verify system flow performance of each CMT in accordance with the System Level OPERABILITY Testing Program.

10 years

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