RS-24-101, License Amendment Request for One-Time Extension of Standby Gas Treatment System Technical Specifications Completion Time to Support Piping Repair

License Amendment Request for One-Time Extension of Standby Gas Treatment System Technical Specifications Completion Time to Support Piping Repair

ML24309A271
Person / Time
Site:	Quad Cities
Issue date:	11/04/2024
From:	Humphrey M Constellation Energy Generation
To:	Office of Nuclear Reactor Regulation, Document Control Desk
References
RS-24-101
Download: ML24309A271 (1)

Text

4300 Winfield Road Warrenville, IL 60555 630 657 2000 Office RS-24-101 10 CFR 50.90 November 4, 2024 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Quad Cities Nuclear Power Station, Units 1 and 2 Renewed Facility Operating License Nos. DPR-29 and DPR-30 NRC Docket Nos. 50-254 and 50-265

Subject:

License Amendment Request for One-Time Extension of Standby Gas Treatment System Technical Specifications Completion Time to Support Piping Repair

Reference:

Letter from B. Wake (Constellation Energy Generation, LLC) to U.S. NRC, "Licensee Event Report 254/2022-003-00 'Both Trains of Standby Gas Treatment Inoperable Due to Blockage in the Common Discharge Line,'" dated September 1, 2022 In accordance with 10 CFR 50.90, "Application for amendment of license, construction permit, or early site permit," Constellation Energy Generation, LLC (CEG) requests an amendment to Renewed Facility Operating License Nos. DPR-29 and DPR-30 for Quad Cities Nuclear Power Station (QCNPS), Units 1 and 2. The proposed change extends the Completion Time for Technical Specifications (TS) 3.6.4.3, "Standby Gas Treatment (SGT) System," Required Action D.1 on a one-time basis to support repair of the SGT common discharge exhaust line.

Specifically, the proposed change extends the Required Action D.1 Completion Time from 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> to 14 days. This temporary one-time TS change is needed to allow sufficient time to perform physical modification work to repair the SGT common discharge exhaust line, which has experienced blockage due to water intrusion as described in the Reference. The portion of the pipe being repaired extends from the Turbine Building to the station chimney, which includes some underground piping. This work is expected to take no more than 14 days.

Interim actions have been put in place to mitigate the impact of water intrusion in the common discharge line until such time that a permanent solution can be implemented. However, these interim actions create an unnecessary burden to plant personnel by requiring increased monitoring of the SGT system flow paths as well as more frequent operation of the SGT system.

Repair of the common discharge line under the existing TS requirements would require an unnecessary shutdown of both QCNPS Unit 1 and Unit 2 because the SGT system is a shared system between both units that is required to be operable in Modes 1, 2, and 3. The proposed change supports implementation of a permanent repair to the SGT system without an

November 4, 2024 U.S. Nuclear Regulatory Commission Page 2 unnecessary shutdown of both QCNPS Unit 1 and Unit 2. Based on these factors, CEG is requesting NRC approval of the proposed change within 10 months (i.e., by September 4, 2025). Once approved, the amendment will be implemented within 60 days. This implementation period will provide adequate time for the affected station documents to be revised using the appropriate change control mechanisms.

This request is subdivided as follows.

• provides a description and evaluation of the proposed change.

• provides a markup of the affected TS page.

The proposed change has been reviewed by the Plant Operations Review Committee in accordance with the requirements of the CEG Quality Assurance Program.

In accordance with 10 CFR 50.91, "Notice for public comment; State consultation,"

paragraph (b), CEG is notifying the State of Illinois of this application for license amendment by transmitting a copy of this letter and its attachments to the designated State Official.

There are no regulatory commitments contained in this letter. Should you have any questions concerning this letter, please contact Mr. Kenneth M. Nicely at (779) 231-6119.

I declare under penalty of perjury that the foregoing is true and correct. Executed on the 4th day of November 2024.

Respectfully, Mark Humphrey Sr. Manager Licensing Constellation Energy Generation, LLC Attachments:

1. Evaluation of Proposed Change

2. Markup of Technical Specifications Page cc:

NRC Regional Administrator, Region III NRC Senior Resident Inspector - QCNPS Illinois Emergency Management Agency - Division of Nuclear Safety Humphrey, Mark D.

Digitally signed by Humphrey, Mark D.

Date: 2024.11.04 11:26:38 -06'00'

ATTACHMENT 1 Evaluation of Proposed Change Page 1 1.0

SUMMARY

DESCRIPTION 2.0 DETAILED DESCRIPTION

3.0 TECHNICAL EVALUATION

3.1 Background

3.2

System Description

3.3 Temporary Modification 3.4 Radiological Evaluation 3.5 Risk Insights 3.6 Preliminary Repair Schedule

4.0 REGULATORY EVALUATION

4.1 Applicable Regulatory Requirements/Criteria 4.2 No Significant Hazards Consideration 4.3 Conclusions

6.0 REFERENCES

ATTACHMENT 1 Evaluation of Proposed Change Page 2 1.0

SUMMARY

DESCRIPTION In accordance with 10 CFR 50.90, "Application for amendment of license, construction permit, or early site permit," Constellation Energy Generation, LLC (CEG) requests an amendment to Renewed Facility Operating License Nos. DPR-29 and DPR-30 for Quad Cities Nuclear Power Station (QCNPS), Units 1 and 2. The proposed change extends the Completion Time for Technical Specifications (TS) 3.6.4.3, "Standby Gas Treatment (SGT) System," Required Action D.1 on a one-time basis to support repair of the SGT common discharge exhaust line.

Specifically, the proposed change extends the Required Action D.1 Completion Time from 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> to 14 days. This temporary one-time TS change is needed to allow sufficient time to perform physical modification work to repair the SGT common discharge exhaust line, which has experienced blockage due to water intrusion as described in Reference 1. The portion of the pipe being repaired extends from the Turbine Building to the station chimney, which includes some underground piping. This work is expected to take no more than 14 days.

Interim actions have been put in place to mitigate the impact of water intrusion in the common discharge line until such time that a permanent solution can be implemented. However, these interim actions create an unnecessary burden to plant personnel by requiring increased monitoring of the SGT system flow paths as well as more frequent operation of the SGT system.

Repair of the common discharge line under the existing TS requirements would require an unnecessary shutdown of both QCNPS Unit 1 and Unit 2 because the SGT system is a shared system between both units that is required to be operable in Modes 1, 2, and 3. The proposed change supports implementation of a permanent repair to the SGT system without an unnecessary shutdown of both QCNPS units.

2.0 DETAILED DESCRIPTION Limiting condition for operation (LCO) 3.6.4.3 requires two SGT subsystems to be operable in Modes 1, 2, and 3, and during movement of recently irradiated fuel assemblies in the secondary containment. Condition D applies with two SGT subsystems inoperable when either unit is in Mode 1, 2, or 3. Required Action D.1 is to restore one SGT subsystem to operable status, with a Completion Time of one hour.

The proposed change provides a temporary one-time extension to the Required Action D.1 Completion Time to allow sufficient time to perform physical modification work to repair the SGT common discharge line. Specifically, the proposed change adds a Note to the Completion Time for Required Action D.1 that states:

Or 14 days, to support the rehabilitation of the 24-inch SGT common discharge line pipe section. The 14-day extended period shall only be used once and may not be used after May 31, 2026. During the extended period, the temporary discharge line that routes the SGT system exhaust through the Turbine Building exhaust ventilation duct, that is described in Attachment 1 of letter RS-24-101 dated November 4, 2024, shall be in service, except when initially connecting the temporary discharge line and again when restoring the original configuration. If the temporary discharge line becomes unavailable during the extended period (i.e., except when initially connecting the temporary

ATTACHMENT 1 Evaluation of Proposed Change Page 3 discharge line and again when restoring the original configuration), the Required Action is to immediately initiate actions to restore the temporary discharge line.

A markup of the proposed change is provided in Attachment 2.

3.0 TECHNICAL EVALUATION

3.1 Background

On July 4, 2022, QCNPS Unit 2 experienced a manual reactor scram due to a Feedwater regulatory valve that failed in the closed position and locked up, causing a decrease in reactor water level. As a result of the scram, the B train of the SGT system automatically started. The normal flow rate of one train of SGT is 3600-4400 cfm; however, the flow rate observed with the B train running was degraded and oscillating flow between 2400-2600 cfm. Operations personnel manually secured the B train of the SGT system and started the A train, which also indicated degraded and oscillating flow. Troubleshooting efforts identified a partial blockage in the SGT system 24-inch common discharge line. The flowrate slowly increased as the A train continued to operate. The event was reported to the NRC in Reference 1.

CEG's causal evaluation determined that the cause of the low flow condition on both trains of SGT was due to partial water blockage in the SGT 24-inch common discharge line. The source of the water intrusion was determined to be from either condensation from the main chimney exhausts, or groundwater intrusion from a flaw in the buried common discharge line pipe section.

CEG plans to install a modification on the buried 24-inch common discharge line pipe section to address the concern with water intrusion. The portion of the pipe being repaired extends from the Turbine Building to the station chimney, which includes some underground piping. CEG's preliminary review of the modification in accordance with 10 CFR 50.59, "Changes, tests and experiments," concluded that prior NRC approval of the repair is not required. However, installation of the modification will result in both SGT subsystems being inoperable for longer than the current TS 3.6.4.3 Required Action D.1 Completion Time of one hour. Therefore, the proposed change requests NRC approval of a temporary one-time extension of the Required Action D.1 Completion Time to 14 days. This work is expected to take no more than 14 days.

3.2

System Description

The SGT system is classified as a Class I system at QCNPS. The function of the SGT system is to ensure that radioactive materials that leak from the primary containment into the secondary containment following a design basis accident (DBA) are filtered and adsorbed prior to exhausting to the environment. The SGT system removes fission products from the air in the secondary containment by adsorption in an activated charcoal filter pack before the air is discharged to the environment through the 310-foot chimney.

The SGT System consists of two fully redundant subsystems that are shared between Unit 1 and Unit 2, each with its own set of ductwork, dampers, charcoal filter train, and controls. Each charcoal filter train consists of a demister, an electric heater, a rough prefilter, a high efficiency

ATTACHMENT 1 Evaluation of Proposed Change Page 4 particulate air (HEPA) filter, a charcoal adsorber, a second HEPA afterfilter; and a centrifugal fan. The demister is provided to remove entrained water in the air, while the electric heater reduces the relative humidity of the airstream to less than 70 percent. The prefilter removes large particulate matter, while the HEPA filter removes fine particulate matter and protects the charcoal from fouling. The charcoal adsorber removes gaseous elemental iodine and organic iodides, and the final HEPA filter collects any carbon fines exhausted from the charcoal adsorber.

Each SGT subsystem is capable of processing the secondary containment volume, which includes both Unit 1 and Unit 2. The internal pressure of the secondary containment is maintained at a negative pressure of greater than or equal to 0.25 inches water gauge when the SGT system is in operation, which represents the internal pressure required to ensure zero exfiltration of air from the building when exposed to a 35 mph wind.

The SGT system automatically starts and operates in response to actuation signals indicative of conditions or an accident that could require operation of the system. Following initiation, the pre-selected subsystem train inlet and outlet dampers will automatically open, the associated train's cooling air damper closes, and the associated fan starts. The Reactor Building suction damper for the subsystem on the unaffected reactor unit closes and the subsystem's associated cooling air damper remains open to provide decay heat removal. After secondary containment isolation, the SGT subsystem, under calm wind conditions, holds the building at an average negative pressure of 0.25 inches water gauge. A failure of the primary SGT subsystem to start within 25 seconds will initiate the automatic start and alignment of the standby SGT subsystem.

The design basis for the SGT system is to mitigate the consequences of a loss-of-coolant accident (LOCA). For this analyzed event, the SGT system is assumed to be automatically initiated following the LOCA to reduce, via filtration and adsorption, the radioactive material released to the environment.

3.3 Temporary Modification CEG plans to install a temporary modification to minimize, to the extent practical, the time when both SGT subsystems are unavailable. The intent of the temporary modification is to maintain availability of the SGT system during the rehabilitation of the 24-inch common discharge line.

The temporary discharge line will be routed from the open end of the SGT common discharge line in the Turbine Building to the Turbine Building exhaust ventilation duct. This will provide an alternate flow path from the SGT system charcoal filter trains to the main chimney.

Under this configuration, both SGT subsystems will remain inoperable because the Turbine Building exhaust ventilation duct does not meet seismic design criteria. In addition, a portion of the Turbine Building exhaust ventilation duct is routed outside above ground, and therefore, is susceptible to tornado missiles. Although inoperable, both SGT subsystems will remain available to provide a filtered flow path to the main chimney for elevated releases in the event of a DBA LOCA. Implementation of the temporary modification will require periods of complete unavailability of the SGT system, both when initially connecting the temporary discharge line and again when restoring the original configuration. Additional detail regarding the periods of complete unavailability of the SGT system is provided in Section 3.6.

ATTACHMENT 1 Evaluation of Proposed Change Page 5 3.4 Radiological Evaluation An evaluation of the impact on the UFSAR Chapter 15 alternative source term (AST) LOCA dose analysis was performed assuming restoration of the SGT system does not occur. This analysis addresses both offsite and control room doses. In addition, this analysis does not credit the fission product removal function of the SGT system that is expected from implementation of the temporary modification discussed in Section 3.3 above. For the discussions given below, use of the term Reactor Building is synonymous with secondary containment.

The analysis modeled three distinct release pathways (i.e., main steam isolation valve (MSIV) leakage, containment leakage, and Engineered Safety Feature (ESF) recirculation system leakage), which is consistent with the current licensing basis UFSAR Chapter 15 AST LOCA analysis. However, the analysis assumed that the SGT system was unavailable.

The first release pathway is through MSIV leakage, where steam leaks past the MSIVs and is released to the environment directly from ground level at the MSIV room. This release path is not impacted by the unavailability of the SGT system because the release is assumed to be directly from the MSIVs to the environment.

The second release pathway is containment leakage, which assumes the air in containment leaks into the Reactor Building. From there, the normal release path to the environment is via the SGT system. However, with the SGT system unavailable, the Reactor Building is assumed to leak directly to the environment.

The third release pathway is ESF leakage, where the sump recirculation leaks directly into the Reactor Building. That leakage then aerosolizes as outlined in Regulatory Guide (RG) 1.183, Revision 0 (i.e., Reference 2) and leaks to the environment in the same manner as the containment leakage case.

The analysis was performed to determine the impact to the dose results under the assumption that the SGT system is unavailable following a DBA LOCA. The limiting results were determined by summing the dose results of the three leakage paths mentioned above plus an addition for shine related dose.

For the MSIV leakage case, there are no changes for the UFSAR Chapter 15 AST LOCA dose analysis as all releases are directly from the MSIVs to the environment.

For the containment leakage case, the SGT system was assumed to be isolated, so no ventilation systems were assumed to be operating. Therefore, the only driving force for airborne leakage from the Reactor Building to the environment during this period would be post-accident airborne leakage from containment to the Reactor Building followed by airborne leakage to the environment. The UFSAR Chapter 15 AST LOCA analysis currently assumes a containment leakage of 3% per day for the first 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, which is then reduced by 50% per day afterwards.

This same release rate was used in the analysis to conservatively bound the leakage from the Reactor Building to the environment. However, the assumed value of containment leakage was reduced to a value that bounds the most recent limiting Integrated Leak Rate Test (ILRT) testing results of either unit (i.e., 0.62% per day for the first 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, then 50% per day afterwards) to

ATTACHMENT 1 Evaluation of Proposed Change Page 6 better capture actual containment leakage. The activity release rate to the environment from the Reactor Building conservatively assumed the bounding leakage assumption of 3% per day for the first 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, then reduced by 50% per day afterwards. Lastly, the release point without SGT system operation was conservatively assumed to be the most limiting ground level release location which coincides with the edge of the MSIV room currently used for MSIV leakages.

For the ESF recirculation system leakage case, the ESF was assumed to leak directly into the Reactor Building. For this assessment, the ESF leakage was reduced to the actual plant administrative limit of 10 gallons per hour. That ESF leakage into the Reactor Building then aerosolizes, consistent with the analysis of record, and then leaks to the environment at a rate of 3% per day leakage for the first 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, then reduced by 50% per day afterwards consistent with the containment leakage case. The same conservative release point of the MSIV room was assumed for the ESF release path case.

Other assumptions for all leakage cases used for the analysis were the same as used in the current UFSAR Chapter 15 AST LOCA analysis of record. A summary of the key input changes are shown in the following table.

Key Input Changes to AST LOCA Analysis Key Input Assumption Used in Current Licensing Basis DBA-LOCA Analysis Assumption Used in Radiological Evaluation with No SGT System Operation SGT System Operation Automatically initiated following a LOCA with operation throughout the 30-day post-LOCA period SGT system does not operate at any point during the 30-day post-LOCA period Primary Containment Leakage Rate (0 - 1 day) 3% of primary containment air weight per day 0.62% of primary containment air weight per day Primary Containment Leakage Rate (1 - 30 days) 1.5% of primary containment air weight per day 0.31% of primary containment air weight per day Reactor Building Leakage (0 - 1 day)

NA, SGT is used to control building ventilation 3% of the Reactor Building air weight per day Reactor Building Leakage Rate (1 - 30 days)

NA, SGT is used to control building ventilation 1.5% of the Reactor Building air weight per day ESF Leakage 120 gallons per hour 10 gallons per hour Figure 1 depicts the activity flow path models for the impacted cases of Reactor Building leakage and ESF leakage.

ATTACHMENT 1 Evaluation of Proposed Change Page 7 Figure 1: Containment and ESF Leakage RADTRAD Nodalization Results of the radiological evaluation assuming that the SGT system is unavailable are shown in the following table. The results show sufficient margin to the regulatory limits for both offsite (i.e., Exclusion Area Boundary (EAB) and Low Population Zone (LPZ)) and control room (CR) doses. In addition, a secondary assessment was performed to determine the dose impact if operators in the control room were to don self-contained breathing apparatus (SCBA) equipment within the first 30 minutes of a postulated DBA LOCA. Use of SCBA equipment significantly reduced control room dose impacts.

For this evaluation, the following dose results were determined:

Dose Results (rem)

Current Licensing Basis No SGT Assessment No SGT Assessment With SCBA CR EAB LPZ CR EAB LPZ CR EAB LPZ Total Dose 3.99 19.65 4.22 4.83 19.66 3.55 0.64 19.66 3.55 Regulatory Limit 5

25 25 5

25 25 5

25 25

ATTACHMENT 1 Evaluation of Proposed Change Page 8 3.5 Risk Insights This license amendment request is not a risk-informed request and, therefore, a risk evaluation is not required. However, to provide additional information, CEG is providing risk insights related to the proposed change.

The SGT system provides a method to maintain the Reactor Building at a negative pressure and to filter the exhaust of radioactive matter from Reactor Building spaces to the environment.

Additionally, it is used to maintain the integrity of secondary containment during a primary to secondary containment instrument line break. These functions are designed to help mitigate both LOCAs and refueling accidents. However, for Probabilistic Risk Assessment (PRA) accident scenarios, SGT is considered insufficient to provide any Core Damage Frequency (CDF) or Large Early Release Frequency (LERF) mitigation capabilities, so despite being the primary method for venting of the torus or drywell to control primary containment pressure and hydrogen concentration in the containment, SGT is not modeled in the PRA.

As a qualitative discussion of the UFSAR credited SGT functions, the PRA does not model refueling accidents, as these occur when the reactor is outside of the applicable online Modes (i.e., Modes 1, 2, and 3). For LOCAs and other modeled accident scenarios, SGT is considered in the PRA to be insufficient to provide any CDF or LERF mitigation capabilities for PRA accident scenarios. Although for the UFSAR it is the primary method for venting of the torus or drywell to control primary containment pressure and hydrogen concentration in the containment, SGT is not modeled in the PRA. Therefore, there is no quantitative impact to either the Full-Power Internal Events (FPIE) PRA or Fire PRA (FPRA) models, and all further discussion regarding the risk impact of extending the SGT is qualitative.

There is a low frequency of any LOCA occurring during the repair window. Additionally, because of the ability to maintain the design function of the SGT system through similar systems as well as the installation of the temporary modification, the inoperability of SGT during this evolution results in a minimal increase to risk. The temporary modification will not meet seismic design requirements and a portion of the Turbine Building exhaust ventilation duct will be routed outside and above ground, thus being susceptible to tornado missiles. However, augmented primary containment venting (APCV) and the hardened containment vent system (HCVS) will still be available and can be credited during these events. Additionally, the SGT system repair is not anticipated to introduce any unique challenges related to external hazards nor does it increase the likelihood of these events. Therefore, the risk impact assessed for external hazards poses no unique risks that are not captured through the FPIE model and the qualitative results combined with effective compensatory measures to mitigate risk ensure the proposed TS change is of low risk.

The identification of Risk Management Actions (RMAs) was derived from the qualitative discussions of the various hazards as well as generally high-risk structures, systems, and components (SSCs) and operator actions from the base PRA model. None of the RMAs were credited numerically in the base risk analysis; the identified compensatory actions would further lessen the overall risk incurred during the extended periods. The compensatory actions that are outlined below provide additional assurance that the risk during the extended allowed outage time will be minimized.

ATTACHMENT 1 Evaluation of Proposed Change Page 9 The following compensatory measures are recommended to limit the risk impact of the SGT system unavailability.

Implement all fire RMAs for the configuration per procedural guidance in OP-AA-201-012-1001 and WC-AA-101-1006.

Limit any maintenance activities while the SGT system is unavailable, especially those activities which could cause an Interfacing Systems Loss of Coolant Accident (ISLOCA).

Prohibit movement of recently irradiated fuel assemblies in the Secondary Containment.

Protect the APCV system, the HCVS, and the SGT temporary modification.

Protect the following, generally important SSCs:

o 125V DC o AC Power Perform pre-job briefs to increase awareness of various operator actions to help minimize risk while the SGT is inoperable:

o Initiate Drywell/Torus Venting QCOP 1600-13 (Post-Accident Venting of The Primary Containment) o Align Fire Protection to Safe Shutdown Makeup Pump (SSMP) Room Coolers QCOP 2900-02 (Safe Shutdown Makeup Pump System Start Up) o Initiate SSMP QCOP 2900-02 (Safe Shutdown Makeup Pump System Start Up) 3.6 Preliminary Repair Schedule CEG's preliminary repair schedule for the rehabilitation of the SGT common discharge line is shown below. Based on the activities shown, the work is expected to take up to 14 days.

Therefore, the proposed change extends the TS 3.6.4.3 Required Action D.1 Completion Time from 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> to 14 days to support the repair.

ATTACHMENT 1 Evaluation of Proposed Change Page 10 Project Task Duration (hours)

OPS HANG TAG OUTS 8

OPS ENTER TS 3.6.4.3 COND D INOP BOTH TRAINS OF SGT 0

MMD PERFORM CUTS AND UNBOLTING TO REMOVE PIPE SECTION FOR REPAIRS SGT LINE 1/2-7509-24" 12 MMD RIG PIPE SECTION FOR PIPE FLANGE CLEARANCE 4

MMD FITUP/TAC WELD PIPE FLANGES 8

CONTINGENT: MMD PERFORM SCAFFOLD MOD TO SUPPORT PIPE SECTION REMOVAL 8

MMD RIG PIPE SECTION FOR PIPE TO FLOOR FOR MODIFICATION 4

VN PERFORM INITIAL INSPECTION OF PIPING FOR REPAIRS SGT LINE 1/2-7509-24" 12 MMD INSTALL TMOD FOR SGT SYSTEM AVAILABILITY 4

OPS TL T/O XXXX SGT LINE 1/2-7509-24" AND PERFORM PMT OF BOTH TRAINS SGT 4

OPS BOTH TRAINS OF SGT AVAILABLE 0

CONTINGENT: VN PERFORM WATER REMOVAL DRYING AS REQUIRED 36 CONTINGENT: VN PERFORM REPAIRS / PATCH AS REQUIRED TO SGT LINE 1/2-7509-24" 24 CONTINGENT: END TERMINATION PREPS IF REQUIRED TO SGT LINE 1/2-7509-24" 24 VN PERFORM PIPING COATING / REPAIRS TO SGT LINE 1/2-7509-24" 96 VN PERFORM INSP OF PIPING AFTER COATING / REPAIRS SGT LINE 1/2-7509-24" 8

QC PERFORM INSP OF PIPING AFTER COATING / REPAIRS SGT LINE 1/2-7509-24" 4

CONTINGENT: VENDOR PERFORM SPOT REPAIRS TO INSTALLED LINER POST INSPECTION 24 OPS REHANG T/O XXXX SGT LINE 1/2-7509-24" 4

OPS BOTH TRAINS OF SGT UNAVAILABLE 0

MMD REMOVE TMOD 4

MMD RIG REMOVED PIPING SECTION BACK INTO PLACE 4

MMD FIT UP/TORQUE BOLTED CONNECTIONS FOR PIPING SECTION 8

OPS F/C T/O XXXX SGT LINE 1/2-7509-24" 4

OPS PERFORM PMT OF BOTH TRAINS SGT 4

OPS EXIT TS 3.6.4.3 COND D INOP BOTH TRAINS OF SGT 0

TOTAL DURATION 308

ATTACHMENT 1 Evaluation of Proposed Change Page 11

4.0 REGULATORY EVALUATION

4.1 Applicable Regulatory Requirements/Criteria 10 CFR 50.36(c) provides that TS will include limiting conditions for operation (LCOs), which are the lowest functional capability or performance levels of equipment required for safe operation of the facility. When a limiting condition for operation of a nuclear reactor is not met, the licensee will shut down the reactor or follow any remedial action permitted by the TS until the condition can be met. The proposed change involves extending the Completion Time for TS 3.6.4.3, Required Action D.1, from 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> to 14 days on a one-time basis. The LCO itself remains unchanged, as do the required remedial actions or shut down requirements in accordance with 10 CFR 50.36. In addition,10 CFR 50.36 requires that a licensee's TS be derived from the analyses and evaluation included in the safety analysis report. The proposed change does not affect compliance with the intent of 10 CFR 50.36.

10 CFR 50.67, "Accident source term," allows certain licensees to voluntarily revise the accident source term used in design basis radiological consequence analyses. The AST methodology described in 10 CFR 50.67 has been adopted at QCNPS using the methodology of RG 1.183, "Alternative Radiological Source Terms for Evaluating Design Basis Accidents at Nuclear Power Reactors," Revision 0. The SGT system is designed to limit the TEDE within the guidelines of 10 CFR 50.67 at the site boundary and low population zone. The proposed change provides a one-time extension to the Completion Time for TS 3.6.4.3, Required Action D.1, and does not involve a permanent change to the DBA LOCA analysis for QCNPS. In addition, a radiological evaluation has concluded that the regulatory limits for offsite and control room dose continue to be met with the SGT system unavailable. The proposed change does not affect compliance with the intent of 10 CFR 50.67.

The SGT system charcoal adsorbers at QCNPS are periodically tested in accordance with TS 5.5.7, "Ventilation Filter Testing Program (VFTP)," and Revision 2 of RG 1.52, "Design, Testing, and Maintenance Criteria for Post Accident Engineered-Safety-Feature Atmosphere Cleanup System Air Filtration and Adsorption Units of Light-Water-Cooled Nuclear Power Plants." The proposed change does not affect compliance with TS 5.5.7 or RG 1.52, Revision 2, because no changes are being made to the testing program for the SGT filtration system.

Based on the review of the above requirements, CEG has determined that the proposed change does not require any exemptions or relief from regulatory requirements, other than revising the TS as described.

4.2 No Significant Hazards Consideration In accordance with 10 CFR 50.90, "Application for amendment of license, construction permit, or early site permit," Constellation Energy Generation, LLC (CEG) requests an amendment to Renewed Facility Operating License Nos. DPR-29 and DPR-30 for Quad Cities Nuclear Power Station (QCNPS), Units 1 and 2. The proposed change extends the Completion Time for Technical Specifications (TS) 3.6.4.3, "Standby Gas Treatment (SGT) System," Required Action D.1 on a one-time basis to support repair of the SGT common discharge exhaust line.

Specifically, the proposed change extends the Required Action D.1 Completion Time from

ATTACHMENT 1 Evaluation of Proposed Change Page 12 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> to 14 days. This temporary one-time TS change is needed to allow sufficient time to perform physical modification work to repair the SGT common discharge exhaust line, which has experienced blockage due to water intrusion. The portion of the pipe being repaired extends from the Turbine Building to the station chimney, which includes some underground piping. This work is expected to take no more than 14 days.

According to 10 CFR 50.92, "Issuance of amendment," paragraph (c), a proposed amendment to an operating license involves no significant hazards consideration if operation of the facility in accordance with the proposed amendment would not:

(1)

Involve a significant increase in the probability or consequences of any accident previously evaluated; or (2)

Create the possibility of a new or different kind of accident from any accident previously evaluated; or (3)

Involve a significant reduction in a margin of safety.

CEG has evaluated the proposed change, using the criteria in 10 CFR 50.92, and has determined that the proposed change does not involve a significant hazards consideration. The following information is provided to support a finding of no significant hazards consideration.

1.

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

Response: No The proposed change does not involve a significant increase in the probability of an accident previously evaluated because the SGT system is not an initiator of an accident.

Rather, the SGT system functions following a design basis accident (DBA) loss-of-coolant accident (LOCA) to ensure that radioactive materials that leak from the primary containment into the secondary containment are filtered and adsorbed prior to exhausting to the environment.

The consequences of a DBA LOCA have been evaluated, assuming that the SGT system is unavailable for the 30-day post-LOCA period. The results show that the offsite and control room dose consequences continue to meet applicable regulatory limits.

Increasing the completion time for two SGT subsystems inoperable from one hour to 14 days on a temporary, one-time, basis does not result in a significant increase in the consequences of a DBA-LOCA event nor change the evaluation of DBA-LOCA events as stated in the UFSAR evaluation. Movement of recently irradiated fuel within Secondary Containment will be prohibited during the extended LCO period, to preclude a fuel handling accident, which might lead to a radiological consequence.

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

ATTACHMENT 1 Evaluation of Proposed Change Page 13

2.

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

Response: No The proposed changes do not create the possibility of a new or different kind of accident from any accident previously evaluated because there are no credible new failure mechanisms, malfunctions, or accident initiators that not considered in the design and licensing bases. The accident analyses affected by this extension are the radiological events that are discussed in the UFSAR. The potential for the loss of other plant systems or equipment to mitigate the effects of an accident is not altered. The proposed change does not require any new operator response or introduce any new opportunities for operator error not previously considered.

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 change involve a significant reduction in a margin of safety?

Response: No The increase in completion time for SGT does not result in any effect on the margin of safety. A temporary modification will be in place to maintain availability of the SGT system during the rehabilitation of the 24-inch common discharge line, except when initially connecting the temporary discharge line and again when restoring the original configuration. Although inoperable, both SGT subsystems will remain available to provide a filtered flow path to the main chimney for elevated releases in the event of an accident. In addition, a radiological evaluation has concluded that control room and offsite dose limits will continue to be met with the SGT out of service following a DBA LOCA.

In addition, implementation of the compensatory measures minimizes the probability that an accident will be initiated and maximizes the probability that accident mitigation equipment will be available. Thus the potential impact of extending the completion time is small.

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

Based on the above evaluation, CEG concludes that the proposed change presents no significant hazards consideration under the standards set forth in 10 CFR 50.92, paragraph (c),

and accordingly, a finding of no significant hazards consideration is justified.

4.3 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 Commission's regulations,

ATTACHMENT 1 Evaluation of Proposed Change Page 14 and (3) the issuance of the amendment will not be inimical to the common defense and security or the health and safety of the public.

5.0 ENVIRONMENTAL CONSIDERATION

CEG has determined that the proposed amendment would change a requirement with respect to installation or use of a facility component located within the restricted area, as defined in 10 CFR 20, "Standards for Protection Against Radiation." However, 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 effluent that may be released offsite, or (iii) a significant increase in individual or cumulative occupational radiation exposure. Accordingly, the proposed amendment meets the eligibility criterion for categorical exclusion set forth in 10 CFR 51.22, "Criterion for categorical exclusion; identification of licensing and regulatory actions eligible for categorical exclusion or otherwise not requiring environmental review,"

paragraph (c)(9). Therefore, pursuant to 10 CFR 51.22, paragraph (b), no environmental impact statement or environmental assessment needs to be prepared in connection with the proposed amendment.

6.0 REFERENCES

1.

Letter from B. Wake (Constellation Energy Generation, LLC) to U.S. NRC, "Licensee Event Report 254/2022-003-00 'Both Trains of Standby Gas Treatment Inoperable Due to Blockage in the Common Discharge Line,'" dated September 1, 2022

2.

NRC Regulatory Guide 1.183, "Alternative Radiological Source Terms for Evaluating Design Basis Accidents at Nuclear Power Reactors," Revision 0, dated July 2000

ATTACHMENT 2 Markup of Technical Specifications Page Quad Cities Nuclear Power Station, Units 1 and 2 Renewed Facility Operating License Nos. DPR-29 and DPR-30 REVISED TECHNICAL SPECIFICATIONS PAGE 3.6.4.3-2

SGT System 3.6.4.3 Quad Cities 1 and 2 3.6.4.3-2 Amendment No. 273/268 ACTIONS CONDITION REQUIRED ACTION COMPLETION TIME C. (continued)

C.2 Suspend movement of recently irradiated fuel assemblies in secondary containment.

Immediately D. Two SGT subsystems inoperable in MODE 1, 2, or 3.

D.1 Restore one SGT subsystem to OPERABLE status.

1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> E. Required Action and associated Completion Time of Condition D not met.

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NOTE-----------

LCO 3.0.4.a is not applicable when entering MODE 3.

E.1 Be in MODE 3.

12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> F. Two SGT subsystems inoperable during movement of recently irradiated fuel assemblies in the secondary containment.

F.1

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NOTE--------

LCO 3.0.3 is not applicable.

Suspend movement of recently irradiated fuel assemblies in secondary containment.

Immediately

• Or 14 days, to support the rehabilitation of the 24-inch SGT common discharge line pipe section. The 14-day extended period shall only be used once and may not be used after May 31, 2026. During the extended period, the temporary discharge line that routes the SGT system exhaust through the Turbine Building exhaust ventilation duct, that is described in Attachment 1 of letter RS-24-101 dated November 4, 2024, shall be in service, except when initially connecting the temporary discharge line and again when restoring the original configuration. If the temporary discharge line becomes unavailable during the extended period (i.e.,

except when initially connecting the temporary discharge line and again when restoring the original configuration), the Required Action is to immediately initiate actions to restore the temporary discharge line.