ML25303A324

License Amendment Request - Proposed One-Time Change to Technical Specification 3.8.3 to Support Inspection of Fuel Oil Storage Tank 21

ML25303A324
Person / Time
Site:	Calvert Cliffs
Issue date:	10/30/2025
From:	Para W Constellation Energy Group
To:	Office of Nuclear Reactor Regulation, Document Control Desk
References
TS 3.8.3
Download: ML25303A324 (1)

Text

200 Energy Way Kennett Square, PA 19348 www.constellation.com 10 CFR 50.90 October 30, 2025 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Calvert Cliffs Nuclear Power Plant, Unit 2 Renewed Facility Operating License No. DPR-69 NRC Docket No. 50-318

SUBJECT:

License Amendment Request - Proposed One-Time Change to Technical Specification 3.8.3 to Support Inspection of Fuel Oil Storage Tank 21 Pursuant to 10 CFR 50.90, Application for amendment of license, construction permit, or early site permit," Constellation Energy Generation, LLC (CEG), proposes a change to the Technical Specifications (TS) of Renewed Facility Operating License No. DPR-69 for Calvert Cliffs Nuclear Power Plant (CCNPP), Unit 2.

The proposed change is a one-time extension to the TS 3.8.3, Diesel Fuel Oil, Condition C Completion Time (CT) for Fuel Oil Storage Tank (FOST) 21 to allow the FOST to be out-of-service for the required Maryland state inspection and any associated maintenance of the tank during the 2027 Unit 2 Refueling Outage for up to 14 days. The inspection and associated maintenance cannot be accomplished within the TS CT of 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br />.

provides an evaluation of the proposed change. Attachment 2 provides compensatory measures required for the proposed extended CT. Attachment 3 provides the marked-up TS pages indicating the proposed change. Attachment 4 provides a markup of the affected TS Bases pages. TS Bases changes are provided for information only and will be incorporated in accordance with the TS Bases Control Program upon implementation of the approved amendment.

CEG requests approval of the proposed license amendment by July 30, 2026. The proposed license amendment request, if approved, will be implemented within 90 days of issuance.

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

There are no regulatory commitments contained in this submittal.

In accordance with 10 CFR 50.91, "Notice for public comment; State consultation," paragraph (b), CEG is notifying the State of Maryland of this application for license amendment by

License Amendment Request Proposed One-Time Change to Technical Specification 3.8.3 Docket No. 50-318 October 30, 2025 Page 2 transmitting a copy of this letter and its attachments to the designated State Official.

Should you have any questions concerning this submittal, please contact Adam Donell at (267) 533-5156.

I declare under penalty of perjury that the foregoing is true and correct. Executed on the 30th day of October 2025.

Respectfully, Wendi Para Sr. Manager - Licensing Constellation Energy Generation, LLC Attachments:

1. Evaluation of Proposed Change

2. Fuel Oil Storage Tank 21 Inoperable Extended Completion Time Compensatory Measures

3. Proposed Technical Specification Change (Markup)

4. Proposed Technical Specification Bases Change (Markup) (For Information Only) cc:

USNRC Region I, Regional Administrator USNRC Senior Resident Inspector - Calvert Cliffs Nuclear Power Plant USNRC Project Manager, NRR - Calvert Cliffs Nuclear Power Plant Z. Barthel, State of Maryland

ATTACHMENT 1 License Amendment Request Calvert Cliffs Nuclear Power Plant, Unit 2 Renewed Facility Operating License No. DPR-69 NRC Docket No. 50-318 Evaluation of Proposed Change

Subject:

License Amendment Request - Proposed One-Time Change to Technical Specification 3.8.3 to Support Inspection of Fuel Oil Storage Tank 21 1.0

SUMMARY

DESCRIPTION 2.0 DETAILED DESCRIPTION 2.1 System and Inspection Descriptions 2.2 Current TS Requirements 2.3 Proposed Change

3.0 TECHNICAL EVALUATION

3.1 Safety Analysis 3.2 Risk Assessment Insights and Compensatory Measures

4.0 REGULATORY EVALUATION

4.1 Applicable Regulatory Requirements/Criteria 4.2 Precedent 4.3 No Significant Hazards Consideration 4.4 Conclusions

6.0 REFERENCES

License Amendment Request Proposed One-Time Change to Technical Specification 3.8.3 Page 1 of 16 1.0

SUMMARY

DESCRIPTION Pursuant to 10 CFR 50.90, Application for amendment of license, construction permit, or early site permit," Constellation Energy Generation, LLC (CEG), proposes a change to the Technical Specifications (TS) of Renewed Facility Operating License No. DPR-69 for Calvert Cliffs Nuclear Power Plant (CCNPP), Unit 2.

The proposed change is a one-time extension to the TS 3.8.3, Diesel Fuel Oil, Condition C Completion Time (CT) for Fuel Oil Storage Tank (FOST) 21 to allow the FOST to be out-of-service for the required Maryland state inspection and any associated maintenance of the tank during the 2027 Unit 2 Refueling Outage for up to 14 days. The inspection and associated maintenance cannot be accomplished within the TS CT of 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br />.

2.0 DETAILED DESCRIPTION 2.1 System and Inspection Descriptions 2.1.1 Offsite Circuit System Description 13.8 kV System:

CCNPP Updated Final Safety Analysis (UFSAR) (Reference 6.10) Figure No. 8-1 provides an Electrical Main Single Line Diagram for CCNPP. Offsite power is supplied to the 500 kV Switchyard from the transmission network by three 500 kV transmission lines. Two electrically and physically separated circuits supply electric power from the 500 kV Switchyard to two 13.8 kV buses and then to the four 4.16 kV Engineered Safety Feature (ESF) buses (two per Unit). A third 69 kV/13.8 kV offsite power source that may be manually connected to either 13.8 kV bus is available from the Southern Maryland Electric Cooperative (SMECO) and is currently out of service. The SMECO offsite power source is not used to carry loads for an operating unit.

The required TS offsite power circuits are the two 13.8 kV service buses (Nos. 11 and 21),

which can be powered by:

a. Three 500 kV lines, two 500 kV buses each of which have connections to a 500 kV line that does not pass through the other 500 kV bus and three P-13000 (500 kV/13.8 kV) transformers; or

b. One 500 kV line, one 500 kV bus, and one or two P-13000 (500 kV/13.8 kV) transformers, and the 69 kV/ 13.8 kV SMECO line. The SMECO line is not assumed to be available during the 2027 Unit 2 Refueling Outage.

Each offsite circuit includes the cabling to and from a 13.8/13.8 kV voltage regulator, 13.8/4.16 kV unit service transformer, and one of the two breakers to each 4.16 kV ESF bus. Transfer capability between the two required offsite circuits is by manual means only. The required circuit breaker to each 4.16 kV ESF bus must be from different 13.8/4.16 kV unit service transformers for the two required offsite circuits. Thus, each unit is able to align one 4.16 kV ESF bus to one required offsite circuit, and the other 4.16 kV ESF bus to the other required offsite circuit.

License Amendment Request Proposed One-Time Change to Technical Specification 3.8.3 Page 2 of 16 2.1.2 Onsite Circuit Electrical Distribution 4.16 kV System:

The AC sources to the Class 1E Electrical Power Distribution System consist of the offsite power sources starting at the 4.16 kV ESF buses and the onsite diesel generators (DGs). As required by 10 CFR 50 Appendix A, General Design Criteria (GDC) 17, the design of the AC electrical power system has sufficient independence and redundancy to ensure a source to the ESF buses assuming a single failure.

The Class 1E AC Distribution System is divided into two redundant load groups so that the loss of one group does not prevent the minimum safety functions from being performed. Each load group has connections to two offsite sources and one Class 1 EDG at its 4.16 kV 1E bus.

The 4.16 kV system is designed to function reliably and supply power during normal operation and under accident conditions. The system will supply power to the 4.16 kV auxiliary loads from the 13.8 kV system through the six-unit service transformers. There are six 4.16 kV buses per unit, two of which supply power to the ESF. The ESF electrical system incorporates the two-channel concept, i.e., independent electrical controls and power systems supply redundant 4.16 kV ESF systems. The 4.16 kV ESF electrical system meets the single failure criterion defined in IEEE 279, Section 4.2, and is designed as a Class 1E system.

Whenever offsite power is available, the 4.16 kV system is supplied by the 13.8 kV system.

Each 4.16 kV bus can be fed from either of two 13.8 kV sources of auxiliary power through different unit service transformers. Normally, Buses 11, 12, and 13 are fed from unit Service Transformer U-4000-11, Bus 14 from U-4000-21, Buses 21 and 22 from U-4000-12, Buses 23 and 24 from U-4000-22, Buses 15 and 16 from U-4000-13, and Buses 25 and 26 from U-4000-

23. Transfers, if required, are performed manually or, for Busses 12, 13, 15, 16, 22, 23, 25, and 26, automatic fast bus transfer schemes are installed. For 4.16 kV buses 12, 13, 15, and 16, an automatic (provided that permissives are met) fast bus transfer from the normal power source to the alternate power source will occur upon the loss of the normal power source. For 4.16 kV Buses 22, 23, 25 and 26, an automatic supervised bus transfer (fast transfer or in-phase transfer) from the normal power source to the alternate power source will occur upon the loss of the normal power source. Modifications planned to the site electrical distribution system may change the normal lineups and fast transfer schemes described above prior to implementation of the proposed change.

Two of the 4.16 kV buses for each unit (11 and 14 for Unit 1; 21 and 24 for Unit 2) supply power to the ESF systems. These four buses are considered the onsite Class 1E AC electrical power distribution system. The two buses feed redundant equipment. Each of the two buses per unit are supplied from separate EDGs. These buses are located in separate Seismic Category I rooms. Feeder cables from the EDGs and from ESF equipment are also located within Seismic Category I structures, and separation is maintained between the feeder cables of the two buses.

In the event of a loss of offsite power to a 4.16 kV ESF bus, if required, the ESF electrical loads will be automatically sequenced onto the EDG in sufficient time to provide for safe shutdown for an anticipated operational occurrence (AOO) and to ensure that the containment integrity and other vital functions are maintained in the event of a design bases accident.

License Amendment Request Proposed One-Time Change to Technical Specification 3.8.3 Page 3 of 16 The ESF buses are equipped with one set of under voltage sensing relays, and upon receipt of a two-out-of-four logic signal, the EDGs are energized to supply power.

2.1.3 Emergency Diesel Generators The EDGs are designed to furnish onsite power to reliably shut down the plant and maintain it in a safe shutdown condition under all conditions including accidents. Four safety-related EDGs (1A, 1B, 2A, 2B) are provided for the plant although each Unit requires only one EDG to supply the minimum power requirements for its ESF equipment. The Unit 1 4.16 kV ESF Buses are 11 and 14. The Unit 2 4.16 kV ESF Buses are 21 and 24. EDG 1A is connected to 4.16 kV ESF Bus 11, 1B is connected to 4.16 kV ESF Bus 14, 2A is connected to 4.16 kV ESF Bus 21, and 2B is connected to 4.16 kV ESF Bus 24.

The continuous service rating for the 1A EDG is 5400 kW and for the 1B, 2A, and 2B EDGs is 3000 kW. The EDG's capacities are tested routinely in accordance with TS and Surveillance Frequency Control Program (SFCP) requirements per STP-O-8A-1, 8B-1, 8A-2, 8B-2 (Reference 6.2).

The EDGs are automatically started by either a 4.16 kV bus Under Voltage (UV) or Safety Injection Actuation Signal (SIAS). However, in the latter case, actual transfer to the bus is not made until the preferred source of power is lost. When all four EDGs are available, the design provides power for two independent systems for safety injection, containment spray, and related 480 Volt auxiliary devices for the unit incurring the accident. In addition, it provides power to operate two sets of equipment for shutting down the non-accident unit.

During accident conditions accompanied by simultaneous loss of offsite power, the Loss of Coolant Incident (LOCI) sequencers start automatically to load the EDGs sequentially. Similarly, the shutdown sequencer for the non-accident unit loads the EDGs sequentially to maintain safe shutdown conditions. The sequencing is performed so that essential loads are started within the time limits of the appropriate safety analyses.

In addition, the non-safety related Station Blackout (SBO) diesel generator (also referred to as 0C DG or SBO diesel) is designed to provide a power source capable of starting and supplying the essential loads necessary to safely shutdown one unit and maintain it in a safe shutdown condition during an SBO event. The SBO diesel generator has the ability to supply any of the four ESF buses. The SBO Diesel is capable of supplying the same emergency loads as the EDGs.

The SBO diesel generator is started manually and is paralleled onto an ESF bus when it is determined that the EDG dedicated to that bus is not available to supply plant loads. The SBO diesel generator is connected to the onsite 4.16 kV ESF buses through a Class 1E breaker, a non-Class 1E breaker, and a Class 1E disconnect switch, all of which are normally open.

Operator action is required to isolate the safety related diesel generator (1A, 1B, 2A, or 2B EDG) dedicated to the ESF bus. The SBO diesel generator is then started manually, connected to the selected ESF bus (11, 14, 21 or 24), and automatically loaded using the load sequencer.

The SBO diesel generator is capable of powering a single safety-related train of equipment on one unit.

Regarding onsite fuel storage for EDGs, there are two (No. 11 and No. 21) fuel oil storage tanks

License Amendment Request Proposed One-Time Change to Technical Specification 3.8.3 Page 4 of 16 (FOSTs), each sized to hold 107,000 gallons of usable fuel oil that provide adequate fuel capacity, that supply fuel oil to the 1B, 2A, and 2B EDGs. The 1A EDG has a FOST (No. 1A) sized to hold 75,677 gallons of fuel. As described in the UFSAR (Reference 6.10), the design of the EDG fuel oil system is based on fuel oil capacity of seven days following a design basis accident, which assumes one EDG powering one unit under accident conditions (3500 kW) and one EDG powering the opposite unit under normal shutdown conditions (3000 kW) for seven days (or the time required to replenish fuel oil from an offsite source following a design basis event, whichever is longer).

Regarding the onsite fuel storage for the SBO Diesel, there are two fuel oil day tanks connected in series, that have a combined capacity sufficient to allow the SBO diesel to operate at 100%

nominal load, without fuel transfer to the day tanks, for a period of four hours. Replenishment of the fuel oil day tanks is accomplished using FOST 11.

In addition, as part of the response for EA-12-049, "Order Modifying Licenses with Regard to Requirements for Mitigating Strategies for Beyond Design-Basis External Events" (Reference 6.3), CCNPP has implemented a FLEX strategy that has made available the following additional onsite portable diesel generators for powering ESF equipment for extended loss of ac power (ELAP), loss of ultimate heat sink (LUHS) and beyond design basis external events (BDBEE):

Two (2) FLEX diesel generators 500 kW 480 V Four (4) FLEX diesel generators 100 kW 480 V The two on-site 500 kW and four on-site 100 kW 480 VAC FLEX DGs are available to power 480 VAC ESF buses for transitional phase (Phase 2) coping strategies.

Additionally, four portable 1 MW diesel generators are available offsite to power 4.16 kV safety buses for powering longer term (Phase 3) loads. All FLEX diesel generators include connecting devices and plant implementing procedures.

Regarding the onsite fuel storage capability for FLEX diesel generators, CCNPP uses two fuel tanker trucks to provide fuel to each of the FLEX diesel powered diesel generators. Procedure FSG-5, "Initial Assessment and FLEX Equipment Staging," (Reference 6.4) directs the operating crew to provide diesel fuel sources and refueling means to support the continuous operation of applicable FLEX equipment for an indefinite period.

The FLEX DGs will be used in accordance with existing approved procedures that implement and support Mitigating Strategies Order EA-12-049. No new activities (deployment, staging, timing and use of FLEX DGs) are being proposed for this LAR that have not already been NRC reviewed to support Mitigating Strategies Order EA-12-049.

During the extended 14-day CT, should an SBO event occur, procedures EOP-7-1, AOP-3B-2, or AOP-3F-2 (References 6.5, 6.6, and 6.12) would be used. If an SBO condition exists (SBO Diesel unavailable), an Extended Loss of AC Power (ELAP) would be declared one hour from the loss of all AC power. The FLEX Guidelines (FSG) would then be utilized to address the BDBEE. FSG-5, "Initial Assessment and FLEX Equipment Staging," has the major action and time frames that would be implemented for activities to be completed using the FLEX DGs.

License Amendment Request Proposed One-Time Change to Technical Specification 3.8.3 Page 5 of 16 2.1.4 Station Blackout (SBO) Description With the addition of a non-safety related diesel generator (0C DG) for SBO response, CCNPP is required to cope with an SBO for one hour, which is the maximum time assumed to start and load the non-safety-related SBO DG.

The CCNPP SBO scenario is as follows: Both units are at full power when offsite power is lost.

Only one unit is assumed to be in an SBO condition. Three EDGs fail to start. The fourth EDG starts and loads the shutdown loads for one unit. The other unit is in an SBO. Restoration of AC power after a blackout was assumed to be from an onsite diesel generator. This was because restoration of offsite sources could take in excess of four hours for major grid blackouts.

2.1.5 FOST 21 Inspection Description The planned Calvert Cliffs Unit 2 Reload 27 (CC2R27) outage scope includes required draining, cleaning, and inspection of FOST 21 in accordance with the sites Individual Oil Operations Permit 2023-OPT-2092 (Reference 6.1). Special condition I.A.9 of the permit requires that a minimum of 75% of the tank bottom plates shall be evaluated using magnetic flux leakage scanning and 100% of the floor plate welds and shell-to-floor wells shall be evaluated by an inspection technique other than visual inspection. The tank inspection requirements in the permit were updated to align with changes to Code of Maryland Requirements (COMAR)

Section 26.10.18.11H.

Diesel fuel oil (DFO) drained from FOST 21 will be stored in double-walled containers onsite in close proximity to the FOSTs. A hose will be staged and capable of connecting to refill FOST 21 in a timely manner. The Operations department will refill FOST 21 using the normally installed unloading pump when it is ready to be returned to service and will be prepared for refilling in the event of an emergency. The DFO will be filtered using the normally installed filter before returning to the tanks to ensure quality of the DFO. The Chemistry department will sample the DFO once returned to the tanks to ensure the fuel cleanliness meets required parameters.

It is estimated that the required draining, inspecting, and refilling of FOST 21 will take approximately ten days. The requested 14-day Completion Time includes some margin should the evolution take longer than expected, providing time to complete any necessary repairs, if required. Details of the planned 2027 inspection were provided in a letter to the Maryland Department of the Environment (Reference 6.8).

2.1.6 Defense-in-Depth (DID) Strategy The SBO Diesel has enough capacity on its own to simultaneously power accident loads on the operating unit and safe shutdown loads on the other unit. Furthermore, the FLEX diesel generators provide an added DID capability. They have adequate capacity to provide power during ELAP, LUHS and BDBEE events. There are existing procedures for all the equipment discussed, and operators have been trained and are familiar with the equipment. Work instructions, and associated training, briefings, and walkthroughs will be developed to provide additional DID for the proposed change as described in Section 3.

License Amendment Request Proposed One-Time Change to Technical Specification 3.8.3 Page 6 of 16 2.2 Current TS Requirements For Unit 2, the TS allow FOST 21 to have a fuel oil volume less than a 7 day supply for 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> either when not in MODES 1 through 4 or when not between April 1 and September 30, or both.

If FOST 21 fuel oil volume is not restored to a 7 day or more supply within 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br />, TS 3.8.3 Condition F, and Action F.1 would require Unit 2 EDGs (i.e., 2A and 2B EDGs) supported by FOST 21 be declared inoperable. Inoperability of the 2A and 2B EDGs during a Unit 2 Refuel Outage would require entry into Unit 2 Limiting Condition for Operation (LCO) 3.8.2 Condition B and Action B.1, which requires suspension of movement of irradiated fuel assemblies, and Action B.2, which requires suspension of operations involving positive reactivity additions that could result in loss of required SDM or boron concentration.

Inoperability of the 2A and 2B EDGs would also require entry into Unit 1 LCO 3.8.1 Condition E and Action E.1, which requires verification that both LCO 3.8.1.b EDGs are operable, the other unit's EDG is operable, and the 0C EDG is available within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />. Because both Unit 2 EDGs would be inoperable, Unit 1 LCO 3.8.1 Condition F would be entered, and Action F.1.1 would require one train of CREVS and CRETS be declared inoperable within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. Inoperability of one train of CREVS would require entry into LCO 3.7.8 Condition C, and Action C.1 would require restoration of the inoperable CREVS train within 7 days. If the inoperable CREVS train were not restored within 7 days, LCO 3.7.8 Condition G would require Unit 1 to be in MODE 3 in 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and MODE 5 in 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />. The total time from the lowering of FOST 21 fuel volume to less than a 7-day supply to requiring Unit 1 to be in MODE 3 would be approximately 12 days.

License Amendment Request Proposed One-Time Change to Technical Specification 3.8.3 Page 7 of 16 2.3 Proposed Change The required actions and completion times for TS LCO 3.8.3, Condition C, will be updated on TS Page 3.8.3-3:

1. Update action C.3 to C.3.1.

2. Allow either existing action C.3.1 (renumbered from action C.3) OR the following new C.3.2 actions as follows:

---

NOTE ------

Required Actions C.3.2.1, C.3.2.2, and C.3.2.3 are allowed only when all of the following are true:

1. Unit 2 is in MODE 5 or 6, or is defueled.

2. Actions are performed between October 1 and March 31.

3. Performance of actions is once and in support of FOST 21 required state inspection and associated maintenance activities during the Unit 2 2027 Refuel Outage.

4. Compensatory measures specified within Attachment 2 to the Constellation Energy Generation, LLC letter dated October 30, 2025, are in place.

C.3.2.1 Verify available fuel oil volume of OPERABLE FOST 11 greater than or equal to a 7-day supply. (1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> AND once per 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> thereafter)

AND C.3.2.2

---

NOTE ------

Only applicable while in standby.

Verify required DG day tank contains at least a 1-hour supply of fuel oil. (1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> AND once per 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> thereafter)

AND C.3.2.3 Restore FOST 21 fuel oil volume to within limits. (14 days)

The proposed change is shown in the TS Markup in Attachment 3.

Surveillance Requirements (SRs) associated with other in-service but protected equipment were reviewed. Any impacts due to the requested change will be managed by the SFCP.

License Amendment Request Proposed One-Time Change to Technical Specification 3.8.3 Page 8 of 16

3.0 TECHNICAL EVALUATION

The Technical Evaluation examined the impacts to the Plant Safety Analysis, and the Risk Analysis from a one-time extension of the CT for FOST 21 inoperable to 14 days.

3.1 Safety Analysis There are two principal design criteria for the FOSTs: (1) design basis accident requirements, and (2) requirements for protection against external phenomena such as earthquakes and tornadoes. A tornado/missile event is not assumed to occur simultaneously with a design basis accident (LOCA).

The design of the EDG fuel oil system is based on a fuel oil capacity of seven days following a design basis accident. Specifically, IEEE-308 requires that, for multiunit stations, sufficient fuel oil be available to run one EDG powering one unit under accident conditions (3,500 kW) and one EDG powering the opposite unit under normal shutdown conditions (3,000 kW) for seven days (or the time required to replenish fuel oil from an offsite source following a design basis event, whichever is longer). The specific emergency diesel generator fuel oil volumes (equivalent to duration based requirements) contained in the fuel oil storage tanks referenced in Technical Specification 3.8.3 and the day tanks referenced in Technical Specification 3.8.1 are calculated using the method provided in American National Standards Institute N195-1976, Section 5.4, as endorsed by Regulatory Guide 1.137, Revision 1, Section C.1.c. The fuel oil calculation is based on applying the conservative assumption that the emergency diesel generator is operated continuously at rated capacity. This is one of two approved methods specified in Regulatory Guide 1.137, Revision 1. FOST 11 and FOST 21 each contain a volume of fuel oil in excess of that needed to satisfy this requirement. The minimum required volume under design basis accident conditions (LOCA) and tornado/missile conditions is in the Technical Specifications and is controlled administratively.

Although protection against earthquakes was an original design criterion for the FOSTs, protection against tornadoes was not. In 1972 (during construction of CCNPP Units 1 and 2), the decision was made to protect FOST 21 from tornadoes and horizontal tornado missiles by adding a Seismic Category I concrete enclosure. Bursting pressures are relieved by baffled, missile proof vents. This structure will also withstand the impact of a transmission tower falling on it without damage to the FOST. The enclosure also acts as a dike for FOST 21 with fuel being supplied by way of a non-safety-related line. In the event of a tornado, only FOST 21 is credited.

It is assumed that one Fairbanks Morse diesel on each unit would be loaded to 3,000 kW. Thus, the minimum fuel oil requirement is somewhat less than that required under design basis accident conditions. The minimum Technical Specification volume maintained for these conditions in FOST 21 is the same as that required under design basis accident conditions.

Since FOST 21 is a support system for the EDGs, removal of the FOST from service would normally render the system inoperable and result in the associated EDG being declared inoperable after 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> during the period FOST 21 will be out-of-service for inspection. During this period, FOST 11 will be available to supply fuel oil to the Unit 2 (2A and 2B) EDGs. Because FOST 11 is not tornado protected, work instructions will be developed to refuel FOST 21 using the temporarily offloaded fuel oil in the event that FOST 11 is unavailable during the extended CT. The proposed change limits implementation of the extended CT to the time of year when tornadoes are less likely and ensures predicted weather conditions are evaluated and included

License Amendment Request Proposed One-Time Change to Technical Specification 3.8.3 Page 9 of 16 in the risk assessment of the scheduled inspection activities. These compensatory measures will ensure a very low likelihood exists for a tornado event that could cause a loss of FOST 11 during the extended CT.

As detailed in Section 3.2, Risk Assessment Insights and Compensatory Measures, CCNPP will protect and restrict planned maintenance on FOST 11, DG 0C, at least one Unit 2 EDG (2A or 2B), and associated support systems to ensure they remain operable while FOST 21 is drained for inspection. Although FOST 11 is not tornado protected, the risk assessment and compensatory measures in Section 3.2 support the use of FOST 11 as acceptable to supply the Unit 2 EDGs when the requirements of the proposed amended TS are met. Additional compensatory measures protect and restrict planned maintenance on other equipment important to offsite or onsite power reliability.

If, during the extended CT, an unforeseen circumstance causes the inability to complete the inspection within 14 days or maintain the required compensatory measures with FOST 21 drained, the site will follow TS 3.8.3 Action F.1 to immediately declare the associated EDGs inoperable.

3.2 Risk Assessment Insights and Compensatory Measures This proposed license amendment is not a risk-informed request; therefore, a risk evaluation is not required. However, to provide additional information, CCNPP is providing risk insights (Reference 6.7) related to the proposed change.

A qualitative assessment was performed to determine whether the requested 14-day CT could cause a significant increase in Core Damage Frequency (CDF) or Large Early Release Frequency (LERF). The determination of not risk significant is based on a review of the inspection activities that determines that the activity a) does not impact the availability of the diesel generators, and b) introduces essentially no change in the plant configuration due to implementation of adequate compensatory measures. From a qualitative perspective, the risk associated with the inspection/repair of FOST 21 is not risk-significant for the following reasons:

Adequate supply of diesel fuel oil is stored in FOST 11 which will be aligned prior to drain down and maintenance activities of FOST 21. Probabilistic risk assessments for Internal Events hazards analyze an exposure window of 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.

There is no increase in Fire CDF since the offloaded diesel fuel oil is planned to be stored away from mitigation systems credited in the PRA in accordance with Nuclear Electric Insurance Limited Loss Control Manual Standard 3.2.27 (Reference 6.11).

The inspection activity does not introduce any new accidents that may impact CDF or LERF.

There is no impact to Unit 2 EDG availability since they will be aligned to FOST 11.

There is no impact to EDG success criteria due to the inspection activities for FOST 21.

No new common cause failure modes are introduced and no increase in the likelihood of existing common cause failure modes have been identified.

The activity would not impact the defense in depth of functions credited in the Outage Shutdown Safety Plan (Reference 6.9) for the applicable Unit 2 outage.

In the event of a prolonged LOOP, additional fuel oil would be available on-site from the temporary storage tanks. Therefore, the risk impact of the proposed extension due to

License Amendment Request Proposed One-Time Change to Technical Specification 3.8.3 Page 10 of 16 the impacts to the EDGs is considered to be insignificant, since the fuel oil could still be supplied to each of the EDGs, which is the only function of the main fuel oil storage tank for the EDGs in the Internal Events and Fire PRA model.

Additional defense in depth is provided by FLEX. All FLEX diesel generators include connecting devices and plant implementing procedures. Regarding the onsite fuel storage capability for FLEX diesel generators, CCNPP uses two mobile fuel tanker trucks to provide fuel to each of the FLEX diesel powered diesel generators. Procedure FSG-5, "Initial Assessment and FLEX Equipment Staging," directs the operating crew to provide diesel fuel sources and refueling means to support the continuous operation of applicable FLEX equipment for an indefinite period.

CCNPP will have an approved Shutdown Safety Plan prior to commencing inspection activities to ensure adequate defense in depth for key safety functions are maintained.

The inspection activities are planned during the 2027 Unit 2 Refueling Outage, which is scheduled for the February-March timeframe. Thunderstorms, hurricanes, and other tornado/high winds related events are not frequent but possible during this time. The temporary DFO storage tanks are made of a double-wall design but are not considered missile protected.

The FOST 11 is also not protected from tornadoes. CCNPP will consider the potential for inclement weather, such as hurricanes, thunderstorms and ice storms, in the risk assessment of the scheduled inspection and repair activities. The assessment will consider contingencies needed to restore the tank and refill the inventory if inclement weather poses an imminent threat to the long-term availability of offsite power.

In conclusion, these activities do not cause a significant increase in CDF or LERF. Therefore, extending the Completion Time to 14 days is acceptable on a one-time basis given compensatory measures are implemented prior to and during the inspection activities as specified in Attachment 2.

4.0 REGULATORY EVALUATION

4.1 Applicable Regulatory Requirements/Criteria The proposed change has been evaluated to determine whether applicable regulations and requirements continue to be met. CCNPP was not licensed to the General Design Criteria (GDCs) listed in 10 CFR Part 50, Appendix A, but was licensed based on the Atomic Energy Commission (AEC) proposed Principal Design Criteria (PDCs) published on July 10, 1967. The relevant principal design criteria for CCNPP are described in Appendix 1C of the CCNPP UFSAR. CEG has determined that the proposed change does not require any exemptions or relief from the following current applicable regulations and regulatory requirements, which were reviewed in making this determination:

10 CFR 50.36, Technical Specifications 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 shall shut down the reactor or follow any remedial action permitted by the technical specifications until the condition can be met."

License Amendment Request Proposed One-Time Change to Technical Specification 3.8.3 Page 11 of 16 The proposed change involves an extension of the allowed outage time for FOST 21 under limited circumstances and on a one-time basis. The LCOs themselves remain unchanged, as do the shut down requirements in accordance with 10 CFR 50.36.

Additional required remedial actions are established, under certain conditions, as described in Sections 2.3 and 3 to ensure the proposed change will not reduce the functional capability or performance levels of the EDGs below what is required for safe operation of the facility. 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 CCNPP's compliance with the intent of 10 CFR 50.36.

10 CFR 50.63, Loss of all alternating current 10 CFR 50.63 requires that light water-cooled nuclear power plants licensed to operate be able to withstand for a specified duration and recover from a station blackout (SBO).

The station blackout diesel (0C) is fueled from FOST 11, which is not impacted by the proposed change. The proposed change does not alter CCNPP's duration (coping time) or affect its compliance with the intent of 10 CFR 50.63.

10 CFR 50.65, Requirements for monitoring the effectiveness of maintenance at nuclear power plants 10 CFR 50.65 requires that when performing maintenance activities (including but not limited to surveillance, post-maintenance testing, and corrective and preventive maintenance), the licensee shall assess and manage the increase in risk that may result from the proposed maintenance activities. The scope of the assessment may be limited to structures, systems, and components that a risk-informed evaluation process has shown to be significant to public health and safety. The maintenance activities associated with this change will be assessed and the increased risk will be managed in accordance with 10 CFR 50.65 (a)(4).

The proposed change does not affect CCNPP's compliance with the intent of 10 CFR 50.65.

Regulatory Guide 1.137, Revision 1, Fuel Oil Systems for Standby Diesel Generators Regulatory Guide (RG) 1.137 indicates that the requirements for the design of fuel-oil systems for diesel generators that provide standby electrical power included in ANSI N195-1976, "Fuel Oil Systems for Standby Diesel-Generators," provide a method acceptable to the NRC staff for complying with the pertinent requirements of General Design Criterion (GDC) 17, Electric power systems (similar in part to UFSAR Appendix 1C Criteria 24, Emergency Power for Protection Systems, and 39, Emergency Power for Engineered Safety Features). RG 1.137 provides a discussion of the two methods for calculation of fuel oil storage requirements set forth in Section 5.4 of ANSI N195-1976.

The two methods are (1) calculations based on the assumption that the diesel generator operates continuously for 7 days at its rated capacity, and (2) calculations based on the time-dependent loads of the diesel generator. For the time-dependent load method, the minimum required capacity should include the capacity to power the engineered safety features.

License Amendment Request Proposed One-Time Change to Technical Specification 3.8.3 Page 12 of 16 Fuel oil storage volume and quality will continue to be determined in accordance with RG 1.137.

The proposed change does not affect CCNPP's compliance with the intent of RG 1.137.

UFSAR Appendix 1C Criterion 2, Performance Standards (Similar to GDC 2, Design bases for protection against natural phenomena)

UFSAR Appendix 1C Criterion 2 requires that those systems and components of reactor facilities which are essential to the prevention of accidents which could affect the public health and safety or to mitigation of their consequences be designed, fabricated, and erected to performance standards that will enable the facility to withstand, without loss of the capability to protect the public, the additional forces that might be imposed by natural phenomena such as earthquakes, tornadoes, flooding conditions, winds, ice, and other local site effects. The design bases so established shall reflect: (a) appropriate consideration of the most severe of these natural phenomena that have been recorded for the site and the surrounding area and (b) an appropriate margin for withstanding forces greater than those recorded to reflect uncertainties about the historical data and their suitability as a basis for design.

The proposed change does not alter the plant design. The current TS allow crediting FOST 11 fuel oil volume for a limited time in place of or in addition to the FOST 21 fuel oil volume, with the allowed FOST 21 outage time varying based on plant and environmental conditions. The proposed change modifies TS to include an additional FOST 21 allowed outage time, under limited circumstances, on a one-time basis, and with appropriate compensatory measures in place, for the temporary draining of FOST 21 for the purposes of cleaning, inspection, and repair, as necessary, to ensure it is maintained in accordance with state requirements as a reliable source of diesel fuel oil for the EDGs.

The proposed change does not affect CCNPP's compliance with the intent of UFSAR Appendix 1C Criterion 2.

UFSAR Appendix 1C Criterion 24, Emergency Power for Protection Systems, and Criterion 39, Emergency Power for Engineered Safety Features (Similar to GDC 17, Electric power systems and GDC 18, Inspection and testing of electric power systems)

UFSAR Appendix 1C Criterion 24 requires that in the event of loss of all offsite power, sufficient alternate sources of power be provided to permit the required functioning of the protection systems.

UFSAR Appendix 1C Criterion 39 requires that an alternate power system be provided and designed with adequate independency, redundancy, capacity, and testability to permit the functioning required of the engineered safety features. As a minimum, the onsite power system and the offsite power system shall each, independently, provide this capacity assuming a failure of a single active component in each power system.

The proposed change does not alter the plant design. The proposed change modifies TS, under limited circumstances, on a one-time basis, and with appropriate compensatory measures in place, to allow the temporary draining of FOST 21 for the

License Amendment Request Proposed One-Time Change to Technical Specification 3.8.3 Page 13 of 16 purposes of cleaning, inspection, and repair, as necessary, to ensure it is maintained in accordance with state requirements as a reliable source of diesel fuel oil for the EDGs.

The proposed change does not affect CCNPP's compliance with the intent of UFSAR Appendix 1C Criteria 24 and 39.

4.2 Precedent The following precedents are applicable to this submittal in that the U.S. NRC previously granted other licensees similar extensions to FOST CTs on a one-time basis.

1. Letter from Thomas J. Byrd (U.S. NRC) to John Dent, Jr. (Nebraska Public Power District), Cooper Nuclear Station - Issuance of Amendment No. 276 Regarding Revision to Technical Specification 3.8.3, Diesel Fuel Oil, Lube Oil, and Starting Air, to Allow for Cleaning, Inspection and Any Needed Repairs during Refuel Outage 33 (EPID L-2023-LLA-0126), dated July 3, 2024 (ADAMS Accession No. ML24134A178).

2. Letter from Michelle C. Honcharik (U.S. NRC) to Mr. Randall K. Edington (Nebraska Public Power District), Cooper Nuclear Station - Issuance of Amendment RE: One-Time Extension of Diesel Generator Allowed Outage Time from 7 Days to 14 Days (TAC No.

MC3770), dated October 15, 2004 (ADAMS Accession No. ML042920532).

3. Letter from Robert F. Kuntz (U.S. NRC) to Mr. Christopher P. Domingos (Northern States Power Company - Minnesota), Monticello Nuclear Generating Plant - Issuance of Amendment No. 209 RE: 10-Year Inspection of the Diesel Generator Fuel Oil Storage Tank (EPID L-2021-LLA-0231), dated December 27, 2022 (ADAMS Accession No. ML22318A215).

4. Letter from Dennis J. Galvin (U.S. NRC) to Mr. William R. Gideon (Duke Energy Progress, LLC), Brunswick Steam Electric Plant, Units 1 and 2 - Issuance of Amendment Nos. 290 and 318 to Revise Note on Brunswick TS 3.8.3 for One-Time Extension of Main Fuel Oil Storage Tank Completion Time (EPID L-2018-LLA-0110),

dated May 6, 2019 (ADAMS Accession No. ML19018A206).

5. Letter from Stewart N. Bailey (U.S. NRC) to Mr. James Scarola (Carolina Power & Light Company), Brunswick Steam Electric Plant, Units 1 and 2 - Issuance of Amendment Related to Main Fuel Oil Storage Tank (TAC Nos. MD3305 and MD3306), dated September 27, 2007 (ADAMS Accession No. ML072600327).

4.3 No Significant Hazards Consideration Constellation Energy Generation, LLC (CEG), proposes a change to the Technical Specifications (TS) of Renewed Facility Operating License No. DPR-69 for Calvert Cliffs Nuclear Power Plant (CCNPP), Unit 2.

The proposed change is a one-time extension to the TS 3.8.3, Diesel Fuel Oil, Condition C Completion Time (CT) for Fuel Oil Storage Tank (FOST) 21 to allow the FOST to be out-of-service for the required Maryland state inspection and any associated maintenance of the tank during the 2027 Unit 2 Refueling Outage for up to 14 days. The inspection and associated maintenance cannot be accomplished within the TS CT of 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br />.

CEG has evaluated whether or not a significant hazards consideration is involved with the proposed amendment by focusing on the three standards set forth in 10 CFR 50.92, Issuance

License Amendment Request Proposed One-Time Change to Technical Specification 3.8.3 Page 14 of 16 of amendment, as discussed below:

1.

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

Response: No.

The proposed change will allow an extended out-of-service time for FOST 21 for the completion of the state required inspection and associated maintenance activities. FOST 21 is a support system for the EDGs, which are designed to furnish onsite power to reliably shut down the plant and maintain it in a safe shutdown condition under all conditions including accidents. Since the EDGs are not accident initiators, the probability of occurrence of accidents previously analyzed will not be increased by the proposed change.

The proposed amendment will not change the function of the equipment assumed in the plant safety analyses for accident mitigation. Initial conditions will be met and compensatory measures will be taken prior to removing FOST 21 from service. With FOST 21 drained, FOST 11 ensures that at least seven days of fuel oil will be available for operation of one diesel generator (DG) on each unit, assuming one unit under accident conditions with a DG load of 3500 kW, and the opposite unit under normal shutdown conditions with a DG load of 3000 kW. The allowance to permit internal inspection of FOST 21 while Unit 2 is in MODE 5 or 6, or is defueled, and Unit 1 is operating does not impact the availability of the Emergency Diesel Generators (EDGs) to perform their intended safety function.

Unlike FOST 21, FOST 11 is not tornado protected. The risk assessment and compensatory measures support the use of FOST 11 as acceptable to supply the Unit 2 EDGs when the requirements of the proposed amended TS are met. While FOST 21 is out of service, the availability of other fuel oil sources, along with required compensatory measures, ensure that an adequate supply of fuel oil remains available. The proposed change does not cause a significant increase in CDF or LERF.

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

2.

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

Response: No.

Creation of the possibility of a new or different kind of accident requires creating one or more new accident precursors. New accident precursors may be created by modifications of plant configuration, including changes in allowable modes of operation.

The proposed change does not involve a physical change to the design of the Diesel Fuel Oil system, nor does it alter the assumptions of the accident analyses. The diesel fuel oil drained from FOST 21 is planned to be stored away from mitigation systems credited in the Fire PRA. The allowance to permit internal inspection of FOST 21, which

License Amendment Request Proposed One-Time Change to Technical Specification 3.8.3 Page 15 of 16 is tornado protected, and use FOST 11, which is not tornado protected, for the extended period does not introduce any new failure modes.

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 proposed change does not alter the method of operation of the Diesel Fuel Oil system. The current TS allow crediting FOST 11 fuel oil volume for a limited time in place of or in addition to the FOST 21 fuel oil volume, with the allowed FOST 21 outage time varying based on plant and environmental conditions. The proposed change modifies TS to include an additional FOST 21 allowed outage time, under limited circumstances, on a one-time basis, and with appropriate compensatory measures in place, for the temporary draining of FOST 21 for the purpose of inspection to ensure it is maintained in accordance with state requirements as a reliable source of diesel fuel oil for the EDGs. The availability of the EDGs to perform their intended safety function is not impacted and the assumptions of the accident analyses are not altered. A slight reduction in the margin of safety is incurred during the proposed extended CT due to the increased risk that an event could occur in a 14-day period versus a 48-hour period. The event of concern differentiating use of FOST 21 and FOST 11 is a tornado event. This increased risk is judged to be minimal because the proposed change does not impact the availability of the diesel generators and introduces essentially no change in the plant configuration due to implementation of adequate compensatory measures.

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

Based on the above, CEG concludes that the proposed amendment presents no 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.

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

License Amendment Request Proposed One-Time Change to Technical Specification 3.8.3 Page 16 of 16 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

6.1 Calvert Cliffs Nuclear Power Plant, LLC, Individual Oil Operations Permit No. 2023-OPT-2092, dated July 25, 2025.

6.2 STP-O-8A-1, Test of the 1A DG AND 11 4KV BUS UV," Revision 40A, and 8B-1 (Revision 40), 8A-2 (Revision 38), 8B-2 (Revision 39) for 1B, 2A and 2B EDG respectively.

6.3 Exelon Letter RS-16-141, James Barstow to U.S. NRC, "Revised Final Integrated Plan Document - Mitigating Strategies NRC Order EA-12-049, dated August 9, 2016.

6.4 Procedure FSG-5, "Initial Assessment and FLEX Equipment Staging," Revision 3.

6.5 Procedure EOP-7-1, "Station Blackout," Revision 21.

6.6 Procedure AOP-3B-2, "Abnormal Shutdown Cooling Conditions," Revision 29.

6.7 CA-LAR-023, Risk Assessment Input for Calvert Cliffs Diesel Fuel Oil Technical Specification Change, Revision 0.

6.8 Constellation Letter to Chris Ralston and Brad Barzin (Maryland Department of the Environment) from Larry D. Smith (Constellation), Calvert Cliffs Nuclear Power Plant API 653 Out-of-Service tank inspections for the 11, 21, and 1A Fuel Oil Storage Tanks, dated September 23, 2025.

6.9 Procedure OU-AA-103, Shutdown Safety Management Program, Revision 24.

6.10 Calvert Cliffs Updated Final Safety Evaluation Report, Revision 54.

6.11 Nuclear Electric Insurance Limited Loss Control Manual, January 2025 Edition.

6.12 Procedure AOP-3F-2, "Loss of Offsite Power While in Modes 3, 4, 5, or 6," Revision 18.

ATTACHMENT 2 License Amendment Request Calvert Cliffs Nuclear Power Plant, Unit 2 Renewed Facility Operating License No. DPR-69 NRC Docket No. 50-318 Fuel Oil Storage Tank 21 Extended Completion Time Compensatory Measures

License Amendment Request Proposed One-Time Change to Technical Specification 3.8.3 Page 1 of 1 Fuel Oil Storage Tank 21 Inoperable Extended Completion Time Compensatory Measures Description Due Date / Event

1.

Develop approved work instructions to restore temporarily off-loaded diesel fuel oil to Fuel Oil Storage Tank (FOST) 21.

Prior to removing FOST 21 from service.

2.

Provide, in accordance with station procedures, training, briefings, and walkthroughs to implement the approved work instructions.

Prior to removing FOST 21 from service.

3.

Develop an approved Shutdown Safety Plan to ensure adequate defense in depth for key safety functions are maintained and identify additional required protected equipment.

Prior to removing FOST 21 from service.

4.

Establish the required initial conditions and equipment alignment to FOST 11.

Prior to removing FOST 21 from service.

5.

Administratively verify availability of at least 1 FLEX diesel generator 500 kW 480 V, at least 1 FLEX diesel generator 100 kW 480 V, and at least 1 FLEX diesel fuel tanker truck.

Prior to removing FOST 21 from service and while FOST 21 is inoperable.

6.

Consider the potential for inclement weather, such as hurricanes, thunderstorms and ice storms, in the risk assessment of the scheduled inspection and repair activities. The assessment will consider contingencies needed to restore the tank and refill the inventory if inclement weather poses an imminent threat to the long-term availability of offsite power.

Prior to removing FOST 21 from service and while FOST 21 is inoperable.

7.

Protect FOST 11, DG 0C, at least one Unit 2 EDG (2A or 2B), and associated support systems in accordance with approved procedures.

Prior to removing FOST 21 from service and while FOST 21 is inoperable.

8.

Protect at least 2 of the 3 500 kV transmission lines and notify Transmission Service Operator in accordance with approved procedures. Elective switchyard activities and other elective on-site electrical maintenance that could cause any unstable offsite or on-site power conditions will not be scheduled.

Prior to removing FOST 21 from service and while FOST 21 is inoperable.

9.

Protect at least 1 of the 2 13.8 kV service buses, and associated support systems, capable of providing offsite power to Unit 2 4.16 kV Engineered Safety Feature (ESF) buses in accordance with approved procedures.

Prior to removing FOST 21 from service and while FOST 21 is inoperable.

10.

Protect at least 1 of the 2 Unit 2 4.16 kV ESF buses, and associated support systems, in accordance with approved procedures.

Prior to removing FOST 21 from service and while FOST 21 is inoperable.

ATTACHMENT 3 License Amendment Request Calvert Cliffs Nuclear Power Plant, Unit 2 Renewed Facility Operating License No. DPR-69 NRC Docket No. 50-318 Proposed Technical Specification Change (Markup)

TS Page 3.8.3-3

Diesel Fuel Oil 3.8.3 CALVERT CLIFFS - UNIT 1 3.8.3-3 Amendment No. 306 CALVERT CLIFFS - UNIT 2 Amendment No. 284 ACTIONS (continued)

CONDITION REQUIRED ACTION COMPLETION TIME C.

---

NOTE-------

Only applicable to Unit 2.

FOST 21 with fuel oil volume less than a 7 day supply.

C.1 Verify combined available fuel oil volume of FOST 21 and OPERABLE FOST 11 greater than or equal to a 6 day supply.

AND C.2

---

NOTES ------

1.

Only applicable during MODE 1, 2, 3, or 4.

2.

Only applicable between April 1 and September 30.

Restore FOST 21 fuel oil volume to within limits.

AND C.3 Restore FOST 21 fuel oil volume to within limits.

1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> 2 hours 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> D.

One or more DGs with stored fuel oil total particulates not within limits.

D.1 Restore fuel oil total particulates to within limits.

7 days C.3.1 Add Insert 1 as part of Condition C

Insert 1 OR

---

NOTE ------

Required Actions C.3.2.1, C.3.2.2, and C.3.2.3 are allowed only when all of the following are true:

1. Unit 2 is in MODE 5 or 6, or is defueled.

2. Actions are performed between October 1 and March

31.

3. Performance of actions is once and in support of FOST 21 required state inspection and associated maintenance activities during the Unit 2 2027 Refuel Outage.

4. Compensatory measures specified within Attachment 2 to the Constellation Energy Generation, LLC letter dated October 30, 2025, are in place.

C.3.2.1 Verify available fuel oil volume of OPERABLE FOST 11 greater than or equal to a 7-day supply.

AND C.3.2.2 ------ NOTE ------

Only applicable while in standby.

Verify required DG day tank contains at least a 1-hour supply of fuel oil.

AND C.3.2.3 Restore FOST 21 fuel oil volume to within limits.

1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> AND once per 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> thereafter 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> AND once per 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> thereafter 14 days

ATTACHMENT 4 License Amendment Request Calvert Cliffs Nuclear Power Plant, Unit 2 Renewed Facility Operating License No. DPR-69 NRC Docket No. 50-318 Proposed Technical Specification Bases Change (Markup) (For Information Only)

TS Bases Pages B 3.8.3-3 B 3.8.3-4 B 3.8.3-5 B 3.8.3-6 B 3.8.3-9

Diesel Fuel Oil B 3.8.3 BASES CALVERT CLIFFS - UNITS 1 & 2 B 3.8.3-3 Revision 49 is required to be within limits when the associated DG is required to be OPERABLE.

For both Unit 1 and Unit 2, the FOST No. 1A associated DG is only DG No. 1A. For Unit 1, the FOST No. 21 associated DGs are DG Nos. 1B and 2B. For Unit 2, the FOST No. 21 associated DGs are DG Nos. 2A and 2B. Alignment does not affect the association of DG and FOST since the individual DG fuel oil day tank provides sufficient volume for the DG to perform its safety function while re-alignment is accomplished, if necessary.

ACTIONS The ACTIONS Table is modified by a Note indicating that separate Condition entry is allowed for each DG. This is acceptable, since the Required Actions for each Condition provide appropriate compensatory actions for each inoperable DG subsystem. Complying with the Required Actions for one inoperable DG subsystem may allow for continued operation, and subsequent inoperable DG subsystem(s) are governed by separate Condition entry and application of associated Required Actions.

A.1, B.1, B.2, C.1, C.2, and C.3 In this Condition, the seven day fuel oil supply for a DG is not available. However, fuel oil volume reduction is limited to 6/7 of the required volume which will provide sufficient capacity to operate one DG on one unit on accident loads, and one DG on the other unit on shutdown loads for approximately six days. The fuel oil level ensuring a six day supply is 42,430 gallons (FOST No. 1A) and 72,860 gallons (FOST No. 11, FOST No. 21). These circumstances may be caused by events such as full load operation required after an inadvertent start while at minimum required level; or feed and bleed operations, which may be necessitated by increasing particulate levels or any number of other oil quality degradations. This restriction allows sufficient time for obtaining the requisite replacement volume and performing the analyses required prior to addition of fuel oil to the tank. A period of 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> is considered sufficient to complete restoration of the required level prior to declaring the DG inoperable.

This period is acceptable based on the remaining capacity (approximately six days), the fact that procedures will be C.3.1, C.3.2.1, C.3.2.2, and C.3.2.3

Diesel Fuel Oil B 3.8.3 BASES CALVERT CLIFFS - UNITS 1 & 2 B 3.8.3-4 Revision 49 initiated to obtain replenishment, and the low probability of an event during this brief period.

Condition A addresses only FOST No. 1A which is tornado protected and which contains sufficient fuel for seven days of required operation of DG No. 1A. It supports both Unit 1 and Unit 2 equipment since DG No. 1A provides power for equipment which is shared by both units, e.g., the CREVS.

Condition B addresses only FOST No. 21 which is tornado protected and which contains sufficient fuel for seven days of required operation of two DGs. Fuel Oil Storage Tank No. 21 supports both Unit 1 and Unit 2 equipment, but Condition B is written for Unit 1 only to reflect the Unit 1 requirements for DG Nos. 1B and 2B. For an accident, Unit 1 requires either DG No. 1A or both DG Nos. 1B and 2B (since DG No. 2B powers equipment which is redundant to some equipment powered by DG No. 1A, e.g., CREVS). Since DG No. 1A is supported by FOST No. 1A and the redundant required equipment is powered by DG Nos. 1B and 2B which are supported by FOST No. 21, at least one full train of required equipment is supported by a tornado protected FOST even with an inoperable FOST or DG. Therefore, low fuel oil volume in FOST No. 21 can be supplemented by the fuel oil volume of an OPERABLE FOST No. 11 to assure the necessary volume. Required Action B.1 requires the combined volume of FOST No. 21 and an OPERABLE FOST No. 11 to be verified to be greater than 6/7 of the required volume within one hour. The Completion Time of one hour is consistent with the time needed to verify through administrative means that the backup FOST is OPERABLE.

Required Action B.2 requires the combined volume of FOST No. 21 and an OPERABLE FOST No. 11 to be 85,000 gallons within 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br />. In addition, if FOST No. 21 is not restored and FOST No. 11 continues to be relied upon, Required Action B.2 must be repeated every 31 days. This effectively replaces the SR 3.8.3.1 periodic surveillance of available DG fuel oil volume for the inoperable FOST No. 21.

Since FOST No. 11 is not required by the LCO, FOST No. 11 may be considered OPERABLE only when the stored fuel oil meets SR 3.8.3.2 and SR 3.8.3.3, and is capable of being delivered to the required DG, i.e., the necessary piping and valves are capable of performing their safety function.

Insert 1

Insert 1:

For FOST No. 21 only, under limited circumstances, and with appropriate initial and ongoing compensatory measures in place, an extended period of 14 days is considered sufficient to complete restoration of the required level prior to declaring the DG inoperable. This period is acceptable based on the required capacity remaining in FOST No. 11 (at least 7 days), the requirement for Unit 2 to be in MODE 5, 6, or defueled, the low probability of an event during this brief period, and additional compensatory measures required to remain in place during this period.

Diesel Fuel Oil B 3.8.3 BASES CALVERT CLIFFS - UNITS 1 & 2 B 3.8.3-5 Revision 2 Specific alignment to a particular FOST is not required since the individual DG fuel oil day tank provides sufficient volume for the DG to perform its safety function while re-alignment is accomplished, if necessary. Further, if any fuel oil in FOST No. 11 above the 33,000 gallons reserved for emergency DG use is credited for DG use, appropriate administrative controls must be in place to assure its retention for this purpose.

Condition C also addresses only FOST No. 21 which is tornado protected and which contains sufficient fuel for seven days of required operation of two DGs. Fuel Oil Storage Tank No. 21 supports both Unit 1 and Unit 2 equipment, but Condition C is written for Unit 2 only to reflect the Unit 2 requirements for DG Nos. 2A and 2B. For an accident, Unit 2 requires either DG No. 2B or both DG Nos. 1A and 2A (since DG No. 1A powers equipment which is redundant to some equipment powered by DG No. 2B, e.g., CREVS). Unlike Unit 1, at least one full train of required equipment is not supported by a tornado protected FOST with an inoperable FOST or DG since most of the redundant required equipment is powered by DG Nos. 2A and 2B which are both supported by FOST No. 21. Therefore, low fuel oil volume in FOST No. 21 can only be supplemented by the fuel oil volume of an OPERABLE FOST No. 11 to assure the necessary volume when the probability for a tornado is sufficiently low. This is reflected in Note 2 for Required Action C.2 which addresses the inoperability of FOST No. 21 from April 1 to September 30. During the time of low tornado probability, the Unit 2 requirements for the inoperability of FOST No. 21 are very similar to the Unit 1 requirements for inoperability of FOST No. 21. It is acceptable for the combined volume of FOST No. 11 and FOST No. 21 to be considered in providing 6/7 of the required volume for the 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> allowed by Required Action C.3.1.

Required Action C.1 requires the combined volume of FOST No. 21 and an OPERABLE FOST No. 11 to be verified to be greater than 6/7 of the required volume within one hour.

Required Action C.3 then requires the volume of FOST No. 21 to be restored to within volume limits within 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br />.

However, during tornado season, i.e., from April 1 to September 30, the fuel oil volume of FOST No. 11 is not allowed to be credited and the fuel oil seven day volume of C.3.1

Diesel Fuel Oil B 3.8.3 BASES CALVERT CLIFFS - UNITS 1 & 2 B 3.8.3-6 Revision 2 FOST No. 21 must be restored within two hours as indicated in Required Action C.2. Required Action C.2 is also modified by a Note such that it is only required during the operation of Unit 2 in MODEs 1, 2, 3, or 4 since the unit is already shutdown if it is in another MODE or condition. An OPERABLE FOST No. 11 is determined as described above in the discussion for Condition B.

D.1 This Condition is entered as a result of a failure to meet the acceptance criterion of SR 3.8.3.2. Normally, trending of particulate levels allows sufficient time to correct high particulate levels prior to reaching the limit of acceptability. Poor sample procedures (bottom sampling),

contaminated sampling equipment, and errors in laboratory analysis can produce failures that do not follow a trend.

Since the presence of particulates does not mean failure of the fuel oil to burn properly in the diesel engine, and particulate concentration is unlikely to change significantly between SR Frequency intervals, and proper engine performance has been recently demonstrated (within 31 days), it is prudent to allow a brief period prior to declaring the associated DG inoperable. The seven day Completion Time allows for further evaluation, resampling, and re-analysis of the DG fuel oil.

E.1 With the new fuel oil properties defined in the Bases for SR 3.8.3.2 not within the required limits, a period of 30 days is allowed for restoring the stored fuel oil properties to within the new fuel oil limits. This period provides sufficient time to test the stored fuel oil to determine that the new fuel oil, when mixed with previously stored fuel oil, remains acceptable, or restore the stored fuel oil properties to within the new fuel oil limits. This restoration may involve feed and bleed procedures, filtering, or combinations of these procedures. Even if a DG start and load was required during this time interval, and the fuel oil properties were outside limits, there is a high likelihood that the DG would still be capable of performing its intended function.

Insert 2

Insert 2:

Required Actions C.3.2.1, C.3.2.2, and C.3.2.3 provide conditions under which the Required Action C.3.1 restoration time of 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> may be extended to 14 days. These extended restoration time actions are modified by a note specifying the conditions under which the extended restoration time may be used. The conditions require this extended restoration time to be used only while Unit 2 is in MODE 5, 6, or is defueled, only during periods of low tornado probability, only for the purpose of state required inspection and any associated maintenance activities during the Unit 2 2027 Refuel Outage. Use of the extended restoration time also requires implementation of the compensatory measures specified in Attachment 2 of Reference 5, which are reproduced in the table below.

Description Due Date / Event

1.

Develop approved work instructions to restore temporarily off-loaded diesel fuel oil to Fuel Oil Storage Tank (FOST) 21.

Prior to removing FOST 21 from service.

2.

Provide, in accordance with station procedures, training, briefings, and walkthroughs to implement the approved work instructions.

Prior to removing FOST 21 from service.

3.

Develop an approved Shutdown Safety Plan to ensure adequate defense in depth for key safety functions are maintained and identify additional required protected equipment.

Prior to removing FOST 21 from service.

4.

Establish the required initial conditions and equipment alignment to FOST 11.

Prior to removing FOST 21 from service.

5.

Administratively verify availability of at least 1 FLEX diesel generator 500 kW 480 V, at least 1 FLEX diesel generator 100 kW 480 V, and at least 1 FLEX diesel fuel tanker truck.

Prior to removing FOST 21 from service and while FOST 21 is inoperable.

6.

Consider the potential for inclement weather, such as hurricanes, thunderstorms and ice storms, in the risk assessment of the scheduled inspection and repair activities. The assessment will consider contingencies needed to restore the tank and refill the inventory if inclement weather poses an imminent threat to the long-term availability of offsite power.

Prior to removing FOST 21 from service and while FOST 21 is inoperable.

7.

Protect FOST 11, DG 0C, at least one Unit 2 EDG (2A or 2B), and associated support systems in accordance with approved procedures.

Prior to removing FOST 21 from service and while FOST 21 is inoperable.

8.

Protect at least 2 of the 3 500 kV transmission lines and notify Transmission Service Operator in accordance with approved procedures. Elective switchyard activities and other elective on-site electrical maintenance that could cause any unstable offsite or on-site power conditions will not be scheduled.

Prior to removing FOST 21 from service and while FOST 21 is inoperable.

9.

Protect at least 1 of the 2 13.8 kV service buses, and associated support systems, capable of providing offsite power to Unit 2 4.16 kV Engineered Safety Feature (ESF) buses in accordance with approved procedures.

Prior to removing FOST 21 from service and while FOST 21 is inoperable.

10.

Protect at least 1 of the 2 Unit 2 4.16 kV ESF buses, and associated support systems, in accordance with approved procedures.

Prior to removing FOST 21 from service and while FOST 21 is inoperable.

Diesel Fuel Oil B 3.8.3 BASES CALVERT CLIFFS - UNITS 1 & 2 B 3.8.3-9 Revision 55 particulate concentration in the fuel oil and has a limit of 10 mg/l. It is acceptable to obtain a field sample for subsequent laboratory testing in lieu of field testing.

Because the total stored fuel oil volume for DG Nos. 1B, 2A, and 2B is contained in two interconnected tanks, each tank must be considered and tested separately. There is a separate FOST for DG No. 1A.

The Frequency of this test takes into consideration fuel oil degradation trends that indicate that particulate concentration is unlikely to change significantly between Frequency intervals.

SR 3.8.3.3 Microbiological fouling is a major cause of fuel oil degradation. There are numerous bacteria that can grow in fuel oil and cause fouling, but all must have a water environment in order to survive. Removal of water from the fuel storage tanks eliminates the necessary environment for bacterial survival. This is the most effective means of controlling microbiological fouling. In addition, it eliminates the potential for water entrainment in the fuel oil during DG operation. Water may come from any of several sources, including condensation, ground water, rain water, and contaminated fuel oil, and from breakdown of the fuel oil by bacteria. Frequent checking for and removal of accumulated water minimizes fouling and provides data regarding the watertight integrity of the fuel oil system.

The Surveillance Frequency is controlled under the Surveillance Frequency Control Program. The presence of water does not necessarily represent failure of this SR provided the accumulated water is removed during performance of the surveillance test.

REFERENCES 1.

UFSAR 2.

ASTM Standards 3.

Regulatory Guide 1.137, "Fuel-Oil Systems for Standby Diesel Generators," October 1979 4.

ANSI N195-1976, Fuel Oil Systems for Standby Diesel-Generators, April 1976, Section 5.4

5. Constellation Energy Generation, LLC letter, "License Amendment Request - Proposed One-Time Change to Technical Specification 3.8.3 to Support Inspection of Fuel Oil Storage Tank 21," dated October 30, 2025.