ML21225A353

Spent Fuel Pool Cooling - Shutdown Cooling Systems Licensing Design Basis License Amendment Request Supplement

ML21225A353
Person / Time
Site:	Calvert Cliffs
Issue date:	08/13/2021
From:	David Helker Exelon Generation Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
Download: ML21225A353 (32)

Text

200 Exelon Way Exelon Generation Kennett Square, PA 19348 www.exeloncorp.com 10CFR50.90 August 13, 2021 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555-0001 Calvert Cliffs Nuclear Power Plant, Units 1 and 2 Renewed Facility Operating License Nos. DPR-53 and DPR-69 Docket Nos. 50-317 and 50-318

Subject:

Spent Fuel Pool Cooling - Shutdown Cooling Systems Licensing Design Basis License Amendment Request Supplement

References:

1. Calvert Cliffs Nuclear Power Plant Spent Fuel Pool Cooling - Shutdown Cooling Licensing Design Basis License Amendment Request Pre-submittal Meeting, dated May 24, 2021 (ML21144A017)

2. Spent Fuel Pool Cooling - Shutdown Cooling Licensing Design Basis License Amendment Request, dated June 14, 2021 (ML21165A406)

3. Public Meeting with Exelon Generation Company, LLC (Exelon) to Discuss License Amendment Request Involving Spent Fuel Pool Cooling at Calvert Cliffs Nuclear Power Plant, conducted on July 13, 2021 (ML21194A142)

Per Reference 2, in accordance with 10 CFR 50.90, Application for amendment of license, construction permit, or early site permit, Exelon Generation Company, LLC (Exelon) requested changes to the Licensing Design Basis for the Spent Fuel Pool Cooling (SFPC)

System of the Calvert Cliffs Nuclear Power Plant, Units 1 and 2 (CCNPP). The proposed changes would revise the Updated Final Safety Analysis Report (UFSAR) Section 9.4, Spent Fuel Pool Cooling System, design basis to allow for partial and full core offloads without being supplemented with one train of the Shutdown Cooling (SDC) system. In addition, the Spent Fuel Pool temperature would be allowed to increase from a maximum of 120 qF and 130 qF for partial and full core offloads, respectively, to a maximum of 150 qF under certain conditions. The proposed license amendment request (LAR) changes were initially discussed in an NRC pre-submittal meeting conducted on May 24, 2021 (Reference 1).

During the LAR Acceptance Review process, additional questions arose on the scope of the NRC review. An NRC public meeting (Reference 3) was conducted on July 13, 2021 to discuss and clarify the original LAR. As a result of these discussions, Exelon has decided to supplement the original request and more narrowly focus the request to specific plant Refueling Outage conditions. As discussed in Attachment 1, the scope of the request has been revised to include only full core offloads during refueling outages conducted when the spent fuel pooling cooling system (SFPC) service water temperature can be maintained below 50 qF and the SDC system is unavailable to assist the SFPC system, if required. This Supplemental LAR supersedes the previous LAR (Reference 2).

CCNPP Spent Fuel Pool Cooling / Shutdown Cooling Systems Licensing Design Basis Change August 13, 2021 Page 2 provides a description and evaluation of the proposed changes. Attachment 2 provides a revised markup of the affected Technical Requirements Manual (TRM) pages. provides a revised markup of the affected Updated Final Safety Analysis Report (UFSAR) pages.

The proposed changes have been reviewed by the CCNPP Plant Operations Review Committee (PORC) Chair in accordance with the requirements of the Exelon Quality Assurance Program and it was decided that an additional PORC review was not required.

Exelon requests approval of the supplemented LAR by January 14, 2022. Once approved, the amendment shall be implemented prior to the start of the Unit 1 2022 Refueling Outage, for which this supplemented license amendment request is needed to support.

In accordance with 10 CFR 50.91, Notice for public comment; State consultation, paragraph (b), Exelon is notifying the State of Maryland of this supplemented application for license amendment by transmitting a copy of this letter and its attachments to the designated State Official.

Should you have any questions concerning this supplemental submittal, please contact Frank Mascitelli at (610) 765-5512.

I declare under penalty of perjury that the foregoing is true and correct. This statement was executed on the 13th day of August 2021.

Respectfully, David P. Helker Sr. Manager - Licensing and Regulatory Affairs Exelon Generation Company, LLC Attachments: 1. Evaluation of Proposed Changes

2. Markup of Proposed Technical Requirements Manual Pages

3. Markup of Proposed UFSAR Pages cc: Regional Administrator, Region I, USNRC USNRC Senior Resident Inspector, CCNPP Project Manager [CCNPP] USNRC S. Seaman, State of Maryland

ATTACHMENT 1 Evaluation of Proposed Changes Calvert Cliffs Nuclear Power Station, Units 1 and 2 Renewed Facility Operating License Nos. DPR-53 and DPR-69 Docket Nos. 50-317 and 50-318

Subject:

Spent Fuel Pool Cooling - Shutdown Cooling Systems Licensing Design Basis License Amendment Request Supplement 1.0

SUMMARY

DESCRIPTION 1.1 Reason for Evaluation 1.2 Detailed Evaluation of Problem/Changes 2.0 DETAILED DESCRIPTION

2.1 System Description

2.2 Detailed Licensing Bases Changes

3.0 TECHNICAL EVALUATION

3.1 Spent Fuel Pool Cooling System 3.2 Spent Fuel Pool Heat-up Analysis 3.3 Structural Integrity of the Spent Fuel Pool 3.4 Impact on the SFP Cooling/Purification System 3.5 Impact of SFP Temperature on the criticality analyses 3.6 Radiological consequences during a Fuel Handling Incident including control room operator dose 3.7 Risk Assessment 3.8 Single Failure Analysis 3.9 Conclusion/Findings

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

Evaluation of Proposed Change Attachment 1 Spent Fuel Pool Cooling - Shutdown Cooling Systems Page 1 of 23 Licensing Design Basis Change Docket Nos. 50-317 and 50-318 1.0

SUMMARY

DESCRIPTION This LAR supplement will reduce the scope of the LAR submitted on June 14, 2021 (ADAMS Accession Number ML21165A406). Exelon Generation Company, LLC (Exelon), proposes reduced scope changes limited to full core offloads during certain Refueling Outages (RFOs) for the changes to the Spent Fuel Pool Cooling (SFPC)

System Licensing Design Basis of the Renewed Facility Operating License Nos.

DPR-53 and DPR-69 for Calvert Cliffs Nuclear Power Plant, Units 1 and 2 (CCNPP),

respectively.

1.1 Reason for Evaluation:

This activity is for the upcoming 2022 winter Refueling Outage (RFO) and future certain RFOs. For 2022 winter RFO Outage (CC1R26), Unit 1 full core offload, this activity develops a new methodology to obtain margin in heat removal capability by raising the maximum allowable SFP water temperature from 130 °F to 150 °F. The current UFSAR (Reference 1) assumes the SFP cooling system is supplemented with one Shutdown Cooling Heat Exchanger (SDCHX) from the offload unit. However, during certain RFOs, one loop of SDC will be required operable per TS 3.9.4, Shutdown Cooling (SDC) and Coolant Circulation-High Water Level. The second SDC loop will be out of service (not operable) for scheduled outage work. Thus, no SDC loop will be available during certain winter RFOs as supplemental support to cool the SFP. The methodology developed by this activity instead will credit the time it takes for the bulk SFP water to heat up to 150 °F.

The proposed changes would revise the Updated Final Safety Analysis Report (UFSAR) Section 9.4, Spent Fuel Pool Cooling System, design basis (Reference 1) to allow for a full core offload without being supplemented with one loop of Shutdown Cooling (SDC) system during winter RFOs. In addition, the Technical Requirements Manual (TRM) Section 15.9 Refueling Operations, will be revised to provide for additional limits on operation based on number of fuel assemblies offloaded, time after shutdown and spent fuel pool heat load margins and Service Water temperature. A new TRM Section 15.9.5, Spent Fuel Pool (SFP) Cooling Heat Removal During Full Core Offload will also be created to provide SFPC system specifications for Full Core Offload.

The results of SAS2H/ORIGEN-S sequence of the SCALE 4.4 code system have been utilized to calculate decay heat loads. Manual computations are performed in Excel Spreadsheet to calculate decay heat loads for various scenarios. Heat balance calculations are also performed between the SFP decay heat loads as a function of decay time and the heat removal capacities for both normal and abnormal operations.

The proposed permanent change to the SFPC system licensing design basis would allow for a full core offload without the availability of being supplemented with one loop of the SDC system during common SDC maintenance outages. It expected that

Evaluation of Proposed Change Attachment 1 Spent Fuel Pool Cooling - Shutdown Cooling Systems Page 2 of 23 Licensing Design Basis Change Docket Nos. 50-317 and 50-318 during every other future Refueling Outage, the unit may be in this plant configuration for ASME code required work. The change in calculational methodology used in the Spent Fuel Pool Heat-up Analysis involves the development of a new methodology to obtain margin in heat removal capability by raising the maximum allowable spent fuel pool (SFP) water temperature from 130°F to 150°F.

Specifically, the NRC is being asked to:

x Approve the proposed permanent change to the SFPC system licensing design basis that would allow for a full core offload without the availability of being supplemented with one loop of the Shutdown Cooling (SDC) system during certain Refueling Outages. This includes approving the proposed UFSAR markups in Attachment 3.

x Approve the change in calculational methodology as described in the Section -

Technical Evaluation, used in the Spent Fuel Pool Heat-up Analysis to obtain margin in the SFPC heat removal capability by raising the maximum allowable spent fuel pool (SFP) water temperature from 130°F to 150°F.

x Approve the TRM changes (Attachment 2), as a preliminary 50.59 review indicated that these TRM changes would require prior NRC approval.

1.2 Detailed Evaluation of Problem/Changes:

Despite the existing potential to exceed the heat removal capability of the SFP cooling system, CCNPP existing licensing basis does not give credit to the time it takes the SFP water content to heat up to gain additional margin in the decay heat removal of the SFP. Giving credit to the time of heat up of SFP water requires a change to the methodology applied in the UFSAR. The methodology changes in this activity require a License Amendment Request (LAR).

2.0 DETAILED DESCRIPTION 2.1 System Description The primary purpose of the Spent Fuel Pool Cooling (SFPC) and Purification System is to remove decay heat from the spent fuel stored in the spent fuel pool. The SFPC system is classified as a non-safety related system. The SFPC system assists in the safety related function of the Spent Fuel Pool to keep the irradiated spent fuel adequately covered with water and to prevent the SFP from boiling.

The secondary purposes include:

x Provide cooling for refueling pools.

x Maintain clarity & activity levels in the spent fuel pool, refueling pools, &

Evaluation of Proposed Change Attachment 1 Spent Fuel Pool Cooling - Shutdown Cooling Systems Page 3 of 23 Licensing Design Basis Change Docket Nos. 50-317 and 50-318 refueling water tanks.

x Transferring water to and from refueling water tanks as needed.

A simplified diagram of the SFPC System is shown in Technical Evaluation Section 3.1. The SFPC System is a closed-loop system consisting of two half-capacity pumps and two half-capacity heat exchangers in parallel, a bypass filter that removes insoluble particulates, and a bypass demineralizer that removes soluble ions. The SFPC heat exchangers are cooled by Service Water (SRW). The SRW heat exchangers are cooled by the Salt Water cooling system, with supply and return to the Chesapeake Bay.

Skimmers are provided in the SFP to remove accumulated dust from the pool. The clarity and purity of the water in the SFP, refueling pool, and the RWT are further maintained by passing a portion of the flow through the bypass filter and/or demineralizer. The SFP filter and demineralizer removes fission products from the cooling water in the event of a leaking fuel assembly.

Connections are provided for tie-in to the SDC system to provide for additional heat removal in the event that 1830 fuel assemblies are contained in the pool. When the pressure in the SDC system is greater than the design pressure of the SFPC system, the SFPC system is isolated from the SDC system via two manual isolation valves.

Although not required by the design code, double valve isolation is provided at this system interface to meet the original FSAR design basis.

The entire SFPC system is tornado-protected and is located in a Seismic Category I structure. Borated makeup water comes from the Refuel Water Tank (RWT). Non-borated makeup water comes from the demineralized water system.

2.2 Detailed Licensing Bases Changes TRM Proposed Changes A new TRM Section 15.9.5, Spent Fuel Pool (SFP) Cooling Heat Removal During Full Core Offloads, has been developed (see Attachment 2). Full core offloads will be conducted based on number of fuel assemblies offloaded, time after shutdown, service water temperature, number of operable trains of the SFPC System, SFP initial temperature, and SDC System availability. If limits are not met, movement of irradiated fuel assemblies from the reactor to the spent fuel pool will be immediately suspended, and actions will be immediately initiated to restore the plant to within limits. Note that if the SDC is available to support the full core offloads, TRM 15.9.5 will not be entered.

Evaluation of Proposed Change Attachment 1 Spent Fuel Pool Cooling - Shutdown Cooling Systems Page 4 of 23 Licensing Design Basis Change Docket Nos. 50-317 and 50-318 Updated Final Safety Analysis (UFSAR) Changes The following paragraphs in UFSAR Section 9.4, Spent Fuel Pool Cooling System, Section 9.4.1, Design Basis, are being changed (see Attachment 3):

From:

The SFPC system is common to both units. The pool contains water with the proper dissolved concentration of boron and has the capacity to store 1830 fuel assemblies.

The SFPC system is designed to remove the maximum decay heat expected from 1613 fuel assemblies, not including a full core off-load. The maximum pool temperature in this case is 120°F. The system is also capable of being used in conjunction with the SDC system to remove the maximum expected decay heat load from 1830 fuel assemblies, including a full core discharge. The maximum SFP temperature in this case is 130qF To:

The SFPC system is common to both units. The pool contains water with the proper dissolved concentration of boron and has the capacity to store 1830 fuel assemblies.

The SFPC system is designed to remove the maximum decay heat expected from 1613 fuel assemblies, not including a full core off-load. The maximum pool temperature in this case is 120°F. The system is capable of being used to remove the maximum expected decay heat load during winter RFO from 1830 fuel assemblies, including a full core discharge. The maximum SFP temperature in this case is 150°F.

The system is also capable of being used in conjunction with the SDC system to remove the maximum expected decay heat load, other than winter RFO, from 1830 fuel assemblies, including a full core discharge. The maximum SFP temperature in this case is 130qF.

From:

The total SFP decay heat load as a function of decay time is compared to the heat removal capacity from both loops of SFPC as a function of SRW temperature, supplemented with one loop of SDC to show what time after shutdown is acceptable for each SRW temperature condition to maintain the pool at a temperature at 130 °F.

A maximum SRW temperature of 81 °F is required to support a minimum decay time of 4.5 days.

To:

The total SFP decay heat load as a function of decay time is compared to the heat removal capacity from both loops of SFPC as a function of SRW temperature, supplemented with one loop of SDC to show what time after shutdown is acceptable for each SRW temperature condition to maintain the pool at a temperature at 130 °F.

Evaluation of Proposed Change Attachment 1 Spent Fuel Pool Cooling - Shutdown Cooling Systems Page 5 of 23 Licensing Design Basis Change Docket Nos. 50-317 and 50-318 A maximum SRW temperature of 81 °F is required to support a minimum decay time of 4.5 days.

For full core offloads with SRW temperature equal to or below 50qF, two loops of SFPC is acceptable to maintain the pool at a temperature of 150qF or lower. For the SRW temperature of 50 qF, a minimum decay time of 5.86 days is required to maintain the pool within the temperature limit of 150qF.

From:

In the normal case (i.e., with no full-core off load), if one SFPC loop is lost, a decay time of 4.5 days and a maximum SRW temperature of 54 °F are required for the remaining SFPC loop to be able to remove the decay heat while maintaining the pool temperature at 155 °F. In the case of total loss of SFPC with 1613 fuel assemblies in the pool, it would take more than 9 hours1.041667e-4 days <br />0.0025 hours <br />1.488095e-5 weeks <br />3.4245e-6 months <br /> to raise the pool temperature from 155 °F to 210 °F.

To:

In the normal case (i.e., with no full-core off load), if one SFPC loop is lost, a decay time of 4.5 days and a maximum SRW temperature of 54 °F are required for the remaining SFPC loop to be able to remove the decay heat while maintaining the pool temperature at 155 °F. In the case of total loss of SFPC with 1613 fuel assemblies in the pool, it would take more than 9 hours1.041667e-4 days <br />0.0025 hours <br />1.488095e-5 weeks <br />3.4245e-6 months <br /> to raise the pool temperature from 155 °F to 210 °F.

In the case of total loss of SFPC with 1830 fuel assemblies in the pool, it would take 6.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> to raise the pool temperature from 150 °F to 212 °F.

3.0 TECHNICAL EVALUATION

3.1 Spent Fuel Pool Cooling System:

The SFPC system (Figure 1) is a closed-loop system consisting of two half capacity pumps and two half capacity heat exchangers in parallel, a bypass filter that removes insoluble particles, and a bypass demineralized that removes soluble ions. The SFPC heat exchangers are cooled by Service Water (SRW). Connections are provided for tie-in to the SDC system to provide for additional heat removal in some events. When the pressure in the SDC system is greater than the design pressure of the SFPC system, the SFPC system is isolated from the SDC system via two manual isolation valves.

Evaluation of Proposed Change Attachment 1 Spent Fuel Pool Cooling - Shutdown Cooling Systems Page 6 of 23 Licensing Design Basis Change Docket Nos. 50-317 and 50-318 Fuel Ttansfer Tube Unitl Shutdown Cooling Unit2 Shutdown Cooling SFP Pum p 11 Shutdown SFP Pump 12 Cooling Figure - 1 Spent Fuel Pool Cooling System 3.2 Spent Fuel Pool Heat-up Analysis (Reference 2):

The purpose of this analysis is to determine the amount of delay time, after shutdown, required before starting the fuel discharge to the SFP. To determine the required time delay, a time dependent heat transfer model using Microsoft Excel has been generated to illustrate the maximum spent fuel temperature for given inputs. This evaluation focuses on the development of the SFP temperature model, and the results associated with typical conditions during February, as this is when the Spring 2022 RFO will begin.

Design Inputs The analysis is based on the following inputs:

• The maximum temperature of the Spent Fuel Pool is 150 °F.

• The full core decay heat as a function of time since shutdown is taken from Table D8-11 of Ref. [3].

• The cooling capacities (heat removal capacity) are taken from Reference 4.

• The maximum capacity of the spent fuel pool storage tray is 1830 assemblies (Reference 3).

• There are 217 fuel assemblies in a full core load per Reference 3.

• The spent fuel pool temperature for February is taken to be 92 °F, the maximum temperature logged for February of 2021 from plant data.

Evaluation of Proposed Change Attachment 1 Spent Fuel Pool Cooling - Shutdown Cooling Systems Page 7 of 23 Licensing Design Basis Change Docket Nos. 50-317 and 50-318

• The rate of fuel movement to the SFP is taken to be six fuel assemblies per hour.

Assumptions

• The water level in the Spent Fuel pool is assumed to be constant, such that the volume is constant at 79,000 cf. This is conservative as the model takes no credit for the addition of cool water to maintain level lost to evaporation or for the cooling associated with evaporation.

• The fuel assemblies stored in the spent fuel pool are all assumed to be the bounding case Westinghouse VAP fuel from Reference 3.

• The SFP contains 1830 fuel assemblies with each fuel assembly subjected to different periods of irradiation and decay as shown in Table E7-9 of Reference 3.

However, the heat load associated with the stored fuel in the SFP is assumed to be constant, not decaying. This is conservative as there will still be a slight decay over time; however, it is nearly constant over the time frame of new fuel is charge.

• Assume no thermal cross communication between the reactor cavity and the spent fuel pool.

• For simplicity, the bounding average age of the fuel assemblies in the pool is assumed as follows: For Cases 1 and 2, 125 fuel assemblies are assumed to be 60 days old and the remaining stored fuel assemblies are assumed to be two years old.

Case 3 and 7 assume 125 fuel assemblies are 330 days old, and the remaining 1488 stored fuel assemblies in the SFP are 2 years old. For Cases 4, 5, and 6 it is assumed that all stored fuel in the SFP is two years old. Using this assumption, the decay heat for the stored fuel is summarized as follows:

Table-1 Decay Heat Stored Fuel Age of Stored Fue l Decay Heat of Stored Assemb lies Fue l, Ostore d (btu/hr) 125 @60 Days 2.02 X 107 1488 @ 2 years 125 @ 330 Days 1.60 X 107 1488 @ 2 Years 1613 @ 2 years 1.49 X 107

• The service water (SRW) temperature is assumed to be 5 °F warmer than the bay temperature of 42 °F. This is based on engineering judgement and a design Temperature Difference of 5 °F on the service water heat exchangers. Therefore, in this analysis at February conditions, the SRW temperature is taken to be 47 °F.

• According to References 5 and 6 the high Bay water temperature is 90°F.

Methodology:

The calculation of pool temperature rise starts with the following equation:

Evaluation of Proposed Change Attachment 1 Spent Fuel Pool Cooling - Shutdown Cooling Systems Page 8 of 23 Licensing Design Basis Change Docket Nos. 50-317 and 50-318

= Equation 1 Where m is the mass (lbm) of the water in the pool, cp is the specific heat (1 btu/lbm-

) 7LVWKHWHPSHUDWXUHULVH ) DQG4LVWKHQHWHQHUJ\LQSXWLQWKHVSHQWIXHO

pool calculated as follows:

= + -- Equation 2 Q Stored is the heat associated with the existing fuel stored in the SFP. The spent fuel pool has the capacity to hold 1830 fuel assemblies. The maximum amount of fuel assemblies stored in the SFP, allowing room for a full core off-load, is 1830 - 217 = 1613 fuel assemblies. The heat load associated with the stored fuel will be taken to be constant (not decaying). This is conservative, as the heat output will be reduced over time, however the decay rate is greatly reduced over time. N is the number of assemblies moved from the reactor into the spent fuel pool during unloading. Q Reactor is the heat load per full core of spent fuel (217 fuel assemblies). As the heat load output from the core is decaying, Q Reactor is dependent on the time elapsed since the shutdown. The decay heat table is given in Reference 3.

The fuel assemblies are moved into the spent fuel pool at a rate of six fuel assemblies per hour or one fuel assembly every 10 minutes. This is simplified in the analysis as the heat load associated with one fuel assembly is instantaneously applied at the beginning of the time step, and that complete heat load is applied over the entire time step. The heat associated with one additional fuel assembly is added every 10 minutes until the entire quantity of fuel assemblies have been moved to the SFP (either a partial load or full core off-load of 217 fuel assemblies).

For this analysis, the cooling capacity associated with 50 °F service water is used. This is conservative, as the cooling capacity would be improved at a lower SRW temperature.

The net heat load calculated is multiplied by the time step to provide the heat (Btu) input, and Equation 1 is solved for temperature change in the spent fuel pool. Time since shutdown is adjusted in the model until the maximum SFP temperature is 150 °F. The result is an earliest possible time since shutdown to begin moving fuel into the SFP (at a rate of six assemblies per hour) such that the temperature in the SFP does not exceed 150 °F.

The spent fuel pool temperature would be at a steady equilibrium when the net heat load in the pool is zero; the point in which the cooling capacity is equal to the heat load in the pool. In this analysis, the spent fuel pool is taken to be a fixed volume of water, the heat load associated with the stored fuel is considered constant (not decaying). To find this equilibrium SFP temperature, the relevant cooling capacity equation is set equal to the stored fuel heat load and then the equation is solved for SFP temperature, TSFP.

Evaluation of Proposed Change Attachment 1 Spent Fuel Pool Cooling - Shutdown Cooling Systems Page 9 of 23 Licensing Design Basis Change Docket Nos. 50-317 and 50-318 To provide a bounding operator reactor time, a case study is performed for a full core offload, where both cooling loops are lost at the time of fuel discharge completion (217 new spent fuel assemblies have been added to the spent fuel pool). This time to boil calculation is based on a given starting time of 5 days based on conversations with site personnel. When all fuel assemblies have been added (6.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> after shutdown) the spent fuel pool cooling is set to zero, and the water temperature will rise due to the total decay heat in the pool. The time to boil is provided as follows:

=  Equation 3 Where t boil is the time at which the temperature reaches 212°F, and t discharge completion is the time in which the last fuel assembly was discharged to the spent fuel pool.

Cases Analyzed:

All following cases use a service water temperature of 50 °F, and an initial spent fuel pool temperature of 92 °F, as described in the inputs and assumptions.

Case 1: This is a bounding scenario in which a full core offload occurs while there is also a partial offload of 125 fuel assemblies in the pool that is 60 days old, and the rest of the stored fuel is assumed to be two years old. This was based on a bounding case presented in Ref. [3], postulating that an inspection and partial discharge of fuel had occurred 60 days before this full core offload.

Case 2: This is the same as Case 1, but with single cooling loop in operation.

Case 3: This case is a repeat of Case 1 with the removal of conservatism associated with the stored fuel assemblies in the SFP. Two cooling loops are in operation and the stored fuel in the SFP includes 125 assemblies at 330 days old and 1488 fuel assemblies at two years old.

Case 4: This case is provided to illustrate a full core offload, and all stored fuel assemblies in the spent fuel pool are assumed to be two years old.

Case 5: This case illustrates a partial discharge of 145 fuel assemblies into the SFP, and all stored fuel in the SFP is assumed to be two years old.

Case 6: This is the same as Case 5, but with single loop SFP cooling capacity used.

Case 7: This is the time to boil calculation and is set to a start time of five days after shutdown. The stored fuel in the pool is taken to be the same as Case 3, with 125 assemblies that are 330 days old, and the remaining stored fuel is taken to be 2 years old. The loss of both cooling loops occurs immediately after the last fuel assembly is discharged to the SFP (time of 6.5 days after shutdown).

The Heat-up Analysis Results:

These results are produced by inputting a maximum SFP temperature of 150 °F and solving for an initial time (time since shutdown) to begin fuel discharge to the SFP.

As summarized in Table 2 below, Case 1 illustrates a full core offload, and a conservatively high initial decay heat load due to the stored fuel in the SFP. For this

Evaluation of Proposed Change Attachment 1 Spent Fuel Pool Cooling - Shutdown Cooling Systems Page 10 of 23 Licensing Design Basis Change Docket Nos. 50-317 and 50-318 bounding case, beginning the fuel discharge to the SFP at 4.36 days after shutdown, the SFP temperature does not exceed 150°F. Based on these same conservative heat loads in the pool, a full core offload is not feasible with a single cooling loop, as shown by Case 2. Case 3 represents the most realistic scenario for the Spring 2022 RFO with a full core offload and two cooling loops in operations. Case 3 also considers a reasonable stored fuel decay heat estimate of 125 fuel assemblies that are 330 days old, with the rest conservatively assumed to be two years old. Case 3 illustrates that a full core offload with two cooling loops in service could begin as early as 2.98 days. To provide further guidance for Case 3, the SFP Temperature vs. Time Since Shutdown is plotted in Figure 2 with a fuel discharge starting time of 5 days.

Case 4 illustrates a full core discharge, two cooling loops in service, and all stored fuel in the spent fuel pool is taken to 2 years old. The resulting required decay time is 2.74 days. Case 5 illustrates that the cooling system can easily maintain the SFP temperature below 150°F for decay heat associated with a partial offload, even at very early start times. The start time in this scenario would not be limited by required decay time, but more likely by the time required to remove the head from the reactor vessel. Case 6 illustrates with a cooling loop out of service, even a partial offload of 145 fuel assemblies is not feasible. The bulk temperature in the spent fuel pool would exceed 150 °F unless the decay time after shutdown is greater than 20 days.

Table 2 Fuel Discharge to SFP Starting Time Results Time After Time to Number of Time After Shutdow n Reach SFP Number of New Fue l Age of Stored Shutdow n to for Fuel Temp of Cooling Assemblies Fue l Begin Fue l Discharge 150°F (after Loops Discharged Assemblies Discharge Completion discharge into SFP begins) 125@ 60 Days 5.86 Days Case 1 2 217 4.36 Days 2.34 Days 1488@ 2 Years 125@ 60 Not Feasible Days Case 2 1 217 (Greater than N/ A N/A 1488 @ 2 100 Days)

Years 125 @ 330 Days Case 3 2 217 2.98 Days 4.48 Days 2.20 Days 1488@ 2 Years Case 4 2 217 2 Years 2.74 Days 4.24 2.2 1 Days Case 5 2 145 2 Years 0.42 Days 1.42 1.65 Days Case 6 1 145 2 Years 21.79 Days 22.79 4 .14 Days

Evaluation of Proposed Change Attachment 1 Spent Fuel Pool Cooling - Shutdown Cooling Systems Page 11 of 23 Licensing Design Basis Change Docket Nos. 50-317 and 50-318 Table 3 Time to Boil After Loss of Cooling Results Number of New Time After Fue l Assemb li es Age of Stored Shutdown to Coo ling Loops Time to Bo il Discharged into Fue l Assemb li es Beg in Fuel SFP Discharge Loss of Both Coo ling Loops 125 @ 330 days Case 7 at Time of Fuel 217 5 Days 8.67 hours7.75463e-4 days <br />0.0186 hours <br />1.107804e-4 weeks <br />2.54935e-5 months <br /> 1488 @ 2 Years Discha rge Comp letion Case 7 provides a time to boil if both cooling loops are lost after all fuel has been discharged to the spent fuel pool. Given a discharge start time of 5 days after shutdown and loss of cooling at 6.5 days and at the time of complete fuel discharge the SFP temperature is calculated to be 128.76 qF, the time to boil will be 8.67 hours7.75463e-4 days <br />0.0186 hours <br />1.107804e-4 weeks <br />2.54935e-5 months <br /> as shown in Table 3.

Spent Fuel Pool Temperature vs. Time Since Shutdown S0°F SRW Temp, 2 Cooling Loop, Full Core Discharge, 6/hr@ 5 Days After Shutdown 150

_ Max SFP Temp at 7.35 Days, 138.83 "F U:- 140 0

(lJ

,3 130

~

(lJ 0..

E 120

~

0 0 110 a..

(lJ u.. 100 C

(lJ 0..

V) 90 Fuel discharge to SFP complete .

80 5.0 6.0 7.0 8.0 Time Since Shutdown {days)

Figure 2 Spent Fuel Pool Temperature for a Full Core Offload Beginning 5 Days After Shutdown Assuming SFP cooling is lost at the time of fuel discharge completion, the time to boil

Evaluation of Proposed Change Attachment 1 Spent Fuel Pool Cooling - Shutdown Cooling Systems Page 12 of 23 Licensing Design Basis Change Docket Nos. 50-317 and 50-318 is 8.67 hours7.75463e-4 days <br />0.0186 hours <br />1.107804e-4 weeks <br />2.54935e-5 months <br /> (Case 7, Table 3). The maximum boil-off rate for this condition is 93.9 gallons per minute (gpm) (Attachment 2, Note: Attachments in Section 3.0 of this LAR refer to Attachments in ECP-21-000209, Rev 0001, Modify Spent Fuel Pool Decay Heat Analysis for Full Core Offload, Reference 17). Makeup water can be supplied indefinitely to the SFP at a rate of at least 150 gpm. It can usually be supplied at a greater rate for a period of many days. The makeup water flow path is as follows (Reference 1):

a. Source - Well water,

b. Potable makeup Demineralizers

- Typical capacity 150 gpm or more

c. Demineralized water storage tank

- Storage capacity 350,000 gallons

d. Four reactor coolant makeup pumps (Normally run one per unit)

- Capacity 165 gpm each, less than amount required for each coolant makeup

e. Two RWTs

- Storage capacity 420,000 gallons

- Required to have 400,000 gallons during operation

- During refueling this water has been transferred to the refueling pool where it is also available for pumping if conditions permit

f. Two Spent Fuel Cooling Pumps (one per RWT)

- Capacity 1390 gpm each

g. Spent Fuel Pool Items a, b, c and d are Non-Safety-Related and items e, f and g are Safety-Related items (See References 7 to 10) 3.3 Structural Integrity of the Spent Fuel Pool:

According to Reference 11, the structural analysis for the SFP does not require a change as long as the maximum bulk SFP water temperature remains below 150 °F.

It also states that the maximum temperature of 212 °F was considered for Refueling outage and the concrete and rebar stresses will still remain within allowable limits.

Therefore, the current licensing basis for the SFP structural analysis accommodates the increased SFP allowable maximum temperature of 150°F.

3.4 Impact on the SFP Cooling/Purification System:

The major SFP cooling components that may be impacted by SFP temperature raising from 130°F to 150°F are the pumps, heat exchangers, fuel pool filter, fuel pool demineralizer, piping, fittings, and valves. Per M-0212 Specification, Fuel Pool Cooling Pumps, the SFP pumps will circulate borated spent fuel pool water at a maximum temperature of 150°F. The shell and tube side of the heat exchangers have design temperatures of 200°F. This will not be challenged with the proposed SFP temperature increase. The fuel pool filter and demineralizer both have design

Evaluation of Proposed Change Attachment 1 Spent Fuel Pool Cooling - Shutdown Cooling Systems Page 13 of 23 Licensing Design Basis Change Docket Nos. 50-317 and 50-318 temperatures of 250°F which is well above the 150°F change. The SFP piping, fittings, and valves are all designed to withstand temperatures up to 150°F (Attachment 3).

3.5 Impact of SFP temperature rise on the criticality analyses:

The subject of this activity is to change the SFP bulk temperature. The SFP bulk temperature change might impact the fuel reactivity in the SFP. The criticality analyses for both Units SFPs cover the SFP bulk temperature range from 40°F and 155°F (References 9 to 15). The Unit 1 pool has higher reactivity at 40°F while the Unit 2 pool has higher reactivity at 155°F. Since the SFP bulk temperature change in this activity, for both cases, is still within the range from 40°F and 155°F, there is no impact on the SFP criticality analyses (Attachment 4).

3.6 Radiological consequences during a Fuel Handling Incident including control room operator dose:

For radiological consequences during a Fuel Handling Incident, FHI, Reference 16 has been reviewed. In the Reference, SFP temperature is not an input to the calculation of validation of Calvert Cliffs Fuel Handling Accident (FHA) for Increased Fuel Rod Pressure of 1400 psig. Therefore, an increased SFP temperature condition does not impact the analyses associated with an FHA (Attachment 5). Note the Reference 16 calculation uses the term Fuel Handling Accident and the UFSAR uses the term Fuel Handling Incident. Both terms refer to same event and analysis.

3.7 Risk Assessment:

There is no SFPC model in the CCNPP Probabilistic Risk Analysis (PRA) as it does not have any impact on core damage. SFPC has been considered from a defense-in-depth perspective and the decision tree associated with it can be seen below.

Although spent fuel pool cooling is not considered in the PRA as it does not provide core damage mitigation, risk can be assessed from a defense-in-depth perspective.

Three aspects are considered when assessing defense in depth:

o Heat load in the pool o SFP Cooling loops available o Alternate inventory control sources available The pool is considered to be under a high heat load when the unit is defueled, the pool temperature is above 200°F, or the time for the pool to reach 200°F is less than 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. Alternate inventory control sources include the 2 trains from each of the demineralized water transfer pumps and 2 trains (1 apiece) from each RWT.

Evaluation of Proposed Change Attachment 1 Spent Fuel Pool Cooling - Shutdown Cooling Systems Page 14 of 23 Licensing Design Basis Change Docket Nos. 50-317 and 50-318

- Numbtr of Altt1natt6FP IC 2 - SoureuAvailablt? <2

- .... Numb*r of SFPCool ing Loops Av*il*bl t7 1 I "

lo

>*2

.... Number o f A ltema'teSF'P IC

- Sou1cuAv1ilable? <2 NO AnyHREs inprouress OR i$

8 tht pool undt1H1gh Het1t? YES

>=2

. - Sourf;esAvallable'?

Numb tr ofA ltt1natt6f P IC

<2

__ -- LoopsAvail.1bl 2 >=2

, Number of SFP Cooling t?

1 0

- Numberof A ltematiGFPIC

- SourcuAvaitablt? <2

>;;2

.... N umb et ofA ltemateSFP IC u - SourcnAv,itablt? <2 Figure 2 Decision tree associated with SFPC GREEN: Based on the combination of available pathways and activity types a failure or error could be easily mitigated without presenting a significant challenge in that Key Safety Function. This represents optimal defense-in-depth with all or nearly all mitigation equipment available.

YELLOW: Based on the combination of available pathways and activity types a failure or error can still be mitigated but might present a challenge in that Key Safety Function. This represents lowered defense-in-depth with more than the minimum pathways available.

ORANGE: Based on the combination of available pathways and activity types a failure or error would potentially lead to the loss of the Key Safety Function.

This represents no defense-in-depth with the minimum pathways available.

RED: Based on the combination of available pathways and activity types the Key Safety Function is potentially not maintained. This represents a condition in which the safety function is not supported relative to its success criteria.

Optimal defense-in-depth is considered to be the key safety function, in this case SFPC, plus 2 additional success pathways (B=N+2). If the pool is not under a high heat load, then some loss of redundancy is acceptable among the SFP cooling loops and alternate inventory control sources. If the pool is under a high heat load, a loss of one SFPC loop is considered to be nominal defense-in-depth (B=N+1) as long as two or more alternate inventory control sources are available. If both SFPC loops are lost, redundancy is lost, and it is considered marginal defense-in-depth (B=N). It should be noted that from past experiences there have been no Maintenance Rule Functional

Evaluation of Proposed Change Attachment 1 Spent Fuel Pool Cooling - Shutdown Cooling Systems Page 15 of 23 Licensing Design Basis Change Docket Nos. 50-317 and 50-318 Failures or Condition Monitoring Events since 2002 to present (Attachment 6).

3.8 Single Failure Analysis:

In a refueling outage if one train of SFPC is lost while the other train of SDC is still out of service for maintenance, the SFP temperature would be monitored, and appropriate actions would be taken per alarm manual 1C13 if a SFP high temperature alarm would be received. One of the actions in the alarm manual directs operators to AOP-06F, Spent Fuel Pool Cooling System Malfunctions, (Reference 18) which provides guidance to consider aligning SDC if the unit is defueled per OI-03B-1(2),

Shutdown Cooling, (Reference19). Section 6.13 of OI-03B-1(2) addresses aligning the SDC to the SFP (Attachment 7). This alignment can occur relatively quickly with the spool piping connections preinstalled prior to offloading the core.

In the case of total loss of SFPC with 1830 fuel assemblies in the pool, it would take 6.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> to raise the pool temperature from 150 °F to 212 °F. The maximum boil-off rate for this condition is 93.9 gallons per minute (gpm). The time to heat up the bulk water to boiling provides sufficient time to establish an alternate means of cooling, and the makeup rate exceeds the rate of water loss due to boil-off.

3.9 Conclusion/Findings:

x A calculation has been performed to determine the earliest time after shutdown to begin fuel discharges while the SFP temperature remains within the limit of 150°F.

The rate of fuel assembly movement to the SFP is assumed to be 6 fuel assemblies per hours.

x Based on the results for full core offload, abnormal operation (Case 1) a limiting decay time of 4.36 days is needed to remove the SFP decay heat load. In this case the time after shutdown for fuel discharge completion is 5.86 days and it takes 2.34 days to reach SFP temperature of 150°F after discharge begins.

x Based on the results for full core offload, normal operation (Case 3) a limiting decay time of 2.98 days is needed to remove the SFP decay heat load. In this case the time after shutdown for fuel discharge completion is 4.48 days and it takes 2.2 days to reach SFP temperature of 150°F after discharge begins.

However, this case cannot happen since the time allowed by the TRM to start discharging is 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> after shutdown, but it indicates that if we start discharging any time later than that calculated in Case 3, the SFP temperature remains below 150°F.

x In the case of total loss of SFPC with 1830 fuel assemblies in the pool, it would take 6.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> to raise the pool temperature from 150 °F to 212 °F. The maximum boil-off rate for this condition is 93.9 gallons per minute (gpm). The time to heat up the bulk water to boiling provides sufficient time to establish an alternate means of

Evaluation of Proposed Change Attachment 1 Spent Fuel Pool Cooling - Shutdown Cooling Systems Page 16 of 23 Licensing Design Basis Change Docket Nos. 50-317 and 50-318 cooling, and the makeup rate exceeds the rate of water loss due to boil-off. Note the difference in time to boil of 6.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> and the 8.67 hours7.75463e-4 days <br />0.0186 hours <br />1.107804e-4 weeks <br />2.54935e-5 months <br /> identified in Case 7 and Table 3 is that Case 7 also included the time the SFP temperature rose from 128.76 °F (calculated temperature of pool right after the last fuel assembly was moved to the SFP) to 150 °F.

x The analysis shows that the SFP water will remain subcooled and the effects of changes in this activity on the local SFP water temperature are acceptable. There is no adverse impact on cooling/purification system, structural integrity, criticality, and radiological consequences during a fuel handling event including control room operator dose, due to SFP maximum water temperature limit being raised from 130°F to 150°F.

x Although there is a very small reduction in the margin of safety by allowing the SFP bulk temperature limit to change from 130qF to 150qF for a full core offload without the availability of a SDC loop assistance, it has been shown that this temperature rise is bounded by the existing analyses. These analyses include:

SFP Heat-up Analysis, structural analysis, dose consequence analysis of the Fuel Handling Incident, and spent fuel thermal hydraulic analysis. Adequate margins are maintained by the actions and changes proposed by this License Amendment Request.

4.0 REGULATORY EVALUATION

4.1 Applicable Regulatory Requirements/Criteria The proposed changes have been evaluated to determine whether applicable regulations and requirements continue to be met. Exelon has determined that the proposed changes do not require any exemptions or relief from regulatory requirements 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 will shut down the reactor or follow any remedial action permitted by the technical specifications until the condition can be met. The proposed changes do not involve or require TS LCOs for the SFPC System.

General Design Criteria 5, Sharing of Structures, systems, and components GDC Criterion 5, states that structures, systems, and components important to safety shall not be shared among nuclear power units unless it can be shown that such sharing will not significantly impair their ability to perform their safety functions,

Evaluation of Proposed Change Attachment 1 Spent Fuel Pool Cooling - Shutdown Cooling Systems Page 17 of 23 Licensing Design Basis Change Docket Nos. 50-317 and 50-318 including, in the event of an accident in one unit, an orderly shutdown and cooldown of the remaining units. CCNPP was originally licensed to AEC Draft AEC Criterion 4 (Sharing of systems). Standard Review Plan (SRP) 9.1.3 II, Acceptance Criteria, for spent fuel pool cooling systems states in part, this SRP section describes staff positions related to the design of the spent fuel pool cooling and cleanup system, whose safety function is to ensure that no single failure will prevent the system from cooling the spent fuel. The proposed changes do not affect CCNPPs compliance with the intent of GDC 5.

General Design Criterion 44, Cooling water GDC Criterion 44 states in part: "A system to transfer heat from structures, systems, and components important to safety, to an ultimate heat sink shall be provided. The system safety function shall be to transfer the combined heat load of these structures, systems, and components under normal operating and accident conditions. Suitable redundancy in components and features, and suitable interconnections, leak detection, and isolation capabilities shall be provided to assure that for onsite electric power system operation (assuming offsite power is not available) and for offsite electric power system operation (assuming onsite power is not available).

There is not a direct correlation for GDC Criterion 44 to pre-GDC Criteria. There is a similar correlation for pre-GDC 44 concerning ECCS cooling, which states in part, At least two emergency core cooling systems, preferably of different design principles, each with a capability for accomplishing abundant emergency core cooling, shall be provided. Each emergency core cooling system and the core shall be designed to prevent fuel and clad damage that would interfere with the emergency core cooling function and to limit the clad metal-water reaction to negligible amounts The SFPC system provides two trains designed to keep the spent fuel adequately cooled.

The proposed changes do not affect CCNPPs compliance with the intent of GDC 44.

The CCNPP SFPC system was not originally licensed to single failure criteria and is not safety related. The proposed changes do not affect CCNPPs compliance with the intent of GDC 44.

10 CFR 50 Appendix A, General Design Criterion (GDC) 61, Fuel Storage and Handling and Radioactivity Control (For CCNPP, this correlates to pre-GDC criterion 67)

GDC 61 requires that fuel storage and handling systems be designed to ensure adequate safety under anticipated operating and accident conditions. Specifically, GDC 61 requires (1) periodic inspections; (2) suitable radiation shielding; (3) appropriate containment, confinement, and filtering systems; (4) residual heat removal capability consistent with its importance to safety; and (5) prevention of significant reduction in fuel storage inventory under accident conditions. Pre-GDC Criterion 67, Fuel and Waste Storage Decay Heat, states that reliable decay heat removal systems shall be designed to prevent damage to the fuel in storage facilities that could result in radioactivity release to plant operating areas or the public environs. The proposed changes do not affect CCNPPs compliance with the intent of GDC 61.

Regulatory Guide (RG) 1.13 Rev 2, Spent Fuel Pool Storage Facility Design Basis.

Evaluation of Proposed Change Attachment 1 Spent Fuel Pool Cooling - Shutdown Cooling Systems Page 18 of 23 Licensing Design Basis Change Docket Nos. 50-317 and 50-318 NRC issued this regulatory guide to provide current guidance regarding the design basis for spent fuel storage facilities. This regulatory guide endorses (with certain additions, clarifications, and exceptions) Design Objectives for Light-Water Spent Fuel Storage Facilities at Nuclear Power Plants, which the American National Standards Institute/American Nuclear Society issued as ANSI Standard N210-1976/ANS-57.2-1983.

RG exceptions state in part that the ANSI/ANS-57.2-1983 states that spent fuel pool water should be maintained below 66qC (150qF) during normal operating conditions.

By contrast, this regulatory guide specifies that pool water should be maintained below 60qC (140qF) for all heat load conditions, including full-core offloads during refueling.

The proposed changes have been evaluated in accordance with RG 1.13 and have been found to be acceptable per the revised SFP Heat-up Analysis to maximum SFP temperature of 150qF.

NUREG 0800, Standard Review Plan (SRP) 9.1.3 Spent Fuel Pool Cooling and Cleanup System All nuclear reactor plants include a spent fuel pool for the wet storage of spent fuel assemblies. The methods used to provide cooling for the removal of decay heat from the stored assemblies vary from plant to plant, depending upon the individual design.

The safety function to be performed by the system in all cases remains the same; that is, the spent fuel assemblies must be cooled and must remain covered with water during all storage conditions. Other functions performed by the system but not related to safety include water cleanup for the spent fuel pool, refueling canal, refueling water storage tank, and other equipment storage pools; means for filling and draining the refueling canal and other storage pools; and surface skimming to provide clear water in the storage pool.

SRP 9.1.3 III, Review Procedures, Section1.D states in part:

The minimum heat removal capacity with the forced-circulation cooling system in operation, the pool at the design temperature of the structure, and the heat sink at its maximum design temperature is greater than 0.3 percent of the reactor rated thermal power. The cooling system retains at least half of its full heat removal capacity assuming a single active failure. This capacity provides reasonable assurance that the pool temperature will remain within design bounds for the structure during full core discharges to the spent fuel pool when the forced-circulation cooling system is in operation, and ensures that significant heat removal capacity will remain available when an active component is unavailable due to a single failure or maintenance. The forced cooling capacity remaining following a single failure is adequate due to the low probability that the single failure would occur coincident with maximum decay heat load and the maximum heat sink temperature The proposed changes do not affect CCNPPs compliance with the intent of SRP 9.1.3 requirements for the heat removal capability of the SFPC system and the requirements to maintain sufficient water in the spent fuel pool.

Evaluation of Proposed Change Attachment 1 Spent Fuel Pool Cooling - Shutdown Cooling Systems Page 19 of 23 Licensing Design Basis Change Docket Nos. 50-317 and 50-318 4.2 Precedent Turkey Point Units 3 and 4 - Issuance of Amendments Regarding Reduction in Decay Time from 100 to 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> (TAC NOS. MB6549 AND MB6550), dated March 4, 2003 (ML0306207460) provides relevant insights and review criteria as the reduction in decay time resulted in an increase in heat load to the SFPC system and SFP bulk temperature.

The subject of Turkey Point (TP) LAR was reduction in minimum decay heat time for reactor subcriticality prior to removing irradiated fuel from the reactor vessel from 100 hr to 72 hr. TP demonstrated that the bulk water temperature in the SFP remains below the design bulk SFP water temperature for planned offloads, and below the boiling (212 °F) for unplanned offloads, the time to heat up the bulk water to boiling provides sufficient time to establish an alternate means of cooling, and the make-up rate exceeds the rate of water loss due to boil-off. TP used the same methodology in their UFSAR allowing to vary the actual offload start time, average offload rate, and actual cooling water average temperature. The actual heat load in the SFP was used, rather than assuming the heat load from a full SFP. The calculation methodology was accepted in predicting the maximum bulk SFP temperature for planned offloads to maintain the bulk SFP temperature below the design temperature.

Assuming SFP cooling is lost at the time of peak pool temperature, the time to boil, the maximum boil-off rate, and make-up rate for this condition were evaluated. It was shown that during time to boil there is sufficient time to establish make-up to the SFP.

The analysis showed that the SFP water will remain subcooled and the effects of reduced decay time on the local SFP water temperature are acceptable. TP evaluated the impact of the proposed amendment in the SFP cooling system including structural integrity of the SFP, radiological consequences, and control room habitability.

Calvert Cliffs Units 1 and 2 TS Amendment Nos. 47 and 30, respectively, to increase the spent fuel storage capability up to a maximum of 1760 fuel assemblies in the spent fuel pool through the use of high density borated spent fuel racks, dated September 19, 1980 (ML003773029). Section 3.2 (Spent Fuel Cooling) of the Safety Evaluation Report provides relevant insights and review criteria for original licensing design bases for the SFPC System.

4.3 No Significant Hazards Consideration Pursuant to 10 CFR 50.90, Application for amendment of license or construction permit, Exelon Generation Company, LLC (Exelon), proposes a permanent change to the Licensing Design Bases of the Spent Fuel Pool Cooling System (SFPC) system of Renewed Facility Operating License Nos. DPR-53 and DPR-69 for Calvert Cliffs Nuclear Power Plant Units 1 and 2 (CCNPP). The proposed change also involves a change in calculational methodology used in the Spent Fuel Pool Heat-up Analysis The proposed permanent change to the SFPC system licensing design basis would allow for a full core offload without the availability of being supplemented with one

Evaluation of Proposed Change Attachment 1 Spent Fuel Pool Cooling - Shutdown Cooling Systems Page 20 of 23 Licensing Design Basis Change Docket Nos. 50-317 and 50-318 loop of the Shutdown Cooling (SDC) system during certain Refueling Outages. The change in calculational methodology used in the Spent Fuel Pool Heat-up Analysis involves the development of a new methodology to obtain margin in heat removal capability by raising the maximum allowable spent fuel pool (SFP) water temperature from 130°F to 150°F. The current Updated Final Safety Analysis (UFSAR) assumes the SFP cooling system is supplemented with one Shutdown Cooling Heat Exchanger (SDCHX) from the offload unit in order to keep the bulk temperature below 130qF.

However, during certain Refueling Outages, one loop of SDC will be required to be operable per TS 3.9.4, Shutdown Cooling (SDC) and Coolant Circulation-High Water Level. The second SDC loop will be out of service for scheduled outage work (ASME code required work). Thus, no SDC loop will be available as a supplemental assist to cool the SFP. The methodology developed by this activity instead will credit the time it takes for the bulk SFP water to heat up to 150°F. A new section to the Technical Requirements Manual, Section 15.9.5, Spent Fuel Pool (SFP) Cooling Heat Removal During Full Core Offloads, has been developed to support the new SFP Heat-up Analysis.

Exelon has evaluated whether a significant hazards consideration is involved with the proposed amendment by focusing on the three standards set forth in 10 CFR 50.92, Issuance 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 accident of concern related to the proposed changes is the Fuel Handling Incident (FHI). This accident assumes a dropped fuel assembly. For radiological consequences the bounding analysis has been reviewed for an FHI. In the bounding analysis, SFP temperature is not an input to the calculation, Validation of Calvert Cliffs FHA for Increased Fuel Rod Pressure of 1400 psig, and therefore, there is no impact on the consequences of an FHI analysis. The proposed changes do not involve any physical alterations, or new or different types of equipment, or new system operating procedures. Therefore, the probability of the FHI has not increased.

Regarding impact to reactivity of the spent fuel in the SFP, the criticality bounding analysis has been reviewed for the impact of a rise in the SFP bulk temperature. The criticality analyses for both Units SFPs cover the SFP bulk temperature range from 40°F and 155°F. The Unit 1 SFP has higher reactivity at 40°F while the Unit 2 pool has higher reactivity at 155°F. Since the SFP bulk temperature change in this activity, for both cases, is still within the range from 40°F and 155°F of the criticality bounding analysis, there is no impact on the SFP criticality.

Therefore, the proposed change does not involve a significant increase in the

Evaluation of Proposed Change Attachment 1 Spent Fuel Pool Cooling - Shutdown Cooling Systems Page 21 of 23 Licensing Design Basis Change Docket Nos. 50-317 and 50-318 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.

The impact of the proposed change is limited to fuel handling operations and spent fuel pool cooling. No physical plant changes to existing systems are proposed to accommodate allowing the spent fuel pool bulk temperature to heat up from 130qF to 150qF. The same water makeup systems are available for makeup to the spent fuel pool. Hence, no new failure modes are created that would cause a new or different kind of accident from any accident previously evaluated. The supporting analysis for allowing the spent fuel pool to heat up to 150qF demonstrates that the associated increase in water temperature heat load will not cause any spent fuel pool (SFP) component or structure to operate outside design limits. Adequate margins to safety are maintained with respect to SFP water temperature and structural thermal loading.

Additional operating limits have been established with the additional Technical Requirements Manual (TRM) changes that include time after shutdown for fuel moves for decay heat; requirement for two operating SFPC trains; and lower Service Water (SWR) temperature requirements and initial SFP temperature being maintained below 92qF. In the case of total loss of SFPC system with 1830 fuel assemblies in the pool, it would take 6.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> to raise the pool temperature from 150 °F to 212 °F. The maximum boil-off rate for this condition is 93.9 gallons per minute (gpm). The time to heat up the bulk water to boiling provides sufficient time to establish an alternate means of cooling, and the makeup rate (150 gpm) exceeds the rate of water loss due to boil-off.

Assuming a total loss of SFPC system at the time of peak SFP temperature, the time to boil, the maximum boil-off rate, and make-up rate for this condition were evaluated.

It was shown that during time to boil there is sufficient time to establish make-up to the SFP with existing systems and procedures. The analysis showed that the SFP water will remain subcooled and the effects of the elevated SFP bulk temperature are acceptable.

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

3. Does the proposed change involve a significant reduction in a margin of safety?

Response: No.

The proposed change in plant operation does not significantly reduce the margin of safety because of the additional operating constraints imposed by changes in the Technical Requirements Manual. Although there is a very small reduction in the margin of safety by allowing the SFP bulk temperature limit to change from 130qF to 150qF for a full core offload without the availability of a SDC loop assistance, it has

Evaluation of Proposed Change Attachment 1 Spent Fuel Pool Cooling - Shutdown Cooling Systems Page 22 of 23 Licensing Design Basis Change Docket Nos. 50-317 and 50-318 been shown that this temperature rise is bounded by the existing analyses. These analyses include: SFP Heat-up Analysis, structural analysis, dose consequence analysis of the Fuel Handling Incident, and spent fuel thermal hydraulic analysis.

Adequate margins are maintained by the actions and changes proposed by this License Amendment Request.

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

Based on the above, Exelon 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

The proposed change 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, or would change an inspection or surveillance requirement. However, the proposed change does not involve (i) a significant hazards consideration, (ii) a significant change in the types or significant increase in the amounts of any effluents that may be released offsite, or (iii) a significant increase in individual or cumulative occupational radiation exposure. Accordingly, the proposed change meets the eligibility criterion for categorical exclusion set forth in 10 CFR 51.22(c)(9). Therefore, pursuant to 10 CFR 51.22(b), no environmental impact statement or environmental assessment need be prepared in connection with the proposed change.

6.0 REFERENCES

1. Updated Final Safety Analysis Report, UFSAR, Rev 51 Chapter 9.4 Spent Fuel Pool Cooling System

2. ILD-PWP-303 Rev. 1, CCNPP Spent Fuel Pool Heat-up Analysis 3 CA06535 Rev. 0002, SFP Decay Heat for 24-M VAP and Framatome Core with App. K Power Uprate

4. CA03959 Rev. 0000, Spent Fuel Pool Heat Removal Capability

Evaluation of Proposed Change Attachment 1 Spent Fuel Pool Cooling - Shutdown Cooling Systems Page 23 of 23 Licensing Design Basis Change Docket Nos. 50-317 and 50-318 5 ECP-16-000587, Hot Bay water issue

6. CA10191 Rev 0000, Justification for Continuous operation Hot Bay Water Issue

7. DWG 60730SH0001, Chemical and Volume Control System

8. DWG 60731SH0001, Safety Injection & Containment Spray System

9. DWG 60716, Spent Fuel Pool Cooling Pool Fill & Drain System

10. DWG 60706SH0002, Service Water Cooling System

11. CA09085, Rev 0000, Spent Fuel Pool

12. CA06011, Rev 0000, Unit 1 Spent Fuel Pool Enrichment Limit With Soluble Boron Credit

13. CA06015, Rev 0000, Unit 2 Spent Fuel Pool Criticality Analysis With Soluble Boron Credit But Without Boraflex Credit

14. CA07456, Rev 0000 Unit 1 Spent Fuel Pool Enrichment Limit With Soluble Boron Credit For Areva Fuel

15. CA07142, Rev 0000, Unit 2 Spent Fuel Pool Criticality Analysis With Soluble Boron And Burnup Credit For Areva Fuel

16. CA06067, Rev 0000, Validation Of Calvert Cliffs Fuel Handling Accident For Increased Fuel Rod Pressure Of 1400 PSIG

17. ECP-21-000209, Rev 0001, Modify Spent Fuel Pool Decay Heat Analysis for Full Core Offload

18. AOP-6F, Spent Fuel Pool Cooling System Malfunctions, Revision 00701

19. OI-03B-1(2), Shutdown Cooling, Revisions 03400(03100)

CCNPP Final Response and Close-out to Generic Letter 2004-02 November 25, 2020 Page 1 ATTACHMENT 2 Calvert Cliffs Nuclear Power Station, Units 1 and 2 Renewed Facility Operating License Nos. DPR-53 and DPR-69 Markup of Proposed Technical Requirements Manual Pages TRM Pages 75 76

Rev. 01000 Page 75 of 79 15.9.5 Spent Fuel Pool (SFP) Cooling Heat Removal During Full Core Offloads NORMAL TNC 15.9.5 The Spent Fuel Pool Cooling system is required to CONDITION have cooling capacity to maintain temperature in the Spent Fuel Pool >50°F and <150°F during a full core offload when Shutdown Cooling system is initially unavailable to assist with Spent Fuel Pool Cooling.

a. TheSFPwater temperature shallbe >50 qF and <150 qF;

b. Two SFP Cooling Systems shall be OPERABLE, each commensurate with the SFP heat load; and

c. The combination of Service Water (TSRW) temperature and time after shutdown shall be met per Table 1 below.

APPLICABILITY During full core offload and until core is reloaded.

TABLE 1- Addition of recently irradiated fuel assemblies to the Spent Fuel Pool using Two SFP Cooling Loops Time to Start Time to Complete T SRW (°F) Initial SFP Temperature (°F)

Discharge (days) Discharge (days) 3 4.5  

CONTINGENCY MEASURES Nonconformance Contingency Measures Completion Time A. SFP temperature not A.1 Suspend movement of Immediately within limit. irradiated fuel assemblies from the reactor to the SFP.

AND A.2 InitiateactiontorestoreSFP Immediately temperature to within limit.

Rev. 01000 Page 76 of 79 B. One required SFP B.1 Suspend movement of Immediately CoolingSystem irradiated fuel assemblies from inoperable. the reactor to the SFP.

AND B.2 Initiate action to restore a Immediately second SFP Cooling System to OPERABLE status.

AND B.3 Restore second SFP Cooling Loop 3 Hours C. Combination of Service C.1 Suspend movement of Immediately Water temperature irradiated fuel assemblies from (TSRW) and minimum the reactor to the SFP.

time after shutdown not met.

D. Contingency Measures and D.1 See Section 15.0.3 Completion Time of Condition A, B, or C not met VERIFICATION REQUIREMENTS TVR Verification Frequency 15.9.5.1 Verify SFP temperature is within limit. 12 Hours 15.9.5.2 Verify two SFP Cooling Systems are OPERABLE, Once prior to each commensurate with the SFP heat load moving irradiated associated with the full core offload. fuel assemblies from the reactor to the SFP and every 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> thereafter 15.9.5.3 Verify combination of the Service Water Once prior to temperature (TSRW) and minimum time after moving irradiated shutdown met. fuel assemblies from the reactor to the SFP and every 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> thereafter

ATTACHMENT 3 Calvert Cliffs Nuclear Power Station, Units 1 and 2 Renewed Facility Operating License Nos. DPR-53 and DPR-69 Markup of the Proposed UFSAR Pages 9.4-1 9.4-2 9.4-3

Page 9.4-1 INSERT 1, for UFSAR Rev 9.4 SPENT FUEL POOL COOLING SYSTEM 9.4.1 DESIGN BASIS The SFPC system is common to both units. The pool contains water with the proper dissolved concentration of boron and has the capacity to store 1830 fuel assemblies.

The SFPC system is designed to remove the maximum decay heat expected from 1613 fuel assemblies, not including a full core off-load . The maximum pool temperature in this case is 120°F. The system is also capable of being used in conjunction with the SOC system to remove the maximum expected decay heat load from 1830 fuel assemblies, including a full core discharge. The maximum SFP temperature in this case is 130°F.

Insert 1 for CCNPP UFSAR Chapter 9.4 Markup The SFPC system is common to both units. The pool contains water with the proper dissolved concentration of boron and has the capacity to store 1830 fuel assemblies.

The SFPC system is designed to remove the maximum decay heat expected from 1613 fuel assemblies, not including a full core off-load. The maximum pool temperature in this case is 120

°F. The system is capable of being used to remove the maximum expected decay heat load during winter RFO from 1830 fuel assemblies, including a full core discharge. The maximum SFP temperature in this case is 150°F. The system is also capable of being used in conjunction with the SDC system to remove the maximum expected decay heat load, other than winter RFO, from 1830 fuel assemblies, including a full core discharge. The maximum SFP temperature in this case is 130F.

INSERT 2, for ECP-20-000436 insert:

Page 9.4-2 The total SFP decay heat load as a function of decay time is compared to the heat removal capacity from both loops of SFPC as a function of SRW temperature, supplemented with one loop of SDC to show what time after shutdown is acceptable for each SRW temperature condition to maintain the pool at a temperature at 130 °F. A maximum SRW temperature of 81 °F is required to support a minimum decay time of 4.5 days.

Insert 2 for CCNPP UFSAR Chapter 9.4 Markup The total SFP decay heat load as a function of decay time is compared to the heat removal capacity from both loops of SFPC as a function of SRW temperature, supplemented with one loop of SDC to show what time after shutdown is acceptable for each SRW temperature condition to maintain the pool at a

temperature at 130 °F. A maximum SRW temperature of 81 °F is required to support a minimum decay time of 4.5 days.

For full core offloads with SRW temperature equal to or below 50F, two loops of SFPC is acceptable to maintain the pool at a temperature of 150F or lower. For the SRW temperature of 50F, a minimum decay time of 5.86 days is required to maintain the pool within the temperature limit of 150F.

INSERT 3, for ECP-20-000436 Page 9.4-3 In the normal case (i.e., with no full-core off load), if one SFPC loop is lost, a decay time of 4.5 days and a maximum SRW temperature of 54 °F are required for the remaining SFPC loop to be able to remove the decay heat while maintaining the pool temperature at 155 °F.

In the case of total loss of SFPC with 1613 fuel assemblies in the pool, it would take more than 9 hours1.041667e-4 days <br />0.0025 hours <br />1.488095e-5 weeks <br />3.4245e-6 months <br /> to raise the pool temperature from 155 °F to 210 °F.

Insert 3 for CCNPP UFSAR Chapter 9.4 Markup In the normal case (i.e., with no full-core off load), if one SFPC loop is lost, a decay time of 4.5 days and a maximum SRW temperature of 54 °F are required for the remaining SFPC loop to be able to remove the decay heat while maintaining the pool temperature at 155 °F. In the case of total loss of SFPC with 1613 fuel assemblies in the pool, it would take more than 9 hours1.041667e-4 days <br />0.0025 hours <br />1.488095e-5 weeks <br />3.4245e-6 months <br /> to raise the pool temperature from 155 °F to 210 °F.

In the case of total loss of SFPC with 1830 fuel assemblies in the pool, it would take 6.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> to raise the pool temperature from 150 °F to 212 °F.