CNL-24-004, Application to Modify the Watts Bar Nuclear Plant, Unit 1 and Unit 2 Technical Specifications for Main Control Room Chiller Completion Time Extension (WBN-TS-23-13)

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Application to Modify the Watts Bar Nuclear Plant, Unit 1 and Unit 2 Technical Specifications for Main Control Room Chiller Completion Time Extension (WBN-TS-23-13)
ML24095A159
Person / Time
Site: Watts Bar  Tennessee Valley Authority icon.png
Issue date: 04/04/2024
From: Hulvey K
Tennessee Valley Authority
To:
Office of Nuclear Reactor Regulation, Document Control Desk
References
CNL-24-004, WBN-TS-23-13
Download: ML24095A159 (1)
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Text

1101 Market Street, Chattanooga, Tennessee 37402 CNL-24-004 April 4, 2024 10 CFR 50.90 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, D.C. 20555-0001 Watts Bar Nuclear Plant, Units 1 and 2 Facility Operating Licenses Nos. NPF-90 and NPF-96 NRC Docket Nos. 50-390 and 50-391

Subject:

Application to Modify the Watts Bar Nuclear Plant, Unit 1 and Unit 2 Technical Specifications for Main Control Room Chiller Completion Time Extension (WBN-TS-23-13)

In accordance with the provisions of Title 10 of the Code of Federal Regulations (10 CFR) 50.90, "Application for amendment of license, construction permit, or early site permit," Tennessee Valley Authority (TVA) is submitting a request for an amendment to Facility Operating License Nos. NPF-90 and NPF-96 for the Watts Bar Nuclear Plant (WBN), Units 1 and 2, respectively.

The proposed change revises WBN Units 1 and 2 Technical Specification (TS) 3.7.11 "Control Room Emergency Air Temperature Control System (CREATCS)," to modify the TS Actions for two inoperable CREATCS trains. The proposed change provides 96 hours0.00111 days <br />0.0267 hours <br />1.587302e-4 weeks <br />3.6528e-5 months <br /> to restore one CREATCS train to operable status provided mitigating actions ensure the control room temperature is controlled. The mitigating actions include the current installation of a non-safety related chiller with a dedicated diesel generator to provide power to the non-safety related system.

The enclosure to this submittal provides a description and technical evaluation of the proposed change, a regulatory evaluation, and a discussion of environmental considerations. Attachment 1 to the enclosure provides the existing WBN Unit 1 TS pages marked up to show the proposed changes. Attachment 2 to the enclosure provides the existing WBN Unit 2 TS pages marked up to show the proposed changes. Attachment 3 to the enclosure provides the existing WBN Units 1 and 2 TS Bases pages marked up to show the proposed changes. Changes to the existing TS Bases are provided for information only and will be implemented under the TS Bases Control Program.

TVA has determined that there are no significant hazards considerations associated with the proposed changes and that the TS changes qualify for a categorical exclusion from environmental review pursuant to the provisions of 10 CFR 51.22(c)(9). In accordance with 10 CFR 50.91(b)(1), TVA is sending a copy of this letter and enclosure to the Tennessee State Department of Environment and Conservation.

U.S. Nuclear Regulatory Commission CNL-24-004 Page 2 April 4, 2024 TVA requests approval of the proposed license amendment within one year of the date this application with implementation within 60 days of issuance of the amendment.

There are no new regulatory commitments associated with this submittal. Please address any questions regarding this request to Stuart L. Rymer, Senior Manager, Fleet Licensing, at slrymer@tva.gov.

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

Respectfully, Kimberly D. Hulvey Director, Nuclear Regulatory Affairs

Enclosure:

Evaluation of Proposed Change cc (Enclosure):

NRC Regional Administrator - Region II NRC Senior Resident Inspector - Watts Bar Nuclear Plant NRC Project Manager - Watts Bar Nuclear Plant Director, Division of Radiological Health - Tennessee State Department of Environment and Conservation Digitally signed by Edmondson, Carla Date: 2024.04.04 11:11:30 -04'00'

Enclosure CNL-24-004 E1 of 14 Evaluation of Proposed Change

Subject:

Application to Modify the Watts Bar Nuclear Plant, Unit 1 and Unit 2 Technical Specifications for Main Control Room Chiller Completion Time Extension (WBN-TS-23-13)

Table of Contents Contents 1.0

SUMMARY

DESCRIPTION........................................................................................ 2

2.0 BACKGROUND

.......................................................................................................... 2 3.0 DETAILED DESCRIPTION........................................................................................ 3 3.1 CREATCS System Description

... 3 3.2 MCR Non-Safety Related Chilled Water Equipment Description

... 3 3.3 Description of the Proposed Change

... 4 3.4 Reason for the Proposed Change

... 5

4.0 TECHNICAL EVALUATION

....................................................................................... 8 4.1 Risk Insights

. 11

5.0 REGULATORY EVALUATION

................................................................................. 11 5.1 Applicable Regulatory Requirements and Criteria

. 11 5.2 Precedent

. 11 5.3 No Significant Hazards Considerations Analysis

. 12 5.4 Conclusions

. 13

6.0 ENVIRONMENTAL CONSIDERATION

.................................................................... 13

7.0 REFERENCES

......................................................................................................... 14 Attachments

1. Proposed TS Changes (Mark-Ups) for WBN Unit 1
2. Proposed TS Changes (Mark-Ups) for WBN Unit 2
3. Proposed TS Bases Page Changes (Mark-Ups) for WBN Units 1 and 2 (For Information Only)

Enclosure CNL-24-004 E2 of 14 1.0

SUMMARY

DESCRIPTION In accordance with the provisions of Title 10 of the Code of Federal Regulations (10 CFR) 50.90, "Application for amendment of license, construction permit, or early site permit," Tennessee Valley Authority (TVA) is submitting a request for an amendment to Facility Operating License Nos. NPF-90 and NPF-96 for the Watts Bar Nuclear Plant (WBN), Units 1 and 2, respectively.

The proposed change revises WBN Units 1 and 2 Technical Specification (TS) 3.7.11 "Control Room Emergency Air Temperature Control System (CREATCS)," to modify the TS Actions for two inoperable CREATCS trains. The proposed change provides 96 hours0.00111 days <br />0.0267 hours <br />1.587302e-4 weeks <br />3.6528e-5 months <br /> to restore one CREATCS train to operable status provided mitigating actions ensure the control room temperature is controlled. The mitigation actions include the current installation of a non-safety related chiller with a dedicated diesel generator to provide power to the non-safety related system.

2.0 BACKGROUND

In References 1 and 2, TVA submitted a request for an amendment to revise WBN Units 1 and 2 TS 3.7.11 to add a one-time change of a footnote to the Completion Time for Required Action A.1 to allow one CREATCS train to be inoperable for up to 60 days while performing modifications to the WBN Units 1 and 2 Main Control Room (MCR) CREATCS chillers. The proposed amendment also added a one-time change of a footnote to the Completion Time for Required Action E.1 to allow delayed entry into TS Limiting Condition for Operation (LCO) 3.0.3 for up to 4 days (96 hours0.00111 days <br />0.0267 hours <br />1.587302e-4 weeks <br />3.6528e-5 months <br />) in the event that both CREATCS trains are inoperable during the modifications to the CREATCS chillers. In Reference 3, the Nuclear Regulatory Commission (NRC) approved References 1 and 2. In Reference 4, TVA submitted a license amendment request (LAR) to revise the timeframe of the above footnotes to begin no earlier than July 1, 2023, and end no later than December 31, 2024. Reference 4 was approved by the NRC in Reference 5. However, installation of the MCR chillers is on hold as a result of operational issues identified on the similarly designed Shutdown Board Room (SDBR) chiller during post installation testing. These operational issues included control system challenges and compressor oil issues which prevented the chiller from operating reliably over the entire range of conditions (low load vs. design basis load) without manual adjustments. TVA is currently working with the vendor to develop corrective actions to ensure reliable operation of these chillers once permanently installed in the plant.

As described in References 1, 2, 3, and the NRC regulatory audit (Reference 6), a non-safety related chiller will be used to support MCR cooling during the CREATCS chiller replacements. This system is capable of providing adequate cooling to maintain the MCR within its normal temperature band. TVA plans to keep the non-safety related chiller available to provide backup cooling in the event both CREATCS become inoperable. A similar chiller is being used for the replacement of the B SDBR chiller.

Enclosure CNL-24-004 E3 of 14 3.0 DETAILED DESCRIPTION 3.1 CREATCS System Description A description of the CREATCS is provided in Section 3.1 to Reference 1.

3.2 MCR Non-Safety Related Chilled Water Equipment Description A description of the non-safety related chiller is provided in Section 3.2 to Reference 1, the TVA response to EMIB-RAI-1 in Reference 2, the NRC Safety Evaluation in Reference 3, and the NRC regulatory audit summary in Reference 6.

As noted in Reference 1, the major components of the non-safety related chiller include the following.

Air cooled chilled water package Chilled water pump Power supply, cables, and connections Chilled water supply and return hoses Demineralized water source Engineered penetrations with isolation valves Backup diesel generator (DG) with fuel tank The non-safety related chiller described in References 1, 2, 3, and 6 was initially planned to be a temporary system during the MCR CREATCS chiller project.

However, TVA has decided to retain the non-safety related chiller. Therefore, the chiller and supporting equipment will be available to be attached to the existing air handling units through permanent connections in the CREATCS chilled water loop.

The component ratings for these connections bound the maximum system pressure of the non-safety related chiller. Also, the non-safety related chiller is not a high energy line system, and evaluation and qualification of the system piping for pipe rupture and pipe whip is not required.

The portion of the non-safety related chiller piping system located in seismically qualified structures has been evaluated for internal pressure, deadweight, and seismic loading conditions, and meets the requirements of Seismic Category I(L),

which is defined in Watts Bar Updated Final Safety Analysis Report (UFSAR)

Section 3.2.1. In particular, those fluid containing elements which are included in Seismic Category I(L) are seismically qualified to meet the intent of position 2 regarding design interface between seismic Category I and non-seismic Category I plant features as delineated in Regulatory Guide 1.29, Seismic Design Classification for Nuclear Power Plants.

Reference 3 also describes how the piping and support including the weld as well as the valves for the control room envelope (CRE) penetrations were seismically analyzed. Also, as noted in Reference 3, the flooding effect of potential pipe leakage from the non-safety related chiller water system in the Main Control Room Habitability Zone (MCRHZ) is bounded by the current flooding analysis.

As noted in Reference 3, the non-safety related chiller working in conjunction with each air handling unit (AHU) is capable of meeting the cooling requirements of the MCRHZ during plant normal operations.

Enclosure CNL-24-004 E4 of 14 The power supplies for the non-safety related chiller (including the backup DG) are described in Section 3.1.3 of Reference 3, which notes that the dedicated DG fuel oil tanks capacity provides a 12-hour run time for the chiller skid without fuel oil replenishment, which is an adequate time to take replenishing measures from alternate sources.

The location of the non-safety related chiller is described in Section 3.1.4 of Reference 3, which notes that in the event that non-safety related 480 volt alternating current source is lost and the skids DG is required to operate to power the non-safety related chiller, the distance of the skid from the fresh air intakes that any DG exhaust fumes emitted from the skid would be sufficiently diluted so as not to provide a threat to MCR habitability or auxiliary building accessibility.

The ability of the non-safety related chiller to maintain control room habitability including CRE integrity and MCRHZ temperature control is described in Section 3.2 of Reference 3.

The non-safety related chiller is already installed at the required location and the actions needed to connect it to the to the AHU in the Control Building are described in Section 3.2.1 to Reference 1 and are described below.

The actions needed to connect the non-safety-related chiller to the MCR AHU include final routing and connection of hoses using permanent branch connections which have been installed at each MCR AHU. The permanent branch connections include isolation valves and flanges such that the hoses/fittings can be connected to the flanges with the branch line valves closed, or the hoses and fittings can be staged for installation when needed. Supply and return hoses/fittings will be routed from the non-safety related chiller in the plant yard, similar to the arrangement which has been successfully used to supply chiller water to the B SDBR AHUs. The non-safety related chiller will primarily be powered from an electrical feed from the Westinghouse pad, which is typically used to supply power to temporary equipment during outages. A backup diesel generator will also be available to supply power to the non-safety related chiller via a transfer switch, similar to the arrangement for the B SDBR temporary chiller. These electrical connections between the Westinghouse pad, transfer switch, and backup diesel generator will be either be pre-installed or the equipment and cables will be staged such that they can be quickly connected.

These actions will be proceduralized before implementing this LAR.

3.3 Description of the Proposed Change The proposed change revises the Required Actions applicable when two CREATCS trains are inoperable. The proposed Required Actions require immediate initiation of an action to implement mitigating actions to ensure control room temperature will not exceed 90 degrees Fahrenheit (°F), or if one CREATCS train is not restored to operable status within 96 hours0.00111 days <br />0.0267 hours <br />1.587302e-4 weeks <br />3.6528e-5 months <br /> while in Modes 1, 2, 3, or 4, the unit must 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 />. In Mode 5 or 6, or during movement of recently irradiated fuel assemblies, immediate suspension of movement of recently irradiated fuel assemblies is required.

Enclosure CNL-24-004 E5 of 14 The changes to WBN Units 1 and 2 TS 3.7.11 are described in greater detail below:

The existing Conditions D and E are modified to a new condition D. The new Condition D states, Two CREATCS trains inoperable. New Required Action D.1 requires initiation of action to implement mitigating actions, immediately.

New Required Action D.2 requires verifying control room temperature is less than or equal to () 90°F immediately and once per hour thereafter. New Required Action D.3 requires restoring one CREATCS train to operable status within 96 hours0.00111 days <br />0.0267 hours <br />1.587302e-4 weeks <br />3.6528e-5 months <br />. The three Required Actions are linked with the logical connector AND.

A new Condition E is added. The new Condition E states, Required Action and associated Completion Time of Condition D not met in MODE 1, 2, 3, or 4.

New required Action E.1 requires being in Mode 3 within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />. New required Action E.2 requires being in Mode 5 within 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />. The two new Required Actions are linked with the logical connector AND.

A new Condition F is added. The new Condition F states, Required Action and associated Completion Time of Condition D not met in Modes 5 or 6, or during movement of recently irradiated fuel assemblies. New required Action F.1 requires immediate suspension of movement of recently irradiated fuel assemblies.

The existing temporary footnote for the Completion Time of Required Action E is being deleted. A separate LAR will be required to revise the completion dates for the current footnote to Required Action A once a revised schedule for completion of the MCR chiller replacement project is established. to the enclosure provides the existing WBN Unit 1 TS pages marked up to show the proposed changes. Attachment 2 to the enclosure provides the existing WBN Unit 2 TS pages marked up to show the proposed changes. to the enclosure provides the existing WBN Units 1 and 2 TS Bases pages marked up to show the proposed changes. Changes to the existing TS Bases are provided for information only and will be implemented under the TS Bases Control Program.

3.4 Reason for the Proposed Change The current WBN 1 and 2 TS 3.7.11 requires an immediate disruption of plant operations in the event both CREATCS trains become inoperable. The proposed change adds a new Condition D for two CREATCS trains inoperable which allows 96 hours0.00111 days <br />0.0267 hours <br />1.587302e-4 weeks <br />3.6528e-5 months <br /> to restore one CREATCS train to Operable status by implementing mitigating actions (including the use of a non-safety related chiller) and verifying control temperature is 90°F every hour (consistent with the current temporary measures for the MCR chiller replacement project that were previously reviewed and approved by the NRC in Reference 3). Allowing for 96 hours0.00111 days <br />0.0267 hours <br />1.587302e-4 weeks <br />3.6528e-5 months <br /> to restore an inoperable CREATCS train to operable status minimizes the potential safety consequences and operational risks associated with the disruption of plant operations. The basis for the 96 hours0.00111 days <br />0.0267 hours <br />1.587302e-4 weeks <br />3.6528e-5 months <br /> is discussed in Section 4 to this enclosure.

Enclosure CNL-24-004 E6 of 14 The Current TS Action is Not Commensurate with the Safety Function The CREATCS is not directly credited with preventing or mitigating an accident in the safety analysis. Unavailability of the CREATCS will not directly impact plant safety provided actions are in place to ensure operator habitability and equipment operational requirements are not exceeded. Plant staff can monitor control room temperature readily in the control room to ensure it remains habitable and that control room temperature will not exceed equipment operational requirements.

Mitigating actions can be used to ensure control room temperature is controlled.

Therefore, requiring an immediate disruption of plant operation or plant activities is not commensurate with the level of degradation associated with two inoperable CREATCS trains.

The Requirements are not Consistent with Other WBN TS WBN TS 3.7.12, Auxiliary Building Gas Treatment System (ABGTS), provides a 7-day Completion Time for two inoperable trains due to an inoperable Auxiliary Building Secondary Containment Enclosure boundary and does not require a disruption of plant operations for two or more inoperable trains. The 7-day Completion Time is reasonable based on the determination that the mitigating actions will ensure protection of MCR occupants within analyzed limits while limiting the probability that MCR occupants will have to implement protective measures that may adversely affect their ability to control the reactor and maintain it in a safe shutdown condition in the event of a design basis accident.

Additionally, there are current WBN TS which provide a 30-day Completion Time for an inoperable train and do not require a disruption of plant operations for two or more inoperable trains. Systems are provided with a 30-day Completion Time to restore an inoperable train because the system is of low safety significance or is only relied on for low probability events. For example:

TS 3.3.3, Post Accident Monitoring (PAM) Instrumentation, provides 30 days to restore one or more functions with one or more required channels inoperable and 7 days to restore one or more functions with two or more required channels inoperable for certain functions with more than one required channel.

TS 3.4.15, RCS Leakage Detection Instrumentation, provides 30 days to restore the required containment sump monitor and the required containment atmosphere radioactivity monitor to operable status.

The Requirements are not Consistent with Similar Requirements in the Standard TS (STS)

There are TS in the Westinghouse improved STS (NUREG-1431, Revision 5) which provide a Completion Time for two inoperable filtration systems due to an inoperable building boundary. These include TS 3.7.10, Control Room Emergency Filtration System, TS 3.7.12, Emergency Core Cooling System Pump Room Exhaust Air Cleanup System, and TS 3.7.13, Fuel Building Air Cleanup System. The Completion Time was found to be acceptable for these TS based on the low probability of an event and the use of compensatory measures. The same justification of the low probability of an event and the use of compensatory measures is applicable to the proposed change.

Enclosure CNL-24-004 E7 of 14 The NRCs improved STS for all other plant designs provide a Completion Time to restore one inoperable control room cooling train. However, instead of an LCO 3.0.3 entry, other plant designs provide a Completion Time to restore one inoperable control room cooling train to operable status when both trains are inoperable. For example:

NUREG-1432, Revision 5, the improved STS for Combustion Engineering plants, TS 3.7.12, Control Room Emergency Air Temperature Control System (CREATCS), provides 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> to restore one of two inoperable control room cooling trains.

NUREG-1433, Revision 5, the improved STS for Boiling Water Reactor (BWR)/4 plants, TS 3.7.5, [Control Room Air Conditioning (AC)] System, provides 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> to restore one of two operable control room cooling subsystems provided control room area temperature is verified to be below a plant-specific limit every 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />.

NUREG-1434, Revision 5, the improved STS for BWR/6 plants, TS 3.7.4,

[Control Room Air Conditioning (AC)] System, provides 7 days to restore one of two inoperable control room cooling subsystems provided control room area temperatures verified to be below a plant-specific limit every 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />.

In addition to the reasons described above, situations have occurred in which both WBN CREATCS trains were inoperable and entry into LCO 3.0.3 was required. A review of operating history for WBN discovered the following events.

On May 9, 1997, TVA reported an event for WBN Unit 1 (ML073250262). While attempting to switch from the Train A MCR heating, ventilation, and air conditioning (HVAC) to the Train B HVAC for post maintenance testing, the handswitch which controls the Train A HVAC was placed in pull-to-lock while the Train B HVAC handswitch was also in the pull-to-lock position. Due to both trains of CREATCS being inoperable, Action E of LCO 3.7.11 was entered, which required entry into LCO 3.0.3 until the Train A HVAC was returned to service.

On September 24, 1998, TVA reported an event for WBN Unit 1 (ML073250317) where WBN Unit 1 entered LCO 3.0.3 when power to Train B of CREACTCS was lost and Train A was out of service due to being in the "pull-to-lock stop" position to ensure that both trains will not operate simultaneously. Because the control switch for Train A was in the pull-to-lock stop position, the shutdown of Train B resulted in both trains being inoperable.

On August 7, 2019, TVA reported an event for WBN Unit 1 (ML19219A219) where a significant air leak on an inline air filter was identified. This air leak impacted operation of the CREATCS A Train. At the time of this event, CREATCS B Train was out of service for planned maintenance, which resulted in the entry of LCO 3.0.3.

On April 27, 2023, WBN Unit 2 entered LCO 3.0.3 due to the loss of 1B MCR chiller when the 1B-B 6.9 kV shutdown board de-energized and the subsequent failure of the 1A-A MCR chiller to start. This event was not reportable to the NRC.

In each of these cases, the proposed LAR would have prevented entry into LCO 3.0.3.

Enclosure CNL-24-004 E8 of 14

4.0 TECHNICAL EVALUATION

The non-safety related chiller to be used for temporary cooling of the MCR CREATCS exceeds the minimum capacity of 150 tons noted in Reference 6. The cooling load of the area served by the MCR CREATCS is 85 tons, which is significantly lower than the rated capacity of the non-safety related chiller system. A similar non-safety related chiller is being utilized for the replacement of the B SDBR Chiller and the system has proven reliable during replacement of that safety-related chiller. The cooling load of the area served by the SDBR chilled water system is 116 tons, which is also significantly lower than the rated capacity of the non-safety related chiller. Thus, the significantly higher rated capacity of the non-safety related chiller ensures that design conditions are maintained during normal and accident modes of operation.

The use of the non-safety related chiller will not impact operability of the CRE and will not directly impact TS 3.7.10, Control Room Emergency Ventilation System (CREVS). When implementing this mitigating action (i.e., use of a non-safety related chiller), the corresponding CREATCS train fans must be operable to provide air movement. If the corresponding CREATCS train fans are not operable, the mitigating action will not be capable of maintaining control room temperature and TS 3.7.11 Condition E or F, as appropriate, will be entered.

The proposed change provides three new Required Actions to be followed when two CREATCS trains are inoperable. A new Required Action D.1 states, "Implement mitigating actions" with a Completion Time of "Immediately." TS Bases include a listing of mitigating actions which can be taken to control temperature. Examples include use of a non-safety related chiller with a dedicated DG to provide power to the non-safety related system, opening cabinet doors, use of fans, and use of ice vests. These mitigating actions were evaluated by the NRC in Reference 3.

Also, as described in Section 3.4.1.2 to Reference 3, there are existing actions operators may take should the operators attempt to remove heat from the MCR. In the event it becomes necessary to abandon the MCR entirely, the operators have the ability to control the MCR from the Auxiliary Control Room in accordance with the plant abnormal operating procedures. The Auxiliary Control Room is a physically independent location outside of the Control Building and meets the separation criteria of General Design Criterion 19 in Appendix A to 10 CFR Part 50.

The non-safety related chiller is described in further detail in Section 3.2 to this enclosure.

A new Required Action D.2 states, "Verify control room temperature 90°F with a Completion Time of Immediately and once per hour thereafter. The purpose of the Required Action is to ensure the control room temperature is being controlled. If it cannot be verified that the control room temperature is 90°F, subsequent actions are required based upon the mode of operation. As noted in References 1 and 3, the 90°F temperature limit provides adequate margin between the normal MCR operating temperature of 75°F and a limit that ensures that the equipment operability limit of 104°F is not exceeded. By maintaining the MCR temperature at or below 90°F, the operability requirements for safety-related functions provided by equipment and instrumentation in the MCR, as well as habitability needs for operating personnel, is satisfied.

Enclosure CNL-24-004 E9 of 14 Subsequent to immediate control room temperature verification, the 1-hour frequency is adequate given the indications available in the control room and evaluation to be completed prior to use of the mitigating actions to maintain temperature. Control room temperature data is measured and displayed in the control room, and operators will have awareness of temperature trending relative to the 90°F limit. With hourly temperature monitoring, a degraded condition will be identified before temperature limits were reached and unit shutdown activities will be initiated. Additionally, with operators continually stationed in the MCR, temperature increases of this magnitude would most likely be identified before the hourly monitoring requirement. This provides time for MCR conditions to be assessed if the operable CREATCS train is declared inoperable. When WBN is in the proposed TS 3.7.11.D, operations personnel will place heightened attention on restoring a train of CREATCS to operable status and satisfying the other associated Required Actions to prevent a dual-unit shutdown.

Also as noted in References 1 and 3, to support the one-hour frequency for temperature monitoring, TVA evaluated the effect of a loss of cooling on the MCR temperature by performing an analysis of the heat-up of the MCR and surrounding areas. The analysis assumed normal operating heat loads, normal average initial room temperatures, summertime maximum outdoor temperatures, one AHU operating, and no chillers in operation. The calculation demonstrated that the temperature increase from 75°F (normal MCR operating temperature) to 104°F takes approximately 5.3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br />. This temperature response does not credit the non-safety related chiller system cooling.

Furthermore, as noted in Reference 3, The licensee provided a calculation of the time that it will take for the MCR and surrounding areas to heat up before the heat-up starts to affect the operability of equipment and challenge operator comfort. The licensee suggests that the calculated time is sufficient enough that operators will be well aware of the heat-up prior to reaching 90 °F, specifically stating, the MCR temperature data is measured and displayed from readily available equipment in the MCR and operators will have awareness of temperature trending relative to the 90°F limit.

As noted in Reference 2, based on the figures in Calculation MDQ00003120090157, Revision 7 (which was reviewed by the NRC in Reference 6), the MCR temperature will continue to rise slowly over this time. The actions and measures to assure a safe shutdown of both WBN units after the loss of both trains of CREATCS when the MCR temperature starts at 90°F include:

Requesting for priority maintenance to restore the inoperable CREATCS train and reviewing the operation of the temporary non-safety related chiller to ensure that it continues to supply chilled water to the MCR HVAC system; Compensatory actions to remove heat from the MCR; and If necessary, implementing existing procedures to abandon the MCR and shutdown both units from outside the MCR.

Thus, adequate margin to operational limits for control room equipment is maintained. Subsequent to immediate control room temperature verification, the 1-hour frequency is adequate given the indications available in the control room and evaluation to be completed prior to use of the mitigating actions to maintain

Enclosure CNL-24-004 E10 of 14 temperature. Control room temperature data is measured and displayed in the control room, and operators will have awareness of temperature trending relative to the 90°F limit. When WBN is in Condition D of TS 3.7.11, operations personnel will place heightened attention on restoring a train of CREATCS to operable status and satisfying the other associated Required Actions to prevent a dual-unit shutdown.

The proposed 96 hour0.00111 days <br />0.0267 hours <br />1.587302e-4 weeks <br />3.6528e-5 months <br /> Completion Time to restore a CREATCS is reasonable based on past operating experience for restoring a CREATCS train to service as described in Table 3 of Reference 1. Below is a summary of recent MCR chiller outages:

On January 5, 2022, WBN Units 1 and 2 entered the 30-day completion time for TS 3.7.11, Condition A, due to a component outage for the B MCR chiller. The B MCR chiller was restored to operable status on January 9, 2022, at 1159 for a total outage time of 103 hours0.00119 days <br />0.0286 hours <br />1.703042e-4 weeks <br />3.91915e-5 months <br />.

On February 5, 2023, WBN Units 1 and 2 entered TS 3.7.11, Condition A due to a failure of the A MCR chiller. The A MCR chiller was restored to operable status on February 7, 2023, at 1000 for a total outage time of 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />.

On February 4, 2024, WBN Units 1 and 2 entered TS 3.7.11, Condition A due to a failure of the A MCR chiller. The A MCR chiller was restored to operable status on February 9, 2024, for a total outage time of approximately 122 hours0.00141 days <br />0.0339 hours <br />2.017196e-4 weeks <br />4.6421e-5 months <br />.

The proposed 96 hour0.00111 days <br />0.0267 hours <br />1.587302e-4 weeks <br />3.6528e-5 months <br /> Completion Time will only apply when both CREATCS trains are out of service. In that case site personnel would work expeditiously to restore a CREATCS train to service in order to avoid entering TS LCO 3.0.3.

Thus, the proposed 96 hour0.00111 days <br />0.0267 hours <br />1.587302e-4 weeks <br />3.6528e-5 months <br /> Completion Time of new Required Action D.3 is considered adequate given the mitigating actions and the low probability of an accident that would require the CREATCS, provides a reasonable time to diagnose, plan, repair, and test most problems with the CREATCS, while minimizing the period of time that control room occupants might have to respond to an event while utilizing the mitigating actions. Therefore, 96 hours0.00111 days <br />0.0267 hours <br />1.587302e-4 weeks <br />3.6528e-5 months <br /> is sufficient time in most circumstances to restore at least one CREATCS train to operable status while minimizing the length of time in which the CREATCS is inoperable and potentially avoiding unnecessary impact to plant operations.

Should a component required by the CREATCS be unable to perform its required function, LCO 3.7.11 will be declared not met and all applicable Actions will be followed. Specifically, if both trains of CREATCS are inoperable, then proposed TS 3.7.11 Condition D will be entered. A new Condition E states, "Required Action and associated Completion Time of Condition D not met in MODE 1, 2, 3, or 4."

Should the mitigating actions not be implemented, control room temperature not be maintained 90°F, or if one CREATCS train is not restored to operable status within 96 hours0.00111 days <br />0.0267 hours <br />1.587302e-4 weeks <br />3.6528e-5 months <br /> while in Modes 1, 2, 3, or 4, the unit must 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 allowed Completion Times are reasonable, based on operating experience, to reach the required unit conditions from full power conditions in an orderly manner and without challenging plant systems. Currently LCO 3.0.3 must be entered immediately per current TS 3.7.11 Condition E. LCO 3.0.3 requires entry to MODE 3 within 7 hours8.101852e-5 days <br />0.00194 hours <br />1.157407e-5 weeks <br />2.6635e-6 months <br /> and MODE 5 in 37 hours4.282407e-4 days <br />0.0103 hours <br />6.117725e-5 weeks <br />1.40785e-5 months <br />. The proposed Completion Times of 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> for MODE 3 and 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br /> for MODE 5 are within the current TS

Enclosure CNL-24-004 E11 of 14 limits.

A new Condition F states, Required Action and associated Completion Time of Condition E not met in Mode 5 or 6, or during movement of recently irradiated fuel assemblies." Should the mitigating actions not be implemented, control room temperature not be maintained 90°F, or if one CREATCS train is not restored to operable status within 96 hours0.00111 days <br />0.0267 hours <br />1.587302e-4 weeks <br />3.6528e-5 months <br /> while in Modes 5 or 6, or during movement of recently irradiated fuel assemblies, movement of recently irradiated fuel assemblies must be suspended immediately. The Required Action minimizes the potential for a radioactive release which might require control room isolation and subsequent cooling.

4.1 Risk Insights See Section 3.5 of Reference 1.

5.0 REGULATORY EVALUATION

5.1 Applicable Regulatory Requirements and Criteria See Section 4.1 to Reference 1.

5.2 Precedent As noted in Section 2.0 to this enclosure, in Reference 3, the NRC approved, in part, a one-time change of a footnote to the Completion Time for WBN Units 1 and 2 TS 3.7.11, Required Action E.1 to allow delayed entry into TS LCO 3.0.3 for up to 4 days (96 hours0.00111 days <br />0.0267 hours <br />1.587302e-4 weeks <br />3.6528e-5 months <br />) in the event that both CREATCS trains are inoperable during the modifications to the CREATCS chillers.

In 2018, the NRC approved an equivalent LAR for the Control Room Cooling System for Byron and Braidwood Nuclear Plants, Units 1 and 2 (Reference 7). In the event that both trains of control room cooling become inoperable, the license amendment allows 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> to return one train to operable, while requiring mitigating actions to keep the control room temperature less than or equal to 80 °F, such as the use of a Control Room Cooling System purge mode, use of non-safety chilled water sources, or use of supplemental coolers.

Similarly, on March 8, 2024, NRC issued a license amendment (Reference 8) to Duke Energy Carolinas, LLC for the Catawba Nuclear Station, Units 1 and 2, to revise TS 3.7.11, Control Room Area Chilled Water System (CRACWS), to allow a completion time of 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> to restore one of the two CRACWS trains to operable status, provided mitigating actions (including the use of a non-safety related chiller) to ensure the control room temperature is controlled, rather than require immediate entry into TS LCO 3.0.3 and commencing a plant shutdown within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />.

Enclosure CNL-24-004 E12 of 14 5.3 No Significant Hazards Considerations Analysis Tennessee Valley Authority (TVA) is requesting an amendment to Facility Operating Licenses NPF-90 and NPF-96 for the Watts Bar Nuclear Plant (WBN), Units 1 and 2, respectively.

The proposed change revises WBN Units 1 and 2 Technical Specification (TS) 3.7.11 "Control Room Emergency Air Temperature Control System (CREATCS)," to modify the TS Actions for two inoperable CREATCS trains. The proposed change provides 96 hours0.00111 days <br />0.0267 hours <br />1.587302e-4 weeks <br />3.6528e-5 months <br /> to restore one CREATCS train to operable status provided mitigating actions ensure the control room temperature is controlled and the control room temperature is maintained less than or equal to 90°F. The mitigation actions include the current installation of a non-safety related chiller with a dedicated diesel generator to provide power to the non-safety related system.

TVA evaluated whether or not a significant hazards consideration is involved with the proposed amendments by focusing on the three standards set forth in Title 10 of the Code of Federal Regulations (10 CFR) 50.92, "Issuance of Amendment," as discussed below:

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

Response: No.

The CREATCS is used to maintain an acceptable temperature environment for control room personnel and equipment during normal and emergency conditions.

The CREATCS is not an initiator of any accident previously evaluated.

As a result, the probability of an accident previously evaluated is not increased.

The consequences of an accident during the proposed 96 hour0.00111 days <br />0.0267 hours <br />1.587302e-4 weeks <br />3.6528e-5 months <br /> Completion Time are no different than the consequences of an accident in Modes 1, 2, 3, and 4 during the existing one-hour Completion Time provided in Limiting Condition for Operation (LCO) 3.0.3 to prepare for a shutdown. The only accident previously evaluated in Modes 5 or 6 is a fuel handling accident. The accident evaluation does not assume a loss of offsite electrical power or additional failures, and the mitigating actions to maintain control room temperature less than or equal to 90°F will still be available should a fuel handling accident occur. As a result, providing 96 hours0.00111 days <br />0.0267 hours <br />1.587302e-4 weeks <br />3.6528e-5 months <br /> to restore one train of control room cooling does not significantly increase the consequences of a fuel handling accident over the current requirement.

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.

Plant equipment controlled from the control room and operator response actions in response to a design basis accident will be maintained as currently designed

Enclosure CNL-24-004 E13 of 14 and applied. No new equipment or operator responses are required in response to a design basis accident as part of this proposed change. The proposed change will not alter the design or function of the control room or the CREATCS system. Should the new Required Actions not be met, the existing and proposed Required Actions require preparation for an orderly unit shutdown, or suspension of movement of recently irradiated fuel assemblies, as applicable based on the mode of applicability.

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 provides a limited period of time to restore an inoperable CREATCS train instead of interrupting plant operations, possibly requiring an orderly unit shutdown, or suspension of movement of recently irradiated fuel assemblies. A plant disruption or transient may be avoided with mitigating actions taken and the control room temperature maintained. The potential to avoid a plant transient in conjunction with maintaining the control room temperature offsets any risk associated with the limited Completion Time. The proposed change does not impact a design basis, TS LCO, limiting safety system setting, or safety limit specified in TSs.

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

Based on the above, it is concluded that the proposed amendment does not involve a significant hazards consideration under the standards set forth in 10 CFR 50.92(c),

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

5.4 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 Commission's 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.

6.0 ENVIRONMENTAL CONSIDERATION

A review 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, or would change an inspection or surveillance requirement. 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 radioactive effluents that may be released offsite, or (iii) a significant increase in individual or cumulative occupational radiation exposure.

Accordingly, the proposed amendment meets the eligibility criterion for categorical

Enclosure CNL-24-004 E14 of 14 exclusion set forth in 10 CFR 51.22(c)(9). Therefore, pursuant to 10 CFR 51.22(b),

no environmental impact statement or environmental assessment need be prepared in connection with the proposed amendment.

7.0 REFERENCES

1. TVA letter to NRC, CNL-20-012, Application to Modify the Watts Bar Nuclear Plant Unit 1 and Unit 2 Technical Specifications for Main Control Room Chiller Completion Time Extension (WBN-TS-18-16), dated May 19, 2020 (ML20140A342)
2. TVA letter to NRC, CNL-20-091, Response to Request for Additional Information Regarding Application to Modify the Watts Bar Nuclear Plant Unit 1 and Unit 2 Technical Specifications for Main Control Room Chiller Completion Time Extension (WBN-TS-18-16) (EPID L-2020-LLA-0114), dated December 16, 2020 (ML20351A424)
3. NRC letter to TVA, Watts Bar Nuclear Plant, Units 1 and 2 - Issuance of Amendment Nos. 145 and 51 for One-Time Change to Technical Specification 3.7.11 to Extend the Completion Time for Main Control Room Chiller Modifications (EPID L-2020-LLA-0114),

dated May 5, 2021 (ML21078A484)

4. TVA letter to NRC, CNL-23-015, Expedited Application to Modify the Watts Bar Nuclear Plant, Unit 1 and Unit 2 Technical Specifications for Main Control Room Chiller Completion Time Extension (WBN-TS-22-08), dated February 27, 2023 (ML23058A447)
5. NRC letter to TVA, Watts Bar Nuclear Plant, Units 1 and 2 - Issuance of Amendment Nos. 162 And 69 Regarding Change to Date in Footnotes for Technical Specification 3.7.11, Control Room Emergency Air Temperature Control System (CREATCS) (EPID L-2023-LLA-0029), dated June 7, 2023 (ML23122A232)
6. NRC letter to TVA, Watts Bar Nuclear Plant, Units 1 and 2 - Regulatory Audit Summary Related to Request to Technical Specification 3.7.11, Control Room Emergency Air Temperature Control System (CREATCS) (EPID L-2020-LLA-0114), dated January 26, 2021 (ML21012A084)
7. NRC letter to Exelon Generation Company LLC, Byron Station, Unit Nos. 1 and 2, and Braidwood Station, Units 1 and 2 - Issuance of Amendments Regarding Control Room Ventilation Temperature Control System (CAC Nos. MF9932, MF9933, MF9934, and MF9935; EPID L-2017-LLA-0247), dated April 30,2018 (ML18054B436).
8. NRC letter to Duke Energy Carolinas, LLC, Catawba Nuclear Station, Units 1 and 2 -

Issuance of Amendment Nos. 319 and 315 To Technical Specification 3.7.11, Control Room Area Chill Water System (CRACWS) (EPID L-2023-LLA-0093), dated March 8, 2024 (ML24017A065)

Enclosure CNL-24-004 Proposed TS Changes (Mark-Ups) for WBN Unit 1

CREATCS 3.7.11 Watts Bar-Unit 1 3.7-26 Amendment 35, 132, 145, 162, ACTIONS (continued)

CONDITION REQUIRED ACTION COMPLETION TIME D.

Two CREATCS trains inoperable in MODE 5 or 6, or during movement of irradiated fuel assemblies.

D.1 Initiate action to implement mitigating actionsSuspend movement of irradiated fuel assemblies.

AND D.2 Verify control room temperature 90°F.

AND D.3 Restore one CREATCS train to OPERABLE status.

Immediately Immediately and once per hour thereafter 96 hours0.00111 days <br />0.0267 hours <br />1.587302e-4 weeks <br />3.6528e-5 months <br /> E.

Required Action and associated Completion Time of Condition D not metTwo CREATCS trains inoperable in MODE 1, 2, 3, or 4.

E.1 Be in MODE 3Enter LCO 3.0.3.

AND E.2 Be in MODE 5 6 hour6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />sImmediately**

36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br /> F.

Required Action and associated Completion Time of Condition D not met in MODE 5 or 6, or during movement of irradiated fuel assemblies.

F.1 Suspend movement of irradiated fuel assemblies Immediately SURVEILLANCE REQUIREMENTS SURVEILLANCE FREQUENCY SR 3.7.11.1 Verify each CREATCS train has the capability to remove the assumed heat load.

In accordance with the Surveillance Frequency Control Program

    • An allowance to monitor the main control room temperature every hour and verify the main control room temperature is less than or equal to 90°F is permitted for up to four days in lieu of the immediate entry into LCO 3.0.3. If the main control room temperature exceeds 90°F, or the duration

CREATCS 3.7.11 Watts Bar-Unit 1 3.7-27 Amendment 35, 132, 145, 162, without a train of CREATCS being OPERABLE exceeds four days, immediate entry into LCO 3.0.3 is required. This provision is only applicable during modification activities planned for the upgrade of the main control room chillers beginning no earlier than July 1, 2023, and ending no later than December 31, 2024, provided compensatory measures are implemented as described in TVA letter CNL-20-012, dated May 19, 2020.

Enclosure CNL-24-004 Proposed TS Changes (Mark-Ups) for WBN Unit 2

CREATCS 3.7.11 Watts Bar-Unit 2 3.7-24 Amendment 51, 69, 3.7 PLANT SYSTEMS 3.7.11 Control Room Emergency Air Temperature Control System (CREATCS)

LCO 3.7.11 Two CREATCS trains shall be OPERABLE.

APPLICABILITY:

MODES 1, 2, 3, 4, 5, and 6, During movement of irradiated fuel assemblies.

ACTIONS CONDITION REQUIRED ACTION COMPLETION TIME A. One CREATCS train inoperable.

A.1 Restore CREATCS train to OPERABLE status.

30 days

  • B. Required Action and associated Completion Time of Condition A not met in MODE 1, 2, 3, or 4.

B.1 Be in MODE 3.

6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> AND B.2 Be in MODE 5.

36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br /> C. Required Action and associated Completion Time of Condition A not met in MODE 5 or 6, or during movement of irradiated fuel assemblies.

C.1 Place OPERABLE CREATCS train in operation.

Immediately OR C.2 Suspend movement of irradiated fuel assemblies.

Immediately (continued)

An allowance is permitted for one CREATCS train to be inoperable for up to 60 days. This TS provision is only authorized for one entry per train during modification activities planned for the upgrade of the main control room chillers beginning no earlier than July 1, 2023, and ending no later than December 31, 2024, provided compensatory measures are implemented as described in TVA letter CNL-20-012, dated May 19, 2020.

CREATCS 3.7.11 Watts Bar-Unit 2 3.7-25 Amendment 36, 51, 69, ACTIONS (continued)

CONDITION REQUIRED ACTION COMPLETION TIME D. Two CREATCS trains inoperablein MODE 5 or 6, or during movement of irradiated fuel assemblies.

D.1 Initiate action to implement mitigating actionsSuspend movement of irradiated fuel assemblies.

Immediately AND D.2 Verify control room temperature 90°F.

Immediately and once per hour thereafter AND D.3 Restore one CREATCS train to OPERABLE status 96 hours0.00111 days <br />0.0267 hours <br />1.587302e-4 weeks <br />3.6528e-5 months <br /> E. Required Action and associated Completion Time of Condition D not metTwo CREATCS trains inoperable in MODE 1, 2, 3, or 4.

E.1 Be in MODE 3Enter LCO 3.0.3.

6 hour6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />sImmediately**

AND E.2 Be in MODE 5.

36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br /> F. Required Action and associated Completion Time of Condition D not met in MODE 5 or 6, or during movement of irradiated fuel assemblies.

F.1 Suspend movement of irradiated fuel assemblies Immediately An allowance to monitor the main control room temperature every hour and verify the main control room temperature is less than or equal to 90°F is permitted for up to four days in lieu of the immediate entry into LCO 3.0.3. If the main control room temperature exceeds 90°F, or the duration without a train of CREATCS being OPERABLE exceeds four days, immediate entry into LCO 3.0.3 is required. This provision is only applicable during modification activities

CREATCS 3.7.11 Watts Bar-Unit 2 3.7-26 Amendment 36, 51, 69, planned for the upgrade of the main control room chillers beginning no earlier than July 1, 2023, and ending no later than December 31, 2024, provided compensatory measures are implemented as described in TVA letter CNL-20-012, dated May 19, 2020.

CREATCS 3.7.11 Watts Bar-Unit 2 3.7-25a Amendment 36, 51, 69, SURVEILLANCE REQUIREMENTS SURVEILLANCE FREQUENCY SR 3.7.11.1 Verify each CREATCS train has the capability to remove the assumed heat load.

In accordance with the Surveillance Frequency Control Program

Enclosure CNL-24-004 Proposed TS Bases Page Changes (Mark-Ups) for WBN Units 1 and 2 (For Information Only)

CREATCS B 3.7.11 BASES (continued)

Watts Bar-Unit 1 B 3.7-52 Revision 64, Amendment 50, APPLICABLE heat loads from the control room, which include consideration of equipment SAFETY ANALYSES heat loads and personnel occupancy requirements, to ensure equipment (continued)

OPERABILITY (Ref. 3).

The CREATCS satisfies Criterion 3 of the NRC Policy Statement.

LCO Two independent and redundant trains of the CREATCS are required to be OPERABLE to ensure that at least one is available, assuming a single failure disabling the other train. Total system failure could result in the equipment operating temperature exceeding limits in the event of an accident.

The CREATCS is considered to be OPERABLE when the individual components necessary to maintain the control room temperature are OPERABLE in both trains. These components include the chillers, AHUs, and associated temperature control instrumentation. In addition, the CREATCS must be operable to the extent that air circulation can be maintained.

APPLICABILITY In MODES 1, 2, 3, 4, 5, and 6, and during movement of irradiated fuel assemblies, the CREATCS must be OPERABLE to ensure that the control room temperature will not exceed equipment operational requirements following isolation of the control room.

In MODE 5 or 6, CREATCS is required during a control room isolation following a waste gas decay tank rupture.

ACTIONS A.1 With one CREATCS train inoperable, action must be taken to restore OPERABLE status within 30 days. In this Condition, the remaining OPERABLE CREATCS train is adequate to maintain the control room temperature within limits. However, the overall reliability is reduced because a single failure in the OPERABLE CREATCS train could result in loss of CREATCS function. The 30 day Completion Time is based on the low probability of an event requiring control room isolation, the consideration that the remaining train can provide the required protection, and that alternate safety or nonsafety related cooling means are available, including the option to provide normal cooling with a non-safety related chiller and the remaining train in standby.

CREATCS B 3.7.11 BASES Watts Bar-Unit 1 B 3.7-54 Revision 64, 162, 172, Amendment 50, 132, 145, ACTIONS C.1 and C.2 (continued)

(continued)

An alternative to Required Action C.1 is to immediately suspend activities that present a potential for releasing radioactivity that might require isolation of the control room. This places the unit in a condition that minimizes accident risk.

This does not preclude the movement of fuel to a safe position.

D.1, D.2, and D.3 If both CREATCS trains are inoperable, the CREATCS may not be capable of performing its intended function. Therefore, the control room area temperature is required to be monitored to ensure that temperature is being maintained low enough that equipment in the control room is not adversely affected and habitability is maintained. The following mitigating actions will be used to maintain control room area temperature A non-safety related chiller system with a DG to provide power to the non-safety related system will be operated.

With both CREATCS trains inoperable, TVA will employ a graded approach to defense-in-depth and protected equipment strategies based on the operating status of the affected unit. The risk of the activity will be assessed and managed, including the use of physical barriers as needed.

TVA procedures will preclude work on or near protected equipment and limit access to the area to emergency situations and non-intrusive monitoring of running equipment per operator rounds.

Other mitigating actions such as opening cabinet doors, use of fans to circulate air within the MCRHZ, use of ice vests, may be employed.

With the control room temperature being maintained within the temperature limit, 96 hours0.00111 days <br />0.0267 hours <br />1.587302e-4 weeks <br />3.6528e-5 months <br /> is allowed to restore a CREATCS train to OPERABLE status. This Completion Time is reasonable considering that the main control room (MCR) temperature is being maintained within limits and the low probability of an event occurring requiring control room isolation (Ref 4). The specified temperature limit of 90°F is above the normal operating temperature of the MCR (approximately 75°F), providing operational flexibility when implementing the mitigating actions.

This temperature does not impact the operability of equipment or habitability of the MCR. The limit of 90°F maintains margin below the lowest specification for the MCR equipment cabinets of 104°F (Ref. 4).In MODE 5 or 6, or during movement of irradiated fuel assemblies, with two CREATCS trains inoperable, action must be taken immediately to suspend activities that could result in a release of radioactivity that might require isolation of the control room. This places the unit in a condition that minimizes risk. This does not preclude the

CREATCS B 3.7.11 BASES Watts Bar-Unit 1 B 3.7-54a Revision 64, 162, 172, Amendment 50, 132, 145, ACTIONS movement of fuel to a safe position.

(continued)

E.1 and E.2 In MODE 1, 2, 3, or 4, if the inoperable CREATCS trains cannot be restored to OPERABLE status within the required Completion Time, the unit must be placed in a MODE that minimizes the risk. To achieve this status, the unit must be placed in at least MODE 3 within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />, and in MODE 5 within 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />. The allowed Completion Times are reasonable, based on operating experience, to reach the required unit conditions from full power conditions in an orderly manner and without challenging unit systems.

If both CREATCS trains are inoperable in MODE 1, 2, 3, or 4 the CREATCS may not be capable of performing its intended function. Therefore, LCO 3.0.3 must be entered immediately. The Completion Time is modified by a footnote that states an allowance to monitor the main control room temperature every hour and verify the main control room temperature is less than or equal to 90°F is permitted for up to four days in lieu of the immediate entry into LCO 3.0.3. If the main control room temperature exceeds 90°F, or the duration without a train of CREATCS being OPERABLE exceeds four days, immediate entry into LCO 3.0.3 is required. This provision is only applicable during modification activities planned for the upgrade of the main control room chillers beginning no earlier than July 1, 2023, and ending no later than December 31, 2024, provided the following compensatory measures are implemented as described in TVA letter CNL-20-012, dated May 19, 2020.

  • A temporary, non-safety related chiller system with a temporary DG to provide power to the temporary chiller system will be installed and operated as described in the LAR.
  • Instructions for operation of the temporary cooling equipment will be provided.
  • During replacement of the CREATCS chillers, TVA will employ a graded approach to defense-in-depth and protected equipment strategies based on the operating status of the affected unit. The risk of the activity will be assessed and managed, including the use of physical barriers as needed. Additionally, TVA procedures preclude work on or near protected equipment and limit access to the area to emergency situations and non-intrusive monitoring of running equipment per operator rounds.
  • During replacement of the CREATCS chillers, no elective maintenance will be performed on TS related support equipment for the Operable CREATCS chiller except for any required TS SRs.

The purpose of the footnote is to ensure the MCR temperature is being

CREATCS B 3.7.11 BASES Watts Bar-Unit 1 B 3.7-54a Revision 64, 162, 172, Amendment 50, 132, 145, ACTIONS E.1 and E.2 (continued)

(continued) controlled. The specified temperature limit of 90°F is above the normal operating temperature of the MCR (approximately 75°F), providing operational flexibility when implementing the mitigating actions. This temperature does not impact the operability of equipment or habitability of the MCR. The limit of 90°F maintains margin below the lowest specification for the MCR equipment cabinets of 104°F.

Subsequent to immediate MCR temperature verification, the one-hour frequency is adequate given the indications available in the MCR. Main control room temperature data is measured and displayed from readily available equipment in the MCR and operators will have awareness of temperature trending relative to the 90°F limit.

F.1 In MODE 5 or 6, or during movement of irradiated fuel assemblies, with two CREATCS trains inoperable, action must be taken immediately to suspend activities that could result in a release of radioactivity that might require isolation of the control room. This places the unit in a condition that minimizes risk. This does not preclude the movement of fuel to a safe position.

SURVEILLANCE SR 3.7.11.1 REQUIREMENTS This SR verifies that the heat removal capability of the system is sufficient to remove the heat load assumed in the sizing calculations in the control room.

This SR consists of a combination of testing and calculations. This is accomplished by verifying that the system has not degraded. The only measurable parameters that could degrade undetected during normal operation are the system air flow and chilled water flow rate. Verification of these two flow rates will provide assurance that the heat removal capacity of the system is still adequate. The Surveillance Frequency is controlled under the Surveillance Frequency Control Program.

REFERENCES

1.

Watts Bar FSAR, Section 9.4.1, "Control Room Area Ventilation System."

2.

Watts Bar FSAR, Section 3.7.3.18, Seismic Qualification of Main Control Room Suspended Ceiling and Air Delivery Components.

3.

NRC Safety Evaluation dated February 12, 2004, for License Amendment 50.

4.

NRC Safety Evaluation dated May 5, 2021, for License Amendment 145

CREATCS B 3.7.11 Bases (continued)

Revision Watts Bar - Unit 2 B 3.7-60 Amendment APPLICABLE SAFETY ANALYSES (continued) capable of removing sensible and latent heat loads from the control room, which include consideration of equipment heat loads and personnel occupancy requirements, to ensure equipment OPERABILITY (Ref. 3).

The CREATCS satisfies Criterion 3 of 10 CFR 50.36(c)(2)(ii).

LCO Two independent and redundant trains of the CREATCS are required to be OPERABLE to ensure that at least one is available, assuming a single failure disabling the other train. Total system failure could result in the equipment operating temperature exceeding limits in the event of an accident.

The CREATCS is considered to be OPERABLE when the individual components necessary to maintain the control room temperature are OPERABLE in both trains. These components include the chillers, AHUs, and associated temperature control instrumentation. In addition, the CREATCS must be operable to the extent that air circulation can be maintained.

APPLICABILITY In MODES 1, 2, 3, 4, 5, and 6, and during movement of irradiated fuel assemblies, the CREATCS must be OPERABLE to ensure that the control room temperature will not exceed equipment operational requirements following isolation of the control room.

In MODE 5 or 6, CREATCS is required during a control room isolation following a waste gas decay tank rupture.

ACTIONS A.1 With one CREATCS train inoperable, action must be taken to restore OPERABLE status within 30 days. In this Condition, the remaining OPERABLE CREATCS train is adequate to maintain the control room temperature within limits. However, the overall reliability is reduced because a single failure in the OPERABLE CREATCS train could result in loss of CREATCS function. The 30 day Completion Time is based on the low probability of an event requiring control room isolation, the consideration that the remaining train can provide the required protection, and that alternate safety or non-safety related cooling means are available, including the option to provide normal cooling with a non-safety related chiller and the remaining train in standby.

CREATCS B 3.7.11 Bases (continued)

Watts Bar - Unit 2 B 3.7-62 Revision 47, 71, Amendment 51, 69, ACTIONS (continued)

C.1 and C.2 (continued)

In MODE 5 or 6, or during movement of irradiated fuel, if the inoperable CREATCS train cannot be restored to OPERABLE status within the required Completion Time, the OPERABLE CREATCS train must be placed in operation immediately. This action ensures that the remaining train is OPERABLE, that no failures preventing automatic actuation will occur, and that active failures will be readily detected.

An alternative to Required Action C.1 is to immediately suspend activities that present a potential for releasing radioactivity that might require isolation of the control room. This places the unit in a condition that minimizes accident risk. This does not preclude the movement of fuel to a safe position.

D.1, D.2, and D.3 If both CREATCS trains are inoperable, the CREATCS may not be capable of performing its intended function. Therefore, the control room area temperature is required to be monitored to ensure that temperature is being maintained low enough that equipment in the control room is not adversely affected and habitability is maintained. The following mitigating actions will be used to maintain control room area temperature A non-safety related chiller system with a DG to provide power to the non-safety related system will be operated.

With both CREATCS trains inoperable, TVA will employ a graded approach to defense-in-depth and protected equipment strategies based on the operating status of the affected unit. The risk of the activity will be assessed and managed, including the use of physical barriers as needed.

TVA procedures will preclude work on or near protected equipment and limit access to the area to emergency situations and non-intrusive monitoring of running equipment per operator rounds.

Other mitigating actions such as opening cabinet doors, use of fans to circulate air within the MCRHZ, use of ice vests, may be employed.

With the control room temperature being maintained within the temperature limit, 96 hours0.00111 days <br />0.0267 hours <br />1.587302e-4 weeks <br />3.6528e-5 months <br /> is allowed to restore a CREATCS train to OPERABLE status. This Completion Time is reasonable considering that the main control room (MCR) temperature is being maintained within limits and the low probability of an event occurring requiring control room

CREATCS B 3.7.11 Bases Watts Bar - Unit 2 B 3.7-62a Revision 47, Amendment 51, ACTIONS (continued)

D.1, D.2, and D.3 (continued) isolation (Ref 4). The specified temperature limit of 90°F is above the normal operating temperature of the MCR (approximately 75°F), providing operational flexibility when implementing the mitigating actions. This temperature does not impact the operability of equipment or habitability of the MCR. The limit of 90°F maintains margin below the lowest specification for the MCR equipment cabinets of 104°F (Ref. 4).In MODE 5 or 6, or during movement of irradiated fuel assemblies, with two CREATCS trains inoperable, action must be taken immediately to suspend activities that could result in a release of radioactivity that might require isolation of the control room. This places the unit in a condition that minimizes risk. This does not preclude the movement of fuel to a safe position.

E.1 and E.2 In MODE 1, 2, 3, or 4, if the inoperable CREATCS trains cannot be restored to OPERABLE status within the required Completion Time, the unit must be placed in a MODE that minimizes the risk. To achieve this status, the unit must be placed in at least MODE 3 within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />, and in MODE 5 within 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />. The allowed Completion Times are reasonable, based on operating experience, to reach the required unit conditions from full power conditions in an orderly manner and without challenging unit systems.If both CREATCS trains are inoperable in MODE 1, 2, 3, or 4, the CREATCS may not be capable of performing its intended function.

Therefore, LCO 3.0.3 must be entered immediately. The Completion Time is modified by a footnote that states an allowance to monitor the main control room temperature every hour and verify the main control room temperature is less than or equal to 90°F is permitted for up to four days in lieu of the immediate entry into LCO 3.0.3. If the main control room temperature exceeds 90°F, or the duration without a train of CREATCS being OPERABLE exceeds four days, immediate entry into LCO 3.0.3 is required. This provision is only applicable during modification activities planned for the upgrade of the main control room chillers beginning no earlier than July 1, 2023, and ending no later than December 31, 2024, provided the following compensatory measures are implemented as described in TVA letter CNL-20-012, dated May 19, 2020.

A temporary, non-safety related chiller system with a temporary DG to provide power to the temporary chiller system will be installed and operated as described in the LAR.

Instructions for operation of the temporary cooling equipment will be provided.

During replacement of the CREATCS chillers, TVA will employ a graded approach to defense-in-depth and protected equipment strategies

CREATCS B 3.7.11 Bases Watts Bar - Unit 2 B 3.7-62a Revision 47, Amendment 51, ACTIONS (continued) based on the operating status of the affected unit. The risk of the activity will be assessed and managed, including the use of physical barriers as needed. Additionally, TVA procedures preclude work on or near protected equipment and limit access to the area to emergency situations and non-intrusive monitoring of running equipment per operator rounds.

During replacement of the CREATCS chillers, no elective maintenance will be performed on TS related support equipment for the Operable CREATCS chiller except for any required TS SRs.

The purpose of the footnote is to ensure the MCR temperature is being controlled. The specified temperature limit of 90°F is above the normal operating temperature of the MCR (approximately 75°F), providing operational flexibility when implementing the mitigating actions. This temperature does not impact the operability of equipment or habitability of the MCR. The limit of 90°F maintains margin below the lowest specification for the MCR equipment cabinets of 104°F. Subsequent to immediate MCR temperature verification, the one-hour frequency is adequate given the indications available in the MCR. Main control room temperature data is measured and displayed from readily available equipment in the MCR and operators will have awareness of temperature trending relative to the 90°F limit.

F.1 In MODE 5 or 6, or during movement of irradiated fuel assemblies, with two CREATCS trains inoperable, action must be taken immediately to suspend activities that could result in a release of radioactivity that might require isolation of the control room. This places the unit in a condition that minimizes risk. This does not preclude the movement of fuel to a safe position.

SURVEILLANCE REQUIREMENTS SR 3.7.11.1 This SR verifies that the heat removal capability of the system is sufficient to remove the heat load assumed in the sizing calculations in the control room. This SR consists of a combination of testing and calculations. This is accomplished by verifying that the system has not degraded. The only measurable parameters that could degrade undetected during normal operation are the system air flow and chilled water flow rate. Verification of these two flow rates will provide assurance that the heat removal capacity of the system is still adequate. The Surveillance Frequency is controlled under the Surveillance Frequency Control Program.

CREATCS B 3.7.11 Bases Watts Bar - Unit 2 B 3.7-62b Revision 47, Amendment 51, REFERENCES

1.

Watts Bar FSAR, Section 9.4.1, Control Room Area Ventilation System.

2.

Watts Bar FSAR, Section 3.7.3.18, Seismic Qualification of Main Control Room Suspended Ceiling and Air Delivery Components.

3.

NRC Safety Evaluation dated February 12, 2004, for License Amendment 50.

4.

NRC Safety Evaluation dated May 5, 2021, for License Amendment 145

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