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)

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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)
ML20351A424
Person / Time
Site: Watts Bar  Tennessee Valley Authority icon.png
Issue date: 12/16/2020
From: Polickoski J
Tennessee Valley Authority
To:
Document Control Desk, Office of Nuclear Reactor Regulation
References
CNL-20-091, EPID L-2020-LLA-0114
Download: ML20351A424 (32)
v • d • e


Text

Tennessee Valley Authority, 1101 Market Street, Chattanooga, Tennessee 37402 CNL-20-091 December 16, 2020 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:

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)

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. NRC Electronic Mail to TVA, Request for Additional Information Regarding TVA's Request to Revise TS 3.7.11 Related to the MCR Chiller Replacement (EPID L-2020-LLA-0114), dated November 17, 2020 (ML20322A441)

In Reference 1, Tennessee Valley Authority (TVA) submitted 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 amendment revises WBN Units 1 and 2 Technical Specification (TS) 3.7.11 "Control Room Emergency Air Temperature Control System (CREATCS)," 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 CREATCS chillers. The proposed amendment also adds 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 four days in the event that both CREATCS trains are inoperable during the modifications to the CREATCS chillers. The proposed changes are in support of modifications to the WBN Units 1 and 2 Main Control Room (MCR) CREATCS chillers.

U.S. Nuclear Regulatory Commission CNL-20-091 Page 2 December 16, 2020 In Reference 2, the Nuclear Regulatory Commission (NRC) issued a Request for Additional Information (RAI) and requested TVA respond by December 17, 2020. Enclosure 1 provides the TVA response to the RAI.

Additionally, the timeframe for performing the modifications to the WBN Units 1 and 2 MCR CREATCS chillers has been delayed from the timeframe of May 1, 2021, to October 1, 2022, in Reference 1, to the timeframe of May 1, 2022, to May 1, 2023.

Accordingly, Enclosure 2 provides a revised Section 2.2 and Section 3.4.1 of the enclosure to Reference 1 to reflect the revised dates. Enclosure 3 provides the revised WBN Units 1 and 2 TS 3.7.11 pages marked-up to reflect the revised dates and the response to STSB-RAI-1. Enclosure 4 provides the revised WBN Units 1 and 2 TS 3.7.11 pages retyped to reflect the revised dates and the response to STSB-RAI-1. Enclosure 5 provides the revised 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. Enclosures 2, 3, 4, and 5 supersede the corresponding information provided in the enclosure to Reference 1.

This letter does not change the no significant hazard considerations nor the environmental considerations contained in Reference 1. Additionally, in accordance with 10 CFR 50.91(b)(1), TVA is sending a copy of this letter and the enclosure to the Tennessee Department of Environment and Conservation.

There are no new regulatory commitments associated with this submittal. Please address any questions regarding this request to Kimberly D. Hulvey at (423) 751-3275.

I declare under penalty of perjury that the foregoing is true and correct. Executed on this 16th day of December 2020.

Respectfully, James T. Polickoski Director, Nuclear Regulatory Affairs & Support Services Enclosures

1. Response to NRC Request for Additional Information
2. Revised Section 2.2 and Section 3.4.1 of the enclosure to CNL-20-012
3. Revised TS Changes (Mark-Ups) for WBN Units 1 and 2 TS 3.7.11
4. Revised TS Change (Final Typed) for WBN Units 1 and 2 TS 3.7.11
5. Revised TS Bases Page Changes (Mark-Ups) for WBN Units 1 and 2 (For Information Only) cc (see Page 3)

U.S. Nuclear Regulatory Commission CNL-20-091 Page 3 December 16, 2020 cc (Enclosures):

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

Enclosure 1 Response to NRC Request for Additional Information NRC Introduction By letter dated May 19, 2020, Tennessee Valley Authority (TVA) submitted a license amendment request (LAR) to revise the technical specifications for the Watts Bar Nuclear Plant (WBN), Units 1 and 2 (Agencywide Documents and Access Management System Accession No. ML20140A342). The requested changes would revise WBN, Units 1 and 2, Technical Specification (TS) 3.7.11 "Control Room Emergency Air Temperature Control System (CREATCS)," 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 CREATCS chillers. Additionally, 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 four days in the event that both CREATCS trains are inoperable during the modifications to the CREATCS chillers would be added. The one-time TS changes are limited to the time that the CREATCS modifications are being performed between the timeframe of May 1, 2021, and October 1, 2022.

The U.S. Nuclear Regulatory Commission (NRC) staff is reviewing the request and has identified areas for which additional information is needed prior to completing its review.

The staffs requests for additional information (RAI) are below.

SCPB-RAI-1 Regulatory Basis Appendix A to Part 50 of Title 10 of the Code of Federal Regulations (10 CFR) contains the principal design criteria for a proposed facility that must be included in an application for a design certification, combined license, design approval, or manufacturing license, respectively. These General Design Criteria (GDC) establish the minimum requirements for the principal design criteria for water-cooled nuclear power plants similar in design and location to plants for which construction permits have been issued by the Commission.

GDC 19, Control room, states, in part:

A control room shall be provided from which actions can be taken to operate the nuclear power unit safely under normal conditions and to maintain it in a safe condition under accident conditions, including loss-of-coolant accidentsEquipment at appropriate locations outside the control room shall be provided (1) with a design capability for prompt hot shutdown of the reactor, including necessary instrumentation and controls to maintain the unit in a safe condition during hot shutdown, and (2) with a potential capability for subsequent cold shutdown of the reactor through the use of suitable procedures.

Issue TVA has proposed a one-time change to the footnote for the TS 3.7.11, Condition E, completion time to allow a four-day delayed entry into LCO 3.0.3. The proposed change states that main control room (MCR) temperature will be monitored every hour to verify that it is less than or equal to 90 degrees Fahrenheit (°F), and that if the temperature goes CNL-20-091 E1-1 of 8

Enclosure 1 above 90 °F, or the duration without a train of CREATCS being operable exceeds four days, immediate entry into LCO 3.0.3 is required.

As stated in LAR Section 3.4.2:

The proposed footnote to WBN Units 1 and 2 TS 3.7.11, Condition E, is also based on verifying that the MCR temperature is less than or equal to 90°F. The temperature limit for MCR equipment operability is 104°F. 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.

The LAR further states:

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 heatup of the MCR and surrounding areas. The analysis assumed normal operating heat loads, normal average initial room temperatures, summertime maximum outdoor temperatures, one [air handling unit] AHU operating, and no chillers in operation. The calculation demonstrates 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 temporary chiller system cooling.

During the regulatory audit, the staff audited the evaluation referenced above. Calculation MDQ00003120090157, Revision 7, Main Control Room Floor (EL. 755.0) Transient Temperature Analysis, contains Figure H.4, Cases H1 through H3 Main Control Room Temperatures, which shows the calculated MCR transient temperatures. Figure H.4 supports the passage above and indicates that with normal heat loads (i.e., non-LOCA), the time to heat up the MCR to 104 °F from approximately 75 °F for the worst case (i.e., Case H1) is 5.28 hours3.240741e-4 days <br />0.00778 hours <br />4.62963e-5 weeks <br />1.0654e-5 months <br />. This figure also indicates that the MCR would reach 106°F after 7 hours8.101852e-5 days <br />0.00194 hours <br />1.157407e-5 weeks <br />2.6635e-6 months <br /> and 118°F after 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, absent a cooling water supply.

The proposed one-time change to the footnote for the TS 3.7.11, Condition E, completion time would allow the MCR temperature to reach 90°F before LCO 3.0.3 is entered.

LCO 3.0.3 requires that the reactor shall be placed in MODE 3 within 7 hours8.101852e-5 days <br />0.00194 hours <br />1.157407e-5 weeks <br />2.6635e-6 months <br />; MODE 4 within 13 hours1.50463e-4 days <br />0.00361 hours <br />2.149471e-5 weeks <br />4.9465e-6 months <br />; and MODE 5 within 37 hours4.282407e-4 days <br />0.0103 hours <br />6.117725e-5 weeks <br />1.40785e-5 months <br />.

The staff notes that the MCR could reach the 104°F limit for MCR operability and the safety-related equipment operability/integrity could be challenged well before reaching MODE 3 within 7 hours8.101852e-5 days <br />0.00194 hours <br />1.157407e-5 weeks <br />2.6635e-6 months <br />; therefore, the staff requires additional information to find that the proposed TS change is acceptable.

Request Provide a discussion and justification of the measures, mitigation, or procedures that TVA will implement 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.

CNL-20-091 E1-2 of 8

Enclosure 1 TVA Response to SCPB-RAI-1 WBN Units 1 and 2 TS 3.7.11, Condition E, requires immediate entry into TS LCO 3.0.3 if two CREATCS trains become inoperable in Modes 1, 2, 3, or 4. This would initiate a dual-unit shutdown which requires the units to be in in Mode 3 within seven hours; Mode 4 within 13 hours1.50463e-4 days <br />0.00361 hours <br />2.149471e-5 weeks <br />4.9465e-6 months <br />; and Mode 5 within 37 hours4.282407e-4 days <br />0.0103 hours <br />6.117725e-5 weeks <br />1.40785e-5 months <br />. As noted in the LAR, while performing the chiller replacement on one of the CREATCs trains, if the second train of CREATCS would become inoperable, the proposed footnote to TS 3.7.11, Condition E, would allow a delayed entry into TS LCO 3.0.3 for no longer than four days provided that the MCR temperature is monitored every hour to verify that the MCR temperature is less than or equal to 90°F.

During this timeframe, the temporary chiller will be available to provide cooling to the MCR.

If the MCR temperature exceeds 90°F, both units would immediately enter TS LCO 3.0.3 and initiate a dual-unit shutdown. Operators would perform the same actions for a dual-unit shutdown as they would for any entry into TS 3.0.3. However, as noted in the above RAI, the MCR temperature would be at 90°F rather than the normal ambient temperature of 75°F. The below information describes the actions and measure 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.

Actions taken by the unit operators would include a request for priority maintenance to restore the inoperable CREATCS train and reviewing the operation of the non-safety related chiller system to ensure that it continues to supply chilled water to the MCR HVAC system.

The non-safety related chiller system is designed to provide adequate cooling to maintain the MCR at its nominal operating temperature.

If the temporary chiller system were to fail, the MCR could heat up as described in Calculation MDQ00003120090157, Revision 7, which indicates that the MCR heat-up from 75°F to 104°F would take about 5.28 hours3.240741e-4 days <br />0.00778 hours <br />4.62963e-5 weeks <br />1.0654e-5 months <br />. Because operators will be monitoring the MCR temperature every hour, it could take the MCR operators an hour to discover that the MCR temperature had risen beyond 90°F, which would leave approximately 4.28 hours3.240741e-4 days <br />0.00778 hours <br />4.62963e-5 weeks <br />1.0654e-5 months <br /> of continued heat up before the MCR temperature reaches 104°F. Additionally, the WBN dual-unit Updated Final Safety Analysis Report (UFSAR) Section 9.4.1.3 states, All MCR equipment operates normally at an ambient temperature of 75°F. Abnormal excursions of short duration (12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> or less) to 104°F maximum and 60°F minimum may occur without adverse effects on the equipment. Combined with the calculated temperature rise, the equipment in the MCR will perform its function for approximately 17.28 hours3.240741e-4 days <br />0.00778 hours <br />4.62963e-5 weeks <br />1.0654e-5 months <br /> after a loss of cooling, and at least 16.28 hours3.240741e-4 days <br />0.00778 hours <br />4.62963e-5 weeks <br />1.0654e-5 months <br /> after the operators determined the MCR temperature exceeded 90°F.

As noted previously, while performing the chiller replacement activities, if both CREATCS trains become inoperable and the MCR temperature exceeds 90°F, both units would enter TS LCO 3.0.3 and commence a controlled shutdown in accordance with normal plant operating procedures. The length of the shutdown activities would be dependent on unit conditions at the time the shutdown commenced, but in no case would exceed the times required by TS LCO 3.0.3. Shutdown to Mode 3 would occur within seven hours of entry in the TS LCO 3.0.3, within the 16.28 hours3.240741e-4 days <br />0.00778 hours <br />4.62963e-5 weeks <br />1.0654e-5 months <br /> that the MCR equipment provides reliable operation. Mode 4 (13 hours1.50463e-4 days <br />0.00361 hours <br />2.149471e-5 weeks <br />4.9465e-6 months <br /> from entry into TS LCO 3.0.3) would also be achieved within the 16.28-hour period that the MCR equipment remains reliable. Plant conditions are monitored as required by operating procedures directing these shutdown evolutions.

CNL-20-091 E1-3 of 8

Enclosure 1 Achieving Mode 5 conditions is allowed to take as long as 37 hours4.282407e-4 days <br />0.0103 hours <br />6.117725e-5 weeks <br />1.40785e-5 months <br /> from entry into TS LCO 3.0.3, which is approximately 20.7 hours8.101852e-5 days <br />0.00194 hours <br />1.157407e-5 weeks <br />2.6635e-6 months <br /> past the documented instrument reliability duration described above. As noted in the RAI, based on the figures in Calculation MDQ00003120090157, Revision 7, the MCR temperature will continue to rise slowly over this time. As described below, there are actions available to the operators to attempt to remove heat from the MCR and procedures to abandon the MCR, if necessary.

To provide ventilation to the MCR with a loss of both trains of the CREATCS, the actions initially designed for smoke removal from the MCR can be used. There is no permanent equipment dedicated to smoke removal functions. However, equipment such as the battery room exhaust fans, spreading room exhaust fans, and toilet and locker room exhaust fans can be used with combinations of dampers and/or doors and portable ducts, and fans to evacuate smoke (or heated air) from the Control Building spaces. Operators can manually start any one of the toilet and locker room, battery room, and spreading room exhaust fans, align dampers, and open doors to remove air. The normal ventilation exhaust systems can generally be used to duct smoke directly outside. However, upon loss of power to the permanent fans, loss of air supply to dampers, and closure of fire/smoke dampers, portable ductwork and fans powered by portable generators, can be used to direct smoke through doorways or hatches to the outside of the building via the Turbine Building. In addition, natural venting may be used in some areas for smoke removal. These smoke removal actions would also be useful in removing heated air from the MCR.

In the unlikely event that the operators determined that the units could not be effectively controlled from the MCR, the units can be safely maintained and shutdown, if necessary, from the Auxiliary Control Room (ACR) in accordance with the plant Abnormal Operating Instructions. WBN has an auxiliary control system to address situations requiring MCR abandonment. This system is located outside of the control building and is physically independent of the control building. The design provides appropriate means to isolate the necessary safe shutdown equipment and control features from the control building. The system is provided to satisfy General Design Criteria (GDC) 19 in Appendix A to 10 CFR 50 and 10 CFR 50 Appendix R Section III.G.3 and III.L. In order to meet GDC 19 requirements, the auxiliary control system instrumentation and controls are physically remote from, and their circuits are electrically separated from, their counterparts in the MCR. In order to meet Appendix R requirements, the auxiliary control system is both physically and electrically independent of the control building. Neither GDC 19 nor Appendix R requires redundant auxiliary control systems (e.g., a Train A and Train B auxiliary control systems). This system and the associated operating procedure allow control of the units from Mode 3 to cold shutdown (Mode 5).

Therefore, with these actions and design attributes in place, both units can be safety brought to a Mode 5 condition if all cooling is lost in the MCR and the MCR heats up beyond 90°F while in TS 3.7.11, Condition E.

CNL-20-091 E1-4 of 8

Enclosure 1 EMIB-RAI-1 Regulatory Basis GDC 4, Environmental and dynamic effects design bases, states, in part, that [t]hese structures, systems, and components shall be appropriately protected against dynamic effects, including the effects of missiles, pipe whipping, and discharging fluids, that may result from equipment failures and from events and conditions outside the nuclear power unit.

Issue In Section 3.2, MCR Temporary Chilled Water Equipment Description, of the Enclosure to the LAR, TVA stated that a temporary nonsafety-related chiller system will be installed and used to support MCR cooling during the CREATCS chiller replacements, and that the temporary system is capable of providing adequate cooling to maintain the MCR within its normal temperature band.

In addition, in Section 3.2.1, MCR Temporary Air Conditioning Equipment Description, TVA stated that the temporary chiller equipment is nonsafety-related, but appropriate measures will be taken to minimize the potential for failure of the temporary chiller system and the control room envelope (CRE) boundary. In particular, TVA stated that the temporary hoses, pipe, and fittings are qualified for adequate pressure to protect against rupture and pipe whip, and that the valves at the penetrations are qualified for seismic retention to maintain the integrity of the control room envelope boundary. However, the TVA did not provide sufficient information to substantiate the above two statements.

The NRC staff notes that the temporary chiller equipment installation, though nonsafety-related, supports the safety function of MCR cooling during the CREATCS chiller replacements.

Request

a. Provide details on the qualification of the temporary hoses, pipe, and fittings for adequate pressure and any other applicable loads to protect against rupture and pipe whip.
b. Describe the rupture and pipe whip effects that have been considered.
c. Describe how the valves at the penetrations will be qualified for seismic retention to maintain the integrity of the CRE boundary including a description of the seismic effects that would be considered.

TVA Response to EMIB-RAI-1

a. The temporary chiller system hoses, adapters, pipe, and fittings at the penetrations for the CRE boundary are rated to a minimum of 125 pounds per square inch gauge (psig).

The pressure at the penetrations where these components enter the control building mechanical equipment room is 34.02 pounds per square inch absolute (psia)

(19.32 psig) with one pump supplying the system at 53.24 pounds per square inch differential (psid). Adding a second pump in series will impart the same differential pressure as the first pump (53.24 psid) resulting in a maximum pressure entering the Control Building Mechanical Equipment Room of 72.56 psig (19.32 psig plus 53.24 psid). Because the system pressure for the temporary system at the penetrations on the CNL-20-091 E1-5 of 8

Enclosure 1 Control Building side (i.e., 72.56 psig) is less than 125 psig, the component ratings bound the maximum system pressure of the temporary chiller system. Item b below provides further information on the qualification of the temporary hoses, pipe, and fittings for adequate pressure and any other applicable loads to protect against rupture and pipe whip effects.

b. As stated in item a above, the system pressure is less than 125 psig. Therefore, the component ratings bound the maximum system pressure of the temporary chiller system, protecting against rupture and pipe whip. The threshold for a system to be considered a high energy line is 275 psig and 200°F. Therefore, the temporary chiller system 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 existing flood protection features are adequate to accommodate any postulated leakage. The piping has been evaluated for internal pressure, deadweight, and seismic loading conditions, and meets the requirements of Seismic Category IL, which is defined in the WBN UFSAR, Section 3.2.1, as follows:

Piping, pumps, valves, and other fluid system components which must retain limited structural integrity because their failure could jeopardize to an unacceptable extent the achievement of a primary safety function or because they form an interface between Seismic Category I and non-Seismic Category I plant features, are designated by TVA as Seismic Category I(L) (i.e., limited requirements). Those fluid containing elements which are included in Seismic Category I(L) are seismically qualified to meet the intent of position 2 of Regulatory Guide 1.29. For Unit 2 the Seismic Category I(L) is subdivided into categories IL(A) Pressure boundary and position retention and IL(B) position retention.

Piping at the penetration is qualified for seismic retention (see item c below), which further provides protection against pipe whip and rupture.

c. The following information describes how the valves at the penetrations will be qualified for seismic retention to maintain the integrity of the CRE boundary including a description of the seismic effects that would be considered.

The cross-sectional area of the penetrations into the mechanical equipment rooms is bounded by the available breach margin for the CRE. The implementation instructions for installation of the temporary chiller system includes a requirement to coordinate the activity with other work requiring CRE breaches to ensure the margin is maintained.

Valves at the penetrations of the CRE boundary are supported from a short section of cantilevered pipe. The pipe (coupling) is welded to a baseplate which is attached to the Control Building (EL. 755.0) side of the penetration using concrete expansion anchors.

The valves, attached piping, baseplate, and anchorage are classified as Seismic Category I(L)A.

Conservative dead weight values were seismically accelerated considering the seismic response spectra from TVA report CEB-80-27, Revision 5, "Watts Bar Nuclear Plant Dynamic Earthquake Analysis of the Auxiliary Control Building and Response Spectra for Attached Equipment," and used to generate forces and moments for evaluation of piping, baseplates, and anchorage. The piping is considered rigid due to the short piping span and close proximity of the anchor. Unfactored stress allowables for American Society for Testing and Materials (ASTM) A53 schedule 40 Grade B pipe (12 ksi per ANSI B31.1) were used along with American Society of Mechanical Engineer (ASME) Boiler and Pressure Vessel (B&PV) Code equations to evaluate the piping. The CNL-20-091 E1-6 of 8

Enclosure 1 attaching structure (plate stress and anchorage) was also evaluated and the calculated stresses were determined to be acceptable in accordance with the requirements of the applicable design criteria.

A ball valve for the temporary chiller system is located in the piping prior to it entering the CRE boundary; however, the ball will not be installed in the highest stressed location. Further, the piping uses threaded joints and ball valve construction is typically at least as strong as a threaded joint. The ball valve is made of 316 stainless steel while the allowable stress for ASTM A53 is considered, conservatively. In accordance with the ASME B&PV Code,Section III - Division 1, subsection NC, Class 2 Components, Figure NC*3673.2(b)-1, a stress intensification factor (SIF) of 2.3 was utilized to accurately consider the threaded connection. The SIF is a factor applied to stresses in Code stress equations for Classes 2 and 3 piping which represents the reduction of endurance strength of a particular piping component over that of a straight pipe with a girth butt weld. Therefore, the computed stresses envelope the ball valve.

STSB-RAI-1 Regulatory Basis In 10 CFR 50.36, Technical specifications, the NRC established its regulatory requirements related to the content of TSs. Pursuant to 10 CFR 50.36, TSs are required to include items in the following categories: (1) safety limits, limiting safety system settings, and limiting control settings; (2) LCOs; (3) surveillance requirements; (4) design features; and (5) administrative controls. The regulation does not specify the particular requirements to be included in a plants TSs.

The regulation at 10 CFR 50.36(a)(1) states, in part, A summary statement of the bases or reasons for such specifications shall also be included in the application, but shall not become part of the technical specifications.

As required in 10 CFR 50.36(b), the technical specifications will be derived from the analyses and evaluation included in the safety analysis report, and amendments thereto.

As required in 10 CFR 50.36(c)(2), LCOs are the lowest functional capability or performance level of equipment required for safe operation of the facility. When LCOs are not met, the licensee shall shut down the reactor or follow any remedial action permitted by the TSs until the LCOs can be met.

Issue In Section 3.7 of the Enclosure to the LAR, TVA concluded that a one-time change of the TS 3.7.11 Completion Times is acceptable and stated:

The proposed one-time LAR in support of the modifications to the CREATCS trains is acceptable based on the compensatory measures and the low probability of an event requiring MCR isolation, the consideration that the remaining train can provide the required protection, and that alternate non-safety related cooling means are available.

CNL-20-091 E1-7 of 8

Enclosure 1 The proposed footnote for Condition A Completion Time stipulates that the allowance for a 60 day inoperability for one CREATCS train is contingent on implementation of compensatory measures as described in TVA letter CNL-20-012. The proposed footnote for Condition E Completion Time allows monitoring temperatures in lieu of immediate entry into LCO 3.0.3 but does not contain a similar contingency requiring implementation of compensatory measures as described in TVA letter CNL-20-012.

Request Explain why requiring implementation of compensatory measures such as those described in TVA letter CNL-20-012 is not necessary for the footnote for Condition E Completion Time.

TVA Response to STSB-RAI-1 As noted in WBN Units 1 and 2 TS 1.3, Completion Times:

If situations are discovered that require entry into more than one Condition at a time within a single LCO (multiple Conditions), the Required Actions for each Condition must be performed within the associated Completion Time. When in multiple Conditions, separate Completion Times are tracked for each Condition starting from the time of discovery of the situation that required entry into the Condition.

WBN Units 1 and 2 TS 3.7.11, Condition A, is entered when there is one CREATCS train inoperable. WBN Units 1 and 2 TS 3.7.11, Condition E, is entered when there are two CREATCS trains inoperable. Therefore, in accordance with WBN Units 1 and 2 TS 1.3, the required completion time of WBN Units 1 and 2 TS 3.7.11, Condition A, is still in effect when WBN Units 1 and 2 TS 3.7.11, Condition E, is entered. Therefore, the proposed compensatory measures, as described in TVA letter CNL-20-012 (Reference), will still apply when WBN Units 1 and 2 TS 3.7.11, Condition E, is entered. For purposes of clarity, the proposed footnote for WBN Units 1 and 2 TS 3.7.11, Condition E, has been modified to also refer to the compensatory measures, as described in the referenced letter. Additionally, the last sentence in the proposed change to the TS 3.7.11 Bases has been slightly modified to more accurately reflect the location of the MCR temperature indication (i.e., from centralized location to readily available equipment in the MCR.) to this submittal provides a revised Section 2.2 and Section 3.4.1 of the enclosure to the referenced letter to reflect the revised footnote for WBN Units 1 and 2 TS 3.7.11, Condition E. Enclosure 3 to this submittal provides the revised WBN Units 1 and 2 TS 3.7.11 pages marked up to reflect the revised footnote for WBN Units 1 and 2 TS 3.7.11, Condition E. Enclosure 4 to this submittal provides the revised WBN Units 1 and 2 TS 3.7.11 pages retyped to show the proposed changes. Enclosure 5 to this submittal provides the revised 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. Enclosures 2, 3, 4, and 5 supersede the corresponding information provided in the enclosure to the referenced letter.

Reference 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)

CNL-20-091 E1-8 of 8

Enclosure 2 Revised Section 2.2 and Section 3.4.1 of the enclosure to CNL-20-012 CNL-20-091

Enclosure specifying more stringent seismic qualification requirements to ensure sufficient qualification and associated documentation; seismic testing will be of particular emphasis in the factory acceptance tests. A qualified vendor was chosen to provide the equipment for the CREATCS chiller, and a verification of the seismic qualification is planned to be performed.

The enclosed LAR reflects information similar to References 1 through 3, with the exception that Reference 1 also addressed planned upgrades to the shutdown board room (SDBR) chillers. The currently planned upgrades to the CREATCS chillers also involve upgrades to the SDBR chillers; however, the SDBR chillers are non-TS support systems for the safety related 6.9kV and 480V switchgear and associated equipment. Therefore, they are not within the scope of this LAR.

2.2 Description of the Proposed Change The LAR proposes the following changes to the WBN Units 1 and 2 TS 3.7.11.

  • The following footnote is added to the Completion Time for Required Action A.1:
  • 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 May 1, 2022, and ending no later than May 1, 2023, provided compensatory measures are implemented as described in TVA letter CNL-20-012, dated May 19, 2020.
  • The following footnote is added to the Completion Time of Required Action E.1 of WBN Units 1 and 2 TS 3.7.11:
    • 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 degrees Fahrenheit (°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 May 1, 2022, and ending no later than May 1, 2023, provided compensatory measures are implemented as described in TVA letter CNL-20-012, dated May 19, 2020.

Attachment 1 to the enclosure provides the existing WBN Units 1 and 2 TS pages marked up to show the proposed changes. Attachment 2 to the enclosure provides the existing WBN Units 1 and 2 TS pages retyped 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.

2.3 Reason for the Proposed Change TVA is replacing the CREATCS chillers to improve their efficiency. Replacement of each CREATCS chiller requires that the associated CREATCS train be taken out of service and declared inoperable. The upgrades to the CREATCS chillers are CNL-20-012 E4 of 24

Enclosure Table 2 Train B CREATCS Replacement Schedule Duration Activity (hours)

Reinstall supports for new CREATCS chiller unit 168**

Leak test, charge, pre-operational inspection 132 Remove temporary chilled water system/ restore MCR AHU for the CREATCS chiller train 31*

Perform PMT on MCR HVAC system and declare CREATCS 218 equipment operable Total time for Train B chiller replacement 922 hours0.0107 days <br />0.256 hours <br />0.00152 weeks <br />3.50821e-4 months <br /> or 38.4 Days Activity performed in parallel with chiller replacement activities and are not included in the total activity time

    • Activity performed in parallel with piping re-installation activities and are not included in the total activity time Based on the above information, a 60-day Completion Time is considered reasonable for restoration of an inoperable CREATCS train during the planned upgrade of the MCR chillers.

A period of 12 months, from May 1, 2022, to May 1, 2023, is requested for the performance of the CREATCS chiller replacements. This duration provides scheduling flexibility to consider refueling outages, weather conditions and scheduled plant maintenance.

3.4.2 Technical Specification 3.7.11, Condition E WBN Units 1 and 2 TS 3.7.11, Condition E states that if two CREATCS trains are inoperable in Modes 1, 2, 3, or 4, then the unit immediately enters TS LCO 3.0.3.

Technical Specification LCO 3.0.3 requires that the Unit be placed in Mode 3 within six hours and Mode 5 within 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />. This required shutdown would apply to both Units, because they share a common MCR.

While performing the upgrades to one of the CREATCS chillers, the affected train is declared inoperable and TS 3.7.11, Condition A has been entered. During this time, if the opposite CREATCS train were declared inoperable, a proposed extension of four days is requested prior to entering LCO 3.0.3. Four days is a reasonable timeframe to perform maintenance to restore a CREATCS train to operable status based on a review of previous maintenance history as shown in Table 3.

CNL-20-012 E13 of 24

Enclosure 3 Revised TS Changes (Mark-Ups) for WBN Units 1 and 2 TS 3.7.11 CNL-20-091

CREATCS 3.7.11 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 A.1 Restore CREATCS train to 30 days*

inoperable. OPERABLE status.

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

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 C.1 Place OPERABLE CREATCS Immediately associated Completion Time of train in operation.

Condition A not met in MODE 5 or 6, or during movement of OR irradiated fuel assemblies.

C.2 Suspend movement of irradiated Immediately fuel assemblies.

(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 May 1, 2022, and ending no later than May 1, 2023, provided compensatory measures are implemented as described in TVA letter CNL-20-012, dated May 19, 2020.

Watts Bar-Unit 1 3.7-25 Amendment 35, 85, 112, XXX

CREATCS 3.7.11 ACTIONS (continued)

CONDITION REQUIRED ACTION COMPLETION TIME D. Two CREATCS trains D.1 Suspend movement of Immediately inoperable in MODE 5 or 6, or irradiated fuel assemblies.

during movement of irradiated fuel assemblies.

E. Two CREATCS trains E.1 Enter LCO 3.0.3. Immediately**

inoperable in MODE 1, 2, 3, or 4.

SURVEILLANCE REQUIREMENTS SURVEILLANCE FREQUENCY SR 3.7.11.1 Verify each CREATCS train has the capability to remove In accordance with the assumed heat load. 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 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 May 1, 2022, and ending no later than May 1, 2023, provided compensatory measures are implemented as described in TVA letter CNL-20-012, dated May 19, 2020.

Watts Bar-Unit 1 3.7-26 Amendment 35, 132, XXX

CREATCS 3.7.11 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 A.1 Restore CREATCS train 30 days*

inoperable. to OPERABLE status.

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

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 C.1 Place OPERABLE Immediately associated Completion CREATCS train in Time of Condition A not met operation.

in MODE 5 or 6, or during movement of irradiated fuel OR assemblies.

C.2 Suspend movement of Immediately irradiated fuel assemblies.

D. Two CREATCS trains D.1 Suspend movement of Immediately inoperable in MODE 5 or 6, irradiated fuel assemblies or during movement of irradiated fuel assemblies.

  • 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 May 1, 2022, and ending no later than May 1, 2023, provided compensatory measures are implemented as described in TVA letter CNL-20-012, dated May 19, 2020.

Watts Bar - Unit 2 3.7-24 Amendment XX

CREATCS 3.7.11 ACTIONS (continued)

CONDITION REQUIRED ACTION COMPLETION TIME E. Two CREATCS trains E.1 Enter LCO 3.0.3. Immediately**

inoperable in MODE 1, 2, 3, or 4.

SURVEILLANCE REQUIREMENTS SURVEILLANCE FREQUENCY SR 3.7.11.1 Verify each CREATCS train has the capability to In accordance with remove the assumed heat load. 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 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 May 1, 2022, and ending no later than May 1, 2023, provided compensatory measures are implemented as described in TVA letter CNL-20-012, dated May 19, 2020.

Watts Bar - Unit 2 3.7-25 Amendment 36, XX

Enclosure 4 Revised TS Changes (Final Typed) for WBN Units 1 and 2 TS 3.7.11 CNL-20-091

CREATCS 3.7.11 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 A.1 Restore CREATCS train to 30 days*

inoperable. OPERABLE status.

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

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 C.1 Place OPERABLE CREATCS Immediately associated Completion Time of train in operation.

Condition A not met in MODE 5 or 6, or during movement of OR irradiated fuel assemblies.

C.2 Suspend movement of irradiated Immediately fuel assemblies.

(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 May 1, 2022, and ending no later than May 1, 2023, provided compensatory measures are implemented as described in TVA letter CNL-20-012, dated May 19, 2020.

Watts Bar-Unit 1 3.7-25 Amendment 35, 85, 112, XXX

CREATCS 3.7.11 ACTIONS (continued)

CONDITION REQUIRED ACTION COMPLETION TIME D. Two CREATCS trains D.1 Suspend movement of Immediately inoperable in MODE 5 or 6, or irradiated fuel assemblies.

during movement of irradiated fuel assemblies.

E. Two CREATCS trains E.1 Enter LCO 3.0.3. Immediately**

inoperable in MODE 1, 2, 3, or 4.

SURVEILLANCE REQUIREMENTS SURVEILLANCE FREQUENCY SR 3.7.11.1 Verify each CREATCS train has the capability to remove In accordance with the assumed heat load. 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 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 May 1, 2022, and ending no later than May 1, 2023, provided compensatory measures are implemented as described in TVA letter CNL-20-012, dated May 19, 2020.

Watts Bar-Unit 1 3.7-26 Amendment 35, 132, XXX

CREATCS 3.7.11 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 A.1 Restore CREATCS train 30 days*

inoperable. to OPERABLE status.

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

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 C.1 Place OPERABLE Immediately associated Completion CREATCS train in Time of Condition A not met operation.

in MODE 5 or 6, or during movement of irradiated fuel OR assemblies.

C.2 Suspend movement of Immediately irradiated fuel assemblies.

D. Two CREATCS trains D.1 Suspend movement of Immediately inoperable in MODE 5 or 6, irradiated fuel assemblies or during movement of irradiated fuel assemblies.

  • 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 May 1, 2022, and ending no later than May 1, 2023, provided compensatory measures are implemented as described in TVA letter CNL-20-012, dated May 19, 2020.

Watts Bar - Unit 2 3.7-24 Amendment XX

CREATCS 3.7.11 ACTIONS (continued)

CONDITION REQUIRED ACTION COMPLETION TIME E. Two CREATCS trains E.1 Enter LCO 3.0.3. Immediately**

inoperable in MODE 1, 2, 3, or 4.

SURVEILLANCE REQUIREMENTS SURVEILLANCE FREQUENCY SR 3.7.11.1 Verify each CREATCS train has the capability to In accordance with remove the assumed heat load. 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 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 May 1, 2022, and ending no later than May 1, 2023, provided compensatory measures are implemented as described in TVA letter CNL-20-012, dated May 19, 2020.

Watts Bar - Unit 2 3.7-25 Amendment 36, XX

Enclosure 5 Revised TS Bases Page Changes (Mark-Ups) for WBN Units 1 and 2 (For Information Only)

CNL-20-091

CREATCS B 3.7.11 BASES ACTIONS A.1 (continued)

(continued)

The Completion Time is modified by a footnote that states an allowance is permitted for one CREATCS train to be inoperable for 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 May 1, 2022, and ending no later than May 1, 2023, 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.

B.1 and B.2 In MODE 1, 2, 3, or 4, if the inoperable CREATCS train cannot be restored to OPERABLE status within the required Completion Time, the plant must be placed in a MODE that minimizes the risk. To achieve this status, the plant 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 plant conditions from full power conditions in an orderly manner and without challenging plant systems.

(continued)

Watts Bar-Unit 1 B 3.7-53 Revision 45 Amendment 35, XX

CREATCS B 3.7.11 BASES ACTIONS 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 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 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 May 1, 2022, and ending no later than May 1, 2023, 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.

(continued)

Watts Bar-Unit 1 B 3.7-54 Revision 45 Amendment 35, XX

CREATCS B 3.7.11 BASES ACTIONS E.1 (continued)

(continued)

  • 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 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.

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.

(continued)

Watts Bar-Unit 1 B 3.7-54a Revision 64, 162 Amendment 50, 132, XX

CREATCS B 3.7.11 BASES ACTIONS A.1 (continued)

(continued)

The Completion Time is modified by a footnote that states an allowance is permitted for one CREATCS train to be inoperable for 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 May 1, 2022, and ending no later than May 1, 2023, 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.

(continued)

Watts Bar - Unit 2 B 3.7-61

CREATCS B 3.7.11 BASES ACTIONS B.1 and B.2 (continued)

In MODE 1, 2, 3, or 4, if the inoperable CREATCS train cannot be restored to OPERABLE status within the required Completion Time, the plant must be placed in a MODE that minimizes the risk. To achieve this status, the plant 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 plant conditions from full power conditions in an orderly manner and without challenging plant systems.

C.1 and C.2 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 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.

Watts Bar - Unit 2 B 3.7-62 Revision 34 Amendment 36, XX

CREATCS B 3.7.11 BASES ACTIONS E.1 (continued)

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 May 1, 2022, and ending no later than May 1, 2023, 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.

Watts Bar - Unit 2 B 3.7-62a Revision 34 Amendment 36, XX

CREATCS B 3.7.11 BASES ACTIONS E.1 (continued)

(continued)

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.

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.

Watts Bar - Unit 2 B 3.7-62b Revision 34 Amendment 36, XX

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