ML20135H270

Summary of May 5, 2020, Teleconference Call with Tennessee Valley Authority Regarding a Planned License Amendment Request for Watts Bar Nuclear Plant, Units 1 and 2

ML20135H270
Person / Time
Site:	Watts Bar
Issue date:	05/28/2020
From:	Kimberly Green NRC/NRR/DORL/LPL2-2
To:
Green K
References
EPID L-2020-LRM-0035
Download: ML20135H270 (5)

Text

May 28, 2020 LICENSEE: Tennessee Valley Authority FACILITY: Watts Bar Nuclear Plant, Units 1 and 2

SUMMARY

OF MAY 5, 2020, TELECONFERENCE CALL WITH TENNESSEE VALLEY AUTHORITY REGARDING A PLANNED LICENSE AMENDMENT REQUEST FOR WATTS BAR NUCLEAR PLANT, UNITS 1 AND 2 (EPID L-2020-LRM-0035)

On May 5, 2020, a Category 1 public teleconference call was held between the U.S. Nuclear Regulatory Commission (NRC) staff and representatives of Tennessee Valley Authority (TVA).

The purpose of the meeting was to discuss TVAs planned license amendment request (LAR) for Watts Bar Nuclear Plant (WBN), Units 1 and 2. The LAR would seek to revise WBN Technical Specification (TS) 3.7.11, Control Room Emergency Air Temperature Control System (CREATCS), to support modifications to the CREATCS chillers at both units.

The meeting notice and agenda, dated April 22, 2020, are available at Agencywide Documents Access and Management System (ADAMS) Accession No. ML20125A355. TVAs slides for the meeting are available at ADAMS Accession No. ML20125A324. A list of participants is provided as an enclosure to this summary. No regulatory decisions were made at this meeting.

TVA began its presentation by providing background information and the basis for the proposed request related to the replacement of the CREACTS chillers. TVA noted that the NRC previously issued a similar license amendment for WBN Unit 1, in 2011 (ADAMS Accession No. ML110190280) to allow one CREATCS train to be inoperable for up to 60 days while performing the modifications to the CREATCS chillers. However, the modifications to the WBN Unit 1 CREATCS chillers were not performed due to issues with the seismic qualification of the replacement chiller units.

TVA described the function of the CREATCS, which is to provide temperature control for the common main control room (MCR) during normal operation and following isolation of the MCR.

The CREATCS consists of two independent and redundant trains that provide cooling of recirculated MCR air as well as introducing fresh air. Each train consists of an air-handling unit (AHU), water chiller, chilled water pump, and associated piping, ductwork, instrumentation, and controls to provide for MCR temperature control.

TVA proposes to replace each of the CREATCS chiller packages, but noted that AHUs, chilled water pumps and chilled water piping will not be changed. TVA estimates that it will take 55.7 days and 38.2 days to replace the Train A and Train B chillers, respectively. TVA explained that the difference in time between Train A and Train B replacements is due to the proposed replacement of the shutdown board chiller which is in close proximity to the Train A CREATCS chiller unit. Therefore, TVA plans to revise TS 3.7.11 Required Action A.1 Completion Time for restoration of one inoperable CREATCS train from 30 days to 60 days, and

add a footnote that only permits one entry per train during modification activities associated with the replacement of the MCR chillers beginning no earlier than May 1, 2021, and ending no later than October 1, 2022, provided that compensatory measures are implemented as described in the LAR.

TVA explained that during CREATCS chiller replacement, the affected CREATCS train will be inoperable; however, train components will remain functional with the exception of the chilled water pump and the chiller unit. Therefore, to provide defense in depth for cooling the MCR, a temporary chiller unit will be installed and connected to the functional CREATCS AHU. If the temporary chiller unit fails, the operable CREATCS train will automatically start on high AHU temperature or may be manually started to maintain the MCR temperature.

TVA described the temporary, nonsafety-related chiller system that it plans to install and use to support MCR cooling during the CREATCS chiller replacements. The temporary chilled water system will be connected to a temporary dedicated 320 kilowatt diesel generator so that it can operate independently of site power. TVA stated that it performed a calculation that considered the operational heat loads, the nominal rating of the temporary chiller unit, and nominal temporary chilled water pump ratings, and determined that the MCR temperatures would remain below 80 °F. Because the temporary chiller is not proposed as a safety-related substitute for the permanent CREATCS chillers, TVA stated that safety-related design criteria associated with weather and missile protection will not be applied. Based on the timeframe in the footnote TVA could perform the replacement during the summer. The NRC staff asked if TVA plans to perform the replacement in the summer. TVA stated that it preferred not to replace the chillers in the summer and the timing would depend on schedules. However, the calculations it performed to determine what the temperature in the MCR would be considered the maximum summertime temperatures. The NRC staff also asked about the cooling capacity of the temporary chiller. TVA stated that the cooling capacity of the temporary chiller is comparable to the original chiller.

TVA then explained what would happen if the other CREATCS train should be declared inoperable. Currently, if two trains of CREATCS are declared inoperable during MODE 1, 2, 3, or 4, Limiting Condition for Operation (LCO) 3.0.3 is required to be entered immediately. TVA plans to request a temporary one-time revision to TS 3.7.11 Required Action E.1 to allow a four-day delayed entry into LCO 3.0.3, which it based on corrective maintenance repair times.

A footnote will also be proposed that will require monitoring of the MCR temperature hourly to ensure it remains below 90 °F. If the temperature goes above 90 °F or the duration of two trains of CREATCS inoperability exceeds four days, then immediate entry into LCO 3.0.3 would be required. A footnote is proposed to be added. As with the proposed footnote for Required Action A, the provision for Required Action E would only be applicable from May 1, 2021 until October 1, 2022. The NRC staff asked if the compensatory measures that will be described in the LAR will refer to this proposed footnote. TVA stated that the footnote for Required Action E.1 will not be limited to a one-time entry as for Required Action A.1; therefore, there will not be separate compensatory actions.

To support the one-hour frequency for temperature monitoring TVA said that it 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. TVA evaluated two cases: (1) Normal operating heat loads, summertime maximum outdoor temperatures, one AHU operating, no chillers in operation and (2) loss-of-coolant accident (LOCA) heat loads, summertime maximum outdoor temperatures, no AHUs running, no chillers in operation. TVA concluded that an increase in temperature from 75 °F (normal MCR operating temperature) to 104 °F will take approximately 5.6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> for the

normal operating heat load case and 4.6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> for the LOCA heat load case. TVA explained that the 90 °F temperature limit provides 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.

TVA further explained that delayed entry into LCO 3.0.3 is also needed to allow stabilization of the water and air flow from the modified CREATCS train during post modification testing, and that this impact is due to the automatic start signals from the modified train requiring the operable train to start inappropriately and repeatedly. Also, this type of entry into TS 3.7.11, Condition E would only be used in direct support of post modification testing and only when the potential for anomalous water and/or air flow in the modified CREATCS train is possible.

TVA plans to submit the LAR by the end of May 2020 and will request approval within one year.

No comments or public meeting feedback were received.

Please direct any inquiries to me at 301-415-1627, or Kimberly.Green@nrc.gov.

/RA/

Kimberly J. Green, Senior Project Manager Plant Licensing Branch II-2 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. 50-390, and 50-391

Enclosure:

List of Participants cc: Listserv

LIST OF PARTICIPANTS MAY 5, 2020, PUBLIC TELECONFERENCE CALL TENNESSEE VALLEY AUTHORITY REGARDING PLANNED LICENSE AMENDMENT REQUEST WATTS BAR NUCLEAR PLANT, UNITS 1 AND 2 Name Organization Kim Green U.S. Nuclear Regulatory Commission (NRC)

Matthew Hamm NRC David Nold NRC Chang Li NRC Russell Wells Tennessee Valley Authority (TVA)

Kim Hulvey TVA Dean Baker TVA Ron Rogers TVA Jeff Swanson TVA Tom Coulter TVA Chris Kerlin TVA Andy Taylor TVA Jerry Thompson TVA Damon Fegley TVA Joel Riddle Enercon Paul Schoepf Enercon Pat Furio Enercon Enclosure

ML20135H270 *via email OFFICE NRR/DORL/LPL2-2/PM NRR/DORL/LPL2-2/LA* NRR/DORL/LPL2-2/BC* NRR/DORL/LPL2-2/PM NAME KGreen BAbeywickrama UShoop KGreen DATE 05/20/2020 05/18/2020 05/27/2020 05/28/2020