ML20213C711

Summary of July 28, 2020, Teleconference Call with Tennessee Valley Authority Regarding a Planned Alternative Request for Watts Bar Nuclear Plant, Unit 1

ML20213C711
Person / Time
Site:	Watts Bar
Issue date:	08/25/2020
From:	Kimberly Green Plant Licensing Branch II
To:	Jim Barstow Tennessee Valley Authority
Green K
References
EPID L-2020-LRM-0047
Download: ML20213C711 (5)

Text

August 25, 2020 LICENSEE: Tennessee Valley Authority FACILITY: Watts Bar Nuclear Plant, Units 1 and 2

SUMMARY

OF JULY 28, 2020, TELECONFERENCE CALL WITH TENNESSEE VALLEY AUTHORITY REGARDING A PLANNED ALTERNATIVE REQUEST FOR WATTS BAR NUCLEAR PLANT, UNIT 1 (EPID L-2020-LRM-0047)

On July 28, 2020, the U.S. Nuclear Regulatory Commission (NRC) staff conducted a Category 1 public teleconference with representatives of Tennessee Valley Authority (TVA). The purpose of the call was to discuss TVAs planned alternative request for Watts Bar Nuclear Plant (WBN),

Unit 1 regarding the residual heat removal (RHR) pump 1B-B.

The meeting notice and agenda, dated May 27, 2020, are available at Agencywide Documents Access and Management System (ADAMS) Accession No. ML20197A244. TVAs slides for the meeting are available at ADAMS Accession No. ML20209A070. 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 describing RHR pump 1B-B, which is a vertically mounted centrifugal pump with the pump impeller attached to the motor shaft. The pump motor does not have its own support foundation or structure. The pump bowl is attached to a support table structure in three locations.

TVA recounted the testing history and trending of the pump. Group A tests are performed quarterly. Comprehensive pump tests (CPT) can only be performed when the reactor vessel head is off, i.e., during refueling outages. The Group A test vibration reference values at 700 gallons per minute (gpm) are higher than the CPT vibration reference values at 4262 gpm.

TVA reported that the pump hydraulic values for both Group A and CPT are in the acceptable range with no adverse trend. However, slightly elevated vibration levels were first noticed in May 2018 during quarterly Group A pump testing. In October 2018 (U1R15 refueling outage),

vibration levels were also slightly elevated during the CPT. TVA stated that after the U1R15 refueling outage, vibration levels on the quarterly Group A test exhibited a step change and plateaued except location A-H, which increased just prior to U1R16 (May 2020). During the CPT conducted during the U1R16 refueling outage, vibration levels at four of the five locations exhibited an increase in level from the U1R15 CPT with locations A-H and A-V both entering the alert range. The NRC staff asked if TVA could include the pump curve and show the reference points for the Group A test, CPT, and shutdown cooling flow rates. TVA stated that it would provide that information in the alternative request.

TVA performed troubleshooting of vibration levels of the pump/motor and associated support structure during U1R16 refueling outage with the pump operating in RHR shutdown cooling mode at a flow rate of approximately 2000 gpm. TVA Identified some evidence of looseness in the support structure and other indications such as cracked and missing paint near certain mechanical fasteners of the support structure that indicated the framing had shifted.

TVA performed a quarterly Group A test on June 8, 2020, which showed one vibration location with a step increase in level, one location with marked decrease in level, and the other three locations with a slight increase in levels. TVA also compared the bearing oil analyses performed in December 2019 and May 2018. TVA stated that no moisture was present, the viscosity, wear metals, and chemistry values were all within normal operating ranges, but that iron content increased from 30 to 53 ppm; however, this was likely due to legacy material or content drawn into the sample via the sampling pathway. The NRC staff asked when the next bearing oil analysis is scheduled. TVA replied that it believes that the oil analysis is an 18-month preventative maintenance, but there is a work request to do a follow-up analysis in September when the next Group A test is performed. TVA agreed to provide a commitment in the alternative request to provide the NRC with the results of the oil analysis when they are available.

TVA performed a Group A test on June 24, 2020. TVA retorqued the bolting of the support structure in the area that had shown evidence of looseness or slippage. TVA noted that there was no appreciable change in vibration level after retorqueing of the support structure.

However, three of the five monitored bearing locations (A-H, A-A, and B-H) exhibited an increase from the June 8, 2020, Group A test. The NRC staff asked why TVA had performed the Group A test in June. TVA replied that the June 8th test was the regularly scheduled quarterly test. The Group A test performed on June 24th was a post-maintenance test to assess the retorquing that was done on the support structure bolting. The NRC staff asked how much of an increase in vibration was observed between June 8th and June 24th tests. TVA agreed to provide that information in the alternative request.

The WBN Unit 1 Inservice Testing Program Code of Record is the American Society of Mechanical Engineers (ASME) Operation and Maintenance (OM) Code, 2004 Edition through 2006 Addenda. When a measured test parameter value falls within the alert range, OM Code paragraph ISTB-6200(a) requires the frequency of testing to be doubled until the cause of deviation is determined and the condition is corrected. TVA stated that RHR Pump 1B-B vibration levels entered the alert range of the CPT performed in May 2020 (U1R16 refueling outage). As such, doubling the two-year CPT frequency would require that the next CPT be performed in May 2021 per paragraph ISTB-6200(a). The frequency grace period of ASME Code Case OMN-20 would allow the CPT to be deferred to August 2021. However, the next opportunity to perform the CPT, when the reactor vessel head will be off is during the next scheduled refueling outage, which is U1R17 in October 2021. The NRC staff asked TVA about the duration of the alternative request. TVA said that it plans to request the duration of alternative to be until the end of the U1R17 refueling outage currently scheduled for October 2021. TVA stated that it will perform corrective actions in accordance with paragraph ISTB-6200 if any of the Group A test measured values enter the alert or required action range.

The NRC staff asked what the required action is if the next quarterly Group A test falls in the alert range. TVA replied that per the OM code the test frequency would be doubled to 45 days.

TVA plans to submit alternative request to the NRC by August 14, 2020, and will request approval before May 20, 2021, which is when TVA would be required to perform the next CPT due to the increased frequency per OM Code paragraph ISTB-6200(a).

Because the next quarterly Group A test will be performed in September 2020, which is after the planned submittal date for the alternative request, the NRC staff asked if TVA could provide the results of the test. TVA stated that it could provide a commitment in the alternative request to provide the NRC the results of the next Group A test. The NRC staff stated that this was acceptable.

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 JULY 28, 2020, PUBLIC TELECONFERENCE CALL TENNESSEE VALLEY AUTHORITY REGARDING PLANNED ALTERNATIVE REQUEST WATTS BAR NUCLEAR PLANT, UNIT 1 Name Organization Kim Green U.S. Nuclear Regulatory Commission (NRC)

Bob Wolfgang NRC Nick Hansing NRC Tom Stephen NRC Russell Wells Tennessee Valley Authority (TVA)

Mark Gowin TVA Gary Jordan TVA Mark Fegley TVA Gordon Williams TVA Daniel Ward TVA Enclosure

ML20213C711 *via e-mail 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 08/10/2020 08/06/2020 08/21/2020 08/25/2020