ML18283B059

NRR E-mail Capture - Additional Information Needs Identified During Audit - Sequoyah 1 and 2, Request to Modify Essential Raw Cooling Water Motor Control Center Breakers Revise Updated Final Analysis Report (SQN-TS-17-04)

ML18283B059
Person / Time
Site:	Sequoyah
Issue date:	10/10/2018
From:	Samson Lee Plant Licensing Branch 1
To:	Wells R Tennessee Valley Authority
References
L-2018-LLA-0060
Download: ML18283B059 (2)

Text

1 NRR-DMPSPEm Resource From:

Lee, Samson Sent:

Wednesday, October 10, 2018 11:51 AM To:

Wells, Russell Douglas Cc:

Hon, Andrew

Subject:

additional information needs identified during audit - Sequoyah Nuclear Plant, Units 1 and 2, Request to Modify Essential Raw Cooling Water Motor Control Center Breakers and to Revise Updated Final Analysis Report (SQN-TS-17-04) (EPID: L-2018-LLA-0060)

Mr. Wells, The NRC staff is continuing the regulatory audit for the subject Sequoyah license amendment request. Below is additional information need identified in the electrical engineering area.

Talking Point 5 Explain how the licensee will meet its design basis licensing criteria under the following scenario:

An operator working on ERCW MCCs 1A and 2A (train A) leaves them inadvertently connected when fed from offsite power. Nothing abnormal is detected/alarmed, since offsite circuits/power to both 6.9 kV shutdown boards 1A and 2A are in synch (no failure - the operator error is undetected). At a later time, one of the components/system on 1B or 2B (train B) becomes inoperable (say EDG 1B or 2B - single failure);

LOOP/LOCA occurs and all four EDGs start. Since 6.9 kV shutdown boards 1A and 2A were previously inadvertently connected through ERCW MCCs 1A and 2A, the EDGs 1A and 2A try to connect to 6.9 kV shutdown boards 1A and 2A respectively - but may get connected in out-of-phase condition (through connection of ERCW MCCs 1A and 2A, previously undetected). Both EDGs (1A and 2A) may trip due to electrical/mechanical transients likely to happen under out-of-phase condition. Only one EDG on train B remaining - not adequate to meet the LOOP/LOCA conditions.

Please propose logistics to facilitate the audit.

Thanks, Sam

Hearing Identifier:

NRR_DMPS Email Number:

613 Mail Envelope Properties (Samson.Lee@nrc.gov20181010115100)

Subject:

additional information needs identified during audit - Sequoyah Nuclear Plant, Units 1 and 2, Request to Modify Essential Raw Cooling Water Motor Control Center Breakers and to Revise Updated Final Analysis Report (SQN-TS-17-04) (EPID: L-2018-LLA-0060)

Sent Date:

10/10/2018 11:51:00 AM Received Date:

10/10/2018 11:51:00 AM From:

Lee, Samson Created By:

Samson.Lee@nrc.gov Recipients:

"Hon, Andrew" <Andrew.Hon@nrc.gov>

Tracking Status: None "Wells, Russell Douglas" <rdwells0@tva.gov>

Tracking Status: None Post Office:

Files Size Date & Time MESSAGE 1361 10/10/2018 11:51:00 AM Options Priority:

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