ML12268A156

IR 1320006; B2F26 U2 Trip SAT C-Phase Found Open

ML12268A156
Person / Time
Site:	Byron
Issue date:	01/30/2012
From:	Exelon Generation Co
To:	NRC/RGN-III
References
FOIA/PA-2012-0287
Download: ML12268A156 (2)

Text

I AR 01320006 Report Aft Fac: Byron AR Type: CR Status: APPROVED Aft Unit: 02 Owed To: A88230CAP Due Date: 02/29/2012 Aft System: SY Event Date: 01/30/2012 CR 2/A Disc Date: 01/30/2012 LevellClass:

How H02 Orig Date: 01/30/2012 Discovered:

WRIPIMS 00391884 Equip Tag: 2SATDISC - U-2 SAT TRANSFORMER DISC AR:

Action Request Details

Subject:

U-2 TRIP SAT C-PHASE FOUND OPEN (b)(6)

Description:

Originator ISupv Contacted:

Condition

Description:

Walk down of the Switch Yard following the U-2 Reactor Trip identified the bus section between the SAT Disconnect Switch (Bus 13) and the Revenue Meter (Combi Unit) has failed. The flexible section of the bus and the S-Bus are leaning against the Combi Unit Support Stanchion. Two (2) of the four (4) C-phase bus insulator sections are laying on the ground. The insulator is a stack of four insulating sections, Two are still connected to the overhead support structure and two are on the ground. The Insulator supports the bus from above. The S-bus termination pad and the disconnect termination pad may both be damaged. The C-phase bus failure cause appears to be due to the overhead supporting bushing/insulator failure. The following buses were walked down as well: 241/242/243/244 (4kV) and 256/257/258/259 6.9kV). In general A-phase time delay Overcurrent relay flags were up as were the Bus 241 AB Phase and BC Phase Degraded Voltage Relays. The Bus 242 BC Degraded Voltage Relay Flag was also up. Bus 244 had no relay Flag up. No bus had a C-phase Over Current Relay Flag up, suggesting the cause was a loss of C-Phase Bus, and supported by switchyard walk down results.

Immediate actions taken:

Initiated IR. Communicated findings to OCC Recommended Actions:

Create WR for repair Operable Basis:

U-2 SAT are offslte power for U-2 and alternate power for U-1. Both units are in, LCOAR for offsite power.

Reportable Basis:

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Functionality Basis:

Failure has resulted in loss of function of U-2 SAT and disconnect.

Reviewed by:-101/30/2012 13:54:39 CST Reviewer Connmi*f I.

Rolling to WR prior to SOC based on immediate need for support.

• (b)(6) 0/02 1 SOC Reviewed by[ 01/30/2012 16:28:01 CST SOC Comments:

Sig Level 2 due to Plant Trip. Risk is high due to plant trip and challenges associated with the trip. Uncertainty is medium as the walkdown has discovered failed components in the switchyard. A root cause investigation is appropriate for this event. - (mkp 01/30/2012)

Close to WR generated outside of SOC. ZINWR 1/30/12 Assignments Assign #: Assigned Status: AWAIT/C To:

Aff Fac: Byron Prim Grp: ACAPALL Due Date: 02/04/2012 Assign Type: TRKG Sec Grp: Orig Due Date:

Priority:

Schedule Ref:

Unit Condition:

Subject/Description: U-2 TRIP SAT C-PHASE FOUND OPEN