ML20086K873

Special Rept SR-91-007-00:on 911111,diesel Generator a Loaded to 4.3 MW & Tripped.Caused by Inadequate Positioning of Turbocharger Inlet Air Butterfly Valve Limit Switch Mounting Bracket.Limit Switch Repositioned

ML20086K873
Person / Time
Site:	Waterford
Issue date:	12/11/1991
From:	Packer D ENTERGY OPERATIONS, INC.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
SR-91-007-00, SR-91-7, W3B5-91-0331, W3B5-91-331, NUDOCS 9112130339
Download: ML20086K873 (3)

Text

{{#Wiki_filter:4 M. 1 pf E'ntergy 5"'~a o - * " '"c-Operations W3B5-91-0331 A4.05 QA December 11, 1991 U.S. Nuclear Regulatory Commission ATTENTION: Document Control Desk Washington, D.C. 20555

SUBJECT:

Waterford 3 SES Docket No. 50-382 Licensr> No. NPF-38 Reporting of Special Report Gentlemen: Attached 1. Special Report Number SR-91-007-00 for Waterford Steam Electric Station Unit 3. This Special Report is submitted pursuant to 10CFR50.36(c) (2) and Technical Specifications 4.8.1.1.3 and 6.9.2 Very truly yours, h g D.F. Packer General Manager Plant Operations DFP/ HIC /rk Attachment cc: Messrs. R.D. Martin G.L. Florreich J.T. Wheelock - INPO Records Center E.L. Blake N.S. Reynolds NRC Resident Inspectors Office a r,,s n 3 . u v.t.. v 9112130339 911211 -{ g 2_1 PDR ADOCK 05000382 S FDR t/ /

)hY' If '. o .g ..e mg 4 SPECIAL REPORT SR-91-007 s GCRTABLE OCCbRRENCE: On Novemh -- 11, 1991, at 1443 hours, Emergency Diesel Generator (EDG) 'A' was started ano loaded to 4.3 me : swatts (MW', to Operating Proct: dure (0P)903-068, "EDG Operab1]ity Test Verifiestion". At 1532 hours, EDG 'A' tripped. This .I event is classified so *n invalid failure and is reported in accordance with Technical Specificatior. (TS) 4.8.1.1.3. INITIAE CONDITIONS: Plant power: 100% Mody i Procedure being performed: OP-903-068, FDG Operability 'i. <erification. t }, 6 Event Sequence- ~ - At 1423 houro EDG ' A' was started to perform OP-903-068. - At 1443 hours EDG 'A was loaded to 4e3 MW. - At 1502 hours t'.te EDG 'A' tripped and was declared' inoperable. Technical Specification (T.S.) 4.8.1.. actions b and d were entered. - At 1517 hours T.S. 4.8.1.' a-tion d was completed. - at 1543 hours OP-903-066 was completed satisfactory for EDC 'A' per T.S. 4.8.1.1 action b. - At 1752 houre EDG 'A' was started. - At 1754 hours EDG ' A' was carrying; the load. - At 1759 hours EDGA' loaded to 4.3 }rd. - At 1859 hours commenced unlosiing EDG 'A'. - At 1903 hours EDG 'A' output breaker was opened. ~ - bt 1911 hours secured EDG 'A'. - At 1937 hours EDG ' A' was declared operable and T,5

4. A.i.1 was exite.

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~- 4 4 / + y At the time of the EDG trip, indications in the control room showed the EDG 'A' " output breaker trip / trouble" alarm, the EDG 'A' output breaker opening, and EDG ' A' stopping wit' t a cool down cycle. When EDG 'A' tripped, there were numerous local alarms associated with an EDG trip. The auxiliary operator cleared the alarms. The caly unusual alarm that the local operator could remember being lit prior to clearing all alarms was the " Engine Overspeed" alarm. "his alarm is actuated by the overspeed governor or by depressing the limit switch actuation button adjacent to the turbocharger inlet butterfly valve handle. During this event the EDG turbocharger inlet air butterfly was open, and the overspeed governor had not actuated. ROOT CAUSE: The root cause of the EDG trip was inadequate positioning of the turbocharger inlet air butterfly valve limit switch mounting bracket, which resulted in less than adequate contact between the air inler butterfly valve handle and the limit switch actuation button. Engine vib. nion providad enough motion to actuate the switch. During troubleshooting the switch could be actuated by lightly pressing on the butterfly valve handle, CORRECTIVE ACTIONS: The limit switch was reposicioned so thit the turbocharper inlet air butterfly s valve handle would better depress the actuating button end the EDG 'B' limit switch mounting bracket was inspected with no similar discrepancy found. During retueling outage 5, the limit switch mounting bracket will be removed to determine if the mounting bracket can be improved to prevant recurrence. SAFETY SIGNIFICANCE: I This f ailure is classified as an invalid f ailure since the limit switch causing the shutdown is bypassed in the emergency r. ode. There have been two valid failures of EDG 'A' and one valid failure of EDG 'B' at Waterford 3 e since the operating license was issued. The current surveillance test i-*erval is at least once per 31 days, which is in conformance with the sebadule of Degulatory Position C.2.d. The EDG would have performed as I designed 'a the emergency mode; therefore, this event did not threaten the health and safety of the public or plant personnel. SIMILAR EVENTS: NONE 2 g}}