05000388/LER-1985-001, :on 850112,HPCI Turbine Failed to Trip During Hot Functional Test HF-252-011.Caused by Broken Stop Valve Actuator Shaft.Actuator Shaft Replaced

:on 850112,HPCI Turbine Failed to Trip During Hot Functional Test HF-252-011.Caused by Broken Stop Valve Actuator Shaft.Actuator Shaft Replaced

ML20107A247
Person / Time
Site:	Susquehanna
Issue date:	02/08/1985
From:	Keiser H, Stanley R PENNSYLVANIA POWER & LIGHT CO.
To:	NRC OFFICE OF ADMINISTRATION (ADM)
References
LER-85-001, LER-85-1, PLAS-036, PLAS-36, NUDOCS 8502190345
Download: ML20107A247 (3)

LER-1985-001, on 850112,HPCI Turbine Failed to Trip During Hot Functional Test HF-252-011.Caused by Broken Stop Valve Actuator Shaft.Actuator Shaft Replaced

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(v), Loss of Safety Function
3881985001R00 - NRC Website

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During a scheduled Hot Functional Test (HF-252-011), which was part of the Unit'2 Power Ascension Program, the High Pressure Coolant Injection (HPCI) turbine failed to trip. Operators attspted to trip the HPCI turbine per the test procedure by depressing the HPCI Turbine Trip pushbutton. A turbine trip due to Stop Valve (FV-25612) closure was expected, when no trip occurred, the turbine was stopped by closing the Steam Supply Valve (E41-HV-2F001).

Investigation revealed the hydraulically cperated stop valve actuator shaft.

was broken at the coupling to the valve shaft. The cause for the stop valve remaining open and resulting actuator failure was due to a valve position sensor bracket working its way loose and rotating around the stop valve coupling on which it was mounted. The bracket wedged itself between the actuator housing and the shaft coupling. The actuator shaft was replaced.

The HPCI System was declared operable at 2130 on January 13, 1985. The valve position sensor bracket which had been used during testing was removed at the ccmpletion of the hot functional testing.

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.u o ec r.,,,, aaw,nm The High Pressure Coolant Injection (HPCI) System was started at 0315 on January 12, 1985, in accordance with Hot Functional Test HF-252-Oll (HPCI Turbine Controller System Tune Up). At 0716 on January 12, 1985, Operations attemped to trip the HPCI Turbine by depressing the HPCI Turbine Trip Pushbutton in the Control Pocxn; this should have tripped the HPCI Turbine by closing the Stop Valve (FV-25612) which admits steam to the turbine. The HPCI did not trip and was stopped by closing the Turbine Steam Supply Valve (E41-HV-2F001).

Investigation revealed the hydraulically operated stop valve actuator shaft was broken at the valve shaft to actuator shaft coupling. The cause for the stop valve remaining open and resulting actuator failure was a loose valve position sensor bracket. The bracket had rotated around the stop valve coupling on which it was mounted and wedged itself between the actuator housing and the shaft coupling. The actuator shaft was replaced, and the HPCI system was declared operable at 2130 on January 13, 1985. The valve position sensor bracket used to provide information during testing was removed at the cmpletion of the hot functional testing.

i As an interim measure, a modified sensor bracket will be installed when needed for HPCI testing. The bracket will be inspected prior to test initiation and prior to a HPCI trip to ensure proper orientation, and will be removed at test empletion. A permanent design is being pursued.

'Ihe valve position sensor is used during testing for information gathering; the position sensor is not required for plant operation. The sensor bracket did not affect the initiation of the HPCI systs in that when it loosened and rotated it came to rest under the stop valve coupling tnere by preventing the stop valve frm closing, but did not prevent the stop valve frczn opening.

There are eleven (11) other valves which contain external valve position sensor brackets. These sensor brackets and similar brackets on Unit 1 are being reviewed for adequacy of installation.

NR FORw 368A

Pennsylv nia Pow:r & Light Company '

o Two North Ninth Street

• Allentown, PA 16101 e 215 1 770-5151 February 8, 1985 U.S.. Nuclear Regulatory Ccanission Document Control Desk Washington, DC 20555 SUSQUEHANNA STEAM ELECTRIC STATION LICENSEE EVENT REPORT 85-001-00 ER 100450 FILE 841-23 PLAS- 036 Docket No.

50-388 License No. NPF-22 Attached is Licensee Event Report 85-001-00. This event was detennined reportable per 10CFR50.73(a) (2) (v), in that the HPCI Systen was declared inoperable to facilitate repair of the Steam Admission Stop Valve Actuator.

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H.W. Keiser Superintendent of Plant-Susquehanna RWS/pjg cc: Dr. Thcmas E. Murley Regional Administrator, Region I U.S. Nuclear Regulatory Ccmnission

- 631 Park Avenue King of Prussia, PA 19406 Mr. R.H. Jacobs Senior Resident Inspector U.S. Nuclear Regulatory Ccximission P.O. Box 52 Shickshinny, PA 18655

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