ML20084S585

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AO 50-265/75-44:on 751107,RCIC Turbine Tripped.Caused by Failure of Hydraulic Fluid servo-valve Actuator.Actuator Replaced & Overspeed Trip Mechanism Repaired
ML20084S585
Person / Time
Site: Quad Cities Constellation icon.png
Issue date: 11/17/1975
From: Kalivianakis N
COMMONWEALTH EDISON CO.
To: James Keppler
NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML20084S575 List:
References
AO-50-265-75-44, NUDOCS 8306170121
Download: ML20084S585 (4)
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(V V REPORT NUMBER: A0 50-265/75-44 REPORT DATE: November 17, 1975 OCCURRENCE DATE: November 7, 1975 FACILITY: quad-Cities Nuclear Power Station Cordova, Illinois 61242 IDENTIFICATION OF OCCURRENCE:

Reactor Core Isolation Cooling (RCIC) system turbine tripped during Unit Two surveillance testing.

CONDITIONS PRIOR TO OCCURRENCE:

Unit Two was in the RUN mode at zero HWe. Pos t maintenance outage sur-veillance testing was in progress.

DESCRIPTION OF OCCURRENCE:

At 1:03 p.m. on November 7,1975, during Uni t 2 post maintenance outage RCIC surveillance testing with the reactor operating at 920 psig, the RCIC turbine tripped due to high exhaust pressure. Previously, at 6:10 a.m.

of thot day, the RCIC system had met all flav and logic system functional test requirements at a reactor pressure of 200 psig.

Ini tial investigations revealed that the pilot valve plunger on the EGR Actuator had broken. The EGR Actuator controls the remote servo valve which operates the turbine inlet steam governing valve.

Upon completion of the Act'uator repai rs subsequent testing revealed additional failures of the turbine mechanical overspeed trip mechanism and the turbine shaf t driven oli pump.

DESIGNATION OF APPARENT CAUSE OF OCCURRENCE:

Equipment Failure The high backpressure was caused by the failure of the hydraulic fluid servo-valve actuator which controls the RCIC turbine inlet steam governing valve.

The Actuator assembly contains its own integral gear type pump to develop hydraulic pressure to the remote servo. The Actuator pilot valve plunger failed and thus caused a loss of hydraulic control pressure to the remote servo. The loss of hydraulic control at the remote servo allowed an ex-cessive amount of steam to enter the RCIC turbine through the governing valve thus creating a high turbine backpressure and the resultant turbine trip.

c O ,

o A0 50-265/75-44 November 17, 1975 The turbine mechanical overspeed trip mechanism failure was caused by a l

Jam nut on the adjusting spring becoming loosened. This failure then caused portions of the trip mechanism to become damaged and thus resalt in its failure. The failure of the trip mechanism in turn caused excessive loading on the shaf t driven oil pump which thus resulted in its failure.

ANALYSIS OF OCCURRENCE:

The safety implications of this occurrence were minimal because the HPCI system was operable at the time of the RCIC failure. . HPCI could have been used to supply water to the reactor vessel if needed. Thus, safe operation of the plant and the health and safety of the public excre not af fected as a result of this occurrence.

CORRECTIVE ACTION:

Immediately af ter the RCIC system operation was found unsatisfactory, the High Pressure Coolant injection system was tested in accordance with Section 3 5.E.2 of the Technical Specifications and proven operable.

The EGR Electro-Mechanical Hydraulic Actuator was replaced according to Work Request No. 4379-75 The subsequent repai rs to the overspeed trip mechanism and the shaft driven oil pump were performed and documented 'according to Work Request No. 4431-75 All repai rs were completed and the RCIC system was returned to service on November 15, 1975 at approximately 4:00AM. This was 15 hours1.736111e-4 days <br />0.00417 hours <br />2.480159e-5 weeks <br />5.7075e-6 months <br /> beyond the allowable outage time designated by the Technical Speci fi ca ti ons .

Because it was anticipated that the work was going to take longer than the outage time provided by the Technical Specifications, approval was requested and granted by the Office of Nuclear Reactor Regulation to extend the allow-able outage time up to 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. Continued operation under the extension was dependant on the HPCI system being tested for operability each 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />.

The extension time was needed because even though the maintenance personnel were working around the clock on the job, the availability of replacement parts extended beyond the specified time.

FAILURE DATA:

This is the first failure of this type, so there are no safety impilcations based on cumulative experience related to this occurrence.

The EGR Actuator is manufactured by the Woodward Governor Co. as part number A8250-1335P and serial number 879232. The turbine mechanical over-speed trip mechanism is manufactured by the Terry Steam Turbine Co. as part number 8-29592 and serial number 35689 The oil pump gears are part numbers 40 and 52 on Terry Steam Turbine Co. drawing 7757HE.

-"4** COm^T.wsalth Edison m b b C Quad bJs Nuclear Power Station I

(

('v;'cyx' - Post Off;ce Box 21G

  1. / Cordova. llhnois 61242 Telephone'309/654 2241 V ,

NJK-75-581 i November 17, 1975 Director of Of fice of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, D.C. 20555 Refe rence: quad-Cities Nuclear Power Station Docket No. 50-265, DPR-30, Uni t 2 Appendix A, Sections 1.0.A.2, 3 5.E.1, 6.6.B.I.a, 6.6.B.3.a.

Enclosed please find Abnormal Occurrence Report No. A0_50-265/75-44 for quad-Cities Nuclear Power Station. This occurrence was previously repor Ed'to Region Ill, Office of Inspection and Enforcement by telephone on November 8, 1975 and to you and Region ill, Office of Inspection and Enforcement by telecopy on November 10, 1975 1

This report is submitted to you in accordance with the requirements of Technical Specifications 6.6.B. l.a. and as a Special Report in accordance with Technical Speci fication 6.6.B.3.a.

Very truly yours, I COMMONWEALTH EDISON COMPANY QUAD-CITIES NUCLEAR POWER STATION j -

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N.J. Ka1ivianakis '

Station Superintenden't 4

NJK/JCV/vmb cc: Region 111, Office.of Inspection and Enforcement G.A. Abrell l

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l COPY SENT REGIONT i

13229

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