ML20086B827
| ML20086B827 | |
| Person / Time | |
|---|---|
| Site: | Wolf Creek  |
| Issue date: | 06/28/1995 |
| From: | Hagan R WOLF CREEK NUCLEAR OPERATING CORP. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| ET-95-0064, ET-95-64, NUDOCS 9507060118 | |
| Download: ML20086B827 (3) | |
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A 1 U' W$LF CREEK NUCLEAR OPERATING CORPORATION f
i Fiobert C. Hagan Vce Presden: Engmeering June 28, 1995 ET 95-0064 U. S. Nuclear Regulatory Commission ATTN:
Document Control Desk Mail Station P1-1 37 Washington, D.
C.
20555
Subject:
Docket No. 50-482: Special Report 95-001 Gentlemen:
The attached Special Report is being submitted in accordance with Wolf Creek Generating Station Technical Specification ' 4. 8.1.1. 3 concerning an invalid failure of Emergency Diesel Generator "B."
If you should have any questions regarding this response, please contact me at (316) 364-8831, extension 4553, or Mr. William M.
Lindsay at extension 8760.
Ve truly you k
\\
Robert C. Haga RCH/jad Attachment cc L.
J. Callan (NRC), w/a D.
F.
Kirsch (NRC), w/a J.
F.
Ringwald (NRC), w/a J. C. Stone (NRC), w/a i
9507060118 950628 PDR ADOCK 050004B2 O3.. p t ut s
eDR
. P O. Box 411/ Barlington. KS 66839 / Phone: (316) 364-8831 An Equal Opponunity Employer MT/HC/ VET
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. Attachment to ET 95-0064 t
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Page 1 of 2 -
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Special Report 95-001 Javalid Failure of
- roency Diesel Generator "B" This report describes an invalid failure of Emergency Diesel Generator (EDG)
"B" which occurred on May 31, 1995.
This report is being-submitted in accordance with Wolf Creek Generating Station (WCGS) Technical Specification L
4.8.1.1.3, Daggription of Eventst On May 31, 1995, at approximately 1043 hours0.0121 days <br />0.29 hours <br />0.00172 weeks <br />3.968615e-4 months <br />, the output breaker for the "B"
i EDG tripped during the performance of routine monthly testing.
The EDG had j
been started at approximately 1024 hours0.0119 days <br />0.284 hours <br />0.00169 weeks <br />3.89632e-4 months <br />, in accordance with the applicable WCGS testing procedure and the output breaker was closed at approximately 1042 hours0.0121 days <br />0.289 hours <br />0.00172 weeks <br />3.96481e-4 months <br />.
Upon closure of the output breaker, the EDG governor was adjusted to pick up a small load.
However, load increased to 7.1 megawatts electrical.
Subsequent to the unanticipated increase in load, WCGS Control Room personnel attempted to reduce load to the procedurally specified level when the load l
dropped to o megawatts electrical and the EDG output breaker tripped'due to 1
the activstion of a directional power relay (reverse power).
WCGS Operations personnel reset the EDG output breaker at approximately 1127 j
~
hours and re-closed the output breaker at approximately 1130 hours0.0131 days <br />0.314 hours <br />0.00187 weeks <br />4.29965e-4 months <br />.. Control Room persennel again adjusted the governor to pick up a small load and again
]
the EDG load increased to 7.1 megawatts electrical.
WCGS Control Room i
personnel attempted to return the load to the level prescribed in the testing procedure when the load dropped to o megawatts electrical and the EDG output 1
breaker tripped at approximately.1131 hours0.0131 days <br />0.314 hours <br />0.00187 weeks <br />4.303455e-4 months <br />.
The - "B" - EDG was secured at approximately 1136 hours0.0131 days <br />0.316 hours <br />0.00188 weeks <br />4.32248e-4 months <br /> and the EDG output breaker was place in pull-to-lock (msnual block to prevent closure) at approximately 1150 hours0.0133 days <br />0.319 hours <br />0.0019 weeks <br />4.37575e-4 months <br />.
WCGS Control Room personnel verified the "A"
EDG and Turbine Driven Feedwater Pump were operable at approximately 1232 hours0.0143 days <br />0.342 hours <br />0.00204 weeks <br />4.68776e-4 months <br />.
This event occurred during routine testing, as require by Plant Technical Specification 4. 8.1.1.2 (f).
The EDG was unavailable for approximately 47.9 hours1.041667e-4 days <br />0.0025 hours <br />1.488095e-5 weeks <br />3.4245e-6 months <br />.
During this time period the cause of the problem was determined and corrected.
Root Cause and Corrective Actions Root cause:
Troubleshooting started on the governor circuitry af ter the second breaker j
trip occurred.
The resistive box, applicable circuit fuses, unit parallel i
I relay contacts, cable between the 'EGA (Governor Control Box) and EGB (Hydraulic Actuator), and motor operated potentiometer were all verified to be in acceptable condition.
Troubleshooting indicated that the problem was either in the EGA or the EGB.
The EDG was started and the control room
e Attachm:nt to ET 95-0064 Page 2 of 2 4
operator used the speed control handswitch to adjust engine speed up and down several times to see if the EGB was responding properly to changes from the EGA.
The EGB responded without anomalies. Therefore, the problem appeared to be the EGA.
Electrical Maintenance installed a new EGA and a Colt-Fairbanks Morse field service representative adjusted the new unit.
After replacement, the EDG was successfully paralleled to the grid. Also, Procedure STS KJ-015B,
' Manual / Auto Start, Synchronization & Fast Loading of Emergency D/G NE02" (full loading the EDG in 60 seconds), was performed satisfactorily.
The summing junction on the EGA receives three inputs (speed reference, speed feedback, and droop). When the three voltages add up to zero, the speed (load when paralleled) will remain steady. When the summing junction becomes a non-zero value, the hydraulic actuator will move the fuel racks on the EDG to drive the summing junction potential back to a zero value (by speed feedback and droop, if parallel operation).
The EGA operated properly when thr, unit was not in parallel operation with the grid.
This was demonstrated during the two previous attempts to parallel the EDG (as discussed in the event description) and the run which checked the hydraulic actuator.
The EDG did not respond properly af ter the EDG output breaker was closed (that action which initiates the droop signal). It can be concluded from this that the droop circuitry was not operating properly.
When the EDG is in the isochronous (emergency) mode, the droop circuitry is isolated from the summing junction.
Therefore, this failure did not adversely affect the function of the EDG when in the isochronous (emergency) mode.
Immediate Corrective Action:
The EGA was replaced and EDG
- B" was evaluated and determined to be operable.
E11ture Cerrgetive Actign1 The EGA will be sent to Colt for repair and returned to Wolf Creek for use as a spare part.
Emilure classification 1 In the event of an emergency, EDG
- B" would have started and supplied power to its emergency bus as required.
The droop circuit is only used when in the test mode.
Therefore, this failure is classified as an invalid failure in accordance with Position C.2.e (2) Regulatory Guide 1.108, Revision 1.