ML20084C132
| ML20084C132 | |
| Person / Time | |
|---|---|
| Site: | Turkey Point  |
| Issue date: | 12/20/1974 |
| From: | Schmidt A FLORIDA POWER & LIGHT CO. |
| To: | Case E US ATOMIC ENERGY COMMISSION (AEC) |
| References | |
| RO-251-74-6, NUDOCS 8304070540 | |
| Download: ML20084C132 (2) | |
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/N Mr. Edson G.
Case, Acting Director
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Dear Mr. Case:
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UNUSUAL EVENT NO. 251-74-6
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5 TURKEY POINT PLANT UNIT NO. 4 N C
j DOCKET NO. 50-251 0
FAILURE OF TURBINE CONTROL VALVE D
SPRING ADJUSTING BOLT
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In accordance with Technical Specification 6.6.2b, the following unusual event is reported:
On December 1, 1974, planned shutdown of Turkey Point Unit No. 4 was in progress.
Problems were encountered in affecting complete shutdown, and the turbine was tripped at 6:40 A.M.
Generator I
output at the time of the turbine trip was approximately 300 MNo.
Investigation of the turbino control problem revealed that No.
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turbine control valve spring adjusting bolt had failed causing
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the control valve to remain ~open.
With this one valve remaining continued governor adjustments resulted in the interceptor
- open, valves closing.
This appeared as a turbine run-back to the operating personnel and the load decrease in conjunction with the opening of the reheat safety valves was the reason for tripping the turbine.
The purpose of the control valve spring adjusting bolt is to compress the compression springs which hold the valve tightly on the seat when the valve is in the closed position.
The failure
- of the bolt was in the threaded area and appeared to have occurred in several increments rather than all at once.
Immediate corrective action consisted of replacing the defective bolt and "Zyglo" testing the remaini.ng three bolts for No. 4 turbine.
No defects viere found in the other three bolts.
The 12331 8304070540 741220 PDR ADOCK 05000251 S
PDR COPY SENT ITGION
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Mr. Edson G.
Case, Acting Director Page Two December 20, 1974 bolts for turbine No. 3, which was down for overhaul, were also "Zyglo" tested and one of these was found to be defective.
The turbine vendor, Westinghouse, is analyzing the two defective bolts as to material and mode of failure.
Permanent corrective action will be based on the Westinghouse analysis and recommenda-tions.
Very truly yours,
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D. Schmidt Vice President Power Resources GEL /cpc cc:
Mr. Norman C. Moseley Jack R.
Newman, Esquire g,
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