ML20137L621
| ML20137L621 | |
| Person / Time | |
|---|---|
| Site: | Fermi  |
| Issue date: | 01/15/1986 |
| From: | Lenart R DETROIT EDISON CO. |
| To: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| References | |
| NP860021, NUDOCS 8601280039 | |
| Download: ML20137L621 (4) | |
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January 15, 1986 NP860021 Mr. James G. Keppler-PE pin RW110 Regional Administrator g{"
Region III ig ya U. S. Nuclear Regulatory Commission s
k, 799 Roosevelt Road js Glen Ellyn, Illinois 60137 995 3
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Dear Mr. Keppler:
f1LE
Reference:
Fermi 2 NRC Docket No. 50-341 NRC License No. NPF-43
Subject:
Diesel Generator Start Failure Please find enclosed our report on the start failure of Emergency Diesel Generator (EDG) 13 on December 17, 1985.
This report is submitted to you in accordance wtih Fermi 2 Technical Specifications 4.8.1.1.3 and 6.9.2.
If you have any questions regarding this matter, please call Mr. L. P. Bregni, Compliance Engineer, at (313) 586-5313.
Sincerely, r4~
Enclosure cc:
P. M. Byron M. David Lynch G. C. Wright U.S. NRC Document Control Desk Washington, D.C. 20555 8601290039 860115' JAN 211986 PDR ADOCK 05000341 S
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U Mr. Cames G. Keppler January 15, 1986 NP860021 Page 2 t
Diesel Generator Start Failure J
]
1.
Emergency Diesel Generator Involved:
)
EDG 13 2.
Identification of Failure Failure date:
December 17, 1985
==
Description:==
. This was the second start failure of EDG 13 since the issuance of the Fermi 2. operating license.
At the time of this start failure, there had been 25 previous valid test starts _since the OL was issued.
This start failure is considered an
" invalid-test" start f ailure under Section C.2.e. (2) _
of Regulatory Guide 1.108, because the slow start method used in this event is bypassed during emergency starts when the EDG is in " standby", and I
the Field Failure trip (loss of generator field) l which initiated this failure is bypassed during l
emergency starts.
d 3.
Cause of Fallorer On December 17, 1985, EDG 13 tripped on a Field.
Failure (loss of generator field) during the performance of. a slow start of the engine.
The normal method for a slow start of the EDG is as follows:
1)
Deenergize the exciter 2)
Adjust mechanical governor speed adjust knob to its minimum setting (equivalent to an ongine speed of ' 400 rpm) 3)
Start the. engine at 400 rpm l
4)
Gradually-increase engine speed with the mechanical governor speed knob to its maximum setting i
s
d, 4
Mr. James G. Keppler January 15, 1986 NP860021 Page 3 (continued)
Diesel Generator Start' Failure 5)
Reenergize the exciter and let the electric governor, which is normally set for approximately 900 rpm (or 60 Hz), take control of the engine and immediately lower the speed to 900 rpm (engine speed is controlled by the governor, 3
either electrical or mechanical, with.the lower setting; however the electric governor is deactivated when the exciter is deenergized).
4
]
During the performance of this slow start the first operator, who was located at the engine skid, increased engine speed with the mechanical governor until a reading of 905 rpm was indicated on the engine tachometer.
A second operator, at the local control panel, was told by the first operator that the engine speed was adequate.
The second operator then reenergized the exciter and attempted to increase engine rpm with the electric governor so that the engine could be synchronized ~ to the g r id.
Engine speed, however, would not increase.
When he observed no -response to the engine speed change command, the second operator realized that the electric governor was not controlling engine speed because the mechanical gove~rnor was not-adjusted to its maximum setting.
He told the first operator to increase the mechanical governor to Its maximum setting.
This caused the EDG to operate at an abnormally high 945 rpm (63Hz) with the exciter already energized.
The EDG subsequently tripped on field failure, since the exciter field amperage, which is required to maintain a nominal EDG.
ouput voltage of 4160 volts, dropped below the less than or equal to 30 amps de field failure setpoint.
The procedure being used to start the EDG and increase engine speed to greater than 900 rpm was not sufficiently specific in requiring a maximum setting of the mechanical governor and was-misinterpreted by the operators.
A modification allowing slow start capability of EDG 13.had recently been installed; therefore, little experience had been obtained using the new slow start procedure.
4
Mr. James G. Keppler.
' January 15, 1986 NP860021 Page 4 (continued)
Diesel Generator Start Failure 4.
Corrective Measures Taken:
The slow start procedures for EDG 's 11, 12, 13 and 14 have been modified to provide clearer instructions for operators.
Each procedure now specifies a specific number to which the mechanical governor speed adjust knob is to be set when increasing EDG speed.
5.
Lenoth of Time Unit Unavailable EDG 13 was out-of-service for special testing at the time of the field failure trip, therefore EDG availability was not lost.
6.
Current Surveillance Test Interval:
The current surveillance test interval is once per 31 days.
7.
Verification of Conformance of Test Interval:
Because this start f ailure occurred during an
" invalid test" as defined by Regulatory Guide 1.108, the diesel generator surveillance test. interval is not affected.
The current surveillance test interval is in conformance with Regulatory Position C.2.d of U.S. NRC Regulatory _ Guide 1.108 and in conformance-with Fermi 2 Technical Specification Table 4.8.1.1.2-1.
.