ML17173A450

Forwards LER#78-033/03X-1

ML17173A450
Person / Time
Site:	Dresden
Issue date:	12/12/1978
From:	Stephenson B COMMONWEALTH EDISON CO.
To:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML17173A451	List: ML17173A450 ML20027A563
References
NUDOCS 7812270300
Download: ML17173A450 (3)

Text

CommonweA Edison 1.

Dresden Nuclea.,wer Station R.R. #1 Morris, Illinois 60450 Telephone 815/942-2920

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December 12, 1978 BBS LTR #78-1594 James ~. Keppler, Regional Director Directorate of Regulatory Operations - Region III U.S. Nuclear Regulatory Commission 799 Roosevelt Road Glen Ellyn, IL 60137 Reportable.Occurrence "Update Report" /178-033/03X-1, Docket #050-237 is hereby submitted to your office to supplement Licensee Event Report 78-033/03L-0 concerning the overspeed and subsequent trip of the Unit 2 Diesel Generator. It addresses the final corrective actions taken to prevent recurrence and: a change in classification.of . .Items 18 and 19 on the Licensee Event Report form. This event was reported to you under Dresden Nuclear Power Station Technical Specifications 6.6.B.2.(c),

observed inadequacies in the implementation of administrative or procedural controls which threaten to cause a reduction of degree of redundance provided in reactor protection systems or engineered safety feature systems.

• BBS/deb Enclosure cc: Director of Inspection & Enforcement Director of Management Information & Program Control File/NRC

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e LICENSEE,EVENT REPORT UPiiiE REPORT PR8POUS REPORT DATE 6-21-78 CONTROL BLOCK: (PLEASE PRINT OR TYPE ALL REQUIRED INFORMATION)

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/While U-2 was locked in refuel during an outage, a test was performed on U-2 D/G Q[[IJ I to measure its overshoot and overspeed setpoint. The diesel tripped four times during!

~ I startup due to overspeed. Since the unit was not at power, this event has little

[Q]]J I safety significance. Similar events had occurred on U2/3 D/G (LER#77-024/01X-l,

[QJ]J I 77-025/031-0 & 78-021/031-0, Docket #050-237). However, this is the first time this

~ I event occurred on this diesel unit.

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CI:::[§] j*Gov. speed was found* set too high. Further test revealed over speed trip wouJd occur ITfil i:due to overshoot if speed was set above 63 Hz. The diesel surv. pr.cc. calls for

!:III] la setting of 61 Hz at end of test. Reason for high settings could not be found. To

[JJJ] I prevent recurrence the overspeed trip setpoint was raised and a caution was added to

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8 9 80 FACILITY STATUS  % POWER OTHER STATUS METHOD OF DISCOVERY DISCOVERY DESCRIPTION GTIJ l!!J@ l.9..1 0 I QJ@.._I__N_A_ _ _~ UJ01 Overshoot and Overspeed Setpoint Test!

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ATTACHMENT TO LICENSEE EVENT REPORT78-033/03X~l COMHONWEALTH EDISON COMPANY (CWE)

DRESDEN UNI'F-2 (ILDRS-2)

DOCKET ti 050-237 While Unit 2 was locked in refuel during an outage, a test was performed by electrical maintenance to measure the overshooting and overspeed setpoint of Unit 2 diesel generator. The diesel tripped four times on overspeed during start up. Since Unit 2 was in refuel, this event is of little safety significance.

Western Engine representative was called in immediately to investigate this event. He found the governor speed setting was too high. The setting was lowered and the diesel was started with no problem. The governor speed should have been set at 61 Hertz (915 rpm) at the conclusion of the last surveillance test of the diesel according to the diesel surveillance procedure.

• It is. possible that the operato~ set the speed too high at that time or someone actuated the governor switch sometime prior to starting the diesel for surveillance.

On June 15, 1978, another Western Engine representative was called in to further investigate the problem. It was found that if the governor speed was set at 61 Hertz (915 rpm), the overshoot was to 980 rpm, and at the maximum setting which is 64 Hertz (960 rpm) the overshoot was about

• 1050 rpm. At a speed setting of 62.5 Hz (940 rpm), the overshooting was to about 1020 rpm. Since the overspeed trip setpoint of this diesel was tested to be 1030 rpm, any speed setting above 63 Hertz would result in overspeed due to the overshooting. *since the maximum range of the frequency meter in the Control Room is 62 Hertz, it is very unlikely that the operator would set the speed above 62 Hertz. The exact reason for the high speed setting cannot be determined at this time. All operators were instructed not to set the speed above 61 Hertz.

Measurements of overshooting and overspeed setpaint have been performed on the other two diesel generators and resulted. in similar values.

Therefore any corrective measures to be done on Unit 2 diesel were

. also applied to the other_ two diesel gerier-~tors; *:,' :* * : : . . * :..' '*

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" '.. - To prevent recurrence; the overspeed tri~ setpoint was raised to 1035 rpm on all diesels as suggested by manufacturer. A caution was also added to the surveillance proceduJ'.'.e to make the operator aware of this failure pos-sibility. In order to prevent the speed switches being actuated inadvertently, the switches will be covered by plastic boxes.

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