ML20084R535

AO 50-249/75-14:on 750310,operator Heard Air Blowing Inside Diesel Generator Which Revealed Air Receiving Tank Outlet Valves Closed & Generator Inoperable.Caused by Personnel Error.Operability Check Changed

ML20084R535
Person / Time
Site:	Dresden
Issue date:	03/18/1975
From:	Stephenson B COMMONWEALTH EDISON CO.
To:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML20084R523	List: ML20084R528 ML20084R535 ML20084R543
References
166, AO-50-249-75-14, RO-50-249-75-14, NUDOCS 8306150164
Download: ML20084R535 (3)

Text

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Comm zith Edis n One First nal Piara. Chicago, litinois

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/ Address Hop!y to: Post Office Box 767

, Chicago, lilinois 60600 BBS Ltr. #166 Dresden Nuclear Power Station R.R. #1 Morris, IL 60450 March 18, 1975 James G. Keppler Regional Director ,

Directorate of Regulatory Operations - Region III U.S. Nuclear Regulatory Comission 799 Roosevalt Road Glen Ellyn, IL 60137

SUBJECT:

REPORT OF AENORMAL OCCURR ECE PER SECTION 6.6.A 0F THE TECHNICAL SPECIFICATIONS UNIT '3 DIESEL GENERATOR INOPERABLE, References 1) Regulatory Guide 1.16 Rev 1. Appendix A

2) Notification of Region III of U.S. Nuclear Regulatory Comission Telephone P. Johnson, 1030 hrs, 10 Mar 75 Telegram: J. G. Keppler, 1040 hrs, 10 Mar 75 a-IA ~ ~ -

Report Number: 50-294/7514 Report Date: March 18, 1975 -

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Occurrence Date: March 10, 1975 Facility: Dresden Nuclear Power Station, Morris, IL IDENTIFICATION OF OCCURRENCE Unit 3 Diesel Generator found inoperable.

CONDITIONS PRIOR TO OCCURRENCE Prior to the occurrence Unit 3 was in the Run mode with a themal power of 1311 megawatts and a steady state electrical load of 416 megawatts.

DESCRIPTION OF OCCURRENCE A review of the unit log books and surveillance records has determined that the following sequence of events occurred

! March 4, 1975

• In order to perform a monthly inspection of the 2/3 diesel generator, the Unit 3 diesel generator was checked for operability at 0325 hrs on March 4,1975 i 8306150164 751021 l PDR ADOCK 05000249 p.o-  !

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. James G. Kippler Mar:h 18, 1975 '

O O The procedurs for thn diesel generator consist:d of two esotions. Tha first

- section required that the diesel be started and operated approximately one half hour. The second section required that the diesel air start motor operability l be checked. Fbr the second section the procedure calla for both air receiving tank outlet valves to be temporarily closed. It is believed that at this time the outlet valves were inadvertantly left closed makir4 the Unit 3 diesel generator impossible.

At about 0500 hrs on March 4, 1975, the Unit 2/3 diesel generator was removed from service in order to perform a monthly inspection. The monthly inspection was completed at'0353 hrs on March 5, 1975 and the diesel generator was returned to service.

March 10. 1975 On March 10, 1975, at about 0840 hrs an operator in the area of the Unit 3 diesel generator heard air blowing inside the diesel room. On inspection it was discovered that the air receiving tank outlet valves were closed, and that the diesel generator was inoperable.

DESIGNATION OF APPARE2TT CAUSE OF OCCURRENCE (PERSONNEL ERROR)

The cause of the problem is considered to be operator error.

ANALYSIS OF OCCURRENCE While both diesels were out of service, all off site power lines were available, all Unit 3 battery systems were operational, and a tic line between Unit 2/

Unit 3 was available, if required.

There are two conditions which contribute to allowing an operator to make this error, the first being the sequence of testing for the diesel generator operability test and the second being the location of low air pressure sensors.

Concerning the diesel generator operability check, the procedure calls for the air etart motor operability to be checked after the diesel operability check.

In this test sequence any errors in the air start motor operability test will not be found during a diesel operability test. In regards to the location of the low air pressure sensors, these censors are presently located upstream of the air receiving tank outlet valves. In this location the outlet valves could be closed and the sensors would fail to pick up low air pressure to the air start motors.

CORRECTIVE ACTION

[ The icznediate corrective action taken was to return the Unit 3 diesel generator i to service. The diesel generator operability check is also going to be changed I

so that the air start pressure will be tested prior to an operability run on the diesel. In addition the location of the low air pressure sensors will be relocated to a position down stream of the receiving tank outlet valves.

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, James G. K;ppler March 18, 1975

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• FAILURE DATA Review of past diesel generator failures disclosed no record of an inoperable ,

4 diesel due to a closure of the receiving tank outlet valves.

Sincerely,

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.B St enson Superint dent Dresden Nuclear Power Station BBS:TEL:slb i

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