ML17252B562

LER 78-036/03L-0 for Dresden, Unit 2 Re a SBGT Failed to Start Upon Auto Initiation from a Spurious Reactor Bldg. Hi Rad Signal

ML17252B562
Person / Time
Site:	Dresden
Issue date:	07/05/1978
From:	Stephenson B Commonwealth Edison Co
To:	James Keppler NRC/RGN-III
References
BBS 78-1019 LER 78-036/03L-0
Download: ML17252B562 (3)

Text

Comm&ealth Edison Dresden ~ear Power Station R.R. #1 Morris, Illinois 60450 Telephone 815 /942-2920 CJ

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">l James G. Keppler, Regional Director Directorate of Regulatory Operations - Region III U.S. Nuclear Regulatory Commission 799 Roosevelt Road Glen Ellyn, IL 60137 Reportable Occurrence Report #78-036/03L-0, Docket #050-237 is hereby submi.tted to your off:ice in accordance with Dresden Nuclear Power Station Technical Specification 6.6.B.2.(b), conditions leading to operation in a degraded mode permittedby a limiting condition for operation or plant shutdown required by a limiting condition for operation.

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r- Stephenson Superintendent Dresden Nuclear Power Station BBS/kmh Enclosure CC: Director of Inspection & Enforcement Director of Management Information & Program Control File/NRC REGUU\TORY DOCKET .F'ltE COPY,

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U.S. NUCl_EAR REGULATORY COMMISSION 17-77).

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I On June 5,. 1978, while Unit 2 and 3 were in normal operation, "Av SBGT failed to C2:IIJ start upon auto initiation from a spurious reactor bldg. Hi Rad signal. 'B' SBGT

~ auto started suc*cessfully. A tubing in the flow control panel was found broken. The

• [QJ}] flow control damper was left wide open until' new tubing could be obtained. On

~ June 9, 1978, I A' SBGT again failed to start upon auto initiation and 'B' SBGT auto

~ started. Since the redundant system was available the safety significance of these

~ events was minimal. This event is -not repetitive.

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I After the second failure a blown fuse was found which tripped the train on auto start.I Q]JJ It was replaced and the train was auto started *and ran successfully. Apparently _the ITI2J first failure was also caused by this* blown fuse. Because of the singularity of

[ill] this event no future corrective action is deemed necessary.

rrm 7 B 9 80 FACILITY t3()\ METHOD OF ~

STATUS  % POWER OTHER STATUS ~ DISCOVERY DISCOVERY DESCRIPTION (31

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RELEASED OF RELEASE AMOUNT.OF ACTIVITY~ LOCATION OF RELEASE @

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NUMBER (.;:;\TYPE DESC.:RIPTION ~

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Joe Chan 265 0 0.

NAME OF PREPARER PHONE: -

.'="1' ATTACHMENT TO LICENSEE EVENT REPORT 78-036/031-0 COMHONWE.ALTH EDISON COMPANY (CWE) -

DRESDEN UNIT -2 (ILDRS-2)

DOCKET if 050-237 On June 5,_ 1978 during normal plant operation, "A" SBGT system failed to start upon auto initiation from a spurious Reactor Building ventilation radiation monitor trip. "B" train auto started when the "A" train failed to supply the required flow rate. "B" train operated for 10 hrs. which proved its operability as required by Tech. Spec. 4.7.B.l.a.

It was determined that the flow through the "A" train wa.s low because the blower suction valve was slow to open. An investigation revealed that a piece of tubing in the flow control panel was broken causing the valve to open slowly. The "A" train blower suction valve was manually placed in the full open position and the "A" tr3in was declared operable after it was manually started and run seccessfully for 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br />. The valve will be left in the full op~n position until replacemen~ tubing can be obtained and installed.

Since the redundant train auto* sta.rted and ran successfully, the safetysignificance of this event is minimal.

On June 9, 1978, the "A" SBGT failed to start again upon auto initiation when the Unit 3 instrument bus was deenergized. "B" SBGT auto started and ran successfully for 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br />; It was then found th~t a fuse in the heater operation sensing circuit was blown which prevented the auto start of the tr~in. The train is designed to trip ~pan auto sta~t if the heater fails to operate, but is not tripped upon manual start by this fuse failure. The fus*:::! was replaced and the train was auto started and ran successfully. The failure of the fuse wa's probably caused by a dirty relay* .contact or by deterioration of" the contact. The relay contact was cleaned and properly adjusted. The fuse is.manufactured by BUSS. Apparently both failure[;! were due to the blown fuse. Because of the singular nature of this event no further corrective action is de~~d necessary.