ML18348A272

License Event Report E1976-045-00 Re Failure of DBA Sequencer to Operate

ML18348A272
Person / Time
Site:	Palisades
Issue date:	12/21/1976
From:	Bixel D Consumers Power Co
To:	James Keppler NRC/RGN-III
References
LER 1976-045-00
Download: ML18348A272 (4)

Text

consumers

• Power company

~\egu\atory Docket f\\e.

General Offices: 212 West Michigan Avenue, .Jackson, Michigan 49201

• Area Code 517 788-0550

...~----"'---.. ---

D~cember 21, 1976 ,, .

I;*\' *

. :;*. /

Mr James G Keppler . .

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Office of Inspection & Enforcement Region III US Nuclear Regulatory Commission 799 Roosevelt Road Glen Ellyn, IL 60137 DOCKET 50-255, LICENSE *DPR

• PALISADES PLANT, ER-76~45 -

DBA SEQUENCER Attached is a Licensee Event Report relating to the Palisades Plant. This report concerns failure of part of the automatic sequencer designed to place safety system loads on the emergency diesel generator *. These safety systems could have been manually started should that have been required.

David A Bixel Assistant Nuclear Licensing Administrator DEC 2 3 1976

e LICENSEE EVENT REPORT- Palisades Plant

. 'CONTROL BLOCK: I I I I I I I [PLEASE PRINT ALL REQUIRED INFORMATION]

1 6 LICENSE EVENT LICENSE NUMBER TYPE TYPE I ol ol-1 ol ol ol ol ol-1 ol ol 14111111111. lol1I 15 25 26 30 31 32 REPORT REPORT TYPE. SOURCE OOCKF;T NUMBER EVENT DATE REPORT DATE *

@IT]coN'T I *I *I l1.J L1J I ol sl ol-1ol21 sl sl I ii 2 I o I 2 I 1 I 6 I l1l2l2l1l 1l 6I 7 8 57 58 59 60 61 68 69 74 75 80 EVENT DESCRIPTION

~!During a rerun of a test (to check other equipment) which was successfully conducted I 7 8 9 80 lol31 Iabout one day earlier; DBA seguencer 34-1 failed to operate. In accordance with the I 7 8 9 80 lol41 I Technical Specifications the redundant channel was then tested and similarly DBA se~ I 7 8 9 80 10151 7 8 I guencer 9 . .

34-2 failed to operate. With this second failure a standard (normal) plant I 80 lol61 I shutdown was commenced. See attached Event Description for more details. (ER-76-45) I 7 8 9 PRIME 80 SYSTEM CAUSE COMPONENT COMPONENT CODE CODE COMPONENT CODE SUPPLIER MANUFACTURER VIOLATION 7

@0 IE! El 8 9 10 l!....J 11 I I I N I s I T I R j .u I 12 17 w 43 IE I 0 I 2 I 0 I 44 47 L.!.J 48 CAUSE DESCRIPTION lol0I I The sequencer clutch failed to reset due to insufficient clutch disk gap. The most *I 7 8 9 80 lolsl I probable cause of the disk gap problem was set screw slippage. See Event Description I 7 8 9 80

~ITIQI I for additional details. I

~9 . FACILITY METHOD OF 80 STATUS  % POWER OTHER STATUS DISCOVERY DISCOVERY DESCRIPTION

[ill] L!J 9

l1lolol 10 . . 12 NA I L£.I NA I 7 8 13 44 45 46 .80 FORM OF rn w ACTIVITY CONTENT RELEASED UJ _,________

OF RELEASE AMOUNT OF ACTIVITY

_I LOCATION OF RELEASE 7 8 9 PERSONNEL EXPOSURES 10 11 NA 44 ~-----------------------------------------*

45 NA 80 NUMBER TYPE DESCRIPTION DE] Lo I oIo I ~ NA 7 8 9 11 12 13 80 PERSDNNEL INJURIES NUMBER DESCRIPTION EE!lololol NA 7 8 9 11 12 80

. --Probable Consequences ~

IIIfil I If an SIS would have occurred and standby power were not available (Contd on Line 18) 7 8 9 80 LOSS OR DAMAGE TO FACILITY fifil w TYPE DESCRIPTION NA

'7 8 9 10 PUBLICITY EJZl None 7 8 9

• ADDITIONAL FACTORS

~ I( Contd From Line l5) some safety-related equipment would have had to be manually started.j 7 8 9 80.

7illfil89~*--------------------------------------------------------------------------------------------------~ 00

• LICENSEE EVENT REPORT ER-76-45 Docket 50-255 Continuation of Event Description

Background

On December 8, 1976, the quarterly safeguards test (Q0-1) was conducted success-fully except for one discrepancy (charging pump P55C should not have started).

Part of the evaluation of this deviation required a rerun of a portion of the test to verify the cause of the pump start. At 1118 hours0.0129 days <br />0.311 hours <br />0.00185 weeks <br />4.25399e-4 months <br /> on December 9, the test was run and it was found that one of the two left .channel DBA sequencers (34-1) failed to operate. Repair personnel were promptly notified of the problem and cor-rective action was initiated.

Initial Action In accordance with Technical Specifications, the operability of the right channel SIS/DBA sequencer was determined prior to commencing the repair of the left chan-nel. At 1222 hours0.0141 days <br />0.339 hours <br />0.00202 weeks <br />4.64971e-4 months <br />, the right channel portion of Q0-1 was run and it was found that one of the two right channel sequencers (34-2) also failed to operate. Based on this additional failure, reactor shutdown was commenced and the normal shutdown rate was established by 1250 hours0.0145 days <br />0.347 hours <br />0.00207 weeks <br />4.75625e-4 months <br />. Concurrent with the shutdown, repair of the right channel sequencer was begun.

Findings Upon inspection of the sequencer, it was determined that the clutch was still engaged and that the unit had failed to reset. The unit was reset and the clutch gap adjusted. At approximately. 1315 hours0.0152 days <br />0.365 hours <br />0.00217 weeks <br />5.003575e-4 months <br /> the right channel portion of Q0-1 was run to verify proper operation of 34-2. The test was successful and proper reset of the unit was observed. The test was rerun a second time and again successful operation of the unit was observed.

Upon completion of repair and testing of the right channel, the failed left chan-nel sequencer (34-1) was investigated. The unit was found to have the same prob-lems as 34-2 and it was repaired and tested. By approximately 1400 hours0.0162 days <br />0.389 hours <br />0.00231 weeks <br />5.327e-4 months <br />, both channels had been repaired, tested, and returned to service.

Evaluation and Follow-Up The clutch disk assemblies for sequencers 34-2 and 34-1 had been previously re-placed and adjusted on October 5, 1976 and October 14, 1976, respectively. At this time, the clutch disk clearance was set at approximately 0.020". The unit was tested several times and Q0-1 was used for the operational check of the com-pleted work. Satisfactory operation was obtained in each case. (It should be noted that the clutch disk gap setting is the result of a trade off between (1) a large gap which insures easy resetting of the unit and (2) a small gap which results in greater spring tension producing a minimum of clutch slippage.)

• Since the operability of the unit was demonstrated several times after the clutch replacement, it is concluded that the clearances set during the clutch replacement were adequate. The clutch gap apparently changed during the two months following the repair preventing clutch disengagement.

Subsequent to resetting the clutch disk gap after this event, the set screws for the clutch collars were further tightened to minimize the possibility of recurrence.

In addition to the mechanical adjustment discussed above, temporary procedural controls will be instituted. For test situations requiring operation of the sequences, the sequencers will be visually inspected after sequencer operation to insure that the reset function of each unit performs satisfactorily .