ML20090E432

AO 50-237/75-52:on 751116,MSIV AO 2-203-1C Closing Time Found Below Tech Spec Section 3.7.D.1.Caused by Out of Adjustment Hydraulic Bleedoff Valve.Bleedoff Valve Readjusted

ML20090E432
Person / Time
Site:	Dresden
Issue date:	11/20/1975
From:	Stephenson B COMMONWEALTH EDISON CO.
To:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
References
13509, 769-75, AO-50-237-75-52, NUDOCS 8303310593
Download: ML20090E432 (2)

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November 20, 1975 604)(y'" ,.

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Mr. James G. Keppler, Regional Director - g 8

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Directorate of Regulatory Operation - Region III Of' 'J' A'q U.S. Nuclear Regulatory Commission '

799 Roosevelt Road j(h ("'{W{Tij[V, Glen Ellyn, Illinois 60137 * **

SUBJECT:

REPORT OF ABNORMAL OCCURRENCE PER SECEION 6.6. A 0F Tile TEC11NICAL SPECIFICATIONS RAPID CLOSURE OF UNIT-2 MAIN STEAM ISOLATION VALVE 203-lC

References:

1) Regulatory Guide 1.16 Rev. 1 Appendix A

2) Notification of Region III of U.S. Nuclear Regulatory Commission Telephone: Region III Headquarters, Duty Office. 0855 hours0.0099 days <br />0.238 hours <br />0.00141 weeks <br />3.253275e-4 months <br /> on November 16, 1975 '

Telegram: J. Keppler, 1250 hours0.0145 days <br />0.347 hours <br />0.00207 weeks <br />4.75625e-4 months <br /> on November 17, 1975 Report Number: 50-237/1975-52 Report Date: November 20, 1975 Cccurrence Date: November 16, 1975 IDENTIFICATION OF OCCURRENCE Main steam isolation valve A0 2-203-1C closed in less than 3.0 seconds, which is contrary to section 3.7.D.1 of the Technical Specifications.

CONDITIONS PRIOR TO OCCURRENCE Unit-2 was in the Run mode at a power level of 428 MWt and 103 MWe. Quarterly surveillance testing of the main steam isolation valves was in progress.

DESCRIPTION OF OCCURRENCE At approximately 0330 hours0.00382 days <br />0.0917 hours <br />5.456349e-4 weeks <br />1.25565e-4 months <br /> on November 16, 1975, main steam isolation valve 203-1C exhibited a closure time of 2.7 seconds'. Technical Specifications require that for closure time t, 10 sec. < t < 5.0 sec. The valve was Icft in the isolated position, and the unit was subsequently shut down.

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,DESICNATION OF APPARENT CAUSE OF OCCURRENCE (Component Failure)

Inspection of valve 203-1C revealed that the hydraulic biced-off valve was out of adjustment. The bleed-off valve controls the rate of oil exchange across the valve operator piston, thus controlling the valve's rate of closure. The biced-off valve adjustment discrepancy was attributed to normal valve wear. ,

ANALYSIS OF OCCURRENCE All eight main steam isolation valves had been satisfactorily tested on September 9, 1975. Had a reactor scram occurred while valve 203-1C was out of adjustment, the resultant premature isolation of the "C" main stean line would have presented minimal se;fety implications. The remaining three steam lines would have effectively equalized any pressure spike, thereby precluding the possibility of a significant transient within the reactor vessel. This' occurrence did not endanger plant personnel or the general public.

CORRECTIVE AtrION Following shutdown of the unit, the bleed-off valve on 203-lc was readjusted to bring the valve closure time within specifications. At 1720 hours0.0199 days <br />0.478 hours <br />0.00284 weeks <br />6.5446e-4 months <br /> on November 16, valve 203+1C was successfully tested three times, with an average closure time of 3.6 seconds. The valve was then returned to service in preparation for unit start-up.

FAILURE DATA Four similar isolation valve timing. failures have occurred at Dresden since-1970.

The main steam isolation valves are air-operated, 20" Y-pattern globe. valves, manufactured by Crane Valve Co.- ,

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