ML20003H754

LER 81-021/03L-0:on 810401,half Trip Occurred from Steam & Feedwater Rupture Control Sys Channel 1 Low Steam Generator Level Trip.Caused by Power Supply Failure.Power Supply Replaced Per Work Order on 810402

ML20003H754
Person / Time
Site:	Davis Besse
Issue date:	05/01/1981
From:	Trautman D TOLEDO EDISON CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML20003H753	List: ML20003H752 ML20003H754
References
LER-81-021-03L, LER-81-21-3L, NUDOCS 8105070396
Download: ML20003H754 (2)

Text

NRC FOH3 366 U. S. NUCLE Al C E".UL ATZY COMMISSION V 719

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EVENT DESCRIPTION AND PROBABLE CONSEQUENCES h O 2 l (NP-33-81-23) On April 1, 1981 at 1855 hours0.0215 days <br />0.515 hours <br />0.00307 weeks <br />7.058275e-4 months <br />, a half trip from the Steam and Feedwateri l

g l Rupture Control System (SFRCS) Channel 1 low steam generator level trip occurred.

o 4 l Immediate investigation showed the cause to be a failed +24VDC power suppiv (PS02). 1

[TTT] l Since the failure placed the channel in the tripped condition, the action statement l l0is] l requirements of T.S. 3.3.2.2 were being met. There was no danger to the health and I o 7 l safety of the public or station personnel. The redundant channels 2/4 were operable l I

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34 35 36 3J 40 41 42 43 33 CAUSE DESCRIPTION AND CORRECTIVE ACTIONS h lThe cause of the half trip was the failure of the +24VDC power supply (PS02). The { i i o lcause of the failure of the power supply is unknown. Under Maintenance Work Order l

, i

, , lIC-343-81, the failed supply was replaced at 1455 hours0.0168 days <br />0.404 hours <br />0.00241 weeks <br />5.536275e-4 months <br /> oa April 2, 1981. The supply l the vendor for analysis.

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2191 NSUE8! NA l llll111111IIII 81-04 8105070316Dan Trautman PHONE:

(419) 259-5000, Ext.

NAME OF PREPAHEH

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TOLEDO EDISON COMPA'NY DAVIS-BESSE NUCLEAR POWER STATION UNIT ONE ,

SUPPLEMENTAL INFORMATION FOR LER NP-33-81-23 DATE OF EVENT: April 1, 1981

_ FACILITY: Davis-Besse Unit 1 IDENTIFICATION OF OCCURRENCE: Steam and Feedwater Ruptu.re Control System (SFRCS)

Channel I half trip caused by loss of +24 VDC power supply in Steam Generator Level Instrumentation Channel 1 Condition Prior to Occurrence: The unit was in Mode 1 with Power (MWT) = 2492 and Load (Gross MWE) = 837 Description of Occurrence: On April 1, 1981 at 1855 hours0.0215 days <br />0.515 hours <br />0.00307 weeks <br />7.058275e-4 months <br /> a half trip from the SFRCS Channel 1 low steam generator level trip occurred. Investigation revealed that the trip was caused by a loss of +24VDC power supply (PS02) in Steam Generator Level Instrument Channel 1. Upon receiving the half trip ~from SFRCS Channel 1; no further action was required as delineated by the action statement of Technical Speci-fication 3.3.2.2 since the channel was already in the tripped condition. After the control room ventilation was restored, the +24VDC power supply PS02 was then reset and checked periodically to verify its performance.

After approximately 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> of observia. ion to determine if the regulation of the power supply would stabilize and based pon past experience with this particular type of power supply, it was felt that replacement of PS02 +24 VDC power supply in Steam Generator Level Instrument Channel I was warranted to alleviate further prob-lems. The regulation of the power supply had degraded which began to cause drift-ing of the power supply. The power supply was replaced on April 2,1981.

Designation of Apparent Cause of Occurrence: The cause of the half trip was the failure of the +24VDC power supply (PS02). The cause of the failure of the power l supply is unknown at this time. It is being returned to the vendor for analysis.

l 1 Analysis of Occurrence: There was no danger to the health and safety of the public

' or en station personnel. The redundant channels 2/4 of SFRCS were operabic at the

[ time of the occurrence. In addition the slight drifting of PS02 after energization would allow for minimal effects to steam generator level instrument inaccuracies as verified by manufacturer's instructions.

L Corrective Action: The defective power supply was replaced under Maintenance Work Order IC-343-81 on April 2, 1981 at 1455 hours0.0168 days <br />0.404 hours <br />0.00241 weeks <br />5.536275e-4 months <br />. Power supplies for the SFRCS and l

Steam Generator Level Instrument cabinets were monitored to detect drif t at an early l

stage. Recent checks have shown no further difficulties to this point.

Failure Data: A previous failure was reported in NP 33-79-79 (LER 79-70).

i LER 81-021 l

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