ML19309G063

LER 80-027/03L-0:on 800331,operations Received Half Trip of Steam & Feedwater Rupture Control Sys 1/3.Caused by Failure of +15-volt Dc Power Supply in Steam Generator Level Instrumentation Cabinet 1.Power Supply Replaced

ML19309G063
Person / Time
Site:	Davis Besse
Issue date:	04/28/1980
From:	Trautman D TOLEDO EDISON CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML19309G062	List: ML19309G061 ML19309G063
References
LER-80-027-03L, LER-80-27-3L, NUDOCS 8005020298
Download: ML19309G063 (2)

Text

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5$n"C' 60 l L l@l 0 DOCKET bl l 5 l NUMB 0 l-ER l 0 l 368 l 469 l 6 EVENT @l DATE 0131311 ( 8 l RiPORT 14 75 0 l@l 014 50l 2l 8l 8 l 0 DATE EVENT DESCRIPTION AND PROBABLE CONSEQUENCES h 10 l 2 l l (NP-33-80-36) On 3/31/80 at 1154 hours0.0134 days <br />0.321 hours <br />0.00191 weeks <br />4.39097e-4 months <br /> operations received a half trip of Steam and l

,o,3, lFeedwater Rupture Control System Channel 1/3. This half trip was due to a trip of thel 0 4 l +15 volt power supply PS03 in Steam Generator Level Instrumentation Cabinet 1. The l 10 i s i unit entered the action statement of Technical Specification 3.3.2.2 which requires l o e l the inoperable section to be placed in the tripped condition within one hot c. There l 0 7 l was no danger to the public o'r station personnel. The channel failed in the safe l o 3 l direction. The other channels were operable during this event. l OE CODE S SC E COMPONENT CODE SUSCOD'E S E O 9 l Cl H l@ y@ l Gl@ l Il Nl Sl Tl Rl Ul@ ]@ g @

12 13 18 19 20 7 8 9 to 11 OCCURRENCE REPORT REVISION SEQUE NTI AL EVENT YE AR REPORT NO. CODE TYPE .

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{C jglJ4B jg l3%Z l g {36g 31l 0l hURSl 40 0l l ]g l2y lg l N jg l44S l 2 [ 5 l 477 lg 33_. 41 4 43 CAUSE DESCRIPTION AND CORRECTIVE ACTIONS h i o lThe cause was a f ailure of the +15 volt DC power supply PS03 in Steam Generator Level l lTTT1 1I nstrumentation Cabinet 1.

This power supply wss being monitored from a previous fail-t

, , jure. A check sheved the output voltage had slowly increased until the overvoltage pro ;

, 3 l tection circuit actuated. Under MWO IC-24-80 the defective power supply was replaced.l

, , l Channel I was declared operable at 1701 hours0.0197 days <br />0.473 hours <br />0.00281 weeks <br />6.472305e-4 months <br /> on 3/31/80. ,

80 7 8 9 SA S  % POWER OTHER STATUS Dls RY DISCOVERY DESCRIPTION i s l_EJ @ l 0l 6l2lglNA l ] gl Operator observation l A TIVITY C TENT RELE ASED oP RELEASE LOCATION oF RELE ASE 1 6 W @ [_,Zjg l NA AuouNT oP ACriviTv 44 l NA 45 hl 80 l

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TOLEDO EDISON COMPANY DAVIS-BESSE NUCLEAR POWER STATION UNIT ONE SUPPLEMENTAL INFORMATION FOR LER NP-33-80-36 DATE OF EVENT: March 31, 1980 FACILITY: Davis-Besse Unit 1 IDENTIFICATION OF OCCURRENCE: Partial de-energization of Steam and Feedwater Rupture Control System (SRCS) Channel 1 Conditions Prior to Occurrence: The unit was in Mode 1, with Power (MWT) = 1717.5 and Load (Gross MWE) = 524.

Description of Occurrence: At 1154 hours0.0134 days <br />0.321 hours <br />0.00191 weeks <br />4.39097e-4 months <br /> on March 31, 1980, operations personnel ,

received a one half trip on SFRCS Channels 1/3. This half trip was due to a trip of the +15 volt power supply PS03 in Steam Generator Level Instrumentation Cabinet 1.

This placed the unit in the action statement of Technical Specification 3.3.2.2 which requires the inoperable section to be placed in the tripped condition within one hour during Modes 1, 2, and 3. The inoperable section was already in the tripped condition.

Designation of Apparent Cause of Occurrence: The apparent cause of this occurrence was found to be failure of the +15 volt DC power supply PS03 in Steam Generator Level Instrumentation Cabinet 1. A previous trip from the same power supply had occurred on January 31,1980 (see Licensee Event Report NP-33-80-15). Initial troubleshooting under Maintenance Work Order (MWO) IC-245-80 revealed no apparent problems within the cabinet or the power supply. Chart recordings of the power supply output indicated that over the time period from the previous occurrence to the present, power supply cutput voltage drifted in excess of one volt. Finally, the power supply output increased to 16.5 volts DC where the overvoltage protection circuit actuated causing the output to drop to zero volts DC resulting in a half trip to SFRCS Channel 1. Prior to any disruption in the circuirry the input voltage was checked and found to be within the design tolerance of the power supply, confirming no problems in the input circuitry.

Analysis of Occurrence: There was no danger to the health and safety of the public or to station personnel. The other SFRCS channel was operable during the time that SFRCS Channel 1 was inoperable. The SFRCS Channel 1 failed in the safe direction.

Corrective Action: The defective power supply was replaced under MWO IC-246-80. All l SFRCS power supply outputs will be monitored on a periodic basis to check for drift.

Channel 1 was declared operable at 1701 hours0.0197 days <br />0.473 hours <br />0.00281 weeks <br />6.472305e-4 months <br /> on March 31, 1980. The failed power supply was returned to the vendor for analysis.

Failure Data: Previous +15 volt DC power supply failures (Sorenson) are reported in Licensee Event Reports NP-33-79-113 (79-097), NP-33-79-148 (79-131), and NP-33-80-15 ,

(80-011). -- -

LER #80-027 l