05000346/LER-1978-006-03, /03L-0:on 780107,computer Alarm Indicated That Steam & Feedwater Rupture Control Sys Steam Generator to Feedwater Differential Pressure Channel 1 Had Tripped.Caused by Component Failure.Input Buffer 1-3 in Channel 1 Replaced

/03L-0:on 780107,computer Alarm Indicated That Steam & Feedwater Rupture Control Sys Steam Generator to Feedwater Differential Pressure Channel 1 Had Tripped.Caused by Component Failure.Input Buffer 1-3 in Channel 1 Replaced

ML19326A176
Person / Time
Site:	Davis Besse
Issue date:	02/01/1978
From:	TOLEDO EDISON CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML19326A172	List: 05000346/LER-1978-006, Forwards LER 78-006/03L-0 05000346/LER-1978-006-03, /03L-0:on 780107,computer Alarm Indicated That Steam & Feedwater Rupture Control Sys Steam Generator to Feedwater Differential Pressure Channel 1 Had Tripped.Caused by Component Failure.Input Buffer 1-3 in Channel 1 Replaced
References
LER-78-006-03L, LER-78-6-3L, NUDOCS 8002030039
Download: ML19326A176 (2)

LER-1978-006, /03L-0:on 780107,computer Alarm Indicated That Steam & Feedwater Rupture Control Sys Steam Generator to Feedwater Differential Pressure Channel 1 Had Tripped.Caused by Component Failure.Input Buffer 1-3 in Channel 1 Replaced

Event date:
Report date:
3461978006R03 - NRC Website

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l a 121 l At 1145 hours0.0133 days <br />0.318 hours <br />0.00189 weeks <br />4.356725e-4 months <br /> on 1/7/78. nersonnel received a computer alarri l

g o # 3 r l Feedwater Ruoture Control System Steam Cencrator to Feeduster Dif ferentici Pressure ITT7] } Trip for Channel 1.

This placed the unit in Action Statement 13 o# Tech Snec 3.3.2.2 l

I E"T1 Iwhich requires all Steam Generator to Fetdwater Differential Pressure Switches in l o is j l Modes 1. 2 and 3.

The unit entered Mode 4 to perfo-m outane maintenance at 2100 hour0.0243 days <br />0.583 hours <br />0.00347 weeks <br />7.9905e-4 months <br />sf l

[oliJ-Qhich renovcd the unit frort the Action Statement.of Tech Soc.c 3.3.2.2.

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The No. 2 circuit on Inntit Buffer I s i g o l lThe cause of this occurrence is component On 1/7/78, ocrsonnel reoineed Inn,it 9._, F e -i g 11-3 in C5762A had failed to the trip state.

l1-3 in SFRCS Channel 1.

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DAVIS-BESSE UNIT ONE NUCLEAR POWER STATION SUPPLEMEMTAL INFORMATION FOR LER NP-33-78-07 v

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f DATE OF EVENT:

January 7, 1978 a

a FACILITY: Davis-Besse Unit 1 1

IDENTIFICATION OF OCCURRENCE: Failure of Input Buffer 1-3 for Steam and Feedvater Rupture Control System Channel 1.

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I Conditions Prior to Occurrence: The unit was in Mode 3, with Power (MWT) = 0, i

and Load (MWE) = 0.

j Description of Occurrence: At 1145 hours0.0133 days <br />0.318 hours <br />0.00189 weeks <br />4.356725e-4 months <br /> on January 7,1978, Operations personnel received a computer alarm indicating a Steam and Feedwater Rupture Control System (SFRCS) Steam Cenerator to Feedwater Differential Pressure Trip for Channel 1.

The resulting investigation indicated a single failure in the input circuit from pressure dif ferential indication switch 2686A.

No other pressure differential j

indicating suitch.es monitoring the Steam Cenerator to Feedwater Differential 4

Pressure were'in the tripped state. This placed the unit in Action Statement 13 of Technical Specification 3.3.2,2 which requires all Steam Generator to Feedwater Differential Pressure Switches in Modes 1, 2 and 3.

Since the input was placed

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and lef t in the tripped condition since the time of the. trip, the Action Statement

" required action was fulfilled.

The unit entered Mode 4 to perform outage main-tenance at 2100 hours0.0243 days <br />0.583 hours <br />0.00347 weeks <br />7.9905e-4 months <br />, which removed the unit from the Action Statement of Tech-nical Specification 3.3.2.2.

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i Designation of Apparent Cause of Occurrence: The cause of this. occurrence is component failure. The No. 2 circuit on Input Buffer 1-3 in C5762A had failed to the trip state.

The input buffer assembly was returned to the manufacturer

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who discovered a diode had failed causing the input buf fer failure..

4 Analysis of Occurrence: There was no danger to the health 'and safety of the public or to unit personnel.

The failure of Input Buffer 1-3 in C5762A immediately put the channel in the tripped state. Redundant Steam Cenerator to Feedwater Differ-ential Pressure inputs w'ere also available.

.C$rrective Action: Cn January 7,1973, Instrument and Control personnel replaced j,

., Input Buffer 1-3 in SFRCS Channel-1. On January 10, 1978, all. functional testing (ST 5031.14) and' response time testing (ST 5031.09) was completed on the new input--

l buffer and the channel was declared operable, i Failure Data: One pievious failure has occurred on these input buffers as dis,

NP-32-77-16.

v / cussed in-Licensee Event Report 4

'LF.R 473-006 O

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