05000317/LER-1981-007-03, /03L-0:on 810112,engineered Safety Features Actuation Sys Sensor Channel Ze for Steam Generator 12 Pressure Placed Out of Svc.Caused by Failure of Transmation Isolator (230IT) 1-E/E-1023B.Isolator Output Found Low

/03L-0:on 810112,engineered Safety Features Actuation Sys Sensor Channel Ze for Steam Generator 12 Pressure Placed Out of Svc.Caused by Failure of Transmation Isolator (230IT) 1-E/E-1023B.Isolator Output Found Low

ML19343C133
Person / Time
Site:	Calvert Cliffs
Issue date:	02/11/1981
From:	Davis S, Rizzo P BALTIMORE GAS & ELECTRIC CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
Shared Package
ML19343C125	List: 05000317/LER-1981-007, Forwards LER 81-007/03L-0 05000317/LER-1981-007-03, /03L-0:on 810112,engineered Safety Features Actuation Sys Sensor Channel Ze for Steam Generator 12 Pressure Placed Out of Svc.Caused by Failure of Transmation Isolator (230IT) 1-E/E-1023B.Isolator Output Found Low
References
LER-81-007-03L, LER-81-7-3L, NUDOCS 8102180692
Download: ML19343C133 (2)

LER-1981-007, /03L-0:on 810112,engineered Safety Features Actuation Sys Sensor Channel Ze for Steam Generator 12 Pressure Placed Out of Svc.Caused by Failure of Transmation Isolator (230IT) 1-E/E-1023B.Isolator Output Found Low

Event date:
Report date:
3171981007R03 - NRC Website

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1. G EVENT DESCRIPTION AND PRC8ABLE CONSEQUENCES h i o 121 l At 1245 Engineered Safety Features Actuation System (ESFAS) Sensor I

Channel ZE for #12 Steam Generator (SG) pressure was placed out of ser-l

. i o i 31 1 io ui l vice per T.S. 3.3.2.1 to correct an erroneous sensor input. At 1335 #12 l

l0i3i l SG pressure sensor channel was returned to service. The three redundant I

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33 34 35 37 40 48 42 43 44 47 CAUSE DESCRIPTION AND CORRECTIVE ACTIONS h l i 101 1 Transmation Isolator (230!T) 1-E/E-10238 failed its output was low by I

m1 6". and drifting. The SG Pressure Trio bvoass in Channel "B" would there-I fore have been enabled at greater than 685 psia, the Technical Speciff-l gi Lu_31 l cation maximum. The isolators will be modified as documented in Facil-I ii t i l ity Change Request 80-25 to increase their reliability.

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50-317 LICENSE NO. OPR-53 EVENT DATE 01-12-81 REPORT DATE 02-11-81 ATTACHMENT CAUSE DESCRIPTION AND CORRECTIVE ACTIONS (CONT'D)

The as-found condition for 1-E/E-10238 was an output approximate 6%

low as compared to a given input. During attempts to recalibrate the instrument the output drifted and the instrument was replaced with a spare.

The measured deviation would have caused a low SG Pressure single channel trip conservatively early in a decreasing pressure transient. The low signal level would also have caused Channel "B'

Low SG Pressure Trip Bypass bistable to actuate at approximately 732.5 psia vice the Technical Specification of less than 685 psia (Table 3.3-3 Notation C). Since the bypass function requires actuation of 3 of 4 channels' Block bistables, signals from 2 additional channels would have been required to bypass the #12 SG Low Pressure Trip.

The Transmation Model 230IT Isolators are to be modified by implementation of Facility Change Request 80-25. This change will increase reliability by replacing several parts which exhibit high failure rates.

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