ML20040G930

LER 82-001/03L-0:on 820108,subchannel B of Tis 4477 to Turbine Bldg Main Steam Line Leak Detection Sys Found W/ Nonconservative Trip Setting Greater than Tech Spec Limit. Caused by Instrument Drift.Tis 4477 Recalibr & Tested

ML20040G930
Person / Time
Site:	Duane Arnold
Issue date:	02/05/1982
From:	Varner D IES UTILITIES INC., (FORMERLY IOWA ELECTRIC LIGHT
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML20040G925	List: ML20040G924 ML20040G930
References
LER-82-001-03L, LER-82-1-3L, NUDOCS 8202160632
Download: ML20040G930 (2)

Text

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EVENT oEsCairTios ANr PaosAsta CcNsEcVENCES h lo 121 I While perforrino surveillance testino on the turbine buildina main steam i ITTT1 I line leak detection system, Subchannel B of TIS 4477 was found to have a l lo I A I I nonconservative trio settino of >204 decrees F. Technical Soecificatinn T l l o i s i I able 3.2-A reouires setnoint </= 200 decrees F. Instrument tolerance is + I 10 is I l /- 4 doorpos F_ Podundant (witchoc worn within enneificatinn. Seven Drevi l t o 171 I ous similar occurrences (see A0 74-18 and 75-49: and R0 76-09. 77-61. 78- I Io is i l 28, 80-25 and 81-02). I 1 ee so CE CE 56 C E COMPONENT CCOE SusCCCE su e loisi IC IDl @ [Ej @ l El @ l Il NI Si Tl RI Ul @ l Sl @ lZ l @

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CAUSE DEScalpTICN AND COnaECTIVE ACTICNS 27 i n t o 1 l Instrument drift. TIS 4477 is a Rosemount Model 3000A temperature indicat I litil I inq switch. TIS 4477 was recalibrated and tested sat. To reduce inst. dri 1 si12i l ft, existing switches in the test circuits will be replaced with those co I l

1ii3tl ntaininq cold contacts. This chance will be done on switches in steam tun I t i 1 11 nel and turbine bido. main steam leak detection system.  !

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DUANE ARN0LD ENERGY CENTER

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l. Iowa Electric Lighti and Power Company , ,

~ Licensee Event Report - Supplemental Data Docket No. 050-0331 Licensee Event Report Date: 2-5-82 Reportable. Occurrence No.: 82-001 Event Description-During normal operation while performing surveillance testing on the turbine building main steam line leak detection system, Subchannel B of TIS 4477 was found-to have a nonconservative trip setting of >204 degrees F. Technical

. Specification Table 3.2-A requires a trip setpoint of </= 200 degrees F.

The instrument tolerance is +/- 4 degrees F. Redundant switches in the logic were tested and were found to be within specification. ~ Because of the one-out-of-two-twice trip logic and the four completely independent channels, the nonconservative trip setting of TIS 4477 would not have prevented the logic from performing its intended design function. There have been seven previous similar occurrences (see A0 74-18 and 75-49; and R0 76-09, 77-61, 78-28,80-25,and81-02).

Cause Description The cause is attributed to instrument drift. TIS 4477 is a Rosemount Model 3000A temperature indicating switch.

Corrective Action TIS 4477 was recalibrated and tested satisfactorily prior to being returned to service. To reduce the susceptibility of Rosemount Model 3000A temperature indicating switches to instrument drift, a design change has been initiated to replace the existing switches in the test circuit with those containing gold contacts. This design change will be performed on all temperature ,

indicating switches in the steam tunnel and turbine building main steam line leak detection systems.

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