ML19347E427

LER 81-041/03L-0:on 810323,pressurizer Level Indicators for Channels 1-L-68-339,1-L-68-325C & 1-L-68-326C Showed 15% Lower Level than Redundant Channels.Caused by Increased Static Head in Common Sense Line Due to Reservoir Mod

ML19347E427
Person / Time
Site:	Sequoyah
Issue date:	04/21/1981
From:	Harding M, Wilkey A TENNESSEE VALLEY AUTHORITY
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML19347E426	List: ML19347E425 ML19347E427
References
LER-81-041-03L-03, LER-81-41-3L-3, NUDOCS 8104270351
Download: ML19347E427 (2)

Text

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l 8 61 OoCEET NUM0EH 69 74 73 EVEf 7 CESCRIPTION ANO PnOSA8LE CONSEQUENCES h 10.121 l With Unit I at 97% nower. pressurizer level channels 1-L-68-339, 1-L-68-325C, and l I o I 3 I l 1-L-68-326C declared' inoperable when the associated indicators were observed to be - l l o 14 l l 15% lower than' redundant channels. The plant entered action statement 7 of LCO 3.3.1.1 l 0 s Iand action statement "a" of LCO 3.3.3.5. After corrective actions were performed, .l 1 O ls 1 l 1-LI-68-339 was observed to be 8%' higher than redundant channels on 4/2/81. The l g [ bistable was again tripped per action statement 7 of LCO 3.3.1.1. There has been no' ' l

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l i l o l l The' apparent cause of the error was an increased static head in o' common serine line due i (TTi 1 I to a condensato reservoir modirication made under ECN L5392 l

A modification to i ,,;7i l L-68-325C and 326C sense lines and a rescaling of the outputs for LI-68-339 were per- ~

g l formed in order to return the loops to service under work plan 9117. Looo Ll68-339 in f i i , .1 [ scheduled to be returned to its original configuration during the next unit outage.

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$s $s l Name of Preparer: A. M. Wilkey/M. R. Hardfrw Phone: (615) 842-8317 - -s 8104270351 - - -

• . 9- Tann:seco Velley Auth2rity S;quoyah Nuciccr Plcnt LER SUPPLEMENTAL INFORMATION SQRO-50-327/81041 Technical Specifications Involved: 3.3.3.1 an?

3.3.3.5 Reported Under Technical Specification: 6.9.1.13.b ,

Date of Occurrence: 3/23/81 Time of.0ccurrence: 1510 CST Identification and Description of Occurrence:

1. During channel check on 3/23/81, pressurizer level loop L-68-339 was discovered to be indicating approximately 15% lower than redundant channels. The loop was declared inoperable and the bistable was tripped in accordance with action statement 7 of LCO 3.3.1.1.

Auxiliary control room loops L-68-325C and L-68-326C were also declared inoperable since they shared a common sensing line and were also indicating approximately 15% low. The plant entered action statement "a" of LCO 3.3.3.5.

2. On 4/2/81, a channel check of L-68-339 revealed that loop to be reading approximately 8% high. The loop bistable was tripped in accordance with action statement 7 of LCO 3.3.1.1.

Analysis of Occurrence

1. The error was caused by an increased static head in the sense line resulting from a condensate reservoir modification made under ECN L5392.

2 .' The corrective actions taken to correct for the error discovered on t 1/21/81 were not adequate. The plant has tripped the associated hintable which will remain tripped until the next unit outage.

Corrective Action

1. The pressurizer high level trip bistable setpoint was shifted from 92% to 76% to compensate for the low level readings. Temporary scales were installed on the level indicators to directly read the level. The auxiliary control room loops were retubed to the sensing i loop of 1-LT-68-335 returning them to an operable status. These actions were performed on work plan 9117.

l 2. During the next unit outdge, loop L-68-339 is scheduled to be returned to its original configuration.

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