05000327/LER-1980-202-03, /03L-0:on 801225,steamline Pressure & Flow Channel S/G-3 Train a Failed High & S/G-1,2 & 4 Train B Failed Low. Caused by Freezing of Unprotected Sense Lines.Lines Thawed. Design Changes Initiated

/03L-0:on 801225,steamline Pressure & Flow Channel S/G-3 Train a Failed High & S/G-1,2 & 4 Train B Failed Low. Caused by Freezing of Unprotected Sense Lines.Lines Thawed. Design Changes Initiated

ML19341B502
Person / Time
Site:	Sequoyah
Issue date:	01/22/1981
From:	Mcgriff J, Wilkey A TENNESSEE VALLEY AUTHORITY
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML19341B501	List: 05000327/LER-1980-202, Forwards LER 80-202/03L-0 05000327/LER-1980-202-03, /03L-0:on 801225,steamline Pressure & Flow Channel S/G-3 Train a Failed High & S/G-1,2 & 4 Train B Failed Low. Caused by Freezing of Unprotected Sense Lines.Lines Thawed. Design Changes Initiated
References
LER-80-202-03L, LER-80-202-3L, NUDOCS 8102020389
Download: ML19341B502 (3)

LER-1980-202, /03L-0:on 801225,steamline Pressure & Flow Channel S/G-3 Train a Failed High & S/G-1,2 & 4 Train B Failed Low. Caused by Freezing of Unprotected Sense Lines.Lines Thawed. Design Changes Initiated

Event date:
Report date:
3271980202R03 - NRC Website

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60 Gl DOC u t T NUMO E M G8 t9 (VENT DAf t 74 JS REFQRT DAT E 80 EVENT DESCAtPTION AND PROSA8LE CONSEQUENCES h loi2l l At 86% RTP, S/G-3 train A steamline pressure and flow channels failed high at 0441 CST. I l o t a l l Action statements of' LCO 3.3.3.7(a), 3.3.1.1(7), and 3.3.2.1(16) were in effect until i

Iop4l l operability was restored at 0621 CST. At 0649 CST S/G-1, 2, & 4 train B feedwater flow l ib6TO I channels failed low and plant entered action statement 7 of LCO 3.3.1.1.

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l o !s j l train A feedwater flow channel subsequently failed low at 0852 CST, the plant prepared l loj7; l for shutdown per LCO 3.0.3 but remaine4 at power when operability was restored at 0934 l go;eil CST. No effect on public health or safety. Previous occurrences - none.

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Tennassaa Vallsy Authority Seqt'oyah Nuclear Plant LER SUPPLEMENTAL LNFORMATION SQRO-50-327/80202 Technical Specification Involved:

3.0.3, 3.3.1.1, 3.3.2.1, 3.3.3.7 Raported Under Technical Specification:

6.9.1.13.b Date of Occurrence:

12/25/80 Time of Occurrence:

0441 CST Identification and Description of Occurrence:

At 0441 CST the train A steamline pressure channel (P-1-20A) and the associated steamline flow channel (F-1-21A) for steam generator #3 failed high. The plant entered action statement "a" of LCO 3.3.3.7 and the affected trip bistables were placed in the manually-tripped co'dition as specified by action statement 7 of LCO 3.3.1.1 and action statement 16 of LCO 3.3.2.1 until operability was restored at 0621 CST. At 0649 CST train B feedwater flow channels for steam generator #1 (F-3-35B), steam generator

1. 2 (F-3-48B) and steam generator #4 (F-3-103E) failed low. The affected trip bistables were placed in the manually-tripped condition in accordance with action statement 7 of LCO 3.3.1.1.

Subsequently at 0852 CST the train A feedwater flow channel for steam generator #1- (F-3-35A) also faile d low.

- Although the flow channels failed in the conservative direction, the plant -

prepared for shutdown in accordance with LCO 3.0.3 but remained in Mede 1 when operability of the flow channels was restored at 0934 CST.

Conditions Prior to Occurrence:

Unit in Mode 1 at 86% RTP Apparent Cause of Occurrence:

The steamline pressure and flow channels failed high because the associated

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steamline pressure transmitter's sense lines in the east valve room were frozen. The transmitter is located near the air intake louvers in the east valve room which were open allowing the sense lines to freeze.

The feedwater flow channels failed low when the associated sense lines became frozen inside a building wall penetration. Heat tracing for the lines did not extend into the penetration and therefore that portion of the sense lines was unprotected.

Analysis of Occurrence:

The f ailure of the steamline pressure channel resulted in one accident monitoring

.steamline pressure channel for steam generator #3 being inoperable for less chan two hours. Since the steamline flow and pressure channels failed high, the associated reactor. protection and ESF trip functions were performed.

Since the feedwAP.er flow channels failed low, the required protective functions were performed and operation of the plant was never less conservative than the-limiting condition for operation specified by LCO 3.3.1.1.

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LER SUPPLEMENTAL INFORMATION (Continued)

Corrective Action

The sense lines were taawed by applying additional heat and insulation. A design change request has been initiated to have the necessary heat tracing and insulation installed to prevent re-occurrence.

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