05000328/LER-1981-107-03, /03L-0:on 810831,while in Mode 3,on Two Occasions, Ice Condenser Lower Inlet Doors Were Opened Slightly & Ice Bed Temp Exceeded 27 F.Caused by High Differential Pressure. Doors Closed & Temp Returned to Normal

/03L-0:on 810831,while in Mode 3,on Two Occasions, Ice Condenser Lower Inlet Doors Were Opened Slightly & Ice Bed Temp Exceeded 27 F.Caused by High Differential Pressure. Doors Closed & Temp Returned to Normal

ML20010J502
Person / Time
Site:	Sequoyah
Issue date:	09/28/1981
From:	Green H TENNESSEE VALLEY AUTHORITY
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML20010J497	List: 05000328/LER-1981-107, Forwards LER 81-107/03L-0 05000328/LER-1981-107-03, /03L-0:on 810831,while in Mode 3,on Two Occasions, Ice Condenser Lower Inlet Doors Were Opened Slightly & Ice Bed Temp Exceeded 27 F.Caused by High Differential Pressure. Doors Closed & Temp Returned to Normal
References
LER-81-107-03L, LER-81-107-3L, NUDOCS 8110050166
Download: ML20010J502 (3)

LER-1981-107, /03L-0:on 810831,while in Mode 3,on Two Occasions, Ice Condenser Lower Inlet Doors Were Opened Slightly & Ice Bed Temp Exceeded 27 F.Caused by High Differential Pressure. Doors Closed & Temp Returned to Normal

Event date:
Report date:
3281981107R03 - NRC Website

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LER SUPPLEMENTAL INFORMATION 1,

Technical Specification Involved:

3.6.5.1 and 3.6.5.3 l

SQRO-50-328/81107 6.9.1.13.b t

Reported Under Technical Specification:

n.:tc os occurrence:

1.

8-31-81 Time of Occurrence:

1.

2320 CDT i

2.

1530 CDT 2.

9-02-81 l

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identification and Description of Occurrence:

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i On 8-31-81 at 2320(C), the Unit 2 ice condenser ice bed temperature exceeded 27 F and the ice condenser lower inlet doors discovered slightly opened.

1.

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On 9-02-81 at 1530(C), the Unit 2 ice condenser ice bed temperature exceeded 27 F and the ice condenser lower inlet doors discovered slightly or*ned.

2.

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Conditions Prior to Occurrence:

Unit 2 in Mode 3 with RCS temperature and pressure at 547 F and 2235 psig.

1.

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Unit 2 in Mode 3 with RCS temperature and pressure at 547 F and 2240 psig.

t 2.

Apparent Cause of Occurrence:

Due to improper sealing of the reactor vesselmissile shield, leakage past The differ-1.

the seal created a pressure imbalance in lower containment.

This ential pressure caused the lower inlet doors to open slightly.

to enter the ice condenser and caused an increase l

condition allowed heat The high humidity caused the ice condenser l

in humidity in the ice condenser.

air handling units to frost over which reduced cooling and allowed the ice i

bed temperature to rise.

Due to the lower containment personnel airlock being out of service, personnel traveling to lower containment were entering upper containment 2.

through the upper containment airlock and then entering lower containment The hatch was not being used via the divider barrier " submarine" hatch.

The differ-properly creating a pressure imbalance in lower containment.

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This ential pressure caused the lower inlet doors to open slightly.

condition allowed heat to enter the ice condenser and caused an increase in tiumidity in the ice condenser. The hlrh humidity caused the ice con-denser air handling units to frost over which reduced cooling and allowed the ice bed temperature to rise.

Analysis of Occurrence:

On both occasions the lower inlet doors being open resulted in entry into LCO 3.6.5.3 and the high ice bed temperature resulted in entry into LCO 3.6.5.1.

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Tinniss'es Vallsy Auth:rity Sequoych Nuc1ccr Plcnt LER SUPPLEMENTAL INFORMATION i

Corrective Action

The reactor vessel missile shield seal was adjusted to prevent leakage.

1.

This allowed the lower inlet doors to remain closed. The air handling units were manually defrosted until the frosting was brought under control and the ice condenser temperature dropped. The ice bed temperature returned below 27 F by 0220(C) on 9-01-81.

Access to the lower containment was restricted until the lower containment 2.

This allowed the lower inlet personnel airlock was returned to service.The air handling units were manually defrosted doors to remain closed.

until the frosting was brought under control and the ice condenser temper-ature dropped. The ice bed temperature returned below 27 F by 1100(C) on 9-03-81.

Failure Data:

Similar Occurrences - Reference SQRO-50-327/81088, 81082, 80177, 80142, 80135, 80079, and 80064.

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