ML20028A593

LER 82-123/01T-0:on 821029 & 1109,during Mode 6 Operation, Control Room Emergency Vent Sys Declared Inoperable Due to Partial Closing of Suction Dampers 0-31A-102 & 0-31A-103. Caused by Duct Vibration.Design Change Being Expedited

ML20028A593
Person / Time
Site:	Sequoyah
Issue date:	11/10/1982
From:	Hardin M, Rogers H TENNESSEE VALLEY AUTHORITY
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML20028A589	List: ML20028A588 ML20028A593
References
LER-82-123-01T, LER-82-123-1T, NUDOCS 8211220319
Download: ML20028A593 (2)

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• • LER SUPPLDENTAL INFORMATION e

Technical Specification Involved: 3.7.7 SQRO-50-327/82123 Reported Under Technical Specification: 6.9.1.12.b Date of Occurrence: 10/29/82, Time of Occurrence: 1500 CST Identi_f_ic_ation _and D_escription of Occurrence:

At 1500 CST on 10/29/82, during a walkdown of the control room emergency ventilation system, suction dampers 0-31A-102 and -103 were found parcially closed. This would have prevented the system f rom maintaining a flow rating of 4000 cfm in the event of control room isolation. A similar event occurred at 0800 CST on 11/09/82. Upon discovery of each event, the unit entered the action statements of LC0 3.7.7 and 3.0.3.

Conditicns Prior to Occurrence:

For both events unit 1 was in node 6 (refueling) and unit 2 was in mode 1

• (96% power) .

Apparent Cause of Occurrence _:

The louvered dampers are held open by an adjustment screw. In each case, vibration of the duct and damper from air flow across the damper caused the adjustment screw to loosen and the damper to partially close.

Analysis of Occurrence:

In the event of control room isolation, the control room emergency ventilation system is designed to provide 4000 cfm (1 10%) air flow to the control room.

Suction dampers 0-31A-102 and -103 are common to both trains of 4he emergency air cleanup fans. These dampers are preset to casure 3800 cfm (- 10%) flow of ,

filtered air to the control room. When the dampers vibrated partially closed, the system would have been unable to meet the needed flow criteria.

Corrective Action:

For each event, the damper was immediately opened to the preset position and the adjustment screw tightened. Measures are being taken to block the damper in the open position to maintain system operability. The design of a new damper is being reviewed by Design through DCR 1650. Until modifications are made, a daily surveillance will be performed to verify the damper setting.

Failure Data:

None.