ML19263C535

LER 79-002/03L-0 on 790110:during Freon Test,Noted That Freon Penetration Through Charcoal Absorbers Exceeded Tech Spec Max.Caused by One of Charcoal Clamping Levers Not Being Fully Latched

ML19263C535
Person / Time
Site:	Quad Cities
Issue date:	02/05/1979
From:	Schnitzmeyer J COMMONWEALTH EDISON CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML19263C532	List: ML19263C531 ML19263C535
References
LER-79-002-03L-03, LER-79-2-3L-3, NUDOCS 7902260451
Download: ML19263C535 (3)

Text

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[o 2 l While performing a freon test, procedure QTS 260-2, on the 1/2B Standby Gas Treat- l o 3 l ment System (SBGT), it was determined that the freon penetration through the charcoal l This exceeded the 1% limit specified in Technical Spec 'i ca t i on l o 4 l absorbers was 12.1%.

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33 34 3b 36 31 40 42 43 CAUSE DESCRIPTION AND CORRECTIVE ACTIONS 1 0 10ne of the four charcoal bed assembly clamoina levers was not fully latched. This l The I l i l i l l a l lowed a sma l l f raction of the f reon to bvoass three of the charcoal cells.

1 7 ] gasket and charcoal cells were inspected and relatched. A second freon test was l li 3 l performed satisfactorily. A charge to procedure QTP 400-3 will be implemented l 3 4 ] to check these levers on a weekly basis. lX 80 7 8 9

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l. LER HUMBER: 79-02/03L-0

11. LICENSEE NAME: Commonwealth Edison Company 0.uad-Cities Nuclear Power Station 111. FACILITY NAME: Unit One IV. DOCKET NUMBER: 050-254 V. EVENT DESCRIPTION:

On January 10, 1979, Technical Staff personnel were performing a freon test, procedure QTS 260-2, on 1/2B Standby Gas Treat-ment System (SBGT). At 5:35 p.m., it was determined that the freon penetration through the charcoal absorbers was 12.1%.

This exceeds the 1% limit specified in Technical Specification 3.7.B.2.a.2. The redundant SBGT System was started and run for 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> to prove operability as requi red.

VI. PROBABLE CONSEQUENCES OF THE OCCURRENCE:

The 1/2A SBGT System was operable during the time when the leakage of the 1/2B SBGT System exceeded the limit. A freon test was performed on 1/2A SBGT System on January 9, 1979 and the leakage was found to be 0.62%. Furthermore, the 1/2B SBGT System was operable and capable of maintaining negative pressure on secondary cotainment i f i t had been requi red. The filter differential pressures were normal, and the heater and fan operation were acceptable. The HEPA filters were tested and found to be acceptable using a DOP test (procedure QTS 260-1) .

Vll. CAUSE:

An inspection revealed that one of the four charcoal bed clamping rack locking levers was out of the full forward position. This allowed a small fraction of the air fiow to bypass three of the charcoal beds. By moving these levers forward, pressure is applied to the downstream closed end of the charcoal cells. In this manner, the charcoal cells are pressed firmly against a verticle baffle plate which is fitted with a gasket to assure a good seal. Slots in the baffle give access to the interior of each charcoal cell. The air must therefore pass upward and downward through the charcoal beds.

The housing is provided with a total of four levers and by moving these levers forward, all twelve charcoal cells are locked into place. Gravity in addition to mechanical resistance maintains the mechanism in the proper position. The reason the lever was out of position is not known. The SBGT Systems are manufactured by the Barnebey Cheney Company.

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Vill. CORRECTIVE ACTION:

The baffle plate to charcoal cell assembly gasket was inspected to assure it was in good condition. The charcoal cells were replaced and the clamping rack locking levers re-engaged. A freon test was subsequently performed and the leakage was found to be 0.93% which satisfies the Technical Specifications.

A change to the Technical Staft weekly in plant inspection, procedure QTP 400-3, will be implemented to visually check that the charcoal filter latching levers are in the full forward engaged position.