ML19329E362

Forwards IE Circular 77-10, Vacuum Conditions Resulting in Damage to Liquid Process Tanks. Action Required

ML19329E362
Person / Time
Site:	Midland
Issue date:	07/18/1977
From:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
To:	Howell S CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.)
References
NUDOCS 8006120672
Download: ML19329E362 (1)

Text

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CENTF1,L FILES

~F' 181977 Dochet Ho. 50-329 Dochet Ho. 50-330 Concencra Pcuer Co.npany i

AIYd: fir. Stephen li. Howoll VL a President l'/45 Ileat P;2rnall

• cad Jackson, MI 49201 Gantleman:

j The encioned Circular lio. 77-10 ic fortrarded to you for information. If there arc any rtucations related to your undcr-etanding of the cetions required, please contact this office.

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Sincerely,

!.j James G. Keppler Director

Enclosure:

IE Circular i

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July 18, 1977 IE Circular No. 77-10

-VACUUM CO IDITIO:IS RESULTI:!C III DA'! AGE TO LIQUID l'ROCESS TA!!KS Description of Circumstances On January 31, 1977, at the Portland General Electric Company's Trojan

' Nuclear-Station, a vacuum uns pulled on a Chemical and Volume Control System holdup tank which caused the tank to buckle inuardly and crack at the junction of two buckled arcas.

(LER 50-344/77-02)

Radioactive cover gas escaped from the tank to the fuel building exhaust ventilation and ultimately through the anniliary building ventilation stack to the environment. During the period of January 31 through' February 7,1977, (date of discovery) approximately 62.5 curies of nobic gases were reler. sed to the environment. The occurrence was caused by malfunctions of both the primary (waste gas decay tank collection header) and the backup (nitrogen pressuri=ation system) cover gas supply pressure regulators during pu= pout of the tank contents. The malfunction of the primary regulator was due to moisture accumulation which led to the forma-tion of a water column on the dischargo side of the pressure regulator.

The regulator in the backup nitrogen supply system malfunctioned at_the came time, but the cause has not been determined. There were no alarms or remote indication for the-holdup tank or the gas control header to indicate abnormal pressure or to indicate the operating status of the nitrogen supply systc=.

A similar event occurred at the Sacramento Municipal Utility District's Rancho Seco nucicar station uherein the Reactor Coolant System Drain Tank partially collapsed under vacuum conditions and in doing so cracked an inlet line attached to thc. tank (LER 50-312/77-03). The first indica-tion of the condition was detceted by the radiation monitor that sanples the ventilation exhaust in an area' adjacent to the room in which the damaged tank was located. Radioactive gases were relcased through the failed line between January 12 and February 16, 1977.

During this period,approxicately 9 curies of radioactive gas 'ere released. The

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w cause of' this occurrence was attributed to the tank not being properly vented by the operator during discharge af its liquid contents.

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• 1' IE Circular No. 77 - 2, July 18,-1977 It is recommended that you examine the systems of your reactor facility (ict:) that contain low pressure precess or holdup tanha and assure that adequate yeasures have been taken to protect against vacuum conditions that could result in tank inward buchling and failure with subsequent-release of radioactive material'or cause other detrimental effects with regard to the overall safety of plant operations.

It is also recommended that you examine your capability to detcet and locato possible leaks of radioactive material from such tanks.

No written respense to this Circular is required.

If you desire additional information regarding this matter, contact the Director of the appropriate NRC Regional Office.

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