05000338/LER-1979-114-03, /03L-0:on 790912,temp at Top Corner of Steam Generator Support Exceeded Tech Spec Limit.Caused by Heaters Being Left on Too Long When Control Resistance Temp Detector Failed to Cycle Heaters Automatically

/03L-0:on 790912,temp at Top Corner of Steam Generator Support Exceeded Tech Spec Limit.Caused by Heaters Being Left on Too Long When Control Resistance Temp Detector Failed to Cycle Heaters Automatically

ML19209C453
Person / Time
Site:	North Anna
Issue date:	10/12/1979
From:	Cartwright W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML19209C450	List: 05000338/LER-1979-113-03, /03L-0:on 790912,pressurizer Level Channel II Gave Erratic Indication on Control Board.Cause Unknown.Testing Revealed No Problems 05000338/LER-1979-114-03, /03L-0:on 790912,temp at Top Corner of Steam Generator Support Exceeded Tech Spec Limit.Caused by Heaters Being Left on Too Long When Control Resistance Temp Detector Failed to Cycle Heaters Automatically ML19209C449
References
LER-79-114-03L, LER-79-114-3L, NUDOCS 7910150583
Download: ML19209C453 (2)

LER-1979-114, /03L-0:on 790912,temp at Top Corner of Steam Generator Support Exceeded Tech Spec Limit.Caused by Heaters Being Left on Too Long When Control Resistance Temp Detector Failed to Cycle Heaters Automatically

Event date:
Report date:
3381979114R03 - NRC Website

text

NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION (7 /7)

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2 On September 12, 1979, during Mode 1 coeration, the temoerature at the too corner of I

] a steam generator support exceeded the Technical Specification limit of 355 F.

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3 lthe support temperature was returned to below 355 F within th_e 4 hour4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> + e limit i

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Virginia Electric and Power Company North Anna Power Station, Unit #1 Docekt No. 50-338

Attachment:

Page 1 of 1 Report No. LER 79-114/03L-0

Description of Event

On September 12, 1979, during steady state o sration at 69% power, the e

temperature at the top level corner of a steam generator support exceeded 355"F which is contrary to T.S. 3.4.10.2.b.

Probable Consequences of Occurrence The consequences of this event were minimal because the f.emperature of the steam generator support was returned to below 355'F within the time limit allowed by the ACTION statement. As a result, the health and safety of the general public were not affected by this event.

Cause of Occurrence The high steam generator support temperature was caused by the support heaters being lef t on for too long a time.

This resulted from the control RTD's failing to cycle the heaters automatically.

Immediate Corrective Action

The support heaters were turned of f until the teraperature of the steam generator support return (d to acceptable limits.

Scheduled Corrective Action A design change will be implemented to replace the defective RTD's during the current refueling outage.

Acticas Taken to Prevent Recurrence Operations personnel were instructed to check for trends while taking logs.

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