ML20064F241

/03l-0 on 781024:following a Reactor Trip,The Containment Bulk Avg Temp Exceeded 105 Degrees F Tech Spec Limit Due to Steam Loss to Chilled Water Sys Vacuum Refrigeration Unit

ML20064F241
Person / Time
Site:	North Anna
Issue date:	10/24/1978
From:	Cartwright W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:
Shared Package
ML20064F229	List: ML20064F225 ML20064F235 ML20064F241 ML20064F253
References
LER-78-110-03L, LER-78-110-3L, NUDOCS 7811280326
Download: ML20064F241 (2)

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O l2l lFollowing a rea'ctor trip, the containment bulk average temperature exceeded the 1 0 l3 j i technical specification limit of 105 degrees F. The consequences were limited due to l lO ;4; lthe availability of Unit #1 Chilled Water System. Unit #2 Chilled Water System.had l O isi i been supplying cooling water to Unit #1 containment cooling system. I O s I -

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CAUSE DESCRIPTION AND CORRECTIVE ACTIONS h ji ioj [Following the reactor trip, Auxiliary Steam was lost which supplies steam to the 1 3 3 l vacuum refrigeration unit of the Chilled Water System. Difficulties in restartino I

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'. Report No. LER 78-110/03L-0 Description of Event While in Mode 3 operational status on October 24, 1978, the containment bulk average temperature exceeded the plant technical specification limit of 105 F. The bulk average temperature stayed above this temperature for 72 minutes. '

This increase occurred following a reactor trip.

Consequences of Event The c.onsequences of this high Unit #1 containment bulk average temperature were limited. Each unit's Chilled Component Cooling Water Subsystem can be supplied with cooling water from either unit's Chilled Water System. When the Unit #2 Chilled Water System, which had been supplying cooling water to the Unit #1 Chilled Component Cooling Water Subsystem, failed to restart, the Unit

1. 1 Chilled Water System was immediately put into operation. At no time was the public's safety or welfare endangered.

v Cause On October 24, 1978, the Unit #1 reactor tripped. This reactor trip caused the auxiliary steam supply, which provides steam to several systems, including the Chilled Water System,to be discontinued. The containment air is cooled by three. recirculation air coolers.which are supplied by Chilled Component Cooling Water Subsystem. The chilled water is cooled by the Chilled Water (CD) System, which is a steam vacuum refrigeration system.

In the event of a reactor trip, the oil fired auxiliary boilers are brought on line and used to supply auxiliary steam. Since it requires some time to get boilers up to operating temperature and pressure, auxiliary steam was not immediately available. When auxiliary steam became available, problems were encountered with restarting the Unit #2 Chiller which was supplying chilled water to the Unit #1 Chilled CC System and the Unit #1 chiller was brought on line.

( Immediate Corrective Action As soon as auxiliary steam was available, efforts were made to restart the Unit #2 chiller. When it became troublesome, the Unit #1 Chiller was put into operation. This soon brought the containment bulk average temperature under control and returned it to within the technical specification limit.

Action Taken to Prevent Recurrence To prevent recurrence of this situation, the reliability and performance of the Chilled CC and CD System must be upgraded. Currently, a redesign and improvement of these systems is underway. The main thrust of these efforts will be the addition of a mechanical chiller to the CD System.

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