ML20217A127

Proposed Tech Specs Bases Section 3.10.B,updated to Require That Station Battery,Eccs Instrumentation Battery,Or Uninterruptable Power Sys Battery Be Considered Inoperable If Any One Cell Is Below Specification Cell Voltage

ML20217A127
Person / Time
Site:	Vermont Yankee
Issue date:	03/13/1998
From:	VERMONT YANKEE NUCLEAR POWER CORP.
To:
Shared Package
ML20217A114	List: ML20217A108 ML20217A127
References
NUDOCS 9803240269
Download: ML20217A127 (1)

Text

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MSEs.: ' 3.10 (cont'd)

3. Adequate power is available to operate the emergency safeguards equipment from either startup transformer or for minimum engineered safety features from either of the emergency diesel generators.

Therefore, reactor operation is permitted for up to seven days with both delayed-access off-site power sources lost. ,

Each of the diesel generator units is capable of supplying 100.

percent of the minimum emergency loads required under postulated design basis accident conditions. Each unit is physically and electrically independent of the other and of any off-site power source. Therefore, one diesel generator can be allowed out of-service for a period of seven days without jeopardizing the safety of the station.

In the event that both startup transformers are lost, adequate power is available to operate the emergency safeguards equipment from either of the emergency diesel generators or from either of the delayed-access off-site power sources. Also, in the event that both emergency diesel generators are lost, adequate power is available immediately to operate the emergency safeguards equipment from at

.least one of the startup transformers or from either of the delayed-access off-site power sources within six hours. The plant is designed to accept one hundred percent load rejection without adverse offacts to the plant or the transmission system. Network stability analysis studies indicate that the loss of the Vermont Yankee unit will not cause instability and consequent tripping of the connecting 345 Av and 115 kV lines. The Vernon feed is an independent source. Thus, the availability of the delayed-access off-site power sources is assured in the event of a turbine trip.

l' Therefore, reactor operation is permitted with the startup transformers out of service and with one diesel generator out of service provided the NRC is notified immediately of the event and restoration plans.

Either of the two station batteries has enough capacity to energize the vital buses and supply d-c power to the other emergency equipment for 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> without being recharged. In. addition, two 24 volt ECCS Instrumentation batteries supply power to instruments that provide automatic initiation of the ECCS and some reactor pressure and level indication in the Control Room.

Due to the high reliability of battery systems, one of the two '

batteries may be out of service for up to three days. This minimizes the probability of unwarranted shutdown by providing adequate time for reasonable repairs. A station battery, ECCS Insttunentation battery, or terruptible Power System battery g is considered inoperable if c :

ne cell is out of service. A l cell will be considered out or ==svace if its float voltage is below 2.13 volts and the specific gravity is below 1.190 ,at 77'F.

The Battery Room is ventilated to prevent accuadlation of hydrogen gas. With a complete loss of the ventilation system, the accumulation of hydrogen would not exceed 4 percent concentration in 16 days. Therefore, on loss of Battery Room ventilation, the use of portable ventilation equipment and daily sampling provide assurance that potentially hazardous quantities of hydrogen gas will not accumulate.

C. The minimum' diesel fuel supply of 25,000 gallons will supply one 4

diesel generator for a minimum of seven days of operation satisfying the load requirements for the operation of the safeguards equipment.

Additional fuel'can be obtained and delivered to the site from nearby sources within the seven-day period.

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