ML20211D155

Proposed Tech Specs Pages,Revising Degraded Voltage Relay as-left Setpoint Tolerances

ML20211D155
Person / Time
Site:	Three Mile Island
Issue date:	08/20/1999
From:	GENERAL PUBLIC UTILITIES CORP.
To:
Shared Package
ML20211D136	List: ML20211D132 ML20211D155
References
NUDOCS 9908260187
Download: ML20211D155 (7)

Text

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1920-99-20295 Proposed Revised Technical Specification Pages 3-37.a and 4-7 l

and UFSAR pages 8.2-3 and 8.2-5

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i 9908260187 990820 PDR ADOCK 05000289 P

PDR

(4) Minimum allowed setting is 3740 volts. Maximum allowed setting is 3773 volts.

(5) Minimum allowed time is 8 seconds. Maximum allowed time is 12 seconds.

(6) Minimum allowed setting is 2200 volts. Maximum allowed setting is 2860 volts.

(7) Minimum allowed time is 1.0 second. Maximum allowed time is 2.0 seconds.

Bases High Reactor Building Pressure The basis for the 30 psig and 4 psig setpoints for the high pressure signal is to establish a setting which would be reached in adequate time in the event of a LOCA, cover a spectrum of break sizes and yet be far enough above normal operation inaximum internal pressures to prevent spurious initiation (Reference 1).

Low Reactor Coolant System Pressure The basis for the 1600 and 500 psig low reactor coolant pressure setpoint for high and low pressure injection initiation is to establish a value which is high enough such that protection is provided for the entire spectrum of break sizes and is far enough below normal operating pressure to prevent spurious initiation. Bypass of HPl below 1775 psig and LPI below 925 psig, prevents ECCS actuation during normal system cooldown (References 1 and 2).

4.16 ES Bus Undervoltage Relavs The basis for the degraded grid voltage relay setpoint is to protect the safety related electrical equipment from loss of function in the event of a sustained degraded voltage condition on the offsite power system. The timer setting prevents spurious transfer to the onsite source for transient conditions.

The loss of voltage relay and timers detect loss of offsite power condition mid initiate transfer to the onsite source with minimal time delay.

The minimum and maximum degraded voltage setpoint are "as found" readings.

References (1) UFSAR, Table 7.1-3 (2) UFSAR, Section 14.1.2.10 " Steam Generator Tube Failure" 3-37a Amendment No. 70, 73, 3, P,149,157,159

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TMI-1/FSAR The TMI-1 Plant Electrical Distribution system design will adequately protect the safety related electric equipment from loss of capability of redundant safety loads, their control circuitry and associated electrical components required for performing safety functions as a result of sustained degraded voltage from the offsite electric grid system.

Loss of voltage protection on the 4160 V safety buses is provided by three solid state instantaneous relays on each bus arranged in a two-out-of-three coincident logic scheme with a voltage setpoint 58 percent of nominal bus voltage and a time delay of 1.5 seconds. These relays will trip the safety bus feeder breaker, initiate load shedding, start the respective diesel generator and sound an annunciator in the main Control Room.

Degraded grid voltage protection on the 4160 V safety buses is provided by three additional relays on each hu. arranged in a two-out-of-three coincident logic with a voltage setpoint 90.4 pwcent of nominal bus voltage, and a time delay of 10 seconds.

These relays will trip the associated safety bus feeder breaker, initiate load shedding, start the diesel generator and sound an annunciator in the main Centrol Room. This second level undervoltage protection setpoint provides the necessary protection of 480 volt safety related electrical loads for the worst case electrical lineup and loading during the initial stages of a design basis LOCA, assuming a degraded grid condition, and one (1) auxiliary transformer in operation. If the degraded grid condition persists, operators may be required to take manual action in response to the 480 V bus undervoltage alarms to restore voltage or to transfer to the standby Diesel Generators in order to assure adequate voltage to the Battery Chargers and other NSR loads. The above revised undervoltage protection setpoint will result in an increased probability of separation of the remaining ES bus from the 230 kV system during a postulated accident coincident with maximum BOP loads, a single auxiliary transformer operation and a degraded grid event, while the offsite system is still capable of providing power to the plant. However, neither the accident nor the degraded grid alone results in any event-related electrical system transfers that would cause loss of an auxiliary transformer or the automatic transfer of loads. Accordingly, it is concluded that simultaneous occurrence of these unrelated events is a very low probability, and the intent of requiring an adequate level of undervoltage protection is maintained by the revised degraded voltage setpoint. Technical Specification Section 3.5.3 provides inspection and testing requirements for these relays and timers.

Additional undervoltage protection is provided by relays on the 480 V safety busas.

These relays annunciate in the Control Room at approximately 92 percent of the nominal rating of the motors (460V) connected to these buses to alert the operators to a low voltage condition to allow time to shed unnecessary loads to restore voltage and preclude trips, if possible.

8.2-3 UPDATE-15 4/00 l

1 i

I TMI-1/FSAR 8.2.2.1 Sinale Line Diaoram Drawing E-206-011 is a single line diagram of the Unit 1 distribution system.

8.2.2.2 Auxiliary Transformers Two." full-size" auxiliary transformers are connected to different 230 kV buses and provide a l

source of power for startup, operations, shutdown, and after shutdown requirements. Each transformer has the MVA capacity to handle all of the above loads. During single transformer operation under the heavy loads of full power operations, design basis LOCA loads and wiiin input voltage near minimum the transformer output voltage would lead to undervoltage separation of 1 or both ES buses from the transformer. The ES loads will then be automatically placed on the emergency diesel generators. During single transformer operation, Circulating Water pump operation must be limited to a maximum of 5 pumps, to ensure that under LBLOCA conditions with worst case electrical loading on the 1E distribution.

- system, separation from the grid does not occur within the normal range of the grid. Either of the two transformers will also serve as a standby source in the event of one auxiliary transformer failure, with a further source as noted in Subsections 8.2.3.1.b and 8.5.2. Each of the aforementioned transformers has two isolated secondary windings, one at 6900 V and one at 4160 V, for the purposes outlined in the following subsections.

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. Technical Specification Section 3.7.2 restricts single auxiliary transformer operation to a period

- of 30 days only, during which both emergency diesel generators (EDG) must be operable with one EDG running continuously within 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> after the loss of one auxiliary transformer. This ensures a continuously available power supply for the engineered safeguards equipment.

8.2.2.3 6900 V Auxiliary System The 6900 V auxiliary system is designed solely for the 9000 hp reactor coolant pump motors.

. This system is arranged into two bus sections, each feeding two motors. During normal operation one bus is fed from each auxiliary transformer, although either transformer is capable of feeding both buses.' Automatic transfer will take place in either direction, by relay action, if a source bus or transformer failure occurs. Normal bus transfers initiated at the discretion of the operator for test or maintenance purposes will be " live bus" transfers, i.e., the incoming source feeder circuit breaker will be closed onto the running bus section and the outgoing source feeder circuit breaker will be tripped, which will result in transfers without power interruption. Manual paralleling of sources which are out of phase is prevented by the use of synchronism check relays.

Emergency transfers which result upon loss of normal unit sources will be rapid bus transfers, j

l.e., the outgoing source feeder circuit breaker will be tripped and its interlocks will permit the

. incoming source feeder circuit breaker to close. This will result in a transfer within six cycles.

8.2-5 UPDATE-15 4

4/00

Certificate of Service for Technical Specification Change Request No. 283 i

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1920-99-20295 UNITED STATES OF AMERICA NUCLEAR REGULATORY COMMISSION IN THE MATTER OF DOCKET NO. 50-289 GPU NUCLEAR INC.

LICENSE NO. DPR-50 I

. CERTIFICATE OF SERVICE This is to certify that a copy of Technical Specification Change Request No. 283 to Appendix A of the Operating License for Three Mile Island Nuclear Station Unit 1, has, on the date given below, been filed with executives of Londondeny Township, Dauphin County, Pennsylvania; Dauphin County, Pennsylvania; and the Pennsylvania Department of Environmental Protection, Bureau of Radiation Protection, by deposit in the United States mail, addressed as follows:

Dr. Edward Swartz, Chairman Ms. Sally S. Klein, Chairman Board Supervisors of Board of County Commissioners of Londonderry Township Dauphin County R. D. #1, Geyers Church Road P.O. Box 1295 Middletown, PA 17057 Harrisburg, PA 17120 Director, Bureau ofRadiation Protection l

PA Dept. of Environmental Protection Rachael Carson State Office Building P. O. Box 8469 Harrisburg, PA 17105-8469 Attn: Mr. Stan Maingi GPU NUCLEAR INC.

BY:

Am V c President and Diskethr, TMI i

M,2d 9

DATE:

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