ML19289F205
| ML19289F205 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs  |
| Issue date: | 04/30/1979 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML19289F198 | List: |
| References | |
| NUDOCS 7906040405 | |
| Download: ML19289F205 (6) | |
Text
ENCLOSURE SAFETY EVALUATION OF THE PROPOSED INTERIM MODIFICATION OF THE PLANT 125V DC SYSTEM 0F CALVERT CLIFFS, UNITS 1 AND 2 INTRODUCTION The proposed design modification of the 125v de system of Calvert Cliffs, Units 1 and 2, was submitted by the licensee in order that the system, after implementation of the modification, will be able to undergo its battery capacity discharge testing without degradation of the de system.
Calvert Cliffs, Units 1 and 2, have four safety-related 125 v dc buses (buses 11,12, 21, ar.d 22) that are shared by both the units.
Each bus has its associated 1350 ampere-hour battery and two 400 ampere battery chargers.
The proposed design modification involves the procurement and installation of a fully qualified 1500 ampere-hour spare battery capable of replacing any of the four safety-related batteries during plant operation.
The present Technical Specifications allow battery capacity discharge testing only during unit shutdown and the proposed changes to the Technical Specifications would allow these tests to be performed during plant operation.
The proposed design modification was presented by the licensee at ti meeting on December 16, 1978.
In February 1979, BG&E informed the staff that the final installation of the proposed new spare battery will not be completed in time to allow the licensee to conduct the required battery discharge tests.
The licensee proposed an interim temporary installation of the new spare battery. By letter dated March 12,1979, the licensee submitted the details of the proposed interim temporary installation of the spare battery and the proposed changes to the Technical Specification.
The proposed modification to the Calvert Cliff, Units 1 and 2,125v de system consists of a spare, fully qualified,1500 amper-hour battery, a 1200 ampere tra nsfer switch, and 1200 ampere disconnect switches (See Figure 1). The associated charger and its disconnect switches are non-safety related and are only used to keep the spare battery continuously float charged until the battery is required to backup a safety-related 125v dc battery.
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- The new system will be installed such that no permanent connections will be made to the existing 125v dc buses thus preventing any cross-connections between different buses. At the time of the battery dis-charge tests the cables will be connected between the 1200 ampere disconnect switch and the bus of the battery which is to be tested.
Due to the legnth of the time necessary for the construction of the battery room in which the. spare battery will be finally located, the licensee has stated that the battery room will not be completed in time for the capacity discharge tests of the existing 125v dc battery.
Therefore, the licensee is proposing to locate the new battery temporarily on the turbine deck directly outside the future permanent location (see Figure 2). The battery will be seated on 1/2 inch ~ thick plywood and 1/4 inch thick rubber mat directly on the turbine deck, and will be enclosed by a temporary barrier.
The temporary cables from the battery to its 1200 ampere disconnect switch will be routed above a drop ceiling until they drop into the permanent conduit.
All switching equipment will be located in the cable spreading room where the existing dc switchgear is located.
The licensee has stated that the spare battery is safety-related and fully qualified and tested in the same manner as the original batteries.
DISCUSSION The proposed modification of the 125v dc system and the proposed interim temporary installation of a spare battery will allow battery capacity discharge testing of the safety related batteries, one at a time, without any degradation of the 125v dc system.
The existing 125v dc batteries at Calvert Cliffs, Units 1 and 2, are each rated 1350 ampere-hour. The new spare battery is rated at 1500 ampere-hour and hence has sufficient capacity to replace the existing batteries, one at a time, during discharge tests. The charger associated with the new spare battery will keep the spare battery fully charged at all times.
The spare battery, and associated transfer siwtch and disconnect switches are fully qualified, safety-related equipment. The spare battery will be temporarily located on the turbine deck for the duration of the first series of battery capacity discharge tests.
All other equipment (the transfer switch, disconnect switches, battery charger and associated switches) will be located in its pemanent 2235 320 location in the cable spreading room where the existing de switchgear is located.
The proposed new system will be installed such that no permanent connections will be made to the existing 125v de buses.
This will ensure that no cross-connections exist between different buses. Only at the time of the tests will the cables from the dis-connect suitch to the 125v dc bus be connected.
The arrangement of the disconnect switch, transfer swi tch and the connections of the cable, will assure that the modified system, discharge tests, meet the plant single failure criterion.
The proposed revision to the Technical Specification requires that the spare battery be under constant surveillance during the tests.
The duration of the battery capacity discharge test would require 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> for each battery or approximately four days for all four ba tteri es. The temporary location of the spare battery and the temporary cables will only be required for this period. Once the tests are complete, all temporary cables will be removed and the battery will be relocated in its permanent location.
The licensee will provide details of the permanent location of the spare battery, the permanent cable details and other relevant details prior to permanent installation C0_NCLUSION Based on our review, we find that:
1.
The proposed design modification to the 125v de system of Calvert Cliffs, Units 1 and 2, will enable battery capacity discharge tests to be performed on the existing batteries during plant operation without any degradation of the 125v dc system.
2.
The proposed modification and the proposed temporary installa-tion does not violate the plant single failure criterion.
3.
The spare battery has sufficient capacity to perform the function of the battery it replaces during the tests.
4.
The spare battery and associated equipment required to implement the proposed modification will be a fully-qualified, safety-related backup battery system.
5.
Except for the location of the spare battery, the interim (tem-porary) installation of the spare battery system meets the, installation requirement of the safety-related 125v dc system.
The temporary connections will only be mquired for a period of approximately four days during the discharge tests of the plant four safety related 125v dc batteries.
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6.
The proposed change to the Technical Specification will assure that the spare battery will be under constant surveillance during the tests.
Accordingly, we conclude that the proposed interim (temporary) installa-tion of a spare battery, the associated proposed design modification to Calvert Cliffs, Units 1 and 2,125v dc system, and the proposed change to the Technical Specifications are acceptable.
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