ML20149D378

Safety Evaluation Supporting Amends 5 to Licenses NPF-72 & NPF-75

ML20149D378
Person / Time
Site:	Braidwood
Issue date:	01/27/1988
From:	Office of Nuclear Reactor Regulation
To:
Shared Package
ML20149D359	List: ML20149D356 ML20149D378
References
NUDOCS 8802090473
Download: ML20149D378 (4)

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UNITED STATES

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r SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION

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7, RELATED TO AMENDMENT NO. 5 TO FACILITY OPERATING LICENSE N0. NPF-72 1

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AND AMENDMENT NO. 5 TO FACILITY OPERATING LICENSE NO. NPF-75 I

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BRAIDWOOD STATION, UNITS 1 AND 2

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DOCKET NOS. STN 50-456 AND STN 50-457 3 f(

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1.0 INTRODUCTION

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By letter dated December 3,1987, Commonwealth Edison Company (the licensee) c ;.2 4 !., C.

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6 requested an amendment to the Technical Specifications for the Braidwood W

Station, Units 1 and 2.

The proposed changes would modify the D.C. system i h i')::V., f 1-

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Technical Specifications to permit a crosstie between the Unit I and Unit 2 Class 1E 125-Vdc buses under limiting conditions for operation.

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'; p 2.0 EVALUATION

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Braidwood Unit 1 and Unit 2 each have two Class 1E 125-Vdc buses which meet

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the capability, independence, redundancy, and testability requirements of GDC

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7 17 and 18 of 10 CFR 50, Appendix A.

The present Technical Specifications are

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applicable to single unit (Unit 1) operation.

If one of the 125-Vdc buses is inoperable (LCO 3.8.2.1), the following Action statements apply:

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E-With one of the required battery banks and/or charges inoperable.

Y a.

7 restore the inoperable battery bank and/or battery bus to OPERABLE k

status within 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> or be in at least HOT STANDBY within the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and in COLD SHUTDOWN within the following 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />.

b.

With the normal full capacity charger inoperable:

1) restore the affected battery and/or battery bus to operable status with the opposite unit's full capacity charger within 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> er be in at I

least HOT STANDBY within the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and in COLD SHUTDOWN within the following 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />, and 2) restore the normal full capacity charger to operable status within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> or be in at least HOT o

s STANDBY within the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and in COLD SHUfDOWN within the following 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />.

For two unit operation, the licensee proposes to add the following Action statements:

c.

Use of the D.C. crosstie breakers between opposite unit D.C. buses (bus 111 and 211, or bus 112 and 212) shall be limited to the following:

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- (1) With a normal full capacity charger inoperable, comply with action statement (b) above.

(2) With a D.C. bus inoperable or not energized on a shutdown unit (Mode 5 or 6), the affected D.C. bus may be energized from the operating unit (Mode 1,2,3 or 4) opposite D.C. bus via the crosstie breakers after limiting the D.C. loads on the affected D.C. bus; operation may then continue for up to 7 days or open the crosstie breakers.

The following surveillance requirecent would also be added:

4.8.2.1.3 At least once per 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />, when in specification 3.8.2.1.c.(2), verify the total crosstie loading will not exceed 63 amps.

The licensee sumarizes the effect of the proposed Technical Specification changes as follows:

(1) With both units operating and one battery charger fails, the D.C.

crosstie may be used for up to 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> to maintain the D.C. bus in an operable status while the battery charger is being repaired.

(2) With one unit operating and the other unit shutdown with a battery and its associated battery charger out of service, the D.C. crosstie may be used for up to 7 days to maintain the D.C. bus in an operable status.

For the first situation, each battery will be connected to its bus and one battery charger will serve both buses.

For this situation, use of the D.C.

crosstie will not exceed the design parameters of the D.C. system.

For the second situation, the battery charger and battery of the operable D.C.

bus will supply both cuses. However, the D.C. crosstie will be limited to 63 amps (per proposed surveillance requirenent 4.8.2.1.3) so as not to exceed the capacity of the operable battery.

The licensee states that the D.C. bus loading, when using the crosstie, will be restricted 50 that the capacity of the operating unit's battery will not be exceeded in the event of a single failure and simultaneous accident and loss of offsite power conditions. These were the conditions assumed for a D.C. bus in previously evaluated accidents, thus the probability or consequences of accidents previously evaluated are not changed by the proposed Technical Specification changes.

The staff has made further inquiries by telephone as to the adequacy of one battery charger to supply the nonnal loads of both D.C. buses simultaneously.

The licensee stated that the charger has a nominal capability of 400 amperes

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', and a 10 percent overload capability whereas the nomal load on each D.C. bus would be less than 130 amperes. Thus, if the battery charger is operable, there would be no net drain on the battery during non-emergency conditions.

Further, the Byron /Braidwooo FSAR (Section 8.3.2) indicates that a battery charger failure would be imediately detectable through a low voltage relay on the D.C. bus and various alarm relays on the charger.

Under this situation, the Technical Specifications would require the battery charger to be restored to OPERABLE status within two hours or actions must be taken to achieve HOT STANDBY within the next six hours and COLD SHUTDOWN within the following 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />.

The FSAR also indicates that a breaker exists on either side of the crosstie which would isolate any potential short circuit from either unit. These breakers are coordinated with the D.C. bus main breaker to assure the crosstie will isolete from the affected D.C. bus before the battery would be isolated.

This wou;: prevent a cascade from one bus to the other during the time the two buses are crosstied.

The staff notes that the existing Technical Specifications require extensive testing cn a 7 day cycle to assure that each D.C. bus, battery bank, and associated charger is operable. Additionally, power failure and undervoltage alarms would alert the operators of any absolute failure of a D.C. bus or an A.C. power supply to the battery charger.

Therefore, the possibility of an undetected inoperability of a D.C. bus is remote.

The staff also notes that loss of all offsite power will not directly affect the D.C. bus or the battery chargers to the D.C. batteries because the ciesel generators would be available to supply D.C. power to the battery chargers.

The evaluation has disclosed no conditions resulting from the crosstie operation under the Technical Specification changes that would significantly impact the capability, independence, redundancy, and testability requirements of GDC 17 and GDC 18 of 10 CFR 50, Appendix A.

As such, the margin of safety is not reduced.

Similarly, the evaluation has disclosed no conditions that would significantly impact the health and safety of the public.

3.0 ENVIRONMENTAL CONSIDERATION

This amendment i'1volves a change in the installation or use of the facilities components located within the restricted areas as defined in 10 CFR 20. The staff has deternined that this amendment involves no significant increase in the amounts, and no significant change in the types, of any effluents that may be released offsite and that there is no significant increase in individual or cumulative occupational radiation exposure. The Comission has previously issued a proposed finding that this amendment involves no significant hazards consideration and there has been no public coment on such finding.

Accordingly, this amendment meets the eligibility criteria for categorical exclusion set forth in 10 CFR Sec. 51.22(c)(9).

Pursuant to 10 CFR 51.22(b) i no environmental impact statement or environmental assessment need be prepared in connection with the issuance of this amendment.

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4.0 CONCLUSION

We have concluded, based on the considerations discussed above, that:

(1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, and (2) such activities will be conducted in compliance with the Comission's regulations and the issuance of this amendment will not be inimical to the comon defense and security or to the health and safety of the public.

Principal Contributor:

S. Sands Dated:

January 27, 1988

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