ML20207B745
| ML20207B745 | |
| Person / Time | |
|---|---|
| Site: | Byron  |
| Issue date: | 12/12/1986 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20207B741 | List: |
| References | |
| NUDOCS 8612290061 | |
| Download: ML20207B745 (4) | |
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)g UNITED STATFS pe NUCLEAR REGULATORY COMMISSION o
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WASHINGTON, D. C. 20555
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1 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMEf'DMENT NO. 5 TO FACILITY OPERATING LICENSE NOS NPF-37 and NPF-60 COMMONWEALTH EDISON COMPANY BYRON STATION, UNITS 1 AND__2 DOCKET NOS. STN 50-454 AND STN 50-455
1.0 INTRODUCTION
By applications dated August 13, 1986 and August 27, 1986, Comonwealth Edison (licensee) requested amendments to the Technical Specifications for Byron Station,
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Units 1 and 2.
The August 13, 1986 application requested that "86% of total i
volume" be replaced by "50%" for the water level in the ultimate heat sink
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cooling tower basin. The August 27, 1986 application requested an amendment that would permit a crosstie between Units 1 and 2 Class IE 125-Vdc buses under limiting conditions for operation.
2.0 DISCUSSION AND EVALUATION 2.1 Cooling, Tower Basin Level The licensee intends to increase the physical water level in the cooling tower basin to provide more margin to the low level at which the essential service water diesel driven pumps receive an auto start signal. The increased level is above the range of the existing instrument. The licensee intends to replace this instrument with an instrument with greater range; 86% on the old instrument corresponds exactly with 50% on the new instrument. Thus, the minimum water level in the basin is not being changed by this amendment. Therefore, we find this change acceptable.
2.2 DC Crosstie Unit 1 and Unit 2 each have two Class 1E 125-Vdc buses which meet the capability, independence, redundancy and testability requirements of'GDC 17 and 18 of 10 CFR 50, Appendix A.
The present Technical Specifications are 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:
8612290061 061212 DR ADOCK 0500 4
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a.
With one of the required battery banks and/or chargers inoperable, restore the inoperable battery bank and/or battery bus to OPERABLE 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 /> 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 />, 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 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 />.
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:
(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 requirement would also be added:
4.8.2.1.3 At least crce per 12 hcurs, when in specification 3.8.2.1.c.2), verify the total crosstie loading will not exceed 63 amps.
The licensee summarizes the effect of the Technical Specification changes as follows:
1.
With both units operating and one battery charger fails, the D.C. crosstie i
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.
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The licensee explains that, 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 buses. However, the D.C. crosstie will be limited to 63 amps 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 so 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 consecuences of accidents previously evaluated are not changed by the proposed Technical Specification changes.
The staff made further inquiries by telephone as to the adequacy of one battery charger to supply the normal loads of both D.C. buses simultaneously. The licensee stated that the battery charger has a nominal capability of 400 amperes and a 10 percent overload capability whereas the normal load on each D.C. bus would be less than 100 amperes. Thus, if the battery charger is operable, there would be no net drain on the battery during non-emergency conditions.
Further, the licensee advised that a battery charger failure would be inmediately detectable through a low voltace relay on the D.C. bus and various alarm relays on the charger. Under this condition, the Technical Specifications would require the battery charger to be restored to OPERABLE status within two hours or actions taken to achieve 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 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 licensee also notes that a fault on one of the D.C. buses, during the time that the two buses are crosstied, will not cascade to the other bus because a breaker exists on either side of the crosstie and these breakers are coordinated with the D.C. bus main breakers to assure that the crosstie will isolate before i
the battery would be isolated.
The staff notes that the existing Technical Specifications require extensive test-ing on a 7 day cycle to assure that each D.C. bus, battery bank and associated charger is operable. Also, power failure and undervoltage alarms would readily alert the operators to any absolute failure of a D.C. bus or A.C. power supply to the battery charger. Thus, the possibility of an undetected inoperability of l
a D.C. bus is remote. Such inoperability could be significant if the bus was thought to be operable and was then crosstied as the power source to a D.C.
bus that was known to be inoperable.
The staff also notes that loss of all offsite power will not directly affect the D.C. buses or the battery charges to the D.C. batteries because the diesel gen-crators would be available to supply D.C. power to the battery charges.
. Our 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 requirerents of GDC 17 and 18 of 10 CFR 50, Appendix A.
Similarly, our evaluation has disclosed no conditions that would significantly impact the health and safety of the public. We there-fore find the licensee's proposed Technical Specification changes to be acceptable.
ENVIRONMENTAL CONSIDERATION These amendments involves a change in the installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20.
The staff has determined that the 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 Commission has previously issued a proposed finding that this amendment involves no significant hazards consideration and there has been no public comment 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) no environmental impact statement or environmental assessment need be prepared in connection with the issuance of this amendment.
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 Commission's regulations and the issuance of this amendment will not be inimical to the common defense and security or to the health and safety of the public.
Dated: December 12, 1986 PRINCIPAL CONTRIBUTOPS:
A. Toalston L. Olshan i
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