ML20059J034
| ML20059J034 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs  |
| Issue date: | 10/29/1993 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20059J029 | List: |
| References | |
| NUDOCS 9311100325 | |
| Download: ML20059J034 (5) | |
Text
,
[y na I UNITED STATES v9 t
[ g.), 'O f j NUCLEAR REGULATORY COMMISSION f
W ASHINGTON, D.C. 20555-0001
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION I
RELATED TO AMENDMENT N0.183 TO FACILITY OPERATING LICENSE NO. DPR-53 AND AMENDMENT NO.160 TO FACILITY OPERATING LICENSE NO. DPR-69 BALTIMORE GAS AND ELECTRIC COMPANY CALVERT CLIFFS NUCLEAR POWER PLANT. UNIT NOS. 1 AND 2 DOCKET NOS. 50-317 AND 50-318
1.0 INTRODUCTION
By letter dated April 1, 1993, as supplemented on July 22 and September 8, 1993, the Baltimore Gas and Electric Company (the licensee) submitted a request for changes to the Calvert Cliffs Nuclear Power Plant, Unit Nos. I and 2, Technical Specifications (TS). The requested changes would revise TS 3
3/4.8.2, "Onsite Power Distribution Systems AC Power Distribution -
4 Operating," in relation to the actions to be taken if any of the 120 volt alternating current (VAC) vital busses are not operable. The existing TS 3.8.2.1 action statement requires that an inoperable vital bus be restored to operable status within 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-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 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 proposed action statement change would provide an additional option. An inoperable vital bus could be powered from its associated backup bus within the first 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> and the vital bus restored to operable status by reenergizing the l
vital bus from its associated inverter, which is the normal source of power, 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 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 />.
2.0 BACKGROUND
Each of the Calvert Cliffs units has four uninterruptible direct current /AC inverters. Each of the inverters normally powers an associated 120 VAC vital bus which, in turn, energizes an assc416ted reactor protection system (RPS) and engineered safety features actuat A system (ESFAS) sensor channel. Two of the four vital busses provide power for the corresponding ESFAS actuation channels.
When an inverter is inoperable, the associated vital bus is deenergized. The plant's current TSs, as noted above, allows up to 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> for the vital bus to be restored to operable status. During the time that the vital bus is deenergized, the associated sensor channel is in the tripped condition which increases the likelihood of a spurious RPS/ESFAS actuation.
In addition, an inoperable vital bus could render one of the two ESFAS actuation channels inoperable.
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Each unit has an inverter backup bus which can be used as a source of power i
for the vital busses and can be manually connected to one vital bus at a time.
Although the inverter backup bus is fed from a Class IE regulated transformer that, in turn, is backed by an emergency diesel generator, it is not capable of providing uninterruptible power to the vital busses during design basis events such as a loss of offsite power.
Thrrefore, it is not considered an l
emergency source of power. Currently when the inverter backup bus is used, l
j the vital bus it is powering is declared inoperable and an 8-hour action statement is entered.
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As previously noted, the licensee has requested that an inoperable vital bus l
which is powered from its associated backup bus within the first 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> have l
l the allowed outage time extended to 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> while it is being powered from the inverter backup bus. This change would provide more time to complete repairs and post-maintenance testing necessary to return an inoperable inverter to service.
r 3.0 EVALUATION The licensee has proposed the following specific changes to the Calvert Cliffs Unit I and Unit 2 TSs:
r Chance 1: Under Specification 3.8.2.1 add " energized from its associated inverter" after each 120 volt A.C. vital bus.
Chance 2: Delete the current entry under ACTION for Specification i
3.8.2.1 and substitute the following:
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ACTION:
a.
With less than the above complement of 4160 and 480-volt
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A.C. buses OPERABLE, restore the inoperable bus to 4
OPERABLE status within 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> or be in at least HOT t
STAleBY 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 />.
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With less than the above complement of 120-volt A.C. vital busses OPERABLE, either:
j 1.
Restore the de-energized vital bus to OPERABLE status by re-energizing the vital bus from its associated i
inverter 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 l
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 j
the following 30 hour3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />s:
l OR
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' l 2.
Power the vital bus from the associated backup bus within 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />.
Restore the vital bus to OPERABLE status by re-energizing the vital bus from its associated inverter 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 STAND 8Y 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 i
SHUTDOWN within the following 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />.
Although the current TSs do not explicitly address the use of the inverter backup busses, the licensee declar es the related vital bus inoperable when a backup bus is utilized as discussed in the background section of this evaluation. The nat effect of the proposed changes to the TSs is to recognize an inverter backup bus as an alternate source for a vital bus and to extend i
its use from the current 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> to 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. This is consistent with the l
current staff position and Standard TSs which consider the 24-hour limit i
acceptable based on engineering judgment. This judgment takes into consideration the time required to repair an inoperable inverter and the additional risk for the specific unit while powering a vital bus from an interruptible inverter backup bus should a loss of offsite or onsite AC power occur. This judgment is balanced against the risk associated with a forced i
shutdown and potential challenges to the safety systems during that shutdown.
Therefore, the staff has determined that the proposed changes are considered ~
acceptable.
4.0 STATE CONSULTATION
In accordance with the Commission's regulations, the Maryland State official was notified of the proposed issuance of the amendments. The State official had no comments.
5.0 ENVIRONMENTAL CONSIDERATION
The amendments change a requirement with respect to installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20. The NRC staff has determined that the amendments involve 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 the l
amendments involve no significant hazards consideration, and there has been no i
public comment o.: such finding (58 FR 28052 and 58 FR 50965). Accordingly, the amendments meet the eligibility criteria for categorical exclusion set forth in 10 CFR 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 the amendments.
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6.0 CONCLUSION
The Comission has 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, (2) such I
activities will be conducted in compliance with the Commission's regulations, f
and (3) the issuance of the amendments will not be inimical to the comon defense and security or to the health and safety of the public.
i Principal Contributor:
F. Burrows Date: October 29, 1993 i
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October 29, 1993 Docket Nos. 50-317 and 50-318 Mr. Robert E. Denton Vice President - Nuclear Energy Baltimore Gas and Electric Company Calvert Cliff.c Nuclear Power Plant 1650 Calvert Cliffs Parkway Lusby, Maryland 20657-4702
Dear Mr. Denton:
SUBJECT:
ISSUANCE OF AMENDMENTS FOR CALVERT CLIFFS NUCLEAR POWER PLANT, j
UNIT N0. 1 (TAC NO. M86138) AND UNIT NO. 2 (TAC N0. M86139)
The Commission has issued the enclosed Amendment No.183to Facility Operating License No. DPR-53 and Amendment No.160to Facility Operating License No.
DPR-69 for the Calvert Cliffs Nuclear Power Plant, Unit Nos. I and 2, respec-tively. The amendments consist of changes to the Technical Specifications (TS) in response to your application transmitted by letters dated April 1, 1993, as supplemented on July 22 and September 8,1993.
The amendments revise TS 3/4.8.2, "0nsite Power Distribution Systems AC Power Distribution - Operating," in relation to the actions to be taken if any of the 120 volt alternating current vital busses are not operable. The allowed outage time of 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> for an inoperable vital bus can be extended to 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> when the vital bus is being powered from the inverter backup bus.
A copy of the related Safety Evaluation is enclosed. A Notice of Issuance will be included in the Commission's next regular biweekly Federal Reaister notice.
Sincerely, Original signed by:
Daniel G. Mcdonald, Senior Project Manager Project Directorate I-I Division of Reactor Projects - I/II Office of Nuclear Reactor Regulation
Enclosures:
1.
Amendment No.183 to DPR-53 2.
Amendment No.160 to DPR-69 3.
Safety Evaluation cc w/ enclosures:
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0FFICIAL RECORD COPY FILENAME: CC86138.AMD