ML20076G601
| ML20076G601 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 10/14/1994 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20076G600 | List: |
| References | |
| NUDOCS 9410200093 | |
| Download: ML20076G601 (3) | |
Text
a secoqk UNITED STATES y-NUCLEAR REGULATORY COMMISSION f
WASHINGTON, D.C. 20565-0001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT N0.180 TO FACILITY OPERATING LICENSE NO. DPR-65 NORTHEAST NUCLEAR ENERGY COMPANY THE CONNECTICUT LIGHT AND POWER COMPANY THE WESTERN MASSACHUSETTS ELECTRIC COMPANY MILLSTONE NUCLEAR POWER STATION. UNIT NO. 2 DOCKET NO. 50-336
1.0 INTRODUCTION
By letter dated May 6, 1994, as supplemented August 16, 1994, the Northeast Nuclear Energy Company (the licensee) submitted a request for changes to the Millstone Nuclear Power Station, Unit No. 2 Technical Specifications (TS).
The requested changes would change TS 3.8.2.3 and 3.8.2.4, " Electrical Power Systems - DC Distribution," and Surveillance Requirements (SR) of TS 4.8.2.3.2.c.2.
The August 16, 1994, letter provided clarifying information that did not change the initial proposed no significant hazards consideration det:ermination.
These proposed TS changes were submitted by the licensee to take advantage of their reevaluation of the design of the 125 VDC system at Millstone Unit 2.
The NRC electrical distribution system functional inspection (EDSFI) team reviewed the licensee's design and concluded it was adequate.
2.0 BACKGROUND
The 125 VDC system has two battery systems which are separated into trains A and B.
Each train has one 125 VDC switchgear assembly, two 125 VDC battery chargers operating in a parallel redundant mode, and four DC distribution panels. A swing charger is available to support either train if required.
The licensee's original plant design determined that a DC charging capacity of 800 amperes was required. The requirement was based on an estimated continuous load of 346 amperes and a required battery charging current of 416 amperes for a total of 762 amperes. The charging current would have recharged the discharged battery in 5.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br />. This evaluation resulted in a design with two 400 amp chargers per train.
9410200093 941014 PDR ADOCK 05000336 P
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.., The licensee reevaluated the DC system utilizing actual loads (not nameplate data), and assuming a worst case by cross tying DC buses and supplying them with one battery and one battery charger.
The calculations determined that the continuous load for each DC bus was 154 amperes with 246 amperes of charging capacity to recharge a battery.
The calculation demonstrated that one charger with a charging capacity of 400 amperes is sufficient to provide the continuous DC loads, and is capable of recharging a fully discharged station battery in 10.37 hours4.282407e-4 days <br />0.0103 hours <br />6.117725e-5 weeks <br />1.40785e-5 months <br />. This recharging time is within the 12-hour recharging time discussed in Section 8.3.2 of the Millstone Unit 2 FSAR. The NRC EDSFI team review of the licensee's calculation of the 125 VDC system at Millstone Unit 2 concluded that the licensee used conservative assumptions in their voltage drop calculation. The team concluded that there were no problems with DC load voltages, even at the minimum battery voltage of 105 VDC. The team concluded that a single charger with a charging capacity of 400 i
amperes has sufficient capacity to supply the connected bus loads and recharge a fully discharged battery within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />.
3.0 EVALUATION The staff has evaluated the proposed revisions submitted by the licensee as follows:
Revision to Existina TS Section 3.8.2.3 Modify the LC0 for TS 3.8.2.3, TRAIN "A" and TRAIN "B," by replacing the phrase "and a full capacity charger" with the phrase "and at least 400 ampere charging capacity."
Revision to Existina TS Section 3.8.2.4 Modify the LC0 for TS 3.8.2.4 by replacing the phrase "and charger" with the phrase "and at least 400 ampere charging capacity."
Revision to Existina Surveillance Reouirement (SR) Section 4.8.2.3.2.c.3 Modify SR 4.8.2.3.2.c.3 by replacing the phrase "at least 800 amperes at a minimum of 130 volts for at least 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />" with the phrase "at least 400 amperes at a minimum of 130 volts for at least 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />."
The licensee's original calculation to size the Class lE battery chargers resulted in a requirement for two 400 ampere chargers operating in a parallel redundant mode.
The new calculations show that a single charger with a charging capacity of 400 amperes is sufficient to provide the connected DC bus loads and is capable of recharging a fully discharged station battery in less than 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> as stated in the Millstone Unit 2 FSAR.
The staff has evaluated the licensee's proposed TS revisions based on the licensee's reevaluation of the 125 VDC system and the EDSFI team inspection report and finds these changes acceptable.
Based on the above evaluation, the staff has determined that the proposed changes to the Technical Specifications are acceptable.
4.0 STATE CONSULTATION
In accordance with the Commission's regulations, the Connecticut State official was notified of the proposed issuance of the amendment. The State official had no comments.
5.0 ENVIRONMENTAL CONSIDERATION
The amendment changes a requirement with respect to installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20 and changes surveillance requirements. The NRC 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 the amendment involves no significant hazards consideration, and there has been no public comment on such finding (59 FR 32232). Accordingly, the amendment meets '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 amendment.
5.0 CONCLUSION
The Commission has concluded, based on the considerations discussed above, that:
(1) there is reasonable assurance that the health arid safety of the public will not be endangered by operation in the proposed manner, (2) such activities will be conducted in compliance with the Commission's regulations, and (3) the issuance of the amendment will not be inimical to the common defense and security or to the health and safety of the public.
Principal Contributor:
C. Thomas Date:
October 14, 1994
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