PURPOSE AND SCOPE

Existing design basis calculations for the DC electrical distribution system have been found, in some cases, to be unavailable or inadequate. The DC Voltage Profile Study has been undertaken to establish current, readily accessible DC electrical distribution system design basis calculations. Calculations to be provided include those to establish battery loading, DC distribution system voltage, battery charger sizing, DC system fault current and coordination, and DC system cable amperage capacity. The 1991 electrical distribution system functional inspection reaffirmed the need to upgrade or develop certain calculations which are a part of this project.

Once complete, this project will document the capability or the present configuration and loading, and provide a basis to support future modifications and 10 CFR 50.59 safety evaluations. For a proposed change to the DC distribution system, documentation will be easily accessible to demonstrate whether a proposed change to the DC distribution system will cause overloading of components. The ability to quickly and accurately respond to design basis issues which may arise during an audit will be greatly enhanced.

II. EVALUATION

Schedule Index: 10 - Upgrade or development of design basis calculations is not expected to have a substantial effect on DC distribution system design or operation. However, the project includes additional calculations to analyze battery loading profiles. The results of these calculations could lead to procedural or hardware changes that would increase the plant's ability to withstand station blackout. A nuclear scaling factor of 0.2 is assigned because of this potential low impact on core damage frequency (0.2 x 32). This project should have no appreciable effect on personnel safety, unit availability, unit capacity, or ALARA, but should reduce research time on modifications and engineering evaluations and analyses (plant enhancement, 0.5 x 8).

Economic Aspects: Once this project is completed, no continued costs are anticipated. Ongoing resource savings are expected in the future, due to reduction of time spent on modification and engineering evaluation preparation.

Related Standards: The applicable Work Management Policy is design documentation.

Other Considerations: The calculations being developed are required by the NRC and presently either do not exist or are not in a usable form for the Brunswick units.

III. CONCLUSION

To meet established commitments, the DC Voltage Profile study will proceed as scheduled.