ML20034D204
| ML20034D204 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 09/25/1991 |
| From: | Calvo J Office of Nuclear Reactor Regulation |
| To: | Hehl C NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| Shared Package | |
| ML20034D205 | List: |
| References | |
| TAC-M80428, NUDOCS 9110030149 | |
| Download: ML20034D204 (1) | |
Text
t v-l 4 Septe'ter 25. '991 f
Dccket t'o.
EC-336 Distribution:
Docket File FEttCRANDU!' FOR:
Charles W. Fehl, Director PD I-4 Memo Divisicn of Reactor Projects JCalvo Region I Silorris GSVissing FFCth Jose A. Calvo, Assistant Director fKTrehan
- cr Region I Reactors g
Eivision of Reactor Projects - 1/11 Cffice of Nuclear Reactor Regulation 4M SUSJECT:
MILLSTCNE 2 - TIA - CCMPLIANCE WITH GDC-17 TAC f480428 Ey memorandur: dated ray 20, 1991, Pegion I requested assistance to determine whether the offsite power system at Millstone 7 meets GDC 17 and whether the cccrdinatico of the protective devices for Class 1E 4 kV breakers is adequate.
The staff has evaluated the licensee's response of May 2, 1991, and has concluded that since the requirements of GDC 17 do not assume a single failure coincident with an accident ard loss of onsite power supplies, the design l
con < plies with the requirements of GDC 17 and is, therefore, acceptable.
In regard to the need for coordination of protective devices, IEEE 308 1974 Paragraph 5.2.1(6) states " Protective devices shall be provided to limit the degradation of tFe Class IE power systems." Good engineering practice I
inplements this criterion by a design which isolates a fault to a localized area without affecting other sources or loads unnecessarily.
Such is not the case in this instance. The staff finds that the design for the coordi.
l nation of the electrical protective devices to be inadequate in that the fault will result in unnecessary isolation of the unfaulted Class 1E bus from tre preferred offsite power supply. Therefore, it will be prudent for the licensee to employ a bus differential scheme or fast acting overcurrent relays so as to isolate cnly the faulted bus.
The enclosure provides our Safety Evaluation.
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/s/
Jose A. Calvo, Assistant Director for Region I Reactors Divisico of Reactor Projects - 1/11 Office of Nuclear Reactor Regulation cc:
F. Fosa J. Wiggins E.
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