ML20033H110
| ML20033H110 | |
| Person / Time | |
|---|---|
| Issue date: | 04/02/1990 |
| From: | Rosa F Office of Nuclear Reactor Regulation |
| To: | Pareto V DEVONRUE, LTD. |
| References | |
| NUDOCS 9004180184 | |
| Download: ML20033H110 (3) | |
Text
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3 APR 2 1990
- r. Vittorf o Pareto DEV0NRUE 180 Lincoln Street Boston, Massachusetts 02111
Dear Mr. Pareto:
Your letter of March 27, 1990, documented your understanding of our telephone conversation of March 26, 1990, regarding questions concerning a two unit nuclear plant site with 2/3 EDG configuration (i.e., EAC Category "D").
The staff has reviewed your letter and marked it to reflect our more detailed understanding of the conversation regarding this matter.
The marked copy of your letter is attached.
In addition it is highly desirable that the alternate ac (AAC) power source be diverse from the plant emergency ac sources. (EDGs). As you heard in the March 20, 1990, meeting between NRC and Connonwealth Edison, the NRC staff feels y
strongly that the AAC power source should be diverse in order to gain relaxa-A tion in 2/3 EDG configuration reliability target.
Also in this meeting, the NRC staff agreed that this AAC power source could be non-class IE.
I hope this will clarify the understanding of NRC staff position on this subject.
Sincerely,
,0thinctOkntdby Faust Rosa, Chief Electrical Systems Branch Division of Systems Technology
Attachment:
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i March 27,1990 s
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Mr. Faust Rosa, Chief f
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Office of Nuclear Reactor Regulation
.. 3"E' Electrical Systems Branch U.S. Nuclear Regulatory Commission l.
Washington, D.C. 20555
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Dear Mr. Rosa:
I would like to take this opportunity to confirm our telephone cony rsation last Mon ny, March 26,
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1990. As you m3y recall,I asked some questions concerning the jypothetical case of a two unit power plant with a 2/3 EDG configuration (i.e., EAC category 'D '). Per NUMARC 87 00, this j
requires them to maintain a 97.5% target reliability with a four hourloping durationY,1 understand that if their EAC classification was either A, B, or C, they would have the option of selecting a lower target reliability (i.e.,95%) in exchange for a longer coping duration (i.e., eight hours).
l Ilowever, due to the relatively smaller diesel generator redundancy associated with 'D' plants, this flexibility is not available.
On the other hand, NUMARC 87 00 does not require power plants in this condition to purchase a diesel generator as an Alternate AC power source; this alternative is not anticipated in Table 3 8.
Thus, the question arises: Is it possible to configure an Alternate AC power source that would
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allow utilities in these specific circumstances to select a lower target reliability, i.e. 95%, in l -
exchange for an 8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> coping duration?
t My understanding of your reply is that this would indeed be possible under the following circumstances:
1.
The AAC source is a Class lE power source that is sized to powerfil>Wfe shutd6n4thA at both units.
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2 2.
The AAC source is connectable to all safeguard busses at the sitC.
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D NRC 900341/VEP, dated Msch 27,1990 I appreciate the time you took to discuss this issue. Please let me know ifI misunderstood any of these requirements.
Sincerely, I
(V W f 'ittorio Paret,
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