ML20072Q591
| ML20072Q591 | |
| Person / Time | |
|---|---|
| Site: | North Anna  |
| Issue date: | 12/19/1990 |
| From: | Stewart W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| RTR-REGGD-01.097, RTR-REGGD-1.097 90-672, NUDOCS 9012260207 | |
| Download: ML20072Q591 (2) | |
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O VlltOINIA F,Li:rTwie Axn l'own:: Cowliw sy H i t'll M O N il, VI H O I N T A
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December 19,1990 U. S. Nuclear Regulatory Commission Serial No.
90 672 Attn: Documer.t Control Desk NL&P/TAH R3 Waehington, D. C. 20555 Docket Nos. 50 338 50 339 License Nos. NPF 4 NPF 7 I
Gentlemen; VIRGINIA ELECTRIC AND POWER COMPANY llORTH ANNA POWER STATION UNITS 1 At{Q_2 R EGULATORY GUIDE 1.97 INSTRUMENTATION The NRC, by letter dated October 26, 1990, requested additional inforn'ation concerning our implementatior, of Criterion 9, interfaces, provided in Regulatcry Guide 1.97 (RG 1.97). The questions addressed certain aspects of the electrica,'nterface between various RG 1.97 instrumentation and the plant's process computer.
After additional engineering evaluation, we have determined that the most prudent course of action is to ensure that the electricalisolation of the instrumentation is not in question. Therefore, rather than provide the additionalinformation requested, Virginia Electric aild Power Company will implement the appropriate modifications to ensure 4
that the electrical ! solation of the devices in question clearly meet Criterion 9 of RG 1.97.
We havo identified two alternate means of accomplishing the isolation. The first option is to install additional qualified isolators in the instrument loops. The output of these isolators will provide the signals for the RG 1.97 indication devices. The plant process computer would remain connected to the existing isolation devices.
The second option is to install digital to analog converters in the appup ials Emergency Response Facility computer outputs. The output of these isolato"s will provide the input signals for the plant process computer and the plant process computer inputs would thereforo be reraoved from the instrument process racks.
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9012260207 901219 J
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D Docket fJos. 50 338 !t 339 Sorial No 00 679 We wili parform an engineering study to determine the most appropriato means of accomplishing the upgrado.
This study is scheduled to be completed by September 30,1992. Wo will provido to you the resultn of that study and the schedule for implomontation by October 31,1992.
If you have questions or require additionalinformation, please contact us.
Very truly yours,
\\\\ kh ~y, Nu.S%hh W. L. Stowart Senior Vice President Nuclear cc: U. S. Nuclear Regulatory Commission 101 Marietta Street, N.W.
Suito 2900 Atlanta, Georgia 30323 Mr. M. S. Lessor NRC Senior Resident inspcefor North Anna Power Station l
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