ML17037B666

Letter Providing Additional Information Describing a Design Modification to Assure Operation of Equipment and Associated Controls During a Degraded Condition

ML17037B666
Person / Time
Site:	Nine Mile Point
Issue date:	11/30/1976
From:	Rhode G Niagara Mohawk Power Corp
To:	Lear G Office of Nuclear Reactor Regulation
References
Download: ML17037B666 (6)

Text

U.S. NUCLEAR REGULATORY C SSION NRC FoRM 195 I2-7G)

NRC DISTRIBuTION FoR PART 50 DOCKET IVIATERIAL DOCKET NUMBER 50-220 FILE NUMBER TO:

Hr. Gehrge Lear FROM:

Niagara Mohawk Power Corp.

Syracuse, New York Hr. Gerald K. Rhode DATE OF DOCUMENT 11/30/76 DATE RECEIVED 12/8/76, gLETTE R J5OR IG INAL OCOP Y DESCRIPTION 0 NOTOR IZE D JKJNCLASSIF I E D PROP INPUT FORM ENCLOSURE NUMBER OF COPIES RECEIVED One signed'tr.

w/attached....re their 10/18/76 ltr.

and our 8/11/76 ltr....concerning degraded grid voltage condition.

(2-P)

PQ NOT ZZZOVZ PLANT NAME:

Ninr Hile Point ill SAFETY ASSIGNED AD:

R C

MANA E LIC ASST Lear Nowicki Parrish FOR ACTION/INFORMATION PROJECT MANAGER~

LIC ASST

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November 30, 1976 Ik@gJ~

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Director of Nuclear Reactor Regulation Attn:

Hr. George Lear, Chief U ~ S. Nuclear Regulatory Commission Washington, D. C.

20555 Re:

Nine Mile Point Unit 1 Docket No. 50-220 DPR-63

Dear Hr. Lear:

Hy October 18, 1976 letter provided an analysis of Nine Hile Point Unit 1 during a degraded grid voltage condition.

The attachment t'o this letter provides additional information describing a design modification t'o assure operation of equip-ment and associated controls during a degraded condition.

This information completes our response to your August 11, 1976 letter.

Very truly yours, NIAGARA MOHAWK POWER CORPORATION E

LD H DE Vzce Pre ident E gineering

/sz Att'achment

4~

I All

guestion No.

4 Provide a descri ption of any proposed actions or modifications to your facility based on the results of the analyses performed in response to items 1-3 above.

R~es nse Two,additional undervoltage relays will be installed on each 4160 volt powerboard (powerboards 102 and 103).

The new relays will have inverse time and fast reset time characteristics.

The set point of each relay will be 3600 volts.

This is the minimum operating voltage level for the 4000 volt motors.

The logic scheme for the new undervoltage relays will be the same as the existing undervoltage relays described in Response 2 of the October 18, 1976 letter.

The existing undervoltage relays with the present setting of 3257 volts will be retained to provide backup protection for the new undervo'ltage relays.

The modification will be installed during the Spring, 1977 refueling outage.