ML20137W921

Requests Addl Comments Re Offsite Power Sys Designs for Older Operating Plants as Result of Lessons Learned from Maine Yankee Independent Safety Assessment.Response Requested within 30 Days of Receipt of Ltr

ML20137W921
Person / Time
Site:	Vermont Yankee, Maine Yankee
Issue date:	04/17/1997
From:	Rooney V NRC (Affiliation Not Assigned)
To:	Reid D VERMONT YANKEE NUCLEAR POWER CORP.
References
TAC-M97960, NUDOCS 9704210094
Download: ML20137W921 (4)

Text

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A fh47f 9 1" ' UNITED STATES j

' - p!u NUCLEAR REGULATORY COMMISSION j' s WASHINGTON, D.C. EsseH001

. April'17, 1997 6 %e...,

i c' Mr. Donald A.. Reid '

.Vice Presiderot, Operations i: '

Vermont Yankee Nuclear Power Corporation Ferry Road ,

i Brattleboro, VT '05301:

1

SUBJECT:

ADDITIONAL COMENTS REGARDING OFFSITE POWER SYSTEM DESIGN - VERMONT YANKEE NUCLEAR POWER' STATION-(TAC NO. M97960) l e Dear'Mr. Reid.

l By letter, dated February 25, 1997, the.NRC staff requested information from 1 Lyou to assist in our review of,offsite power system designs for older  !

operating plants as a result of lessons learned from the Maine Yankee . )

-Independent Safety Assessment. You resp'onded to that request'by letter dated i i.' March 26, 1997. -On April 10, 1997, we had a telephone discussion with you in '

I Lwhich we clarified our understanding of your response and sought to more

clearly communicate our initial concern regarding your letter.

Our understanding of tif issue is as follows:

['

1.- Vermont Yankee was licensed with one immediately available offsite power circuit and two delayed offsite power circuits. The immediately 4

available offsite circuit is the 115-kV bus which can be powered from I

.either the Keene ifne or the 345-kV switchyard through the 345/115-kV 1 F .autotransformer. The delayed offsite power circuits are (1) the 345-kV l switchyard through the main and unit auxiliary transformers once a backfeed is established by removing the main generator links;'and (2) the Vernon Hydroelectric Station power line, which connects directly to one of the safety buses through a 13.2/4.16-kV transformer. .)

2. The Vernon Hydroelectric Station, however, was used as an alternate ac

'(AAC)' power source during the Vermont Yankee 10 CFR 50.63, "Statica l Blackout," review. In lieu of demonstrating that Vermont Yankee could  ;

p cope with a Station Blackout-(SBO), you chose:to rely. on the Vernon I

Hydroelectric Power Station as an AAC source, and the staff accepted the ]

Vernon Hydroelectric Station as an AAC source. Two of the most l important~ requirements for an AAC power source are (1) it must be i

.connectable but not normally connected to the preferred (offsite) or x onsite emergency power systems; and (2)'it must have minimal potential F -for common cause failure with the offsite or the onsite ac power-sources.

P} >

)ko P our concern is that since the Vernon Hydroelectric Station is credited as an AAC power source to satisfy the requirements of 10 CFR 50.63, how does Vemont g Yankee meet its design requirement for offsite power. It appears that Vermont-Yankee needs to rely on the backfeed source of offsite power as one of the two  :

n ' required offsite power circuits. The FSAR,.however, does.not discuss the

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', Mr. ' Donald A. Reid April 17, 1997

. the adequacy of this delayed power source. In accordance with GDC-17, for a delayed offsite power circuit to be considered an acceptable source of offsite )

power, it must be shown that power can be reestablished in sufficient time to i

prevent fuel design limits and design conditions of the reactor coolant pressure boundary from being exceeded.

In your March 26, 1997, response to the staff, you stated that no analysis has been performed to demonstrate that the backfeed power source can be established in sufficient time to prevent fuel design limits and design conditions of the reactor coolant pressure boundary from being exceeded. You further stated that the Vernon Hydroelectric Tie is acceptable for complying ,

with both GDC-17 and 10 CFR 50.63 because it performs a dual' function. i l

An AAC power source can not serve as one of the two GDC-17 offsite power sources. It is inconsistent to claim that an offsite. power circuit can double

- as arc AAC power source to satisfy the requirements of 10 CFR 50.63, which assumes a loss of offsite power. Therefore, it appears necessary to either  ;

l (1) demonstrate the adequacy of the backfeed power source as a delayed offsite l power source, or (2) consider the Vernon Hydroelectric Station as the delayed

offsite power source, in which case you would need to perform a coping 4 analysis to satisfy the requirements of 10 CFR 50.63.

Your response to the concerns expressed in this letter is requested as soon as possible, but no later than 30 days from the date of receipt of this letter.

1

. Sincerely, ORIGINAL SIGNED BY:

Vernon L. Rooney, Senior Project Manager Project Directorate I-3 Division of Reactor Projects - I/II Office of Nuclear Reactor Regulation Docket No. 50-271 ,

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Mr. Donald A. Reid April 17, 1997 the adequacy of this delayed power source. In accordance with GDC-17, for a delayed offsite power circuit to be considered an acceptable source of offsite power, it must be shown that power can be reestablished in sufficient time to prevent fuel design limits and design conditions of the reactor coolant ,

pressure boundary from being exceeded. ,

In your March 26, 1997, response to the staff, you stated that no analysis has been performed to demonstrate that the backfeed power source can be established in sufficient time to prevent fuel design limits and design conditions of the reactor coolant pressure boundary from being exceeded. You further stated that the Vernon Hydroelectric Tie is acceptable for complying with both GDC-17 and 10 CFR 50.63 because it performs a dual function.

- An AAC power source can not serve as one of the two GDC-17 offsite power sources. It is inconsistent to claim that an offsite power circuit can double

• as an AAC power source to satisfy the requirements of 10 CFR 50.63, which assumes a loss of offsite power. Therefore, it appears necessary to (1)

- demonstrate the adequacy of the backfeed power source as a delayed offsite power source, or (2) consider the Vernon Hydroelectric Station as the delayed offsite power source, in which case you would need to perform a coping analysis to satisfy the requirements of 10 CFR 50.63.

Your response to the concerns expressed in this letter is requested as soon as {

possible, but no later than 30 days from the date of receipt of this letter.

Sincerely,

/

/ 1 Vernon L. Rooney, Seniov Project Manager Project Directorate I-3 Division of Reactor Projects - I/II  ;

Office of Nuclear Reactor Regulation i Docket No. 50-271 cc: See next page i

4 u

e 4

+ ,

y Vermont Yankee Nuclear Power Vermont Yankee Nuclear Power Station Corporation. ,

cc:

Mr.~ Peter LaPorte, Director-Regional Administrator, Region I ATTN:~ James Muckerheide U. S. Nuclear Regulatory Commission Massachusetts Emergency Management 475 Allendale Road Agency-

~ King.of Prussia, PA 19406 400 Worcester Rd.

P.O. Box 1496 R. K. Gad, III Framingham, MA 01701-0317

-Ropes & Gray One International Place Mr. Raymond N. McCandless Boston,' MA 02110-2624 Vermont Division of Occupational and Radiological Health Mr. Richard P.'Sedano, Commissioner Administration Building Vermont Department of Public Service Montpelier, VT 05602 120 State Street, 3rd Floor Montpelier, VT 05602 Mr. J. J. Duffy Licensing Engineer Public Service Board Vermont Yankee Nuclear Power State of Vermont Corporation 120 State Street 580 Main Street Montpelier, VT 05602 Bolton, MA 01740-1398 Chairman, Board of Selectmen Mr. Robert J. Wanczyk Town of Vernon Director of Safety and Regulatory P.O. Box 116 Affairs Vernon, VT 05354-0116 Vermont Yankee Nuclear Power Corp.

Ferry Road Mr. Richard E. McCullough Brattleboro, VT 05301 1 Operating Experience Coordinator Vermont Yankee Nuclear Power Station Mr. Ross B. Barkhurst, President P.O. Box 157 Vermont Yankee Nuclear Power

Governor Hunt Road Corporation Vernon,.VT 05354 Ferry Road Brattleboro, VT 05301 G. Dana Bisbee, Esq.

Deputy Attorney General Mr. Gregory A. Maret, Plant Manager 33 Capitol Street Vermont Yankee Nuclear Power Station Concord, NH 03301-6937 P.O. Box 157

, Governor Hunt Road J

Resident Inspector Vernon, VT 05354 3 Vermont Yankee Nuclear Power Station

U.S. Nuclear Regulatory Commission P.O. Box 176

i. Vernon, VT 05354 Chief, Safety Unit Office of the Attorney General One Ashburton Place, 19th Floor Boston, MA 02108

.