Effect of a DC Power Supply Failure on ECCS Performances (Generic Letter 80-35)


                               UNITED STATES 
                          WASHINGTON, D.C. 20555 

                               APRIL 25 1980 

Docket No. 50-271 

     Mr. Robert L. Smith 
     Licensing Enginer 
     Vermont Yankee Nuclear Power 
     25 Research Drive 
     Westboro, Massachusetts 01581 

     Dear Mr. Smith: 

     It has generally been recognized that the loss of a direct current (DC)
     power supply could disable several emergency core cooling system 
     components and thereby could result in a limiting single failure 
     condition for some breaks. The enclosed letter report was submitted to 
     the NRC staff by the General Electric Company to provide a definitive, 
     generic, reference analysis of the effects of DC power supply failures 
     on ECCS conformance calculations. The NRC staff is reviewing the 
     analysis which compares the peak cladding temperatures associated with 
     various postulated DC power supply failure (ECCS equipment 
     availability) cases to the peak cladding temperatures for a HPCI (small 
     break) failure and LPCI injection valve (large break) failure cases. 
     Since the study was based on plant design information which may have 
     been incomplete or out-of-date, some uncertainty exists whether the 
     worse ECCS system availability combinations have been identified for 
     your operating BWRs. Accordingly, in order that we may have an adequate 
     level of assurance that the systems combinations assumed in the generic 
     analysis are conservative for Vermont Yankee Nuclear Power Station, we 
     request that you confirm the conclusion of the reference study 
     regarding the minimum ECCS equipment availability with a DC power 
     supply failure. Include in your response a list of the ECCS equipment 
     that would be for large and small (1) recirculation loop discharge 
     breaks, and (2) recirculation loop suction breaks. The listing of 
     equipment available should take into account not only DC power supply 
     failure, but also loss of equipment due to water spillage. 
     Please provide a schedule for your response within 30 days of the 
     receipt of this letter. 

Mr. Robert L. Smith               - 2 -                      APRIL 25 1980 

This request for generic information was approved by GAO under clearance 
number B-180225(579018); this clearance expires October 31, 1980. 


                                        Thomas A. Ippolito, Chief 
                                        Operating Reactors Branch #3 
                                        Division of Operating Reactors 

General Electric Company letter 
     (R. E. Engle) to USNRC (P.S. 
     Check), "DC Power Source Failure 
     for BWR/3 and 4," dated November 1, 

cc w/enclosure
See next page

Mr. Robert L. Smith               - 3 -                      APRIL 25 1990 


Ms. J. M. Abbey
Vermont Yankee Nuclear Power
77 Grove Street
Rutland, Vermont 05701 

Mr. Louis H. Heider,
  Vice President
Vermont Yankee Nuclear Power
25 Research Drive
Westboro, Massachusetts 01581 

John A. Ritsher, Esquire
Ropes & Gray
225 Franklin Street
Boston, Massachusetts 02110 

Laurie Burt
Assistant Attorney, General
Environmental Protection Division
Attorney General's Office
One Ashburton Place, 19th Floor
Boston Massachusetts 02108 

Ronald J. Wilson
810 18th Street, N. W.
Suite 802
Washington, D. C. 20006 

Honorable M. Jerome Diamond
Attorney General
State of Vermont
109 State Street
Pavilion Office Building
Montpelier, Vermont 05602 

Mr. J. E. Griffin, President
Vermont Yankee Nuclear Power
77 Grove Street
Rutland, Vermont 05701

John R. Stanton, Director
Radiation Control Agency
Hazen Drive
Concord, New Hampshire 03301 

John W. Stevens
Conservation Society of
  Southern Vermont
P. O. Box 256
Townshend, Vermont 05353 

Dr. Mars Longley, Director
Occupational & Radiological Health
10 Baldwin Street
Montpelier, Vermont 05602 

New England Coalition on Nuclear 
Hill and Dale Farm West Hill - Faraway Road 
Putney, Vermont 05346 

Public Service Board
State of Vermont
120 State Street
Montpelier, Vermont 05602 

W. P. Murphy, Plant Superintendent
Vermont Yankee Nuclear Power
P. O. Box 157
Vernon, Vermont 05354 

Mr. Charles Sheketoff
Assistant Director
Vermont Public Interest
  Research Group, Inc.
26 State Street
Montpelier, Vermont 05602 

Brooks Memorial Library
224 Main Street
Brattleboro, Vermont 05301


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