ML20197E644
| ML20197E644 | |
| Person / Time | |
|---|---|
| Site: | Seabrook  |
| Issue date: | 05/13/1986 |
| From: | Devincentis J PUBLIC SERVICE CO. OF NEW HAMPSHIRE |
| To: | Noonan V Office of Nuclear Reactor Regulation |
| References | |
| SBN-1050, NUDOCS 8605150292 | |
| Download: ML20197E644 (3) | |
Text
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SEABROOK STATION Engineering Offica May 13, 1986 SBN-1050 Putsc Sen4ce of New Hampshire T.F.
B7.1.2 United States Nuclear Regulatory Commission Washington, DC 20555 Attention:
Mr. Vincent S. Noonan, Project Director PWR Project Directorate No. 5
References:
(a) Construction Permits CPPR-135 and CPPR-136, Docket Nos. 50-443 and 50-444 (b) USNRC Letter, dated April 22, 1985, " Request for Additional Information Regarding Post-Fire Safe Shutdown Capability", G. W. Knighton to R. J.
Harrison (c) PSNH Letter (SBN-836), dated July 3,1985, " Response to 410 Series RAIs (Post-Fire Shutdown Capability)",
J. DeVincentis to G. W. Knighton
Subject:
Response to RAI 410.58 (Multi-High Impedance Fault)
Dear Sir:
In RAI 410.58, Reference (b), the Staff expressed a concern regarding the potential for multi-high impedance f aults in ac power circuits which could result in the loss of power to safe shutdown equipment.
In response to RAI 410.58, we stated our position in Reference (c) regarding the above concern. Our position is summarized below:
Although a high impedance f ault might occur in a cable subjected to fire damage, current industry codes for f ault current calculation preclude the possibility of supply breaker trip for any one such f ault occurring in a branch circuit. Postulating multiple high impedance faults simultaneously in branch circuits soes beyond the bounds of conservative electrical distri-bution design.
In such a scenario, each branch circuit cable (carrying a different load current) would have to fail along its length in such a manner as to result in a unique insulation resistance that will produce a leakage current to ground (or conductor to conductor), nich added to the conductor load would result in a current just below the protective device rating.
These fault currents would then have to be sustained long enough to cause l
the supply breaker to trip. Thus, an improbable combination of temporary leakage currents in different cables would have to occur at once to trip the supply breaker.
8605150292 860513 N(
PDR ADOCK 05000443 F
PDR it i
Seabrook Station Construction Field Office. P.O. Box 700. Seatxook, NH O3874
a-4 e
United States Nuclear Regulatory Commission Attention:
Mr. Vincent S. Noonan Page 2 We still believe that this type of fault condition is not credible.
However, we will add a general note in the safe shutdown and cooldown procedures from the 051200.01 and 051200.02 to alert plant personnel to trip all bus loads prior to restoration of power to the bus and to restart only necessary loads sequentially, should a loss of power occur to a bus due to fire.
Very truly yours, John DeVincentis Director of Engineering cc: Atomic Safety and Licensing Board Service List r
1 l
l r.
'l Diane Curren. Erguire Calvia A. Canneg' i
Narmon & Weise City Manager 2001 8. Street, W.W.
City Nall Suite 430 126 Daniel Street Portsmouth, M 0380,1 l
Washington, D.C.
20009 Sherwin E. Turk Esq.
Stephen E. More111. Esquire i
office of the Exo:utive Legal Director Attorney Ceneral U.S. Nuclear Regulatory Commission Coorse Dana Bisbee, Esquire Tenth yloor Assistant Attorney General 1
Washington, DC 20555 Office of the Attorney General 4
25 Capitol Street Robert A. Backus, Esquire Concord, M 03301-4397 114 Lowell Street P.O. Box 516 Nr. J. F. Wadeau Manchester, NN 03105 Selectmen's Offlee 10 Central Road Philip Ahrens, Esquire Rye, NH 03870 Assistant Attorney General Department of The Attorney General Mr. Angie Nachiros Statehouse Station M Chairman of the Board of Selectmen kugusta NB 04333 Town of Newbury Newbury, MA 01950 Mrs. Sandra Cavutis Chairman, Board of Selectmen Mr. William S. Lord RFD 1 - Box 1154 Board of Selectmen Kennsington, M 03427 Town Nell - Friend Street i
Asesbury, N& 01913 Carol S. Sneider, Esquire Assistant Attorney General Senator Gordes J. Numphrey Department of the Attorney General 1 Fillsbury Street one Ashburton Place, 19th Floor Concord, M 03301 I
Boston, MA 02104 (ATTN: Norb Boynton)
Senator Gordon J. Numphrey N. Joseph Flynn Esquire U.S. Senate Office of General Counsel Washington, DC 20510 yederal Beersency Management Agency g (ATTN: Tom Burack) 500 C Street, SW '
l Washingto;, DC 20472 i
Richard A. Hampe, E:q.
Hampe and McNicholas Paul McEachern, Esquire 35 Fleasant Stecet Matthew T. Brock. Esquire Concord, NH 03301 Shaines & McEachern i
25 Naplewood Avenue Donald E. Chick F.O. Box 360 Town Manager Portsmouth, M 03801 Town of Exeter 10 Front Street Gary W. Holmes, Esq.
Exeter, M 03833 Nolmes & Ells 47 Winnacunnet Road Brentwood Board of Selectmen Naapton, NH 03041 RFD Delton Road Brentwood, NH 03833 Mr. 53 Thomas FEMA Region I Peter J. Mathews, Mayor 442 John W. McCormack PO & Courthouse City Hall Bostois, MA 02109 Newburyport. NA 01950 Stanley W. Knowles, Chairman Board of Selectmen F.O. Box 710 North Hampton. NN 03862
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