ML20028D286

Notifies That New Westinghouse Dropped Rod Evaluation Process Will Be Applied to Cycle 5 Design.Review of Westinghouse Re Process Requested

ML20028D286
Person / Time
Site:	Farley
Issue date:	01/11/1983
From:	Clayton F ALABAMA POWER CO.
To:	Varga S Office of Nuclear Reactor Regulation
References
TAC-48040, TAC-48041, NUDOCS 8301170289
Download: ML20028D286 (3)

Text

MiiHng AIdrus Alabama Power Company 600 North 18th Street i

Post Office Box 2641 Birmingham, Alabama 35291 Telephone 205 783-6081 F. L. Clayton, Jr.

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AlabamaPower the southem electrc system J anua ry 11, 1983 Docket No. 50-348 f

Director, Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Washington, D. C.

20555 Attention:

Mr. S. A. Va rga Joseph M. Farley Nuclear Plant - Unit 1 New Rod Drop Methodology

References:

(1) Westinghouse letter NS-TMA-2063, 3/30/79 (2) Westinghouse letter NS-TMA-2167,11/28/79 (3) Westinghouse letter NS-EPR-2509, 10/6/81 (4) Westinghouse letter NS-EPR-2545,1/20/82 (5) Alabama Power Company letter, 12-12-80, F. L. Clayton, Jr. to Messrs. Varga and Schwencer Gentlemen:

In 1979, Westinghouse identified to the Core Performance Branch of the NRC (References 1 and 2) a concern with regard to certain assumptions employed in the dropped rod accident safety analysis applicable to some Westinghouse NSSS designs.

This concern was derived primarily from the potential for an unanalyzed power overshoot while in automatic control following selected dropped rod events when the plant was in power ranges in excess of 90% which did not result in a reactor trip.

l The concern was applicable to Westinghouse plants which rely upon the Power Range Neutron Flux - High Negative Rate Reactor Trip to mitigate the consequences of the dropped rod accident.

Alabama Power Company was notified by Westinghouse of their determination that this concern constituted an Unreviewed Safety Question under 10CFR50.59 applicable to the Farley Plant.

Following recommenda-tions by Westinghouse, the NRC subsequently required operational restrictions above 90% power (either manual rod control or restricted rod insertion limits when in automatic rod control) to address this concern on an interim basis and requested further evaluations be conducted to resolve this issue.

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3 Mr. S. A. Varga January 11, 1983 Director, Nuclear Reactor Regulation Page 2 U. S. Nuclear Regulatory Commission Westinghouse subsequently performed a comprehensive evaluation of this problem which resulted in the development of a new dropped rod methodology.

It is our understanding that a meeting was held in August 1981 between members of the Core Performance Branch and Westinghouse to discuss the new Dropped Rod Evaluation process (Reference 3).

This process demonstrated that the DNB design basis can be met for this event.

Westinghouse has notified Alabama Power Company that this evaluation process results in conclusions allowing removal of the interim operating requirements on rod control and insertion upon final approval by your staff.

It is also our understanding that, upon acceptance of the Westinghouse report documenting this process (Reference 4) by the NRC Staff, the removal of operating restriction would take place.

This letter serves as formal notification that the new Westinghouse Dropped Rod Evaluation Process documented to you in Reference 4 will be applied to the Farley-1 Cycle-5 design and to future cycle designs.

The results are expected to confirm that the DNB design basis is met for the dropped rod accident.

Upon verification of acceptable results, the interim restrictions discussed in Reference 5 will no longer be necessary.

However, since explicit NRC approval has not been received to date, we will operate under the interim restrictions until formally notified by your staf f.

We formally request that your staff review the material i

submitted to you as Reference 4 at the earliest feasible date and subsequently remove the interim operational restrictions effective with Cycle-5.

Yours very truly,

@[ dbl l 1

K. L. Cl ayton, J r.

FLCJr/MDR:jc-D28 Attachment cc:

Mr. R. A. Thomas Mr. G. F. Trowbridge Mr. J. P. O'Reilly Mr. E. A. Reeves Mr. W. H. Bradford Mr. C. H. Berlinger, Branch Chief Core Performance Branch t

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Mr. W. O. Whitt Mr. R. P. Mcdonald Mr. H. O. Th rash Mr. O. D. Ki n gsl ey, J r.

Mr. W. G. Hairston, III Mr. J. W. McGowan Mr. C. D. Nesbitt Mr. R. G. Berryhill Mr. D. E. Mansfield Mr. J. A. Ripple Mr. E. A. Worden Mr. W. G. Ware Mr. L. B. Long Mr. J. R. Crane Mr. K. C. Gandhi