ML20003D646

Ro:Recently,Insufficient Time Noted for Operators to Take Required Actions in Two Boron Dilution Events.Cause Not Stated.Shutdown Margin for Modes 4 & 5 Will Be Changed. Source Range Setpoint Will Be Changed to 2 Times Background

ML20003D646
Person / Time
Site:	Summer
Issue date:	03/23/1981
From:	Nichols T SOUTH CAROLINA ELECTRIC & GAS CO.
To:	Harold Denton Office of Nuclear Reactor Regulation
References
NUDOCS 8103300070
Download: ML20003D646 (1)

Text

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SOUTH CAROLINA ELECTRIC a GAS COMPANY Post orrsct oox 764 @

COLUM8sA, SOUTH CAROLINA 29218 '

h T. C. NicHots.Ja. March 23, 1981

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Mr. Harold R. Denton, Director kgp[g - I Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Washington, D. C. 20555

Subject:

Virgil C. Summer Nuclear Station Docket No. 50/395 Boron Dilution Event

Dear Mr. Denton:

Recently, in discussion with the Reactor Systems Branch regarding boron dilution events, it was noted that insufficient times are available for operators to take. required actions in two of the events which were evaluated. SCE&G will resolve the matter by increasing the shutdown margin from 1%$ for modes 4 and 5 to2%$andbychangingthesetpointonthesourcerangeinstrumentationfrom5 times background to 2 times background. These changes will result in increasing the times from alarm to operator action to approximately 10 minutes. The start-

. up case in the FSAR will be rewritten to better describe the event where, in fact, no problem really exists. Additional information to better describe the refueling case and to justify the use of 150 gpm for flow from the reactor make-up tank will be provided later.

When details of our solution are finalized, you will be informed. If you have any questions, please let us know.

Very truly yours,

[

T. C. Nichols, Jr.

RBC:TCN:glb cc: V. C. Summer H. N. Cyrus G.-H. Fischer -J. B. Knotts, Jr.

T.'C. Nichols, Jr. J. L. Skolds C. A. Price B. A. Bursey D. A. Nauman O. S. Bradham-W. A. Williams, Jr.- ISEG

.R. B. Clary PRS A. R. Koon NPCF A.'A.-Smith File 4 82 0s a n no7o . -