ML19305D811

Final Deficiency Rept Re Measurement of Steam Generator Water Level.Steam Generator Impulse Lines Are Being Thermally Insulated to Minimize Heatup.Mod Will Ensure Proper Accuracies W/O Requiring Large Setpoint Increase

ML19305D811
Person / Time
Site:	Summer
Issue date:	04/08/1980
From:	Crews E SOUTH CAROLINA ELECTRIC & GAS CO.
To:
References
NUDOCS 8004150548
Download: ML19305D811 (2)

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April 8, 1980 Mr. James P. O'Reilly United States Nuclear Regulatory Commission Region II 101 Marietta Street, N. W. ,

Suite 3100 Atlanta, CA 30303

Subject:

Virgil C. Summer Nuclear Station, Unit 1 Reportable Item in Accordance with 10CFR50.55(e)

Steam Generator Level Indication Nuclear Engineering File: 3.1051

Dear Mr. O'Reilly:

On July 10, 1979, South Carolina Electric and Gas Company (SCE&G) informed NRC of a potential significant deficiency concerning measurement of steam generator water level. On September 27, 1979, SCE&G reported that there was no change in the status reported July 10, 1979. The purpose of this letter is to inform you that Westinghouse has recommended a fix which is being implemented for the V. C. Summer Nuclear Station.

High energy line breaks inside containment could result in heatup of the steam generator level measurement reference leg. Increased '

reference leg water column temperature will result in a decrease of the t water column density with consequent apparent increase in thE indicated steam generator water level (i.e., apparent level exceeding actual level). This potential level bias could result in delayed protection signals (reactor trip and auxiliary feedwater initiation) which are based on low-low steam generator water level.

It has been determined that for V. C. Summer Nuclear Station which l has an automatic steamline isolation system on low steamline pressure only that boiling will not occur in the reference legs of the intact steam generators. These steam generator level impulse lines, however, '

are being thermally insulated to minimize their heatup during the time required to perform a trip function af ter a high energy line break ,

inside the containment. This modification will limit the increase in the low-low steam generator water level set point to 2% to compensate for heatup errors and is based on conservative estimates of containment conditions following an event.

30/9 SCE  !

tl0 8004150548

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r Mr. James P. O'Reilly Page 2 April 8, 1980 The insulation is considered a solution to ensure proper accuracies without requiring a large increase in the trip setpoint that might interfere with normal plant operation. Th s renpense is the final report on this item. .If further informati n is deemed necessary, please contact us.

er 't y yours, /

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. . ws, Jr.

BSM:rm CC: Office of Inspection and Enforceme Washington, DC Messrs: V. C. Summer E. H. Crews, Jr.

H. T. Babb M. B. Whitaker D. A. Nauman J. Skolds H. Radin NPCF/Dixon File

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