ML19339B879
| ML19339B879 | |
| Person / Time | |
|---|---|
| Site: | Summer  |
| Issue date: | 11/03/1980 |
| From: | Nichols T SOUTH CAROLINA ELECTRIC & GAS CO. |
| To: | Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8011100357 | |
| Download: ML19339B879 (2) | |
Text
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south CAROLINA ELECTRIC a GAS COMPANY POST OF FICE BOM 764 CotuMeiA, South CAROLINA c92i8 T. C. NicMots. J R, v.<, e.,m....o c.%. o ccom November 3, 1980
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.t-LN) 1 Mr. Harold R. Denton, Director M.
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Office of Nuclear Reactor Regulation
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U. S. Nuclear Regulatory Commission m
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Subject:
Virgil C. Summer N car 8Mion Docket No. 50/395 NRC Questions on Steam Generator
>bdifications and Control Rod Guide Tube Support Pins
Dear Mr. Denton:
In Mr. A. Schwencer's 5/30/80 letter, the NRC requested additional infornation regarding steam generator modifications, control rod guide tube support pins, and level measurement errors due to temperature effects on level instrument reference 1 cgs.
South Carolina Electric and Gas Company, acting for itself and as agent for South Carolina Public Service Authority, herewith provides forty-five (45) copics of the requested information on the support pins.
Information on level measurement and steam generator modifications will be provided at a later date.
Cont rol Rod Guide Support Pins Laboratory testing, conducted by Westinghouse as part of an investi-gation into the support pin cracking problem, indicates that susceptibility to stress corrosion cracking decreases with increasing solution heat treatment temperature. These test have established that the Westinghouse current manufacturing process, which utilizes a solution heat treatment at 2000 F, results in support pins which are highly resistant to stress corrosion cracking.
The support pins which Westinghouse supplied for the Virgil C. Summer Nuclear Station were pins having solution heat treatment at temperatures less than 1800 F.
The potential impact on Upper Head Injection (UHI) plants and non-UHI plants has been evaluated by Westinghouse.
Since the V. C. Summer Nuclear Station is a non-UHI plant, control rod operation is not jeopardized by a broken pin due to the small gap clearance between the non-CHI guide tube and the core plate. This was previously reported to the NRC in Westinghouse letter NS-TMA-2099.
a Mr. Harold R. Denton November 3, 1980 Page Two Control Rod Guide Support Pins (con't)
In the unlikely event that a pin leaf should be broken off, the broken leaf could represent a loose part, which can have some small potential for interfering with control rod movement. However, due to the configuration of the internals, this is highly unlikely to occur and no broken leaves have ever be2n found in on-site inspections.
Westinghouse plans to conduct ultrasonic inspection of guide tube support pins at two or more operating domestic plants.
Since the recults of this inspection program may not be available until after fuel load and added margin to minimize the potential for support pin cracking after Summer Station begins operation is desirable, SCE&G has replaced the existing pins with pins which have been solution heat tested in the range of 1950 F to 2000 F.
If you require additional information, please let us know.
Very truly yours, k,
y t
T. C. Nichols, Jr.
RBC:TCN:rh cc:
V. C. Summer G. H. Fischer T. C. Nichols, Jr.
E. H. Crews, Jr.
O. S. Bradham O. W. Dixon, Jr.
R. B. Clary W. A. Williams, Jr.
B. A. Bursey J. B. Knotts J. L. Skolds NPCF/Whitaker File