ML19337A076
| ML19337A076 | |
| Person / Time | |
|---|---|
| Site: | Summer  |
| Issue date: | 09/03/1980 |
| From: | Nichols T SOUTH CAROLINA ELECTRIC & GAS CO. |
| To: | |
| References | |
| REF-PT21-80-204-003 10CFR-050.55E, 10CFR-50.55E, NUDOCS 8009080337 | |
| Download: ML19337A076 (3) | |
Text
,
jJ3 SOUTH CAROLINA ELECTRIC a gas COMPANY post ornes nex to.
CotuMe:A. south CAROUNA 29216 T.C.NacMots Ja.
September 3, 1980 Mr. James P.LO'Reilly US Nuclear Regulatory Commission Region II Suite 3100 101 Marietta Street, N. W.
Atlanta, GA 30303 Subj ect: Virgil C. Summer Nuclear Station, Unit 1 Docket No. 50/395
~
Reportable Substantial Safety Hazard Control Rod Guide Tube Support Pin Cracking
Dear Mr. O'Reilly:
South Carolina Electric & Gas Company (SCE&G) reported a substantial safety hazard as defined by 10CFR21 to you in a letter dated March 27, 1980.
This concern deals with a potential stress corrosion cracking problem of the control rod guide tube support pins supplied by Westinghouse for the Virgil C.
Summer Nuclear Station.
Laboratory testing, conducted by Westinghouse as part of an investigation into the support pin cracking problem, indicates that susceptibility to stress corrosion cracking decreases with increasing solution heat treatment temperature.
.These tests have established that the Westinghouse current manufacturing process, which utilizes a solution heat treatmenc at 2000 F, results in support pins which are highly resistant to stress corrosion cracking. The support pins which Westinghouse supplied for the V. C. Summer Nuclear Station, Unit 1, vere pins having solution heat treatment at trsperatures less than 1800 F.
The potential impact on Upper Head Injection (UHI) plants a d 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 jenoard'. zed by a broken pin due to the small gap clearance between the non-Ud1 as de tube and the core plate. This was previously reported to the NRC ir Westinghouse letter NS-TMA-2099.
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 been found in on-site inspections.
3o/7 s
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a Mr. James P. O'Reilly Page 2 September 3, 1980 Westinghouse plans to conduct ultrasonic inspection of guide tube support
-pins at two or more operating domestic p1. ants.
Since the results of this inspection prograa may not be evailable until after fuel load and added margin to minimize the potential for sopport pin cracking after Su=mer Station begins operation is desirable, SCE&G will replace the existing pins with pins which have been solution heat treated in the range of 1950 F to 2000 F.
The pin replacement is scheduled to be performed in October, 1980.
This response is the final report on this item, if further information is deemed necessary, please contact us.
Very truly yours, T. C. Nichols, Jr.
BSM:rm CC: Messrs.
V. C. Summer E. H. Crews, Jr.
G. H. Fischer D. A. Nauman
- 0. W. Dixon, Jr.
H. T. Babb
- 0. S. Bradham R. B. Clary W. A. Williams, Jr.
B. A. Burcey T. B. Conner, Esquire NPCF/Whitaker File U. 3. Nuclear Regulatory Commission Division of Inspection oaa Caforcement pf's. Nuclear Regulata;y Commission g
Document Managemen. Branch
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