ML20211B620
| ML20211B620 | |
| Person / Time | |
|---|---|
| Site: | Vogtle  |
| Issue date: | 05/23/1986 |
| From: | Foster D GEORGIA POWER CO. |
| To: | Grace J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| References | |
| GN-922, NUDOCS 8606110785 | |
| Download: ML20211B620 (3) | |
Text
Georgia Fbwer Company K
Fbst Off;ce Box 282 Waynesboro. Georgia 30830 Telephone 404 554-9961. Ext. 3360 404 724-8114. Ext. 3360
&,? '. k D. o. Foster Georgia Power
- , p,'
tre southem entrc system May 23, 1986 United States Nuclear Regulatory Commission Region II File: X7BG03-M98 Suite 2900 Log:
GN-922 101 Marietta Street, Northwest Atlanta, Georgia 30323
Reference:
Vogtle Electric Generating Plant-Units 1 and 2; 50-424; 50-425; Manually Operated Butterfly Valves; GN-869 dated April 10, 1986 Attention: Mr. J. Nelson Grace In our previous correspondence on this subject, Georgia Power Company indicated that handwheels for some manually coerated butterfly valves were found to rotate freely without moving the valve disc.
The actuator gear boxes (Fisher Controls Model 1073) were examined for the valves that failed to operate.
Teeth were found to be broken off from the worm gear sectors of these valves, allowing free rotation of the handwheel and rendering the valves inoperable. The valve vendor conducted metallur-gical tests on a sample from the failed parts and determined the worm gear material to be within ASTM specification requirements.
The valves in question range in size from 8" to 16".
A total of eleven valves have been identified which failed to operate when the handwheel is rotated.
The 8" valves use a smaller size actuator than the 10" and larger valves, which all use the same size actuator.
The valve vendor, Fisher controls, reported that no failures have been experi-enced with these valves except when they were subjected to excessive force on the handwheel.
In 1982, the larger actuator was redesigned to provide added strength to the worm gear sector.
The Vogtle valves are apparently equipped with worm gears of the weaker design.
From examinations of the smaller actuators, it was noted that manu-facturing inconsistencies exist in some of the worm gear sectors so that a partial tooth is left on the end which contacts the open travel stop.
The partial tooth is very weak and can easily be broken off.
Once the partial tooth is broken, the travel stop will then hit the adjacent teeth away from the base and at an angle that could easily overstress and break additional teeth.
Attached Figure A shows a correctly manufactured worm gear sector and Figure B shows a sector with a partial tooth.
8606110785 860523 PDR ADOCK 05000424 i
S PDR lll
Page Two The valve failures are attributed to inconsistencies in the manufac-turing of the worm gear sectors of the smaller actuators and use of an obsolete weaker-designed worm gear section in the larger actuators.
Georgia Power Company has identified a total of 89 manually operated butterfly valves per unit with Fisher Controls Model 1073 actuators.
An evaluation is in progress to determine if any safety impacts could result from the failure of eny of these valves.
Georgia Power Company expects to inform the USNRC of the results of this evaluation by June 27, 1986.
This response contains no proprietary information and may be placed in the NRC Public Document Room.
Your/ ruly, t r
[Y I
D. O. Foster REF/D0F/tdm Attachment xc:
U. S. Nuclear Regulatory Commission Document Control Desk Washington, D. C.
20555 J. H. Miller R. A. Thomas L. T. Gucwa J. P. O'Reilly D. R. Altman C. W. Hayes G. F. Head P. R. Bemis G. A. McCarley R. E. Conway J. A. Bailey D. S. Read J. T. Beckham
- 0. Batum Sr. Resident (NRC) l
'R. H. Pinson G. Bockhold C. S. McCall (0PC)
P. D. Rice C. E. Belflower J. E. Joiner (TSLA)
B. M. Guthrie J. F. D'Amico D. C. Teper (GANE)
D. E. Dutton E. D. Groover NORMS l
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, Travel stop e
O 1~ worm gear sector Model 1073 size 1 actuator FIGURE A d' _.,..,
Travel stop
-Partial tooth g,
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worm gear sector
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l Model 1073 size 1 actuator FIGURE B i
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