ML20080G441
| ML20080G441 | |
| Person / Time | |
|---|---|
| Site: | Palo Verde  |
| Issue date: | 01/26/1984 |
| From: | Van Brunt E ARIZONA PUBLIC SERVICE CO. (FORMERLY ARIZONA NUCLEAR |
| To: | Bishop T NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| References | |
| ANPP-28732-BSK, DER-83-62, NUDOCS 8402130391 | |
| Download: ML20080G441 (4) | |
Text
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r, HECElvEo finc Arizona Public Service Company l}, [g g,,
q P O. BOX D666 e PHOENIX, Am2ONA 85036 WO.Y mE January 26, 1984 ANPP-28732-ESK/TRB U. S. Nuclear Regulatory Commission Region.V Creekside Oaks Office Park 1450 Maria Lane - Suite 210 Walnut Creek, CA-94596-5368 Atterition: Mr. T. W. Bishop, Director Division'of Resident Reactor Projects and Engineering Programs
Subject:
Final Report --DER 83-62 A 50.55(e) Reportable Condition Relating to Core Support Barrel Snubbers Have Loose Or Missing Cap Screw Retainer Pins-File: 84-019-026; D.4;33.2
Reference:
A) Telephone Conversation between P. Narbut and R. Tucker on September 19,.1983
.B) ANPP-28073, dated October 24, 1983 (Interim Report)
Dear Sir:
Attached 'is our final written report of the deficiency referenced above,
-which has been_ determined to be Not Reportable under the requirements of 10CFR50.55(e).-
Very truly yours, YOLO kg E. E. Van Brunt, Jr.
APS Vice President, Nuclear ANPP Project Director EEVB/TRB:ru Attachment cc:
-See Page Two
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Mr. T. W.' Bishop DER 83-62 Page'Two
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- 3. Richard DeYoung, Director it Office of Inspection and Enforcement U; S.-Nuclear Regulatory Commission Washington,'D. C. 20555 T. G. Woodi', Jr. ;
W. E. Ide ^
D. B. Fasnacht -
A. C. Rogers
' B. S. Kaplan[
J. Vorees-J. R._Bynum-P. P. Klute
-A. C. Gehr W.-J. Stubblefield'
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W..G.-Bingham R. L. Patterson R. W. Welcher H. Foster D.-R. Hawkinson L.
E.' Vorderbrueggen.
G. A. Flore111 S. R. Frost J. - Self '
D.- Canady i
I Records Center
- Institute of Nuclear Power Operations 1100 Circle 75 Parkway, Suite 1500 Atlanta, GA 30339 1
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FINAL REPORT - DER 83-62 DEFICIENCY EVALUATION 50.55(e)
ARIZONA PUBLIC SERVICE COMPANY (APS)
PVNGS UNIT 1 I. Description of Deficiency During inspection of the Unit 1 Reactor Vessel (RV) after hot functional testing, it was revealed that the Core Support Barrel (CSB) snubbers had loose or missing cap retained pins. The snubber locations were identified as O degree azimuth, 50 degree azimuth and 180 degree azimuth. The core barrel snubbers are supplied by Combustion Engineering (C-E)
II. Analysis of Safety Implications C-E. letter V-CE-19266 addresses the analysis of safety implications as follows:
The design of the Core Support Barrel Snubber lug requires that the reactor vessel lug shims be removable to accommodate field sizing and machining operations.
The resulting bolted connection incorporates a torquing arrangement to ensure a tight shim assembly during plant operation. A final torque of 275 ft-lbs is applied to each snubber attachment bolt to accomplish this purpose. To further assure that the bolts remain in placa, staking pins are inserted to prevent rotation of the bolts. They are secured by upsetting material above the pin in the slot cut in the snubber shim for pin insertion. Finally, the shims, pins and bolts are captured in the assembly by the RV snubber lug and the CSB bracket geometry.
Following the hot functional testing of ANPP Unit 1, two staking pins were found to be missing. Also, several of the other pins were discovered to be loose in their holes.
It is not known when the two pins became lost; they were photographed in place one week prior to installation of the core support barrel into the vessel. One possibility is that hot functional testing vibratory loads contributed to their becoming 1cose, allowing them to be lost during CSB disassembly operations. They cannot become lost once the CSB is in place.
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winal' Report. DER 83-62 3
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s If the pins are not present during plant' operation the bolts are'still expected to retain their applied torque due to the
< factithat anticipated vibratory loads are too small'to affect
.the bolt'preload. Other factors such as the bolt length to
' diameter relationship and the direction of the vibratory lo' ads s
- work'to reinforce the rotention'of bolt'preload.
In essence,
'for the bolts to work loose, vibratory ' loads must change the
' original preload and this is not expected.
s i
Howeverl in the unlikely event that the bolt loses its prelcad,1the shim will-be ' retained by the close. tolerance of
- .015" maximum between shia and bracket surfaces and also by the geometry of _the bracket.- The; shim is physically held in i
' place.with.or without'the' bolts?being-tight.
C-E concludes
- that with the shim held in place, it provides the support
. required during a Design Basis Event. -Therefore,' the safety of operation would not be adversely. impacted.-
t Based on the above, this condition is evaluated. as not reportable under the requirements of 10CFR50.55(e),and -
10CFR21, since if this condition were to remain uncorrected, it-would not represent a'significant safety condition.
III.' Corrective Action C-E'has defined the corrective action as follows:
A. A field. retrofit has been initiated to replace the lost pins and to check all staking pins and pin' holes to determine whether or not drawing tolerances have been met.
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For closer control longer staking pins;and smaller gap at the top of the pin'has'been stipulated in the field retrofit. ' Meeting all installation requirements will assure,that the pins are properly lo6ated prior to
. installing the Core Support Barrel.
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JB. NCR SM-2578 will be dispositioned as " Repair" in accordance
'with C-E: field' retrofit-instructions above.
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' C. C-E will issue site process sheets to perform inspections 2
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on Units 2 &.3 to. ensure all staking pins are properly
. installed.
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