ML18283B375
| ML18283B375 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 08/05/1976 |
| From: | Gilleland J Tennessee Valley Authority |
| To: | Moseley N NRC/IE, NRC/RGN-II |
| References | |
| Download: ML18283B375 (5) | |
Text
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'ENNESSEE VALLEYAUTHOR CHATTANOOGA. TENNESSEE 37401 August 5~ 1976 l,';
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~,I Mr. Norman C; Moseley, Director Office of Inspection and Fnforcement U.S. Nuclear Regulatory Commission Region XX Suite 818 230 Peachtree
- Street, NH.
Atlanta, Georgia 30303
Dear Mr. Moseley:
BROHNS FFRRY NUCLEAR PLANT UNIT 3 RFPORTABLF, DEFICIFNCY-RPV STABILIZER PLATES XNSTALLED INCORRECTLY XE CONTROL NO.
HO 1340 F2 Initial report of the subject reportable deficiency was made to G. R. Klingler, NRC-XE, Region H:, on May 13,
- 1976, and was followed by our June 14, 1976, letter, J. E. Gilleland to No C. Moseley, Fnclosed is our final report concerning this deficiency.
Very truly yours,
~~f~~
J.
Eo Gilleland Assistant Manager of Power Enclosure CC (Enclosure):
Dr. E. Volgenau, Director Office of Inspection and Enforcement U.S. Nuclear Regulatory Commission Uashington, DC 20555 An Equal Opportunity Employer
ENCLOSURE j3HONNS FERRY NUCLEAR PLANT UNIT 3 RPV STABILIZER PLATES INSTALLED INCORRECTLY DDR 232 FINAL REPORT On flay lg, 1976, an initial report was made by telephone to NHC-OIE Region ii Inspector Gerald R. Klingler by J.
G. Adair, T. M. Barkalow, and S. H. Ni;nde1 in accordance with 10CFH50.55(e).
Subsequently, a written interim report on this deficiency was submitted to Norman C.Moseley (NRC-OIE) from J.
E. Gilleland
{XVA) on June 14, 1976.
This is the final report on DDR 232.
Description of Deficienc The General Electric Company released a field, disposition instruction (FDI) requesting that an inspection be performed. on the reactor pressure vesse3.
(RPV) seismic stabilizers at Browns Ferry Nuclear Plant.
The purpose of the inspection was to ensure the stabilizers were instal1ed with sufficient clearances to permit xelative deflections between the xeactor pressure vessel and the shield. wall without binding and inducing cyclic stresses in the stabilizers.
Vhen performing this inspection it was discovered that part of the stabilizer assembly had been incorrectly installed..'earing plates at each end ox the assembly had. been installed 90 degrees from their intended.
orientation, see figure 1, attached..
Cause of.Defi.ciencv The stabilizer bearing p3ates were originally installed xotated 90.degrees from their intended. orientation.
Safet im lications The RPV stabilizers are the seismic restraints for the reactor pressure vesse1.
The bearing plates that were incorrectly installed are the bearing suxfaces between the HPV stabilizer assemblies and the bumper assemblies
~amounted on the biological shi.eld wa3.1.
The bearing plate of a stabilizer assembly directly reacts against a shim plate welded to the bracket.
This shim plate, i.s "U"-shaped to allow for movement of the stabili er assembly due to therma1 expansion of the RPV (see figure 1).
(lith the bearing plate installed. rotated 90 degrees from the correct orientation, the emount of bearing surface b> "ween it and the shim plate is reduced..
It is possible that tne thermal expansion of the RPV could move the stabi3.i er assembly so that one edge of the bearing plate is above the cut-out portion of the shim pl te.
During a seisinic event this orientation could lead to the bearing plate "punching thrn>>>..h" one side of the shim plate cut-out resulting in binding of the stabilizer assembly which could impair its operability.
'The RPV would not be damaged due to the stabilizer assembly binding, but the stabilizer could be damaged to the extent that replacement would be necessary.
Dcscri tion of Corrective Action General Electric was notified of this deficiency and recommended that TVA jsJplement one of two fixe":
(1) rotate the bearing plate 90 degrees to the correct orientation, or (2) replace the shim plate on the bumper bracket with a new design of different dimensions.
Since the stabilizers are fully assembled and are located in an area with limited access, rotation of the bearing plates would have been very difficult.
- Xnstead, new shim plates have been fabricated. and have been installed.
These new shim plates increase the amount of bearing surface area available and decrease the likelihood of a bearing plate " punchingthrough" the shim plate cut-out (see figure 2 for new shim plate dimensions).
Means Taken to Prevent a Recurrence At the time the RPV stabilizer assemblies were installed there was not a
'ormal Quality Assurance Program for Browns Ferry.
Since that time a f>rmal program has been developed and implemented.
This program decreases the probability of incorrect installatidn of equipment and Qh hold points are identified to verify critical dimensions and orientations.
Since no further s'bilizers are to be added to'rowns Ferry, this particular deficiency will not recur.
The current formal QA Program significantly decreases the chance of recurrence of a similar deficiency.
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