ML18283B374
| ML18283B374 | |
| 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: ML18283B374 (10) | |
Text
830 Power Building TENNESSEE VALLEYAVTHORITY CHATTANOOGA, TENNESSEE 3740t AUG 5-1975 Mr. Norman C. Moseley, Director Office of Xnspection and Enforcement UiS ~ Nuclear Regulatory Commission Region XI - Suite 818 230 Peachtree Street, Rf.
Atlanta, Georgia 30303 Dear Mr. Moseleys BROWS PERRY NUCLPJQt PLANT UNXT 3 REPORTABLE DEFICIENCY-RPV STABILIZER PLATES INSTALLED INCORRECTLY - IE CONTROL NO, HO 1340 P2
, Initial report of the sub)ect reportable deficiency +as made to G. R. Klingler, NRC-XE, Region XX, on May 13, 1976,
.and was followed by our June 14'976 'etter, J, E. Gilleland to N. C. Moaeley.
Enclosed is our final report concerning this deficiency, Very truly yours, J, E, Gilleland Assistant Manager of Power Enclosure CC (Enclosure):
Dr. E. Volgenau, Director.~
Office of Inspection and Enforcement U.ST Nuclear Regulatory Commission Uashington, DC 20555 An Equal Opportunity Employer
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ENCLOSURE BROWNS FERRY NUCLEAR PLANT UNIT 3 RPV STABILIZER PLATES INSTALLED INCORRECTLY DDR 232
. FINAL REPORT On May 13, 1976, an initial report was made by telephone to NRC-OIE Region II Inspector Gerald R. Klingler by J.
G. Adair, T.
W. Barkalow, and. S. H. Mi:ndel in accordance with 10CFR50.55(e).
Subsequently, a written interim report on this deficiency was submitted to Norman C.Hoseley~ (NRC-OIE) from J.
E. GillelancL (TVA) on June 14, 1976.
This i.s the fina1 report on DDR 232.
Descri tion of Deficienc The General Zlectri.c Company xeleased a field disposition instruction (FDI) xequesting that an inspection be performed on the reactor pressure vessel (RPV) seismic stabilizers at Browns Ferry Nuclear Plant.
The puxpose of the inspection was to ensure the stabilizers were installed with sufficient clearances to permit relative deflections between the reactor pressure vessel and the shield waU. without binding and, inducing cyclic stresses in the stabilizer".
When performing this inspection it was discovered that part of the stabilizer assembly had been incorrectly i.nstalled. 'aring plates at each end of the assembly had been installed. 90 degrees from their intended orientation, see figure 1, attached.
Cause of Deficienc The stabilizer bearing plate were originally installed rotated 90 degrees from their intended orientati.on.
Safet Im lications The RPV stabilizers are the seismic restraints for the reactor pressure vessel.
The bearing plates that were incorrectly installed are the bearing surfaces between the RPV stabilizer assemblies and. the bumper assemblies amounted on the bi.ologica1 shield wall.
The bearing plate of a stabili.zer assembly directly reacts against a shim plate welded to the bracket.
This shim plate is "U"-shaped to a1low for movement of the stabili er assembly due to thermal expansion of the RPV (see figure 1).
With the bearin'g plate i.nstalled rotated 90 degrees from the correct orientati.on, the amount of bearing surface b~"ween it and the shim plate is reduced..
It is possible that the thermal expansion of the RPV could move the stabilizer assembly so that one edge of the bearing plate is above the cut-out porti.on of the shim plate.
During a seismic event this orientation could lead to the bearing plate "punching theo>>eh" 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.
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Descri tion of Corrective Action General Electri.c. was notified of this defici.ency and recommended that TVA implement one of two fixes:
(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 formal Quality Assurance Program for Browns Ferry.
Since that time a f'orma1 program has been developed and implemented.
This program decreases the probability of incorrect installation of equipment and ~ hold points are identified to verify critical dimensions and orientations.
Since no further stabilizers are to be added to Browns Ferry, this particular deficiency will not recur.
The current formal gA Program significant~ decreases the chance of recurrence of' similar deficiency.
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FIGURE 2
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