ML20085G504

Seventh Interim Deficiency Rept Re Potential Design Deficiency in Valve Yoke to Motor Mount Weld.Initially Reported on 740514.SWRI Will Perform Tests to Locate Source of Vibrations

ML20085G504
Person / Time
Site:	Browns Ferry
Issue date:	03/17/1975
From:	Gilleland J TENNESSEE VALLEY AUTHORITY
To:	Knuth D NRC OFFICE OF INSPECTION & ENFORCEMENT (IE)
Shared Package
ML20085G493	List: ML20085G489 ML20085G504 ML20085G551 ML20085G575
References
NUDOCS 8308290112
Download: ML20085G504 (3)

Text

6 f b li, pLuilo9 dt Q 'o 9 ENNESSEE VALLEY AUTHORITY V

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E hy M 2 CH ATTANOOGA. TENN ESSEE 37401 b-

'D 6-198 Marca 17, 1975 Mr. Donald F. Knuth. Director Office of Inspection and Enforcement U.S. Nuclear Regulatory Commission Washington, DC 20555

Dear Mr. Knuth:

BROWNS FERRY NUCLEAR PLANT UNITS 2 AND 3 - POTENTIAL DESIGN DEFICIENCY IN VALVE YOKE TO MOTOR MOUNT WELD Initial report of the subject potential deficiency was made on May 14, 1974, and was followed by our June 14, July 15, August 12, September 13, 1974, January 15, 1975, and our March 3,1975, letters, J. E. Gilleland to Donald F. Knuth.

Because the yoke to motor base welds of FCV-74-58 in unit 1 failed, similar valves (FCV's 74-58 and 74-72) in units -

l 2 and 3 may be subject to the same type of failure.

. The enclosed seventh interim report discusses a vibration

. problem which we believe is the cause of this and perhaps certain

. . other related problems at Browns Ferry Nuclear Plant. It also provides you with additional information which we have to date

' and the schedule for further testing and for submittal of a draft of the final report.

Very truly yours,

)'  ?  ?

' '/ W J. E. Gilleland Assistant Manager of Power Enclosure CC (Enclosure):

Mr. Norman C. Moseley, Director Office of Inspection and Enforcement U.S. Nuclear Regulatory Commission Region II - Suite 818 230 Peachtree Street, NW.

Atlanta, Georgia 30303 8308290112 761122 j d c2 g <je 26o PDR ADOCK 05000260 PDR S

An Equal Opportunity Employer fo /17 .

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I ENCLOSURE F. . ~

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BROWNS FERRY NUCLEAR PLANT UNITS 1, 2, AND 3 -

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FAILURE OF THE WELD BEIVEEN THE YOKE AND MOTOR MOUNTING PLATE FOR SIi o A FLOW CONTROL VALVES (FCV'S) 74-58 AND 74-72 j E:. 3 DDN NO. 191 3).h.%

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SEVENTH INTERIM REPORT

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On May 14, 1974, an initial report regarding the subject deficiency was made Q-l;.

by telecon to W. S. Little, AEC-DRO Inspector, Region 11. The report was made j by L. D. Weber and J. A. Raulston in compliance with paragraph 50.55(e) of Cl:

10CFR50. nere have been six interim reports previous to this report. Wese .fff were dated June 14, 1974, July 15, 1974, August 12, 1974, September 13, 1974, g;p January 15, 1975, and March 3,1975. +

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- In our sixth interim report concerning the failure of the weld between the %p .:.% *

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yoke and motor mounting plate and a torus spray valve (74-58) in the RHR Nd i y system, we mentioned a Southwest Research Institute (SWRI) technical report  ? Q.

d that is to be submitted in the near future. B is report will discuss a g .[j;j vibration problem which we believe is the cause of this and perhaps certain other ..%

related problems at 3rowns Ferry. h is letter is to inform you of additional [g[

information we have to date and to provide the schedule for further testing and je.,

for a draft of the final report. Gn.{

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x .u The initial indication of pessible vibrational problems in Browns Ferry q. ;.Q;.3, 4 Unit I was the failure of Limitorque mounting bolts on operators of two RHR jQ ; _ .

valves (74-72 and 74-58). We AEC was informed of this by DDN 144 on P...<Q June 30, 1973. Le failure originally was attributed to the increased weight ppQ of replacement operators on those valves. A second failure in Unit 1 occurred J1 s4 ) .

on June 12, 1974, when the veld between the yoke and the motor mounting plate Yn~

failed on valve 74-58. This was reported by Abnormal Occurrence BFAO-50-259/7428W i e and was followed by DDN 191 on May 14, 1974. At that time TVA considered that 9p these failures might be causedt by pipe vibrations. @h MQ TVA retained the services of Southwest Research Institute to perform tests to i locate the source of these vibrations. We have recently received the results @? [$.

D $ 4, of SWRI's initial tests, and we now believe that several other Abnormal $7 Occurrences may be attributed to pipe vibrations. We initial SWRI tests $p were conducted in November and December 1974, and TVA now plans for additional M.~ 2 J .L tests and a draf t of the final report to be completed by the end of April.

SWRI has indiciated that they believe the vibrations in the RHR system are h@

O. . . . s being caused by an excessive pressure drop across the flow control valve near P. . ~ .

the discharge into the suppression chamber. The low downstream pressure $@C condition is also a contributing factor. At the present time TVA is planning to modify Unit 3 to test various possible solutions proposed by SWRI. In the . .

meantime, certain attachments to Units 1 and 2 have been temporarily modified by the addition of stiffners so that the vibrations will not endanger the safe operation of these units until a permanent solution can be obtained.

When tests on Unit 3 are completed and we have received, reviewed, and approved ~

the final report from SWRI, TVA will forward the report to the NRC. TVA plans  :

to reference this report in support of DDN 191 and in the future when describing

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any permanent modification to the plant that might be recommended by this study.