ML19347B490

Fourth Interim Deficiency Rept Re Broken tie-down Studs in Containment Bldg Unit 1 Polar Crain Rail Sys.Caused by Incomplete Fusion of Stud Welds & Deviations from Design. Studs to Be Removed,Eliminated from Design & Replaced

ML19347B490
Person / Time
Site:	South Texas
Issue date:	09/15/1980
From:	Oprea G HOUSTON LIGHTING & POWER CO.
To:	Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
References
10CFR-050.55E, 10CFR-50.55E, ST-HL-AE-535, NUDOCS 8010150162
Download: ML19347B490 (6)

Text

77L The Light Company a,-> uomim- m> moo s<-a- nouu)eusoun Seotember 15, 1980 ST-HL-AE-535 SFN: V-0530 Mr. Karl Seyfrit Director, Region IV Nuclear Regulatory Commission 611 Ryan Plaza Drive, Suite 1000 Arlington, Texas 76012

Dear Mr. Seyfrit:

South Texas Project Units 1&2 Docket Nos. STN 50-498, STN 50-499 Fourth Interim Report on the Reportable Deficiency Concerning Polar Crane Rail Tie-Down Studs On March 20, 1980, pursuant to 10CFR50.55(e), Houston Lighting & Power Comoany notified your office of a reportable deficiency concerning broken tie-down studs in tha Reactor Containment Building Unit 1 polar crane rail system. The fourth recort on the status of the investigation of this defi-ciency has been attached to this letter. The next report on this concern will be submitted to your office by November 28, 1980.

If there are any questions, please contact Mr. L. R. Jacobi at (713) 481-7217.

Very truly yours ,

l G. U. Oprea, Jr.

Executive Vice President PLW/ojb Attachment 8 01015 0/GP- 5  ;

September 15, 1980

, ST-HL-AE-535 SFN: V-0530 Houston Ughting & Power Company Page 2 e

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, cc: D. G. Barker 4

C. L. McNeese H. R. Dean R. L. Beeth j J. D. Parsons

. A. J. Granger i R. A. Frazar

M. D. Scwharz (Baker & Botts) j R. Gordon Gooch (Baker & Botts) 1 J. R. Newman (Lewenstein, Newman, Reis, Axelrad & Toll)

Director, Office o.f Inspection & Enforcement Nuclear Regulatory Commission Washington, D. C. 20555

M. L. Borchelt Executive Vice President i Central Power & Light Company

P. O. Box 2121 Ccrpus Christi, Texas 78403

R. L. Range l Central Power & Light Company P. O. Box 2121 i

Corpus Christi, Texas 78403 i

R. L. Hancock Director of Electrical Utilities City of Austin P. O. Box 1088 Austin, Texas 78767 T. H. Muehlenbeck City of Austin I P. O. Box 1088 l Austin, Texas 78767 J. B. Poston j Assistan General Manager of Ocerations  !'

City Public Service Board j P. O. Box 1771 San Antonio, Texas 78296 A. vonRosenberg City Public Service Board P. O. Box 1771 San Antonio, Texas 78296 i

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September 15, 1980 ST-HL-AE-535 Houston Lighting & Power Company SFN: V-0530 Page 3 t

I Charles Bechoefer, Esquire

! Chairman, Atomic Safety & Licensing Board

U. S. Nuclear Regulatory Commission j Washington, D. C. 20555 Dr. James C. Lamb, III J13 Woodhaven Road Chapel Hill, North Carolina 27514 Dr. Emmeth A. Luebke ,

Atomic Safety & Licensing Commission

U. S. Nuclear Regulatory Commission Washington, D. C. 20555 Steven A. Sinkin, Esquire 116 Villita Street San Antonio, Texas 78205 Citizens for Equitable Utilities

c/o Ms. Peggy Buchorn i Route 1, Box 432 Brazoria, Texas 77422 Richard W. Lowerre, Esquire

l. Assistant Attorney General for the State of Texas P. O. Box 12548 Capitol Station i Austin, Texas 78711 Henry J. McGurren, Esquire j Hearing Attorney Office of the Executive Legal Director U. S. Nuclear Regulatory Commission i Washington, D. C. 20555 4

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September 15, 1980

. ST-HL- AE-5 35 SFN: V-0530 Page 4 l

Fourth Interim Report Polar Crane Rail Tie-Down Studs Description of Incident A full description of the incideat is provided in the first interim report (ST-HL-AE-449) dated April 16, 1980. A stud test plan and other investigative activities were performed by Pittsburgh - Des Moines Steel Company (PDM), the containment liner contractor. PDM concluded that several stud welds wert inadequate and that the acceptability of all the polar crane rail tie-down studs is questionable. These results of the PDM investigation were presented in the second interim report (ST-HL- AE-484) of June 23, 1980.

Subsequent to PDM's evaluation of the cause of tie-down stud failure, Brown S Root performed an independent evaluation of the as-built conditions of the polar crane rail system and the crane operation to determine if any other causes contributed to the stud failures. In the August 1, 1980, third interim report (ST-HL-AE-503), several preliminary observations resulting from the ,

Brown S Root investigation were stated. This investigation has been completed and the Brown S Root evaluation of the as-built conditions indicated the following:

(1) Center-to-center distances between studs range from 8 1/S" to 9 1/4"_against S 3/4" as depicted on the design drawings. The incorrect installation of studs (i.e. center-to-center distances) contributed to the misfit of the rail holding system, and thereby, induced higher stresses in the stud welds.

(2) The as-built curvature of rails deviated from the design curva ture. This deviation increased the stresses in the stud welds and reduced the required expansion gap at rail joints.

(3) At many splice locations, the splice bolts and plates interfere with clip plates and studs. At some locations, the studs and clip

. plates are damaged by splice bolts and splice plates, respectively.

i Rail splice bolts were found to be loose between A:imuth 5* to 20*,

i 170" to 185* , and 95* to 110* .

(4) Generally, the clip plates are in contact with the rail as required by design. However, between A:imuth 35* to 30 , 65* to 30 , and

, 80* to 95., some plates are not in contact with the rail.

The design required the clip plates to be sheared off 3/8" at splice locations only. However, all 624 clip plates were sheared 3/8".

This reduced the design contact area between rail and clip plate which is essential for proper fastening of the rail.

September 15, 1980 ST-HL-AE-535 SFN: V-0530 Page 5 (5) The as-built drawings indicate a considerable gap between the rail and the filler plate. The gap measured between rail and filler plate varies from 0" to 1".

(6) The rails rotated as a rigid body approximately 1" (7) Some bolts connecting the crane girder top flange to the lateral support were found to be loose.

Conclusions The investigation of this deficiency resulted in the following conclu-sions:

(1) Porosity and lack of complete fusion of stud welds (as discussed in the second interim report) are the causes of the 3 failures.

(2) Deviations from the design, as observed in the as-built conditions, increased the stresses in the studs. However, the effects of these deviations were not enough by themselves to have caused the stud failures.

(3) The stud failures were not caused by inadequate design.

Corrective Action As stated in the first interim report, a " hold" was placed on the operations of the polar crane as the immediate action taken after discovery of the failed tie-down studs. This " hold" is still in effect and will not I be lifted until the deficient condition is repaired. Resolution of this l prob 1 m requires the elimination of the use of studs and that other observed J deviations be corrected. The repairs will be conducted as follows: 1 (1) The floating clamp system will be used for holding the polar crane rails to the girders. l l

(2) Existing studs will be removed. l (3) Shop-welded filler plate and clip plat s assemblies will be field welded to the top flange of crane girders. This system eliminates the use of studs. This will provide higher strength and will avoid the installation problems associated with stud welding.

(4) Curvature of all the rails will be corrected to conform to the design curvature.

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- ST-HL-AE-535 j- SFN: V-0530 j Page 6 i

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l (5) Splice locations and details will be resolved such that inter-i ference of bolts and clamps is avoided.

(6) All bolts in the crane rail, girder, and bracket system will be j checked and retightened or replaced as necessary.

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{ Brown & Root has issued drawir;s to PDM which define repair details and

] installation procedures. PDM is currently preparing detailed repair and

, installation procedures.

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t j Recurrence Control i

1 Measures to prevent a recurrence of this deficiency will be addressed 4 in the next report which will be submitted to the Region IV office.of the NRC l

by November 28, 1980.

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Safety Analysis No detailed safety evaluation was performed on the deft -ient tie-down stud condition. However, due to the number of failed studs, loss of adequate j load bearing capability of the rail clip system was assumed.

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