ML19338D688
| ML19338D688 | |
| Person / Time | |
|---|---|
| Site: | South Texas  |
| Issue date: | 09/15/1980 |
| From: | Oprea G HOUSTON LIGHTING & POWER CO. |
| To: | |
| References | |
| 10CFR-050.55E, 10CFR-50.55E, ST-HL-AE-535, NUDOCS 8009230658 | |
| Download: ML19338D688 (6) | |
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c The Light Company liouston Lighting & Power P.O. Box 1700 }{ouston. Texas 77001 (713)228-9211 September 15, 1980 ST-HL-AE-535 SFN: V-0530 Mr. Karl Seyfrit Director, Region IV Nuclear Regulatory Comission 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 Company notified your office of a reportable deficiency concerning broken tie-down studs in the Reactor Containment Building Unit 1 polar crane rail system. The fourth report 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, G. W. Oprea, Jr.
Executive Vice President PLW/o.ib Attachment (3o19 5ifi 800923o 653 3
S;ptembsr 15, 1980 ST-HL-AE-535 l
SFN: V-0530 Houston Ughting & Power Company Page 2 cc:
D. G. Barker C. L. McNeen H. R. Dean R. L. Beeth J. D. Parsons A. J. Granger R. A. Frazar (Baker &Botts'f M. D. Scwharz (Baker & Botts R. Gordon Gooch J. R. Newnan (Lowenstein, Newman, Reis, Axelrad & Toll)
Director, Office of Inspection & Enforcement Nuclear Regulatory Consnission Washington, D. C. 20555
- M. L. Borchelt Executive Vice Prasident Cer. tral Power & Light Company
.P. O. Box 2121 Corpus Christi, Texas 78403 R. L. Range Central Power & Light Company P. O. Box 2121 Ccrpus Christi, Texas 78403 R. L. Hancock Director of Electrical Utilities City of Austin i
P. O. Box 1088 Austin, Texas 78767 T. H. Muehlenbeck City of Austin en P. O. Box 1088 Austin, Texar 78767 J. B. Poston Assistan General Manager of Operations City Public Service Board P. 0. Box 1771 San Antonio, Texas 78296 A. vonRosenberg City Public Service Board P. O. Box 1771 San Antonio,. Texas 78296
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ST-HL-AE-535
- Houston Lighting & Power Coinpany SFN: V-0530
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Page 3 Clurles Bechoefer, Esquire
. Chairman, Atomic. Safety & Licensing Board U.
S.~ Nuclear Regulatory Comission Washington, D. 1:. 20555 Dr. James C. Lamb,.III 313 Woodhaven Road Chapel Hill, North Carolina 27514 Dr. Omneth A. Luebke Atomic Safety & _ Licensing. Commission U. S. Nuclear Regulatory Commission Washington, D. C. 20555 Steven A. Sinkin, Esquire
~ l 116 Villita Street San Antonio, Texas 78205
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Citizens 'for' Equitable Utilities c/o Ms. Peggy Buchorn Route 1, Box 432 Brazoria, Texas 77422
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Richard W. Lowerre, Esquire Assistant Attorney General for the State of Texas P. O. Box 12548 Capitol Station.
Austin,
- xas 78711
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Henry J.~ McGurren, Esquire Hearing Attorney Office of the Executive Legal Director U. S. Nuclear Regulatory Commission Washington, D. C. 20555 1
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Septemb3r 15, '1980 ST-HL-AE-535 SFN: V-0530
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Fourth Interim Report Polar Crane Rail Tic-Down Studs _
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i Description of Incident _
i port A full description of the incident is provided in the first inter m reA st e
l Company (PDM), the (ST-HL-AE-449) dated April 16, 1980.
activities were performed by Pittsburgh - Des Moines SteePDM concluded tha d
inadequate and that the acceptability of all the polar crane containment liner contractor.
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is questionable.
1 23, 1980.
second interim report (ST-HL-AE-484) of June
', l Subsequent to PDM's evaluaticn of the cause of tie-down stud failure, ditions of Brown 4 Root performed an independent evaluation of the as-built con j
determine if any other the polar crane rail system and the crane operation toIn the August 1, 1980, third interim causes contributed to the stud failures.
i from the report (ST-HL-AE-503), several preliminary observations result ngThis investig Brown 6 Root investigation were stated.and the Brown G Root evalu dicated the following:
(1) Center-to-center distances between studs range from 8 1/8" to The 91/4" against 8 3/4" as depicted on the design drawings.
incorrect installation of studs (i.e. center-to-cente induced higher stresses in the stud welds.
(2) The as-built curvature of rails deviated from the designTh welds and reduced the required expansion gap at rail joints.
curvature.
(3) At many splice locations, the splice bolts and plates interfereAt s with clip plates and studs.
plates are damaged by splice bolts and splice pl 170* to 185*, and 95* to 110*.
(4) Generally, the clip plates are in contact with the rail as required However, between A:imuth 35* to 50*, 65* to 80*, and by design.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 However, all 624 clip plates were sheared 3/8".
This reduced the design contact area between rail and clip plate locations only.
which is essential for proper fastening of the rail.
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i' SIptemb;r 15, 1980 ST-HL-AE-535 SFN: V-0530 Page 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 complet'e fusion of stud welds (as discussed in the second interim report) are the causes of the stud 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 i
stud failures.
(3) The stud failures were not caused by inadequate design.
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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 be lifted until the deficient condition is repaired.
Resolution of this problem requires the elimination of the use of studs and that other observed deviations be corrected. The repairs will be conducted as follows:
(1) The floating clamp system will be used for holding the polar crane rails to the girders.
_(2) Existing studs will be removed.
(3) Shop-welded filler plate and clip p'. ate 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' SFN: V-0530 Page 6.
(5) Sp1' ice ' locations arid details will be resolved such.that inter-fer'ence of bolts and clamps is avoided.
(6) All bolts in the crane rail, girder, and bracket system will be checked and retightened or replaced as necessary.
Brown' S Root has issued drawings to PDM which define repair details and installation procedures. PDM is currently preparing detailed repair and installation procedures.
Recurrence Control Measures to prevent a recurrence of this deficiency will be addressed in the next report which will be submitted to the Region IV office of the NRC by November.28, 1980.
I Safety Analysis No detailed safety evaluation was performed on the deficient tie-down
- stud condition. However, due to the number of failed studs, loss of adequate i
Ioad bearing capability of the rail clip system was assumed.
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