ML19345G596

Final Deficiency Rept Re tie-down Studs in Unit 1 Reactor Containment Bldg Polar Crane Rail Sys,Initially Reported on 800320.Floating Clamp Sys Will Hold Polar Crane Rail to Girders

ML19345G596
Person / Time
Site:	South Texas
Issue date:	04/01/1981
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-645, NUDOCS 8104070576
Download: ML19345G596 (7)

Text

.

The Light company n.,_,,, u,e,-,,,<., m 8.,x i- n...,,.,,,. rmomi am, men April 1,1981 ST-HL-AE-645 SFN: V-0530

~gs' n,,

N Mr. Karl Seyfrit g'/ k pl*

,; / [ 'i ',

Director, Region IV j ,,_ ** < i. u ,,

Nuclear Regulatory Commission 0

'W.,C6jg ~ -

611 Ryan Plaza Drive, Suite 1000 Arlir.gton, Texas 76012 $  %$P% 7/

/

Dear Mr. Seyfrit:

South Texas Project U'

Units 1&2 Docket Nos. STN 50-498, STN 50-499 Final Report Concerning the Polar Crane Rail Tie-Down Studs On March 20, 1980, pursuant to 10CFR50.55(e), Houston Lighting & Power Company notified your office of an item concerning tie-down Ituds in the Unit 1 Reactor Containmer.t Building polar crane rail system. The final report on this item has been attached.

i If you have any questions, p1hase contact Mr. Michael E. Powell at (713) 676-8592.

Very truly yours ,

k /

[ G e'a r Executive Vi President 1

i PLW/ par i Attachment

{#oli 3s l ,

810.40705 % ,g

i Houston Lighting & Power Company April 1,1981 cc: J. H. Goldberg ST-HL-AE-645 D. G. Berker SFN: V-0530 Page 2 C. G. Robertson Howard Pyle R. L. Waldrop H. R. Dean D. R. Beeth J. D. Parsons L. K. English J. W. Briskin R. A. Frazar STP RMS H. 5. Phillips (NRC)

J. O. Read (Read-Poland,Inc.)

M. D. Schwarz (Baker &Botts)

R. Gordon Gooch (Baker & Botts)

J. R. Newman (Lowenstein, Newman, Reis, & Axelrad)

Director, Office of Inspection & Enforcement Nuclear Regulatory Commission War.hington, D. C. 20555 Charles Bechhoefer, Esquire M. L. Borchelt President Chairman, Atomic Safety & Licensing Board Central Power & Light Company V. 5. Nuclear Regulatory Commission P. O. Box 2121 Washington, D. C. 20555 Corpus Christi, Texas 78403 R. L. Range Dr. James C. Lamb, III Central Power & Light 313 Woodhaven Road P. O. Box 2121 Chapel Hill, North Carolira 27514

' Corpus Christi, Texas 78403 R. L. Hancock Mr. Ernest E. Hill Director of Electrical Utilities ' Lawrence Livernore Laboratory City of Austin University of California P. 0. Box 1088 P. O. Box 808, L-123 Austin, Texas 78767 Livermore, California 194550 T. H. Muehlenbeck Citizens for Equitable Utilities, Inc.

City of Austin c/o Ms. Peggy Buchorn P. O. Box 1088 Route 1, Box 1684 Austin, Texas 78767 Brazoria, Texas 77422 J. B. Poston Pat Coy Assistant General Manager of Operations Citizens Concerned About Nuclear Power City Public Service Board 5106 Casa Oro San Antonio, Texas 78233 P. O. Box 1771 San Antonio, Texas 78296 A. vonRosenberg Lanny Sinkin City Public Service Board 2207-D, Nueces P. O. Box 1771 Austin, Texas 78705 San Antonio, Texas 78296 Brian E. Berwick, Esquire Bernard M. Bordenick, Esquire Assistant Attorney for the State of Texas Hearing Attorney Office of the Executive Legal Director P.-0. Box 12548. U. S. Nuclear Regulatory Conmission Capitol Station W %hin? g D. C. 20555

FINAL REPORT CONCERNING THE POLAR CRANE RAll TIE-DOWN STUDS

1.

SUMMARY

Ouring a routine construction operation, the operator of the Unit 1 polar crane observed some unusual vibrations. During his inspection of the polar crane rail, he observed that seven of the rail tie-down studs (Figure 1) were loose. The B&R Quality Assurance Department was notified and during a random inspection of approximately fifty studs, twenty-five additional loose, broken, bent, or improperly positioned studs were discovered. A "nold" was subsequently pl8Ced on the operation of the polar crane.

Ine clipt used to hold the rail to the support girder system were neld by threaded stud and nut coanections. Under horizontal loading, a local failure of a few studs could propagate the failure to adjacent studs. In such an event, tne track could lose its alignment, possibly resulting in derailment of the polar crane.

Tne investigation of tnis deficiency resulted in tne followinq conclusions:

(1) Porosity and Idck of complete fusion of the vendor-faoricated stod walds (as discussed in the second interin report) were the primary 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 nave caused the stud failures.

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

II. .DESCalPTION OF laCIDENT A full description of the incident has already teen provided in the first interim report. - A stud test plan and other investigative activities were performed by Pittsburgh - Des Moines Steel. Company (POM). POM concluded tnat several stud welds were inadequate and tnat tne acceptability of all the polar crane rail tie-down studs was questionable. These results of the PDf investigation were presented in the second interim report.

Subsequent to PVM's evaluation of tne cause of tie-down stud failure, drown d Root performed an independent evaluation of the as-built conditions of tne polar crane rail systen and tne crane operation to dettraine if any other causes contributed to the stud failuras. In the third interim report, several preliminary observations restiting from the Brown & Root investigation were 1-

stated. Inis investigation nas been completed and the Brown &

Root evaluation of the as-built conditions indicated the following:

(1) Center-to-center distances between studs ranged from 8 1/8" to 91/4", rather than measuring 8 3/4" as depicted on the design drawings. Inis contributed to the misfit of the rail nolding system, and thereby, induced higher stresses in the stud welds.

(2) Tne as-built curvature of rails deviated from the design curvature. Inis increased the stresses in the stud welds and reduced tne expansion gap at rail joints.

(3) A: many splice locations, the splice bolts and plates interfered with clip plates and studs. At sone locations, tne studs and clip plates were damaged by splice bolts and splice plates, respectivelg. Rail0splice be loose between Azimutn 5 to 20 bolts were found to

, 170 to 185 , and 95 to 110 .

(4) Generally, the clip plates were in contact with the rail as required by' design. However, between Azimutn 35 to 50 , 65 to 30 ,-and 800 to 95 , some plates were not in contact witn the rail.

The design required the clip plates to be sheared off 3/8" at splice locations only. However, all 624 clip plates were sneared 3/8". This reduced the design contact area between rail'and clio plate.

(5) Tnere was an excessive gap between the rail and tne filler plate wnich varied from 0" to 1".

(6) ine rails rotated as a rigid body approximately 1".

(7) Some' bolts connecting tne crane girder top flange to the lateral support were found to be loose.

111. CORRECTIVE ACTION l

l As stated in the first interim report, a "nold" was placed on tne  %

! operations of the polar crane as the immediate action taken after i

discovery of tne failed tie-down studs. This "nold" is still in effect and will not be lifted until the. tie-down system is repaired. The repairs will be conducted as follows:

(1) A _ floating clamp system will be used for holding the polar crane rails to tne girders.

J(2) Existing studs will be removed.

n 2

~

(3) Ratner tnan using studs in tne rail tie-down system, shop-welded filler plate and clio plate assemblies will be field welded to tne top flange of crane girders. This will

. provide nigner strength and will avoid the installation proolens associated witn stud welding. This system is descriDed in Figure 2.

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

(b) Splice locations and details will be resolved such that interference of bolts and clamps is avoided.

(b) All bolts in tna Crane rail, girder, and bracket system will be cnecked end retigntened or replaced as necessary.

Brown & Root nas issued drawings to PDM which define repair details and installation procedures. PDM has prepared detailed repair and installation procadures. Due to revision of the construction schedule, repairs to the polar crane rail systen are seneduled to be completed by October, 1981.

IV. RECURR2HCE CUNTROL For recurrence control, Brown & Root nes airected PDM to include tne following steps in tne welding procedures:

(1). Requalify welding procedure and welders or site using tne same equipment set-up that will be used durin5 production.

(2) Increase surveillance and inspection for each production.

A no-load test will-be conducted wnicn will serve to verify the operability of the crane. This test is not intended to verify tne ddequdCy of tne repair and, therefore, disposition of tne non-conforming tie-down studs is not contingent upon conoletion of tne no-load test.

Since the design nas been changed to eliminate the use of studs, tnis item will not recur.

V. SAFETY EVALUATION.

Tne circular polar crane ' rail track is designed to carry the polar crane wnen it is under maximum design loading. The rail is

.attacned to tne support girder system witn a floating clip system.

Tnese clips were neld oy tnreaded stud and nut connections. A

'sketen of tnis systen is provided as figure ~1. Horizontal loads imposed on tne oridge of tne crane would be transmitted first to tne rail track, tnen to tne support girders througn the clip. stud systen. Under sucn loading, a local failure of a few studs

~

potentially~ could have propagated the failure-to adjacent. studs.

In sucn.an event, tne track mignt nave lost its alignnent, possioly resulting in derailment- of tne polar crane.

t 3'

- i t

I l

1" p X 2 3/4" (A.W.)

THREADED WELD STUD (TYP.)

l 1"p SELF-LOCK NUT-(TYP.)*

CRANE RAll 146-0156 (TYP.)

E- Q' '

M l ,3 _ 010 1331 (TYP.)

/

/////////////>

l 3 s CRANE GIRDER , k 'ALL NUTS SNUG-TIGHT

-)_ -)_

I  ;

TYPICAL SECTION THRU CRANE RAll l FIGURE 1 l I

l l

1 l l I. - ~ . , . -,

• % 175 i Crane Rail Top of Rail

. -0" 120 Must Be Maintained During

[

[ Fabrication & Erection Clip Plates 3/4" X 4" X O'-6" ( A-36)

' /g! -

~/1 \ T.O. Girder El. 140'-6" g y,  ; j,gy , n f '

/ /

/ /

l' J o Filler Plates 3

tiet Plates % - " X 3 " X O ' -8" ( A- 36) t i y

r s

• 1"

- 3" . 2 3/4". -

Girder 4. Sym. Abt.1 Rail

' ' A e r v.NsssNN n/ //////,

-- U / /m/// $

- 0

+4 skNNN /! 13 y s "

s 9l le r

/ .

g ) ( / lh

/

)N [

% Clip & Filler

+/

l l IMj r Plates s

N Ed

/ l'a f

/ ' "

m N s L'l l'> /

y Q

N d NNW O /

/

[/ h 13 V///N 6

7 f,

=

q l hTNN N'NN ///// '//

/ &

y

/p g K T.O. Girder 1

q Crane Rail l " Filler Plates 3/4" Clip Plates l

FIGURE 2 l

l

. ,. . . .-. . .. .._.. -. -. . ..- . . -. .- .. - - - -