ML18025A201

Definitive Report of Deficiencies in Fabricated Structural Steel Members (Box Column Supports)

ML18025A201
Person / Time
Site:	Susquehanna
Issue date:	08/29/1975
From:	Curtis N Pennsylvania Power & Light Co
To:	O'Reilly J NRC Region 1
References
840-4, ER 100450, ER 100508, PLA-82
Download: ML18025A201 (49)

Text

y1

,,tg TWO HORTH NINTH STREET, ALLENTOWN, PA. 18101 PHONE: (21$ ) 821-5151 i

August 29, 1975 Mr. J. P. O'Beilly.

Director Region I U.S. Nuclear Regulatory Comm ssion 931 Park Avenue

'King of Prussia, Penrsylvania lo406 SUSQUEPQG1A STEALS ELIECTBIC STATION DEFINITIVE REPORT 0" DEFICIENCIES IN BOX COLUM'UPPORTS DOCKET NOS.: 50-387 and 50-388 LICENSE NOS.: CPPB-101 and CPPR-102 ERs 100450/100508 FILE 840-4 PLA-82

~

Dear Mr. O'Reilly:

This letter trarsmits the subject report whicn supplements PLA-74, dated July 25, 15'75 and, s interded. to complete PPSL's responsibility in reporting the deiiciencies in fabricated structural steel me hers (Box Co"um Supports) which had been located in position for 'nstalla-tion.in Susquehanna Unit 1 8 2 .structures.

As inaicated in the attached report, the de'cision has been made to reaesign the struc ures and to replace all eight units, including those found not to contain aefects. 'he replacement units employ material changes and weld joint configurations which wiII faci'tate fabrication ana should preclude the recurrence of the lamellar tearing phenom'enon experienced in original'nits.

In addition to those corrective measures identified in PLA-74 and, the attached Bechtel detailed report, PPKL has concurred in .ar. increase in Bechtel surveillance activ'ties at the vendor's fabrication facility.

(Bethlehem Steel Company's Pottstown, PA plant).

Additionally, rece'ving and preinstallation activities at the SSES site will'e aligned to perform a fina'isLLal examination oefore the new units are permanently corn@i.tted to the plant struc ure.

Sle await your advice .should you have any further auestions or concerns on this matter.

kwCurtis N. 7i.

~~

Very 'truly yours Vice Presi'aent - "ngineering 0 Construction 4

APS b 87)-../-

PENNSYLVANIA POWER S, LIGHT COMPANY

Agan

'f

) "

~ ~

", j~(ply,t ~

ll t i >. ~ I 'a

/I V

<D

~ ~

TWO NORTH NINTH STREET, ALLENTOWN~ PA. 18101 PHONE~ t215) 821 5151 Mr. J. P. O'Reilly Pm-82 Pa e 2 Sworn to and subscribed before me this l975.

Notary Public My commission expires:

cc: Mr. Donald F. Knuth Director Office of Inspection and Enforcement U.S.. Nuclear Regulatory Commission Washington, D.C. 20555

~ft

%,v ~ t,~ p, j>>

4

~ y II t Qt 4

II 1

a C s ~

~ u

REPORT ON DEFICIENCY

'IN BOX COLUMN SUPPORTS FOR THE SUSQUEHANNA NUCLEAR PLANT Prepared by G. Shah Checked by J. N. Mu'ay Approved by M. J. Lidl 9ECHTE L'ONE R CORPORATION'an Francisco California

~

4

'f ~

bb

~

~ 0 TABLE OF CONTENTS 1.0 Introduction 2.0 Description of Deficiency 2.1 Box Column Base Description 2.2 Description of First Crack 2.3 Visual and NDE Inspection 3.0 Investigation 3.1 NDE -.Shop 3.2 NDE - Field 3.3 Analytical Investigations 3.4 =

Lamellar Tearing 3.5 Conclusion 4.0 Remedial Measures Appendices:

A. Design Criteria B. 5DE Reports C. Design Considerations Figures 1 Original Column-Base Detail 2 Redesigned Column-Base Detail

s I P

+wI

)'I

~ )

4 ~

I 1 a

0 1.0 introduction This report is prepared in accordance with the requirements described in Title 10, Code of Federal Regulations, Part 50, Section 50.55(e).

Hairline aracks were found in major weldments at the bas'e of box columns. The significance of'these linear 'indications has been evaluated and it is concluded that the box column bases which were found to be defective, represent a,deficiency in construction (fabrication) which will require extensive repair or rede-sign and replacement, and which, were the defi-ciencies to have remained uncorrecrted, could have an adverse effect on the structure in the performance of the intended safety function.

2.0 Description of Deficiency 2.1 Box Column Base Description Four (4) box colums are provided in the Reactor Building of each unit.

These box columns support the con-crete girders which form the walls of the spent fuel pool and dryer and separator pool. They also support the intermediate floors. Figure 1 shows the details of the box column and its base.

As shown in Figure 1 the column is 3'-0" square and made of four steel plates welded together with partial penetration welds. Top.of the column "is rigidly connected to the steel box girder"which is provided below the fuel pool girders. con-'rete At the bottom, stiffeners and base plates are welded to the column to transmit the design loads. As shown in Figure 1, the base plate stiffeners are welded to the column with full penetration butt welds, while fillet weld is used to con-nect them with the base plate. Nominal fillet weld is provided between the base plate and the column. Zn order to re-duce the base plate thickness, a system (B-2la)

"l ~

V g

~ Vl V

Page 2 of main and secondary stiffener is provided.

The design criteria for box column base is discussed in Appendix A of this. report.

2.2 Description of First Crack During the course of random visual inspec-tion of installed structures of Unit 1, PL's Quality Assurance engineers noted the appearance of welds'n four {4) box column bases and questioned their compliance with ANS Dl.l. PL Deficiency Report No. 0022 was issued to document the condition.

Subsequently, closer inspection revealed the existence of a visible hairline crack at the toe of,a full penetration weld between a stif-fener and the box column.S-27.5. Bechtel NCR (Nonconformance Report) 376 was issued request-ing further non-destructive examination. It was.decided to carry out the ultrasonic exami-nation (UT) to establish the extent of the crack.

The UT examination was carried out by Bechtel's NDE Subcontractor, Peabody Testing Company. The results of UT examination revealed that the crack extended into the base metal. The crack was ap-proximately 37" long and located at approximately 1-3/8" from the face of the column. Appendix B shows the details of UT examination.

2.3 Visual and NDE Inspection Further visual examinations of welds revealed a similar subject condition on box column Support

~

Q-36. The UT examination revealed a crack varied from surface to l-l/4" depth and was approximately 27" long. NCR 377 documented the defective condi-tion of column base Q-36.

P Since identical design details were used on all box columns, it was decided to perform UT examina-tion on all remaining seven columns. Bethlehem Steel Corporation, Pottstown Plant, carried out the task. The UT examination was carried out. on all the columns in the field.

II g ~

s ~ ~

II a

Page 3- -

0 Four additional column bases Q-22, Q-36, S-30.5 .

~

and S-36 were found to have additional indica-tions (interpreted subsequently as lamellar tear-ing) in the base material of the box column. Two additional NCRs 401 and 402 were issued to do-cument these defects.

Appendix B describes the details .of UT. NDE of the columns indicated that three (3) columns did not show any'efects. Before these defects were observed, small cranes had been installed on top of erected columns for lifting reinforcing bars.

The loads applied to these columns through the cranes are considerably smaller than the inservice column loads.

3. 0 Investigations 3.1 NDE Shop The full penetration butt welds joining the

'tiffe>>ers to'the box columns were 100% UT examined in the shop of Bethlehem Steel Corporation prior to shipment. All fillet-welds were 100% examined. by Hagnetic Particle Testing (HT). The column bases were also post weld heat treated as specified, after fabrica-tion in the shop.

3.2 NDE Field The UT examination that was performed in the field has been described in detail under Sec-tion 2.3 of this report.

The limited amount of magnetic particle (HT) testing was also performed-for fillet welds joining the stiffeners to the base plates.

MT examination was performed since analytical investigations described in Section 3.3 below indicated if one of the two welds (; tiffener to box column or stiffener to base jlate) is adequate, the load can be transferred satis-factorily.

3 ' Analytical Investigations if N

Analytical investigation was made to check the design loads could be adequately transfer-red to the foundation from the column even 4

It 4

~

~ 4

' Vt tV 4' V 41

~ ~

Page 4 with the observed linear indications in the base metal. The following are the

.analytical considerations:

. (a) Column base will be subjected to axial loads only..

(b) The column stiffeners where linear indications were found, would be subjected to compressive and shear stresses from the base plate loading.

(c) Compressive stresses can be ade-quately transferred through the cracks.

(d) Xt is questionable. if shear stres-ses can be adequately transferred from stiffener to the column un-der the existing condition. However,

'the base plate along with stiffeners would be able to transfer shear forces.

From the above mentioned analytical considera-tions, it was concluded that the box column base would adequately transfer the load with the existing linear indications provided these indications would not propagate.

3.4 Lamellar Tearing Bechtel's metallurgical staff was further consulted 1

to identify-the observed linear indications and to determine if 'hese indications would propagate through the application of external design loads.

Metallurgical staff indicated that the observed de-fects were classical examples of lamellar tearings.

These are caused by the shrinkage of we. 9 metal which induced stresses in the base meta,'n a direc-tion transverse to the material "grain"." Lamellar tearing phenomenon has received attention in the industry fairly recently, and therefore, several as-pects of this phenomenon are not yet fully defined and understood.

Further evaluation by metallurgists from Bechtel and Bethlehem Steel Corporation indicated that (B-21a)

V "J

1I V

< age 5 most probably the lamellar tears would not pro-pagate any further since the stress due to weld shrinkage is relieved due to lamellar tears. This conclusion is again augmented by the fact that di-rect tensile load will not be applied to the af-fected area.

3.5 Conclusion Since it is not possible to establish conclusively the lamellar tears will not propagate under 'hat service loads, we have to conclude that the obs'erved defects are reportable. lf lamellar tears 'would have propagated extensively, then this deficiency might have adversely affected the structural integ-rity of the plant.

4.0 Remedial Measures Even though on a d

purely theoretical basis, monstrated that the column bases would function it could be it ade-'mo quately, was considered prudent to repair or rejec t the existing column bases. Because of the indeterminate nature of the lamellar tearing phenomenon and the in-it

~

herent risks in attempting repairs, was decided to replace all eight (8) column support bases with new sup-ports having a different design detail.

The new design of the column base considerably reduces the poossibility of lamellar tears. Appendix C of this report out-lines the details of redesign of the base connection. Figure 2 shows the revised column base details.

The rationale of redesigned base can be summarized as follows:

detail for the revised detail i.", such 1

(a) The weld that the possibility of lamellar tears have been greatly reduced.

(b) Neither base plate nor box column is subjected

'to thorough thickness loading during application of design loads.

(c) .The redesigned base of box column will adequately transfer the design lo~g3s during service life of the plant.

(B-21a)

APPENDIX A DESIGN CRITERIA

s q ~ a ~ e t ~

~

~ g a

l .0 ,Loads Box columns are designed to support following loads:

(a) During construction Box colum'upports the crane load, load of intermediate foaming and of the wet concrete of the fuel pool concrete girders.

(b) During plant operation.

Box column is designed to transfer loads of intermediate floors and fuel pool concrete girders.

2.0 Loading Combinations and Allowable Stresses:

The detailed design criteria is outlined in Appendix "C" "Structural Design and Loading Criteria" of Preliminary Safety Analysis Report (B-21a)

APPENDIX B ULTRASONIC EXAHINATINONS

w u,p'b h y 1II, 'I y H'

'i

't r

J ~

~ ~ ~

4

~ r

s p

a ~s n =sas se

'4t

~

~

~ ~

~ ~ '

t I

P

/ P 0

C'

'e

~

I 0

1 h

E 1

f

~ 4, lip, l~

~1 k ylh N

II N

~ ~

~

1

~ I I I 4 r'

~

4 1 ~ N 4>>

~ 4

~ 4 4

4 a

0 4I 4 ) 1 }'8 l.

r ~ '

I I 4 II, 4

~ 4' 4

C ~ 1 4"

~ N

~ ~

P a ~

4 a

4 a <<~

4 4 I 4 a Na I

~ 4 4

~ 4 Na I ~~

~

II N,N Tl' 4 44

%4 4 I 'I 4 I

'a ger

,a a

44~a ~ 'T.~~ a>,4>> ~

rarN' ~ ~

4 la ~

~" I'

~4 ~ I ~

C g

4 I. ~ g l ~

~ ~

0

1 4 4 ~ 4

~

I 4 4

rl

\ ,I 4

%(4 rra 4 II Ia 4 ~

4 ~

~ ~4 aae ~ 4 'Ia 4 I

4 4 ~

I ~ 4

~ 4 ~ 4 4~ Ia 4 - ~4 ~

e ~ II 4

r V 4

~ ~ ~ ~ 4 ~ e ~

I 4

~4 4~

4 wa =. aaa err 4

I* ~~ ~ 4 4

~4 I ~

4 4

~ I

~ * ~

I 4\ ~ I 4 ~ ~ ' \4 444.:

4

~ ~ ~,

I

~

4 4 '

ar 4 4

~

I ~

4 I 4

>> ~ << ~" 4 I 7 4

'I 4 I c

I 4

II

P s

~ ~

~ ~

~

~ S C ~

~ ~

e P

I

~ ~

e Ie f '

e ~

~ e e

S

~ ~ ~

~ I p ~ r '

v ~

~ V r

~ C lt 1 I II E dh

~ 4' hd 4 II)V 4 ~

I vl r ~"

4 ~ EE4 I~

4 4 ', 4 d ~ I 44 I ~

~ "

4~ ~

~ I E

4 4 d d ~

~ I ' I 'll E

4 V

4

~ E ~ ~ Erd I I

d E

4 4 ~

q 'VIE E

d E ~

E ~

d E ~ E

'I IV ~

E

~ ~

II Ir ~

4 I**

t, t ~

4 4 I~ D 4 I I' 4 4 ~

4 ~ 4 4 r4

'4 41,4) AII Jl ~ 4 l Ml ~I At I 'I

~ ~

4 1

~

~

)4 'I 4

'1 4 4 ~

4

'I 4 44 4 AA 4 I

~

t 'I tr 4

",1 I

4 D 4 4 ~ 4 ~ \ ~

~ 4 A

AI ~ ~

I 4

4~ 4

~4 I ~

4 4

4 A . I 4 ~

~ 4'4 4

4 t '" 4

)4 ', 'I r

4

W

~ ~

t ~ ~

i

~ . ~ c t

~ ~

~ S ~

J ROM

/

~be1 $

j) ~ 0

'f

APPENDIX C DESIGN CONSIDERATIONS

~ el 1.0 Original Column Base Following assumptions were made in the design:

(a) The- box column was assumed to be a continuous member, with a pinned base and supported laterally at intermediate levels. Therefore, the column base was designed mainly for axial loads.

(b) Because of the rigid connection with box girders at the top, moments are transmit-ted to the column top depending on the re-lative stiffenesses of the column and the girder.

(c) Column load is distributed un i forml y over the entire area of the base plate.

(d) Stiffeners and base plate act as a composite section for transmitting design loads.

2.0 Redesigned Column Base The major change made 'in the redesign of box column base is elimination of stiffeners for the base plate.

The base plate utilizes the original erection bolts as shown in Figure l.

(B-21a)

5 t.

FIGURE 1 ORIGINAL COLUMN BASE DETAIL

IP 4 ~ ~ 44 4

l."39.~ HG i'Sr/FF, A

~

rg $ 1/iF AS ~ <<ttt 2 II /0 g 808'.

'sr/FF..4's 0 z 0/fM//og 8047 le'Irp

/ ~

I

.~ I I'~

I

.,I I

I S-3 tt

~

I I

.II

. rvP

~

l

. +jit it 3'C'ATA//

I /:c 3 C 3 0 8 ~ / 0 Lp PlAfd ~

t SYR ABoe7 Box'olflpfN tt POX'E/IA i II lj;.'I II lI I II - I ll.

t !I I .

r g/~~ gf HNf r)J+

3~

~ ~ tt It //Ot F 2g<'~

p2$ 5F/Fr-

~/k sir/F 8 r sr//r: 8 c 7/oh'.

GANl'SE 3 a~Sr P rg =/-0

'4

~

t FIGURE ORIGINAL CCLUMN BASE DETAILS

'1 1 y t r 0 ~

/

FIGURE 2 REDESIGNED COLUHN BASE DETAILS

Sr 4 r r

~Q I

AE

'%1

~1 vo g ~ '

k

~ 0 ~

0' l

'L