ML20092D718

Weld Overlay Design for Indications in Peach Bottom,Unit 3 4-Inch Jet Pump Instrumentation Nozzle

ML20092D718
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Site:	Peach Bottom
Issue date:	06/30/1984
From:	Branlund B GENERAL ELECTRIC CO.
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ML20092D702	List: ML20092D697 ML20092D707 ML20092D712 ML20092D718 ML20092D721
References
MAR-84-20, NUDOCS 8406220120
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Text

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DRF #137-0010 O MAR 84-20 BIB 04. DA 1

l WELD OVERLAY DESIGN FOR HE INDICATIONS IN HE PEAG BOTIUM UNIT 3 -

4-ING JET PUNP INSHUW.NTATION N0ZZLE June 1984 O

Prepared By: . dbr, d .

B. J. Branimad, Engineer Mechanics Analysis 4

Reviewed By: b ,

H. 8. Nekte, Principal Engineer Mechanics Analysis Approved By:&S. Ranganath, Manager p Mechanics Analysis v

8406220120 840620 PDR ADOCK 05000278 p PDR

DRP #137-0010 MAR 84-20 l

IMPORTANT NOTICE REGARDING CONTENTS OF THIS REPORT PLEASE READ CAREFULLY This report was prepared by General Electric solely for '

the use of the Philadelphia Electric Company. The information ,

i contained in this report is believed by General Electric to be an accurate and true representation of the facts known, obtained or i

provided to General Electric at the time this report was prepared.

The only undertakings of the General Electric Company i respecting information in this document are contained in Philadelphia Electric Company Purchase Order No. FSR-320-N6610 dated June 8, 1984, and nothing contained in this document shall i

be construed as changing said contract. The use of this l

i information except as defined by said contract, or for any purpoue other than that for which it is intended, is not authorizedt and with respect to any such unauthorized use,

neither General Electric Company nor any of the contributors to this document makes any representation or warranty (express or

implied) as to the completeness, accuracy or usefulness of the-information contained in this document or that such use of such information may not infringe privately owned rightst nor do they

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assume any responsibility for liability or damage of any kind i

which may result from such use of such information. ..

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1. ABSH ACT 1 l l

2. INIRODUCTION 2

3. WELD OVERLAY DESIGNS 4 3.1 Methodology for Determining the Minimum Required Weld 4 .

Overlay Thicknesses 3.2 Applied Stresses at the Weld Overlay Locations 6 3.3 Weld Overlay Thickne ss Results 6 3.4 Weld Overley Widths 6 3.5 Weld Overlay Designs 7

4. REFERENCES 8 ILLUS'IRATIONS FIGURE 1 Weld Overlay Design 9 O

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1. ABSTRACT O

In June 1984 General Electric Company, in conjunction with Sonic Systems, Inc., performed ultrasonic examinations of the Safe End to Nozzle, Safe End to Penetration Seal, and Penetration Seal Assemb'1y welds on the Peach Bottom #3 4-inch Jet Pump Instrumentation Nozzle. The examination revealed three circumferential indications, one in the #2 weld of the ' A' loop and two in the

1. 2 weld of the 'B' loop. Due to minimum separation, the two indications in f

the 'B' loop were considered to be one continuous indication.

It was decided to weld overlay repair the welds in each loop. 1%e weld overlay was designed using the criteria to provide in11 structural

! reinforcement of the cracked region while maintaining the ASIE Code safety margins. The weld will consist of a sealing pass and a weld overlay 1/8-inch thick and 1.5 inches wide with a 3/1 transition.

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INTRODUCTION In June 1984 General Electric Company, in conj unction with Sonic Systems, Inc., performed ultrasonic examinations of the Safe End to Nozzle, Safe End to Penetration Seal, and Penetration Seal Assembly welds on the Peach Botton Unit 3 4-inch Jet Pump Instrumentation Nozzle. The examination revealed three circumferential indications in the #2 weld: one in the ' A' loop and two in the 'B' loop. The configuration of the #2 weld does not allow complete examination, the scanning surf ace on either side of the weld is not large enough to examine the weld root and weld crown effectively. The configuration 4 also prevents gathering data points needed to estimate the through-wall

, dimension of the indications. The through-wall dimension is, therefore, an

estimate.

Analysis of the indications produced the following data:

J i 'A' Loop Weld #2

() Length (1) through-wall (a)

= .75 inch

= .175 inch measured thickness (t) = .360 inch all = .23 .

a/t = 48.6%

The ' A' loop circumferential fisw was later reezamined and the length was measured at 1.0 inch.

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'B' Loop. Weld #2 Length (1) = 1.87 inches through-wall (a) = .075 inch l

mea sured thickne ss (t) = .340 inch a/1 = .04 a/t = 22%

i loop circumferential flaw was also reexamined and found to be leaking, The 'B' indicating a through-wall flaw.

It was decided to weld overlay repair the weld in each loop. The overlay is designed to provide full structural reinforcement of the cracked region while maintaining the ASME Code safety margins. This report provides a l recommendation for the design of the weld overlay to meet these Code safety margins and the specific geometric considerations for both welds.

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'3. WELD OVERLAY DESIGN ANALYSIS O The criterion used to design the weld overlay for the 4-inch Jet Pump

- Instrumentation Nozzle is to provide full structural reinforcement of the cracked region maintaining the ASM! Code safety margins. This evaluation 4

l conservatively assumes that the flaws are fully circumferentist and will extend through the susceptible material of the original pipe wall. With this f

assumption, no credit is taken for the beneficial compressive residual

! stresses induced by the heat sink weld overlay process that would oppose crack ,

l e xtension through the thickne ss. The postulated through-wall cracks also provide assurance that the overlay design is independent of the crack size as determined by the ultrasonic testing. IGSCC crack growth into the weld overlay material beyond the first layer is not expected since the weld material away cros the fusion line is not susceptible.

! 3.1 Methodoloav for Determinina the Minimum Reanired Wald Overlav Thickness l

The minimum weld overlay thickness necessary to achieve full structural O reintercement of the fla is that thiciness hich ro ides the a. ro riate f actor of safety against not section collapse of the adj acent material. For a j fully circumferential crack, the depth that not section collapse occurs is a funtion of the material flow stress, the overall wall thickness including the weld overlay, and the applied primary membrane and bending stresses. The primary membrane stress is produced by pressure, and the primary bending I

stress is the sum of the dead weight and seismic stresses.

< Paragraph IVB-3640 of Appendia I to Section II. Reference 1, sontains tables of the allowable circumferential flew depth to pipe thiekness ratios (a/t) for various applied primary stress ratios (P,+ P b)/8 .'m The 4-inch Jet Pump i

Instrumentation Nossle welds are subjected to primary loads where the i

(P, + Pb l/8 mratios are less than 0.6 af ter weld overlay thickness adjustment (assuming a design stress intensity Sh of 16.9 kai for 304 stataloss steel).

i The tables of Reference 1 do not apply for these low stress ratios. Instead, I

the allowable flaw depth to thickness ratio must be calculated from the actual o

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i applied loads. Assuming that the indications are fully circumferential, the O method described in Reference 2 can be used. In this report a relationship between the applied loads, the flow ctress, and the critical crack depth to thickne ss ratio is defined by Equations (1) and (2).

P A

n (1 t B) a#

p= (1) 2A I

2a (2 A) sin p (2) i P b" n where i

af = Material Flow Stress = 3 S, P, = Primary Membrane Stress Pb = Primary Bending Stress a = Crack Depth

! t = Tot a l Thickne s s (pipe wall + weld overlay thickness) l (:)

These equations cannot be solved directly for the allowable flaw depth to thickne ss ratio, so en iterative approach must be used. In the iteration scheme, a weld overlay thickness is assumed and the primary stresses are adjusted to the new total thickness. The allowable Pb corresponding to the new thickness and the adjusted primary membrane stress is calculated from P +P Equations (1) and (2). The allowable ( ', ) 4 Factor of Safety is then m

• P +P l compared to the actual adjusted ', . If the allowable is less than the m

• actual, then the assumed weld overlay thickness is insufficient to provide full structural reinforcement and the procedure is repeated using a larger weld overlay thickne ss. The iteration is performed until the minimum required weld overisy thickness is determined. A factor of safety of 3.0 is used in accordance with the ASME.fcode,Section II, Perssraph ITB-3640 l C:)

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4 I 3.2 Aonlied Stresses at the Wald Overlav Locations O

The design specification for the Peach Botton Unit 3 4-inch Jet Pump Instrumentation Nozzle, Reference 3, did not provide information regarding normal operation stresses; therefore, the stresses were estimated. As discussed in Section 3.1 the primary membrane stress is produced by pressure, i the pressure at normal operation is known to be 1.05 ksi resulting in a primary membrane stress of 3.5 ksi. The primary bending stress is the som of the dead weight and seismic stress. However, since the dead weight sad  ;

seismic loads are unknown, but expected to be small, the primary bending i stress was conservatively chosen to be 4.5 ksi.

l 3.3 Weld Overlav Thickness Results The iterative calculations described in Section 3.1 were performed using the stresses described in Section 3.2. The flow stress ag is taken as

. 3 S,, and the pressure used in calculating the primary membrane stress is the normal operating pressure of 1050 psi. The thickness generated by this calculation is the minimum necessary for the overlay to maintain the required 3.0 factor of safety. As shown in Figure 1, a thickness of 1/8-inch is the recommended design thickne ss.

l 3.4 Veld Overlav Widths Unlike the thickness requirements for weld overlay designs, which are based on satisfying the safety margins of the A8agt Code, there are no guidelines for determining the weld overlay widths. Former overley design specifications recommended a conservative width of one attensation length ftt on either side of the weld material (total width of 2 fRt).. General Electrie has performed finite element studies which compared the stresses obtained when modeling pipes with weld overlay widths of one attenuation length to those of two attenuation lengths for fully streamferential through-wall eracks. Ross1ts showed that there is no significant difference between the stresses obtained l

i for the two widths and it was concluded that the additional material of the wider overlay contributes little to the overall structural reinformeenent of '

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.the weld. Therefore, a minimum weld overlay width of 43Itf is used as the basis for the recommended overley designs. This reduction in width greatly reduces the time required for applicatios of the weld overlays. Even thossh the width based on the criteria of mfit would be 1 inch, the width was chosen as 1.5 inch to assure that the overlay would cover the heat affected zone as well as the  ;

weld.  ;

3.5 VsJd Over13y_Q331ggs  !

The spect(fc overlay des %3n shown in Figure 1 was also based on consideration of such (mitors as the riistive thicknesses of the butt welding members, the l weld crown seemetry, the estent of the original heat affected zone, and the l

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proximity' tb eccentricity in the reducer. The slope of the overlay end was se t to three-to-one (width-to-thickness) to reduce stress concentration

- effects.

A further consideration was weld metal-base metal dilution in the first weld t overlay layer. The overlay-base metal mining results in a lessening of the

() weld material's resistance to IGSCC close to the fusion line. Tins an effectiv'e thickneas (that thickness of overlay deposited af ter the first weld layer) was used as the specified overlay design thiekness dimension, providing thy minimum required overlay thickness plus margin, in assordance with Reference 4.

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4. RElIRENCES

1. ASME Boller and Pressure Vessel Code.Section II. 1980 Edition. including Appendix 1 ' Acceptance Criteria for Flaws in Austenitic Piping,' approved April 1983.

2. Rangana th, S. and Mehta, E. S. , ' Engineering Methods for the Assessment of Ductile Fracture Margin in Nuclear Power Plant Piping,' Elastle-Plastle .

Eta.cture: Second Svanosium. Volume II-Fracture Resistance Curves and Enmineerina Aeolications. ASTM STP-803,1983, pp. 309-33 0.

3. Pesch Botton III Stress Resort prepared by Babcock and Wilson Co.

4. Letter from William J. Dircks, NRC to the Commissioners, NRC, ' Staff 1

Requirements for Reinspection of BWR Piping and Repair of Cracked Piping,'

November 7,1983, SECY-83-267C.

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w Figure 1 O

c W" MIN  %

See N;te 1 w g~ min = = __ ej[',DN 5 4> 'W g MIN WIDTH qg - FIPI r A 3 LA * ' P.

//}Yf//// N NN ' U u

Eccentric Reducer g "

g ,

="T" MIN l Safe End id

( WELD 1

Eccentric Reducer to Safe End

= w" MIN -

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[M e w," = = c$o@N =  ; 'Wg " >

MIN WIDTH MIN - FIRST 3 II LAYER

' V/

//f////H/H////)W N

- x U

L BUTT WE LD l

Eccentric r" MIN Reducer OVERLAY Safe End TwicxuEss See Note 2

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n 6d - ( WELD Wy = 0.5 inch W = 1.5 inches T

min

= 0.125 inch Notes:

1. Weld may be blended in area of transition.

2. Weld metal must be deposited in a minimum of two layers beyond the first layer. -

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