ML18059A516

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Nonproprietary Exam...Sections of Pressurizer PORV Line Safe-End Failure from Palisades Nuclear Generating Station.
ML18059A516
Person / Time
Site: Palisades Entergy icon.png
Issue date: 10/31/1993
From: Hall J, Thomas Magee, Owens C
ABB COMBUSTION ENGINEERING NUCLEAR FUEL (FORMERLY
To:
Shared Package
ML18059A493 List:
References
TR-MCC-306, TR-MCC-306-01, TR-MCC-306-1, NUDOCS 9312010254
Download: ML18059A516 (58)
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Text

_J r

J

  • J
  • EXAMINATION OF SECTIONS OF THE PRESSURIZER PORV LINE SAFE-END FAILURE FROM THE PALISADES NUCLEAR GENERATING STATION

]

J TR-MCC-306 l

l PALISADES, P.O. C-0008170

...J J

OCTOBER 1993 l

...J

  • ~-:*--~. OWENS T. P. MAGEE J. F. HALL ABB COMBUSTION ENGINEERING NUCLEAR SERVICES COMBUSTION ENGINEERING, INC.

1000 PROSPECT HILL ROAD WINDSOR, CONNECTICUT 06095-0500 DISK 101 Jr~---

r 9312010254 93l101 PDR ADOCK 05000255

\.

S PDR

ENCLOSURE 2 Consumers Power Company Palisades Plant Docket 50-255 METALLURGICAL EXAMINATION REPORT - NON-PROPRIETARY EXAMINATION OF SECTIONS OF THE PRESSURIZER PORV LINE SAFE-END FAILURE FROM THE PALISADES NUCLEAR GENERATING STATION

{TAC No. 87760)

November I, 1993

I

~

  • l_J EXAMINATION OF SECTIONS OF THE PRESSURIZER PORV LINE SAFE-END FAILURE FROM THE PALISADES NUCLEAR GENERATING STATION l

~

l I

J TR-MCC-306 OCTOBER 1993 l

1 I

J MATERIALS AND CHEMISTRY

]

ABB-CE NUCLEAR OPERATIONS COMBUSTION ENGINEERING, INC .

LEGAL NOTICE This report was prepared as an account of work performed by Combustion Engineering, Inc. Neither Combustion Engineering nor any person acting on its behalf:

A. Makes any warranty or representation, express or implied including the warianties of fitness for a p~rticular purpose or merchantability, with respect to the accuracy, completeness, or usefulness of the information contained in this report, or that the use of any information, apparatus, method, or process disclosed in this report may infringe privately owned rights, or B. Assumes any liabilities with respect to the use of, or for damages resulting from the use of, any information, apparatus, method or process disclosed in this report.

  • Section Title TABLE OF CONTENTS Page

1.0 INTRODUCTION

1-1

2.0 BACKGROUND

2-1 3.0 CHEMICAL ANALYSIS SAMPLES 3-1 4.0 FRACTURE SURFACE SAMPLE 4-1 4 .1 General 4-1 4.2 Microhardness Survey 4-1 4.3 Dual Etch Metallography 4-1 4.4 Sensitization Test 4-2 4.5 Axial Crack Characterization 4-2 5.0 REPAIR WELD - MOUNT NUMBER 3 SAMPLE 5-1 6.0 DISCUSSION 6-1

7.0 CONCLUSION

S 7-1 A ATTACHMENT 1 A-1

  • Figure LIST OF FIGURES 3-1 As-Received Weld Metal Sample. 3-3 3-2 As-Received Inconel 600 Base Metal Sample. 3-4 3-3 Oxalic Acid Etch of Weld Sample Showing Multiple Passes 3-5 (15-20). Two Exposures Shown to Highlight Different Areas.

3-4 Sketch of Weld Sample Sectioning. 3-6 3-5 EDS Results from Weld Sample #1. 3-7 3-6 EDS Results from Weld Sample #2. 3-8 3-7 EDS Results from Weld Sample #3. 3-9 3-8 EDS Results from Weld Sample #4. 3-10 3-9 EDS Results from Base Metal Sample. 3-11 4-1 Inconel 600 Half of Safe-End Fracture. 4-5 4-2 Fracture Surface Near ID and EDS Spectra. 4-6 4-3 Center of Fracture Surface, Typical of Most of Fracture, 4-7 Showing "Rock Candy" Appearance of Intergranular Fracture.

4-4 Closeup of Grain Facet. 4-8 4-5 Fracture Lip Region Near OD. 4-9 4-6 Plot of Microhardness Results from HAZ and Base Metal.* 4-10 4-7 Dual Etch Metallography on Base Metal Near ID. 4-11 4-8 Dual Etch Metallography on Base Metal at Mid-Wall. 4-12 4-9 Dual Etch Metallography on Base Metal Near OD. 4-13 4-10 Dual Etch Metallography on Base Metal on HAZ Near ID. 4-14 4-11 Dual Etch Metallography on Base Metal at Mid-Wall. 4-15 4-12 Dual Etch Metallography on Base Metal Near OD. 4-16 4-13 High Magnification Micrograph of Base Metal Boundary 4-17 Carbides H3 P04 Etch.

1----- -

LIST OF FIGURES (continued}

ie Figure 4-14 High Magnification Micrograph of HAZ Boundary 4-18 Carbides H3 P04 Etch.

4-15 Polished and Etched Section of Modified Huey Test 4-19 Sample.

4-16 ID Surface Axial Crack. 4-20 4-17 View of ID Surface Axial Crack. 4-21 5-1 Micrographs of Mount #3 Showing Repair Weld Region. 5-2 5-2 Original Weld EDS Spectra, Near ID. 5-3 5-3 Stainless Steel EDS Spectra, Near Weld. 5-4 5-4 Original Weld EDS Spectra, Near Stainless Steel 5-5 5-5 Repair Weld Near ID and Original Weld. 5-6 5-6 Repair Weld Near Stainless Steel. 5-7

  • 3-1 LIST OF TABLES WELD METAL ANALYSIS RESULTS 3-12 3-2 ALLOY 600 BOX METAL ANALYSIS RESULTS 3-13 5-1

SUMMARY

OF PRINCIPLE ELEMENTS FROM SEMI-QUANTITATIVE 5-8 ANALYSIS OF EDS SPECTRUM

  • Section

1.0 INTRODUCTION

The Palisades plant is a two loop pressurized water reactor (PWR) designed by Combustion Engineering (C-E) that entered into commercial operation in December 1971. The Palisades pressurizer was included as part of C-E's scope of supply and it wai delivered with an Inconel 600 (NiCrFe) safe-end at the top to receive the field welded 4 inch stainless steel pipe connection to the power operated relief valve (PORV). The Inconel 600 safe-end was supplied in the stress relieved condition and was derived from SB-166 forged bar stock.

On September 16, 1993 a leak was discovered in the 4 inch PORV line at the top of the pressurizer. Upon further investigation it was confirmed that a circumferential crack had developed near the safe-end weld. Plant cooldown was initiated. A root cause investigation was initiated by Palisades and several sample sections were sent to ABB Combustion Engineering Nuclear Services for examination under Palisades P.O. C-0008170. The objectives of this examination were to:

(1) Perform chemical analysis of the safe-end base metal and weld metal.

(2j Characterize the fracture surface, the heat affected zone (HAZ) and the Inconel 600 base metal.

(3) Characterize what appeared to be a weld repair included in sample mount #3 supplied by Palisades.

  • 1-1

The objectives were accomplished by a variety of examinations and tests via:

~

visual examination scanning electron microscopy energy dispersive spectroscopy analysis

  • light optical microscopy
  • microhardness testing
  • bulk chemical analysis
  • microstructure evaluation
  • sensitization assessment The examination of the 4 samples submitted is compete. The purpose of this report is to document the results and provide conclusions based on an evaluation of the results .
  • 1-2
  • Section

2.0 BACKGROUND

The Palisades in-service inspection program identified a possible flaw in the PORV nozzle safe-end to stainless steel pipe weld during the June 1993 refueling outage. This possible flaw indication was evaluated and determined at that time to be an original construction flaw which would not impact structural integrity.

On September 16, 1993, during heatup following a refueling outage, plant operating personnel noticed an increasing trend in the containment sump level.

Shortly thereafter, an auxiliary operator conducting rounds in containment reported a steam leak near the pressurizer. On closer inspection an unisolable leak was identified in the power operated relief valve (PORV) line near the pressurizer nozzle. While cooling down, at low pressure, further visual inspection confirmed the presence of a circumferential crack in or adjacent to the Inconel 600 safe-end to pipe weld.

On September 17, 1993 the crack was further defined as approximately 3 inches in length which is about 20% of the circumference.

A doughnut section encompassing part of the safe-end containing the crack and a portion of the PORV line was removed for repair purposes and metallurgical evaluation. This section was divided with one part being evaluated by Consumers Power Company and ABB Combustion Engineering while the other part was provided to the USNRC for evaluation at Brookhaven National Laboratory .

  • 2-1
  • Section 3.0 CHEMICAL ANALYSIS SAMPLES Samples of weld metal and Inconel 600 base metal were taken in a region remote from the cracked region and sent to ABB Combustion Engineering Materials/Chemical Technology for chemical analysis. Photographs of these samples were taken and are shown in Figures 3-1 and 3-2.

It was reported by CPCo that there were 4 distinct weld passes visible in the weld and the objective of this task was to obtain chemical analysis in each of the 4 weld zones. On examination of the as-received etched weld metal it was not obvious that 4 distinct passe~ were present. The prepared surfaced was reground, polished and etched using 10% oxalic acid. Upon re-examination it was clear that there were perhaps 15 to 20 passes, seen in Figure 3-3.

To produce 4 samples for analysis, drilling with a small diameter bit was attempted to produce chips but this approach proved difficult. It was decided to cut the weld into 4 sections using Al 203 cutoff wheels and obtain chemical analysis on each. The sketch in Figure 3-4 approximates the weld sectioning.

A 1/4 inch thick section was used and the likely high dilution areas were set aside as shown in the sketch. A new file was obtained and was successful in generating filings appropriate for analysis from each of the four cut samples.

Except for ~arbon analysis the bulk elemental analysis was obtained using an inductively coupled plasma (ICP) spectrometer. Carbon was determined on a LECO IR-412 instrument using the combustion technique.

Table 3-1 lists the analysis results obtained on the weld sample along with 1968 code requirements for 1-82 and 1-182 weld filler metals for comparison.

Energy Dispersive Spectroscopy (EDS) analysis was also performed on each of 3-1

the weld samples (1 through 4) and the results are included as Figures 3-5 through 3-8 respectively .

Samples from the base metal were similarly prepared and analyzed using the ICP and combustion techniques. The results of this analysis are tabulated in Table 3-2 along with the 1965 code requirements for SB-166 bar for comparison.

The EDS results for the base metal are shown in Figure 3-9 .

  • 3-2

- -~-CS

~;~3<;':".**--- ...

~~* .i,**--~ -**'-**-

    • '7 *'

107270 2.25X 107271 2.25X Figure 3-1. As-Received Weld Metal Sample.

  • 3-3

107272 2.25X 107273 2.25X Figure 3-2 . As-Received Inconel 600 Base Metal Sample.

  • 3-4

,. I 107484 7X 107483 7X Figure 3-3. Oxalic Acid Etch of Weld Sample Showing Multiple Passes (15-20).

Two Exposures Shown to Highlight Different Areas.

3-5

ID I

I \

~\

lweld ,

Sample\

. #A

'lwe 1 d \

Not 1C~m-p~~}-~'-\-

1Weld ' Not Used 1Sample #2 \ Used

\ \

I I I \

1 Not . weld \

Us e d , SaJTI p 1 e \

1

' #1 \

\

OD \

\

Figure 3-4 . Sketch of Weld Sample Sectioning.

  • 3-6

N I

c F*

c 'N

          • N********AI"*****E:**** ................

T r** .J I: ~::-"">-~0c::c:*~--,-~~'°"" .,' .. }i!!:

I:: Ll.L 0 F'AL I :=.ADE:=. >-IEL_D :=.At1PLE 4F 1 SO: QUANTIFY PALISADES WELD SAMPLE #1 Standard'ess Analysis

0.0 !.V 40.0 Degree~

Chi-sqd 4 . 17 El ement F:el f:. ...:rat i o Net Counts Ni-L 0.3151 1 +/- 0.01315 '.2805 +/- 1 17 Si-k (l, (l(i 14::' +/- (l I (l(1r:1J: 1730 +/- 383 Nb-L 0 .01331 +/- (l. (l(J(17:. 1 13::'1 +/- 636 T i-f* . 0.00179 +/- (l . (i(l(lJ9 1637 +/- 3:.3 c.~-f (l.15(*74 +/- c.*:i >10:

1 10913':* +/- 740

~e-f. (l . 0195 1 +/- 0 .c:i1:i(J7 3 1 1637 +/- 4J(l N" -f* 0.47:88 +/- (l. (l(l'.: 1 t:  ::'()4 73(1 +/- 937 Al -f.: (l. (1(1! ]7 +/- (l. (:(:(i:~c:; 1 :'(':" +/- J(J7 Mn-f (l. 023':*6 +/- (1, (1(1(i80 15::'70 +/- 559 ZAF Correction ::'0.00 ! V 40,00 deg t"*:J .ot I terat ions ,.,

E ~ E'i*en: f. -rat  ! C* z ..,

C:. F 'ZA~ At0°-:-,'f. W':'I.

S:-f <) . l)(1: . 9!8 -1 ,]49!Jt:. I ' .999 l .9':*7 r) .81 (l .4*:.

\:ti-L (i .(l~Cf

,(l(:J

* (18] (1 .c
os

.o:s 1 .457 (l .993 1 .71

,-,

  • Ji) - .79 (l .:6

- -* 1 .i:1:.3

~

( I 1 . (: i. ~ (: ,.., __

...,  :*) .ee Cr--~ I l . :: l l ,1:11 6 1 . 0::'4 (l .0:*7 (l .964

--,.., .69 R..,

--. .64

' - I Fe-r l .::i:s l . (l l  : 1 . (14:: ( l . 58(l 1) .9~7 ..:.

N i. - ~ ~) . 68() (l Q*~=-*  ! .<:CB 1 . (1(1(1 1 .1:1:*0 67 . ,..,..,

..:.....:... 69

.~....)

.. ' -f (; I ::1i:1: (* ,94':

-- - 69 (1 .999

  • b 1 :-. ,' .(*9 (1 :1 Mr,-f I . <::J4 1 . (i3:: 1 . (l 1 :. (l . 9(l(l (> .943 J .31 3 Vi' Tc":.;.  ;

= 1 (l(l * (11) ,~ 0 Figure 3-5. EDS Results from Weld Sample #1.

3-7

.. - :. ; - =-

I.

    • c*************

R

                                      • ... ~

I!1: 'i u

!1'Il  ! 1*

I

... ***** ......... *********** ****************** ...................... :\1 * ~~  :** " .. j i

' I

              • y~~=~;~_.;~=;-;~!~~~--~- Af1.**t.~Ji**~:-:**=---*~-

. .1

~ LLL:

2*00 F'ALISRC>E:= >~ELD SRMF'LE 'it2 SC*: OUANT IF Y PALISADES WELD SA~PLE ~:

Standardless Ana1ys:s 20.0 ~V 40.0 Degrees c

Ct-:1-sqc *-'. 19 Element Rel l*:.-ra t lo Net [cur.ts Ni-L (1.34120 +/- 0.01:9:-. 3347 +/- 127 s i-f*: 0.00123 +/- 0 .0(10::::. 1651 +/- :95 Nb-L (1. (11583 +/- 1) .0(1(174 14834 +/- 694 Ti -1 0 . (!021)9 +/- 1) .(H)1)37 2106 +, - 369 Cr-* (I 14912 +/- (l * (1(1(!9 7 118981 +/- 77"2

- e-f. (l,(11838 +/- (l. (1(ir)68 1 19(13 +/- 44(i r-.: -1 (1.44891 +/- o .O(i=:o: 214195 +/- 964 Mn-1: 1:i . o:J::3 +/- (I
  • 0(H) 8 2 16589 +/- ':*84 ZAc:- [ C*rrec t i or1 :'(I. (l(l ~v 4,:, . (l(: deg No .of Iterations E. emE*nt I -r8.t i a A F ZAF Atom~ Wt~

Si-I-. 0 .1)(>~ 0.917 ~

124 (1 .999 1 .944 r), 73 (1,36 r-.:b-L (1 .0:"4 1 .(18:: 1 .343 (1 .998 1 .449  :- . 12 3.43 Ti-> 1). 0(13 1 .(ll 6 1 . (l5J 0.928 ( 1 .99] (1. 37 (I. J !

Cr-1*: 0.:?:.3 1 . 1) 14 1 .(124 0.929 (I. 96':*  :*J. 77  :: 1 .54 Fe-f'

_, (1 .(1:8 (1 .672 1 . (111)

(l. 9q 1 l

1

.(144

. (i:*9 (l .883 l

  • r:1(:r)

(I. 931 1 . (' :*r:*

2 .63 66.q':

--. .56 68 .:.1 Mn-* (1. (135 1 . 031 1 . 015 (I

  • 9(12 0.944 3.43 3.28 Tc-ta l = 1 (ir:i. (ir~1f.

Figure 3-6. EDS Results from Weld Sample #2.

3-8

.................. ';... '""' .. ,v ... ...._. ~ t.,1 ~.._~,. ""'-' ~..,f(J

                • .............. *********:***************** ..*****'.********** *************=************************:*********-**** ********:********

r, I

l.

I- II

~

F. **!

I I

L~ l)i._l\.O

=:- to:::.::::

200 FFi'- I SAC>E::O- >~ELD SAr1F'LE # 3 SC: QUANTIFY PALISADES WELD SA~P'-E M3 FILE 23 DIS~ 13

=~andardles~ Ana~y~;~

20.0 ~V 40.0 ~e;~ees

<=

Ch1-sqd = ._1 * "'""

Element F:el

  • k-ratio Net Counts N1-L 0.27555 +/- 0.01208 2716 +/- 119 si -t< 0.00087 +/- 0.00021 11 7(1 + / -  ::s:I Nb-L 0.01303 +/- 0.00072 12:.:65 +/- 677

.,.. i-t*: o .t)(i:so +/- (: .1:1(H)J8 :c:.3: +/- 385 Cr -t* 0.15987 +/- 0.00100 1::21:.: +/- 8(15 Fe-t*. 0.04370 +/- 0.00081  :*8426 +/- 530 N1-f< 0.48139 +/- 0.002!1 230769 +/- 1 (112 Mr.-f (1.(i=:3(1c:;. +/- r).(i(1<)8':1 16':*6:. +/- 61 (l zc:..= Correction 2(l . (l(! ~* v 40 .0*:1 deg

  • '**='.of Iterations

~ 1 ~~e'"'t f'.-~-e>t10 z A F ZC:..F C:..toll'*'I. Wt/.

s i -t (l. ()1:11 (;. 91 7 2. 1:*9 (J.999 1 . 9': 0 (' (l .47 (1. :J r*~:J-L (l * (1 1 E? 1 . (1'.?:: 1 . :*44 (> ,998 1 . 4':.(1 1 . ':"9 ~.58

.,.. i -t (l . (.I(::: I . (:: 6 1 .t)5~ 0.9.:8 (1 .991 (1. 41 (1. 34 Cr-f i::.:: 1 e 1 .(I 1 :. 1 . *:i::J (I. 9::'7 0.962  :'J. 13 ~1 . 1)1 Fe-~ (I . (161) 1 . (l l (: 1 . t) 4 :" 0.887 (1 .934 5.71 5.57 r-.J i - ~  ::1 .6':*8 (1 .991 1 .*)32 1 . (1!)(1 1 . (1::'2 6':..58 67.27

...... : - ~ (1. r:1J: 1 . (lJ 1 1 . (114 ('. 9':it.. (l,9C7 *J. ! 1 ~.QC:*

Total= 1 (t(I. (l(J:~

Figure 3-7. EDS Results from Weld Sample #3.

3-9

.. ,_\..I' !;"\,.'I * \... \..'\...'Ir...,* 0:- * ,....._,.!,

I

.. * * * * *- * * * * * * * * * * * . . . . . . . . . . . . . . . . . . . . *1I

... N

  • 1 I I II N, ....

I' SC: C!UANTIFY F*ALISADES WEL[1 SAMF*:...E #4 FILE '.::4 DISf*. 13 Standardless Analysis 20.0 kV 40.0 Degrees Chi-sqd 4 .8<)

E1ement Rel f**.-rat 1 o Net Counts N1-L f). 3::::'61 7 +/- (1 * (11 ::6':* 33:.:: +/- 130

1-f** (l,(1(11'.
'E +,

,_ (l . (11)(1'.: l 1791 +/- 298 Nb-L (1.C)l ':*36 +/- (* . *)(lf)7 l l':".104 +/- 696 T 1-f 0. (>(':'SJ +/- (l * [:ll)(l36 2667 +/- 379 Cr-t (i. 1443:: +/- (;I (J1)(19 J 12<)6JS +/- 781 Fe-1* f). (138::::'8 +/- (. 0 1::(1r:i76  ::196':1 +!- 517 N1-f 0. 4:.(17 ! +/- (l. (11:i ! qq 2 .::.J1)8 +/- 995 Mn-I (1.0::*1J4 "t-/- (1 . (H.i:>8(l 1 ':"908 +/-  :.q:,

ZAF Corre::t1on ::*:*.(1(* IV 4(1,r)(l de:;;

No. of I t era t 1 on s E1 e~1er-1t f *-ra~ 10 z A F zAi:- Atom4 Wt4 s ~ -~ -. 1 ~C" ,, .::!6 (1 . '~!(;:  ::.

- ~ -* l) .999 1 . 94':* (1. 74 N~-L T.

(l . (l =*:?

(1 . r)::14  :

'i? =- 1 .343 0.998 1 . 449 - . o::

~

3.27

. ~:' : t: (1. 994

-I

  • l ,(15] (l .929 (1 .44 0.37
,--f* (1 .- ~.

l 1

  • r"1: 4 1 .r:i:: 4 c) .9::::'7 c) .963 ~~

.46  :(l .36 Fe-f (l. (lC:16 1 . :> l !,\ 1 ,1)4:2 (l .885 (l . 9J:: ' :1 .36  : . . 2:

Ni-k (1 .66( 1 1:1 ,99: 1 . 031 1 , (IC)(l ,l * (l::::' l 65 .89 67 .45 M: -I (*

  • Qr_ 7

(?

  • 1*1~

 :* !  ! . (11 c-,

- (1 91"11:'",

3 * (1C Total =

- ,9b

~

l (1(1 . (1<)'%

Figure 3-8. EDS Results from Weld Sample #4.

3-10

. **************~************************. ************-********* ,1I i

II I

I

  • r y - CT . - . .. ... . .. I

..T tL~1**~\ ~)Ii I['....*..~.:\. . . ..

I

.,.--,-------*--~------u \p \_,.-,, . /,

27%DT RT= 0sec SO:

PALISADES BASE METAL Standardless An2lys1s 20.0 kV 40.0 Degrees Chi-sod 4 .75 El eo-ment Rel I-ratio Net Counts Ni-~ (l. ':*2137 +/- (l .(H)227 230753 +I- 1 (ll)5 Fe-f< (l .06073 +/- 0 . (ll)(l89 36478 +/- 534 Cr-f (l. 1 1677 +/- (l. (l(l(l92 86422 +/- 682 N1-L (l. 29403 +/- (l,(ll'.::53 267'5 +/- 1 14 i:,* -f 0 . (l(l 1 ':*6 +/- (l. (>0031 +/-

1396 280

=

T:

l

-l

-~:*

(l. 00129 (l * (l(i 1 :.J

+/-

+/-

(l. (l(l(>28 (l. (l(l(lJ9 16(1 3 +/- 343 14:9 +/- 36=*

Mn-f* (J * (J(J::::'71 +I- (l. <)(>074 1798 +/- 488 ZAF Cs-rect1on ?0.00 ~V 40.00 ~eg No.of I':erat1or1s = 1 E 1 E-mer*":. i' _,_ ?'t. l - - z A  ;::-

ZAF At *:*m~~ Wt ..

r, ~ -f

e-t

!) .736 (l .99c 1 .(1,:::. 1 . (lt)(l 1 _,_ *.::1 7:: .""~

7"" 12 0 .1)86 1 Ji!":* 1 . (1~:: 1) .861 (l .9(>3 7 .8':* 7 .74

r-f* (> ! 65 1 . (i:(i 1 .(>': l

'1) *. 91 1) (J .947 .

17 (::' 15 .61

.::.1 -r'°.

5 1-f.

(l .002 (l * (>(I::

(l ,949 (1 .921

~

~.

.853 192 (1 (ll)(l

.999

~

~

~

  • 7l)6

. (11 7 1 -..,-

(l .74 (1  :.q (l . 3"7 T 1-' (l . (i(:: 1 . o:.~ (> .:6

~-

-I (l .</'4 1 * (l:'!)

l . (>'.:"& 1

  • r)l J (l .934 (1 .888 1 . 0(J2 (l 932 (1 (l

~-.

(l .3.:

Tc*t 2 ; = 1 *)(l * (l(i*1.

Figure 3-9. EDS Results from Base Metal Sample.

3-11

Table 3-1 WELD METAL ANALYSIS RESULTS (wt.%}*

Weld Sample Location . 1968 Code Element l 2 .  :.:...' . 3* . -*:*- . 4 *.: . . SB-304 SB-195 (I-82) . (I-182)

Ni 74.25 74.90 69.89 69. 77 67 min. Rem Cr 19.92 20.23 20.62 20.88 (20**} 13-17 Fe 2.99 5.30 3.84 6. 71 <3.0 6.0-10.0 Mn 2.92 3.13 2.35 2.58 2.25-3.5 5.0 to 9.'5 Si 0 .12 0 .14 0.11 0.18 <0.5 <1.0 Cu 0.06 0.06 0.05 0.09 <0.05 <0.50 Al 0.05 0.06 0.05 0.06 - -

p 0.037 0.037 0.029 0.030 - -

s 0.031 0.012 0.025 0.018 <0.015 <0.015 Ti 0.02 0.02 0.02 0.02 - <l. 0 c-- 0.012 0.051 0.020 0.056 <0.10 <0.10 Co 0.01 0.02 0.02 0.04 (with -

Ni}

Cb - 1.0 to 2.5 (Cb+ Ta}

  • ILP Analysis except for carbon
    • Nominal, no amount specified 3-12

Table 3-2 ALLOY 600 BASE METAL ANALYSIS RESULTS (wt.%)*

Base Meta 1 . '1965 ASME Code Element Analysis SB-166 Bar Ni 75.92 72.0 min.

Cr 16 .17 14.0 to 17.0 Fe 7.43 6.0 to 10.0 Mn 3.32 1.0 max.

c 0 .131 0 .15 max.

Cu 0.11 0.5 max.

Si 0 .13 0.5 max.

s <0.001 0.015 max.

Section 4.0 FRACTURE SURFACE SAMPLE 4.1 GENERAL A portion of the lnconel 600 half of the safe-end fracture, shown in Figure 4-1 was sent to ABB/CE for characterization. The fracture surface had been replicated and some of the replicating material remained on the surface. The sample was cleaned in an ultrasonic bath of acetone to remove the replicating material so that it wouldn't charge up in the SEM. By cutting axially in 2 locations the sample was divided into essentially 3 equal size pieces. A sketch is provided in Figure 4-1 detailing the sectioning scheme. A photo-montage was recorded for each third of the fracture surface. Single SEM views along with EDS results were obtained on several locations on the center piece of the fracture. The locations of the micrographs and EDS spectra are shown on the sketch in Figure 4-1 and the results for the identified locations are shown in Figures 4-2 through 4-5 respectively.

Figure 4-2 shows a region on the fracture surface near the inner wall of the pipe. At lower magnification (about lOX) this region was unusual in that it had the appearance of a ductile fracture, but upon closer examination it does not have ductile dimpling typical of ductile tearing. The appearance of the grain~ are unusual and do not clearly resemble any one known fracture of Alloy 600. Their appearance suggests intergranular fracture followed by abrasion of some sort which rounded off the sharp edges of the "rock candy" shaped fracture grains. EDS analysis of this region shows a typical Alloy 600 spectra.

Figure 4-3 shows an example of what most of the fracture surface looked like.

It shows a typical intergranular fracture "rock candy" appearance. Figure 4-4 shows a closeup of one of the grain facets. The grain surface has a rough appearance, suggesting an older surface .

  • 4-1

Figure 4-5 shows a region near the OD which was out of the fracture plane and did not appear as an intergranular fracture. This region may represent a portion of the crack that extended intn the weld, although the EDS spectra shown in Figure 4-5 closely resembles that of Alloy 600.

4.2 MICROHARDNESS SURVEY A longitudinal section near the midline of the center section of the fracture sample was prepared and Knoop microhardness transverses were taken in the HAZ and base metal regions across the thickness of the sample from ID to OD.

Indentations were made on a Shimadzu Type M78328 microhardness tester, using a Knoop indenter, under a 300 grain load for 15 seconds. Indentations were measured at a magnification of 400X in microns, and converted to HK300 in accordance with ASTM E384. The results of these traverses are shown in Figure 4-6. The base metal traverse was made about 1/2 inch from the fracture.

Readings in the HAZ were taken as close to the fracture as deemed feasible, ie., about 5 to 10 mils away. There is a great deal of variability in the micror.ardness across the nozzle wall, however the general trends show that the microhardness near the HAZ was less than that of the bulk alloy. The microhardness values are very high, especially near the periphery of the bulk metal. Pressurizer instrumentation nozzles made of SB-166 forged bar stock from Calvert Cliffs 2 had a bulk metal microhardness of about 175 HK300 and about 210 HK 300 near its cracks. A rough correlation of material strength and hardness would suggest that the bulk metal has an ultimate strength of 135 KSI (at 300 HK300 ) and 105 KSI (at 230 HK300 ) near the HAZ. The yield strength of the material is not related to the microhardness, since the diamond indenter penetrates and plasticly deforms the metal. The ultimate strength of the material as listed in the original material certification report was 114 KSI.

4.3 DUAL ETCH METALLOGRAPHY The microstructure of the material was evaluated by performing a dual etch on longitudinal sections. In the dual etch, areas from each section are etched fir~t with orthophosphoric acid to reveal the location and distribution of carbides. The same areas are then examined after a nital etch to show the 4-2

grain boundary network. This permits an assessment of carbide distribution with respect to the grain boundary network. A microhardness indent is used to

  • assist in the tdentification of areas to be examined.

Dual etch metallography was performed on the HAZ and on the base metal. In each case a micrograph set was obtained near the ID surface, mid-wall and near the OD surface. These dual etch sets can be seen in Figures 4-7 through 4-12.

These photomicrographs show good correspondence between carbides and grain boundaries. The grains are very large, mostly ASTM size 00. The orthophosphoric acid etch photomicrograph shown in Figure 4-12 clearly shows the HAZ, a region having absolutely no intragranular indications. The HAZ is about 30 mils wide. The orthophosphoric acid etch revealed indications that appeared to line up in three directions. These are not carbides but rather are etch pits due to stress relaxation. The structure is similar to that of a failed SONGS-3 pressurizer nozzle, having large grains and numerous intergranular carbides.

An attempt was made to resolve the grain boundary particles employing higher magnification and the H3 P04 etch. The results are shown in Figures 4-13 and 4-14 for the base metal and HAZ respectively. In both cases the carbides are extremely fine.

4.4 SENSITIZATION TEST A section from the center third of the overall fracture sample was modified Huey tested, mounted, polished and etched in Glycerigia to assess the degree of attack. The micrograph in Figure 4-15 shows the attack to be fairly equal on the ID and OD surfaces but slightly deeper at the fracture surface. The Modified Huey test is a 25% boiling HN03 acid exposure for a period of 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br />.

4.5 AXIAL CRACK CHARCTERIZATION An axial intergranular crack was observed on the ID surface during the SEM 4-3

examination of the fracture surface. This crack was observed running from the

  • fracture surface into the lnconel base metal and is shown.in Figure 4-16.

These SEM micrographs also show a closeup of a narrow circumferential groove on the inner surface. This groove also has a spherical droplet of weld metal on it. EDS analysis of this material showed that it had the same composition as the original l-82 weld material. The axial crack seems to be unrelated to the groove or the droplet. This crack was examined in metallographic mounts and was found to be 0.065" long (radial view) and 0.085" into the wall dimension (axial view as shown in Figure 4-17) .

  • 4-4

OD I Figure 4-5 I

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Figures- ,

4-3 & 4-4 'Figure 4-2

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  • ., *t***.* *-~*:.:'~~- -

107303 2.SX Figure 4-1. Inconel 600 Half of Safe-End Fracture.

4-5

1-(>ct-IQ~) \HJ:5~:13 PwL!S~O[S r~H~TUP[-~UCTIL[ R[G"ON NEAR ID Zl10i'~~I. 001 900 soc Vf!r t . 7~86 counts D1sp* l 22Z . . c Cr r.

Mn N1 0 N1 Cr re-l c. *I *t., I 4- 0.000 Rang** 20.460 20.220 -*

216004 107406 lOOX EDS Srectra Figure 4-2. Fracture Surface Near ID and EDS Spectra.

4-6

107418 SOX Figure 4-3. Center of Frar ture Surface, Typical of Most of Fracture, Showing "Rnck Candy" Appearance of Intergranular Fracture.

4-7

107407 200X Figure 4-4.

  • Closeup of Grain Facet.

4-8

!-Oct-1993 09:03:32 PALISADES rRACTURE LIP REGION NEAR OD 2002941. 002 Pr" t et* 900 ... c.

Vt"rt

  • 5907 counts D1sp* I Elopsed* 201 Sf' Ct Quantll!JC)

<N1 Cr r.

Cr N1 N1 TI Hn r.

'.1 0

l l 2 14 16 I 9 110 112 I I~ 116 118

  • - 0.000 Rangf!* 20.460 koV Int pgr 8 I 8 . 20.2~0 -*

171761 107409 ~

SOX EDS Spectra Figure 4-5. Fracture Lip Region Near OD.

4-9

.\

  • '440 Palisades PORV Nozzle Mlcrohanfnen
  • I 420 38.6 Re 400 36.8 Re 0

0 P")

'380

'3&0 Bull 34.8 Re 32.8 Re

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  • ~ 30.4 Re c 320

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.: 240

. II \ J 220 r\1 \ ~ I

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200

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180 0 200 Df.tance from ID (mil*)

Figure 4-6. Plot of Microhardness Results from HAZ and Base Metal.

4-10

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107435 75X 107434 75X Figure 4-7. Dual Etch Metallography on Base Metal Near ID.

4-11

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107436 75X 107437 75X Figure 4-8. Dual Etch Metallography on Base Metal at Mid-Wall.

4-12

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'4t Figure 4-9. Dual Etch Metallography on Base Metal Near OD.

4-13

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107438 75X ... 107439 75X Figure 4-10 Dual Etch Metallography on HAZ Near ID.

4-14 itft.1

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107441 75X 107440 75X Figure 4-11. Dual Etch Metallography on HAZ at Mid-Wall.

4-15

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'l 107431 75X 107430 75X Figure 4-12. Dual Etch Metallography on HAZ near OD.

4-16

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I 107305 so ox 107300 1250X Figure 4-13. High Magnification Micrograph of Base Metal Boundary Carbides H3 P04 Etch.

4-17

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4-18

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  • ..fA 107429 SOX Figure 4-15. Polished and Etched Section of Modified Huey Test Sample.

4-19

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107411 20X 107414 60X Figure 4-16. ID Surface Axial Crack.

4-20

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4-21

(

Section 5.0 REPAIR WELD - MOUNT NUMBER 3 SAMPLE A metallographic mount identified as #3 was sent to ABB/CE for examination.

The section includes what appears to be an ID repair weld. A low magnification SEM view of the repair weld is shown in Figure 5-1. EDS spectra were recorded in areas as noted on the micrograph in Figure 5-1. These spectra are shown in Figures 5-2 through 5-6 respectively. Table 5-1 summarizes the major elements in each of these EDS spectra. Table 5-1 shows that the repair weld has a composition between that of the original weld and the stainless steel. This difference in composition explains why this weld region etched differently than the other material .

  • 5-1

~

i I

107486 4X Figure 5-4 Figure 5-3

- Figure 5-2 Figure 5-5 Figure 5-6 107485 12X Figure 5-1. Micrographs of Mount #3 Showing Repair Weld Region.

5-2

1-0ct.-1993 10:06:24 PALISHDES FRACTURE -WELD AREA 2.

2002941.005 Preset= 900 secs Ver*t= 4544 counts Disp= 1 Elapsed= 205 secs

<Ni Cr Mn Cr Ni 0 Fe Ni Nb Ti Fe Nb d.1. --

,J,,J.f,..::-*A""'*~.-,N~"(J.":: ~: A~. ;

,. :;© iii~I>.-~ -

l 2 l4 6 I8 110 112 I 14 116 118 0.000 Range= 20.460 keV Integral 8 =

20 . .220 146062 Figure 5-2. Original Weld EDS Spectra, Near ID.

5-3

1-0ct-1993 10:57:27 PRLISADES FRACTURE WELD AREA 2 2002941.006 Pr-*eset:::

Vert:: 2000 counts Disp::: 1 900 secs Elapsed::: 216 secs Oua.ntex >

<Fe Cr>

Fe Ni Cr Mn Mo

........,,.,_ .*/ ..,,,

16 18 Integral 8 20.220 -*

2.32613 Figure 5-3. Stainless Steel EDS Spectra, Near Weld.

5-4

1-0ct-1993 10:33:14 PALISADES FRACTURE WELD AREA 3 2002941.007 F'r*eset = 900 secs Vert= 8526 counts Disp= 1 Elapsed= 201 secs iJuantex >

<Ni Cr*

Cr Mn Ni Fe Ni 10 12 14 16 1 E:

keV 20.220 -*

Integral t3 = 229880 Figure 5-4. Original Weld EDS Spectra, Near Stainless Steel.

5-5

1-0ct-1993 10:45:37 P~LISADES FRACTURE WELb AREA 4 2002941.008 Preset= 900 secs Vert= 5436 counts Disp= 1 Elapsed= 200 secs Quantex> <Fe Cr <Ni Mn s Cr Fe Ni P Ti 0 Ni 10 12 14 16 18 keV- 20.220 -*

Integral 8 = 237289 Figure 5-5. Repair Weld Near ID and Original Weld.

5-6

1-0ct-1993 11:05:46 PALISADES FRACTURE WELD AREA 1 2002'341. 004 Pr~eset= 900 secs Vert= 2000 counts Disp= 1 Elapsed= 205 secs Quantex> <Fe <Ni Cr>

Mn Cr Ni Fe p

Mo Mo

,.:v .*

18 2El. 220 -*

Integral 8 = 275152 Figure 5-6. Repair Weld Near Stainless Steel.

5-7

l Table 5-1

SUMMARY

OF PRINCIPAL ELEMENTS FROM SEMI-QUANTITATIVE ANALYSIS OF EDS SPECTRUM - MOUNT #3 LOCATION NICKEL CHROMIUM - IRON I I I I I Figure 5-2 58.91 24.51 4.91 Original Weld Figure 5-3 15.09 16.08 62.88 316 S/S Figure 5-4 65. IO 22 .10 3.98 Original Weld Figure 5-5 41.93 17.54 32.38 Repair Weld Figure 5-6 43.05 17.64 28.43 Repair Weld

  • 5-8

i D

Section 6.0 DISCUSSION In evaluating the bulk chemistry results it became evident that some form of contamination had occurred in generating the filings. Higher values than expected were recorded for manganese and sulfur. Carbon analysis results also exceeded.the reported value on the CMTR for the safe-end.

To clarify this issue additional samples of the base metal were prepared and submitted to another laboratory for check analysis for carbon and manganese.

These results were reported as 0.089% for carbon and 0.25% for manganese which is in reasonable agreement with the CMTR (see attachment 1).

The chemical analysis for the safe-end base metal is as expected. The results for the 4 locations analyzed in the weld indicate that a high nickel alloy filler metal was used in all cases.

The as-received fracture surface exhibited a light brown color and was very obviously an intergranular crack as evidenced by the large grains (rated as ASTM 00). By the nature of the submitted sample ABB/CE can not make any statements as to the origin of the crack (ID vs OD). Based on the crack length at the ID and OD Palisades has concluded that the failure was PWSCC.

The microhardness surveys were useful in documenting the softening that occurred in the HAZ. This is important because the crack initiated and propagated in the HAZ and not the harder base metal characterized by the 77.5 KSI yield *strength- on the CMTR. The resulting circumferential crack associated with the butt weld is dramatically different than in previously examined partial penetration welds of nozzles that exhibit axial cracking in the base metal and typically not in close proximity to the weld. The high values of hardness in the base metal surfaces, particularly the OD, could be

  • 6-1

l .*~

due to straightening in bar form as well as nozzle machining.

The dual etch metallography performed in the HAZ and base metal indicates good correspondence. That is, there is little or no evidence of prior history "ghost" boundaries. Ghost boundaries are carbides that aligned with the grain boundaries of a previous structure. During annealing, new grain boundaries may form, but if the annealing temperature is not high enough, the carbides will not dissolve and will remain in the same position. However, in the case of the Palisades material, the annealing temperature was sufficiently high to dissolve these carbides, which then precipitated on the new grain boundaries upon cooling. As pointed out in Section 4 the grain boundary carbides are very fine but appear to be a continuous network.

Based on the attack shown in Figure 4-15 it appears that some degree of sensitization is present in the safe-end.

As pointed out in Section 4.5 a secondary crack, axial in nature, was observed to be present on the ID surface. Metallographic measurements indicated 20%

penetration into the wall dimension of the safe-end .

  • 6-2
  • Section

7.0 CONCLUSION

S

1. The Alloy 600 safe-end was welded to the PORV stainless line with high nickel alloy filler metal.
2. An intergranular crack was initiated and propagated in the "softened" HAZ.
3. The microstructure in the HAZ showed the presence of a fine continuous network of grain boundary carbides which is a desirable condition for PWSCC resistance.
4. Some degree of sensitization was present in the safe-end.
5. The ID repair weld, although showing dilution from the Type 316 stainless steel, was made with high nickel alloy filler metal.

7-1

,, .,: - .\*

  • ATTACHMENT 1 A-1

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