ML20101Q343
| ML20101Q343 | |
| Person / Time | |
|---|---|
| Site: | Brunswick  |
| Issue date: | 06/30/1992 |
| From: | Bowerman B, Czajkowski C, Milian L, Roberts T, Schuster M BROOKHAVEN NATIONAL LABORATORY |
| To: | Office of Nuclear Reactor Regulation |
| References | |
| CON-FIN-L-1438 BNL-NUREG-52331, NUREG-CR-5885, NUDOCS 9207140248 | |
| Download: ML20101Q343 (124) | |
Text
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D AVAILABluTY NOTICE Avaltabety of Reference Matenals Cned M NRC Pubhontons Most documents cited h NRC publicauons wal be avalable from one of the fotowing sources:
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NUl(liG/ Cit-5SS5 llNI .-N Ul(liG--52331
' Metallurgical Evaluation of Weld Overlaid Pipe Sections From Brunswies Unit 2 .
Nuclear Power Station
- - - . . _ . . . - _ . - . - - . ---T Alanusenpt Completed: June 1992 I) ate Published: June 1992 Pregured t>y C. Cajlowski,11. Ilowerman, hl. Rhuster, T, lloberts,1. hiilian linckhaven National latwatoiy Upton, NY 1197 -
Prepared for Diiision of Engineering Technology Office of Nuclear Reactor llegulation U.S. Nuclear llegulatory Commission Washington, DC 20555 NitC FIN 1,1438 e
.. .. _ _ _ _ _ - . . _ - - _ _ _ _ _ - - _ _ _ _ - _ - - _ _ - - _ ~
ABSTRACT A metallurgical assessment of four sections of weld overlaid pipe was performed. The investigation consisted of strain gage measurements, metallographic sectioning and mounting, scanning electron microscopy, hardness and ferrite measurements, radiography and dye penetrant examinations. A review of the fabrication history and original p.eservice and inservice examinations was performed and compar: son was made to the actual cracks revealed af ter sectioning. In general, the report concludes that this weld quality of the overlays was consistent with ASME quality code class welds with adequate average "as deposited" ferrite readJngs of fN>7. The chemical analysis of the welds were normal for the alloys used (type 304 stainless steel, type 308 weld metal). The ! study also concludes that the ultrasonic inspection techniques used for inservice inspection of the overlays may not accurately deplet the top 25'r. of the pipe in all cases and that crack growth is possible af ter weld overlay under certain conditions. ;
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i c : l I TABLE Of CONTENTS i r EAGE ABSTRAC1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111 I LIST OF FIGURES. . . . . . . . . . . . . . . . . . . . . . . . . . . . . vil : + LIST Or TABLES . . . . . . . . . . . . . . . . . . . . . . . . . . . . xi EXECUTIVE
SUMMARY
. . . . . . . . . . . . . . . . . . . . . . . . . . . . xili ! ACKNOWLEDGEMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . xvii
- 1. INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 ,
- 2. INSPECTION BACKGROUND . . . . . . . . . . . . . . . . . . . . . . . 5
- 3. VISUAL . INSPECTION / DYE PENETRANT EXAMINAT!0N/ RADIOGRAPHY. . . . . . . 7 Ie
-h
, 4 SECTIONING AND-STRAIN GAGE HEASUREMENTS/ FERRITE HEASUREMENT . . . . 25
- 5. OPTICAL HICROSCOPY . . . . . . . . . . . . . . . . . . . . . . . . 31 6.-
CHEMICAL ANALYSIS (BY WAVELENGTH DISPERSIVE SPECTROSCOPY) . . . . . 45
- 7. MICR0 HARDNESS HEASUREMENTS. . . . . . . . . . . . . . . . . . . . . 47 r
- 8. ELECTRON HICROSCOPY EVALUATION. . . . . . . . . . . . . . . . . . . 49
- 9. - CONCLUSIONS . . . . . . . . . . , . . . . . . . . . . . . . . . . . 65 *
-10. REFERENCES. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
'll. ATTACHMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . .
67 1 l
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LIST Of FIGURES PR Figure 1 Layout of Reactor Recirculation System and location of the four weld samples (BRK3, BRG4 BRJ2, and BRJ3 - boxed). . . . .. ... ... ..... 3 Figure 2 The relative location of the NRC sample velds is shown in the above three sketches ... .. . .. 4 Figure 3 "As received" section of pipe from Brunswick Unit 2 (Typical) . . . . . . . . . . . . . . . . . .. .. 8 _ Figure 4 Ileavy coating of slag and oxide is seen after opening the end cap of 12BRG4 pipe .... ...... . 9 Figure 5 0xide was somewhat less dense on the inside ! surface of pipe 12BKJ2 . . . . , . . . . . . .. . 10 Figure 6 The relati5e thickness of the oxide coating can be seen in the photograph of 12BRJ3. .......... . 11 Figure 7 A generally thinner layer of exide was seen on the inside surfaces of 12BRK3, , . . . . . . . . . . . . . . 12 Figure 8 A linear indicatian (-l inch ling) is seen at stations 17-16 after dye penetrant examination of . . . . . . 13 Figur( 9 A 7 1/2" long indication was noteo on 12BRG4 after dye penetrant was applied (stations 34-25). . . . . ..... 14 Figure 10 A third linear indication was seen (-l 3/4" long) - between stations 39-36 on 12BRG4 (arrows) . . . ..... 15 Figure 11 A discontinuous indication (-l 1/2 long) was seen between stations 7-5 on 12BRK3 (arrows) . . . . . .. 17 Figure 12 A small indication (-1/2" long was seen at station marker 32 on 12BRK3 (arrows) . . . . . , . . . . . 18 Figure 13 Pipe 12BRJ2 had one small indication (-1/2" long) located between markers 24-23 (arrows). . . . . . . . . . . . 19 Figure 14 A " crazed" markers 9-7 ap(pearing indication was seen between-l 1/2" long) 20 on 12BRJ3 (arrows vii
LIST OF FIGURES (cont.) EaGL Figure 15 A second indication (-3/8" long) was seen on 21 12BRJ3 at station marker 32 (arrows) . . . . . . . . . . . . Figure 16 A .200" long crack was seen in this cross section of 12BRG4 at stat;on 16 . . . . . . . . . . . . . . . . . . . 34 Figure 17 A crack .132" long was seen between stations 16-17 on 12BF?,4 . . . . . . . . . . . . . . . . . . . . . . . . . . 35
- tigure 18 A crack essentially "through wall" (up to weld ,
overlay) was seenfat station 29 on 12BRG4. The crac k wa s . 738" l ong . . . . . . . . . . . . . . . . . . . . . 36 Figure.19 A second crack .266" in length was seen on the same cross-section'at marker 29. This crack - entered into the weld metal (original weld). This crack initiated i 0.015" from the weld root and was .255" away from the initiation site of the crack in Figure 18. (Same side 37 of the weld)._. . . .-. . . . . . . . . . . . . . . . . . . . Figure 20 Station 30 of 12BRG4 cross section disclosed a .302" '
.long crack which penetrated the weld metal deposit (original weld) . '. . . . . . . . . ... . . .' . . . . . . . . 38
- Figure 21 Two axial components were seen on a polished face perpendicular to the crack in Figure 20 . . . . . . . . . . . 39 Figure 22 A crack (.308" long) was associated with 12BRG4 40 at marker 31 . . . . . . . . . . . . . . . . . . . . . . . .
Figure 23 Marksr 38 of 12BRG4 bad a .584" long crack'in_ evidence. The left hand crack is.unetched while the right hand photograph shows the crack's relation to the. weld deposit-(after-etching).. . . . . . . . . . . . . . . . . . . 41 , Figure 24 A .200" long array of cracks was seen at marker
' 22 of pipe-12BRJ2 . . _, , . .-. . . ._, . . . . . . . . . . -42
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'V io 35- ihis1.328" long crack was'seen on the 32 marker cross-r
-section on pipe 12BRJ3 . .. . . . . . . . . . . . . . . . . .
43 viii 4
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-. .. . - .= - - _- - .- - ._ - - _. .. - - - - .. - - - - - - - - _ _ _
LIST OF FIGURES (cont.) . c ESGE r i r Figure 126 8ow magnification fractograph of fracture face from ; 42BRG4 pipe "throughwall" crack . . . . . . . . . . . . . . 50- , figure 27 Crack seen in Figure 26 was intergranular in appearance . . . 51 j Figure 28a No evidence of crack blunting was seen at the crack / : , overl ay in te r f ace . . . . . . . . . . . . . . . . . . . . . . 51 i Figure 28b Sharp intergranular facets are evident in the same interface . . . . . . . . . . . . . , . . . . . . . . . . . . 51 Figure 28c A third area showing no definite crack blunting . . . . . . . 51 ; Figure 29 SEM photograph of a smaller intergranular crack * (station marker 38) from pipe 12BRG4. . . . . . . . . . . . . 52 . Figure 30 Low magnification fractograph of intergranular crack from BRJ2 station marker 22 . . . . . . . . . . . . . . . . . . 54 1 Figure 31a Higher magnification SEM photo of fracture face on i
.BRJ2 (station marker 22). . . . . . . . . . . . . . . . . . . 55 Figure 32b, Second intergranular area (typical) seen on BRJ2 (station marker 22) . . . . . . . . . . . . . . . . . . . . .
55 figure 32 Sketch of weld overlay design for pipes 12BRJ2. l and 12BRK3. . . . . . . . . .-. . . . . .-. . . . . . . . . . 57 Figure 33 - Sketch of weld overlay design for 12BRG4. . . . . . . . . . . 58 - e f I IX ;
. . ~ , _ , ~. , . - . , - _ . . . . . ~ . _ _ , - . . - . . _ . _ . _ _ _ _ _ _ . . . _ . _ - . - _ . . _ , . _ . . _ . _ , _ , _ , . _ . _ .
LIST OF 1 ABLES EAGE Table 1 Mark locations and numbering rules. . . . . . .... .. . 23 Table 2 Correlated station numbers ........ ..... . . 24 Table 3 Locations of section cuts ......... .. . ... 25 Table 4 Strain gage data . ................... 28 Table 5 Ferritescope data (% ferrite) . . . . . . . . . . . . . . . 30 Table 6 Identification of metallurgical sections cut for metallography . . . . . . . . . . . . . . .... .. . 32 Table 7 Ferrite readings on metallurgical cross sections. . . . . 44 lable 8 Wavelength dispersive spectroscopy results. . . . ... . 45 Table 9 Microhardness readings. . . . . . ..... ...... . 48 Table 10 Crack l ocation data . . . . . . . . . . . . . . . . . . . . 59 Table 11 Comparison of NDE Data (12BRJ2) . . . . . . . . . . . . . . 60 Table 12 Comparison of NDE Data (12BRJ3) . . . . . . . ... . ... 61 Table 13 Comparison of NDE Data (12BRK3) . . . . . . ....... 62 Table 14 Comparison of NDE Data (12BRG4) . . . . . . . . . . . . . . 63 xi
I [XECU11VE
SUMMARY
I t four pieces of radioactive stainless steel from the Brunswick Unit 2 plant ! l were evaluated at Brookhaven National Laboratory. The pieces of pipe were 12 inch diameter, approximately 12 inches long, and each contained an overlaid weld. ' The four sections of pipe and their approximate crack lengths were identified as: l i Vertical to Elbow 2B32 Recirc. 12" BRJ2 2.25", 12% thru wall ! Horizontal to Elbow 2B32 Recirc. 12" BRJ3 1.75", 11% thru wall ' Safe end to Horizontal 2632 Recirc. 12" BRC4 2.0", 14% thru wall ! l 1.25", 7% thru wall l Horizontal to Elbow 2B32 Recirc. 12" BRK3 1.25", 5% thru wall ! These pipes had been in service for three (3) refueling cycles prior to removal. The proposed metallurgical assessment of the four samples was to entail the following (as applicable) steps:
- Review the fabrication history, material certifications of both original and overlay repair methods for the four weldments.
- h Review __the nondestructive test data (ISI/ PSI) for the four weldments.
rootograph + "as received" the four pieces of pipe and perform a visual examination of same, o Radiograph to characterize the weldments/ overlay prior to cutting the pipe.
- Strain gage measurements.
Netallurgically examine the four samples using the following techniques: a) scanning electron microscopy ' b) wavelength dispersive spectroscopy (WDS) c) dye or fluorescent penetrant d) metallographic grinding / polishing / etching e) optical metallography f) microhardness measu_rements-g)- ferrite measurements Provide a chemical analysis of the overlay material original weldment and base metal for the four samples (EDS). Dye penetrant' results on the pipes' inside surfaces compared to the utility U.1._ data revealed the following: xiii I
.. f
12BRG4 Three indications were noted on this pipe, lhey were of the following lengths: 1 inch, 7.5 inches and 1.5 inches. The utility had reported that this weld had only two indications: length 2.0 inches,14% thru wall and 1.25 inches, 7% thru wall. 12fifLQ Two indications were noted on this pipe, lhey were both 1.5 inches long. The utility reported one 1.25 inches long indication at 5% thru wall for this weld. 12BRJ2 This weld showed a faint 1.5 inch long indication. The utility report one 2.25 inch indication at 12% thru wall for this weld. 12BRJ3 Two indications were seen on this weld.- The first was approximately 2 I inches long and the second approximately 3/8 inches long. The utility reported one 1.75 inch long indicatinn at 11% thru wall for this weld. Procedures were developed to determine the residual stresses of the welds in areas where cracks werr identified. To accomplish this, strain gages were installed adjacent to and across selected cracks in the welds on the interior of the pipe sections and on the outer pipe circumference at locations corresponding to the interior surface strain gages. The gages were zerced before the pipes , were sectioned, then readings were taken after the pipes had been cut, in general, the pipes had reasonably high residual compressive stresses on the inside surface and residual tensile stresses on the exterior surface. Pipe 12BRG4 did have very low residual compressive stresses on its inside surface which indicated that the overlay technique may not always provide the necessary compressive stresses required on the pipes' inside diameters. Ferrite readings _ performed on the four pipe sections indicated that all "as deposited" weld metal exceeded FN 7. Only four readings (on 12BRG4) were below FN 8 out of approximately 480 readings. Optical microscopy revealed that all of the cracks were intergranular in i nature. The large crack (7.5 inches long) in 12BRG4 was essentially "through wall" (original pipe) for approximately 30% of its length. This is in distinct contrast to the original inspection data which showed a two inch long 14% through wall crack and a second crack 1.25 inches and 7% through wall. The following conclusions were drawn. from the investigation:
- The chemical analyses (WDS) of the base metal / weld metal and overlay materials appeared normal for the alloys used (A240 Type.304 stainless steel, SFA 5.4 308 weld L xiv-L l
L
The ferrite numbers recorded (IN >7) for all of the overlaid welds were consistent with industry practice. One reading was below the recommended FN 7.5 minimum outlined in USNRC Generic Letter 88 01. Considering the fact that the recording was FN 7.3 and that all other ferrite measurements on this pipe were above FN 7.5 this is considered acceptable. The quality of the overlays was consistent with that expected in an ASME pressure boundary weld. There was no evidence of porosity, lack of fusion, lack of penetration or weld metal cracking (other than IGSCC). The evaluation of the ultrasonic test data coupled with the input and re evaluations by General Electric Co., indicated that for . certain overlay configurations, ultrasonic inspection may not { i provide an accurate picture of the top 25% (original pipe wall) of l the pipe. Comphring the metallurgical sectioning of the four pipes ; to the dye penetrant results also gives rise to questions regarding i overcalls and undercalls on IGSCC. Ihree indication (2 or 12BRK3 ' and 1 on 12BRJ2) did not reveal cracks after sectioning. The comparison of cracks to ultrasonic test data also evidences the fact that the sizing / locating of cracks (before overlay) is not an " exact science" and results of these inspections should be carefully evaluated. i lhe stress calculations (based upon the strain gar" measurements) indicate that crack crowth (propagation) af ter w 4 overlay is a distinct possibility. This conclusion is be upon the low recorded residual compressive stresses observed t, ipe 12BRG4. It could not be positively determined if crack growth occurred after overlay by the metallurgical tests performed. i i F t xv
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l ACKNOWLEDG[MENTS i The authors with to thank D. Horno and K. WC ourton for their tremendous help in tne strain gage and microhardness measurements; the BNL Welding Shop for the radiography A. Lopez for the first draf t of this report and V. Morante for its completion. The authors alsn wish to thank P. 500 for his review and ! constant support. , s f 4 i -
. xvii
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- l. INTRODUCTION Weld overlay repairs on intergranular stress corrosion cracked (IGSCC) piping was initially considered as a short term repair by the U.S. Nuclear Regulatory Commission (NRC) and was accepted provided that no more than two additional fuel cycles were completed. The issuance of Generic letter 88-01 (by the USNRC) allows weld overlay repaired piping to continue to operate as long as a satisfactory ultrasonic examination is performed on the repaired piping every other fuel cycle. This evaluation must show no significant growth (propagation) of existing cracks and no initiation of new cracks. Many overlays have been applied in boiling water reactor (BWR) plants. The NRC believed that there was a need to confirm the. effectiveness of weld overlay repairs (in mitigating the IGSCC) by metallurgically examining sevaral overlay repaired ' ids.
Pursuant to this end, the USNRC (Haterials and Chemical Engineering Branch) . contracted with Brookhaven National Laboratory (BNL) to perform the metallurgical ' assessment. prior to the placing of the contract wit BNL, Carolina Power and Light (CP&L) had offered the NRC some piping which-had been in service for multiple fuel cycles.
~
On December 6,1989, a joint NRC/BNL team visited the Brunswick Nuclear Units. The purpose of the site visit was to elicit information from the licensee regarding sections of weld overlaid stainless steel piping to be sent to BNL for metallurgical evaluation. Discussions with the utility personnel -revolved about the size, configu-ration, shipping . condition, radiolytic condition, and identification of the specimens to be sent to BNL from Brunswick Unit 2. The following information was gathered during the discussions:
- 1) Four pieces of radioactive stainless steel pipe would be sent to BNL. The pieces of pipe are 12 inch diameter, approxi-mately 12 inches long, and each will contain an overlaid weld.
The four sections of pipe and their approximate crack lengths e e identified as: Vertical tt flW 2832 Recirc. 12" BRJ2 2.25", 12% thru wall 11orizontal tt abow 2832 Recirc. 12" BkJ3 1.75", 11% thru wall ! Safe end to Horizontal 2832 Recirc. 12" BRG4 2.0", 14% thru wall i 1.25", 7% thru wall l Horizontal to Elbow 2B32 Recirc. 12" BRK3 1.25", 5% thru wall These pipes had been in service for three (3) refueling cycles prior to removal. Figure 1 is a layout d, ing showing the location of the four referenced welds. A cutaway view of $ vessel and the specimens' locations relative to the riser and containment is .icted in Figure 2. 1
.- . - . . ~ . _ . _ . . _ _ . _ . _ _ _ _ _ _ _ , _ _ , _ - . _ _ . - . _ , . . _ , . _ _ . . _ . . . _ _ . . ~ . _ . . _ . _
The pipe specimV1 chosen had interior "smearable" contamination levels of between 2000 -- 4000 dpm (disintegrations per minute). These levels were determined after " fixing" the containments on the pipes' inside surfaces with water soluble glue. The actual contamination levels were considered to be much higher-(factorof2-10). The proposed metallurgical assessment of the four samples was to entail the following (as applicable) steps:
- Review the fabrication history and material certifications of both original and overlay repair methods for the four weld overl ays .
- Review the nondestructive test data (ISI/ PSI) for the four weldments.
- Photograph "as received" the four pieces of pipe and perform a visual examination of same.
- Radiogre h to characterize the weldments/ overlay prior to cutting the pipe (4 pieces).
- Hetallurgically examine the four samples using the following techniques:
a) scanning electron microscopy b) wavelength dispersive spectroscopy (WDS)_ c) dye or fluorescent penetrant d) metallographic grinding / polishing / etching e) optical metallography f) microhardness measurements g) ferrite measurements
- Provide a chemical analysis of the overlay material original weldmer.t and base metal for the four samples (EDS).
- Perform tensile tests (if feasible) for the original weld metal, base metal, overlay / interface.
This report documents the results of the metallurgical evaluation. 2
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- - Utill 2 - RE ACTOR COO _ ANT REC.RClLALOfi $YSIEfA Plh4G mm 10 nr p AcaE.eJ -.rvrut *v Figure 1 Layout of Reactor Recirculation System and location of the f0ur weld samples (BRK3. BRG4, i
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t
- 2. INSPECTION BACKGROUND A . review of- inspection data (supplied by CP&L) revealed the following inspection history for the. welds:
Weld B32-RR-12"-BRG4 (0.7" wall thickness)
* ' Pre:ervice inspection (PSI) was done on June 27, 1974, using ultrasonic examination. The inspection showed non-relevant indications due to 10 geometry.
*- Inservice inspection (ISI) was done using ultrasonic examinations on November 11, 1983. The inspection disclosed IGSCC at (L )22-24 (station 3
numbers) 14% through wall and (L2 )23% - 26 (station numbers) 7% through wall (depth).
- ISI (after overlay was applied) performed on November 14, 1983. Ihis overlay examination was conducted concurrently with bond examination.
Visual inspection disclosed no apparent discontinuitiet. UT inspection also showed no apparent discontinuities. Penetrant examination (after overlay). shosed na apparent discontinuities.
- L ISI per formed on March 15, 1986. Penetrant examination disclosed no apparent discontinuities (after additional overlay was applied). IGSCC indications at 22.75" and 24.75" were located prior to additional overlay by ultrasonic examination. Non-relevant indications were noted (ID
, geometric reflectors) by ultrasonic examination af ter overlay repair.
Both IGSCC indications were not observed after additional overlay repair. No reportable indications were recorded in the top 25% of the base material or overlay material.
ISI-performed on January 29, 1988. Ultrasonic examination disclosed no indications associated with IGSCC. Inside surface geometric reflectors were noted-by examination.
Weld B32-RR12"-BR)2 (0.68" wall)
*- PSI performed on September 17, 1974, b) ultrasonic examination. No recordable indications noted.
- -
- ISI performed on November 16, 1983, by ultrasonic examination. IGSCC
.noted at (L )38 3/4" 12% thru wall depth approximately L - 2.25" in 3 3 length. ID counterbore reflector noted at 22"
- No 1983 original overlay data available.
- ISI performed on March 1, 1986. Penetrant examination showed no recordable indications-(after additional overlay was applied).
IGSCC indication at 38" was not seen after additional-overlay was applied. Ultrasonic examination showed no recordable indications in top 25% of base metal. 5
- ISI performed on February 4, 1988, by ultrasonic examination. No indications associated with IGSCC were seen. Non-relevant indications both up stream and down stream side of the weld were noted during the examination.
B32-RR-12"-BRJ3 (0.68" wall thickness)
- PSI performed on September 17, 1974, by ultrasonic examinction. No rejectable indications noted. 10 geometric reflector identified at 27" (station marker).
- ISI performed November 10, 1983, by ultrasonic examination. IGSCC indication noted at (L2 ) 14" - 15 3/4" (station markers), L = 1 3/4",
11% thru wall. Af ter overlay inspection data showed no recordable defects (November 11,1983).
- ISI performed on April 7, 1986, by penetrant examination. No recordable indications were noted (after additional overlay was applied). IGSCC at 14" - 15 3/4" was not observed. A new IGSCC indication was found at 23.5" to 24.5" approximately 35% thru wall. ID geometric reflectors were also noted.
- ISI performed on January ?7,1988. None of the previously recorded IGSCC indication were observed during this examination.
H32-RR-12" BRK1 (0.71" wall thickness)
- PSI performed on September 17, 1974, by ultrasonic examination. No rejectable indications were noted. ID geometric reflector identified at 27.5.
- ISI performed on November 17, 1983, by ultrasonic examination. IGSCC indication noted at (L 35.5" to 36.75"; L - 1%"; ~5% thru wall. At (L2 )
20.12" - 25.5", an 10.3) Geometric reflector was noted.
- ISI performed on November 15, 1983. Overlay examination conducted concurrently with bond examination. Penetrant examination showed no apparent discontinuities. Ultrasonic examination reported no apparent discontinuities.
- ISI performed on April 8,1986. The IGSCC indication (comment of 1986 review) was not detected af ter overlay. Penetrant examination showed no recordable indications (after additional overlay was applied). The IGSCC indication at 36" was not observed after additional overlay was applied.
No IGSCC indications in overlay or top 25% of base metal.
- ISI performed on January 26, 1988, by ultrasonic examination. IGSCC indication was recorded at location 17.9". The indication is contained within the top 25% of the base material and does -not extend into the overlay material. This indication was recorded but not reported during the previous outage. Non-relevant root geometric reflectors were also reported.
6
- 3. VISUAL INSPECTION /0YE PENETRANT EXAMINATION / RADIOGRAPHY Four sections of radioactively contaminated pipe were received at BNL. The pipes were .12 inches in diameter and approximately 15 inches in length. The pipes were typically covered at both ends and wrapped in duct tape (Figure 3).
Removal of the end coverings and duct tape revealed that the inside surface of each of the pipes was covered with a heavy oxide' coating and slag from the cutting process (Figures 4 - 7). There were no top dead center (TDC) or zero markings (station markers) readily evident on the pipe sections. In order to preserve and not marr the features of any intergranular cracks (on the pipes' -inside surfaces) the oxide was removed manually with a hammer and cold chisel. After the oxide was removed, the inside surfaces of the four pipe sections were wiped down with methanol allowed to dry, and then subjected to dye penetrant examination by the following procedure: ' The materials used for the dye penetrant were: Magnaflux - Penetrant SKL-HF/S, Developer SKD-S, and Cleaner SKC-NF/ZC-7. The procedure used for the dye penetrant inspection of the pipe follows:
- 1. All dye penetrant examinations were performed in a hot cell at approximately room temperature (-70"F).
- 2. Cleaner - The pipe surface to be tested was wiped clean and then allowed to dry for approximately ten minutes.
- 3. Penetrant - After the penetrant was applied, it was allowed to stand for ten minutes (dwell time).
- 4. Cleaner - The penetrant was wiped off and the area allowed to dry for an additional ten minutes.
- 5. Developer - The developer was applied and the surface t
examined. The following sections describe the results of the dye penetrant examination: 12BRG4 An approximately one inch long indication was noted between station markers 16-17 (Figure 8). A second indication approximately 7%" in length was located between stations 34 and 25 (Figure 9). A third indication (Figure 10) approximately 1%"slong was located between stations 38 and 36. The utility had reported that this weld had only two indications: length 2.0", 14% thru wall 1.25", 7% thru wall 7
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12BRK3 Faint dye penetrant indications (Figure 11) were seen between areas 7-5, approximately 1%" in length (di: continuous) and at marker 32 (Figure 12), approximately 1%" in length.
- The utility reported one 1.25" long indication at 5% thru wall for this weld.
HI&l2 This weld (Figure 13) showed a faint 1%" long indication between station ] markers 24-23.
- The utility reported one 2.25" long indication at 12% thru wall for this "
weld. 12BRJ3 Two indications (Figures 14 and 15) were seen on this weld. The first was approximately 2" long between markers 7-9 and the second approximately 3/8" long between markers 33-32.
- The utility reported one 1.75" long indication at 11% thru wall for this weld.
To further characterize the indications, radiography was performed on the four pieces of pipe. A total of 44 radiographs were made of the pipe sections (11 per pipe) and these films were interpreted and compared to the dye penetrant examination data. There was no definitive correlation noted between the radiographs and the dye penetrant indications since the IGSCC cracks do not manifest themselves conspicuously by this (radiography) nondestructive examination technique. .. During these comparisons, the importance of accurate labeling of station markers became apparent if BNL was to correlate its inspections with the PSI and ISI data generated by the utility. The locations of the cracks were identified in relation to station numbers which were marked on the outer diameter of the overlay boundary with the pipe. The station numbers were placed after selecting a zero point; station locatior.3 are spaced one inch apart starting from the zero point. .The BNL examination of the pipe prior to the x-ray radiography (the first stage of the project) failed to identify clearly any zero marks which may have been used by the utility or their contractors for in situ NDE. Therefore, BNL placed an arbitrary zero mark on each overley and assigned station numbers from this zero point. The zero mark consisted of "0>" with the ">" aligned along the pipe axis. 16
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After the x-ray radiography was completed, BNL repeated its inspection of the overlays and recorded the locations of all markings on the pipes which could be zero marks. Possible marks included flow direction indicators ("f" next to an arrow), a 5-dot pattern which looked like the 5 on gambling dice, and one pipe, a dotted "V." BNL communicated with General El'ctric (GE), the contractor which had installed the overlays, and clarified ti,e locations of the zero points GE had used for installing and evaluating the overlays. The original pipe had zero points which consisted of interrupted dnt "V" marks, with the "V" aligned circumferentially in the direction of increasing station numbers. Unfortunately, the original zero marks were probably covered by the overlay, (according to the GE contact person). BNL pointed out that the zero mark on 12BRG4 (the straight pipe to " pup" weld) was visible, and that the overlay for the elbow welds were the main concern. The rules GE used for placement of their zero marks on elbow welds follow.
- 1) The zero point is along the outer radius of the elbow;
- 2) station numbers increase circumferentially using the right hand rule;
- 3) the " thumb" for the right hand rule points in the direction of water flow;
- 4) station numbers are placed on the downstream edge of the overlay.
According to General Electric, the 5-dot pattern markings were placed on the pipes to monitor shrinkage, and that there should be four spaced uniformly on each pipe on either side of the overlayc. GE stated that the flow direction marks had been placed by the utility on the overlay-pipe sections after the sections had been removed from service. Using the above information, two tables were prepared. Table I shows the GE zero point and the flow mark locations in terms of BNL station numbers and the 3 rule (right- or left-hand) which applies to BNL station numbers. Table 2
~
correlates the BNL station numbers with those GE used. These numbers are approximate since the fractional space between the last mark (40 or 41) and the zero point was assumed to be one inch for this correlation. This process for correlation of station numbers was reviewed with GE person at San Jose and determined to be accurate when comparing the BNL numbering system to the GE labeling procedure [ l ]. 22
i Table 1 Mark incations and number:.:9 rules. ! I 5 BNL- ; Station ! Overlay Harx or Feature Number Comment ! 12BRJ2 F (with arrow) 2% BNL Nos. left cnd to arrow. . elbow outer radius 3 ;
- 0) (BNLzero) BNL Nos, right-hand to ">"
0 - BNL station nos, upstream side of overlay. , 12BRJ3 F (with arrows) 37% BNL Nos, right-hand to arrow, elbow outer radius 36% , 0> (BNL zero) 0 BNL Nos. left hand to ">" ! BNL station nos, downstream sida of overlay. , 12BRK3 F (with arrow) % BNL Nos, left-hand to arrow. ! elbow outer radius 3 ! l1>(BNL~zero) 0 BNL Nos. left-hand to ">" BNL station nos. downstream side of overlay. 12BRG4 F (with arrow) 4% BNL Nos. right-hand.to arrow dotted ">" points to station No. 3 2 , 0> (BNL zero) 0 BNL Nos. left-hand to ">" ; l BNL station no_s. downstream side of overlay. 5 23
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Table 2 Correlated station numbers") Overlay Overlay Overlay Overlay 12BRJ2 12BRJ3 12BRK3 12BRG4 BNL GE BNL GE BNL GE BNL GE 0 3 0 4.5 0 3 0 40 1 2 1 5.5 1 2 1 41 2 1 -2 6.5 2 1 2 0 3 0 3 7.5 3 0 3 1 4 40 4 8.5 4 40 4 2 5 39 5 9.5 5 39 5 3 6 38 6 10.5 6 38 6 4 7 17 7 11.5 7 37 7 5 8 2r 8 12.5 8 36 8 6 ! 9 35 9 13 5
. 9 35 9 7 10 34 10 14.5 10 34 10 8 11 33 11 15.5 11 33 11~ '9 12 32 12 16.5 12 32 12 10 13 '31- 13 17.5 13 31 13 11 14 30 14 18.5 14 30 14 12 15 29 15 19.5 15 29 15 13 16 28 16 20.5 16 28 16 14 17 27 17 21.5 17 27 17 15 18 26- 18 22.5 18 26 18 16 .
19 25- ~19 23.5 19 25 19 17 20- 24 20 24.5 20' 24 20 18 , 21' 23 21 25.5 21 23 21 19' 22 22' 21 26.5 22 22 22 20 - 23 21 23 27.5 23 21 23 21 24' 20 24 28.5 24 20 24 22 25: 19- -25 29.5 25 19 25 23 i 26 18- 26 30.5 26 18_ 26- .4~ 2 27 17 27 31.5 27 17 27 25 28 16 28 32.5 28 1C 28 12 6 ! t 29 15 29 33.5 29 15 29 27 30 14 30 34.5- 30 14 30 28 31 13 31 35.5 -31s 13 31 29-3? 12- 32 36.5 -32 12 32 30 33 11- -33 37.5 33 llL 33 31 r 34 10 34 38.5 34 10 34 32 i
.35 9 35 39.5 35 9 35 33 !
L~ 36 8- 36 40.5 36 8 36 34
'37 71 37- 0.5 37 7- 37 35 38 6 13 8 1.5 38 6- 3E 36 39: 5 39 2.5 39 5 35 37 40 4 ~40 3.5 40 4 4 ', 38
/t 39 ,
.a) A'ssumes that the fractional space between highest station and zero point is l exactly one inch. _42 5
1 l
- 4. SECTIONING AND STRAIN GAGE MEASUREMENIS/fERR11E HEASUREMENT Early in the investigation, procedures were developed to determine the residual stresses of the weld; in areas where cracks were identified. To accomplish this, strain geges were installed adjacent to and across selected cracks in the welds on the interior of the pipe sections and on the outer pipe circumference at locations corresponding to the interior surface strain gages.
The gages were zeroed before the pipes were sectioned, then readings were taken after the pipes had been cut. Three non-destructive tests were conducted before the strain gages were installed: dye-penetrant examinations, ferrite measurements, and x-ray radiography. All three are described elsewhere in the report. The dye-penetrant tests revealed several probable crack locations in each pipe. The crack locations formed the basis for the pipes' initial sectioning plan; Table 3 lists the station numbers identifying the sections of interest. (The station numbers - ) for the sectioning plan were the samt as those used for the x ray radiography 1 tests. The numbers represent inches measured from an arbitrary zero point on the outer diameter of the pipe along the edge of the overlay.) The overlays were cut into sections with a band saw to avoid the possibility of heat affecting the strain gage measurements. The cuts were made in accordance with the attached cutting sheets (Attachments 1-4). Table 3 Locations of section cuts (*) Overlay identification No. Station locations 3 12BRJ2 from 13 to 16 12BRJ2 from 22 to 26 12BRJ3 from 5 to 9 12BRJ3 from 34 to 38 12BRK3 from 4 to 8 12BRK3 from 30 to 34 12BRG4 from 15 to 18 12BRG4 from 21 to 34 12BRG4 from 34 to 39 (*) Station numbers are same as those used in x-ray radiography tests. 25
Precision strain gages from Heasurements Group, Inc. (Micro Heasurements Division, Raleigh, NC, gage type CEA 09-250VN-120) were used to make the measurements. The gages were installed following the procedures provided by Micro Heasurements (M M). Installation included the following steps: surface preparation, gage attachment with epoxy, and soldering electrical lead wires to the gages. Surface- preparation consisted of cleaning the area of interest with a carbide grinder, then - degreasing with acetone and methanol. The areas of interest were approximately 5 cm by 5 cm (2 in by 2 in.) squares at the middle of cracks. which had been identified earlier using dye-penetrant tem Two squares, one on the crack (pipe interior) and one on the pipe exterf v surface at the same location, were prepared, The squares were large enough w install two strain gages. Epoxy resin obtained from H-M (M Bond AE-10) was applied to the clean metal surface and the gages, and the gages were mounted on the surface aligned perpendicularly to the crack (along the axis of the pipe) using tape (as described in H-M Instruction Bulletin B-137-II). A slight pressure load (less than 30 psi) was applied to the gages while the epoxy cured for a minimum of 12 hours. After the epoxy cured, the tape was removed and the strain gages were cleaned with the methanol. Then wire leads were soldered to the strain gages via separate terminal blocks and jumper wires (Heasurements Group Technical Bulletins TT.-603 and TT-609). The strain gage measurements consisted of determining the electrical resistance of the gage before and after pipe sectioning. Before sectioning, the , gages' resistances nre measured ("7eroed" in a resistance bridge) with a strain gage readout 'ev i ce. Following sectioning, the gages' readings were obtained : with the reaovat system, which automatically converts gage resistance to units of micro-inch / inch. Table 4 lists the strain gage results for each overlay. Except for overlay ' 12BRG4, one locatinn on each pipe was tested. Since 12BRG4 had the largest cracks, strain gage-tests.were made at two locations. The strain gage readings were, for the most part, cui tant with what was expected. Positive readings show that the strain gages exWrienced tensile stress. Conversely, negative' readings indicate that the gage underwent compression. These readings are useful in that the stress state of the overlay, before the sections were cut, is opposite to the' readings obtained with the gages - after the cuts are made. Thus, a positive gage reading indicates a compressive residual stress, while a negative gage reading- results when the overlay had a tensile compressive stress. The strain gage readings for overlays 12BRJ2,12BRJ3, and-12BRK3 were all consistent in showing compressive residual stresses on the-inner diameter. For overlay 12BRG4, gages 17 and 18 at station 29 show compressive stresses, while ; at station 38, only gage 14 indicated a compressive stress. Gage 13 immediately adjacent to gage 13 had a negative value, suggesting a tensile stress. However, . the readinq on this gage fluctuated from -166 to -526. The reason for the instability in-the reading is not .n, and the results for gage 13 should be considered tentative because of ths .nstable reading, , b 26
...___.._._._..y i
i Six of the ten strain gage readings on the outer diameters of the overlays ! were negative, corresponding to residual tensile stresses. Three of the four ! exceptions, gages 11,12, and 20 were not measurable, showing open circuits when ! attached to the gage readout system. Gage 19 had a positive reading, indicating l a compressive stress on the outer surface of the overlay. : The last column of Table 4 depicts the stress measurements obtained when I the strain gage data was entered into the formula: , i
' ")
E(Modulus of Elasticity) c = "((Strain) e i i The Modulus of Elasticity chosen was 27.6 X 10' psi [ 14 ) for 18 8 i stainless steel, it is readily evident from the table that the stress distribution in 12 ! BRG 4 pipe is markedly different than that seen in the other pipe sections. The ' reading at gage 13 shows a tensile stress in an area where residual compression should be the nonn and its adjacent gage (14) only attained 3.42 ksi compression while comparable sections were in excess of 10 ksi compression on the inside pipe . surface. i t i w 4 i ? : i 27 1 1
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Table 4 Strain gage data Pipe and Gaga Strain Position Stress ** Station Number No. (pin /in) on Pipe (Ksi) 12BRJ2 - 14 1 751 10 20.73C 2 543 10 14.99C 3 1164 00 32.13T 4 -1144 OD 31.57T 12BRJ3 - 35 5 491 10 13.55C 6 392 10 10.82C 7 -1291 00 35.63T ! 8 1147 00 31.66T 12BRK3 - 5 9 . 843 ID 23.27C
.9 ?37 10 24.49C 11 i pen OD -- >
.IL . ' . y en 00 -
12BRG4 - 38 13 526* ID 14.52T 14 124 10 3.42C l , 15 -217 OD 5.99T 16 -184 00 5.08T 12BRG4 29 17 26 ID 7.18C 18 319 ID 8.800 19 74 OD 2.04C 20 open OD --
- readings fluctuated from -166 to -526.
**C = Compressive Stress 1 - Tensile Stress-1 28
L i
- After the strain gage measurements were performed, the various sections were ;
cut into smaller pieces for optical microscopy, electron microscopy and l microhardness measurements. ; i Prior to the sectioning and strain gage measurements of the four pipe ! sections, ferrite measurements were done on all four pipes' outside surfaces t (weld overlay area The requirement for ferrite control and content in i austenitic stainless). steel welds has been documented in at least two Regulatory i
- Guides [1,2) and is considered a first order defense against microfissuring and .
SCC prevention in the deposited weld metal. Additionally [3], at least one study l considers the role of delta ferrite quite important in reducing the susceptibility of austenitic materials to intergranular cracking. The instrument used to make the ferrite readings on the specimens was a Ferritescope. The ferritescope operation (according to its manufacturer) "...is based on_ a magneto induction principle, whereby the relative permeability of the specimen (which bears a known relationship to its ferrite content) is measured. When the probe is place on the material to be tested, a closed magnetic ; circuit is formed and excited by a low frequency magneto-motive force. The 4 resultant field induces i voltage in a pick-up coil (located in the probe), the ' magnitude of which is a measure of the relative permeability and hence the ferrite content of pick-up coil is amplified in a meter unit and the resultant amplitude indicated on a meter which is calibrated in either % fe or WRC ferrite figures. ; The configuration of the alternating field in the material is governed primarily by the construction of_ the probe, this being designed so as to minimize ' any field attenuation due to eddy currents and thus eliminate the effect of , material conductivity from the measurement..." i The instrument was recalibrated af ter each specimen was set in order to assure accurate readings. Measurements were taken at three points of the overlay i at each of the station locations. The "A" readint is on the overlay near the
- thinner of the two pipe sections joined; the "B" reading in- the center of the overlay; and the "C" reading near the thicker of the pipe sections. Table 5 tabulates the readings by pipe and station number. it is evident that the majority of the readings are ferrite number (fN) 8.0 or greater to approximately FN 13.3. The only readings less than 8.0 were the four readings on 12BRG4: 7.3, 7.5, 7.9 and 7.9. All of the "as deposited" ferrite readings measured would be ;
considered -acceptable in making a weld overlay. - i 29
Table 5 Ferritescope data (% ferrite) Pipe 128RJ2 Pipe 12BRJ3 Pipe 12BRK3 Pipe 12BRG4 Station . No. A B C- A B C A B C A B C 0 10.3 10.8 11.9 9.3 10.5 8.7 9.8 11.3 12.3 10.0 8.7 8.3 1 9.5 11.5 11.4 10.0 10.4 9.4 9.0 10.5 10.0 8.7 8.7 8.6 2 10.2 11.0 11.5 10.8 10.0 10.7 9.1 9.3 9.6 9.1 8.2 8.0 3 -10.2 10.8 12.1 10.8 11.0 10.P 10.3 11.7 9.2 8.4 9.2 9.0 4 10.2 11.0 12.2 10.2 10.0 11.5 10.3 11.6 8.8 8.7 9.0 7.3 5 10.0 11.6 11.5 10.3 10.2 9.7 9.8 9.4 10.3 8.7 8.3 7.9 6 9.9 11.0 11.4 10.1 10.4 10.0 9.7 10.6 9.7 8.5 9.3 9.2 7- 9.5 11.6 10.9 11.5 11.2 12.9 9.2 9.9 8.8 9.2 8.7 8.1 8 10.0 10.8 10.7 10.8 10.4 12.8 9.6 11.2 9.3 9.2 8.4 7.9 9 9.5 11.1 10.8 11-0 12.0 11.8
. 9.7 11.3 9.3 8.9 8.7 8.1 10 9.5 10.9 11.0 11.0 11.0 12.5 9.8 9.8 9.4 8.6 8.4 9.0 11" 10.3 11.2 11.6 '10.5 11.3 11.7 9.4 9.5 9.2 9.8 8.2 8.2 12 10.3 10.5 12.5 10.5 10.7 13.2 9.8 11.5 8.7 11.2 9.5 9.3 13
- 10.8 11.3 10.5 10.2 13.2 9.3 11.3 9.7 10.3 9.7 8.2 9.0 10.5 12.5 11.9 10.6 12.8 9.1 11.3 8.7 10.7 9.0 8.6 15 -9.2 SG 11.8 10.7 9.8 12.0 9.0 10.6 9.9 10.0 9.2 7.5 16 10.5 10.8 12.2 10.3 9.7 13.0 9.5 11.5 9.0 10.8 9.4 9.2 17 10.5 11.2 12.2 9.5 13.0 12.7 10.6 10.8 9.9 10.4 9.4 9.0 18 9.3 10.7 12.0 11.2 10.5 13.2 9.8 12.3 10.6 10.6 8.7 10.3 19 9.6 11.3 11.8 10.2 9.9 13.0 10.3 10.6 10.0 10.7 8.8 9.6 20 10.7 10.4 12.5. 10.4 11.8 13.3 10.0 11.2 9.5 11.5 8.2 8.9 5 21 8.3 10.7 12.6 10.7 12.4 '12.4 10.2 11.2 8.8 10.9 8.3 8.4 22 9.2 11.7 12.1 9.7 12.5 11.3 10.1 10.8 10.3 11.7 8.9 9.2 '
23 10.2 11.0 12.8 10.3 12.1 11.3 10.6 12.1 10.5 11.8 8.8 10.6 24 10.0 10.0 12.8 10.3 11.5 9.3 10.2 11.5 9.7 10.7 9.6 10.7 25 11.1 11.7 12.4 9.6 12.1 8.7 10.8 12.0 9.4 10.3 9.3 10.0 26 10.7 L10.2 12.5 9.9- 11.6 9.8 10.7 11.2 10.0 10.2 8.3 8.9 l
-27' 11~ 1 11.2 12.0 9.9 11.9 9.2 10.2 11.7 8.8 11.1 9.5 10.5 28 11.3 11.4 12.7 9.8 9.8- 9.7 10.7 11.7 10.0 9.8 9.1 10.5 :
29 43.2 11.8 13.0 10.0 11.4 10.2 10.6 10.8' 8.4 9.0 9.2 11.4 i 130 9.3 11.7 11.9 10.0 10.8 9.7 -10.1 11.6 9.2 8.5 9.2 11.2 31- 11.4 10.0 -13.3 9.3 10.5 -10.7- 10.1 11.7 8,5 8.4 8.4 10.2 32 9.7 11.2 12.6 8.9 10.0 10.0 10.9 11.8 9.4 8.9 9.8 11.1 ; 33 9.2.:11.3 12.4 10.5 9.2 10.1 10.2 10.8 9.7 9.7 9.0 9.3
' 34_ 8.7 10.9 12.3 9.7 9.6 9,1 10.6 -11.2 9.7 10.0 8.7- 9.0
, 35 11.1 12.2 12.6 9.3 10.9 10.6 10.0 11.9 9.4 10.3 10.0 '9.0 36- 10.5 10.1 13.2 10.0 10.3 10.2 10.4 11.3 8.9 10.4 8.8 8.5 37- 11.2 - 11.6' 12.6 10.2 11.0 9.3 10.5 11.3 9.7 9.7 9.9 9.6 38- 9.3 11 0- 12.-5 9.9--11.0 9.3 10.0- 12.7' 9.2 10.6 9.3 - 9.4
.39- _9. 7- 10.3 12.3 10.0 10.8- 9.1 -10.0 11.2 9.6 9.0- 8.7- 8.6 14 0 9.8 10.5 12.3 9.3 11.7~ 9.1 9.1 11.0 12.6 9.4 8.6 8.1 41 9.2 8.7 9.6 30
- 5. OPTICAL MICROSCOPY The various cut sections (resulting from the strain gage measurements) were ,
further sectioned into smaller specimens suitable for optical microscopy. These ! specimens were ground, metallurgically polished using ASTM A 262, Practice A l oxalic acid etching. ; Intergranular corrosion is commonly defined as a local attack on the grain ! boundaries of a metal by a corrosive media, j In stainless steel, susceptibility to intergranular corrosion is enhanced by the sensitization process. Sensitization can be described as the formation of chromium carbide precipitates in the grain boundaries of an austenitic stainless steel and the resultant depletion of Cr, brought about _by heating the steel in the temperature range 500 800"C [4,5). This temperature range is achieved readily during the welding process where the normal temperature of welding exceeds 1600*C during fusion welding. ! Therefore, the welded base material could receive a sensitizing heat treatment : in the critical range (500-800*C) at some point outward from the weld fusion line which would be maintained long enough to precipitate Cr carbide at the grain boundaries. This is not to say that the welding process alone will induce a : sensitization effect on the base material, as the degree of material ' sensitization is a cumulation of the material's prior thermal and mechanical treatments, weld cycle history, (number of passes, heat input, etc.) material -chemistry, thickness and thermal conductivity, and time at temperature in the sensitization range. In order to measure a materials' degree of sensitization, the American Society for Testing and Matcrials (ASTM) has published Standard A-262, " Standard Recommended Practices for Detecting Susceptibility to intergranular Attack in. Stainless Steels." This standard includes a rapid screening test: Practice A - Oxalic Acid Etch Test for_ Classification of Etch Structures of Stainless Steels. This practice is described in A 262 as:' "1.3 The oxalic acid etch test is a rapid method _ of - identifying, by simple etching, those specimens of certain-stainless -steel grades which are essentially free of susceptibility to intergranular attack associated with Cr carbide precipitates. These specimens will-have_ low corrosion rates :n certain corrosion tests and therefore can be eliminated (screened) from testing as ' acceptable,'" For purposes of this investigation, the polished specimens were etched with a current density of ~1 A/cm2 for 1.5 min. in a 10% oxalic acid + demineralized water solution. The. cathode used for tiie etching was a. piece of 304 stainless steel .while the polished specimen was used as the anode. ' The welded cross sections were then examined on a metallograph. The results of the etching are shown in the metallurgical cross sections photoraphed in this part of the report. In all cases, the structures observed had' at least one grain completely " ditched" which would have classified the. structure as sensitized. Table 6 is a listing of all of the cross sectioned examined and the location 31
(marker number) where each section was cut. The twenty one sections which were polished were removed from sections where the dye penetrant examination had indicated that a discontinuity was present. Eleven cracked cross sections were revealed from the twenty one sections cut. Of the four pipes examined, only 12BRK3 had no cracks evident after sectioning. Table 6 Identification of metallurgical sections cut far metallography. Specimen Identification Location Connents G4B1 (Pipe 12BRG4) 16 Cracked G482 16 17 Cracked G4D1 25 Not cracked G402 28% Cracked G4D3 284-29 Cracked G4d4 30 Cracked G4D5 30 31 Cracked examined by 5:M G4D6 31 32 Cracked G4El 38 Cracked G4E2 38-39 Cracked J2B (Pipe 12BRJ2) 14% Not cracked J2C 14%-15 Not cracked J2El 22 Cracked J2E2 23 Not cracked J3B1 (Pipo 12BRJ3) 7% Not cracked J382 7%-8 Not cracked J3D 32 Cracked K3B1 (Pipe 12BRK3) 6 3/4 Not cracked K3B2 6 3/4 - 7 Not cracked K3D1 32% Not cracked K3D2 32%-33 Not cracked 32 V
Ploe 12DRG4 With the exception of two axial cracks (figure 21) all of the cracks , associated with this weld were circumferential in direction. The cracks were ! intergranular in appearance (figures 16 23) and all were associated with the I heat affected zone (HAZ) of the original weld. The cracks all initiated on the inside surface of the subject weld and were located on the pipe side (not pup piece) of the weld. t The nominal wall thickness for this pipe was approximately 0.7" (18m). The cracks examined ranged from a minimur. (0.132",13.5m) between stations 1611 to a maximum of 0.738" (18.7m) at station 29. 1he longest crack (figure 18) propagated through the entire thickness of the pipe and stopped just short (less ! than 0.010",1.25m) of the weld overlay in the section examined. Some of the ' cracks examined (Figures 19, 20, 21) penetrated into the original weld metal (not the overlay) for a few grains. A circumferential crack (figure 20) had two axial ' cracksassociatedwithit(figure 21). These cracks ranged in depth from 0.246" , (6.25m) deep (penetrated a few microns into the weld) to 0.282" (7.2mm) deep. ' One crack was seen on 12BRG4 (figure 22) which was not seemingly associated with the pipe's inside surface. This crack was 0.308"(7.8m) in length and did . not intersect the inside pipe wall at the location of the section (marker 31). , A 0.584" (14.8m) long crack was located at marker 38 on 12BRG4 (figure 23). ; This crack barely penetrated the weld zone (etched structure). > 12BRJ2 ; A 0.200" (5.lmm) long array of intergranular cracking (figure 24) was - associated with this weld at marker 2?. The crack was exceedingly branched and initiated at the fusion zone (original weld root) and heat affected zone interface. The crack had the appearance of entering the weld metal (original . weld) and then traveling some distance through wall until it entered the weld metal further along the crack path. 12BRJ3 figure 25 is a photomicrograph of a 0.328" (8.3mm) long crack associated with the weld's heat affected zone. This crack was located at marker 28%; was ' circumferential in direction and appeared to have started to propagate into the original weld metal deposit. Some additional ferrite readings were performed on selected cross-sections. These were performed on the overlay area, the original weld metal and the base ,
-metal. Table 7 is a tabulation of the data. The readings (all above 7.0 for i original weld metal on overlay) indicate that there was probably excessive weld metal to base metal dilution during the welding process at those locations where the-cracks entered the original weld metal.
12BRK3
-No cracks evident after cross sectioning and metallurgically polishing.
33
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Table 7 Ferrite readin9s on metallurgical cross sections Cross-section Pipe _( marker location) ferrite Number 12BRG4 30 overlay - 10.5, 9.3, 10.7 original weld - 11.7 base metal 0.1 12BRG4 16 overlay - 11.7, 11.2, 10.5, 9.6, 10.7 original weld - 7.2 base metal - 0.0, 0.5 12BRG4 28% overlay - 9.4, 11.0, 9.9. 9.3, 10.5, 10.9 original weld - 11.4 base metal - 0.1 k 44
- 6. CHEMICAL ANALYSIS (BY WAVELENGlH DISPERSIVE SPECTROSCOPY)
Various methods of decontamination and cleaning operations (including metallurgical grinding and pol:shing' were performed on samples cut from the pipes in order to send out specimens for elemental chemical analysis. The piping material was radioactively activated (not contaminated). Af ter cleaning it was - found. that these levels of activation precluded the offsite shipment of the ' samples-for evaluation. The alternate chemice.1 analysis technique of wavelength dispersive spectroscopy (WDS) was considered adequate to evaluate the alloying additions in the specimens. ! l WDS is an analytical technique, capable of performing elemental analysis of ! microvolumes, typically on the order of a few cubi microns in bulk samples and ) considerably less in thinner sections. Analysis of x-rays emitted from a sample is accomplished by crystal spectrometers which separate the x-rays from the individual elements present according to their characteristic wavelengths. The feature of electron beam microanalysis that best describes this technique is its mass sensitivity. For example, it is often possible to detect less than 10* grams of an element present in a specific micravolume of a sample. The minimum detectable quantity of a given element or its detectabilitg limit varies with many factors, and in most cases is less than 101 grams /microvolume. (Note: WDS will only detect elements with atomic numbers greater than 11 so certain light elements will not be detected.) i Twelve specimens from the four pipes (three from each section) were cut out. ~ The specimens consisted of a sample from the individual overlay, base metal and original weld metal. Each of the specimens were metallurgically ground, polished and analyzed by . WDS. Each specimen was analyzed in three locations with the average composition ' for each sample recorded in Table 8. With the exception of the 128RJ2 overlay (only 7.66% Ni), and the 12BRG4 weld metal (only 7.29% Ni) all the readings were within the range of values expected for the Type 304 stainless steel and type 308 v weld metal. The typical values for the alloys are included in the table. [ t t 45
.____ _ ___,a.-,._ _ _._ _ _ _._ _ _ . _ _ _ _ _ . . . _ _ . _ , _
Table 8 Wavelength dispersive spectroscopy results ANALYSIS OF STAINLESS STEEL (WElGHT %) Sample fe Cr Ni Mn St J2S2 OVERLAY 67.93 21.92 7.66 1.62 0.87 J253 RING 69.85 18.89 8.50 1.82 0.94 J252 25 26 69.91 18.99 8.06 2.02 1.02 J3 RING A+32 69.72 19.20 8.03 1.98 1.06 _J,3S2 OVERLAY 67.21 20.44 9.59 1.87 0.90 J351 33-34 68.65 19.86 8.97 1.31 1.23 G4811 RING 70.88 19.12 7.29 1.80 0.91 G4S6 OVERLAY 67.38 20.70 9.18 1.90 0.84 G453 39-40 68.87 19.00 8.92 1.76 1.22 K353 34 35 68.14 19.85 9.09 1.94 0.98 . K3S3 OVERLAY 67.43 19.36 10.64 1.85 0.88 > K3S7 RING 69.23 18.9) 9.40 1.35 1.12 l l Typical ASME 5.4, 308 Balance 18-21 9-11 0.5-2.5 0.90 , Weld Typical ASTM A240. Type Balance 18 20 8-12 2.0. 1.0 _30455 t 46
- 7. MICR0 HARDNESS MEASUREMENTS
.in-order to obtain an insight into the mechanical properties of a typical overlay weldment, one section of pipe 12BRG4 was cut, metallurgically ground and polished and then tested for r crohardness. Table 9 shows a sketch of the specimen and the readings taken at various locations. With the exception of one hard spot ne:r the outside edge of the overlay (overlay / pipe interf ace) the remainder of the readings were reasonably consistent for 304 stainless steel and for the type 308 overlay material.
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A - overlay f B - original weld t C - overlay / base metal interface (HAZ) 3 0 - original weld HAZ Arrows indicate direction of impression taking (1 ...N) Impressions taken ~0.020" Area A - 1 - 237.8 Area B - 1 - 217.4 2 - 184.0 2 - 234.2 3 - 196.9 3 - 228.4 4 189.0 4 - 226.2 5 - 193.3 4 Area C - 1 - 342.6 Area ll 220.6 2 - 202.4 2 - 206.2 3 - 205.4 3 - 212.2 4 - 202.4 4 - 231.8 5 - 216.4 Vickers hardness Numbers: 6- 193.3 11 - 205.4 16 - 220.6 21 - 217.4 7- 187.3 12 - 211.2 17 - 215.4 22 - 222.8 8- 195.1 13 - 226.2 18 - 215.4 23 - 225.0 9- 196.9 14 - 222.8 19 - 211.2 10 - 200.6 15 - 212.2 20 - 210.2 4P, I l
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- 8. SCANNING ELECTRON HICROSCOPY f.VALVATION '
Various specimens (with cracks in them) were notched and chilled to liquid nitrogen temperature. A counter force was applied to the notched area while one part of the specimen was locked in a vise. This method will open fractures with i minimum damage to the fracture face. One of the goals for this project was to determine if crack growth could have continued after weld overlay. Various methods of oxide stripping were tried to accomplish this end; to no avail. It was decided that the fractures to be examined would be deoxidized using an electrolytic process (described below) before further SEM examinations were dono: : A working solution of Endox-214 is prepared by adding 8 ounces of Endox 214 powder to 1000 ml of cold water and stirring until it is completely dissolved. A small amount of photoflow is added to the solution to aid the wetting of the specimen and eliminate some of : the featuring during the electrochemical cleaning step. A glass beaker with 500 ml of the Endox-214 solution is placed in an ultrasonic cleaner. The specimen is made the cathode, and a ' platinum ytre loor is the anode. A current density of approximately 250 mA/cm is applied for 15 seconds. Remove the specimen from the electrolyte and ultrasonically wash it in a detergent solution consisting of Alconox and Photoflow for one minute, then rinse in clean water, dip in methanol and dry in hot air. The above procedure comprises one cycle, it may be necessary to repeat the above cycle several times before removing all the corrosion products. It is not possible to predetermine the exact number of cleaning cycles for any given specimen, since it depends upon the severity of the oxidation, roughness of surface, and the physical size of the sample. Observe the specimen optically after each cycle so that the process can be discontinued af ter the oxide or the corrosion product is removed and the specimen surface looks clean. Af ter the . specimen is thoroughly dry, examine it immediately or store in a desiccator. ' Figure 26 shows a fracture face after the treatment. The fracture was entirely intergranular (Figure 27). There was no evidence of beach marks (where crack growth may have ceased due to overlay) or any evidence that the crack did or did not propagate during service (after overly applied). The crack itself appeared to have just entered into the overlay (Figures 28a - c) and had sharp features to all of the intergranular facets. There was no definitive evidence of crack blunting; although the overlay ferrite values (recorded earlier) would indicate that blunting should have occurred or would eventually occur.
-_One of the smaller cracks on 12BRG4 was also examined (Figure 29). This crack was also entirely intergranular with no evidence of beach marks, etc.
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For purposes of this discussion, the method of repair / stress redistribution is the continuous weld overlay. -This method of mitigation consists of welding a continuous (360 degrees) band of 308L (stainless steel) weld metal directly onto the outside surface of a cracked pipe (weld directly over a defect area).
The noimal process ut, sized for depositing a uniform weld layer is automatic gas tungsten arc welding (GTAW). This method of mitigation produces a high toughness weld deposit resistant to stress corrosion cracking (normally deposited metal has a ferrite number greater than 8). The weld overlay process also tends to produce compressive residual stresses on the affected pipes' inside surfaces and partially through the wall thickness.
The two overlay designs [13] used for the four evaluated weldments; 12BRG4, 12BRJ2, 12BRJ3 and 12BRK3 are seen in Figures 32 and 33. Pipes 12BRJ2, 12BRJ3 and 12BRK3 were overlaid using the design in Figure 32. This design essentially centers the weld below the_ overlay to obtain a uniform stress distribution over the affected weld. There is also a reasonably good access for the ultrasonic inspection of these welds since there are no close welds to interfere with the ultrasonic signal.
The design of the overlay for 12BRG4 (Figure 33) was configured differently from the other three examined welds. The difference resulted from the addition of a " pup" piece of stainless steel between the original pipe and the safe end.
This-configuration shifted the overlay off center - away from the " pup piece."
This shifting might result in misleading or erroneous ultrasonic inspection data.
The importance of this issue lies in the "inspectability" of weld overlaid joints.
This investigation has identified visible cracks in locations and sizes which differ from those reported by the utility and its contractors:
Vertical to Elbow 2B32 Recirc. 12" BRJ2 2.25", 12% thru wall I Horizontal to Elbow 2B32 Recirc. 12" BRJ3 1.75",11% thru wall Safe end to Horizontal 2B32 Recirc. 12" BRG4 2.0", 14% thru wall 1.25", 7% thru wail Horizontal to Elbow 2832 Recirc. 12" BRK3 1.25", 5%thruwall Locations of the cracks found at BNL are compared with these crack
-locations (reported.by the inspection-contractor) in Table 10. Comparisons for each individual weld are shown in Tables 11-14.
It is also seen that some indications which are seen visually and by dye penetrant will not be crack related as evidenced by no cracks in- the metallurgical cross sections removed from 12BRK3 and 12BRJ3 (Tables 12-and 13).
These observations lead to one of two possible scenarios:
- 1) That the crack on BRG4 was pre-existing in a 7 1/2" length and virtually: "through wall" in depth and was neither located nor sized by-the ultrasonic inspection system used; the GE Smart System; or
- 2) That crack growth occurred in the "through wall" crack after weld overlay was applied.
56
, - - , - . , - - . . ~ ~ %,m--- -
,. --,, .m_ y , , - , - , --# - , , . . . .c .----m--m, ,- -, rr-
- . . . . - . .- . . . ~ , . ~ . - ,. . - . . . - . . - . - -
' .i f i se* urxsuuu s TWE Jost WsLD CVERLAY 18" WIN = >
/ 12. oJ7 Twicx
- WALL 304 3: PtPt
+
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I
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v
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. AswaLDaosunPAca LONG' ACCEPTABLE rom
- QVEnLAY TApfR RAOlus -
staow -
1.TnAmsmous fL CONFIGURATION OF 12" ELBOW TO PIPE. WELD OVERLAY.
Figure 32 Sketch of weld overlay design'for pipes 128RJ2,128RJ3, and 12BRK3.
57
. -; .= -, - . .-. . - - . . - . - . . . - - - . . - . . . . . - . , . . . . , , - . . . - .
s 3.0" MIN
'I
-: = - e.s M N AS WELDED SURFACE ACCEPTABLE FOR OVERLAY ~ * ' ' " '"' INCONEL 800 YAPER TAANSITIONS SAFE-END USE E101 TO DEFINE MAX EDOE OF SAFE END TO
- 0.W WN " PUP" PIECE WELD TYPE 308L WELD OVERLAY
/M/M/MEM/
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" POP"-PIECE TO SAFE-END TO NOZZLE WELO CONFIGURATION OF SAFE END TO PIPE WELD OVERLAY (TilERMAL SLEEVE CMITTED)
Figure 33 Sketch of weld overlay design for pipe 12BRG4.
Table 10 Crack location data BNL.(visual) vs. Utility / Contractor V - visual (BNL)
U - ultrasonic (GE)
PT - dye penetrant indications Overlay Overlay Overlay Overlay -
12BRJ2 12BRJ3 12BRK3 12BRG4 BNL GE BNL GE BNL GE BNL GE O 3 0 4.5 0 3 0 40 1 2 1 5.5 1 2 1 41
~
2 1 2 6.5 2 1 2 0 3 0 3 7.5 3 0 3 1 4 40 4 8.5 4 40 4 2
-5 39 5 9.5 5 39 5 3 6 38 U 6 10.5 38 6 7 37 7 11.5 PTf6 7 37 7 4
5
-8 36 PT/V 8 12.5 8 36 U 8 6
.9 35 I 9 13.5 9 35 9 7 10 34 10 10 34- 10 8
- 14. 5(U 11 33 11 15.5l 11 33 11 9 12- 32 12 16.5 12 32- 12 10 13 31 13 17.5 13 31 13 11 14 30 14 18.5 14 30 14 12 15 29 15 19.5 15 29 15 13-16 28 16 20.5 16 28 16 14 17 27 17 21.5 17 27 PT/V 17 15 18 26 18 22.5 18 26 18 16 19 25 19 23.51g 19- 25 19 17 20 24 20 24.51 20 24 20 18 21 23 21 25.5 21 23 21 19 22 22 22 26.5 22 22 U 22 20 PTIV 23-
~
21 -23 27.5 23 .21 23 21 24 20 24- 28.5 24 20~ 24 221 25 19 25 ' 29.5 25 19 25- 231 y
- 26. 18 26 30.5 26- 18 26 24j 27 17 .27 31.5 27 17fU / 27 25
-28 16 28 32.5 28 16 28 26 29 15. 29 33.5 29 15 l 29 27 30 14 30 34.5- 30' 28 31 14 PT/Vi 30 13 31 35.5- 31 13 31 29 32 12 f32 36.5 32 12 32 30 33 11 PT/V133 37.5 PTl33 - 11 \33 31 34 10 34 38.5 34 10 34 32 35 9 35 39.5 35 9 35 33 36 8 36 40.5 36 8 36 34 37 7 37 0.5 37 38 7 PT/V 37 35 6 38 1.5 38 6 38 36 39 5 39 2.5 39 5 39 37 40 4 40 3.5 40 4 40 38 41 39
- No-cracks detected by BNL after metallographic sectioning in any location.
1 59
TABLE 11 l
Comparison of NDE Data Utility Ultrasonic Tests BNL Dye Penetrant Tests /
Metallurgical Sectioning 0
0 12BRJ2
( %
l 9.5 28.5 9.5 28.5 L1 19 19
- L. - 0.500" long crack;
' 2h through wall 0 0 " deep) t ough all IO.08 deep) .
e Circumferential i
TABLE 12 Comparison of NDE Data Utility Ultrasonic Tests BNL Dye Penetrant Tests /
Metallurgical Sectioning 0 12BRJ3 0 7
L2 L1
~
28.5 .
9.5 28.5i 9.5
)
l Li 19 19 e 1983 ISI - L - 1.75" Long, o Two indications located by dye 11% through wall (0.07" deep). = 1.5"long; penetrant L2 = 0.375" L,long.
- 1986 ISI - L# - 1.0" long, e L 0.375" long crack;
-30% through wall (0.204" deep). 4b through wall (0.328" deep).
- Circumferential
- Circumferential
TABLE 13 .
Comparison of NDE Data Utility Ultrasonic Tests- . BNL Dye Penetrant Tests /
. Metallurgical Sectioning 0 12 BRK3. O.
L2 bl I Li ;
1 g
28.5 9.5 28.5 l 9.5 i
L2 N .
3 19 19 e 1983 ISI - L, - 1.25" long;
- Two indications located by 5% through wall (0.036". deep);
dye penetrant - L, - 1.5" long
~
L2 - ID Geometric Reflector.' (discontinuous); L2 - 0.5" long e 'Circumferential-
- Circumferential
-o 1988 ISI - IGSCC recorded at top 25% of base metal (L3 ). o' No cracks present after eCircumferential . sectioning..
i t L
+-em-- - . _ -
-TABLE 14-Comparison of NbE Data Utility Ultrasonic Tests BNL Dye Penetrant Tests /-
Piletallurgical Sectioning 0 12BRG4 L3 0 Li 28.5 9.5 28.5 l 9.5 w
L2 N
L
.1 9 19
- 1983 ISI - L - 2.0" long; i
- L - 7.5" long (essentially 14% through wall (.100" deep; through wall for 30% length) .
L 1.25" long; 7% through wall
- Circumferential and axial (2.0=50" deep) - Split signals on UT components
- Both Circumferential
- L2- 1.0" long; 29% through wall (.200" deep)
- Circumferential
*L 1.75" long; 83% through 3wall (-20% of length .538" deep)
- Circumferential
In order to enhance this report's data base, both the Electric Power Research Institute's, J. A. Jones (Nondestructive Evaluation) NDE Center and General Electric Company (San Jose, California) were invited to participate in performing additional ultrasonic examination of the four pipe pieces prior to their being sectioned. Both EPRI (by telephone) and GE (formally - Attachment
- 6) declined the invitation.
The BNL investigator had a meeting with the appropriate cognizant GE inspection personnel where both image data and video CRT display data from the original inspection of the four overlays were reviewed. The data and displays were reviewed in an effort to correlate the BNL observations to the UT signals recorded. Attachment 7 is a letter documenting this comparison. The UT results, although somewhat more definitive, were " inconclusive."
GE was kept informed during the various stages of the investigation, in fact, subsequent discussions with GE revealed that due to the problem of access -
to weld 12BRG4 (Attachment 8) ultrasonic examination may have been severely limited. The scenarios that an almost "through wall" crack may not have been detected prior to overlay became a distinct possibility. At this stage of the evaluation, GE was requested to review the collected inspection reports for the overlay of 12BRG4 for objective evidence that the pipe (during overlay) was filled with water (necessary to obtain criterion compressive stresses) and that there was no evidence of a weld " blow through" from a "through wall" crack being welded with a back pressure of water in the pipe.
GE was also requested to re-evaluate the possibility that crack growth could have occurred on 12BRG4 af ter weld overlay was applied. This request resulted in GE (Attachment 9) performing a series of fracture mechanics analyses using weld residual stress assumptions. The analysis concluded:
"In conclusion, the results generally show that the flaw growth for the bounding assumptions are consistent with the UT findings and destructive examination. It does point out that without the full benefit of compressive stress from the thermal treatment, some crack growth in the original pipe cannot be ruled out.
However, the industry standard is for full structural overlays which take no credit for the original pipe wall thickness and are made of a material resistant to Intergranular Stress Corrosion Cracking.
Therefore, even with the observed growth, the overlay will meet the ASME Code structural margin requirements."
An amended letter was sent to BNL by GE (Attachment 10). Although, it did not change the original conclusions, it expanded on the previous history of weld overlay and axial cracking. Discussions with GE personnel at this time disclosed no evidence of " blow through" on 12BRG4 during the welding of the overlay which was of concern at the onset of the investigation.
64
-9. CONCLUSIONS
'The. aforementioned documentation review, nondestructive testing, metallurgical assessment and utility / contractor (CP&L/GE) discussions have led to the following conclusions:
- The chemical analyses (WDS) of the base metal / weld metal and overlay materials appeared normal for the alloys used (A240 Type 304 stainless steel, SFA 5.4 308 weld metal). The hardness values were also consistent with those expected in this type of weldment.
- The ferrite numbers recorded (FN>7) for all of the overlaid welds were consistent with industry practice. One reading was.below the recommended FN 7.5 minimum outlined in VSNRC Generic Letter 88-01.
Considering the fact .that the recording was FN 7.3 and that all other ferrite measurements on this pipe were above FN 7.5, this is considered acceptable.
- The quality of the overlays was consistent with that expected in an ASME pressure boundary weld. There was no evidence of porosity, lack of fusion,. lack of penetration, or weld metal cracking (other
. than IGSCC).
* ..The evaluation of.the ultrasonic. test data coupled with the input and re-evaluations by GE indicated- that for certain overlay configurations, ultrasonic inspection may. not provide an accurate picture of the top 25% (original pipe wall) of the pipe. Comparing the metallurgical sectioning of the-four pipes to the dye penetrant results also gives rise to questions regarding overcalls and undercalls on IGSCC. Three ~ indications (2 on 12BRK3 and 1 on 12BRJ3) did not. reveal cracks after sectioning. The comparison of cracks to ultrasonic test data also evidences the fact that the sizing / locating of cracks (before overlay) is not an " exact science" j -and results of these inspections should be carefully evaluated.
- The stress calculations (based upon-the strain gage measurements) indicate that crack growth (propagation) after weld' overlay is a distinct possibility. This conclusion is based upon -the low recorded residual compressive stresses observed on pipe 12BRG4.
- It could not be positively determined if crack growth occurred after
. overlay.by the metallurgical- tests performed.
65
- 10. REFERENCES
- 1. GE Procedure-GE- ADM-1005, Rev. O, 9/11/89; GE Proprietary not publicly available.
- 2. USNRC Regulatory Guide 1.44, May 1973.
- 3. USNRC Regulatory Guide 1.31, Rev. 3, April 1978.
- 4. Devine, T.M., J. Electrochem. Soc., Vol. 126, March 1979, pp. 374-385.
- 5. Cowan, R.L, and Tedmon, C.S., Jr.. Advances in Corrosion Science and TechnolooY, Vol. 3, 1973, p. 293.
- 6. Pande, C.S. , Suenaga, M., Vyas, B., Isaacs, H.S. , and Hailing, O.F.,
Scripta Metallurgical, Vol. 11, 1977, p. 68' %
- 7. USNRC NUREG-0531, February 1979.
- 8. USNRC NUREG-75/067, Pipe Crack Study Group Report, October 1975.
- 9. Fox, M., Proceedings: Seminar on Countermeasures for Pipe Cracking in BWR's EPRI, Vol. 1, Workshop Report, May 1980, Paper No. 1.
j 10. Chrenko, M., Proceedings: Seminar on Countermeasures for Pipe Cracking in BWR's, EPRI, Vol. 2 Workshop Report, May 1980, Paper No. 21.
j 11. Weldina Handbook, Vol. 4, Seventh Edition,1982 American Welding Society.
- 12. Gihaan, J.D., Giannuzzi, A.J., Childs , W.J. , Paper 130, Corrosion 83 (NACE) Conference, Anaheim, CA, 1983.
- 13. EPRI NN-2033-SY-LD, Project T119, September 1981.
- 14. Baumeister, T., and Marks, L., Standard Handbook for Mechanical Enaineer_1, -
7th Edition, pp. 5-6, 1958, 1967 McGraw-Hill.
66
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ATTACINENT 1 9
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ATTAC1DiENT 2
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ATTAclMENT 4 30
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GE Nuclear Energy c ,, w r<c m ,
US Cost tv kenu e Se Ji5e CA 95'25 ATTACINENT 5 August 24,1990 Mr. C. Czagowski Brookhaven National Laboratory Building 830 Upton, New York 11973
Subject:
Brunswick Pipe Overlay Samples Oear Mr. Czajkowski: As we discussed recently, we have concluded that any ultrasonic tests prior to sample cutting would not be useful due to known limitations in inspecting the the inner wall of the pipe through weld overlays. Therefore, we recommend you proceed with the strain gage residual stress program as planned. We are interested in providing technical support related to analysis of the ultrasonic examination data. We believe our input may be of particular value in understanding the ultrasonic examination techniques for examination of the welds and in interpreting the data from both the pre- and post-overlay examinations. We will provide you a summary of the pnor examinations, and would like to participate with you in evaluating any differences between the UT and destructive metallographic results. We have begun collecting the ISI data repoits and expect to have completed the process in the near future. We have also assigned Doug Henry from my organization as the the Project Engineer. When our review of this prior examination data is complete, Doug will contact you. However, if any specific questions develop as your work progresses please feel free to call me at (408) 925-6771, or Doug at (408) 925-3398. Sincerely,
/,~ h T. L. Chapman, Mar,ager Reactor & Fuel Exam: nation Technology cc: R. Herman, NRC R. Jones, EPRI S. Walker, EPRI NDE Center G Gordon, GE D. Henry, GE TLC 90106 71
l GE Nuclear Energy
... m.
m ATTACIMENT 6 November 20, 1990 Carl J. Czajkowski Brookhaven National Laboratory Department of Nuclear Energy Building 830 30 Railroad Avenuo Upton, NY 11973 _.
Dear Mr. Czajkowski:
This letter transmits the results of the ShART UT ultrasonic examination data review performed during your visit on November 14 and 15, 1990, in support of the metallurgical examination of overlayed pipe weld samples from Brunswick Unit 2. Both the Image data and the video CRT display data were included in this review. Depth ectimates have been provided where they could be reasonably ascertained, however, it should be noted that the depth measurements show these indications to be at the accepted threshold of detectabilJty using this technique. Nevertheless, we hope this information has been helpful to your metallurgical examination. We look forward to meeting with you again in January following completion of your metallurgical examination. - If you have any additional questions or if wo can be of further assistance, please do not hesitate to call me at (408) 925-3398. Sincerely, Jay A af Douglas Henry cc: T. L. Brinkman T. L. Chapman J. P. Clark D. E. Delwiche E. R. Dykes G. M. Gordon i D. W. Sandusky 72
[J __ PROJECT 2 BROOKHAVEN-NATIONAL LABORATORY METALLURGICAL INVESTIGATION.0F OVERLLY WELDS PROM NORTH CAROLINA POWER &
- LIGHT -BSEP - UNIT.2: ' REVIEW SMART UT RESULTS FROM 1988 OUTAGE
SUBJECT:
GENERAL. ELECIRIC SMART- UT . ULTRASONIC DATA FOR OVERLAY WELDS: :2B32-RR-12-BR-J3
-2B32-RR-12-BR-K3
-2B32-RR-12-BR-G4 2B32-RR-12-BR-J2 PREPARED BY: DOUG'EDGEL, G.E. hC DATE: NOVEMBER 16,1990 On November 15 and 16,_1990 a review of the SMART UT data,
~ including the video CRT display data, for the above mentioned welds was performed.: An effort was made to correlate SMART UT data with penetrant indications which the Brookhaven-examination had recorded.. As a result, indications recorded for this review include both
- indications which were previously_ recorded as relevant or non-relevant.- The following indications were noted during
-this data review (see 1988 SMART UT Data for correlation):
WELD NO./ EXAM LOCH 10N DEPTH from O.D. 2B32-RR-12-BR-G4/ 19" to 22.2" LKDN I.D. g 60 RL 23.3" TO 24.6" LKDN- I.D. 23" TO 24" -LKUP-I.D. 8" TO 10" LKUP I.D. 2 3. 8 UPST .62" 2B32-RR-12-BR-K3/ .4" TO-1.7":LKDN - I.D. 60 RL -8.6" TO 12" LKDN I.D. 3 2. 4 TO 3 3. 3 " LKDN I .' D . 34.4" TO 36.5" LKDN I . D. - 21.3" TO 23.5" LKDN I.D.- 1.2" TO-1.9" LKUP - I.D. 8.9" TO 9.5'? LKUP I.D. 10.2"1TO-11.6" LKUP I.D. ; 19.4" TO 21" LKUP I.D. 17.9"'UPST .62" 2B32-RR-12-BR-J2 19.3" TO 19.4" LKUP .73"
. 2B32-RR-12-BR-J3 7.9" TO 8.1" LKUP 1.D.
UPST = Upstream _ side of_ weld (Axial indication) LKUP =-Looking upstream LKDN = Looking downstream 73 I
GE Nuclear Energy ne w w tx cm m 175 Catwr kr%e SJn J:se CA 95t25 ATTACIMENT 7 April, 1, 1991 e Mr. C. Czajkowski Department of Nuclear Energy Brookhaven National Laboratory Upton, New York 11973
Dear Mr. Czajkowski:
Pursuant to our discussion today on your investigation of Brunswick 2 overlayed pipe sample BR-G4, we are providing background technical information related to the ultrasonic examination data and possible crack growth scenarios. We believe this input may be of particular value in understanding the results of ultrasonic examinations performed in 1986 and 1988. Figure 1 illustrates the coverage limitation on BR-G4 due to the offset of the weld under the overlay as compared with the coverage which would be obtained on a weld centered undar the overlay. Referring to Figure 1 (a), the angle beam examination looking in the upstream direction'would be the most likely to detect the crack based on orientation; however, due to the offset, the area of the heat affected zone (HA7) containing the crack cannot be scanned in this direction. While the area of the IIAZ containing the weld can be scanned by the angle beam looking downstream, the orientation of the crack is not such that the soundbeam will be reflected back toward the transducer. If the weld were centered under the overlay, a suf ficient -mean path would exist for detection of a similar crack in the upper 25% of the original pipe wall on either side of the weld, as shown f 6 in Flyt;e 1 (b) and (c). A second factor considered-was the crack growth during the period from the 1988 examination to the removal of the pipe from the system in 1989. While Ultrasonic examination c techniques for overlay examination may detect smaller flaws, they are primarily relied upon for detection of cracks which have propagated to 75% or more of the original pipe wall thickness. In order to evaluate the crack growth, a fracture mechanics analysis was performed to determine if the flaw in Weld BR-G4 could grow from less than 74% to 98% of the original wall thickness between 1988 and 1989 while starting from a flaw depth of less than 50% in 1983. 74
C. Z. CZAJKOWSKI April 1, 1991 A crack growth analysis was performed to determine the depth of the crack after approximately four 18 month operating cycles. The Buchalet-Barford polynomial fit method was used to calculate the stress intensity factors. Crack Growth was deternined using the upner bound weld sensitized crack growth. The two following analyses were performed:
- 1) the first used a pressure stress of 4 ksi, a thermal stress of 6 ksi, and a linear weld residual stress distribution of -5 ksi on the inside diameter and 30 kai on the outside diameter.
- 2) the second used a pressure stress of 4 ksi, a thermal stress of 6 ksi, and a linear weld residual stress distribution of -10 kai on the inside diameter ano 30 ksi on the outside diameter.
The results of analysis 1 are shown in Figure 2 and of analysis 2 are shown in Figure 3. These figures show that both analyses result a growth of less than 74% to 100% between 1988 and 1989 while starting from a flaw depth of less than 50% in 1983. - If any further questions develop as your work progresses please feel free to call me at (408) 925-3398. Sincerely, -
, , st1 D. O. Henry Attachments cc: B. J. Branlund T. L. Brinkman T. L. Chapman J. P. Clark G. M. Gordon E. Kiss 75
FIGURE 1. Ultrasonic Exanination Coverage rx/m T / X. a>
/SE EXT -
/ PIPE (\
\
/ /~ ... .
n . , . . K (b)
/SE EXT - \_/ PIPE l< SCAN PATH d (21/2')
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(a) Offset Weld Showing Coverage Linitation For Weld BR-G4 (b) Coverage at Ends of Scan Path For Weld Centered under Overlay (c) Scan Path On Overlay With Same Length as BR-G4 For Centered '.leid 76
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Figure 3 Residual Stress of -10. to 30 ksi 100 C 90 - N S m 80 - 74% Crack Length 0 c
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l GF Nuclear Energy wt.. o-w,
< . a ', otar' ATTAClutENT 8 BVR Technology Materials Monitor 6 Structural Analysis Services April 15, 1991 BJB 9105 I
Mr. C, Czajkovski Department of Nuclear Energy _ Brookhaven National Laboratory Upton, New York 11973
Subject:
Tracture Mechanics Analysis of the Plaw in Veld 12BRC4 2'8 for Brunswick Unit 2
Reference:
Letter to Mr. C. Czajkowski from D. O. llenry dated April 1, 1991
Dear Mr. Czajkowski:
As discussed in the reference letter, destructive examination of Veld 12BRC4-29 by Brookhaven National Laboratories revealed a flaw apnroximately 98% through the original pipe wall thickunan (hereafter i ed "through the pipe wall"). This wold was removed from the B : wick Unit 2 Power Plant during a piping replacement in 1989. An ult:casonic exarnination (UT) of the weld in 1988 showed no observable - flaw in the outer 25% (i.e. a flaw depth of 75% or more) of the original pipe wall thickness, UT crimination is generally '.ied upon to detect flaws that have propagated to 75% or more of the original pipe wall thickness. Per your recent request, the purpose of this letter is to provide additional d,nformation related to the flaw growth for Veld 12BRC4 29. The analysis presented in thir. 1ctter addresses the following three findings: e 1) Destructive examination revealed a flaw nearly 100% through the pipe wall in 1989, e
- 2) UT observed no flaw in 1988 (i.e. The flaw size was less than 75% through the pipe wall).
79
e 3) UT observed a flaw less than 50% through the pipe wall in 1983. Also, flaws greater than 50% typically grow through the pipe wall durf ng overlay application. There was no indication of through-wall flaw growth during the overlay application in 1983. A series of fracture inechanics analysc.s were performed using a reasonable set of weld residual stress assumptions. The veld residual stress resulted f roin the thermal treatment of the veld; the the rrma l treatreent was a result of the weld overlay applied on Veld 12BRG4 29. The two following conniderations were used to choose the residual stress distributions to be analyzed: Q e The strain data shown in Table 1 for Veld 12BRC4 29 reay not be reliable, since cracking of the section may have relieved much of the residual stress that had existed in the section prior to the destructive exarnination.
- The strain data shown in Table 1 provides an entirnate of the residual stress .n Velds 12BRJ2 14 and 12BPJ3-35; this data can only be used to e s t irna t e the residual stress on the inside and outside d i a rn e t e r of the pipe and says nothing about the through thickness distribution. Therefore, this data was used to e s tiina te the magnitude of residual stress in Vold 12BRG4-29 before ,
any flaw growth had occurred; in the absence of through-thickness data a linear distribution was used. i There were six residual stress distributions used to bound the data. For each stress distribution an applied stress of 10 ksi (pressure stress - 4 ksi and thermal stress - 6 ksi) was superimposed on each of the six residual stress distributions. The six cases and the rationale for choosing the distribution are shown in Tabin 2. Figures 2 through 6 show the results of the analysis for Cases 2 through 6, respectively. As expected, Case 1 resulted in no growth of the flaw. The results of Cases 2, 3, 5, and 6 demonstrated that any 80
l C. Z. Czajkowski April 15, 1991 partial benefit produced results that were consistent with the findings of the UT inspection and the destructive examination. The results of Cane 4, while not in total agreen;ent with the findings, were still very close. In conclusion, the results generally show that the flaw growth for the bounding assurnt tions are consistent with the UT findings and destructive examination. It does point out that without the full benefit of cornpressive stress f rorn *he thermal t r e a t ro e n t , s orne crack growth in the original pipe cannot be ruled out, llowever, the industry standard is for full structural overlays which take no credit for the original pipe wall thickness and are inade of a material resistant to Intergranular Stress Corrumon Crackint,. Therefore, even with the observed growth, the overlay will rnoot the ASME Codo structural tuargin requirements. Details of the calculations are contained in DRP 137 0010, Report No. SASR 91-32. If you have any questions, feel free t c. call rno at (408) 925-1472. Sincerely,
'h lo d% N B.J. Branlund Attachments cc: T. L. Brinkman T. L, Chapman J. P. Clark G. M. Gordon E. Kiss D. O. llenry S. Ranganath 81
C. Z. Czajkowski -4 - April 15, 1991 Table 1 Strain Cage Data Pipe ar' Cage Strain Stress
- Position Station F *>( lio (pin /in) (ksi) on Pipe 12BRJi- 1 751 23 ID 2 543 -16 ID 3 -1164 35 OD 4 1144 34 OD 12BRJ3-35 5 491 15 ID 6 392 12 ID -
7 -1291 39 OD 8 1147 34 OD 12BRC4-29 17 26 1 ID 18 319 -9 ID 19 74 -2 OD 20 open OD
- A teodulus of elasticity of 30 x 10 ksi was used to calculate stress.
4 e 82
C. Z. Czajkowski April 15, 1991 Table 2 List of Linear Stress Distributions Case Residual Stress Rationale ID OD (ksi) (ksi) 1 -30 30 This case represents full benefit from the thermal treatinent.
,1 5 30* This cose rr. presents a marginal lack of benefit 1*pm the thermal treatment.
3 10 30* This case represents s orne benefit from the t h e r rn a l treatment and is a conservative representation of the strains measured in Velds 12BRJ2 14 and 12BPJ3-35. 4 -5 - 2* This case represents a best estimate of the veld residual stress measured in 12BRC4-29. It should be re-emphasized that this data may be unreliabic. 5 -5 5 This case represents a ruinirnura bene fit frorn the thermal treatment. 6 0 0 This case r2 presents no c ornp r e s s ive stress benefit from the therrnal treatment.
- The resultant force of a residual stress distribution is zero, (i.e.
for a linearized stress, the magnitudo of the stress on the inside and outside surface should be equal and opposite in sign). lloveve r , around the circumference there can bn localized variations in the residual stress, such that the sum of the stresses around the circumference has a resultant force of zero. 83
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GE fluclear Energy
<4 o ( , , , ,
~ < ae ATTACINENT 9 FNR Technology Materials Monitor I. Structural Analysis Services April 17, 1991 BJB 9106 Mr. C. Czajkowski Department of Nuclear Energy _
Brookhaven National Laboratory Upton, New York 11973
Subject:
Fracture Mechanics Analysis of the Flaw in Veld 12BRC4 29 for Brunswick Unit 2
Reference:
Letter to Mr. C. Crajkowski from B. J. Branlund dated April 16, 1991 (BJB 9105)
Dear Mr. Czajkowski:
/s well as sending the reference letter to you on April 16, 1991,
~
an additional copy was sent to the CE weld overlay application experts. Based on their ccmments, we wish to clarify and correct one statement made in the referenced letter. Specifically, the assertion that
". . flaws greater than 50% typically grow through ti.* pipe wall during ,
overlay application". There has been no analytical data or field experience indicating that flaws >50% through-wall grow during the overlay application. There have been cases where axial cracks have grown through wall and leaked when the first overlay layer was deposited. In some cases, these cracks (which are often difficult to size by ultrasonics due to their short aspect ratio and tip location relative to the edge of the weld crown) could have been reported to be 50% through-wall, lloweve r , experienco with axial cracks and wold overlay application is that the cracks had to be nearly through wall prior to overlay application. In this case, the heating / melting from the welding combined with the water pressure in the 89
C. Z. Czajkowski April 17 1991 pipe.. would cause a " blow through" or Icak during the overlay welding. It was this experience with axial cracks that led to the confusion on our part in the referenced letter. Therefore, a corrected finding 3) is provided in the revised letter enclosed herein. It should now read:
- 3) t!T observed a flaw less than 50% through the pipe wall in 1983.
Since this revision to finding 3) does not contribute to the
-conclusions, this revi:ilon will not influence any of the results or conclusions of the reference letter.
Sincerely, B. J. Branlund I Engineer, Materials Monitoring & Structural Analysis Services l
Attachment:
cc: T. L. Brinkman i n T. L. Chapman l LJ. P. Clark
~ '
O. M. Gordon E. Kiss D. O. Henry S. Ranganath 7 s 90
)
~'
GE iluclear Energy ATTAclNENT 10 BVR Technology Haterials Monitor & Structural Analysis Services April 17, 1991 BJB 9105, Revision 1 Mr. C. Czajkowski Department of Nuclear Energy Brookhaven Nat.ional Laboratory Upton, New York 11973
Subject:
Fracture Mechanics Analysis of the flaw in Weld 12BRG4 29 for Brunswick Unit 2
Reference:
Letter to Mr. C. Czaj kows ki from D. O. Itenry dated April 1, 1991
Dear Mr. Czajkowski:
As discussed in the reference letter, destructive exarnination of Weld 12BRC4-29 by Brookhaven National Laboratories revealed a flaw approximately 98% through the original pipe wall thickness (hereafter called "through the pipe wall"). This weld was removed from the Brunswick Unit 2 Power Plant during a piping replacement in 1989. An ultrasonic examination (UT) of the veld in 1988 showed no observable flaw in the outer 25% (i.e. a flaw depth of 75% or mote) of the original pipe wall thickness. UT examination is generally relied upon to detect flaws that have propagated to 75% or more of the original pipe wall thickness. Per your recent request, the purpose of this letter is to provide additional information related to the flaw growth for Weld 12BRC4 29. The analysis presented in this letter addresses the following three findings:
- 1) Destructive examination revealed a flaw nearly 100%
through the pipe wall in 1989. e 2) UT observed no flaw in 1988 (i.e. The flav size was less than 75% through the pipe wall). 91
C Z. Czajkowski April 17, 1991 e 3) UT observed a flaw less than 50% through the pipe wall in 1983. A series of fracture mechanics analyses were perforrned using a reasonable set of weld residual stress assunptions. The weld residual stress resulted froin the the rinal treatment of the weld; the the rrna l treattnent was a result of the veld overlay applied on Veld 12BRC4-29. The two followirr, considerations were used to choose the residual stress distributions to be analyzed: __ e The strain data shown in Table 1 for Veld 12BRG4 29 may not be reliable, since cracking of the section may have relieved much of the residual stress that had existed in the section prior to the destructive examination. e The strain data shown in Table 1 provides an estimate of the residual stress in Welds 12BRJ2 14 and 12BFJ3 35; this data can only be used to estiinate the residual stress on the inside and outside d i sin c t e r of the pipe and says nothing about the through thickness distribution. Therefore, this data was used to estimate the magnitude of residual stress in Weld 12BRC4 29 before any flaw growth had occurred; in the absence of through thickness data a linear distribution was used. There were six residual stress distributions used to bound the data, For each stress distribution an applied stress of 10 kai (pressure s, tress - 4 ksi and thermal stress - 6 ksi) was superimposed on each of the six residaal stress distributions. The six cases and the rationale for choosing the distribution are shown in Table 2.
- Figures 2 through 6 show the results of the analysis for cases 2 through 6, respectively. As expected, Case 1 resulted in no growth of the flaw. The results of Casem 2, 3, 5, and 6 demons,trated that any o partial benefit produced resui inat were consistent with the findings 92
C. Z. Czajkowski April 17, 1991 of the UT inspection and the destructive e x arnina t i on . The results of Case 4, while not in total agreernent with the findings, were att11 very. close. In conclusion, the results generally show that the flaw growth for the bounding assurnptions are consistent with the UT findings and destructive e x a rni na t i on . It does point out that without the full benefit of cornpressive stress f r orn the the rrnal treattnent , s orne crack growth in the original pipe cannot be ruled out. Ilowever, the industry standard is for full structural overlays which take no credit for the original pipe wall thickness and are made of a material resistant to Intergranular Stress Corrosion Cracking. Therefore, even with the observed growth, the overlay will meet the ASME Code structural margin requirements. Details of the calculations are contained in DRF 137 0010, Report No. SASR 91-32. Ir you have any questions, feel free to call no at (408) 925-1472. Sincerely, D .Scd - B. J. Branlund Engineer, Materials Monitoring & Structural Analysis Services Attachments cc: T. L. Brinkrnan T. L. Ch.pman J. P. Clark C. M. Cordon E. Kiss D. O llenry S. Ranganath 93
C. Z. Crajkovski 4- April 17- 1991 Table 1 Strain Cage Data Pipe and Cago Strain Stress
- Position Station Humber No (pin /in) (ksi) on Pipe 12BRJ 2 14 1 751 23 1D 2 543 16 ID 3 1164 35 OD 4 1144 34 OD 12BRJ 3 35 5 491 15 ID _
6 392 12 ID 7 1291 39 OD 8 1147 34 OD 12BRG4-29 17 26 1 ID 18 319 9 ID 19 74 2 OD 20 open OD l'
- A modulus of clasticity of 30 x 10 kai was used to calculate stress.
94
4 C. Z. Czajkowski - 5- April 17, 1991 Tabic 2 List of Linear Stress Distributions Case Residual Stress Rationale-ID OD (ksi) (ksi) , 1 -30 30 This case represents full benefit frotn the the rreal treatreent . 2 -5 30* This case represents a marginal lack of benefit f roin the therrmal treatment. _ 3 10 30* This case represents m orne benefit f roin the thermal treatment and is a conservative representation of the strains measured in Welds 12BR12-14 end 12BPJ 3- 35. 4 5 2* This case represents a best e s t i rna t e of the ~ weld residual stress recasured in 12BRC4 29. lt should be re ernphasized that this data inay be unreliable. 5 *5 5 This case represents a ininiinurn bene fit froin the thermal treatment. 6 0 0 This case represents no c ornp re s s ive stress benefit from the therinal treatreent.
- The resultant force of a residual stress distritution is zero, (i.e.
for a linearized stros::, the inagnitude of the stress on the inside and outside surface should be equal and opposite in sign), llowever, around the circumference there can be localized variations in the residual stress, such that the sum of the stresses around the circumference has a resultant force of zero. 95
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' &r'O 5 7. The chemical analysis of the welds.were normal for the alloys used (type 304 stainless steel, type 308 weld metal).
The. study also concludes that the ultvasonic inspection techniques used for inservice inspection of the overlays.may not accurately depict the top 25% of the pipe in all cases and that crack growth is possible af ter weld overlay under certain conditions, u.atywvaoscotscnwives,o.. , ,. .,,,,,-. .,- . ., o ...na ,u n u mi u Weld overlaid Pipe; Stainless Steel; BWR; Metallurgical Evaluatton; Unlimited
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