ML20237A614
| ML20237A614 | |
| Person / Time | |
|---|---|
| Site: | Quad Cities  |
| Issue date: | 12/04/1987 |
| From: | COMMONWEALTH EDISON CO. |
| To: | |
| Shared Package | |
| ML20237A601 | List: |
| References | |
| GL-84-11, NUDOCS 8712150131 | |
| Download: ML20237A614 (15) | |
Text
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q December 4, 1987
Subject:
Summary Report regarding Ultrasonic Examinations performed during the Fall 1987 Refueling Outage Quad Cities Unit 1 I - BACKGROUND Extensive ultransonic examination program of IGSCC susceptible stainless steel piping welds by EPRI qualified inspectors has been performed during the 1987 Quad. Cities Unit i refueling outage.
The original inspection plan which conforms to generic letter 84-11 requirements includes ultrasonic examination of 29 previously examined welds, 21 not previously examined welds, I weld' with known flaws, and 3 ' weld overlays. Attachment A titled " Augmented Stainless Steel - Weld Inspection Plan - Fall 1987 - Quad Cities, Unit One" provides the details of the inspection scope.
A total of 146 piping welds and 17 overlay welds were' inspected during this 1987 outage. The additional 95 welds examined are as follows"
- 1. In the original.and the expanded namples all but four (4) recirculation piping welds 12" - larger were inspected due to flaws, mostly axially oriented, u scovered in seven (7)
. recirculation piping welds.
- 2. Due to flaws discovered in six (06) welds examined prior to Mechanical Stress Improvement Process (MSIP) all but four (4) stainless steel core spray welds were inspected. MSIP was applied to all unflawed and accessible core spray welds inside the drywell. The two (2) uninspected welds are located on section of piping outside the drywell with operating temperature of less than 2000F. The other two (2) welds are inaccessible, i
l 3. All but six (6) stainless steel LPCI welds were inspected due to l flaws discovered in one (01) pre-MSIP examination. MSIP was applied to all accessible LPCI welds between the isolation valves and drywell penetrations. The four (4) uninspected LPCI welds are located on section of piping outside the drywell with operating temperature of less than 2000F, The other two (2) welds are inaccessible.
8712150131 871210 4 R ADOCK 0500 L._ _ . _ _ _ _ _ _ _ . __-
The following table contains break down of welds inspected by system and size.
84,11+ISI ist 2nd Not MSIP W.O.L.
Size Total Orig. P l_an Expan. Expan. Exam gplied Insp.
Recirculation Outlets 28" 30 6+1+2(1) 6 11 4 0 0 Noz-SE 28" 2 1 0 0 1 0 0 Header 22" 20 5 2 11 0 0 2 Risers 12" 41 5 8 14 0 0 15 Noz-SE 12" 10 2 0 0 8 0 0 RHR LPCI 16" 32 7 19(2) 0 6 18 0 SDC 20" 17 6 0 0 11 0 'O Core Spray 10" 32 6 6+16(3) 0 4 20 0 Jet Pump Inst. 12",8",4" 10 2 0 0 0 8 0 l Recire, l Hd. Sp., 6" 12 3 0 0 9 0 0 i
Hd Vt, CRD, RWCU 4" 26 7 0 0 19 0 0 I
Total 232 53 57 36 70 38 17-(1) 6 welds were in the 84-11 inspection scope, 1 weld with known flaw (02BS-S9), 2 welds were in Sect XI inspection scope.
(2) 19 additional welds were inspected because of MSIP inspection requirement.
(3) 6 welds were inspected because of flaws discovered in the original sample. 16 additional welds were inspected because of MSIP inspection requirement.
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II- INSPECTION RESULTS
- Summary of flaws observed Weld No. Flaw Characterization Remarks 12" recirculation 02C-S3 Pipe side:
(Elbow - Pipe) 0.75" x 10%TW - axial 0.8.5" x 10%TW - axial 02D-S3 Pipe side:
(Elbow - Pipe) 0.2" x 10%TW - axial 0.1" min x 10%TW - axial 02E-S3 Pipe side:
(Elbow - Pipe) -
1.0" x 15%TW - axial 02F-S3 Pipe side:
(Elbow - Pipe) 0.8" x 9%1W - axial 0.56" x 20%TW'- axial .
0.88" x 13%TW - axial 0.76" x 27%TW - axial 0.72" x 10%TW - axial Elbow side t
l 0.40" x 14%TW - axial 1
02M-S4 Elbow side (Pipe - Elbow) 1"L x 17% - 22% TW - axial 22" recirculation 028-F1 Pipe side Scan on pipe side (Valve - Pipe) 3" x 26%TW - circumferential only.
0.2" min x 24%TW - axial 28" recirculation "
02BS-S5 Pipe side l (Pipe - Tee) 2" min x 15%TW - circumferential Scan on pipe side 4" x 25%TW - circumferential only.
0.2" min x 20%TW - axial 0.3" x 20%TW - axial 02BS-S9 Pipe side (Pipe - Elbow) 3.5" x 35% - circumferential See " Specific Weld 1.5" x 20% - circumferential Discussion" for 6" x_(0% - circumferential additional details.
Elbow side 3"'x 40% - circumferential 2" x 35% .circumferential 3.25" x 35% - circumferential-1.5" x 30% - circumferential 2.5" x 44% - circumferential 0.1" min x 35% - axial 1 ,
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16" LPCI 108D - S13 Pipe side (Pipe - Elbow) Post MSIP results 1.5" x 18%TW - circumferential 4.75" x 20TW - circumferential 10" Core Spray 14A - F2 Pipe side (Pipe - Safe End) Automated Scan 0.64" x 23%TM - axial 14A - S8 Elbow side (Pipe - Elbow) 1.5" x 19%1M - circumferential 0.1" min x 32%TM - axial 14A - S9 Pipe side (Elbow - Pipe) 0.3"L x 20%TW - axial Elbow side
- 0.45"L x 17%TM - axial 14A - Fil Elbow side (Valve - Elbow) 0.1" min x 20%TW - axial 148 - F2 Pipe side (Pipe - Safe End) Automated Scan 0.4" x 14%TM - axial 0.35" x 11%TW - axial 148 - S8 Upstream Elbow side (Elbow - Elbow) 0.6" x 17%TW - axial 0.5" x 10%TM - axial 0.5" x 25%TW - axial ,
{
0.4" x 14%TM - axial j
Note: Flows measurements reported here are made by GE inspectors !
who are EPRI qualified in flaw detection and sizing.
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. MSpecific Weld Discussion ;
l
. a/,02BS-S9 02BS-S9 is a 28-inch pipe-to-elbow weld in the suction side of the recirculation system. This weld was IHSI treated in 1984 and has been previously reported as flawed in both the 1984 (post IHSI) and 1986 l examinations. In spite of some interpretation problems associated with the 360 degree intermittent root (ID) geometry on both side of this {
weld, there was reasonable agreement between the 1984 and 1986 results.
The current examination results shown in Table 1 have generally j confirmed the previous flaw indications, as well as the extensive root l
geometry. On cursory review, the data would seem to indicate that the approximately 7 inches of ISGCC (24% through-wall depth max.) reported in 1986 has " grown" to approximately 23 inches of combined length and a maximum depth of 44%. In addition, four (4) new circumferential flaws and one (1) new axial flaw have been identified in the current examination.
An automated scan of tbs weld was performed and generally confirmed the flaw determination; and the presence of intermittent ID geometry.
Upon more detailed study of the data, several observations can be made, including:
The large majority of the flaws are located around the 180 degree location corresponding to the intrados region of the elbow, possibly relating to an area of higher bending stresses or more difficult UT examination due to contour. Root (ID) geometry has been observed in '
this weld in all examinations intermittently for 360 degrees on both the pipe and elbow sides of the weld re -
Typically circumferentially-oriented IGSCC is located parallel and close to the weld root, making the ultrasonic signals hard to differentiate.
Metallographic examinations performed on similar 28-inch Quad Cities ,
and Dresden weldments (original shop welds) has exhibited a "backwelded" root condition from original shop fabrication. The i ultrasonic signal from this has previously been confused with shallow circumferential IGSCC.
Fracture mechanics analysis of this weld would most likely be able to demonstrate structural integrity for continued operation for a subsequent fuel cycle, though the presence of the axially-oriented flaw and the axial components of the circumferentially-oriented flaws is a concern. Factors such as the availability of welding services, etc.
therefore a leak barrier weld overlay repair was applied during this outage.
4 Tabl9 1 1
Comparison of Ultrasonic Examination Results Quad Cities Unit 1 - Weld 02BS-S9 i 1986 1987 Flaw Orientation / Flaw Description Location Orientation / i Description Location i 1" x 15% circ./ pipe not observed 1.5" x 24% circ./ pipe 3.5" x 35% circ.M/ pipe )
1" x 23% circ./ elbow 3" x 40% circ.*/ elbow i 2.5" x 20% circ./ elbow 2.5" x 44% circ */ elbow -
4" 10 geometry pipe 6" x 40% circ.M/ pipe (1" + 5" intermit.)
1" x 15% circ./ elbow not observed .
e.ot observed 2" x 35% circ.*/ elbow >
not observed 1.5" x 30% circ.*/ elbow not observed 3.25" x 35% circ.*/ elbow not observed 1.5" x 20% circ.*/ pipe not observed 0.1" min. x 35% axial i
1
. i circ * = axial component noted associated with circumferential flaw l
j
b/ 108D-S13 i 10BD-S13 is a 16-inch pipe-to-elbow weld in the 8 loop discharge of the LPCI injection system. i This weld was not IHSI treated in 1984 and has not been previously examined. !
An ultrasonic examination was performed on this weld prior to the application of MSIP and it was found to contain three (03) relatively short, shallow circumfertial flaws, all on the pipe side of the weld.
analysis permit a repair usingFlaw characterization and fracture mechanics MSIP. Ultrasonic examination after MSIP showed that flaws dimensions have not changed except that two (02) separate circumferential flaws reported in pre-MSIP examination are now combined into one circumferential flaw of 4.75 inches long.
- CDiscussion Regarding Flawed IHSI Treated Welds
' An inspection of the construction radiographs, the IHSI treatment records and the ISI records for the three (03) large diameter welds with IGSCC like UT flaw indications suggest the following:
- Post weld grinding appears to be implicated in all of the flaw evaluations and may not be fully compensated for in IHSI treatment of large diameter joints.
- The IHSI treatments of two of the three lerge diameter welds inspected (welds 02B-Fi and 02BS-SS) indicate that the IHSI treatment was marginal. The IHSI treatment for weld 02BS-S9 appeared to be well within the EPRI guidelines.
1 WELD REPAIRS USummary of Weld Repairs A total of thirty one (31) flawed stainless steel piping welds have been identified at Quad Cities Unit 1 since 1982 in the recirculation (24),
core spray (6) and LPCI (1) systems. A total of thirty (30) weld overlay repairs have been applied, with one (1) weld " repaired" by use of stress improvement (MSIP).
I Seventeen (17) flaws had been identified in UT examinations conducted {
prior to the current refueling outage, with fourteen (14) new flawed j weldments identified in the current outage. The large majority of the '
new flaws are axially oriented. The limited number of circumferential flaws detected during the current outage have been relatively'short
(< 20% of circumference) and shallow (< 30% through-wall).
l l The attached table 2 summarizes the weld overlay status and design bases for all flawed welds at Quad Cities Unit 1.
as follows: The data can be summarized 1
Three (3) existing weld overlay repairs were re-examined using the EPRI-developed ultrasonic (UT) examination technique and automated UT equipment. These weld overlays all exceed the standard weld overlay thickness required by NUREG 0313 and were surface conditioned for UT examination in accordance with the EPRI criteria in 1986. These 3 welds contained circumferential flaws whose extent was >10% of the pipe circumference, s
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- Summary of Weld Repairs 'l Twelve (12) enisting weld overlay repairs were built up to a thickness a
, which exceeds the standard weld overlay thickness required by NUREG 0313 -
and were surface conditioned in accordance with the EPRI criteria during the current outage. All 12 will be UT examined using the EPRI
(
techniques and automated equipment. The flaws originally reported in-these welds were primarily axial flaws with any circumferential flaws not exceeding 10% of the pipe circumference.
One (1) existing leakage barrier weld overlay on a 12-inch recirculation riser weld remains under a.previously (1984) installed Pipelock, . I Fourteen (14) new weld overlay repairs were installed during the current outage as a result of newly identified IGSCC flaws. The large' majority of these repairs will be built up (if required), surface conditioned and -
UT examined using EPRI or equivalent techniques at a subsequent refueling outage.
One (1) weld (10BD-S13) was reported as flawed prior to and af ter application of the MSIP. This weld was treated and'will be re-examined at the next refueling outage, i
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Table 2 Weld Overlay Status' ard Design Bases .
. Quad Cities Unit 1 Current Flaw Weld Overlay Remarks
. Weld No. Characterization Design (5) 12-inch recirculation riser welds -
02C-S3 2 axials leak barrier (4) 1987 exam 02C-S4 4" cire, &'3 axials standard (1) 1984 exam 02D-S3 2 axials leak' barrier (4) 1987 exam l 02D-S4 2 axials standard (2) 1984 exam 02E-S3 1 axial leak barrier (4) 1987 exam 02E-S4 4 1" cire. & 8 axials standard (2) 1984 exam 02F-S3 6 axials standard (2) 1987 exam-02F-S4 3 axials standard (2) 1984. exam 02G-S3 { 1" circ. 6 8 axials standard (2) 1984 exam 02G-S4 1" circ. & 1 axial standard (2) 1984 exam 02H-S3 3" circ. 6 3 axials standard (2)- 1984 exam 1
02H-S4 4 axials standard (2) 1904 exam .
1 02J-F6 7'axials standard (2) 1984 exam ~
02J-S3 < 1" circ. 6 1 axial standard (2) . 1984 exam 02J-S4 13.3" circ & 9 axials standard (1) 1984 exam 02K-S3 10.6" circ. & 5 axials . standard (1) 1984 exam l
02K-S4 2 axials standard (2) 1984 exam 02M-S3 3 axials leak barrier Pipelock '
, installed -
1984 exam 02M-S4 1 axial standard (2)
~
1987 exam I
22-inch recirculation welds -
l 028-F1 3" circ. 6 1 axial leak barrier (4) 1987 exam (26%' max) 028-S7 'I axial standard (2) 1984 exam.
028-S10 2" circ. & 3 axials standard (2) 1984 exam
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' ' Table 2 (continued)
Weld Overlay Status and Design Bases Quad Cities Unit 1 Current Flaw Weld Overlay Remarks Weld No. Characterization Design (5) 28-inch recirculation welds -
028-S5 9" circ & 2 axials leak barrier & 1987 exam (25% max.) resid. stress (3) 028-S9 23.25" circ.-& 1 axial leak barrier & 1987 exam (44% max.) resid stress (3) 16-inch LPCI weld -
10BD-S13 6.25" circ.'(20% max.) no weld overlay .1987 exam MSIP " repair" 10-inch core spray welds -
14A-F2 1 axial leak barrier (3) 1987 exam 14A-S8 1.5" circ. & 1 axial standard (4) l's87 exam 14A-S9 2 axials leak barrier (3) 198) exam 14A-S11 1 axial leak barrier (3) 1987' exam 14B-F2 2 axials leak barrier (3) 1987 3xam 148-S8 4 axials leak barrier (3) 1987 exam Notes:
(1) surface conditioned and UT examined 1986 and 1987 (2) surface conditioned and UT examined in 1987 (3) to be surfs.ce conditioned and/or built-up and UT examined in subsequent refueling outage. ' A UT bonding check was performed during the current outage. >
1 (4) to be surface conditioned and UT examined in subsequent refueling outage.
(5) identifies the year of UT examination results and initial' weld overlay repair.
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, III - WELD OVERLAY EXAMINATION During the current (1987) refueling outage at Quad Cities Unit 1, all !
seventeen (17) standard weld overlay repairs were ultrasonically examined using the EPRI - developed techniques. All but one of these examinations were perfortaed using automated examination equipment (GE SMART UT).
Fifteen (15) overlay welds were originally applied in prior refueling outages, of which, three (03) were built up.to the " standard" or full structural design, surface conditioned and examined in the 1986 outage.
These three welds contained circumferential flaws whose extent was 10%, ,
Twelve (12) were built up as required and surface conditioned during the I current outage. Two (02) new 12-inch weld overlays were also surface conditioned and examined during the current outage'.
A summary of the weld overlay examination results and thickness is found in Table 3.
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Table 3
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Weld Overlay Ultrasonic Examination Results i
Quad Cities Unit 1 Fall 1987 Outage Minimum Remaining Weld overlav Ligament Remarks 02C-S4 0.40 Autornated Scan 02J-S4 0.33 Automated Scan 020-S4 0.38 Automated Scan 02E-S4 0.36 Automated Scan 02F-S3 0.49 Automated Scan 02F-S4 0,41 Automated Scan 02G-S3 0.38 Automated Scan 02G-S4 0.32 Automated Scan 02H-S3 0.43 Automated Scan 02H-S4 0.35 Automated Scan 02J-S3 0.37 Automated Scan 02J-F6 0.26 Automated Scan 02K-S3 0.35 Automated Scan 02K-S4 0.37 Automated Scan 02M-S4 0.32 Manual Scan
- 028-S7 0.56 Automated Scan 028-S10 0.45 Automated Scan
- Specific Weld Overlav Discussion The following sections provide a detailed review and comparison of the 1986 manual and the 1987 automated UT examination data for weld o erlays 02C-S4, 02J-S4, and 02K-S3, a/ Weld Overlav 02C-S4 Five (5) axial flaws were observed in 1986, as well as a small area (5/16" x 5/8") characterized as " lack of bond". The current examination also reports five (5) axial flaws in the same locations as the 1986 examination, but not the lack of bond.
The consistency of flaw locations and the measurements of remaining ligament between the two examinations demonstrates the effectiveness of this weld overlay.
There is sufficient weld overlay deposit above each flaw such that the required full structural thickness (0.235") is maintained. The deepest flaws are located in the dilution zone.
Comparison of UT Data - Weld Overlay 02C-S4 1987 Examination 1986 Examination length, in, remain. liq. length, in, remain, lig.
0.3 0.40 0.5 0.48 0.27 0.50 0.35 0.48 1
0.21 0.48 0.3 0.48 0.57 0.48 0.5 0.48 0.33 0.61 0.3 0.66 l b/ Weld Overlav 02J-S4 i
Sixteen (16) axial flaws were detected in the UT examination of this weld overlay in 1986. During the current examination, there were eleven ~
(11) axial flaws reported. No circumferential flaws or lack of bond were reported in either examination, i
The minimum value of the remaining ligament reported in 1986 has not significantly changed in the 1987 examination, though there are variations in the values for individual flaws. The required full structural weld overlay thickness of 0.265 inches is maintained above all flaws, though seven (7) flaws penetrating into the first weld overlay layer.
I The following table is a comparison of the results. For convenience and clarity of presentation, the reported indications are grouped by general !
location, rather than attempt to perform a "one-to-one" correlation.
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. Comparison of the UT Examination Results I Weld 09erlay 02J-S4 s
1987 Examination 1986 Examination Location No. of Flaws Remain. Lig. No. of Flaws Remain. Liq.
O to 8" 5 0.35 - 0.42 8 0.35 - 0.45 12" -
2 0.34 - 0.46 l
19" - 1 0.52 27 to 34" 6 0.33 - 0.42 5 0.40 - 0.48 l
c/ Weld Overlay 02K-S3 i
In the 1986 manual examination, four (4) circumferential flaws were j observed in the inner 50% of the original pipe wall under this weld i overlay. Additionally, one (1) axial flaw was reported with a remaining ligament of 0.42 inches. All flaws were on the downstream (pipe) side i of the weld overlay. -
j l
In the current examination, three (3) of the previously reported snort ;
circumferential flaws (remaining ligaments 0.85 to 0.88 inches) are l reported as a single circumferential flaw 3.2 inches long with a minimum remaining ligament of 0.50 inch. The axial flaw reported in 1986 has shown no change in the remaining ligament (0.42 inches). Additionally, three (3) axial flaws are reported, generally in the intrados region of the pipe-to-elbow, with remaining ligaments of 0.35 to 0.40 inches.
These axial flaws compare well in location and spacing with the UT examination results reported on the weldment prior to weld overlay i application. It is therefore believed that these three axial flaws '
located in a more difficult region of the weld overlay to examine were
" missed" in the 1986 manual examination. All flaws reported in the current examination are also located on the downstream (pipe) side of the weld.
The ultrasonic examination results support the following observations and conclusions:
The flaws most commonly observed are axial flaws which are located under the weld overlay and are located in the upper 25% of the original pipe wall.
In all cases, except for " leak barrier" overlay, the " remaining ligament," that is the minimum amount of sound metal remaining above the crack tip, exceeds the requirements for a " standard" or " full structural" weld overlay per.NUREG-0313. This is very conservative since the standard weld overlay thickness is circumferential crack, even though the flaws are axially-oriented.
As reported in 1986, axial flaws have been observed with crack tips i located in the weld overlay dilution zone or first layer. In all cases, this first layer did not. meet the delta ferrite requirement
( > 7.5 FN) and was " discarded," that is not counted in the weld
, overlay thickness. The 1987 examinations show no change in this.
The current automated UT examination technique. appears to be "better" axial f laws am in providing or more permanent reference.than the previous manua
-14"
ATTACHMENT A AUGMENTED STAINLESS STEEL 3- WELD INSPECTIOB PLAM
' FALL'1987 l QUAD CITIES UNIT ONE 84-11 84-11 NOT- 84-11.
PREV. NOT PREV. PREV. i SIZE TOTAL WOL EXAM. EXAM. EXAM. EXAM, ..WOL j l
RECIRCULATION OUTLETS 28" 30 NA 30- NA 6. NA j N0Z-SE 28" 2 NA 2 NA 1(A) NA-HEADER 22" 20 2 16 2 3 2 RISERS' 12" 41 14 27 NA 5 NA- 3 N0Z-SE 12" 10 ' NA 4 6 NA(A) 2(A) ;
RHR LPCI 16" 32 , NA 14 18 3 4 ,
SDC 20" 17 NA 10 7 2 4 CORE SPRAY 10" 32 NA 12 20 2 4 JET PUMP 12",8",4" 10 NA 10 NA 2 NA INST.
RECIRC, H.S.,
HV, CRD,RWCU 6" 12 NA 8 4(B) 2 1 4" 26 NA 17 9 3 i 4
WELD WITH KNOWN FLAWS 1 29 21' 3' PREV. EXAMINED WELD SAMPLE 29 NOT PREV. EXAM. WELD SAMP. 21 WELD OVERLAY SAMPLE _3 54 INSPECTIONS.
(A) THE N0Z-SE WELDS ARE CONSIDERED A SEPARATE CATEGORY FROM SUSCEPTIBLE PIPING WELDS. THESE WELDS HAVE A CORROSION RESISTANT CLADDING ON THE 10 OVER THE WELD AND ADJACENT HAZ'S, -TWO (2) 12" N0Z-SE WELDS (INCLUDING THERMAL SLEEVE ATTACHMENT WELDS) AND ONE (1) 28" N0Z-SE WELD WILL BE-EXAMINED.
(B) THREE (3) WELDS ARE INACCESSIBLE NOTE 1 SAMPLE EXPANSION IF FLAWS ARE FOUND WITHIN THE INSPECTION SAMPLE OF A SPECIFIC PIPING-CATEGORY, ANOTHER. EQUIVALENT SAMPLE OF THE'SAME NUMBER IN THAT CATEGORY WILL BE INSPECTED. CATEGORIES ARE DEFINED BY THE HORIZONTAL LINE ON THE TABLE.
-0100S
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