ML20207H366
| ML20207H366 | |
| Person / Time | |
|---|---|
| Site: | Quad Cities  |
| Issue date: | 12/30/1986 |
| From: | Turbak M COMMONWEALTH EDISON CO. |
| To: | Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| 8786D, NUDOCS 8701070514 | |
| Download: ML20207H366 (26) | |
Text
,
/
h Commonwealth Edison 1
{
One First National Plan, Chicago, Illinois g-f Address Reply to: Post Office Box 767 Chicago, Illinois 60690 - 0767 December 30, 1986 Mr. Harold R.
Denton, Director Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washingto, D.C.
20555
Subject:
Quad Cities Station Unit 2 Inservice Inspection Information NRC Docket No. 50-265
Dear Mr. Denton:
As discussed yesterday, we are submitting a preliminary report of the inservice inspection and repair activities performed at Quad Cities Station Unit 2 during the current refueling outage.
The following report is divided into six separate attachments:
1.
This attachment is a summary of the augumented stainless steel ultrasonic examinations performed during the 1986 refueling outage.
Compliance to the NRC accepted sampling plan submitted by Commonwealth Edison (July 15, 1986) has been demonstrated.
Additionally, it should be noted that all IGSCC-susceptible piping welds equal to or greater than 12-inch have been examined in the recirculation system.
2.
Quad Cities 2 Stainless Steel " Flaw List" This attachment lists the flawed welds, when they were identified and their disposition.
3.
Discussion and Observations Regarding Ultrasonic Examinations of Previously Flawed Stainless Steel Welds This attachment discusses the UT examination results and actions for the (10) weldments which have been reported as flawed from previous outages.
4.
Discussion and Observations Regarding "New" Flaws Observed in IHSI-Treated Recirculation System Welds This attachment discusses the UT examination results for the five (5) welds in the recirculation system currently reported as flawed and that previously were not reported as flawed.
Q 05000265 g
PDR t
5.
Discussion and Observations Regarding Ultrasonic Examinations of Weld Overlay Repaired Stainless Steel Welds This attachment discusses the ultrasonic examination results from the UT examinations of the twenty (20) weld overlay repairs performed this outage (14 upgraded and 6 new).
6.
Nutech transmittal dated December 30,1986-This letter summarizes both the flawed pipe analyses for the weld overlayed welds and the weld overlay repairs, including criteria employed in the analyses.
This preliminary report is being submitted to you to provide an overview of Quad Cities Unit 2 and to gain your concurrence with leaving the end cap weld overlay in its present condition.
A final report of ISI cctivities will be submitted during the week of January 5, 1987.
Quad Cities Unit 2 is currently scheduled for restart on January 18, 1986.
Resolution of this issue by December 31, 1986 will support this restart date and is in accordance with the time frame we discussed in our telephone conversation of December 29, 1986.
Please direct any additional questions regarding this issue to this office.
Very truly yours, l
L 5
ff7Q l
~
S.Turb k /
y t
Opera g-Plant Licensing Director DLW/saj 8786D cc:
Resident Inspector - Quad Cities T.S. Rotella - NRR M.C.
Parker l
Augmented Inspection Results Quad Cities Unit 2, Fall 1986 Outage Augumented inspections of IGSCC Susceptible piping were conducted during the Quad Cities Unit 2 Fall 1986 refueling outage.
The inspections followed the inspection plan submitted to the NRC on July 15, 1986 and approved by the NRC by letter dated November 5, 1986.
Examinations were performed by General Electric with evaluations of indications made by Special level II ultrasonic (UT) examiners qualified by EPRI after September 10, 1985.
Data packages were reviewed by CECO UT parsonnel and final acceptance or evaluations of indications were made by CECO Level III personnel.
Indications of IGSCC were found in previously unflawed welds in the recirculation system.
Sample expansions resulted in all of the large diameter (12 inch and above) recirculation system welds being examined.
A total of 127 IGSCC susceptible were examined during the Fall 1986 outage compared to 67 welds called for in the' inspection plan.
Table 1 is reproduced from the previously submitted Augmented Inspection Plan.
Table 2 provides a summary of examinations actually performed during the outage.
The total of 20 weld overlays examined includes the 14 listed in the plan and 6 new overlays.
The previous overlays were upgraded to full structural design thickness.
The new overlays were applied to full structural design criteria.
Each of the overlays was surface finished to parmit application of EPRI techniques for overlay UT examination.
A CECO procedure was implemented by GE personnel qualified by EPRI for weld overlay examination.
The overlay weld metal and the upper 25 percent of the original piping material were examined.
Nineteen weld overlays had sound weld metal of sufficient thickness.to meet the design criteria.
One weld overlay (weld 02A-S10) was found to have axial indications in the overlay such that the full structural' design criteria were not met.
This weld is addressed elsewhere in this. report.
l Ten welds previously reported-as2containing IGSCC flaw indication were examined this outage.
All-of:these welds were treated by l
induction heating stress improvement (IHSI)2in 1983 and have previously l
b:en shown to be acceptable based on flawed pipe analyses.
Of these welds, two (both end caps) showed the presence of axial flaws and were weld overlay repaired.
Welds 02BS-F14 was re-evaluated as ID geometry and 02BS-F12, based on a metallurgical plug sample remover in a previous l
outage, is not flawed.
Flawed pipe analyses have been performed on the remaining six welds and one additional flawed weld detected during the current outage and demonstrate the acceptability of continued operation without weld overlay repair.
Two 12 inch Recirculation safe ends were inspected this outage i
using CECO developed procedures proven on a mock up of the thermal sleeve I
attachment weld.
This provided confidence in the UT examinations.
No flaw indications of crevice corrosion or IGSCC were detected.
Details of this program will be contained in a future report to the NRC.
l I
8791D/rr
~
TABLEI Quad Citles Unit 82 84-11 Augmented Inspection Plan I
2 3
4 5
6 7
8 9
10 1986 1985 1983 1986 WELD IHSI 84-11 84-11 83-02 84-11 WELD OVERLAY MITIGATED TUTAL SYSTEM SIZE TOTAL EXAMS EMAMS SAMLE OVERLAYS SAMLE CRACKS SAMLE Rectreulation l l
l l
l l
l l
l l
Risers l
12" l,44 l
13 l
22 l
7 l
7 l
T' l
2 l
16 - l SE (Thermal l 12" l 10 l 1
l 9
l 2
l 0
l 0
l 0
l 2
l Sleeve) l l
l l
l l
l l
l l
Header l
22" l 22 l 4
l 16 l
4 l
0
-l 0
l 2
l 6
l outlets l
28" l 30 1 2 l 17 1
4 1
5 1
5 1
6 1
15 l
l LPCI l
16" l-62a l 6
l 23 l
6 l
0 l
0 l
0i l
6 l
SDC l
20" l 18e l 3
l 11 l
3 l
2 l
2 l
0 l
5 l
CS l
10" l 27a 1 5
1 20 1
5 1
0 1
0 1
0 1
5 l
HS/RUCU l
6" l 13 a 1 6
1 4
1 3
1 0
1 0
l l
3 l
Recirc/CRD l
l l
l l
l l
l l
l 8
HS/HV l
4" l 34 l 10 1
23 1
7 1
0 1
0 1
0 1
7 l
l JPI l
l 10 l 10 1
0 1
2 1
0 1
0 1
0 1
2 l
240 43 14 10 67 N
COI.lN98 e
3-TOTAL STAINLESS STEEL WELDS SUSCEPTIBLE TO IGSCC ON A PARTICULAR SYSTEM OR SIEE.
4-TOTAL WELDS EXAMINED UNDER GENERIC LETTER 84-!! CRITERIA. EXAMINERS WERE QUALIFIED TO TffE 83-02 REQUALIFICATION.
j 5-1UTAL WELDS EXAMINED UNDER THE 83-02 RegUALIFICATION.
)
6-GENERIC LETTER 1986/84-11 SANLE.
7-1VrAL WEl.D OVERLAYS ON A PARTICULAR SYSTEM AND SIER.
8-GENERIC LETTER 84-11 WELD OVERLAY SA M LE.
OVERLAID WELDS WITH CRACKS OREATER THAN 10%
l OF THEIR CIRCUHFERANCE WILL BE INSPECTED.
l 9-TOTAL CRACKED WELDS WITH IHSI AS A MITIGATOR.
10 - GENERIC LETTER 84-11 1986 TOTAL SAM LE.
NOTE: a 16" WEl.DS ON LPCI, 2-20" WELDS ON SDC, 2-10" WELDS ON COttE SPRAY, 3-6" WELDS ON REACTOR WATER CLEAN UP AND l-4" WELD ON HEAD SPRAY ARE INACCESSIBLE TO UT.
l 32118/34 l
I I
l\\)llJl l
\\l lil ll l
l 14 i
d r
e l e sn ab di 420 2
6 5
5 4
7 2
7 t mfl m 423 2
ouOea 1
TN WxE y
d r
e d
a t se m
I ak n m
Sgci u
Hiam 205 0
0 0
0 0
0 0
7 S
It ra iCx n
M E
o i
2 t
- c t e ipn s sd
.Un ye 2
I dan s
lli 026 0
0 2
0 0
0 0
0 e ed erm 1
2 l
e Wea i
b t t vx ain OE T Cem dg u auA Q yran i
420 0
2 8
7 3
4 0
m l
423 1
3 1
2 1
3 1
i a
l t
e o
r T
P 2" " "
28 2
6 0
0 6
4 122 1
1 2
1 ez i
S l )
ae s mv srt re D
m nree ee I
C S
U R e oedl hl C
D C
C CV ti sat TS P
S W /H s ti eu
(
L R C/
I y aRHO
/
RS P
S l
E S IH J
u S
H C c
E k
r R
jD i
/ 0 c
W9 e
L7 R
D8 j
I lll!
llll
Attachm3nt 2 Paga 1 of 2 Quad Cities 2 Stainless Steel " Flaw List" Weld Flaw Identified Action /
Number 1983 1985 1986 Year Remarks Reactor Recirculation -
12-inch-02C-S3 (1) x Weld Overlay /1986 02D-S3 x
x x
OK as-is 02D-F6 x
n/a Weld Overlay /1983 02E-F6A x
n/a Weld Overlay /1985 02F-F6 x
n/a n/a Weld Overlay /1983 02G-S3 x
n/a n/a Weld Overlay /1983 02J-F6 x
n/a n/a Weld Overlay /1983 02K-S3 (1) x Weld Overlay /1986 axial flaw 02K-S4 (1) x Weld Overlay /1986 axial flaw 02M-S3 x
x n/a Weld Overlay /1985 02M-S4 x
x x
OK as-is 02M-F7 x
x n/a Weld Overlay /1985 orig. called lack of fusion - ISGCC id'd 1985 22-inch-02A-S10 x
x x
Weld Overlay /1986 02B-S9 x
x x
Weld Overlay /1986 (1) Not examined in 1985.
8787D-1
Attachm:nt 2 Paga 2 of 2 Quad Cities 2 Stainless Steel " Flaw List" Wald Flaw Identified Action /
Number 1983 1985 1986 Year Remarks Reactor Recirculation -
28-inch-02AS-S4 x
x n/a Weld Overlay /1985 02AS-S6 x
x x
OK as-is 02AS-S9 x
n/a n/a Weld Overlay /1983 02AS-S12 x
x x
OK as-is 02AS-F14 x
x x
OK as-is-02AD-F12 x
x x
OK as-is_
02BS-F2 (1) x Weld Overlay /1986 02BS-S3 x
n/a n/a Weld Overlay /1983 02BS-F7 n/a n/a Weld Overlay /1983 02BS-S12 x
n/a n/a OK as-is Plug sample shows weld root geometry examined in 1985 and 1986 02BS-F14 x
x Orig 83/85 flaw eval. as root geom 02BD-S6 x
n/a n/a Weld Overlay /1983 02BD-F8 (1) x OK as-is Residual Heat Removal -
10S-F1 x
n/a n/a Weld Overlay /1983 10S-F5 x-x n/a Weld Overlay /1985 Reactor Water Cleanup -
12S-S27 x
n/a n/a Replaced /1983 (1) Not examined in 1985.
8787D-2
Discussion and Observations Regarding Untrasonic Examinations of Previsouly Flawed Stainless Steel Welds Quad Cities Unit 2
Background
Extensive ultrasonic.(UT) examination-programs of IGSCC susceptible stainless steel piping welds have been performed during both the 1983 and 1985 Quad Cities Unit 2 refueling outages.
As a result of these examinations, IGSCC. flaw indications:have been identified in a number of welds.
Flawed pipe analyses have been performed by Nutech for each lof these welds, with weld overlay repairs being utilized for the majority of these welds.
Ten (10) welds. reported.as flawed were left as-is and were re-examined during the-current 1986 outage.
The UT data has all been reviewed, in most cases, physically re-examined by CECO-SMAD and the results compared to.the: previous UT results.
All of these 10 weldments were IHSI treated during the 1983 outage.
The flaw data reported from prior examinations and the UT data excerpted from the current CECO-SMAD reviewed reports for these welds has been tabulated in Table 1 and is presented for general information~.
This data and some specificEnotes and observations made by the CECO-SMAD Level IIIs, as well as general observations, are presented for information and discussion.--In addition, actions based on historical design assumptions, preliminary and previous analyses and general regulatory guidance are presented in Table 2.
Comparison of Examination Results In general:
0 The UT indications from circumfereniially-oriented flaws recorded this-outage show no significant changes in length or depth from the previous examinations.
0 In some cases,.the current flawndata:is reported as longer than 1
previously reported to the NRC in:the. final flaw disposition reports.
Some of these previouslyireported lengths were based on use of artificial intellignece (ALN),uindependent examination (UTL, P-scan) or '.tallurgical " plug"rsamples.
\\
8787D-3
- page 2 -
Specific Weld Discussion Welds 02D -S3, 02M-S4, 02AD-F12, 02AS-S6, and 02AS-S12 No significant changes have been observed this outage in the UT flaw signals from the previous outages.
As with past outages, flawed pipe (fracture mechanics) analyses will justify continued operation with IHSI and without any further repair.
The UT flaw signal previously observed has been re-evaluated as ID (root) geometry.
This weld was shown to be acceptable for continued operation based on previous flawed pipe analysis.
No significant change was observed in the identified circumferential UT flaw signals.
A weld overlay repair has been implemented as a result of the presence of axial flaws detected in the automated UT examinations.
No significant change was observed in the identified circumferential flaws.
A weld overlay repair has been implemented as a result of the presence of axial flaws detected in both the manual and automated UT examinations.
See also specific discussions regarding this weld in other attachments.
In 1983, a plug sample was removed from this weld at the region of maximum reported flaw depth due to a difference between " calls" from various UT examination techniques.
This sample showed no cracking, but ratiter a geometric condition resulting f rom a backewlded root.
The UT indication (signal) observed in 1986 shows no change from that previously observed.
A "what-if" flawed pipe analysis would demonstrate the currently reported flaw to be acceptable.
- Paga 3 -
Specific Weld Discussion Weld 02AS-F14 -
The length _(43 inch) and depth ( 20%) reported in 1986 has not changed since the 1983 and 1985 examinations.
Observations and Conclusions Based on a review of the current UT examination results and comparisons with previously reported flaw data, the lack of any significant change in the UT indications'(signals) demonstrates the effectiveness of the 1983 IHSI treatment as a " repair" for, circumferentially-oriented IGSCC.
8787D-5 i
~
- Page 4 -
Table 1 Comparison of Ultrasonic Examination Results - Flawed Welds 4
Quad Cities Unit 2 Wald Reported Ultrasonic Examination Results 1983 1985 1986 Remarks 02D-S3 1/2" x 25%
1/2" x 28%
0.6 x 17%
IHSI'd in 1983 (12")
(pipe side)
(pipe side)
(pipe side)
Results very similar to 1985 02M-S4 1/2" x 9%
1/2" x 15%
1/2 x 12%
IHSI'd in 1983 (12")
(elbow side)
(elbow side)
(elbow side)
No change from 1983/85 l
02A-S10 4" x 26%
4" x 16%
360 deg int &
IHSI'd in 1983 (22")
(cab side)
(cab side) 4" x 26% w/
multiple axials Int 360 listed (cap side) as "possible" 4" as
" clear" l
02B-S9 17" (total) 17" (total) 42" (int.)
IHSI'd in 1983 (22")
x 15%
x 15%
x 17% w/
(cap side)
(cap side) multiple axials No "significant" (cap side) change in circ. UT indications.
f Flaw listed as L
"possible" 02AD-F12 24"(int) x 1" x 16%
1" x 17%
IHSI'd in 1983 (28")
10%
(pipe side)
(pipe side)
(pipe side)
Excellent comparison w/1985 02AS-S6 7-1/2" x 21%
8" x 18%
8" x 18%
IHSI'd in 1983 (28")
(upstr. side) (upstr. side) (upstr. side)
No "significant change from 83/85 8787D-6 i
I s
-w r
--ww.
sen-e.-e-
-,-e r
e - r emev,--
e-ev-.
eo--wmvwm---
emvm rr-
<w~
-m-r-~w.-+~
e m-e-o----.mn+-,-
w--v-re-~-w
- Page 5 -
Table 1 (Continued)
Comparison of Ultrasonic Examination Results - Flawed Welds Quad Cities Unit 2 Wsid Reported Ultrasonic Examination Results 1983 1985 1986 Remarks 02AS-S12 1" x 8%
2-1/2" x 15%
2" x 22%
IHSI'd in 1983 (28")
2" x 9%
(elbow side)
(elbow side)
(elbow side) 8" x 4%-
6" x 4%
No "significant" 8" x 14%
6-1/2" x 15%
5" x 13%
change 4" x 11% *
(pipe side)
(pipe side)
(pipe side)
- Not reported in 1983 02AS-F14 43" x 20%
43" x 13%
43" (int.)
IHSI'd in 1983 (28")
(pipe side)
(pipe side) x 14%
(pipe side)
No "significant" change 02BS-S12 32" x 16%
36" x 21%
36" x 13%
IHSI'd in 1983 (28")
(pipe side)
(pipe side)
(pipe side)
No "significant" change See note 1 02BS-F14 5-1/4"(total) 1" x 10%
ID (root)
IHSI'd in 1983 (28")
x 18%
(pipe side) geometry (pipe side)
No change in UT signal Signals re-eval in 1986 as ID geometry 4
8787D-7 i
i
- Page 6 -
Table 2 Actions Resulting from Ultrasonic Examination - Flawed Welds Quad Cities Unit 2 Wald Reported Ultrasonic Number Examination Results Action Remarks 02D-S3 0.6" x 17%
Leave as-is
'IHSI'd in 1983 (12")
Results "very similar" to 1985 02M-S4 1/2" x 12%
Leave as-is IHSI'd in 1983 (12")
(elbow side)
No change from 1983/85 02A-S10 360 deg. intermit, possible Weld overlay IHSI'd in 1983 (22")
w/4" x 26% circ. and multiple axials (cap side) i 02B-S9 9 separate circs. 11.6" Weld overlay IHSI d in 1983
'(22")
total combines length x 17% w/ multiple axials No "significant" (cap side) change in UT indication 83/85 &
86 Flaw listed as "possible"
~02AD-F12 1" x 17% (pipe side)
Leave as-is IHSI'd in 1983 (28")
Excellent l
comparisen w/1985 02AS-S6 8" x 18% (upstrm.)
Leave as-is IHSI'd in 1985 (28")
No "significant"
-(cap side) change from 83/85 i
--m------_------mm---------m-------m------m-m---**M6M--*--MMMMM------""-MM 8787D-8
- Page 7 -
Table 2 (Continued)
Actions Resulting from Ultrasonic Examination - Flawed Welds Quad Cities Unit 2 Wald Reported Ultrasonic Number Examination Results Action Remarks 02AS-S12 2" x 22% (elbow side)
Leave as-is IHSI'd in 1983 (28")
6" x 4% and 5" x 13%
(pipe side)
No "significant" change 02AS-F14 43" (intermit. x 14%
Leave as-is IHSI'd in 1983 (28")
(pipe side)
No "significant" change 02BS-F14 36" x 13% (pipe side)
Leave as-is IHSI'd in 1983 (28")
No "significant" chnage See note 1 l
02BS-F14 ID (root) geometry No action IHSI'd in 1983 (28")
Flaw reported in 1983/85 re-eval. as l
geometry l
l Note 1 -
Metallurgical plug sample remove'd-in 1983 from " flaw" indication.
Results demonstrated indication the~ result of backwelded root.
8787D-9 i
i
, ~,
r Attechment 4 Discussion and Obsarvations Regarding "New" Flaws Observed in IHSI-Treated Recirculation System Welds Quad Cities Unit 2
Background
Extensive ultrasonic (UT) examination programs designed to detect intergranular stress corrosion cracking (IGSCC) in the austenitic stainless steel primary piping at Quad Cities Unit 2 have been performed in 1983, 1985 and 1986.
All accessible, susceptible stainless steel wolds were examined in 1983 as part of an NRC mandated inspection program.
In addition, induction heating stress improvement (IHSI) was parformed as mitigation against any new IGSCC and as a " repair" for some wolds containing IGSCC.
A total of approximately 100 welds, primarily in the recirculation system, were treated.
A sample (approximately 70 ueids) of flawed, unflawed and some previously uninspected welds were examined in 1985 and demonstrated an excellent correlation with the 1983 reraits (Reference 1).
Laricy the. current 1986 refueling outage,.UT. examinations of all the large d)ameter recirculation system piping welds were performed (excluding nozzle to safe end welds where a sample was examined).
This was the result of new flaw indications detected in both the original and expanded examination samples.
In total, five (5) additional flawed welds l
were identified, all of which had received INST trs*tment in 13fd and had not Dean reunxamined in 1938:
A sownArt df the DF re mj iv9 ist Lnese five i
flawed welds ).e contained in Table 1.
Some general observations related to the examination results reported in i
Table 1 include:
O All five welds were examined in 1983 after IHSI treatment.
O No UT examinations were performed on any of the five welds during the 1985 examination program.
O In the case of the two 28-inch welds, there was previously reported ID-related UT signals (e.g. root geometry).
Specific Background - Treatment and UT Examinations The summary of each individual weld examinations follows.
l 02K-S3 and 02K-S4 are 12-inch recirculation welds on the K riser (both i
albow-to-pipe).
Induction heating stress improvement (IHSI) was performed on both of these welds by GE-in the 1983 refueling outage, with l
the record indicating successful treatment of both welds.
l
UT cxemination was parformsd aftor the IHSI treatmsnt by Lambart, MacGill and Thomas (LMT) and reviewed by Commonwealth Edison (CECO-SMAD) level IIIs as part of the extensive stainless steel examination program during the 1983 refueling outage.
No reportable-indications (NRI) were noted in the 02K-S3 weld and intermittent 360 degree OD geometry (confirmed by finger dampening) was noted in the 02K-S4 weld.
No UT examinations were scheduled or performed on this weld during the 1985 refueling outage.
During the week of November 3, 1986, a worker in the drywell visually observed a " drop of water" adjacent to weld 02K-S3.
The report was further investigated by Station ISI and a small pinhole leak adjacent to the weld was observed.
A " tool mark" or gouge on the outside surface of the pipe was noted at the flaw.
Ultrasonic examination confirmed the leak in 02K-S3 as an axially-oriented crack.
The signal amplitude on 02K-S3 was noted as quite low, as would be expected based on the flaw orientation / location and the presence of water (a UT couplant) in the flaw.
The adjacent riser weld on the K-riser, 02K-S4, (elbow-to-pipe) was UT examined and small axial crack was noted in this weld as well.
The leak in 02K-S3 was excavated and manually seal welded.
Subsequently, both 02K-S3 and 02K-S4 have been weld overlay repaired.
The original weld overlay design was a two layer leakage barrier.
Due to schedule relief and manpower availability, these two weld overlays were " upgraded" to " full structural" design.
02C-S3 is a 12-inch recirculation weld on the C riser (clbow-to-pipe).
Induction heating stress improvement (IHSI) was performed on this weld in the 1983 refueling outage, with the records indicating a successful treatment.
The previous UT examination was performed.after IHSI by LMT and showed no reportable indications in 1983.
No examination was planned or performed in 1985 on this weld.
The current (1986) UT examination of this wel'd indicated a circumferential crack 1-% inches long with a through-wall depth of 29%.
An axially-oriented crack was identified. associated with this circumferential flaw.
02C-S3 was weld overlay repaired with a-full structural design.
~
02BS-F2 is a 28-inch safe end-to-elbow weld in the B loop recirculation pump suction.
In 1983, this weld was successfully IHSI treated by GE.
This weld was UT examined by LMT both pre-and post-IHSI in 1983.
Both counterbore and root geometric indications were noted in the pre-IHSI UT examination.
In the post-IHSI UT examination, " grain noise" was reported (counterbore and root geometry has been assumed).
No UT examination was planned or performed during the 1985 refueling outage.
Th3 current 1986 examination reports a 15 inch long circumferential flaw Qn thn olbow sido with a maximum depth of 73% through-wall.
The flaw is noted as being "very close" to the root.
In discussions with Mr. Brian Wilson (CECO-SMAD), it was indicated that the flaw is between 50% through wall and the 73% maximum depth for about 8 inches, with shallower ends.
The flaw is located in the upper half of the weld (between approximately 9:00 and 11:30).
02BS-F2 was weld overlay repaired with a full structural design.
Wald 02BD-F8 -
02BD-F8 is a 28-inch valve-to-elbou weld in the recirculation pump discharge piping.
This weld was successfully IHSI treated by GE in 1983.
The 1983 UT examination (post-IHSI) by LMT reported 360 degree ID (root) geometry.
No UT examination of this weld was planned or performed in 1985.
Manual UT examination of this weld in 1986 reported 360 degree intermittent root geometry and total combined length of 4-% inches of circumferential cracking on the elbow side (over 12 inches of the pipe circumference from the 70 to the 82 inch markers).
The maximum depth is 15% through-wall.
The crack signal reported in 1986 is " clearly separate" from the root geometry signal
(" double signals").
An axial flaw indication was noted in the original scan, but was identified as due to root geometry by re-examination.
To further resolve the flaw indications, an automated UT scan was performed on this weld.
This automated examination did not identify the axial indication.
The circumferential flaw signals were very close to the root geometric signals and could not be distinguished by the automated UT, possibly due to the sweep requirements of the CECO procedure.
A flawed pipe analysis performed by Nutech in accordance with Code and g
NRC requirements will result in no need for weld overlay repair of this weld.
7 General Observations Several general observations can be made regarding the 1983 UT examination techniques and changes over the past three years.
Recent changes in examiner qualification have demonstrated an enhanced level of skill is required to achieve qualification today, as opposed to 1983.
In addition, the " passing grade" of 80% would demonstrate the
" acceptability" of miscalling a limited number of flaw signals.
CECO-SMAD reviews of the UT results included both a " paper" review of most welds and " hands-on" examination of any flaws or other areas at the discretion of CECO-SMAD.
This would potentially allow a flaw to escape the review of CECO-SMAD, provided it was missed by the UT subcontractor.
UT examination performed in the nuclear industry in 1983 has in hindsight shown a demonstrated lack of reliability in the resolution of ID (root, etc...) geometry versus IGSCC.
Ariel Flcws -
It is generally accepted in the nuclear industry that limitations in transducer placement (due to weld crowns) and the nature (morphology) and location of axially-oriented IGSCC makes flaw detection and/or depth sizing unreliable.
This lack of reliable detection leads to the most probable conclusion that these flaws were present and undetected in the 1983 UT examinations.
Circumferential Flaws -
Much of the general observations regarding flaw detection in 1983 applies to the three flawed welds containing circumferential IGSCC.
Combining the potential for " Missing" flaws with the number of flaws actually datected in 1983 illustrates a very reasonable track record for the 1983 examinations.
IHSI Effectiveness -
The flaw characterizations reported in 1986 are consistent with the premise thtt the existing detected flaw is the same as IHSI-treated in 1983.
The UT flaw characterization from the current examination of weld 02BS-F2 can be used to, in effect, infer the past " flaw history" of this weld.
It would follow that the flaw was similar in length and that the currently reported deep section of the flaw (approximately 8 inches) was, in all likelihood, fairly deep () 40% through-wall) during IHSI treatment.
The length was then " pinned" by the stress improvement and the deep section exhibited IGSCC crack growth due to the combination of the applied (loadings) and tensile residual stresses (stress improvement), resulting in the currently measured depth (maximum 73%
through-wall).
If the premise is taken that the flaw was not present in 1983 and has been initiated and, at least, grown to its current length and depth during the previous three years of operation,: the only technical rationale to the observed flaw is that IHSI (or even the typical as-butt welded residual stress pattern) is not effective in redistribution of residual stresses or that the currently accepted IGSCC crack growth correlations are not valid.
The effectiveness of the 1983 IHSI treatments is further demonstrated by the stability of the previously reported IGSCC flaw indications from 1983 and 1985.
A discussion of this data is contained in a companion report
(" Discussion and Observations Regarding Ultrasonic Examination of previously Flawed Stainless Steel Welds").
Conclusion From the flaw characterizations, IHSI records and other observations regarding the new IGSCC flaws detected in the current (1986) examination program, it is concluded that the observed IGSCC flaws were present in 1983.
The effects of the IHSI treatment on IGSCC flaw detectability, the presence of adjacent root geometry, the difficulty in detection of axially-oriented IGSCC, enhanced examiner training / experience and miscellaneous other factors all combine to make this conclusion reasonable.
J
Tar'e 1 Comparison of Ultrasonic Examination Results for "New" IGSCC Flaws in IHSI Treated Welds Weld 1983 1986 Number UT Exam UT Exam Remarks Results Results 02K-S3 NRI Single axial-Not examined in 1985 (12-inch) elbow side -
leaking 02K-S4 OD geometry Single axial Not examined in 1985 (12-inch) pipe side 02K-S3 NRI circ: 1-%" x 29%
Not examined in 1985 (12-inch) x 29% w/one axial - elbow side 02BD-F8 360 Deg. ID 2 circs: 4-%"
Not examined in 1985 (28-inch) root geom.
(total) over 12" x 15%
" clearly separate" Automatic UT used in from root geometry 1986 to suppl. manual 02BS-F2 Grain noise, Circ: 15" x 73%
Not examined in 1985 (28-inch) root & counter flaw noted close bore geometry to root geometry Root geometry and signal counterbore also noted in 1983 pre-IHSI exam.
I 8788D/rr 4
[
I References
- 1. G. Frizzell, C. Froehlich and D. Pitcairn, " Evaluation and Actions for Ultrasonic Examination Results at the Quad Cities Nuclear Power Plant,"
presented at the 1986 ANS meeting in Reno, Nevada.
8788/rr i
1 e
l i
e t
T Attachment.5 N
Discussion and Observations Regarding Ultrasonic Examinations of Weld Overlay Repaired Stainless Steel Welds Quad Cities Unit 2
Background
~
Ultrasonic (UT) examination performed on'the primary austenitic stainless I
- nteel piping welds during the 1983, 1985 and_1986 Quad Cities-Unit 2-refueling outages have revealed some indications of'IGSCC.
Flawed pipe j
and other analyses have been performed-bycNut'ech to determine the need
~
i for repairs.
If the UT flaw characterizationkrequired repair, weld
- overlays have been utilized.
Fourteen'(14)qweld overlays applied in the 1983 and 1985 refueling outages have been " upgraded" to an inspectable full structural design which considers long design life.
In addition, wnld overlay repairs have been.applieditoisixd(6) additional welds during the 1986 refueling outage due to the identification of new or additional flaw indications.
E l:T== -
1 As part of the weld overlay upgrades, the sur2 aces of the weld overlays have been conditioned to allow for UT examination in accordance with the recently developed EPRI NDE. Center criteria-and CECO-developed procedures.
The examinations have been performed by the CECO inservice inspection subcontractor (GE) and reviewed by CECO-SMAD Level III's.
i l,
All twenty (20). weld overlays have been UT examined.
The examination results'for the majority of these weld. overlays have indicated no reportable indications.
In other cases, flaws have been detected in the base metal under the weld overlay.
In two cases, flaws were detected in the weld overlay.
These are discussed individually.
l
- Wald Overlay 02C-S3 The ultrasonic examination of the weld overlay on weld 02C-S3 (12-inch pipe-to-elbow riser weld) revealed two (2) axial flaws.
These flaws are
- located at approximately the 16 to 17!(indication 1) and 35 to 36 inch
. locations (indication 2) and have a minimum remaining ligament of 0.34 and 0.52 inches respectively.
The pre-overlay UT examination results for-this weld reported an 1-1/4 inch by 29% maximum through-wall circumferential flaw with an associated i
axial flaw (at the 38 inch location).
A " steam blow-out" at this l
location occurred during weld overlay application and was repaired.
I l
l i
r-,-
c.__,,_.,,.,---,
-- - - -.,,_.-.. _,--.,-.~... ~ _. _ _, -.. -..-.. _ _ -,...
~.....
..c
, ~... - -
Page 2 Indication 1 represents the deepest of the two flaws detected in the post-wold overlay UT examination.
From the thickness data developed as part of the weld overlay application, the flaw penetrates the (0.12 to 0.13 inch thick) first layer of the weld overlay by 0.03 inch.
Based on a total weld overlay thickness at this location of 0.374 inch and a minimum design thickness of 0.28 inch, the remaining weld overlay ligament exceeds the minimum design by 0.06 inch.
' Indication 2 is located well (over 1/8 inch) within the base metal under the weld overlay.
This demonstrates the effective repair of this steam blow-out.
Weld Overlay 02A-S10 This weld was examined in all three recent refueling outages (1983, 1985 and 1986).
This weld, as well as the other end cap-to-header weld, were IHSI treated in 1983.
Along with root and counterbore ID geometry, a short (4") and shallow (16 to 26%) circumferential flaw was reported on the cap side in both the 1983 post-IHSI and 1985 examinations.
Significant re-examination time was spent on this and the other end cap by CECO-SMAD Level III's due to difficulties in interpretation (end cap curvature).
In the 1986 manual UT examinations, a4 inch by 26% circumferential flaw and a "possible" intermittent 360 degree circumferential flaws were observed along with ID geometry.
Two (2) axial IGSCC flaws were also reported, all on the cap side.
At this point, the need for a weld overlay repair was recognized.
It was decided to utilize automated UT on this weld (and the other end cap) to define the extent of circumferential cracking, and therefore, assist in weld overlay design (leakage barrier vs. long life full-structural).
In the automated examination, nine (9) separate short, shallow circumferential flaws (total length 8.6 inches and maximum depth 26%)
were ovserved.
Multiple (29) possible axial flaws were also recorded.
All flaws were on the cap side.
In all cases, the maximum depth of the circumferential flaws has not changed.
Page 3 Weld Overlay Design The 1983/1985 flaw characterization of 02A-S10 did not require repair by flawed pipe analysis, either with or without consideration of the beneficial IHSI residual stress pattern.
Based on the 1986 manual UT data (presence of the axial flaws), a leakage barrier (2 layer 0.125 inch minimum) weld overlay was designed by Nutech.
Based on:
o the r'ed to make temporary attachments to the end cap for mounting welding machines, o the large number of possible axials reported in the automated UT scan, o the desire to perform a " final" fix to these welds, and o the schedule and favorable prices from the welding subcontractor; a long design life full structural weld overlay' design (0.380 inch thick) was elected by CECO.
Weld Overlay Application The OD surface of weld 02A-S10 and pipe was mechanically prepared, cleaned and liquid penetrant examined (no PT indications) prior to weld overlay application.
The (0.06 inch thick) first weld overlay layer delta ferrite was less than 7.5 FN in some locations.
This is historically a problem with the ring header probably due to the chemical composition of header material.
Filler metal used was "high" delta ferrite wire (approx, 11-12 FN).
This layer was " discarded."
Nine (9) " steam blow-outs" were also observed'in the first four layers at seven separate azimuthal locations.
All steam blow-outs were repaired using the following standard practices:
Excavate Seal Weld PT Fill Out Surface condition locally Liquid penetrant (PT) examine, and Apply at least one complete layer by machine velding (AU-GTAW) over all repairs.
This repair was successfully applied to 02K-S3 and 02C-S3 (12-inch riser walds) this outage by the maintenance contractor.
On this weld, it is believed that the contractor tried to minimize excavation depth to
" prevent any leakage."
The outside surface of the weld overlay was then surface conditioned for UT of the weld overlay using EPRI/ CECO Techniques.
Page 4 Neld Overlay Examination After surface conditioning, the weld overlay was checked for thickness, length and contour; followed by liquid penetrant examination (no PT indications).
Ur examination revealed 7 or 8 axial flaws in the weld overlay with a remaining ligament at or below the 0.38 inch full structural weld overlay design thickness.
Additionally, a2 inch long circumferential indication was observed at the weld overlay / base metal interface (0.42 inch remaining ligament).
The current repair options for this weld overlay include:
1.
Add additional layer (s) of weld overlay-to make remaining ligament =
design thickness.
The potential for unknown flaw behavior from welding might result in " worse" condition after' welding and grinding.
This repair technique leaves flaws in weld overlay with the potential need for additional examination, analysis, and probable repairs later.
2.
Excavate flaws, repair and add additional machine layer.
The possibility exists for a flaw to leak excessively and require system draining.
The unit is refueled and ready for hydro-testing at this time.
3.
Leave as-is for fuel cycle and re-examine and repair next refueling outage.
This would appear to be the most technically sound approach at this time.
No flaw growth is. expected due to IGSCC due to the high delta ferrite.
Minor flaw growth due to fatigue has been conservatively calculated and accounted for.
The remaining ligaments are sufficient for, as:a-minimum, limited service.
l DLW/j k 8789D I
I l
l i
FLAWED PIPE ANALYSIS The following criteria was used by NUTECH to justify continued operation of flaws examined during the Quad Cities Unit 2 1986 outage:
j o
The beginning-of-cycle bounding flaw size used in the analysis was the as-measured flaw depth by 360*
circumferential length (conservative).
o The flaw growth evaluation was based upon a conservative crack growth law derived from NUREG-1061, Volume 1 crack growth data, using a combination of dead weight, internal pressure, weld overlay shrinkage, and differential thermal expansion loads, o
Calculation of IGSCC flaw growth was based upon conservative post-IHSI through-wall mitigated residual stress distributions.
o The predicted end-of-cycle flaw size was compared to 2/3 of the ASME Section XI, Table IWB-3641-1 allowable flaw depth values for a combination of dead weight, internal pre =sure, arid seismic
.ds as required by Generic Letter 84-11.
o Since the allowable flaw sizes in ASME Section XI, paragraph IWB-3640 were revised to take account of the potential low fracture toughness associated with flux shielded welds, the predicted end-of-fuel cycle (evaluation period) flaw size was compared to ASME Section XI, Table IWB-3641-5 allowable flaw depth values for a combination of dead weight, internal pressure, seismic, and differential thermal expansion / weld overlay shrinkage stresses.
Using the above criteria, the following welds have been determined to be acceptable for at least one additional fuel cycle of operation:
0 2 D-S 3 02AS-F14 02M-S4 0 2 AD-F12 02AS-S6 0 2B D-F8 02AS-S12 December 30,1986 nutp_qh
o WELD OVERLAY REPAIR EVALUATION The following criteria was used by NUTECH to design / evaluate weld overlay repairs examined during the Quad cities Unit 2 1986 outage:
o Existing circumferential flav depth was assumed to equal 100% of the original pipe wall thickness by a conservative 360' length.
o Existing axial flaw depth was assumed to be a minimum of 100% of the original pipe wall thickness over its measured length.
If an axial flaw was drawn up into the overlay due to a steam blow-out, the actual flaw depth was used, o
Credit was taken for the first layer if the delta ferrite content was at least 7.5 FN.
o Under-the-overlay repair fatigue crack growth was calculated for a 30 year design life based upon a i
conservative fatique crack growth correlation derived from data presented in EPRI Document NP-2423-LD.
o For circumferential flaws, the weld overlay repair strength for a combination of dead weight, internal pressure, and seismic stresses was compared to the net section collapse criteria of ASME Section XI',
Table IWB-3641-1.
o For axial flaws, the weld overlay repair was compared to
" leak barrier" weld overlay criteria (1/8" minimum thickness).
Using the above criteria, weld overlays have been designed for the following welds for balance-of-plant life:
02C-S3 10S-Fi 0 2 D-F6 10S-F5 02E-F6A 02A-S10 02F-F6 02B-S9 02G-S3 02AS-S4 02J-F6 02AS-S9 02K-S3 02BD-S6 02K-S4 02BS-F7 02M-F7 02BS-S3 02M-S3 02BS-F2 December 30,1986 nutggh
._