Text

Submits Final Rept on Piping Insp,Providing Description of Flaws Found & Analytical & Repair Actions Taken During Winter 1986 Refueling Outage.Rev 0 to CEC-73-203, Evaluation & Disposition of Flaws... Encl
	ML20209G406
Person / Time
Site:	Quad Cities
Issue date:	01/19/1987
From:	Johnson I; COMMONWEALTH EDISON CO.
To:	Harold Denton; Office of Nuclear Reactor Regulation
Shared Package
ML20209G412	List: ML20209G406; ML20209G440;
References
	8786D, NUDOCS 8702050360
	Download: ML20209G406 (38)
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Chicago, Illinois 60690 - 0767 January 19, 1987 Mr. Harold R. Denton, Director Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission W:shington,

D.C.

20555

Subject:

Quad Cities Station Unit 2 Inservice Inspection Information NRC Docket No. 50-265

References:

1)

M.S. Turbak to H.R. Denton dated December 24, 1986.

2)

M.S. Turbak to H.R. Denton dated December 30, 1986.

3)

I.M.

Johnson to H.R. Denton dated January 15, 1986.

Dear Mr. Denton:

This final report of the Quad Cities Station Unit 2 Piping Inspection provides a description of flaws found, analytical and repair actions taken during the Winter 1986 Refueling Outage.

This report is an update of the preliminary report (Reference 2) submitted at the request of your staff.

Attachments 1 thru 4 have been revised for clarity only. has been updated to reflect changes in the status of the 22 inch pipe-to-end cap weld (02A-S10) as previously reported in Reference

3. has been changed from a letter summary of the flawed pipe analyses to the actual NUTECH Engineers report.

1.

This attachment is a summary of the augmentsd 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.

dh 8702050360 B70119 PDR ADOCK 05000265 I'

. 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.

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.

" Evaluation and disposition of flaws at Quad Cities Nuclear Power Plant Unit 2 (1986 Outage)," prepared by:

Nutech Engineers, San Jose, California.

This report summarizes analysis performed by NUTECH Engineers to evaluate flaw indications, including criteria employed in the analysis.

Please direct any additional questions regarding this issue to this office.

Very truly yours, I.M.

Jo nson Nuclear Licensing Administration DLW/rr 8786D cc:

Resident Inspector - Quad Cities T.S. Rotella - NRR D.

Danielson - Region III M.C.

Parker page 1 of 3 January 19, 1987 Augmented Inspection Results Quad Cities Unit 2, Fall 1986 Outage Augmented 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 personnel 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 welds were examined during the Fall 1986 outage compared to 61 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 permit 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.

Ten welds previously reported as containing IGSCC flaw indication were examined this outage.

All of these welds were treated by induction heating stress improvement (IHSI) in 1983 and have previously been 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.

Weld 02BS-F14 was re-evaluated as ID geometry and 02BS-F12, based on a metallurgical plug sample removed in a previous 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 which demonstrate the acceptability of continued operation without weld overlay repair.

Two 12 inch Recirculation safe ends were inspected this outage using CECO developed procedures proven on a mock up of the thermal sleeve 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

Attcchment 1 Page 3 of 3 January 19, 1987 Table 2.

Quad Cities Unit #2 Preliminary Augmented Inspection Summary Total IHSI Number Weld Mitigated Of Overlays Cracks Welds System Size Total Examined Examined Examined Recirculation Risers 12" 44 10 2

44 Ileader 22" 22 2

0 22 Outlets 28" 30 6

5 30 SE (Thermal Sleeve) 12" 10 0

0 2

LPCI 16" 32 0

0 6

SDC 20" 18 2

0 5

CS 10" 27 0

0 5

IIS/RWCU 6"

13 0

0 4

RECIRC/CRD

!!S/IIV 4"

34 0

0 7

JPI 10 0

0 2

20 7

127 e

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l Attachm:nt 2 Pago 1 of 2 January 19, 1987 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-l 02A-S10 x

x x

Weld Overlay /1986 1

028-S9 x

x x

Weld Overlay /1986 (1) Not examined in 1985.

,-y

Page 2 of 2 January 19, 1987 Quad Cities 2 Stainless Steel " Flaw List" Weld 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 -

105-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.

6 0

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Page 1 of 7 January 19, 1987 Discussion and Observations Regarding

,Untrasonic Examinations of Previsouly Flawed Stainless Steel Welds Quad Cities Unit 2

4 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 of 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 specific notes and observations made by the CECO-SMAD Level IIIs, as well as general observations, are i

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.

1 Comparison of Examination Results In general:

e 0

The UT indications from circumferentially-oriented flaws recorded this outage show no significant changes in length or depth from the previous examinations.

O In some cases, the current flaw data is reported as longer than previously reported to the NRC in the final flaw disposition reports.

Some of these previously reported lengths were based on use of artificial intellignece (ALN), independent examination (UTL, P-scan) or metallurgical " plug" samples.

l. -. -

page 2 of 7 January 19, 1987 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.

Weld 02BS-F14 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.

Weld 02B-S9 -

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.

Weld 02A-S10 -

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.

Weld 02BS-S12 -

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 rather a geometric condition resulting from a backwelded 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.

Pago 3 of 7 i

January 19, 1987 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, circumferential1y-oriented IGSCC.

--.,.,,-,-n.

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Attachmsnt 3 Pago 4 of 7 January 19, 1987 Table 1 Comparison of Ultrasonic Examination Results - Flawed Welds Quad Cities Unit 2 Weld 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)

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)

No change from 1983/85 02A-S10 4" x 26%

4" x 16%

360 deg int &

IHSI'd in 1983 (22")

(cap side)

(cap side) 4" x 26% w/

multiple axials Int 360 listed (cap side) as "possible" 4" as " clear" 02B-S9 17" (total) 17" (total) 42" (int.)

IHSI'd in 1983 (22")

x 15%

x 17% w/

(cap side)

(cap side) multiple axials No "significant" (cap side) change in circ.

UT indications.

Flaw listed as "possible" 02AD-F12 24"(int) x 1" x 16%

1" x 17%

IHSI'd in 1983 l

(28")

10%

(pipe side)

(pipe side) l (pipe side)

Excellent comparison w/1985 02AS-S6 7-1/2" x 21%

8" x 18%

IHSI'd in 1983 (28")

(upstr. side) (upstr. side) (upstr. side)

No "significant change from 83/85

Attachmsnt 3 Paga 5 of 7 January 19, 1987 Table 1 (Continued)

Comparison of Ultrasonic Examination Results - Flawed Welds Quad Cities Unit 2 Weld 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) 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)

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)

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 pago 1 of 6 January 19, 1987 Discussion and Observations 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 welds were examined in 1983 as part of an NRC mandated inspection program.

In addition, induction heating stress improvement (IHSI) was performed as mitigation against any new IGSCC and as a " repair" for some welds containing IGSCC.

A total of approximately 100 welds, primarily in the recirculation system, were treated.

A sample (approximately 70 welds) of flawed, unflawed and some previously uninspected welds were examined in 1985 and demonstrated an excellent correlation with the 1983 results (Reference 1).

During the current 1986 refueling outage, UT examinations of all the large diameter 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 were identified, all of which had received IHSI treatment in 1983 and had not been re-examined in 1985.

A summary of the UT results for these five flawed welds is contained in Table 1.

Some general observations related to the examination results reported in Table 1 include:

All five welds were examined in 1983 after IHSI treatment.

e No UT examinations were performed on any of the five welds e

during the 1985 examination program.

In the case of the two 28-inch welds, there was previously e

reported ID-related UT signals (e.g. root geometry).

Specific Background - Treatment and UT Examinations The summary of each individual weld examinations follows.

Welds 02K-S3 and 02K-S4 -

02K-S3 and 02K-S4 are 12-inch recirculation welds on the K riser (both elbow-to-pipe).

Induction heating stress improvement (IHSI) was performed on both of these welds by GE in the 1983 refueling outage, with the record indicating successful treatment of both welds.

page 2 of 6 January 19, 1987 UT examination was performed after the IHSI treatment by Lambert, 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.

Weld 02C-S3 -

02C-S3 is a 12-inch recirculation weld on the C riser (elbow-to-pipe).

Induction heating stress improvement (IMSI) 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 i

reportable indications in 1983.

No examination was planned or performed in 1985 on this weld.

The current (1986) UT examination of this weld indicated a circumferential crack 1-% inches long with a through-wall depth of 29%.

j An axially-oriented crack was identified associated with this circumferential flaw.

02C-S3 was weld overlay repaired with a full structural design.

Weld 02BS-F2 -

i 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.

,r,-_, - - - - - -, - - -

..-.,.4-page 3 of 6 January 19, 1987 The current 1986 examination reports a 15 inch long circumferential flaw on the elbow side 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.

Weld 02BD-F8 -

02BD-F8 is a 28-inch valve-to-elbow weld in the recirculation pump discharge piping.

This weld was successfully IHSI treated by GE in 1933.

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 NRC requirements will result in no need for weld overlay repair of this weld.

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.

page 4 of 6 January 19, 1987 Axial Flaws -

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 detected 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 that 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.

Pago 5 of 6 January 19, 1987 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.

9 i

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Attachm3nt 4 Pago 6 of 6 January 19, 1987 Table 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 02C-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 l

(28-inch) root & counter flaw noted close bore geometry to root geometry Root geometry and I

signal counterbore also noted in 1983 pre-IHSI exam.

l

Attachmant 5 Pago 1 of 5 January 19, 1987 Discussion and Observations Regarding Ultrasonic Examinations of Weld Overlay Repaired Stainless Steel Welds Quad Cities Unit 2

Background

Ultrasonic (UT) examinations were performed on the primary austenitic stainless steel piping welds during the 1983, 1985 and 1986 Quad Cities.

Unit 2 refueling outages and have revealed some indications of IGSCC.

Flawed pipe and fracture mechanics analyses have been performed by Nutech in.accordance with Code and NRC requirements (ASME Section XI) to determine the need for repairs.

If the UT flaw characterization required repair, weld overlays have been typically utilized.

Fourteen (14) weld overlays applied in the 1983 and 1985 refueling outages were " upgraded" to an inspectable full structural weld overlay design which considers long design life.

In addition, weld overlay repairs were3 applied to six (6) additional welds during the 1986 refueling outage due to the identification of new or additional flaw indications.

(See Attachment 4).

As part of the weld overlay upgrades, the surfaces 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 UT examinations have been performed by recent EpRI NDE center trained and qualified examiners of the CECO inservice inspection subcontractor (GE) and reviewed by CECO-SMAD Level III's.

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.

The flaws in these weldments are discussed individually.

Weld Overlay 02C-S3 The ultrasonic examination of the 02C-S3 weld overlay (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 axial flaw (at the 38 inch location).

A " steam blow-out" at this location occurred during weld overlay application and was repaired.

1

I page 2 of 5 January 19, 1987 Indication 1 represents the deepest of the two flaws detected in the post-weld 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 over 0.37 inch and a minimum design thickness of 0.28 inch, the remaining weld overlay ligament exceeds the minimum design thickness by 0.06 inch.

Indication 2 which was at the steam blowout location, 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 was 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.

Fracture mechanics analyses have demonstrated acceptance of this weld without weld overlay repair in 1983 and 1985.

Significant re-examination time was spent on this weld and the other end cap welds by CECO-SMAD Level III's due to difficulties in UT examination signal interpretations (due to end cap curvature).

In the 1986 manual UT examinations, the previously reported a 4 inch by 26% circumferential flaw and a "possible" intermittent 360 degree circumferential flaw were observed along with ID geometry.

Two (2) axial IGSCC flaws were also reported, with all flaws detected on the cap side.

At this point, the need for a weld overlay repair was recognized.

prior to weld overlay application it was decided to utilize automated UT on this weld 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 OK depth of the circumferential flaws has not changed.

Attachmsnt 5 page 3 of 5 January 19, 1987 Weld Overlay Design The 1983/1985 flaw characterization of 02A-S10 did not require repair based on flawed pipe analysis, either with or without consideration of the beneficial IHSI residual stress distribution.

Several factors entered into CECO's decision to apply a long life full structural weld overlay to this weld.

These include:

The desire to minimize future temporary attachments to the end cap for mounting the welding machine and automated UT equipment.

o the large number of possible axials flaws reported in the automated UT

scan, o the desire to perform a " final" fix to this weld, and o the schedule and favorable prices from the welding subcontractor; Weld Overlay Application The OD surface of weld 02A-S10 and pipe was mechanically prepared, cleaned and liquid penetrant examined prior to weld overlay application.

The liquid penetrant (PT) examination prior to weld overlay application revealed no indications.

The first weld overlay layer failed to meet the 7.5 FN (10%) delta ferrite requirement of the process specification on the header side, but was satisfactory on the cap side.

The filler metal had a delta ferrite content of 11-12%.

l These blow outs were observed in layers 1, 2,

3 and 4 and repairs were performed after layers 2, 3, and 4 were completed.

Multiple repairs were i

performed and multiple axial flaws were observed in some of these blow l

out locations.

Six layers, including the discarded first layer, were applied and the weld overlay was surface conditioned for weld overlay UT cxamination.

Attachmant 5 page 4 of 5 January 19, 1987 Weld Overlay Examination After surface conditioning, the weld overlay was checked for thickness, length and contour; followed by liquid penetrant examination (no PT indications).

The results of this examination showed several flaws in the weld overlay material.

Based on the total weld overlay thickness of 0.42 inches, including'the discarded first layer, one circumferential flaw (2 inches long with ninimum remaining ligament of 0.42 inches) and 11 axial flaws (minimum remaining ligament of 0.28 inches) were reported.

Analyses based on these results demonstrated acceptable safety margins (IWB-3640) and CECO preferred to leave this weld overlay as-is for the subsequent fuel cycle.

Based on discussions with the NRC and due to possible outage schedule constraints, the approach of applying an additional layer of weld overlay as requested by the staff was elected.

A seventh layer was applied using low heat input and bead overlap parameters aimed at minimizing additional flaw propagation due to the high strains / temperatures of the welding.

.An automated UT examination was performed in conjunction with manual UT czamination of the surface conditioned seven layer weld overlay.

Ultrasonic measurements after the additional layer showed a weld metal thickness of 0. 48 inches on the cap side compared to the previous 0.42 inches.

Both manual and automated ultrasonic data was collected on the remaing ligaments over the flaws.

The personnel who performed the examinations and made evaluations of the data were qualified at the EPRI NDE Center for examination of weld overlays.

Manual and automated examinations were made of the entire circumference of the cap side wf the weld.

The results of the GE SMART Image System generally paralled the manual examination results with some variations in i

remaining ligament, length, and location.

The automated examination found one circumferential and 8 axial flaws to be present in the weld overlay metal.

A comparison of the manual and automated UT data for the flaws with the shortest ligaments of sound metal is as follows:

4 Least Ligament (inches) l Manual Automated Average l

Mean Range Circumferential 0.28 0.24-0.32 0.38 0.33 Axial 0.35 0.3 -0.4 0.35 0.34 Axial 0.26 0.24-0.28 0.36 0.31 Axial 0.28 0.26-0.30 0.44 0.36 1

I

Page 5 of 5 January 19, 1987 The manual UT data sheet noted tnat the weld was very noisy around the cracked areas and difficult to examine.

A letter from the GE Level III who conducted the automated examination is appended to this attachment letter.

This letter also notes high noise levels, but states these signals were non-relevant and posed no limiting interpretation problems with automated data equipment.

The flaws with the least remaining ligaments were in locations where steam blowouts occurred during overlay welding and localized weld repairs were made.

While the most conservative basis for evaluation of weld 02A-S10 would be to use the manual data, the automated data is believed to be equally valid.

In a conversation with personnel of the EPRI NDE Center, GE, and our Technical Center, it was stated that the expected crack sizing tolerance between examinations was approximately 0.1 inches.

It was agreed that the comparisons of manual and automated data discussed were within expectations for independent examinations.

The weld overlay design thickness of 0.38 inches in Reference 2 was based on nominal piping wall thickness and included a conservatively calculated 0.030 inches of crack growth by fatigue over a 30 year lifetime for the circumferential flaw.

A revised design thickness has been calculated based on the minimum wall thickness of 0.979 inches and climination of the fatigue crack growth allowance.

Basing the design on minimum wall thickness is consistent with designs previously applied to riser welds.

Elimination of the fatigue crack growth allowance is appropriate for an overlay intended for one cycle of operation.

The new design thickness for the overlay on weld 02A-S10 is 0.33 inches.

Commonwealth Edison has considered both sets of UT data in evaluating the remaining ligament of the flaws.

The mean of the manual UT data when averaged with the automated, provides a remaining ligament of 0.33 inches for the circumferential flaw.

The three deepest axial flaws have average remaining ligaments of 0.31 to 0.36 inches.

On this basis, the short circumferential flaw meets the full structural (standard) overlay, design thickness.

The deepest axial flaw is marginally less than the design thickness for a circumferential flaw, but significantly exceeds the requirements for a leakage barrier overlay for axial flaws.

An ASME Section XI evaluation in accordance with IWB-3642 has been performed for the minimum ligaments of the manual sizing and acceptance of the flaws for an operating cycle has been demonstrated.

8924D

Attachmont 3 Page 6 of 7 January 19, 1987 Table 2 Actions Resulting from Ultrasonic Examination - Flawed Welds Quad Cities Unit 2 Weld Reported Ultrasonic Number Examination Results Action Remark

___________________________________________________________s 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) 02B-S9 9 separate cires. 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 comparison w/1985 02AS-S6 8" x 18% (upstrm.)

Leave as-is IHSI'd in 1983 (28")

i No "significant" (cap side) change from 83/85 2

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Attachmont 3 Page 7 of 7 January 19, 1987 Table 2 (Continued)

Actions Resulting from Ultrasonic Examination - Flawed Welds Quad Cities Unit 2 Weld 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-S12 36" x 13% (pipe side)

Leave as-is IHSI'd in 1983 (28")

No "significant" chnage See note 1 02BS-F14 ID (root) geometry No action IHSI'd in 1983 (28")

Flaw reported in 1983/85 re-eval.

as geometry Note 1 - Metallurgical plug sample removed in 1983 from " flaw" indication.

Results demonstrated indication the result of backwelded root.

,m

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t Page 1 of 6 January 19, 1987 l

Discussion and Observations Regarding "New" Flaws Observed in IHSI-Treated Reci,rculation System Welds Quad Cities Unit 2 Background p 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.