ML16076A352

Plants, Units 1 and 2 - E-mail Re. Draft Report Concerning Dissimilar Metal Weld Indication on Pressurizer Safety Relief Nozzel to Safe End Weld

ML16076A352
Person / Time
Site:	Calvert Cliffs
Issue date:	02/24/2016
From:	Tom Loomis Exelon Generation Co
To:	Alexander Chereskin Plant Licensing Branch 1
Chereskin A, NRR/DORL/LPL1-1, 415-2549
References
Download: ML16076A352 (10)

Text

From: Loomis, Thomas R:(GenCo -Nuc) <thomas.loomis@exeloncorp.com>

Sent: Wednesday, February 24, 2016 8:21 AM To: Chereskin, Alexander Cc: Villar, Enrique:(GenCo-Nuc)

Subject:

[External_Sender] Draft for 1100 Discussion Attachments: 10CFRSO SS(a) Evaluation 2016-02-23 1700 DRAFT .docx Alex Here is an unverified draft for discussion at the 1100 call.

Thanks Tom This Email message and any attachment may contain information that is proprietary, legally privileged, confidential and/or subject to copyright belonging to Exelon Corporation or its affiliates ("Exelon"). This Email is intended solely for the use of the person(s) to which it is addressed. If you are not an intended recipient, or the employee or agent responsible for delivery of this Email to the intended recipient(s), you are hereby notified that any dissemination, distribution or copying of this Email is strictly prohibited. If you have received this message in error, please immediately notify the sender and permanently delete this Email and any copies.

Exelon policies expressly prohibit employees from making defamatory or offensive statements and infringing any copyright or any other legal right by Email communication. Exelon will not accept any liability in respect of such communications. -EXCIP 1

10 CFR 50.55a February XX, 2016 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington , DC 20555-0001 Calvert Cliffs Nuclear Power Plant, Unit 1 Facility Operating License No. DPR-53 NRC Docket No. 50-317

Subject:

Report Concerning Dissimilar MetallJA*liw*cation on Pressurizer Safety Relief Nozzle to Safe End Weld Examinations performed during the curren tall8trr Plant, Unit 1 have identified a change fro pressurizer safety relief nozzle to safe en Mechanical Stress Improvement Process (M performed to meet ASME Code se N-770-1 a l=WllMl::1\1 mitigated weld whose volumetric xamination volume that exceed the marizing the evaluation , along law or flaw growth is to be than modes 5 or 6."

ilar metal (OM) butt welds within the scope

Mmti.re eling outage using Section XI ,

ffected weld will be repaired by full structural ents i is letter. If you have any questions concerning this sat (610) 765-5510.

Respectfully, James Barstow Director - Licensing & Regulatory Affairs Exelon Generation Company, LLC

Attachment:

Report Concerning Dissimilar Metal Weld Indication on Pressurizer Safety Relief Nozzle to Safe End Weld

Report Concerning Dissimilar Metal Weld Indication on Pressurizer Safety Relief Nozzle to Safe End Weld Page 1 cc: Regional Administrator, Region I, USNRC USNRC Senior Resident Inspector, CCNPP USNRC Project Manager [CCNPP]

S. T. Gray, State of Maryland

Report Concerning Dissimilar Metal Weld Indication on Pressurizer Safety Relief Nozzle to Safe End Weld Page 2 Purpose of Evaluation:

During examinations performed to meet ASME Code Case N-770-1 and 10 CFR 50.55a(g)(6)(ii)(F) requirements, a change was obseNed from previous examinations in an axial indication in a pressurizer safety relief nozzle to safe end dissimilar metal butt weld that was mitigated by the Mechanical Stress Improvement Process (MSIP) in 2006.

10 CFR 50.55a(g)(6)(ii)(F)(6) states: "For any mitigated weld whose volumetric examination detects growth of existing flaws in the required examination volume that exceed the previous IWB-3600 flaw evaluations or new flaws, a report summ the evaluation, along with inputs, methodologies, assumptions, and causes of th aw or flaw growth is to be provided to the NRC prior to the weld being placed i ce other than modes 5 or 6."

Evaluation Id), also designated as lnseNice Inspection 0-1, Inspection Item d array ultrasonic

,.._,,_npendix VIII ,

ystems, to detect a length and

• d examination volume from the El 03-08 guidance for ry Water Stress Corrosion eet the requirements of icated in Table 1 below.

e Achieved - 2016 Exams Combined Coverage Assessment 100% 100%

100% 100%

Carbon Steel 100% 100%

Nozzle SA-508,

~ilj{ UT data identified one axially oriented defect indication, which is contained within the wel terial, exhibiting characteristics indicative of PWSCC. The measured depth of the indication was 81.6% through-wall including clad thickness. In addition, eight indications characterized as embedded fabrication flaws were detected during the data evaluation. See Figure 1 for a graphic representation of the indications in this weld as reported in 201 O along with an approximation of the 2016 flaw characteristics. To confirm that the flaw has changed since the last examination, another NOE vendor performed a manual encoded phased array UT examination and confirmed that the flaw was ID connected and had a through-wall extent of 67.2%.

Report Concerning Dissimilar Metal Weld Indication on Pressurizer Safety Relief Nozzle to Safe End Weld Page 3 Figure 1 Annotated Figure 6-1 from 2010 EPRI Report Showing 2016 Flaw Approximate Size and Location UT .2010 Final Call in 2010 lnlU;iftj Reoortl!d Ct'CA "

grouped two embedded non-PW SCC flaws 2016 Approximate Flaw Depth RT Approximate Flaw Depth

= RT Indication (Actual Depth & Size Not Depicted on Sketch)

=UT lndication(s) 2010 View Look ing Upstream (Into pressurizer) chanic stress improvement process (MSIP) application in e application of MSIP identified an axial flaw in the same location as the 2 reported to be 8% through-wall and was acceptable per IWB-3500. UT examinat1 ely following the MSIPapplication confirmed the indication was still present and a e 8% through-wall depth. lnservice examinations in 201 O also reported the same throug all depth.

Inputs Following the examination in 2006 and application of MSIPa flaw evaluation of the axial flaw was performed and submitted to the NRC. A non-linear finite element analysis using the ANSYS Program was performed for the application of MSIP. This analysis confirmed that an axial PWSCC flaw of 8% depth would be contained within the compressive hoop stress zone of

Report Concerning Dissimilar Metal Weld Indication on Pressurizer Safety Relief Nozzle to Safe End Weld Page 4 the post MSIP stress profile at operating conditions. The post MSIP stress profile is compressive from the ID of the pipe wall to an extent of approximately 50% of the through-wall depth. As shown in Figure 2, the hoop stress then becomes tensile out to the OD, reaching tensile stress values of about 55 ksi at 80% through-wall and reducing to about 44 ksi at the OD of the pipe.

Figure 2 2006 Post MSIP+Operating Stress Calculated Hoop Stress Through Wall at Nominal Flaw Position (Path along butter interface) '

PATH HOOP DIST STRESS inch si 0.000 2,278 0.068 -1 ,124 0.135 -7,546 0.203 -24,114 0.271 -42,931 0.338 -47,583 0.406 -49,002 0.473 -47,203 0.541 -34,280 0.609 -20,561 0.676 -8,4 0.744 -8 0.812 1.353

Report Concerning Dissimilar Metal Weld Indication on Pressurizer Safety Relief Nozzle to Safe End Weld Page 5 80,000 60,000 40,000 20,000 0

1.4

-20,000

-40,000

-60,000 The results of the phased array performed in 201 how that the axial flaw is widest at the ID (I owe ower in the center -1 /3rd of the flaw and becomes wider in the top -1/3 below). The PWSCC flaw indication is narrower ction in the middle through-wall range of the flaw w

Report Concerning Dissimilar Metal Weld Indication on Pressurizer Safety Relief Nozzle to Safe End Weld Page 6 Figure 3 2016 Axial Flaw Characteristics Flaw as illustrated with CAD software 0.23 in A E. N Methodologies tion history of weld 4-SR-1006-1 was reviewed to confirm fabrication repairs, construction examination and inservice examination results. The inservice examinations from 2006 (pre- and post-MSIP), 2010, and 2016 were reviewed to confirm if the flaw observed in 2016 was present and not called in the previous years. See Table 2 for a summary of exams performed. The post-MSIP stress profiles were reviewed both in 2006 and 201 Oto confirm the extent of the compressive stress region and effectiveness of the MSIP application . Physical measurements were also performed in 2010 to confirm the MSIP parameters were met.

Report Concerning Dissimilar Metal Weld Indication on Pressurizer Safety Relief Nozzle to Safe End Weld Page 7 Table 2 4-SR-1006-1 DM Weld Ins ection Histor Liquid Radiograp Manua Auto Year Visual Penetra Comments hy I UT UT nt 1972 Yes Yes ASME Ill ; 1 PT surface re air 1973 Yes Yes Yes E XI Pre-Service Exam 1980 Yes Yes 2004 Yes 2006 Yes 2010 Yes 2016 Yes

• Circumferential scans only.

Assumptions 1.

2. h wall axial extent than e allowed 30% through wall re preliminary as the station will be

1) s ineffective allowing the existing axial flaw to grow,

2) A new in d in the weld , or

3) Prior NOE ~-a pre-existing flaw larger than 30% through-wall prior to MSIP (either -80% tt~*IFtrall or some value between -30% and 80%)

The first potential cause was ruled out due to extensive reviews of the MSIP implementation documentation and by obtaining independent field measurements to confirm the required parameters were met. The second potential cause was ruled out since the MSIP application was found to have been performed correctly. It is not plausible that a new ID flaw could initiate and grow through the compressive stress region to the currently observed flaw depth. Also, this axial indication is in the same location as the previously identified axial indication just with a larger through-wall extent, so it would not be considered a new flaw.

Report Concerning Dissimilar Metal Weld Indication on Pressurizer Safety Relief Nozzle to Safe End Weld Page 8 The third potential cause is considered to be the most likely cause for the change in the axial indication's through wall extent from 201 O to 2016. The data collected in 2016 was reviewed by Exelon , EPRI and inspection vendor NOE personnel. After this review, the 2006 inspection vendor personnel reviewed the pre-MSIP and post-MSIP data collected in 2006 as well as the data collected in 2010. The team came to a consensus that the 2016 reported flaw is ID connected , the NOE data quality is good and the proper techniques were used.

The 2016 examination technique included a larger aperture search unit, additional angles, lower frequency, and enhanced focusing. This data imaged th viously reported axial flaw, but with a much deeper extent. After carefully reviewing t it was determined that this optimized technique may have provided sufficient d etect the connection of the flaws that were previously seen in the other examinations. rication flaws and a potential repair area made depth sizing more difficult.

Due to limitations with the data collection J4itir't *v*~~ examination, the upper portion of the flaw may not have been de ta quality was improved and some indications above the ID connect .-l&Jare not in the pre-MSIP data, but there was no clear connection re treated as two unrelated indications. The stre file indicate connected flaw and the fabricati

From: Loomis, Thomas R:(GenCo -Nuc) <thomas.loomis@exeloncorp.com>

Sent: Wednesday, February 24, 2016 8:21 AM To: Chereskin, Alexander Cc: Villar, Enrique:(GenCo-Nuc)

Subject:

[External_Sender] Draft for 1100 Discussion Attachments: 10CFRSO SS(a) Evaluation 2016-02-23 1700 DRAFT .docx Alex Here is an unverified draft for discussion at the 1100 call.

Thanks Tom This Email message and any attachment may contain information that is proprietary, legally privileged, confidential and/or subject to copyright belonging to Exelon Corporation or its affiliates ("Exelon"). This Email is intended solely for the use of the person(s) to which it is addressed. If you are not an intended recipient, or the employee or agent responsible for delivery of this Email to the intended recipient(s), you are hereby notified that any dissemination, distribution or copying of this Email is strictly prohibited. If you have received this message in error, please immediately notify the sender and permanently delete this Email and any copies.

Exelon policies expressly prohibit employees from making defamatory or offensive statements and infringing any copyright or any other legal right by Email communication. Exelon will not accept any liability in respect of such communications. -EXCIP 1

10 CFR 50.55a February XX, 2016 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington , DC 20555-0001 Calvert Cliffs Nuclear Power Plant, Unit 1 Facility Operating License No. DPR-53 NRC Docket No. 50-317

Subject:

Report Concerning Dissimilar MetallJA*liw*cation on Pressurizer Safety Relief Nozzle to Safe End Weld Examinations performed during the curren tall8trr Plant, Unit 1 have identified a change fro pressurizer safety relief nozzle to safe en Mechanical Stress Improvement Process (M performed to meet ASME Code se N-770-1 a l=WllMl::1\1 mitigated weld whose volumetric xamination volume that exceed the marizing the evaluation , along law or flaw growth is to be than modes 5 or 6."

ilar metal (OM) butt welds within the scope

Mmti.re eling outage using Section XI ,

ffected weld will be repaired by full structural ents i is letter. If you have any questions concerning this sat (610) 765-5510.

Respectfully, James Barstow Director - Licensing & Regulatory Affairs Exelon Generation Company, LLC

Attachment:

Report Concerning Dissimilar Metal Weld Indication on Pressurizer Safety Relief Nozzle to Safe End Weld

Report Concerning Dissimilar Metal Weld Indication on Pressurizer Safety Relief Nozzle to Safe End Weld Page 1 cc: Regional Administrator, Region I, USNRC USNRC Senior Resident Inspector, CCNPP USNRC Project Manager [CCNPP]

S. T. Gray, State of Maryland

Report Concerning Dissimilar Metal Weld Indication on Pressurizer Safety Relief Nozzle to Safe End Weld Page 2 Purpose of Evaluation:

During examinations performed to meet ASME Code Case N-770-1 and 10 CFR 50.55a(g)(6)(ii)(F) requirements, a change was obseNed from previous examinations in an axial indication in a pressurizer safety relief nozzle to safe end dissimilar metal butt weld that was mitigated by the Mechanical Stress Improvement Process (MSIP) in 2006.

10 CFR 50.55a(g)(6)(ii)(F)(6) states: "For any mitigated weld whose volumetric examination detects growth of existing flaws in the required examination volume that exceed the previous IWB-3600 flaw evaluations or new flaws, a report summ the evaluation, along with inputs, methodologies, assumptions, and causes of th aw or flaw growth is to be provided to the NRC prior to the weld being placed i ce other than modes 5 or 6."

Evaluation Id), also designated as lnseNice Inspection 0-1, Inspection Item d array ultrasonic

,.._,,_npendix VIII ,

ystems, to detect a length and

• d examination volume from the El 03-08 guidance for ry Water Stress Corrosion eet the requirements of icated in Table 1 below.

e Achieved - 2016 Exams Combined Coverage Assessment 100% 100%

100% 100%

Carbon Steel 100% 100%

Nozzle SA-508,

~ilj{ UT data identified one axially oriented defect indication, which is contained within the wel terial, exhibiting characteristics indicative of PWSCC. The measured depth of the indication was 81.6% through-wall including clad thickness. In addition, eight indications characterized as embedded fabrication flaws were detected during the data evaluation. See Figure 1 for a graphic representation of the indications in this weld as reported in 201 O along with an approximation of the 2016 flaw characteristics. To confirm that the flaw has changed since the last examination, another NOE vendor performed a manual encoded phased array UT examination and confirmed that the flaw was ID connected and had a through-wall extent of 67.2%.

Report Concerning Dissimilar Metal Weld Indication on Pressurizer Safety Relief Nozzle to Safe End Weld Page 3 Figure 1 Annotated Figure 6-1 from 2010 EPRI Report Showing 2016 Flaw Approximate Size and Location UT .2010 Final Call in 2010 lnlU;iftj Reoortl!d Ct'CA "

grouped two embedded non-PW SCC flaws 2016 Approximate Flaw Depth RT Approximate Flaw Depth

= RT Indication (Actual Depth & Size Not Depicted on Sketch)

=UT lndication(s) 2010 View Look ing Upstream (Into pressurizer) chanic stress improvement process (MSIP) application in e application of MSIP identified an axial flaw in the same location as the 2 reported to be 8% through-wall and was acceptable per IWB-3500. UT examinat1 ely following the MSIPapplication confirmed the indication was still present and a e 8% through-wall depth. lnservice examinations in 201 O also reported the same throug all depth.

Inputs Following the examination in 2006 and application of MSIPa flaw evaluation of the axial flaw was performed and submitted to the NRC. A non-linear finite element analysis using the ANSYS Program was performed for the application of MSIP. This analysis confirmed that an axial PWSCC flaw of 8% depth would be contained within the compressive hoop stress zone of

Report Concerning Dissimilar Metal Weld Indication on Pressurizer Safety Relief Nozzle to Safe End Weld Page 4 the post MSIP stress profile at operating conditions. The post MSIP stress profile is compressive from the ID of the pipe wall to an extent of approximately 50% of the through-wall depth. As shown in Figure 2, the hoop stress then becomes tensile out to the OD, reaching tensile stress values of about 55 ksi at 80% through-wall and reducing to about 44 ksi at the OD of the pipe.

Figure 2 2006 Post MSIP+Operating Stress Calculated Hoop Stress Through Wall at Nominal Flaw Position (Path along butter interface) '

PATH HOOP DIST STRESS inch si 0.000 2,278 0.068 -1 ,124 0.135 -7,546 0.203 -24,114 0.271 -42,931 0.338 -47,583 0.406 -49,002 0.473 -47,203 0.541 -34,280 0.609 -20,561 0.676 -8,4 0.744 -8 0.812 1.353

Report Concerning Dissimilar Metal Weld Indication on Pressurizer Safety Relief Nozzle to Safe End Weld Page 5 80,000 60,000 40,000 20,000 0

1.4

-20,000

-40,000

-60,000 The results of the phased array performed in 201 how that the axial flaw is widest at the ID (I owe ower in the center -1 /3rd of the flaw and becomes wider in the top -1/3 below). The PWSCC flaw indication is narrower ction in the middle through-wall range of the flaw w

Report Concerning Dissimilar Metal Weld Indication on Pressurizer Safety Relief Nozzle to Safe End Weld Page 6 Figure 3 2016 Axial Flaw Characteristics Flaw as illustrated with CAD software 0.23 in A E. N Methodologies tion history of weld 4-SR-1006-1 was reviewed to confirm fabrication repairs, construction examination and inservice examination results. The inservice examinations from 2006 (pre- and post-MSIP), 2010, and 2016 were reviewed to confirm if the flaw observed in 2016 was present and not called in the previous years. See Table 2 for a summary of exams performed. The post-MSIP stress profiles were reviewed both in 2006 and 201 Oto confirm the extent of the compressive stress region and effectiveness of the MSIP application . Physical measurements were also performed in 2010 to confirm the MSIP parameters were met.

Report Concerning Dissimilar Metal Weld Indication on Pressurizer Safety Relief Nozzle to Safe End Weld Page 7 Table 2 4-SR-1006-1 DM Weld Ins ection Histor Liquid Radiograp Manua Auto Year Visual Penetra Comments hy I UT UT nt 1972 Yes Yes ASME Ill ; 1 PT surface re air 1973 Yes Yes Yes E XI Pre-Service Exam 1980 Yes Yes 2004 Yes 2006 Yes 2010 Yes 2016 Yes

• Circumferential scans only.

Assumptions 1.

2. h wall axial extent than e allowed 30% through wall re preliminary as the station will be

1) s ineffective allowing the existing axial flaw to grow,

2) A new in d in the weld , or

3) Prior NOE ~-a pre-existing flaw larger than 30% through-wall prior to MSIP (either -80% tt~*IFtrall or some value between -30% and 80%)

The first potential cause was ruled out due to extensive reviews of the MSIP implementation documentation and by obtaining independent field measurements to confirm the required parameters were met. The second potential cause was ruled out since the MSIP application was found to have been performed correctly. It is not plausible that a new ID flaw could initiate and grow through the compressive stress region to the currently observed flaw depth. Also, this axial indication is in the same location as the previously identified axial indication just with a larger through-wall extent, so it would not be considered a new flaw.

Report Concerning Dissimilar Metal Weld Indication on Pressurizer Safety Relief Nozzle to Safe End Weld Page 8 The third potential cause is considered to be the most likely cause for the change in the axial indication's through wall extent from 201 O to 2016. The data collected in 2016 was reviewed by Exelon , EPRI and inspection vendor NOE personnel. After this review, the 2006 inspection vendor personnel reviewed the pre-MSIP and post-MSIP data collected in 2006 as well as the data collected in 2010. The team came to a consensus that the 2016 reported flaw is ID connected , the NOE data quality is good and the proper techniques were used.

The 2016 examination technique included a larger aperture search unit, additional angles, lower frequency, and enhanced focusing. This data imaged th viously reported axial flaw, but with a much deeper extent. After carefully reviewing t it was determined that this optimized technique may have provided sufficient d etect the connection of the flaws that were previously seen in the other examinations. rication flaws and a potential repair area made depth sizing more difficult.

Due to limitations with the data collection J4itir't *v*~~ examination, the upper portion of the flaw may not have been de ta quality was improved and some indications above the ID connect .-l&Jare not in the pre-MSIP data, but there was no clear connection re treated as two unrelated indications. The stre file indicate connected flaw and the fabricati