L-PI-15-106, Submittal of 10 CFR 50.55a Requests: Relief from Impractical Examination Coverage Requirements for the Fourth Ten-Year Lnservice Inspection Program Interval

Submittal of 10 CFR 50.55a Requests: Relief from Impractical Examination Coverage Requirements for the Fourth Ten-Year Lnservice Inspection Program Interval

ML15355A253
Person / Time
Site:	Prairie Island
Issue date:	12/21/2015
From:	Davison K Northern States Power Co, Xcel Energy
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
L-PI-15-106
Download: ML15355A253 (19)

Text

(l Xcel Energy December 21, 2015 L-PI-15-106 10 CFR 50.55a U S Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Prairie Island Nuclear Generating Plant Units 1 and 2 Dockets 50-282 and 50-306 Renewed License Nos. DPR-42 and DPR-60 10 CFR 50.55a Requests: Relief from Impractical Examination Coverage Requirements for the Fourth Ten-Year lnservice Inspection Program Interval Pursuant to 10 CFR 50.55a, "Codes and Standards," paragraph (g)(5)(iii), Northern States Power Company, a Minnesota Corporation (NSPM), d/b/a Xcel Energy requests relief from examination coverage requirements imposed by the American Society of Mechanical Engineers Boiler and Pressure Vessel Code,Section XI, "Rules for lnservice Inspection of Nuclear Power Plant Components," for the Prairie Island Nuclear Generating Plant (PINGP).

This 10 CFR 50.55a request is for weld examinations performed during the Fourth Ten-Year Inspection Interval Units 1 and Unit 2 December 21, 2004 through December 20, 2014, where the required coverage of "essentially 100 percent" could not be obtained when examined to the extent practical. The basis for the 10 CFR 50.55a request is that compliance with the examination coverage requirement is impractical due to plant design. The details of the 10 CFR 50.55a request are provided in the enclosure for 1-RR-4-11, Rev 0 (PINGP Unit 1) and 2-RR-4-11, Rev 0 (PINGP Unit 2).

PINGP is submitting this requestfor the Fourth Ten-Year lnservice Inspection Interval which ended December 20, 2014.

• If there are any questions or if additional information is needed, please contact Ms.

Pamela Johnson, at 651-267-6829.

1717 Wakonade Drive East

• Welch, Minnesota 55089-9642 Telephone: 651.388.1121

Document Control Desk Page 2 Summary of Commitments This letter contains no new commitments and no revisions to existing commitments.

0Kevin0- C~,, c.,,~\~'( h~

Daviso;u I""'IZ-"*~ 1\A-vl~-:.......,/

Site Vice President, Prairie Island Nuclear Generating Plant Northern States Power Company - Minnesota Enclosure cc: Administrator, Region Ill, USNRC Project Manager, PINGP, USNRC Resident Inspector, PINGP, USNRC

ENCLOSURE 10 CFR 50.55a Request 1-RR-4-11, Rev. 0 (PINGP Unit 1) 10 CFR 50.55a Request 2-RR-4-11, Rev. 0 (PINGP Unit 2)

Request for Alternative for Limited Examinations Fourth Interval Units 1 and 2 Alternative in Accordance with 10 CFR 50.55a(z)(2) 16 Pages Follow

L-PI-15-1 06 Enclosure 10 CFR 50.55a Request 1-RR-4-11, Rev. 0 (PINGP Unit 1) 10 CFR 50.55a Request 2-RR-4-11, Rev. 0 (PINGP Unit 2)

Request for Alternative for Limited Examinations Fourth Interval Units 1 and 2 Alternative in Accordance with 10 CFR 50.55a(z)(2)

1. ASME Code Components Affected Code Class: ASME Section XI, Class 2 Components: Unit 1 - Residual Heat Removal (RHR) Heat Exchanger 12 Head-to-Shell Weld (W-1)

Unit 1 - RHR Heat Exchanger 12 Shell-to-Flange Weld (W-2)

Unit 1 - RHR Heat Exchanger 12 Welded Attachment (H-2/IA)

Unit 2- RHR Heat Exchanger 21 Welded Attachment (H-2/IA)

Unit 2- RHR Heat Exchanger 22 Head-to-Shell Weld (W-1)

Code: ASME Section XI, 1998 Edition through the 2000 Addenda Examination Category: c-A and c-c Item Numbers: C1.10, C1.20 and C3.10

2. Applicable Code Edition and Addenda

• The American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code, Rules for Inservice Inspection of Nuclear Power Plant Components,Section XI, 1998 Edition with Addenda through 2000 as conditioned by 10CFR50.55a, is the code of record for the Prairie Island Units 1 and 2, 4th 10-year interval.

• Code Case N-460, "Alternative Examination Coverage for Class 1 and 2 Welds,Section XI, Division 1" as approved by Regulatory Guide 1.147, Inservice Inspection Code Case Acceptability, ASME section XI, Division 1, Revision 17.

Page 1 of 16

L-PI-15-1 06 Enclosure 10 CFR 50.55a Request 1-RR-4-11, Rev. 0 (PINGP Unit 1) 10 CFR 50.55a Request 2-RR-4-11, Rev. 0 (PINGP Unit 2)

Request for Alternative for Limited Examinations Fourth Interval Units 1 and 2 Alternative in Accordance with 10 CFR 50.55a(z)(2)

3. Applicable Code Requirements Table 1 Code Requirements Exam Item Examination Requirements Cat. No.

C-A 1.10 Mandatory Essentially 100% volumetric examination of the Appendix I weld length for the volume shown in Figure and III IWC-2500-1.

C-A 1.20 Mandatory Essentially 100% volumetric examination of the Appendix I weld length for the volume shown in Figure and III IWC-2500-1.

C-C 3.10 Essentially 100% surface examination of the required areas of each welded attachment.

Conditions:

(1)

(a) The attachment is on the outside surface of the pressure retaining component.

(b) The attachment provides component support as defined in NF-1110.

(c) The attachment weld joins the attachment either directly to the surface of the component or to an integrally cast or forged attachment to the component.

(d) The attachment weld is full penetration, fillet, or partial penetration, continuous, or intermittent (2) The extent of examination includes essentially 100% of the length of the attachment weld at each attachment subject to examination.

(3) Selected samples of welded attachments shall be examined each inspection interval.

( 4) For multiple vessels of similar design, function, and service, only one welded attachment of only one of the multiple vessels shall be selected for examination.

Page 2 of 16

L-PI-15-1 06 Enclosure 10 CFR 50.55a Request 1-RR-4-11, Rev. 0 (PINGP Unit 1) 10 CFR 50.55a Request 2-RR-4-11, Rev. 0 (PINGP Unit 2)

Request for Alternative for Limited Examinations Fourth Interval Units 1 and 2 Alternative in Accordance with 10 CFR 50.55a(z)(2)

Note: As defined by ASME Code Case N-460, essentially 100% means more than 90% of the examination volume of each weld where reduction in coverage is due to interference by another component or part geometry.

4. Impracticality of Compliance Due to the configuration, it is not possible to meet the examination coverage requirements of ASME Section XI, 1998 Edition with Addenda through 2000, as clarified by Code Case N-460. Relief is requested in accordance with 10CFR50.55a(z)(2). The limited examinations subject to this request are a result of attempts to perform the examinations during the 4th interval.

When examined, the welds listed within this request did not receive the required Code coverage due to their configuration, presence of permanent attachments and proximity to building structure. These limitations prohibit essentially 100%

coverage of the listed ultrasonic and surface examinations.

Table 2 summarizes the percent of Code coverage obtained with references to figures that show the extent of coverage and the limitations, and photographs of the obstructions.

5. Burden Caused by Compliance Examination Category C-A, Unit 1 and 2- RHR Heat Exchanger 12 and 22, respectively Head-to-Shell Weld (W-1) and Unit 1-RHR Heat Exchange 12 Shell-to-Flange Weld (W-2)

The RHR heat exchanger is a 24 inch vessel with a "U" shaped tube bundle. The stainless steel channel head for the heat exchanger consist of a weld-neck flange welded to one end of the shell (Weld 2) and an elliptical head welded to the other end of the channel head shell (Weld 1). The length of the shell between the flange and the elliptical head is 13 inches. The 13 inch long shell section contains two nominal pipe size (NPS) 8 nozzles with 12 inch diameter reinforcing rings. The nozzles are located 180° apart. In between the two nozzles, there are integrally welded supports that span most of the distance between the nozzles.

Page 3 of 16

L-PI-15-1 06 Enclosure 10 CFR 50.55a Request 1-RR-4-11, Rev. 0 (PINGP Unit 1) 10 CFR 50.55a Request 2-RR-4-11, Rev. 0 (PINGP Unit 2)

Request for Alternative for Limited Examinations Fourth Interval Units 1 and 2 Alternative in Accordance with 10 CFR 50.55a(z)(2)

The nozzle reinforcing rings and the integrally welded supports interfere with scanning Weld 1 on the heat exchangers of both units.

The nozzle reinforcing rings, the integrally welded supports, and the configuration of the weld-neck flange interfere with scanning Weld 2 on the Unit 1 heat exchanger.

The configuration described is typical of Units 1 and 2.

To obtain full Code coverage of the subject welds would require a significant modification or replacement of the heat exchangers to increase the shell length of the channel head to provide an increased distance from the nozzles and supports to the welds. For Weld 2, an alternative configuration of the weld-neck flange would also be required. Due to the current configuration, there are no other volumetric techniques that would provide increased coverage.

Examination Category c-c, Unit 1 and 2- RHR Heat Exchanger 12 and 21, integral attachment weld {H-2/IA)

The RHR heat exchanger is a 24 inch vessel with a "U" shaped tube bundle. The stainless steel channel head for the heat exchanger consist of a weld-neck flange welded to one end of the shell and an elliptical head welded to the other end of the channel head shell. The length of the shell between the flange and the elliptical head is 13 inches. The 13 inch long shell section contains two NPS 8 nozzles with 12 inch diameter reinforcing rings. The nozzles are located 180° apart. In between the two nozzles, there are integrally welded supports that span most of the distance between the nozzles. The integrally welded supports are in close proximity to concrete pedestals that support the heat exchangers.

The close proximity of the concrete pedestals limits access to the bottom fillet weld that attaches the horizontal support plate to the channel shell of the heat exchangers.

The configuration described is typical of both heat exchangers of Units 1 and 2.

Page 4 of 16

L-PI-15-1 06 Enclosure 10 CFR 50.55a Request 1-RR-4-11, Rev. 0 (PINGP Unit 1) 10 CFR 50.55a Request 2-RR-4-11, Rev. 0 (PINGP Unit 2)

Request for Alternative for Limited Examinations Fourth Interval Units 1 and 2 Alternative in Accordance with 10 CFR 50.55a(z)(2)

To obtain full Code coverage for surface examination of the attachment welds would require significant modification or replacement of the heat exchangers to increase the distance between the concrete support pedestals and the exchanger shell.

Due to the current configuration, there are no other surface techniques that would provide increased coverage.

6. Proposed Alternative and Basis for Use Proposed Alternative:

There are no proposed alternatives.

Basis:

The examination coverage described in Table 2 and the applicable Figures represent the maximum obtainable coverage. RHR heat exchanger shell-to-flange, shell-to-head, and attachment welds were examined in the third interval and found to have similar limitations as follows: Weld 1 of the Unit 1 RHR heat exchanger 12 was ultrasonically examined and found to be limited to 74%

coverage. Weld 2 of the Unit 1 RHR heat exchanger 12 was ultrasonically examined and found to be limited to 27% coverage. The attachment welds of one support of the Unit 1 RHR heat exchanger 12 were surface examined found to be limited to 71% coverage. The attachment welds of both supports of the Unit 2 RHR heat exchanger 21 were surface examined found to be limited to 85% coverage. Weld 1 of the Unit 2 RHR heat exchanger 22 was ultrasonically examined and found to be limited to 74% coverage.

The examinations of the fourth interval did not identify any indications of defects or unacceptable conditions according to the acceptance criteria of ASME Section XI, IWC-3510 and IWC-3512.

The fourth interval examination of Weld 2 (Figure 3) identifies "best effort" coverage that is in excess of the reported Code coverage. Best effort coverage Page 5 of 16

L-PI-15-1 06 Enclosure 10 CFR 50.55a Request 1-RR-4-11, Rev. 0 (PINGP Unit 1) 10 CFR 50.55a Request 2-RR-4-11, Rev. 0 (PINGP Unit 2)

Request for Alternative for Limited Examinations Fourth Interval Units 1 and 2 Alternative in Accordance with 10 CFR 50.55a(z)(2) includes areas of the required volume that are in the path of the projected sound beam, but ar~ beyond the qualified limit.

The RHR heat exchangers are within the ASME Section XI, Class 2 boundaries and in addition to' the volumetric examinations required by Examination Category C-A, the heat exchangers are also pressure tested once each inspection period in accordance with Examination Category C-H. None of the pressure tests have identified evidence of leakage from the welds that are subject of this relief request.

The Unit 1 and 2 RHR heat exchangers are the original vessels and there has been no degradation of the channel heads identified since initial operation.

Additionally, the Fifth 10 Year Interval Inservice Inspection program has been prepared using Code Case N-716-1, "Alternative Piping Classification and Examination Requirements". For the Fifth Ten Year Interval, the Unit 1 and Unit 2 RHR heat exchangers are considered Low Safety Significant and the welds that are subject of this relief request will not be subject to examination.

In accordance with 10 CFR 50.55a(g)(S)(iii), Prairie Island has determined that conformance with the requirements of ASME Section XI, Table IWC-2500-1, Examination Category C-A and Code Case N-460 for examination of the welds subject of this request is impractical. The impracticality has been demonstrated by the examinations performed during the Fourth Ten Year Interval as described herein.

7. Duration of Proposed Relief This relief request is applicable to the Prairie Island Unit 1 and 2 Fourth Ten Year Inservice Inspection Interval.

8. Precedents:

Page 6 of 16

L-PI-15-106 Enclosure 10 CFR 50.55a Request 1-RR-4-11, Rev. 0 (PINGP Unit 1) 10 CFR 50.55a Request 2-RR-4-11, Rev. 0 (PINGP Unit 2)

Request for Alternative for Limited Examinations Fourth Interval Units 1 and 2 Alternative in Accordance with 10 CFR 50.55a(z)(2)

Prairie Island Nuclear Generating Plant Request for Relief No. 11 dated May 29, 2001. (Accession No. ML011550260)

Prairie Island Nuclear Generating Plant Request for Relief No. 9 dated November 16, 2002. (Accession No. ML023290578)

Prairie Island Nuclear Generating Plant Request for Relief No. 16 dated January 7, 2004. (Accession No. ML040150068)

Nuclear Regulatory Commission Letter to Kewaunee Power Station dated September 20, 2012

Subject:

Kewaunee Power Station- Evaluation of Relief Request Number RR-G-5 Regarding Fourth 10-Year Interval Inservice Inspection Program (TAC No. ME7378) (Accession No. ML12249A44)

9. References Title 10 of the Code of Federal Regulation, Part 50.55a, Codes and Standards.

ASME Section XI, "Rules for Inservice Inspection of Nuclear Power Plant Components", 1998 Edition through the 2000 Addenda ASME Section XI, Division 1, Code Case N-460, "Alternative Examination Coverage for Class 1 and Class 2 Welds" Regulatory Guide 1.147, Inservice Inspection Code Case Acceptability, ASME section XI, Division 1, Revision 17 NRC Presentation "Coverage Relief Requests" dated January 13- 15, 2015 presented at the Industry/NRC NDE Technical Information Exchange Public Meeting Page 7 of 16

L-PI-15-1 06 Enclosure 10 CFR 50.55a Request 1-RR-4-11, Rev. 0 (PINGP Unit 1) 10 CFR 50.55a Request 2-RR-4-11, Rev. 0 (PINGP Unit 2)

Request for Alternative for Limited Examinations Fourth Interval Units 1 and 2 Alternative in Accordance with 10 CFR 50.55a(z)(2)

Table 2 Component System Exam ASME Angles Figure and Impracticality of Other Examination Configuration Component ID Year Section XI (s)/ Photograph Compliance Results Material Coverage and Exam Results

(%) Wave Modes Unit 1 Residual Residual Heat 2009 Exam Cat C- 45° s 1 Inservice examination Surface examination Heat Exchanger Removal A 60° s limited due to welded is not required by 12 Head to Weld 1 Item No. 70° 5 1 support proximity to Code.

Shell Summary No. C1.20 60° L weld on shell side and System Pressure test; 303053 Rgure No. nozzle reinforcement Acceptable Stainless to IWC-2500-1 plates on shell I head Stainless covering weld.

No Recordable 74% Indications Unit 1 Residual Residual Heat 2012 Exam Cat C- 450 s 3 Inservice examination Surface examination Heat Exchanger Removal A 60° s limited due to flange is not required by 12 Shell to Weld 2 Item No. 70° s configuration. Shell side Code.

Flange Summary No. C1.10 is limited due to welded System Pressure test; 303054 Figure No. attachments and nozzle Acceptable Stainless to IWC-2500-1 reinforcement plates.

Stainless No Recordable L___ - - - - L_ - -- - -

32% Indications 1

This weld was scanned with the 70° shear wave, but no additional coverage was obtained, therefore the 70° shear wave is not shown on Figure 1.

Page 8 of 16

L-PI-15-106 Enclosure 10 CFR 50.55a Request 1-RR-4-11, Rev. 0 (PINGP Unit 1) 10 CFR 50.55a Request 2-RR-4-11, Rev. 0 (PINGP Unit 2)

Request for Alternative for Limited Examinations Fourth Interval Units 1 and 2 Alternative in Accordance with 10 CFR 50.55a(z)(2)

Table 2 I Component System Exam ASME Angles Figure and Impracticality of Other Examination Configuration Component ID Year Section XI (s)/ Photograph Compliance Results Material Coverage and Exam Results

(%) Wave Modes Unit 1 Residual 2012 Exam Cat C- N/A 3 Inservice examination System Pressure test; Heat Exchanger Residual Heat c limited due to welded Acceptable 12 welded Removal Item No. support proximity to Attachment Attachment Weld C3.10 building structure.

H-2/IA Summary No. 75%

323052 Unit 2 Residual Residual Heat 2010 Exam Cat C- N/A Not Shown. Inservice examination System Pressure test; Heat Exchanger Removal c Similar to limited due to welded Acceptable 21 welded Attachment Weld Item No. HX 12 support proximity to Attachment H-2/IA C3.10 Photograph building structure.

Summary No. 3.

521419 - -~

85% - - - -

-~

- -~

Page 9 of 16

L-PI-15-106 Enclosure 10 CFR 50.55a Request 1-RR-4-11, Rev. 0 (PINGP Unit 1) 10 CFR 50.55a Request 2-RR-4-11, Rev. 0 (PINGP Unit 2)

Request for Alternative for Limited Examinations Fourth Interval Units 1. and 2 Alternative in Accordance with 10 CFR 50.55a(z)(2)

Table 2 Component System Exam ASME Angles Figure and Impracticality of Other Examination Configuration Component ID Year Section XI (s)/ Photograph Compliance Results Material Coverage and Exam Results

(%) Wave Modes Unit 2 Residual Residual Heat 2013 Exam Cat C- 45° s 2 Inservice examination Surface examination Heat Exchanger Removal A 60° L limited due to welded is not required by 22 Head to Weld 1 Item No. support proximity to Code.

Shell Summary No. C1.20 weld on shell side and System Pressure test; 501477 Figure No. nozzle reinforcement Acceptable Stainless to IWC-2500-1 plates on shell I head Stainless covering weld.

No Recordable 74% Indications Page 10 of 16

L-PI-15-1 06 Enclosure 10 CFR 50.55a Request 1-RR-4-11, Rev. 0 (PINGP Unit 1) 10 CFR 50.55a Request 2-RR-4-11, Rev. 0 (PINGP Unit 2)

Request for Alternative for Limited Examinations Fourth Interval Units 1 and 2 Alternative in Accordance with 10 CFR 50.55a(z)(2)

ISI-93B W-1 Summary No: 303053

.49" .63" 53.

16" area with no coverage dne to Nozzle Saddle welds Total Weld Length=76" Shell A240TP3M Required Exam Volume- .73 Sq. Inches Head Side Circ. Examination Cover.age Achieved .73 Sq.lnches (79%)

Shell Side Examination Coverage Achieved 69% Head Side Examination Coverage Achieved 79%

Total Examination Coverage Achieved 74%

Figure l Page 11 of 16

L-PI-15-106 Enclosure 10 CFR 50.55a Request 1-RR-4-11, Rev. 0 (PINGP Unit 1) 10 CFR 50.55a Request 2-RR-4-11, Rev. 0 (PINGP Unit 2)

Request for Alternative for Limited Examinations Fourth Interval Units 1 and 2 Alternative in Accordance with 10 CFR 50.55a(z)(2) 2ISI-69B W-1 SummaryNo: 501477

.49" .63" 53*

16" area wiihno cm'l!r.!ge dill! 1o Noxzle Saddle welds Total WeldLengih=76" Required Exam VolUIDI>- .73 Sq. Inches Axial Elu!miJJati.on Cm*ernge A chi~ .73 Sq. Jnclie>

(79%)

Head Side! Circ. F.xamination Coverage Aclll.eved .73 Sq. Inches (79%)

Shell Side Examination Coverage Achieved 69% Head Side Examination Coverage Achieved 7!)0/a Total Examination Coverage Achieved 74%

Figure2 Page 12 of 16

L-PI-15-1 06 Enclosure 10 CFR 50.55a Request 1-RR-4-11, Rev. 0 (PINGP Unit 1) 10 CFR 50.55a Request 2-RR-4-11, Rev. 0 (PINGP Unit 2)

Request for Alternative for Limited Examinations Fourth Interval Units 1 and 2 Alternative in Accordance with 10 CFR 50.55a(z)(2)

ISI-93B W-2 Summary No: 303054

.73" .62" .49"

-Total weld Length 76"

-8 11 area with no coverage due to four welded supports (2" each) on shell side

-16" Area with no coverage due to the two nozzle saddle welds (811 each)

Required Exam Volume- 1.25 Sq. Inches Best Effort Axial Examination Coverage Achieved .3& Sq. Inches Exam Coverage (30"/.)

Circ. Examination Coverage Achieved .43 Sq. Inches (34%)

Total Examination Coverage Achieved 32%

Figure 3 Page 13 of 16

L-PI-15-1 06 Enclosure 10 CFR 50.55a Request 1-RR-4-11 Rev. 0 (PINGP Unit 1)

I 10 CFR 50.55a Request 2-RR-4-11 Rev. 0 (PINGP Unit 2)

I Request for Alternative for Limited Examinations Fourth Interval Units 1 and 2 Alternative in Accordance with 10 CFR 50.55a(z)(2)

Photograph 1 Unit 1, Residual Heat Exchanger 12 Head-to-Shell Weld (Weld 1)

Page 14 of 16

L-PI-15-1 06 Enclosure 10 CFR 50.55a Request 1-RR-4-11, Rev. 0 (PINGP Unit 1) 10 CFR 50.55a Request 2-RR-4-11, Rev. 0 (PINGP Unit 2)

Request for Alternative for Limited Examinations Fourth Interval Units 1 and 2 Alternative in Accordance with 10 CFR 50.55a(z)(2)

Photograph 2 Unit 2, Residual Heat Exchanger 22 Head-to-Shell Weld (Weld 1)

Page 15 of 16

L-PI-15-106 Enclosure 10 CFR 50.55a Request 1-RR-4-11, Rev. 0 (PINGP Unit 1) 10 CFR 50.55a Request 2-RR-4-11, Rev. 0 (PINGP Unit 2)

Request for Alternative for Limited Examinations Fourth Interval Units 1 and 2 Alternative in Accordance with 10 CFR 50.55a(z)(2)

Photograph 3 Unit 1, Residual Heat Exchanger 12 Shell-to-Flange Weld (Weld 2)

Page 16 of 16

(l Xcel Energy December 21, 2015 L-PI-15-106 10 CFR 50.55a U S Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Prairie Island Nuclear Generating Plant Units 1 and 2 Dockets 50-282 and 50-306 Renewed License Nos. DPR-42 and DPR-60 10 CFR 50.55a Requests: Relief from Impractical Examination Coverage Requirements for the Fourth Ten-Year lnservice Inspection Program Interval Pursuant to 10 CFR 50.55a, "Codes and Standards," paragraph (g)(5)(iii), Northern States Power Company, a Minnesota Corporation (NSPM), d/b/a Xcel Energy requests relief from examination coverage requirements imposed by the American Society of Mechanical Engineers Boiler and Pressure Vessel Code,Section XI, "Rules for lnservice Inspection of Nuclear Power Plant Components," for the Prairie Island Nuclear Generating Plant (PINGP).

This 10 CFR 50.55a request is for weld examinations performed during the Fourth Ten-Year Inspection Interval Units 1 and Unit 2 December 21, 2004 through December 20, 2014, where the required coverage of "essentially 100 percent" could not be obtained when examined to the extent practical. The basis for the 10 CFR 50.55a request is that compliance with the examination coverage requirement is impractical due to plant design. The details of the 10 CFR 50.55a request are provided in the enclosure for 1-RR-4-11, Rev 0 (PINGP Unit 1) and 2-RR-4-11, Rev 0 (PINGP Unit 2).

PINGP is submitting this requestfor the Fourth Ten-Year lnservice Inspection Interval which ended December 20, 2014.

• If there are any questions or if additional information is needed, please contact Ms.

Pamela Johnson, at 651-267-6829.

1717 Wakonade Drive East

• Welch, Minnesota 55089-9642 Telephone: 651.388.1121

Document Control Desk Page 2 Summary of Commitments This letter contains no new commitments and no revisions to existing commitments.

0Kevin0- C~,, c.,,~\~'( h~

Daviso;u I""'IZ-"*~ 1\A-vl~-:.......,/

Site Vice President, Prairie Island Nuclear Generating Plant Northern States Power Company - Minnesota Enclosure cc: Administrator, Region Ill, USNRC Project Manager, PINGP, USNRC Resident Inspector, PINGP, USNRC

ENCLOSURE 10 CFR 50.55a Request 1-RR-4-11, Rev. 0 (PINGP Unit 1) 10 CFR 50.55a Request 2-RR-4-11, Rev. 0 (PINGP Unit 2)

Request for Alternative for Limited Examinations Fourth Interval Units 1 and 2 Alternative in Accordance with 10 CFR 50.55a(z)(2) 16 Pages Follow

L-PI-15-1 06 Enclosure 10 CFR 50.55a Request 1-RR-4-11, Rev. 0 (PINGP Unit 1) 10 CFR 50.55a Request 2-RR-4-11, Rev. 0 (PINGP Unit 2)

Request for Alternative for Limited Examinations Fourth Interval Units 1 and 2 Alternative in Accordance with 10 CFR 50.55a(z)(2)

1. ASME Code Components Affected Code Class: ASME Section XI, Class 2 Components: Unit 1 - Residual Heat Removal (RHR) Heat Exchanger 12 Head-to-Shell Weld (W-1)

Unit 1 - RHR Heat Exchanger 12 Shell-to-Flange Weld (W-2)

Unit 1 - RHR Heat Exchanger 12 Welded Attachment (H-2/IA)

Unit 2- RHR Heat Exchanger 21 Welded Attachment (H-2/IA)

Unit 2- RHR Heat Exchanger 22 Head-to-Shell Weld (W-1)

Code: ASME Section XI, 1998 Edition through the 2000 Addenda Examination Category: c-A and c-c Item Numbers: C1.10, C1.20 and C3.10

2. Applicable Code Edition and Addenda

• The American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code, Rules for Inservice Inspection of Nuclear Power Plant Components,Section XI, 1998 Edition with Addenda through 2000 as conditioned by 10CFR50.55a, is the code of record for the Prairie Island Units 1 and 2, 4th 10-year interval.

• Code Case N-460, "Alternative Examination Coverage for Class 1 and 2 Welds,Section XI, Division 1" as approved by Regulatory Guide 1.147, Inservice Inspection Code Case Acceptability, ASME section XI, Division 1, Revision 17.

Page 1 of 16

L-PI-15-1 06 Enclosure 10 CFR 50.55a Request 1-RR-4-11, Rev. 0 (PINGP Unit 1) 10 CFR 50.55a Request 2-RR-4-11, Rev. 0 (PINGP Unit 2)

Request for Alternative for Limited Examinations Fourth Interval Units 1 and 2 Alternative in Accordance with 10 CFR 50.55a(z)(2)

3. Applicable Code Requirements Table 1 Code Requirements Exam Item Examination Requirements Cat. No.

C-A 1.10 Mandatory Essentially 100% volumetric examination of the Appendix I weld length for the volume shown in Figure and III IWC-2500-1.

C-A 1.20 Mandatory Essentially 100% volumetric examination of the Appendix I weld length for the volume shown in Figure and III IWC-2500-1.

C-C 3.10 Essentially 100% surface examination of the required areas of each welded attachment.

Conditions:

(1)

(a) The attachment is on the outside surface of the pressure retaining component.

(b) The attachment provides component support as defined in NF-1110.

(c) The attachment weld joins the attachment either directly to the surface of the component or to an integrally cast or forged attachment to the component.

(d) The attachment weld is full penetration, fillet, or partial penetration, continuous, or intermittent (2) The extent of examination includes essentially 100% of the length of the attachment weld at each attachment subject to examination.

(3) Selected samples of welded attachments shall be examined each inspection interval.

( 4) For multiple vessels of similar design, function, and service, only one welded attachment of only one of the multiple vessels shall be selected for examination.

Page 2 of 16

L-PI-15-1 06 Enclosure 10 CFR 50.55a Request 1-RR-4-11, Rev. 0 (PINGP Unit 1) 10 CFR 50.55a Request 2-RR-4-11, Rev. 0 (PINGP Unit 2)

Request for Alternative for Limited Examinations Fourth Interval Units 1 and 2 Alternative in Accordance with 10 CFR 50.55a(z)(2)

Note: As defined by ASME Code Case N-460, essentially 100% means more than 90% of the examination volume of each weld where reduction in coverage is due to interference by another component or part geometry.

4. Impracticality of Compliance Due to the configuration, it is not possible to meet the examination coverage requirements of ASME Section XI, 1998 Edition with Addenda through 2000, as clarified by Code Case N-460. Relief is requested in accordance with 10CFR50.55a(z)(2). The limited examinations subject to this request are a result of attempts to perform the examinations during the 4th interval.

When examined, the welds listed within this request did not receive the required Code coverage due to their configuration, presence of permanent attachments and proximity to building structure. These limitations prohibit essentially 100%

coverage of the listed ultrasonic and surface examinations.

Table 2 summarizes the percent of Code coverage obtained with references to figures that show the extent of coverage and the limitations, and photographs of the obstructions.

5. Burden Caused by Compliance Examination Category C-A, Unit 1 and 2- RHR Heat Exchanger 12 and 22, respectively Head-to-Shell Weld (W-1) and Unit 1-RHR Heat Exchange 12 Shell-to-Flange Weld (W-2)

The RHR heat exchanger is a 24 inch vessel with a "U" shaped tube bundle. The stainless steel channel head for the heat exchanger consist of a weld-neck flange welded to one end of the shell (Weld 2) and an elliptical head welded to the other end of the channel head shell (Weld 1). The length of the shell between the flange and the elliptical head is 13 inches. The 13 inch long shell section contains two nominal pipe size (NPS) 8 nozzles with 12 inch diameter reinforcing rings. The nozzles are located 180° apart. In between the two nozzles, there are integrally welded supports that span most of the distance between the nozzles.

Page 3 of 16

L-PI-15-1 06 Enclosure 10 CFR 50.55a Request 1-RR-4-11, Rev. 0 (PINGP Unit 1) 10 CFR 50.55a Request 2-RR-4-11, Rev. 0 (PINGP Unit 2)

Request for Alternative for Limited Examinations Fourth Interval Units 1 and 2 Alternative in Accordance with 10 CFR 50.55a(z)(2)

The nozzle reinforcing rings and the integrally welded supports interfere with scanning Weld 1 on the heat exchangers of both units.

The nozzle reinforcing rings, the integrally welded supports, and the configuration of the weld-neck flange interfere with scanning Weld 2 on the Unit 1 heat exchanger.

The configuration described is typical of Units 1 and 2.

To obtain full Code coverage of the subject welds would require a significant modification or replacement of the heat exchangers to increase the shell length of the channel head to provide an increased distance from the nozzles and supports to the welds. For Weld 2, an alternative configuration of the weld-neck flange would also be required. Due to the current configuration, there are no other volumetric techniques that would provide increased coverage.

Examination Category c-c, Unit 1 and 2- RHR Heat Exchanger 12 and 21, integral attachment weld {H-2/IA)

The RHR heat exchanger is a 24 inch vessel with a "U" shaped tube bundle. The stainless steel channel head for the heat exchanger consist of a weld-neck flange welded to one end of the shell and an elliptical head welded to the other end of the channel head shell. The length of the shell between the flange and the elliptical head is 13 inches. The 13 inch long shell section contains two NPS 8 nozzles with 12 inch diameter reinforcing rings. The nozzles are located 180° apart. In between the two nozzles, there are integrally welded supports that span most of the distance between the nozzles. The integrally welded supports are in close proximity to concrete pedestals that support the heat exchangers.

The close proximity of the concrete pedestals limits access to the bottom fillet weld that attaches the horizontal support plate to the channel shell of the heat exchangers.

The configuration described is typical of both heat exchangers of Units 1 and 2.

Page 4 of 16

L-PI-15-1 06 Enclosure 10 CFR 50.55a Request 1-RR-4-11, Rev. 0 (PINGP Unit 1) 10 CFR 50.55a Request 2-RR-4-11, Rev. 0 (PINGP Unit 2)

Request for Alternative for Limited Examinations Fourth Interval Units 1 and 2 Alternative in Accordance with 10 CFR 50.55a(z)(2)

To obtain full Code coverage for surface examination of the attachment welds would require significant modification or replacement of the heat exchangers to increase the distance between the concrete support pedestals and the exchanger shell.

Due to the current configuration, there are no other surface techniques that would provide increased coverage.

6. Proposed Alternative and Basis for Use Proposed Alternative:

There are no proposed alternatives.

Basis:

The examination coverage described in Table 2 and the applicable Figures represent the maximum obtainable coverage. RHR heat exchanger shell-to-flange, shell-to-head, and attachment welds were examined in the third interval and found to have similar limitations as follows: Weld 1 of the Unit 1 RHR heat exchanger 12 was ultrasonically examined and found to be limited to 74%

coverage. Weld 2 of the Unit 1 RHR heat exchanger 12 was ultrasonically examined and found to be limited to 27% coverage. The attachment welds of one support of the Unit 1 RHR heat exchanger 12 were surface examined found to be limited to 71% coverage. The attachment welds of both supports of the Unit 2 RHR heat exchanger 21 were surface examined found to be limited to 85% coverage. Weld 1 of the Unit 2 RHR heat exchanger 22 was ultrasonically examined and found to be limited to 74% coverage.

The examinations of the fourth interval did not identify any indications of defects or unacceptable conditions according to the acceptance criteria of ASME Section XI, IWC-3510 and IWC-3512.

The fourth interval examination of Weld 2 (Figure 3) identifies "best effort" coverage that is in excess of the reported Code coverage. Best effort coverage Page 5 of 16

L-PI-15-1 06 Enclosure 10 CFR 50.55a Request 1-RR-4-11, Rev. 0 (PINGP Unit 1) 10 CFR 50.55a Request 2-RR-4-11, Rev. 0 (PINGP Unit 2)

Request for Alternative for Limited Examinations Fourth Interval Units 1 and 2 Alternative in Accordance with 10 CFR 50.55a(z)(2) includes areas of the required volume that are in the path of the projected sound beam, but ar~ beyond the qualified limit.

The RHR heat exchangers are within the ASME Section XI, Class 2 boundaries and in addition to' the volumetric examinations required by Examination Category C-A, the heat exchangers are also pressure tested once each inspection period in accordance with Examination Category C-H. None of the pressure tests have identified evidence of leakage from the welds that are subject of this relief request.

The Unit 1 and 2 RHR heat exchangers are the original vessels and there has been no degradation of the channel heads identified since initial operation.

Additionally, the Fifth 10 Year Interval Inservice Inspection program has been prepared using Code Case N-716-1, "Alternative Piping Classification and Examination Requirements". For the Fifth Ten Year Interval, the Unit 1 and Unit 2 RHR heat exchangers are considered Low Safety Significant and the welds that are subject of this relief request will not be subject to examination.

In accordance with 10 CFR 50.55a(g)(S)(iii), Prairie Island has determined that conformance with the requirements of ASME Section XI, Table IWC-2500-1, Examination Category C-A and Code Case N-460 for examination of the welds subject of this request is impractical. The impracticality has been demonstrated by the examinations performed during the Fourth Ten Year Interval as described herein.

7. Duration of Proposed Relief This relief request is applicable to the Prairie Island Unit 1 and 2 Fourth Ten Year Inservice Inspection Interval.

8. Precedents:

Page 6 of 16

L-PI-15-106 Enclosure 10 CFR 50.55a Request 1-RR-4-11, Rev. 0 (PINGP Unit 1) 10 CFR 50.55a Request 2-RR-4-11, Rev. 0 (PINGP Unit 2)

Request for Alternative for Limited Examinations Fourth Interval Units 1 and 2 Alternative in Accordance with 10 CFR 50.55a(z)(2)

Prairie Island Nuclear Generating Plant Request for Relief No. 11 dated May 29, 2001. (Accession No. ML011550260)

Prairie Island Nuclear Generating Plant Request for Relief No. 9 dated November 16, 2002. (Accession No. ML023290578)

Prairie Island Nuclear Generating Plant Request for Relief No. 16 dated January 7, 2004. (Accession No. ML040150068)

Nuclear Regulatory Commission Letter to Kewaunee Power Station dated September 20, 2012

Subject:

Kewaunee Power Station- Evaluation of Relief Request Number RR-G-5 Regarding Fourth 10-Year Interval Inservice Inspection Program (TAC No. ME7378) (Accession No. ML12249A44)

9. References Title 10 of the Code of Federal Regulation, Part 50.55a, Codes and Standards.

ASME Section XI, "Rules for Inservice Inspection of Nuclear Power Plant Components", 1998 Edition through the 2000 Addenda ASME Section XI, Division 1, Code Case N-460, "Alternative Examination Coverage for Class 1 and Class 2 Welds" Regulatory Guide 1.147, Inservice Inspection Code Case Acceptability, ASME section XI, Division 1, Revision 17 NRC Presentation "Coverage Relief Requests" dated January 13- 15, 2015 presented at the Industry/NRC NDE Technical Information Exchange Public Meeting Page 7 of 16

L-PI-15-1 06 Enclosure 10 CFR 50.55a Request 1-RR-4-11, Rev. 0 (PINGP Unit 1) 10 CFR 50.55a Request 2-RR-4-11, Rev. 0 (PINGP Unit 2)

Request for Alternative for Limited Examinations Fourth Interval Units 1 and 2 Alternative in Accordance with 10 CFR 50.55a(z)(2)

Table 2 Component System Exam ASME Angles Figure and Impracticality of Other Examination Configuration Component ID Year Section XI (s)/ Photograph Compliance Results Material Coverage and Exam Results

(%) Wave Modes Unit 1 Residual Residual Heat 2009 Exam Cat C- 45° s 1 Inservice examination Surface examination Heat Exchanger Removal A 60° s limited due to welded is not required by 12 Head to Weld 1 Item No. 70° 5 1 support proximity to Code.

Shell Summary No. C1.20 60° L weld on shell side and System Pressure test; 303053 Rgure No. nozzle reinforcement Acceptable Stainless to IWC-2500-1 plates on shell I head Stainless covering weld.

No Recordable 74% Indications Unit 1 Residual Residual Heat 2012 Exam Cat C- 450 s 3 Inservice examination Surface examination Heat Exchanger Removal A 60° s limited due to flange is not required by 12 Shell to Weld 2 Item No. 70° s configuration. Shell side Code.

Flange Summary No. C1.10 is limited due to welded System Pressure test; 303054 Figure No. attachments and nozzle Acceptable Stainless to IWC-2500-1 reinforcement plates.

Stainless No Recordable L___ - - - - L_ - -- - -

32% Indications 1

This weld was scanned with the 70° shear wave, but no additional coverage was obtained, therefore the 70° shear wave is not shown on Figure 1.

Page 8 of 16

L-PI-15-106 Enclosure 10 CFR 50.55a Request 1-RR-4-11, Rev. 0 (PINGP Unit 1) 10 CFR 50.55a Request 2-RR-4-11, Rev. 0 (PINGP Unit 2)

Request for Alternative for Limited Examinations Fourth Interval Units 1 and 2 Alternative in Accordance with 10 CFR 50.55a(z)(2)

Table 2 I Component System Exam ASME Angles Figure and Impracticality of Other Examination Configuration Component ID Year Section XI (s)/ Photograph Compliance Results Material Coverage and Exam Results

(%) Wave Modes Unit 1 Residual 2012 Exam Cat C- N/A 3 Inservice examination System Pressure test; Heat Exchanger Residual Heat c limited due to welded Acceptable 12 welded Removal Item No. support proximity to Attachment Attachment Weld C3.10 building structure.

H-2/IA Summary No. 75%

323052 Unit 2 Residual Residual Heat 2010 Exam Cat C- N/A Not Shown. Inservice examination System Pressure test; Heat Exchanger Removal c Similar to limited due to welded Acceptable 21 welded Attachment Weld Item No. HX 12 support proximity to Attachment H-2/IA C3.10 Photograph building structure.

Summary No. 3.

521419 - -~

85% - - - -

-~

- -~

Page 9 of 16

L-PI-15-106 Enclosure 10 CFR 50.55a Request 1-RR-4-11, Rev. 0 (PINGP Unit 1) 10 CFR 50.55a Request 2-RR-4-11, Rev. 0 (PINGP Unit 2)

Request for Alternative for Limited Examinations Fourth Interval Units 1. and 2 Alternative in Accordance with 10 CFR 50.55a(z)(2)

Table 2 Component System Exam ASME Angles Figure and Impracticality of Other Examination Configuration Component ID Year Section XI (s)/ Photograph Compliance Results Material Coverage and Exam Results

(%) Wave Modes Unit 2 Residual Residual Heat 2013 Exam Cat C- 45° s 2 Inservice examination Surface examination Heat Exchanger Removal A 60° L limited due to welded is not required by 22 Head to Weld 1 Item No. support proximity to Code.

Shell Summary No. C1.20 weld on shell side and System Pressure test; 501477 Figure No. nozzle reinforcement Acceptable Stainless to IWC-2500-1 plates on shell I head Stainless covering weld.

No Recordable 74% Indications Page 10 of 16

L-PI-15-1 06 Enclosure 10 CFR 50.55a Request 1-RR-4-11, Rev. 0 (PINGP Unit 1) 10 CFR 50.55a Request 2-RR-4-11, Rev. 0 (PINGP Unit 2)

Request for Alternative for Limited Examinations Fourth Interval Units 1 and 2 Alternative in Accordance with 10 CFR 50.55a(z)(2)

ISI-93B W-1 Summary No: 303053

.49" .63" 53.

16" area with no coverage dne to Nozzle Saddle welds Total Weld Length=76" Shell A240TP3M Required Exam Volume- .73 Sq. Inches Head Side Circ. Examination Cover.age Achieved .73 Sq.lnches (79%)

Shell Side Examination Coverage Achieved 69% Head Side Examination Coverage Achieved 79%

Total Examination Coverage Achieved 74%

Figure l Page 11 of 16

L-PI-15-106 Enclosure 10 CFR 50.55a Request 1-RR-4-11, Rev. 0 (PINGP Unit 1) 10 CFR 50.55a Request 2-RR-4-11, Rev. 0 (PINGP Unit 2)

Request for Alternative for Limited Examinations Fourth Interval Units 1 and 2 Alternative in Accordance with 10 CFR 50.55a(z)(2) 2ISI-69B W-1 SummaryNo: 501477

.49" .63" 53*

16" area wiihno cm'l!r.!ge dill! 1o Noxzle Saddle welds Total WeldLengih=76" Required Exam VolUIDI>- .73 Sq. Inches Axial Elu!miJJati.on Cm*ernge A chi~ .73 Sq. Jnclie>

(79%)

Head Side! Circ. F.xamination Coverage Aclll.eved .73 Sq. Inches (79%)

Shell Side Examination Coverage Achieved 69% Head Side Examination Coverage Achieved 7!)0/a Total Examination Coverage Achieved 74%

Figure2 Page 12 of 16

L-PI-15-1 06 Enclosure 10 CFR 50.55a Request 1-RR-4-11, Rev. 0 (PINGP Unit 1) 10 CFR 50.55a Request 2-RR-4-11, Rev. 0 (PINGP Unit 2)

Request for Alternative for Limited Examinations Fourth Interval Units 1 and 2 Alternative in Accordance with 10 CFR 50.55a(z)(2)

ISI-93B W-2 Summary No: 303054

.73" .62" .49"

-Total weld Length 76"

-8 11 area with no coverage due to four welded supports (2" each) on shell side

-16" Area with no coverage due to the two nozzle saddle welds (811 each)

Required Exam Volume- 1.25 Sq. Inches Best Effort Axial Examination Coverage Achieved .3& Sq. Inches Exam Coverage (30"/.)

Circ. Examination Coverage Achieved .43 Sq. Inches (34%)

Total Examination Coverage Achieved 32%

Figure 3 Page 13 of 16

L-PI-15-1 06 Enclosure 10 CFR 50.55a Request 1-RR-4-11 Rev. 0 (PINGP Unit 1)

I 10 CFR 50.55a Request 2-RR-4-11 Rev. 0 (PINGP Unit 2)

I Request for Alternative for Limited Examinations Fourth Interval Units 1 and 2 Alternative in Accordance with 10 CFR 50.55a(z)(2)

Photograph 1 Unit 1, Residual Heat Exchanger 12 Head-to-Shell Weld (Weld 1)

Page 14 of 16

L-PI-15-1 06 Enclosure 10 CFR 50.55a Request 1-RR-4-11, Rev. 0 (PINGP Unit 1) 10 CFR 50.55a Request 2-RR-4-11, Rev. 0 (PINGP Unit 2)

Request for Alternative for Limited Examinations Fourth Interval Units 1 and 2 Alternative in Accordance with 10 CFR 50.55a(z)(2)

Photograph 2 Unit 2, Residual Heat Exchanger 22 Head-to-Shell Weld (Weld 1)

Page 15 of 16

L-PI-15-106 Enclosure 10 CFR 50.55a Request 1-RR-4-11, Rev. 0 (PINGP Unit 1) 10 CFR 50.55a Request 2-RR-4-11, Rev. 0 (PINGP Unit 2)

Request for Alternative for Limited Examinations Fourth Interval Units 1 and 2 Alternative in Accordance with 10 CFR 50.55a(z)(2)

Photograph 3 Unit 1, Residual Heat Exchanger 12 Shell-to-Flange Weld (Weld 2)

Page 16 of 16