ML042220042

Evaluation of Relief Request No. 16 for the Unit 2 3rd 10-year Interval Inservice Inspection Program

ML042220042
Person / Time
Site:	Prairie Island
Issue date:	10/18/2004
From:	Raghavan L NRC/NRR/DLPM/LPD3
To:	Solymossy J Nuclear Management Co
Chawla M, 415-8371, NRR/DLPM
References
TAC MC1775
Download: ML042220042 (11)

Text

October 18, 2004 Mr. Joseph M. Solymossy Site Vice President Prairie Island Nuclear Generating Plant Nuclear Management Company, LLC 1717 Wakonade Drive East Welch, MN 55089

SUBJECT:

PRAIRIE ISLAND NUCLEAR GENERATING PLANT, UNIT 2 - EVALUATION OF RELIEF REQUEST NO. 16 FOR THE UNIT 2 3RD 10-YEAR INTERVAL INSERVICE INSPECTION PROGRAM (TAC NO. MC1775)

Dear Mr. Solymossy:

By a letter dated January 7, 2004, Nuclear Management Company, LLC (NMC, the licensee),

submitted Relief Request No. 16, Revision No. 0, for Prairie Island Unit 2. The request was for limited examinations associated with the 3rd 10-year Interval Inspection Examination Plan, for which Nuclear Regulatory Commission (NRC) issued its evaluation on February 22, 1996.

A request for additional information was sent to NMC via e-mail on April 8, 2004 (ADAMS Accession Number ML042150331). This information was discussed with NMC representatives during telephone conversations held on April 14, 2004, and April 20, 2004. NMC provided a revised submittal dated May 28, 2004, providing additional information in response to NRC request dated April 30, 2004. The revised submittal, also excluded weld W-36 (ID # 500861),

for which relief was requested in the original submittal.

The NRC staff has evaluated the licensees request for relief and has granted the relief pursuant to Title 10 of the Code of Federal Regulations (10 CFR) Section, 50.55a(g)(6)(i) for the third 10-year inservice inspection interval at Prairie Island Nuclear Generating Plant, Unit 2.

The NRC staff concludes that, to examine the subject welds as required by the Code, the welds would have to be redesigned and modified resulting in a considerable burden on the licensee.

As a result, the NRC staff has determined that compliance with the Code volumetric coverage requirements is impractical for the subject welds.

The NRC staff has determined that this granting relief pursuant to 10 CFR 50.55a(g)(6)(i) is authorized by law and will not endanger life or property, or the common defense and security, and is otherwise in the public interest giving due consideration to the burden upon the licensee that could result if the requirements were imposed on the facility. The examinations conducted by the licensee did not detect any significant degradation, and therefore provide reasonable assurance of structural integrity.

J. Solymossy A copy of our related safety evaluation is also enclosed.

Sincerely,

/RA/

L. Raghavan, Chief, Section 1 Project Directorate III Division of Licensing Project Management Office of Nuclear Reactor Regulation Docket No. 50-306

Enclosure:

Safety Evaluation cc w/encl: See next page

ML042220042 OFFICE PDIII-1/PM PDIII-1/LA SC:EMCB OGC PDIII-1/SC NAME MChawla THarris TChan RHoefling LRaghavan DATE 10/18/04 10/18/04 08/25/04 09/01/04 10/18/04 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION THIRD 10-YEAR INTERVAL INSERVICE INSPECTION REQUEST FOR RELIEF NO. 16 (REVISION NO. 0)

PRAIRIE ISLAND NUCLEAR GENERATING PLANT UNIT 2 NUCLEAR MANAGEMENT COMPANY, LLC.

DOCKET NO. 50-306

1.0 INTRODUCTION

The U.S. Nuclear Regulatory Commission (NRC) staff has reviewed and evaluated the information provided by Nuclear Management Company, LLC (the licensee), in a letter dated January 7, 2004, which seeks relief to the requirements of the 1989 Edition of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code)Section XI at Prairie Island Nuclear Generating Plant (PINGP), Unit 2. The licensee provided additional information in its letter dated May 28, 2004.

2.0 REGULATORY REQUIREMENTS The inservice inspection of the ASME Code Class 1, Class 2, and Class 3 components shall be performed in accordance with Section XI of the ASME Code and applicable editions and addenda as required by Title 10 of the Code of Federal Regulations (10 CFR) 50.55a(g), except where specific written relief has been granted by the Commission pursuant to 10 CFR 50.55a(g)(6)(i).

Pursuant to 10 CFR 50.55a(g)(4), ASME Code Class 1, 2, and 3 components (including supports) must meet the requirements, except the design and access provisions and the preservice examination requirements, set forth in the ASME Code,Section XI, Rules for Inservice Inspection of Nuclear Power Plant Components, to the extent practical within the limitations of design, geometry, and materials of construction of the components. The regulations require that inservice examination of components and system pressure tests conducted during the first 10-year interval and subsequent intervals comply with the requirements in the latest edition and addenda of Section XI of the ASME Code incorporated by reference in 10 CFR 50.55a(b) on the date 12 months prior to the start of the 120-month interval, subject to the limitations and modifications listed therein. The components (including supports) may meet the requirements set forth in subsequent editions and addenda of the ASME Code incorporated by reference in 10 CFR 50.55a(b) subject to the limitations and modifications listed therein and subject to Commission approval. The applicable ASME Code of record for the third 10-year inservice inspection (ISI) interval at PINGP, Unit 2, is the 1989 Edition of ASME Section XI, with no addenda.

3.0 TECHNICAL EVALUATION

3.1 Code Requirements for which Relief is Requested ASME Section XI (1989 Edition, no addenda) Code requires full examination coverage of ISI components per Categories B-A and B-J of Table IWB-2500-1, and Categories CA, C-F-1 and C-F-2 of Table IWC-2500-1. NRC Regulatory Guide 1.147 endorses the use of Section XI Code Case N-460, Alternative Examination Coverage for Class 1 and Class 2 Welds. This code case allows greater than 90 percent coverage of a weld to meet the essentially 100 percent requirement.

3.2 Licensees Code Relief Request Relief is requested from performing a full Code coverage volumetric examination and a full code coverage surface examination of the Class 1 and Class 2 welds, except for Category C-A welds, for which only volumetric examination is required.

3.3 Components for which Relief Is Requested ASME Section XI, Class 1, Table IWB-2500-1, Examination Category B-A; Examination Category B-J; Table IWC-2500-1, Examination Category C-A; and Examination Category C-F-1.

Category Item ID No. Description Volumetric Limitation Coverage

(%)

B-A B1.40 W-6 Head to 58.68 Limited to flange configuration 501733 Flange (lifting lugs).

B-J B9.10 W-6/ Elbow to 69 Limited due to configuration and 2LSU Pump material attenuation.

501145 B-J B9.11 W-2 Elbow to 39.25 Limited due to four welded 501900 Pipe support attachments.

B-J B9.11 W-3 Pipe to 75 Limited due to restraint.

501813 Elbow B-J B9.31 W-12 Nozzle to 50 Limited due to Nozzle weld 501939 Pipe configuration.

C-A C1.20 W-1 Head to 74 Limited due to inlet / outlet 501477 Shell reinforcing rings and two welded supports.

Category Item ID No. Description Volumetric Limitation Coverage

(%)

C-F-1 C5.21 W-11 Valve to 50 Limited on valve side due to 505055 Elbow configuration.

C-F-1 C5.21 W-14 Elbow to 50 Limited on valve side due to 505058 Valve configuration.

C-F-1 C5.21 W-17 Pipe to 50 Limited on flange side due to 505370 Flange configuration.

In addition to volumetric examinations, relief is requested from performing 100 percent surface examination on Safety Injection Elbow to Pipe Weld (W-2).

3.4 Licensees Basis for Requesting Relief:

In its submittal, the licensee provided its regulatory basis for requesting relief as stated below.

This request is submitted pursuant to 10 CFR 50.55a(g)(5)(iv) which states, Where an examination requirement by the code or addenda is determined to be impractical by the licensee and is not included in the revised ISI program as permitted by paragraph (g)(4) of this section, the basis for this determination must be demonstrated to the satisfaction of the Commission.

The regulation further states in 10 CFR 50.55a(g)(1) that, For a boiling or pressurized water-cooled nuclear power facility whose construction permit was issued before January 1, 1971, components (including supports) must meet the requirements of paragraphs (g)(4) and (g)(5) of this section to the extent practical. 10 CFR 50.55a(g)(4) states, Throughout the service life of a boiling or pressurized water-cooled nuclear power facility, components (including supports) which are classified as ASME Code Class 1, Class 2, and Class 3 must meet the requirements, except design and access provisions and preservice examination requirements, set forth in Section XI of editions of the ASME Boiler and Pressure Vessel Code ... to the extent practical within the limitations of design, geometry and materials of construction of the components.

Prairie Island was designed and constructed prior to development of ASME XI, therefore, design for accessibility and inspection coverage is not in many cases, sufficient to permit satisfying the current Code requirements. Limitations to inspections are primarily due to design obstructions, component configurations and interference. In the case of circumferential welds, a limitation from ultrasonic examination may exist simply because of weld joint configuration as with a pipe to valve or fitting weld.

The licensee stated that the required surface examination was performed using either magnetic particle or liquid penetrant tests. One hundred percent or essentially 100 percent of the required surface area was inspected except for Safety Injection Weld (W-2), where only 52.9 percent was achieved due to physical constraint. No relevant indications were detected from the surface examination.

Regarding volumetric examination, physical limitations due to geometric configuration of the welded areas, restrict coverage of the category B-A, B-J, C-A and C-F-1 welds and make it impossible to achieve 100 percent of the total examination volume required by IWB-2500-1 and IWC-2500-1 of ASME Section XI. Specific limitations to each item are summarized below.

Part A: Category B-A, Pressure Retaining Welds in Reactor Vessel Reactor Vessel Weld (W-6), Head to Flange:

The required volumetric examination of the weld required volume (WRV) was limited from the flange side of the weld due to weld joint configuration and close proximity of the flange to the intersecting radius of the reactor head. In addition, there are three 5.5 inch wide lifting lugs located approximately 120 degrees apart and 3 inches from the toe of the weld on the head that prevent 100 percent scanning and axial coverage from the head side of the weld. The axial WRV was limited to approximately 43.4 percent using a 45-degree shear wave and 41.9 percent using a 60-degree shear wave. Circumferential scanning in the clockwise and counterclockwise direction of the WRV was limited to 66.7 percent again by the flange and could only be performed on the head side of the weld. The credited volumetric examination of the WRV was limited to 58.68 percent.

Part B: Category B-J, Pressure Retaining Welds in Piping Reactor Coolant (RC) Weld (W-6/2LSU) Elbow to Pump:

This piping weld is subject to be examined by both volumetric and surface examination methods. The volumetric examination was performed using personnel and procedures qualified in accordance with Appendix III. The examination was conducted using 45 refracted longitudinal transducers. The pump and piping elbow material are cast austenitic stainless steel. In addition, the attenuation of the cast stainless material of the pump and elbow impedes the examination and use of other angles. The examination is limited to 48 percent in the axial direction and 90 percent in the circumferential direction from the piping elbow side of the weld due to the weld joint configuration connection to the pump. The credited volumetric examination of the WRV was limited to 69 percent and only a single-sided examination could be performed.

Safety Injection (SI) Weld (W-2), Elbow to Pipe:

This piping weld is subject to be examined by both volumetric and surface examination methods. The volumetric examination was performed using personnel and procedures qualified in accordance with Appendix VIII, Supplement 2. The examination was conducted using 45 and 60-degree transducers. The elbow and piping material are austenitic stainless steel. The examination is limited to 34.5 percent in the axial direction and 44 percent in the circumferential direction due to four welded support lugs covering the weld. The credited volumetric examination of the WRV was limited to 39.25 percent.

In addition to volumetric examinations, relief is requested from performing 100 percent surface examination on SI elbow to pipe weld (W-2). The exam was limited due to four welded support lugs covering the weld. As a result, 52.9 percent of the area was inspected.

SI Weld (W-3), Pipe to Elbow:

The examination is limited to 50 percent in the axial direction due to a non-removable restraint on the upstream side of the weld. One hunder percent of the circumferential direction was examined. The credited volumetric examination of the WRV was limited to 75 percent and only a single-sided examination could be performed for the axial direction. It should be noted that the volumetric examination was performed through 100 percent of the Code WRV; however, the Performance Demonstration Initiative (PDI) Appendix VIII procedure used is not qualified for the detection of flaws on the far side of single-sided access examinations on austenitic stainless steel piping welds.

RC Weld (W-12), Nozzle to Pipe:

The examination is limited to 50 percent in both the axial and circumferential directions from the nozzle side of the weld due to the weld joint configuration of the branch connection to the process pipe. The credited volumetric examination of the WRV was limited to 50 percent and only a single-sided examination could be performed. It should be noted that the volumetric examination was performed through 100 percent of the Code WRV; however, the PDI Appendix VIII procedure used is not qualified for the detection of flaws on the far side of single-sided access examinations on austenitic stainless steel piping welds.

Part C: Category C-A Pressure Retaining Welds in Pressure Vessels Residual Heat Removal Weld (W-1), Head to Shell:

The examination was conducted using a 45 and 60-degree transducers. The head and shell materials are austenitic stainless steel. The examination is limited in all scan directions due to outlet/inlet nozzle reinforcing rings and two welded supports. The credited volumetric examination of the WRV was limited to 74 percent.

Part D: Category C-F-1 Pressure Retaining Welds in Austenitic Stainless Steel or High Alloy Piping SI Weld (W-11), Valve to Elbow:

The examination is limited to 50 percent in both the axial and circumferential directions from the piping side of the weld due to the weld joint configuration connection to the valve. The credited volumetric examination of the WRV was limited to 50 percent and only a single-sided examination could be performed. It should be noted that the volumetric examination was performed through 100 percent of the Code WRV; however, the PDI Appendix VIII procedure used is not qualified for the detection of flaws on the far side of single-sided access examinations on austenitic stainless steel piping welds.

SI Weld (W-14), Elbow to Valve:

The examination is limited to 50 percent in both the axial and circumferential directions from the piping elbow side of the weld due to the weld joint configuration connection. The credited volumetric examination of the WRV was limited to 50 percent and only a single-sided examination could be performed. It should be noted that the volumetric examination was performed through 100 percent of the Code WRV; however, the PDI Appendix VIII procedure used is not qualified for the detection of flaws on the far side of single-sided access examinations on austenitic stainless steel piping welds.

Safety Injection (SI) Weld (W-17), Pipe to Flange:

The examination is limited to 50 percent in both the axial and circumferential directions from the piping side of the weld due to the weld joint configuration connection to the flange. The credited volumetric examination of the WRV was limited to 50 percent and only a single-sided examination could be performed. It should be noted that the volumetric examination was performed through 100 percent of the Code WRV; however, the PDI Appendix VIII procedure used is not qualified for the detection of flaws on the far side of single sided access examinations on austenitic stainless steel piping welds.

In discussing the above limitations, the licensee stated that the techniques employed for the examination provided for a best effort examination. The licensee stated that visual examinations were performed on all of the subject welds during pressure testing in 2003. No leakage was detected in any of the welds. This supports the fact that leakage integrity has not been compromised.

3.5 NRC Staff Evaluation The ASME Code,Section XI, 1989 Edition, no addenda, Category B-A and B-J of Table IWB-2500-1, and C-F-1 of Table IWC-2500-1 require surface and volumetric examination of pressure-retaining welds in Class 1 and Class 2 systems. The Code requires volumetric examination only on Category C-A welds.

PINGP Unit 2 was designed and constructed prior to the development of ASME Section XI. In many cases, component configurations and interference cause limitations to ISI inspections.

As a result, Code-required volumetric examination of the subject Class 1 and Class 2 welds

was limited to less than essentially 100 percent. In addition, Code-required surface examination of one of the Category B-J welds was limited to less than essentially 100 percent.

For each of the welds examined, physical limitations due to geometric configuration of the welded areas restricted coverage of the category B-A, B-J, C-A and C-F-1 welds and made it impractical to achieve 100 percent of the total examination volume required by the Code. As an alternative to the ultrasonic examination, radiography was considered and determined to be an unacceptable substitute due to radiological constraints and weld configuration. Surface examination was limited to 52.9 percent on one of the B-J weld (Safety Injection elbow to pipe).

The licensee provided detailed information regarding the specific limitation for each item. To examine these welds as required by the Code, the welds would have to be redesigned and modified which would result in a considerable burden on the licensee. The licensee conducted these examinations to the fullest extent practical, and obtained from 39.25 percent to 75 percent of volumetric coverage of the subject welds, and completed 100 percent of the Code-required surface examinations, except for SI weld (W-2), where only 52.9 percent of the required area was examined due to physical constraint. These examinations should have detected any significant degradation, if present, and provide reasonable assurance of structural integrity. In addition, the licensee performed visual examination (VT-2) on all of the subject welds during pressure testing in 2003. No leakage was detected in any of the welds, which indicated that leakage integrity has not been compromised.

4.0 CONCLUSION

The staff has reviewed the information provided and concludes that to examine the subject welds as required by the Code, the welds would have to be redesigned and modified resulting in a considerable burden on the licensee. As a result, the staff has determined that compliance with the Code volumetric coverage requirements is impractical for the subject welds. The licensee conducted these examinations to the extent practical. Therefore, relief is granted pursuant to 10 CFR 50.55a(g)(6)(i) for the third 10-year ISI interval at PINGS, Unit 2. The staff has determined that this grant of relief is authorized by law and will not endanger life or property, or the common defense and security and is otherwise in the public interest giving due consideration to the burden upon the licensee that could result if the requirements were imposed on the facility.

All other ASME Code Section XI requirements for which relief was not specifically requested and approved in this relief request remain applicable, including third party review by the Authorized Nuclear Inservice Inspector.

Principal Contributor: Bart Fu

Prairie Island Nuclear Generating Plant, Units 1 and 2 cc:

Jonathan Rogoff, Esquire Tribal Council Vice President, Counsel & Secretary Prairie Island Indian Community Nuclear Management Company, LLC ATTN: Environmental Department 700 First Street 5636 Sturgeon Lake Road Hudson, WI 54016 Welch, MN 55089 Manager, Regulatory Affairs Nuclear Asset Manager Prairie Island Nuclear Generating Plant Xcel Energy, Inc.

Nuclear Management Company, LLC 414 Nicollet Mall, R.S. 8 1717 Wakonade Drive East Minneapolis, MN 55401 Welch, MN 55089 John Paul Cowan Manager - Environmental Protection Division Executive Vice President & Chief Nuclear Minnesota Attorney Generals Office Officer 445 Minnesota St., Suite 900 Nuclear Management Company, LLC St. Paul, MN 55101-2127 700 First Street Hudson, WI 54016 U.S. Nuclear Regulatory Commission Resident Inspector's Office Craig G. Anderson 1719 Wakonade Drive East Senior Vice President, Group Operations Welch, MN 55089-9642 Nuclear Management Company, LLC 700 First Street Regional Administrator, Region III Hudson, WI 54016 U.S. Nuclear Regulatory Commission 801 Warrenville Road Lisle, IL 60532-4351 Administrator Goodhue County Courthouse Box 408 Red Wing, MN 55066-0408 Commissioner Minnesota Department of Commerce 121 Seventh Place East Suite 200 St. Paul, MN 55101-2145 November 2003