ML15265A164

Request 14R-17 Relief from the Requirements of the ASME Code

ML15265A164
Person / Time
Site:	Dresden
Issue date:	10/30/2015
From:	Travis Tate Plant Licensing Branch III
To:	Bryan Hanson Exelon Generation Co, Exelon Nuclear
Russel Haskell, NRR/DORL
References
CAC MF3352, CAC MF3353
Download: ML15265A164 (22)

Text

Mr. Bryan C. Hanson Senior Vice President UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 October 30, 2015 Exelon Generation Company, LLC President and Chief Nuclear Officer (CNO)

Exelon Nuclear 4300 Winfield Road Warrenville, IL 60555

SUBJECT:

DRESDEN NUCLEAR POWER STATION, UNITS 2 AND 3-REQUEST 14R-17 RELIEF FROM THE REQUIREMENTS OF THE ASME CODE (CAC NOS. MF3352 AND MF3353)

Dear Mr. Hanson:

By letter dated December 30, 2013, as supplemented by letters dated October 16, 2014, and May 21, 2015 (Agencywide Documents Access and Management System (ADAMS) Accession Nos. ML13364A361, ML14293A255, and ML15141A324, respectively), Exelon Generation Company, LLC (EGC or the licensee) submitted a request to the U.S. Nuclear Regulatory Commission (NRC) for relief from certain American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code),Section XI, requirements associated with the fourth inservice inspection interval at Dresden Nuclear Power Station, Units 2 and 3.

Specifically, pursuant to Title 10 of the Code of Federal Regulations (10 CFR), paragraph 50.55a(g)(5)(iii), EGC requested relief from the "essentially 100 percent" volumetric coverage requirements of ASME Code,Section XI, for the subject welds on the basis that the code requirement is impractical.

The NRC has reviewed the subject request and concludes, as set forth in the enclosed safety evaluation, that EGC has adequately addressed all of the requirements set forth in 10 CFR 50.55a(g)(5)(iii).

If you have any questions, please contact Ms. Eva Brown at 301-415-2315.

Docket Nos. 50-237 and 50-249

Enclosure:

Safety Evaluation cc w/encl: Distribution via Listserv Sincerely, Travis L. Tate, Chief Plant Licensing 111-2 and Planning and Analysis Branch Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION 1.0 SCOPE FOURTH 10-YEAR INSERVICE INSPECTION INTERVAL REQUEST FOR RELIEF 14R-17 EXELON GENERATION COMPANY, LLC DRESDEN NUCLEAR POWER STATION, UNITS 2 AND 3 DOCKET NOS. 50-237 AND 50-249 By letter dated December 30, 2013 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML13364A361 ), Exelon Generation Company, LLC (EGC or the licensee) submitted Request for Relief 14R-17 from the requirements of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code),Section XI, Rules for lnservice Inspection of Nuclear Power Plant Components, for Dresden Nuclear Power Station, Units 2 and 3 (DNPS 2 and 3). The request for relief applies to the fourth 10-year inservice inspection (ISi) interval, in which the licensee adopted the 1995 Edition through the 1996 Addenda of ASME Code,Section XI, as the code of record (COR). The U.S. Nuclear Regulatory Commission (NRC or Commission) requested that the licensee provide further information, and the licensee provided a response to the request for additional information (RAI) in letters dated October 16, 2014 (ADAMS Accession No. ML14293A255), and May 21, 2015 (ADAMS Accession No. ML15141A324).

Specifically, pursuant to paragraph 50.55a(g)(5)(iii) of Title 10 of the Code of Federal Regulations (10 CFR), the licensee requested relief from the "essentially 100 percent" volumetric coverage requirements of ASME Code,Section XI, for the subject welds on the basis that the code requirement is impractical.

2.0 REGULATORY EVALUATION

Pursuant to 10 CFR 50.55a(g)(4), ASME Code Class 1, 2, and 3 components (including supports) shall meet the requirements, except the design and access provisions and the preservice examination requirements, set forth in the ASME Code,Section XI, 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, which was incorporated by reference in 10 CFR 50.55a(b), 12 months prior to the start of the 120-month interval, subject to the limitations and modifications listed therein.

Enclosure Paragraph 50.55a(g)(5)(iii) of 10 CFR, states, in part, that licensees may determine that conformance with certain ASME Code requirements is impractical and that the licensee shall notify the Commission and submit information in support of the determination. Determination of Impracticality in accordance with this section must be based on the demonstrated limitations experience when attempting to comply with the code requirements during the ISi interval for which the request is being submitted. Requests for relief made in accordance with this section must be submitted to the NRC no later than 12 months after the expiration of the initial 120-month inspection interval or subsequent 120-month inspection interval for which relief is sought.

The regulations in 10 CFR 50.55a(g)(6)(i), state that the Commission will evaluate determinations under paragraph (g)(5) of this section that code requirements are impractical.

The Commission may grant such relief and may impose such alternative requirements as it determines 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 licensee has requested relief from ASME Code requirements pursuant to 10 CFR 50.55a(g)(5)(iii). The ASME Code COR for DNPS 2 and 3, fourth 10-year ISi interval program, which ended on January 19, 2013, is the 1995 Edition, including the 1996 Addenda,Section XI, of the ASME Code.

Based on the above, and subject to the following technical evaluation, the NRC staff finds that regulatory authority exists for the licensee to request, and the Commission to authorize, the alternative requested by the licensee.

3.0 TECHNICAL EVALUATION

The information provided by the licensee in support of the request for relief from ASME Code requirements has been evaluated and the bases for disposition is documented below. For clarity, the request has been evaluated in several parts according to ASME Code Examination Category.

3.1 Request for Relief 14R-17. Part A ASME Code.Section XI, Examination Category B-A, Items B 1.12 and 1.40. Pressure Retaining Welds in Reactor Vessels ASME Code Requirement ASME Code,Section XI, Examination Category 8-A, Items 81.12 and 81.40, requires essentially 100 percent volumetric and surface examination, as applicable, as defined by Figures IWB-2500-2 and IWB-2500-5, of the length of reactor pressure vessel (RPV) longitudinal shell welds and head-to-flange welds. "Essentially 100 percent," as clarified by ASME Code Case N-460, Alternative Examination Coverage for Class 1 and Class 2 Welds, is greater than 90 percent coverage of the examination volume, or surface area, as applicable.

ASME Code Case N-460 has been approved for use by the NRC in Regulatory Guide (RG) 1.147, Revision 17, "lnservice Inspection Code Case Acceptability."

Licensee's ASME Code Relief Request In accordance with 10 CFR 50.55a(g)(5)(iii), the licensee requested relief from the ASME Code-required volumetric examination for the RPV longitudinal shell welds and head-to-flange welds listed below in Tables 3.1.1 (DNPS 2) and 3.1.2 (DNPS 3).

Table 3.1.1 - ASME Code,Section XI, Examination Category B-A Unit 2)

ASME Coverage Code Weld ID Weld Type Obtained Item (Percent) 81.12 2/1/RPVSHELL/2-SC1 A-VERT Longitudinal Weld 88.0 81.12 2/1/RPVSHELL/2-SC18-VERT Longitudinal Weld 40.2 81.12 2/1/RPVSHELL/2-SC1 C-VERT Longitudinal Weld 40.2 81.12 2/1/RPVSHELL/2-SC1 D-VERT Longitudinal Weld 71.4 81.12 2/1 /RPVSHELL/2-SC2A-VERT Longitudinal Weld 69.0 81.12 2/1 /RPVSHELL/2-SC28-VERT Longitudinal Weld 78.2 81.12 2/1 /RPVSHELL/2-SC2C-VERT Longitudinal Weld 87.0 81.12 2/1 /RPVSHELL/2-SC3A-VERT Longitudinal Weld 69.1 81.12 2/1 /RPVSHELL/2-SC38-VERT Longitudinal Weld 72.9 81.12 2/1 /RPVSHELL/2-SC3C-VERT Longitudinal Weld 68.7 81.12 2/1 /RPVSHELL/2-SC3D-VERT Longitudinal Weld 73.7 81.12 2/1 /RPVSHELL/2-SC3E-VERT Longitudinal Weld 74.2 81.12 2/1 /RPVSHELL/2-SC4C-VERT Longitudinal Weld 85.7 81.40 2/1 /RPVUPPHD/2-THD-FLG Vessel Upper Top Head-to-65.01 Flange Weld 1 Coverage percentage updated with second RAI response dated May 21, 2015.

Table 3.1.2

• ASME Code, Secti()n XI, Examination Category B-A Unit 3)

ASME Coverage Code Weld ID Weld Type Obtained Item (Percent) 81.12 3/1/RPVSHELL/3-SC1A-VERT Longitudinal Weld 85.0 81.12 3/1/RPVSHELL/3-SC1 B-VERT Longitudinal Weld 39.8 81.12 3/1/RPVSHELL/3-SC1 C-VERT Longitudinal Weld 83.4 81.12 3/1 /RPVSHELL/3-SC2A-VERT Longitudinal Weld 75.8 81.12 3/1 /RPVSHELL/3-SC2C-VERT Longitudinal Weld 84.2 81.12 3/1 /RPVSHELL/3-SC3A-VERT Longitudinal Weld 22.6 81.12 3/1 /RPVSHELL/3-SC3B-VERT Longitudinal Weld 66.0 81.12 3/1 /RPVSHELL/3-SC3C-VERT Longitudinal Weld 55.7 81.12 3/1 /RPVSHELL/3-SC3D-VERT Longitudinal Weld 71.8 81.12 3/1 /RPVSHELL/3-SC4B-VERT Longitudinal Weld 80.2 81.40 3/1 /RPVUPPHD/3-THD-FLG Vessel-Upper Top Head-to-67.02 Flange Weld Licensee's Basis for Relief Request RPV Longitudinal Shell Welds - The completed examination was limited due to proximity of the jet pump diffuser, shroud repair lower contact, jet pump restrainer, jet pump riser brace, lower specimen and upper specimen brackets, feedwater sparger, core spray downcomer piping, lower guide rod, core spray piping and piping bracket, shroud repair tie rod, upper guide rod, tie-rod stabilizer bracket, dryer bracket, steam dryer support, and mismatch between the RPV and flange, as applicable.

RPV Upper Top Head-to-Flange Welds (DNPS 2 and 3) - The completed examination coverage was limited due to flange configuration.

Licensee's Proposed Alternative Examination The licensee did not propose any alternative examinations for the subject welds. However, the licensee's examinations were performed to the maximum extent practical.

NRC Staff Evaluation

The ASME Code requires essentially 100 percent volumetric and surface examination, as applicable, of pressure retaining welds in the RPV. However, for the subject welds at DNPS, complete examinations are restricted by their design geometry and the proximity of surrounding appurtenances. In order to effectively increase the examination coverage, the RPV and adjacent components would require design modifications or replacement. This would place a 2 Coverage percentage updated with second RAI response dated May 21, 2015.

burden on the licensee; thus, examining essentially 100 percent of the ASME Code-required volumes is considered impractical.

The design of the DNPS RPVs limit the examination of the subject welds as shown in sketches provided by the licensee in its October 16, 2014, response to an RAI. The RPV longitudinal shell welds listed in Tables 3.1.1 and 3.1.2 were examined using 45-degree shear and 70-degree refracted longitudinal wave scans with equipment, procedures, and personnel that have successfully passed performance demonstration requirements listed in ASME Code,Section XI, Appendix VIII. The RPV top head-to-flange welds were examined using 60-degree refracted longitudinal waves. A 45-degree shear wave technique was also employed on DNPS 2 to size two reflectors that were detected and observed during previous examinations.

These reflectors had not changed in size since the last examination and were found acceptable per ASME IWB-3000. In a safety evaluation (SE) dated March 29, 2012 (ADAMS Accession No. ML120820266), the NRC authorized DNPS, for the remainder of the fourth 10-year ISi, to implement Mandatory Appendix I, 1-2600, from ASME Code 2007 Edition through 2008 Addenda, which permits the use of Appendix VIII performance demonstrated techniques to be used for components for which Appendix VIII is not mandatory in the current ASME Code COR.

Examinations of the longitudinal shell welds were performed with automated ultrasonic (UT) inspection equipment from the inside surface of the RPV, while the top head shell-to-flange welds were performed manually from the outside diameter (OD).

For the subject RPV longitudinal shell welds at DNPS, UT examinations were restricted due to the close proximity of the jet pump diffuser, shroud repair lower contact, jet pump restrainer, jet pump riser brace, lower specimen and upper specimen brackets, feedwater sparger, core spray downcomer piping, lower guide rod, core spray piping and piping bracket, shroud repair tie rod, upper guide rod, tie-rod stabilizer bracket, dryer bracket, steam dryer support, and inner diameter (ID) shell transition between the RPV and flange, as applicable. The licensee was able to obtain between 22.6 percent and 88.0 percent of the required ASME Code volume to be completed as shown in Tables 3.1.1 and 3.1.2. Only embedded reflectors believed to be fabrication flaws were detected; thus, no service-induced indications were observed during any of the volumetric examinations on the longitudinal shell welds.

The UT examinations for the subject RPV head-to-flange Welds 2/1/RPVUPPHD/2-THD-FLG (DNPS 2) and 3/1/RPVUPPHD/3-THD-FLG (DNPS 3) were restricted due to flange configuration. These welds are oriented nearly parallel to the flange OD surface, requiring all UT exams to be performed from the head side of the weld. The licensee was able to obtain 65.0 percent and 67.0 percent, respectively, of the required ASME Code volume to be completed. These coverage percentages were updated in the May 21, 2015, licensee's response to the NRC's RAI. Full coverage was achieved during the magnetic particle surface examination for these welds. With the exception of the two reflectors detected at DNPS 2 as discussed above, no recordable indications were observed during these volumetric or surface examinations.

The licensee has shown that it is impractical to meet the ASME Code-required essentially 100 percent volumetric examination coverage for RPV longitudinal shell and head-to-flange welds at DNPS due to their design geometries and proximity of integral RPV appurtenances.

Based on the volumetric coverage obtained, along with the examination of other RPV pressure retaining welds, the NRC staff concludes that if significant service-induced degradation had occurred, evidence of it would have been detected by the examinations that were performed.

Furthermore, the staff determines that the examinations performed provide reasonable assurance of structural integrity of the subject welds.

3.2 Request for Relief 14R-17. Part 8, ASME Code.Section XI, Examination Category 8-0, Items 83.90 and 83.100, Full Penetration Welded Nozzles in Vessels ASME Code Requirement ASME Code,Section XI, Examination Category 8-0, Items 83.90 and 83.100 require 100 percent volumetric examination, as defined by Figures IWB-2500-7 (a) through (d), as applicable, of full penetration Class 1 RPV nozzle-to-vessel welds and nozzle inside radius sections, respectively. ASME Code Case N-460, as an alternative approved for use by the NRC in RG 1.147, Revision 17, states that a reduction in examination coverage due to part geometry or interference for any Class 1 and 2 weld is acceptable provided that the reduction is less than 10 percent (i.e., greater than 90 percent examination coverage is obtained).

Licensee's ASME Code Relief Request In accordance with 10 CFR 50.55a(g)(5)(iii), the licensee requested relief from the ASME Code-required volumetric examinations for the RPV nozzle-to-vessel welds and nozzle inside radius sections listed below in Tables 3.2.1 (ONPS 2) and 3.2.2 (ONPS 3).

Table 3.2.1.. ASME Code,Section XI,* Examination Cateaorv B-D Unit 2)

ASME Coverage Code Weld ID Weld Type Obtained Item Percent 83.90 2/1/RPVSHELL/N19A-2 Nozzle-to-Vessel Weld 47.7 83.90 2/1 /RPVSH ELL/N 198-2 Nozzle-to-Vessel Weld 38.0 83.90 2/1/RPVSHELL/N1 A-2 Nozzle-to-Vessel Weld 27.2 83.90 2/1/RPVSHELL/N18-2 Nozzle-to-Vessel Weld 26.0 83.90 2/1 /RPVSH ELL/N2A-2 Nozzle-to-Vessel Weld 39.2 83.90 2/1/RPVSHELL/N28-2 Nozzle-to-Vessel Weld 39.2 83.90 2/1 /RPVSH ELL/N2C-2 Nozzle-to-Vessel Weld 42.0 83.90 2/1 /RPVSHELL/N2F-2 Nozzle-to-Vessel Weld 42.0 83.90 2/1 /RPVSHELL/N2H-2 Nozzle-to-Vessel Weld 42.0 83.90 2/1 /RPVSHELL/N30-2 Nozzle-to-Vessel Weld 33.5 83.90 2/1 /RPVSHELL/N4A-2 Nozzle-to-Vessel Weld 39.3 83.90 2/1 /RPVSHELL/N48-2 Nozzle-to-Vessel Weld 39.3 83.90 2/1 /RPVSHELL/N4C-2 Nozzle-to-Vessel Weld 39.3 Table 3.2.1

• ASME Code,Section XI, Examination Category B-D (Unit 2)

ASME Coverage Code Weld ID Weld Type Obtained Item Percent 83.90 2/1 /RPVSH ELL/N4D-2 Nozzle-to-Vessel Weld 39.3 83.90 2/1 /RPVSHELL/N5A-2 Nozzle-to-Vessel Weld 28.5 83.90 2/1 /RPVSHELL/N58-2 Nozzle-to-Vessel Weld 31.0 83.90 2/1 /RPVSHELL/N9-2 Nozzle-to-Vessel Weld 75.0 83.90 2/1/RPVUPPHD/N18A-2 Nozzle-to-Vessel Weld 74.2 83.100 2/1 /RPVSHELL/N58-1 Nozzle Inside Radius 86.0 Table 3.2.2 - ASME Code, SeeUon XI, Examination Category B-D Unit 3)

ASME Coverage Code Weld ID Weld Type Obtained Item Percent 83.90 3/1 /RPVSH ELL/N 19A-2 Nozzle-to-Vessel Weld 53.0 83.90 3/1/RPVSHELL/N198-2 Nozzle-to-Vessel Weld 38.0 83.90 3/1/RPVSHELL/N1A-2 Nozzle-to-Vessel Weld 25.0 83.90 3/1/RPVSHELL/N18-2 Nozzle-to-Vessel Weld 31.3 83.90 3/1 /RPVSHELL/N28-2 Nozzle-to-Vessel Weld 41.7 83.90 3/1 /RPVS H ELL/N2D-2 Nozzle-to-Vessel Weld 42.0 83.90 3/1 /RPVSHELL/N2E-2 Nozzle-to-Vessel Weld 42.0 83.90 3/1 /RPVSHELL/N2G-2 Nozzle-to-Vessel Weld 41.7 83.90 3/1 /RPVSHELL/N3A-2 Nozzle-to-Vessel Weld 31.0 83.90 3/1 /RPVSHELL/N38-2 Nozzle-to-Vessel Weld 31.0 83.90 3/1 /RPVSHELL/N3C-2 Nozzle-to-Vessel Weld 35.0 83.90 3/1 /RPVSHELL/N3D-2 Nozzle-to-Vessel Weld 40.8 83.90 3/1 /RPVSHELL/N4A-2 Nozzle-to-Vessel Weld 36.3 83.90 3/1 /RPVSHELL/N48-2 Nozzle-to-Vessel Weld 36.3 83.90 3/1 /RPVSHELL/N4C-2 Nozzle-to-Vessel Weld 36.3 83.90 3/1 /RPVSHELL/N4D-2 Nozzle-to-Vessel Weld 36.3 83.90 3/1 /RPVSHELL/N5A-2 Nozzle-to-Vessel Weld 29.0 83.90 3/1 /RPVSHELL/N58-2 Nozzle-to-Vessel Weld 36.0 83.90 3/1 /RPVSHELL/N9-2 Nozzle-to-Vessel Weld 62.0 83.90 3/1/RPVUPPHD/N18A-2 Nozzle-to-Vessel Weld 66.6 83.90 3/1 /RPVU PPHD/N 188-2 Nozzle-to-Vessel Weld 66.6 83.90 3/1 /RPVUPPHD/N8-2 Nozzle-to-Vessel Weld 74.3 Licensee's Basis for Relief Request RPV nozzle-to-vessel welds (DNPS 2 and 3) - The completed examination was limited due to nozzle configuration, insulation support interference, insulation support bracket below the nozzle, proximity of the insulation support bracket, stabilizer lug below the nozzle, stabilizer bracket, thermocouples and insulation support ring, as applicable.

RPV nozzle inside radius section (DNPS 2) - The completed examination was limited due to a stabilizer lug below the nozzle.

Licensee's Proposed Alternative Examination The licensee did not propose any alternative examinations for the subject welds. However, the licensee's examinations were performed to the maximum extent practical.

NRC Staff Evaluation

The ASME Code requires 100 percent volumetric examination of Class 1 nozzle-to-vessel welds and inside radius sections. However, the design configuration of the subject welds, the curvature of the nozzle blend radii, and the proximity of surrounding appurtenances limit access for UT scanning. In order to effectively increase the examination coverage, the nozzle-to-vessel welds would require design modifications. This would place a burden on the licensee; thus, obtaining 100 percent of ASME Code-required volumetric examinations is considered impractical.

The RPV nozzle-to-vessel welds and inside radius sections listed in DNPS 2 (Table 3.2.1) and DNPS 3 (Table 3.2.2) are constructed of carbon steel material with stainless steel inside diameter surface cladding applied to minimize corrosion. These full penetration butt welds extend the full thickness of the vessel head, and the nozzle configurations are of the "set-in" design, which essentially makes the welds concentric rings aligned nearly parallel with the nozzle axes in the through-wall direction of the vessel. This nozzle design geometry limits ASME Code-required UT angle beam examinations to be performed primarily from the vessel side of the welds. Other interferences that caused scanning limitations were insulation support interferences, insulation support bracket, stabilizer bracket, thermocouples, insulation support ring, and stabilizer lug below the nozzle.

As shown on the sketches, included in the licensee's October 16, 2014, response to the NRC's RAI, examinations of the subject RPV nozzle-to-vessel welds and inside radius sections have been completed to the extent practical with volumetric coverage ranging from approximately 25.0 to 86.0 percent (see Tables 3.2.1 and 3.2.2) of the ASME Code-required volumes. The examination volumes, where accessible, included the weld and base materials near the inside surface of the weld joint, which are high regions of stress, and where one would expect degradation sources to be manifested should they occur. The RPV nozzle-to-vessel welds and inside radius sections were conducted with equipment, procedures, and personnel that have been performance demonstrated to the requirements outlined in ASME Code,Section XI, Appendix VIII, using 0-degree longitudinal wave, 45-and 55-degree refracted shear wave, and 50-, 60-, and 70-degree refracted longitudinal wave examinations, as applicable. No unacceptable indications were observed in these welds.

Although UT scans were primarily limited to the vessel side, studies have found that inspections conducted through carbon steel are equally effective whether the UT waves have only to propagate through the base metal, or have to also propagate through the carbon steel weldment. 3 Therefore, it is expected that the UT techniques employed by the licensee on the RPV nozzle-to-vessel welds and inside radius sections would detect structurally significant flaws that might occur on either side of the welds due to the fine-grained carbon steel microstructures present in these materials.

The licensee has shown that it is impractical to meet the ASME Code-required 100 percent volumetric examination coverage for the subject nozzle-to-vessel welds and inside radius sections due to nozzle design, curvature of the nozzle blend radii, and adjacent obstructions.

Based on the volumetric coverage obtained for the subject welds, and considering the licensee's performance of UT techniques employed to maximize this coverage, the NRC staff concludes that if significant service-induced degradation had occurred, evidence of it would have been detected by the examinations that were performed. Furthermore, the staff determines that the examinations performed provide reasonable assurance of structural integrity of the subject welds.

3.3 Request for Relief 14R-17, Part C. ASME Code,Section XI. Examination Category 8-K. Items 810.1 O and 810.20. Welded Attachments for Vessels. Piping. Pumps, and Valves ASME Code Requirement ASME Code,Section XI, Examination Category 8-K, Items 810.10 and 810.20, requires essentially 100 percent surface examination, as defined by Figures IWB-2500-13, -14, and -15, as applicable, of selected integrally welded attachments to Class 1 pressure vessels and piping, respectively. "Essentially 100 percent," as clarified by ASME Code Case N-460, is greater than 90 percent coverage of the examination volume, or surface area, as applicable. ASME Code Case N-460 has been approved for use by the NRC in RG 1.147, Revision 17.

3 P. G. Heasler, and S. R. Doctor, 1996. Piping Inspection Round Robin, NUREG/CR-5068, PNNL-10475, U.S. Nuclear Regulatory Commission, Washington, DC.

Licensee's ASME Code Relief Request In accordance with 10 CFR 50.55a(g)(5)(iii}, the licensee requested relief from the ASME Code-required surface examination of integrally welded attachments to Class 1 pressure vessels and piping shown in Tables 3.3.1 (DNPS 2) and 3.3.2 (DNPS 3).

Table 3.3.1 - ASME Code,Section XI, Examination Category B*K Unit 2)

ASME Coverage Code Weld ID Weld Type Obtained Item Percent 810.10 2/1/RPVSHELL/M-11750-1 (IWA)

Integral Welded 56.0 Attachment 810.20 2/1 /1506-16/M-1164D-296(1WA)

Integral Welded 50.0 Attachment Table 3.3.2 - ASME Code,Section XI, Examination Category B-K Unit 3)

ASME Coverage Code Weld ID Weld Type Obtained Item Percent 810.10 3/1/RPVSHELL/M-1211 D-1 (IWA)

Integral Welded 60.0 Attachment 810.20 3/1/0202A-28/M-1193D-1002(1WA)

Integral Welded 88.0 Attachment Licensee's Basis for Relief Request Pressure Vessel Integral Attachment Weld (DNPS 2) - The completed examination was limited due to inaccessibility to the bottom of the lug.

Piping Integral Attachment Weld (DNPS 2) - The completed examination was limited due to the inner weld on the attachment was not accessible and could not be prepped.

Pressure Vessel Integral Attachment Weld (DNPS 3) - The completed examination was limited due to being only able to examine three sides of the lug.

Piping Integral Attachment Weld (DNPS 3) - The completed examination was limited due to presence of sway brace which reduced accessibility.

Licensee's Proposed Alternative Examination The licensee did not propose any alternative examinations for the subject welds. However, the licensee's examinations were performed to the maximum extent practical.

NRC Staff Evaluation

The ASME Code requires essentially 100 percent surface examination of Class 1 pressure vessel and piping integral attachment welds. However, surface examination for the subject welds are limited due to their design configurations. In order for the licensee to obtain 100 percent of the ASME Code-required surface examination coverage, the integral attachment welds would have to be redesigned and modified. This would place a burden on the licensee; therefore, the ASME Code examination requirements are considered impractical.

As shown on the sketches and technical descriptions included in the licensee's October 16, 2014, response to the NRC's RAI, surface examinations of the DNPS 2 low pressure coolant injection system piping welded attachment 2/1/1506-16/M-1164D-296(1WA) and RPV shell to stabilizer bracket support 2/1/RPVSHELL/M-1175D-1(1WA), and DNPS 3 RPV shell to stabilizer bracket support 3/1/RPVSHELL/M-1211 D-1 (IWA) and recirculation system piping lugs 3/1/0202A-28/M-1193D-1002(1WA), have been performed to the extent practical, with the licensee obtaining coverage ranging from approximately 50.0 to 88.0 percent of the ASME Code-required surface areas (see Tables 3.3.1 and 3.3.2). The examinations were limited due to inaccessibility of bottom lugs and inner weld attachments, and obstructions caused by adjacent components such as stabilizers, the bioshield, and sway braces. No unacceptable indications were detected during these surface examinations.

The licensee has shown that it is impractical to meet the ASME Code-required surface examination coverage for the subject Class 1 pressure vessel and piping integral attachment welds. However, based on the level of surface coverage obtained, the NRC staff concludes tha, if significant service-induced degradation had occurred, evidence of it would be have been detected by the examinations that were performed. Furthermore, the staff determines that the examinations performed provide reasonable assurance of structural integrity of the subject welds.

3.4 Request for Relief 14R-17. Part D. ASME Code.Section XI, Examination Category B-M-1. Item 812.40. Pressure Retaining Welds in Valve Bodies ASME Code Requirement ASME Code,Section XI, Examination Category B-M-1, Item 812.40, requires essentially 100 percent volumetric examination, as defined by Figure IWB-2500-17, of selected Class 1 valve body welds, NPS 4 inch in diameter, or larger. "Essentially 100 percent," as clarified by ASME Code Case N-460, is greater than 90 percent coverage of the examination volume, or surface area, as applicable. ASME Code Case N-460 has been approved for use by the NRC in RG 1.147, Revision 17.

Licensee's ASME Code Relief Request In accordance with 10 CFR 50.55a(g)(5)(iii), the licensee requested relief from the ASME Code-required 100 percent volumetric examination of Class 1 main steam relief system valve body welds 2/1/3001 D-6/ERV-2-203-3D(WELD) (DNPS 2) and 3/1/3001 B-6/ERV-3-203-3B(WELD)

(DNPS 3).

Licensee's Basis for Relief Request The completed examinations were limited due to integrally welded cage on the valve ID.

Licensee's Proposed Alternative Examination The licensee did not propose any alternative examinations for the subject welds. However, the licensee's examinations were performed to the maximum extent practical.

NRC Staff Evaluation

The ASME Code requires 100 percent volumetric examination of Class 1 pressure retaining welds in valve bodies nominally 4-inch in diameter or greater. However, the valves' design configuration and permanently attached appurtenances do not allow full coverage with radiographic examination. In order to effectively increase the examination coverage, the valves would require a design modification. Imposition of this requirement would create a burden on the licensee; therefore, the ASME Code-required 100 percent volumetric examinations of the valve body welds are considered impractical.

As shown on the sketches and technical descriptions included in the licensee's submittals, access for examination of the subject welds is limited to due to an integrally welded cage on the valve ID. The radiographic examinations achieved a significant amount of the ASME Code-required volumetric coverage with estimates of 87.3 (DNPS 2) and 89.4 (DNPS 3) percent being obtained. No unacceptable indications were noted during the volumetric examinations.

The licensee has shown that it is impractical to meet the ASME Code-required 100 percent volumetric examination coverage for the subject valve body-to-canopy welds due to their design configuration. However, based on the significant volumetric coverage obtained, the NRC staff concludes that if significant service-induced degradation had occurred, evidence of it would have been detected. Furthermore, the staff determines that the examinations performed provide reasonable assurance of structural integrity of the subject welds.

3.5 Request for Relief 14R-17, Part E, ASME Code,Section XI, Examination Category C-8, Item C2.21, Pressure Retaining Nozzle Welds in Class 2 Vessels ASME Code Requirement ASME Code,Section XI, Examination Category C-8, Item C2.21, requires 100 percent volumetric and surface examination, as defined by Figure IWC-2500-4(a) or (b), as applicable, of nozzle-to-shell (or head) welds in Class 2 vessels. ASME Code Case N-460, as an alternative approved for use by the NRC in RG 1.147, Revision 17, states that a reduction in examination coverage due to part geometry or interference for any Class 1 and 2 weld is acceptable provided that the reduction is less than 10 percent (i.e., greater than 90 percent examination coverage is obtained).

Licensee's ASME Code Relief Request In accordance with 10 CFR 50.55a(g)(5)(iii), the licensee requested relief from the ASME Code-required volumetric examination of Class 2 nozzle-to-head welds shown in Tables 3.5.1 (DNPS 2) and 3.5.2 (DNPS 3).

Table 3.5.1-ASME Code, SecUon XI, l::xamination Category C-B j Unit 2)

ASME Coverage Code Weld ID Weld Type Obtained Item Percent C2.21 2/2/1302A-12/12-9 ISO Condenser Nozzle Weld 50.0 C2.21 2/2/13028-12/12-8 ISO Condenser Nozzle Weld 50.0 C2.21 2/2/1303A-8/8-9 ISO Condenser Nozzle Weld 50.0 C2.21 2/2/12038-8/8-8 ISO Condenser Nozzle Weld 50.0 Table 3.5.2-ASME Code Section XI, Examination Category C-B (Unit 3)

ASME Coverage Code Weld ID Weld Type Obtained Item Percent C2.21 3/2/1302A-12/12-8 ISO Condenser Nozzle Weld 37.8 C2.21 3/2/13028-12/12-9 ISO Condenser Nozzle Weld 37.8 C2.21 3/2/1303A-8/8-8 ISO Condenser Nozzle Weld 50.0 C2.21 3/2/13038-8/8-9 ISO Condenser Nozzle Weld 52.3 Licensee's Basis for Relief Request The completed examination coverage was limited due to component configuration.

Licensee's Proposed Alternative Examination The licensee did not propose any alternative examinations for the subject welds. However, the licensee's examinations were performed to the maximum extent practical.

NRC Staff Evaluation

The ASME Code requires 100 percent volumetric and surface examinations of Class 2 nozzle-to-shell (or head) welds. However, for the subject nozzle-to-head (or shell) welds on the isolation condenser system vessels, complete examinations are limited due to the nozzles' configurations. In order to achieve greater volumetric coverage, the nozzles and vessels would have to be redesigned and modified. This would place a burden on the licensee; therefore, the ASME Code volumetric examination is considered impractical.

The subject nozzle-to-vessel welds shown in Tables 3.5.1 (DNPS 2) and 3.5.2 (DNPS 3) are constructed of SA-182 F1 carbon steel materials. The design configurations of these nozzles have weld volumes which are aligned approximately normal to the forged nozzle cylinder and include a curvature, or blend radii, to the vessel shell. This geometry restricts ultrasonic scanning to the nozzle side of the welds.

As shown on the sketches and technical descriptions included in the licensee's October 16, 2014, response to the NRC's RAI, examinations of the isolation condenser nozzle-to-vessel welds have been completed to the extent practical with single-side volumetric coverage ranging from approximately 37.8 to 52.3 percent (see Tables 3.5.1 and 3.5.2) of the ASME Code-required volumes. The examination volumes included the accessible portions of the weld and base materials near the inside surface of the weld joints which are high regions of stress, and where one would expect degradation sources to be manifested should they occur. Although UT scans were primarily limited to the nozzle side, studies have found that inspections conducted through carbon steel are equally effective whether the UT waves have only to propagate through the base metal, or have to also propagate through the carbon steel weldment. 4 Therefore, it is expected that the UT techniques employed by the licensee on the isolation condenser nozzle-to-vessel welds would detect structurally significant flaws that might occur on either side of welds due to the fine-grained carbon steel microstructures present in these materials.

The isolation condenser nozzle-to-vessel weld examinations were performed with 45-, 60-,

and 70-degree shear waves, as applicable. In an SE dated March 29, 2012 (ADAMS Accession No. ML120820266), the NRC authorized DNPS, for the remainder of the fourth 10-year ISi, to implement Mandatory Appendix I, 1-2600, from the 2007 Edition through 2008 Addenda which permits the use of Appendix VIII performance demonstration techniques to be used for components to which Appendix VIII is not mandatory in the current ASME Code COR. The licensee completed the ASME Code-required surface examinations on the subject welds with no limitations. Several recordable indications were identified during the volumetric examinations performed in 2008 on the isolation condenser vessel at DNPS 3; these were all determined to be embedded reflectors, not typical of service degradation, and found acceptable per ASME Code, IWC-3000. No other indications were observed during any of the volumetric or surface examinations.

The licensee has shown that it is impractical to meet the ASME Code-required 100 percent volumetric examination coverage for the subject isolation condenser vessel nozzle-to-shell welds due to the nozzles' design configurations. However, based on the volumetric and full surface coverage obtained, the NRC staff concludes that if significant service-induced degradation had occurred evidence of it would be have been detected by the examinations performed.

Furthermore, the staff determines that the examinations performed provide reasonable assurance of structural integrity of the subject welds.

4 P. G. Heasler, and S. R. Doctor, 1996. Piping Inspection Round Robin, NUREG/CR-5068, PNNL-10475, U.S. Nuclear Regulatory Commission, Washington, DC.

3.6 Request for Relief 14R-17, Part F. ASME Code.Section XI. Examination Category C-C. Item C3.20. Integral Attachments for Class 2 Vessels.

Piping, Pumps. and Valves. DNPS 2 ASME Code Requirement ASME Code,Section XI, Examination Category C-C, Item C3.20, requires essentially 100 percent surface examination, as defined by Figure IWC-2500-5, of welded attachments to Class 2 piping. "Essentially 100 percent," as clarified by ASME Code Case N-460, is greater than 90 percent coverage of the examination volume, or surface area, as applicable. ASME Code Case N-460 has been approved for use by the NRC in RG 1.147, Revision 17.

Licensee's ASME Code Relief Request In accordance with 10 CFR 50.55a(g)(5)(iii), the licensee requested relief from the ASME Code-required surface examinations for integral attachment weld 2/2/2304-14/M-1151 D-1 O (IWA).

Licensee's Basis for Relief Request The completed examination was limited to 81.6 percent coverage due to only examining three sides since presence of pipe clamp prevented examining fourth side.

Licensee's Proposed Alternative Examination The licensee did not propose any alternative examinations for the subject welds. However, the licensee's examinations were performed to the maximum extent practical.

NRC Staff Evaluation

The ASME Code requires 100 percent surface examination of the subject Class 2 integral attachment vessel weld on DNPS 2. However, surface examinations are limited due to inaccessibility and interference caused by piping support members. In order for the licensee to obtain 100 percent of the ASME Code-required examination coverage, the integral attachment welds would have to be redesigned and modified. This would place a burden on the licensee; therefore, the ASME Code examination requirements are considered impractical.

As shown on the sketches and technical descriptions included in the licensee's October 16, 2014, and May 21, 2015, submittals, magnetic particle examination of the welded attachment on the high pressure coolant injection system discharge line has been performed to the extent practical, with the licensee obtaining surface examination coverage of approximately 81.6 percent of the ASME Code requirements. Three of the four sides of eight welded lugs were examined. There is a permanent piping support covering the fourth side of each of the eight lugs making this side inaccessible for surface examination. There were no reportable indications detected during the surface examinations performed.

The licensee has shown that it is impractical to meet the ASME Code-required surface examination coverage for the subject Class 2 integral attachment vessel welds. However, based on the significant surface coverage obtained, if significant service-induced degradation had occurred, evidence of it would be have been detected by the examinations that were performed. Furthermore, the NRC staff determined that the examinations performed provide reasonable assurance of structural integrity of the subject welds.

3.7 Request for Relief 14R-17, Part G, ASME Code.Section XI, Examination Category R-A. Items R1.11 and R1.20. Risk Informed Piping Examinations ASME Code Requirement The examination requirements for the subject piping welds at DNPS are governed by a Risk-Informed lnservice Inspection (RI-ISi) program that was approved by the NRC in an SE dated September 4, 2003 (ADAMS Accession No. ML032370480). The RI-ISi program was developed in accordance with the Electric Power Research Institute Topical Report (TR)-112657, Revision B-A, "Revised Risk-Informed lnservice Inspection Evaluation Procedure." As part of the NRG-approved program, the licensee has implemented inspection requirements listed in ASME Code Case N-578-1, "Risk-Informed Requirements for Class 1, 2 or 3 Piping, Method B,Section XI, Division 1," with more detailed provisions contained in TR-112657. The TR includes a provision for requesting relief from volumetric examinations if 100 percent of the required volumes cannot be examined.

Table 1 of ASME Code Case N-578-1 5 assigns Examination Category R-A, Items R1.11 and R1.20, to piping inspection elements subject to thermal fatigue, and elements not subject to a known damage mechanism, respectively. Table 1 of Code Case N-578-1 requires 100 percent of the examination location volume, as described in Figures IWB-2500-8( c}, 9, 10, or 11, as applicable, including an additional Y2-inch of base metal adjacent to the ASME Code volume, be completed for selected Class 1 piping welds. ASME Code Case N-460, as an alternative approved for use by the NRC in RG 1.147, Revision 16, states that a reduction in examination coverage due to part geometry or interference for any Class 1 and 2 weld is acceptable provided that the reduction is less than 10 percent (i.e., greater than 90 percent examination coverage is obtained).

Licensee's ASME Code Relief Request In accordance with 10 CFR 50.55a(g)(5)(iii), the licensee requested relief from 100 percent volumetric examination of Class 1 piping welds shown in Tables 3.7.1 (DNPS 2) and 3.7.2 (DNPS 3).

Table 3.7.1-ASME Code, Examination Cateaory R-A (Unit 2)

ASME Coverage Code Weld ID Weld Type Obtained Item Percent R1.11 2/1/1001A-16/16-11 Tee-to-Pipe 36.0 R1.11 2/1 /1001 B-16/16-2 Flange-to-Pipe 85.0 s ASME Code Case N-578 has not been approved for use in RG-1.14 7, Revision 17. Licensees base their RI-ISi inspection sample size and examination methodology on Table 1 of ASME Code Case N-578.

Table 3.7.1-ASME Code, Examination Category R-A(Unit 2)

ASME Coverage Code Weld ID Weld Type Obtained Item Percent R1.11 2/1/10058-14/14-7 Valve-to-Pipe 50.0 R1.20 2/1 /1403-1OM/-103 Valve-to-Pipe 81.0 R1.20 2/1 /1404-1 OM/-112 Valve-to-Pipe 85.7 Table 3.7.2-ASME Code, Examination Category R-A (Unit 3)

ASME Coverage Code Weld ID Weld Type Obtained Item Percent R1.11 3/2/32048-18/18-1 Valve-to-Tee 78.9 R1.20 3/1 /1302-14/14-9(A)

Flange-to-Pipe 50.0 Licensee's Basis for Relief Request The completed examination coverages for DNPS 2 were limited due to component configuration and for DNPS 3 limited examinations where due to valve and flued head configurations.

Licensee's Proposed Alternative Examination The licensee did not propose any alternative examinations for the subject welds. However, the licensee's examinations were performed to the maximum extent practical.

NRG Staff Evaluation Examination requirements for the subject piping welds at DNPS 2 and 3 are governed by a RI-ISi program that was approved by the NRG in an SE dated September 4, 2003. This program assigns Examination Category R-A, Items R1.11 and R1.20, to piping inspection elements subject to thermal fatigue and piping elements not subject to a known damage mechanism, respectively. The program requires inspection of 100 percent of the defined examination volumes for Class 1 and 2 circumferential piping welds. However, the design configurations of the subject welds limit volumetric examinations. In order to increase coverage, the welds would have to be re-designed and modified. This would place a burden on the licensee; therefore, the ASME Code-required volumetric examinations are considered impractical.

As shown in the sketches provided in the licensee's October 16, 2014, response to the NRC's RAI, examinations of the subject welds have been performed to the extent practical, with the licensee obtaining volumetric coverage ranging from approximately 36.0 to 85.7 percent (see Tables 3.7.1 and 3.7.2) of the required volumes of the welds. The limitations encountered during the performance of the UT examinations were caused by existing weld configurations and adjacent appurtenances in these valve-to-pipe, valve-to-tee, tee-to-pipe, and flange-to-pipe weld geometries (see Tables 3.7.1 and 3.7.2 for specific weld configurations). These configurations limit UT scan access primarily to one side of the subject piping welds. The licensee stated that selection of one-sided examinations (e.g., pipe-to-valve welds) would normally be avoided for these risk-informed piping examinations, but in some cases, no other choices were available that would have resulted in increased volumetric coverage.

Volumetric examinations on the subject welds were conducted with equipment, procedures and personnel that had been demonstrated to the requirements outlined in ASME Code,Section XI, Appendix VIII. These techniques have been demonstrated for flaws located on the near-side of the welds for austenitic stainless steel materials and both near-and far-side detection of flaws for carbon steel materials. For these reasons along with the above physical limitations, the licensee has only taken partial credit for the ASME Code-required inspection volumes on the subject austenitic piping welds. The licensee's ultrasonic techniques included 45-degree shear waves and 45-, 60-, and 70-degree refracted longitudinal waves, as applicable.

Longitudinal waves have been shown to provide enhanced detection on the far-side of austenitic stainless steel welds.6*7*8 While the licensee has only taken credit for limited volumetric coverage obtained from primarily one side, it is expected that the techniques employed would have provided coverage beyond the near-side of the welds. The UT examinations did not reveal any unacceptable indications.

The licensee has shown that it is impractical to meet the ASME Code-required volumetric examination coverage for the subject welds due to their design configurations and materials of construction. Based on the ultrasonic results and coverage obtained, the NRC staff concludes that, if significant service-induced degradation had occurred in the subject welds, evidence of it would have been detected by the examinations performed. Furthermore, the staff determines that the examinations performed provide reasonable assurance of structural integrity of the subject welds.

4.0 CONCLUSION

As set forth above, the NRC staff determines that 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 given due consideration to the burden upon the licensee that could result if the requirements were imposed on the facility.

Furthermore, the staff concludes that the examinations performed to the extent practical provide reasonable assurance of structural integrity of the subject components. Accordingly, the NRC staff concludes that the licensee has adequately addressed all of the regulatory requirements set forth in 10 CFR 50.55a(g)(5)(iii). Therefore, the NRC staff grants relief pursuant to 6 F.V. Ammirato, X. Edelmann, and S.M. Walker, Examination of Dissimilar Metal Welds in BWR Nozzle to-Safe End Joints, 81h International Conference on NDE in the Nuclear Industry, ASM International, 1987.

7 P. Lemaitre, T.D. Koble, and S.R. Doctor, PISC Ill Capability Study on Wrought-to-Wrought Austenitic Steel Welds: Evaluation at the Level of Procedures and Techniques, Effectiveness of Nondestructive Examination Systems and Performance Demonstration, PVP-Volume 317, NOE-Volume 14, ASME, 1995.

8 M.T. Anderson, A.A. Diaz, AD. Cinson, S.L. Crawford, S.E. Cumblidge, S.R Doctor, K.M. Denslow, and S. Ahmed, 2011. An Assessment of Ultrasonic Techniques for Far-Side Examinations of Austenitic Stainless Steel Piping Welds, NUREG/CR-7113, PNNL-19353, U.S. Nuclear Regulatory Commission, Washington, DC.

10 CFR 50.55a(g)(6)(i) for the subject examinations of the components contained in request for relief 14R-17, for the fourth 10-year ISi interval at DNPS 2 and 3.

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

Principal Contributors:

T. Mclellan, NRR S. Cumblidge, NRR Date of issuance: October 3 O, 2O1 5

ML15265A164 OFFICE LPL3-2/PM LPL3-1/PM LPL3-2/LA DE/EPNB/BC NAME RHaskell KGreen SRohrer DAiiey (JTsao for)

DATE 9/22/15 9/22/15 10/30/15 06/29/15 OFFICE LPL3-2/PM LPL3-2/BC NAME BPurnell TTate DATE 9/24/15 10/30/15