ML14175B593

Proposed Alternative to Utilize Code Case N-786, Alternative Requirements for Sleeve Reinforcement of Class 2 and 3 Moderate-Energy Carbon Steel Piping Section XI Division1

ML14175B593
Person / Time
Site:	Calvert Cliffs, Dresden, Peach Bottom, Nine Mile Point, Oyster Creek, Byron, Three Mile Island, Braidwood, Limerick, Ginna, Clinton, Quad Cities, LaSalle
Issue date:	07/31/2014
From:	Travis Tate Plant Licensing Branch III
To:	Pacilio M Exelon Generation Co, Exelon Nuclear
Joel Wiebe, NRR/DORL 415-6606
References
TAC MF0804, TAC MF0805, TAC MF0806, TAC MF0807, TAC MF0808, TAC MF0809, TAC MF0810, TAC MF0811, TAC MF0812, TAC MF0813, TAC MF0814, TAC MF0815, TAC MF0816, TAC MF0817, TAC MF0819, TAC MF0820, TAC MF4030, TAC MF4031, TAC MF4032, TAC MF4033, TAC MF4034
Download: ML14175B593 (15)

Text

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 July 31, 2014 Mr. Michael J. Pacilio Senior Vice President Exelon Generation Company, LLC President and Chief Nuclear Officer (CNO)

Exelon Nuclear 4300 Winfield Road Warrenville, IL 60555

SUBJECT:

BRAIDWOOD, UNITS 1 AND 2; BYRON STATION, UNIT NOS. 1 AND 2; CALVERT CLIFFS NUCLEAR POWER PLANT, UNITS 1 AND 2; CLINTON POWER STATION, UNIT NO.1; DRESDEN NUCLEAR POWER STATION, UNITS 2 AND 3; R.E. GINNA NUCLEAR POWER PLANT, LASALLE COUNTY STATION, UNITS 1 AND 2; LIMERICK GENERATING STATION, UNITS 1 AND 2; NINE MILE POINT NUCLEAR STATION, UNITS 1 AND 2; OYSTER CREEK NUCLEAR GENERATING STATION; PEACH BOTTOM ATOMIC POWER STATION, UNITS 2, AND 3; QUAD CITIES NUCLEAR POWER STATION, UNITS 1 AND 2; AND THREE MILE ISLAND NUCLEAR STATION, UNIT 1- PROPOSED ALTERNATIVE TO UTILIZE CODE CASE N-786, "ALTERNATIVE REQUIREMENTS FOR SLEEVE REINFORCEMENT OF CLASS 2 AND 3 MODERATE-ENERGY CARBON STEEL PIPING SECTION XI, DIVISION 1" (TAC NOS. MF0804, MF0805, MF0806, MF0807, MF0808, MF0809, MF0810, MF0811, MF0812, MF0813, MF0814, MF0815, MF0816, MF0817, MF0818, MF0819, MF0820, MF4030, MF4031, MF4032, MF4033, AND MF4034)

Dear Mr. Pacilio:

By letter dated February 27, 2013 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML13059A498), as supplemented by letters dated June 24, 2013, December 12, 2013, and April 28, 2014 (ADAMS Accession Nos. ML13176A143, ML13351A410, and ML14119A289, respectively), Exelon Generation Company, LLC (Exelon) requested relief from the requirements of American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code),Section XI, IWA-4000, for the repair of degraded Class 2 and 3, moderate-energy carbon steel piping at Braidwood Station, Units 1 and 2; Byron Station Unit Nos. 1 and 2; Calvert Cliffs Nuclear Power Plant, Units 1 and 2; Clinton Power Station, Unit 1; Dresden Nuclear Power Station, Units 2 and 3; R. E. G;nna Nuclear Power Plant; LaSalle County Station, Units 1 and 2; Limerick Generating Station, Units 1 and 2; Nine Mile Point Nuclear Station, Units 1 and 2; Oyster Creek Nuclear Generating Station; Peach Bottom Atomic Power Station, Units 2 and 3; Quad Cities Nuclear Power Station, Units 1 and 2; and Three Mile Island Nuclear Station, Unit 1.

Specifically, pursuant to Title 10 of the Code of Federal Regulations (1 0 CFR) 50.55a(a)(3)(ii),

Exelon proposed to repair defects in ASME Code. Class 2 and 3, moderate energy piping without removing the existing defect by placing one of three classes of sleeves around the piping, thereby, restoring structural and/or leak tightness integrity to the pipe on the basis that

M. Pacilio compliance with the specified ASME Code requirements would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety. The NRC staff has reviewed the subject request and concludes, as set forth in the enclosed safety evaluation (SE),

that the proposed alternative provides reasonable assurance of structural integrity and leak tightness of the subject components and that complying with the specified ASME Code requirements would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety. Accordingly, the NRC staff concludes that Exelon has adequately addressed all of the regulatory requirements set forth in 10 CFR 50.55a(a)(3)(ii).

Therefore, the NRC staff authorizes the use of Relief Request 10 CFR 50.55a, Revision 3, for the repair of ASME Code, Class 2 and 3, moderate energy carbon steel piping at the plants specified above for the specific 10-year inservice inspection interval as documented in Table 1 of this SE.

The authorization of Relief Request, 10 CFR 50.55a, Revision 3, does not imply or infer NRC approval of ASME Code Case N-786.

All other ASME Code,Section XI, requirements for which relief was not specifically requested and authorized by the NRC staff will remain applicable including third-party review by the Authorized Nuclear lnservice Inspector.

If you have any questions, please contact Joel S. Wiebe, Senior Project Manager, at (301) 415 6606 or via e-mail at Joei.Wiebe@nrc.gov.

Sincerely,

~I C/~

. d ~

i-n Travis L. Tate, Chief Plant Licensing 111-2 and Planning and Analysis Branch Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. STN 50-456, STN 50-457, STN 50-454, STN 50-455, 50-461, 50-317, 50-318, 50-237, 50-249, 50-373, 50-374, 50-352, 50-353, 50-220, 50-410, 50-219, 50-277, 50-278, 50-244, 50-254, 50-265 AND 50-289

Enclosure:

Safety Evaluation cc w/encl: Distribution via Listserv

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 PROPOSED ALTERNATIVE TO REPAIR DEGRADED CLASS 2 AND 3 PIPING USING SLEEVES EXELON GENERATION COMPANY, LLC BRAIDWOOD STATION, UNITS 1 AND 2; BYRON STATION, UNIT NOS, 1 AND 2; CALVERT CLIFFS NUCLEAR POWER PLANT, UNITS 1 AND 2; CLINTON POWER STATION, UNIT 1; DRESDEN NUCLEAR POWER STATION UNITS 2 AND 3; R.E. GINNA NUCLEAR POWER PLANT; LASALLE COUNTY STATION, UNITS 1 AND 2; LIMERICK GENERATING STATION, UNITS 1 AND 2; NINE MILE POINT NUCLEAR STATION, UNITS 1 AND 2; OYSTER CREEK NUCLEAR GENERATING STATION; PEACH BOTTOM ATOMIC POWER STATION, UNITS 2 AND 3; QUAD CITIES NUCLEAR POWER STATION, UNITS 1 AND 2; AND THREE MILE ISLAND NUCLEAR STATION, UNIT 1 DOCKET NOS. STN 50-456, STN 50-457, STN 50-454, STN 50-455, 50-461, 50-317, 50-318, 50-237, 50-249, 50-373, 50-374, 50-352, 50-353, 50-220, 50-410, 50-219, 50-277, 50-278, 50-244, 50-254, 50-265 AND 50-289

1.0 INTRODUCTION

By letter dated February 27, 2013 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML13059A498), as supplemented by letters dated June 24, 2013, December 12, 2013, and April28, 2014 (ADAMS Accession Nos. ML13176A143, ML13351A410, and ML14119A289, respectively), Exelon Generation Company, LLC (Exelon) requested relief from the requirements of American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code),Section XI, IWA-4000, for the repair of degraded Class 2 and 3 moderate-energy carbon steel piping at Braidwood Station, Units 1 and 2; Byron Station, Unit Nos. 1 and 2; Calvert Cliffs Nuclear Power Plant, Units 1 and 2; Clinton Power Station, Unit 1; Dresden Nuclear Power Station, Units 2 and 3; R. E. Ginna Nuclear Power Plant, Enclosure

LaSalle County Station, Units 1 and 2; Limerick Generating Station, Units 1 and 2; Nine Mile Point Nuclear Station, Units 1 and 2; Oyster Creek Nuclear Generating Station; Peach Bottom Atomic Power Station, Units 2 and 3; Quad Cities Nuclear Power Station, Units 1 and 2; and Three Mile Island Nuclear Station, Unit 1.

Specifically, pursuant to Title 10 of the Code of Federal Regulations (1 0 CFR) 50.55a(a)(3)(ii),

Exelon proposed to repair defects in ASME Code, Class 2 and 3, moderate energy piping without removing the existing defect by placing one of three classes of sleeves around the piping, thereby, restoring structural and/or leak tightness integrity to the pipe on the basis that compliance with the specified ASME Code requirements would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.

2.0 REGULATORY EVALUATION

In this relief request Exelon requested authorization of an alternative to the requirements of ASME Code,Section XI, Article IWA-4000 pursuant to 10 CFR 50.55a(a)(3)(ii).

Section 50.55a(g)(4) of 10 CFR states, in part, that 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, "Rules for lnservice Inspection (lSI) of Nuclear Power Plant Components."

Section 50.55a(a)(3) of 10 CFR states, in part, that alternatives to the requirements of 10 CFR 50.55a(g) may be used, when authorized by the NRC, if Exelon demonstrates (i) the proposed alternatives would provide an acceptable level of quality and safety or (ii) compliance with the specified requirements would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.

Based on the above evaluation, and subject to the following technical evaluation, the NRC staff finds that it has the regulatory authority to authorize an alternative proposed by Exelon.

3.0 TECHNICAL EVALUATION

3.1 The Licensee's Alternative Components for which Relief is Requested The affected components are ASME Code, Class 2 and 3, moderate energy carbon steel piping systems that carry fluid at a maximum operating temperature and pressure of less than or equal to 200 degrees Fahrenheit and less than or equal to 275 psig, respectively.

Applicable ASME Code Edition and Addenda The applicable Code of Record and associated 10-year lSI intervals for each affected plant are listed in Table 1 below. Exelon requested to use the proposed alternative for the remainder of each plant's 10-year lSI interval.

Table 1 lSI ASME CODE PLANT START END INTERVAL EDITION Braidwood Station, Third 2001 Edition, July 29, 2008 July 28, 2018 Units 1 and 2 through 2003 October 17, October 16, Addenda 2008 2018 Byron Station, Third 2001 Edition, January 16, July 15, 2016 Units Nos. 1 and 2 through 2003 2006 Addenda Calvert Cliffs Nuclear Fourth October 10, Power Plant, Units 1 2004 Edition 2009 June 30, 2019 and 2 Clinton Power Third 2004 Edition July 1, 2010 June 30, 2020 Station, Unit No. 1 Dresden Nuclear Fifth 2007 Edition, January 20, January 19, Power Station, Units through 2008 2013 2023 2 and 3 Addenda R. E. Ginna Nuclear Fifth 2004 Edition January 1, December 31, Power Plant 2010 2019 LaSalle County Third 2001 Edition, October 1, September 30, Stations, Units 1 through 2003 2007 2017 and 2 Addenda Limerick Generating Third 2001 Edition, February 1, January 31, Station, Units 1 through 2003 2007 2017 and 2 Addenda Nine Mile Point Fourth 2004 Edition August 23, August 22 Nuclear Station Unit 2009 2019 1

Nine Mile Point Third 2004 Edition April 5, 2008 April 4, 2018 Nuclear Station Unit 2

Oyster Creek Fifth 2007 Edition, January 15, January 14, Nuclear Generating through 2008 2013 2023 Station Addenda Peach Bottom Fourth 2001 Edition, November 5, November 4, Atomic Power through 2003 2008 2018 Station, Units 2 Addenda and 3 Quad Cities Nuclear Fifth 2007 Edition, 2008 April 2, 2013 April 1, 2023 Power Station, Units Addenda 1 and 2 Three Mile Island Fourth 2004 Edition April 20, 2011 April 19, 2022 Nuclear Station, Unit 1

Proposed Alternative In lieu of ASME Code,Section XI, IWA-4000, Exelon proposed an alternative method to repair degradation in ASME Code, Class 2 and 3, moderate energy carbon steel piping. Exelon's proposed alternative is based on ASME Code Case N-786 but contains certain aspects which deviate from the Code Case. Exelon's proposed alternative addresses the three repair options which are Type A sleeves, partial-structural Type B sleeves, and full-structural Type B sleeves. The general design and construction requirements of each of these repair methods are as follows:

Type A Sleeve The Type A sleeve consists of two semi-cylindrical sections of rolled plate which are placed over the defect area and longitudinally welded to form a sleeve over the degraded pipe. The ends of the sleeve are not welded to the pipe but under certain circumstances may be sealed.

Hardenable filler material may be used to fill gaps between the sleeve and the pipe. The Type A sleeve is intended to be used when reinforcement of thinned areas is required. The Type A sleeve may only be used when the pipe is capable of meeting longitudinal strength requirements and when the degradation which has occurred in the pipe in conjunction with the predicted degradation during the duration of the repair is not expected to result in leakage. The maximum duration of a Type A sleeve repair is until the next refueling outage.

Partial-Structural Type B Sleeve The partial-structural Type B sleeve consists of two semi-cylindrical sections of rolled plate which are placed over the defect area and longitudinally welded to form a sleeve over the degraded pipe. The ends of a partial-structural Type B sleeve are fillet welded to the pipe. Filler and gasket material may be used between the pipe and the sleeve as needed. The partial-structural Type B sleeve is intended for use for pressure plus partial-structural reinforcement of thinned areas that penetrate, or are expected to penetrate, the wall and cause leakage. The partial-structural Type B sleeve is designed to accommodate design loadings at the segment being reinforced, taking partial credit for the degraded segment after factoring in predicted degradation over the life of the repair. Partial credit is considered taken if the design relies on any portion of the segment of piping beneath the sleeve, other than the base metal beneath the attachment welds, to provide structural or pressure integrity. The maximum duration of a partial-structural Type B sleeve repair is until the next refueling outage.

Full-Structural Type B Sleeve The full-structural Type B sleeve consists of two semi-cylindrical sections of rolled plate which are placed over the piping defect and longitudinally welded to form a sleeve over the degraded pipe. The ends of a full-structural Type B sleeve are welded to the pipe using partial penetration attachment welds. Filler and gasket material may be used between the pipe and the sleeve as needed. The full-structural Type B sleeve is intended for use for pressure plus

full-structural reinforcement of thinned areas that penetrate, or are expected to penetrate the wall and cause leakage. The full-structural Type B sleeve is designed to accommodate pressure plus axial and circumferential design loadings at the location for the design life of the repair without taking credit for any portion of the degraded segment. A full-structural Type B sleeve repair has no defined life and may remain in service as long as the repair remains serviceable.

Exelon's proposed alternative to the requirements of ASME Code,Section XI, paragraph IWA 4000, is to follow the requirements contained in ASME Code Case N-786 with the following modifications:

1. General Requirements Paragraph 1(e) of Code Case N-786 states that "... this Case may be applied only to piping not required to be ultrasonically examined for inservice inspection ... " The proposed alternative added the following limitation: " ... use of this repair method will be limited to pipe and fittings; as a result the following condition shall apply to the application of Code Case N-786:

Reinforcing sleeves may not be applied to pumps, valves, expansion joints, vessels, heat exchangers, tubing, or flanges; and may not be applied over flanged joints, socket welded or threaded joints, or branch connection welds ... "

2. Initial Evaluation Section 2 of the Code Case N-786 requires the inspection of the degraded area prior to sleeve installation. The proposed alternative clarified the exact method and area that will be inspected. Before repairing the subject piping, Exelon will ultrasonically measure the material beneath the pipe surface to which the reinforcing sleeve is to be applied to establish the existing wall thickness and the extent and configuration of the degraded area to be reinforced.

Exelon will also examine the adjacent area to verify that the repair will encompass the entire unacceptable area, and that the adjacent base material is of sufficient thickness to accommodate the attachment welds at the edges of the sleeve.

The area of evaluation will be dependent on the degradation mechanism present, but shall extend at least 0. 75vRTnom (R and T are the radius and nominal thickness of the pipe, respectively) beyond the edge of any sleeve attachment weld. If the cause of the degradation is not determined, the maximum permitted service life of any reinforcing sleeve shall be the time until the next refueling outage.

Section 2(b) of the code case states that the cause, the extent, and the rate of degradation in the piping shall be determined and evaluated to ensure that there will be no other unacceptable locations within the surrounding area that could affect the integrity of the reinforced areas for the life of the repair. The proposed alternative added the following requirements to calculate the rate of degradation (corrosion rate).

Corrosion Rate Determination Exelon states that the thickness of each sleeve is sufficient to support the required design loads plus a corrosion allowance equal to, or greater than, two times the maximum rate observed at the location of the repair for the duration of the repair or between inspections. If the degradation rate at the repaired location is unknown, Exelon will apply four times the maximum degradation rate observed for that pipe system or a similar pipe system at the same plant site for the same degradation mechanism. If both the degradation rate at the repaired location and the cause of the degradation are not conclusively determined, Exelon will apply four times the maximum degradation rate observed for all degradation mechanisms observed for that pipe system or a similar pipe system at the same plant site.

Exelon stated that wall thickness measurements would be obtained during periodic inspections of full-structural Type B sleeve repairs. Exelon stated that such inspections would be conducted at least each refueling outage. Exelon also stated that, depending on the extent of corrosion observed (corrosion rate), the frequency of inspections could be increased to ensure that the thickness of the repair would not infringe upon the minimum design thickness as required by the Construction Code or ASME Code, Section Ill. Exelon stated that a full-structural Type B sleeve would be removed prior to infringing upon minimum design requirements.

3. Design Sections 3.1 (a) and 3.1 (b )(2) of Code Case N-786 state that the maximum service life of Type A and partial-structural Type B sleeves is until the next refueling outage. Exelon confirmed these limitations by stating that in the absence of specific regulatory relief, Type A and partial structural Type B sleeves would be removed during the next scheduled refueling outage even if (a) the interval was short, e.g., one month; (b) significant difficulties were encountered; or (c) the next refueling outage was after the end of the current lSI interval.

Section 3.1 (b)(1) of the code case states that the full-structural Type B sleeve is designed for long-term use. The proposed alternative clarified that the full-structural Type B reinforcing sleeve will be removed and an IWA-4000 repair or replacement will be performed prior to the time that inservice monitoring indicates that pressure integrity (leak tightness) or structural integrity could be impaired based on measured degradation between monitoring activities.

4. Water Backed Applications The proposed alternative is consistent with Code Case N-786.

5. Installation Section 5(g) of the code case states that " ... provision for venting during the final closure weld or pressure testing shall be made if necessary ... " The proposed alternative clarified that for the Type 8 sleeve, small branch connections may be needed for venting, injecting hardenable filler or for system leakage test connections. The branch connection designs would meet Construction Code design requirements, and would impose negligible stress on the reinforcing

sleeve. Exelon has clarified the code case to require that: "Branch connections may be installed on reinforcing sleeves only for filling or venting purposes during installation or leakage testing of the sleeve, and shall be limited to Nominal Pipe Size (NPS) 1 or smaller in size."

Exelon noted that piping as small as 1-inch NPS (nominal pipe size) schedule XXS could be repaired as long as the Construction Code can be satisfied, including monitoring requirements.

6. Examination The proposed alternative is consistent with Code Case N-786.

7. Pressure Testing The proposed alternative is consistent with Code Case N-786.

8. lnservice Examination Section 8 of the code case does not provide requirements for the inservice examination of the Type A and partial-structural Type B sleeves. The proposed alternative requires that for Type A sleeve and partial-structural Type B sleeves, Exelon will visually observe these two types of sleeves at least once per month to monitor for evidence of leakage. If the areas containing these sleeves are not accessible for direct observation, then monitoring will be accomplished by visual assessment of surrounding areas or ground surface areas above such sleeves on buried piping, or monitoring of leakage collection systems, if available.

Paragraph 8(b) of ASME Code Case N-786 states that " ... the owner shall prepare a plan for thickness monitoring of full-structural reinforcing sleeves and their attachment welds using ultrasonic or direct thickness measurements ... " Exelon revised the Relief Request to read:

" ... the Owner shall prepare and implement a plan for thickness monitoring ... " Exelon stated that it will perform a baseline thickness examination for the full-structural Type B sleeve, partial penetration attachment welds, and surrounding areas, followed by similar thickness monitoring inspections every refueling outage.

Paragraph 8(b) of ASME Code Case N-786 states that monitoring activities shall be performed during the first two refueling outages after installation and at least every fourth refueling outage thereafter. Exelon revised the requirement and stated that it will ultrasonically examine the full-structural Type B sleeves every refueling outage.

If a buried piping system carrying radioactive fluid was repaired by the proposed alternative, Exelon will monitor and detect radioactive fluid leakage in accordance with the standard plant monitoring practices for all buried piping containing radioactive fluids. Exelon states that it is committed to Nuclear Energy Institute (NEI) 07-07, "Industry Ground Water Protection Initiative-Final Guidance Document," dated August 2007, and monitoring required by ASME Code Case N-786.

For degradation caused by cavitation, the proposed alternative requires that thickness monitoring by inspection is needed to be performed at a minimum of every refueling outage for the life of the repair.

Hardship Justification Exelon stated that the relief request permits the installation of technically sound temporary repairs in the form of Type A or partial-structural Type B reinforcing sleeves where there is inadequate time for evaluation, design, material procurement, planning and scheduling of an appropriate permanent repair or replacement, due to the impact on system availability, maintenance rule applicability, or availability of replacement materials. Additionally, the relief request permits installation of technically sound long-term repairs configured to permit on-going degradation monitoring, equal to or exceeding the level of quality and safety associated with permanent ASME Code repairs or replacements. The alternative in some cases could necessitate extending technical specification actions to install a permanent repair/replacement, putting the plant at higher safety risks than warranted compared with the short time necessary to install a technically sound sleeve repair. Exelon further stated that without the use of this Code Case in some situations, it may be necessary to shut the plant down in order to perform a code repair/replacement activity; however, this results in an unnecessary plant transient and the loss of safety system availability as compared to maintaining the plant online.

Duration of Proposed Alternative Exelon stated that the proposed alternative is for the remainder of each plant's 10-year inspection interval as specified in Table 1 above. Installation of reinforcing sleeves in accordance with this request cannot take place after the end of the 10-year lSI interval for the unit. Any Type A and partial-structural Type B reinforcing sleeves installed before the end of the 10-year in service inspection interval will be removed during the next refueling outage, even if that refueling outage occurs after the end of the 10-year lSI interval.

3.2 NRC Staff Evaluation The NRC staff evaluated the technical aspects of this request against the criteria contained in 10 CFR 50.55a(3)(ii), the existence of a hardship or unusual difficulty without a compensating increase in quality or safety. The NRC staff evaluated the first criterion, hardship or unusual difficulty with respect to issues such as plant and personnel safety, plant transients, or environmental impacts. The NRC staff finds that the second criterion, without a compensating increase in quality or safety, is met if the proposed alternative provides reasonable assurance of structural and leak tight integrity of the subject components In its review of this request, the NRC staff considered Exelon's proposed alternative to consist precisely of ASME Code Case N-786, which has not been approved for use by the NRC, and the modifications as discussed above. For clarity, the NRC staff's review of the proposed alternative will follow the organizational structure of the code case. The NRC staff's review of this request is limited to the context of the Exelon fleet request only and does not constitute a generic review of the code case.

1. Hardship The NRC staff evaluated Exelon's assertion that repairing the subject piping in accordance with the ASME Code,Section XI, constituted a hardship. The NRC staff finds that performing the

above specified ASME Code compliant repairs may result in the need for a plant shutdown or delay in startup, which would not be necessary if the proposed alternative is authorized. The NRC staff, therefore, finds that requiring ASME Code compliant repairs under the conditions outlined in Exelon's request constitutes a hardship.

2. General Requirements The NRC staff reviewed Section 1, General Requirements, of the code case and Exelon proposed modifications as described above. The NRC staff finds that the contents of this section, as modified, provide reasonable limitations to the use of the proposed alternative. In particular, the NRC staff notes the limitation of the use of the proposed alternative to piping other than piping requiring inservice ultrasonic examination to be of significance as such examinations cannot be performed through sleeves.

The NRC staff finds the general requirements as proposed by Exelon to be acceptable.

3. Initial Evaluation The NRC staff reviewed Section 2, Initial Evaluation, of the code case and Exelon's proposed modifications as described above. The NRC staff finds that paragraph 2(a) of this subsection when enhanced as proposed by Exelon, i.e., that the extent of the initial inspection will be based on the corrosion mechanism involved but will extend at least 0. 75"RT nom (R is the radius of the pipe and Tis the thickness) beyond the edge of any sleeve attachment weld, to be a reasonable means to assure that the sleeve repair will be welded to a section of pipe with sufficient strength to support the repair. The NRC staff also finds that paragraph 2(c) represents a generally accepted method to evaluate the effects of the attachment of the sleeve to the piping.

The NRC staff found the corrosion rate discussion of paragraph 2(b) of the code case to be of critical importance to the acceptability of the proposed alternative. The NRC staff finds the requirements included in paragraph 2(b) of the code case to be insufficient to assure that the sleeve repair will be appropriately sized and installed. Alternatively, the NRC staff finds that Exelon's proposed alternative, i.e., the use of plant-specific, measured corrosion rates, the requirement that the corrosion mechanism be determined or the repair removed at the next refueling outage, and the use of a safety factor of either 2 or 4 as described above will provide a sufficiently conservative potential rate of degradation to ensure that the sleeves will perform their intended functions for either the life of the repair (Type A and partial-structural Type B) or until the next scheduled inspection (full structural Type B). The NRC staff further finds acceptable that the relief request has specified acceptance criteria to remove a degraded full-structural Type B sleeve prior to either the sleeve, attachment welds, or the pipe wall beneath the attachment welds reaching the minimum design thickness as required by the Construction Code or the ASME Code, Section Ill.

The NRC staff finds the initial evaluation requirements as proposed by Exelon to be acceptable.

4. Design The NRC staff reviewed Section 3, Design, of the code case and Exelon proposed modifications as described above. The NRC staff finds that the descriptions of each type of sleeve -- Type A, partial structural Type B, and full-structural Type B -- to be adequate. The NRC staff finds that the allowable duration for use of each type of sleeve to be consistent with the intended function described, as well as initial and subsequent inspection requirements.

The NRC staff finds that the specified mechanical design requirements for each type of sleeve are consistent with accepted design practices.

The NRC staff took particular note of footnote 1 to paragraph 3.1 (a) of the code case. This footnote states that:

If a Type A or partial-structural Type B reinforcing sleeve is installed during a refueling outage, the maximum permitted service life is one fuel cycle, until the next refueling outage.

The NRC staff notes that this criterion differs from that used in many alternatives to the ASME Code which have been authorized by the NRC staff. Frequently, such authorizations have permitted the use of an alternative to the ASME Code when such a need arose during operation, but have precluded the use of the alternative when the need was discovered during an outage. In this case, due to (1) the insignificant difference in the time period in which a Type A or a partial-structural type B repair could remain in place; (2) the confirmation by Exelon that Type A and partial-structural type B would be removed at the next refueling outage; and (3) the adequate plant-specific method of estimating corrosion rates employed, the NRC staff finds that the difference in safety associated with the use of the proposed alternative beginning during an outage as compared to a subsequent point during plant operation is negligible.

Additionally, the NRC staff finds Exelon's statement regarding the lack of ability to use this alternative for defects discovered during an outage being an impediment to the conduct of inspections to be reasonable.

The NRC staff finds the design requirements as proposed by Exelon to be acceptable.

5. Water Backed Applications The NRC staff reviewed Section 4, Water Backed Applications, of the code case. Exelon proposed no modifications to this section of the code case. Per the requirements of Section 4 of the code case, Exelon will use manual shielded metal arc welding and low-hydrogen electrodes to weld the reinforcing sleeves on water backed piping. For piping materials other than P-No. 1 Group 1, Exelon will perform a surface examination of welds no sooner than 48 hours2 days <br />0.286 weeks <br />0.0658 months <br /> after completion of welding. The NRC notes that after welding, Exelon will perform examinations to identify any potential fabrication defect(s) in accordance with ASME Code, Section Ill. The staff finds that Section 4 of the code case specifies adequate requirements for welding on water backed pipe to minimize cracking and, therefore, the requirements for water backed applications are acceptable.

The NRC staff finds Section 4 of the code case to be acceptable.

6. Installation The NRC staff reviewed Section 5, Installation, of the code case and the licensee's proposed modifications as described above. The staff noted the potential need to install branch connections on Type B sleeves for the purpose of venting, injecting hardenable filler, or providing leakage test connections. Based upon engineering judgment, the NRC staff finds that Exelon's assertion that branch connections for the above described purposes may be required to be reasonable. The NRC staff also finds that the limitation on the use of branch connections for the above stated purposes, as well as the size limitation (1 inch normal pipe size (NPS) or smaller) to be reasonable because the limitation on branch connection size is needed to minimize any potential forces and moments originated from the branch connection to affect the structural integrity of the installed sleeve. The NRC staff further finds that the installation of branch connections of this size and for this purpose will not adversely affect the structural or leak-tight integrity of the repair sleeve.

In its review, the NRC staff also considered Exelon's assertion that sleeve repairs could be made to piping as small as 1 inch NPS schedule XXS. The NRC staff found no reason to believe that such Construction Code compliant repairs could not be made. The NRC staff notes, however, that Exelon must verify compliance with the Construction Code for each repair.

The NRC staff finds the installation requirements as proposed by Exelon to be acceptable.

7. Examination The NRC staff reviewed Section 6, Examination, of the code case. Exelon proposed no modifications to this section. The proposed alternative will follow the requirements of the Construction Code or ASME Code, Section Ill, in the examination of the installed sleeve and will disposition of any examination results accordingly. The NRC staff finds the acceptance examination is adequate to provide reasonable assurance of the structural integrity of the repaired pipe and, therefore, is acceptable.

8. Pressure Testing The NRC staff reviewed Section 7, Pressure Testing, of the code case. Exelon proposed no modifications to this section of the code case. The NRC staff finds that the proposed pressure testing is acceptable because it is consistent with IWA-5000 of the ASME Code,Section XI.

The NRC staff finds Section 7 of the code case to be acceptable.

9. lnservice Examination The NRC staff reviewed Section 8, lnservice Examination, of the code case and Exelon proposed modifications as described above. In its review of paragraphs (a) and (c) of the code case, the NRC staff found that these paragraphs adhere to generally accepted procedures.

The NRC staff noted that for Class 2 piping, Table IWC-2500-1 of the ASME Code,Section XI, requires a surface and/or volumetric examination for Examination Category C-F-2 components (i.e., pressure retaining welds in carbon steel or low alloy steel piping) once every inspection

interval (using the 2007 edition of the ASME Code as an example). The NRC staff also noted that for Class 3 piping, Table IWD-2500-1 of the ASME Code,Section XI, requires a VT-1 visual examination for a sample of Examination Category D-A components (i.e., welded attachments for pressure vessels, piping, pumps and valves) during each inspection interval.

The NRC staff found the requirements of paragraph (b) of the code case to be deficient especially with respect to the concept of inspecting the full-structural Type B sleeve on the first two refueling outages following installation and then every fourth outage. The NRC staff reasoned that nondestructive examination of the sleeve would not provide any indication regarding the actual corrosion activity occurring under the sleeve until a through wall leak of the original pipe developed. At that point, due to the localized environment which exists between the sleeve and the pipe, the corrosion rate may differ substantially from other areas of the pipe.

The NRC staff envisioned a scenario in which the original pipe began to leak into the annular space between the pipe and the sleeve shortly after the second refueling outage. Under the inspection plan proposed in the code case, this sleeve would not be inspected for four refueling outages. The NRC believes that there is a possibility that the sleeve could corrode through before the sleeve is inspected again. The licensee's proposal to inspect the full-structural Type B sleeve every refueling outage resolves this concern. The NRC staff is not aware of any operating experience which would predict that, even in the presence of a crevice such as the annular space between the pipe and the sleeve, the rate of corrosion would increase to the point that through wall corrosion of the sleeve would occur prior to the next refueling outage while the pipe around the sleeve would not be significantly corroded.

Additionally, the NRC staff found that Exelon's proposal to inspect the sleeves on a monthly basis for leakage and to adhere to plant commitments to NEI 07-07 for pipes carrying licensed material to be necessary components of a long term inspection plan.

The NRC staff finds the inservice examination requirements as proposed by Exelon to be acceptable.

In summary, the NRC staff determined that the conditions and requirements in the relief request are acceptable based on the above evaluation. The NRC staff finds that the proposed repair will provide reasonable assurance of the structural integrity and leak tightness of the repaired pipe. The NRC staff's conclusion is based on: (1) The scope of application is clearly defined, (2) Exelon will design and install the sleeve in accordance with the Construction Code, ASME Code, Section Ill, and other relevant industry codes, (3) Exelon will examine and evaluate the pipe prior to sleeve installation, (4) Exelon will perform acceptance examinations and inservice examinations to verify the pipe wall thickness and condition of the repair, and (5)

Exelon will perform pressure test in accordance with IWA-5000 of the ASME Code,Section XI.

4.0 CONCLUSION

As set forth above, the NRC staff determined that the proposed alternative provides reasonable assurance of structural integrity and leak tightness of the subject components and that complying with the specified ASME Code requirements would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety. Accordingly, the NRC staff concludes that Exelon has adequately addressed all of the regulatory requirements

set forth in 10 CFR 50.55a(a)(3)(ii). Therefore, the NRC staff authorizes the use of Relief Request 10 CFR 50.55a, Revision 3, for the repair of ASME Code, Class 2 and 3, moderate energy carbon steel piping at the plants specified above for the specific 10-year lSI interval as documented in Table 1 of this SE.

The authorization of Relief Request 10 CFR 50.55a, Revision 3, does not imply or infer NRC approval of ASME Code Case N-786. All other ASME Code,Section XI, requirements for which relief was not specifically requested and authorized by the NRC staff will remain applicable including third-party review by the Authorized Nuclear lnservice Inspector.

Principal Contributors: J. Tsao D. Alley Date of issuance: July 31 ' 2014

ML14175B593 OFFICE LPL3-2/PM LPL3-2/LA LPL3-2/BC NAME JWiebe SRohrer TTate DATE 6/25/14 7/30/14 7/31/14