CNRO-2015-00017, Entergy Submits Relief Request RR EN-15-1 - Proposed Alternative to Use ASME Code Case N-789-1, Alternative Requirements for Pad Reinforcement of Class 2 and 3 Moderate Energy Carbon Steel Piping for Raw Waster Service, Section XI, D

Entergy Submits Relief Request RR EN-15-1 - Proposed Alternative to Use ASME Code Case N-789-1, Alternative Requirements for Pad Reinforcement of Class 2 and 3 Moderate Energy Carbon Steel Piping for Raw Waster Service, Section XI, Division

ML15159A200
Person / Time
Site:	Palisades, Indian Point, Grand Gulf, Pilgrim, Arkansas Nuclear, River Bend, Waterford, FitzPatrick
Issue date:	06/05/2015
From:	Ford B Entergy Nuclear Operations, Entergy Operations
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
CNRO-2015-00017
Download: ML15159A200 (17)

Text

• Entergy

-~~*

Entergy Operations, Inc.

Entergy Nuclear Operations, Inc.

1340 Echelon Parkway Jackson MS 39213 Bryan 5. Ford Senior Manager, Fleet Regulatory Assurance CNR0-2015-00017 June 5, 2015 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001

SUBJECT:

Relief Request Number RR EN-15-1 -Proposed Alternative to Use ASME Code Case N-789-1, "Alternative Requirements for Pad Reinforcement of Class 2 and 3 Moderate Energy Carbon Steel Piping for Raw Water Service, Section XI, Division 1" Arkansas Nuclear One, Units 1 & 2 Palisades Nuclear Plant Docket Nos. 50-313 & 50-368 Docket 50-255 License Nos. DPR-51 & NPF-6 License No. DPR-20 Grand Gulf Nuclear Station, Unit 1 Pilgrim Nuclear Power Station Docket No. 50-416 Docket No. 50-293 License No. NPF-29 License No. DPR-35 James A Fitzpatrick Nuclear Power Plant River Bend Station, Unit 1 Docket No. 50-333 Docket No. 50-458 License No. DPR-59 License No. NPF-47 Indian Point Energy Center, Units 2 & 3 Waterford 3 Steam Electric Station Docket Nos. 50-247 & 50-286 Docket No. 50-382 License Nos. DPR-26 & DPR-64 License No. NPF-38

Dear Sir or Madam:

Pursuant to 10 CFR 50.55a(z)(2), Entergy Operations, Inc. and Entergy Nuclear Operations, Inc. (hereafter referred to collectively as "Entergy") hereby request NRC approval of a relief request to the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code, Section XI, "Rules for lnservice Inspection of Nuclear Power Plant Components," on the basis that the current code requirements result in hardship and/or unusual difficulty. The proposed relief request is provided in the attachment to this letter.

Specifically, this request is for application of American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code, Code Case N-789-1, for Class 2 and Class 3 moderate energy raw water piping system repairs resulting from degradation mechanisms such as erosion, corrosion, cavitation and pitting at the Entergy nuclear plants listed above.

The information provided in the attachment demonstrates that the proposed request provides an acceptable level of quality and safety and that compliance with the specified requirements

CNR0-2015-00017 Page 2 of 3 of ASME Section XI would result in a hardship and/or unusual difficulty without a compensating increase in the level of quality and safety.

This relief request is proposed for the 10-year lnservice Inspection (lSI) intervals for the facilities as identified in Section 2 of the attached relief request.

Since this relief request could be needed at any time to address an emergent condition, Entergy requests NRC approval as soon as possible or by June 5, 2016.

This letter contains no new commitments.

If you have any questions, please contact Mr. Bryan Ford, Senior Manager, Fleet Regulatory Assurance at (601) 368-5516.

Sincerely, BSF/ghd/aye

Attachment:

Relief Request Number RR EN-15-1 cc: J. Forbes (ECH)

T. Mitchell (ECH)

J. Ventosa (WPO)

D. Jacobs (ECH)

M. Perito (ECH)

J. Kowalewski (ECH)

M. Woodby (ECH)

J. Browning (ANO)

K. Mulligan (GGNS)

E. Olson (RBS)

M. Chisum (WF3)

B. Sullivan (JAF)

L. Coyle (IPEC)

J. Dent (PIL)

T. Vitale (PAL)

D. Mannai (WPO)

G. H. Davant (ECH)

All above w/o attachments NRC Region I Administrator NRC Region Ill Administrator NRC Region IV Administrator NRC Project Manager (ANO)

NRC Project Manager (GGNS)

NRC Project Manager (RBS)

NRC Project Manager (WF3)

NRC Project Manager (IPEC)

CNR0-2015-00017 Page 3 of 3 NRC Project Manager (JAF)

NRC Project Manager (PIL)

NRC Project Manager (PAL)

NRC Senior Resident Inspector (ANO)

NRC Senior Resident Inspector (GGNS)

NRC Senior Resident Inspector (RBS)

NRC Senior Resident Inspector (WF3)

NRC Senior Resident Inspector (IPEC)

NRC Senior Resident Inspector (JAF)

NRC Senior Resident Inspector (PIL)

NRC Senior Resident Inspector (PAL)

ATTACHMENT CNR0-2015-00017 RELIEF REQUEST RR EN-15-1

Attachment to CNR0-2015-00017 Page 1 of 6 RELIEF REQUEST RR EN-15-1

1. ASME Code Component(s) Affected This relief request applies to all ASME Class 2 and 3 moderate energy carbon steel raw water piping systems. Raw water is defined as water such as a river, lake, or well or brackish/salt water used in plant equipment, area coolers, and heat exchangers. In many plants, it is referred to as "Service Water." Moderate energy is defined as less than or equal to 200°F (93°C) and less than or equal to 275 psig (1.9 MPa) maximum operating conditions.

2. Applicable Code Edition and Addenda

The following table identifies the ASME Section XI Code of Record for performing lnservice Inspection (lSI) activities at each Entergy site.

lSI ASME Section XI Interval Interval Plant Interval Edition/Addenda Start End Arkansas Nuclear One 4 2001 Edition I 2003 Addenda 5131108 5130117 Unit 1 (AN0-1)

Arkansas Nuclear One 4 2001 Edition I 2003 Addenda 3126110 3125120 Unit 2 (AN0-2)

Grand Gulf Nuclear Station 3 2001 Edition I 2003 Addenda 5131108 611117 (GGNS)

Indian Point Energy Center 4 2001 Edition I 2003 Addenda 311107 5131116 Unit 2 (IPEC-2) (Note 1) 5 2007 Edition I 2008 Addenda 611116 5131126 Indian Point Energy Center 4 2001 Edition I 2003 Addenda 7121109 7120119 Unit 3 (IPEC-3)

James A. FitzPatrick 4 2001 Edition I 2003 Addenda 311107 12/31116 (JAF) (Note 1) 5 2007 Edition I 2008 Addenda 111117 12131126 Palisades (PLP) (Note 21 5 2007 Edition I 2008 Addenda 12113115 12112125 Pilgrim Nuclear Power Station (PNPS) (Note z) 5 2007 Edition I 2008 Addenda 711115 6130/25 River Bend Station (RBS) 3 2001 Edition I 2003 Addenda 5131108 11130117 Waterford Unit 3 (WF3) 3 2001 Edition I 2003 Addenda 5131108 6130117 Notes:

1) The 4th lSI intervals for IPEC-2 and JAF end soon after the requested relief request approval date.

1 Therefore, Entergy requests the NRC to approve this alternative for the 4th and 5 h IPEC-2 and JAF intervals.

1

2) The 4 h lSI intervals for PLP and PNPS end prior to the requested relief request approval date.

1 Therefore, Entergy requests the NRC to approve this alternative for the 5 h PLP and PNPS lSI intervals.

Attachment to CNR0-2015-00017 Page 2 of6 The table above identifies the ASME Section XI Code of Record for performing lSI activities at each Entergy nuclear plant. However, it should be noted that ASME Section XI repair/replacement activities at all Entergy nuclear plants are performed in accordance with a standardized Repair/Replacement Program that is based on a common Edition/Addenda of ASME Section XI which, at present, is the 2001 Edition/ 2003 Addenda. As Entergy nuclear sites update their lSI Programs in accordance with 10 CFR 50.55a(g)(4)(ii), Entergy will also update the Code bases of the Repair/ Replacement Program to a later Edition/Addenda of ASME Section XI. The planned update to the Repair/Replacement Program is scheduled for 2017 and no later than December 31, 2017. The Repair/Replacement Program update must comply with 10 CFR 50.55a and, where appropriate, in accordance with 10 CFR 50.55a(g)(4)(iv) and 10 CFR 50.55a(z). (Ref: PNPS PRR-26, dated November 26, 2014; ML1434280001)

3. Applicable Code Requirements The Editions/Addenda of ASME Section XI for which the alternative is requested are specified in Section 2, above. Subsection IWA-4000 of these Editions and Addenda provide requirements for welding, brazing, metal removal, and installation of repair/replacement activities.

4. Reason for Request

IWA-4000 requires replacement or internal weld repair of wall-thinning conditions resulting from degradation to be in accordance with the Owner's Requirements and the original or later Construction Code. However, the repair and replacement provisions of IWA-4000 cannot always be utilized when degradation or leakage is identified during plant operations. Other approved alternative repair or evaluation methods are not always practicable because of wall thinness and/or moisture issues. The proposed alternative will permit installation of a technically sound temporary repair to provide adequate time for evaluation, design, material procurement, planning, and scheduling of an appropriate permanent repair or replacement of the defective piping, considering the impact on system availability, maintenance rule applicability, and availability of replacement materials. Without this repair option, compliance with the specified requirements of IWA-4000 would result in hardship and/or unusual difficulty

- including higher risks associated with plant shut-downs and extended technical specification actions -without a compensating increase in the level of quality and safety.

5. Proposed Alternative and Basis for Use Pursuant to 10CFR50.55a(z)(2), Entergy proposes to implement the requirements of Code Case N-789-1 as a temporary repair of degradation in Class 2 and 3 moderate energy raw water piping systems resulting from mechanisms such as erosion, corrosion, cavitation, or pitting, but excluding conditions involving flow accelerated corrosion (FAG), corrosion-assisted cracking, or any other form of cracking. These types of defects are typically identified by small leaks in the piping system or by pre-emptive, non-code required examinations performed to monitor the degradation mechanisms. This repair technique involves welding a metal reinforcing pad - pressure pad or structural pad - to the exterior of the piping system to reinforce the degraded area and restore pressure integrity. This repair technique will be used when it is determined that the temporary repair method is suitable for the particular defect and type of degradation present. Code Case N-789-1 is included in the enclosure of this request.

Attachment to CNR0-2015-00017 Page 3 of6 The Code Case requires that the cause of the degradation be determined, and that the extent and rate of degradation in the piping be evaluated to ensure there are no other unacceptable locations within the surrounding area that could affect the integrity of the repaired piping. The area of evaluation is dependent on the degradation mechanism present.

Entergy implementation of Code Case N-789-1 will include the following restrictions and clarifications:

1) Regarding paragraph 3.1 (a)( 1) of the Code Case, Entergy designs of pressure pads will be based on a corrosion rate of 2 times the actual measured corrosion rate in that location. If a repair must be performed without sufficient time to determine the actual rate of corrosion at the repair location, then the pressure pad design will be based on a corrosion rate that is 4 times the estimated maximum (worst-case) corrosion rate for the same degradation mechanism in that system or a similar system at the same plant site.

2) Paragraph 3.2(i) of the Code Case includes an incorrect reference to NC-2650 for the flexibility analysis associated with Class 2 designs. The correct reference should be NC-3650. Entergy will comply with NC-3650.

3) When gasket material is used in accordance with paragraph 3.2(1) of the Code Case (water-backed applications), Entergy will also require removal of any residual moisture by heating prior to welding.

4) Regarding paragraph 8(b) of the Code Case, Entergy will perform monitoring on a monthly basis during the first quarter as required by Code Case N-789-1. The subsequent monitoring frequency shall be based on corrosion rates calculated using reductions in thicknesses since the previous monitoring inspection, but at least quarterly.

5) Sections 1, 3, 5, and 6 of the Code Case specify that materials, design, installation, and examination of reinforcement pads shall be performed in accordance with the Construction Code or ASME Section Ill applicable to each Entergy site. As allowed by IWA-4200 and IWA-4411, later Editions and Addenda of the Construction Code or ASME Section Ill may be used provided any required reconciliations are performed. However, only Editions/Addenda of ASME Section Ill that have been approved by the NRC in 10 CFR 50.55a will be used.

6) Entergy performs repair/replacement activities in accordance with a fleet-wide, standardized Repair/Replacement Program based on the 2001 Edition/2003 Addenda of ASME Section XI. Therefore, this Edition/Addenda of AS ME Section XI will be used by all plants whenever the Code Case refers to IWA-4000 until the code bases of the Repair/Replacement Program is updated as noted in Section 2 of this request.

Code Case N-789-1 includes requirements for incorporating actual or estimated corrosion rates in the design of all reinforcing pads. For pressure pads that cannot be directly measured for the on-going effects of corrosion, rates of twice the measured actual or four times the worst-case corrosion for the system must be incorporated in the design. Structural pads are required to be directly measured for the on-going effects of corrosion, so these conservative multipliers do not apply to the design of reinforcing pads. In addition, compensatory measures are included to account for any uncertainties in the corrosion rates used, thus providing reasonable assurance that structural integrity and leakage integrity will

Attachment to CNR0-2015-00017 Page 4 of 6 be maintained. These measures include limiting the design life of reinforcing pads to a maximum of one refueling cycle, and requiring on-going monitoring as follows:

• For structural pads, including their attachment welds and the surrounding area, a baseline thickness examination will be performed followed by monthly thickness monitoring for the first three months. The subsequent examination frequency will be based on the results of corrosion rates calculated as a result of this monitoring, but at a minimum of quarterly.

• Areas containing pressure pads will be visually observed at least once per month to monitor for evidence of leakage. If the areas containing pressure pads are not accessible for direct observation, then monitoring will be accomplished by visual assessment of surrounding areas, or ground surface areas above pressure pads on buried piping, or by monitoring of leakage collection systems, if available.

Regardless of when during a fuel cycle a repair is performed, each repair will be considered to have a maximum service life until no later than the end of the next refueling outage, when a permanent repair or replacement must be performed. The Code Case specifies additional requirements for design of reinforcing pads, installation, examination, pressure testing, and inservice monitoring.

Code Case N-789-1 was approved by ASME Codes and Standards on November 13, 2013; however, it has not been incorporated into Regulatory Guide 1.147, "lnservice Inspection Code Case Acceptability, ASME Section XI, Division 1,"and, thus, is not available for application at nuclear power plants without specific NRC approval.

6. Duration of Proposed Alternative Use of the proposed alternative is requested for the duration of the lSI intervals identified in Section 2. In the case of IPEC-2 and JAF, approval of this relief request is anticipated within 1 year prior to the end of the 41h lSI intervals; therefore, this request also includes the 51h lSI intervals for those units.

Code Case N-789-1, paragraph 1(e) requires that reinforcing pads, including those installed during refueling outages, shall not remain in service beyond the end of the next refueling outage. Therefore, regardless of when the pressure or structural pad is installed, Entergy will comply with this requirement with the following clarifications:

• Reinforcing pads installed before the end of the 10-year lSI interval will be removed during the next refueling outage after installation, even if that refueling outage occurs after the end of the 10-year lSI interval. In this case, absent detrimental defects or degradation, duration of the proposed alternative would be until the first refueling outage after the end date of the lSI interval for the applicable Entergy plant.

• Some piping systems are required to be functional and cannot be repaired during refueling outages. The repair of this piping can only be performed when the plant is operating. For this unique case, the reinforcing pad will have to be removed prior to, but no later than, the refueling outage unless specific regulatory relief is obtained.

Attachment to CNR0-2015-00017 Page 5 of 6

7. Precedents A similar alternative was approved for application of Code Case N-789 for ten (10) Exelon Nuclear Power Plants (a total of 17 Units) on May 10, 2012 (Reference 2). Differences between that Code Case and Code Case N-789-1 referenced in this relief request are as follows:

• Design: Paragraph 3.1(a) was revised to clarify the difference between pressure pads and structural pads.

• Design Requirements: Figure 2 was clarified to agree with 3.1(a)(1) to require the design corrosion rate for pressure pads to be twice the actual measured corrosion rate at the location, or if not known then four times the maximum corrosion rate for the system. (See clarification 1 Section 5, above.)

• Water-Backed Applications: A new paragraph 4(b) was inserted: "When welding a reinforcing pad to a leaking area, precautions shall be taken to prevent welding on wet surfaces, such as installation of a gasket or sealant beneath the pad."

• Pressure Testing: A new sentence was added to 7: "Reinforcing pads attached to piping that has not been breached shall be equipped with pressure taps for performance of pressure testing."

• lnservice Monitoring:

A new sentence was added to paragraph 8(b ): "Provisions shall be made for access to structural pads on buried piping during operation in order to accomplish these examinations."

A new paragraph 8(c) was added requiring pressure pads to be monitored once per month for leakage.

Paragraph 8(e) of the revised Code Case now specifically requires that all reinforcing pads, regardless of when they are installed, shall have a maximum service life until the end of the next refueling outage.

The NRC also approved an alternative for application of Code Case N-789-1 for two (2) Excel Energy Nuclear Power Plants on May 4, 2015 (Reference 3). A similar repair relief request (RR-3-43) was approved for Indian Point Nuclear Generating Unit No. 3 on February 22, 2008 (Reference 1).

8. References

1) Entergy Indian Point Nuclear Generating Unit No. 3, Safety Evaluation for Temporary Non-Code Repair (Relief Request RR-3-43), February 22, 2008- See Adams Accession No. ML080280073

2) Exelon Generation Company, LLC, Safety Evaluation for Use of Code Case N-789, May 10, 2012- See Adams Accession No. ML12121A637

3) Excel Energy Safety Evaluation for Use of Code Case N-789-1, May 4, 2015- See Adams Accession No. ML15079A003

Attachment to CNR0-2015-00017 Page 6 of 6

9. Enclosure

1. ASME Code Case N-789-1, "Alternative Requirements for Pad Reinforcement of Class 2 and 3 Moderate-Energy Carbon Steel Piping for Raw Water Service, Section XI, Div. 1"

RELIEF REQUEST RR EN-15-1 ENCLOSURE ASME Code Case N-789-1, Alternative Requirements for Pad Reinforcement of Class 2 and 3 Moderate-Energy Carbon Steel Piping for Raw Water Service, Section XI. Division 1

CASE CASES OF ASME BOILER AND PRESSURE VESSEL CODE N-789-1 Approval Date: November 13, 2013 Code Cases will remain available for use until annulled by the applicable Standards Comm ittee.

Case N-789-1 (e) Reinforcing pads, including those installed during a Alternative Requirements for Pad Reinforcement of refueling outage, shall not remain in service beyond the Class 2 and 3 Moderate-Energy Carbon Steel Piping for end of the next refueling outage.

Raw Water Service (/] This Case may only be applied to piping not required Section XI, Division 1 to be ultrasonically examined for inservice inspection.

Inquiry: As an alternative to replacement or internal weld repair in accordance with IWA-4400, what require- 2 INITIAL EVALUATION ments may be applied for wall reinforcement of Class 2 (a) The material beneath the surface to which the rein-and 3 moderate-energy carbon steel raw water 1 piping forcing pad is to be applied and the adjacent area shall be systems that have experienced internal wall thinning from ultrasonically measured to establish the existing wall localized erosion, corrosion, and cavitation or pitting? thickness and the extent and configuration of degradation to be corrected by the reinforcing pad.

Reply: It is the opinion of the Committee that, in (b) The cause and rate of degradation shall be deter-lieu of meeting IWA-4400, areas of Class 2 and 3 mined. If the cause is determined to be flow-accelerated moderate-energy [i.e., less than or equal to 200°F (93°C) corrosion (FAC), corrosion-assisted cracking, or any other and less than or equal to 275 psig (1.9 MPa) maximum op- form of cracking, this Case shall not apply. The extent and erating conditions] carbon steel raw water piping experi- rate of degradation in the piping shall be evaluated to en-encing internal wall thinning from localized erosion, sure that there are no other unacceptable locations within corrosion, and cavitation or pitting may have the wall re- the surrounding area that could affect the integrity of the inforced by applying reinforcing pads to the outside sur- repaired piping. The dimensions of the surrounding area face of the piping in accordance with the following to be evaluated shall be determined by the Owner, consid-requirements. Excluded from these provisions are condi- ering the type of degradation present.

tions involving flow-accelerated corrosion (FAC), (c) The effects of the repair on the piping and any re-corrosion-assisted cracking, or any other form of cracking. maining degradation shall be evaluated in accordance with IWA-4311.

1 GENERAL REQUIREMENTS 3 DESIGN (a) Application of the reinforcing pad shall be per-formed in accordance with a Repair/Replacement Plan sa- 3.1 TYPES OF REINFORCING PADS tisfying the requirements of IWA-4150. (a) Reinforcing pads may be used for leak prevention (b) The design, materials, and installation shall meet the only (pressure pad), or for leak prevention plus structural requirements of the Construction Code and IWA-4000, ex- reinforcement of thinned areas including areas that do, or cept as stated in this Case. are expected to, penetrate the piping wall (structural pad).

(c) If the minimum required thickness of reinforcing (1) Pressure pads are designed to retain pressure, pad necessary to satisfy the requirements of 3 is greater and may be used only where the piping is predicted to re-than the nominal thickness for the size and schedule of tain full structural integrity until the next refueling outage the piping, this Case shall not be used. assuming a corrosion rate of either 2 times the actual mea-(d) Additional reinforcement or repair is not permitted sured corrosion rate in that location, or 4 times the esti-on top of an existing reinforcing pad. mated maximum corrosion rate for the system.

1 Raw water is defined as water such as from a river, lake, or well or brackish/salt water; used in plant equipment, area coolers, and heat exchangers. In many plants it is referred to as "Service Water:*

The Committee's function is to establish rules of safety, relating only to pressure integrity, governing the construction of boilers, pressure vessels, transport tanks and nuclear components, and lnservice inspection for pressure integrity of nuclear components and transport tanks, and to interpret these rules when questions arise regarding their intent This Code does not address other safety issues relating to the construction of boilers, pressure vessels. transport tanks and nuclear components, and the inservice inspection of nuclear components and transport tanks. The user of the Code should refer to other pertinent codes, standards, laws, regulations or other relevant documen ts.

1 (N-789-1) NC-SUPP. 4 Copyright ASME lntemalional (BPVC)

Prcvi:ted by IHS under Hcense with ASME X llc:ansee=Amaren Energy Services/9970656101 , User:O'Sullivan. J m No reproduction or networil.ing permitted without license from IHS Not for Resale , 06/0512014 11 .45 22 MOT

CASE (continued)

N-789-1 CASES OF ASME BOILER AND PRESSURE VESSEL CODE (2) Structural pads are designed for pressure plus applied for tees and branch connections when the toe of structural reinforcement and may be used where the pip- the attachment weld is not less than 2.5~Rtnom from ing is predicted not to retain full structural integrity until any branch reinforcement in Figure 1.

the next refueling outage.

(j) Corners of reinforcing pad plates shall be rounded 3.2 GENERAL DESIGN REQUIREMENTS - with radii not less than the reinforcing pad thickness, PRESSURE AND STRUCTURAL PADS and the toes of attachment welds at the corners shall have 1 in. (25 mm) minimum radius.

(a) The design of reinforcing pads shall be in accor- (k) The distance between toes of attachment welds and dance with the applicable requirements of the Construc- other attachments or branch reinforcement (Figure 1 and tion Code or Section lli (NC-3100, ND-3100 and 2) shall not be less than the following equation:

NC-3600, ND-3600 including Appendix II).

(b) The reinforcing pad shall be sized to encompass the d = Z.S~Rtnom unacceptable area with the attachment welds located on adjacent base material of sufficient thickness to accommo- where date the design stresses.

(c) The plate for the reinforcing pad shall be rolled or d = minimum distance between toes of fillet welds of otherwise formed to fit the contour of the piping to adjacent fillet welded attachments achieve proper weld fit-up. R = the outer radius of the piping (d) The thickness of the reinforcing pad shall be suffi- tnam = nominal thickness of the piping cient to maintain required thickness until the next refuel- (I) When permitted by the design, suitable gasket mate-ing outage. rial may be applied inside the pad to prevent moisture (e) The tensile strengths of the plate and weld filler me- during welding (see Figures 1 and 2).

tal for the reinforcing pad shall be at least that specified for the base metal to which it is applied. 3.3 SPECIFIC DESIGN REQUIREMENTS-(f) The predicted maximum degradation of the rein-PRESSURE PADS fo~ced piping until the next refueling outage shall be in-chided in the design. The predicted degradation of the Pressure pads shall meet the requirements of 3.2, piping shall be based on in-situ inspection of, and estab- Figure 2, and the following:

lished data for, similar base metals in similar environ- (a) Fillet-welded pressure pads shall be designed to ments. If the reinforcing pad is predicted to become withstand the membrane strain of the piping in accor-exposed to the raw water, the predicted degradation of dance with the requirements of the Code specified in the reinforcing pad shall be based upon established data 3.2(a) such that the following criteria are satisfied:

for base metals or weld metals with similar chemical com- (1) The allowable membrane stress is not exceeded in position to that used for the reinforcing pad. the piping or the pad.

(g) Material for reinforcing pads shall be ferritic, with (2) The strain in the pad does not result in fillet weld welds of compatible weld filler metal. stresses exceeding allowable stresses for such welds.

(h) The following factors shall be included, as applic- (b) Design as a reinforced opening in accordance with able, in the design and application of the pad: the Construction Code shall satisfy (a).

(1) shrinkage effects, if any, on the piping (c) As an alternative to (a), pressure pads may be de-(2) stress concentrations caused by installation of the signed as structural pads in accordance with 3.4 or as pre-reinforcing pad or resulting from existing and predicted qualified designs in accordance with 3.5.

piping internal surface configuration (3) effects of welding on any interior coating 3.4 SPECIFIC DESIGN REQUIREMENTS -

(4) added weight of the pad with respect to any de- STRUCTURAL PADS sign analyses that could be affected Structural pads shall meet the requirements of 3.2, (i) If flexibility analysis was required by the original Figure 1, and the following:

Construction Code, the effect of the reinforcing pad shall (a) Unless otherwise established by analysis in accor-be reconciled with the original analysis. For rectangular-dance with the requirements of 3.2(a), structural pads shaped reinforcing pads on piping designed to NC-2650, shall be attached by partial penetration attachment welds ND-3650 and aligned parallel or perpendicular to the axis (see Figure 1) that extend for a distance of at least s in of the piping, unless a lower stress intensification factor each direction beyond the area predicted, by the next re-

[SIF or (i)] is established, an SIF (i) of 2.1 shall be applied fueling outage, to infringe upon the required thickness. 2 for reinforcing pads on straight pipe and adjacent welds.

Also, a stress multiplier of 1.7 shall be applied to the SIF s ~ 0.75~Rtnom (i) for standard elbows, and an SIF (i) of 2.1 shall be 2

Design thickness as prescribed by the Construction Code.

NC-SUPP. 4 2 (N-789-1)

Copyright ASME International (BPVC)

Provited by IHS under license with ASME X Licensee=Ameren Energy Services/9970656101, User=O'SuHivan, Jim No reproduction or networking permitted without license from IHS Not ror Resale, 06/0512014 11:45 22 MDT

CASE (continued)

CASES OF ASME BOILER AND PRESSURE VESSEL CODE N-789-1 Figure 1 Structural Pad d

D l

Appropriate gasket material C =predicted circumferential growth of degradation L = predicted axial growth Required thickness treq t

bevel optional

~-- d -----+-1 Limit of Minimum dimensions of plate

_} branch reinforcement

=predicted maximum dimensions of degradation below minimum required thickness d 2: 2.5 ~ Rtnom where (d) Except for the tapered edges, the structural pad plate and attachment welds shall have a uniform R = outer radius of the component thickness.

s = 1 in. (25 mm) minimum tnom = nominal wall thickness of the component (b) The thickness of the partial penetration attachment 3.5 PREQUALIFIED DESIGN welds shall equal the thickness of the pad and the edges of Application of structural pads on straight pipe, standard the welds shall be tapered to the piping surface at a max*

elbows, and associated welds shall be exempt from the re-imum angle ("a" in Figure 1) of 45 deg.

quirements of 3.2(a), provided all of the following condi-(c) Final configuration of the structural pad including tions are satisfied.

attachment welds shall permit the examinations and eva-luations required herein, including any required preser- (a) All other requirements of 3.1, 3.2, and 3.4 are vice or inservice examinations of encompassed or satisfied.

adjacent welds. (b) The axial length of structural pad plus width of par-tial penetration attachment welds shall not exceed the greater of 6 in. (150 mm) or the outside diameter of the piping.

3 (N-789-1) NC-SUPP. 4 Copyright ASME lntematlonal (BPVC)

Prcvi1ed by lHS undtl' license with ASME X L l censee~Amaran Energy Services/9970656101, User-O'Sullivan. Jim No reproduclion or networ1dng penniltad without license from IHS Not for Resale, 06JC512014 11 45 22 MDT

CASE (continued)

N-789-1 CASES OF ASME BOILER AND PRESSURE VESSEL CODE Figure 2 Pressure Pad D

Predicted g rowth of deg radation below minim um wall th ickness based on 2 x 1

or 4 x estimated corrosion rate.

._.--- L--~~1 Appropriate gasket material if required tnom treq Required t /1 t thickness

+

? ~

~

~L, C Minimum dimensions of plate __I

= predicted extent of degradation below minimum wall thickness based on 2 x the measured corrosion rate at the location or 4 x the maximum estimated corrosion rate for the system.

(c) The finished structural pad shall be circular, oval, or (b) When welding a reinforcing pad to a leaking area, rectangular in shape. precautions shall be taken to prevent welding on wet sur-(1) The maximum dimension compensated by a circu- faces, such as installation of a gasket or sealant beneath lar structural pad shall not exceed two-thirds of the nom- the pad.

inal outside diameter of the piping. (c) For piping materials other than P-No. 1, Group 1, the (2) Rectangular structural pads shall be aligned par- surface examination required in 6 shall be performed no allel with or perpendicular to the axis of the piping. sooner than 48 hr after completion of welding.

(3) For oval structural pads, the end radii shall not be less than 0.7S~Rtnom* and the axis of the structural pad 5 INSTALLATION shall be aligned parallel with or perpendicular to the axis of the piping. (a) The base material in the area to be welded shall be cleaned to bare metal.

(b) Weld metal shall be deposited using a groove -

4 WATER-BACKED APPLICATIONS welding procedure qualified in accordance with Section IX and the Construction Code.

(a) Attachment welds on water backed piping shall be (c) Provisions for venting during the final closure weld, applied using the SMAW process with low-hydrogen or for pressurizing for leak-testing, shall be included, if electrodes.

necessary.

NC-SUPP. 4 4 (N-789-1)

Copyright ASME lntamational (BPVC)

Provited by IHS under license with ASME X Licensee=Ameren Energy Services/9970656101 , Usar=O'Sullivan, Jim No reproduction or networ1(ing permitted without license from IHS Not for Resale, 06/0512014 11 45 22 MOT

CASE (continued)

CASES OF ASME BOILER AND PRESSURE VESSEL CODE N-789-1 (d) The surface of the attachment weld shall be pre- Reinforcing pads attached to piping that has not been pared, if necessary, by machining or grinding to permit breached shall be equipped with pressure taps for perfor-performance of surface and volumetric examinations re- mance of pressure testing.

quired by 6. For ultrasonic examination, a surface finish of 250 RMS or better is required.

6 EXAMINATION 8 INSERVICE MONITORING (a) The completed attachment weld shall be examined (a) Upon completion of the repair, inspections shall be using the liquid penetrant or magnetic particle method performed for structural pads, using ultrasonic or direct and shall satisfy the surface examination acceptance cri- thickness measurement, to record the thickness of the teria for welds of the Construction Code or Section Ill plate, the thickness at the attachment welds, including (NC-5300, ND-5300). the underlying base metal, and to the extent examinable (b) Except for the tapered edges, partial penetration at- in a 3 in. (75 mm) wide band, surrounding the repair, as tachment welds, including the piping base metal upon a baseline for subsequent monitoring of the repair.

which they are applied, shall be ultrasonically measured (b) The Owner shall prepare a plan for additional thick-to verify acceptable wall thickness. ness monitoring for structural pads using ultrasonic or di-(c) Partial penetration attachment welds shall be volu- rect thickness measurement to verify that minimum metrically examined when full penetration girth welds in design thicknesses, as required by the Construction Code the piping are required by the Construction Code to be vo-or Section III, are maintained until the next refueling out-lumetrically examined. Where configuration does not per-age. The monitoring shall be monthly for the first quarter mit meaningful volumetric examination, the first layer, and the subsequent frequency shall be based on the re-each Yz in. (13 mm) thickness of weld deposit, and the fi-sults of the monitoring activities, but at least quarterly.

nal surface shall be examined in accordance with (a) in lieu of volumetric examination. Provisions shall be made for access to structural pads (d) If volumetric examination is required, the full vo- on buried piping during operation to accomplish these lume of the attachment weld, excluding the tapered edges, examinations.

but including the volume of base metal required for the in- (c) Areas containing pressure pads shall be monitored tended life of the reinforcing pad, shall be examined in ac- monthly for evidence of leakage. If the areas containing cordance with the Construction Code or Section III, using pressure pads are not accessible for direct observation, either the ultrasonic or radiographic method, and shall, monitoring shall be accomplished by observation of sur-to the depth at the surface of the piping. satisfy the accep- rounding areas or ground surface areas above pressure tance criteria for weldments of the Construction Code or pads on buried piping; or leakage collection systems, if Section Ill (NC-5320, ND-5320 or NC-5330, ND-5330) . available, shall be monitored.

Any volume of the piping beneath the reinforcing pad that (d) If the results of the monitoring program identify is credited in the design shall satisfy the volumetric accep-leakage or indicate that the structural margins required tance criteria of Section III (NC-5320, ND-5320 or by 3 will not be maintained until the next refueling outage, NC-5330, ND-5330), as applicable.

additional repair/replacement activities not prohibited by l(d) shall be performed prior to encroaching upon the de-7 PRESSURE TESTING sign limits.

In lieu of IWA-4540, a system leakage test of the repairI (e) All reinforcing pads, regardless of when installed, replacement activity shall be performed in accordance shall be removed no later than the end of the next refuel-with IWA-5000 prior to, or as part of, returning to service. ing outage.

5 (N-789-1) NC-SUPP. 4 Copyright ASME lntematlonal (BPVC)

Provi:ted by IHS under license with ASME X licensee=Ameren Energy Services/9970656101, Usar=O'Sullivan, Jim No reproduction or networ1dng pennitted without license from IHS Not for Resale, 06/0512014 11:45 22 MDT

INTENTIONALLY LEFT BLANK Cog~ht ASME IM&malional {BPVC.

Prov'dodbyiHSundowlicetwowilnASME X Llcensee-Amtren EfWlrgy Servioa5J9970658101, U&er=O'Sulllvan. Jim No reproduction or NIWOI'fcing penni't&d wi1Mut kensa from IHS Not for Ret81t, 11&1051201 4 11 45 22 MOT