L-14-267, CFR 50.55a Request Number BV3-N-789
| ML14217A471 | |
| Person / Time | |
|---|---|
| Site: | Beaver Valley |
| Issue date: | 08/05/2014 |
| From: | Emily Larson FirstEnergy Nuclear Operating Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| L-14-267 | |
| Download: ML14217A471 (14) | |
Text
FENOCTM Beaver Valley Power Station P.O. Box 4 FirstEnergy Nuclear Operating Company Shippingport, PA 15077 Eric A. Larson 724-682-5234 Site Vice President Fax: 724-643-8069 August 5, 2014 L-14-267 10 CFR 50.55a ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555-0001
SUBJECT:
Beaver Valley Power Station, Unit Nos. 1 and 2 Docket No. 50-334, License No. DPR-66 Docket No. 50-412, License No. NPF-73 10 CFR 50.55a Request Number BV3-N-789 In accordance with the provisions of 10 CFR 50.55a(a)(3)(ii), the FirstEnergy Nuclear Operating Company (FENOC) hereby requests Nuclear Regulatory Commission (NRC) approval to use American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code) Case N-789, "Alternative Requirements for Pad Reinforceme nt of Class 2 and 3 Moderate-En ergy Carbon Steel Piping for Raw Water Service,Section XI, Division 1,"as an alternative to ASME Code Section XI, Paragraph IWA-4400. Details of the proposed alternative are described in Enclosure A.
FENOC requests approval of the proposed alternative by August 31, 2015. A copy of ASME Code Case N-789 is provided as Enclosure B for information.
There are no regulatory commitment s contained in this submittal. If there are any questions or if additional information is required, please contact Mr. Thomas A. Lentz, Manager- Fleet Licensing, at (330) 315-6810.
Sincerely, Eric A. Larson
Enclosures:
A. Beaver Valley Power Station, 10 CFR 50.55a Request BV3-N-789, Revision 0 B. ASME Code Case N-789, "Alternative Requirements for Pad Reinforceme nt of Class 2 and 3 Moderate-En ergy Carbon Steel Piping for Raw Water Service,Section XI, Division 1"
Beaver Valley Power Station, Unit Nos. 1 and 2 L-14-267 Page 2 cc: NRC Region I Administrator NRC Senior Resident Inspector NRC Project Manager Director BRP/DEP BRP/DEP Site Representative
Enclosure A Beaver Valley Power Station 10 CFR 50.55a Request BV3-N-789, Revision 0 (5 pages follow)
Beaver Valley Power Station 10 CFR 50.55a Request BV3-N-789, Revision 0 Page 1 of 5 Proposed Alternative in Accordance with 10 CFR 50.55a(a)(3)(ii)
--Hardship or Unusual Difficulty without Compensating Increase in Level of Quality or Safety--
- 1. ASME Code Components Affected:
American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code) Class 2 and 3 moderate energy carbon steel raw water piping systems.
2. Applicable Code Edition and Addenda
ASME Code Section XI, 2001 Edition through 2003 Addenda is the applicable code edition and addenda for Beaver Valley Power Station, Unit No. 1 (BVPS-1) and Beaver Valley Power Station, Unit No. 2 (BVPS-2) current 10-year inservice inspection intervals.
3. Applicable Code Requirement
ASME Code,Section XI, IWA-4400 provides requirements for welding, brazing, metal removal, and installation of repair/replacement activities.
4. Reason for Request
Background Information ASME Code requirements necessitate replacement or internal weld repair of wall thinning conditions resulting from degradation in Class 2 and Class 3 moderate energy carbon steel raw water piping systems. Such degradation may be the result of mechanisms such as erosion, corrosion, cavitation, and pitting. The repairs or replacements shall be in accordance with the Owner's requirements and the original or later Construction Code.
Other alternative repair methods, such as local weld overlays, are not always practicable because of wall thinness and moisture concerns.
Hardship or Unusual Difficulty Implementing the applicable ASME Code requirements to accomplish a repair or replacement during plant operation at power would necessitate isolating the degraded portion of the system. Isolating a portion of the system would increase plant risk by rendering a safety system unavailable as compared to maintaining the system online to continue to provide redundant system function. This evolution also may require a plant shutdown. In addition, permanent repairs or replacements often require significant time for evaluation, design, material procurement, planning, scheduling, and implementation.
The primary reason for this request is to permit installation of a technically sound
Request BV3-N-789 Page 2 of 5 temporary repair to provide adequate time for implementing an appropriate permanent repair or replacement during a refueling outage.
- 5. Proposed Alternative and Basis for Use:
Proposed Alternative FirstEnergy Nuclear Operating Company (FENOC) proposes to use the requirements of ASME Code Case N-789, "Alternative Requirements for Pad Reinforcement of Class 2 and 3 Moderate-Energy Carbon Steel Piping for Raw Water Service,Section XI, Division 1,"for 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, 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.
ASME Code Case N-789, provided as Enclosure B, was approved on June 25, 2011 by the ASME Board on Nuclear Codes and Standards; however, it has not been incorporated into Nuclear Regulatory Commission (NRC) Regulatory Guide 1.147, "lnservice Inspection Code Case Acceptability, ASME Code Section XI Division 1." As such, ASME Code Case N-789 is not available for application at nuclear power plants without specific NRC approval. Therefore, FENOC requests NRC approval of the proposed alternative to implement this repair technique.
Basis for Use ASME Code Case N-789 applies to Class 2 and 3 moderate energy (that is, less than or equal to 200 degrees Fahrenheit and less than or equal to 275 pounds per square inch gauge pressure maximum operating conditions) carbon steel raw water piping. ASME Code Case N-789, footnote 1, states that:
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 alternative repair technique described in ASME Code Case N-789 involves the application of a metal reinforcing pad welded to the exterior of the piping system that either restores pressure integrity or reinforces the weakened area and restores pressure integrity. The Code case requires the design and examinations to comply with the Construction Code or ASME Code Section Ill. Reconciliation and use of editions and addenda of ASME Code Section Ill will be in accordance with ASME Code Section XI, Paragraph IWA-4220. If an edition of ASME Code Section Ill other than the Construction Code is applied, it will have been accepted by the NRC in accordance with 10 CFR 50.55a. The edition of ASME Code Section XI applicable to the BVPS-1 and BVPS-2 current 10-year inservice inspection intervals, as defined in Section 2, applies to the repair.
Request BV3-N-789 Page 3 of 5 The reinforcing pad may be either a pressure pad or a structural pad. Pressure pads are designed to retain pressure and may be used only where the piping is predicted to retain full structural integrity until the next refueling outage assuming a corrosion rate of either 2 times the actual measured corrosion rate in that location, or 4 times the estimated maximum corrosion rate for the system. Structural pads are designed for pressure plus structural reinforcement and may be used where the piping is predicted not to retain full structural integrity until the next refueling outage. In this context, "full structural integrity" means the piping maintains full capability to withstand structural (mechanical) loading for which it is designed without need for additional support or reinforcement. The appropriate repair technique will be determined based on the characterization of the degradation.
Following discovery of a through-wall flaw, the flaw will be characterized to determine the cause of the degradation. Additionally, the surrounding areas will be examined to bound the degraded area and ensure no other unacceptable locations exist which could affect the integrity of the repaired piping. The area of the reinforcing pad will be determined based on the identified degraded area. Corrosion rates will be established based on the estimated maximum corrosion rate for the system. The development of a corrosion rate based on actual thickness measurements of the degraded area is not feasible due to the time constraints associated with an emergent repair or replacement.
The established corrosion rate will be conservatively multiplied by the safety factor of four established in the Code case to ensure the design of the reinforcing pad (for example, thickness and weld size) will provide a structural or pressure boundary, as appropriate, until the next refueling outage. If the established corrosion rates are less than the actual corrosion, the short duration of the repair, along with the applicable corrosion rate safety factor and inservice monitoring defined in the Code case, provide reasonable assurance that the structural integrity and leakage integrity will be maintained during the one-cycle of application.
When welding a reinforcing pad to a leaking area, precautions will be taken as necessary, such as installation of a gasket or sealant beneath the pad, to prevent welding on wet surfaces.
Baseline thickness examinations will be performed for completed structural pads, attachment welds (except for the tapered edges), and the surrounding areas, followed by monthly thickness monitoring for the first three months, with subsequent monitoring frequency based on the results of this monitoring, but at a minimum frequency of quarterly. For structural pads on buried piping, provisions will be made for access during plant operation in order to perform these examinations.
In order to verify the leak tightness of the pressure pad, areas containing pressure pads shall 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
Request BV3-N-789 Page 4 of 5 monitoring will be accomplished by visual assessment of surrounding areas or ground surface areas above pressure pads on buried piping, or monitoring of leakage collection systems, if available.
For all reinforcing pads, regardless of when during an operating cycle they are installed, the repair will be considered to have a maximum service life of the time until the end of the next refueling outage, and by that time a permanent repair or replacement must be performed. Detailed requirements for design of reinforcement pads, installation, examination, pressure testing and inservice monitoring are provided in ASME Code Case N-789.
Based on the above, the use of ASME Code Case N-789 for temporary repairs is justified, since compliance with the requirements of ASME Code Section XI would result in hardship or unusual difficulty without a compensating increase in the level of quality or safety. 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.
- 6. Duration of Proposed Alternative:
The duration of the proposed alternative extends to the end of the first refueling outage following the end of both the BVPS-1 fourth 10-year inservice inspection interval (that began on April 1, 2008), and the BVPS-2 third 10-year inservice inspection interval (that began on August 29, 2008).
ASME Code Case N-789 reinforcing pads (structural or pressure) installed before the end of the 10-year inservice inspection interval are removed before the end of the refueling outage following their installation, even if that refueling outage occurs after the end of the 10-year interval.
- 7. Precedents:
The NRC approved a similar request to use ASME Code Case N-789 for the 10 nuclear plant sites licensed to Exelon Generation Company, LLC. The NRC letter approving the alternative is referenced below.
NRC Letter to Exelon Nuclear,
Subject:
[Associated plant names listed below]- Request to Use American Society of Mechanical Engineers Boiler and Pressure Vessel Code Case N-789, "Alternative Requirements for Pad Reinforcement of Class 2 and 3 Moderate Energy Carbon Steel Piping for Raw Water Service,Section XI, Division 1,"
[Associated TAG numbers listed below], dated May 10, 2012.
(Accession No. ML12121A637)
Plant Names: Braidwood Station, Unit Nos. 1 and 2; Byron Station, Unit Nos. 1 and 2; Clinton Power Station, Unit No.1; Dresden Nuclear Power Station, Unit Nos. 2 and 3; Lasalle County Station, Units Nos. 1 and 2; Limerick Generating Station, Unit Nos. 1 and 2; Oyster Creek Nuclear Generating Station; Peach Bottom Atomic Power
Request BV3-N-789 Page 5 of 5 Station, Unit Nos. 2 and 3; Quad Cities Nuclear Power Station, Unit Nos. 1 and 2; and Three Mile Island Nuclear Station, Unit No. 1 TAC Nos.: ME7303, ME7304, ME7305, ME7306, ME7307, ME7308, ME7309, ME7310, ME7311, ME7312, ME7313, ME7314, ME7315, ME7316, ME7317, ME7318, and ME7319)
Docket Nos.: STN 50-456, STN 50-457, STN 50-454, STN 50-455, 50-461,50-237, 50-249,50-373,50-374,50-352,50-353,50-219, 50-277, 50-278, 50-254, 50-265, and 50-289)
Enclosure 8 ASME Code Case N-789, "Alternative Requirements for Pad Reinforcement of Class 2 and 3 Moderate-Energy Carbon Steel Piping for Raw Water Service,Section XI, Division 1" (5 pages follow)
CASE CASES OF ASME BOILER AND PRESSURE VESSEL CODE N-789 Approval Date: June 25, 2011 Code Cases will remain available for use until annulled by the applicable Standards Committee.
Case N-789 (d) Additional reinforcement or repair is not permitted Alternative Requirements for Pad Reinforcement of on top of an existing reinforcing pad.
Class 2 and 3 Moderate-Energy Carbon Steel Piping (e) Reinforcing pads, including those installed during a for Raw Water Service refueling outage, shall not remain in service beyond fue Section Xlt Division 1 end of the next refueling outage.
(f) This Case may only be applied to piping not required to be ultrasonically examined for inservice inspection.
Inquiry: As an alternative to replacement or internal weld repair in accordance with IWA-4400, what require-ments may be applied for wall reinforcement of Class 2 2 INI'l'IAL EVALUATION and 3 moderate-energy carbon steel raw water1 piping (a) The material beneath the surface to which the rein-systems that have experienced internal wall thinning from forcing pad is to be applied and the adjacent area shall localized erosion, COlTosion, and cavitation or pitting? be ultrasonically measured to establish the existing wall thickness and the extent and configuration of degradation to be corrected by fue reinforcing pad.
Reply: It is tl1e opinion of the Committee that, in lieu (b) The cause and rate of degradation shall be deter-of meeting IWA-4400, areas of Class 2 and 3 moderate- mined. If the cause is determined to be flow-accelerated energy [i.e., less than or equal to 200°F (93°C) and less corrosion (FAC), corrosion-assisted cracking, or any other than or equal to 275 psig (1.9 MPa) maximum operating form of cracking, this Case shall not apply. The extent and conditions] carbon steel raw water piping experiencing rate of degradation in the piping shall be evaluated to internal wall thinning from localized erosion, corrosion, ensure that fuere are no other unacceptable locations within and cavitation or pitting may have fue wall reinforced by fue surrounding area that could affect the integrity of the applying reinforcing pads to the outside sutface of the repaired piping. The dimensions of fue surrounding area piping in accordance with the following requirements. to be evaluated shall be determined by the Owner, Excluded from these provisions are conditions involving considering the type of degradation present.
flow-accelerated corrosion (PAC), corrosion-assisted (c) The effects of the repair on the piping and any cracking, or any other form of cracking. remaining degradation shall be evaluated in accordance with IW A-4311.
1 GENERAL REQUIREMENTS 3 DESIGN (a) Application of the reinforcing pad shall be per- 3.1 Types of Reinforcing Pads fonned in accordance with a Repair/Replacement Plan sat-isfying the requirements of IWA-4150. (a) Reinforcing pads may be used for pressure only or (b) The design, materials, and installation shall meet for pressure plus structural reinforcement of thinned areas the requirements of the Construction Code and IWA-4000, including areas that do, or are expected to, penetrate the except as stated in this Case. piping wall.
(1) Pressure pads are designed to retain pressure, and (c) If the minimum required thickness of reinforcing pad necessary to satisfy the requirements of 3 is greater may be used only where the piping is predicted to retain than fue nominal thickness for the size and schedule of the full structural integrity until the next refueling outage piping, this Case shall not be used. assuming a corrosion rate of either 2 times the actual mea-sured corrosion rate in that location, or 4 times the esti-1 Raw water is defined as water such as from a river, lake, or well mated maximum corrosion rate for fue system.
or brackish/salt water; used in plant equipment, area coolers, and heat (2) Structural pads are designed for pressure plus exchangers. In many plants it is referred to as "Service Water." . structural reinforcement and may be used where fue piping 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 inservice 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 tho In service inspection of nuclear components and transport tanks. The user of the Code should refer to other pertinent codes, standards, laws, rogulatlons or other relevant documents.
1 (N-789) NC- SUPP. 6
CASE (continued)
N-789 CASES OF ASME BOILER AND PRESSURE VESSEL CODE is predicted not to retain full stmctural integrity until the applied for tees and branch connections when the toe of (
next refueling outage. the attachment weld is not less than 2.5 JRtnom from any branch reinforcement in Fig. 1.
(j) Corners of reinforcing pad plates shall be rounded 3.2 General Design Requirements -Pressure and with radii not less than the reinforcing pad thickness, and Structural Pads the toes of attachment welds at the corners shall have 1 in.
(a) The design of reinforcing pads shall be in accor- (25 mm) minimum radius.
dance with the applicable requirements of the Construction (k) The distance between toes of attachment welds and Code or Section III (NC-3100, ND-31 00 and NC-3600, other attachments or branch reinforcement (Figs. 1 and 2)
ND-3600 including Appendix II). shall not be less than the following equation:
(b) The reinforcing pad shall be sized to encompass the unacceptable area with the attachment welds located on d = 2.5 JRtnom adjacent base material of sufficient thickness to accommo-where date the design stresses.
= minimum distance between toes of fillet welds of
(
(c) The plate for the reinforcing pad shall be rolled or d otherwise formed to fit the contour of the piping to achieve adjacent fillet welded attachments proper weld fit-up. R = the outer radius of the piping (d) The thickness of the reinforcing pad shall be suffi- tnom = nominal thickness of the piping cient to maintain required thickness until the next refueling (l) When permitted by the design, suitable gasket mate-outage. rial may be applied inside the pad to prevent moisture (e) The tensile strengths of the plate and weld filler during welding (see Figs. 1 and 2).
metal for the reinforcing pad shall be at least that specified for the base metal to which it is applied.
(j) The predicted maximum degradation of the rein- 3.3 Specific Design Requirements- Pressure Pads forced piping until the next refueling outage shall be Pressure pads shall meet the requirements of 3.2, Fig. 2, included in the design. The predicted degradation of the and the following:
piping shall be based on in-situ inspection of, and estab- (a) Fillet-welded pressure pads shall be designed to
(
lished data for, similar base metals in similar environments. withstand the membrane strain of the piping in accordance If the reinforcing pad is predicted to become exposed to with the requirements of the Code specified in 3.2(a) such the raw water, the predicted degradation of the reinforcing that the following criteria are satisfied:
pad shall be based upon established data for base metals (1) The allowable membrane stress is not exceeded or weld metals with similar chemical composition to that in the piping or the pad.
used for the reinforcing pad. (2) The strain in the pad does not result in fillet weld (g) Material for reinforcing pads shall be ferdtic, with stresses exceeding allowable stresses for such welds.
welds of compatible weld filler metal. (b) Design as a reinforced opening in accordance with (h) The following factors shall be included, as applica-the Construction Code shall satisfy 3.3(a).
ble, in the design and application of the pad: (c) As an alternative to 3.3(a), pressure pads may be
( 1) shrinkage effects, if any, on the piping designed as structural pads in accordance with 3.4 or as (2) stress concentrations caused by installation of the reinforcing pad or resulting from existing and predicted prequalified designs in accordance with 3.5. (
piping internal surface configuration (3) effects of welding on any interior coating 3.4 Specific Design Requirements -Structural (4) added weight of the pad with respect to any design Pads analyses that could be affected Structural pads shall meet the requirements of3.2, Fig. 1, (i) If flexibility analysis was required by the original 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 shall shaped reinforcing pads on piping designed to NC-2650, be attached by partial penetration attachment welds (see ND-3650 and aligned parallel or perpendicular to the axis Fig. 1) that extend for a distance of at least s in each of the piping, unless a lower stress intensification factor direction beyond the area predicted, by the next refueling
[SIP or (i)] is established, an SIP (i) of 2.1 shall be applied 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 SIP 2
(i) for standard elbows, and an SIP (i) of 2.1 shall be Design thickness as prescribed by the Construction Code.
NC- SUPP. 6 2 (N-789)
CASE (continued)
CASES OF ASME BOILER AND PRESSURE VESSEL CODE N-789 FIG. 1 STRUCTURAL PAD d
Appropriate gasket material C= predicted circumferential growth of degradation L"' predicted axial growth Partial penetration attachment weld~
Ref. 3.4(a) 1+---- Required
~sI thickness tnom . freq t
bevel optional _}
'"'*--- d --~--1 Limit of branch reinforcement Minimum dimensions of plate
=predicted maximum dimensions of degradation below minimum required thickness d 0:: 2.5 ~ Rtnom S :<: 0.75JRt110 m 3.5 Prequalified Design where Application of structural pads on straight pipe, standard elbows, and associated welds shall be exempt from the R = outer radius of the component requirements of 3.2(a), provided all of the following s = 1 in. (25 mm) minimum conditions are satisfied.
tnom = nominal wall thickness of the component (a) All other requirements of 3.1, 3.2, and 3.4 are (b) The thickness of the partial penetration attachment satisfied.
welds shall equal the thickness of the pad and the edges (b) The axial length of structural pad plus width of of the welds shall be tapered to the piping sUlface at a partial penetration attachment welds shall not exceed the maximum angle (" cl' in Fig. 1) of 45 deg. greater of 6 in. (150 mm) or the outside diameter of the (c) Final configuration of the structural pad including piping.
attachment welds shall permit the examinations and evalua- (c) The finished structural pad shall be circular, oval, tions required herein, including any required preservice or or rectangular in shape.
inservice examinations of encompassed or adjacent welds. ( 1) The maximum dimension compensated by a (d) Except for the tapered edges, the structural pad plate circular structural pad shall not exceed two-thirds of the and attachment welds shall have a uniform thickness. nominal outside diameter of the piping.
3 (N-789) NC- SUPP. 6
CASE (continued)
N-789 CASES OF ASME BOILER AND PRESSURE VESSEL CODE FIG. 2 PRESSURE PAD (
2 X or 4 X predicted growth of degradation below minimum required thickness
(
Predicted growth of Appropriate gasket material degradation below minimum required thickness d ~ 2.5 ~ Rtnom Required thickness Minimum dimensions of plate __j
.. 2 x predicted maximum dimensions of degradation below minimum required thickness ( 4 x if rate based on estimate is measured)
(2) Rectangular structural pads shall be aligned (c) Provisions for venting during the final closure weld, parallel with or perpendicular to the axis of the piping. or for pressulizing for leak-testing, shall be included, if (3) For oval structural pads, the end radii shall not necessary.
be less than 0.75)Rtnom* and the axis of the structural pad (d) The surface of the attachment weld shall be pre-shaH be aligned parallel with or perpendicular to the axis pared, if necessary, by machining or glinding to permit of the piping. performance of surface and volumetric examinations required by 6. For ultrasonic examination, a surface finish 4 WATER~BACKED APPLICATIONS of 250 RMS or better is required. (
(a) Attachment welds on water backed piping shall be applied using the SMA W process with low-hydrogen 6 EXAMINATION electrodes. (a) The completed attachment weld shall be examined (b) For piping materials other than P-No. 1, Group 1, using the liquid penetrant or magnetic particle method and the surface examination required in 6 shall be performed shall satisfy the surface examination acceptance criteria for no sooner than 48 hr after completion of welding. welds of the Construction Code or Section Ill (NC-5300, ND-5300).
(b) Except for the tapered edges, partial penetration 5 INSTALLATION attachment welds, including the piping base metal upon (a) The base material in the area to be welded shall be which they are applied, shall be ultrasonically measured cleaned to bare metal. to verify acceptable wall thickness.
(b) Weld metal shall be deposited using a groove - (c) Partial penetration attachment welds shall be volu- (
welding procedure qualified in accordance with Section IX metrically examined when full penetration girth welds in and the Construction Code. the piping are required by the Construction Code to be NC- SUPP. 6 4 (N-789)
CASE (continued)
CASES OF ASME BOILER AND PRESSURE VESSEL CODE N ..789 volumetrically examined. Where configuration does not 8 INSERVICE MONITORING permit meaningful volumetric examination, the first layer, (a) Upon completion of the repair, inspections shall be each~ in. (13 mm) thickness of weld deposit, and the final surface shall be examined in accordance with 6(a) in lieu performed for structural pads, using ultrasonic or direct thickness measurement, to record the thickness of the plate, of volumetric examination.
the thickness at the attachment welds, including the under-(d) If volumetric examination is required, the full vol-lying base metal, and to the extent examinable in a 3 .in.
ume of the attachment weld, excluding the tapered edges, (75 mm) wide band, surrounding the repair, as a basehne but including the volume of base metal required for the for subsequent monitoring of the repair.
intended life of the reinforcing pad, shall be examined in (b) The Owner shall prepare a plan for additional thick-accordance with the Construction Code or Section III, using ness monitoring for structural pads using ultrasonic or either the ultrasonic or radiographic method, and shall, to direct thickness measurement to verify that minimum the depth at the smface of the piping, satisfy the acceptance design thicknesses, as required by the Construction Code criteria for weldments of the Construction Code or or Section III, are maintained until the next refueling out-Section III (NC-5320, ND-5320 or NC-5330, ND-5330).
age. The monitoring shall be monthly for the first quarter Any volume of the piping beneath the reinforcing pad and the subsequent frequency shall be based on the results that is credited in the design shall satisfy the volumetric of the monitoring activities, but at least quarterly.
acceptance criteria of Section III (NC-5320, ND-5320 or (c) If the results of the monitoring program identify NC-5330, ND-5330), as applicable.
leakage or indicate that the structural margins required by 3 will not be maintained until the next refueling outage, additional repair/replacement activities not prohibited by 7 PRESSURE TESTING l(d) shall be performed prior to encroaching upon the In lieu of IWA-4540, a system leakage test of the repair/ design limits.
replacement activity shall be performed in accordance with (d) Reinforcing pads shall not remain in service beyond IWA-5000 prior to, or as part of, returning to service. the end of the next refueling outage.
5 (N-789) NC- SUPP. 6