HNP-12-054, Relief Request I3R-09 Reactor Vessel Closure Head Nozzles Inservice Inspection Program - Third Interval

Relief Request I3R-09 Reactor Vessel Closure Head Nozzles Inservice Inspection Program - Third Interval

ML12131A663
Person / Time
Site:	Harris
Issue date:	05/03/2012
From:	Corlett D Progress Energy Carolinas
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
HNP-12-054
Download: ML12131A663 (26)

Text

~ Progress Energy Serial: HNP-12-054 HAY 3 2012 10 CFR 50.55a ATIN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555 -0001 Shearon Harris Nuclear Power Plant, Unit No. I Docket No. 50-400 I Renewed License No. NPF-63

Subject:

Relief Request J3R-09 Reactor Vessel Closure Head Nozzles Inservice Inspection Program - Third Interval Ladies and Gentlemen:

Pursuant to 10 CFR 50.55a(a)(3)(i), Caro li na Power & Light Company (CP&L), doing business as Progress Energy Carolinas, Inc., hereby requests NRC approval of the attached relief request for the Shearon Harris Nuclear Power Plant, Unit No .1 inservice inspection program, third ten-year interval. CP&L proposes to repair reactor vessel closure head nozzle penetrations utilizing the inside diameter temper bead welding method and has detennined that repair of the nozzle penetrations, utilizing the alternatives specified in this request, will provide an acceptable level of quality and safety. The request describes four nozzles to be repaired. The inspection of the nozzles is not yet complete, so the scope could expand through a supplement to this request.

Relief is requested in accordance with 10 CFR 50.55a(a)(3)(i).

CP&L requests approval of this request by May 18, 20 12, to support startup from the current refueling outage.

Th is document contains no new regulatory comm itments.

Please refer any questions regarding thi s submittal to me at (9 19) 362-3 137.

Sincerely, David H. Corlett Supervisor, Licensing/Regulatory Programs Harris Nuclear Plant

Enclosure:

Relief Request I3R-09 Reactor Vessel Closure Head Nozzles cc: Mr. J. D. Austin, NRC Sr. Resident Inspector, HNP Ms. A. T. Billoch Colon, NRC Project Manager, HNP Mr. V. M. McCree, NRC Regional Administrator, Region" Progress Energy Carolinas. Inc.

11""'5 Nuclear Plilill PO Box lG5 NBW H.II. NC 77562

U.S. Nuclear Regulatory Commission Page 2 HNP-12-054 bcc:

Mr. C. L. Burton Mr. J. M. Griffin Mr. D. T. Conley Mr. E. J. Harkness Mr. D. H. Corlett Mr. E. J. Kapopoulos Jr.

Mr. J. D. Dufner Mr. B. C. McCabe Mr. V. DSouza Mr. G. D. Miller Mr. D. G. Eisenhut Mr. W. T. Russell Mr. D. L. Griffith Mr. J. Scarola HNP NOS NTA Licensing Files (2 copies)

Nuclear Records

U.S. Nuclear Regulatory Commission Relief Request I3R-09 HNP-12-054 Enclosure Page 1 of 24 HNP-12-054 Enclosure Shearon Harris Nuclear Power Plant / Unit No. 1 Docket No. 50-400 / Renewed License No. NPF-63 Relief Request I3R-09 Reactor Vessel Closure Head Nozzles Inservice Inspection Program - Third Ten-Year Interval

U.S. Nuclear Regulatory Commission Relief Request I3R-09 HNP-12-054 Enclosure Page 2 of 24 Proposed Alternative in Accordance with 10 CFR 50.55a(a)(3)(i)

- Alternative Provides Acceptable Level of Quality and Safety -

1. ASME Code Components Affected Components: Reactor Vessel Closure Head Penetration Nozzles 5, 17, 38, and 63.

Code Class: Class 1 Examination Category: B-P Code Item Number: B4.20 (Code Case N-729-1, Alternative Examination Requirements for PWR Reactor Vessel Upper Heads with Nozzles Having Pressure-Retaining Partial-Penetration Welds,Section XI, Division 1

==

Description:==

Reactor Vessel Closure Head Penetration Nozzles Size: 4 Inch Nominal Outside Diameter Material: Inconel SB-167

2. Applicable Code Edition and Addenda Shearon Harris Nuclear Power Plant, American Society of Mechanical Engineers Unit No. 1 (HNP), Inservice Inspection Boiler and Pressure Vessel Code Program (ISI) - Third Interval (ASME Code) Section Xl, 2001 Edition through 2003 Addenda Shearon Harris Nuclear Power Plant, American Society of Mechanical Engineers Unit No. 1, Reactor Vessel Closure Boiler and Pressure Vessel Code Section III, Head Code of Construction 1971 Edition through Winter 1971 Addenda

3. Applicable Code Requirements ASME Code, Section Xl, 2001 Edition through 2003 Addenda IWA-4221(b) states:

An item to be used for repair/replacement activities shall meet the Construction Code specified in accordance with (1), (2) or (3) below.

U.S. Nuclear Regulatory Commission Relief Request I3R-09 HNP-12-054 Enclosure Page 3 of 24 ASME Code, Section Xl, 2001 Edition through 2003 Addenda IWA-4221(c) states in part:

As an alternative to (b) above, the item may meet all or portions of the requirements of different Editions and Addenda of the Construction Code, or Section IIIprovided the requirements of IWA-4222 through IWA-4226, as applicable, are met..

ASME Code, Section Xl, 2001 Edition through 2003 Addenda, subarticle IWA-4400 provides welding, brazing, metal removal, and installation requirements related to repair/replacement activities.

ASME Code, Section Xl, 2001 Edition through 2003 Addenda IWA-4411states:

Welding, brazing, and installation shall be performed in accordance with the Owners Requirements and, except as modified below, in accordance with the Construction Code of the item.

ASME Code, Section Xl, 2001 Edition through 2003 Addenda IWA-4411(a) states in part:

Later editions and addenda of the Construction Code, or a later different Construction Code, either in its entirety or portions thereof, and Code Cases may be used, provided the substitution is as listed in IWA-4221(c).

ASME Code, Section Xl, 2001 Edition through 2003 Addenda IWA-4610(a) states in part:

Thermocouples and recording instruments shall be used to monitor the process temperatures.

Code Case N-638-1, Similar and Dissimilar Metal Welding Using Ambient Temperature Machine GTAW Temper Bead Technique, provides requirements for automatic or machine gas tungsten arc welding (GTAW) of Class 1 components without the use of preheat or postweld heat treatment.

Code Case N-638-1 paragraph 3.0(d) states:

The maximum interpass temperature for field applications shall be 350° F regardless of the interpass temperature during qualification.

Code Case N-638-1 paragraph 4.0(b) states:

The final weld surface and the band around the area defined in paragraph 1.0(d) shall be examined using a surface and ultrasonic methods when the completed weld has been at ambient temperature for at least 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br />. The ultrasonic examination shall be in accordance with Appendix I.

Code Case N-729-1, Alternative Examination Requirements for PWR Reactor Vessel Upper Heads with Nozzles Having Pressure-Retaining Partial-Penetration WeldsSection XI, Division 1, Fig. 2, Examination Volume for Nozzle Base Metal and Examination Area for Weld and Nozzle Base Metal, is applicable to the RVCH nozzle penetrations.

U.S. Nuclear Regulatory Commission Relief Request I3R-09 HNP-12-054 Enclosure Page 4 of 24 ASME Code, Section Xl, 2001 Edition through 2003 Addenda IWA-4611.1(a) states:

Defects shall be removed in accordance with IWA-4422.1. A defect is considered removed when it has been reduced to an acceptable size.

ASME Code, Section Xl, 2001 Edition through 2003 Addenda, IWA-3300 specifies requirements for characterization of flaws detected by inservice examination.

ASME Code, Section Xl, 2001 Edition through 2003 Addenda, IWB-3420 states:

Each detected flaw or group of flaws shall be characterized by the rules of IWA-3300 to establish the dimensions of the flaws. These dimensions shall be used in conjunction with the acceptance standards of IWB-3500.

ASME Code, Section Xl, 2001 Edition through 2003 Addenda IWB-3132.3 states:

A component whose volumetric or surface examination detects flaws that exceed the acceptance standards of Table IWB-3410-1 is acceptable for continued service without a repair/replacement activity if an analytical evaluation, as described in IWB-3600, meets the acceptance criteria of IWB-3600. The area containing the flaw shall be subsequently reexamined in accordance with IWB-2420 (b) and (c).

4. Reason for Request Flaw indications requiring repair have been detected during examination of the HNP Reactor Vessel Closure Head (RVCH) nozzle penetrations. Four nozzles (5, 17, 38, and 63) will be repaired under this request. Figure 10 shows the relative locations of the four nozzles on the RVCH. Table 1 provides information on the flaws leading to the repair activity. All flaws are in the tube outside diameter (OD) extending inward toward the tube inside diameter (ID) and are approximately parallel with the nozzle axis (axially oriented) at the lower toe side of the weld.

Because of the risk of damage to the RVCH material properties or dimensions, it is not feasible to apply the post welding heat treatment requirements of the original Construction Code. As an alternative to the requirements of RVCH Code of Construction, ASME Section III, 1971 including Addenda through Winter 1971, CP&L proposes to perform the repair of the RVCH nozzle penetrations utilizing the Inside Diameter Temper Bead (IDTB) welding method to restore the pressure boundary of the degraded nozzle penetration(s). The IDTB welding method is performed with a remotely operated weld tool, utilizing the machine GTAW process and the ambient temperature temper bead method with 50° F minimum preheat temperature and no post weld heat treatment. The repairs will be performed in accordance with the 2001 Edition through the 2003 Addenda of ASME Section XI, Code Case N-638-1, Code Case N-729-1, and the alternatives discussed below.

U.S. Nuclear Regulatory Commission Relief Request I3R-09 HNP-12-054 Enclosure Page 5 of 24 Basic steps for the IDTB repair are:

1. Removal of lower portion of existing Thermal Sleeve Assembly at applicable penetrations to provide access for IDTB weld repair.

2. Roll expansion above the area of repair. This stabilizes the nozzle to prevent any movement when the nozzle is separated from the nozzle to RVCH J-groove weld.

3. Machining to remove the nozzle to above the J-groove weld eliminating the portions of the nozzle containing unacceptable indications. This machining operation also establishes the weld prep area (Refer to Figure 1).

4. Liquid penetrant (PT) examination of the machined area (Refer to Figure 3).

5. Welding the remaining portion of the nozzle to the RVCH using primary water stress corrosion cracking (PWSCC) resistant Alloy 52M weld material (Refer to Figure 2). Alloy 82 weld material may be used at the interface between the Alloy 182 existing weld and the Alloy 52M new weld if necessary.

6. Machining the weld and nozzle to provide a surface suitable for nondestructive examination (NDE).

7. PT and ultrasonic (UT) examination of the weld and adjacent area (Refer to Figure 3).

8. Abrasive water jet machining remediation on the portion of the remaining nozzle most susceptible to PWSCC. The abrasive water jet machining process removes a small amount of material thickness while imposing compressive residual stress on the nozzle surface.

9. Welding in of new Lower Thermal Sleeve Assembly at applicable locations.

Note that the figures included in this request are provided to assist in clarifying the description above. The location of the weld relative to the inner and outer radii of the head, and the existing J-groove weld will vary depending upon the location of the nozzle and as-found dimensions.

CP&L has determined that repair of the RVCH nozzle penetrations utilizing the alternatives specified in this request will provide an acceptable level of quality and safety. Relief is requested in accordance with 10 CFR 50.55a(a)(3)(i).

U.S. Nuclear Regulatory Commission Relief Request I3R-09 HNP-12-054 Enclosure Page 6 of 24

5. Proposed Alternative and Basis for Use

a. Monitoring of Interpass Temperature Code Case N-638-1 paragraph 3.0(d) states:

The maximum interpass temperature for field applications shall be 350° F regardless of the interpass temperature during qualification.

Code Case N-638-1 states that all other requirements of IWA-4000 must be met when using this Case. IWA-4610(a) requires that thermocouples and recording instruments be used to monitor process temperatures. Direct interpass temperature measurement is impractical to perform during welding operations from inside the RVCH nozzle penetration bore. The maximum interpass temperature will be determined by one of the following methods:

(1) Heat-flow calculations, using at least the variables listed below.

(a) Welding heat input (b) Initial base material temperature (c) Configuration, thickness, and mass of the item being welded (d) Thermal conductivity and diffusivity of the materials being welded (e) Arc time per weld pass and delay time between each pass (f) Arc time to complete the weld (2) Measurement of the maximum interpass temperature on a test coupon that is no thicker than the item to be welded. The maximum heat input of the welding procedure shall be used in welding the test coupon.

This methodology is consistent with the associated requirements specified in Code Case N-638-2 and subsequent versions. Alternatives to Code Case N-638-1 interpass temperature monitoring requirements have been previously approved by the NRC for dissimilar metal weld overlays in HNP Inservice Inspection Relief Request I3R-1, ADAMS Accession Number ML072760737.

CP&L requests relief from using thermocouples and recording instruments to verify process temperatures.

U.S. Nuclear Regulatory Commission Relief Request I3R-09 HNP-12-054 Enclosure Page 7 of 24

b. Acceptance Examination Area Code Case N-638-1 paragraph 4.0(b) states in part:

The final weld surface and the band around the area defined in paragraph 1.0(d) shall be examined using a surface and ultrasonic methods Code Case N-638-1 paragraph 1.0(d) defines the area requiring preheat, and therefore examination, as the area to be welded and the band around the area of at least 1.5 times the component thickness or five inches, whichever is less.

The band includes an annular area extending five inches around the penetration bore on the inside surface of the RVCH. The purpose for the examination of the band is to ensure all flaws associated with the weld repair area have been removed, or addressed, since these flaws may be associated with the original flaw and may have been overlooked. For this modification, the repair welding is performed remote from the known flaws.

The band around the area defined in paragraph 1.0(d) cannot be examined due to the physical configuration of the partial penetration weld. The alternative final examination of the new weld and immediate surrounding area within the bore will be sufficient to verify that defects have not been induced in the low alloy steel RVCH material due to the welding process and will assure integrity of the nozzle and the new weld. Figure 3 identifies the areas for PT and UT examination of the modified nozzle penetration. UT examination will be performed by scanning from the inner diameter surface of the weld. The UT examination is qualified to detect construction type flaws in the new weld and base metal interface beneath the new weld. UT examination acceptance criteria will be in accordance with ASME Section III, 2001 Edition, including Addenda through 2003, NB-5330. The extent of the examination is consistent with Construction Code requirements.

Scanning is performed from the inside surface of the new weld and the adjacent portion of the nozzle, excluding the weld taper. The volume of interest for UT examination extends from at least one inch above the new weld and into the RVCH low alloy steel base material beneath the weld, to at least one-quarter inch depth. The PT examination area includes the weld surface and extends upward on the nozzle inside surface to include the area required by Code Case N-729-1, Figure 2 and at least one-half inch below the new weld. Figure 3 of this request identifies the area for PT examination of the modified nozzle penetration after machining and before welding.

ASME Section III, 2001 Edition including Addenda through 2003, NB-5245, specifies progressive surface examination of partial penetration welds. The original Construction Code requirement for progressive PT examination, in lieu of volumetric examination, was because volumetric examination is not practical for the conventional partial penetration weld configurations. For this modification the weld, except for the taper transition, is suitable for UT examination and a final surface PT examination can be performed as shown in Figure 3.

Code Case N-638-1, Paragraph 4.0(b) requires that the specified volumetric examination be in accordance with Section XI, Appendix I. Paragraph 4.0(e) specifies acceptance criteria to be in accordance with IWB-3000.

U.S. Nuclear Regulatory Commission Relief Request I3R-09 HNP-12-054 Enclosure Page 8 of 24 ASME Code, Section Xl, 2001 Edition through 2003 Addenda, IWB-3000 does not have any acceptance criteria that directly apply to the partial penetration weld configuration. Regulatory Guide 1.147 Rev. 15 has conditionally approved Code Case N-638-1 with the condition that UT volumetric examinations be performed with personnel and procedures qualified for the repaired volume and qualified by demonstration using representative samples which contain construction type flaws. The acceptance criteria of NB-5330, in ASME Section III, 2001 Edition through 2003 Addenda, will apply to all flaws identified within the repaired volume.

ASME Section III, 2001 Edition including Addenda through 2003, NB-5245 requires incremental and final surface examination of partial penetration welds. Due to the welding layer deposition sequence (i.e., each layer is deposited parallel to the penetration centerline), the specific requirements of NB-5245 cannot be met. The Construction Code requirement for progressive surface examination is because volumetric examination is not practical for conventional partial penetration weld configurations. For this modification, the repair weld is suitable, except for the taper transition, for UT examination and a final surface examination.

The final examination of the repair weld and immediate surrounding area will be sufficient to verify that defects have not been induced in the ferritic low alloy steel RVCH base material due to the welding process. PT examination coverage is shown in Figure 3. UT examination will be performed scanning from the inside surface of the weld, excluding the transition taper portion at the bottom of the weld, and adjacent portion of the nozzle bore. The UT examination is qualified to detect flaws in the new weld and base metal interface in the repair region, to the maximum practical extent.

The UT transducers and delivery tooling are capable of scanning from cylindrical surfaces with inside diameters near 2.75 inches. The UT equipment is not capable of scanning from the face of the weld taper. The scanning is performed using 0° L-wave, 45° L-wave, and 70° L-wave transducers. Approximately 70% of the weld surface will be scanned by UT. Approximately 83% of the RVCH ferritic steel heat affected zone will be covered by UT. The UT examination coverage volumes are shown in Figures 4 through 8 for the various scans.

Examination of the area depicted in Figure 3 will assure that all unacceptable flaws associated with the weld repair area have been removed.

CP&L requests relief from examination of the area defined in Code Case N-638-1, paragraph 1.0(d).

c. 48 Hour Hold Code Case N-638-1 paragraph 4.0(b) states in part:

The final weld surface and the band around the area defined in paragraph 1.0(d) shall be examined using a surface and ultrasonic methods when the completed weld has been at ambient temperature for at least 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br />

U.S. Nuclear Regulatory Commission Relief Request I3R-09 HNP-12-054 Enclosure Page 9 of 24 Hydrogen cracking is a form of cold cracking. It is produced by the action of internal tensile stresses acting on low toughness heat affected zones. The internal stresses are produced from localized build-ups of monatomic hydrogen. Monatomic hydrogen forms when moisture or hydrocarbons interact with the welding arc and molten weld pool. The monatomic hydrogen can be entrapped during weld solidification and tends to migrate to transformation boundaries or other microstructure defect locations. As concentrations build, the monatomic hydrogen recombines to form molecular hydrogen - thus generating localized internal stresses at these internal defect locations. If these stresses exceed the fracture toughness of the material, hydrogen induced cracking occurs. This form of cracking requires the presence of hydrogen and low toughness materials. It is manifested by intergranular cracking of susceptible materials and normally occurs within 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> of welding.

The machine GTAW process is inherently free of hydrogen. Unlike the shielded metal arc welding process, GTAW filler metals do not rely on flux coverings that may be susceptible to moisture absorption from the environment. Conversely, the GTAW process utilizes dry inert shielding gases that cover the molten weld pool from oxidizing atmospheres. Any moisture on the surface of the component being welded is vaporized ahead of the welding torch. The vapor is prevented from being mixed with the molten weld pool by the inert shielding gas that blows the vapor away before it can be mixed. Furthermore, modern filler metal manufacturers produce wires having very low residual hydrogen. This is important because filler metals and base materials are the most realistic sources of hydrogen for the automatic or machine GTAW temper bead welding. Therefore, the potential for hydrogen-induced cracking is greatly reduced by using the machine GTAW process. Extensive research has been performed by EPRI. EPRI Report 1013558, Temperbead Welding Applications, 48 Hour Hold Requirements for Ambient Temperature Temperbead Welding (ML070670060) provides justification for starting the 48-hour hold after completing the third temper bead weld layer rather than waiting for the weld to cool to ambient temperature.

CP&L requests relief from commencing the 48 hour5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> hold period when the weld reaches ambient temperature. The 48 hour5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> hold period will commence upon completion of the third weld layer.

This approach has been previously considered by the NRC staff in the conditional approval of N-638-4 in Rev. 16 of Regulatory Guide 1.147 when using austenitic materials and for dissimilar metal weld overlays in the approval of HNP Relief Request I3R-1, ADAMS Accession Number ML072760737.

d. Triple Point Anomaly ASME Section III, 2001 Edition including Addenda through 2003, NB-5330(b) states:

Indications characterized as cracks, lack of fusion, or incomplete penetrations are unacceptable regardless of length.

An artifact of ambient temperature temper bead welding is an anomaly in the weld at the triple point. The triple point is the point in the repair weld where the low alloy steel RVCH base material, the Alloy 600 nozzle, and the Alloy 52M weld intersect. The location of the triple

U.S. Nuclear Regulatory Commission Relief Request I3R-09 HNP-12-054 Enclosure Page 10 of 24 point anomaly is shown in Figure 2. This anomaly consists of an irregularly shaped very small void. Mock-up testing has verified that the anomalies are common and do not exceed 0.10 inches in length and are assumed to exist, for purposes of analysis, around the entire bore circumference at the triple point elevation.

A fracture mechanics analysis has been performed for the design configuration to provide justification, in accordance with Section XI, for operating with the postulated triple point anomaly. The anomaly is modeled as a 0.10 inch, circular crack-like defect, extending 360 degrees around the circumference at the triple point location, considering the most susceptible material for propagation. Postulated flaws could be oriented within the anomaly such that there are two possible flaw propagation paths, as discussed below.

Path 1: Flaw propagation is across the nozzle wall thickness from the OD to the ID of the nozzle housing (analysis paths 1 & 2).

This is the shortest path through the new Alloy 52M weld material. By using a fatigue crack growth rate twice that of the rate of Alloy 600 material, it is ensured that another potential path through the heat affected zone between the new repair weld and the Alloy 600 nozzle material is also bounded.

For completeness, two types of flaws are postulated at the outside surface of the nozzle IDTB repair weld. A 360 degree continuous circumferential flaw, lying in a horizontal plane, is considered to be a conservative representation of crack-like defects that may exist in the weld triple point anomaly. This flaw is subjected to axial stresses in the nozzle. An axially oriented semi-circular outside surface flaw is also considered since it would lie in a plane normal to the higher circumferential stresses. Both of these flaws would propagate toward the inside surface of the nozzle.

Path 2: Flaw propagation extends down the outside surface of the repair weld between the weld and the RVCH (analysis paths 3 through 6).

A cylindrically oriented flaw is postulated to lie along this interface, subjected to radial stresses with respect to the nozzle. This flaw may propagate through either the new Alloy 52M weld material or the low alloy steel RVCH base material.

The results of the analyses demonstrate that the 0.10 inch weld anomaly is acceptable for a 40 year design life of the HNP nozzle repair. The minimum fracture toughness margins for flaw propagation Paths 3 through 6 have been shown to be acceptable compared to the required margins of 10 for normal/upset conditions and 2 for emergency/faulted (and test) conditions per Section XI, IWB-3612. A limit load analysis was performed considering the ductile weld repair material along flaw propagation Path 1 & 2. The analysis showed that for the postulated circumferential flaw the minimum margin on allowable stress is 1.43. For the axial flaw the minimum margin on allowable flaw depth is 3.9. Fracture toughness margins have also been demonstrated for the postulated cylindrical flaws. For the cylindrical flaws, it is shown that the applied shear stress at the remaining ligament is less than the allowable shear stress per NB-3227.2.

U.S. Nuclear Regulatory Commission Relief Request I3R-09 HNP-12-054 Enclosure Page 11 of 24 This evaluation is prepared in accordance with ASME Section XI and demonstrates that for the intended service life of the repair, the fatigue crack growth is acceptable and the crack-like indications remain stable. This satisfies the ASME Section XI criteria but does not include considerations of stress corrosion cracking such as PWSCC. Since the crack-like defects due to the weld anomaly are not exposed to the primary coolant and the air environment is benign for the materials at the triple point, the time-dependent crack growth rates from PWSCC are not applicable.

Relief is requested to permit anomalies, as described herein, at the triple point area to remain in service.

e. Flaw Characterization and Successive Examinations - RVCH Original J-Groove Weld The assumptions of IWB-3600 are that cracks are fully characterized in order to compare the calculated parameters to the acceptable parameters addressed in IWB-3500. The original nozzle-to-RVCH J-groove weld is extremely difficult to examine with UT due to the compound curvature and fillet radius around the nozzle circumference. These conditions preclude ultrasonic coupling and control of the sound beam needed to perform flaw sizing with reasonable confidence in the measured flaw dimensions. Therefore, it is impractical to characterize the flaw geometry that may exist therein. As these J-groove welds have not been examined, they are assumed to have unacceptable flaws.

The J-groove flaws have been evaluated for acceptance in accordance with the analytical evaluation requirements of IWB-3132.3 using worst-case postulated flaw sizes. The results of this evaluation show that, based on a combination of linear elastic and elastic-plastic fracture mechanics analysis of a postulated remaining flaw in the original Alloy 182 J-groove weld and butter material, the HNP RVCH nozzle repair design configuration is considered to be acceptable for 30 years of operation following an IDTB weld repair.

Successive examinations required by IWB-3132.3 will not be performed because analytical evaluation of the worst-case postulated flaw is performed to demonstrate the acceptability of continued operation. A reasonable assurance of the RVCH structural integrity is maintained without the successive examination by the fact that evaluation has shown the worst case flaw to be acceptable for continued operation.

Relief is requested from flaw characterization and subsequent examination requirements.

The potential for debris from a cracking J-groove partial penetration weld was considered.

Radial cracks were postulated to occur in the weld due to the dominance of hoop stresses at this location. This possibility of occurrence of transverse cracks that could intersect the radial cracks is considered remote. There are no forces that would drive a transverse crack. The radial cracks would relieve the potential transverse crack driving forces. Hence it is unlikely that a series of transverse cracks could intersect a series of radial cracks resulting in any fragments becoming dislodged.

U.S. Nuclear Regulatory Commission Relief Request I3R-09 HNP-12-054 Enclosure Page 12 of 24

f. Inservice Inspections Code Case N-729-1 provides requirements for the inservice inspection of RVCHs with nozzles having partial penetration welds. Code Case N-729-1 Table 1, Item 4.20, permits either volumetric or surface examination. Item 4.20 examination requirements are specified in Figure 2 of Code Case N-729-1. The repair proposed by this relief request removes much of the examination area depicted in this figure at several locations. Figure 9 of this relief request will be used to establish the examination area for the preservice inspection following repair and for future inservice inspections. This examination area is equivalent to that required by Figure 2 in Code Case N-729-1, as it examines the nozzle weld and the same area above the nozzle weld as would be required by Figure 2 in the Code Case.

Therefore, inservice inspection will comply with Code Case N-729-1 as modified by 10 CFR 50.55a(g)(6)(ii)(D) and as depicted in Figure 9.

g. General Corrosion Impact on Exposed Low Alloy Steel The IDTB nozzle repair leaves a small portion of low alloy steel in the RVCH exposed to primary coolant. An evaluation was performed for the potential corrosion concerns at the RVCH low alloy steel (LAS) wetted surface. Galvanic corrosion, hydrogen embrittlement, SCC, and crevice corrosion are not expected to be a concern for the exposed LAS base metal. General corrosion of the exposed LAS base metal will occur in the area between the IDTB weld and the J-groove weld. The general corrosion rate is conservatively estimated to be 0.0036 inch/year.

The corrosion of the exposed base metal has negligible impact on the RVCH and is acceptable for 40 years from the time the modification is installed.

CONCLUSIONS Implementation of an IDTB repair to the RVCH nozzle penetrations will produce an effective repair that will restore and maintain the pressure boundary integrity of the HNP RVCH. Similar repairs have been performed successfully and have been in service for several years without any known degradation. The alternative provides improved structural integrity and reduced likelihood of leakage for the primary system. Accordingly, the use of the alternative provides an acceptable level of quality and safety in accordance with 10 CFR 50.55a(a)(3)(i).

6. Duration of Proposed Alternatives The analyses described above and others in the modification that will be implemented under 10 CFR 50.59 support a design life expectancy of 14.8 effective full power years. The analysis results are based upon expected repair parameters which may vary during implementation. The design lifetime is sensitive to the length of the alloy 52M weld ligament, and the actual limiting ligament length may vary from nozzle to nozzle depending upon the as-found and as-left

U.S. Nuclear Regulatory Commission Relief Request I3R-09 HNP-12-054 Enclosure Page 13 of 24 conditions. The design life will be re-evaluated if necessary using as-built data and incorporated into the modification, future NDE inspection schedules, and asset management plans. CP&L plans to replace the RVCH prior to exceeding the design life of the repair.

The provisions of this relief are applicable to the third ten-year inservice inspection interval for HNP which commenced on May 2, 2007 and will end on May 1, 2017. The repairs installed in accordance with the provisions of this relief shall remain in place for the design life of the repair, until another alternative is approved by the NRC, or until the RVCH is replaced.

7. Precedents

1. Davis-Besse Nuclear Power Station Relief Request RR-A34, April 1, 2010, ADAMS Ascension Number ML100960276.

2. Calvert Cliffs Nuclear Power Plant Relief Request RR-PZR-0 1, January 31, 2011, ADAMS Ascension Number ML110340059

8. References

1. EPRI Report 1013558, Temperbead Welding Applications, 48 Hour Hold Requirements for Ambient Temperature Temperbead Welding, EPRI, Palo Alto, CA and Hermann &

Associates, Key Largo, FL, December 2006.

2. ASME Code Case N-638-1 Similar and Dissimilar Metal Welding Using Ambient Temperature Machine GTAW Temper Bead Technique,Section XI, Division 1.

3. NRC Regulatory Guide 1.147, Revision 15, Inservice Inspection Code Case Acceptability, ASME Section XI, Division 1.

4. ASME Code Case N-729-1 Alternative Examination Requirements for PWR Reactor Vessel Upper Heads With Nozzles Having Pressure-Retaining Partial-Penetration Welds,Section XI, Division 1.

U.S. Nuclear Regulatory Commission Relief Request I3R-09 HNP-12-054 Enclosure Page 14 of 24 Figure 1. Machining

U.S. Nuclear Regulatory Commission Relief Request I3R-09 HNP-12-054 Enclosure Page 15 of 24 Figure 2. Welding

U.S. Nuclear Regulatory Commission Relief Request I3R-09 HNP-12-054 Enclosure Page 16 of 24 Figure 3. Examination Areas Pre-Weld PT l-m-n-o-p-q Post-Weld PT m-n-s-p-q-r Post-Weld UT (Weld) a-b-c-d-e-h Post Weld UT (Nozzle Material) e-f-g-h

U.S. Nuclear Regulatory Commission Relief Request I3R-09 HNP-12-054 Enclosure Page 17 of 24 Figure 4. UT 0° and 45° L-wave Beam Coverage Looking Clockwise and Counter-clockwise

U.S. Nuclear Regulatory Commission Relief Request I3R-09 HNP-12-054 Enclosure Page 18 of 24 Figure 5. UT 45° L-wave Beam Coverage Looking Down

U.S. Nuclear Regulatory Commission Relief Request I3R-09 HNP-12-054 Enclosure Page 19 of 24 Figure 6. UT 45° L-wave Beam Coverage Looking Up

U.S. Nuclear Regulatory Commission Relief Request I3R-09 HNP-12-054 Enclosure Page 20 of 24 Figure 7. UT 70° L-wave Beam Coverage Looking Down

U.S. Nuclear Regulatory Commission Relief Request I3R-09 HNP-12-054 Enclosure Page 21 of 24 Figure 8. UT 70° L-wave Beam Coverage Looking Up

U.S. Nuclear Regulatory Commission Relief Request I3R-09 HNP-12-054 Enclosure Page 22 of 24 Figure 9. PSI and ISI Weld and Nozzle Base Metal Surface Examination Area (A-B-C-D)

U.S. Nuclear Regulatory Commission Relief Request I3R-09 HNP-12-054 Enclosure Page 23 of 24 Figure 10. Locations of Nozzles Being Repaired

U.S. Nuclear Regulatory Commission Relief Request I3R-09 HNP-12-054 Enclosure Page 24 of 24 Ind. Depth Thru Orientation Nozzle No. ID/OD to Ind. Wall Length Azimuth Ax/Circ Type 5 1 OD 0.408 0.218 0.56 323° Ax PWSCC 1 OD 0.396 0.230 0.41 5° Ax PWSCC 17 2 OD 0.473 0.153 0.11 26° Ax PWSCC 3 OD 0.476 0.150 0.26 353° Ax PWSCC 1 OD 0.302 0.324 0.74 359° Ax PWSCC 38 2 OD 0.463 0.163 0.37 92° Ax PWSCC 1 OD 0.361 0.265 0.52 233° Ax PWSCC 63 2 OD 0.484 0.142 0.19 282° Ax PWSCC Notes:

1. All flaws are in the tube outside diameter (OD) extending inward toward the tube inside diameter (ID) and are approximately parallel with the nozzle axis (axially oriented) at the lower toe side of the weld.

2. 0° Azimuth is the lowest point (downhill) on the nozzle. Progression is CCW looking up.

3. Tube diameter, OD 4.002", ID 2.750". Thickness, 0.626" Nom.

4. Dimensions are in inches.

5. Scans performed from the tube ID. Flaws are located at the OD.

Table 1. Flaw Characteristics