ML040260237
| ML040260237 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 01/22/2004 |
| From: | Scherer A Southern California Edison Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| EA-03-009 | |
| Download: ML040260237 (8) | |
Text
SOUTHERN CALIFORNIA I EDISON An 0DISON ITERNATION.V L-Company A. Edward Scherer Manager of Nuclear Regulatorv Affairs January 22, 2004 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555
Subject:
Third Ten-Year Inservice Inspection (ISIj Interval Relief Request ISI-3-10 Regarding American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code Case N-638 Similar and Dissimilar Metal Welding Using Ambient Temperature Machine Gas Tungsten Arc Welding (GTAW) Temper Bead Technique to Support Potential Reactor Vessel Head Repairs.
San Onofre Nuclear Generating Station, Units 2 and 3
Dear Sir or Madam,
This letter submits Southern California Edison (SCE) Company's Relief Request ISI-3-10 to obtain permission to perform repair welding using the ambient temperature machine GTAW temper bead technique.
SCE will be performing inspections as required by the February 11, 2003, NRC Order EA-03-009, "Issuance of Order Establishing Interim Inspection Requirements for Reactor Pressure Vessel Head at Pressurized Water Reactors." SCE may need the option of using the ambient temperature machine GTAW temper bead technique in the event repairs are required in the reactor pressure vessel head penetrations and/or the attachment welds.
If repair of a reactor pressure vessel head penetration in Unit 2 is needed, SCE expects to identify that on or about February 26, 2004. If the ambient temperature machine GTAW temper bead technique is required, SCE will need approval of this relief request prior to return to Mode 4, which is currently scheduled for March 15, 2004.
P.O. Box 128 San Clemente, CA 92674-0128 949-368-7501 Fax 949-368-7575 koqq
Document Control Desk January 22, 2004 Should you have any questions, please contact Mr. Jack Rainsberry, Manager, Plant Licensing at (949) 368-7420.
Sincerely, Enclosure cc:
B. S. Mallett, Regional Administrator, NRC Region IV B. M. Pham, NRC Project Manager, San Onofre Units 2, and 3 C. C. Osterholtz, NRC Senior Resident Inspector, San Onofre Units 2 & 3
ENCLOSURE Relief Request ISI-3-10 Request to use the Ambient Temperature Machine GTAW Temper Bead Technique
Proposed Alternative In Accordance with 10 CFR 50.55a(a)(3)(i)
Alternative Provides Acceptable Level of Quality and Safety 1.0 ASME Code Component Affected Reactor Pressure Vessel Head (RPVH), an American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code, Section
, Subsection NB (Class 1) component and includes penetration nozzles for Control Element Drive Mechanisms (CEDM), 91 each, In-Core Instruments (ICI), 10 each, and RPVH vent, one each.
2.0
Applicable Code Edition and Addenda
The Construction Code of Record for Reactor Pressure Vessel Head, ASME Section III, Subsection NB, 1971 Edition through the Summer 1971 Addenda The Third Ten-Year Inservice Inspection Interval Code of Record, ASME Section XI, Division 1, 1995 Edition through the 1996 Addenda 3.0 AoPlicable Code Requirements The topic of this relief request is the potential for repair welding on or within 1/8" of the SA-533 grade B (P-Number 3) ferritic base material of the RPVH in conjunction with repairs to the penetration nozzle or the attachment J-groove welds. The potential repair areas contain P-Number 3 base material and F-Number 43 butter.
The primary ASME Code Section for welding on Code Classified components such as the RPVH is ASME Section XI. Article IWA-4000, contains the rules for repair/replacement activities such as welding.
ASME XI, IWA-4410 (a) and (b) state that such activities shall be performed in accordance with the Owner's Requirements and the Original Construction Code, a later Edition and Addenda of the Construction Code or Code Cases.
Page 1 of 5
Proposed Alternative In Accordance with 10 CFR 50.55a(a)(3)(i)
Alternative Provides Acceptable Level of Quality and Safety 3.0 Applicable Code Requirements (continued)
ASME Xi, IWA-4410(c) states that the alternate rules of IWA-4600 may be used for welding in lieu of the Construction Code requirements. IWA-4600 (b) states that the alternate welding methods of IWA-4630 may be used for welding dissimilar material combinations, as an alternative to Construction Code requirements, when postweld heat treatment is not to be performed.
REQUESTED RELIEF SCE requests relief from the applicable ASME Code requirements and requests to use the rules of ASME Xl Code Case N-638 (Reference 1), with exceptions noted and discussed in Section 5.0, below.
4.0 Reason for the Reauest Repair welding per the Construction Code, ASME IlIl, NB-4620, would require an 11 000F minimum postweld heat treatment. ASME Section Xl provides an alternative to this Construction Code requirement. Repair welding per the alternate methods in ASME Xl, IWA-4630 would eliminate the high temperature postweld heat treatment, but would still require a 300'F preheat. Radiation dose estimates indicate personnel exposure would be on the order of an additional 4.4 Person-Rem per penetration repair to perform the required preheat.
ASME Code Case N-638 (Reference 1) will permit the use of the Ambient Temperature Machine GTAW Temper Bead Technique for the repairs. This technique provides an acceptable level of quality and safety and eliminates the need to install and remove the resistance heating equipment if the alternative repair method in ASME Xl, IWA-4630 were employed. Therefore, repairs could be performed with less personnel radiation exposure.
Page 2 of 5
Proposed Alternative In Accordance with 10 CFR 50.55a(a)(3)(i)
Alternative Provides Acceptable Level of Quality and Safety 5.0 Proposed Alternative and Basis for Use Proposed Alternative SCE proposes to implement Code Case N-638 as follows:
General Requirements Section (1.0), Welding Qualifications Section (2.0),
Welding Procedure Requirements Section (3.0) and Documentation Section (5.0) will be met without exception.
Examination Section (4.0) (a) states that prior to welding, a surface examination will be performed on the area to be welded to verify defect removal. This requirement will be met without exception.
Examination Section (4.0) (b) states that the final weld surface and the band around the repair weld 1-1/2 times section thickness or 5" (whichever is less) shall be examined using the surface and ultrasonic methods once 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 surface examination requirement of Section (4.0) (b) will be met without exception.
o SCE seeks relief from the requirement for ultrasonic examination in Section (4.0) (b).
Examination Section (4.0) (c) states that the removal areas of weld-attached thermocouples shall be ground and examined using a surface examination method. (Note: in the proposed repair, the welding process temperatures for preheat and interpass will be monitored using a hand held infrared device rather than hard-wired thermocouples and therefore this section would not be applicable).
Examination Section (4.0) (d) NDE personnel qualifications will be per ASME Xl, IWA-2300. This requirement will be met without exception.
Examination section (4.0) (e) states that surface examination acceptance criteria will be per NB-5340 or NB-5350 of the Construction Code. This requirement will be met without exception.
Examination section (4.0) (e) also states that ultrasonic examination acceptance criteria shall be per ASME Xl, IWB-3000. Since SCE is requesting relief from the ultrasonic examination requirement, the acceptance criteria will not apply.
Page 3 of 5
Proposed Alternative In Accordance with 10 CFR 50.55a(a)(3)(i)
Alternative Provides Acceptable Level of Quality and Safety 5.0 Proposed Alternative and Basis for Use (continued)
Proposed Alternative (continued)
Code Case N-638 stipulates that the other requirements of ASME Xl, Article IWA-4000 be met. Code Case N-638 provides alternate requirements for the following parts of IWA-4000: IWA-4440, IWA-4600(b), IWA-461 0, IWA-4620 and IWA-4630. All of the other applicable requirements of IWA-4000 will be met without exception.
Basis for Use EPRI Report GC-1 11050, Ambient Temperature Preheat for Machine GTAW Temperbead Applications, (Reference 2) documents a comprehensive study performed on the proposed ambient temperbead process. The report establishes that GTAW is an inherently low hydrogen process regardless of the welding environment and therefore requires no preheat or post weld bake steps for hydrogen removal. The report concludes that no preheat or post weld bake above ambient temperature is required to achieve acceptable weld quality and heat affected zone impact toughness properties using the machine GTAW temperbead repair process and that this was accomplished without risk of hydrogen assisted (delayed) cracking. The basis for their conclusion was extensive documentation from numerous industry qualification tests.
Code Case N-638 has been accepted and approved for use by the NRC per Regulatory Guide 1.147, Revision 13 (Reference 3). However, as noted above, the proposed repair methodology takes exception to the Code Case requirements. Therefore, an approved relief request is required.
The proposed repair methodology takes exception to performing an ultrasonic examination of the temper bead repair area(s). The nozzle geometry and repair weld accessibility are not suitable for obtaining meaningful examination results with the ultrasonic method. As an alternative, it is proposed that a progressive liquid penetrant examination be performed per ASME ll, NB-5245 in lieu of the ultrasonic examination required by Code Case N-638. The repair weld(s) will be examined at one-half the weld deposit thickness or at each V inch of deposit, whichever is less, and again on the final weld surface.
Page 4 of 5
Proposed Alternative In Accordance with 10 CFR 50.55a(a)(3)(i)
Alternative Provides Acceptable Level of Quality and Safety 5.0 Proposed Alternative and Basis for Use (continued)
Basis for Use (continued)
The partial penetration welds of the RPVH nozzles were designed and fabricated in accordance with ASME ll, NB-3352.4 (d). NB-3352.4 (d) specifies that the attachment welds be capable of being examined progressively with the magnetic particle or liquid penetrant method. The Construction Code did not require volumetric examinations of the penetration J-groove welds nor did it require the connections be designed for the capability of volumetric examinations.
Examining the repair welds with the same methodology and acceptance standards of the Construction Code provides an equivalent level of quality to the original equipment manufacturer supplied attachment welds.
Code Case N-638 has been accepted and approved for use by the NRC per Regulatory Guide 1.147, Revision 13. The exception taken to Code Case N-638 requirement to examine repair weld(s) volumetrically and examine the repair weld(s) per the Construction Code rules in lieu of the volumetric examination ensures the repairs meet the same standards as the other penetrations that will not be repaired. Therefore, using the ambient temperature machine (GTAW) temper bead technique, as proposed, provides an acceptable level of quality and safety, as required by 10 CFR 50.55a(a)(3)(i).
6.0 Duration of Proposed Alternative Relief is requested for the third inspection interval at SONGS Units 2 and 3, which is scheduled to end on August 17, 2013.
7.0 References
- 1.
ASME Code Case N-638, Similar and Dissimilar Metal welding Using Ambient Temperature Machine GTAW Temper Bead Technique, Section Xl, Division 1, Code Committee approval September 24, 1999
- 2.
EPRI Report GC-1 11050, Ambient Temperature Preheat for Machine GTAW Temperbead Applications, November 1998
- 3.
Regulatory Guide 1.147, Revision 13, Inservice Inspection Code Case Acceptability, ASME Section Xi, Division 1, June 2003 Page 5of5