LR-N07-0281, Response to Request for Additional Information, Relief Request HC-RR-I2-W02 Proposed Alternative Repair Method
| ML073100717 | |
| Person / Time | |
|---|---|
| Site: | Hope Creek  |
| Issue date: | 10/30/2007 |
| From: | Barnes G Public Service Enterprise Group |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| HC-RR-I2-W02, LR-N07-0281 | |
| Download: ML073100717 (6) | |
Text
PSEG Nuclear LLC P.O. Box 236, Hancocks Bridge, New Jersey 08038-0236 OCT 3 0 2007-1 0CFR50.55a LR-N07-0281 0
PS-G Nuclear LLC United States Nuclear Regulatory Commission Document Control Desk Washington, DC 20555 HOPE CREEK GENERATING STATION FACILITY OPERATING LICENSE NO. NPF-57 DOCKET NO. 50-354
Subject:
RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION, RELIEF REQUEST HC-RR-12-W02 PROPOSED ALTERNATIVE REPAIR METHOD
References:
(1) PSEG Letter LR-N07-0273 RELIEF REQUEST HC-RR-12-W02 PROPOSED ALTERNATIVE REPAIR METHOD Dated: October 19, 2007 In Reference 1, PSEG Nuclear LLC (PSEG) proposed an alternative to the requirements of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code,Section XI, Rules for Inservice Inspection of Nuclear Power Plant Components. This proposed alternative would permit the use of a full structural weld overlay repair for an indication identified in the N2A recirculation inlet nozzle safe-end to nozzle weld joint.
On October 26, 2007, the NRC provided PSEG a draft Request for Additional Information (RAI) on the Reference 1 submittal. PSEG and the NRC discussed the draft RAI in a conference call on October 29, 2007. The response to the RAI is provided in the attachment to this letter.
If you have any questions or require additional information, please contact Mr.
Philip J. Duca at (856) 339-1640.
Sincerely, George P. Barnes Site Vice President - Hope Creek Attachment 95-2168 REV. 7/99
Document Control Desk LR-N07-0281 CC Mr. S. Collins, Administrator - Region I U. S. Nuclear Regulatory Commission 475 Allendale Road King of Prussia, PA 19406 Mr. R. Ennis, Licensing Project Manager - Hope Creek U. S. Nuclear Regulatory Commission Mail Stop 08B1 Washington, DC 20555 Mr. P. Mulligan Bureau of Nuclear Engineering P. O. Box 415 Trenton, NJ 08625 USNRC Senior Resident Inspector - Hope Creek (X24)
Attachment LR-N07-0281 RESPONSE TO RAI #2 FOR RELIEF REQUEST HC-RR-12-W02 NRC RAI #2:
- 1. The relief request states that full ultrasonic examination of the final weld surface and band area (1.5T width) will not be performed. How much of the final weld surface and band area will be examined using the ultrasonic method?
PSEG Response #1:
Code case N-504-3 and Non-mandatory Appendix Q required weld volumes were met during the ultrasonic (UT) examination. The weld and heat affected zone (HAZ) beneath the weld overlay were post-weld overlay volumetrically examined. The ultrasonic examination did not extend up to the very edge of the overlay. Refer to Figures 1 and 2 for extent of coverage attained for scans in the circumferential and axial directions. Surface examinations of the entire weld overlay surface, at least 2inches-inch of the adjacent safe-end surface, and at least 2.5-inch of the adjacent ferritic steel nozzle surface were performed acceptably. These examinations ensure sound weld metal was deposited and that the process has not introduced flaws in the base material.
- 2. Since full ultrasonic examination of the final weld surface and band area (1.5T width) as required by Code Case N-638-1 will not be performed, a much more complete explanation of the examinations that will be performed and the basis for these alternative examinations is required.
PSEG Response #2:
Full UT of the 1.5T band was not performed. Ultrasonic and surface examinations of the weld overlay (welded region) were performed as required by Code case N-504-3 and Non-mandatory Appendix Q. The examination volumes required by these documents were met during the examinations.
The weld overlay extends onto the blend radius of the nozzle beyond the length required by Code Case N-504-3 for structural reinforcement. This extension onto the blend radius eliminates a stress riser on the nozzle and provides additional OD surface area for UT examination of the defect area in the original weld.
Because this is a surface application of the temperbead welding process (specifically performed to minimize heat input to the ferritic steel nozzle), there is minimal impact to the volume of the ferritic steel nozzle material in the area surrounding the weld overlay. Also there is no additional useful information that can be gained by a volumetric examination of the area beyond the physical limits of the weld overlay. The weld and HAZ beneath the weld overlay were post-weld overlay volumetrically examined. The examinations performed have ensured sound weld metal was deposited and that the 1 of 4
Attachment LR-N07-0281 process did not introduce flaws in the base material. Surface examinations of the entire weld overlay surface, at least 2-inch of the adjacent safe-end surface, and at least 2.5-inch of the adjacent ferritic steel nozzle surface were performed acceptably. This is sufficient to verify that defects were not induced in either the ferritic steel nozzle material or stainless steel safe-end due to welding.
Later editions of Section Xl as well as Code Case N-638-2 have deleted the requirement for the 1.5T examination band for both ultrasonic examination and surface examination. This is consistent with the less restrictive requirements for ultrasonic examination of the ferritic nozzle because hydrogen cracking away from the temper bead weld is not considered a concern. The NDE requirements in these documents apply to any type of welding where a temperbead technique is to be employed (which includes weld repairs of excavated flaws) and is not specifically written for weld overlay. For the weld overlay type of repair, any ferritic steel base material cracking would occur in the HAZ directly below or adjacent to the weld overlay and not in the 1.5T examination band of ferritic material beyond the edges of the weld overlay. If this type of cracking had occurred it would have been detected by the NDE of the weld overlay and adjacent ferritic steel surfaces as required by Code case N-504-3 and Non-mandatory Appendix Q.
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Attachment LR-NO7-0281 FIGURE 1 PHASED ARRAY ULTRASONIC EXAMINATION AXIAL COVERAGE RECORD HOPE CREEK RECIRCULATION INLET NOZZLE N2A Phased Array Search Unit Phased Array Search Unit Limit of Code Required Axial Examination Coverage Inconel Buttering Inconel Inconel Buttering Butt Weld Weld & Required Volume Weld Overlay Volume Axial Examination Coverage Summary The Axial coverage of the Weld and Required Volume of the Base Material (WBM) was not limited.
The Axial coverage of the Weld Overlay matedal (NOL) was not limited, except the area of the taper outside the Code Required Volume 3 of 4
Attachment LR-N07-0281 FIGURE 2 PHASED ARRAY ULTRASONIC EXAMINATION CIRCUMFERENTIAL COVERAGE RECORD HOPE CREEK RECIRCULATION INLET NOZZLE N2A Phased Array Search Unit Lh7;-q Phased Array Search Unit 7L7D Limit of Code Required Examination Coverage Inconel Buttering Inconel Inconel Buttering Butt Weld R
T Weld & Required Volume Weld Overlay Volume Circumferential Examination Coverage Summary The Circumferential coverage of the Weld Overlay material (WOL) was limited at each edge of the overlay by 0.50", which is the dimension of the transmit / receive search unit wedge element.
The circumferential coverage the Weld and Required Volume of the Base Material (WBM) was not limited.
All areas were scanned in the Clockwise and Counter-Clockwise directions, T/R positions in the illustration above would be reversed for opposite scans.
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