ML050800037
| ML050800037 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs  |
| Issue date: | 03/08/2005 |
| From: | Vanderheyden G Constellation Energy Group |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| Download: ML050800037 (5) | |
Text
41 George Vanderheyden Vice President Calvert Cliffs Nuclear Power Plant Constellation Generation Group, LLC 1650 Calvert Cliffs Parkway Lusby, Maryland 20657 410.495.4455 410.495.3500 Fax I
Constellation Energy March 8, 2005 U. S. Nuclear Regulatory Commission Washington, DC 20555 ATTENTION:
SUBJECT:
Document Control Desk Calvert Cliffs Nuclear Power Plant Unit Nos. I & 2; Docket Nos. 50-317 & 50-318 Revision to the ASME Section XI Relief Request to Use Weld Overlay and Associated Alternative Technicques
REFERENCE:
(a)
Letter from G. Vanderheyden (CCNPP) to Document Control Desk (NRC), dated March 5, 2005, ASME Section XI Relief Request to Use Weld Overlay and Associated Alternative Techniques In our letter dated March 5, 2005 (Reference a), we submitted a relief request pursuant to 10 CFR 50.55a(a)(3)(i).
The relief requested was for two welds that will have a structural overlay applied, 2-DR-2007-1 (2" diameter drain nozzle on the No. 21 Reactor Coolant System hot leg) and 2-LD-2004-1 (2" diameter letdown line nozzle on the No. 22A Reactor Coolant System cold leg). These welds were examined under the Performance Demonstration Initiative program and determined to have unacceptable indications in the existing Alloy 82/182 welds. We believe that the indications could be due to primary water stress corrosion cracking (PWSCC) based on the signal response received during the ultrasonic test examination, which indicated crack-like responses. In addition, the material of the welds (Alloy 82/182) is known to be susceptible to PWSCC.
This letter also provides a revision to Tables I and 2, contained in Attachment (1) of Reference (a).
Please replace Tables I and 2 provided in Reference (a) with the revised tables contained in Attachment (1) to this letter. The remaining information in Reference (a) remains unchanged.
Should you have questions regarding this matter, we will be pleased to discuss them with you.
GV/PSF/bjd
Document Control Desk March 8, 2005 Page 2 cc:
C. W. Fleming, Esquire R. V. Guzman, NRC S. J. Collins, NRC Resident Inspector, NRC R. I. McLean, DNR
ATTACHMENT (1)
REVISED TABLES I AND 2 Calvert Cliffs Nuclear Power Plant, Inc.
March 8, 2005
ATTACHMENT (1)
REVISED TABLES I AND 2 Table I Relief Requests Related to IWA-4000 IWA4000 Differences/Basis for Relief IWA-4610(a) The area to be welded plus a band around Relief. In lieu of weld-attached thermocouples and the area of at least 1-1/2 times the component thickness recording instruments, we plan to monitor the process or 5 in. (127 mm), whichever is less, shall be preheated temperatures with non-attached devices, e.g., contact and maintained at a minimum temperature of 3501F pyrometers and provide a manual record of the process (I 7700) for the SMAW process and 300'F (1490C) for temperatures.
the GTAW process during welding. The maximum The contact pyrometers used will be calibrated in interpass temperature shall be 450TF (2320C).
accordance with our control and calibration of Thermocouples and recording instruments shall be used measuring and test equipment program.
to monitor the process temperatures. Their attachment Clarification. IWA4610(a) contains two general and removal shall be in accordance with Section Ill.
requirements, I) preheat and interpass temperature criteria and 2) a requirement to monitor process temperatures with thermocouples and recording instruments. The preheat and interpass temperature criteria are superceded by Code Case N-638 so no relief is requested for this requirement.
I
ATTACHMENT (1)
REVISED TABLES 1 AND 2 Table 2 Modifications to Code Case N-504-2 Code Case N-504-2
-DifferencesBasis for Relief Reply: It is the opinion of the Committee that, in Relief. We propose to apply Code Case N-504-2 to the lieu of the requirements of IWA4 120 in Editions ferritic (PI) and nickel alloy (F43/P43) base material as well and Addenda up to and including the 1989 Edition as the austenitic stainless steel (P8) base material.
with the 1990 Addenda, in IWA-4170(b) in the Code Case N-504-2 is accepted without restriction in the 1989 Edition with the 1991 Addenda up to and current NRC Regulatory Guide 1.147. The base material including the 1995 Edition, and in IWA-4410 in the will be ferritic material (PI) with existing nickel alloy weld 1995 Edition with the 1995 Addenda and later metal (F43/P43) to which an austenitic stainless steel (P8)
Editions and Addenda, defect in austenitic stainless pipe is welded. Industry operational experience has shown steel piping may be reduced to a flaw of acceptable that PWSCC in Alloy 82/182 will blunt at the interface with size in accordance with IWB-3640 from the 1983 stainless steel base metal, ferritic base metal, or Alloy Edition with the Winter 1985 Addenda, or later 52/52M/152 weld metal. For additional information on Editions and Addenda, by deposition of weld Alloy 52M, refer to the request below (weld metal).
reinforcement (weld overlay) on the outside surface of the pipe, provided the following requirements are met:
(b) Reinforcement weld metal shall be low carbon Relief. In lieu of austenitic stainless steel filler material, the (0.035% max.) austenitic stainless steel applied reinforcement weld metal will be a nickel alloy.
3600 around the circumference of the pipe, and shall The weld metal will be ERNiCrFe-7A (Alloy 52M, UNS be deposited in accordance with a qualified welding N06054). This weld metal is assigned F43 by ASME per procedure specification identified in the Repair Code Case 2142-2. The requirements of ASME Section 111, Program.
NB-2400 will be applied to all filler material.
The chromium content of Alloy 52M is 28-31.5%, identical to that of Alloy 52. The main difference in Alloy 52 versus Alloy 52M is a higherNiobium content (0.5-1%). The difference in chemical composition between Alloy 52 and Alloy 52M improves weldability of the material, pinning the grain boundaries preventing separation between grains, and hot tearing during weld puddle solidification.
This filler material was selected for its improved resistance to PWSCC. Alloys 52, 52M, and 152 all contain about 30%
chromium that imparts excellent corrosion resistance. The existing Alloy 82/182 weld and the Alloy 52/52M overlay are austenitic and have ductile properties and toughness similar to austenitic stainless steel piping welds at pressurized water reactor operating temperature. These filler materials are suitable for welding over the ferritic nozzle, Alloy 82/182 weld and the austenitic stainless steel piping.
(e) The weld reinforcement shall consist of a Relief. Delta ferrite (FN) measurements will not be minimum of two weld layers having as-deposited performed for this overlay because welds of Alloy delta ferrite content of at least 7.5 FN. The first 52/52M/152 are 100% austenitic and contain no delta ferrite layer of weld metal with delta ferrite content of least due to the high nickel composition (approximately 60%
7.5 FN shall constitute the first layer of the weld nickel).
reinforcement design thickness. Alternatively, first layers of at least 5 FN may be acceptable based on evaluation.
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