05000315/FIN-2010002-03
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Finding | |
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| Description | The inspectors identified an unresolved item (URI) related to the licensees decision to not apply the reactor coolant system construction Code requirements for bending/forming to the MSIP process used on the RCS HL and CL nozzles. On March 5, 2010, the licensee completed a 50.59 Applicability determination (2010-0062) for EC-0000048752 MSIP for Reactor Pressure Vessel Hot and Cold Leg Nozzle Dissimilar Metal Welds. In this document, the licensee concluded that MSIP was a maintenance activity, which restored the applicable system, structure, or component to the as-designed condition. The RV inlet nozzles have a 27.5-inch inside diameter and contained a DM weld (Inconel 82/182), which joins the nozzle to a stainless steel safe-end that is welded to a cast stainless steel RCS pipe elbow. The RV outlet nozzles have a 29-inch inside diameter and contained a DM weld (Inconel 82/182), which joins the nozzle to a stainless steel safe-end that is welded to a centrifugally cast stainless steel pipe. From March 15 17, 2010, the licensee applied the MSIP process to the HL piping adjacent to the HL nozzle DM welds and on the CL pipe elbows adjacent to the nozzle DM welds. The MSIP process applied a radial pressure to permanently reduce the inside and outside diameter of the RCS piping by approximately 12 inch. This pipe forming operation, results in a compressive residual stress at the nearby DM nozzle welds which reduces the weld susceptibility to PWSCC. On March 10, 2010, the inspectors identified that the licensee had not considered and hence not implemented the RCS construction Code requirements for bending or forming pipe. The RCS piping construction Code was (USAS B31.1 1967 Edition) identified in the UFSAR, Section 4.1.6, Codes and Standards. Article 129, Bending and Forming, of the B31.1 Code contained requirements for post bending examinations and heat treatment for stress relief. Specifically, Article 129.1 stated Pipe may be bent to any radius which will result in a bend surface free of cracks, as determined by a method of inspection specified in the design, and substantially free of buckles. And Article 129.3.3 stated Cold Bending and forming of carbon steel having a wall thickness of 14 inch and heavier, and all ferritic alloy pipe in nominal pipe sizes of 4 inches and larger or 12 inch wall thickness or heavier, shall require a stress relieving treatment. The licensee did not perform inspections (PT of external and internal surfaces) in accordance with the applicable pipe and elbow design specifications following bending to verify that the surfaces were free of cracks or buckles. The licensee also did not perform a stress relief treatment for the piping areas subject to bending/forming. The licensee provided a white paper, AEP-10-49, dated March 19, 2010, to support their decision to not apply these requirements. The summary is provided below: Applicable construction Codes for vessels and piping were reviewed in order to address the question of whether there are any requirements that would preclude the use of MSIP. The question was raised because of a concern whether a potential compliance issue with the original construction Code might be raised by application of MSIP. There were no rules found that would categorize MSIP as a bending or forming process, as described by the applicable Codes. Even if the argument is made that MSIP is a forming operation, of sorts, the Code rules exempt the affected materials from any required post-forming heat treatment and retesting of mechanical properties. The piping and safe-end materials are exempt from post-forming heat treatment by the piping Code. They are also exempt in the vessel Code because they are exempt from impact test requirements. This exemption also eliminates the need for qualification of forming operations on austenitic stainless steel and non-ferrous materials. There are no additional Code requirements for re-examination of materials formed during fabrication. The ASME Section III rules for time of examination of piping, tubular products and fittings, which apply to the piping and safe-end, only require examination to be performed after the final heat treatment required by the material specification. No other requirements impose a re-examination of materials after fabrication operations. Strains imparted to the safe-end and weld region are in the austenitic stainless steel or non-ferrous nickel base weld metal of the weldment being mitigated. These materials are exempt from post-forming heat treatment requirements in the applicable piping and vessel Codes of construction. This issue is a URI pending completion of NRC reviews to determine the applicability of the construction code requirements for the MSIP process (URI 05000315/2010002-03; Construction Code Requirements For Bending Not applied to MSIP of RCS Pipe). |
| Site: | Cook  |
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| Report | IR 05000315/2010002 Section 4OA5 |
| Date counted | Mar 31, 2010 (2010Q1) |
| Type: | URI: |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | |
| Inspectors (proximate) | A Dunlop M Marshfield J Lennartz R Walton T Go P Laflamme T Brileym Mitchellj Lennartz T Go P Laflamme J Cameron A Shaikh T Briley M Holmberg C Zoia D Mcneil J Jandovitz |
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Finding - Cook - IR 05000315/2010002 | |||||||||||||||||||||||||||||||||||||||||||
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Finding List (Cook) @ 2010Q1
Self-Identified List (Cook)
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