05000346/FIN-2011004-05
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Finding | |
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| Title | Code Surface Examination Requirements Not Applied to Closure Head Stud Holes |
| Description | The RVCH is a single piece forging fabricated to the SA 508 material standard with an ASME NPT stamp to document that this pressure boundary part was fabricated to the requirements of the 1989 Edition of the ASME Code Section III. The requirements for examination of forgings are contained in the ASME Code Section III, Article NB 2540 Examination and Repair of Forgings and Bars. Specifically, NB-2541(a) requires in part that, In addition, all external surfaces and accessible internal surfaces shall be examined by a magnetic particle (MT) method (NB 2545) or a PT method (NB-2546). Also, NB-4121.3 Repetition of Surface Examinations After Machining required If, during the fabrication or installation of an item, materials for pressure containing parts are machined, then the Certificate Holder shall re-examine the surface of the material in accordance with NB-2500 when: (a) the surface was required to be examined by the MT or liquid penetrant method in accordance with NB-2500; and (b) the amount of material removed from the surface exceeds the lesser of 1/8 inch or 10 percent of the minimum required thickness of the part. For the 60, 7-inch diameter stud holes drilled through the vessel head flange, no surface examinations (e.g., MT or PT) were conducted on the interior bore surfaces of the stud holes. The inspectors observed a licensee demonstration of the potential accessibility of the flange stud holes for MT examination. Specifically, a licensee MT qualified examiner positioned an AC yoke used for MT examinations on the interior bore surfaces of an RVCH flange stud hole. Based on this demonstration, the inspectors estimated that it would be possible to perform an MT exam for accessible portions of the interior bore surfaces for a depth of about 2 inches from the top and bottom flange faces for each of the 60 stud holes. Because this accessible interior surface on the RVCH forging had not been examined by MT or PT, the inspectors were concerned that the RVCH did not meet the requirements of NB-2541(a) and NB-4121.3 discussed above. In response to the inspectors questions, the licensee established a position that accessible interior surfaces of the RVCH stud holes did not require a surface examination. The licensee position was based on Code Interpretation III-1-77-162, which states in part that drilled holes are not considered to be material form surfaces and the requirement for examination of holes (if any) resides in NX-4000 and NX-5000. The licensee concluded that the reexamination of machined surfaces as discussed in NB-4121.3 did not apply to the accessible interior surfaces of the flange stud holes because they were not material form surfaces. This issue is considered an unresolved item pending completion of an NRC staff review to determine an Agency position on the licensees interpretation of these Code requirements. The licensee documented this issue in CR 2011-01739. |
| Site: | Davis Besse  |
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| Report | IR 05000346/2011004 Section 4OA5 |
| Date counted | Sep 30, 2011 (2011Q3) |
| Type: | NCV: |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | |
| Inspectors (proximate) | A Wilson D Kimble J Beavers J Maynen J Neurauter J Steffes L Jones M Bielby M Holmberg R Jones T Bilik T Goa Wilsond Kimble J Cameron J Neurauter J Steffes L Jones M Holmberg M Mitchell P Cardona Morales P Smagacz T Briley T Go |
| INPO aspect | |
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Finding - Davis Besse - IR 05000346/2011004 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Davis Besse) @ 2011Q3
Self-Identified List (Davis Besse)
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