THE EMBEDDED FLAW PROCESS FOR REPAIR OF REACTOR VESSEL HEAD PENETRATIONS AND ITS APPLICATION AT NORTH ANNA UNIT 2

摘要

As a result of an inspection of the reactor vessel upper head penetrations in the rall 2002 outage at North Anna Unit 2, a number of indications were discovered in the attachment welds for the reactor vessel head penetrations. Indications were also found in three penetrations that had been repaired using the Westinghouse embedded flaw weld repair process during the fall outage of 2001. After extensive investigation it was determined that the cracking was mostly in the weld buttering, and that the cracking in the repaired penetrations was the result of inadequate implementation of a qualified repair process. The process was modified slightly as a result of these findings, but the cracking was too extensive to permit a practical repair at North Anna Unit 2. As a result, the head was replaced, and the unit restarted in January of 2003.