Most PWRs have penetrations in the RPV lower heads for in-core nuclear instrumentation. These generally are made of nickel-based Inconel Alloy 600. Weld materials typically 82/182. Operating conditions PWR plants causing alloys cracking through a process called primary water stress corrosion (PWSCC). In 2003, licensee South Texas Project Unit 1 (STP-1) identified apparent boron deposits on head...