Quick fix for Ringhals

摘要

During a non-destructive examination (NDE) at Ringhals in 2003, inspectors found a crack in the area of a control rod drive mechanism (CRDM) housing nozzle at unit 1. The leak in the nozzle was approximately 20mm from the welded joint between the attached scram pipe and the nozzle. While a temporary fix was put into place — causing slightly reduced power output — plant managers evaluated permanent fix options in light of their larger goals to extend plant lifetime. Since the pipe was located in a humanly inaccessible area where the control rod housing penetrates through the reactor pressure vessel, a standard machine tool could not be used. Space limitations complicated the repair; the pipe was only 10cm apart from the other 157 pipes beneath the reactor core. The largest area near the damaged pipe was 8.9cm by 80cm.