Examination of the failed feedwater sparger from Humboldt Bay 3: 1976 outage

During the scheduled refueling and maintenance outage which began in July 1976 an underwater examination of vessel internals by closed circuit television discovered cracks in the leedwater sparger thermal sleeve and at the edge of the thermal sleeve to sparger weld. Apparent cracking was also detected around some of the sparger outlet holes. The sparger and thermal sleeve were later removed from the vessel and visually examined in detail. Portions of the sparger and thermal sleeve were selected and shipped to the Vallecitos Nuclear Center for a laboratory examination to determine the failure mechanism. This was the first occasion on which a comprehensive television examination of the sparger had been made. The plant has been in service since April 1963