A consideration from mechanics for a feedwater line failure at Mihama unit 3 power station

A pipe failure accident of a feedwater line system of Mihama NPP No.3 occurred on August 9, 2004, although a similar accident had occurred in other nuclear power plant and lessons should have been incorporated into maintenance management of nuclear power plant. Based on the accident investigation interim report, examinations of ''pipe failure mechanism''from a mechanics standpoint have been made. As debating materials about a future problem, 1) carbon steel pipe used at temperature 140degC of blue shortness, 2) ductile failure mechanism of thinning pipe due to accelerated effect of flow on erosion and corrosion with oxide films broken away and 3) importance of periodical inspection were pointed out. (T. Tanaka)