The government certified as "appropriate" a 2000 report by Kansai Electric Power Co. on pipe safety measures at its Mihama Nuclear Power Plant in Fukui Prefecture, sources said Thursday.
On Monday, superheated steam exploded from a ruptured coolant water pipe at the plant, killing four employees and injuring seven others, in the nation's worst nuclear plant accident. The pipe was reportedly corroded and never checked in 27 years.
In the 2000 report, Kepco said: "Tests on the thickness (of the pipes for the secondary loop) have been conducted at a large number of spots for a few years. Now that we understand the corrosive tendency of the pipes, we have set a more economical inspection standard."