Kansai Electric Power Co. said the thickness of the pipe, which ruptured and spewed out non-radioactive superheated steam and scalding water onto a group of workers Aug. 9, was below minimum safety standards.

"We conducted visual inspections, but never made ultrasonic tests, which can measure the thickness of a steel pipe," said spokesman Haruo Nakano.

The broken pipe, which was 10 mm thick when it was installed in 1976, measured just 1.4 mm -- way below the legal minimum safety standard of 4.7 mm, he said.

The pipe "showed large-scale corrosion at the area in question," Kepco said separately in a statement.

Seven workers were also injured in the accident at a facility housing the turbines for the No. 3 reactor at the plant in Mihama, Fukui Prefecture, about 320 km from Tokyo.

The accident and suspected lapses deepened concerns about the safety of Japan's 52 nuclear plants, which supply about a third of the country's electricity.

The Japan Times Weekly: Aug. 14, 2004
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