Genkai reactor may have faulty vessel

Study says aging No. 1 unit should be suspended

Kyodo July 24, 2011 http://search.japantimes.co.jp/cgi-bin/nn20110724a3.html

SAGA — A nuclear reactor that began operations 36 years ago at Kyushu Electric Power Co.'s Genkai plant may have a faulty pressure vessel, an analysis by researchers showed Saturday.

The No. 1 reactor, which is currently operating, should be suspended until its safety is confirmed, said Hiromitsu Ino, who led the team.

The analysis detected a possible fault in the process of manufacturing a critical unit encasing nuclear fuel assemblies at the No. 1 reactor, casting doubt over the credibility of previous reactor inspections.

Ino, a professor emeritus at the University of Tokyo, and other experts in metals, performed a close analysis of test data to determine the extent to which steel used for the pressure vessel has degraded.

The analysis of the data, which were disclosed by the utility only in July, showed disparities in the quality of steel used for the vessel, pointing to the possibility of an error during the manufacturing process, Ino said.

The No. 1 unit of the Genkai plant in Saga Prefecture began operating in 1975.

"The technique used in manufacturing reactors in the 1970s was unsophisticated," Ino said. "It's possible that a faulty manufacturing process existed, and the pressure vessel's durability is questionable."

Of the four reactors at the complex, the No. 2 and 3 reactors are currently suspended for regular maintenance