Tohoku Electric Power Co. and Chubu Electric Power Co. admitted Friday they failed to report structural faults in their nuclear plants to the government.

Four minor cracks in pipes carrying primary cooling water were found at Tohoku Electric’s Onagawa No. 1 plant in Miyagi Prefecture during regular checks in 1998 and 2001, officials at the utility said.

They failed to report the cracks because they thought they were not problematic, they said.

The officials said they do not believe they violated the law but came forward at a time when public distrust in the nation’s nuclear power policy has deepened following the widespread coverups involving Tokyo Electric Power Co.

Similar cracks were found at Chubu Electric’s Hamaoka No. 1 and No. 3 plants in Shizuoka Prefecture, a top official of the utility said.

Chubu Electric Vice President Ko Terasawa offered an apology for raising concerns among residents in the town of Hamaoka.

“We are very sorry, but we thought the cracks are minor ones that will not affect safety,” Terasawa said, adding the firm had no intention of hiding the cracks.

Officials of the Nuclear and Industrial Safety Agency, under the Ministry of Economy, Trade and Industry, said later Friday they would look into the cases.

Prompted by the coverup reports, Chugoku Electric Power Co., which operates in the southwestern region of Honshu, centering on Hiroshima Prefecture, and Hokkaido Electric Power Co., which operates in Hokkaido, told the nuclear safety agency it would investigate its own previous reactor checks.

Kansai Electric Power, Shikoku Electric Power and Kyushu Electric Power, as well as Japan Atomic Power Co. and the Japan Nuclear Cycle Development Institute, followed suit.

Tepco saga continues

Tokyo Electric Power Co. has found eight more instances in which structural faults at its nuclear plants have been concealed, adding to the 29 coverups already reported, Tepco officials said Friday.

All of the newly discovered cases involve cracks in pipes that carry primary cooling water in reactors. Such pipes are far more critical than the reactor shrouds at the center of many of the other coverups.

The nation’s largest power supplier has been carrying out an internal investigation into the coverups since the scandal broke in August.

When releasing a report Tuesday on the probe, company investigators said they were searching for other cases.

Officials of the Nuclear and Industrial Safety Agency, under the Ministry of Economy, Trade and Industry, said they will look into the new cases, which may constitute violations of laws.

“We will deal with this problem in a strict manner,” METI chief Takeo Hiranuma said, indicating authorities will conduct on-site investigations.

The Tepco officials said the newly discovered cases were at five of the six reactors at the Fukushima No. 1 plant in Fukushima Prefecture, one of the four reactors at the Fukushima No. 2 plant, and two of the seven reactors at the Kashiwazaki-Kariwa plant in Niigata Prefecture.

During regular checks in 1993 and later, cracks were detected in two to 12 pipes in those reactors.

Employees of Hitachi Ltd. and Toshiba Corp. carried out the checks. Both companies claimed the results of each check were correctly reported to Tepco.

But Tepco workers at the plants apparently judged the cracks posed no immediate threat to safety and failed to report them to the authorities, as required.

Pipes were replaced in the five cases at the Fukushima No. 1 plant by 2001. But the one at the Fukushima No. 2 plant and the two at the Kashiwazaki-Kariwa plant have yet to be attended to.

Currently, the reactor at the Fukushima No. 2 plant and one of the two at Kashiwazaki-Kariwa are shut down.

But the second reactor at Kashiwazaki-Kariwa is running. Tepco officials said the utility will shut down that reactor Friday to conduct an emergency inspection.

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