Fifty turbine blades have been found cracked or broken in a Chubu Electric Power Co. nuclear reactor in Shizuoka Prefecture, the Nagoya-based company said Friday.

The damaged blades were found in two of three low-pressure turbines of the No. 5 reactor at the Hamaoka nuclear plant in Omaezaki after an automatic shutdown of the 1,380-megawatt boiling water reactor on June 15 following excessive vibration in the turbines.

Of 139 blades in the first turbine, excluding those that came off, 28 were partially broken and 18 were cracked, the utility said.

Four blades installed in the second turbine were also found damaged, it said.

Company officials investigating the shutdown said the number of blades that have broken or cracked is expected to increase as the probe is continuing.

A public relations officer at Hitachi Ltd., which manufactured the turbines, said the company believes the cracks resulted from a design problem.

The turbine in question was developed for an improved version of a boiling water reactor. It features a larger wing to propel a generator.

Hitachi has set up an in-house investigative team, the officer said, adding it is likely to take a long time for the team to come up with a conclusion on the cause.

A Chubu Electric official meanwhile said the utility will try to determine the cause of the cracks as soon as possible, adding it will do its utmost to ensure stable power supply.

The Nuclear and Industry Safety Agency of the Ministry of Economy, Trade and Industry plans to order Hokuriku Electric Power Co. to shut down and inspect the turbine blades in a reactor of the same type at its Shika nuclear plant in Ishikawa Prefecture.

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