Tohoku Electric Power said Monday that the halt to operations at a reactor at its Onagawa nuclear power plant in Miyagi Prefecture earlier this month came after part of a guide tube connecting a measuring instrument with the reactor came off.
The problem was apparently due to insufficient tightening of a nut, the company said, adding that it will review the tightening method and check whether the nut is fixed firmly.
It is not known when the No. 2 reactor at the plant will restart and generate electricity.
The reactor was brought back online for the first time in 13 years on Oct. 29. Tohoku Electric suspended operations at the reactor on Nov. 4 after failing to pull out a cable of the measurement instrument mechanically.
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