France also had a shutdown of some nuclear reactors because of concerns over japanese parts The component in question was manufactured by Japan Casting and Forging Corp., which is based in Kitakyushu. In June, ASN pointed to potential weaknesses of the Japanese steel components, with carbon concentrations exceeding standards. The Japanese part is used at 12 nuclear reactors in France, according to local reports. In June, the French regulator, the Autorité de Sûreté Nucléaire (ASN), said it had identified 18 French nuclear power reactors operated by EDF - of both 900 MWe and 1450 MWe capacity - whose steam generators could contain high carbon concentrations.

Only three nuclear reactors are currently online in Japan: two at the Sendai plant and one at Shikoku Electric Power's Ikata station.

Japan's Institute of Energy Economics said Dec. 13 it estimates seven reactors will be restarted by the end of March 2017 and another 19 by March 2018.

About two-thirds of 57 nuclear reactors under construction are expected to come on line in the next three years.