The head of a major inquiry into Japan's nuclear disaster and a former senior cabinet adviser have sounded alarm over plans this week to restart a 44-year old reactor, saying the industry and government have not taken on board the lessons from Fukushima.

Kansai Electric Power, which serves Osaka and its industrial environs - an area with roughly the same economic output as Mexico - will reboot the No 3 reactor at its Mihama station in western Japan on Wednesday.