The companies have agreed to consider together building a sustainable business that focuses on constructing and operating boiling water reactors (BWRs) similar to the ones that melted down at Tokyo Electric's Fukushima plant north of Tokyo after an earthquake and tsunami in 2011.

Japan shut down its nuclear plants nationwide in the wake of the 2011 disaster.

Neither Tokyo Electric or Chubu Electric have restarted any reactors since then, while Hitachi and Toshiba have pulled out of reactor construction plans overseas.

While nine reactors in Japan have been given approval to operate, all of the units have been pressurized water reactors, a different design than BWRs.

Tokyo Electric said on Monday it may start to decommission at least one reactor at its Kashiwazaki-Kariwa plant, the world's biggest nuclear station by capacity, within five years of restarting two of the newer reactors at the site.

(Reporting by Aaron Sheldrick; editing by Christian Schmollinger)