The operator of the Fukushima No. 1 nuclear power plant, which suffered core meltdowns in 2011, is considering a new submersion method for removing radioactive fuel debris that would wholly encase a reactor building in a water-filled, tank-like structure, a source close to the company said Thursday.

Conceptual breakthroughs with the method, whose advantages include using water's ability to interrupt radiation and thereby provide a safer working environment, have made it a promising candidate for the cleanup of the defunct nuclear plant, according to the source close to Tokyo Electric Power Company Holdings (Tepco).

But with no proven track record in the nuclear field, investigations are ongoing into future technological issues and costs, among other contingencies. The source said it could "require advanced technology to stop water leaking out and become a huge construction project."