A key system to clean highly radioactive water started operation on Friday at the troubled Fukushima No.1 nuclear power plant, operator said.

Tokyo Electric Power Co.(TEPCO) announced a revised version of a road map for bringing the ongoing crisis under control and aimed at realizing stable cooling of all the spent nuclear fuel pools in one month. But it did not change its target of bringing the reactors into a condition known as "cold shutdown" by around January.

The full operation of the water treatment is seen as a key step to containing the crisis because it would not only help reduce the polluted water but would create clean water that can be injected into the reactors, which have lost their cooling functions in the wake of the March 11 earthquake and tsunami, Kyodo News reported.