TOKYO (Reuters) - Japan's Fukushima Daini nuclear plant, the companion of the crippled Daiichi plant 10 kilometers away that is still leaking radiation, has cleared a key milestone toward stabilizing, regulators said on Thursday, although the outlook for a restart remains uncertain.
The Nuclear and Industrial Safety Agency said on Thursday it reduced the evacuation zone around the four-reactor, 4,400 megawatt Daini plant after engineers had repaired the cooling systems and maintained the plant in a "cold shutdown" for several weeks.
The magnitude-9.0 earthquake and 15-meter tsunami that struck northeast Japan on March 11 automatically shut the plant, along with the Daiichi facility, and the reactors' cooling systems briefly lost power, leading the government to impose a 10 km evacuation zone the following day.
Thursday's reduction of that zone to 8 km from 10 km was purely symbolic, however, as it remains entirely within the 20 km evacuation zone still in force around the crisis-hit Daiichi plant, where engineers continue struggling to restore cooling systems and staunch radiation leaks.
The government said on Thursday that the 20-km ring around the 4,696 megawatt Daiichi plant would become a no-go zone as of midnight, although engineers would still be able to operate within the area.
A reopening of the Daini plant would require the operator, Tokyo Electric Power Co, to get approval from regional governments and residents.
An agency spokesman said further repair work was needed at the Daini plant but it had stabilized and partially met additional antiquake safety steps the government ordered on March 30.
The volume of radioactive substances inside the plant's four reactors has fallen to less than one-100th the level soon after they were shut and heat from radioactive decay in fuels is under control, substantially diminishing the chances of a serious accident, the agency said in a statement.
(Reporting by Risa Maeda; Editing by Edmund Klamann)