AN aftershock has hit Japan just hours after the country's nuclear safety agency ordered plant operators to beef up their earthquake-preparedness systems.

There were no initial reports of damage from the magnitude-5.9 aftershock and there was no risk of a tsunami similar to the one last month that crippled the Fukushima Dai-ichi nuclear plant, causing Japan's worst-ever nuclear plant disaster.

Japan has been hit by a string of smaller quakes since the magnitude 9.0 earthquake hit the country on March 11.

Meanwhile, the newspaper Asahi Shimbun, citing no sources, reported that a secret plan to dismantle Tokyo Electric Power Co, which runs the radiation-leaking Fukushima plant, was circulating within the government.

The proposal calls for putting TEPCO, the world's largest private electricity company, under close government supervision before putting it into bankruptcy and thoroughly restructuring its assets.

Most government offices were closed today and the report could not be immediately confirmed.

In the wake of the nuclear crisis, the government ordered 13 nuclear plant operators to check and improve outside power links to avoid earthquake-related outages that could cause safety systems to fail as they did at the Fukushima plant, Hidehiko Nishiyama of the Nuclear and Industrial Safety Agency told reporters yesterday.

The operators, including TEPCO, were to report back by May 16.

Power outages during a strong aftershock on April 7 drove home the need to ensure that plants are able to continue to operate crucial cooling systems and other equipment despite earthquakes, tsunamis and other disasters, Mr Nishiyama said.

Utility companies were ordered to reinforce the quake resistance of power lines connected to each reactor or to rebuild them.

They also must store all electrical equipment in watertight structures.

Earlier, the nuclear agency had ordered plant operators to store at least two emergency backup generators per reactor and to install fire pumps and power supply vehicles as further precautions.



Originally published as Big aftershocks continue to jolt Japan