Chief Cabinet Secretary Yukio Edano, second right, gets briefed during his inspection in Minamisoma, Fukushima Prefecture, Japan, Sunday 17 April 2011. (AP)
Japan's top government spokesman said Tuesday that its ongoing Fukushima nuclear crisis is "different in nature" from the Chernobyl disaster in the Ukraine exactly 25 years ago.
Japan has ranked the disaster at its tsunami-hit plant as a "major accident" with the maximum severity ranking of seven on an international scale, the same as Chernobyl, while stressing that it is a less serious accident.
"It is clear that the two cases are different in nature," said the spokesman, Chief Cabinet Secretary Yukio Edano.
"Unfortunately the amount of radioactive material leaked was about one-tenth (of Chernobyl), but at least we were able to avoid explosions of the reactors," he said on the day the world marked 25 years since Chernobyl.
He said Japan had been able to draw on some of the lessons of Chernobyl when it dealt with its own crisis after a massive earthquake on March 11 sent a tsunami crashing into the plant, knocking out its cooling systems.
"Studies and research based on Chernobyl on the impact on health have become an asset shared by all of humanity," Edano said, saying that indirectly they had helped inform Japan's evacuation orders.
Japan has created a 20-kilometre (12 mile) no-go zone around the plant, where workers are still dousing reactors and fuel rod pools with water to prevent them from overheating and melting down.
No-one has died so far of radiation in Japan, unlike in Chernobyl, where two workers were killed by the initial explosions on April 26, 1986 and 28 other rescuers and staff died of radiation exposure in the following months.
Tens of thousands were evacuated and fears remain of the scale of damage to people's health after radioactive material blew into the neighbouring Soviet republics of Belarus and Russia and further into western Europe.
Controversy has raged for years, even between United Nations agencies, over the number of deaths directly caused by the Chernobyl disaster, with estimates ranging from just dozens to tens of thousands.