The nuclear disaster in Japan continues to go from bad to worse (though no doubt the nuclear power zealots will continue to insist its "safe" and our only hope, in spite of all the evidence to the contrary), with the latest earthquake reigniting reactor 4 at Fukushima - Sinister seven: what Japan's new nuclear crisis rating means.
As Japan raised the severity level of its nuclear crisis to match Chernobyl's seven, an Australian scientist explained what that meant.
Chemistry and physics professor Stephen Lincoln, of Adelaide University, said the main worry was the food stock in the ocean, where much of the radioactive material was being released.
While one of the radioactive substances, iodine-131, had a half-life of nine days, two others - caesium-137 and strontium-90 - could be more harmful in the long term as they had half-lives of 30 years, he said.
A half-life is the time taken for half of a sample of a radioactive isotope to decay into other materials.
"[People] should not venture into the ocean [where the radioactive materials are being released]; they should not eat any fish or seaweed from the ocean.
"The living species likely to be most affected are shellfish because they are stationary whereas fish that swim may pass through the area and out again. The shellfish such as mussels, oysters and clams certainly accumulate high levels of radioactivity.
"If they can stop the leaks, then the ocean can disperse the radioactivity until it becomes no more than background."
A level seven incident entails a major release of radiation with widespread health and environmental effects, while a five-rated event is a limited release of radioactive material, with several deaths from radiation, according to the International Atomic Energy Agency.
The scale is designed so the severity of an event is about 10 times greater for each increase in level.
Professor Lincoln said workers at the nuclear plant had to get the cores of the reactors continuously underwater to keep them cool, "otherwise it's going to go on and on and on unfortunately".
The cores, damaged during an earthquake and tsunami on March 11, have being releasing high radioactive substances into the atmosphere and ocean.
Japanese nuclear safety agency officials said the radiation released so far was estimated to be about 10 per cent of that from Chernobyl 25 years ago.
But they fear the total amount of radiation released in Japan may exceed Chernobyl's, spokesman for plant owner Tokyo Electric Power Company (TEPCO) Junichi Matsumoto said at a news conference today.