TOKYO - Contaminated water with dangerously high levels of radiation is leaking from a storage tank at Japan's crippled Fukushima nuclear plant, the most serious setback to the clean up of the worst nuclear accident since Chernobyl.
The storage tank breach of about 300 tons of water is separate from contaminated water leaks reported in recent weeks, plant operator Tokyo Electric Power Co said on Tuesday.
The latest leak, which is continuing, is so contaminated that a person standing 50 centimeters (1.6 feet) away would, within an hour, receive a radiation dose five times the average annual global limit for nuclear workers.
After 10 hours, a worker in that proximity to the leak would develop radiation sickness with symptoms including nausea and a drop in white blood cells.
"That is a huge amount of radiation. The situation is getting worse," said Michiaki Furukawa, who is professor emeritus at Nagoya University and a nuclear chemist.
The embattled utility Tokyo Electric has struggled to keep the Fukushima site under control since an earthquake and tsunami caused three reactor meltdowns in March 2011.
Japan's Nuclear Regulation Authority has classified the latest leak as a level 1 incident, the second lowest on an international scale for radiological releases, a spokesman told Reuters on Tuesday.