TEPCO announced on Thursday that Unit 1 had experienced a meltdown. Most of the fuel rods have melted and fallen to the bottom of the reactor and have created holes in the containment.
The holes in the containment have flooded the basement of Unit 1 with 13 to 14 feet of highly radioactive water. A survey conducted by an unmanned robot on Friday found radiation levels of 1,000 to 2,000 mSv per hour in some parts of the ground level of Unit 1. A dose of 4,000 mSv is considered lethal. Japanese nuclear plant workers are limited to radiation exposure of 250 mSv per year.
TEPCO announced on Sunday that Unit 2 and 3 had also experienced a similar meltdown of their cores.
TEPCO is trying to prevent re-criticality at Unit 3 as temperatures soar.
A food manufacturer conducting private tests has found high levels of plutonium 30 miles away from the Fukushima reactor.
Higher radioactivity detected in Tokyo - Japan's Asahi Shimbun reports about 3,200 and nearly 2-thousand becquerels of radioactive cesium per kilogram were found in the soil of Tokyo districts of Koto and Chiyoda, respectively, from testing conducted between April 10th and the 20th.This amount is higher than what was found in the prefectures near the Fukushima plant and experts warn that other areas may be subject to radiation contamination as clusters of clouds containing radioactive material remain in the atmosphere.
TOKYO, May 15 (Xinhua) -- Key facilities at the Fukushima No. 1 nuclear power may have been damaged by the quake itself that day rather than tsunami-caused power loss that failed the reactor's cooling function, Kyodo News quoted a utility source said Saturday.
Data taken by workers entering the No. 1 reactor building at the crippled plant on the night of March 11 showing the radiation level was as high as 300 millisieverts per hour suggest a large amount of radioactive materials from nuclear fuel in the reactor was already released.
The findings may call for a review of preparedness against quakes at various nuclear power stations in Japan as they have primarily focused on securing auxiliary power supplies and embankment enhancement against tsunami after the Fukushima plant crisis, assuming that reactor facilities at the plant were unscathed by trembling.
On March 11, the power plant was shut down automatically just past 2:46 p.m. following the magnitude-9 quake. Within an hour, it was hit by at least two rounds of tsunami waves. The external power supply was then shut down, disabling the emergency core cooling system from injecting water at 4:36 p.m.
It has been thought that power loss failed the cooling system at the No. 1 reactor, releasing highly radioactive steam from the reactor pressure vessel.
Kyodo said a source at TEPCO admitted the possibility of key facilities having been compromised before the tsunami waves, saying, "The quake's trembling may have caused damage to the pressure vessel or pipes."