Reactor #1- No. 1 unit's reactor core has been damaged, but its containment vessel was not. The building was "severely damaged" by an earlier hydrogen explosion.
Reactor #2- No. 2 unit's containment building, which houses and protects the reactor core, "is damaged and water is leaking." No. 2 unit's turbine building that had radiation levels some 100,000 times normal, utility company and government officials said Sunday, correcting an earlier finding of 10 million times normal. (Here we go again.... one hundred thousand, ten million times... they're not sure?)
High levels of radioactive substances may have come from "melted fuel," Edano said Monday. This could suggest a full or partial meltdown in the No. 2 reactor, which occurs when nuclear fuel rods get so hot that they melt the steel and concrete structure containing them, spilling out in a worst-case scenario into the air and water with potentially deadly results.
Reactor #3- The No. 3 reactor has been of particular concern, experts have said, because it is the only one to use MOX -- a combination of uranium and plutonium fuel considered more dangerous than the pure uranium fuel used in other reactors. This had 10,000 times the amount of radiation typical for that locale, Nishiyama had said. Three workers who stepped in it Thursday tested positive for 173 or more millisieverts of radiation, including two with direct exposure on the skin. Around noon on Monday, all three were released from the National Institute of Radiological Sciences after four scheduled days of treatment and monitoring, the research hospital said.
It was stated Friday that damage was suspected in the reactor, on Saturday its assessment changed to "unknown" -- a further acknowledgment of uncertainty as to whether the contaminated water was the result of a leak in the nuclear reactor core or had some other cause.
(Maybe yes maybe no, best to go with "unknown" as the official word)
The building of the No. 3 reactor was "severely damaged" after an explosion caused by the buildup of hydrogen gas, the Japan Atomic Industrial Forum reported. Its core reactor is also damaged and its fuel rods are either partly or fully exposed.
Reactor #4- Along with the Nos. 5 and 6 reactors, the No. 4 was offline in a scheduled outage when the earthquake hit, and as a result the reactor's water level and pressure are safe. The nuclear fuel rods were in the unit's spent fuel pool, but not the reactor itself. The reactor's pool of spent nuclear fuel was "possibly damaged," which is why authorities have said its water levels are low and why they've made repeated efforts to fill it up with water.
Reactor #5- As with units No. 4 and 6, this reactor was offline in a scheduled outage when the quake hit and there are no major issues with the reactor and core itself. The cooling system in the pool of spent nuclear fuel is thought to be functioning, though there are continued concerns about powering the reactor's cooling system to ensure the fuel rods contained within remain cool. As with unit No. 6, three holes were punched in the building earlier to relieve pressure and prevent a hydrogen explosion.
Reactor #6- Same as #5.
* As reported by CNN
I am convinced the Tokyo corporation that owns these nuclear power plants, needs to have a higher level of oversight, and by oversight I don't mean official announcements that vary from 10,000 to 10 million times radiation leakage numbers. I understand they are in crisis mode and in the midst of a serious & unplanned disaster, but let's face it, if you build a nuclear power plant on an earthquake fault line, it was a disaster they should have been better prepared to handle.
For the record, this is an international matter. Trace levels of radiation from Japan have been registered as far away as the east coast of the U.S. in Massachusetts rainwater.