Check out this video from the live camera monitoring the Fukushima plant earlier this week.
If you watch from about the two minute mark you will begin to see some action and a spark and something extremely nasty begin to develop. This happened during the middle of the night and was later confirmed to be steam from a spent fuel pond. In the hours following there were many independent radiation measurements showing a sharp rise in local radioactivity. Many people posted on TWITTER and advised people with children to be careful and take precautions.
When a pool of fuel becomes too hot it begins to boil and release radioactive steam. This steam can be extremely toxic and hazardous to the environment. It can easily carry radioactive particles to areas very far from the plant, which might explain why there are hot spots of radiation all over the Kanto region in Japan.
This steam is also dangerous because it can cause electrical failure, or instrument fires, and stop the cooling water pumps which would be cause for even greater concern.
As TEPCO attempts to implement its newly devised cooling system this week and try to control the damage at Fukushima, it is apparent that everything is not under control and such information is only given if internet watchdogs are awake and spreading the word.
The radiation levels over the last three months still continue to stay high compared to normal background radiation levels and they do spike every now and then.