FURTHER UPDATE: I found the wikipedia writeup on the incident quite useful - highly factual, and essentially captures all that has happened [Wiki link]
UPDATE: I'm surre there is still great anxiety among the public on the risk of radiation leakage and meltdown at the Japanese reactors. I want to thank the person who posted this excellent step by step explanation of how things will unfold at the reactor. Right now the Japanese are pumping saltwater mixed with boron into the reactor. The boron slows the nuclear reaction and causes the reactors to cool faster - this should work according to the MIT professor but will permanent damage the reactors. Even if this fails completely, the worse case scenario is a systematic cleanup:
Right now there is small radiation leakage because they use salt water instead of pure water which has a tendency to absorb some of the radioactive material. They also have to reduce pressure in the reactor by opening values to and that also leads to limited amount of radioactive material to go to the atmosphere. These amounts are small since they evacuated a large area around the nuclear plants..
We are seeing panic due to a lot of misinformation and the media playing up the situation. Foreign govt precautionary moves such as UK & China wanting to evacuate their citizens from Tokyo is causing panic.
Based on another expert's view roughly 24 hours from this afternoon we will know exactly what is going to happen - success, failure or calamity. I guess in the mean time there is just no way to get people to calm down as it is difficult to get them to gather correct information and think through the situation in a calm manner. When people just read headlines such as this one that just appeared : More nuclear reactors show signs of trouble it can be really scary but actually the Japanese govt was just reporting that 2 other reactors have slightly higher temperatures - the trouble, if any, is small and contained.
Right now there is a panic going on among people and financial markets surrounding the nuclear plants in Japan. Expats are reported fleeing Tokyo and foreign govts have issued warnings about the dangers of radiation for citizens located in Japan. The 24 hour news media reported several blasts and a fire at 3 nuclear plants. The Japanese stock market (Nikkei) plunged by 14% setting off a full blown financial panic in Asia. This is an exercise in cool heads and ability to analyse information in a situation where there is panic, confusion and all out fear.
Nobody actually knows what is going on in those nuclear reactors because they cannot get close enough to take measurements. The official information released talk of a "possible meltdown" adding to the panic.
While there is a possiblity of catastrophy and calamity, human emotion has mingled together with sketchy facts and precautionary assumptions to react as if the worse case scenario which has a finite probabilityof occuring is the primary outcome. The worse case scenario goes something like this - meltdown of the reactor, failure of 2 layers of containment and leakage of radioactive material into environment. Some people are saying the containment vessels might have been damaged by the quake.
Yesterday I watched an expert trying to explain to a reporter the technicalities of these nuclear reactors. The reporter eager to pump up the excitiement surround their failures seemed to ignore what the expert from a university tried to say - the containment vessels are built with safety margins far in excess of what was necessary to withstand the Friday quake. Even if there is a meltdown, radiation would leak but nothing like the Russian Chernobyl disaster would occur. But cleaning up would be extremely messy.
Breaking Headlines such as this one add to the panicL
It is a warning by the Japanese govt that the area surround the plants have dangerous level of radiation after the explosion. You think about it - one would expect radiation at the nuclear plant compound to be quite high after explosion - the explosion releases some of the radioactive gases collected in the reactors.
The final mess assuming that everything fails and nuclear material leaks out of the containment vessels melthing through the surface probably will be quite serious to the environmental. However, the place has been evacuated and an eventual cleanup probably cost several billion dollars.
Compare the damage to the reaction of the financial markets. The Japanese market lost 14% of value - that is equivalent to US$400B and you include losses in regional bourses it will total about US$500B or half a trillion dollars. ....and these losses occurred even before anyone knows what is actually happening in those nuclear reactors. - the explosion seem to have set off the panic. Quite incredible....I would say how panic can set in and spread....
Here a minister tries to explain to the public that people outside the 30Km should stay calm but to no avail:
Foreign investors have flee the Japanese stock market causing a total drop over 1.5 days of 20%. In the Kobe earthquake the Japanese market fell about 21% but that fall took more than 3 months. In the 1st 2 days of the Kobe earthquake, the fall was about 5-6%.