Latrade, two things I cant seem to hear in the media are:
1) The type of radiation and its half life currently being emitted?
2) The length of time it will stay in the environment?
Where can you get the real facts from???
I don't blame the media for not getting into too much detail on the isotopes. But essentially the steam venting that has to take place would release relatively short lived isotopes. That means that even though they may travel some distance, because they decay quite quickly, the immediate danger from exposure to radiation is in the surrounding area of the plant. By the time the particles reach outside the exclusion zone, the amount of radiation drops.
We also see that the peaks in radiation levels are relativley short lived. Again, the media doesn't really clarify this, it will report the high levels (harmful levels) in the immediate area of the plant and then also state an increase in detecting radiation in Tokyo or elsewhere. The difference is the levels in Tokyo, while increasing aren't at a concerning level.
The isotopes and their half life vary, the Nitrogen-16 isotope is very short lived. I was taught at college that by the time you've typed R-A-D-I-O-A-C-T-I-V-E-D-E-C-A-Y it's gone. So that's not a huge concern,
but tritium, iodine-133, cesium-137 and strontium-90, among others, all have much longer half-lives and health risks. Even so the significance of the health risks varies as some don't survive as long in the body as others to do much harm. Iodine is the biggest concern at elevated levels as it collects in the thyroid, the quicker stuff gets out the body the better.
The only realy picture we can get is from monitoring the isotopes. It's likely that the containment vessel in #2 plant has been breached, but we can't be 100% sure as people can't get in to check. We know something is occuring as we know what isotopes there should be from the steam release, but they're also getting isotopes that would indicate exposure of the fuel rods.
Best case scenario with that at this point is that #2 has been breached, worst case scenario (and given the difficulty in getting information could be a reality) is that it's related to the fire at #4 plant and the spent fuel rods.
Sources of good information are diffuclt about the best is the IAEA (International Atomic Energy Agency). Unfortunately their website is down, but they tend to only put up a daily press release there. However, their facebook page is updated very frequently and is the best source I've come across.
As the website is down I can't link to it, so you'll have to do the old google.