Originally Posted by
Salodin
Yes, but a CT scan also ends after a short while. If the radiation persists in that area, then that's horrible for japan. But this is also all assuming it's at that level of radiation in the area, since all they are willing to say is "minimal amount". It's the vagueness that annoys me...
There's nothing vague about it. A millisievert is a unit that represents an amount of energy your tissue would absorb. For instance, according to wikipedia, this are the amounts of millisieverts you could expect to absorb from a few different things.
Code:
Eating 1 banana 0.0001 mSv
Dental X-Ray 0.005 mSv
Mammogram 3 mSv
Brain CT scan 0.8–5 mSv
Chest CT scan 6–18 mSv
Posted already, but this chart may be helpful.
The blue line on the chart is the maximum value observed, in millisieverts per/hour, on the perimeter of the plant. So even at the worst of it, standing at the perimeter of the plant for an entire hour would result in perhaps less radiation than you might absorb in the process of having a single chest CT scan.
Also, these rates are going to decrease in a manner that is inversely proportional to the square of the distance from the source. So, in other words, let's say the perimeter of the plant was 50 meters away from the source (the reactor.) At that point, the greatest rate thus far was 12 mSev per hour. Being 100m away from the source, or around 300 feet away from the reactor, would result in radiation levels of around 3 mSev per hour. Standing there for an hour would yield the radiation dose equivalent of a mammogram.
In reality, that inverse square relationship isn't going to apply exactly as it's only perfectly accurate a source that isn't shielded in any way and that exists in a single point. At places close to the plant, weird geometry and reflections are going produce a variety of results. The 12 mSev max was the point on the perimeter where these factors coalesced to produce the greatest results. Also, the farther away you get, the more applicable the generalization becomes in the sense that those geometry factors are less significant. It will actually decrease faster due to things absorbing some of it along the way.
Either way, you wouldn't want to be just living near the reactor while this is going on. But nobody outside of the employees working near the reactor are in any danger, at this point.