> On Thu, Mar 17, 2011 at 4:48 PM, lbo83235 <lbo83235 at gmail.com> wrote:
>
> > On the off chance that my earlier reference to the half-life of U-235 was
> mis-taken
> > as cheap hystericizing or dopey moralizing, let me elaborate and sharpen
> the point.
>
> I missed it. Had I seen it, I would have considered it hysterical. No
> mistake.
>
> U-235 is not the big issue, precisely because its half-life is in the
> millions of
> years. Less than a millionth of it decays in a year. Besides, it is alpha
> decay.
> Almost anything stops alpha particles -- a few cm of air, a sheet of paper,
> ...
> and they don't do much damage anyway.
This seems accurate - the risk is not U235, but cesium and strontium, both carcinogenic in a big way. But nonetheless, this needs to be put in an epidemiological perspective, rather than an emotional one.
As I mentioned earlier, Iodine is a risk and is by far the most prevalent of the radioactive emissions from meltdown, but actual impact on death rate is very low. Radioactive iodine (I131) can replace non-radioactive iodine I128 binding to thyroid cells and can produce thyroid cancer. However, thyroid cancer has a survival rate of 95%. Further, the half-life of I131 is 8 days, so total impact on population less than the others. Paradoxically, high exposure of I131 is less dangerous than low exposure - high exposure will kill the thyroid cells, rather than cause malignancy. Total deaths from i131 attributed (so far) to Chernobyl is 10.
Cesium137 and Strontium90 have more serious public health impact, both displacing normal minerals in bones (calcium, potassium). Further the half life is 30 years, so they can last a lifetime in the body causing cancer.
Nonetheless, if you believe the IAEA, the worst disaster ever with the worst cleanup safety procedures ever (that is, none) - Chernobyl - had 37 deaths from immediate firefighter exposure, 10 deaths from iodine and perhaps 4,000 expected deaths over the lifetime of the entire population including Cesium and Strontium exposure. This was after total meltdown, evaporation of reactor into the air (with no containment vessel), and the (criminal) use of one-half million people in vicinity after the accident to clean up, etc.
And today, all of the iodine, Cesium and Strontium in the entire area is at safe levels. This surplus death rate is on the same order of the surplus deaths expected among the same population from smoking for perhaps an additional week in their lives - important, but not earth-shattering.
Compare that worst-case possibly of excess deaths to the immediate effects of the tsunami. -- Peter Fay http://theclearview.wordpress.com