Joel wrote, "First, the difference in half-lives conceals several
other factors. Keep in mind that the intensity of radioactive material is
inversely proportional to the half life. The more rapid the rate of decay,
the more intense a source will be and the shorter its half life. Of course,
a shitload of low activity material can emit radiation as intensely as
relatively little highly active material and will do so for a very long time
so the amounts of material that are produced must be considered."
Right on! The media often talks about "highly radioactive
plutonium." If this were the case, Pu would not be around very long. In
addition, most (but not all) Pu isotopes decay be alpha emission, which
means that you could carry Pu around in an envelope in your pocket and not
be exposed to any radiation. As the Pu decays, it will decay into daughter
products that have gamma rays associated with their decay so, in time, the
Pu would start to generate a radiation field, but it would some time.
Joel then continues, "Second, the type of radiation and the type of
material must be considered. The long-lived isotopes (the transuranics,
particularly plutonium) are essentially poisons. They must be ingested to
have any effect, and are most deadly when breathed (recall plutonium is
heavier than lead). I am not saying plutonium is not dangerous. It is,
particularly if there is a chance of ingesting it."
At one time, Bernard Cohen (U of Pittsburgh) reportedly had an open
offer where he would eat one gram of Pu if an anti-nuclear critic would
drink one gram of nicotine. He never had any takers. Pu is very insoluble,
PuO2 even more so. The dangers of breathing in Pu and other actinides is
that, once in the lungs, they tend to stick and decay by alpha emission.
The high (~4 MeV) energy of the alpha particle is deposited in the lung
tissue and causes all the damage in a concentrated area. Exposure to radon
gas is a similar hazard: Ra-222, a daughter of Ra-226, is a gas and can be
inhaled. It has a short half life (~4 d) and, if it decays in the lungs (to
Po-218), the Po-218 is stuck in the lung and will, in time, decay to stable
lead but emit, in the process, emit 3 alpha particles.
Joel the continues, "Third, we live comfortably with natural poisons
whose half life is infinite (e.g. arsenic), and accept the mass production
of many others. I believe the volume of high level waste (highly
radioactive) produced in nuclear reactors is comparativley quite small."
This is often ignored by the media and the general public. Stable
elements, such as As, Hg, Cd, are released in the burning of fossil fuels,
mainly coal. Hg used to be used as a fungicide for grain before it is
planted. There have been cases where people used this grain to feed their
livestock and then became poisoned by eating their livestock. I believe
there was a case like that in Texas years ago.
Chuck Vandergraaf
Pinawa, MB
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