The original reason that oil was first refined was to power kerosene lamps - which up until that time, the 1860's, were fueled by
whale oil. One of the driving forces for the development of petroleum was a shortage of
whales.
It is a mixture of things that causes the continuing oil fetish in my opinion. One is certainly inertia. Another is that we
only count internal costs - the price of oil per barrel - and ignore the external cost - air pollution
including carbon dioxide, health costs, destruction of habitat and land, for example.
If we charged the true external cost of oil, my guess is that oil would easily be measured in the hundreds of dollars, in which case people would
not use it very much.
The most important factor in the continued use of oil is
ignorance. Add a fair amount of panic with a dollop of paranoia and a few wisps of indifference and you have a perfect storm.
Oil depletion is no where near as disastrous as climate change. Oil depletion is a
good thing. Oil use should be phased out and banned as soon as is possible, and replaced by nuclear energy and to the extent they are available, renewable forms of energy.
As for your question about the use of nuclear materials for non-energy use, I would expect, without calculation, that the total amount of radioactivity contained in all the world's medical uses does not even equal the output of a single reactor.
That noted, the entire inventory of nuclear fuel material on the planet does not exceed the radioactivity of the ocean. The inventory of potassium-40 alone in the ocean exceeds 500 billion curies. Here is a calculation from early in my tenure at DU that I did showing this:
http://www.democraticunderground.com/discuss/duboard.php?az=view_all&address=115x5609#20159The Chernobyl reactor is said to have contained about 1 billion curies. (This estimate can be calculated from this reference, table 1:
http://www.unscear.org/docs/reports/annexj.pdf. I have used the column for S1 to estimate this number, converting petabequerels to curies.)
Chernobyl was a reactor at the
end of its fuel cycle when it exploded, thus it's radioactivity was at it's maximum. Thus, for this reason and a lot of other reasons, Chernobyl is the
worst possible case.
It would take, therefore 550 Chernobyl/fuel cycles to equal the normal radioactivity of the ocean from potassium alone. But the radioactivity of the ocean is not just determined by potassium, but also by the uranium present and all of the decay daughters of this uranium. I have argued in the past on this site for removing this radioactivity (from uranium) from the ocean for industrial purposes.
There is an important difference between the radioactivity in a nuclear reactor and the potassium in the ocean. All of the potassium in the ocean is mobile and readily soluble. By contrast, much (but not all) of the material released by the Chernobyl reactor is basically immobile, and will remain for quite some time near the place it landed, mostly the immediate vicinity of the reactor. The most
serious isotopes released were those with the shortest half-life, because half-life is inversely proportional to radioactivity. (The proportionality constant is the negative natural logarithm of the number 2.) Thus much, though certainly not all, of that billion curies has now decayed to background. For instance, all of the cerium-144 released by the reactor is gone and now has transformed into nonradioactive neodymium. All of the radioxenon isotopes are gone. All of the iodine-131 is gone. The disappearance of these highly radioactive isotopes means that a great deal of the radioactivity originally present has decayed away.
It can be shown that the radioactivity associated with nuclear power does not rise linearly with time. On the contrary, it rises, depending on the power used, asymptotically to a defined limit, beyond which it cannot increase unless one increases the power. For an i
th isotope present in a nuclear reactor, as a loose first approximation, the amount of a particular "waste" product approaches its limit (which depends on factors including the fission yield for a reactor type - fast, epithermal, or thermal - and total power of the reactor or a large number of reactors of that type) L
i according to the following equation A
i = L
i(1 - e
-kt) where k is the activity constant (the negative natural logarithm of 2 divided by the half-life), and t is the time that the
ith isotope has been accumulating. Without simplification, the mathematics is somewhat more complex, but that is the basic idea to a first approximation.
A more detailed discussion of this phenomenon, which is almost always overlooked by people who don't know what they are talking about, can be found, among other places in William Stacy's
Nuclear Reactor Physics, (Wiley, 2001) on page 213. (Stacy's solution to the equation, which he provides for Iodine-135 in a function called
I(t) includes another term to include any of the iodine isotope that may have been present before reactor start. If the reactor is starting for the first time, this parameter is equal to zero. His function specifies the parameter I call, for simplicity, "L
i" in terms of its constituents, including fission yield, the half-life of the isotope, the bulk neutron capcture cross section for the isotope, and the neutron flux.)
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