Plutonium
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Plutonium - the 94th element in the classification
of elements - was discovered in 1940 by the American researchers Seaborg,
McMillan, Wahl and Kennedy as the second transuranium element upon bombardment
of uranium-238 with deuterons, thus forming Pu-238. Today 15 Pu-isotopes
are known. Due to its property as fissile material, the isotope Pu-239
(half-life 24,110 years) is of specific importance. The elements 93
and 94 following the 92nd element - uranium - in the classification
of elements have been named analogously to uranium, which is named after
the planet Uranus, 'neptunium' and 'plutonium', the planets Neptune
and Pluto following Uranus. Plutonium is generated by neutron capture
in uranium-238 and two subsequent beta decays according to the following
scheme:
U-238 + n ==> U-239 ==> ß-decay ==> Np-239 ==> ß-decay
==> Pu-239.
In nature, plutonium-239 occurs in tiny quantities
in minerals containing uranium (pitchblende, carnotite) - one Pu atom
per 1 trillion and more uranium atoms. It is formed from U-238 by neutron
capture released upon the spontaneous fission of U-238. In above-ground
nuclear weapon tests, approx. six tonnes Pu-239 were released into the
atmosphere and distributed all over the world, so that in Central Europe
for example, about 60 Bq Pu-239 per m2 have been deposited.
Plutonium is a radiotoxic substance and its chemical toxicity as a heavy
metal is therefore negligible. The radiotoxic effect of plutonium is
very serious in the case of inhalation of the finest Pu aerosols; ingestion
of plutonium is about 10,000 times less dangerous, since only 1/100
percent of plutonium is absorbed by the intestinal mucosa, 99.99% is
excreted immediately.
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11 - 15 March 2018
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30 September - 04 October 2018
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