Natural carbon-14 (C-14) is generated by a (n,p)-reaction
of neutrons of cosmic radiation with nitrogen -14 in the upper atmosphere.
Measurements of wood from the 19th century resulted in about 230 Becquerel
C-14 per kilogram carbon. This natural (pre-industrial) ratio between
the radioactive carbon-14 and the stable carbon-12 in the atmosphere
is today influenced by two opposed effects:
The massive generation of CO2 by burning
fossil C-14-free energy carriers leads to an increase in the proportion
of C-12. Thus the pre-industrial ratio of C-14 to C-12 is reduced.
In the mid-50s, this so-called Suess effect resulted in a five percent
reduction of C-14 activity per kg carbon in the atmosphere.
Nuclear weapon tests in the atmosphere and disposal
from nuclear facilities cause the proportion of C-14 in the atmosphere
The natural concentration of C-14 in the human body
leads to a C-14-activity of about 3 kBq. The resulting effective dose
amounts to 12 µSv/year.
11 - 15 March 2018
30 September - 04 October 2018
Prague, Czech Republic