F. Carbon-14 Background Information Carbon-14 is produced naturally by interaction of cosmic rays with the nitrogen in the atmosphere. Although its radioactive half-life is long - 5760 years - the process of natural production has been going on for such a great time that the rate of production and rate of decay are in equilibrium, i.e., just as much is formed each year as decays away. There is a constant exchange of carbon-14 atoms between the atmosphere and the surface of the earth on the one hand, and the deep ocean on the other, with the latter constituting a reservoir holding about 96 percent of the atoms. Nuclear detonations can also produce carbon-14 by interaction of the neutrons, produced at the time of the explosion, with nitrogen of the atmosphere. Approximately 400 megatons of total yield fired in the air (surface bursts "lose" about one-half of the neutrons into the ground) will produce sufficient amount of carbon-14 to equal the amount normally present in that part of the earth's biosphere that determines radiation exposure to man. However, half of this newly-added carbon-14 “disappears” into the deep ocean within about 33 yearsi>-, One-half of that remaining in the atmosphere likewise "disappears" in the following 33 years, until only a few percent remains. Radioactive isotopes act chemically similar to their stable counterparts so that not only is stable carbon but also carbon-14 found in all living cells. Thus, although carbon-14 emits a beta particle of very low energy that travels a very short distance it nevertheless irradiates 2 >