Tritium (symbol T) is produced in the upper atmosphere by neutron cosmic rays pr

Question

Tritium (symbol T) is produced in the upper atmosphere by neutron cosmic rays primarily through the 14N(n,T)12C and 16O(n,T)14N reactions. Tritium has a half-life of 12.3 years and decays by emitting a beta-particle with a maximum energy of 18.6 keV. Tritium exists in nature almost exclusively as HTO. and in the continental surface waters and the human body it has an atomic T:H ratio of 3.3 x 10^-18. Since the human body is about 10% hydrogen by weight, estimate the tritium activity (Bq) in a 100-kg person.

Explanation / Answer

tritium H3
Bq = [ 0.6931 * m * Na / (t1/2 * M) ]
m = (0.10)(100 000) = 10 000 g
Na = avogadro number 6.02*1023
t1/2 = half-life (12.3)(365)(24)(60)(60)

      = 3.88*108 sec
M = H3 amu 3.016 g/mol

data plug in calculated result
Bq = 3.57*1018 atoms disintegrated per sec

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