Potassium is a crucial element for the healthy operation of the
human body. Potassium occurs naturally in our environment (and
thus our bodies) as three isotopes: Potassium – 39, Potassium – 40
and Potassium – 41. Their current abundances are 93.26%, 0.012%
and 6.728%. A typical human body contains about 3.0 grams of
potassium per kilogram of body mass.
1. How much Potassium – 40 is present in a person with a mass of
80 kg?
2. If, on average, the decay of Potassium – 40 results in 1.10 MeV
of energy absorbed, determine the effective dose (in Sieverts)
per year due to Potassium – 40 in an 80 kg body. Assume an
RBE of 1.2. The half-life of Potassium – 40 is 1.28 x 109 years.