College Physics 10th Edition by Raymond Serway,Chris Vuille

Exercise 45

Many radioisotopes have important industrial, medical, and research applications. One of these is 60 Co, which has a half-life of 5.2 years and decays by the emission of a beta particle (energy 0.31 MeV) and two gamma photons (energies 1.17 MeV and 1.33 MeV). A scientist wishes to prepare a 60 Co sealed source that will have an activity of at least 10 Ci after 30 months of use. What is the minimum initial mass of 60 Co required