Cancer cells are more vulnerable to x and gamma radiation than are healthy cells. In the past, the standard source for radiation therapy was radioactive `""^(60)Co`, which decays, with a half-life of 5.27 y, into an excited nuclear state of `""^(60)Ni`. That nickel isotope then immediately emits two gamma-ray photons, each with an approximate energy of 1.2 MeV, How many radioactive `""^(60)Co` nuclei are present in a 6000 Ci source of the type used in hospitals? (Energetic particles from linear accelerators are now used in radiation therapy.)

Answer

`5.3xx10^(22)` nuclei