You are working as a technician in the radiology department of a large hospital. One of the radioactive isotopes that is used to treat cancer is 60Co. Although use of this isotope is decreasing due to the availability of electrons from linear accelerators, 60Co is still in wide use where accelerators are not available. A radiologist has asked you to supply a container of 60Co, and you need to determine if a particular sample on the supply shelf is still viable for use. During your training, you learned that cobalt is not viable for medical use if its activity has fallen to 60.0% of its activity when delivered to the hospital. The label on the sample states that the delivery date was January 31, over three-and-a-half years ago. It is now December 31. Should you send this sample to the radiologist, or should it be disposed of? (60Co has a half-life of 5.27 yr.)
