Nuclear power plants produce harmful radioactive waste while other forms of electrical generation do not. Mining for coal brings uranium to the surface of earth. That radioactivity can have a greater effect on the environment than nuclear waste. Radiation causes cancer. Thus, it cannot be used to cure cancer.
Excessive radiation can cause cancer.
However, Utilizing the destructive power of radiation on cancerous cells can cure cancer. Once a material is radioactive it is radioactive forever. One can physically remove the radioactive particles from the material or wait for it to decay. Some radioactive decay in a short time while other decays might last longer than 10,000 years.