This book shows how to use radioisotopes and the emitted ionizing radiations effectively and safely. It describes decay and stability criteria, necessary precautions to ensure radiation protection and the detection of alpha, beta and gamma rays including spectrometry. Chapters cover calorimetry, liquid scintillation counting, how to use secondary standard instruments, high resolution detectors and how to calculate counting results estimating uncertainties and allowing for the statistics of radionuclide decays. Other subjects examined include industrial and scientific applications of alpha, beta, and gamma rays, neutrons and high energy radiations.