Radon is a radioactive gas produced from uranium decay, naturally present in rocks and soils. The present book aims mainly to investigate the natural radioactivity, constructs appropriate method to detect and estimate the subsurface distance of the source of radioactivity in natural rocks by using solid state nuclear track detector SSNTD. A study of radon diffusion has been developed and applied to estimate the depth of known radioactive location, containing various amounts of radionuclides, of interest. The columns with multistage solid state nuclear track detectors SSNTD (detector chambers) were prepared and used on drilled borehole and fractured zones. Analyses of these detectors indicate that, the diffusion of radon is markedly exponentially changed as the height from the boundary surface of the radioactive anomalies.