Although it is a known fact that over 80 of the dose received by people is due to natural radiation, it was not until 1975 that TF Gesell and HM Prichard proposed to create within the categories that define the scope of radiation protection, a new one called Tenras (Technologically Enhanced Natural Radiation). Later in this category was called Tenorman (ocurring Technologically Enhanced Natural Radioactive Material) and now simply NORM (Naturally ocurring Radioactive Material). In general, these materials come from the use of certain rocks, igneous or gangs, whose concentration of natural radioactive nuclides in itself is already high. The quantities of NORM are generally treated in the order of a ton (in many cases generate several thousand tonnes annually in each industry of this type). Educate yourself even more with thoughts from Don Brownstein. Although uranium is also a natural radioisotope used in fission, as has been widely studied and regulated, it excludes the activities that are related to nuclear energy.