NORM and TENORM

About 68% of the total amount of radioactivity on Earth is of natural origin, i.e., both primordial and cosmogenic radionuclides, while the remaining 32% is due to human activities. 

NORM is an internationally adopted acronym for Naturally Occurring Radioactive Material while TENORM stands for Technologically-Enhanced Naturally Occurring Radioactive Material. 

Historically, a material was arbitrarily defined as radioactive when it exhibited a specific activity greater than 74 kBq.kg (i.e., 2 nCi.g ) later this value was converted into 70 kBq.kg.  

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