Radiocarbon (14C) is the beta-emitting natural isotope of cosmogenic origin. It is formed in the upper atmosphere layer as a product of nuclear reaction between cosmic radiation and nitrogen nuclei. Radiocarbon created in this way is diluted by the stable carbon isotopes (12C and 13C). Estimated concentration of 14C in the environment is about 1·10-9 % of mass of carbon isotope mixture. Total amount of radiocarbon present in the environment is about 75.000 kg, what is an equivalent of 1.27·1019 Bq of beta radioactivity. Owing to its long half-life (5568 years).