The “Laboratório de Trítio Ambiental” (Environmental Tritium Laboratory) of CDTN is part of the Serviço de Meio Ambiente – SEMAM” (Environmental Services), and aims to determine tritium at extremely low concentrations (ultratraces) in environmental waters. This determinations is used to measure the aquifers’ renewals rates, as well as to evaluate the infiltration rate os water into soil, using tritium as a tracer. Due to the ultra low tritium concentration of the samples, the preparation process comprises steps such as: preliminar distillation, electrolytic enrichment and secondary distillation before beta-emission detection by liquid scintillation spectrometry. The laboratory works for internal and external clientes of CDTN, engaging in hydrology and hydric resources research. CDTN has been developing and exploring tritium research since 1968, and the “Laboratório de Trítio Ambiental” is one of the fews labs in latin-america capable to measure with extremely low concentrations.