[en] Consideration of gaseous impurities in NPP coolants, their sources and the levels of their content is made. The data on the content of gaseoUs impurities (N₂, N₂O and nitrogen oxide) in the nitrine coolant during the reactor loop plant operation are reported. The content of gaseous impurities N₂, N₂O and nitrogen oxide in the nitrine coolant is determined by the method of reaction gas chromatography. As can be seen from the obtained data, nitrogen oxide, N₂ and N₂O are distributed uniformly over the circuit of the plant. Increased content of gaseous impurities and nitrogen oxide is observed in steam-gas chamber of the primary circuit condenser. The obtained data can be used for development of recommendations on regulated content of gaseous impurities in the primary coolant circuit under operational conditions