Full Description ADOPTED_FROM:EN ISO 12799:2019 ISO 12799:2015 describes a procedure for measuring the nitrogen content of UO2, (U,Gd)O2, and (U,Pu)O2 pellets. Nitrogen in nuclear fuel may be present either as elemental nitrogen or chemically combined in the form of nitrogenous compounds. The technique described herein serves to determine the total content of nitrogen excluding those compounds whose decomposition temperature is above 2 200 °C (most notably Pu and U nitrides).