BS ISO 12799:2015 pdf free.Nuclear energy – Determination of nitrogen content in UO 21 (U,Gd)O2 and (U,Pu)O2 sintered pellets – Inert gas extraction and conductivity detection method.
BS ISO 12799 describes a procedure for measuring the nitrogen content of 002, (IJ,Gd)02, and (U,Pu)02 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 Ii nitrides).
2 Principle
For determining the nitrogen content of 002, (U,Gd)02, or (IJ,Pu)02 pellets, an analyser is employed which operates according to the carrier gas principle, using helium as the carrier gas, the nitrogen content being determined in a thermal conductivity cell.
The weighed samples to be analysed are heated in a degassed high purity graphite crucible at a temperature of more than 1 770°C in a helium atmosphere. This high temperature destroys the majority of the nitrogen bearing compounds and causes nitrogen to be released along with other gaseous components like CO. C02, and H2. The released gases are then swept by the carrier gas through oxidation and absorption columns to trap interfering species. The nitrogen passes through without being retained. and its quantity is subsequently measured in the thermal conductivity cell.
3 Interferences
The samples will not be heated to temperatures above 2 200 °C since this would cause a reaction to take place between the 002, (U,Pu)02, or (U,Gd)02 pellet and the graphite, resulting in large quantities of CO2 gas being released. These large quantities of gas can be not completely trapped and would lead to errors in conductivity measurement.
4 Reagents and materials
During the analysis, unless otherwise stated, use only reagents of recognized analytical grade. The reagents and materials below serve as examples to be used according to manufacturer’s recommendation.
4.1 Helium.
Use helium as carrier gas with a purity of a volume fraction 99,995 %.
4.2 Nitrogen.
If nitrogen is used as calibration gas it will be of a purity 99,998 % in volume fraction.BS ISO 12799 pdf free download.