Comparison of single- and dual-axis rotation techniques for total nitrogen in explosives by fast neutron activation analysis

Total nitrogen content in organic explosives and relate materials can be determined by fast neutron activation analysis (FNAA) to an absolute accuracy comparable to wet chemical or combustion analysis, i.e. to within less than 0.1% N. This is accomplished by dual-axis rotation of the sample and a carefully selected reference standard during neutron irradiation. The optimum reference standard is one of similar composition, density, weight and volume to the sample being analyzed. Rapid pneumatic transfer of organic explosives of low mechanical shock sensitivity poses no special safety problems. For large numbers of individual samples, a multiple sample irradiation system with single-axis rotation can be used for more rapid analysis. Precision and accuracy by this method are not as good as compared to a dual-axis rotation technique. Absolute accuracy for total nitrogen is in the order of 0.2%. This method is useful only for those reactions where the half-life of the product is long enough to allow for sequential counting of multiple samples for a single irradiation.