CORRECTIONS FOR VOLUME HYDROGEN CONTENT IN COAL ANALYSIS BY PROMPT GAMMA NEUTRON-ACTIVATION ANALYSIS

Prompt gamma neutron activation analysis, PGNAA, is a useful technique to determine the elemental composition of bulk samples in on-line measurements. Monte Carlo simulation studies performed in bulk coals of different compositions for given sample size and geometry have shown that both the gamma count rate for hydrogen and the gamma count rate per percent by weight for an arbitrary element due to (n, gamma) reactions depend on the volume hydrogen content, being independent of coal composition. Experimental results using a Cf-252 neutron source surrounded by a lead cylinder were obtained for nine different coal types. These show that the gamma-peak originated by (n, n' gamma) reactions in the lead shield depends on the sample density. Assuming that the source intensity is constant, this result enables the measurement of the coal bulk density. Taking into account the results just described, the present paper shows how the gamma-peak intensities can be corrected for volume hydrogen content in order to obtain the percent by weight contents of the coal. The density is necessary to convert the volume hydrogen in percent by weight content and to calculate the bulk sample weight.