Determination of fluorine in steel-making slags by the 14 MeV neutron activation analysis

The content of calcium fluoride in steel-making slag and fluorspars were analyzed to determine fluorine by non-destructive 14 MeV neutron activation analysis. A dual-sample irradiation assembly was used for irradiating a sample to be analyzed and a reference sample with a definite amount of calcium fluoride at the same time. The amount of fluorine was determined from the ratio of the counts in the photopeak areas of 0.197 MeV energy of O-19 calculated by the TPA method in the spectra of both samples. The decay curves for the gross counts, background counts and photopeak area counts were analyzed by the method of least squares using O-19, N-16, F-18 and Al-28 as the factors. As the result, it was confirmed that O-19 was obstructed only by N-16 in this case. The experimental conditions obtained from the study on the optimum conditions of the activation analysis and those obtained by the results of the ratio of photopeak/background agreed well. The actual analytical conditions of 30s for sample irradiation, 60s for decay and 15s for measurement were adopted to allow the decay of N-16, and the effect of N-16 on the counts was suppressed to about 4%. There was a significant difference in the gradients of the calibration curves between synthetic steel-making slag and calcium fluoride standard, therefore it is necessary to use the calibration curves for both. (Kako, I.)