In recent years, the promotion of recycling of steels is desired from the viewpoints of effective usage of resources and restraint of CO2 emission. On the other hand, some elements (As, Sb, Bi, B, Zn and so on) affect seriously the characteristics of recycled steel and it is difficult to refine away these elements from recycled steel in the iron recycling process. These elements are called tramp elements. For that reason, a new technique to determine the tramp elements in steel is demanded.
In this paper, tramp elements, As and Sb, in iron certified reference materials were determined by neutron activation analysis with multiple gamma-ray detection method. For determination of As, two samples (JSS001-5, JSS168-7) were irradiated for 10 min at a neutron flux of 5.2×1017 m-2 s-1 and measured by the multiple gamma-ray detector, GEMINI-II, which consists of 16 Ge detectors with BGO Compton suppressor, for 12 h. For determination of Sb, seven samples (JSS001-5, JSS003-2, 4 and so on) were irradiated for 5 h at a neutron flux of 9.6×1017 m-2 s-1 and measured by GEMINI-II for 24 h. The determined values were in good agreement with the certified and reference values. The lower limit of determination values for As and Sb in high purity iron were 0.01 and 0.003 ppm, respectively. The demand on the limit of determination values for As and Sb is 0.1 ppm. From these results, this method has turned out to be useful for determining As and Sb in recycled steel.