Nondestructive Determination of Major Elements in a Large Sample by Prompt γ Ray Neutron Activation Analysis.

An internal monostandard method is proposed for the nondestructive determination of major elements in large samples by prompt γ ray neutron activation analysis. It successfully overcomes the problems characteristic of large samples, such as the absorption and scattering of incident neutrons and the absorption of emitted γ rays. In order to make this proposed method understood theoretically, an equation is presented and its validity for the analysis of large samples discussed. In principle, the proposed method gives relative contents in large solid samples, whereas it allows absolute determination for samples in solution form. As a demonstration for the analysis of a large solid sample, we analyzed an earthen vessel, and the major elements in the sample (Na, Mg, Al, Si, K, Ca, Ti, Mn, and Fe) were determined within the uncertainty of 10%, except for Mn. This method was also tested for samples in solution form, and it was found that the absolute content of a target element could be obtained by constructing a calibration curve using several known standard solutions of different concentrations. Residual radioactivity after irradiation was also examined and found to be so little that the sample could be taken outside the radiation-controlled area within a few days after the irradiation.