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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.

Nondestructive determination of major and trace elements within voluminous materials has been demonstrated by prompt y-ray neutron activation analysis 9 Some fragmented pieces of pottery bowls considered to have been produced in the late 18th century were analyzed by a new internal monostandard method, and noticeable differences of the elemental contents and significant correlations of the elemental distributions were observed among the samples 9 The possibility of identification of producing areas of unearthened material is demonstrated by the analytical results and the applicability of this method to the investigation of precious samples in a completely nondestructive way is verified in practice 9

Prompt y-ray analysis using the internal monostandard method was applied to voluminous archaeological bronze mirrors produced in ancient China. Sn/Cu content ratios were determined nondestructivel 3, by this method. Furthermore, Au/Cu, As/Cu, and Sb/Cu content ratios were determined by means of measuring decay y-rays emitted from radioactive nuclides produced within samples via (n,y) reactions. It is clear that the Sn/Cu content ratios in bronze mirrors produced in the Sung era is smaller than in ones produced in between the Han and the Tung era.

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