| 摘要 |
PURPOSE:To determine the presence of cracks in the bed by calculating the ratio of a peak counting rate and a variation rate of the peak ratio for Gamma rays from three nuclides - <40>K, <208>Tl and <214>Bi. CONSTITUTION:Gamma rays from nuclides of <40>K, <208>Tl and <214>Bi are detected with a NaI detector on the surface ground part to measure (areas C, A and B in the drawing) a counting rate (window counting rate) in an energy range giving a photoelectric effect on the highest energy (1.46MeV, 2.61MeV and 1.76MeV for respective nuclides). Counting rates D, E and F due to compton scattering contained in the window counting rates of <214>Bi and <40>K are removed to obtain H and G. When G/A, G/H and H/A are subtracted from respective A, H and G with peak values A-C, each peak ratio will be constant for the surface grounds to cancel variations in the peak counting rates of the nuclides depending on geometric conditions. Thus, when <222>Rh rises from cracks of the bed, the peak ratios A and B increases sharply thereby enabling clear determination on the presence of the cracks. |
