科研之友
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摘要
Photoactivation of nuclear isomer In-115m with a halflife of 4.48 h occurs by Co-60 gamma-ray irradiation. This is because the resonance gamma-ray absorption occurs at 1078 keV level for stable I Is In, and that energy gamma-rays are produced by Compton scattering of Co-60 primary gamma-rays. In this work, photoactivation of In-115m was applied to estimate the close rate distribution around a Co-60 irradiation source utilizing a standard close rate taken by alanine dosimeter. The In-115m photoactivation was measured at 10 to 160 cm from the Co-60 source. The derived dose rate distribution shows a good agreement with both alanine dosimeter data and Monte Carlo simulation. It is found that angular distribution of the dose rate along a circumference at radius 2.8 cm from the central axis shows +/- 10% periodical variation reflecting the radioactive strength of the source rods, but less periodic distribution at radius 10 and 20 cm. The In-115m photoactivation along the vertical direction in the central irradiation port strongly depends on the height and radius as indicated by Monte Carlo simulation. It is demonstrated that In-115m photoactivation is a convenient method to estimate the close rate distribution around a Co-60 source.
- 出版日期2010-3
