Determination of X- and gamma-ray emission intensities in the decay of (131)I.

The activity per unit mass of an iodine-131 solution was absolutely standardized by both the 4πß-γ coincidence method and the 4πγ counting technique. The calibrated solution was used to prepare point sources after a preliminary deposit of AgNO3 to prevent the loss of volatile iodine. Relative and absolute photon emission intensities of 15 sgamma-rays and those of the two K X-rays of xenon were determined by gamma-ray spectrometry, with relative uncertainties of 0.8% for the three main emissions.

On scattering effects for volume sources in low-energy photon spectrometry.

In this study, different aspects of the Compton scattering inside volume sources are illustrated using experimental approach and Monte Carlo simulation. For the low-energy range (below 100 keV) scattered events represents around 30% of the whole spectrum. Influence of the source-detector geometry is discussed. The scattering effects induce strong differences in spectrum shape for different geometrical conditions. This should influence efficiency transfer factors. A new approach is proposed, including the scattered events, to avoid complex peak area determination.