Selective detection of fast and thermal neutrons in mixed-radiation fields using tungsten-silica and gold-iodine-silica nanoparticles and their boron-loaded aqueous dispersions.

Tungsten-silica and gold-iodine-silica nanoparticles and their boron-loaded aqueous dispersions were used to selectively detect fast and thermal neutrons in mixed-radiation fields generated by a cyclotron on the order of mSv at a neutron flux of 1.0 ×106(neutron/sec∙cm2). The photo-image intensity, fluorescence spectra, absorption spectra, and XRD of their aqueous dispersions were measured immediately and eighteen days after irradiation. The immediate measurements of photo-image intensity and fluorescence spectral area ratios for gold-iodine-silica nanoparticle aqueous dispersions indicated the dose dependence of photo-image intensity and fluorescence spectral area ratios. Measurements of the relative fluorescence and absorption spectral areas of gold-iodine-silica nanoparticle aqueous dispersions 18 days after irradiation also showed similar dose dependences. The precipitates of gold-iodine-silica nanoparticles showed a linear relationship between the XRD peak ratio and the dose with a correlation coefficient of 0.9. The photo-image intensities, fluorescence spectral area, absorption spectral area, and XRD peak ratios were found to be affected by fast and thermal neutrons. Simple methods of fluorescence, absorption, and XRD measurements are proposed for the selective detection of fast and thermal neutrons in mixed-radiation fields.