Synthesis and characterization of silver/alanine nanocomposites for radiation detection in medical applications: the influence of particle size on the detection properties

Silver/alanine nanocomposites with varying mass percentage of silver have been produced. The size of the silver nanoparticles seems to drive the formation of the nanocomposite, yielding a homogeneous dispersion of the silver nanoparticles in the alanine matrix or flocs of silver nanoparticles segregated from the alanine crystals. The alanine crystalline orientation is modified according to the particle size of the silver nanoparticles. Concerning a mass percentage of silver below 0.1%, the nanocomposites are homogeneous, and there is no particle aggregation. As the mass percentage of silver is increased, the system becomes unstable, and there is particle flocculation with subsequent segregation of the alanine crystals. The nanocomposites have been analyzed by transmission electron microscopy (TEM), UV-Vis absorption spectroscopy, X-ray diffraction (XRD), and Fourier transform infrared (FTIR) spectroscopy and they have been tested as radiation detectors by means of electron spin resonance (ESR) spectroscopy in order to detect the paramagnetic centers created by the radiation. In fact, the sensitivity of the radiation detectors is optimized in the case of systems containing small particles (30 nm) that are well dispersed in the alanine matrix. As the agglomeration increases, particle growth (up to 1.5 mu m) and segregation diminish the sensitivity. In conclusion, nanostructured materials can be used for optimization of alanine sensitivity, by taking into account the influence of the particles size of the silver nanoparticles on the detection properties of the alanine radiation detectors, thus contributing to the construction of small-sized detectors.FAPESPFAPESPCNPqCNPqCAPESCAPE

Alanine/electron spin resonance dosimetry for environmental qualification of electric equipment in a nuclear power plant

International audienceOne of the objectives of the Environmental Qualification Program of Electrical Equipment in a Nuclear Power Plant (NPP) is to demonstrate that electric equipment and cables are not damaged due to the accumulated ra diation dose. This work aimed to assess photon doses to electronic equipment and cables during an operation cycle (~1 year) at the NPP Angra 1, Eletronuclear, Brazil, using alanine/electron spin resonance (ESR) dosimetry. The influence of neutron radiation was evaluated and a dose survey at the NPP was performed. Alanine dosimeters were placed at 85 positions adjacent to the reactors room. Neutron influence was assessed using hydroxyapatite dosimeters. For a 1-year operation cycle, doses ranged from <0.5 Gy to ~7 kGy, according to the position of the dosimeters, demonstrating alanine’s ability to operate over a wide dose range. Alanine/ESR dosimetry can be used as part of the Environmental Qualification Program of Electrical Equipment in an NPP