Radioactive Games? Radiation Hazard Assessment of the Tokyo Olympic Summer Games.

We conducted a comprehensive radiation hazard assessment of the Tokyo Olympic Games (Tokyo 2020, postponed to 2021). Our combined experimental and literature study focused on both external and internal exposure to ionizing radiation for athletes and visitors of the Games. The effective dose for a visit of 2 weeks ranges from 57 to 310 µSv (including flight dose). The main contributors to the dose are cosmic radiation during the flights (approximately 10-81%), inhalation of natural radon (approximately 9-47%), and external exposure (approximately 8-42%). In this complex exposure, anthropogenic radionuclides from the Fukushima nuclear accident (2011) always play a minor role and have not caused a significant increase of the radiological risk compared to pre-Fukushima Japan. Significantly elevated air dose rates were not measured at any of the Tokyo Olympic venues. The average air dose rates at the Tokyo 2020 sites were below the average air dose rates at the sites of previous Olympic Games. The level of radiological safety of foods and water is very high in Japan, even for athletes with increased water and caloric demands, respectively.

Separation of Ultratraces of Radiosilver from Radiocesium for Environmental Nuclear Forensics.

The presence of environmental radiosilver and the investigation of the 108mAg/110mAg isotopic ratio in the aftermath of a nuclear power plant accident provide valuable information on the condition of the control rods of pressurized water reactors. However, the detection of minute amounts of the γ-emitting radiosilver isotopes is often thwarted by the presence of concomitant and dominating γ emitters, primarily 137Cs, which results in increased detection limits in the γ spectra. We developed a rapid and robust separation protocol for trace silver extraction in the presence of overwhelming activities of 137Cs via the autodepostion of silver on a copper plate. This method achieved a quantitative removal of interfering 137Cs in the deposition product and proved to be very efficient (yields >70% for aqueous samples), rapid (results within 4 h), and robust with respect to varying salinities and composition of the water samples. The autodeposition approach is also applicable for organic samples after acid-assisted microwave digestion. By applying the established sequential extraction protocols for soil, the fate of freshly deposited radiosilver and radiocesium in soil was investigated. Silver showed a high affinity to the soil with a pronounced (>90%) accumulation in the residual fraction after the sequential extraction, whereas radiocesium exhibited higher mobility, allowing for the extraction of major fractions in the first extraction steps. The composition of the aqueous contamination matrix (CaCl2 or Ca(NO3)2) had a significant influence on the binding properties of cesium on soil.

Halide ion influence on the formation of nickel nanoparticles and their conversion into hollow nickel phosphide and sulphide nanocrystals.

A dependence of the formation of tri-n-octylphosphine-capped Ni nanocrystals on the presence of halide ions during their synthesis is shown. For the application-oriented synthesis of Ni particles, this information can be crucial. Furthermore, Ni nanoparticles can be converted to nickel phosphide or sulphide by heating them up in the presence of a phosphorus or sulphur source, resulting in either solid or hollow nanocrystals, formed via the nanoscale Kirkendall effect, depending on the synthesis route. By adjusting the Ni crystallite size in the initial nanoparticles via the halide ion concentration the cavity size of the resulting hollow nanocrystals can be tuned, which is otherwise impossible to realise for particles of a similar total diameter by using this process. The synthesised hollow Ni3S2 nanocrystals exhibit a much sharper localised surface plasmon resonance (LSPR) band than all previously presented particles of this material, which is known to show molar extinction coefficients at the LSPR maximum similar to Au. This narrow linewidth could be explained by the nanoparticles' high crystallinity resulting from the Kirkendall process and is interesting for various possible optical applications such as surface-enhanced Raman spectroscopy owing to the low cost of the involved materials compared to the widely used noble metals.