Evaluation of the Caesium-137 Activity at the Rochedo Dam, Goiás, Brazil

In 1987, in Goiânia (Goiás, Brazil) a radiological accident occurred due to the violation of a capsule containing Cs-137, previously used in radiotherapy equipment. The source contained caesium chloride and, due to the high solubility of this compound in water, there was contamination of people and consequent dispersion in the environment. The waste was discharged into the river network and after four years, a high concentration of Cs-137 was still observed in the sediments at the Rochedo dam, in Piracanjuba, Goiás, 80 kilometres downstream of the Metropolitan Region of Goiânia. This research analysed the Cs-137 activity in sediment samples and water samples from the Rochedo dam, with the purpose of updating the radiological monitoring data of the region and also to verify if the perceived values would indicate any threat to the environment and public health. The Cs-137 activity was detected in 93.8% of the analysed samples, whose values varied from traces to 2.25 Bq/L. The results for all water samples and for 53.8% of the sediment samples were below the minimum detectable activity by the equipment. This study showed that Cesium-137 activity seem to be very low in the water resources and sediments of the Rochedo dam and it seems to not offer radiological risks for public health and the environment.

Tolerance of High Oral Doses of Nonradioactive and Radioactive Caesium Chloride in the Pale Grass Blue Butterfly Zizeeria maha

The biological effects of the Fukushima nuclear accident have been examined in the pale grass blue butterfly, Zizeeria maha (Lepidoptera: Lycaenidae). In previous internal exposure experiments, larvae were given field-collected contaminated host plant leaves that contained up to 43.5 kBq/kg (leaf) of radioactive caesium. Larvae ingested up to 480 kBq/kg (larva), resulting in high mortality and abnormality rates. However, these results need to be compared with the toxicological data of caesium. Here, we examined the toxicity of both nonradioactive and radioactive caesium chloride on the pale grass blue butterfly. Larvae were fed a caesium-containing artificial diet, ingesting up to 149 MBq/kg (larva) of radioactive caesium (137Cs) or a much higher amount of nonradioactive caesium. We examined the pupation rate, eclosion rate, survival rate up to the adult stage, and the forewing size. In contrast to previous internal exposure experiments using field-collected contaminated leaves, we could not detect any effect. We conclude that the butterfly is tolerant to ionising radiation from 137Cs in the range tested but is vulnerable to radioactive contamination in the field. These results suggest that the biological effects in the field may be mediated through ecological systems and cannot be estimated solely based on radiation doses.

Physico-chemical characterization of caesium and strontium using fluorescent intensity of bacteria in a microfluidic platform

Recently, the impact of radioactive caesium (Cs) and strontium (Sr) on human health and the ecosystem has been a major concern due to the use of nuclear energy. However, this study observed changes in green-fluorescent (GFP)-tagged Pseudomonas aeruginosa PAO1 biofilms by injecting non-radioactive caesium chloride (CsCl) and strontium chloride (SrCl 2 ) into microstructures embedded in polydimethylsiloxane microfluidic devices, which were used due to their strong toxicity limitations. Four types of microstructures with two different diameters were used in the study. The change of biofilm thickness from fluid velocity and wall shear stress was estimated using computational fluid dynamics and observed throughout the experiment. The effect of pore space became a significant physical factor when the fluid was flowing through the microfluidic devices. As the pore space increased, the biofilm growth increased; therefore, triangular microstructures with the largest pore space showed the best growth of biofilm. Caesium chloride (CsCl) and strontium chloride (SrCl 2 ), less toxic than radioactive caesium (Cs) and strontium (Sr), completely eradicated the P. aeruginosa PAO1 biofilm with low concentrations. The combined effect of toxicity, fluid velocity, wall shear stress and microstructures increased the efficiency of biofilm eradication. These findings on microfluidic chips can help to indirectly predict the impact on human public health and ecosystems without using radioactive chemicals.

Wetting Behaviour of Gold Electrode and Molten Alkali Chlorides

The potential dependence of the contact angle between a gold electrode and lithium, sodium, potassium, rubidium, and caesium chloride melts was studied using the meniscus weight method to establish the patterns of wettability of solid surfaces by ionic melts when changing the composition of the salt phase and the jump of the electric potential. It is found that the forms of the contact angle versus the potential curve of Au change from a convex to a camel-like shape with two maxima upon replacing the lithium chloride with the caesium chloride melt. This phenomenon is explained by the assumption that the adsorption of the halide anions at the positively charged electrode surface has a chemical rather than electrostatic character. The adsorption process is accompanied by a charge transfer through the interface and the formation of covalent bonds between the adsorbent and adsorbate.

Atoms, Molecules and Solids

Chapter 9 presents an introductory overview of quantum chemistry and solid state physics. First, the Periodic Table is examined in terms of atomic structure, electron orbitals and the shell model. Simple polar and non-polar molecules are considered in terms of the overlap of atomic orbitals which gives rise to covalent bonding between atoms. Hückel theory is used to analyse the electronic structure of benzene and polyene molecules. These ideas are extended to periodic solids. Bloch’s theorem is used to explain their band structure in terms of molecular orbital theory. Band theory provides an explanation of the distinctions between metals, semi-conductors and insulators. Caesium chloride is used to illustrate how the band structure and properties of an ionic compound arise from its atomic structure. Metals are discussed, with emphasis on copper as an illustrative example, and the significance of the Fermi surface is explained. Ferromagnetism is considered in the transition metals.

Properties of Thorium Compounds: Application of Interionic Potential Theory

In the present work structural and mechanical properties of ThC and ThO compounds have been carried out using desirable modified inter-ionic potential theory (MIPT), which parametrically includes the effect of Coulomb screening. The transition from rock salt to caesium chloride occurs around 40.0 GPa and 65.0 GPa in the case of ThC and ThO respectively. We have also calculated bulk (B0), Young (E), and shear moduli (G), Poisson ratio (υ) and anisotropic ratio (A) in NaCl-type structure for these compounds and differentiate them with other experimental and theoretical results which show a good agreement.