Nuclear water droplets

M.L. Hyder, Measurements of Iodine Uptake in Falling Water Droplets , Nuclear Technology, 94(1991)80. 

CLOUD CHAMBER EFFECT. The cloud chamber effect refers to a mist of tiny water droplets or condensation cloud that is temporarily formed around the fireball generated by a nuclear weapon explosion. This effect is produced by the expansion of air in the negative-pressure phase of the blast wave (a nuclear detonation produces a negative-pressure phase, followed by a positive-pressure phase, which is experienced as the shock wave). The drop in pressure brings about an equivalent drop in temperature, and as a consequence, any water vapor present condenses. See also BHANGMETER. 

Freeze-fracture TEM combined with nuclear magnetic resonance and quasielastic light scattering was used to study the microstructure of surfactant-water systems and dynamics of o/w and bicontinuous ME systems [41], The authors reported a rather abrupt transition from a discontinuous droplet (o/w) to bicontinuous (oil-and-water) microstructure occurring at low surfactant concentration, close to a three-phase region in the constructed phase diagram of pentaethylene glycol dodecyl ether, water, and octane [41],... 

The experiments have proved that membrane distillation can be applied for radioactive wastewater treatment. In one-stage installation the membrane retained all radionuclides and decontamination factors were higher than those obtained by other membrane methods. The distillate obtained in the process was pure water, which could be recycled or safely discharged into the environment. It seems the process can overcome various problems of evaporation such as corrosion, scaling, or foaming. There is no entrainment of droplets, which cause the contamination of condensate from thin-film evaporator. Operation at low evaporation temperature can decrease the volatility of some volatile nuclides present in the waste, such as tritium or some forms of iodine and ruthenium. The process is especially economic for the plants, which can utilize waste heat, e.g., plants operating in power and nuclear industry. 

The breakdown of the stable emulsions and subsequent separation to oil and water (demulsification) are important in nuclear, petroleum, and environmental technologies. The emulsion stability is primarily induced by the use of surfactants and is enhanced by reduced size and narrow size distribution of the emulsion droplets. Disruption to low interfacial activity (hence instability) can be achieved by using demulsification agents, which are, however, costly and environmentally undesirable, as they are irrecoverable. Demulsification can also be achieved by electric and/or centrifugal fields, or by chemical treatment of the emulsion. 

When surface active agents are considered, a further complication may be encountered. Because of their surface active nature, the surfactants not only emich at the surfaces, but also form extended structures themselves. At low concentrations, the surfactants remain as dissolved monomers or asssociate to oligomers. However, when the critical micellization concentration (cmc) is surpassed, a cooperative association is activated to micelles (1 to 10 nm) consisting typically of some 50 to 100 monomers. At stiU higher concentrations, or in the presence of cosurfactants (alcohols, amines, fatty acids, etc.), liquid crystalline phases may separate. These phases have an infinite order on the x-ray scale, but may remain as powders on the NMR (nuclear magnetic resonance) scale. When the lamellar liquid crystalline phase is in equilibrium with the liquid micellar phase the conditions are optimal for emulsions to form. The interface of the emulsion droplets (1 to 100 pm) are stabilized by the lamellar liquid crystal. Both the micelles and the emulsions may be of the oil in water (o/w) or water in oil (w/o) type. Obviously, substances that otherwise are insoluble in the dispersion medium may be solubilized in the micelles or emulsified in the emulsions. For a more thorough analysis, the reader is directed to pertinent references in the literature. ... 

Carlstrom, G. and Halle, B., Water dynamics in microemulsion droplets. A nuclear spin relaxation study, Langmuir, 4, 1346-1352 (1988). 

A keen interest in microemulsions of fluorocarbons in water was kindled by the need for synthetic oxygen earners in blood (see Section 10.4). Gerbacia and Rosano [121] prepared a stable fluorocarbon emulsion using a mixture of fluorinated and hydrocarbon-type nonionic surfactants. The droplet size was not determined, however, and the emulsions were not characterized. Oliveros et al. [122] prepared perfluorinated microemulsions consisting of four components (1) sodium perfluorooctanoate, an anionic fluorinated surfactant (2) 2,2,3,3,4,4,4-heptafluoro-1-butanol (3) perfluorohexane (4) water. The pseudoternary-phase diagram (Fig. 4.40) shows two regions. Mi and Mi, of respective W/0 and OAV microemulsions [122]. These optically transparent microemulsions were characterized by nuclear magnetic resonance spectroscopy. 

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