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Energy and the First Law of Thermodynamics
Published in Kavati Venkateswarlu, Engineering Thermodynamics, 2020
Except for radioactivity, most of the transformations of states of matter that occur at terrestrial temperatures are chemical. At very high temperatures (exceeding 106 K) that are usually attained in the stars, nuclei collide and undergo nuclear reactions just like molecules collide and react at terrestrial temperatures. The electrons and nuclei of atoms are totally uncertain at these temperatures. Matter turns into an unknown state and the transformations that take place are between nuclei, and hence it is called nuclear chemistry. The nuclear reactions that occur in stars called nucleosynthesis result in the elements heavier than hydrogen on earth and other planets. Just like unstable molecules that dissociate into other more stable molecules, the radioactive elements are formed due to disintegration of some of the unstable nuclei that were synthesized in the stars.
Chemical Aspects of Nuclear Processes
Published in Ivan G. Draganić, Zorica D. Draganić, Jean-Pierre Adloff, Radiation and Radioactivity on Earth and Beyond, 2020
Ivan G. Draganić, Zorica D. Draganić, Jean-Pierre Adloff
The total number of nucleons, as well as that of the individual protons and neutrons, is always preserved in a nuclear reaction. Quite often the total mass of the products of the nuclear reaction is smaller than that of the sum of target nucleus and projectile. In this case, the missing mass is converted into energy according to Einstein’s relation, E=mc2. This energy appears as kinetic energy of the emitted particle. In other instances, the products of the reaction are heavier than the total initial mass of the reacting species. Here, energy must be supplied to induce the reaction. This is usually achieved by conveying sufficient kinetic energy to the projectile, whereby part of the energy is converted into mass. Energy can also be furnished by heating the reactants, but in nuclear chemistry the amounts of heat required are enormous. In the laboratory, only the fusion of hydrogen to deuterium can be realized by supplying heat, and then only under very special conditions (Chapter 10). In the Sun and stars such a reaction is quite common.
Decisions, Risks and Barriers
Published in Jan Hayes, Operational Decision-making in High-hazard Organizations, 2017
The barriers approach is also an effective way of integrating compliance with rules with the operational managers’ own expertise and judgement. In Story 2, for example, the barrier that was in danger of being breached was a rule – the maximum allowable concentration of a contaminant. The nuclear chemistry department sets this limit based on exposure limits. It is not an operational issue and the operational managers would be in no position to fix a maximum acceptable value based on their professional knowledge, as it falls under the purview of a different profession. Instead, once they are informed (by way of a procedure) that this limit is important, they proceed on that basis and use their operational expertise to manage the facilities within that limit.
Thermochemistry of uranium sulfide cations: guided ion beam and theoretical studies of reactions of U+ and US+ with CS2 and collision-induced dissociation of US+
Published in Molecular Physics, 2023
Sara Rockow, Amanda R. Bubas, Steven Peter Krauel, Brandon C. Stevenson, P. B. Armentrout
One method of separation under investigation is the use of soft Lewis bases, in the form of either selective sulfurisation with CS2 [2–4] or multidentate ligands, [5,7] for separating lanthanides, uranium, and transuranic elements. Research by Sato et al. examined the sulfurisation of lanthanide and actinide compounds (Eu2O3, Nd2S3, ThO2, and U3O8) using CS2 over a range of temperatures [2–4]. They found that selective sulfurisation of Eu, Nd, Th, and U was possible based on the varying reactivities of each compound over the temperature ranges studied (673 - 1273 K). Chelating agents containing sulfur or nitrogen donor ligands are also promising candidates for selective extraction of actinides from lanthanide waste in SNF [5,7]. Because of the complexities of aqueous nuclear chemistry, the mechanisms behind lanthanide/actinide extraction are often unclear or unknown [7]. The literature on actinide sulfide thermochemistry is sparse as a result of the related expenses and hazards of research with radioactive elements. The combined complexity of the real-world systems and the limited amount of fundamental research makes the development of new separation techniques challenging. Studies of the fundamental thermochemistry of uranium sulfide systems provide the framework necessary to expand investigations into more complex systems. Fundamental studies also offer the unique opportunity to identify periodic trends that can be used to guide the nuclear industry’s development of more effective waste management methods.
Chemical and other aspects of Rutherford’s nuclear atom
Published in Journal of the Royal Society of New Zealand, 2021
Rutherford’s attitude to chemistry was ambiguous. On the one hand, he rated traditional chemistry lowly as compared to physics. And yet, on the other hand, his own work relied to a large extent on chemical methods and collaboration with trained chemists. Whether Rutherford saw his work on radioactivity and nuclear physics as contributions to chemistry or not, in fact much of it was. The new field of nuclear chemistry, a successor discipline to radiochemistry, emerged in the 1930s and Rutherford was unintentionally one of its fathers. While Rutherford has long been recognised as a towering figure in the history of twentieth-century physics, he also has a place, if admittedly a more modest one, in the history of chemistry. He contributed to the discovery of radon and was the first to predict the isotopes of hydrogen and helium, not to mention the neutron. Perhaps most importantly, he and his collaborators paved the way for the synthesis of new species of chemical elements by means of nuclear transmutations.
CHERNE: prehistory and early days of the network
Published in Radiation Effects and Defects in Solids, 2019
José Ródenas, François Tondeur, Tomáš Čechák, Ladislav Musilek, Herwig Janssens, Ulrich W. Scherer, Friedrich Hoyler, Domiziano Mostacci
After having participated in many previous courses and having been a co-organizer of SPERANSA 2006, AcUAS decided to organise a course on handling of open radionuclides and radiochemistry. It was named Jülich Nuclear Chemistry Summer School, or in brief, JUNCSS. The application was submitted through CTU as we believed to have a higher chance of acceptance, and it was indeed accepted. The students were again accommodated in the visitor’s residence of Jülich Research Centre. The first week started with experiments on radiation detection and measurement in the Nuclear Physics Laboratory. In the second week the students extensively performed radiochemical experiments in the Radiochemistry Laboratories. We followed the proven schedule of previous CHERNE courses by preparing the students with brief lectures in the morning covering the relevant topics. In addition, visits were organised to institutes of Jülich Research Centre, e.g. the fusion experiment TEXTOR, the radionuclide production, or the decommissioning site of the High-Temperature Reactor HTR. During the weekend touristic tours were organised with visits to Aachen and Cologne besides of the historical sites in Jülich. In the first year 2007, we had 10 students, 16 in 2008, 13 in 2009. It was decided to maintain the course even when the grant had expired. So, we had sequels in 2010 and 2011 with 14 and 15 students, respectively (Figure 4).