Nuclear chemistry, small scale

In 1934, nuclear physics was young and the neutron had only just been discovered, yet the transuranium project was approached with a remarkable degree of confidence. The concepts from chemistry and nuclear physics that framed and guided the investigation were never seriously questioned, even though the synthesis and identification of new elements was, by definition, a leap into the unknown. Similarly, researchers were relatively unconcerned about the limitations of their small-scale experiments, even though the experiments themselves were notoriously difficult due to the tiny quantities of radioactive material. 

Solvent Extraction and Ion Exchange in Small-Scale Nuclear Chemistry 2410... 

Besides the classical techniques for structural determination of proteins, namely X-ray diffraction or nuclear magnetic resonance, molecular modelling has become a complementary approach, providing refined structural details [4—7]. This view on the atomic scale paves the way to a comprehensive smdy of the correlations between protein structure and function, but a realistic description relies strongly on the performance of the theoretical tools. Nowadays, a full size protein is treated by force fields models [7-10], and smaller motifs, such as an active site of an enzyme, by multiscale approaches involving both quantum chemistry methods for local description, and molecular mechanics for its environment [11]. However, none of these methods are ab initio force fields require a parameterisation based on experimental data of model systems DPT quantum methods need to be assessed by comparison against high level ab initio calculations on small systems. 

A pulse of electrons of high kinetic energy (1-3 eV) in metals can be generated in atomic/molecular processes. Detection of this electron flow has become one of the frontier areas of research in the surface physics and chemistry communities. Showing that nuclear motion couples to electronic excitation is more difficult if the excitation is too small to cause emission. Relaxation of these hot electrons happens on the femtosecond to picosecond timescale, and their mean free path is on the order of 10 nm. This implies two detection strategies the first is to obtain sufficient time resolution to observe these excitations. The second is to employ an energy barrier at nanometer scale for the irreversible transport of hot electron flows. 

The fate of actinide elements introduced into the environment is of course not merely a scientific issue. The disposal of the by-products of the nuclear power industry has become a matter of public concern. For each 1000 kg of uranium fuel irradiated in a typical nuclear reactor for a three-year period, about 50 kg of uranium are consumed. In addition to a large amount of energy evolved as heat, 35 kg of radioactive fission products and 15 kg of plutonium and transplutonium elements are produced. Many of the fission-product nuclides are stable, but others are highly radioactive. All of the fission products are isotopes of elements whose chemical properties are well-understood. The transuranium elements produced in the reactor by neutron capture, however, have unique chemical properties, which are reasonably well-understood but are not always easily inferred by extrapolation from the chemistry of the classical elements. Plutonium is fissile and can be recycled as a nuclear fuel in conventional or breeder reactors, but the transplutonium elements are not fissile to the extent of supporting a nuclear chain reaction, and in any event they are produced in amounts too small to be of interest for large-scale uses. The transplutonium elements must therefore be secured and stored. 

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