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High-Energy (X-Ray and γ-Ray) Photon Interactions with Matter
Published in Harry E. Martz, Clint M. Logan, Daniel J. Schneberk, Peter J. Shull, X-Ray Imaging, 2016
Harry E. Martz, Clint M. Logan, Daniel J. Schneberk, Peter J. Shull
The height and shape of the fission barrier are dependent on the particular nucleus being considered. Fission can be induced by exciting the nucleus to an energy equal to or greater than that of the barrier. This can be done by γ-ray excitation (photofission) or through excitation of the nucleus by the capture of a neutron, proton, or other particle (particle-induced fission).
Chelate assisted phytoextraction for effective rehabilitation of heavy metal(loid)s contaminated lands
Published in International Journal of Phytoremediation, 2023
Akshaya Prakash Chengatt, Nair G. Sarath, Delse Parekkattil Sebastian, N. Shibin Mohanan, E. S. Sindhu, Satheesh George, Jos T. Puthur
Cadmium is a toxic heavy metal that naturally occurs along with zinc or lead in zinc or lead deposits. Usually, it exists in the form of a divalent cation that is combined with other elements (Jaishankar et al.2014). Commercially, cadmium is used for galvanizing steel and as a nuclear fission barrier. It is also used in lasers, paint pigments, batteries, television screens, cosmetics, etc. All these are potential sources of cadmium pollution in the environment.
Manhattan Project: The Story of the Century, by Bruce Cameron Reed. Springer Nature Switzerland AG, 2020,
Published in Technometrics, 2022
In the following research, Bohr from Copenhagen and J. Wheeler from Princeton University calculated characteristics of fission barrier and activation energy needed to induce elements to fission via the compound nucleus incorporating the bombarding neutrons. They concluded that slow neutrons of any little kinetic energy can start U-235 fission. Concerning U-238, the bombarding neutrons should be faster, but on the other hand their scattering becomes more inelastic, meaning that they lose much energy and cannot trigger the chain-process, thus for fission aims the U-235 should be isolated up to 90% from its sibling isotope. By itself the U-238 is nonfissile, but by capturing a neutron it becomes U-239 of Z92, which sheds in beta-decay into the next element Neptunium Np-239 with its Z93, and in another beta-decay it transforms into Plutonium Pu-239 with Z94. The latter one is an even/odd element, fissile under slow-neutron bombardment, and L. Turner of Princeton University described in 1940 the path to bomb building. For practical applications in a reactor or a bomb, the self-sustaining chain-fission reaction requires a critical minimum mass of U-235, or Pu-239. Applying time-dependent diffusion theory of thermodynamics, French physicist F. Perrin published in 1939 an estimation, and the critical mass occurred to be unfeasible 44 tons, so he considered reduction of a big mass by surrounding the material with a tamper to reflect the escaped neutrons back to fissile area. German physicist S. Flügge in Berlin estimated the radius of such a bomb as 50 cm. Rudolf Peierls developed explicit formulas for estimating the critical mass. Born in Germany and emigrated to England in 1933, he was invited by M. Oliphant to work with him in the University of Birmingham, and later O. Frisch joined this group. As Jewish refugees he and Peierls were very concerned about fission research going in Germany, and they began to work on finding experimental parameters of cross-sections needed for estimation of the critical mass. The further work in fission required to separate U-235 isotope from the whole uranium ore by the known at that time method of mass spectroscopy, that was fulfilled by A. Nier, the expert who built such tools in the Minnesota University and sent the miniscule samples of 1-2 nanograms of U-235 to Columbia University for further experiments. Such a sample could be obtained during a dozen hours of enrichment, and to collect one kilogram would require some 600 million years of continuous operation.