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Nuclear Fuels, Nuclear Structure, the Mass Defect, and Radioactive Decay
Published in Robert E. Masterson, Introduction to Nuclear Reactor Physics, 2017
In addition to the 92 naturally occurring elements, there are approximately 25 additional elements that have been created by man. These elements are sometimes called man-made elements. Man-made elements are made by bombarding a natural element with protons from a nuclear accelerator. They can also be made by bombarding uranium atoms in a nuclear reactor with low-energy neutrons. If the energy of the neutrons is just right, the uranium atom will absorb one of these neutrons and convert it to a proton. The conversion process is known as beta decay, and beta decay then creates a new element with a higher atomic number Z. Beta decay also releases an additional electron from the nucleus in the process. The reader should refer to Tables 6.5 and 6.6 to obtain a summary of each element and to determine whether it occurs in nature or is artificially produced. Elements in the table with atomic numbers greater than 92 are artificial in nature. Hence they are referred to as man-made elements. The most common man-made elements are Neptunium, Plutonium, Americium, Berkelium, Californium, and Einsteinium. With the exception of Plutonium-239, which has a half-life of about 25,000 years, all of these elements are highly unstable, and they do not exist in nature in meaningful quantities. On average, about one new man-made element is discovered every 4 or 5 years. Additional man-made elements beyond the 25 mentioned here may be added to the Periodic Table from time to time.
Elements, Isotopes, and Their Properties
Published in Robert E. Masterson, Nuclear Engineering Fundamentals, 2017
In addition to the 92 naturally occurring elements, there are approximately 25 additional elements that have been created by man. These elements are sometimes called man-made elements. Man-made elements can be made by bombarding a natural element with protons from a nuclear accelerator. They can also be made by bombarding uranium atoms in a nuclear reactor with low-energy neutrons. If the energy of the neutrons is just right, the uranium atom will absorb one of these neutrons and convert it to a proton. The conversion process is known as beta decay (see Chapter 6), and beta decay then creates a new element with a higher atomic number Z. Beta decay also releases an additional electron from the nucleus in the process. The reader can refer to Table 9.6 to obtain a summary of each element and to determine whether it occurs in nature or is artificially produced. Elements in the table with atomic numbers greater than 92 are artificially produced. Hence, they are referred to as man-made elements. The most common man-made elements are neptunium, plutonium, americium, berkelium, californium, and einsteinium. With the exception of Plutonium-239, which has a half-life of about 25,000 years, all of these elements are highly unstable and they do not exist in nature in meaningful quantities. On average, about one new man-made element is discovered every 4 or 5 years. Additional man-made elements beyond the 25 mentioned here may be added to the periodic table from time to time.
The Other Energy Sources
Published in Anco S. Blazev, Power Generation and the Environment, 2021
NOTE: The minor actinides include neptunium, americium, curium, berkelium, californium, einsteinium, and fermium. The most important isotopes in spent nuclear fuel are neptunium-237, americium-241, americium-243, curium-242 through -248, and californium-249 through -252.
Combination of DGA and LN Columns: A Versatile Option for Isotope Production and Purification at Oak Ridge National Laboratory
Published in Solvent Extraction and Ion Exchange, 2021
Richard T. Mayes, Shelley M. VanCleve, Jay S. Kehn, Jordan Delashmitt, Josh T. Langley, Brian P. Lester, Miting Du, L. Kevin Felker, Lætitia H. Delmau
Isotope production has been at the heart of Oak Ridge National Laboratory (ORNL) since the Graphite Reactor in the very early days of the laboratory. In the early 1960s, the Atomic Energy Commission established the Transplutonium Element Production program at ORNL in association with the High Flux Isotope Reactor (HFIR) to produce californium, berkelium, einsteinium, and fermium isotopes.[1–3] Since then, isotope production has been widely expanded to provide a variety of isotopes for space exploration, medical treatments, fundamental research, and other industrial purposes. The most common production mode is target irradiation in the reactor followed by their dissolution with subsequent separations by solvent extraction or ion exchange, the final separation of the individual actinides using alpha-hydroxy isobutyric acid eluents being done with a cation exchange column .[4–8] All the separations for all the isotopes that could be recovered from the target irradiations at HFIR and follow-on processing at the Radiochemical Engineering Development Center (REDC) cannot be enumerated. Instead, this study aims to demonstrate the performance of two specific chromatographic resins that, when combined, show that radioisotopes can be recovered and purified very efficiently in quantities that can be produced in a very limited number of locations in the world.