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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
Besides Pu-239, the most commonly used isotopes of plutonium are Pu-238 and Pu-241. Plutonium-238 has a half-life of 88 years and is an abundant source of alpha particles (ionized helium nuclei). The process of alpha decay allows it to produce useful quantities of decay heat for about 100 years. Because the heat production can be maintained for so long, it is a popular energy source for small, portable electric generators called isotopic thermoelectric generators. These generators have been used to power spaceships, satellites, and even some space probes built by NASA. They are much more reliable than ordinary batteries over very long periods of time. A picture of a Plutonium-238 sphere generating its own heat and light is shown in Figure 6.17b. This particular sphere was used to power a satellite that was sent into orbit. The other commonly used isotope of Plutonium is Pu-241. Pu-241 has a radioactive half-life of 14.4 years, and decays quickly into Americium-241. Americium-241 is a strong alpha emitter, and it is commonly used in household smoke detectors. Because Pu-241 has such a short half-life, it is not very practical to use as a conventional nuclear fuel. These pellets are used for devices known as radioisotope thermoelectric generators. They are made of PuO2. The image in Figure 6.17 was provided by the U.S. Department of Energy. (See Image ID 2006407 at http://www.doedigitalarchive.doe.gov and search for plutonium AND light.)
Pyrochemical Treatment of Salts
Published in Thomas E. Carleson, Nathan A. Chipman, Chien M. Wai, Separation Techniques in Nuclear Waste Management, 2017
Weapons- and reactor-grade plutonium metal contain a mixture of isotopes: 238Pu, 239Pu, 240Pu, 241Pu, and 242Pu. The decay of 241Pu results in the formation of its daughter product, 241 Am, which is an alpha emitter with a half-life of 13.2 years. Americium-241 further decays to its daughter product 237Np, a 60-keV gamma emitter with a half-life of 458 years.1 This radiation emission presents a health hazard to those working in both the energy- and weapons-related fields. In addition, the impurities in the plutonium metal alloy change both its nuclear and mechanical properties. Americium can be periodically removed from plutonium by the MSE process. MSE separates americium from plutonium metal by a pyrochemical oxidation reaction followed by molten-salt solvent extraction.
Radioactive Materials and Radioactive Decay
Published in Robert E. Masterson, Nuclear Engineering Fundamentals, 2017
Americium-241 is commonly used as an ionizing agent in household smoke detectors. Polonium-210 is used for eliminating the static charge in fabrics in textile mills, and it is also used on brushes for removing the dust from photographic films. Radon is a colorless, odorless, tasteless, naturally occurring, radioactive noble gas that is formed from the decay of Radium-226. It is one of the heaviest substances that remains as a gas under normal conditions. Its most stable isotope, Rn-222, has a half-life of 3.8 days, and it is used in nuclear medicine for the treatment of various forms of cancer.
241Am Neutron Capture Cross Section Measurement using the NaI(Tl) spectrometer of the ANNRI beamline of J-PARC
Published in Journal of Nuclear Science and Technology, 2023
Gerard Rovira, Atsushi Kimura, Shoji Nakamura, Shunsuke Endo, Osamu Iwamoto, Nobuyuki Iwamoto, Tatsuya Katabuchi, Yu Kodama, Hideto Nakano, Yaoki Sato
Americium-241 (t = 432.2 yr) is one of the most abundant MAs present in spent nuclear fuel and is set to become the second major component of the ADS core. Recent studies were performed with isotope concentrations of 20.72% for 241Am, only behind 237Np with 31.97% [2] and have identified 241Am as the main contributor to changes in ADS criticality among all MAs present in the ADS core [4]. Moreover, owing to the fact that 241Am presents one of the highest neutron capture cross sections among all MAs in the lower energy region, transmutation with thermal neutrons has also been deemed possible with a high relative transmutation rate [5] and, at the same time, burn-up studies of MOX fuels have remarked the importance of accurate nuclear data in the resolved resonance region for 241Am, as it exhibits a large sensitivity to the 238Pu production [6].