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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.)
An introduction to the international nuclear power industry
Published in Geoffrey Rothwell, Economics of Nuclear Power, 2016
Nuclear power plants can be classified by means of a few characteristics, as in Figure 1.2. First, a reactor has either a ‘fast’ or ‘slow’ chain reaction. In fast reactors, energy released in the chain reaction is not slowed by intentionally capturing (‘moderating’) neutrons. Neutrons can be captured to convert more uranium to more plutonium than moderated reactors (as well as to produce other isotopes); hence these are sometimes known as ‘fast breeder reactors’. Fast reactors are also known as ‘liquid-metal reactors’ (LMRs), because liquid metals, such as sodium, are used to cool the reactor and transfer heat. There are several isotopes of plutonium (Pu), from Pu–238 to Pu–244.
Introduction
Published in G. Vaidyanathan, Dynamic Simulation of Sodium Cooled Fast Reactors, 2023
Natural uranium contains about 0.7% U235 and 99.3% U238. In any reactor some of the U238 component is turned into several isotopes of plutonium during its operation. Two of these, Pu239 and Pu241, then undergo fission in the same way as U235 to produce heat. In a fast neutron reactor (FNR) this process can be optimized so that it “breeds” fuel. Some U238 is also burned directly with neutron energies above 1 MeV (fast fission).
Improved Disposition of Surplus Weapons-Grade Plutonium Using a Metallic Pu-Zr Fuel Design
Published in Nuclear Technology, 2023
Braden Goddard, Aaron Totemeier
Despite the closure of the MFFF before its completion, the United States and other countries have had considerable experience using MOX fuel in commercial LWRs (Refs. 11, 12, and 13). MOX fuel has been used in commercial nuclear reactors since the 1980s, with most of its current use occurring in France, other countries in Europe, and Japan.14 These countries primarily use MOX fuel that contains recycled plutonium from used LWR fuel. This recycled plutonium has higher concentrations of non-239Pu isotopes of plutonium and is thus less fissile compared with weapons-grade plutonium. While MOX fuel that contains recycled plutonium must have 7% to 11% of its heavy metal as plutonium, with the rest consisting of depleted uranium, MOX fuel that uses weapons-grade plutonium needs only a 5% plutonium heavy metal fraction due to the large 239Pu isotopic abundance.
Core calculations for small modular reactor during burnup cycle
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2021
Javad Karimi, Mohsen Shayesteh, Mehdi Zangian
Figure 20 shows the changes in the atomic density of different uranium isotopes versus time. According to this figure, the atomic density of uranium isotopes 235 and 238 at the beginning of the reactor operation, when it has fresh fuel, reaches maximum values, and gradually decreases over time. At the beginning of the reactor cycle, there is no U-236 in the reactor core, but it gradually increases with neutron capture by U-235. Figure 21 shows the trend of changing the atom density of different plutonium isotopes versus time. At the beginning of the reactor operation, the amount of plutonium in the core is zero, but gradually, with successive neutron capture and beta decays by U-238, the various isotopes of plutonium are produced and their values have upward trend over time. But there is an exception for the Pu-239. After a certain time, the amount of Pu-239 in the core reaches a maximum and the upward trend stops.
Spent Nuclear Fuel Incineration by Fusion-Driven Liquid Transmutator Operated in Real Time by Laser
Published in Fusion Science and Technology, 2021
T. Tajima, A. Necas, G. Mourou, S. Gales, M. Leroy
The PUREX process gives the initial loading of plutonium for Case 3 with the mass shown in Fig. 10a and isotopic concentrations shown in Table I. The loading is adjusted to achieve a steady 100-MW thermal output. After 1 year the amount of plutonium decreased by 46% to 51 kg as shown in Fig. 10a. Notably, this is done unevenly isotope-wise as the fissile isotopes of plutonium are transmuted at a higher rate. The initial fissile plutonium concentration of 68% drops to 63% fissile at the end of the year. This decrease in the weapons-grade plutonium during transmutation serves as a proliferation deterrent. Regarding the plutonium, 37 kg is converted into FPs, and 6 kg is converted into other TRUs including 3 kg of americium and 3 kg of curium and less than 20 g of other TRUs. The burnup by fission is