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Types of Reactors and Their Design Parameters
Published in Robert E. Masterson, Nuclear Engineering Fundamentals, 2017
The uranium in the earth’s crust consists of mostly Uranium-238 (about 99.3% by weight) and about 0.71% by weight U-235. This type of uranium is commonly referred to as natural uranium. Unfortunately, for reasons that were explained in another chapter, natural uranium is not a particularly good nuclear fuel (except in CANDU reactors) because the coolant or moderator absorbs too many neutrons to keep a reactor critical. Because of this, there are not enough neutrons left to sustain a nuclear chain reaction. To compensate for this neutron deficiency the concentration of Uranium-235 in light water reactors is artificially increased to between 2.5% and 5% using a process known as uranium enrichment. The enriched fuel is then known as enriched uranium. The process of enriching natural uranium is not particularly complicated, but it does take some time to explain. For this reason, the interested reader should consult a reactor physics book, or a nuclear fuel cycle book such as Cochran and Tsoulfanidis (refer to the references at the end of the chapter) to learn more about how the process works. The original process for enriching natural uranium was called the gaseous diffusion process, but unfortunately, it turned out to be very energy-intensive, and consumed large amounts of electric power.
Uranium Enrichment
Published in Kenneth D. Kok, Nuclear Engineering Handbook, 2016
Nathan (Nate) Hurt, Kenneth D. Kok
Enriched uranium is a critical component in civilian nuclear power generation, naval power generation, and military nuclear weapons. One of the forms in which uranium exists in nature—the U235 isotope—is fissionable, that is, can be caused to split and release tremendous amounts of energy. To build a weapon or make it usable as reactor fuel, the desirable U235 isotope must be enriched from the very low concentrate (0.7%) found in nature where the balance (99.3%) is U235. Enrichment is therefore the term used to describe processes by which the U235 concentration is increased above its naturally occurring level.
Nuclear Fuel Materials
Published in C. K. Gupta, Materials in Nuclear Energy Applications, 1989
A cycle in which spent fuel is processed to allow recovery of uranium only with the high- level waste with plutonium and higher transuranic elements being treated as waste is shown in Figure 2. This cycle is suitable for reactor systems using low-enriched fuel such as LWRs and AGRs as shown in the figure. The recovered uranium is recycled to these reactor systems via the enrichment plant where its fissile component concentration is raised from about 0.8 to 3% which is suitable for reuse in the low-enriched fueled reactor systems.
ATR Compendium: Irradiation Test Capabilities
Published in Nuclear Technology, 2018
Samuel E. Bays, Gilles J. Youinou, Misti Lillo, Paul Gilbreath
In support of the National Nuclear Security Administration objective to reduce the nuclear proliferation risk worldwide, the ATR irradiates nuclear fuel experiments utilizing low-enriched uranium (LEU) (<20% 235U). Several U.S. and foreign research reactors currently use high-enriched uranium (HEU), which is considered an unacceptable proliferation risk due to the potential diversion of HEU for nonreactor uses. The goal of fuel qualification for U.S. reactors is to develop and qualify U-Mo monolithic fuels with the highest possible LEU density (~16 g U/cm3) suitable for use in these research reactors. The selected design for the generic fuel system is referred to as “base fuel” and comprises a uranium–10 wt% molybdenum alloy (U-10Mo) in the form of a monolithic foil, with thin zirconium (Zr) interlayers, clad in aluminum alloy, Al-6061. LEU conversion in the European Union’s research reactors is supported by the European Mini-Plate Irradiation Experiment (EMPIRE) test series. This fuel is similar to the U-Mo monolithic fuel, but the European reactors can tolerate a lower LEU density, allowing the use of dispersion fuel where uranium-molybdenum alloy particles are dispersed throughout an aluminum matrix. Figure 12 shows a temperature contour map of EMPIRE capsule C, plates 1 and 3, generated by the ABAQUS code.27
Uranium-based TRU multi-recycling with thermal neutron HTGR to reduce environmental burden and threat of nuclear proliferation
Published in Journal of Nuclear Science and Technology, 2018
Yuji Fukaya, Minoru Goto, Hirofumi Ohashi, Xing Yan, Tetsuo Nishihara, Yasuhiro Tsubata, Tatsuro Matsumura
In the proposed cycle, recovery uranium is enriched and recycled. Uranium isotopes except for 235U and 238U are important as well. 236U would be accumulated and affect criticality; other components are released as depleted uranium to the environment, and they might have significant toxicity. To assess the feasibility of this cycle, a method for evaluating multi-component of uranium enrichment is necessary.