What is a breeder reactor? Discuss nuclear fission, energy released; creation of

Question

What is a breeder reactor? Discuss nuclear fission, energy released; creation of fissile nuclides; breeding ratio. Discuss Fissile and fertile nuclides; Different fuel cycles Expand on the impact of using breeder reactors more extensively (for [instance, impact on uranium reserves) Discuss some concerns of breeder reactors (accidents, reprocessing, proliferation, etc.). Why can breeders increase proliferation risk? Operating breeders: a quick summary of what is operational. Can a nuclear reactor explode like an atomic bomb? Explain the concept of Fission chain reaction Controlled and uncontrolled fission; explain difference between bomb and reactor The life of a neutron (what can happen to a neutron from its creation until reaction)-no need to review in detail, but address other possibilities for neutrons besides causing fission. Discuss the possibility that other types of explosions can occur (steam explosions, similar to other plants)

Explanation / Answer

A breeder reactor is a nuclear reactor capable of generating more fissile material than it consumes because its neutron economy is high enough to breed fissile from fertile material like uranium-238 or thorium-232. Breeders were at first considered superior because of their superior fuel economy compared to light water reactors. Interest in breeders reduced after the 1960s as more uranium reserves were found, and new methods of uranium enrichment reduced fuel costs. Breeder reactors could in principle extract almost all of the energy contained in uranium or thorium, decreasing fuel requirements by nearly two orders of magnitude compared to traditional once-through light water reactors, which extract less than 1% of the energy. This could greatly dampen concern about fuel supply or energy used in mining. In fact, with seawater uranium extraction, there would be enough fuel for breeder reactors to satisfy our energy needs for as long as the current relationship between the sun and Earth persists, about 5 billion years at the current energy consumption rate (thus making nuclear energy as sustainable in fuel availability terms as solar or wind renewable energy). Nuclear waste became a greater concern by the 1990s. Breeding fuel cycles became interesting again because they can reduce actinide wastes, particularly plutonium and minor actinides. After the spent nuclear fuel is removed from a light water reactor, after 1000 to 100,000 years, these transuranics would make most of the radioactivity. Eliminating them eliminates much of the long-term radioactivity of spent nuclear fuel. In principle, breeder fuel cycles can recycle and consume all actinides, leaving only fission products. So, after several hundred years, the waste's radioactivity drops to the low level of the long-lived fission products. If the fuel reprocessing process used for the fuel cycle leaves actinides in its final waste stream, this advantage is reduced. There are two main types of breeding cycles, and they can both reduce actinide wastes: The fast breeder reactor's fast neutrons can fission actinide nucleii with even numbers of both protons and neutrons. Such nucleii usually lack the low-speed "thermal neutron" resonances of fissile fuels used in LWRs. The thorium fuel cycle simply produces lower levels of heavy actinides. The fuel starts with few isotopic impurities (i.e. there's nothing like U238 in the reactor), and the reactor gets two chances to fission the fuel: First as U233, and as it absorbs neutrons, again as U235. A reactor whose main purpose is to destroy actinides, rather than increasing fissile fuel stocks, is sometimes known as a burner reactor. Both breeding and burning depend on good neutron economy, and many designs can do either. Breeding designs surround the core by a breeding blanket of fertile material. Waste burners surround the core with non-fertile wastes to be destroyed. Some designs add neutron reflectors or absorbers. Today's LWRs do breed some plutonium. They do not make enough to replace the uranium-235 consumed. Only about 1/3 of fissions over a fuel element's life cycle are from bred plutonium. However, LWRs are not able to consume all the plutonium and minor actinides they produce. Nonfissile isotopes of plutonium build up. Even with reprocessing, reactor-grade plutonium can be recycled only once in LWRs as mixed oxide fuel. This reduces long term waste radioactivity somewhat, but not as much as purpose-designed breeding cycles. Breeding ratio One measure of a reactor's performance is the "breeding ratio" (the average number of fissile atoms created per fission event). Historically, attention has focused on reactors with low breeding ratios, from 1.01 for the Shippingport Reactorrunning on thorium fuel and cooled by conventional light water to over 1.2 for the Russian BN-350 liquid-metal-cooled reactor. Theoretical models of breeders with liquid sodium coolant flowing through tubes inside fuel elements ("tube-in-shell" construction) show breeding ratios of at least 1.8 are possible. The breeding ratios of ordinary commercial non-breeders are lower than 1; however, industry trends are pushing breeding ratios steadily higher, blurring the distinction. Types of breeder reactors Two types of breeder reactors are possible: Fast breeder reactor or FBR which uses fast (unmoderated) neutrons to breed fissile plutonium from fertile uranium-238 (it can also breed fissile uranium-233 from thorium) Thermal breeder reactor which uses thermal spectrum (moderated) neutrons to breed fissile uranium-233 from thorium (thorium fuel cycle) Reprocessing Actinides Half-life Fission products 244Cm 241Puƒ 250Cf 227Ac? 10–22 y medium m is meta 85Kr 113mCd¢ 232Uƒ 238Pu 243Cmƒ 29–90 y 137Cs 90Sr 151Sm¢ 121mSn ƒ for fissile 249Cfƒ 242mAmƒ 251Cfƒ[11] 140 y – 1.6 ky No fission products have a half-life in the range of 91 y – 210 ky 241Am 226Ra?[12] 247Bk 240Pu 229Th 246Cm 243Am 5–7 ky 4n 245Cmƒ 250Cm 239Puƒ 8–24 ky 236Npƒ 233Uƒ 230Th? 231Pa? 32–160 ky 248Cm 4n+1 234U? 211–348 ky 99Tc ¢ can capture 126Sn 79Se 236U 237Np 242Pu 247Cmƒ 0.37–23 My 135Cs¢ 93Zr 107Pd 129I long 244Pu ? for NORM 4n+2 4n+3 80 My 6-7% 4-5% 1.25% 0.1-1%

Related Questions

Navigate

• Browse (All)
• Browse W
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.