Plutonium-239, breeder reactors using

The amount of U-235 present in a nuclear fuel rod is gradually depleted, and ultimately there is insufficient present for the economic generation of power. A fast-breeder reactor uses the interaction of U-238 with energetic (fast) neutrons to generate the plutonium isotope Pu-239. As Pu-239 can be used as a nuclear fuel, a breeder reactor produces more fuel than it consumes. The sequence of steps is ... 

Breeder reactors use the more common uranium-238 isotope, which is bombarded with neutrons. Through a three-step process, the iuanium-238 is converted to plutonium-239, which is fissionable and can then be used to fuel another reactor. The major controversy in the United States concerns the extreme chemical toxicity of plutonium and its difficulty in handling. 

Full advantage of the neutron production by plutonium requires a fast reactor, in which neutrons remain at high energy. Cooling is provided by a hquid metal such as molten sodium or NaK, an alloy of sodium and potassium. The need for pressurization is avoided, but special care is required to prevent leaks that might result in a fire. A commonly used terminology is Hquid-metal fast-breeder reactor (LMFBR). 

The technologically most important isotope, Pu, has been produced in large quantities since 1944 from natural or partially enriched uranium in production reactors. This isotope is characterized by a high fission reaction cross section and is useful for fission weapons, as trigger for thermonuclear weapons, and as fuel for breeder reactors. A large future source of plutonium may be from fast-neutron breeder reactors. 

Uses of Plutonium. The fissile isotope Pu had its first use in fission weapons, beginning with the Trinity test at Alamogordo, New Mexico, on July 16, 1945, followed soon thereafter by the "Litde Boy" bomb dropped on Nagasaki on August 9, 1945. Its weapons use was extended as triggers for thermonuclear weapons. This isotope is produced in and consumed as fuel in breeder reactors. The short-Hved isotope Tu has been used in radioisotope electrical generators in unmanned space sateUites, lunar and interplanetary spaceships, heart pacemakers, and (as Tu—Be alloy) neutron sources (23). 

In fast (neutron) reactors, the fission chain reaction is sustained by fast neutrons, unlike in thermal reactors. Thus, fast reactors require fuel that is relatively rich in fissile material highly enriched uranium (> 20%) or plutonium. As fast neutrons are desired, there is also the need to eliminate neutron moderators hence, certain liquid metals, such as sodium, are used for cooling instead of water. Fast reactors more deliberately use the 238U as well as the fissile 235U isotope used in most reactors. If designed to produce more plutonium than they consume, they are called fast-breeder reactors if they are net consumers of plutonium, they are called burners . 

Another option is to use nuclear energy. Whereas technologically, with the development of breeder reactors, the uranium resources can be considered non-exhaustible and reactor technology can be considered safe [4] a serious concern is the proliferation of plutonium for nuclear weapons. There is also the unproven solution for disposal of radioactive material. 

Since plutonium is the actinide generating most concern at the moment this review will be concerned primarily with this element. However, in the event of the fast breeder reactors being introduced the behaviour of americium and curium will be emphasised. As neptunium is of no major concern in comparison to plutonium there has been little research conducted on its behaviour in the biosphere. This review will not discuss the behaviour of berkelium, californium, einsteinium, fermium, mendelevium, nobelium and lawrencium which are of no concern in the nuclear power programme although some of these actinides may be used in nuclear powered pacemakers. Occasionally other actinides, and some lanthanides, are referred to but merely to illustrate a particular fact of the actinides with greater clarity. 

The most common use of uranium is to convert the rare isotope U-235, which is naturally fissionable, into plutonium through neutron capture. Plutonium, through controlled fission, is used in nuclear reactors to produce energy, heat, and electricity. Breeder reactors convert the more abundant, but nonfissionable, uranium-238 into the more useful and fissionable plutonium-239, which can be used for the generation of electricity in nuclear power plants or to make nuclear weapons. 

The plutonium fuel in a breeder reactor behaves differently than uranium. Fast neutrons are required to split plutonium. For this reason, water cannot be used in breeder reactors because it moderates the neutrons. Liquid sodium is typically used in breeder reactors, and the term liquid metal fast breeder reactor (LMFBR) is used to describe it. One of the controversies associated with the breeder reactor is that it results... 

Breeder reactors were developed to use the 97% of natural uranium that occurs as nonfis-sionable U-238. The idea behind a breeder reactor is to convert U-238 into a fissionable fuel material. A reaction to breed plutonium is ... 

Deriving electrical energy from nuclear fission produces almost no atmospheric pollutants, such as carbon dioxide, sulfur oxides, nitrogen oxides, heavy metals, and airborne particulates. Although not discussed in the text, there is also an abundant supply of fuel for nuclear fission reactors in the form of plutonium-239, which can be manufactured from uranium-238. Use the keyword Breeder Reactor on your Internet search engine to learn about how this is so. 

When the fuel is initially loaded into die reactor, the core region will typically contain from 10 to 15% fissile isotopes with the remainder being ijSU. Essentially all of the blanket will be 238U. As energy is extracted from the fissile isotopes, they become depleted (the initial plutonium is gradually used up), However, in a breeder reactor, new plutonium will be formed in die cure and blanket regions faster Ilian it is consumed. Additionally, undesirable fission products are formed which must ultimately be removed. This process is schematically illustrated in Fig. 31. The before chart... 

In a typical fast breeder nuclear reactor, most of the fuel is 238U (90 to 93%). The remainder of the fuel is in the form of fissile isotopes, which sustain the fission process. The majority of these fissile isotopes are in the form of 239Pu and 241Pu, although a small portion of 235U can also be present. Because the fast breeder converts die fertile isotope 238 U into the fissile isotope 239Pu, no enrichment plant is necessary. The fast breeder serves as its own enrichment plant. The need for electricity for supplemental uses in the fuel cycle process is thus reduced. Several of the early hquid-metal-cooled fast reactors used plutonium fuels. The reactor Clementine, first operated in the Unired States in 1949. utilized plutonium metal, as did the BR-1 and BR.-2 reactors in the former Soviet Union in 1955 and 1956, respectively. The BR-5 in the former Soviet Union, put into operation in 1959. utilized plutonium oxide and carbide. The reactor Rapsodie first operated in France in 1967 utilized uranium and plutonium oxides. 

One of the many problems of nuclear power is the availability of fuel uranium-235 reserves are only about 0.7% those of the nonfissile uranium-238, and the separation of the isotopes is costly (Section 17.12). One solution is to synthesize fissile nuclides from other elements. In a breeder reactor, a reactor that is used to create nuclear fuel, the neutrons are not moderated. Their high speeds result in the formation of not only uranium-235 but also some fissile plutonium-239, which can be used as fuel (or for warheads). However, breeder reactors are more hazardous to operate than nuclear power plants. They run very hot, and the fast reactions require more careful control than a reactor used for nuclear power generation. Because of safety concerns, their use is still controversial. 

The most abundant isotope of uranium, 238U, does not undergo fission. In a breeder reactor, however, a 238U atom captures a neutron and emits two /3 particles to make a fissionable isotope of plutonium, which can then be used as fuel in a nuclear reactor. Write a balanced nuclear equation. 

In breeder reactors, the most common isotope of uranium, U-238, can be converted by neutron bombardment into fissionable Pu-239 (plutonium-239). The excess nuclear fuel can be used in other reactors or to build nuclear weapons. 

---