Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Nuclear fission reactor control

Within nuclear reactors, neutrons are a primary product of nuclear fission. By controlling the rate of the nuclear reactions, one controls the flux of neutrons and provides a steady supply of neutrons. For a diffraction analysis, a narrow band if neutron wavelengths is selected (fixing X) and the angle 20 is varied to scan the range of values. [Pg.652]

The fuel in a nuclear fission reactor is generally "U atoms arranged appropriately in a reactor vessel. Neutrons instigate fission of nuclei ofatoms and liberate energy. The energy output may be controlled either by regulating the fuel and/or adjusting the neu-... [Pg.861]

Erbium has limited commercial use, but it is used as an alloy metal for vanadium to make it easier to work and to form spring steel. The oxide of erbium is pink, which is used to color glass and to make lasers that will operate at normal room temperatures. It has hmited use as control rods in nuclear fission reactors. [Pg.298]

Nuclear fission reactors ( nuclear power reactors ) are devices that use controlled neutron-induced fission to generate energy. While a complete description of the design of these devices is beyond the scope of this book, there are certain basic principles related to nuclear reactors that are worth studying and that can be described and understood with a moderate effort. [Pg.384]

In a nuclear fission reactor, the fission reaction is controlled by inserting materials to absorb some of the neutrons so that the mixture does not explode. The energy that is produced can be safely used as a heat source in a power plant. [Pg.1026]

What starts the chain reaction that occurs in nuclear fission reactors used today What keeps it going How is its rate controlled ... [Pg.781]

Figure 17.12 Schematic diagram of a nuclear fission reactor. The fission reaction is controlled by cadmium or boron rods. The heat generated by the reaction is used to produce steam for the generation of electricity. Figure 17.12 Schematic diagram of a nuclear fission reactor. The fission reaction is controlled by cadmium or boron rods. The heat generated by the reaction is used to produce steam for the generation of electricity.
The composition of boron carbide is approximately 80 atomic percent boron. The material is often considered as a source of boron, without the high reactivity of the latter. Like boron, B4C has a high neutron capture cross-section for thermal neutrons and a low secondary gamma radiation. As such, it provides an excellent neutron absorber and is used extensively to control the neutron flux in nuclear fission reactors, such as the boiling water, pressurized water, and fast breeding reactors. It is also used for the compact storage of spent fuel rods.l l... [Pg.322]

A nuclear fission reactor is a device that permits a controlled chain reaction of nuclear fissions. In power plants, a nuclear reactor is used to produce heat, which in turn is used to produce steam to drive an electric generator. A nuclear reactor consists of fuel rods alternating with control rods contained within a vessel. The fuel rods are the cylinders that contain fissionable material. In the light-water (ordinary water) reactors commonly used in the United States (see Figure 21.19), these fuel rods contain uranium dioxide pellets in a zirconium alloy tube. Natural uranium contains only 0.72% uranium-235, which is the isotope that undergoes fission. The uranium used for fuel in these reactors is enriched so that it contains about 3% of the uranium-235 isotope. Control rods are cylinders composed of substances... [Pg.889]

Nuclear fission reactor a device that permits a controlled chain reaction of nuclear fissions. (21.7)... [Pg.1117]

As the US nuclear program continued after flie war, the Chicago Pile 1 had demonstrated the ability to build and control a nuclear fission reactor and had provided useful technical and operational information about running a nuclear reactor. However, the Chicago Pile 1 was never intended to bean industrial reactor, and it was not capable of converting large quantities of into Pu. Instead, new larger reactors in much more... [Pg.68]

The basic requirements of a reactor are 1) fissionable material in a geometry that inhibits the escape of neutrons, 2) a high likelihood that neutron capture causes fission, 3) control of the neutron production to prevent a runaway reaction, and 4) removal of the heat generated in operation and after shutdown. The inability to completely turnoff the heat evolution when the chain reaction stops is a safety problem that distinguishes a nuclear reactor from a fossil-fuel burning power plant. [Pg.205]

Fermi began to assemble a nuclear pile in a squash court under the football stands at the University of Chicago. This was really the first nuclear power reactor, in which a controlled, self-sustaining series of fission processes occurred. The controls consisted of cadmium rods inserted to absorb neutrons and keep the reactor from going... [Pg.500]

It IS often stated that unclear fusion tvill produce no radioactive hazard, but this is not correct. The most likely fuels for a fusion reactor would be deuterium and radioactive tritium, which arc isotopes of hydrogen. Tritium is a gas, and in the event of a leak it could easily be released into the surrounding environment. The fusion of deuterium and tritium produces neutrons, which would also make the reactor building itself somewhat radioactive. However, the radioactivity produced in a fusion reactor would be much shorter-lived than that from a fission reactor. Although the thermonuclear weapons (that use nuclear fusion), first developed in the 1950s provided the impetus for tremendous worldwide research into nuclear fusion, the science and technology required to control a fusion reaction and develop a commercial fusion reactor are probably still decades away. [Pg.849]

A nuclear power plant generates electricity in a manner similar to a fossil fuel plant. The fundamental difference is the source of heat to create the steam that turns the turbine-generator. A fossil plant relies on the combustion of natural resources (coal, oil) to create steam. A nuclear reactor creates steam with the heat produced from a controlled chain reaction of nuclear fission (the splitting of atoms). [Pg.866]

Uranium-235 and U-238 behave differently in the presence of a controlled nuclear reaction. Uranium-235 is naturally fissile. A fissile element is one that splits when bombarded by a neutron during a controlled process of nuclear fission (like that which occurs in a nuclear reactor). Uranium-235 is the only naturally fissile isotope of uranium. Uranium-238 is fertile. A fertile element is one that is not itself fissile, but one that can produce a fissile element. When a U-238 atom is struck by a neutron, it likely will absorb the neutron to form U-239. Through spontaneous radioactive decay, the U-239 will turn into plutonium (Pu-239). This new isotope of plutonium is fissile, and if struck by a neutron, will likely split. [Pg.868]

The energy produced in a nuclear reactor vessel is the result of a nuclear fission (atom splitting) process that occurs when sufficient nuclear material is brought together (critical mass). Under these circumstances, a chain reaction occurs and an external supply of neutrons is not required. A nuclear fuel control rod system raises or lowers the nuclear fuel (which is contained within fuel rods) inside the reactor vessel. [Pg.65]

To slow down and control the rate of reaction, a moderator is also required. Typically, the moderator is boric acid, graphite, or heavy water (D20) and is present in the high-purity water, which also serves as a primary coolant for the fuel and the reactor vessel. The tremendous heat generated by nuclear fission is transferred to this closed-loop coolant, which is contained within a reactor primary-coolant circulation system. The high-purity water coolant also contains a suitable pH buffer such as lithium hydroxide, which has the additional effect of limiting the corrosion of fuel-cladding and other components. [Pg.65]

Because the isotope uranium-235 is fissionable, meaning that it produces free neutrons that cause other atoms to split, it generates enough free neutrons to make it unstable. When the unstable U-235 reaches a critical mass of a few pounds, it produces a self-sustaining fission chain reaction that results in a rapid explosion with tremendous energy and becomes a nuclear (atomic) bomb. The first nuclear bombs were made of uranium and plutonium. Today, both of these fuels are used in reactors to produce electrical power. Moderators (control rods) in nuclear power reactors absorb some of the neutrons, which prevents the mass... [Pg.313]

Nuclear reactor is an arrangement in which the energy produced in a nuclear fission can be used in a controlled manner to produce steam which can run the turbine and produce electricity. Nuclear reactor consists of following parts... [Pg.206]

A fission reactor contains three components nuclear fuel rods, control rods, and a liquid (usually water) to transfer the heat created by fission from the reactor to the turbine. The nuclear fuel is primarily uranium-238 plus about 3 percent uranium-235. Because the uranium-235 atoms are so highly diluted with... [Pg.128]

The second paper of 1940 [3 ], entitled Kinetics of Uranium Chain Decay, is no less significant than the first. This pioneering work yielded a whole series of brilliant results for the first time, the need to take into account the role of delayed neutrons in the kinetics of chain nuclear reactions was shown (it is precisely the delayed neutrons which ensure easy control of nuclear reactors), the influence of heating on the kinetics of a chain process was considered in detail, and a number of conclusions were reached which are of much importance for the theory of reactor control. This same paper predicted the formation in the process of chain fission of new, previously unknown, nuclei which strongly absorb neutrons, a prediction which was later fully confirmed. [Pg.31]

A nuclear reactor is a device in which nuclear chain reactions are initiated, controlled, and sustained at a steady rate. Nuclear reactors are used for many purposes, but the most significant current uses are for the generation of electrical power and for the production of plutonium for use in nuclear weapons. Currently, all commercial nuclear reactors are based on nuclear fission. The amount of energy released by one kg 235U is equal to the energy from the combustion of 3000 tons of coal or the energy from an explosion of 20,000 tons of TNT (Trinitrotoluene, called commonly dynamite). [Pg.71]

Nuclear Reactor An apparatus in which the nuclear fission chain can be initiated, maintained and controlled so that energy is released at a specific rate. [Pg.23]


See other pages where Nuclear fission reactor control is mentioned: [Pg.861]    [Pg.861]    [Pg.1003]    [Pg.1003]    [Pg.84]    [Pg.852]    [Pg.892]    [Pg.476]    [Pg.261]    [Pg.217]    [Pg.1256]    [Pg.780]    [Pg.959]    [Pg.383]    [Pg.186]    [Pg.386]    [Pg.11]    [Pg.217]    [Pg.394]    [Pg.1041]    [Pg.378]   
See also in sourсe #XX -- [ Pg.864 ]




SEARCH



Fission reactors

Nuclear fission

Nuclear reactors

Reactors control

© 2024 chempedia.info