Nuclear chain reactions reactions

Figure 12.11 Three chains of nuclear reactions that constitute hydrogen burning and convert protons into 4He. The rate-limiting step in all reactions is the first reaction to create the deuterium.

Chain reaction (nuclear) a self-sustaining fission process caused by the production of neutrons that proceed to split other nuclei. (21.6)... 

Nuclear fission reactions that cause other fissions are chain reactions. Chain reactions must be controlled to generate usable energy. 

Use the following terms to complete the concept map below critical mass, chain reaction, nuclear fission, and nucleon. 

The explanation of this behavior, which has paramount importance to the nuclear industry, was given by Allen [3]. After World War II, Allen depicted a model of water decomposition under radiation that considers the production and consumption of Hj. The key role of OH, H2 and O2 involved in the chain as a carrier or a breaker is clear (see Inset). Within this chain reaction, the reaction between H2 and O2 (which is thermodynamically favorable) takes place in water at high temperature only in the presence ofa catalyst such as copper or silver cations. In the radiolysis of water, the reaction can take place at room temperature in the presence of free radicals which form the molecular products H2, H2O2 and O2 at the first step inside the tracks or the spurs. Subsequently in the bulk of the solution, the free radicals which have escaped recombination in the tracks recombine as molecular products into water. The molecular products are formed in the nanosecond range and their recombination takes place in the millisecond range. 

The Sun is primarily composed of hydrogen and helium, along with smaller amounts of heavier elements such as calcium, iron, magnesium, aluminum, nickel, etc. The temperature in its interior is believed to be as high as 2 x 107 K, due to a chain of nuclear reactions which convert H into He. This energy is radiated to the upper convective levels, undergoing a series of absorption and emission processes. 

Ceramic a nonmetallic material made from clay and hardened by firing at high temperature it contains minute silicate crystals suspended in a glassy cement. (16.5) Chain reaction (nuclear) a self-sustaining fission process caused by the production of neutrons that proceed to split other nuclei. (20.6)... 

The following month, on April 22, Joliot, von Halban and Kowarski published a second paper in Nature concerning secondary neutrons. This one, Number of neutrons liberated in the nuclear fission of uranium, rang bells. Calculating on the basis of the experiment previously reported, the French team found 3.5 secondary neutrons per fissioa The interest of the phenomenon discussed here as a means of producing a chain of nuclear reactions, the three men wrote, was already mentioned in our previous letter. Now they concluded that if a sufficient amount of uranium were immersed in a suitable moderator, the fission chain will perpetuate itself and break up only after reaching the walls limiting the medium. Our experimental results show that this condition will most probably be satisfied. That is, uranium would most probably chain-react. 

SECTIONS 21.7 AND 21.8 Uranium -235, uranium-233, and plutonium-239 undergo fission when they capture a neutron, splitting into lighter nuclei and releasing more neutrons. The neutrons produced in one fission can cause further fission reactions, which can lead to a nuclear chain reaction. A reaction that maintains a constant rate... 

States. German chemist Otto Hahn and Austrian physicist Else Meitner discover chain reaction nuclear fission. American physicist Isidor Isaac Rabi develops the technique of magnetic resonance. German chemist... 

Chain reaction, nuclear a self-sustaining series of nuclear... 

In nuclear chemistry, a fission reaction (see atomic energy) may be initiated by a neutron and may also result in the production of one or more neutrons, which if they reacted in like manner could start a chain reaction. Normally, moderators such as cadmium rods which absorb neutrons are placed In the reactor to control the rate of fission. 

Chain reactions do not go on forever. The fog may clear and the improved visibility ends the succession of accidents. Neutron-scavenging control rods may be inserted to shut down a nuclear reactor. The chemical reactions which terminate polymer chain reactions are also an important part of the polymerization mechanism. Killing off the reactive intermediate that keeps the chain going is the essence of these termination reactions. Some unusual polymers can be formed without this termination these are called living polymers. 

The nuclear reactor is a device in which a controlled chain reaction takes place involving neutrons and a heavy element such as uranium. Neutrons are typically absorbed in uranium-235 [15117-96-17, or plutonium-239 [15117 8-5], Pu, nuclei. These nuclei spHt, releasing two fission fragment nuclei... 

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