What is the importance of thermal neutrons in nuclearprocesses? a. Thermal neutr
ID: 1756760 • Letter: W
Question
What is the importance of thermal neutrons in nuclearprocesses?a. Thermal neutron capture results inuranium fission.
b. Thermal neutrons are sources of gammarays.
c. Thermal neutrons are released inradioactive decay.
d. Thermal neutrons are commonly releasedin fusion reactions.
e. Thermal neutrons are necessary in the fusion ofdeuterium. What is the importance of thermal neutrons in nuclearprocesses? Thermal neutron capture results inuranium fission. Thermal neutrons are sources of gammarays. Thermal neutrons are released inradioactive decay. Thermal neutrons are commonly releasedin fusion reactions. Thermal neutrons are necessary in the fusion ofdeuterium.
Explanation / Answer
A thermal neutron is a free neutron with a kinetic energy level ofca. 0.025 eV (approx. 4.0e-21 J; 2.4 MJ/kg, hence a speed of 2.2km/s). They are named 'thermal' as this level of kinetic energy issimilar to the average kinetic energy of the molecules in aroom-temperature gas (see kinetic theory for energies and rmsspeeds of molecules). After a number of collisions with nuclei,neutrons arrive at this energy level, provided that they are notabsorbed. Thermal neutrons have a much larger effective cross-section thanfast neutrons, and can therefore be absorbed more easily by anyatomic nuclei that they collide with, creating a heavier - andoften unstable - isotope of the chemical element as a result. Most fission reactors use a neutron moderator to slow down, orthermalize the neutrons that are emitted by nuclear fission so thatthey are more easily captured, causing further fission. Others,called fast breeder reactors, use fast neutrons directly.
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