Where does nuclear energy come from? The Q value of a nuclear reaction, the fission chain reaction and how a reactor controls it, and fusion in the Sun and in the laboratory. The energy calculations that boards, JEE, NEET and A-Level ask.
3 lessons, about 2 h4 simulations10 problems9 practice questionsPython in every lesson
Created by StemPy LabA nuclear reaction changes nuclei by a collision, and it obeys the conservation of mass number, charge, energy and momentum. The Q value is the energy released. If is negative, the projectile needs a threshold energy above .
When a neutron splits a uranium-235 nucleus, about MeV is released and two or three neutrons come out. If, on average, one of these neutrons splits another nucleus, the chain goes on steadily, and this is how a reactor works. A moderator slows the neutrons, control rods absorb them, and a coolant takes the heat.
In fusion two light nuclei join and release energy, as the binding energy curve shows. The nuclei repel one another, so fusion needs a very high temperature. In the Sun, four protons make one helium-4 nucleus and release MeV, and this keeps the Sun shining. On Earth the deuterium-tritium reaction releases MeV.
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