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16 Cards in this Set
- Front
- Back
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How to estimate the strong nuclear force |
Calculate the electrostatic force of repulsion between two protons at a distance of 1fm. |
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Binding Energy |
The work that must be done to separate a nucleus into its constituent protons and neutrons. |
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Mass Defect |
The difference between the sum of the masses of the individual nucleons and the mass of the nucleus. |
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Nuclear Fission |
The process whereby a large unstable nucleus splits into two fragments which are more stable than the original. |
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Nuclear Fusion |
The process of making small nuclei fuse together to form a larger nucleus. The product has more binding energy per nucleon than the original. |
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Induced Fission |
Bombarding a nucleus with neutrons in order to cause it to split into equal two roughly equal fragments. |
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Chain Reaction |
Neutrons are released in a fission event which in turn induce fission in other nuclei causing a chain reaction. |
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How is energy released in nuclear fission? |
The resultant fragments repel each other with sufficient force to overcome the strong nuclear force. The fragments therefor gain kinetic energy. The energy released is equal to the change in binding energy. |
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How is energy released in nuclear fusion? |
The two nuclei become even more tightly bound together, as a result energy is released equal to the increase in binding energy.
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How does fusion occur in the sun? |
Atoms are stripped of their electrons forming a plasma. The nuclei of the plasma move at very high speeds due to the very high temperature. They fuse because because they have enough kinetic energy to overcome the electrostatic forces of repulsion due to their charge, and come close enough to interact via the strong nuclear force. |
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Function of the Control Rods |
To absorb neutrons. The depth of the control rods is adjusted to keep the number of neutrons in the core constant so that on average one fission neutron per fission event goes on to produce one further fission. This keeps the release of fission energy constant. |
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Function of the moderator |
Slows down neutrons because they so that they are travelling slow enough to cause another fission. The neutrons are slowed when they collide with the atoms in the moderator. Their kinetic energies are compatible to the kinetic energies of the moderator molecules. Water in the cores acts as the moderator as well as the coolant. |
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Critical mass |
The minimum mass required for a chain reaction to occur. If the mass is smaller than the critical mass, then too many neutrons escape the material without causing fission as the surface area to mass ratio is too high. |
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Safety Features of a nuclear reactor |
The core is a thick steel vessel that can withstand high pressure and temperature in the core. Can also absorb Beta radiation and some of the Gamma radiation and neutrons from the core. The core is in a building with very thick concrete walls which absorb the neutrons and gamma radiation that escape from the reactor vessel. Fuel rods are inserted and removed via a remote handling device. |
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Why are spent fuel rods more radioactive than they were before they where used in the reactor? |
Before they were used they contained only U-235 and U-238 which emit only alpha radiation which is absorbed by the fuel cans. After use, they emit Beta and Gamma radiation due to the many neutron rich fission products that form |
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Mass Difference |
The difference between the mass of the nucleus, and the total mass of the individual nucleons that make it up |
