Nuclear energy Flashcards
What element is used to generate power
Uranium 235
How is nuclear fission used to generate power?
neutrons travelling slowly enough to be captured by a U-235 nuclei are fired at U-235.
The nucleus becomes very unstable and splits into two or more smaller pieces, and energy is released in terms of heat.
Nuclei fission can only happen if the number of nuclei doesn’t decrease.
What are the names of neutrons that induce fission reactions.
Thermal neutrons - a neutron with low speeds.
Their mean kinetic energy is 3/2kT where k is the Boltzmann constant and T is the absolute temperature.
What is the role of the moderator in nuclear reaction
its job is to slow down neutrons so they can be absorbed by the nuclei.
They rapidly collide with these particles which absorb the kinetic energy. Once they are the correct speed they can continue to be captured by the uranium
What is the mass defect?
A nucleus has a mass that is less than the mass of the protons and the neutrons that make it up. This occurs because work must be done to overcome the strong nuclear forces that bind nucleons together.
What is binding energy per nucleon?
Total binding energy / number of nucleons
Experimental data shows binding energy is higher in more stable nucleons.
What features does binding energy against nucleon number have?
binding energy per nucleon increases rapidly and is about 8Mev for elements heavier than lithium
Helium is very stable relative to low mass nuclei, explaining why alpha decay is more common than proton emission
Binding energy is max at Fe 56 at 8.79 Mev and decreases from there
Lighter elements tend to fuse whereas heavier elements tend to undergo fission
What is the role of control rods in nuclear reactions?
They absorb neutrons, slowing down the rate of reaction because less neutrons are available to cause fission reactions.
What is the coolant - nuclear power?
fluids that absorb heat from the reactor and transfer the heat away to drive turbines and prevent overheating. It circulates through tubes inside the reactors core and then passes a heat exchange where the heat is transferred to a secondary cooling system.
What are the safety measures in nuclear power station?
- the reactor is covered by shielding to protect workers from radiation.
- during an emergency cooling rods drop down immediately.
- Nuclear waste is handled remotely
- low level waste (clothes papers rags) are encased in cement and stored until they are no longer radioactive
mid level waste(chemical sludge/resin) is encased in steel drums and stored securely underground. - high level waste (fuel rods) stored under water to cool them, and then they are mixed with molten glass and solidified in steel containers.
What is induced fission
When a larger nucleus splits into two smaller one by bombardment
What is U?
1/12 the mass of an atom of carbon 12
