Chapter 26 - Nuclear Physics Flashcards
Pair production
Replacement of a single photon with a particle and corresponding antiparticle of the same total energy.
Mass defect
Difference between mass of completely separated nucleons and the mass of the nucleus.
Binding energy
Minimum energy required to completely separate a nucleus into its constituent protons and neutrons.
The greater the BE per nucleon…
The more stable the nucleus.
What is the most stable isotope?
Fe-56.
Fusion
Two nuclei with low A (atomic number) join to form a nucleus with a higher A which has greater BE per nucleon so energy is released.
Fission
High A nucleus splits to form two lower A nuclei which have higher BE per nucleon so energy is released.
Thermal neutron.
Mean KE similar to thermal energy of particles in reactor core.
What happens in induced nuclear fission?
U-235 absorbs slow/thermal neutron to form unstable U-236.
This splits to release daughter nuclei and fast neutrons.
What does a coolant do in a fission reactor?
Removes thermal energy produced by the fission reaction.
Moderator (fission reactor).
Slows down fast neutrons so they are more likely to be absorbed by U-235 nuclei e.g. water or carbon.
Control rods (fission reactor)
Absorbs neutrons and ensures 1 slow neutron survives per fission reaction.
Can be lowered to slow/stop reaction.
What is the environmental impact of nuclear reactors?
Toxic waste is produced and is difficult to dispose of.
What happens in nuclear fusion?
Nuclei brought together within 10 to the -15 m.
Strong nuclear force attracts them into a larger nucleus.
Why are high temperatures needed for nuclear fusion to occur?
Repulsive electrostatic force is very strong at small distances so nuclei need to move faster in order to get close enough to fuse.
