Nuclear Decay Flashcards
What makes a nucleus unstable (4)
- Too many neutrons
- Too few neutrons
- Too many nucleons (i.e. Too heavy)
- Too much energy
What 2 forces act in nucleus?
Strong force
Electromagnetic force
When does alpha emission occur?
Occurs in very heavy nuclei (proton no of 82 or more) as the nuclei are too massive to be stable.
E.g Uranium and Radium
When does β- emission occur?
Decay of electron & antineutrino occurs in neutron rich isotopes.
Neutron changes to proton.
When does gamma emission occur?
Emission occurs in ‘excited’ nuclei with too much energy.
- Often happens after alpha or beta decay.
Rules of conservation in nuclear reactions
In nuclear reactions:
- Energy
- Momentum
- Proton number
- Nucleon number
What is not conserved in nuclear reactions?
Mass
What is the mass defect?
Difference in mass of a nucleus and its constituent nucleons
Binding energy
Energy needed to separate all nucleons in a nucleus.
Energy required to pull apart a nucleus is equal to energy released when nucleus is formed . Thus binding energy = mass defect
Why does fission release energy?
Smaller nuclei produced have larger binding energies per nucleon
What are thermal neutrons
Low energy neutrons which are most likely to cause fission
Why does spontaneous fission limit the number of possible elements?
Larger nuclei are more unstable and are more likely to spontaneously fission.
Why do neutrons need to be slowed down in the reactor?
So that they can induce fission in other nuclei and cause a chain reaction
What type of moderator prevents meltdowns?
Ones that absorb more neutrons the higher the temperature is.
- It will naturally slow down the reaction
What is the critical mass
Amount of fuel required to keep chain reaction going at a steady rate (where one fission follows another)
