6: Nuclear Physics Flashcards
What neucleus is the most stable?
Iron
Describe nucler fission.
When large nuclei are unstable and randomly split into two small nuclei
Describe nuclear fussion
When two small neuclei combine to create a larger neucleus
When is energy released by neucear fision or fussion?
When the average binding energy per neuclon is increasing.
Difine Activity
The rate of decay of the radioactive nuclei in a given isotope. It is proportional to the total number of nuclei in the sample and is measured in Becquerels.
Define Binding energy
The amount of energy required to split a nucleus into all its separate constituent nucleons. It is equivalent to the mass defect.
Define chain reaction
The process of the neutrons released by a fission reaction inducing further fissile nuclei to undergo fission
Define Coolant
A substance that passes through nuclear reactors and is responsible for removing heat from the core. This heat is then used to generate energy.
Define critical mass
The smallest mass of fissile material required in a fission reactor for a chain reaction to be sustained.
Define Mass defect
The difference in mass between a nucleus and the sum of the masses of its constituent nucleons.
Define Moderator
A material in nuclear reactors that absorbs energy from fast moving neutrons, to slow them down to speeds that can be absorbed by fissile neutrons to induce fission.
What was the rutherford scattering experement?
An experiment involving firing alpha particles at a thin gold foil and observing their deflections. It showed the existence and nature of the nucleus.
What was the progression of the atomic models?
1803- Dalton - Indivisble particles
1897- Thompson- Plum pudding model
1911- Rutherford - Empty space and orbiting electrons
1913- - Electrons orbit in shells
1919- - Proton and neutron discovered
What are alpha particles (radiation) properties and uses?
- strongly ionising
-slow moving - stopped by air/ paper
- deflect in a magnetic field
Smoke detectors (smoke durtubts current of alpha particles between two metal plates)
What are beta particles (radiation) properties and uses?
-Mildly ionising
-fast moving
- stopped by a few mm of aluminium
-negatively charged
- deflected in a magnetic field
Thickness detectors, if count rate is too low thickness will be ajusted.
What are gamma particles (radiation) properties and uses?
- Weakly ionising
-travels at the speed of light
-stopped by several cm of lead of m of concrete
-chargeless - unaffected by magnetic and electric fields
Used as a steriliser
Safe use of radiation
Store in a lead box away from people
Time, reduce time you are in contact with the source
Distance away from the source should be a long as possibe
What nuclei are used for nuclear fusion?
Deuterium and tritium
What proton number is needed for an isotope to emitt alpha radiation?
greater than 60
Inverse Square-Law:
A law that governs the intensity of gamma radiation. It means that the intensity of radiation at any point is inversely proportional to the square of the distance from its souce
It is essential for there to be a vacuum in the chamber because
• To prevent the a particles being absorbed or scattered;
• By air molecules;
