Radiation and radioactivity

Radiation and radioactivity

1. Defintions

   • Mass (nucleon) number: total number of protons and neutrons
   • Atomic (proton) number: number of protons/ = electrons
   • Isotopes: atoms with same number of protons as neutrons

2. Alpha = 'helium nuclei'

   • > Have a large positive charge
   • > When passed next to an atom it can pull a negatively charged electron from orbit
   • > Blocked by paper and cardboard
   • Made up of 2 protons & 2 neutrons

3. Beta = 'emitted electrons from a nucleus'

   • > Negatively charged
   • > Cause ionisation and push out electrons - (like charges repel)
   • Blocked by thin alumninum

4. Gamma = 'a type of electromagnetic radiation'

   • > Opposite to Alpha particles
   • > They can interact with electron orbiting, alike Beta, and transfer energy
   • > If the electron gets enough energy it can break free from the atom
   • > They are blocked by thick lead.

5. Radioactivity: Unstable nuclei decay - in the process ionising radiation. When the nucleus does decay, it splits into 'alpha', ''beta and 'gamma' radiation

6. Nuclear Fission - to split the nucleus

   • 1 > Neutron is absorbed by the Uranium nucleus and becomes unstable
     • 2 > The unstable uranium splits into 2 nulcei, with additional energy is released
       • 3 > Each of the 2 -3 neutrons can be absorbed by another uranium atom
         • This undergoes more fission - a chain reaction

7. Nuclear Fusion - small nuclei joining together

   • > You need high pressure > Less radioactive emissions & Releases more energy per kg
   • > Fusing together of Hydrogen nuclei resulting in the formation of Helium, the nuclei repel each other naturally, so kinetic energy is needed
   • > No radioactive waste is produced > Sustainable energy source

8. How can radiation be detected?

   • A 'Geiger- Muller' tube can detect radiation
   • Radiation is measured in Milliseverts (MSV)

9. 50% Radon gas

10. Half life

    • Radioactive decay is a random event. Half life is the time it takes for half of the un-decayed nuclei in a sample of decay

11. Dangers of radioactivity

    • Alpha radiation cannot penetrate your skin (eat/drink it) ionises strongly inside the body. They are the least dangerous!
    • Beta radiation damages cells inside the body and have a higher range. Outside the body they have a penetrating power - but ionise less strongly
    • Gamma radiation rays pass through without any damage. They are very difficult to stop - when absorbed by an atom, they can cause a lot of damage
    • The main effect of radiation is the damage to cells in your body. Low doses cause minor damage - yet sometimes make mutant cells which cause cancer. High doses kill cells and cause radiation to high exposure.

12. Nuclear power stations

    • Critical mass: all atoms move at the same time. To keep a chain reaction going, you need enough uranium to prevent neutrons escaping
    • Uncontrolled chain reaction: when the mass of uranium is too large and the rate of the fission reaction increases too rapidly
    • Moderator (carbon) is used to slow down fast neutrons so they are more likely to collide

Images and files in the map