P6- Radioactive Materials

P6- Radioactive Materials

1. Radioactivity

   • Isotopes
     • Isotopes are atoms with the same number of protons but different number of neutrons
     • Usually elements only have one or two stable isotopes
     • Some isotopes are radioactive the nucleus is unstable so it decays and emits radiation like carbon 14
   • Radioactive elements emit ionising radiation all the time
   • they are unstable and decay to become more stable
   • unstable atoms decay at random

2. Radiation

   • Alpha
     • high ioninsation
     • low penetration
     • Made up of two protons and two neutrons mass of 4 and charge 2+
     • Nuclear equation
     • blcked by skin paper
   • Beta
     • meduim ionisation
     • medium penetration
     • Beta particals are identical to electrons no mass and charage -1
     • During Beta decay a neutron in the nucleus turns into a proton
     • Nucleaer equation
     • Blcked by thin sheet of metal
   • Gamma
     • hight penetration
     • Low ionisation
     • Gamma ray is just energy it has 0 charge and 0 mass
     • Blcked by thick lead or concerete

3. Nuclear Fission

   • Chain Reaction
     • when neutrons split the nucleus and releases more neutrons these neutrons go on to split more nuclei causing a chain reaction
   • Controlling reaction
     • The fuel used in the reaction is placed in fuel rods fuel rods capture and emit neutrons
     • Control rods absorb some of the neutrons to slow down the reaction
     • Coolant (water or oil) is used to take away the heat produced by the process
   • Nuclear waste
     • Low level waste
       • disposed by burying it in secure landfill sites
     • Intermediate level waste
       • sealed in concrete blacks and then put in steel canisters for storage
     • High level waste
       • sealed in glass and steel and cooled for about 50 years before it is moved
     • canisters for intermediate and high level wast buried underground it can be difficult to find places as they need to be geologically stabel
   • Nuclear fission is the process of splitting a large atom (uranium or plutonium) by fireing a slow moving neutron whith produces lots of energy and more nuetrons and nuclear waste

4. Nuclear Fusion

   • Electrostatic repulsion
     • Nucleus in an atom is positive this makes it hard to fuse atoms together as their is a strong electrostatic repulsion between the two atoms seaperating them
   • Strong Nuclear Force
     • the protons in an atom is held together by the strong force which is stronger than electrostatc repulsion
     • it has a short range hold atoms together at a small distance (1 x 10-15)
     • High temperatures are required for fusion to take place
   • Nuclear Fusion is when two nuclei can combine (fuse) together to create a larger nucleus and release a lot of energy

5. Rutherford

   • he fired positive charged alpha particles at thin gold foil
   • most of the alpha particles when straight through but some of them came back
   • He discovered that the nucleus was positive otherwise the positive alpha particles wouldn't repell by the nucleus

6. Half Life

   • Half life is the time taken for half of the radioactive nuclei now present to deacy
   • When an unstable nucleus decays and emits radiation means one more radioactive nucleus isn't their to decay later
   • Short half life means activity falls quickly because lots of the nuclei decay
   • Long half life means the activity falls slowly because most of the nuclei don't decay for a long time

7. Dangers form Radiation

   • Ionising radiation can break molecules into smaller bits called ions wich can cause damage to cells
   • Irradiation
     • Being exposed to radiation without coming into contact with the source
   • Contamination
     • Picking up some radioactive material eg breathing it in

8. Using ionising radiation

   • Background radiation
     • Natural radioactive elements in the air soil rocks
     • Space cosmic rays form the sun
     • Human activity nuclear explosions waste from nuclear power plants
   • Treat cancer
     • Gamma rays can kill cancer cells
     • Some normal cells may be damaged causing radiation sickness
   • Sterilising medical equipment
     • Gamma rays kill the microbes on medical equipment
     • Better than boiling plastic equipment which could damage
     • Strong radioactive source that has a long half life so that it doesn't need replacing often
   • Sterilising food
     • Gamma rays kill microcbes keeping food fresher for longer
     • the food is not radioactive so its safe to eat
   • Tracers
     • Radioactive molecule that is injected into people
     • they can detect cancer or weather an organ is working properly
     • Tracers must be gamma or Beta so radiation passes out of the body and short half life so the radioactivity inside patient disapers qucikly

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