Radioactivity

Radioactivity

1. Three types of radiation particle

   • Alpha
     • 2 nutrons to electrons same as a helium particle.  Weak penertration Very ionising 
     • alpha decay
       • When an alpha particle is emitted from the nucleus it, the nucleus,  looses to neutrons and two protons from the nucleus. This means that its atomic number goes down by two and its mass number goes down by 4. 
   • beta
     • This is a very fast moving electron  Moderately penertrating Moderately ionizing 
     • beta decay
       • In Beta decay a neutron changes into a proton plus an electron. The proton stays in the nucleus and the electron leaves the atom with high energy, and we call it a beta particle. When a beta particle is emitted from the nucleus the nucleus has one more proton and one less neutron. This means the atomic mass number remains unchanged and the atomic number increases by 1.
   • Gamma
     • High energy electro magnetic radiation most penetrating Weak ionising ability
     • Gamma decay

2. penetrating ability

   • alpha
     • Alpha has a very weak penetrating ability.  It can be stopped by your hand or even just a piece of paper. 
     • Stopped by paper or a few centimetres of air
   • gamma
     • Very high penetrating ability. It can go through most materials. Can be stopped/absorbed by lead because of its very high density. 
     • Stopped by thick lead or a few metres of concrete
   • beta
     • As per most of abilities is it in-between gamma and alpha particles. It can go through your hand and a sheet of paper for example but it can be stopped by aluminium which is of medium density. 
     • Stopped by a few mm of aluminium or a few metres of air

3. Detecting radiation

   • Photographic film
     • People who work on radioactive plants will wear badges with photographic film inside. The darker the film the higher amounts of radiation they have been exposed to. The get an accurate measure of how much radiation they are receiving the badges will have different materials such as Alumminium and copper. 
   • Geiger-Muller tube
     • The Geiger-Muller tube detects radiation. Each time it absorbs radiation, it transmits an electrical pulse to a counting machine. This makes a clicking sound or displays the count rate. The greater the frequency of clicks, or the higher the count rate, the more radiation the Geiger-Muller tube is absorbing.

4. half life

   • There are two definitions of half-life, but they mean essentially the same thing: the time it takes for the number of nuclei of the isotope in a sample to halvethe time it takes for the count rate from a sample containing the isotope to fall to half its starting level
   • the time it takes for the number of nuclei of the isotope in a sample to halve
   • the time it takes for the count rate from a sample containing the isotope to fall to half its starting level

5. Nuclear Fission

   • Used in power plant  Fission- means the splitting of
   • process
     • Uranium or plutonium is used because they're atoms have rather large nuclei and are very easy to split up.
     • hit by a neutron
       • This causes the nuclei to: Split into two smaller nuclei known as daughter nuclei which are radioactive. Two or three more neutrons are released Energy is released in the form of kinetic energy.   
       • The extra flying neutrons cause more collisions
         • The more neutrons there are the higher chance of they're being more collisions with the other uranium atoms this means that they're is a chain effect occurring leading to more and more kinetic energy being produced. 
       • The rate of reactions is controlled
         • The 'controllers' will insert and remove carbon rods into the container to maintain a steady rate of reaction. 
   • how energy is harvested
     • Nuclear reactors use the heat from nuclear reactions in the nuclear fuel to boil water. Just as in conventional power stations, the steam from the boiling water makes a turbine spin, which in turn makes the generator turn.
     • Waste products
       • No CO2 is produced unlike many energy making processes.  Plutonium can be used to make nuclear bombs. Other waste products are strored in barrels underground. 

6. A radioactive substance contains unstable nuclei

   • An unstable nucleus becomes stable by emitting radiation

7. Radioactive decay is a random event

   • We cannot predict or influence when it will happen

8. An isotope is an atom with the same number of protons but a different number of neutrons

9. Carbon dating

   • All living objects take in carbon, some of which is radioactive C14
   • When things die they have a certain % C14, which will only get smaller
   • The half life of C14 is 5700 years
   • If its too young not enough of the carbon will have decayed to give significant difference between the original and present amount of C14

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