Radiation True or False? You are being bombarded with radiation right now. You are giving off radiation right now Your breakfast was irradiated with deadly radiation You can see radioactivity You can feel radioactivity Radioactive substances are only harmful if you touch them If you are irradiated then you become radioactive Radioactivity is not very useful We completely understand what causes radioactivity Do you know the three types of radioactivity. Write them down.. True True True ?? False False False False False False ?

PM S5 K1: Distinguish between stable and radioactive isotopes and describe the conditions under which the nucleus is unstable.

? Alpha radiation -  Helium nuclei Description: 2 neutrons, 2 protons (helium nuclei) Electric Charge: +2 Relative Atomic Mass: 4 Penetration power: Stopped by paper or a few cm of air Ionisation effect: Strongly ionising Effects of Magnetic/Electric Field: Weakly deflected Helium nuclei ?

Beta radiation -  high energy electron Description: Electric Charge: -1 Relative Atomic Mass: 1/1860th Penetration power: Stopped by few mm of aluminium Ionisation effect: Weakly ionising Effects of Magnetic/Electric Field: Strongly deflected high energy electron

Gamma radiation -  Electromagnetic radiation Description: High energy electromagnetic radiation Electric Charge: Relative Atomic Mass: Penetration power: Reduced by several cms of lead or several metres of concrete Ionisation effect: Very weakly ionising Effects of Magnetic/Electric Field: NO deflection Electromagnetic radiation

Let’s have a look at some radioisotopes. Think about how we may be able to use them!

The penetration power of the three types of radiation.    Skin or paper stops ALPHA Thin aluminium stops BETA Thick lead reduces GAMMA Thin mica

So what exactly does cause this radiation? . First we need to look at the structure of the atom

Draw diagrams to represent:

How did you go? 6 protons 6 neutrons 6 electrons 6 protons 7 neutrons

What do we call these? 6 protons 6 neutrons 6 electrons 6 protons

Isotopes Atoms of the same element with different numbers of neutrons

Isotopes Atoms of the same element with different numbers of neutrons Because they have the same number of electrons there is NO difference to their chemical behaviour.

Stable and unstable Isotopes There are over 2000 different isotopes that have been discovered so far. Only 279 are stable – they do not emit radiation. The rest are unstable and are called radioisotopes The nuclei rearrange to become more stable. As they do so they emit radiation. But which ones are unstable? Lets have a look at some of these isotopes.

Stable and unstable Isotopes So why are some nuclei unstable? Some nuclei are unstable because of the proton to neutron ratio. For light elements, stable nuclei have a proton:neutron ration close to 1:1. For heavy elements the stable nuclei have a proton:neutro ratio close to 1:1.5

Stable and unstable Isotopes p = n

Uses of radiation

Thickness Control Mill If not enough radioactivity is detected then the rollers compress to make the material thinner. This method is used in the manufacture of lots of sheet materials: plastics, paper, sheet steel. A radioactive source is on one side of the material and a detector on the other. If too much radioactivity is getting through, then the material is too thin and the rollers open up a bit to make the material thicker. Beta Source detector Hydraulic ram Electronic instructions to adjust rollers.

Leak detection in pipes The radioactive isotope is injected into the pipe. Then the outside of the pipe is checked with a Geiger-Muller detector, to find areas of high radioactivity. These are the points where the pipe is leaking. This is useful for underground pipes that are hard to get near. GM tube The isotope must have a short half life so the material does not become a long term problem. The radioactive isotope must be a gamma emitter so that it can be detected through the metal and the earth where the pipe leaks. Alpha and beta rays would be blocked by the metal and the earth.

Cobalt-60 Sterilisation Gamma rays are used to kill bacteria, mould and insects in ood. Also used to kill bacteria on hospital equipment. This is useful particularly on packaged food or on plastic items which would be damaged by heat sterilisation. It can affect the taste and the vitamin content, but it lengthens the shelf life. Gamma Source unsterilised sterilised

Sterilisation Gamma Source unsterilised sterilised Cobalt-60 is used as it is a gamma emitter – very penetrating. It has a half life of 5.3 years so the machines can run cheaply without regular maintenance. You don’t need external power to produce the gamma rays as you do with x-rays Cobalt-60 is held in a chemically inert form in a sealed container. When the cobalt-60 is exhausted it can easily be replaced. Gamma Source unsterilised sterilised

Radioactive half-life The average time taken for half of the substance to decay is called the radioactive half-life.

What is the half life of Carbon-15? Radioactive half-life What is the half life of Carbon-15?

PM S5 K5 – Identify one use of a named radioisotope: in industry In medicine PM S5 K6 – Describe the way in which the above named industrial and medical isotopes are used and explain their use in terms of their chemical properties. (This is your homework – ask for a handout! Include something about half life in your answers.) Start by reading p98-101. Cobalt-60 and Technetium 99 are easy to research but it is entirely up to you.

Think about this! What happens if radiation is incident upon a living cell? Radiation can ionise cells which causes cellular damage. If the exposure is high, it can kill the cell. If the exposure is lower it can cause cancer. The higher the exposure, the higher the risk of cancer.

PM S5 P6 – Use available evidence to analyse benefits and problems with the use of radioactive isotopes in industries and medicine Read p98 and from what you have learnt today make a list of benefits. Read p 101 and from what you have learnt today make a list of problems.

Sensitive monitoring of inductrial processes PM S5 P6 – Use available evidence to analyse benefits and problems with the use of radioactive isotopes in identified industries and machines. Benefits: Non-invasive diagnostic procedures Treatement of cancers Sensitive monitoring of inductrial processes Sterilisation Non-invasive examination of pipes / aircraft etc. Problems: Tissue damage for people exposed Risk of cancer if exposed Genetic damages to people exposed Hard to dispose of some isotopes (long half-life)