Presentation on theme: "Radiation True or False?"— Presentation transcript:
1Radiation True or False? You are being bombarded with radiation right now.You are giving off radiation right nowYour breakfast was irradiated with deadly radiationYou can see radioactivityYou can feel radioactivityRadioactive substances are only harmful if you touch themIf you are irradiated then you become radioactiveRadioactivity is not very usefulWe completely understand what causes radioactivityDo you know the three types of radioactivity. Write them down..TrueTrueTrue ??FalseFalseFalseFalseFalseFalse?
2Let’s have a look at some radioactive samples Think about how we may be able to use them!
3The penetration power of the three types of radiation. Skin or paperstops ALPHAThin aluminiumstops BETAThick leadreduces GAMMAThin mica
4So what exactly does cause this radiation? . First we need to look at the structure of the atom
6How did you go? 6 protons 6 neutrons 6 electrons 6 protons 7 neutrons
7What do we call these? 6 protons 6 neutrons 6 electrons 6 protons
8IsotopesAtoms of the same element with different numbers of neutrons
9PM S5 K1: Distinguish between stable and radioactive isotopes and describe the conditions under which the nucleus is unstable.
10Isotopes Radioisotopes Atoms of the same element with different numbers of neutronsBecause they have the same number of electrons there is NO difference to their chemical behaviour.RadioisotopesAtoms with unstable nuclei which are radioactive.They emit radiation to become stable.
11Stable 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 radioisotopesThe nuclei rearrange to become more stable.As they do so they emit radiation.But which ones are unstable?Lets have a look at them
12Stable and unstable Isotopes This line is where the no. protons = no. neutrons
13Why are some nuclei unstable All atoms with atomic no > 83 are unstableOther nuclei are unstable because of the proton to neutron ratio.For light elements, stable nuclei have a proton:neutron ration close to 1:1.2412For heavy elements the stable nuclei have a proton:neutron ratio closer to 1:1.520682Mg is stable 12p, 12nPb is unstable 92 p, 114 n
14There are four main types of radiation that can be given out by a nucleus of an atom:
15Alpha radiation - He Description: 2 neutrons, 2 protons (like a helium nuclei)Symbol 424 means mass = 42 means 2 protonsHe
16Beta radiation - - e high energy electron Description: Electric Charge:Symbol 0 or 0-1 -1The 0 means mass = 0How can the nucleus emit an electron?Because a neutron turns into an electron and a proton!The -1 means that the electron is the opposite of a proton.ehigh energy electron
17Positron emission - + e positive electron Description: Positively charged electronElectric Charge:Symbol 0+1The 0 means mass = 0How can this happen?Because a proton an electron and a neutron.The +1 means that the positron was made from a proton.epositive electron
18Gamma radiation - Electromagnetic radiation Description: High energy electromagnetic radiationElectric Charge:Relative Atomic Mass:Electromagnetic radiation
19Can you tell why the different types of emitters are located together? This line is wherep = n
20Radioactive half-life What do we mean by half-life?
21Radioactive half-life The average time taken for half of the substance to decay is called the radioactive half-life.
22Once an atom in a sample decays that atom is no longer radioactive. Radioactive half-lifeOnce an atom in a sample decays that atom is no longer radioactive.
24Thickness 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 SourcedetectorHydraulicramElectronic instructions to adjust rollers.
25Leak 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 tubeThe 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.
26PM S5 K5. Identify one use of a named radioisotope: - in industry- in medicinePM S5 K6. Describe the way in which the above named industrial and medical radioisotopes are used and explain their use in terms of their properties.
27Cobalt-60 Sterilisation Gamma rays are used to kill bacteria, mould and insects in food. 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 Sourceunsterilisedsterilised
28Sterilisation 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-raysCobalt-60 is held in a chemically inert form in a sealed container.When the cobalt-60 is exhausted it can easily be replaced.Gamma Sourceunsterilisedsterilised
29Cobalt-60 production.Iron-58 placed in a nuclear reactor and bombarded with neutrons. One neutron is absorbed and iron-59 is formedIron-59 is formed which decays into cobalt-59 plus a beta particleCobalt-59 is then placed in a nuclear reactor and bombarded with neutrons. One neutron is absorbed and cobalt-60 is formed.Can you write equations for these nuclear processes?
32Technitium is useful because it is a transition metal and therefore chemically binds easily with atoms (such as N) in biological molecules.It also has a half life of 6 hours so it does not expose the patient to radiation for any significant length of time.
33In all other respects the carrier molecule is identical to normal biological equivalent Tc-99m
34The biological molecule is introduced into the body
35The Tc-99m is carried to the specific organ (depends on the molecule)
36Special gamma cameras then take pictures of the gamma rays emitted by the technetium-99m
37The benefits: surgeons and doctors can make an accurate diagnosis without performing surgery The problems: Tissue damage – leading to sickness and ultimately death for high exposure Can cause cancer – leukemia/lung – up to 20 years after treatment Genetic damage causes deformities in offspring.
38Production of technetium-99m Molybdenum-98 absorbs a neutron to make molybdenum-99. Molybdenum-99 decays to make technetium99-m Mo-99 is delivered to hospitals in a “generator” Over time this produces Tc-99m which the hospitals extract when they need it. Please make a note to find more out about this when we go to ANSTO.
39PM S5 P2 – Use available evidence to analyse benefits and problems with the use of radioactive isotopes in industries and medicineRead 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.
40PM S5 P2 – Use available evidence to analyse benefits and problems with the use of radioactive isotopes in identified industries and machines.Benefits:Problems:
41Sensitive monitoring of industrial processes PM S5 P2 – Use available evidence to analyse benefits and problems with the use of radioactive isotopes in identified industries and machines.Benefits:Non-invasive diagnostic proceduresTreatment of cancersSensitive monitoring of industrial processesSterilisationNon-invasive examination of pipes / aircraft etc.Problems:Tissue damage for people exposedRisk of cancer if exposedGenetic damages to people exposedHard to dispose of some isotopes (long half-life)