Presentation is loading. Please wait.

Presentation is loading. Please wait.

Online Course : Introduction to Radiation Click here to start!

Similar presentations


Presentation on theme: "Online Course : Introduction to Radiation Click here to start!"— Presentation transcript:

1 Online Course : Introduction to Radiation Click here to start!

2 Description This online course, designed and developed by the Radiation Safety Institute of Canada, is meant to give you a brief introduction to radiation. The following topics will be covered : What is radiation? The different types of ionizing radiation Introduction to units and regulatory limits on exposure Background radiation Uses of ionizing radiation Effects of radiation on your body Simple safety measures to reduce your exposure If you are interested in learning more about radiation, please contact the Radiation Safety Institute of Canada (www.radiationsafety.ca). We offer an array of courses for professionals, and information for the public.www.radiationsafety.ca Enjoy! Continue

3 Atoms protons, neutrons, and electrons. Nucleus All matter is made up of atoms. The different elements are simply made up of atoms with different numbers of protons, neutrons, and electrons. Click on the different particles to learn more about them! Continue

4 Atoms protons, neutrons, and electrons. Nucleus All matter is made up of atoms. The different elements are simply made up of atoms with different numbers of protons, neutrons, and electrons. Click on the different particles to learn more about them! Protons : Electrical charge : + 1 Since the proton has a charge, it interacts with other charged particles. It is attracted by particles of opposite charge (like the electron), and repelled by like charges (like other protons) Mass : kg ~ 1 unit of mass u This mass is about equal to the mass of the neutron. Size : meters The proton is times smaller than the atom. This means that the atom is mostly empty space!! Back

5 Atoms protons, neutrons, and electrons. Nucleus All matter is made up of atoms. The different elements are simply made up of atoms with different numbers of protons, neutrons, and electrons. Click on the different particles to learn more about them! Neutrons : Electrical charge : 0 The neutron is neutral, so it does not interact electrically with other particles. It is insensitive to other charges. Mass : kg ~ 1 unit of mass u This mass is about equal to the mass of the proton. Size : m The neutron is times smaller than the atom. This means that the atom is mostly empty space!! Back

6 Atoms protons, neutrons, and electrons. Nucleus All matter is made up of atoms. The different elements are simply made up of atoms with different numbers of protons, neutrons, and electrons. Click on the different particles to learn more about them! Electrons : Electrical charge : - 1 Since the electron has a charge, it interacts with other charged particles. It is attracted by particles of opposite charge (like the proton), and repelled by like charges (like other electrons) Mass : kg The electron is almost 2000 times less massive than the neutron and the proton. Its mass in an atom is therefore negligible. Size : m The electron is 1000 times smaller than protons and neutrons. Back

7 Atoms protons, neutrons, and electrons. Nucleus All matter is made up of atoms. The different elements are simply made up of atoms with different numbers of protons, neutrons, and electrons. Click on the different particles to learn more about them! Nucleus : Electrical charge : Z (Atomic Number, number of protons) Mass : A (Mass Number, number of protons and neutrons) The nucleus is the sum of its parts. Its mass is about equal to the mass of the neutrons and protons in it, and is given in units of mass u by A, the mass number. Its charge is positive and equal to the number Z of protons inside it. Size : m The nucleus is times smaller than the atom as a whole. The atom is therefore mostly empty space! Back

8 Radioactivity Unstable Atom Continue Stable! Radiation Nuclear ForcesNuclear Forces keep the nucleus together. When they are not strong enough, the nucleus is unstable and must release energy to become stable. Anything emitted from an unstable nucleus as it become stable is radiation, and the atom is called a radioactive atom, a radioisotope, or a radionuclide Back

9 Radioactivity Nuclear Forces keep the nucleus together. When they are not strong enough, the nucleus is unstable and breaks apart under the electric forces of the protons. Stable Atom Unstable Atom Nuclear Forces : The nucleus is made up of positive charges and neutral charges. If only electromagnetic forces existed, the nucleus would never be, as the protons should repel. However, on the scale of the nucleus, another physical force exists : the Strong force, which binds nucleons (for or purposes, protons and neutrons) together, regardless of their charge. The Strong force acts only on a very short scale, but on that scale, it is more powerful than the electromagnetic force. Protons therefore repel each other, unless they are essentially touching, as they are in a nucleus, in which case they are tightly bound by the strong force. Large nuclei, however, have diameters bigger than the range of the strong force. The strong force and the electromagnetic forces therefore compete. If the electromagnetic force is stronger, the nucleus is unstable and will have to undergo a radioactive decay. Back

10 Types of Radioactive Decay A radioactive decay is a process in which the unstable nucleus releases energy. There are several types of radioactive decays. Click on each to lean more about them! Alpha Decay Gamma Decay Neutron Radiation Beta Decay Radioactive Decay Continue Back

11 Types of Radioactive Decay A radioactive decay is a process in which the unstable nucleus releases energy. There are several types of radioactive decays. Click on each to lean more about them! Alpha Decay Gamma Decay Neutron Radiation Beta Decay Radioactive Decay Continue Alpha Decays : An alpha particle is comprised of 2 protons and 2 neutrons. An alpha decay occurs when heavy particles (Z > 82, i.e. elements heavier than lead) release this heavy particle to reach stability. Alpha particles are heavy and doubly charged. They therefore interact strongly with other charged particles, releasing their energy quickly and over a short distance. As such, a piece of paper, or your dead layer of skin, is enough to stop this type of radiation. However, if ingested, this type of radiation can be quite damaging. Examples of alpha decays Back

12 Examples of Alpha Decay Uranium MeV Alpha Thorium-234 Radon-222Radium MeV Alpha Back

13 Examples of Alpha Decay Uranium MeV Alpha Thorium-234 Radon-222Radium MeV Alpha + + This notation designates the isotope of Uranium which contains 238 nucleons (protons and neutrons). All Uranium atoms have 92 protons, but can have anywhere between 140 and 146 neutrons. The atoms with different numbers of neutrons are called isotopes. Uranium-238, the most common uranium isotope found in nature, has 92 protons and 146 neutrons, for a total of 238 nucleons.... Close Back

14 Examples of Alpha Decay Uranium MeV Alpha Thorium-234 Radon-222Radium MeV Alpha This is the kinetic energy, or energy of motion, of the alpha particle. It is indicative of how much energy this particle can deposit in matter. 1 MeV = eV 1 eV = 1.6 x J This is the kinetic energy, or energy of motion, of the alpha particle. It is indicative of how much energy this particle can deposit in matter. 1 MeV = eV 1 eV = 1.6 x J Close Back

15 Types of Radioactive Decay A radioactive decay is a process in which the unstable nucleus releases energy. There are several types of radioactive decays. Click on each to lean more about them! Alpha Decay Gamma Decay Neutron Radiation Beta Decay Radioactive Decay Continue Beta Decays: Beta particles are small charged particles. An electron ejected from the nucleus is a negative beta particle. The positron, the electrons anti-particle, is a positive beta particle. Beta particles are charged, so they quickly deposit their energy through electric interactions with matter. A layer of plastic or aluminum is therefore an efficient shield against beta radiation. Beta radiation occurs when, to become stable, a nucleus changes a neutron into a proton, in which case an electron is ejected, or a proton into a neutron, in which case a positron is ejected. Positive Beta Decay (β + decay) : Negative Beta Decay (β - decay) : p+p+ p+p+ n0n0 n0n0 + - p+p+ n0n0 + - Proton Neutron Electron Positron Examples of Beta Decay Back

16 Examples of Beta Decay Phosphorus-32 Beta particle (electron) Sodium-22 Beta particle (positron) Sulfur-32 Neon Back

17 Types of Radioactive Decay A radioactive decay is a process in which the unstable nucleus releases energy. There are several types of radioactive decays. Click on each to lean more about them! Alpha Decay Gamma Decay Neutron Radiation Beta Decay Radioactive Decay Continue Gamma decay: A gamma ray is an energetic photon liberated from a nucleus. Unlike alpha and beta decays, a gamma decay does not change the nature of the radioactive particle. A gamma ray is simply a bundle of energy, liberated from an unstable particle for it to reach a more stable state. Gamma decays typically follow alpha or beta decays, liberating excess energy which was not removed during the previous decay. Since gamma rays are electrically neutral, they do not interact as readily with matter. They can only be slowed down or stopped in direct collisions with electrons. Thick layers of lead are required to reduce their intensity. Example of gamma decays... Back

18 Types of Radioactive Decay A radioactive decay is a process in which the unstable nucleus releases energy. There are several types of radioactive decays. Click on each to lean more about them! Alpha Decay Gamma Decay Neutron Radiation Beta Decay Radioactive Decay Continue Gamma decay: A gamma ray is an energetic photon liberated from a nucleus. Unlike alpha and beta decays, a gamma decay does not change the nature of the radioactive particle. A gamma ray is simply a bundle of energy, liberated from an unstable particle for it to reach a more stable state. Gamma decays typically follow alpha or beta decays, liberating excess energy which was not removed during the previous decay. Since gamma rays are electrically neutral, they do not interact as readily with matter. They can only be slowed down or stopped in direct collisions with electrons. Thick layers of lead are required to reduce their intensity. Example of gamma decays A photon is an electromagnetic wave, with a frequency and a wavelength. Photons with different frequencies and wavelengths are detected very differently. All of the light that we see comes from photons with a certain wavelength. The colour we perceive is dependant on the exact wavelength of the photons. Less energetic photons, with longer wavelengths, compose radio frequencies, microwaves and infrared light, and higher energy photons comprise UV light, X-rays, and gamma rays. Close Back

19 Example of Gamma Decay Neon-22* Sodium-22 Beta particle Gamma ray Neon-22 Unstable Stable! Back

20 Types of Radioactive Decay A radioactive decay is a process in which the unstable nucleus releases energy. There are several types of radioactive decays. Click on each to lean more about them! Alpha Decay Gamma Decay Neutron Radiation Beta Decay Radioactive Decay Continue Neutron radiation : Neutrons are never emitted on their own from an unstable nucleus. However, during nuclear fission of a heavy element, for example Uranium-235 or Plutonium-239, several neutrons can be ejected along with the fission products. Since neutrons have no charge, they only interact with particles through direct collisions. They deposit most of their energy in collisions with particles of similar sizes, such as protons. Unfortunately, the tissue in our body is made of 60% water, which contains two Hydrogen atoms, each made of a single proton. Neutrons therefore can deposit a lot of energy in our body, and can be very damaging. Thick layers of water, preferably heavy water, or other materials heavy in hydrogen (concrete, paraffin) are required to shield from neutron radiation.heavy water Example of neutron radiation Back

21 Types of Radioactive Decay A radioactive decay is a process in which the unstable nucleus releases energy. There are several types of radioactive decays. Click on each to lean more about them! Alpha Decay Gamma Decay Neutron Radiation Beta Decay Radioactive Decay Continue Neutron radiation : Neutrons are never emitted on their own from an unstable nucleus. However, during nuclear fission of a heavy element, for example Uranium-235 or Plutonium-239, several neutrons can be ejected along with the fission products. Since neutrons have no charge, they only interact with particles through direct collisions. They deposit most of their energy in collisions with particles of similar sizes, such as protons. Unfortunately, the tissue in our body is made of 60% water, which contains two Hydrogen atoms, each made of a single proton. Neutrons therefore can deposit a lot of energy in our body, and can be very damaging. Thick layers of water, preferably heavy water, or other materials heavy in hydrogen (concrete, paraffin) are required to shield from neutron radiation.heavy water Example of neutron radiation Heavy water is water in which the hydrogen atoms are made up of a proton and a neutron, instead of simply a proton. This hydrogen isotope is called deuterium. Heavy water is used in CANDU reactors. Close Back

22 Fission fragment Photon Neutron Example of Neutron Radiation Back

23 Ionization When radiation is energetic enough, it interacts with matter by knocking electrons out of their orbits. Alpha and beta particles interact with atoms electrically, and strip electrons from their orbit in that manner, where as photons can give all or a fraction of their energy to electrons, liberating them from their orbit. Either way, you are left with two pieces of an atom, a positive and a negative one. These are called ions, and the process of forming these is called ionization. Neutral Atom Positive Ion Negative Ion Replay! ContinueBack

24 Ionization When radiation is energetic enough, it interacts with matter by knocking electrons out of their orbits. Alpha and beta particles interact with atoms electrically, and strip electrons from their orbit in that manner, where as photons can give all or a fraction of their energy to electrons, liberating them from their orbit. Either way, you are left with two pieces of an atom, a positive and a negative one. These are called ions, and the process of forming these is called ionization. Neutral Atom Negative Ion Positive Ion BackContinue

25 Ionizing and Non-Ionizing Radiation Ionizing Radiation is radiation which can create ions. Alpha particles, beta particles, gamma rays and X-rays are always ionizing. This is dangerous radiation, since ions travelling through your body can break your DNA and the cells in your body, potentially leading to mutated cells, which can form cancer. Non-ionizing radiation, on the other hand, is photons which are not energetic enough to create ions. It therefore will not produce breaks in your cells and DNA, and should not lead to cancers related to radiation exposure. Radio waves MicrowavesVisible Light Infrared light Non-Ionizing Rad.... Click on the types of non- ionizing radiation to learn more! ContinueBack

26 Ionizing and Non-Ionizing Radiation Ionizing Radiation is radiation which can create ions. Alpha particles, beta particles, gamma rays and X-rays are always ionizing. This is dangerous radiation, since ions travelling through your body can break your DNA and the cells in your body, potentially leading to mutated cells, which can form cancer. Non-ionizing radiation, on the other hand, is photons which are not energetic enough to create ions. It therefore will not produce breaks in your cells and DNA, and should not lead to cancers related to radiation exposure. Radio waves MicrowavesVisible Light Infrared light Non-Ionizing Rad. X-rays, like gamma rays, UV, visible light, infrared, microwaves, and radio waves, are simply photons. However, they are quite energetic, second only to gamma rays. They are produced when electrons lose energy, either within their orbits around a nucleus, or when they interact with matter, notably with other electrons. Close Click on the types of non- ionizing radiation to learn more! BackContinue

27 Ionizing and Non-Ionizing Radiation Ionizing Radiation is radiation which can create ions. Alpha particles, beta particles, gamma rays and X-rays are always ionizing. This is dangerous radiation, since ions travelling through your body can break your DNA and the cells in your body, potentially leading to mutated cells, which can form cancer. Non-ionizing radiation, on the other hand, is photons which are not energetic enough to create ions. It therefore will not produce breaks in your cells and DNA, and should not lead to cancers related to radiation exposure. Radio waves MicrowavesVisible Light Infrared light Non-Ionizing Rad. Continue Microwaves : Since microwaves heat food so quickly, there is a common misconception that they are highly energetic. In fact, microwaves are much less energetic than visible light, which is bombarding you eyes constantly. The reason microwaves heat food so quickly is simply that the size of the wave is perfectly in tune with the size of a water molecule, making it possible to transfer a maximum of its energy to water. In physics, this is called a resonance frequency. The common analogy for this type of phenomenon is pushing a kid on a swing: if you try to push someone while he is only midway through his natural swinging motion, your push will be very inefficient, since you must first stop the persons motion, and then give him an opposite one. However, if you stand a few feet behind him, and give him a push when he is at his maximum height, all of the energy you transfer will go into increasing his velocity and height. Similarly, microwaves are just the right size to vibrate water molecules most efficiently. Back

28 Ionizing and Non-Ionizing Radiation Ionizing Radiation is radiation which can create ions. Alpha particles, beta particles, gamma rays and X-rays are always ionizing. This is dangerous radiation, since ions travelling through your body can break your DNA and the cells in your body, potentially leading to mutated cells, which can form cancer. Non-ionizing radiation, on the other hand, is photons which are not energetic enough to create ions. It therefore will not produce breaks in your cells and DNA, and should not lead to cancers related to radiation exposure. Radio waves MicrowavesVisible Light Infrared light Non-Ionizing Rad. Continue Radiowaves : There has been much discussion on RF energy and radio-waves in recent months. The concern regards the effect of cell phone use, and its possible link to certain forms of brain cancer. As radiofrequencies are not ionizing, there is no reason to think that they would produce the same effect as, for example, X-rays and the decay of uranium. Regarless, research has been going into determining if cell phones, cell phone towers, and power lines could have adverse health effects. For more information on these topics, consult the following pages : Health Canada : World Health Organization : Back

29 Ionizing and Non-Ionizing Radiation Ionizing Radiation is radiation which can create ions. Alpha particles, beta particles, gamma rays and X-rays are always ionizing. This is dangerous radiation, since ions travelling through your body can break your DNA and the cells in your body, potentially leading to mutated cells, which can form cancer. Non-ionizing radiation, on the other hand, is photons which are not energetic enough to create ions. It therefore will not produce breaks in your cells and DNA, and should not lead to cancers related to radiation exposure. Radio waves MicrowavesVisible Light Infrared light Non-Ionizing Rad. Continue Visible Light : Did you know your eyes are sensitive to as few as 5 to 9 photons? Heres some literature if you are interested : Back

30 Ionizing and Non-Ionizing Radiation Ionizing Radiation is radiation which can create ions. Alpha particles, beta particles, gamma rays and X-rays are always ionizing. This is dangerous radiation, since ions travelling through your body can break your DNA and the cells in your body, potentially leading to mutated cells, which can form cancer. Non-ionizing radiation, on the other hand, is photons which are not energetic enough to create ions. It therefore will not produce breaks in your cells and DNA, and should not lead to cancers related to radiation exposure. Radio waves MicrowavesVisible Light Infrared light Non-Ionizing Rad. Continue Infrared Light: Though our eyes cannot see infrared photons, our body can still sense them, because infrared light is essentially heat. Ovens are producers of infrared radiation. If you look at the electromagnetic spectrum, youll notice that Infrared light is just slightly less energetic than red light. Now it makes sense for the coils in your oven to emit a deep red glow when they are heating up : they are emitting lots of photons with energies around and slightly lower than visible red light. Back Courtesy NASA/JPL-Caltech Electromagnetic Spectrum Energy Increasing

31 Units and Limits of Radiation There are two types of SI units used to describe a dose of radiation : a Gray (Gy), and a Sievert (Sv). Grays measure absorbed dose, whereas Sieverts account for the type of radiation which delivered the dose. For beta particles and photons, a Gray is equivalent to a Sievert. However alpha particles are much more damaging than photons, so a Gray of absorbed dose is translated to 20 Sieverts of equivalent dose. Other common units are the rad, where 1 rad = 0.01Gy, and the rem = 0.01Sv. Effective Dose Limits in Canada: PersonPeriod Effective Dose (mSv) NEW, including a pregnant NEW 1-yr dosimetry period50 5-yr dosimetry period100 Pregnant NEWBalance of the pregnancy 4 A person who is not a nuclear energy worker 1 calendar year1... BackContinue

32 Units and Limits of Radiation There are two types of SI units used to describe a dose of radiation : a Gray (Gy), and a Sievert (Sv). Grays measure absorbed dose, whereas Sieverts account for the type of radiation which delivered the dose. For beta particles and photons, a Gray is equivalent to a Sievert. However alpha particles are much more damaging than photons, so a Gray of absorbed dose is translated to 20 Sieverts of equivalent dose. Other common units are the rad, where 1 rad = 0.01Gy, and the rem = 0.01Sv. Effective Dose Limits in Canada: PersonPeriod Effective Dose (mSv) NEW, including a pregnant NEW 1-yr dosimetry period50 5-yr dosimetry period100 Pregnant NEWBalance of the pregnancy 4 A person who is not a nuclear energy worker 1 calendar year1 SI units is the abbreviation for the International System Units, developed in the 1960s, and based on metre-kilogram-second units. Close... BackContinue

33 Units and Limits of Radiation There are two types of SI units used to describe a dose of radiation : a Gray (Gy), and a Sievert (Sv). Grays measure absorbed dose, whereas Sieverts account for the type of radiation which delivered the dose. For beta particles and photons, a Gray is equivalent to a Sievert. However alpha particles are much more damaging than photons, so a Gray of absorbed dose is translated to 20 Sieverts of equivalent dose. Other common units are the rad, where 1 rad = 0.01Gy, and the rem = 0.01Sv. Effective Dose Limits in Canada: PersonPeriod Effective Dose (mSv) NEW, including a pregnant NEW 1-yr dosimetry period50 5-yr dosimetry period100 Pregnant NEWBalance of the pregnancy 4 A person who is not a nuclear energy worker 1 calendar year1... NEW stands for Nuclear Energy Worker. Typically, anyone who could receive more than 1 mSv/yr of occupational exposure must sign a form attesting that they understand the responsibilities and limits of a NEW, and accept the designation. Close BackContinue

34 Typical Doses SourceDose (mSv)Dose (mrem) Background Radiation3.6 mSv/yr360 mrem/yr Chest X-ray0.1 mSv10 mrem Chest CT scan6 mSv600 mrem Chest, abdomen and pelvis CT10 mSv1 rem Screening mammography3 mSv300 mrem Whole body MRI*0 mSv Here are average doses received from typical diagnostic procedures. Note that these numbers are highly dependant on the anatomy to be imaged and on the size of the patient. Background radiation will be discussed on the next page. * MRIs do not use ionizing radiation, therefore do not deliver a dose. Instead, they exploit the magnetic properties of hydrogen atoms to produce an image. ContinueBack

35 Background Radiation There are several types of radiation which give you a continuous dose, and which you can do very little about. This background radiation is estimated to give Canadians a dose of about 2-4 mSv/year, and is not counted in the dose limits listed previously. Click on the different types of background radiation to learn more about them! Radon, 56% X-rays, 11% Internal, 11% Contributions to the Background Radiation: Cosmic, 8% Terrestrial, 8% Nuclear medicine, 3% Consumer products, 3% Note : Doses received from industries such as uranium mining and nuclear power plants are too small to be accounted for, assuming no major incident. ContinueBack

36 Background Radiation There are several types of radiation which give you a continuous dose, and which you can do very little about. This background radiation is estimated to give Canadians a dose of about 2-4 mSv/year, and is not counted in the dose limits listed previously. Click on the different types of background radiation to learn more about them! Radon, 56% X-rays, 11% Internal, 11% Contributions to the Background Radiation: Cosmic, 8% Terrestrial, 8% Nuclear medicine, 3% Consumer products, 3% Continue Radon : It is estimated that in Canada, the average radiation dose from Radon over one year is about 2.0 mSv. Note that is this very dependant on location. Radon is a gas, created through the decay chain of natural uranium found in soil. It is colourless and odourless, making it impossible to detect without special equipment. Radon is an alpha emitter, and is therefore a health hazard if inhaled. Furthermore, the decay products of Radon are also radioactive and dangerous for your health. Radon contributes largely to our background radiation dose, as it typically rise from the ground and seeps through cracks in the wall into homes and offices. It tends to accumulate in poorly ventilated areas such as basements and attics. For more information on radon and radon testing, visit : Health Canada: RSIC : Back

37 Background Radiation There are several types of radiation which give you a continuous dose, and which you can do very little about. This background radiation is estimated to give Canadians a dose of about 2-4 mSv/year, and is not counted in the dose limits listed previously. Click on the different types of background radiation to learn more about them! Radon, 56% X-rays, 11% Internal, 11% Contributions to the Background Radiation: Cosmic, 8% Terrestrial, 8% Nuclear medicine, 3% Consumer products, 3% Continue Internal Sources of Radiation: Our bodies contain natural radionuclides, such as Potassium-40 and Carbon-14. This internal radiation is estimated to give an average yearly dose of 0.4 mSv. This dose is small, and no dietary habits would or should reduce this. Potassium is essential to our bodily functions, notably to regulate body fluids and water transport between cells. So keep eating your bananas. For more information, read Back

38 Background Radiation There are several types of radiation which give you a continuous dose, and which you can do very little about. This background radiation is estimated to give Canadians a dose of about 2-4 mSv/year, and is not counted in the dose limits listed previously. Click on the different types of background radiation to learn more about them! Radon, 56% X-rays, 11% Internal, 11% Contributions to the Background Radiation: Cosmic, 8% Terrestrial, 8% Nuclear medicine, 3% Consumer products, 3% Continue X-rays : X-rays are energetic photons created when electrons lose energy, through a variety of events. Because of their high energy, many X-rays can traverse materials unharmed, while others interact with atoms in the material, depositing some or all of their energy. This is the idea behind X-ray imaging and CT- scans : X-rays are directed towards a patient, and film or an electronic detector behind the patient collects the photons which did not interact. The denser tissues and organs, like bone, will absorb more photons, hence allow fewer to reach the film, than lungs for example, which are full of air. This is how contrast in the image is achieved. X-rays are performed on a regular basis at dentist offices and in hospitals, where CT scans are common as well. They are also used in industry, to sterilize foods and image equipment and materials. On average, Canadians receive a yearly dose from these X-rays of about 0.4 mSv. Note that this is from normal, daily exposure and does not include the exposure from planned hospital visits. A typical chest X-ray gives a dose of about 0.1 mSv, while a CT-scan of the chest gives a much higher dose of about 6 to10 mSv. Back

39 Background Radiation There are several types of radiation which give you a continuous dose, and which you can do very little about. This background radiation is estimated to give Canadians a dose of about 2-4 mSv/year, and is not counted in the dose limits listed previously. Click on the different types of background radiation to learn more about them! Radon, 56% X-rays, 11% Internal, 11% Contributions to the Background Radiation: Cosmic, 8% Terrestrial, 8% Nuclear medicine, 3% Consumer products, 3% Continue Cosmic Rays : Cosmic rays are energetic particles coming from the Sun and elsewhere in the universe, entering our atmosphere at high speeds. Most cosmic rays are protons, though some are alpha particles, electrons, and gamma rays. Our atmosphere, and notably the Earths magnetic field, are decent shields from this radiation, making it so that in Canada, this radiation only accounts for an average yearly dose of about 0.3 mSv. The dose from cosmic rays is very variable, increasing when solar flares occur. It is also dependant on latitude, the radiation being smallest at the equator. This is due to the Earths magnetic field, which deflects these particles towards the poles, creating beautiful auroras. Finally, radiation from cosmic rays increases with altitude. A typical cross-country flight may give an additional dose of mSv. This is small and should not be a reason not to fly. Note that the new Backscatter X-ray scanners at airports give a dose of mSv, considerably less radiation than the plane ride will itself provide. Back

40 Background Radiation There are several types of radiation which give you a continuous dose, and which you can do very little about. This background radiation is estimated to give Canadians a dose of about 2-4 mSv/year, and is not counted in the dose limits listed previously. Click on the different types of background radiation to learn more about them! Radon, 56% X-rays, 11% Internal, 11% Contributions to the Background Radiation: Cosmic, 8% Terrestrial, 8% Nuclear medicine, 3% Consumer products, 3% Continue Terrestrial Sources: Natural radioactive materials, such as uranium, thorium and radium, exist in soil, building materials and water. These radioisotopes are present in small concentrations, and deliver an average dose of about 0.3 mSv per year in Canada. The level of radiation from terrestrial sources obviously vary heavily with location, since it is dependant on the geology of the area. Back

41 Background Radiation There are several types of radiation which give you a continuous dose, and which you can do very little about. This background radiation is estimated to give Canadians a dose of about 2-4 mSv/year, and is not counted in the dose limits listed previously. Click on the different types of background radiation to learn more about them! Radon, 56% X-rays, 11% Internal, 11% Contributions to the Background Radiation: Cosmic, 8% Terrestrial, 8% Nuclear medicine, 3% Consumer products, 3% Continue Nuclear Medicine : In nuclear medicine, radioisotopes are used to image or treat patients. PET scanners are an example of nuclear medicine, and are typically used to image the metabolic activity or the functionality of an organ. A radioactive source which decays through positive beta decay is administered to a patient. As the source decays, it emits positrons, which in turn annihilate with electrons, emitting two photons travelling in opposite directions. These photons are captured by detectors, which then reconstruct an image. Brachytherapy, or internal radiotherapy, is another form of nuclear medicine, in which a radioactive source is placed directly into the body, in or around an area that requires treatment (e.g. a tumour). The use of nuclear medicine is essential to our healthcare system. However, the use of these radioisotopes gives us an additional yearly dose of about 0.1 mSv. Note that this is from light exposure from sources used in nuclear medicine, and does not include individual doses to people which were treated or imaged using nuclear medicine. Back

42 Background Radiation There are several types of radiation which give you a continuous dose, and which you can do very little about. This background radiation is estimated to give Canadians a dose of about 2-4 mSv/year, and is not counted in the dose limits listed previously. Click on the different types of background radiation to learn more about them! Radon, 56% X-rays, 11% Internal, 11% Contributions to the Background Radiation: Cosmic, 8% Terrestrial, 8% Nuclear medicine, 3% Consumer products, 3% Continue Consumer products : A few consumer products, such as smoke detectors, old luminous dials, and thorium oxide coated gas lamps, used for camping, are radioactive. The average dose we receive from all of these sources over one year is calculated to be around 0.1 mSv. This is a small dose, and should not particularly concern you. However, if you want to reduce this dose, just be aware of the radioactive objects around you, try to limit your time around the object and distance yourself from it. Doubling your distance from a radioactive source reduces your exposure by a factor of four or more, depending on the type of radiation emitted. For a description of radioactive items around you, visit Back

43 Industrial and Medical Uses of Radioactivity Radiation and radioactivity are commonly used in medicine, academia, and industry. If good work habits and appropriate safety measures are followed, the advantages of using radiation far outweigh the possible negative effects. Academic Research Medical Applications Sterilization Density and moisture content evaluation Nuclear Power Plants Quality Control (Industrial Radiography) Here are a few examples of areas in which a radioactive isotope or radiation is used. Click on the different branches of industry to learn more! ContinueBack

44 Industrial and Medical Uses of Radioactivity Radiation and radioactivity are commonly used in medicine, academia, and industry. If good work habits and appropriate safety measures are followed, the advantages of using radiation far outweigh the possible negative effects. Academic Research Medical Applications Sterilization Density and moisture content evaluation Nuclear Power Plants Quality Control (Industrial Radiography) Here are a few examples of areas in which a radioactive isotope or radiation is used. Click on the different branches of industry to learn more! Continue Nuclear Power : Nuclear power plants use the energy emitted from the fission of certain isotopes of uranium, plutonium and/or thorium to produce power. When slow neutrons strike these heavy isotopes, their nucleus breaks, releasing various fission products, high speed neutrons, and energy. This energy can be used to heat water, producing steam, which in turn can be sent through a steam turbine to produce electricity. Nuclear power accounts for 15% of Canadas electricity, using about 18 units each producing MW of power. Nuclear power plants and other nuclear reactors must abide to very strict regulations and requirements, making them incredibly safe. Nuclear power and the debates surrounding it are fascinating. You can read more about it at : Back

45 Industrial and Medical Uses of Radioactivity Radiation and radioactivity are commonly used in medicine, academia, and industry. If good work habits and appropriate safety measures are followed, the advantages of using radiation far outweigh the possible negative effects. Academic Research Medical Applications Sterilization Density and moisture content evaluation Nuclear Power Plants Quality Control (Industrial Radiography) Here are a few examples of areas in which a radioactive isotope or radiation is used. Click on the different branches of industry to learn more! Continue Medical Applications: Since the discovery of radiation in 1895, high energy photons have been used for imaging. Over time, more sophisticated apparatuses were developed, using radiation both as a diagnostic and a therapeutic tool. Weve already discussed the use of X-rays and CT-scan, along with PET scans and brachytherapy. The other main use of radiation in medicine is radiation therapy, of which brachytherapy is an example.X-rays and CT-scanPET scans and brachytherapy Radiation therapy (radiotherapy, radiation oncology), is the use of ionizing radiation in the treatment of cancer. In this science, large doses of radiation are administered to an area as localized around a tumour as possible. These doses are large enough to kill the affected cells, thereby controlling the tumour. Radiation therapy can be delivered using brachytherapy, Cobalt-60 machines, linear accelerators, or orthovoltage machines, delivering lesser energies. Furthermore, photons, electrons, and even hadrons can be used to treat cancers.... Back

46 Industrial and Medical Uses of Radioactivity Radiation and radioactivity are commonly used in medicine, academia, and industry. If good work habits and appropriate safety measures are followed, the advantages of using radiation far outweigh the possible negative effects. Academic Research Medical Applications Sterilization Density and moisture content evaluation Nuclear Power Plants Quality Control (Industrial Radiography) Here are a few examples of areas in which a radioactive isotope or radiation is used. Click on the different branches of industry to learn more! Continue Medical Applications: Since the discovery of radiation in 1895, high energy photons have been used for imaging. Over time, more sophisticated apparatuses were developed, using radiation both as a diagnostic and a therapeutic tool. Weve already discussed the use of X-rays and CT-scan, along with PET scans and brachytherapy. The other main use of radiation in medicine is radiation therapy, of which brachytherapy is an example.X-rays and CT-scanPET scans and brachytherapy Radiation therapy (radiotherapy, radiation oncology), is the use of ionizing radiation in the treatment of cancer. In this science, large doses of radiation are administered to an area as localized around a tumour as possible. These doses are large enough to kill the affected cells, thereby controlling the tumour. Radiation therapy can be delivered using brachytherapy, Cobalt-60 machines, linear accelerators, or orthovoltage machines, delivering lesser energies. Furthermore, photons, electrons, and even hadrons can be used to treat cancers. Hadrons are particles made up of quarks. The best known hadrons are protons and neutrons, both made up of 3 quarks. Here, hadrons simply represent protons, neutrons, and the nucleus of other atoms. Close Back

47 Industrial and Medical Uses of Radioactivity Radiation and radioactivity are commonly used in medicine, academia, and industry. If good work habits and appropriate safety measures are followed, the advantages of using radiation far outweigh the possible negative effects. Academic Research Medical Applications Sterilization Density and moisture content evaluation Nuclear Power Plants Quality Control (Industrial Radiography) Here are a few examples of areas in which a radioactive isotope or radiation is used. Click on the different branches of industry to learn more! Continue Quality Control : In industrial radiography, radiation is used to image materials such as pipes, notably to find flaws in welds. Industrial radiography is a major component of non-destructive testing (NDT), and uses X-rays and gamma rays for imaging. Typical sources are Iridium-192 (1.04 MeV and 1.46 MeV gamma) and Cobalt- 60 (1.17 and 1.33 MeV gamma). Density and Moisture Content Evaluation: Nuclear gauges, or nuclear density gauges, contain a radioactive source, such as Cesium-137 or Radium-226, which emits a directed beam of radiation, and a sensor which measures the amount of radiation which strikes it. With proper calibration, the information received by the sensor indicates the density or moisture content of the material through which the radiation passed. Nuclear gauges are heavily used in road construction, to test the density of the concrete used. Back

48 Industrial and Medical Uses of Radioactivity Radiation and radioactivity are commonly used in medicine, academia, and industry. If good work habits and appropriate safety measures are followed, the advantages of using radiation far outweigh the possible negative effects. Academic Research Medical Applications Sterilization Density and moisture content evaluation Nuclear Power Plants Quality Control (Industrial Radiography) Here are a few examples of areas in which a radioactive isotope or radiation is used. Click on the different branches of industry to learn more! Continue Sterilization: X-rays, gamma rays, electrons, and subatomic particles are often used to sterilize equipment and foods. Radiation is an effective tool in killing microbes, bacteria and small insects, and can delay ripening of fruit and increase re-hydration capabilities. It is therefore used not only to sterilize medical equipment and suspicious mail, but also food items. Using X-rays and gamma rays to irradiate materials or foods does not make these substances radioactive. The photons which are absorbed can kill cells and microorganisms, but will not alter the stable nature of the nuclei in the material. Irradiation using neutrons or heavier particles, however, may alter the nature of the nuclei, making them radioactive. This is taken into account when a suitable type of radiation is chosen. Back

49 Industrial and Medical Uses of Radioactivity Radiation and radioactivity are commonly used in medicine, academia, and industry. If good work habits and appropriate safety measures are followed, the advantages of using radiation far outweigh the possible negative effects. Academic Research Medical Applications Sterilization Density and moisture content evaluation Nuclear Power Plants Quality Control (Industrial Radiography) Here are a few examples of areas in which a radioactive isotope or radiation is used. Click on the different branches of industry to learn more! Continue Academic Applications: Since Wilhem Röntgen discovered radiation in 1895, research into the area has been an important branch of physics. However, interest in this research increased tremendously during World War II, when countries were racing to develop nuclear weaponry. The first nuclear reactors were then built to produce Plutonium-239 by bombarding Uranium-238 with neutrons. These reactors were typically smaller than the nuclear power reactors currently in use. Many of these nuclear reactors, and more recent versions of them, are still used today, and are known as research reactors. They are used to investigate new fuels, coolants and moderators for use in nuclear power plants, to produce radioisotopes for nuclear medicine, and in materials testing. In materials testing, the nuclear reactor is used as a neutron source. Since neutrons do not interact electrically with charged particles, they are a good probe into molecular structures : they can get a lot closer to nuclei than protons can. Back

50 Effects of Radiation on your body As we saw previously, ionizing radiation breaks atoms apart into positive and negative components. When this occurs in a cell, it can damage the cell beyond repair, killing it, or it can damage chromosomes, leading to defects in cell reproduction. The radiation can thereby lead to two types of effects : Deterministic Stochastic A damaged chromosome can typically repair itself. However, an incorrect repair can lead to cell death or to a mutation. A typical mutation may involve a cell which has lost the ability to control its reproduction. In this case it can divide at a fast rate, creating a tumour. (Click on the above to learn more) ContinueBack

51 Effects of Radiation on your body As we saw previously, ionizing radiation breaks atoms apart into positive and negative components. When this occurs in a cell, it can damage the cell beyond repair, killing it, or it can damage chromosomes, leading to defects in cell reproduction. The radiation can thereby lead to two types of effects : DeterministicStochastic A damaged chromosome can typically repair itself. However, an incorrect repair can lead to cell death or to a mutation. A typical mutation may involve a cell which has lost the ability to control its reproduction. If the cell reproduces much faster than it should, a tumour may be created. Continue Deterministic Effect : A deterministic effect is one which will definitely occur when exposed to a certain threshold of radiation. An example of a deterministic effect is a sunburn. Different people may have different thresholds for sunburns, but no matter who you are, your skin will burn if you are exposed to high levels of UV rays with no protection. Deterministic effects due to ionizing radiation start around an acute dose of 250 mGy (250 mSv of gamma rays). Note that this dose is quite high, equivalent to 25 CT scans of your whole middle region at the same time. Around those levels, the patient may start experiencing radiation sickness, with symptoms such as nausea, and at higher levels fatigue, vomiting, and reduction in blood cells. At an acute dose of 3.5 Gy of gamma rays (3.6 Sv), 50% of those affected would die within weeks if untreated. Typically death ensues from a severe lack of red blood cells, white blood cells, and/or plateles. Even higher radiation levels can affect the gastrointestinal tract, leading to death through dehydration, or can affect your nervous system, at which point your entire body can shut down within hours. The doses required for these effects are on the order of 15 Gy. Back

52 Effects of Radiation on your body As we saw previously, ionizing radiation breaks atoms apart into positive and negative components. When this occurs in a cell, it can damage the cell beyond repair, killing it, or it can damage chromosomes, leading to defects in cell reproduction. The radiation can thereby lead to two types of effects : DeterministicStochastic A damaged chromosome can typically repair itself. However, an incorrect repair can lead to cell death or to a mutation. A typical mutation may involve a cell which has lost the ability to control its reproduction. If the cell reproduces much faster than it should, a tumour may be created. Continue Stochastic Effect : A stochastic effect is probabilistic, which means it will not necessarily occur. However, increasing your exposure increases the odds that it will. An example of a stochastic effect is developing lung cancer from smoking cigarettes. Smoking does not insure that you will develop lung cancer, yet it increases your odds of developing it. Furthermore, the more you smoke, the higher your chances of getting lung cancer are. Stochastic effects from radiation occur due to chronic exposure, in other words an accumulation of low doses of radiation. As all radiation has a certain probability of creating a mutation, the more radiation one is exposed to, the higher the chance a negative mutation will occur. The most important stochastic effect from radiation exposure is cancer. The projected risk of developing a fatal cancer as a result of radiation exposure is ~4% per 1000 mSv, over a lifetime. Before radiation exposure is accounted for, a persons risk of developing cancer is 25%. After an integrated chronic exposure of 1 Sv, that persons risk increases to 29%. Cancer does not develop immediately after exposure. Depending on the area exposed, cancers take on average 8 to 30 years to develop. Back

53 The Basics of Radioprotection Measures to insure radiation safety are very dependant on the type of radiation used, its energy, its form (gas, liquid, powder,...), its activity, etc. Before using any radiation source or device, make sure you are qualified to do so and understand the safety procedures associated with the source or device. This course is not meant as a radioprotection guide. However the absolute basics of radiation protection are listed below (Click to learn more) : Time Shielding Distance Note : These safety principles do not apply to internal radiation (radiation which has been ingested, inhaled, or absorbed by the skin). In these cases, methods for limiting exposure are entirely dependant on the type of radiation. ContinueBack

54 The Basics of Radioprotection Measures to insure radiation safety are very dependant on the type of radiation used, its energy, its form (gas, liquid, powder,...), its activity, etc. Before using any radiation source or device, make sure you are qualified to do so and understand the safety procedures associated with the source or device. This course is not meant as a radioprotection guide. However the absolute basics of radiation protection are listed below : Time Shielding Distance Note : These safety principles do not apply to internal radiation (radiation which has been ingested, inhaled, or absorbed by the skin). In these cases, methods for limiting exposure are entirely dependant on the type of radiation. Continue Time : The time spent around a radioactive substance is directly proportional to the dose received from it (assuming a constant activity). Halving your exposure time halves your dose. Back

55 The Basics of Radioprotection Measures to insure radiation safety are very dependant on the type of radiation used, its energy, its form (gas, liquid, powder,...), its activity, etc. Before using any radiation source or device, make sure you are qualified to do so and understand the safety procedures associated with the source or device. This course is not meant as a radioprotection guide. However the absolute basics of radiation protection are listed below : Time Shielding Distance Note : These safety principles do not apply to internal radiation (radiation which has been ingested, inhaled, or absorbed by the skin). In these cases, methods for limiting exposure are entirely dependant on the type of radiation. Continue Distance : There will be a marked reduction in the radiation field if you increase the distance from a source. For gamma-rays and X-rays, the radiation at any point is inversely proportional to the square of the distance from the source. This means that if you double your distance from a source, the dose rate falls by a factor of 4. If you triple your distance, the dose rate falls by a factor of 9. For charged particles (beta and alpha particles, protons,...), the radiation drops off even more quickly than for photons, since the particles are continuously interacting with other particles. Back These two rectangles are the same size. Notice how the one closer to the source is traversed by more rays than the one further away. The number of rays which pierce the paper follows the inverse square law.

56 The Basics of Radioprotection Measures to insure radiation safety are very dependant on the type of radiation used, its energy, its form (gas, liquid, powder,...), its activity, etc. Before using any radiation source or device, make sure you are qualified to do so and understand the safety procedures associated with the source or device. This course is not meant as a radioprotection guide. However the absolute basics of radiation protection are listed below : Time Shielding Distance Note : These safety principles do not apply to internal radiation (radiation which has been ingested, inhaled, or absorbed by the skin). In these cases, methods for limiting exposure are entirely dependant on the type of radiation. Continue Shielding : Different types and energies of radiation require different amounts and types of shielding. Alpha particles are stopped by a single sheet of paper, or a dead layer of skin. Beta particles require as little as a thin sheet of aluminum or plastic to be stopped, whereas gamma rays and high energy photons require layers of lead or thick layers of concrete for their intensity to be reduced. Paper Aluminum Lead Back

57 Summary In summary, there are several types of ionizing radiation : alpha, beta, gamma and X-ray. These are all produced by unstable particles, except for X-rays, which are produced when electrons lose energy. Background radiation, which arises from multiple sources, delivers about 2-4 mSv of dose to average Canadians. Excluding this radiation, the maximum permissible dose a member of the public can receive, for example from living or working near a nuclear substance, is 1 mSv. Ionizing radiation can break the atoms in your body and deposit energy in your cells. If a large dose is received (> 250mGy), radiation sickness can ensue within hours. Smaller doses received chronically (say 25 mSv/year for 40 years) lead to an increased risk in developing cancer (4% increase after 40 years, for 25 mSv/yr). On average, cancer develops 8 years (thyroid cancer) to 30 years (most other cancers) after exposure. The most basic and most important radioprotection principles are time, distance, and shielding. Take the quiz!

58 Test 1. All types of radiation are dangerous and exposure to them can lead to cancer. True False 2. Beta particles are : Bundles of energy, also known as photons Made up of two protons and two neutrons, in other words the nucleus of Helium Small, charged particles. Examples are electrons and positrons. Neutral hadrons, the most common being neutrons Continue

59 Test 1. All types of radiation are dangerous and exposure to them can lead to cancer. True False 2. Beta particles are : Bundles of energy, also known as photons Made up of two protons and two neutrons, in other words the nucleus of Helium Small, charged particles. Examples are electrons and positrons. Neutral hadrons, the most common being neutrons Wrong. The minimum energy required for ionization is 34 eV. Any radiation from photons with energies below that cannot ionize matter, therefore cannot break atoms in your body, kill cells, or induce mutations. Examples of unharmful radiation are visible light, infrared light, microwaves and radiofrequencies. Continue Try again!

60 Test 1. All types of radiation are dangerous and exposure to them can lead to cancer. True False 2. Beta particles are : Bundles of energy, also known as photons Made up of two protons and two neutrons, in other words the nucleus of Helium Small, charged particles. Examples are electrons and positrons. Neutral hadrons, the most common being neutrons Good ! The minimum energy required for ionization is 34 eV. Any radiation from photons with energies below that cannot ionize matter, therefore cannot break atoms in your body, kill cells, or induce mutations. Examples of unharmful radiation are visible light, infrared light, microwaves and radiofrequencies. Continue

61 Test 1. All types of radiation are dangerous and exposure to them can lead to cancer. True False 2. Beta particles are : Bundles of energy, also known as photons Made up of two protons and two neutrons, in other words the nucleus of Helium Small, charged particles. Examples are electrons and positrons. Neutral hadrons, the most common being neutrons Wrong. Gamma rays are photon. Beta particles arent. Try again! Continue

62 Test 1. All types of radiation are dangerous and exposure to them can lead to cancer. True False 2. Beta particles are : Bundles of energy, also known as photons Made up of two protons and two neutrons, in other words the nucleus of Helium Small, charged particles. Examples are electrons and positrons. Neutral hadrons, the most common being neutrons Wrong. Those are alpha particles. Try again! Continue

63 Test 1. All types of radiation are dangerous and exposure to them can lead to cancer. True False 2. Beta particles are : Bundles of energy, also known as photons Made up of two protons and two neutrons, in other words the nucleus of Helium Small, charged particles. Examples are electrons and positrons. Neutral hadrons, the most common being neutrons Good ! Remember, electrons have a negative charge, and positrons are the electrons anti- particle. In other words, they have the same mass and size than electrons, but they have an opposite charge. In other words, they are positive. Continue

64 Test 1. All types of radiation are dangerous and exposure to them can lead to cancer. True False 2. Beta particles are : Bundles of energy, also known as photons Made up of two protons and two neutrons, in other words the nucleus of Helium Small, charged particles. Examples are electrons and positrons. Neutral hadrons, the most common being neutrons Wrong. Try again! Continue

65 Test 3. Which of the following is acurate? Continue Except if you work in a nuclear power plant or in a hospital, in principle you should never receive any type of dose from ionizing radiation A CT scan gives you about 1-10 mSv of dose, a chest X-ray about 0.1 mSv, and background radiation gives you an annual dose of about 3.6 mSv (Canada). The main source of background radiation, radiation which everyone is constantly exposed to, is from nuclear power plants Of the medical imaging procedures, MRIs give you the most radiation dose.

66 Test 3. Which of the following is acurate? Continue Except if you work in a nuclear power plant or in a hospital, in principle you should never receive any type of dose from ionizing radiation A CT scan gives you about 1-10 mSv of dose, a chest X-ray about 0.1 mSv, and background radiation gives you an annual dose of about 3.6 mSv (Canada). The main source of background radiation, radiation which everyone is constantly exposed to, is from nuclear power plants Of the medical imaging procedures, MRIs give you the most radiation dose. Wrong. Dont forget about background radiation! Everyone receives a bit of radiation from radon, cosmic rays, potassium-40, radioactive elements in our soil, X-rays, nuclear medicine, etc. Furthermore, many industries other than nuclear power plants and hospitals use nuclear sources and X-rays. Sources are used in construction, sterilisation, academia, etc. Try again!

67 Test 3. Which of the following is acurate? Continue Except if you work in a nuclear power plant or in a hospital, in principle you should never receive any type of dose from ionizing radiation A CT scan gives you about 1-10 mSv of dose, a chest X-ray about 0.1 mSv, and background radiation gives you an annual dose of about 3.6 mSv (Canada). The main source of background radiation, radiation which everyone is constantly exposed to, is from nuclear power plants Of the medical imaging procedures, MRIs give you the most radiation dose. Good ! The mili-Sievert [pronounced C-vert) is the SI unit to measure equivalent dose. It accounts for the type of radiation involved. The old unit is the rem, equal to 0.01 Sv. Continue

68 Test 3. Which of the following is acurate? Continue Except if you work in a nuclear power plant or in a hospital, in principle you should never receive any type of dose from ionizing radiation A CT scan gives you about 1-10 mSv of dose, a chest X-ray about 0.1 mSv, and background radiation gives you an annual dose of about 3.6 mSv (Canada). The main source of background radiation, radiation which everyone is constantly exposed to, is from nuclear power plants Of the medical imaging procedures, MRIs give you the most radiation dose. Wrong. Nuclear Power plants expose the public to practically no radiation, even for the people living in close proximity to the plant, due to strict regulations. Natural Radon, and the products of its radioactive decay, is the main source of background radiation. Cosmic rays, terrestrial sources, and internal sources (like potassium- 40) are other examples of background radiation. Try again!

69 Test 3. Which of the following is acurate? Continue Except if you work in a nuclear power plant or in a hospital, in principle you should never receive any type of dose from ionizing radiation A CT scan gives you about 1-10 mSv of dose, a chest X-ray about 0.1 mSv, and background radiation gives you an annual dose of about 3.6 mSv (Canada). The main source of background radiation, radiation which everyone is constantly exposed to, is from nuclear power plants Of the medical imaging procedures, MRIs give you the most radiation dose. Wrong. Magnetic Resonance Imaging uses no ionizing radiation. Instead, it exploits the magnetic properties of protons in hydrogen atoms to make an image. MRIs give no dose. Try again!

70 Test 4. Which of the following is accurate : Continue Radiation sickness, which occurs after an acute dose of at least 250 mSv, includes symptoms such as vomiting, nausea, diarrhoea, and fatigue. A subject is likely to develop cancer within 1-3 years of receiving a dose of 250 mSv. A stochastic effect, such as cancer, is one which will surely occur once a certain level of radiation has been reached. Following an acute dose of 3.5 mSv, half of the people exposed are expected to die within days, if untreated.

71 Test 4. Which of the following is accurate : Continue Radiation sickness, which occurs after an acute dose of at least 250 mSv, includes symptoms such as vomiting, nausea, diarrhoea, and fatigue. A subject is likely to develop cancer within 1-3 years of receiving a dose of 250 mSv. A stochastic effect, such as cancer, is one which will surely occur once a certain level of radiation has been reached. Following an acute dose of 3.5 mSv, half of the people exposed are expected to die within days, if untreated. Good ! Radiation sickness is a deterministic effect, which means that it will occur over a certain threshold, typically estimated to be around 250 mSv. Continue

72 Test 4. Which of the following is accurate : Continue Radiation sickness, which occurs after an acute dose of at least 250 mSv, includes symptoms such as vomiting, nausea, diarrhoea, and fatigue. A subject is likely to develop cancer within 1-3 years of receiving a dose of 250 mSv. A stochastic effect, such as cancer, is one which will surely occur once a certain level of radiation has been reached. Following an acute dose of 3.5 mSv, half of the people exposed are expected to die within days, if untreated. Wrong. First of all, cancer does not typically develop that quickly. Thyroid cancer, has an average latency period, between exposure and the development of cancer, of 8 years, whereas most other types of cancer have a latency period of 30 years. Second, a typical estimate is that your chance of getting cancer rise by 4 % for every 1000 mSv of dose. This means that after receiving 1 Sv of radiation over a long period of time, your probability of developing cancer increases from about 25 % to 29 % Try again!

73 Test 4. Which of the following is accurate : Continue Radiation sickness, which occurs after an acute dose of at least 250 mSv, includes symptoms such as vomiting, nausea, diarrhoea, and fatigue. A subject is likely to develop cancer within 1-3 years of receiving a dose of 250 mSv. A stochastic effect, such as cancer, is one which will surely occur once a certain level of radiation has been reached. Following an acute dose of 3.5 mSv, half of the people exposed are expected to die within days, if untreated. Wrong. Cancer is indeed a stochastic effect of radiation. However a stochastic effect is a probabilistic one. The more radiation you receive, the more probability you have of later developing cancer. However one person can receive a huge dose of radiation every single day, and never develop cancer, whereas another can develop cancer from a single X-ray at the dentist. The latter is very improbable, but still possible. Try again!

74 Test 4. Which of the following is accurate : Continue Radiation sickness, which occurs after an acute dose of at least 250 mSv, includes symptoms such as vomiting, nausea, diarrhoea, and fatigue. A subject is likely to develop cancer within 1-3 years of receiving a dose of 250 mSv. A stochastic effect, such as cancer, is one which will surely occur once a certain level of radiation has been reached. Following an acute dose of 3.5 mSv, half of the people exposed are expected to die within days, if untreated. Wrong. This was a bit of a trick question, if you read it too quickly. The dose at which half of the people exposed die within weeks is 3.5 Sv, not 3.5 mSv, which is 1000 times smaller. Remember the background radiation we get is around 3.6 mSv per year! Try again!

75 Test 5. Which of the following is accurate : Continue Most X-rays and gamma rays can be stopped with a thin layer of plastic. The amount of dose you receive from a gamma source is inversely proportional to the square of the time which you spend around it : if you spend half the time you typically do around a source, your dose decreases by a factor of four. Alpha particles are the easiest to stop, followed by beta and then X-rays and gamma rays. Alpha particles are extremely problematic as a source of external radiation, because being doubly charged and massive, their radiation is very difficult to shield from.

76 Test 5. Which of the following is accurate : Continue Most X-rays and gamma rays can be stopped with a thin layer of plastic. The amount of dose you receive from a gamma source is inversely proportional to the square of the time which you spend around it : if you spend half the time you typically do around a source, your dose decreases by a factor of four. Alpha particles are the easiest to stop, followed by beta and then X-rays and gamma rays. Alpha particles are extremely problematic as a source of external radiation, because being doubly charged and massive, their radiation is very difficult to shield from. Wrong. On the contrary, precisely because these particles are doubly charged and massive, they are very easy to shield from : they readily interact with all matter, depositing all of their energy in a shield as thin as a piece of paper. Alpha particles are a threat for internal radiation, not external. Try again!

77 Test 5. Which of the following is accurate : Continue Most X-rays and gamma rays can be stopped with a thin layer of plastic. The amount of dose you receive from a gamma source is inversely proportional to the square of the time which you spend around it : if you spend half the time you typically do around a source, your dose decreases by a factor of four. Alpha particles are the easiest to stop, followed by beta and then X-rays and gamma rays. Alpha particles are extremely problematic as a source of external radiation, because being doubly charged and massive, their radiation is very difficult to shield from. Wrong. High energy photons are very penetrating, and require thick sheets of lead or blocks of concrete to reduce their intensity. Try again!

78 Test 5. Which of the following is accurate : Continue Most X-rays and gamma rays can be stopped with a thin layer of plastic. The amount of dose you receive from a gamma source is inversely proportional to the square of the time which you spend around it : if you spend half the time you typically do around a source, your dose decreases by a factor of four. Alpha particles are the easiest to stop, followed by beta and then X-rays and gamma rays. Alpha particles are extremely problematic as a source of external radiation, because being doubly charged and massive, their radiation is very difficult to shield from. Wrong. For photonic radiation, dose is inversely proportional to the square of the distance, not time. For all types of radiation, time is directly proportional to dose : if you halve the time around a source, your dose will halve as well. Try again!

79 Test 5. Which of the following is accurate : Continue Alpha particles are extremely problematic as a source of external radiation, because being doubly charged and massive, their radiation is very difficult to shield from. Most X-rays and gamma rays can be stopped with a thin layer of plastic. The amount of dose you receive from a gamma source is inversely proportional to the square of the time which you spend around it : if you spend half the time you typically do around a source, your dose decreases by a factor of four. Alpha particles are the easiest to stop, followed by beta and then X-rays and gamma rays. Good ! More charged and more massive particles are easier to stop than others. It is difficult to reduce the intensity of photons, which have no charge and no mass. That radiation therefore requires more shielding than beta or alpha radiation, which interacts much more with matter. Since alphas are doubly charged, they interact more, therefore travel less far, than singly charged beta particles. Continue

80 The End Thats it! We hope you enjoyed this introduction to radiation. Of course there is much more to learn in this field, especially if your work involves working with nuclear substances or radiation devices. For more information on these subjects, and to learn about the other courses offered by the Radiation Safety Institute of Canada, we encourage you to return to our website.our website If you have comments or questions regarding this course, please send them to ccohalan radiationsafety ca Also, loads of information can be found from the following people : International Atomic Energy Agency (www.iaea.org) Health Canada (www.hc-sc.gc.ca/ewh-semt/radiation/index-eng.php) Canadian Nuclear Safety Commission (www.cnsc.gc.ca) International Commission on Radiological Protection (www.icrp.org) Acknowledgements

81 Close The Radiation Safety Institute of Canada wishes to express its appreciation to the following contributors to this online course : Claire Cohalan Tara Hargreaves Justin McKinnon Don Bell Reza Moridi Brian Bjorndal Ian Watson


Download ppt "Online Course : Introduction to Radiation Click here to start!"

Similar presentations


Ads by Google