PHYS 486 Radiation Physics PDF

PHYS 486 Radiation Physics Chapter 1: Radioactivity Chapter1: Radioactivity 1.1 Introduction Radioactivity, in which charged particles and photons are released from an unstable nucleus. Radioactivity was discovered by Henri Antoine Becquerel when he was conducting experiments in 1...

PHYS 486 Radiation Physics Chapter 1: Radioactivity Chapter1: Radioactivity 1.1 Introduction Radioactivity, in which charged particles and photons are released from an unstable nucleus. Radioactivity was discovered by Henri Antoine Becquerel when he was conducting experiments in 1896 to investigate the phosphorescence of materials. 2 PHYS486 - Dr. Tahani Almusidi Chapter1: Radioactivity 1.1 Introduction The aim of his experiment was to demonstrate that some materials release light after they have been exposed to sunlight. His plan was to expose uranium salts to sunlight and then position them in front of a metal object placed on a photographic plate. If the uranium salts fluoresce, then an image of the object would be observed on the plate. The experiment was inspired by the work of Wilhelm Röentgen, who used the same method in 1895 to discover x-rays. 3 PHYS486 - Dr. Tahani Almusidi Chapter1: Radioactivity 1.1 Introduction By chance, Becquerel could not carry out the experiment due to overcast weather, so he stored the uranium salts and photographic plates together. A few days later when he wished to conduct his experiment, he noticed an image on the plate. This was a rather surprising observation, since the salts and plate had been shielded from sunlight. He attributed the phenomenon to be the emission of some other type of ray from the uranium salts. 4 PHYS486 - Dr. Tahani Almusidi Chapter1: Radioactivity 1.1 Introduction Following further investigation, Becquerel determined that the rays emitted from the uranium salts must be different to x-rays since they could be deflected by electric and magnetic fields, which would not be possible for uncharged x-rays. He had in fact observed spontaneous radioactivity. 5 PHYS486 - Dr. Tahani Almusidi Chapter1: Radioactivity 1.1 Introduction The term radioactivity was first used by Marie Curie and Pierre Curie, who together discovered the elements radium (Ra) and polonium (Po) in their search for radioactive materials other than uranium. 6 PHYS486 - Dr. Tahani Almusidi Chapter1: Radioactivity 1.1 Introduction These three pioneers shared the 1903 Nobel Prize for Physics in recognition of their discoveries. The decay rate of radioactive material is described by its activity, the units of which are the Becquerel (Bq) and Curie (Ci), in honor of their contributions. 7 PHYS486 - Dr. Tahani Almusidi Chapter1: Radioactivity 1.1 Introduction Many important discoveries pertaining to radioactivity were made over the next few years. In 1898, Ernest Rutherford identified two different types of emissions in radioactive decay and called them alpha, α, and beta, β. He would also later name the gamma-ray, γ-ray. He conducted many experiments at the Cavendish Laboratory in Cambridge to characterize α and β properties, including studying how readily stopped they are in materials. This method can still be used today to discriminate α and β particles emitted in radioactive decay. 8 PHYS486 - Dr. Tahani Almusidi Chapter1: Radioactivity 1.2 Form of Radiation Radiation includes charged particles like alpha and beta particles, accelerator-generated beams, as well as uncharged particles such as x-rays, gamma rays, and neutrons. alpha 𝛽+ 𝛽− proton 𝛾 𝑥 − 𝑟𝑎𝑦 neutron 9 PHYS486 - Dr. Tahani Almusidi Chapter1: Radioactivity 1.2 Form of Radiation Radiation emitted particles charge Decay equation Type of parent nuclei Alpha 4 A A−4 2He nuclei positive ZX → Z−2Y + 42He + energy heavy 𝛼 electrons 𝑒 − negative A ZX N → A Z+1Y N−1 + β− + 𝑣ҧ neutron-rich Beta 𝛽 positrons 𝑒 + positive 𝐴 𝑍𝑋 𝑁 → 𝐴 𝑍−1𝑌 𝑁+1 + 𝛽 + + 𝜈 + energy proton-rich Gamma high-energy 𝐴𝑋 ∗ no charge 𝑧 → 𝐴𝑧𝑋 + 𝛾 excited 𝛾 photons 10 PHYS486 - Dr. Tahani Almusidi Chapter1: Radioactivity 1.3 Penetrating powers The three types of radiation have quite different penetrating powers: Alpha particles barely penetrate a sheet of paper. Beta particles can penetrate a few millimeters of aluminum Gamma rays can penetrate several centimeters of lead. 11 PHYS486 - Dr. Tahani Almusidi Chapter1: Radioactivity 1.4 Radioactive decay Law N = N0 N0 Number of nuclei that have N0 Number of nuclei that have not yet decayed not yet decayed N N N = N0 e−λ t time time stable nucleus Radioactivate nucleus 12 PHYS486 - Dr. Tahani Almusidi Chapter1: Radioactivity 1.4 Radioactive decay Law N = N0 e−λ t N0 Number of nuclei that have not yet decayed Where: N N0 represents the number of undecayed radioactive N = N0 e−λ t nuclei at t = 0. 𝜆 is the decay constant, which represents the time probability per second that a given radioactive nucleus Radioactivate nucleus will decay. 13 PHYS486 - Dr. Tahani Almusidi Chapter1: Radioactivity N0 1.4 Radioactive decay Law daughter nucleus Number of nuclei that have During the radioactive decay process: not yet decayed N It seems that the number of undecayed radioactive nuclei (parent nuclei) in a sample decreases exponentially with time. parent nucleus And at the same time the number of formed (Radioactivate nucleus) daughter nuclei (stable nuclei) in a sample increase exponentially with time. time parent daughter a form of + nucleus nucleus radiation 14 PHYS486 - Dr. Tahani Almusidi Chapter1: Radioactivity 1.5 Half-life and mean lifetime The half-life time is the time after which a half of the initially existing atomic nuclei has decayed. At t = T1/2 : N(t = T1/2 ) = 0.5 N0 That means 50% of the isotope decay. The mean lifetime (or lifetime) is the reciprocal of the decay constant: 1 τ= λ The mean lifetime is time period in which the number of nuclei has decayed to a level of 1/e of its initial value (37%). At t = τ: N(t = τ) = 0.37 N0 That means 63% of the isotope decay ln 2 T1/2 = = τ ln 2 λ 15 PHYS486 - Dr. Tahani Almusidi Chapter1: Radioactivity 1.5 Half-life and mean lifetime 16 PHYS486 - Dr. Tahani Almusidi Chapter1: Radioactivity 1.5 Half-life and mean lifetime Example 1: An isotope has a half-life of 6 hours. What is the percentage will be left after 24 hours? 17 PHYS486 - Dr. Tahani Almusidi Chapter1: Radioactivity 1.5 Half-life and mean lifetime Example 1: An isotope has a half-life of 6 hours. What is the percentage will be left after 24 hours? 𝑡=0 𝑡 = 6 ℎ𝑟 𝑡 = 12 ℎ𝑟 𝑡 = 18 ℎ𝑟 𝑡 = 24 ℎ𝑟 percentage 100% 50% 25% 12.5% 6.25% Or: 𝑡 24 ℎ𝑟 1 𝑇1 1 6 ℎ𝑟 𝑃𝑡 = 𝑃𝑡=0 2 = 100% × = 6.25 % 2 2 18 PHYS486 - Dr. Tahani Almusidi Chapter1: Radioactivity 1.5 Half-life and mean lifetime Example 2: Ra-226 has a half-life of 1600 years. How many grams of 0.25 g sample will remine after 4800 years? 19 PHYS486 - Dr. Tahani Almusidi Chapter1: Radioactivity 1.5 Half-life and mean lifetime Example 2: Ra-226 has a half-life of 1600 years. How many grams of 0.25 g sample will remine after 4800 years? 𝑡=0 𝑡 = 1600 𝑦 𝑡 = 3200 𝑡 = 4800 𝑦 0.03125 𝑔 mass 0.25 𝑔 0.125 𝑔 0.0625 𝑔 Or: 𝑡 4800 𝑦 1 𝑇1 1 1600 𝑦 𝑚𝑡 = 𝑚𝑡=0 2 = 0.25 𝑔 × = 0.03125 𝑔 2 2 20 PHYS486 - Dr. Tahani Almusidi Chapter1: Radioactivity 1.6 Activity of a sample (Decay rate) Activity of a sample is the number of decays per second, and it is given by: A(t) = A0 e−λt where the constant A0 = λ N0 represents the decay rate at t = 0. Another helpful equation for the activity is written as: A0 A(t) = 𝑛 2 where 𝑛 represents the number of half-lives that have occurred. 21 PHYS486 - Dr. Tahani Almusidi Chapter1: Radioactivity 1.7 Unit of activity Becquerel (Bq): 1Bq = 1 decays/s Curie (Ci): 1Ci = 3.73 × 1010 decays/s 22 PHYS486 - Dr. Tahani Almusidi Chapter1: Radioactivity 1.7 Unit of activity 1Ci = 3.73 × 1010 Bq The curie is a rather large unit, and the more frequently used activity units are the millicurie (mCi) and the microcurie (μCi). 23 PHYS486 - Dr. Tahani Almusidi Chapter1: Radioactivity 1.7 Unit of activity Example: 24 PHYS486 - Dr. Tahani Almusidi Chapter1: Radioactivity 1.7 Unit of activity Example 2: A sample of the isotope 131I, which has a half-life of 8.04 days, has an activity of 5.0 mCi at the time of shipment. Upon receipt of the sample at a medical laboratory, the activity is 2.1 mCi. How much time has elapsed between the two measurements? 25 PHYS486 - Dr. Tahani Almusidi Chapter1: Radioactivity 1.7 Unit of activity Example 2: A sample of the isotope 131I, which has a half-life of 8.04 days, has an activity of 5.0 mCi at the time of shipment. Upon receipt of the sample at a medical laboratory, the activity is 2.1 mCi. How much time has elapsed between the two measurements? A = 𝐴0 𝑒 −𝜆𝑡 𝐴 = 𝑒 −𝜆𝑡 𝐴0 𝐴 ln = −𝜆𝑡 𝐴0 𝑇1 1 𝐴 1 𝐴 𝐴 8.04 𝑑𝑎𝑦𝑠 2.1 𝑡 = − ln =− ln = − 2 ln =− ln = 10 𝑑𝑎𝑦𝑠 𝜆 𝐴0 ln 2 𝐴0 ln 2 𝐴0 ln 2 5 𝑇1 2 26 PHYS486 - Dr. Tahani Almusidi Chapter1: Radioactivity 1.8 The specific activity The specific activity SA is the activity per unit mass. A(t) SA = M λ NA SA = 𝐀 where NA is Avogadro’s number and 𝐀 is the atomic mass. 27 PHYS486 - Dr. Tahani Almusidi Chapter1: Radioactivity 1.9 Decay Series (Decay Chain) A radioactive nucleus decays into a daughter nucleus. In many cases, the daughter nucleus is also radioactive and decays to produce its own daughter nucleus. The process continues until reaching a daughter nucleus that is stable. The sequence of isotopes, starting with the original unstable isotope and ending with the stable isotope, is called a decay series. 28 PHYS486 - Dr. Tahani Almusidi Chapter1: Radioactivity 1.9 Decay Series (Decay Chain) Thus, a decay series (decay chain) can be defined as a series of isotopes linked in a chain by radioactive decay. The isotopes in the chain decay until a stable nuclide is reached. There are exactly four possible decay chains; the uranium–radium series, the uranium–actinium series, the thorium series, and the neptunium series. The latter no longer occurs in nature on Earth because of the relatively short half-life of neptunium-237 (≈ 2 million years). 29 PHYS486 - Dr. Tahani Almusidi Chapter1: Radioactivity 1.9 Decay Series (Decay Chain) The uranium–radium series radioactive nuclides stable end product The thorium series stable end radioactive nuclides product 30 PHYS486 - Dr. Tahani Almusidi Chapter1: Radioactivity 1.10 Source of Radiation 31 PHYS486 - Dr. Tahani Almusidi Chapter1: Radioactivity 1.10 Source of Radiation 1.10.1 Natural radioactivity (Environmental Radioactivity) Each detector counts a certain rate even if it is not exposed to a radioactive substance. It’s natural and all around us. It comes up from the ground, down through the atmosphere, and even from within our own bodies. The detector is exposed to a radioactive substance. The detector is not exposed to a radioactive substance. 32 PHYS486 - Dr. Tahani Almusidi Chapter1: Radioactivity 1.10 Source of Radiation 1.10.1 Natural radioactivity (Environmental Radioactivity) We cannot eliminate radiation from our environment. We can, however, reduce our risks by controlling, to some extent, our exposure to it. 33 PHYS486 - Dr. Tahani Almusidi Chapter1: Radioactivity 1.10 Source of Radiation 1.10.1 Natural radioactivity (Environmental Radioactivity) This background originates from environmental radiation (cosmic rays and terrestrial radiation) and has to be subtracted from the measured activity. Source activity = measured activity - background 34 PHYS486 - Dr. Tahani Almusidi Chapter1: Radioactivity 1.10 Source of Radiation 1.10.1 Natural radioactivity (Environmental Radioactivity) Natural radioactivity from the environment has two components: Terrestrial radiation from the Earth crust Extraterrestrial radiation (Cosmic rays) from our Sun and our galaxy 35 PHYS486 - Dr. Tahani Almusidi Chapter1: Radioactivity 1.10 Source of Radiation 1.10.1 Natural radioactivity (Environmental Radioactivity) 1.10.1.1 Terrestrial radiation The most important natural isotopes which occur in air, in drinking water, and in food, are the isotopes of hydrogen (tritium: 3H), carbon ( 14C), potassium ( 40K), polonium ( 210Po), radon ( 222Rn), radium ( 226R𝑎), uranium ( 238R𝑎). 36 PHYS486 - Dr. Tahani Almusidi Chapter1: Radioactivity 1.10 Source of Radiation 1.10.1 Natural radioactivity (Environmental Radioactivity) 1.10.1.1 Terrestrial radiation These natural radioactive elements accumulate in the human body after being taken in with food, water, and air so that humans themselves become radioactive. 37 PHYS486 - Dr. Tahani Almusidi Chapter1: Radioactivity 1.10 Source of Radiation 1.10.1 Natural radioactivity (Environmental Radioactivity) 1.10.1.1 Terrestrial radiation Example 1: Sea water also contains a substantial amount of salt. This salt occurs in the from of sodium chloride and potassium chloride. Therefore, the sea water contains also the radioactive potassium ( 40K) isotope leading to an activity of about 12 Bq/L. In contrast, this isotope occurs in ground water only with a concentration of about 0.1Bq/L. 38 PHYS486 - Dr. Tahani Almusidi Chapter1: Radioactivity 1.10 Source of Radiation 1.10.1 Natural radioactivity (Environmental Radioactivity) 1.10.1.1 Terrestrial radiation Example 2: The natural radioactivity of the human body is about 9000 Bq and originates predominantly from ( 40K) and ( 14C). 39 PHYS486 - Dr. Tahani Almusidi Chapter1: Radioactivity 1.10 Source of Radiation 1.10.1 Natural radioactivity (Environmental Radioactivity) 1.10.1.1 Terrestrial radiation Example 3: The soil of the planet Earth contains substances which are naturally radioactive and provide natural radiation exposures. The most important radioactive elements which occur in the soil and in rocks are the long-lived primordial isotopes potassium ( 40K), radium ( 226R𝑎), and thorium ( 232Th). 40 PHYS486 - Dr. Tahani Almusidi Chapter1: Radioactivity 1.10 Source of Radiation 1.10.1 Natural radioactivity (Environmental Radioactivity) 1.10.1.1 Terrestrial radiation The radioisotopes potassium ( 40K), radium ( 226R𝑎), and thorium ( 232Th) also occur in many building materials (such as concrete and bricks). Naturally, the radiation exposure varies with the environment depending on the concentration of radioisotopes in the ground. 41 PHYS486 - Dr. Tahani Almusidi Chapter1: Radioactivity 1.10 Source of Radiation 1.10.1 Natural radioactivity (Environmental Radioactivity) 1.10.1.1 Terrestrial radiation The terrestrial component originates from primordial radionuclides in the earth’s crust, present in varying amount. Components of three chains of natural radioactive elements viz. the uranium series, the thorium and actinium series. 238U, 226Ra, 232Th, 228Ra, 210Pb, 210Po, and 40K, contribute significantly to natural background radiation. 14 Among the singly occurring radionuclides tritium and C (produced by cosmic ray interactions) and 40K (terrestrial origin) are prominent. 42 PHYS486 - Dr. Tahani Almusidi Chapter1: Radioactivity 1.10 Source of Radiation 1.10.1 Natural radioactivity (Environmental Radioactivity) 1.10.1.1 Terrestrial radiation 43 PHYS486 - Dr. Tahani Almusidi  Chapter1: Radioactivity Radioactive 1.10 Source of Radiation Isotopes 1.10.1 Natural radioactivity (Environmental Radioactivity) 1.10.1.1 Terrestrial radiation Thorium series ( 232Th): all isotopes have A = 4n eries) The series end with a stable isotope of lead (Pb) h a long-living eries have A = 4n+2 series have A = 4n series 44 PHYS486 - Dr. Tahani Almusidi  Chapter1: Radioactivity 1.10 Source of Radiation series)1.10.1 Natural radioactivity (Environmental Radioactivity) ith a long-living 1.10.1.1 Terrestrial radiation Uranium series ( 238U): all isotopes have A = 4n+2 series The series end with a stable isotope of lead (Pb) s have A = 4n+2 m series s have A = 4n m series s have A = 4n+3 th a stable isotope 45 PHYS486 - Dr. Tahani Almusidi Chapter1: Radioactivity 1.10 Source of Radiation 1.10.1 Natural radioactivity (Environmental Radioactivity) 1.10.1.1 Terrestrial radiation Actinium series ( 235U): all isotopes have A = 4n+3 The series end with a stable isotope of lead (Pb) 46 PHYS486 - Dr. Tahani Almusidi Chapter1: Radioactivity 1.10 Source of Radiation 1.10.1 Natural radioactivity (Environmental Radioactivity) 1.10.1.1 Terrestrial radiation Radionuclides from these sources are transferred to man through food chains or inhalation. 47 PHYS486 - Dr. Tahani Almusidi Chapter1: Radioactivity 1.10 Source of Radiation 1.10.1 Natural radioactivity (Environmental Radioactivity) 1.10.1.1 Terrestrial radiation Example 3: Radon (Rn) It is a colorless, odorless, tasteless radioactive gas, which comes from the natural decay of radium. Radon itself is radioactive because it also decays, losing an alpha particle and forming the element polonium. Uranium is the first element in a long series of decay that produces radium and radon. Uranium is referred to as the parent element, and radium and radon are called daughters. Radium and radon also form daughter elements as they decay. 48 PHYS486 - Dr. Tahani Almusidi Chapter1: Radioactivity 1.10 Source of Radiation 1.10.1 Natural radioactivity (Environmental Radioactivity) 1.10.1.1 Terrestrial radiation gas gas the parent element 49 PHYS486 - Dr. Tahani Almusidi Chapter1: Radioactivity 1.10 Source of Radiation 1.10.1 Natural radioactivity (Environmental Radioactivity) 1.10.1.1 Terrestrial radiation The decay of each radioactive element occurs at a very specific rate. How fast an element decays is measured in terms of the element half-life. Uranium has a half-life of 4.4 billion years, so a 4.4-billion-yearold rock has only half of the uranium with which it started. The half-life of radon is only 3.8 days. If a jar was filled with radon, in 3.8 days only half of the radon would be left. But the newly made daughter products of radon would also be in the jar, including polonium, bismuth, and lead. 50 PHYS486 - Dr. Tahani Almusidi Chapter1: Radioactivity 1.10 Source of Radiation 1.10.1 Natural radioactivity (Environmental Radioactivity) 1.10.1.1 Terrestrial radiation gas Polonium is also radioactive; it is this element, which is produced by radon in the air and in people’s lungs, that can hurt lung tissue and cause lung cancer. gas the parent element 51 PHYS486 - Dr. Tahani Almusidi Chapter1: Radioactivity 1.10 Source of Radiation 1.10.1 Natural radioactivity (Environmental Radioactivity) 1.10.1.1 Terrestrial radiation Any home or building may have a radon problem, including new and old homes, well-sealed and drafty homes, and homes with or without basements. 52 PHYS486 - Dr. Tahani Almusidi Chapter1: Radioactivity 1.10 Source of Radiation 1.10.1 Natural radioactivity (Environmental Radioactivity) 1.10.1.1 Terrestrial radiation Radon and all other radioactive elements are measured in picocuries. For instance, a house having 4 pCi/L of air has about 8 or 9 atoms of radon decaying every minute in every liter of air inside the house. A ~92 m2 house with 4 pCi/L of radon has nearly 2 million radon atoms decaying in it every minute. 53 PHYS486 - Dr. Tahani Almusidi Chapter1: Radioactivity 1.10 Source of Radiation 1.10.1 Natural radioactivity (Environmental Radioactivity) 1.10.1.1 Terrestrial radiation Radon levels in outdoor air, indoor air, soil air, and ground water can be very different. The reasons lie primarily in the geology of radon the factors that govern the occurrence of uranium, the formation of radon, and the movement of radon, soil gas, and ground water. 54 PHYS486 - Dr. Tahani Almusidi Chapter1: Radioactivity 1.10 Source of Radiation 1.10.1 Natural radioactivity (Environmental Radioactivity) 1.10.1.1 Terrestrial radiation Because radon is a gas, it has much greater mobility than uranium and radium, which are fixed in the solid matter in rocks and soils. Radon can more easily leave the rocks and soils, by escaping into fractures and openings in rocks and into the pore spaces between grains of soil. 55 PHYS486 - Dr. Tahani Almusidi Chapter1: Radioactivity 1.10 Source of Radiation 1.10.1 Natural radioactivity (Environmental Radioactivity) 1.10.1.1 Terrestrial radiation Radon moves more readily through permeable soils, such as coarse sand and gravel, than through impermeable soils, such as clays. Fractures in any soil or rock allow radon to move more quickly. 56 PHYS486 - Dr. Tahani Almusidi Chapter1: Radioactivity 1.10 Source of Radiation 1.10.1 Natural radioactivity (Environmental Radioactivity) 1.10.1.1 Terrestrial radiation Radon in water moves slower than radon in air. The distance that radon moves before most of it decays is less than 1 inch (2.54 cm) in water-saturated rocks or soils, but it is as much as 6 feet (182.88 cm) through dry rocks or soils. Why? Because water also tends to flow much more slowly through soil pores and rock fractures than does air, radon travels shorter distances in wet soils than in dry soils before it decays. 57 PHYS486 - Dr. Tahani Almusidi Chapter1: Radioactivity 1.10 Source of Radiation 1.10.1 Natural radioactivity (Environmental Radioactivity) 1.10.1.1 Terrestrial radiation The ease and efficiency with which radon moves in the pore space or fracture affects how much radon enters a house. If radon is able to move easily in the pore space, then it can travel a great distance before it decays, and it is more likely to collect in high concentrations inside a building. Radon can also enter homes through their water systems. 58 PHYS486 - Dr. Tahani Almusidi Chapter1: Radioactivity 1.10 Source of Radiation 1.10.1 Natural radioactivity (Environmental Radioactivity) 1.10.1.2 Extraterrestrial radiation (Cosmic rays) Cosmic rays are energetic particles that originate from outer space and strike the Earth’s atmosphere. The vast majority of cosmic rays (∼85%) are protons, some 12% are α-particles (helium ions), and 3% are nuclei heavier than helium. In addition, there are about 1% are energetic electrons. It was shown that the cosmic rays were mainly charged particles; however, the term “ray” continues to be used for designation of the extraterrestrial radiation. 59 PHYS486 - Dr. Tahani Almusidi Chapter1: Radioactivity 1.10 Source of Radiation 1.10.1 Natural radioactivity (Environmental Radioactivity) 1.10.1.2 Extraterrestrial radiation (Cosmic rays) Isotopes produced by interactions of cosmic rays with nuclei of the Earth’s cosmogenic isotopes atmosphere, e.g. 14 C, 21Ne, 26Al, 32Si, 36Cl, 39Ar, 41Ca, and 81kr. 239 It is interesting to note that plutonium also occurs as a natural isotope in the Earth’s crust. Pu with a half-life of 24,300 years is prominently produced by cosmic rays via the reaction 60 PHYS486 - Dr. Tahani Almusidi Chapter1: Radioactivity 1.10 Source of Radiation 1.10.1 Natural radioactivity (Environmental Radioactivity) 1.10.1.2 Extraterrestrial radiation (Cosmic rays) Because of the high energies of primary cosmic rays, cascades of secondary and tertiary particles will develop in the atmosphere. At sea level, secondary cosmic rays consist mainly of muons (80%) and electrons (20%). Muons are particles which have similar properties to electrons with the difference that they are about 200 times heavier and are unstable. 61 PHYS486 - Dr. Tahani Almusidi Chapter1: Radioactivity 1.10 Source of Radiation 1.10.2 Man-made Radiation (Artificial) Radiation can be man-made too. Less than 40 years after the radioactive discovery, physicists discovered that radioactive elements can be artificially created. Within a decade of this discovery, scientists had split the atom. These findings allow us to use radioactive materials for beneficial purposes, such as generating electricity and diagnosing and treating medical problems. For these many benefits, excessive radiation exposure can also threaten our health and the quality of our environment. 62 PHYS486 - Dr. Tahani Almusidi Chapter1: Radioactivity 1.10 Source of Radiation 1.10.2 Man-made Radiation (Artificial) 1.10.2.1 Radiation in Medicine The majority of our man-made radiation exposure is from diagnostic x-rays. Physicians use x-rays in more than half of all medical diagnoses to determine the extent of disease or physical injury. 63 PHYS486 - Dr. Tahani Almusidi Chapter1: Radioactivity 1.10 Source of Radiation 1.10.2 Man-made Radiation (Artificial) 1.10.2.1 Radiation in Medicine In the field of nuclear medicine, radioactively labeled compounds (radiopharmaceuticals) are also used to support diagnoses. 64 PHYS486 - Dr. Tahani Almusidi Chapter1: Radioactivity 1.10 Source of Radiation 1.10.2 Man-made Radiation (Artificial) 1.10.2.1 Radiation in Medicine Another source of radiation exposure is radiation therapy. One-third of all successful cancer treatments involve radiation. Precisely targeted radiation destroys cancerous cells while limiting damage to nearby healthy cells. 65 PHYS486 - Dr. Tahani Almusidi Chapter1: Radioactivity 1.10 Source of Radiation 1.10.2 Man-made Radiation (Artificial) 1.10.2.1 Radiation in Medicine For example, radioactive iodine will concentrate in the thyroid gland and can be used to treat thyroid tumors. 66 PHYS486 - Dr. Tahani Almusidi Chapter1: Radioactivity 1.10 Source of Radiation 1.10.2 Man-made Radiation (Artificial) 1.10.2.2 Nuclear Power Plants In nuclear power plants mass is converted into energy according to the famous equation 𝐸 = 𝑚𝑐 2. In fission reactions highly radioactive and also long-lived fission products are generated like cesium or strontium. Nuclear power plants will very likely discharge certain amounts of radioactive substances into air, water, or soil. The national regulations will give clearance levels for possible contaminations of the environment. 67 PHYS486 - Dr. Tahani Almusidi Chapter1: Radioactivity 1.10 Source of Radiation 1.10.2 Man-made Radiation (Artificial) 1.10.2.2 Nuclear Power Plants 68 PHYS486 - Dr. Tahani Almusidi Chapter1: Radioactivity 1.10 Source of Radiation 1.10.2 Man-made Radiation (Artificial) 1.10.2.3 Nuclear Weapons World War Two: The dropping of atomic bombs on Japan certainly represents a major radiation catastrophe with the most severe consequences. The United States' plan for dropping atomic bombs Month Number of atomic bombs August 1945 3 September 1945 3 October 1945 3 69 PHYS486 - Dr. Tahani Almusidi Chapter1: Radioactivity 1.10 Source of Radiation 1.10.2 Man-made Radiation (Artificial) 1.10.2.3 Nuclear Weapons The first atomic bomb (Little Boy; Uranium 235) was dropped on Hiroshima on August 6, 1945. The bomb destroyed the city, killing almost 100,000 people. The city of Hiroshima was essentially leveled. 70 PHYS486 - Dr. Tahani Almusidi Chapter1: Radioactivity 1.10 Source of Radiation 1.10.2 Man-made Radiation (Artificial) 1.10.2.3 Nuclear Weapons Following this attack, on August 9, 1945 another atomic bomb (Fat Man; Plutonium 239) was dropped on Nagasaki. The same effects were felt in this city. The United States was ready to drop another atomic bombs. However, on August 15 Japan surrendered to the allies and World War Two was officially over. 71 PHYS486 - Dr. Tahani Almusidi Chapter1: Radioactivity 1.10 Source of Radiation 1.10.2 Man-made Radiation (Artificial) 1.10.2.3 Nuclear Weapons It is estimated that 140,000 Japanese citizens were killed in Hiroshima and 80,000 in Nagasaki by the end of 1945. Of those, 110,000 died on the day of the bombings. Since then, thousands more have died from delayed radiation effects and injuries attributed to exposure to radiation released by the bombs. The official number of casualties given by the Japanese authorities by the year 2009 is 258,000. Many people also suffered from permanent injuries. Due to genetic effects subsequent generations are also affected. 72 PHYS486 - Dr. Tahani Almusidi Chapter1: Radioactivity 1.10 Source of Radiation 1.10.2 Man-made Radiation (Artificial) 1.10.2.4 Radioactive Waste Radioactive waste can be in liquid or solid form, and its level of radioactivity can vary. Mining, nuclear power generation, and various industrial processes, defense weapons production, nuclear medicine, and scientific research all can produce radioactive waste. 73 PHYS486 - Dr. Tahani Almusidi Chapter1: Radioactivity 1.10 Source of Radiation 1.10.2 Man-made Radiation (Artificial) 1.10.2.4 Radioactive Waste The amount of nuclear waste from nuclear power plants and recycling facilities worldwide is estimated to be about 10,000 tons annually. Items and equipment used during these types of industrial processes and research activities, such as rags, glassware, plastic bags, protective clothing, tools, and machinery, can become contaminated with radioactive material and must be disposed of as radioactive waste. 74 PHYS486 - Dr. Tahani Almusidi Chapter1: Radioactivity 1.10 Source of Radiation 1.10.2 Man-made Radiation (Artificial) 1.10.2.4 Radioactive Waste Radioactive waste can remain radioactive for anywhere from days to hundreds or even thousands of years. Radioactive waste (RW) must be properly managed in order to protect humans and the environment, which means isolating or containing RW so that harmful radionuclides do not escape into the biosphere (e.g. air, soil, and water supplies). 75 PHYS486 - Dr. Tahani Almusidi Chapter1: Radioactivity 1.10 Source of Radiation 1.10.2 Man-made Radiation (Artificial) 1.10.2.4 Radioactive Waste Radioactive Waste (RW) is classified into three types: 1. High-level waste (HLW). 2. Intermediate-level waste (ILW) 3. Low-level waste (LLW) 76 PHYS486 - Dr. Tahani Almusidi Chapter1: Radioactivity 1.10 Source of Radiation 1.10.2 Man-made Radiation (Artificial) 1.10.2.4 Radioactive Waste 1. High-level waste (HLW). spent reactor fuel foreseen for disposal; waste that contains both long-lived and heat-emitting radionuclides. Spent fuel wet storage in France (left) and Sweden (right). Spent fuel dry storage in the United States 77 PHYS486 - Dr. Tahani Almusidi Chapter1: Radioactivity 1.10 Source of Radiation 1.10.2 Man-made Radiation (Artificial) 1.10.2.4 Radioactive Waste 2. Intermediate-level waste (ILW): Intermediate-level waste (ILW) contains quantities of long-lived radionuclides, but does not have self- heating properties. ILW typically exhibits sufficient levels of penetrating radiation to warrant shielding during handling and storage. Certain ILW may have heat generation implications in the short term because of its total radioactivity level. 78 PHYS486 - Dr. Tahani Almusidi Chapter1: Radioactivity 1.10 Source of Radiation 1.10.2 Man-made Radiation (Artificial) 1.10.2.4 Radioactive Waste 3. Low-level waste (LLW): Low-level waste (LLW) is defined as waste that contains radionuclide content above clearance levels or exempted quantities. Despite its low radioactivity, LLW requires isolation and containment for periods of up to a few hundred years. 79 PHYS486 - Dr. Tahani Almusidi Chapter1: Radioactivity 1.10 Source of Radiation 1.10.2 Man-made Radiation (Artificial) 1.10.2.4 Radioactive Waste LLW/ILW storage in Germany (left), and LLW/ILW storage buildings and in-ground storage in Canada (right) 80 PHYS486 - Dr. Tahani Almusidi Chapter1: Radioactivity 1.10 Source of Radiation 1.10.2 Man-made Radiation (Artificial) 1.10.2.5 Accidents Many radiation accidents in the fields of medicine and technology are caused by losses and careless disposal of radioactive material. 81 PHYS486 - Dr. Tahani Almusidi Chapter1: Radioactivity 1.10 Source of Radiation 1.10.2 Man-made Radiation (Artificial) 1.10.2.5 Accidents The reason for unnecessary exposures is frequently due to improper storage of disused radioactive sources. 82 PHYS486 - Dr. Tahani Almusidi Chapter1: Radioactivity 1.10 Source of Radiation 1.10.2 Man-made Radiation (Artificial) 1.10.2.5 Accidents Example 1: Unused sources have been found in scrapyards where they were ‘discovered’ by children, who were fond of finding pieces of e.g. good-looking silver-gray cobalt metal, which, in fact, was highly radioactive and dangerous. 83 PHYS486 - Dr. Tahani Almusidi Chapter1: Radioactivity 1.10 Source of Radiation 1.10.2 Man-made Radiation (Artificial) 1.10.2.5 Accidents Example 2: The reactor catastrophe in Chernobyl (official number of deaths 31, independently estimated number of deaths 4000), 192 cases of death are reported. 84 PHYS486 - Dr. Tahani Almusidi Chapter1: Radioactivity 1.10 Source of Radiation 1.10.2 Man-made Radiation (Artificial) 1.10.2.5 Accidents Example 3: 85 PHYS486 - Dr. Tahani Almusidi