Radiation - PDF

RADIATION Radiation is a form of energy. It can be generated by machines or formed by unstable atoms which undergo radioactive decay. From its source, radiation travels out as energy waves or charged particles. Natural radiation BENEFITS Sustains life on earth The...

RADIATION Radiation is a form of energy. It can be generated by machines or formed by unstable atoms which undergo radioactive decay. From its source, radiation travels out as energy waves or charged particles. Natural radiation BENEFITS Sustains life on earth The distribution of heat helps maintain temperature balances across different regions It is a renewable energy source that can be harnessed through technologies such as solar panels  NEGATIVE IMPACT OF Skin damage SOLAR RADIATION Eye damage Land Use and Habitat Disruption MAN-MADE radiation BENEFITS Carbon-free electricity Nuclear power plants require significantly less land · Nuclear energy generation results in minimal air pollution Job Creation and Economic Benefits NEGATIVE Nuclear power generates IMPACT radioactive waste Environmental Impact of Uranium Mining Thermal Pollution Public Perception and Social Impact The four common radioactive elements found in the periodic table are Uranium, Radium, Polonium, Thorium. URANIUM RADIUM POLUNIUM THORIUM  2 TYPES OF RADIATION 1. IONIZING RADIATION- HAS TOO MUCH ENERGY IT CAN KNOCK ELECTRONS OUT OF ATOMS, A PROCESS KNOWN AS IONIZATION. IONIZING RADIATION CAN AFFECT THE ATOMS IN LIVING THINGS, SO IT POSES A HEALTH RISK BY DAMAGING TISSUE AND DNA IN GENES.  2 TYPES OF RADIATION 2. NON-IONIZING RADIATION- HAS ENOUGH ENERGY TO MOVE ATOMS IN A MOLECULE AROUND OR CAUSE THEM TO VIBRATE, BUT NOT ENOUGH TO REMOVE ELECTRONS FROM ATOMS. EXAMPLES OF THIS KIND OF RADIATION ARE RADIO WAVES, VISIBLE LIGHT AND MICROWAVES.  RADIATION UNITS AND QUANTITIES 1. Exposure The measurement of radiation exposure in air as ionizations per unit mass of air due to x- ray or gamma radiation E = ΓA / d2 where: Units: E = Exposure rate Conventional: Roentgen (R) Γ = Specific gamma ray SI Unit: Coulomb per kilogram (C/kg) constant d = distance from source Conversion: A = source activity 1 R = 2.58 × 10^-4 C/kg 1 C/kg = 3876 R  RADIATION UNITS AND QUANTITIES 2. Absorbed Dose The measurement of radiation absorbed dose (rad) represents the amount of energy deposited per unit mass of absorbing material. D= E/m Units: where: Conventional: Rad D= Absorbed Dose SI Unit: Gray (Gy) E= Energy m= mass Conversion: 1 rad = 0.01 Gy 100 rad = 1 Gy  RADIATION UNITS AND QUANTITIES 3. Dose Equivalent Dose equivalent accounts for the biological effect of different types of radiation. It is calculated by multiplying the absorbed dose by a radiation waiting factor that reflects the relative biological effectiveness of the radiation type. Units: H= (D)(W) Conventional: Rem where: SI Unit: Sievert (Sv) H= Equivalent Dose D= Absorbed Dose Conversion: W= Radiation weighting 1 rem = 0.01 Sv factor 100 rem = 1 Sv  RADIATION UNITS AND QUANTITIES 4. Activity Activity measures the rate of radioactive disintegration per unit time. Units: A= N/t Conventional: Curie (Ci) where: A=total activity SI Unit: Becquerel (Bq) N=number of particles Conversion: t=time 1 Ci = 3.7 × 10^10 Bq  NUCLEAR PHYSICS Nuclear physics is the field of physics that studies atomic nuclei and their constituents and interactions, in addition to the study of other forms of nuclear matter. NUCLEAR STRUCTURE AND STABILITY NUCLEONS (protons and neutrons) - In physics and chemistry, a nucleon is either a proton or a neutron, considered in its role as a component of an atomic nucleus. The number of nucleons in a nucleus defines the atom's mass number (nucleon number). NUCLEAR FORCES AND BINDING ENERGY Nuclear forces, primarily the strong nuclear force, are responsible for binding protons and neutrons (nucleons) together within the nucleus. Despite the repulsive electrostatic force between positively charged protons, the strong nuclear force is much stronger at short distances, holding the nucleus together. Binding energy is the energy required to disassemble a nucleus into its individual nucleons. The greater the binding energy, the more stable the nucleus. For example, iron-56 has one of the highest binding energies per nucleon, making it one of the most stable elements in nature  Nuclear Models Liquid Drop Model: This model treats the nucleus as a collection of nucleons behaving similarly to molecules in a liquid drop. It accounts for nuclear properties like volume, surface energy, and Coulomb repulsion. The model provides a good approximation for explaining nuclear binding energy and fission but fails to capture certain quantum effects. Shell Model: This model views nucleons as occupying discrete energy levels, similar to electrons in an atom. In this model, nucleons fill energy "shells," with nucleons pairing off to increase stability. It is especially effective in explaining why certain numbers of protons or neutrons (the so-called magic numbers) lead to particularly stable nuclei.  Magic Numbers and Nuclear Stability -Magic numbers are specific numbers of protons or neutrons (e.g., 2, 8, 20, 28, 50, 82, 126) that lead to highly stable nuclear configurations. Nuclei with magic numbers of protons or neutrons exhibit enhanced stability due to completely filled nuclear shells, analogous to noble gases in atomic chemistry. The combination of filled shells and strong binding energy leads to reduced decay rates and a lower likelihood of spontaneous fission.  Radioactivity and Radioactive Decay Radioactivity refers to the spontaneous emission of particles or energy from the nucleus of an unstable atom in order to become more stable. This phenomenon leads to radioactive decay, where the unstable nucleus transforms into a different element or isotope. There are three primary types of radioactive decay:.  Types of Radioactive Decay: Alpha Decay: In alpha decay, the nucleus emits an alpha particle, which consists of two protons and two neutrons (a helium nucleus). This causes the original atom to lose two protons, resulting in the formation of a new element that is two places lower on the periodic table. Alpha decay is typically seen in heavy elements like uranium and radium.  Types of Radioactive Decay: Beta Decay: Beta decay occurs when a neutron in the nucleus is converted into a proton, accompanied by the emission of a beta particle, which is a high-energy electron. In beta decay, the atomic number increases by one, changing the element but not the mass number. A different form of beta decay involves the transformation of a proton into a neutron, emitting a positron (positive beta particle).  Types of Radioactive Decay: Gamma Decay: Gamma decay involves the emission of high- energy electromagnetic radiation (gamma rays) from the nucleus. This type of decay usually follows alpha or beta decay, as the nucleus shifts from an excited state to a lower energy state. Gamma rays do not change the number of protons or neutrons, so the element remains the same.  Radioactive Decay Laws and Half-life: Radioactive decay follows an exponential law, meaning the number of undecayed nuclei decreases over time in a predictable way. The rate at which a sample of radioactive material decays is proportional to the number of undecayed nuclei present at any time. The half-life is the amount of time it takes for half of the radioactive nuclei in a sample to decay. Each type of radioactive isotope has a unique half-life, which can range from fractions of a second to millions of years. For example, carbon-14 has a half-life of about 5,730 years, which makes it useful in dating ancient organic materials.  Radioactive Dating Techniques: One of the most important applications of radioactive decay is radioactive dating, used to determine the age of objects based on the known decay rates of radioactive isotopes. Two common techniques include: Carbon Dating (Radiocarbon Dating): This method uses the decay of carbon-14 (C-14) to date materials that were once living, such as wood, bone, or fossils. Since C-14 decays with a half-life of about 5,730 years, it is effective for dating specimens up to around 50,000 years old. Uranium-Lead Dating: Used to date rocks and minerals, uranium- lead dating is based on the decay of uranium isotopes (U-238 and U- 235) into lead isotopes. With a much longer half-life (up to billions of years), this method is particularly useful for dating the Earth’s oldest rocks.  Nuclear Reactions 1. Nuclear Fission and Fusion: Nuclear Fission: Fission occurs when a large, unstable nucleus (like uranium-235 or plutonium-239) splits into smaller nuclei, releasing energy and neutrons. This chain reaction can be controlled for energy production, as seen in nuclear power plants, or uncontrolled, as in nuclear weapons. Nuclear Fusion: Fusion is the process where two light atomic nuclei (like hydrogen isotopes) combine to form a heavier nucleus, releasing even more energy than fission. Fusion powers stars, including the sun, and is considered a potential future energy source due to its efficiency and cleaner byproducts, though it's currently difficult to achieve and control on Earth.  Nuclear Reactions 2. Nuclear Reactors and Energy Production: Nuclear reactors use controlled fission reactions to produce heat, which is used to generate electricity. In a reactor, neutrons initiate the fission of fuel atoms (like uranium), and the heat generated is used to turn water into steam, which drives turbines to produce electricity. These reactors provide a significant source of energy with low greenhouse gas emissions, but they also produce radioactive waste.  Nuclear Reactions 3. Particle Accelerators and Collisions: Particle accelerators are devices that use electric and magnetic fields to propel charged particles, such as protons or electrons, to very high speeds. When these particles collide, they can smash into each other or into a target, causing nuclear reactions that help scientists study the fundamental particles and forces of the universe. Accelerators are essential in physics research and have practical applications in medicine and industry. Applications of Nuclear Physics 1. Nuclear Medicine Imaging: Nuclear medicine uses radioactive isotopes (radioisotopes) to create images of the inside of the body. Techniques like PET (Positron Emission Tomography) scans use radioisotopes injected into the body, which emit radiation detected by scanners, providing detailed images for diagnosing diseases. Radiation Therapy: In cancer treatment, radiation therapy uses high- energy radiation (such as X-rays or gamma rays) to target and destroy cancer cells. Radioactive isotopes can be placed near tumors (brachytherapy) or used externally to shrink or eliminate cancer cells. Applications of Nuclear Physics 2. Nuclear Power and Weapons: Nuclear Power: Nuclear power plants generate electricity by using controlled nuclear fission reactions. This produces large amounts of energy with minimal greenhouse gas emissions, though it creates radioactive waste that must be carefully managed. Nuclear Weapons: Nuclear weapons use uncontrolled fission or fusion reactions to release massive destructive energy. Fission bombs (atomic bombs) and fusion bombs (hydrogen bombs) are the most powerful weapons, capable of immense devastation. Applications of Nuclear Physics 3. Isotope Production and Uses Radioactive isotopes are produced in reactors and particle accelerators for various applications, such as: Medical Uses: Isotopes like technetium-99m are used in diagnostic imaging, while iodine-131 is used to treat thyroid conditions. Industrial Uses: Isotopes are used for non-destructive testing (like X- rays for materials) and tracing processes in environmental studies and chemical research.  INTERACTION OF IONIZING RADIATION WITH MATTER any process by which electrically neutral atoms or molecules are converted to WHAT IS IONIZATION? electrically charged atoms or molecules (ions) through gaining or losing electrons. Directly ionizing radiation- electrically charged particles that have sufficient kinetic energy to produce ionization by collision. These include, but are not limited to, electrons, protons, alpha particles (helium nucleus) and beta particles (high energy electrons). Indirectly ionizing radiation- uncharged particles that can release directly ionizing particles or can initiate a nuclear transformation. Examples include, but are not limited to, neutrons and gamma rays. Types of Ionizing Radiation 1. Alpha Particles: These are heavy, positively charged particles consisting of 2 protons and 2 neutrons. They have a high mass and charge, which makes them highly ionizing but with low penetration power. They can be stopped by a sheet of paper or even the outer layer of human skin. 2. Beta Particles: These are high-energy, high-speed electrons (beta- minus) or positrons (beta-plus). They have less mass and charge than alpha particles, making them less ionizing but more penetrating. They can be stopped by materials like plastic, glass, or a few millimeters of aluminum. 3. Gamma Rays: These are electromagnetic waves with very high energy and no mass or charge. They are highly penetrating and require dense materials like lead or several centimeters of concrete to be effectively stopped 4. X-rays: Similar to gamma rays, X-rays are high-energy electromagnetic waves. They differ primarily in their origin; X-rays are usually produced by electronic transitions in atoms, while gamma rays come from the nucleus. 5 Neutrons: Neutrons are uncharged particles and have considerable mass. They interact with matter primarily through nuclear reactions and can be highly penetrating. Neutron shielding often requires materials rich in hydrogen, like water or polyethylene.  MECHANISMS OF INTERACTIONS Ionization: Ionizing radiation interacts with matter mainly by ejecting electrons from atoms, creating ions. This can lead to a cascade of ionization events, potentially damaging biological molecules or materials. Alpha particles, due to their high mass and charge, cause dense ionization along their path, while beta particles cause less dense ionization. Excitation: Radiation can also excite atoms or molecules to higher energy states without ionizing them. When these excited states return to normal, they release energy as photons, which can contribute to secondary radiation effects.  SCATTERING Elastic Scattering: The incident radiation changes direction but retains its energy. This is common for neutron interactions. Inelastic Scattering: The radiation transfers energy to the material, often leading to excitation or ionization.  ABSORPTION: Photoelectric Effect: Photons are absorbed by atoms, ejecting an electron and leaving the atom in an ionized state. This effect is more significant at lower photon energies and for high atomic number materials. Compton Scattering: Photons scatter off electrons, transferring part of their energy to the electron and continuing with reduced energy. This is significant for intermediate photon energies and in materials with a lower atomic number. Pair Production: At very high photon energies, photons can create an electron-positron pair. This process occurs when the photon energy exceeds 1.022 MeV, the combined rest mass energy of the electron and positron. Bremsstrahlung: When high-energy electrons are deflected by the nucleus of an atom, they emit additional photons. This is a key process in radiation therapy and X-ray production.  BIOLOGICAL EFFECTS The biological impact of ionizing radiation depends on the type and energy of the radiation, as well as the type of tissue exposed. High doses can cause acute radiation syndrome, while lower doses can lead to long-term effects like cancer. Cells can be damaged directly through ionization or indirectly via free radicals generated by water radiolysis.  RADIATION PROTECTION To protect against ionizing radiation, several strategies are employed: Shielding: Using appropriate materials to block or reduce radiation exposure (e.g., lead for gamma rays, plastic or aluminum for beta particles). Distance: Increasing the distance from the radiation source reduces exposure due to the inverse square law. Time: Minimizing the time spent near a radiation source reduces the dose received. Contamination Control: Preventing radioactive substances from spreading and contaminating surfaces or individuals. Thank you!