Radiation: Nuclear Reactions Freddie Arocho-Perez Kaplan University SC300: Big Ideas in Science What is Radiation? 1. Process by which energy is propagated through space or matter. 2. Emission of rays in all directions from a common center. Radioactivity is the process by which an unstable nucleus tries to become more stable by emitting energy from the nucleus. ENERGY Where does it come from? Natural radiation accounts for 82% of our exposure per year! Air Terrestrial (Radon Gas) Food and Water Cosmic Medical X-Rays 15% Nuclear Reactors 0.1% Fallout (Skin-Burn) 0.3% Miscellaneous 1% Man-made radiation accounts for 18% of our exposure each year! NON-IONIZING It causes damage by raising the temperature of the material it is passing through. IONIZING It is able to disrupt chemical bonds in the material. This energy can cause cell damage. Types of Radiation Types of Particles Produced by Ionizing Radiation Particle(Alpha): Very large (Helium nucleus), very slow, positively charged, low energy, stopped by paper. Particle(Beta): Very small (electrons), high speed, charge same as electron, stopped by plastic or gloves. Particle(Gamma): No mass, no charge, speed of light, highest penetrating power, stopped by steel. Types of Particles Produced by Ionizing Radiation Measuring Radioactivity One can use a device like this Geiger Counter to measure the amount of activity present in a radioactive sample. The ionizing radiation creates ions, which conduct a current that is detected by the instrument. Fission Reaction of Uranium-235 Nuclear Fission: - Reactions in which an atoms nucleus splits into smaller parts, releasing a large amount of energy in the process. - Heavy elements can exhibit natural radioactivity and, thus, can decay into lighter elements. - Chain Reaction: A self-sustaining reaction that continues once it has been started. This reaction can be controlled or uncontrolled. Fission Reaction of Uranium-235 Nuclear Power Today Provides almost 20% of worlds electricity (~8% in U.S.). 69% of U.S. non-carbon electricity generation. More than 100 plants in U.S. None built since the 1970s plants in the Europe Leader is France: About 80% of its power from nuclear power. Energy in the United States Early History of Nuclear Power in the U.S. Origins Nuclear Bomb of 1945 known as Fat Man Origins After World War II, development of civilian nuclear program. Atlantic Energy Act of : first commercial nuclear power program. Origins Manhattan Project: Secret government project to create atomic weapons during World War II. After the war, the government encouraged the development of nuclear energy for peaceful civilian purposes. This project led to the technology used in nuclear plants today. The Vision It is not too much to expect that our children will enjoy in their homes [nuclear generated] electrical energy too cheap to meter. Lewis Strauss, Chairman of the U.S. Atomic Energy Commission (1954) Nuclear Reactor The reaction is kept in check by the use of control rods. These block the paths of some neutrons, keeping the system from reaching a dangerous supercritical mass. Magnetic Resonance Imaging (MRI) What is MRI of the Body? Magnetic resonance imaging (MRI) is a non-invasive, usually painless medical test that helps physicians diagnose and treat medical conditions. MR imaging uses a powerful magnetic field and a computer to produce detailed pictures of organs, soft tissues, bone and virtually all other internal body structures. What is MRI of the Body? The images can then be examined on a computer monitor or printed. MRI does not use ionizing radiation (X-rays). Detailed MR images allow physicians to better evaluate parts of the body and certain diseases that may not be assessed adequately with other imaging methods such as X-ray, ultrasound or computer tomography (also called CT or CAT scanning). What are some common uses of the procedure? MR imaging of the body is performed to evaluate: organs of the chest, heart, lungs, and liver. reproductive organs in the male (prostate and testicles) and the female (uterus and ovaries). tumors. coronary artery disease and heart problems. What does the equipment look like? The traditional MRI unit is a large cylinder-shaped tube surrounded by a circular magnet. The person lies on a moveable examination table that slides into the center of the magnet. The computer workstation that processes the imaging information is located in a separate room. How does the procedure work? MRI is especially suited to detecting disorders that increase fluid in diseased areas of the body, for example, areas affected by tumors, infection and inflammation. Sample image: MR of the abdomen showing liver and kidneys - frontal (coronal view) How does the procedure work? Sample image: MR of the knee - side (lateral) view, showing distal or lowest part of femur, the patella (knee cap) and proximal (upper) tibia. The lateral meniscus is seen as a dark bow-tie like structure. The patellar tendon is also clearly seen at the front of the knee connecting the patella with the tibia. How does the procedure work? MR image of the pelvis of a woman shows the uterus (arrow) and ovaries (arrowhead). How does the procedure work? MR image of a pregnant woman shows the babys brain (arrow) and the placenta (arrowhead) in the uterus.