Nuclear Changes Nuclear Energy – An introduction Nuclear Energy – An introduction Chapter 9.

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Slide 1 Nuclear Changes Nuclear Energy An introduction Nuclear Energy An introduction Chapter 9 Slide 2 Radioactivity Radioactive materials have an unstable nucleus that release one or more particles or energy Nuclear radiation refers to the released energy and matter. Slide 3 Where does radiation come from? Radiation is generally produced when particles interact or decay A large contribution of the radiation on the earth is from the sun (solar) or from radioactive isotopes of the elements (terrestrial) Radiation is going through you at this very moment! Slide 4 Isotopes (a review) Whats an isotope? Two or more varieties of an element having the same number of protons but different number of neutrons. Certain isotopes are unstable and decay to lighter isotopes or elements. Deuterium and tritium are isotopes of hydrogen. In addition to the 1 proton, they have 1 and 2 additional neutrons in the nucleus respectively*. Slide 5 Nuclear Radiation As the radioactive nucleus decays, nuclear radiation leaves the nucleus and interacts with other matter. Types of nuclear radiation: (4) 1. Alpha Particles ( ) 2. Beta particles ( ) 3. Gamma rays ( ) 4. Neutron emission Slide 6 1. Alpha Particles: a positively charged particle and has a large mass. (consists of 2 protons and 2 neutrons). Do not travel far because of its size. Can barely travel through a piece of paper. Radium R 226 Radon Rn 222 88 protons 138 neutrons 86 protons 136 neutrons 2 protons 2 neutrons The alpha-particle is a Helium nucleus. Its the same as the element Helium, with the electrons stripped off ! He) + Slide 7 2. Beta Particles: negatively charged particle that has little mass Travels much faster than alpha particles Travel through 3mm of aluminum or 10 mm of woodbut are stopped because they lose energy fairly quickly. Carbon C 14 6 protons 8 neutrons Nitrogen N 14 7 protons 7 neutrons + e-e- electron (beta-particle) We see that one of the neutrons from the C 14 nucleus converted into a proton, and an electron was ejected. The remaining nucleus contains 7p and 7n, which is a nitrogen nucleus. Slide 8 Gamma Rays: are not made of matter and do not have an electric charge Gamma Rays consist of electromagnetic energy called PHOTONS Have very high energycan travel through 60 cm of aluminum or 7 cm of lead Gamma Rays are more dangerous to living things than alpha or beta particles. Slide 9 Gamma particles ( ) In much the same way that electrons in atoms can be in an excited state, so can a nucleus. Neon Ne 20 10 protons 10 neutrons (in excited state) 10 protons 10 neutrons (lowest energy state) + gamma Neon Ne 20 A gamma is a high energy light particle. It is NOT visible by your naked eye because it is not in the visible part of the EM spectrum. A gamma is a high energy light particle. It is NOT visible by your naked eye because it is not in the visible part of the EM spectrum. Slide 10 Gamma Rays Neon Ne 20 + The gamma from nuclear decay is in the X-ray/ Gamma ray part of the EM spectrum (very energetic!) Neon Ne 20 Slide 11 Nuclear Radiation Neutron Emission: The release of a neutron from a nucleusdoes not have any charge. Can travel much farther because they do not lose energy very quickly. Can travel through a 15 cm block of lead. Slide 12 Half-Life The half-life (h) is the time it takes for half the atoms of a radioactive substance to decay. For example, suppose we had 20,000 atoms of a radioactive substance. If the half-life is 1 hour, how many atoms of that substance would be left after: 10,000 (50%) 5,000 (25%) 2,500 (12.5%) 1 hour (one lifetime) ? 2 hours (two lifetimes) ? 3 hours (three lifetimes) ? Time #atoms remaining % of atoms remaining Slide 13 Predicting Age Scientists use the Half-Life of an object to determine its age. For example: Potassium-40 decays to Argon-40, so the ratio of Potassium-40 to argon-40 is smaller for older rocks than it is for younger rocks. Scientists use Carbon-14 to date more recent materials like remains of an animal or parts of ancient clothing. Slide 14 Practicing Half-Life Radium 226 has a half-life of 1599 years. How long would it take seven-eighths of a radium-226 sample to decay? Given: half-life = 1599 years Given: fraction of sample decayed = 7/8 Unknown: fraction of sample remaining Unknown: total time of decay Slide 15 1. Calculate the fraction of radioactive sample remaining. Fraction of sample remaining = 1 7/8 = 1/8 2. Calculate the number of half-lives Amount of sample remaining after one half-life = Amount of sample remaining after 2 half-lives = Amount of sample remaining after 3 half-lives = 1/8 3 Half-lives are needed for one-eighth of the sample to remain undecayed. 3. Calculate the total time required for the radioactive decay. Total time of decay = 3 half-lives x 1599 years = 4797 years Slide 16 Radioactive Dating Game Sign out a laptop Log in and open the Internet Go to phet.colorado.edu New Sims - PhET Simulations New Sims - PhET Simulations Slide 17 Nuclear Energy Basics of Nuclear Power Video Clip Slide 18 Brief History Nuclear energy was first discovered in 1934 by Enrico Fermi The first nuclear bombs were built in 1945 as a result of the Manhattan Project The first plutonium bomb (Trinity) was detonated on July 16, 1945 The first uranium bomb was detonated over Hiroshima on August 6 th 1945 The second plutonium bomb was dropped on Nagasaki on August 9 th 1945 Electricity was produced with nuclear energy in 1951. Slide 19 Fission: History and Overview Discovered 1938 by Otto Hahn and Frittz Strassmann Presented in 1939 by Lise Meitner and Otto Frisch Research of Nuclear Fission began U.S. weapons program 1942 first controlled self sustaining fission reaction by Enrico Fermi Nuclear fission creates Electricity Slide 20 Fission Overview Fission is the process of splitting heavier nuclei into lighter nuclei Fission releases Energy The mass equivalent of 1kg of matter is more than the chemical energy of 22 million tons of TNT Neutrons released by fission can start a chain reactiona continuous series of nuclear fission reactions. Slide 21 Fission Today 435 Nuclear Power plants worldwide 1/6 of the worlds power is nuclear World Energy Consumption doubled by 2050 World will turn to fission energy Slide 22 Slide 23 World Nuclear Power Plants How Stuff Works - Nuclear Energy Slide 24 United States Nuclear Power Plants Slide 25 Nuclear Power in Northeast U.S. Slide 26 Japans Nuclear Power Problems Slide 27 Japans Power Plant Meltdown Japans Nuclear Emergency Japans Nuclear Emergency Efforts to cool down the nuclear reactor Efforts to cool down the nuclear reactor Concerns about Proximity to the Power plant Concerns about Proximity to the Power plant Slide 28 Fusion: Overview and History British Physicists in the 1940s and 50s housed ina hangar at Harwell a device called ZETA-Zero Energy Toroidal Assembly which was the first fusion based operating system Masked in the secrecy of the Cold War Fusion is the production of a thermonuclear reaction in a gas discharge Called fusion because it is based on fusing light nuclei such as hydrogen isotopes to release energy, similar to that which powers the sun and other stars. Slide 29 Slide 30 Fast Facts A vast, new source of energy Fuels are plentiful Inherently safe since any malfunction results in a rapid shutdown No atmospheric pollution leading to acid rain or the greenhouse effect Sunlight is energy released from fusion reactions in the sun. Slide 31 The Future is Fusion The sun is our greatest source of energythe sun uses fusion. The source of fusion is vastly abundant in our oceans (an isotope of hydrogen in water) The waste of fusion is helium, and there is no pollution of long term extent The price of fusion is estimated to be equivalent to that of fossil fuels Fusion can give us energy for millions of years Slide 32 Nuclear Waste Slide 33 Most used Nuclear Waste Sites Slide 34 Nuclear Waste Nuclear Waste has been accumulating since the mid-1940s and is currently in temporary storage at 131 sites in 39 states Nuclear waste remains highly radioactive for thousands of years. It will still be potentially harmful to humans long after the manmade containers holding the waste have disintegrated. Slide 35 Yucca Mountain Will become the nation's first long- term geologic repository for spent nuclear fuel and high-level radioactive waste that is currently stored at 126 sites around the nation. Yucca Mountain is located in a remote desert on federally protected land within the secure boundaries of the Nevada Test Site in Nye County, Nevada. It is approximately 100 miles northwest of Las Vegas, Nevada. Slide 36 Nuclear Radiation Today Slide 37 Radiation You are exposed to radiation everyday Background Radiation nuclear radiation that arises naturally from cosmic rays and from radioactive isotopes in the soil and air We are adapted to survive low levels of this natural source of radiation Radiation is measured in rems or millirems Slide 38 What are the Possible Effects of Radiation? Inside Chernobyl - National Geographic Magazine Inside Chernobyl - National Geographic Magazine Kasakhstan Fallout Video Clip Kasakhstan Fallout Video Clip Safety Videos Duck and Cover Duck and Cover Living Under the Shadow of the Nuclear Umbrella Video Clip Living Under the Shadow of the Nuclear Umbrella Video Clip Slide 39 Radiation Exposure There are many occupations where people are exposed to higher levels of radiation. Nuclear radiation, health physics, radiology, radiochemistry, X-ray technology, MRI It has been decided that these occupations can be exposed to 5000 millirems annually plus regular background radiation. Exposure amounts will also depend on where a person lives. Exposure may increase based on some day-to-day activities as well Slide 40 Radiation Exposure Average annual radiation dose is 360 millirems per person. 300 from natural sources. Sleeping next to someone for 8 hours: 2 mrems Exposure comes from the naturally radioactive potassium in the other person's body Coal plant, living within 50 miles:.03 mrem There is much thorium and uranium in coal. Living within 50 miles of a nuclear power plant adds.009 mrem of exposure. Both figures are considered extremely low levels. Living in a masonry home: 7 mrems Stone, brick and adobe have natural radioisotopes in them. Living on the Earth: 200 mrems We are living in a sea of radon. It is made from the natural decay of uranium and thorium in the soil, left over from the creation of the solar system. Radon is a rare gas that diffuses out of soil and into the air. It contributes more than half of our background Slide 41 Smoking: up to 16,000 mrems The tobacco leaf acts like the absorbing surface of charcoal in a radon test kit. It collects long- lived isotopes of airborne radon, like lead-210 and polonium. Small portions of the lungs can get relatively whopping doses, compared to background levels. Porcelain teeth or crowns: tenths of a rem Uranium is often added to these dental products to increase whiteness and florescence. Air Travel: 1 mrem per 1000 miles 30,000 feet above the ground you're closer to the ionizing radiation (high-energy gammas well as particles) from the sun. Grand Central Station, NYC: 120 mrem for employees Its granite walls have a high uranium content. Brazil Nuts: This is the world's most radioactive food due to high radium concentrations 1000-times that of average foods.The US Capitol Building in Washington DC: This building is so radioactive, due to the high uranium content in its granite walls, it could never be licensed as a nuclear power reactor site. Slide 42 Radiation Exposure 1500% increase in incidence of testicular and ovarian cancer in children on Navaho reservation in uranium mining area 500% increase in bone cancer in children affected by uranium 250% increase in leukemia (all ages) in the Navaho population 200% increase in each of the following non-cancer effects: miscarriage, infant death, congenital defects, genetic abnormalities, learning disorders. Slide 43 400% increase in leukemia incidence in the population living downwind of the Pilgrim nuclear power reactor in Massachusetts in the first 5 years after fuel was know to have leaked excess radioactivity. Baseline: Disease in population before and after Pilgrim radioactive releases and comparison to upwind population. 300400% increase in lung cancer in the general population within the plume of the Three Mile Island accident releases 600700% increase in leukemia in the general population within the plume of Three Mile Island accident releases Baseline: Disease in population upwind (out of the radiation plume path) is compared to disease in population downwind (in the pollution plume.) 50% increase in childhood cancer incidence in the Three Mile Island area for each 10 millirem increase in radiation exposure per year. Slide 44 500% increase in leukemia among Utah nuclear bomb test Downwinders 121% increase in thyroid cancer incidence in the same group 200% increase in breast cancer 700% increase in bone cancer a greater then 120% increase in thyroid cancer in those who drank milk laced with Iodine-131 from atmospheric nuclear weapons tests 200% increase in lung cancer in women who received radiation treatments for breast cancer 6696% increase in early cancer deaths due to background radiation Slide 45 Radiation Exposure in the U.S. Slide 46 Benefits of Nuclear Radiation Nuclear radiation is used in a controlled way Smoke Detectors use nuclear radiation in small amounts Alpha particles are charged and produce an electric current Detecting disease Detecting disease Ultrasound, CT scanning, Radioactive tracers Slide 47 Benefits in Medicine Radioactive tracers are short-lived isotopes that tend to accumulate in specfic cellshelp to find tumors. Slide 48 Benefits in Medicine Radiotherapy is used to treat cancers. Controlled doses of nuclear radiation are used to kill fast growing cells (also damages healthy cells) Slide 49 Uses in Agriculture Radioactive tracers are used to identify the flow of water and how it moves through the crops. Help to identify biochemical processes Slide 50 NUCLEAR RADIATION: A REVIEW Slide 51 Risks of Nuclear Radiation Nuclear radiation reacts with living tissue (alpha, beta, and gamma particles) They change the number of electrons in atoms of living materials Alpha particles stopped by layer of clothing Beta particles travel through a fraction of an inch in solids and liquids Gamma particles depends on energy can travel through several feet. Slide 52 Nuclear Radiation Slide 53 Risk and Amount of Radiation Small amount of nuclear radiation --- changes cannot be detected. Relationship with high levels of nuclear radiation and cancer Cancers related to radiation levels include: leukemia, breast cancer, lung cancer, and stomach cancer

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