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
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  • Radioactivity Radioactive materials have an unstable nucleus that release one or more particles or energy Nuclear radiation refers to the released energy and matter.
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  • 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!
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  • 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*.
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  • 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
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  • 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) +
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  • 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.
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  • 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.
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  • 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.
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  • 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
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  • 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.
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  • 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
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  • 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.
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  • 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
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  • 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
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  • Radioactive Dating Game Sign out a laptop Log in and open the Internet Go to New Sims - PhET Simulations New Sims - PhET Simulations
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  • Nuclear Energy Basics of Nuclear Power Video Clip
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  • 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.
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  • 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
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  • 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.
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  • 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
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  • World Nuclear Power Plants How Stuff Works - Nuclear Energy
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  • United States Nuclear Power Plants
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  • Nuclear Power in Northeast U.S.
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  • Japans Nuclear Power Problems
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  • 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
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  • 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.
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  • 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.
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  • 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
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  • Nuclear Waste
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  • Most used Nuclear Waste Sites
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  • 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.
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  • 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.
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  • Nuclear Radiation Today
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