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Radioactive Decay

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Radioactive Decay North Berwick High School Department of Physics Higher Physics Unit 2 Particles and Waves Section 3 Fission and Fusion Section 3 Fission and Fusion Note Making Make a dictionary with the meanings of any new words. Einstein and nuclear energy 1. Write down Einstein’s famous equation along with units. 2. Explain the importance of this equation and its relevance to nuclear power. A basic model of the atom 1. Copy the components of the atom diagram and state the meanings of A and Z. 2. Copy the table on page 5 and state the difference between elements and isotopes. Radioactive decay 1. Explain what is meant by radioactive decay and copy the summary table for the three types of nuclear radiation. 2. Describe an alpha particle, including the reason for its short range and copy the panel showing Plutonium decay. 3. Describe a beta particle, including its range and copy the panel showing Tritium decay. 4. Describe a gamma ray, including its range. Fission: spontaneous decay and nuclear bombardment 1. Describe the differences between the two methods of decay and copy the equation on page 10. Nuclear fission and E = mc2 1. Explain what is meant by the terms ‘mass difference’ and ‘chain reaction’. 2. Copy the example showing the energy released during a fission reaction. 3. Briefly describe controlled fission in a nuclear reactor. Nuclear fusion: energy of the future? 1. Explain why nuclear fusion might be a preferred source of energy in the future. 2. Describe some of the difficulties associated with maintaining a controlled fusion reaction. Section 3 Fission and Fusion Contents Content Statements .................................................................................... 1 Nuclear reactions: fission and fusion .......................................................... 2 Einstein and nuclear energy ........................................................................ 3 Mass number............................................................................................... 5 Nuclear isotopes .......................................................................................... 6 Radioactive decay ....................................................................................... 6 Radiation ..................................................................................................... 6 Nature ......................................................................................................... 6 Symbol ......................................................................................................... 6 Radioactive decay: representing by symbols and equations ...................... 7 Alpha decay ................................................................................................. 7 Beta decay ................................................................................................... 8 Gamma decay .............................................................................................. 9 Fission: spontaneous decay and nuclear bombardment ............................ 9 Nuclear fission ........................................................................................... 10 Nuclear fission and E = mc2 ....................................................................... 11 Einstein and nuclear energy II ................................................................... 11 Chain reactions .......................................................................................... 13 Energy released from each fission ............................................................ 14 Example ..................................................................................................... 14 Nuclear fission in nuclear reactors ............................................................ 15 Nuclear fusion: energy of the future? ....................................................... 17 Ohmic heating and current drive .............................................................. 21 Neutral beam heating ............................................................................... 21 Radio-frequency heating ........................................................................... 21 Self-heating of plasma ............................................................................... 22 Problems ................................................................................................... 23 Solutions .................................................................................................... 27 Content Statements Content notes context Fission and Nuclear equations to Energy available from fusion. describe radioactive chemical and nuclear decay and fission and sources. fusion reactions. Mass Magnetic containment and energy equivalence, of plasma. including calculations. Joint European Torus Coolant and (JET) containment issues in ITER tokamak nuclear fusion reactors. 1 Section 3 Fission and Fusion Nuclear reactions: fission and fusion Nuclear power has been used to produce electricity in the UK since 1956, when the first large-scale power plant was opened in Cumbria, England. It currently accounts for 10–15% of the UK’s energy needs, although in the past it made a more significant contribution. The first reactor to produce electricity was in Idaho, USA, opening in 1951. It produced sufficient electricity to illuminate four light bulbs. Its purpose was not to produce electricity on a commercial scale but to operate as an experimental reactor. In 1954, Russia generated the first electricity for commercial use using nuclear power. Just under two years later, the UK’s first plant, Calder Hall, produced ten times the power of the Russian plant. In late 2010, there were 441 nuclear plants in 30 countries worldwide (source: http://www.euronuclear.org/info/encyclopedia/n/nuclear-power- plant-world-wide.htm,). Nuclear power remains a controversial issue. It produces vast amounts of electricity without the production of carbon dioxide, which is associated with climate change. It is a very reliable source of energy. However, the waste it produces is radioactive and must be stored, sealed, for thousands of years. During this time it must be protected, eg from geological threats such as earthquakes and volcanic eruptions. 2 Einstein and nuclear energy Scientists’ work on the standard model and subatomic particles, as well as addressing fundamental questions about the structure of matter, has led to the harnessing of the power of the nucleus – nuclear energy. In 1905, a series of four papers by Albert Einstein was published in the journal Annalen der Physik. One of these ‘Does the inertia of a body depend upon its energy content’ led us to one of the best-known relationships in the world: E = mc2 But what does this mean? And what is its significance? In terms of quantities and units, there is nothing particularly challenging in this relationship. E is energy measured in joules (J) E = mc2 m is mass measured in kilograms (kg) c is the speed of light in a vacuum (m s–1) Its importance must be in its significance. The best person to explain this is Albert Einstein himself. You can listen to his explanation here: http://www.aip.org/history/einstein/voice1.htm. This website shows a useful timeline of scientific discovery relevant to the equation E = mc2. http://www.pbs.org/wgbh/nova/teachers/activities/3213_einstein_06.html This website offers more detail to better understand the equation E = mc2. http://www.pbs.org/wgbh/nova/teachers/activities/ 3213_einstein_04.html 3 A basic model of the atom When we consider nuclear energy, we are dealing with energy released from the nucleus of the atom. A basic model of the atom, and its nucleus, is required. In this model the nucleus consists of protons, with mass number 1 and charge +1, and neutrons, with mass number 1 and charge 0. Protons and neutrons are collectively known as nucleons. The total number of protons and neutrons in the nucleus is called the mass number, A. The number of protons in the nucleus is called the atomic number, Z. In a neutral atom the number of protons equals the number of electrons. Components of the atom http://www.atomicarchive.com/Physics/Physics1.shtml 4 The mass numbers, charges and symbols for protons, neutrons and electrons are given below. Particle Mass Charge Symbol number Proton 1 +1 1 p 1 Neutron 1 0 1 n 1 Electron 0* -1 1 e 1 *The mass of an electron is = 1/1840 of the mass of a proton. Each element in the periodic table has a different atomic number and is identified by that number. It is possible to have different versions of the same element, called isotopes. An isotope of an atom has the same number of protons but a different number of neutrons, i.e. the same atomic number but a different mass number. An isotope is identified by specifying its chemical symbol along with its atomic and mass numbers. For example: 5 Nuclear isotopes http://www.atomicarchive.com/Physics/Physics1.shtml Radioactive decay Radioactive decay is the breakdown of a nucleus to release energy and matter from the nucleus. This is the basis of the word ‘nuclear’. The release of energy and/or matter allows unstable nuclei to achieve stability. Unstable nuclei are called radioisotopes or radionuclides. The following is a summary of the nature and symbols for the three types of nuclear radiation. Notice that gamma radiation has zero mass and zero charge. It is an electromagnetic wave. Radiation Nature Symbol Alpha particle Helium nucleus 4 He 2 Beta particle Fast electron 0 1 e Gamma ray High frequency electromagnetic
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