1 Chapter 9 Nuclear Radiation 9.1 Natural Radioactivity Copyright © 2009 by Pearson Education, Inc.
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1 Chapter 9 Nuclear Radiation 9.1 Natural Radioactivity Copyright 2009 by Pearson Education, Inc. Slide 2 2 Radioactive Isotopes A radioactive isotope has an unstable nucleus. emits radiation to become more stable. can be one or more of the isotopes of an element Copyright 2009 by Pearson Education, Inc. Slide 3 3 Nuclear Radiation Nuclear radiation is the radiation emitted by an unstable atom. takes the form of alpha particles, neutrons, beta particles, positrons, or gamma rays. Copyright 2009 by Pearson Education, Inc. Slide 4 4 Types of Radiation Alpha ( ) particle is two protons and two neutrons. Beta ( ) particle is a high-energy electron. 0 e Positron ( +) is a positive electron. 0 e +1 Gamma ray is high-energy radiation released from a nucleus. Slide 5 5 Radiation Protection Radiation protection requires paper and clothing for alpha particles. a lab coat or gloves for beta particles. a lead shield or a thick concrete wall for gamma rays. limiting the amount of time spent near a radioactive source. increasing the distance from the source. Copyright 2009 by Pearson Education, Inc. Slide 6 6 Shielding for Radiation Protection Slide 7 7 Chapter 9 Nuclear Radiation 9.2 Nuclear Reactions Copyright 2009 by Pearson Education, Inc. Slide 8 Changes in Nuclear Particles Due to Radiation When radiation occurs, particles are emitted from the nucleus. mass number may change. atomic number may change. 8 Copyright 2009 by Pearson Education, Inc. Slide 9 9 Summary of Types of Radiation Copyright 2009 by Pearson Education, Inc. Slide 10 10 Producing Radioactive Isotopes Radioactive isotopes are produced when a stable nucleus is converted to a radioactive nucleus by bombarding it with a small particle. in a process called transmutation. Copyright 2009 by Pearson Education, Inc. Slide 11 11 Chapter 9 Nuclear Radiation Copyright 2009 by Pearson Education, Inc. 9.3 Radiation Measurement Slide 12 12 Radiation Measurement A Geiger counter detects beta and gamma radiation. uses ions produced by radiation to create an electrical current. Copyright 2009 by Pearson Education, Inc. Slide 13 13 Radiation Units Units of radiation include Curie - measures activity as the number of atoms that decay in 1 second. rad (radiation absorbed dose) - measures the radiation absorbed by the tissues of the body. rem (radiation equivalent) - measures the biological damage caused by different types of radiation. Slide 14 14 Units of Radiation Measurement Slide 15 15 Exposure to Radiation Exposure to radiation occurs from naturally occurring radioisotopes. medical and dental procedures. air travel, radon, and smoking cigarettes. Copyright 2009 by Pearson Education, Inc. Slide 16 16 Chapter 9 Nuclear Radiation Copyright 2009 by Pearson Education, Inc. 9.4 Half-Life of a Radioisotope 9.5 Medical Applications Using Radioactivity Slide 17 17 Half-Life The half-life of a radioisotope is the time for the radiation level to decrease (decay) to one half of the original value. Copyright 2009 by Pearson Education, Inc. Slide 18 18 Decay Curve A decay curve shows the decay of radioactive atoms and the remaining radioactive sample. Copyright 2009 by Pearson Education, Inc. Slide 19 19 Half-Lives of Some Radioisotopes Radioisotopes that are naturally occurring tend to have long half-lives. used in nuclear medicine have short half-lives. Copyright 2009 by Pearson Education, Inc. Slide 20 20 Medical Applications Radioisotopes with short half-lives are used in nuclear medicine because they have the same chemistry in the body as the nonradioactive atoms. in the organs of the body, they give off radiation that exposes a photographic plate (scan), giving an image of an organ. Thyroid scan Copyright 2009 by Pearson Education, Inc. Slide 21 21 Some Radioisotopes Used in Nuclear Medicine Copyright 2009 by Pearson Education, Inc. Slide 22 22 Chapter 9 Nuclear Radiation 9.6 Nuclear Fission and Fusion Copyright 2009 by Pearson Education, Inc. Slide 23 23 In nuclear fission, a large nucleus is bombarded with a small particle. the nucleus splits into smaller nuclei and several neutrons. large amounts of energy are released. Nuclear Fission Slide 24 24 When a neutron bombards 235 U, an unstable nucleus of 236 U undergoes fission (splits). smaller nuclei are produced, such as Kr-91 and Ba-142. neutrons are released to bombard more 235 U. 1 n + 235 U 236 U 91 Kr + 142 Ba + 3 1 n + 0 92 92 36 56 0 Nuclear Fission Energy Slide 25 25 Nuclear Fission Diagram 1 n + 235 U 236 U 91 Kr + 142 Ba + 3 1 n + energy 0 92 92 36 56 0 Copyright 2009 by Pearson Education, Inc. Slide 26 26 Chain Reaction A chain reaction occurs when a critical mass of uranium undergoes fission. releasing a large amount of heat and energy that produces an atomic explosion. Copyright 2009 by Pearson Education, Inc. Slide 27 27 Nuclear Power Plants In nuclear power plants, fission is used to produce energy. control rods in the reactor absorb neutrons to slow and control the chain reactions of fission. Copyright 2009 by Pearson Education, Inc. Slide 28 Strontium - 90 90 Sr is a product of nuclear fission. It is present in significant amount in spent nuclear fuel and in radioactive waste from nuclear reactors and in nuclear fallout from nuclear tests.nuclear fissionspent nuclear fuel radioactive wastenuclear reactors nuclear falloutnuclear tests For thermal neutron fission as in today's nuclear power plants, the fission product yield from U-235 is 5.8%, from U-233 6.8%, but from Pu-239 only 2.1%.thermal neutronfission product yieldU-235U-233Pu-239 28 Slide 29 Strontium - 90 Together with caesium isotopes 134 Cs, 137 Cs, and iodine isotope 131 I it was among the most important isotopes regarding health impacts after the Chernobyl disaster. 134 Cs 137 Cs 131 I Chernobyl disaster 29 Slide 30 Strontium -90 Strontium-90 is a "bone seeker" that exhibits biochemical behavior similar to calcium, the next lighter Group 2 element. After entering the organism, most often by ingestion with contaminated food or water, about 70-80% of the dose gets excreted.bone seekercalciumGroup 2 element Virtually all remaining strontium-90 is deposited in bones and bone marrow, with the remaining 1% remaining in blood and soft tissues. bonesbone marrow 30 Slide 31 Strontium - 90 Its presence in bones can cause bone cancer, cancer of nearby tissues, and leukemia. Exposure to 90 Sr can be tested by a bioassay, most commonly by urinalysis.bone cancerleukemiabioassayurinalysis 31 Slide 32 Iodine -131 131 I is a fission product with a yield of 2.878% from uranium-235,  and can be released in nuclear weapons tests and nuclear accidents.fission productyield uranium-235 nuclear weapons testsnuclear accidents However, the short half-life means it is not present in significant quantities in cooled spent nuclear fuel, unlike iodine-129 whose half-life is nearly a billion times that of I-131.spent nuclear fueliodine-129 32 Slide 33 Iodine - 131 131 I decays with a half-life of 8.02 days with beta and gamma emissions. This nuclide of iodine atom has 78 neutrons in nucleus, the stable nuclide 127 I has 74 neutrons. On decaying, 131 I transforms into 131 Xehalf-lifebeta gammanuclideatom neutrons 131 Xe The primary emissions of 131 I decay are 364 keV gamma rays (81% abundance) and beta particles with a maximal energy of 606 keV (89% abundance). 33 Slide 34 Iodine -131 The beta particles, due to their high mean energy (190 keV; 606 kev is the maximum, but a typical beta- decay spectrum is present) have a tissue penetration of 0.6 to 2 mm. Due to its mode of beta decay, iodine-131 is notable for causing mutation and death in cells which it penetrates, and other cells up to several millimeters away.beta decay 34