The half- life of C- 14 is roughly

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Chpt 4 Wrap-up Chapter 4. Nuclei and Radioac5vity Student Objec5ves (found in Study Aids sec5on of our website) A(er mastering the concepts of this chapter, you should be able to: 1.

1 Chpt 4 Wrap-up Chapter 4. Nuclei and Radioac5vity Student Objec5ves (found in Study Aids sec5on of our website) A(er mastering the concepts of this chapter, you should be able to: 1. define the term radia%on and give several examples. 2. discuss several natural and man- made sources of radiaeon. 3. define the terms ionizing radia%on and non- ionizing radia%on and discuss why exposure to ionizing radiaeon can lead to adverse health effects. 4. explain what is meant by the terms x- rays, gamma- rays, alpha par%cles, and beta rays. (also neutrons and protons ) 5. discuss the meaning of the term isotopes, and interpret the notaeon for specifying specific isotopes such as 12 C, 13 C, U- 235, and U discuss the meaning of the terms enriched Uranium, and depleted Uranium. 7. solve problems involving radiaeon exposures measured in the units rem and mrem including conversion between rems and Sieverts. 8. disenguish between short- term and long- term health effects of radiaeon exposure. 9. discuss the short- term health effects resuleng from high levels of radiaeon exposure. Chpt 4 Wrap-up 10. apply the linear hypothesis to esemate the number of excess occurrences of cancer in a populaeon exposed to radiaeon. (Hint: memorize the radiaeon exposure that gives an esemated 1% probability of excess cancer occurrences.) Be able to compare this to typical cancer rates. 11. describe the difference between fission and fusion. (Chpt 5) 12. explain the concept of "half- life" and calculate the fraceon of a radioaceve substance which would remain a(er a given number of half- lives has passed 13. explain the science of 14 C daeng and discuss the types of objects and the range of ages for which it is useful. 14. list several methods of radiometric daeng and their corresponding applicaeons. 15. Explain meaning of the terms dirty- bomb & ICBM. (Chpt 5) The half- life of C- 14 is roughly A) 5 min B) 5 days C) 5 thousand years D) 5 million years E) 5 billion years Chpt 5: Chain Reactions, Nuclear Reactors, and Atomic Bombs 1. History of fission A) Lise Meitner & Otto Hahn B) What is fission? C) First atomic reactor 2. Nuclear reactor fundamentals A) Critical Mass B) Neutron Moderator 3. Chain Reactions 4. Nuclear Bombs A) U-235 and Pu-239 B) First use of nuclear bombs 5. Fusion Bombs 6. Reactor Designs and Nuclear Power 7. Concerns A) Reactor accidents B) Dirty Bombs, Waste disposal Today 1

Wads of thermal energy (3300 Wads a(er 87 years) 7% converted to electrical power (from chpt. 4) Natural Radioactive Decay Pu- 238 U- 238 Half- life of 87 years Half- life of 4.

2 Before talking about bombs and reactors, note: Radioisotope Thermoelectric Generator DO NOT use a chain reaction (Discussed in Chpt. 4) First: Radioisotope Thermoelectric Generator DOES NOT use a chain reaction The New Horizons satellite: 11 kg chunk of plutonium Pu > U alpha + energy Half- life 87 years 6600 Wads of thermal energy (3300 Wads a(er 87 years) 7% converted to electrical power (from chpt. 4) Natural Radioactive Decay Pu- 238 U- 238 Half- life of 87 years Half- life of 4.5 billion years Energy release too slow A Radioisotope Thermoelectric Generator is not a nuclear reactor Solution: neutron induced fission Understanding reactors and bombs requires understanding Fission History of Fission 1905 Einstein s E=mc Rutherford s Model of the Atom 1920 s Adempts to induce decay with protons & alphas 1932 Discovery of neutron 1934 Enrico Fermi produces new isotopes using neutron bombardment (discovers neutrons should be slowed) Then story gets complicated Becomes The Nobel Mistake Enrico Fermi Los Alamos Archives 2

Also in 1934: MeeEng of the American AssociaEon for the Advancement of Science Pi<sburgh, PA Einstein at Carnegie InsEtute of Technology, Dec.

He said he would address a small audience in a small place. His subject: "A Simple Proof of the Equivalence of Mass and Energy." (Back to Fission story) Lise Meitner (1878-1968) - 1906 Ph.D. Univ.

Hahn in their lab "It was not only stupid but also very wrong that I did not leave at once.

3 Also in 1934: MeeEng of the American AssociaEon for the Advancement of Science Pi<sburgh, PA Einstein at Carnegie InsEtute of Technology, Dec Sessions and exhibits were staged in the new Mellon InsEtute of Industrial Research building, a vast, square, $4,000,000 structure. Dr. Einstein would have none of that. He said he would address a small audience in a small place. His subject: "A Simple Proof of the Equivalence of Mass and Energy." (Back to Fission story) Lise Meitner ( ) Ph.D. Univ. of Vienna (w/ Ludwig Boltzmann) Berlin's Kaiser Wilhelm Ins%tute for Chemistry (w/ Max Plank) Hitler comes to power Meitner, although from Jewish family, chooses to stay Meitner and Hahn in their lab "It was not only stupid but also very wrong that I did not leave at once. Lise Meitner Further studies creaeng isotopes using neutrons by Odo Hahn, Lisa Meitner, and Fritz Strassman Unusual results with uranium target Germany annexes Austria Meitner escapes to Sweden (encouraged by Hahn) Fermi awarded Nobel Prize for creaeng elements heavier than uranium but is was a mistake Meets secretly with Hahn conenues correspondence and suggests experiments Meitner s carried so much weight we immediately undertook the necessary experiments Strassmann Dear Lise! There is something about the radium isotopes that is so remarkable that for now we are telling only you Perhaps you can suggest some fantasec explanaeon If there is anything you could propose that you could publish, then it would sell In a way be work by the three of us! O<o Hahn from D. Bodanis E=mc 2 A Biography of Lise Meitner Odo Hahn publishes results (without credit to Meitner) Meitner & Frisch publish explanaeon of fission Meitner coins term fission & Meitner contemplates chain reac%on Hahn awarded Nobel Prize in Chemistry for his discovery of the fission of heavy nuclei Was Meitner s contribu%ons suppressed? Meitner becomes member of Royal Swedish Academy of Sciences Meitner develops theory of fission (with nephew Odo Frisch) Uranium is breaking in two! (plus neutrons) This is called fission Used in reactors and atomic bombs (The sun uses fusion ) Visits U.S. as a celebrity, Woman of the Year Max Planck Medal of German Physics Society 3

4 Meitner to Hahn: "You all worked for Nazi Germany. And you tried to offer only a passive resistance. Certainly, to buy off your conscience you helped here and there a persecuted person, but millions of innocent human beings were allowed to be murdered without any kind of protest being udered Meitner s fission Uranium + n - > Barium + Krypton + neutrons+ energy The chain reaceon Extra neutrons might keep process going Why doesn t it happen all the Eme? Small pieces of uranium neutrons escape Impure uranium neutrons absorbed on other nuclei Fast neutrons not very likely to be reabsorbed reactors can use neutron moderator For bomb, need criecal mass of U- 235 or Pu- 239 First Nuclear Reactor Chicago 1942 (Just 3 years a(er Meitner s paper) Team directed by Enrico Fermi Drawing of Chicago Reactor Argonne Na%onal Labs First self- sustained nuclear chain reaceon 3:53 pm Dec 2, tons uranium 40 tons uranium oxide 380 tons graphite moderators (slows down neutrons so they are absorbed) Cadmium control rods Important! Example of a chain-reaction Assume average of 2 new fission decays for every decay (2 neutrons given off and both induce new decays or 3 neutrons given off and 2/3 induce new decays ) Genera5 on Ini5al Nuclei Neutrons emiked Total Fission Decays ,288 1,048,576 1,048,575 Grams U- 235 Used x x x x x x x ,255 4

Chain reactions Uncontrolled chain reaceons cause exponen%al growth eg. fission bomb (runs unel out of fuel) Which of the following does not represent exponeneal growth?

animal populaeon are controlled by food availability 100 Popula5on 0 Time Time 1 2 4 5 6 7 8 9 10 11 A) A computer virus B) Spread of smallpox C) Epidemic of flu D) Illness from anthrax A

5 Chain reactions Uncontrolled chain reaceons cause exponen%al growth eg. fission bomb (runs unel out of fuel) Which of the following does not represent exponeneal growth? Rate SomeEmes rates are controlled eg. animal populaeon are controlled by food availability 100 Popula5on 0 Time Time A) A computer virus B) Spread of smallpox C) Epidemic of flu D) Illness from anthrax A moderator is something that A moderator is something that A) Slows neutrons B) Slows fission fragments C) Fissions more easily than U- 235 D) Speeds up the chain reac5ons A) Keeps a reactor from running out of control B) Is used in a reactor to make the chain reac5on con5nue C) Is moved into the reactor core to stop the chain reac5on 5

Science A 52 Lecture 22 May 1, 2006 Nuclear Power. What is it? What are its problems and prospects?

Science A 52 Lecture 22 May 1, 2006 Nuclear Power What is it? What are its problems and prospects? Lecture 22, 1 Nuclear Fission On of the most interesting accounts a fission and the discovery of the release