Fundamental Atomic Particles Part 2

1. Fundamental Atomic Particles Part 2 Radioisotopes Geological Dating Nuclear Energy (Fission, Fusion and Bombs)

2. Learning Goals Students will be able to: • the types of radioactive decay in elements • explain the term nuclear fission and nuclear fusion • understand the process of nuclear power generation • understand the process of radioactive decay and half-lives

3. Success Criteria Students will be able to: • Explain how much of a radioisotope remains provided ½ life • Determine the decay products of a radioisotope and write a decay equation. • being able to give an example of nuclear fission and nuclear fusion • list the steps required to generate electricity from nuclear fission • giving the advantages and disadvantages of nuclear power generation • explain how the concept of half-lives can be employed for Radiometric Dating

4. Radioisotopes • Some isotopes are unstable. These isotopes regain stability by releasing particles, absorbing particles or releasing radiation. • We call the release of particles “radioactivity” and hence these unstable isotopes are called radioisotopes. • The release of particles and electromagnetic radiation (remember Grade 10 Optics) is called radioactive decay. • Often measure with a Geiger counter.

5. Roentgen (Röntgen) • Radioactivity was discovered by Wilhelm Roentgen in 1895. He was using a Crookes tube to create an electrostatic charge and noticed that it exposed a photographic plate. • He knew some sort of invisible ray or force must be responsible and nicknamed them X-rays (other scientists called them Roentgen Rays)

6. Roentgen (Röntgen) • Roentgen produced the first X-ray, it was a picture of his wife’s hand. She replied that she had “seen her death” when she saw the photographic image. • This set off a flurry of Radioactive research that led to many important discoveries. • Roentgen won the first ever Nobel Prize in Physics in 1901. Element 111 was named after him (Roentgenium)

7. Radioactive Decay • Alpha decay (4α) – the spontaneous emission of a helium nucleus from the atom 226Ra → 222Rn + 4He • These particles are easily blocked by a sheet of paper, but readily damage chromosomes if inhaled or ingested . Alpha decay equation

8. Radioactive Decay • Beta decay (β-) - a neutron is converted into a proton and a beta particle (a high electron created within the nucleus but otherwise indistinguishable from an orbital electron) 14C → 14N + 0β Beta decay equation

9. Radioactive Decay • Gamma decay (0γ) – a gamma particle is a high energy photon which is emitted when the nucleus is in an excited state. • Gamma rays are often given off after other nuclear reactions. • Gamma rays are dangerous because it is hard to block them, but this also makes them useful for medical diagnostics. • Nuclear reactors are surrounded by domes made of lead infused concrete.

10. Radioactive decay summary

11. Decay emissions

12. Radiation have different penetrating abilities

13. Complete these Radioactive Decay Equations: • Write the alpha decay equations for: • Ra-222 • Ac-225 • Au-185 • Gd-149 • Write the beta decay equations for: • Rb-87 • Sr-90 • C-14

14. Complete these Radioactive Decay Equations: α-decay equations β-decay equations

15. Nuclear Reactions

17. Nuclear Fission • http://www.youtube.com/watch?v=mBdVK4cqiFs (Nuclear Fission reaction explained) • http://www.youtube.com/watch?v=_pY5HeZpNr8 (Tyler DeWitt) • Nuclear fission is a process whereby large nuclei are split into smaller nuclei. • We can split up a big (unstable) nucleus by bombarding it with small particles (like neutrons). • The weak nuclear force binding protons and neutrons is overcome and a tremendous amount of energy is released. • On Earth, this is not a natural process! • It does occur in the cores of massive stars and in supernovas.

18. Nuclear Fission • Nuclear fission of heavy elements was discovered on December 17, 1938 by Otto Hahn and his assistant Fritz Strassmann • It was explained theoretically in January 1939 by Lise Meitner and her nephew Otto Robert Frisch. • Frisch named the process after the biological fission of living cells. • It is an exothermic reaction which can release tremendous amounts of energy both as electromagnetic radiation and as kinetic energy of the daughter elements. • Note the huge amount of energy (210 MeV) released.

19. Nuclear Fission • The masses of the products (Krypton, Barium and 3 neutrons) is less that the mass of the reactants (Uranium and a neutron). Where does this mass go? • Mass is converted to energy • Remember Einstein’s E=mc2 (E = energy, m = mass, c = speed of light) • This means a small amount of mass (x c2 which is a massive number) is converted to a huge amount of energy.

20. Nuclear Power Generation • Nuclear Chain Reactions can be used to generate tremendous amounts of heat. • The heat can be used to generate large amounts of electrical power • In Ontario, we have 3 large Nuclear Generating Stations – Pickering, Darlington (near Oshawa) and Bruce (near Goderich) • Nuclear energy is also used to power nuclear submarines and some spacecraft The 3 high energy neutrons released from one nuclear fission go on to start 3 more fission reactions and so on. If left unchecked, a massive nuclear explosion (as in a nuclear bomb occurs) Neutron absorbing control rods slow down the reaction to a manageable pace

21. Nuclear Power • http://www.youtube.com/watch?v=GOx7NMlYl0k (Ontario Power Generation) • http://www.youtube.com/watch?v=ueainTAy7G0 (Tutor Vista) • http://www.youtube.com/watch?v=1U6Nzcv9Vws (ELearnIn)

22. Nuclear reactor (fuel rods and fuel bundles)

23. The CANDU reactor • CANadianDeutueriumUranium Reactor

24. Steps to Generating Nuclear Power • Nuclear Reaction generates heat. • The reaction heats the moderating water (highly radioactive). • This hot, pressurized water heats water (non radioactive) into steam in the steam generator (boilers made right in Cambridge at Babcock-Wilcock). • This pressurized steam turns the turbines. (This steam is cooled by lake water). • The turbines turn the generators (turning massive magnets in a coil). • The generators create electricity.

25. Nuclear Generating Stations Pickering Generating Station (See the containment domes)

26. The Nuclear Power Debate • http://www.youtube.com/watch?v=eWwhRjGBNb4 (top ten facts about Chernobyl) • http://www.youtube.com/watch?v=pNvmShXD0vw Zero Hour: Disaster at Chernobyl (Discovery Channel) (2004)

27. The Nuclear Power Debate Advantages • Tremendous amounts of energy produced • No air pollution from the combustion of hydrocarbons – no CO2 emissions • Canada has a large supply of Uranium Disadvantages • Potential for a nuclear meltdown – Chernobyl, Fukushima, Three Mile Island. • Spent fuel can be used to create nuclear weapons • Long term storage of nuclear waste material (fuel rods are stored on-site in pools for 10-12 years (radioactive for thousands of years)

28. Nuclear Fusion • http://www.youtube.com/watch?v=Cb8NX3HiS4U (Nuclear Fusion | Fusion energy explained) • http://www.youtube.com/watch?v=5KMmlSDWFIc (The race to Nuclear Fusion)

29. Nuclear Fusion • Nuclear fusion is the energy that fuels the sun – hence all life on planet Earth ultimately derives its energy from a fusion reaction in the core of the sun. • It is the opposite of fission – in fusion, two light atoms are fused into larger atoms – typically two isotopes of hydrogen, deuterium (H-2) and tritium (H-3) are fused into a helium. • Since the mass of the products is slightly less than the mass of the reactants, some mass has been converted to energy (remember the famous E=mc2 equation)

30. Nuclear Fusion • It takes temperatures exceeding 15 million degrees K. • In the Universe this only occurs in the cores of stars. • All elements heavier than hydrogen were created by stars and spread through the universe by novas (stellar collapses and explosions). • All elements heavier than iron were created in supernovas (explosions of massive stars). Hence, much of the Earth and the solar system were created from the remnants of a supernova. Take SES4U to learn more

31. Nuclear Fusion • Since you are mostly made of C, H, N and O; you are “star dust”! Listen to the words of the famous song “Woodstock” written by Canadian Joni Mitchell and sung by Crosby, Stills, Nash and Young. • http://www.youtube.com/watch?v=g25DlXOWmMo • This classic “hippie” song is mostly written about the famous Woodstock concert of 1967, but it references the fact that all humans are made from carbon produced billions of years ago.

32. Nuclear Fusion • Despite the temperatures required for fusion, it has been attempted on Earth by Physicists. • The obvious problem is creating temperatures of 15 million K + and coming up with something to contain the extreme heat. (at this heat all matter reaches the 4th state called Plasma in which electrons are stripped from atoms) • The solution is contain the heat in a torus (doughnut) shaped magnetic field. The devices are called Tokomaks. • Another solution uses laser blasts on a hydrogen target.

33. Nuclear Fusion • Currently, we have not been able to gain more energy than we have put into the experiments. • Should humanity ever be able to successfully create a fusion reactor capable of producing energy, a limitless supply of energy would exist. • Famously, a scientist once said “We have been 20 years away from Fusion power for 30 years”

34. Nuclear Weapons • http://www.youtube.com/watch?v=fIbACkLU-38 (How do Nuclear Bombs work?) • http://www.youtube.com/watch?v=Aza-2wopCFY (Effects of a nuclear bomb 2013 HD) • http://www.youtube.com/watch?v=bKFsZ-2Z21c (The Hiroshima Bombing) • http://www.youtube.com/watch?v=h7vyKDcSTaE (The IVY-MIKE test of the first H-bomb)

35. Atomic Bombs • Atomic bombs require uranium-235 and/or plutonium-239 to produce a fission chain reaction • Natural uranium ores contain about 99.28% U-238. Uranium-235 must be enriched in a very difficult and dangerous process from 0.72% to about 3-5% in a nuclear reactor and to about 20% for a nuclear bomb (weapons-grade). • One of the products of nuclear fission in nuclear reactors is plutonium-239. It is unfortunately the key explosive product in modern atomic bombs. • The remaining or depleted uranium is much less radioactive and is used in armour-piercing shells. Many veterans of the Gulf War suffer from health problems due to the chemical effects of depleted uranium

36. Hydrogen Bombs • The more potent H-bomb uses a fission reaction to start a fusion reaction. H-bombs contain U-235 or Pu-239 to start a fission explosion. • The fission explosion starts a fusion reaction with deuterium (an isotope of hydrogen with one neutron). • The deuterium is fused into helium to create a greater (up to 100 times greater than Hiroshima) explosion. Though many H-bombs have been tested, none has ever been used in war. • These are known as thermonuclear weapons

37. Radiometric Dating

38. Radiometric dating • Most igneous rocks contain atoms which are unstable. These “radioisotopes” decay by ejecting particles and releasing radiation. • Uranium – 238 goes through a sequence of decays before eventually turning into lead – 206. The rate at which this decay occurs has be en determined scientifically

39. Radiometric Dating • Igneous rocks containing zircon (ZrSiO4) have atoms of U that substitute for Zr in the crystal structure. • Zircons are perfect for radiometric dating because they do not erode easily and they contain radioisotopes. • Once the zircon crystallizes, from that point on the ratio of U-238/Pb-206 begins to decrease.

40. Radioisotope decay chains • Radioisotopes often decay into other unstable radioisotopes in a chain of α- and β-decay reactions until a stable isotope is formed. • This is the common decay chain from U-235 to Pb-207 or U-238 to Pb-206 • This sequence was determined by the Curies.

41. Radioisotope decay chains • Note how the atomic number changes after each decay (α-decay decreases atomic number by 2 and β-decay increases atomic number by 1)

42. Radiometric Dating • The rate of decay is measured in half-lives. In the case of U-238, half of the material in a rock will decay into Pb-206 in 4.5 billion years. • After several half-lives the amount of original U- 238 decreases to a half, a quarter, an eighth and so on…

43. Radiometric dating • Scientists must choose an appropriate radioisotope for each application. • Which isotope would be useful for dating: • Rocks that are over 2 billion years old? • Dinosaur fossils that are about 200 million years old? • The wood from an ancient ship found at the bottom of the Sea? http://www.youtube.com/watch?v=phZeE7Att_s (Carbon Dating) http://www.youtube.com/watch?v=s0_i8ltnbNU (U-Pb dating and K-Ar dating)

44. Radiometric dating Isotopes Commonly used for Radiometric Dating

45. Carbon-14 Dating • Carbon-14 Dating is more commonly used by Archeologists. • Since all living things contain carbon, this method can date any organic or formerly living thing • C-14 exists is a rare isotope of carbon, existing as only about 1 part per trillion carbon atoms. Thus a sample of carbon needs to be reasonably large (up to 1 gram)

46. Carbon-14 Dating • Carbon-14 is produced continually in the atmosphere and becomes part of many CO2 atoms. • Carbon dioxide is continually taken up by plants and moves through the carbon cycle. • Animals and plants continue to ingest new C-14 as long as they are living. Once an organism dies, it stops taking up new C-14 and the ratio of C-14/C-12 starts to decrease (following the pattern of half-lives seen below)

47. Carbon-14 Dating • Scientists measure the ratio of C-14/C -12 to determine how many half lives have occurred and can date the sample

48. Carbon-14 Dating • Carbon dating mathematical Decay Equation

49. Carbon-14 Dating • Carbon dating can be calculated using a more complex formula, but we will use a more simplified approach. • http://www.chemteam.info/Radioactivity/WS-Half-life-C14only.html. • http://www.youtube.com/watch?v=pUyLtcc3bUA • The links above use better, but more sophisticated approaches for carbon dating questions.

50. C-14 Dating Question • A sample taken from a Woolly Mammoth found frozen in the ice is thawed and analyzed in a lab. It contains 0.32 mg of C-14. When the mammoth was alive the sample would have contained 2.56 mg of C-14. How old is the Mammoth?