1. APES Unit 3 – Energy Lesson 3 – Half Life & Nuclear Decay

2. “Half Life of a Penny” Activity Read the background Follow the procedure, using a can of pennies Answer the questions Graph your data

3. Why is knowing the half life important? The measurement of isotopes has many applications in environmental science as well as in other scientific fields. For example, carbon in the atmosphere exists in a known ratio of the isotopes carbon-12 (99%), carbon-13 (1%), and carbon- 14 (which occurs in trace amounts, on the order of one part per trillion). Carbon- 14 is radioactive and has a half-life of 5,730 years.Carbon-13 and carbon-12 are stable isotopes. Living organisms incorporate carbon into their tissues at roughly the known atmospheric ratio. But after an organism dies, it stops incorporating new carbon into its tissues. Over time, the radioactive carbon-14 in the organism decays to nitrogen-14. By calculating the proportion of carbon-14 in dead biological material—a technique called carbon dating— researchers can determine how many years ago an organism died.

4. Geiger Counters

5. Fission The naturally occurring isotope 235 U, as well as other radioactive isotopes, undergoes a process called fission. Fission - a nuclear reaction in which a neutron strikes a relatively large atomic nucleus, which then splits into two or more parts. This process releases additional neutrons and energy in the form of heat. The additional neutrons can, in turn, promote additional fission reactions, which leads to a chain reaction of nuclear fission that gives off an immense amount of heat energy. In a nuclear power plant, that heat energy is used to produce steam, just as in any other thermal power plant. However, 1 g of 235 U contains 2 million to 3 million times the energy of 1 g of coal.

7. Nuclear reactors A properly designed nuclear reactor will harness the kinetic energy from the three neutrons in motion to produce a self- sustaining chain reaction of nuclear fission. The by-products of the nuclear reaction include radioactive waste that remains hazardous for many half-lives—that is, hundreds of thousands of years or longer.

9. Types of Nuclear Reactors - FISSION Nuclear fission – All commercial power reactors that generally use uranium and its product plutonium as nuclear fuel – Fission reactors can be divided roughly into two classes, depending on the energy of the neutrons that sustain the fission chain reaction: Thermal reactors - (most common) use slowed or thermal neutrons to keep up the fission of their fuel. Fast neutron reactors (less common) use fast neutrons to cause fission in their fuel. No neutron moderator & use less- moderating coolants. More difficult to build and more expensive to operate.

10. Types of Nuclear Reactors - FUSION Nuclear fusion – The reaction that powers the Sun and other stars, where lighter nuclei are forced together to produce heavier nuclei  heat experimental technology, generally with hydrogen as fuel Requires a reactor that will heat material to temperatures 10x those in the core of the Sun

11. Properly Functioning Nuclear Power Plants Objective: harness the heat energy from fission to make steam Must be able to slow down the fission reaction to allow reactions to take place at the right speed. (Add water!) Control rods can be inserted to absorb excess neutrons to slow down or stop the fission reaction. Slowing down must occur to avoid a meltdown

12. Where does the Uranium come from? It may take 2000 pounds of uranium ore to produce 6.6 pounds of nuclear fuel. Miners remove large amounts of host rock, remove the uranium, leave rock pile behind (typically seen in Australia, western US and parts of Canada). Although mining requires fossil fuels and leaves behind a disturbed area, a much smaller volume and mass of uranium is needed to generate a quantity of electricity versus coal.

14. Pros & Cons of Nuclear Energy No air pollution (CO 2 emissions), therefore “clean” energy Allows for independence from fossil fuel resources if limited to begin with. Commonly used in France (70% + ), Germany, Spain, Japan… (US = 20%) Expensive to build, partly b/c of protests & legal battles Where to put radioactive waste? Fear of nuclear weapons Possibility of accidents

15. Accidents that made history March 28, 1979, at the Three Mile Island nuclear power plant in Pennsylvania, operators did not notice that a cooling water valve had been closed the previous day. This oversight led to a lack of cooling water around the reactor core, which overheated and suffered a partial meltdown. The reactor core was severely damaged, and a large part of the containment structure became highly radioactive. An unknown amount of radiation was released from the plant to the outside environment.

16. Chernobyl, Ukraine 10x worse than Hiroshima! April 26, 1986 Routine test + safety regulation violation (deliberate disconnect of emergency cooling systems and control rod removal) = Overheating  BOOM! http://www.youtube.com/watch?v=bSRC1_OZ PIg http://www.youtube.com/watch?v=bSRC1_OZ PIg

17. Radiation & Human Health

19. Use the 2 video clips on the next slide to fill out this chart (handout provided in class) Things the video won’t tell you: Alpha is 2 protons & 2 neutrons which (in this activity) has a mass of 24 g. Beta has (in this activity) a mass of 0.003 g.\ Gamma has no mass. Neutrons are single particles, with a charge of 0, attracted to nothing (b/c it doesn’t have a charge), mass of 6 g. Single 0 no 6 attraction 24 0.003 0

20. Alpha, beta & gamma decay https://www.khanacademy.org/science/chemistry/radioactive-decay/v/types-of-decay Khan Academy explaining how these different types decay – for your viewing pleasure if you want a different explanation Alpha Decay: 2:50-6:08; Beta decay: 6:09 – 8:50; Gamma decay: 11:50 – 12:14 Explanation of alpha, beta & gamma radiation and how to protect from them, and how they can enter the body and biological tissue http://www.youtube.com/watch?v=27qSAqafQ6o 3 types of rays and degree of penetration http://www.youtube.com/watch?v=VTHQYjkCqV0http://www.youtube.com/watch?v=VTHQYjkCqV0

21. 1.Which type of radiation do you think travels the fastest? Why? 2.Which is the heaviest? 3.Which one will move through you the farthest? 4.Which one is the most dangerous from the outside? To which body parts? 5.Which ones might be the most dangerous if they got inside you and moved through the soft tissues of the body? Why?

22. 1.Which type of radiation do you think travels the fastest? Gamma Why? Its so light & tiny 2.Which is the heaviest? alpha 3.Which one will move through you the farthest? alpha 4.Which one is the most dangerous from the outside? gamma To which body parts? Reproductive system 5.Which ones might be the most dangerous if they got inside you and moved through the soft tissues of the body? alpha Why? So big it can puncture holes, moves so slow it can deposit more radiation in you Answers

23. Radiation Predictions-Nuclear Equations

24. Radiation Card Game Rules for Predicting Nuclear Reactions Alpha decay involves the loss of a 4 2 He so the mass decreases by 4 and the atomic number decreases by 2. A beta decay involves the loss of one electron from the nucleus so the mass remains constant and the atomic number increases by 1.

26. Can lower-grade uranium be used? A normal reactor is able to consume less than 1% of the natural uranium that begins the fuel cycle, whereas a breeder reactor can utilize a much greater percentage of the initial fissionable material, and with re-processing, can use almost all of the initial fissionable material. Like a conventional nuclear reactor except that there is an U-238 blanket to capture and reflect neutrons back to the core, and liquid sodium is used as coolant in extreme temperatures surrounding the reactor Also can utilize thorium (more abundant than uranium), so it uses a more easily obtainable fuel & uses less fuel and generating less waste per unit of energy than other reactors.

27. Breeder Reactors

28. So is Nuclear Power Renewable or Non-Renewable? Non-renewable because it requires Uranium, which is mined from the ground. While nuclear power is not the most readily used type of energy, there is still a limited amount of uranium on Earth.