Nuclear1 - Nuclear Fission PhETdocxnuclear1核裂变phetdocx.docx

Nuclear Name: _Page 3 of 3 PhET Simulation: Nuclear Fission 2 eachLearning Goals: After completing this activity, you will be able to explain the concept of a “chain reaction” and how it applies to nuclear fission of Uranium. You will also be able to explain the purpose of the control rods in a nuclear reactor. Directions: Go to the website: /simulations . Click on “Work, Energy, and Power” on the left hand side Choose the simulation titled: Nuclear Fission and then select: “Run Now”. Fission: One Nucleus: 2 each.Select the “Fission: One Nucleus” tab at the top left. Experiment with shooting the neutron gun and watching what happens. Then answer the questions below.1) What happens when the U-235 nucleus is “hit” with a neutron? There are two steps here- describe them both in as much detail as you can. Chain Reaction:Select the “Chain Reaction” tab at the top. Experiment with changing the settings and shooting the neutron gun and watch what happens. Then answer the questions below.2) Set the initial number of U-235 nuclei to 100. What happens when you fire the neutron gun?3) Explain what makes this a “chain reaction”.4) Set the initial number of U-238 nuclei to 100. Explain what happens when you fire the gun and if this is a chain reaction or not. 5) Set the initial numbers of U-235 nuclei and U-238 nuclei to the numbers in the table below. Record your results. 7 Pts.U-2351007050300U-2380305070100% of 235U fissioned after 1 firing # firings required to fission all 235UN/A6) What happens to the reaction as the proportion of U-238 nuclei increases?7) If you were trying to design the most efficient fission reactor possible, what ratio of U-235 to U-238 would you want? Explain why.Nuclear Reactor: Select the “Nuclear Reactor” tab at the top. Experiment with changing the settings and firing the neutrons and watch what happens. Then answer the questions below.8) The bar graphs on the right of the display show the “Power Output” and the “Energy Produced”. What is the difference between these two quantities?9) Watch very closely to the fission reactions as they happen. Specifically watch happens to the loose neutrons after the reaction.a) What happens if the neutrons hit another nucleus?b) What happens if the neutrons hit a control rod?10) Compare the chain reaction that occurs when the control rods are inserted further into the reactor versus when they are pulled all/mostly out of the reactor.11) If the purpose of a nuclear reactor in a power plant is to produce energy, why are there control rods? (When this activity was written, the simulation was called Nuclear Physics. Since then the simulation was divided into 2 simulations: Alpha Decay and Nuclear Fission)Purpose: Describe the process of alpha radiation. Relate potential and total energy to what happens in the nucleus. Investigate a chain reaction.This activity was designed for use in a Global Science class to go along with the chapter on nuclear energy. An example of a student handout follows.Go to /new/index.phpClick on Play with SimsClick on Quantum Phenomena on the left sideClick on Alpha Decay. Also open Nuclear FissionExplore each section of the simulation and then answer the following questions.Alpha Radiation1. Describe how the 211Po atom decays into 207Pb. Include what is happening with the energy and the time it took to decay. You may have to move through the simulation step by step.Fission1. How do the potential and total energy relate to the activity of the U-235 nuclei?2. What is the result of the fission of the 235U?Chain Reaction1. What number of U-235 atoms gives you the highest percent of nuclei fissio