Name______Per. ______Date______
Nuclear Fission Phet Simulation Activity
Go to Phet Simulations at phet.colorado.edu. Find and open the simulation called Nuclear Fission, or go to:
Click on “Run Now.”
For questions about isotopes of uranium, go to:
Fission – One Nucleus:
Click on the “Fission: One Nucleus” tab. Experiment with shooting the neutron gun and watch what happens.
1)What happens when the U-235 nucleus is first “hit” with a neutron? What isotope is made?
What does Wikipedia say about this isotope? If it didn’t fission, where would it end up?
2)What happens after the isotope fissions? What products are made? What are the daughter isotopes? What else is released in the fission process?
3)Look up and list the half-lives of the daughter isotopes. Will these radioisotopes require long-term storage?
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.
4)Click the ‘Reset All’ button and then set the initial number of U-235 nuclei to 100 and U-238 to 0. What happens when you fire the neutron gun?
5)Explain what makes this a “chain reaction”.
6)Click ‘Reset’ and then set the initial number of U-238 nuclei to 100 and U-235 to 0. Explain what happens when you fire the gun. Does this cause a chain reaction? Try multiple times to start a chain reaction with the U-238. Explain why this happens. See U-238 the Wikipedia website for an explanation.
Look up U-239, the product of neutron bombardment of U-238 in
a nuclear reactor.
What is U-239’s half-life? ______
What is the final product in the decay series for U-239? ______
What is its half-life? ______
What does the Wikipedia site say about the use for this final product in the U-239 decay series?
7)Set the initial numbers of U-235 nuclei and U-238 nuclei to the numbers in the table below. Record your results.
U-235 / 100 / 70 / 50 / 30 / 0U-238 / 0 / 30 / 50 / 70 / 100
% of 235U fissioned after 1 firing
# firings required to fission all 235U / N/A
What happens to the reaction as the proportion of U-238 nuclei increases? Explain why this happens.
8)Look up U-238 on the Wikipedia site. Why is having some U-238 in a nuclear reactor important?
9)If you were trying to design the most efficient nuclear fission reactor possible, what ratio of U-235 to U-238 would you want? Keep in mind the issues with keeping chain reactions under control. Explain why you pick this ratio.
10)Look up the percentage of U-235 and U-238 in naturally occurring uranium:
______%U-235______% U-238
What does this imply about what must be done to uranium ore in order to use it in a nuclear reactor? Why do you think they call the processing of uranium ore “enrichment?” This website might help in your understanding:
Nuclear Reactor:
Select the “Nuclear Reactor” tab at the top. Click on the picture box, so you can see what actual rods in a nuclear reactor look like. Experiment with changing the height of the control rod adjustor and firing the neutrons and watch what happens. Then answer the questions below.
11)Watch very closely to the fission reactions as they happen. Specifically watch what 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?
12)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.
13)If the purpose of a nuclear reactor in a power plant is to produce energy, why are there control rods?
14) One way to control the temperature in a nuclear reactor is to keep the control rods fully/mostly inserted, and then keep firing neutrons into the reactor every time the nuclear chain reaction dies down. What would be a disadvantage of this method?
15)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?