Science 1120: Experiment 16: Part II: Fission:

This part of the lab will utilize the Interactive labs developed by the University of Colorado Physics Department

1. Click on the link Nuclear Physics: http://phet.colorado.edu/new/simulations/sims.php?sim=Nuclear_Physics

Trial number	Time (msec)
1
2
3
4
Average

2. The first simulation shows a single U-235 atom undergoing Alpha decay. Click the RESET button. The clock on the right will begin. When the atom has decayed the clock will stop. Record the time in the table at the right. Click reset a 2^nd and 3^rd time and record the time when the atom decays. Determine the average time. Is there a pattern for the decay time?

4. What happens when a U-235 atom decays? __________________

5. Select the FISSION: ONE NUCLEUS option at the upper left and then click on FIRE neutron. What happens to the nucleus after the neutron hits it? _________________. How many particles are produced? ______

6. Next select CHAIN REACTION. You will see one U-235 nucleus in the center. Select FIRE NEUTRON and describe what happens. _____________________

7. Select the number of U-235 and U-238 nuclei as shown in the table below on the left and then FIRE NEUTRON.

Record the percent of nuclei fissioned. Repeat for trials 2 and 3 and record the average.

Number U-235	Number U-238	% Fissioned: 1	% Fissioned: 2	% Fissioned: 3	% Fissioned average
10	50
30	50
10	0
25	0
50	0
100	0

8. What effect does having additional U-238 nuclei on the number of fissioned nuclei?

9. Repeat step 7 with 30 U-235 and 70 U-238 atoms using the containment vessel. What is the result?

10. Repeat step 7 with just 30 U-235 atoms using the containment vessel. What is the result?

11. The ratio of U-235/U-238 in uranium mined from the Earth is 1%. Could mined uranium be used to develop a nuclear bomb? Explain.

12. What is meant by enriching uranium? Why does Uranium need to be enriched in order to be used for a nuclear reactor or for the development of a nuclear weapon?