# Chapter 10 Nuclear Physics Lab.pdfChapter 10 Nuclear Physics 10.1 Nuclear Structure and Stability 10.1.1 Activity: Atomic Number and Nucleon Number 10.2 Radioactivity and Radioactive Decay

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Chapter 10

Nuclear Physics

10.1 Nuclear Structure and Stability

10.1.1 Activity: Atomic Number and Nucleon Number

10.2 Radioactivity and Radioactive Decay

10.2.1 Activity: Types of Radioactive Decay

10.2.2 Activity: Predicting the Half-Life of a Radioactive Isotope

10.2.3 Experiment: Measuring the Half-Life of a Radioactive Isotope

10.2.4 Activity: Radioactive Decay Series

10.3 Nuclear Fission and Nuclear Reactors

10.3.1 Nuclear Fission

10.3.2 The Nuclear Power Plant

10.4 Nuclear Fusion

10.4.1 Nuclear Fission vs. Nuclear Fusion

182 CHAPTER 10. NUCLEAR PHYSICS

10.1 Nuclear Structure and Stability

10.1.1 Activity: Atomic Number and Nucleon Number

Activity:

1. Write the following isotopes in AZX notation. The number of neutrons in the nucleusis given in parentheses.

(a) Carbon (7)

(b) Zinc (36)

(c) Radon (136)

(d) Uranium (147)

2. Using a periodic table, identify the following elements and calculate how many neutronsare in the nucleus.

(a) 2411X

(b) 6529X

(c) 13153 X

(d) 21284 X

3. Two atoms have the same nucleon number. Are both atoms necessarily the sameelement?

10.2. RADIOACTIVITY AND RADIOACTIVE DECAY 183

10.2 Radioactivity and Radioactive Decay

10.2.1 Activity: Types of Radioactive Decay

Activity:

1. Write out the decay process for each of the following isotopes:

(a) decay of 21684 Po

(b) decay of 13755 Cs

(c) + decay of 2211Na

(d) decay of 15266 Dy

2. The chart below shows the masses of several nucleii and nuclear particles. Use thechart to answer the following questions:

Particle/Nucleus Mass (amu)proton 1.007825 4.002603

20680 Hg 205.97749921082 Pb 209.98416321083 Bi 209.984120

23490 Th 234.04359323791 Pa 237.05114023892 U 238.050784

184 CHAPTER 10. NUCLEAR PHYSICS

(a) 23892 U decays by decay. One question that is reasonable to ask is Why does23892

U emit an particle rather than a single proton? Write an equation for eachdecay process and then calculate the energy of the parent nucleus and productsfor each reation. Is emission of a single proton feasible? Why or why not?

3. 21082 Pb can decay either through decay or decay. Write a reaction for each of these

processes and calculate the enrgy released upon transumtation of lead in each case.

10.2. RADIOACTIVITY AND RADIOACTIVE DECAY 185

10.2.2 Activity: Predicting the Half-Life of a Radioactive Isotope

Activity:Suppose you have a collection of 400 cubes in which each cube has 5 white sides and 1 blackside.

1. Assume that each cube represents a radioactive nucleus. If you rolled the cube sometime during a one minute period, what is the probability that a black side will comeup?

2. Suppose you roll a collection of N(0) = 420 cubes during a one minute period. In thisroll, how many of the cubes should have a black side facing up?

This is the number of decayed nucleii N .

3. How many undecayed dice are left after 1 minute? This is your value for N(1).

4. If you remove the decayed dice and roll the remaining N(1) dice, how many will decayin the next minute? How many will remain?

5. In Excel, create a spreadsheet to calculate N(t) and the decay rate N/t for the firstthirty minutes of decay.

186 CHAPTER 10. NUCLEAR PHYSICS

6. Plot N(t) vs. t and fit it with an exponential function. According to this fit, what isthe decay constant of this isotope?

7. Based on the decay constant from your fit, what is the half life of this isotope?

8. Suppose instead of a nucleus decaying when a black side was rolled, it decayed whena white side was rolled? How would this affect the decay rate and the half-life of theisotope?

10.2.3 Experiment: Measuring the Half-Life of a Radioactive Iso-tope

Equipment:420 cubes, each with one black side

Experiment:

1. Divide the cubes among your self and your classmates. Record N(0) = 420 in yourspreadsheet.

2. Roll all four hundred twenty cubes during the first minute. Remove the decayed cubesand record the number of undecayed cubes in your spreadsheet.

3. Repeat this 29 more times and fill the results into your spreadsheet.

10.2. RADIOACTIVITY AND RADIOACTIVE DECAY 187

4. Plot N(t) as a function of time and again calculate the half life of the isotope. Doesit agree with your theoretical prediction? Calculate the percent error. Is there wayto modify the experiment so that the half-life would be closer to the predicted value?Attach your graph in the space below.

188 CHAPTER 10. NUCLEAR PHYSICS

10.2.4 Activity: Radioactive Decay Series

Activity:In the figure below, fill in the missing information into the decay sequence.

232Th

14 billion years

! ?6.7 years

" 228Ac6.1 hours

228Th

1.9 years

!?3.7 days

212Pb

11 hours

!

216At

164 s

"

?220Rn55 s

?

61 minutes

!

"

?

.16 s

?

? ! 208Tl3.1 minutes

212Po

0.3 s

?

! ?stable

"

Figure 10.1

10.3. NUCLEAR FISSION AND NUCLEAR REACTORS 189

10.3 Nuclear Fission and Nuclear Reactors

10.3.1 Nuclear Fission

Activity:

1. Go to the website

phet.colorado.edu/simulations/sims.php?sim=Nuclear_Fission

and click Run Now. A Java applet should load and run on your computer.

2. Select the Chain Reaction tab. The first screeen you see has a single 23592 U nucleus.Fire the neutron gun and observe the reaction. Describe your observations in thespace below.

3. Write a reaction for the process you observed assuming one of the daughter productsis 14156 Ba.

4. Now change the number of 23592 U nuclei to 0 and the number of23892 U nucleii to 1. Fire

the neutron gun at the 23892 U nucleus (you may need to tilt the gun). Describe yourobservations in the space below.

190 CHAPTER 10. NUCLEAR PHYSICS

5. Write a nuclear reaction for the process you observed.

6. Which isotope of uranium undergoes fission according to your observations?

7. Now try different combinations of 23592 U and23892 U nucleii. When do you get a chain

reaction?

8. The natural abundance of 23592 U is less than 1%. According to your observations, cannaturally occuring urnaium be used to carry out a chain reaction? Why or why not?

10.3.2 The Nuclear Power Plant

Activity:

1. In the same simulation that you used in the last activity, click on the Nuclear Reactortab.

10.3. NUCLEAR FISSION AND NUCLEAR REACTORS 191

2. Begin with the control rods all the way in and fire the neutrons. What happens tothe reactor? Describe your observations of the temperature, energy output and poweroutput below. Reset the nucleii.

3. Now pull the control rods all the way out and fire the neutrons. What happens tothe reactor? Describe your observations of the temperature, energy output and poweroutput below. Reset the nucleii.

4. The goal of a nuclear power plant is to keep a fairly constant output power whilekeeping the temperature low enough not to damage the reactor. In this simulation youwant to keep the temeperature at or below the gray region. Run the simulation andattempt to keep the power constant and the temperature under control. In the spacebelow, describe how you had to move the control rods to achieve this.

192 CHAPTER 10. NUCLEAR PHYSICS

10.4 Nuclear Fusion

10.4.1 Nuclear Fission vs. Nuclear Fusion

Activity:

Particle/Nucleus Mass (amu)10n 1.008721H 2.014131H 3.016142He 4.0026

14054 Xe 139.9229438 Sr 93.91523592 U 235.044

1. Calculate the amount of energy released for the following reaction using the values inthe table above:

10n+

23892 U14054 Xe +9438 Sr + 210n

10.4. NUCLEAR FUSION 193

2. Calculate the amount of energy released for the following reaction using the values inthe table above:

21H +

31 H42 He +10 n

3. Which reaction produces the most energy per reaction?

4. In a kilogram of hydrogen there are 6.0 1026 atoms while in a kilogram of uraniumthere are 2.6 1024 atoms. On a per kilogram of fuel basis, which reaction is moreefficient?

5. Which process would be the best for a nuclear power plant? Explain your reasoning.

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