1. Radioactivity and Nuclear Energy
Chapter 19

2. Stable and unstable Most atoms are stable
Meaning they will not fall apart
But all have unstable isotopes that will fall apart over time.
Isotope- atoms with a different number of neutrons
Atoms tend to be stable with the same or slightly larger number of neutrons as protons.

3. Graph of Isotopes
“band of
stability”

4. Radioactivity
(radioactive decay) – the nucleus of unstable atoms breaking apart and emitting particles and/or electromagnetic radiation.
An unstable isotope breaks into a daughter isotope and releases radiation in the process.
Particles and radiation are dangerous.
electromagnetic radiation include things like light, infrared, ultraviolet, x-rays, microwaves, and gamma rays.

5. Radiation It is out there You are exposed to radiation everyday.
Small amounts are not really harmful.
The sun releases radiation that hits the Earth (and you)
Certain products are radioactive (smoke detectors, TV’s and computers)
Even the potassium in bananas is radioactive.

6. Radioactive particles
Only radioactive isotopes will release radiation.
Radioactive isotopes will act exactly like non-radioactive isotopes of the same element until they “fall apart”.
e.g. Carbon -12 is not radioactive. Carbon-14 is radioactive. C-14 will act exactly like C-12 until undergoes radioactive decay.

7. Types of radiation
(alpha)  radiation- 2 protons and 2 neutrons (helium nucleus) are released by the atom
 particle-2 p+ 2 no
(beta)  radiation 1 neutron breaks into a proton and an electron, the electron is released
 particle- an electron
(gamma)  radiation – An energetic atom releases energy as a photon (gamma ray).
There is no particle, just a light pulse.

8. Stopping radiation type of radiation How to stop it Danger Level
a sheet of paper, or skin
Most damaging
 radiation
a sheet of aluminum foil
Damaging
 radiation
several cm of lead
Still damaging

9. diagram

10. Most Dangerous
 particles are the most dangerous if they are not stopped.
They are exceptionally large compared to the other particles
It is like a cannon ball ripping through a cell. If hit, a cell will most likely die.
Because of their size they damage the first thing they hit (they aren’t likely to squeeze through gaps)

11. Continuing
If it hits something nonliving (dead cells or molecules), it will damage the nonliving structure. However, it was already dead.
 particles are much smaller and more likely to squeeze through gaps, penetrating much deeper before hitting and damaging something.
Once the radiation is stopped, it is no longer dangerous. It is only dangerous when it is moving at a high velocity.

12. Where does radiation come from?
only about 18% of the radiation that hits the average person comes from manmade sources.
The majority of that comes from X-rays or related procedures.
The rest are naturally occurring on the Earth.
Mainly Radon gas (naturally occurring)

14. Detecting Radiation
A Geiger counter is the most familiar tool for detecting radiation.
The probe of this device contains argon gas. When radiation hits the gas it ionizes it, or knocks an electron off.
Ar → Ar+ + e-
These electrons falling off creates a weak electric pulse, which makes a speaker click.

15. Half life
Half life is the time it will take for half the material to decay into radiation.
Unstable isotopes have a short half life (3.8 days for Radon-222)
(Carbon-10 has a half life of 19.2 s)
More stable ones have a longer half life (5715 years for Carbon-14)
Stable isotopes have no half life since they do NOT decay. (Carbon-12)

16. More Half life If two half lives pass… the material is not gone
you actually have ¼ remaining
half is left after the first half life, then half of that after the second half life.
Not as much radiation is coming out (since there is less mass) but it is still there.

17. Graphing half life
mass of
isotope
number of half lives

18. Radiodating
The age of materials can be determined if you are capable of comparing the amount of radioactive isotope present now, to the amount of radioactive isotope present at some past date.
Since the half life is a constant rate, you can calculate its age.

19. Finding an age
The amount of some radioactive isotope in an object can be measured.
This amount is compared to the amount assumed to be there when it died.
You count the half lives to determine its age.

20. For example
If you measure 15 g of C-14 and you assume you started with 60 g, then the object is…
11,430 years old
60g30g15g (2 half lives)
5715 years x 2 = 11,430 years

21. Types of radiodating
There are different types of radiodating for different scenarios.
For all radiodating techniques, the amount of a radioactive isotope is compared to an amount present in the past.
The half life is used to determine the age

22. Carbon dating
Dates of some materials can determined using carbon-14 or C-14 dating.
Carbon dating can only be used on things once alive.
Carbon dating is ONLY useful for the recent past (50,000 years maximum)
This is done by measuring the number of radioactive C-14 isotopes.

23. How it works
Radiation on this planet causes radioactive isotopes to form.
A known percentage of the carbon dioxide in the air contains the radioactive C-14 isotope.
This carbon dioxide is used to “build” all living things (plants use it for food, animals eat the plants etc.)

24. Continuing
Therefore all living things are made up of a known percentage of C-14.
Once that living thing dies, it stops taking in new C-14 isotopes.
The radioactive isotope begins to decay at a known rate (half life of 5715 years)

25. Different types of radio-dating

26. Radiodating
Radiodating always require you to determine the amount of radioactive isotopes present in the past and compare it to what is present today.
C-14 works because the amount of C-14 in living things is always the same.
The two types today will compare the amount of daughter isotope present to the amount of radioactive isotope to determine how old it is.

27. Potassium-40 dating
Rocks (never living) can also be dated if they have other certain isotopes.
K-40 decays into Ar-40.
When a rock is formed we can assume all gases would escape, so all argon in a rock should be the product of K-40 decay.
measure the K-40 and compare it to the Ar-40 and you can determine its age.

28. Uranium-238 dating U-238 decays into Pb-206 which is extremely rare.
If you have a rock with U-238 and Pb-206 present, you can assume the Pb-206 came from the decay of U-238.
Scientists have come up with the 4.5 billion year age of the planet using these methods.

29. Other methods
There is a whole list of other isotopes that can be used.
Samarium-neodymium
Rubidium-strontium
Uranium-thorium
Chlorine-36

30. Math
The equation is difficult to use, so instead we will read it off a graph.
Here is equation mf/mi = 1/ 2hl
Percentage left is current mass/initial mass x % = mf/mi x 100
Multiply the number of half lives by the value of one half life to get an age.

31. Problems
If you have 32% of a material left, how many half lives have passed?
1.64 half lives
If you have 17% of Ra-223 left, how old is it?
2.55 half lives x 11 days =
28 days

32. Problems
If original sample had 78 g of Am-241, and you now have 53 g left; how old is the sample?
A sample of Radon-222 is 9.4 days old. There are .27 g present, how much was originally present?

33. Problems
If you have 15 g of Tc-96, and you assume you started with 88 g, how old is the object?
If you have an 8.0 day old sample of Radon-222 and there are 25 g present, how much was there to start?

34. Homework
If original sample had 28 g of Polonium-214, and you now have 13 g left; how old is the sample?

35. Showing Radioactive decay

36. Representing isotopes
Carbon and Carbon- 12
Mass number
The atomic number of Carbon is 6 14 6 C 12 6 C
*mass # on top, atomic # on bottom

37. Showing Alpha Decay + α Rn Po He ~expulsion of 2 p+ and 2 no
Show the alpha decay of Radon-222.
222 86
α decay
218 84
+ α Rn Po
lose 2 p+ so the atomic number is now 84
lose 2 p+ and 2 no so the mass number is now 218
element # 84 is Polonium
The particle is also released 4 2
alpha particle can also be written as He

38. Show the alpha decay of…
Plutonium-244
Polonium-210
Technetium- 98

39. Showing Beta Decay + β Pb Bi e
~conversion of a neutron to a proton and an electron, and expulsion of the electron.
The beta decay of Lead-214
214 82
β decay
214 83
+ β Pb Bi
gain 1 p+ so the atomic number is now 83
lose 1 no and gain 1 p+ so the mass number is the same
element # 83 is Bismuth
The particle is also released -1
beta particle can also be written as e

40. Show the beta decay of…
Potassium-40
Carbon-14
Thorium-234

41. Gamma radiation
In gamma radiation no particle is released, just a “packet” of energy.
Photon- “packet” of energy.
When an atom has too much energy, it is excited, it’s electrons are in higher energy levels.
When they fall back to ground state, they release energy as small little bits.
This energy travels as an electromagnetic wave.

42. Electromagnetic Spectrum

43. Decay Series
More often than not a stable isotope is NOT formed from decay. (,  or others)
You normally form an unstable isotope which decays again
(repeat this several times until you get a stable isotope)
This continual decay is called a decay series.

44. A decay series

45. ~bombs and nuclear power
Nuclear Fission
~bombs and nuclear power

46. Nuclear fission ~the separating of a nucleus of an atom.
This is the process used by nuclear power stations (when it is kept under control).
It is also the process of an atom bomb (when it is allowed to run uncontrolled).

47. Manhattan Project ~construction of the atom bomb, 1942-45
Several scientists associated with this project were Jewish who fled Nazi Germany. Including Fermi and Einstein.
After Germany fell, several tried to stop the bombs from ever being used.
It resulted in the bombing of Hiroshima on Aug 6, 1945 and Nagasaki on Aug 9, 1945.

48. Pre-Manhattan Project
Several scientists fled Nazi Germany, but still had some contact with their old colleagues.
Leo Sziliard and Enrico Fermi built and patented the first nuclear reactor in the United States under the football stadium in the squash courts at the University of Chicago.
Their reactor was far too small to be useful, but the men understood the implications of their discovery.
A “super bomb” could be built with this idea and they knew Germany was working on it.

49. Einstein
Szilard wrote a letter to Einstein, also a Jewish refugee, about his work and the implications.
Einstein signed a letter written by Szilard to president Franklin Roosevelt.
Einstein would later say it was his greatest regret in life.

50. What is needed You need the rare isotope Uranium-235,
or the artificially created Plutonium-239.
The U-235 is bombarded with neutrons, the nucleus absorbs one neutron making the highly unstable U-236.
The nucleus splits in two and releases 3 neutrons.
This releases a lot more energy at once than regular decay ( or ).

51. Difficulties
The hardest part of getting this reaction is having enough fissionable U-235.
Uranium naturally occurs with about 99.8% U-238.
U-238 will act the same chemically and physically to U-235, but it is not fissionable.
Power plants need Enriched Uranium which is about 3-5% U-235
Bombs need Highly Enriched Uranium (HEU) around 90% U-235

52. Nuclear Fission Reaction
235 92 1
[ ]
fission 93 36
140 56
U + n
236 92 U
Kr + Ba 1 +3 n
+energy

53. Chain Reaction
The three neutrons released from the first fission are absorbed by another 3 U-235 atoms.
These atoms each undergo fission and also release 3 neutrons each (9 total).
These hit 9 more U-235 and they undergo fission (releasing 27 neutrons).
Chain Reaction- self sustaining nuclear reaction where one fission causes the fission of others.
(Video)

54. Chain Reaction Diagram

55. Critical mass
~the smallest amount of fissionable material necessary to start a chain reaction.
The fission of 1 g of U-235 releases as much energy as combusting 2700 kg of coal.
The bomb dropped on Hiroshima, “Little Boy” used U The bomb dropped on Nagasaki, “Fat Man”, used Pu-239.
Hiroshima was dropped from the Enola Gay
Nagasaki was dropped from Bockscar
Nagasaki bomb was a 27 kiloton. The largest ever dropped.

56. Bombs Bombs are rated by what an equivalent mass of TNT would do.
Little Boy was a 15 kiloton bomb, Fat Man was a 21 kiloton bomb.
Large atom bombs (fission bombs) can release energy equivalent about 500 kilotons of TNT.
Hydrogen bombs (Fusion bombs) use fission bombs as their starting device.
Fusion bombs can release around the same amount of energy as 50 megatons of TNT (100 atom bombs).

57. Niigata
Kokura

59. Nagasaki Before and After the Bombing

60. Size comparison of bombs
Tsar bomb nuclear bombs detonated

61. Nuclear Power

62. Generators
Generators produce electricity by spinning a coil of wire (solenoid) in front of permanent magnets.
The part of a generator that spins is referred to as a turbine.
Most power plants just try to spin a turbine.

63. Coal Power Plant
The most common type of power plant (the place where electricity is produced) in the United States is a coal plant.
In a coal plant, coal is burned to heat up water. The steam is forced through a pipe and spins a turbine to create electricity.
Natural Gas plants are the 2nd most common, and work the same way.

67. Advantages
The main reason for the popularity of these plants are you can put them anywhere.
All you need to do is ship in the coal or pipe in the natural gas.
They don’t require a relatively large amount of space to produce enough electricity for a city.

68. Disadvantages Both release smoke into the surrounding area.
Higher rates of asthma have been recorded as the number of power plants grow.
Both release carbon dioxide, a greenhouse gas, which may be the largest threat to our survival on this planet.

69. Nuclear Power
Nuclear power is using a nuclear reaction heat up water instead of a fossil fuel.
It works the exact same as a coal or natural gas plant.
The first nuclear power plant was the Obninisk Plant in the USSR in 1954.
The first in the United States was the Shipping Port Reactor in 1957

71. Google Earth US Map of nuclear power plants

72. Google Earth World Map of nuclear power plants

73. Why put them next to population centers?
That’s where the power is needed!
Electricity is lost as you send it across power lines.
The further is it sent, the more you lose.
Research is being done that shows as some materials are super cooled (near absolute zero) they become super conductive losing no electricity.

74. Can a nuclear power plant explode like a nuclear bomb?No
There is not enough U-235 being reacted.
Nuclear plants use a fission reaction to boil water. Steam rises forcing a turbine to spin producing electricity (same way a coal plant works).
The Uranium they are using is not as pure as weapons grade, so it can’t react as quickly.

75. Meltdown
The danger in a power plant is a meltdown of a reactor (not an explosion like a nuclear bomb).
Which is a reactor cracking and leaking radiation and/or radioactive material into the surrounding area.
There have been three major accidental releases of radiation.
Three Mile Island, Chernobyl, and Fukushima

76. Three Mile Island Located in PA The accident occurred in 1979.
A small amount of radiation escaped, it was controlled before it got really bad.
The average person within 10 miles received the radiation of about a chest x-ray.
No deaths or injuries are directly related to it.

77. Chernobyl Located in modern day Ukraine (was the USSR at the time)
Occurred in 1986
A much worse accident (full meltdown)
31 workers and firefighters died right away, 130 suffered acute radiation sickness.
hundreds of thousands of people were hit with a high level of radiation
The long term effects are still being studied.

78. Fukushima Located in Japan, north of Tokyo.
The accident occurred in 2011
Caused by a massive earthquake (9.0) and ensuing tsunami.
This wiped out the cooling system, controls and left the surrounding area without power for weeks.
Unlike the others, this slowly continued as onlookers were unable to contain it.

79. Why use nuclear power?
Taking everything into consideration, it is safer and cleaner than other forms of power.
The accidents were horrible, but they were few.
100’s of people die each year from accidents at coal and hydro plants.
Very few die in the highly regulated nuclear plants.
Coal plants also pour smoke and other pollutants into the air, nuclear plants do not.

80. New nuclear power plants
There was a “freeze” on nuclear power plants for a long time given the concerns.
President Obama has recently signed off on the construction of 3 new reactors in Alabama just recently.

81. Other places nuclear power is used
Submarines- nuclear ships can stay at sea for 25 years without refueling. Compare that to the few weeks a diesel ship could stay at sea.
Space ships commonly use nuclear generators as well.

82. Nuclear Fusion

83. Fusion ~The joining of nuclei to make larger atoms
The Sun produces energy in this manner.
Hydrogen bombs use this process.
Much more energy per gram is released by fusion than is by fission.
Fusion reactions create no radioactive waste
Unfortunately it is much harder to start and control a self sustaining reaction.
It can not be used in a power plant yet.

84. Where elements are made?
Elements are formed in nuclear fusion reactions in stars.
Normally a star gets its energy by fusing 4 hydrogen atoms into a helium atom
4 H  He
As stars get older, they begin to fuse elements into heavier elements

85. Death of a star
Near the end of a star’s “life” it begins to collapse on itself, and making heavier elements
Nova, supernova- explosion of a star
When a star explodes, it sends all the elements it made scattering throughout the universe.

86. How they get here
Clouds of these elements are what planets were formed from.
Asteroids, and comets also could form and come to this planet.

87. Fusion reaction 3 1 2 1 fusion 1 4 2 H + H He + n +energy4 2 H + H He + n
+energy
Hydrogen atoms are fused together to form helium.
Using 4 hydrogen atoms takes more energy, but can be done.
It is easier if you use isotopes of hydrogen Deuterium (D 1 no) and Tritium (T 2 no)

88. Fusion Reaction

89. Radioactive waste Unusable materials that give off radiation
This is produced by enriching uranium, and from the remnants of the spent fuel.
It is also produced by the medical industry and oil and gas drilling and refining.
This is highly dangerous if people were to come in contact with it, so it must be stored in a safe place.

90. Running out of fuel
Like all other sources nuclear fuels are limited to the amount of fuel we can mine.
We are in no danger of running out of uranium but some day that will be a problem.
Breeder Reactors, used currently in Europe, take unusable U-238 and convert it into usable Pu-239 greatly increasing our supply of fuel.
They are not used in the US yet for concerns over their safety.

91. Fusion Reactor
If fusion reactors could run, then it would run off of isotopes of hydrogen.
Dueterium is plentiful enough that there would be not problem for a long time.
If the reaction could use regular hydrogen instead it would be even better.

92. Transmutation of elements
transmutation- changing one element into another.
Done by bombarding an atom with alpha particles or some type of radiation.
All elements outlined on the periodic table are created this way.

93. The more famous ones…
The only synthesized element you probably heard of before this class is Plutonium.
It is used for nuclear reactions (power plants, submarines, A-bombs)
Americium is the most commonly used in smoke detectors.
Research was done at the University of Berkeley, California
refer to elements 95, 97 and 98

94. Dangers of Nuclear Power and Radiation

95. Cells are
undamaged.
radiation
Cells are damaged,
repair damage and….
Operate normally
Cells die as a
result of damage.
operate abnormally (cancer).

96. Effects of radiation Radiation breaks apart cell tissue and DNA.
Cells can repair some of the damage of low level exposure over time.
Higher levels of radiation can cause an increased rate of cancer, sterility, birth defects, death.

97. Radiation does not Cause an instant mutation in a person
(You won’t grow a third eye)
You won’t glow in the dark either
Radiation is measured in mrem (millirems)

98. Doses
The average person receives 360 mrem a year with no adverse effects.
56% of the survivors of 1945 bombing of Hiroshima and Nagasaki were still alive in 1990, and they received ~500,000 mrem.
These effects are still being studied.

99. Biological effects depend on…
1. Energy of Radiation
2. Penetrating ability of radiation
3. Ionization ability of the radiation
4. length of exposure

100. Ionization ability
Radiation can “knock” electrons off of atoms creating ions.
Some radiation is better at this than others.
Ionizing radiation- EM radiation higher than visible light (UV, X-rays, and gamma rays)
Meaning they are good at this.
All radiation lower than this (visible, IR, microwaves, radio waves) are nonionizing.
Meaning they don’t create ions very well.

101. Cell Phones
Cell phones send and receive information using radio waves.
This is nonionizing.
Nonionizing is still dangerous if the energy is high enough (look at a microwave oven).
Cell phones should release radiation in low enough energy levels that they are not harmful.

102. Immediate effects of large doses of radiation
Dose of radiation
Effects
above 5,000 mrem
can cause observable effects (more susceptible to illnesses)
100,000 mrem -200,000 mrem
nausea loss of hair
200,000 mrem-500,000 mrem
ulcers, internal bleeding
above 500,000 mrem
Death

103. Large Scale Nuclear War
The scariest part of large scale nuclear war is that no one on the planet could possibly escape the after effects.
Even if you were outside of all blast regions, you would still be exposed to the fallout.
Fallout is radioactive material spread around from a nuclear explosion.
In a large scale nuclear war, enough radioactive material would be spread to cover the entire planet.

104. Nuclear Winter
Even if you were safe from the fallout (somehow), the planet would enter a nuclear winter.
This is the same idea as a comet hitting the planet and kicking up a huge dust cloud (the theory on what killed the dinosaurs).
Instead of a comet, it would be several nuclear bombs hitting cities. They burn releasing ash and soot into the stratosphere that would takes decades to settle out.

105. What this would do
It would block out sunlight from getting to the surface.
The amount that would be blocked out would depend on the amount of soot in the atmosphere which depends on the number of bombs exploding.
Even a small exchange of nuclear bombs would have a dramatic effect on the planetary climate.

106. Blocked out Sun
Some light would still get through, but average temperatures would fall.
Plants would begin to die.
Crops would fail.
Animals that eat those plants begin to die.
Bodies would begin to pile up, increasing the amount of harmful decomposers.

107. How bad?
According to a report published in The Journal of Geophysical Research in 2007, a war using most of the world’s arsenal would result in a global cooling of about 7-8o C.
The last ice age 18,000 years ago was 5o C colder.
After a decade the planet would still be 4o C, colder.
A war using 50 Hiroshima sized bombs (the approximate arsenal of India and Pakistan) could cool the planet by 2-3o C for almost 10 years

108. Ozone Depletion
The soot could chemically react with the ozone layer in the stratosphere.
This could create “holes” in the ozone layer.
Not only would you have to deal with lower global average temperatures, but the sunlight that does get through would come with dangerous levels of UV radiation.

109. Likely results
This would probably result in a mass extinction of most species across the planet.
Eventually temperatures would return to normal, and new species would come back through evolution.
Given the adaptability and ingenuity of humans, some are likely to survive.
I Don’t Know With What Weapons World War III Will Be Fought, But World War IV Will be Fought With Sticks and Stones~ Albert Einstein

110. Medical Uses of Radioactive Substances

111. Nuclear Medicine
We use radioactive substances in two different ways for medical purposes.
Imaging- taking “pictures” of your internal anatomy.
Therapy- to kill unwanted cells.

112. Imaging
Your eyes can see a very small range of the electromagnetic spectrum (visible light).
However, this energy still has an effect on objects.
Certain materials will absorb the radiation and change colors.
This occurs through an endothermic reaction “burning” the material.
These materials are your radiation “film”

113. X Rays Wilhem RÖntgen described the properties of X-rays in 1895.
He called them “X” because they were an unknown.
Different materials of different densities absorb X-rays differently.
When X-rays hit a film they darken it.
Dense materials like bone absorb the X-rays so they stay lighter.

115. CT Scan
X Rays only give you a 2 D image with all objects superimposed on top of each other.
A CT (computed tomography) scan has the detector and source move so we can get a computer generated 3-D image of the object.

116. MRI Magnetic Resonance Imaging, or Nuclear Magnetic Resonance (NMR).
When using the same principle on anything but people, it is normally called NMR.
The term NMR was first, but since the word nuclear was in it, patients didn’t want it.
This works the same way as a CT scan but uses nonionizing radiation.

117. Radiopharmaceuticals
Instead of keeping the source outside of the body and sending the radiation through a patient, sometimes radioactive substances are administered internally.
The patient is then checked radiation.
This can be used to make an image.

118. Tracers
Sometimes a radioisotope is bonded to a protein to some substance the body processes.
After the isotope inside, it allows doctors to see where it is accumulating in the body.
Radioisotopes chemically bonded is called a tracer.

119. Therapy Radiation treatment is often used to treat cancer.
Chemotherapy works on the same principle, but uses chemicals instead of radioactive substances.
Cancer cells are rapidly dividing cells.
These cells should be weaker than other cells since they are dividing so rapidly.

120. Radiation Radiation is administered to the affected area.
Radiation breaks apart and kills all cells.
Cancer cells should die more easily than healthy cells.
The idea is to continue the treatment until all the cancer cells are dead, then try to nurse the patient back to health.

121. Common isotopes used in nuclear medicine
symbol Z
T1/2
decay β
Imaging:
fluorine-18
18F 9
110 m β+
0.664 (97%)
gallium-67
67Ga 31
3.26 d ec
krypton-81m
81mKr 36
13.1 s IT -
rubidium-82
82Rb 37
1.27 m
3.379 (95%)
technetium-99m
99mTc 43
6.01 h
indium-111
111In 49
2.80 d
iodine-123
123I 53
13.3 h
xenon-133
133Xe 54
5.24 d β-
0.364 (99%)
thallium-201
201Tl 81
3.04 d
Therapy:
yttrium-90
90Y 39
2.67 d
2.280 (100%)
iodine-131
131I
8.02 d
0.807 (100%)
Z = atomic number, the number of protons; T1/2 = half-life; decay = mode of decay photons = principle photon energies in kilo-electron volts, keV, (abundance/decay) β = beta maximum energy in mega-electron volts, MeV, (abundance/decay) β+ = β+ decay; β- = β- decay; IT = isomeric transition; ec = electron capture * X-rays from progeny, mercury, Hg