Content Benchmark P.12.C.3
Students know nuclear reactions convert a relatively small amount of material into a
large amount of energy. I/S
The nucleus of an atom contains two primary particles, the neutron and the proton. When
protons and neutrons form a nucleus, the process involves the conversion of some of the
mass of these particles into energy. This is given by Einstein’s famous equation: E=mc2.
The actual mass of the nucleus is slightly less than when you add the mass of the protons
added to the mass of the neutrons. This loss represents mass that has been converted to
energy.
For more information refer to
http://www.colorado.edu/physics/2000/isotopes/binding_energy.html.
In Einstein’s equation, the amount of mass is multiplied by the speed of light squared (c2
~ 9 × 1016 m2/s2), which is a tremendous quantity. Therefore, a small amount of mass
results can be converted to a substantial amount of energy.
When electrons move from one quantum orbital to another, they emit or absorb visible
light energy. Conversely, in the nucleus of an atom as the protons and neutrons come
together, they emit gamma ray photons, which are much more energetic than visual light
photons. For more information about this process refer to
http://www.lbl.gov/abc/Basic.html#Nuclearstructure
In processes that involve nuclear changes that is, nuclear fission or nuclear fusion,
massive amounts of energy are released through the conversion of mass into energy. The
table below compares the energy released in combustion (chemical) to that released in the
fission and fusion nuclear reactions.
Chemical
Fission
Fusion
Sample Reaction
C + O2 ->
CO2
n + U-235 -> Ba-143
+ Kr-91 + 2 n
H-2 + H-3 ->
He-4 + n
Typical Inputs (to Power
Plant)
Bituminous
Coal
UO2 (3% U-235 +
97% U-238)
Deuterium &
Lithium
Typical Reaction
Temperature (K)
700
1000
108
Energy Released per kg of
Fuel (J/kg)
3.3 x 107
2.1 x 1012
3.4 x 1014
Scientists have long known that nuclear fusion occurs in the sun and in distant stars.
Stars are the building machines of the known elements. Atoms of hydrogen combine to
form helium atoms which combine to form larger elements. Upon violent explosions of
massive stars, called supernovae, elemental material is spewed throughout the universe.
For further information about supernovae, go to
http://spaceplace.nasa.gov/en/kids/phonedrmarc/2003_november.shtml.
Practical applications of nuclear fusion and fission occur on Earth only in human-made
laboratories. Radioactive decay (fission processes) does occur in the Earth’s mantle,
driving convective processes. However, on the surface, fission is a human-made activity.
Nuclear Fission
When nuclear fission occurs, an atom is split into one or more progeny products. In this
reaction, some of the nuclear mass is converted to energy. With the large amounts of
nuclei involved, a tremendous amount of energy is released. The first nuclear fission
reactions were researched and developed for military uses during World War II.
Figure 1. A schematic of fission of U-234 (from
http://www.solcomhouse.com/nuclear.htm)
To learn more about fission reactions in nuclear bombs, go to
http://www.howstuffworks.com/nuclear-bomb.htm
Since World War II no nuclear bombs have been detonated on a population. Many
devices have been tested throughout the years and in Nevada, the Nevada Test Site has
been used for atomic testing.
To learn more about the Nevada Test Site, go to http://www.nv.doe.gov/nts/default.htm
Nuclear power plants sought to use the fission reaction to generate the heat needed to
drive turbines in a process to generate electricity. This process offered an alternative to
coal-fired power plants of the 1950’s. Dirty air, acidic rain, and health hazards due to
smog fueled interest in the building and design of nuclear power plants. Nuclear energy is
one solution to a dependence on fossil fuels.
To learn more about nuclear power plants, go to
http://www.solcomhouse.com/nuclear.htm
For a discussion on the economics of nuclear power plants, go to
http://www.nuc.berkeley.edu/thyd/ne161/ncabreza/sources.html
Nuclear Fusion
When nuclear fusion occurs, two or more lighter elements combine to form a heavier
atom. As with nuclear fission, some of the nuclear mass is converted to energy during the
reaction.
Electrical power generation using nuclear fusion is currently being researched as an
alternative to nuclear fission. Nuclear fusion is also used for military purposes in the
development of the nuclear fusion bombs which are also known as thermonuclear
devices. They are more efficient than nuclear fission bombs. Teller-Ulam designed a
bomb that incorporated a fusion reaction which was detonated by a fission reaction - a
bomb within a bomb.
For further information about thermonuclear weapon, please see
http://science.howstuffworks.com/nuclear-bomb1.htm.
Figure 2.
http://www.solcomhouse.com/nuclear.htm
Fusion reactors have not been practical in the laboratory given that the temperatures
required to fuse two hydrogen atoms is millions of degrees Celsius. However, it has been
estimated that a gallon of water could contain the energy potential of 300 gallons of
gasoline. Research is being done to develop fusion reactors that are practical and safe.
For more information on nuclear fusion go to:
http://fusioned.gat.com/ and http://fusedweb.pppl.gov/.
Content Benchmark P.12.C.3
Students know nuclear reactions convert a relatively small amount of material into a
large amount of energy. I/S
Common misconceptions associated with this benchmark:
1. Students confuse the terms nuclear fission and nuclear fusion or that fission is
more powerful than fusion.
This misconception probably stems from the words being similar. Also, because nuclear
fusion and fission are often discussed in specific unit, this confusion is understandable.
Also, with fission being associated with the World War II atomic bombs, students may
think that these reactions are more energetic than fusion, on a mass per mass basis.
More about fission and fusion confusion can be found at
http://www.physics4kids.com/files/mod_fission.html
2. Students incorrectly believe that nuclear power plants explode like nuclear
bombs.
The reactor accident at Chernobyl caused this belief. While a large explosion and fire
occurred during the Chernobyl accident, the facility was an old graphite reactor design
that is inherently unsafe. Modern nuclear reactors are designed to generate heat to boil
water which turns a turbine generating electricity and the core is confined and has many
safety features to safeguard the plant. In other words, current reactor designs would make
a Chernobyl-type disaster nearly impossible.
To learn more about modern reactor designs and misconceptions associated with nuclear
power, go to http://www.iaea.org/NewsCenter/Statements/2005/ebsp2005n004.html.
3. Students incorrectly believe that radioactivity first appeared during World War
II
Radioactivity is a natural process and current scientific models support that radioactivity
has been around since the universe’s origin. Humans have known about radioactivity and
used it since the 19th century.
More about this misconception and others associated with nuclear reactions can be found
at http://www.lbl.gov/abc/wallchart/chapters/appendix/appendixg.html
4. Students incorrectly think that atoms cannot be changed from one element to
another.
Atoms can be changed to new elements with the addition or subtraction of protons. We
see atoms change in alpha decay, fission and fusion reactions. Students can confuse
changing of an element by addition or subtraction with a proton with isotopes. Isotopes
are in fact the same element where the number of neutrons differs.
To learn more about isotopes, go to
http://www.colorado.edu/physics/2000/isotopes/index.html.
5. Students incorrectly believe that nuclear power plants are the only type of
electrical generation that produces radioactive waste.
Combustion of coal is the most common way to generate electricity in the United States,
as well as other major industrial countries (e.g., China). In the mining of coal, trace
amounts of naturally occurring radioactive material (uranium and thorium) are brought to
the surface. Some of this uranium and thorium is distributed to the environment through
the plant’s stack. While much of the radioactive material is captured in the plant’s air
pollution control equipment, some quantity is released into the atmosphere and does
present a risk to those living near the coal plant. The U.S. EPA monitors releases of
radioactive materials from coal stacks to ensure that releases are under those prescribed
to protect public health and safety. Radioactive wastes are also created from drilling of
oil and natural gas.
To learn more about generation of radioactive waste, go to
http://www.epa.gov/radtown/coal-plant.htm.
Content Benchmark P.12.C.3
Students know nuclear reactions convert a relatively small amount of material into a
large amount of energy. I/S
Sample Test Questions
1. Nuclear fusion reactions
a. involve electrons of one atom reacting with the electrons of another atom.
b. occur commonly on Earth through naturally occurring radioactive materials.
c. cause large atoms to divide into smaller atoms releasing large amounts of energy.
d. cause smaller atoms to combine into larger atoms releasing large amounts of
energy.
2. Nuclear fusion reactions
a. are responsible for the formation of much of the elements.
b. are commonly used in nuclear power plants in the United States.
c. were historically used in Russian-style nuclear reactors.
d. release less energy than fossil fuel combustion.
3. Nuclear fission reactions
a. are responsible for the formation of the known elements.
b. are commonly used in nuclear power plants.
c. are the reactions that power the Sun and other stars.
d. are still in development for commercial power generation.
4. Nuclear energy was first developed for
a. medicinal purposes.
b. to replace fossil fuels.
c. military purposes.
d. as a replacement for steam engines.
5. Nuclear fission and nuclear fusion reactions cause
a. atomic nuclei to change.
b. electrons to release large amounts of energy.
c. protons and electrons to split.
d. neutrons and electrons to fuse.
6. Commercial nuclear reactors in the United States
a. have been built in the last ten years.
b. use recycled nuclear materials.
c. reprocess their wastes for reuse as fuel.
d. have multiple safeguards to prevent accidents.
7. Research into fusion reactors is being conducted by many countries because
a. Fusion reactions release large amounts of energy with minimal waste
b. One pellet of uranium causes too much lost energy
c. Our supplies of hydrogen are limited
d. It will be ready for commercial use in just a few years.
Content Benchmark P.12.C.3
Students know nuclear reactions convert a relatively small amount of material into a
large amount of energy. I/S
Answers to Sample Test Questions
1.
2.
3.
4.
5.
6.
7.
(d)
(a)
(b)
(c)
(a)
(d)
(a)
Content Benchmark P.12.C.3
Students know nuclear reactions convert a relatively small amount of material into a
large amount of energy. I/S
The following list of intervention strategies and resources will facilitate student
understanding of this benchmark.
1. The Savage Sun
The Discovery Channel’s “Savage Sun” video focuses on recent understanding of
the Sun through space-based solar missions. The basic description can be found at
http://school.discovery.com/lessonplans/programs/savagesun/q.html.
An associated lesson plan can be found at
http://school.discovery.com/lessonplans/programs/savagesun/.
2. Modeling Nuclear Fusion in the Sun
The National Solar Observatory (NSO) invites selected teachers to participate in
summer research experiences.
From one former participant, Joey Rogers, comes this activity to model nuclear
fusion in the Sun: http://eo.nso.edu/ret/rogers/lpfuse.htm.
3. Contemporary Physics Education Project (CPEP)
This website contains several pages of explanation, diagrams, and activities
relating to fusion. The project was sponsored by the US Department of Energy
and the University of California Lawrence Livermore National Laboratory.
To access the CPEP site, go to http://fusedweb.pppl.gov/CPEP/Chart.html.
4. Modeling Layers in a Massive Star
NASA’s Imagine the Universe site contains many lessons and activities that
concern astronomical processes, such as nuclear fusion. One of the activities
allows students to model the layers of a massive star that result from a series of
nuclear fusion reactions.
To see this lesson, go to
http://imagine.gsfc.nasa.gov/docs/teachers/lessons/xray_spectra/activityfusion.html.
5.
ABC’s of Nuclear Science
The Lawrence Berkeley Lab has created a comprehensive Web site discussing the
fundamental of nuclear science. This site gives excellent background in the
chemistry and physics of nuclear science including teacher materials and
experiments, as well as posters and other teacher’s guides.
To learn more, go to http://www.lbl.gov/abc/index.html.
6.
Radioactivity Background Information
This site provides the student and the teacher with solid background information
on radioactivity and can be found at http://www.darvill.clara.net/nucrad/.
7.
Nuclear Medicine Information Sheet
Radioactivity, Isotopes and Radioisotopes from Nature, Nuclear Reactors and
Cyclotrons for use in Nuclear Medicine
http://www.ansto.gov.au/info/reports/radboyd.html
8.
Fission Simulations
The University of Colorado’s PhET site contains many physics simulations that
can be used to by students to understand mechanical, electrical, and nuclear
processes. This site provides good simulations for nuclear fission processes that
can be accessed in the “Quantum Phenomenon.”
To access the site home page, go to http://phet.colorado.edu/webpages/simulations-base.html and then click on “Quantum Phenomenon” in the left
hand tool bar.
9.
The History of Nuclear Energy
The University of Missouri at Rolla has created extensive background information
on nuclear energy. This site can be used by students for research and is found at
http://nova.nuc.umr.edu/nuclear_facts/history/history.html
10. Nuclear Weapons-Basics
The Nuclear Age Peace Foundation has created an interesting compilation of
information regarding development of nuclear weapons and their use. This site
can be used by students for research and is found at
http://www.nuclearfiles.org/menu/key-issues/nuclear-weapons/basics/index.htm.