1
What are radioactive isotopes, and why are they important for nuclear power?
INFOGRAPHIC 22.1
The number of _____________ is unique to a given element and gives an element its atomic number.
Protons
Atoms that have the same number of protons and electrons but different numbers of neutrons are called:
radioactive.
ions.
isotopes.
subatomic.
C
2
What types of radiation are produced when an isotope decays? How is the rate of decay of a radioactive atom measured?
INFOGRAPHIC 22.2
After four half-lives, about how much radioactive parent material is left?
25%
40%
0.5%
6.25%
D
In a nuclear fuel assembly, control rods are used to regulate the nuclear reaction. But even if all the control rods are inserted into the fuel assembly, heat is still produced. Explain why.
The nuclear material spontaneously decays, even if the fission reaction has been halted. This spontaneous decay generates heat. (This is why spent fuel rods still generate heat and must remain in a cooling water bath.)
3
How is nuclear energy harnessed to generate electricity in a fission reactor? How safe are nuclear reactors?
INFOGRAPHIC 22.3, INFOGRAPHIC 22.4 AND INFOGRAPHIC 22.5
True or False: Barring a major accident, it is less hazardous to your health to live near a nuclear reactor than a coal-fired power plant.
TRUE
Nuclear fission is a reaction that:
splits an atom, releasing energy.
combines two or more atoms, producing energy.
results in large explosions.
is required to make atoms radioactive.
A
Using Infographic 22.3, describe the steps used in mining and processing uranium to the point where it is packed into fuel rods.
Uranium ore is mined. The ore is crushed and blended with an acid (or base) to separate the uranium from the ore forming yellowcake, uranium oxide. The leftovers (tailings) must be covered with clay and rock to prevent radioactive dust from entering the atmosphere. The yellowcake is concentrated (producing hazardous waste) and formed into pellets, which are loaded into fuel rods. The fuel rods are combined into a fuel rod assembly (interspersed with control rods) and more than 100 fuel assemblies are placed into a reactor core.
4
How dangerous is radiation that is released from radioactive material? What problems are associated with nuclear waste?
INFOGRAPHICS 22.6 AND 22.7
There are different types of radiation. Which one is most energetic and can therefore penetrate many surfaces, including skin?
Alpha radiation
Beta radiation
Gamma radiation
Particle radiation
C
Which of the following is an example of low-level radioactive waste?
Worker clothing and gloves
Tools used in the nuclear facility
Spent fuel rods
a and b are both examples of LLRW
a, b, and c are all examples of LLRW
D
How are spent fuel rods currently disposed of in the United States?
The spent fuel rods are initially stored in steel lined pools on site at the power plant to allow some of the short half-life material to decay. After a few years, it can be moved to above-ground dry cask storage. From here, it should go to an underground storage facility but as yet there is none available so these fuel rods either remain in steel lined pools or in dry cask storage.
5
In a trade-off analysis of nuclear power, what factors must be considered, and what is your own conclusion regarding the future role of nuclear power?
TABLE 22.1
What problem related to nuclear power do we not yet have a workable solution for?
Finding a substitute for uranium once it is used up
Safe disposal of HLRW
Producing stream to turn the turbine that is not radioactive
Controlling the fission reaction
B
What are the pros and cons tof generating energy from a nuclear source versus a fossil fuel source (coal)?
Both damage the environment in the extraction stage and contribute to soil, air, and water pollution though the type of pollution differs: coal mining contributes toxic metals and acids to water and land; uranium mining leaves radioactive tailings. Hazardous waste is produced in processing for both. The waste is radioactive for nuclear fuel; it is toxic for coal processing. The biggest difference may be in the use of the fuel. Both are used for thermoelectric production of electricity: coal is burned (and contributes significant air pollution including mercury, acids, particulates and CO2), but with nuclear power, nothing is burned so it does not contribute to air pollution or significant levels of increasing carbon dioxide. However, nuclear waste is radioactive; at the current time we have no good methods for dealing with its disposal. Finally, in the operation of a nuclear power plant, if something goes wrong it could be catastrophic.
From an economic standpoint, which type of electricity production—nuclear or fossil fuel—is less expensive? Explain. Remember to include both internal and external costs in your answer.
Fossil fuel power plants are cheaper to build than nuclear plants and have a longer lifespan. Operating costs of the two plants are similar. Taking a nuclear power plant offline and making the structure safe costs far more than a similar situation for a coal-fired plant. In the average year where a nuclear accident has not occurred, health costs associated with fossil-fuel use far exceed those of the nuclear industry. However, in the unlikely event of an accident or natural disaster at a nuclear plant, then nuclear fuel costs soar due to clean-up, health costs, etc. In the end, nuclear is probably more expensive than coal.
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