Nuclear Power (College Board AP® Environmental Science): Flashcards
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Define nuclear fission.
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Define nuclear fission.
Nuclear fission is the splitting of a large, unstable nucleus into two smaller nuclei.
What is the difference between spontaneous and induced fission?
Spontaneous fission happens without extra energy entering the nucleus, while induced fission happens after the nucleus first absorbs a neutron.
During induced fission, a uranium-235 nucleus absorbs a neutron and becomes , which is very unstable.
During induced fission, a uranium-235 nucleus absorbs a neutron and becomes uranium-236, which is very unstable.
What products form when a uranium-235 nucleus undergoes fission?
The fission of uranium-235 produces two smaller daughter nuclei, two or three neutrons, and gamma rays.
True or False?
A nuclear power station generates electricity in a completely different way from a fossil fuel power station.
False.
Both use steam to drive turbines that turn generators. The only difference is that a nuclear station produces its heat by fission.
What do control rods do in a nuclear reactor?
Control rods absorb neutrons to control the rate of fission; lowering them decreases the rate of fission.
Define radioactivity.
Radioactivity is the energy emitted by the nucleus of a radioactive isotope, such as uranium-235.
What is the role of the moderator in a nuclear reactor?
The moderator slows down the fast-moving neutrons produced by fission.
True or False?
Environmental factors change the rate of radioactive decay.
False.
Radioactive decay is random and is not affected by environmental factors, so any nucleus can decay at any time.
Why is a nuclear reactor surrounded by shielding?
Steel and concrete shielding absorbs hazardous radiation from the radioactive daughter nuclei and neutrons, keeping the area around the reactor safe for workers.
Define half-life.
An isotope's half-life is the time taken for the activity of a sample to fall by half.
After two half-lives, the activity of a radioactive sample has fallen to of its starting value.
After two half-lives, the activity of a radioactive sample has fallen to 25% of its starting value.
Why is waste from spent fuel rods the most dangerous type of nuclear waste?
The daughter nuclei in spent fuel are more radioactive than the original fuel, and spent fuel rods are also extremely hot.
Because it stays radioactive for thousands of years, high-level nuclear waste is stored until it is no longer harmful.
Because it stays radioactive for thousands of years, high-level nuclear waste is stored underground until it is no longer harmful.
How does thermal pollution from a nuclear power plant harm aquatic ecosystems?
Hot water released into surface water can cause thermal shock and reduces dissolved oxygen, which disturbs the balance of aquatic species.
True or False?
Nuclear power is a renewable resource because it needs only small amounts of uranium.
False.
The supply of uranium ore is finite, so nuclear power is nonrenewable, even though it is a low-carbon source.
How can uranium mine tailings harm the environment?
Mine tailings can contain radioactive elements that contaminate nearby water or soil.
Give two advantages of nuclear power.
Nuclear power is low-carbon, generates electricity reliably on a large scale, reduces reliance on fossil fuels, and increases energy security.
Give two disadvantages of nuclear power.
Nuclear power produces radioactive waste that is expensive to store safely, risks accidents that spread radiation over large areas, has high decommissioning costs, and risks misuse of fuel by terrorists or rogue states.
Give three types of nuclear accident.
Nuclear accidents include meltdowns, explosions, thermal pollution, and the exposure of radioactive components to the environment or to humans.
What caused the partial meltdown at Three Mile Island in 1979?
The partial meltdown at Three Mile Island was caused by a cooling malfunction in reactor 2.
Define half-life.
Radioactive half-life is the amount of time it takes for 50% of a radioactive substance to decay.
How did the Chernobyl accident differ from the one at Three Mile Island?
Chernobyl was a reactor explosion, whereas Three Mile Island was a partial meltdown.
True or False?
Radioactive fallout from Chernobyl stayed within the USSR.
False.
Fallout entered the atmosphere and fell over 40 different countries, including Scandinavia and the UK.
Half-lives of radioactive isotopes vary from less than a second to of years.
Half-lives of radioactive isotopes vary from less than a second to billions of years.
Which type of cancer increased after Chernobyl because of iodine-131 exposure?
Thyroid cancers increased after Chernobyl because of iodine-131 exposure.
Define critical mass.
The critical mass is the minimum amount of fuel needed for a chain reaction.
What chain of events caused the Fukushima-Daiichi disaster in 2011?
An earthquake caused a tsunami that flooded the station, causing a loss of power and of reactor cooling. This led to explosions, a meltdown, and the release of radioactive contamination.
True or False?
The rise in thyroid cancers near Fukushima since 2011 is definitely caused by radiation.
False.
Part of the increase may be because more cases are being detected by the screening program set up after the disaster.
Define enrichment.
Enrichment is the processing of uranium to separate out U-235.
What makes U-235 different from U-238 as a nuclear fuel?
Unlike U-238, U-235 can undergo a self-sustaining fission chain reaction.
Nuclear power facilities use fuel containing about 3% U-235, while nuclear weapons contain about U-235.
Nuclear power facilities use fuel containing about 3% U-235, while nuclear weapons contain about 85% U-235.
True or False?
Most of Earth's natural uranium is U-235.
False.
Less than 1% of Earth's natural uranium is U-235; the most common isotope is U-238.
What do breeder reactors produce from U-238?
Breeder reactors produce plutonium-239 (Pu-239) from U-238.
True or False?
Nuclear waste containing plutonium-239 becomes safe within a few years.
False.
Plutonium-239 has a half-life of 24,000 years, so waste containing it stays radioactive for a very long time.
Why do international inspections monitor Pu-239 production?
Inspections monitor Pu-239 because it can be used to make nuclear weapons.
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