Define nuclear fission .

Nuclear fission is the splitting of a large nucleus into two smaller nuclei.

What is spontaneous fission ?

Spontaneous fission occurs randomly and without additional energy being put into the nucleus.

What is induced fission ?

Induced fission occurs when a stable nucleus splits into small nuclei due to the absorption of a thermal (slow-moving) neutron .

True or False? Uranium-235 is an example of a fissile material.

True. Uranium-235 is an example of a fissile material, this means it can undergo fission reactions - its nuclei can be split apart into smaller nuclei.

True or False? More than one neutron is required to induce fission in a uranium-235 nucleus.

False. Only one neutron is required to induce fission in a uranium-235 nucleus.

What happens when a uranium-235 nucleus is bombarded with fast-moving neutrons?

When a uranium-235 nucleus is bombarded with fast-moving neutrons, they will rebound and fission will not be induced

In what form is energy released from nuclear fission reactions?

In fission reactions, energy is released in the form of kinetic energy of the fragments as well as neutrons and gamma rays.

True or False? In a nuclear fission reaction, the mass of the daughter nuclei is the same as the mass of the parent nucleus

False. In a nuclear fission reaction, the mass of the daughter nuclei is less than the mass of the parent nucleus.

True or False? For nuclear fission to occur, the fission fragments must be more stable than the original nucleus.

True. For nuclear fission to occur, the fission fragments must be more stable than the original nucleus. In other words, the fission fragments must have higher values of binding energy per nucleon than the original nucleus undergoing fission.

True or False? Nuclear fission has a similar energy density to other sources of fuel.

False. Nuclear fission has the highest energy density of any currently used fuel source.

What is a nuclear chain reaction ?

A nuclear chain reaction occurs when: 2 or 3 neutrons are emitted from a fission reaction these neutrons cause further fission reactions more neutrons are emitted the rate of fission reactions increases

What is a thermal neutron ?

A thermal neutron is a neutron which is in thermal equilibrium with the moderator.

True or False? For every fission reaction, there is, on average, one further fission reaction.

True. When the rate of fission is constant , each fission reaction goes on to initiate, on average, one further fission reaction.

What happens if the amount of nuclear fuel in a fission reactor is too low ?

If the amount of nuclear fuel in a fission reactor is below the critical mass , chain reactions will stop or slow down . This is because neutrons can escape the material without hitting any more nuclei.

What happens if the amount of nuclear fuel in a fission reactor is too high ?

If the amount of nuclear fuel in a fission reactor is above the critical mass , chain reactions increase rapidly . If uncontrolled, this can lead to a huge release of energy and even a nuclear explosion.

What is the purpose of control rods in a nuclear reactor?

The purpose of control rods is to absorb neutrons .

What is the purpose of the moderator in a nuclear reactor?

The purpose of a moderator is to slow down neutrons .

Why must neutrons be slowed down in a nuclear reactor?

In a nuclear reactor, neutrons must be slowed down so they can react with the uranium fuel efficiently. This is because slow neutrons are more likely to be absorbed by a uranium nucleus than fast neutrons.

True or False? Lowering the control rods in a nuclear reactor increases the rate of fission.

False. Lowering the control rods decreases the rate of fission as more neutrons are absorbed.

What is the purpose of shielding in a nuclear reactor?

The purpose of shielding is to absorb hazardous radiation .

What is nuclear waste ?

Nuclear waste refers to the leftover radioactive materials associated with the production of nuclear power. Different waste materials can be classed as low-level waste intermediate-level waste high-level waste

How is low-level nuclear waste treated?

Low-level nuclear waste is treated by: encasing it in drums filled with concrete storing it underground for a few years eventually disposing of it in landfill sites

How is intermediate-level nuclear waste treated?

Intermediate-level nuclear waste is treated by: encasing it in steel drums filled with concrete storing it underground in a secured facility

How is high-level nuclear waste treated?

High-level nuclear waste is treated by: recovering useable isotopes of uranium and plutonium encasing it in reinforced steel containers filled with concrete or vitrified with molten glass storing in underwater cooling tanks initially storing it deep underground in a secured facility

Is contaminated clothing classified as low, intermediate, or high-level waste?

Contaminated clothing is classified as low-level waste.

Are spent fuel rods classified as low, intermediate, or high-level waste?

Spent fuel rods are classified as high-level waste.

What are the advantages of nuclear power?

Some of the advantages of nuclear power are: it produces no greenhouse gases or chemical pollution it is a highly reliable method of electricity generation nuclear fuel is widely available and has an extremely high energy density

What are the disadvantages of nuclear power?

Some of the disadvantages of nuclear power are: it produces hazardous radioactive waste with a long half-life (or high activity) the cost of building, operating and de-commissioning reactors is very high there is a (low) threat of serious accidents

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Fission (DP IB Physics)

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Define nuclear fission.

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Define nuclear fission.
Nuclear fission is the splitting of a large nucleus into two smaller nuclei.
What is spontaneous fission?
Spontaneous fission occurs randomly and without additional energy being put into the nucleus.
What is induced fission?
Induced fission occurs when a stable nucleus splits into small nuclei due to the absorption of a thermal (slow-moving) neutron.
True or False?
Uranium-235 is an example of a fissile material.
True.
Uranium-235 is an example of a fissile material, this means it can undergo fission reactions - its nuclei can be split apart into smaller nuclei.
True or False?
More than one neutron is required to induce fission in a uranium-235 nucleus.
False.
Only one neutron is required to induce fission in a uranium-235 nucleus.
What happens when a uranium-235 nucleus is bombarded with fast-moving neutrons?
When a uranium-235 nucleus is bombarded with fast-moving neutrons, they will rebound and fission will not be induced
In what form is energy released from nuclear fission reactions?
In fission reactions, energy is released in the form of kinetic energy of the fragments as well as neutrons and gamma rays.
True or False?
In a nuclear fission reaction, the mass of the daughter nuclei is the same as the mass of the parent nucleus
False.
In a nuclear fission reaction, the mass of the daughter nuclei is less than the mass of the parent nucleus.
True or False?
For nuclear fission to occur, the fission fragments must be more stable than the original nucleus.
True.
For nuclear fission to occur, the fission fragments must be more stable than the original nucleus.
In other words, the fission fragments must have higher values of binding energy per nucleon than the original nucleus undergoing fission.
Calculate the energy released per fission of uranium-235 using the following reaction:
${}_{92}^{235}U + {}_{0}^{1}n \to {}_{36}^{92}{Kr} + {}_{56}^{141}{Ba} + 3 {}_{0}^{1}n$
Uranium-235 has a binding energy of 7.59 MeV per nucleon, krypton-92 has a binding energy of 8.51 MeV per nucleon, and barium 141 has a binding energy of 8.33 MeV per nucleon.
The energy released per fission of uranium-235 is about 174 MeV.
- calculate the binding energy before the reaction = (7.59 × 235)
- calculate the binding energy after the reaction = (8.51 × 92) + (8.33 × 141)
- determine the difference in binding energy = (8.51 × 92) + (8.33 × 141) - (7.59 × 235) = 173.8 MeV
True or False?
Nuclear fission has a similar energy density to other sources of fuel.
False.
Nuclear fission has the highest energy density of any currently used fuel source.
What is a nuclear chain reaction?
A nuclear chain reaction occurs when:
- 2 or 3 neutrons are emitted from a fission reaction
- these neutrons cause further fission reactions
- more neutrons are emitted
- the rate of fission reactions increases
What is a thermal neutron?
A thermal neutron is a neutron which is in thermal equilibrium with the moderator.
True or False?
For every fission reaction, there is, on average, one further fission reaction.
True.
When the rate of fission is constant, each fission reaction goes on to initiate, on average, one further fission reaction.
What happens if the amount of nuclear fuel in a fission reactor is too low?
If the amount of nuclear fuel in a fission reactor is below the critical mass, chain reactions will stop or slow down.
This is because neutrons can escape the material without hitting any more nuclei.
What happens if the amount of nuclear fuel in a fission reactor is too high?
If the amount of nuclear fuel in a fission reactor is above the critical mass, chain reactions increase rapidly.
If uncontrolled, this can lead to a huge release of energy and even a nuclear explosion.
What is the purpose of control rods in a nuclear reactor?
The purpose of control rods is to absorb neutrons.
What is the purpose of the moderator in a nuclear reactor?
The purpose of a moderator is to slow down neutrons.
Why must neutrons be slowed down in a nuclear reactor?
In a nuclear reactor, neutrons must be slowed down so they can react with the uranium fuel efficiently.
This is because slow neutrons are more likely to be absorbed by a uranium nucleus than fast neutrons.
True or False?
Lowering the control rods in a nuclear reactor increases the rate of fission.
False.
Lowering the control rods decreases the rate of fission as more neutrons are absorbed.
What is the purpose of shielding in a nuclear reactor?
The purpose of shielding is to absorb hazardous radiation.
What is nuclear waste?
Nuclear waste refers to the leftover radioactive materials associated with the production of nuclear power. Different waste materials can be classed as
- low-level waste
- intermediate-level waste
- high-level waste
How is low-level nuclear waste treated?
Low-level nuclear waste is treated by:
- encasing it in drums filled with concrete
- storing it underground for a few years
- eventually disposing of it in landfill sites
How is intermediate-level nuclear waste treated?
Intermediate-level nuclear waste is treated by:
- encasing it in steel drums filled with concrete
- storing it underground in a secured facility
How is high-level nuclear waste treated?
High-level nuclear waste is treated by:
- recovering useable isotopes of uranium and plutonium
- encasing it in reinforced steel containers filled with concrete or vitrified with molten glass
- storing in underwater cooling tanks initially
- storing it deep underground in a secured facility
Is contaminated clothing classified as low, intermediate, or high-level waste?
Contaminated clothing is classified as low-level waste.
Are spent fuel rods classified as low, intermediate, or high-level waste?
Spent fuel rods are classified as high-level waste.
What are the advantages of nuclear power?
Some of the advantages of nuclear power are:
- it produces no greenhouse gases or chemical pollution
- it is a highly reliable method of electricity generation
- nuclear fuel is widely available and has an extremely high energy density
What are the disadvantages of nuclear power?
Some of the disadvantages of nuclear power are:
- it produces hazardous radioactive waste with a long half-life (or high activity)
- the cost of building, operating and de-commissioning reactors is very high
- there is a (low) threat of serious accidents

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