Nuclear fission

This question is about the process of controlled nuclear fission in a nuclear reactor.

In a nuclear reactor, uranium‑235 nuclei are split to produce daughter nuclei and neutrons.

State what else is released in nuclear fission that makes the process useful in a nuclear reactor.

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

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

Many of the daughter nuclei produced in nuclear fission are very radioactive.

These daughter nuclei decay by emitting ionising radiation in a random process.

State what is meant by the term ionising radiation.

State what is meant by the term random process.

The diagram shows some parts of a nuclear reactor.

Explain the role of shielding in a nuclear reactor.

This question is about nuclear fission and nuclear fusion.

The table gives some statements about nuclear fission, or nuclear fusion, or both nuclear fission and nuclear fusion.

Place ticks (✓) in the table to show which statements are about nuclear fission and which statements are about nuclear fusion.

Nuclear fission reactors use control rods and a moderator.

Describe the function of the control rods and the function of the moderator in a nuclear fission reactor.

control rods

moderator

Diagram 1 shows some of the stages of electricity generation in a nuclear power station.

Nuclear fission takes place inside the reactor of the nuclear power station.

Give the name of a fuel that could be used in the reactor.

Energy is released from the fuel in the reactor by nuclear fission.

Describe the process of nuclear fission that takes place inside the reactor.

High pressure steam transfers energy from the reactor to a turbine.

The turbine spins as the steam passes through it.

Diagram 2 shows a simplified generator connected to the turbine.

Explain how electricity is generated by the generator.

At night the power station does not need to generate as much electricity.

Suggest how the output of this generator could be reduced.

The generator produces alternating current.

Describe the differences between alternating current (a.c.) and direct current (d.c.).

This question is about nuclear reactions.

Nuclear fusion and nuclear fission release energy from the nuclear stores of atoms.

The table gives some statements about nuclear fusion and some statements about nuclear fission.

Place ticks () in the table to show whether each statement applies to nuclear fusion or nuclear fission.

In nuclear fusion, two positively charged nuclei must overcome the effects of the repulsive electrostatic force between them.

Explain the two conditions needed to overcome the effects of this repulsive force and achieve nuclear fusion.

Describe how a chain reaction occurs in a nuclear fission reactor.

Describe the role of the control rods in a nuclear fission reactor.

Describe how the process of nuclear fission is different from the process of nuclear fusion.

Which of these is the name of the nuclear process that is the main energy source for stars?

Give a reason why the nuclear process in stars does not happen at low temperatures and pressures.

The photograph shows the nuclear fusion reactor called ITER.

Describe the difference between nuclear fusion and nuclear fission.

At ITER, hydrogen-3 and hydrogen-2 will be fused into helium and another particle labelled X.

Complete the nuclear equation for the fusion of hydrogen-3 and hydrogen-2.

Discuss potential safety advantages of a fusion reactor compared with a fission reactor.

You should refer to the products of this fusion reaction and to the fission reaction of uranium.

The half-life of a radioactive isotope is 12 years.

The activity of a sample of this isotope is 120 kBq.

Calculate the activity of this sample after 48 years.

Kori Nuclear Power Plant in South Korea is one of the world’s largest nuclear fission power stations.

The reactors at Kori use nuclear fission to generate electricity.

The products released during nuclear fission have high energy in their kinetic store.

Give a product of nuclear fission.

Give two disadvantages of using nuclear fission to generate electricity.

Kori has a maximum power output of 7.49 × 10⁹W.

State what is meant by the term power.

Calculate the minimum time taken for Kori to transfer 6.4710¹⁴J of energy.

The chart shows the efficiencies of different methods of generating electricity.

The chart shows that the geothermal power station has an efficiency of 15%.

Explain what is meant by an efficiency of 15%.

A small hydroelectric power station has a useful energy output of 6.0 kJ.

Calculate the total energy input for this power station using information from the chart.

Name a fuel used in the reactor of a nuclear power station.

These sentences describe the process of nuclear fission.

Complete these sentences by writing a suitable word in each blank space.

A nucleus absorbs a_........ .

The nucleus formed splits because it is_........ .

The nucleus splits into two smaller nuclei called_........

nuclei and two or three_........ .

The energy released is transferred into the_........

energy store of the fission products.

In extreme conditions, the isotope lithium-6 can be made to undergo nuclear fission.

The lithium-6 nucleus absorbs a neutron and produces an alpha particle and an isotope of hydrogen.

The incomplete nuclear equation for this fission is

Complete the nuclear equation by writing the numbers in the boxes.

Explain why this fission does not cause a chain reaction.

Explain the difference between nuclear fission and nuclear fusion.

Uranium-235 captures a neutron and undergoes nuclear fission in a chain reaction.

The equation shows a possible nuclear fission reaction.

Calculate x, the number of neutrons released by this fission reaction.

Describe what is meant by a chain reaction.

Iodine-129 is an isotope found in radioactive waste from nuclear power stations.

Iodine-129 has a half-life of approximately 15 million years.

A sample of iodine-129 has an activity of 72 kBq.

Show that the time required for the sample to have an activity less than 5 kBq is approximately 60 million years.

Some radioactive waste from nuclear power stations has a very long half-life.

Discuss precautions that must be taken when disposing of this radioactive waste.

The nuclear equation shows how a nucleus of uranium‑236 may undergo nuclear fission.

Determine how many neutrons are released in this fission process.

The table gives some of the constituents of this nuclear fission.

Complete the table by putting one tick () in each row to show whether the constituent is a parent nucleus or a daughter nucleus.

Describe how the neutrons released in this fission process can cause a chain reaction.

This question is about a nuclear fission chain reaction.

Uranium-235 is an isotope of uranium that can undergo nuclear fission.

The table gives some statements about this fission process.

Add ticks (✓) to the table to show which statements are correct.

State which product of nuclear fission causes the next uranium-235 nucleus to split in the chain reaction.

Uranium-235 is radioactive and emits alpha radiation.

Which of these statements describes alpha radiation?

Some of the products of nuclear fission are radioactive because their nuclei have too many neutrons.

These nuclei become more stable when a neutron changes into a proton.

State which type of radiation is emitted by radioactive nuclei with too many neutrons.

This question is about stars.

Describe the stages in the evolution of a star similar in mass to the Sun.

The process of energy release in the core of a star is different to the process of energy release in a nuclear reactor in a power station.

Describe how these processes of energy release are different.