(From LV) Radioactivity

What is radioactivity?

Decay of unstable nuclei to become more stable nuclei, resulting in the emission of alpha, beta, and gamma radiation

What are alpha particles?

Alpha particles are helium nuclei consisting of 2 protons and 2 neutrons

What are beta particles?

Fast-moving electrons

What are gamma particles?

Photons, or particles of light

Order the types of radiation in terms of ionising power.

Alpha has the highest ionising power, followed by beta, and gamma has the lowest

Order the types of radiation in terms of penetrating power.

Gamma has the highest penetrating power, followed by beta, and alpha has the lowest

What is the range of radiation in air (alpha, beta, gamma)?

Gamma has the longest range in air, followed by beta, and alpha has the shortest

What is half-life?

Time taken for the number of unstable nuclei in a sample to decay to half

What does 'random' mean in the context of radioactivity?

In radioactivity, 'random' means we cannot predict exactly when an unstable nucleus will decay

What does 'spontaneous' mean in the context of nuclear decay?

'Spontaneous' means that we cannot physically or chemically cause an unstable nucleus to decay

Does the activity of a radioactive source increase or decrease over time?

The activity of a radioactive source decreases over time

What is radioactive activity measured in?

Radioactive activity is measured in Becquerels (Bq)

What is ionisation?

Ionisation is the creation of an ion by stripping electrons away from atoms

What is the difference between contamination and irradiation?

Contamination is the introduction of radioactive material into or onto an object, while irradiation is the exposure of an object to radiation

What can detect ionising radiation?

Ionising radiation can be detected using a Geiger-Muller detector or photographic film

What is nuclear fission?

Nuclear fission is the splitting of a large nucleus into smaller nuclei with the release of energy

What is a chain reaction in the context of fission?

A chain reaction occurs when a neutron released from a fission reaction is absorbed by other nuclei, causing further fission reactions

What is nuclear fusion?

Nuclear fusion is the process in which two small nuclei collide and join together to form a new nucleus, releasing neutrons

What does the fission of Uranium-235 produce?

The fission of Uranium-235 produces two radioactive daughter nuclei and a small number of neutrons

What do boron control rods do in a nuclear reactor core?

Boron control rods absorb neutrons, controlling the rate of reaction

What does the graphite moderator do in a nuclear reactor core?

The graphite moderator slows neutrons down, as fast neutrons are not easily absorbed by uranium

Why is there concrete shielding around a nuclear reactor?

Concrete shielding absorbs nuclear radiation and prevents it from escaping

What are some differences between nuclear fusion and nuclear fission?

• Fission releases energy when atoms split, while fusion releases energy when atoms join together

• Fusion releases more energy than fission

• Fusion does not produce harmful radioactive waste like fission does

What is fusion an energy source for?

Fusion is an energy source for stars

Why does nuclear fusion not happen at low temperatures and pressures?

• Positively charged nuclei must overcome electrostatic repulsion to bind together

• Requires high kinetic energy and high densities (high pressures) to ensure collisions between nuclei