Topic 11: Nuclear Radiation Flashcards
Activity
The activity of a radioactive source is the number of nuclei that decay per second, measured in Becquerels (Bq)
Alpha radiation
The radiation of a particle containing two protons and two neutrons. It is strongly ionising, slow moving, and positively charged so therefore deflected by a magnetic field
Atomic mass unit
1/12 the mass of a carbon-12 nuclei
Background radiation
Constant radiation everywhere that is due to radioactive substances in the environment
Beta-minus radiation
Radiation consisting of a high-energy electron that is mildly ionising, fast-moving, and negatively charged so therefore deflected by a magnetic field
Beta-plus radiation
Radiation consisting of a high-energy positron that is mildly ionising, fast-moving, and positively charged so therefore deflected by a magnetic field in the opposite direction to beta-minus radiation
Binding energy
The energy required to split a nucleus into its individual nucleons. The greater the binding energy per nucleon, the more stable the nucleus is
Chain reaction
When the fission of one nucleus produces neutrons that cause fission in another nuclei
Control rod
A rod that is inserted into a reaction vessel that stops neutrons preventing them from continuing on to cause more fission reactions. These are made from substances that absorb neutrons without fissioning themselves
Coolant
A fluid that passes around the reaction vessel and carries away any thermal energy produced by the fission reactions. This thermal energy is used to generate steam and drive generators to produce electricity
Cooling pond
A large pool of water that nuclear waste is placed in to allow it to cool to safe temperatures
Critical mass
The minimum amount of a fissile substance needed to maintain a chain reaction and a steady flow of fission
Decay constant
The probability of a decay occurring per unit time
Fuel rod
Contains the fissile material, each rod has many pellets of nuclear fuel which prevents the critical mass of fuel being reaching meaning the reactions are controlled
Gamma radiation
High energy photons, it is weakly ionising, travels at the speed of light and has no charge so is not deflected by magnetic or electric fields
Half-life
The time taken for half of the radioactive nuclei to decay
Moderator
A substance inserted between the nuclear fuel that reduces the speed of neutrons coming from a fission reaction, allowing them to become thermal neutrons that can induce further fission
Nuclear fission
The splitting of a large nucleus to produce smaller nuclei, fast-moving neutrons and energy
Nuclear fusion
The fusing of two smaller nuclei to form a single nucleus producing a large quantity of energy. Very high temperatures and pressures are needed as well as high magnetic fields to contain the fusing plasma
Nuclear waste
The by-product of a nuclear reaction. This waste is no longer undergoing fission that can be used due to the reduced activity, but the waste is still radioactive and will be for thousands of years, so it is stored underground in reinforced containers
Mass defect
The difference between the mass of the nuclei and its individual components. If this mass defect is large and positive, then when a nucleus undergoes fission this mass defect is released as energy. If this mass defect is negative, then when two nuclei are fused together, this mass defect is released as energy
Spontaneous fission
The process by which a nucleus splits without absorbing a thermal neutron
Thermal neutron
A slow-moving neutron that when absorbed by an unstable nucleus causes it to undergo fission
