What is half-life?
The average time taken for half of a radioactive isotope to decay
What is irradiation?
When you are exposed to radiation from a source, but if the source is not on/im you, it can be removed. E.g when radioactive sources are brought into a room you are exposed to radiation but you can stop being irradiated by leaving the room.
In a nuclear reactors what is the function of the control rods?
Height adjusted to control the rate of the chain reaction by absorbing excess neutrons by control rods
What is contamination?
When something radioactive remains on/in you. It cannot be easily removed. So you continue to be exposed to radiation from the source. E.g if you took a source and injected/ inhaled it, you would be contaminated (you continue to be irradiated even if you leave the area
In a nuclear reactor, what is the function of the moderator?
Absorbs some energy of the neutrons to slow down the fast neutrons produced during fission so they can cause further fission reactions.
In a nuclear reactor, what is the function of the coolant?
Transfers thermal energy t- a nearby boiler to drive turbines and generators (like a thermal power station)
What is the function of the reactor vessel and concrete shield?
Shields from ionising radiation given off by fission reaction and prevents it from escaping the core into the environment. The concrete walls absorbs the radiatiom
What is the atomic number?
The number of protons in the nucleus
What is the mass number?
The total number of protons+neutrons
What is an isotope?
Atoms of the same element with the same number of protons but a different number of neutrons
What are alpha, beta and gamma rays?
Ionising radiation emitted from unstable nuclei in a random process
What are the properties of alpha radiation?
Strongly ionising, weakly penetrating (can be stopped by paper)
What are the properties of beta radiation?
Medium ionising, penetrates paper but stopped by 2-3mm of thin aluminium
What are the properties of gamma radiation?
Weakly ionising, highly penetrating (needs thick lead to stop)
How can we test the penetration of different radiation types?
Radioactive sources and materials (paper, aluminium foil, lead) and measure counts with a Geiger-Muller detector
What happens to a nucleus when alpha radiation is emitted?
Loses 2 protons and 2 neutrons (atomic number decreases by 2, mass number decreases by 4)
What happens to a nucleus when beta radiation is emitted?
Atomic number increases by 1, mass number stays the same
What are the sources of artificial background radiation?
Medical x-rays, nuclear power, weapons testing
What are sources of natural background radiation?
Rocks, cosmic rays, radon gas
What is the ‘activity’ in radioactivity?
The number of decays per second, measured in bequerels
How to calculate activity?
Activity = number of decays/ time
What are some uses of radioactivity?
Smoke detectors, thickness control, cancer treatment, medical tracers, sterilisation
Why is ionising radiation dangerous?
Damage dna and cause cell mutation or cancer
How can nuclear reactions produce energy?
Through FISSION or FUSION which release large amounts of energy
